The addition of fibers to strengthen recycled concrete can strengthen the inherent deficits and deficiencies of concrete containing recycled aggregates to some extent and enlarge the concrete’s application range. In order to further promote the development and application of fiber-reinforced brick aggregate recycled concrete, the research results regarding its mechanical properties are reviewed in this paper. The effect of the content of broken brick on the mechanical properties of recycled concrete and the effects of different categories and contents of fiber on the basic mechanical properties of recycled concrete are analyzed. The problems to be solved in research on the mechanical properties of fiber-reinforced recycled brick aggregate concrete are presented, and the related research suggestions and prospects are summarized. This review provides a reference for further research in this field and the popularization and application of fiber-reinforced recycled concrete. With the rapid development of the economy, a large amount of construction waste is produced in the processes of demolition and reconstruction of old buildings and the construction of new buildings, causing severe damage to the ecological environment and produced a large amount of waste. In a 2019 assessment alone, construction waste in the United States and China was found to be approximately 548 million tons and 250 billion tons, respectively [There are many types of research on the mechanical properties of brick aggregate recycled concrete, which mainly focus on physical and mechanical properties, such as compressive properties, flexural properties, elastic modulus, and splitting tensile properties. Most experiments are carried out to explore changes in different brick aggregate or brick concrete aggregate contents. The mechanical properties of recycled concrete tend to decline with the increase in the replacement rate of brick aggregate, including the compressive strength, flexural strength, elastic modulus, and splitting tensile strength ,10,11,12However, some defects in brick aggregate recycled concrete restrict its application in engineering. For example, due to the high porosity of brick aggregate, more water needs to be added during mixing to ensure the concrete’s workability. As a result, the water absorption rate of reclaimed aggregate is much higher than that of natural aggregate, which means that the shrinkage deformation of reclaimed concrete is more significant when water is lost, and the durability of reclaimed concrete is inferior to that of natural aggregate concrete. The experimental results show that the water absorption of recycled aggregate is approximately 15 times that of natural aggregate . HoweverGlass fiber is cheap and lightweight and has good tensile strength, and it has become a focal material in fiber-modified reclaimed concrete research. As early as the 1950s, the former Soviet Union began to use glass fiber as a modified material in concrete . HoweverMost current research focuses on the basic mechanical properties of glass-fiber-reinforced recycled concrete at room temperature. Ali et al.  studied Based on previous research, many more in-depth studies have been conducted on the mechanism of fiber-modified concrete. Wang et al. studied the effects of polypropylene (PP), polyvinyl alcohol (PVA), and polyacrylonitrile (PAN) fibers of varying lengths (10 mm and 20 mm) on the workability, strength, shrinkage, cracking resistance, and durability of panel concrete . For exaResearch on polypropylene fiber-modified brick aggregate recycled concrete is also expanding. Several studies have found that ,62,63 thIn summary, the formation of recycled concrete with waste broken brick as a coarse aggregate is of immense environmental significance. Instead, there is great variation in how the addition of waste broken brick as a coarse aggregate can affect the mechanical properties, making its practical use difficult. This paper mainly introduces the state of research on the mechanical properties of fiber-reinforced brick aggregate recycled concrete in China and other countries. This paper analyzes the present state of research on recycled concrete from the perspectives of the content of waste broken brick and the influences of the type and content of fiber on the mechanical properties of recycled concrete based on a summarization of the effects of polypropylene fiber and glass fiber on RAC. The possibilities and prospects for the development of fiber-modified brick aggregate recycled concrete are discussed.Aggregate with a particle size larger than 4.75 mm  is calleAfter crushing, cleaning, and sieving, the waste bricks from the demolition site are mixed with gradation in proportions to form an aggregate called recycled brick aggregate. Concerning the coarse concrete aggregate, some attention must be paid to performance factors in the engineering application, including the volume density, apparent density, water absorption, and crushing value.As shown in The mechanical properties of BBA  are typically lower than those of NA, making it challenging to popularize BBA in engineering applications. However, the addition of fiber can enhance the strength of RAC, mainly its crack resistance. At present, steel fiber (SF), polypropylene fiber (PF), carbon fiber (CF), polyvinyl alcohol fiber (PVA), and glass fiber (GF) are the main fiber types in this research field . The phyGlass fiber is made from waste glass or glass balls via high-temperature melting, drawing, winding, weaving, and other processes. Its diameter ranges from a few microns to 20 microns, equal to 1/20 to 1/5 the diameter of human hair. Each bundle of filaments consists of hundreds or even thousands of filaments. As a result, the utility model possesses the advantages of being lightweight and having good insulation, strong heat resistance, good corrosion resistance, high tensile strength, and a high elastic modulus .The mechanical properties of recycled concrete are an essential index reflecting the quality of recycled concrete. For instance, using broken red brick as a coarse aggregate significantly impacts the strength of recycled concrete, and it is essential to study its change law.The influence of the replacement rate of recycled brick aggregate on the compressive strength of RBC has yet to be fully determined by domestic and foreign researchers. It can be seen from While Ma et al.’s  experimeThe water–cement ratio also affects the splitting tensile strength of recycled concrete, as displayed in Because of the increase in the BBA, the internal strength of concrete is low;The quality of poor materials is increased, resulting in more easily damaged bond surfaces;It is indicated that the fracture resistance of recycled concrete will be diminished by the addition of too much BBA.The results of polynomial fitting demonstrate that, as a whole, the flexural strength of RAC decreases with the increase in the replacement ratio of BBA. The higher the replacement ratio of BBA is, the faster the strength will decrease. Therefore, when the replacement rate of BBA is high, some measures should be taken to enhance the flexural strength of concrete.As shown in It is clear from the data in It is essential to study the effects of different fiber contents on the mechanical properties of RAC. It is helpful to discover the law of the influence of the fiber content on the mechanical properties in order to determine a production plan that considers both economy and security in practical production.Due to the need for reference data, the authors obtained experimental data. The designed water–cement ratio was 0.4, and the replacement rate of brick and aggregate was 50%. The volume fractions of polypropylene fiber were 0%, 0.3%, 0.6%, 0.9%, and 1.2%, respectively. A 28D cubic compression test was carried out on a 150 mm × 150 mm × 150 mm cubic specimen. It can be seen from the data comparison in 2 of the fitting curve is 0.88. The cubic compressive strength of the recycled concrete increases with the increase in the substitution rate of polypropylene fiber, but the overall growth rate is slow. For recycled concrete’s cubic compressive strength, the improvement effect of polypropylene fiber is insignificant.As shown in In order to enrich the experimental data and enhance the reliability of the analysis results, the authors obtained a set of experimental data. The trial applied a water–cement ratio of 0.4 and a replacement rate of brick-aggregate of 50%. The 28-day splitting tensile strength test was conducted on a cube specimen with glass fiber contents of 0%, 0.3%, 0.6%, 0.9%, and 1.2% and a size of 150 mm × 150 mm × 150 mm. As can be seen from the data in 2 is 0.93. From the relevant results, we can see thar the splitting tensile strength of the recycled concrete rises with the increase in the polypropylene fiber content. When the fiber content is lower, the splitting tensile strength of the recycled concrete increases with the increase in the polypropylene fiber content, the fitting curve is steep, and the splitting tensile strength increases rapidly. However, the slope of the curve decreases when the fiber content is more than 0.4%, and the rate of increase in the splitting tensile strength decreases with the increase in the fiber content.Due to the lack of reference data, the authors obtained a set of experimental data, with the actual water–cement ratio of 0.4, BBA replacement rate of 50%, and size of 150 mm × 150 mm × 150 mm. Cubic specimens with glass fiber volume fractions of 0%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, and 1.2% were subjected to cubic compression tests for 28 days. It can be seen from In Due to the lack of reference data, the authors obtained a set of experimental data. The actual water–cement ratio was 0.4, the BBA replacement rate was 50%, and the volume fractions of glass fiber were 0%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, and 1.2%. The cube specimen, with a size of 150 mm × 150 mm × 150 mm, was subjected to a crack tensile test for 28 days. The data in This paper reviewed the research status of glass-fiber- and polypropylene-fiber-reinforced recycled RAC. The effects of fiber on the mechanical properties of RAC were determined by considering factors such as the replacement rate of BBA, fiber type, and fiber content. Based on the literature review, the following conclusions can be drawn:(1) Compared with natural coarse aggregate (NA), broken red brick aggregate (BBA) made of waste broken brick possesses a lower apparent density and bulk density, with a 19–40% lower apparent density and 20–47% lower bulk density, as well as a higher water absorption and crushing index, with an 11 times to 49 times higher water absorption and 2.2 times to 4 times higher crushing index, which directly indicates that broken red brick coarse aggregate is inferior in strength and stability to natural aggregate.(2) For the optimal replacement rate of recycled concrete BBA, replacing natural aggregate with BBA has little effect on the compressive strength of the opposite side. The overall trend is downward, but it can fulfill the strength requirements of general engineering. Regarding the splitting tensile strength, when the replacement rate of BBA is less than 50%, the strength does not decrease significantly. However, when the replacement rate is more than 50%, the strength decreases considerably, which greatly influences the concrete. Regarding flexural strength, when the replacement rate of BBA is below 30%, it demonstrates a strengthening effect to a certain degree, which is worthy of attention. However, when the replacement rate is above 30%, the concrete strength shows a downward trend. In addition, with an identical aggregate substitution rate of the brick, the water–cement ratio also considerably affects the strength of concrete. When the water–cement ratio is more significant than 0.4, the compressive strength, splitting tensile strength, and flexural strength of the concrete decrease with the increase in the water–cement ratio. In addition, the elastic modulus of RAC decreases significantly with the increase in the replacement rate of brick aggregate, which indirectly indicates that the compressive strength of RAC is lower than that of ordinary concrete under the same water–cement ratio and other conditions. Therefore, on the whole, the mechanical strength of recycled concrete is less than that of ordinary concrete in all aspects when the replacement rate of BBA is higher. In addition, due to the defects of BBA, such as its large porosity, high water absorption, low strength, and bond strength, BBA significantly impacts recycled concrete’s mechanical properties and durability. In order to expand the application scope of recycled concrete in practical engineering, in addition to regulating the replacement rate of BBA and the water–cement ratio, the most useful method is to use fiber materials to produce fiber-reclaimed RAC with better mechanical properties.(3) When the broken brick’s replacement rate is less than 50%, the cubic compressive strength and splitting tensile strength of the recycled concrete are enhanced by PPF. However, it should be noted that when the replacement rate of broken brick is higher, such as 100%, and the content of PPF reaches 0.2–0.3%, the strength of the recycled concrete shows a decreasing trend and starts to become lower than that of recycled concrete without PPF. Therefore, in practical application, it is essential to consider the comprehensive effects of the replacement rate of BBA and the fiber content.(4) Glass fiber with high strength and good toughness has a better modifying effect on the recycled concrete of BBA: the replacement rate of BBA and the content of fiber have a compound effect on the strength of recycled concrete when the replacement rate of BBA is below 50%, and the cubic compressive strength of recycled concrete can be enhanced by adding an appropriate amount of GF, but this is not apparent. On the contrary, when the replacement rate of BBA is high and the replacement rate is 50%, the strength of recycled concrete will be reduced because of the addition of too much GF, as a large amount of alkali-resistant glass fiber weakens the ability for bonding between aggregates and magnifies the original defects of aggregate brick concrete, exceeding the strengthening effect of GF fiber on the cubic compressive strength. On the other hand, with a low replacement rate of BBA, when the content of GF is in a specific range (0–0.6%), the splitting tensile strength of recycled concrete can be enhanced.(5) According to the present research, single-fiber-modified recycled RAC still needs to be improved, and this cannot ultimately improve the performance of RAC. Additionally, because of their high price, some high-performance fibers cannot be extended to the actual construction field. However, research on the hybrid-fiber-reinforced RAC, which can be produced through the positive hybrid effect of fiber, is still in the initial stage at home and abroad. Concrete’s fundamental mechanical properties, failure mechanism, and fiber-reinforced mechanism are still yet to be studied.Currently, in construction, recycled concrete can be utilized for roadsides, gutters , pavemen


The prestressed and steel-reinforced concrete slab (PSRCS) is an innovative composite structural member offering high load capacity and stiffness and exceptional anti-crack performance, making it a leading trend in composite structures. This paper presents the derived calculation formulas for bearing capacity, section stiffness, mid-span deflection of PSRCS. Additionally, a numerical analysis of PSRCS is conducted using ABAQUS software, with several models created to systematically investigate bearing capacity, section stiffness, anti-crack performance, and failure mode. Concurrently, PSRCS member parameters are analyzed for optimal design, and the results of finite element (FE) calculations are compared with theoretical formula calculations. The results demonstrate that PSRCS exhibits superior load capacity, section stiffness, and anti-crack performance comparing to conventional slabs. The parametric analysis offers optimal design for each parameter and presents the corresponding recommended span-to-depth ratios for various spans in PSRCS applications. At the same time, depth and span requirements remain crucial factors in underground space design. However, depth and span are mutually exclusive, making it difficult to balance bearing capacity, crack control, and functional usage in large-span underground structures4. Consequently, traditional practices, such as the underground framework support system at the Messe Bahnhof station in Germany, provide stability and high bearing capacity. Yet, they require numerous columns and have a smaller span, significantly impacting visibility and spatial efficiency5. Most subway tunnels and underground stations utilize arch structures, which improve performance over time as they bear only compressive forces internally, compacting the material. Nevertheless, arch structures present considerable limitations in functional usage, such as clearance and short-side span, and pose maintenance challenges7.Exploiting urban underground resources is a highly effective method for addressing the significant conflict between urban development and limited land availability. Thoughtful planning, development, and use of underground space can substantially support and bolster urban development strategies, emphasizing sustainability worldwideConventional structural forms face challenges in satisfying both load-bearing capacity and crack control requirements when designing large-span underground structures. To address this issue, this paper introduces a suitable structural form for such structures, specifically, the prestressed and steel-reinforced concrete slab (PSRCS). The PSRCS comprises an H-beam, prestressed tendons, longitudinal reinforcement, and stirrup cages. In this novel structure, the H-beam and longitudinal reinforcement act as the primary load-bearing components, while prestressed tendons control overall crack development and distribution. The H-beam is arranged at intervals within the slab, and stirrup cages are placed between adjacent H-beam elements to ensure uniform sectional stiffness distribution and provide positioning and fixation for the prestressed tendons.8 conducted vertical flexural performance tests on simply supported reinforced concrete slabs with varying spans and examined the failure modes and mechanical behavior of composite beam-slab systems, researchers have been investigating the flexural performance of reinforced concrete slabs from structural to material levels. Abdal et al. and Ibrahim et al.10 incorporated short carbon fibers into reinforced concrete one-way slabs and analyzed the influence of these additives on the flexural performance of the slabs. Turco et al.11 examined the impact of the width and thickness of composite material layers on the flexural performance of reinforced concrete beam slabs. Wagner and Gruttmann12 investigated the selection of boundary conditions and the influence of nonlinear material parameter behavior on reinforced concrete ribbed slab systems, addressing the potential for altering material models during the loading process and the associated elasto-plastic behavior, as well as suggesting a proportional adjustment method for the model loading process. Honarvar et al.13 utilized experimental data and finite element models to assess the structural performance of prefabricated ultra-high strength reinforced concrete ribbed slab systems and optimized the design methodology for these systems. To enhance the strength and crack resistance of reinforced concrete slab structures, researchers integrated prestressing tendons, shaped steel, and other components into reinforced concrete slabs to create composite slabs and investigated their related vertical load-bearing performance. Zhang et al.14 introduced a nonlinear analysis method for determining the limit stress of unbonded reinforcement in prestressed concrete slab systems and presented a novel calculation approach for the flexural performance of these systems using static load tests and theoretical analysis. da Silva et al.15 suggested slab, bar, and interface finite element formulations for numerically simulating prestressed concrete beam slabs, emphasizing the inclusion of interface elements that can emulate potential sliding between concrete and prestressed tendons, as well as the stress and strain functions within the reinforcement bundles during vertical loading. Hou et al.16 assessed the flexural performance of prefabricated prestressed concrete bridge deck panels, examining the influence of crucial design parameters on the combined beam-slab flexural performance through monotonic loading tests. da Rocha Almeida et al.17 investigated an analytical method for steel–concrete composite beams with externally applied prestress and evaluated the structural performance of these prestressed steel–concrete composite beams. Oukaili et al.18 introduced a nonlinear analysis method to assess the performance of post-tensioned concrete flexural members with unbonded internal tendons, validating the proposed method through experimental results and finite element models. Research on steel–concrete composite slab systems remains relatively limited. Ayhan et al., Gopinath et al. and Wang et al.21 examined the flexural and bond performance of cold-formed thin-walled steel–concrete composite slabs, while24 concentrated on the flexural performance, working performance, and associated influencing factors of steel–concrete hidden beam slabs. Although direct research on PSRCS is currently scarce, a relatively mature research foundation exists for prestressed and steel-reinforced concrete beams (PSRCB), which exhibit similarities with PSRCS. In recent years, researchers have extensively studied the performance and design methods of PSRCB, offering a more comprehensive understanding of this type of structure. Du et al.25 explored the flexural performance of PSRCB and the bond-slip effects between steel and concrete, conducted static load tests on PSRCB, revised the existing calculation formula for PSRCB's positive cross-section bearing capacity, and obtained bond-slip influence coefficients for different component parts through regression analysis using existing experimental data. Yao and Xiong26 examined the limit values of flexural deformation performance indices for PSRCB, summarized the complete failure characteristics of PSRCB in bending, and provided corresponding macroscopic damage descriptions. Li and Yu et al.28 combined prestressing technology with prefabrication techniques in steel-reinforced concrete structures, proposed partially prefabricated prestressed steel-reinforced concrete (PPPSRC) beams, conducted flexural performance tests, and analyzed the effects of relevant parameters on the failure modes and cross-sectional stress development of PPPSRC beams. Chen et al., Fu et al. and Yao and Xiong31 performed experimental studies on the vertical load-bearing performance and failure mechanisms of prestressed steel-reinforced concrete frames. Research results indicate that PSRCB structures can effectively control crack width, enhance the normal usage performance of the structure, fully utilize the strengths of steel and concrete, and maximize the benefits of different materials.PSRCS represents a novel composite structural form for slabs, which currently lacks research and engineering applications in terms of its flexural performance. Reinforced concrete slabs, prestressed concrete slabs, steel-reinforced concrete slabs, and prestressed steel-reinforced concrete beams are examples of similar flexural members with established research foundations. SinceThe aforementioned research on the vertical load-bearing performance of similar flexural components indicates that whether it involves reinforced concrete ribbed slabs, waffle slabs, prestressed concrete composite slabs, or cold-formed thin-walled steel–concrete composite slabs, none can achieve both high load-bearing capacity and effective crack control simultaneously. The integration of prestress and H-beams is often employed only in frame beam-column systems, with no systematic theoretical research or engineering applications for PSRCS in directly load-bearing components such as slabs. Consequently, investigating the vertical load-bearing performance of PSRCS can broaden the research scope of prestressed steel-reinforced concrete composite structures. Simultaneously, its advantages of high load-bearing capacity and superior crack resistance make it suitable for the design and application of large-span underground structures, providing a theoretical foundation and design reference for future engineering projects.This study examines the load-bearing mechanism of PSRCS under vertical loads. From a theoretical analysis standpoint, the paper presents calculation methods for the bearing capacity, stiffness, and deflection of PSRCS cross-sections. Utilizing ABAQUS finite element software, a comparative analysis highlights the advantages of PSRCS over traditional slab construction systems. A parametric analysis is also conducted to investigate the bearing capacity of PSRCS under various conditions and the stress changes within internal components. Furthermore, the study offers optimal designs for diverse spans and slab thicknesses.32’s research. The complexity of the PSRCS stems from factors like the tensile reinforcement ratio, steel content of the H-beam, H-beam eccentricity, and the height of the prestressed tendons. Consequently, the entire co-working process exhibits complexity. Depending on the neutral axis positions, the PSRCS can be classified into three cases, as depicted in Fig. The unique mechanism of PSRCS differentiates it from traditional unidirectional slabs. For calculations, a cross-section is considered, which includes an H-beam, prestressed tendons, and longitudinal reinforcement under a unit width along the short side of the PSRCS. The following calculation relies on the plane section hypothesis andx/β represents the height of the compression zone; h is the section height of PSRCS; b is the calculation width of the cross section; ba is the width of flange of H-beam; hs is the height between the centers of the upper and lower flanges of the H-beam; hw is the height of H-beam web; ha and h'a are the distances from the centers of the lower and upper flanges of the H-beam to the tension and compression edges of the cross-section, respectively; hp is the distance from prestressed tendons to the tension edge of the cross-section; hr is the distance between the tension reinforcement and the lower edge of the cross-section; ts and t's are the thicknesses of the lower and upper flanges of the H-beam, respectively; tw is the web thickness of H-beam; fr, fpy, and fa are the design yield strength values of the tensile reinforcement, prestressed tendons, and H-beam, respectively; fc is the design compressive strength value of the concrete; Ar is the area of ordinary reinforcement of concrete in the tensile zone; A'r is the area of ordinary reinforcement of concrete in the compressive zone; Ap is the area of prestressed tendons; Aas and A'as are the area of bottom flange and upper flange of H-beam; Aaw is the area of H-beam web; Naw is the axial force of H-beam web; εas is the tensile strain at the center of the upper flange of H-beam; Ea is the elastic modulus of the H-beam.εas is smaller than εa and x/β is smaller than h'a, the relative height of the concrete compressive zone can be calculated as follows:x is the relative height of the compressive zone; εcu represents the ultimate compressive strain of concrete; Maw denotes the bending moment of the H-beam web.In PSRCS, when the H-beam is asymmetrically arranged (with a downward offset) or when the steel ratio is relatively low, the neutral axis may lies above the upper flange of the H-beam. The upper flange, web, bottom flange of the H-beam, as well as tensile reinforcement and prestressed tendons, are assumed to be in tension, and the compressed concrete in the compression zone is partially crushed and ceases to function. For simplicity in calculation, it is considered that the compressed concrete in the compression zone has reached its yield strength. At this point, the analysis focuses on the steel flange near the neutral axis, while the stress states of the other steel components, such as longitudinal reinforcement and prestressed tendons, are considered relatively simple and assumed to have reached their yield strength. Based on the stress balance in the section, when α and β are coefficients of the equivalent rectangular stress pattern, and they are obtained by the method in reference33.The  j and k are determined by the following formula   2) are sThe formula of bearing capacity of PSRCS is calculated as follows:h'a + t's < x/β < h'a + hw + t's, the relative height of the compressive zone in the concrete is calculated as follows:ε'as is the compressive strain of the upper flange of H-beam; ε'a is the yield compressive strain of H-beam.In certain cases, when the neutral axis is located within the web of the H-beam, it is assumed that the upper flange of the H-beam experiences compression, the H-beam web undergoes a combination of compression and tension, and the lower flange of the H-beam, the longitudinal reinforcement, and the prestressed tendons are subjected to tension. In accordance with the stress balance, when The formula of bearing capacity of PSRCS is calculated as follows:Where 34, this paper presents a method for calculating the stiffness of PSRCS under various working stages, as illustrated in Fig. Referring to Liu's study on the stiffness of steel reinforced concrete structuresBe is considered as the summation of the concrete stiffness Bc, the longitudinal reinforcement stiffness Br, the prestressed tendons stiffness Bpy and the H-beam stiffness Ba. And the overall stiffness BE is as follows:Ec is the concrete modulus, Ic is the moment of inertia of the concrete section, Ia, Ir, Ipy are the moment of inertia of the H-beam, longitudinal reinforcement, and prestressed tendons respectively, Aa is the area of the H-beam. When the upper load is less than the cracking load, the PSRCS is in the full-section working state, and its section stiffness Bcc, peripheral concrete stiffness Brc and H-beam stiffness Ba. The calculation of Brc is based on the relevant equations for computing ordinary reinforced concrete structures in the "Concrete Structure Design Code" (GB50010-2010)35. Taking into account the overall force balance, the section steel and prestressed tendons are considered as equivalent longitudinal reinforcements, leading to an update and replacement of the equation. The overall stiffness Bu can be expressed as follows:35 and is used to account for the difference between the design value and characteristic value of concrete strength, ensuring conservative design and high safety levels; Irc and Icc are the moments of inertia of the peripheral region and the core region; Aa is the sectional area of H-beam; ycc is the distance from the centroid of the concrete core region to the compressive area surface; Mcr is the cracking moment, which represents the moment when the concrete section of the beam starts to crack, and can be calculated based on the tensile strength of the concrete, the area of reinforcement, and the effective depth of the beam; Mk is the ultimate moment, indicating the moment when the beam fails due to the yielding of the reinforcement, and is determined by considering the maximum distributed load on the beam, the span of the beam, and the effective depth of the beam; Eav is the average elastic modulus of H-beam, longitudinal reinforcement and prestressed tendons; ρr and ρpy are the reinforcement ratio of longitudinal reinforcement and prestressed tendons, respectively.When the upper load exceeds the cracking load, the peripheral concrete at the bottom experiences cracking and progressively ceases to contribute to the structural performance. Consequently, the neutral axis shifts upward, and the section stiffness comprises the combined stiffness of the core-restrained concrete ye caused under the full working stage, and the second part is the deflection yu caused after the concrete cracking. Equation  and steel-reinforced concrete slab (SRCS), have been modeled, as displayed in Table 38 were utilized to validate the results of the FE model of prestressed composite concrete beams with encased H-steel.Due to the lack of direct research on PSRCS, it is essential to evaluate the accuracy and reliability of this innovative structure in ABAQUS. In this paper, Zheng's experiments38 designed three sets of prestressed composite concrete beams with encased H-steel specimens, as shown in Fig. fptk = 1860 N/mm2, and the controlled tensile stress is σcon = 0.75fptk, which using bonded prestress technology. H-shaped steel is of Q235 strength grade, symmetrically arranged. The concrete's cubic compressive strength fcu = 50.12 N/mm2, axial tensile strength ft = 3.38 N/mm2, and elastic modulus Ec = 3.25 × 104 N/mm2. The measured yield strength fy, ultimate strength fu, and yield strain εy of the reinforcement and steel sections are presented in Table 2 of Ref.35. The loading method involves using hydraulic jacks to symmetrically apply single-point loads at the mid-span of the two spans of the specimen, with simply supported boundary conditions and adjustable hinge supports at the central support.Zheng et al.38 are presented below. The geometry and dimensions of the finite element model are consistent with the YL-2 component in38. Through the mesh sensitivity study, to facilitate computation, the grid size in the span direction is set at 100 mm intervals, while the grid size in the width direction is set at 30 mm intervals. In terms of material properties, the elastic modulus, Poisson's ratios, and yield strengths of concrete and steel are consistent with those in38. For the element type, since the component is a steel–concrete composite structure, both concrete and section steel are modeled using C3D8R solid elements to improve accuracy, while rebars and prestressed tendons are modeled using T3D2 truss line elements. In the selection of boundary conditions, to be consistent with the simple support conditions of the experimental component, the boundary conditions at both ends of the model are defined: one end is a fixed support, restricting its translational and out-of-plane rotational movements, while the other end is set as a sliding support, constraining its out-of-plane translation, vertical displacement, and out-of-plane rotation. Displacement loading is selected, and equivalent displacement corresponding to the experimental limit load is applied. Prestressing is treated using the predefined Fields tool39. The internal contact interaction of the component is handled using embedded constraints. The calculation process employs static force computation.To verify the effectiveness and accuracy of the FE modeling method for PSRC-type components compared to actual tests, the details of the establishment of the finite element model inThe comparative analysis between ABAQUS results and Zheng's experiments results are shown in Fig. It is discovered that there is a general agreement between the failure mode predicted by the FE model and that observed in the test. Some typical comparisons are shown in Fig. 40.The concrete and H-beam are modeled using eight-node reduced integration 3D solid elements (C3D8R). Reinforcements and prestressed tendons are modeled with truss elements (T3D2). All steel components are embedded within the concrete slab, and the slippage between the reinforcement and concrete is not consideredBased on the mesh size convergence study , a 500-mm mesh size was employed for the concrete slab to optimize response capture across the entire region and achieve faster computation speed Fig. . For othEs) and Poison's ratio (νs) are set to 206,000 N/mm2 and 0.3, respectively. If the stress exceeds the yield stress, the hardening modulus E′s is taken as E′s = 0.01Es, in which Es is the elastic modulus of the steel41. C40 grade concrete is employed for the concrete, Q355 grade steel is used for section steel, and HRB400 grade steel bars are utilized for reinforcement, as specified in35. Tensile strength, compressive strength, and yield stress data for concrete and steel can be found in35.The bilinear elastic–plastic stress–strain curve with linear strain hardening is employed to model the H-beam, prestressed tendons, stirrup cages, and reinforcing mesh. When the stress remains within the yield surface, steel exhibits linearly elastic behavior. The Young's modulus  over conventional structures, such as Reinforced Concrete Slabs (RCS) and Steel-Reinforced Concrete Slabs (SRCS), are explored by comparing their load–deflection curves, stress distribution within internal components, plastic development behavior of concrete, and other factors. Furthermore, a parametric analysis is conducted to examine the influence of various parameters on the mechanical performance of PSRCS.Pcr), cracking deflection (Δcr), yield load (Py), yield deflection (Δy), ultimate load (Pu), and ultimate deflection (Δu). Compared to RCS and SRCS, PSRCS demonstrates a higher bearing capacity and distinct characteristic points on the load–deflection curve, as shown in Fig. As illustrated in Fig. 42, the yield point of the model is defined as the point of tangency between the load–deflection curve and a line parallel to the line connecting the origin and the ultimate point. The distance from the yield point to the parallel line is defined as 'd'. When multiple tangent points are present, the point with the largest 'd' value is generally considered as the yield point, as is shown in Fig. Δ, P) are the coordinates of any point on the load–deflection curve,  are the coordinates of the yield point determined by the farthest point method,  are the coordinates of the ultimate point, and 0 ≦ Δ ≦ Δu.The cracking point of the model is defined as the inflection point on the load–deflection curve. In this study, the elastic–plastic transition of PSRCS is determined based on the second derivative extremum of its secant stiffness. According toPu) of PSRCS increases by 8.9% and 75.4% when compared to SRCS and RCS, respectively, and the ultimate deflection (Δu) of PSRCS increases by 25.8% and 39.9% when compared to SRCS and RCS, respectively.The load of the three models exhibits a linear relationship with the mid-span deflection during the elastic stage. As the three models transition to the elastic–plastic stage, the mid-span deflection of the slabs increases significantly due to the gradual yielding and disengagement of the internal bending members. Upon reaching the yield point, the models enter the plastic stage, and the mid-span deflection of the three models rapidly increases with the load, ultimately reaching the ultimate load. Meanwhile, the ultimate load  and steel reinforced concrete slabs (SRCS). The comprehensive parametric analysis of the PSRCS using ABAQUS, assessing the effects of H-beam eccentricity, prestressed degree, and reinforcement ratio on bearing capacity and internal stress components.Based on parameter analysis, the span-to-depth ratio range of PSRCS under different spans was divided, with security limit (minimum slab thickness) and economic value limit(maximum slab thickness) provided. Rational recommended ratios for different spans were also given, offering a design basis for PSRCS application across various spans.This study introduced an innovative prestressed steel reinforced concrete slab (PSRCS) designed for heavy loads and large spans. The advantages of this structure were evaluated through theoretical research and finite element model analysis. Based on the investigations, the following key findings and contributions can be highlighted:These findings provide valuable insights and a solid foundation for further development and application of PSRCS in various engineering projects. Future research could concentrate on carrying out vertical loading tests on PSRCS (currently underway) and comparing the results with the theoretical calculation formulas and finite element analysis presented in this study. Additionally, investigating further design parameters and optimization methods to enhance the performance and cost-efficiency of PSRCS would be valuable.Supplementary Information.


Current treatment agents for HCC are mostly immune checkpoint inhibitors (ICIs) plus bevacizumab and multitarget tyrosine kinase inhibitors (TKIs); however, their limited overall response rate and shorter median progression-free survival (PFS) discourage their frequent use. The development of Mesenchymal Epithelial Transition Factor receptor (MET) Tyrosine Kinase Inhibitors (MET-TKI) has transformed the treatment pattern in MET-altered solid tumors and improved their prognosis. However, the benefits of MET-TKIs in MET-amplified hepatocellular carcinoma (HCC) remain unclear.Here, we present a case of advanced HCC amplified with MET treated with savolitinib, a MET-TKI, after progression from first-line treatment with bevacizumab plus sintilimab.The patient achieved a partial response (PR) to savolitinib in the second line setting. The progression-free survival (PFS) of first-line of bevacizumab plus sintilimab and sequential second-line treatment with MET-TKI, savolitinib, are 3 and over 8 months, respectively. furthermore, the patient still had continuous PR status with manageable toxicities.The present case report provides first-hand evidence that savolitinib may be beneficial for patients with advanced MET-amplified HCC and offers a promising treatment option. In 2020, Hepatocellular carcinoma (HCC) was the sixth most diagnosed cancer and the third leading cause of cancer-related mortality worldwide . HCC is Immune checkpoint inhibitors (ICI) plus bevacizumab are the standard treatment for HCC in the first-line setting , 3. ProlA previous phase 2 study demonstrated that MET-TKI tivantinib could improve the prognosis of advanced HCC in a second-line setting . However2) for one cycle. However, as serum tumor marker levels increased, a CT was performed, which revealed stable disease according to the RECIST 1.1 guidelines; accordingly, two cycles of sintilimab  plus bevacizumab (15 mg/m2) were continued. Due to the continuous elevation of serum tumor markers including AFP, CA19-9, CA15-3 and CEA, disease progression was confirmed with only 3 months progression free survival (PFS). Next-generation sequencing performed on the specimen at initial diagnosis revealed MET amplification . In addition, some missense mutations including oncogene FGFR2, JAK3, RHOA and TP53 frameshift mutation were meaningless, no approved drugs targeting them were available for now , gastric cancer, and colorectal cancer with MET alterations . A previIn summary, it is reasonable to choose savolitinib to treat HCC patients with positive c-MET amplification, and the profile of adverse events is manageable. Furthermore, the c-MET gene test should be performed routinely in patients with HCC. However, since this was only a case report, more randomized clinical trials, including larger sample sizes, were conducted to obtain concrete insights. Our case shows that savolitinib is suitable for treating HCC in patients with MET amplification.The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding authors.Written informed consent was obtained from the participant/patients for the publication of this case report.NNY, ZHZ, SJS, and XYL wrote the manuscript. NNY, ZHZ, and SXG prepared Figures and Tables. All authors have reviewed the manuscript and gave their consent to publication. All authors contributed to the article and approved the submitted version.


The increasing global threat of antibiotic resistance, which has resulted in countless fatalities due to untreatable infections, underscores the urgent need for a strategic action plan. The acknowledgment that humanity is perilously approaching the “End of the Miracle Drugs” due to the unjustifiable overuse and misuse of antibiotics has prompted a critical reassessment of their usage. In response, numerous relevant medical societies have initiated a concerted effort to combat resistance by implementing antibiotic stewardship programs within healthcare institutions, grounded in evidence-based guidelines and designed to guide antibiotic utilization. Crucial to this initiative is the establishment of multidisciplinary teams within each hospital, led by a dedicated Infectious Diseases physician. This team includes clinical pharmacists, clinical microbiologists, hospital epidemiologists, infection control experts, and specialized nurses who receive intensive training in the field. These teams have evidence-supported strategies aiming to mitigate resistance, such as conducting prospective audits and providing feedback, including the innovative ‘Handshake Stewardship’ approach, implementing formulary restrictions and preauthorization protocols, disseminating educational materials, promoting antibiotic de-escalation practices, employing rapid diagnostic techniques, and enhancing infection prevention and control measures. While initial outcomes have demonstrated success in reducing resistance rates, ongoing research is imperative to explore novel stewardship interventions.  The discovery of antibiotics and vaccines has been acknowledged worldwide as two of the most prominent developments in Clinical Medicine. The cascade of antibacterial agents started in the 1940s, when sulfonamides, penicillin, and streptomycin were introduced in the market. There is no doubt that antibiotics have radically changed the future of medicine by curing once lethal infections. Nevertheless, it was established early on that a bacterium, when exposed to antibiotics, develops survival strategies. This raised an unprecedented concern in the history of antibiotic usage for the imperative need for judicious prescription to preserve their unparalleled value and efficacy ,4,5,6,7.New York Times article, on 26 June 1945: “… the microbes are educated to resist penicillin and a host of penicillin-fast organisms is bred out… In such cases the thoughtless person playing with penicillin is morally responsible for the death of the man who finally succumbs to infection with the penicillin-resistant organism. I hope this evil can be averted” [Staphylococcus aureus [Staphylococcus aureus (MRSA) strains emerged in 1961 [Streptococcus pneumoniae and Neisseria gonorrhea [Enterococcus faecium (VRE) and vancomycin-resistant S. aureus (VRSA) [It was Sir Alexander Fleming who made the following cautionary statements in a  in 1961  to be fos (VRSA) .Klebsiella pneumoniae and other Enterobacterales, as well as Pseudomonas aeruginosa and unfortunately pan-drug-resistant (PDR) Acinetobacter baumannii [The rise of the 21st century coincided with the emergence of multidrug-resistant (MDR) Gram-negative bacteria, including extended spectrum beta-lactamases (ESBL) producing Enterobacterales, extensively drug-resistant (XDR) carbapenemase-producing aumannii ,11,12,13aumannii . Cassiniaumannii  reportedaumannii . The buraumannii . Within aumannii . Facing the prophetic announcement made by Jim O’Neill in 2014, where he foresaw an annual global death toll of 10 million people by 2050 due to infections caused from antibiotic-resistant bacteria, involves antimicrobial resistance becoming the leading cause of mortality. This scenario was also accompanied by a staggering economic burden, reaching up to an astonishing USD 100 trillion. The question that arises is how can this alarming situation be addressed and averted? . Even inEvidence demonstrates that at least in hospital settings worldwide, the application of hospital-based programs dedicated to the rational use of antibiotics is urgently required, referred to as Antimicrobial Stewardship Programs (ASPs) . A narraIn this comprehensive narrative review, the current state of evidence was thoroughly investigated concerning antibiotic stewardship within hospital settings. Our analysis not only explored the global landscape but also placed a specific focus on practical applications and real-world examples of Antimicrobial Stewardship practices in Greece. The term “Antimicrobial” should be used interchangeably with “Antibiotic” in this context, as our focus is solely on the stewardship of antibiotics. Clostridioides difficile), and the emergence of resistance as well as the reduction in the existing resistance rates [The current definition of Antimicrobial Stewardship (AS) refers to ‘‘Systemic measurement and coordinated interventions designed to promote the optimal use of antimicrobial agents including their appropriate selection, dosing, route and duration of administration for all patients including those who are critically ill or immunocompromised’’ ,22,23,24ce rates ,22. The To establish and operate an effective AS program, the organization of a multidisciplinary team is required. According to IDSA and SHEA guidelines of 2007, an engaged Infectious Diseases (ID) physician and a clinical pharmacist with Infectious Diseases training, as well as a clinical microbiologist, an Information System Specialist, an Infection Control Professional, and a hospital epidemiologist, should be included as core members . Since AThe collaboration of the AS Team members with the Hospital Infection Control Committee, the pharmacy, and all other hospital therapeutic committees with emphasis on official surgery and Hematology/Oncology representation, whenever required.The support and collaboration of hospital administrators with the medical staff leaders.The negotiation of the ID physician and the head of the pharmacy with the hospital administration, regarding authority and compensation in relation to the expected outcome of the AS program.The hospital administrative support to measure antibiotic consumption and to track use on an ongoing basis through the necessary infrastructure.A comprehensive evidence-based AS program aiming to combat antimicrobial resistance should include the following important issues ,26: The Hospital Leadership Commitment referring to “Dedicated necessary, human, financial and information technology resources” with emphasis on “the necessity of AS programs leaders having dedicated time and resources to operate the program effectively”. Additionally, support from the senior leadership of the hospital, particularly the Chief Medical Officer, the Chief Nursing Officer, and the Director of Pharmacy, is considered critical for the success of AS programs. To be also pointed out is that the hospital leaderships play a critical role in obtaining the resources required to accomplish AS targets.Accountability regarding the appointment of a leader or co-leaders, i.e., a physician and a pharmacist trained in Infectious Diseases, both responsible for the program application and the outcome.Drug Expertise appointment, aiming to lead implementation effort to improve antibiotic use.Tracking antibiotic prescribing, impact of interventions, side effects, and resistance patterns, elements vital for continuous assessment.Reporting at regular time intervals information on antibiotic consumption and incidence of resistance rated to prescribers, pharmacists, nurses, and hospital leadership as well.Education targeting prescribers, pharmacists, and nurses regarding antibiotic resistance, optimal prescribing, and adverse reaction of antibiotics.Action requiring implementation of interventions focusing on a restrictive antibiotic formulary and preauthorization as well as in a prospective audit and feedback, which are both characterized as “priority interventions”.In 2014, the CDC recommended that all acute care hospitals in the United States should implement AS programs. Therefore, the so-called “Core Elements of Hospital Antibiotic Stewardship Programs” by the CDC to support implementation of AS, updated in 2019, was released, discussing lessons learned from a 5-year (2014–2018) accumulated experience . In addiWhen initiating an AS program, the first action should be the calculation of the specific needs of the involved personnel as well as the strategies to be applied ,29. FirsThree interventions have been prioritized by the CDC based on Antimicrobial Stewardship ,22:The restrictive antibiotic formulary and preauthorization are strategies employed as part of ASPs, which aim to ensure the appropriate use of antimicrobial agents in an era of increasing antimicrobial resistance. The restrictive antibiotic formulary strategy involves maintaining a list of approved antibiotics for use within a healthcare institution. The preauthorization strategy requires healthcare providers to obtain approval before prescribing certain antimicrobial agents . In 2017, Goff et al.  proposedBefore the administration of “protected antibiotics,” the prerequisite is obtaining approval from an ID physician, or a pharmacist trained in Infectious Diseases. This program yields several advantages, including the reduction in unnecessary or inappropriate antibiotic usage, optimization of empiric selections, direct control over antibiotic utilization as a passive prescribing barrier, and cost reduction. It also serves as a platform for educating individual prescribers in appropriate antimicrobial chemotherapy, influencing subsequent antibiotic usage positively .However, in cases involving patients with septic shock or those with risk factors suggestive of underlying XDR Gram-negative bacilli  as potenAmong the primary drawbacks of this approach is the potential barrier it poses to the autonomy of prescribers in clinical decision making . AdditioHighly trained personnel, often led by an ID physician, engage in the routine review of antimicrobial orders. The frequency of these reviews typically ranges from daily assessments to twice-weekly evaluations, a schedule determined with the hospital’s size. The purpose of these reviews is to furnish prescribers with written or verbal recommendations concerning their antibiotic selections, thus preserving the autonomy of the prescribing clinicians. It is worth noting that PAF has demonstrated its effectiveness in curbing the inappropriate use of antibiotics across various healthcare settings, encompassing ICUs, pediatric facilities, and community hospitals . In comm“Handshake Stewardship” introduces an innovative approach focused on engaging in ‘face-to-face’ interactions with each department’s staff individually. This approach has demonstrated its ability to enhance the impact of PAF while building collegial relationships ,42. NotaFew studies have compared PAF and preauthorization with conflicting results. In one study, PAF was associated with greater reduction in antibiotics, whereas in another, transition of preauthorization to PAF transaction was linked to an increase in the utilization of broad-spectrum antibiotic prescription ,44. Despp < 0.01). This reduction was accompanied by an increase in the susceptibility of Gram-negative bacilli without any discernible impact on hospital length of stay or mortality rates [Pseudomonas aeruginosa susceptibility to imipenem increased from 65% to 83% (p ≤ 0.1) in ICU isolates. Another study by Rehal et al. [Klebsiella cases, it also resulted in increased imipenem use and a subsequent 69% rise in P. aeruginosa resistance rates. This underscores the importance of carefully monitoring antibiotic resistance rates and dosing when implementing restrictive measures. Furthermore, it is essential to highlight potential communication challenges when obtaining approval for restricted antibiotics via telephone calls [p = 0.0008), without causing any ‘squeezing of the balloon’ effect of other antibiotics like ertapenem, cefepime, or piperacillin–tazobactam. In a retrospective multicenter study, Pakyz et al. evaluated the impact of carbapenem restriction over 5 years in eight university teaching hospitals on the susceptibility of P. aeruginosa isolates. Their findings showed that fewer carbapenem prescriptions (p = 0.04) corresponded to a lower incidence of carbapenem-resistant P. aeruginosa (p = 0.01) throughout the study period [Is there evidence to suggest that antibiotic resistance could be reduced through the implementation of a PAF approach? Preauthorization studies have consistently demonstrated a reduction in antibiotic usage and a decrease in antibiotic resistance, particularly among Gram-negative bacteria. Pioneering work by White et al. in 1997 revealed that implementing preauthorization requests for restricted antibiotics in a county teaching hospital resulted in a remarkable 32% reduction in total parenteral antibiotic expenditures  without negatively impacting patient outcomes [PAF interventions have also demonstrated the ability to reduce antibiotic resistance and rates of outcomes ,52,53,54outcomes .p = 0.001). This suggests that restrictions should be preferred when urgency is a factor [C. difficile infections in hospitalized patients were analyzed [p = 0.0428) and MRSA , as well as C. difficile infections . ASPs proved to be more effective when implemented alongside infection control measures (p = 0.0030), particularly hand hygiene interventions (p < 0.0002). The study acknowledged significant heterogeneity among the studies, partly attributed to the types of interventions and co-resistance patterns of the target bacteria. Nonetheless, these results provide valuable evidence for stakeholders and policy makers supporting the implementation of ASPs to alleviate the burden of infections caused by antibiotic-resistant bacteria.Comparing restriction with PAF as persuasive measures, a meta-analysis of 52 interrupted time series in a Cochrane review found that restrictive interventions had a statistically greater impact on reducing antibiotic-resistant bacteria within a 6-month timeframe . Notably, this reduction did not result in any discernible increase in the resistance rates of non-restricted compounds [Pseudomonas aeruginosa and Klebsiella pneumoniae are presented in In a well-organized Greek study, which sought to assess the impact of a hospital-wide antibiotic restriction policy program on the resistance rates of nosocomial Gram-negative bacteria, spanning from 1998 to 2000, an innovative approach involving a restrictive formulary and preauthorization format was implemented at Sismanoglio Tertiary Hospital in the Athens area. This medium-sized facility achieved a remarkable 45% reduction in the consumption of restricted antibiotics, including aminoglycosides, third-generation cephalosporins, aztreonam, piperacillin/tazobactam, and ciprofloxacin, amounting to a reduction of 7.2 DDD per 100 patient days  (p = 0.034). These reductions were followed by substantial decreases in resistance rates among P. aeruginosa and K. pneumoniae isolates, as elucidated in C. difficile infections per 1000 patients (1.47 in 2015 to 0.86 in 2019), and antibiotic costs (EUR 39.5 in 2015 to EUR 23.69 in 2019) were also observed [In another Greek tertiary hospital, Zanion Hospital located at the Piraeus harbor, with a bed capacity of 427, the impact of a comprehensive ASP spanning 4 years from January 2016 to 2020 was evaluated. This program was overseen by a multidisciplinary team comprising two Infectious Disease physicians, two clinical microbiologists, two pharmacists, an intensivist, and two infection control nurses . The ASP incorporated a combination of a restrictive antibiotic formulary and prospective audit and feedback. An extensive data analysis encompassing the pre-intervention period of 2015 and the intervention period of 2016–2019 was conducted, covering aspects such as antibiotic consumption (expressed as DDD/100 bed days), rates of observed .A. baumannii, P. aeruginosa, and K. pneumoniae, their resistance patterns, and antibiotic consumption. An antibiotic restriction policy was implemented, including restrictions on quinolones and ceftazidime. After an 18-month period, the same parameters were reassessed for an additional 6 months. The results showed a 92.5% reduction in the consumption of restricted antibiotics and a 55.4% reduction in overall antibiotic use. Susceptibility to ciprofloxacin significantly increased, but ceftazidime susceptibility increased only for P. aeruginosa. There were no differences observed in terms of infectious episodes, overall mortality, or ICU ecology.In a study by Ntagiopoulos et al., the impact of an antibiotic restriction policy on antibiotic resistance of Gram-negative bacteria was examined in a Greek ICU . The stuMoment 1: Does the patient have an infection that requires antibiotics?Moment 2: Have I ordered appropriate cultures before starting antibiotics? What empirical antibiotic therapy should I initiate?Moment 3: A day or more has passed. Can I stop antibiotics? Can I narrow therapy? Can I change from iv to per os therapy?Moment 4: What duration of antibiotic therapy is needed for the referred patient’s diagnosis?Based on the local epidemiological data and susceptibility patterns derived from reliable sources, it is imperative for AS programs to tailor their efforts to individual healthcare facilities. The primary objective should be the development of facility-specific therapeutic clinical practice guidelines that address the most prevalent infections. To facilitate the application of AS principles effectively, AS programs should initially incorporate the “4 Moments of Antibiotic Decision,” as elucidated by Tamma et al. . These mLegionella spp and S. aureus, a 2-week duration is recommended. Conversely, many patients receiving antibiotics are diagnosed with asymptomatic bacteriuria, which, except for cases involving pregnancy or invasive genitourinary procedures, does not necessitate treatment [These guidelines should offer healthcare facilities standardized recommendations for selecting the most appropriate antimicrobial agents, particularly for common infections such as community-acquired pneumonia (CAP), urinary tract infections (UTIs), skin and soft tissue infections (SSTIs), and a fever of unknown origin (FUO) in neutropenic patients, and the proper application of surgical prophylaxis. It is worth noting that a significant portion of antibiotics administered in United States hospitals are prescribed for CAP, UTIs, and SSTIs, presenting significant opportunities for enhancing prescription practices . For CAPreatment . In the reatment . When dereatment . Centralreatment . AdditioUndoubtedly, patients in the ICU constitute a unique population. They frequently face life-threatening conditions, often present with severe comorbidities, may be immunocompromised, and possess limited physiological reserves. Moreover, their critical illnesses can significantly influence antibiotic pharmacokinetics, resulting in alterations in plasma levels—either increased or decreased, and sometimes both simultaneously. Beyond the patients themselves, the ICU is an exceptional environment due to differences in infections, pathogens, prescribing practices, and the ICU setting itself . Therefop = 0.008), carbapenems (p = 0.0013), vancomycin (p = 0.004), and metronidazole (p = 0.0004) was significantly reduced, whereas simultaneously, the days of mechanical ventilation (p = 0.0053), days of hospitalization (p = 0.0188), and mortality (p = 0.0367) were also significantly decreased. Authors pointed out that PAF strengthened the relations as well as the co-operation among the different medical specialties in the ICU. It is disconcerting to note that up to 70% of ICU patients receive antibiotics, with 30–60% of these prescriptions deemed inappropriate, unnecessary, or suboptimal ,66. ConsIn a “Before and After Study” assessing the effectiveness of an AS program in critical care, successful outcomes were attributed to an AS leader who was an intensivist with expertise in Infectious Diseases, particularly trained in managing infections in critically ill patients . The intRecognizing that approximately 50 conditions can mimic sepsis , the AS The concept of de-escalation of antibiotics (ADE) has been extensively studied, particularly in ICU patients under the guidance of AS Teams ,75,76,77A. baumannii was isolated; in 18.3%, K. pneumoniae; in 11.7%, P. aeruginosa; and in 15%, E. coli. A lower all-cause 28-day mortality was observed , whereas de-escalation was characterized as a significant factor for 28-day survival (p = 0.005). The study explored why intensivists may be hesitant to engage in de-escalation, with one of the main reasons being a reluctance to change a treatment plan that seems to be working well, along with concerns about the safety of de-escalation [Routsi et al. , in the calation . The DIAcalation , along wcalation , are thecalation . It specThe CDC has established criteria for defining surgical site infections (SSIs) as “an infection related to an operative procedure that occurs at or near the surgical incision  within 30 days of the procedure or within 90 days if prosthetic material is implanted during surgery” . Organ/sThe primary objective of the SAS is to optimize surgical prophylaxis and antimicrobial therapy. The team should actively engage in and oversee the following aspects:Antimicrobial prophylaxis in surgery is directed towards clean-contaminated wounds, defined as operations involving the entry of a viscus during surgery under controlled conditions and without unusual contamination . Clean-cE. coli, as well as skin flora such as Streptococci, methicillin-sensitive S. aureus (MSSA), and coagulase-negative Staphylococci (pathogens that are capable of developing infections whenever foreign bodies are implanted) [The selection should be based on the narrowest spectrum capable of covering the most likely pathogens associated with specific surgical sites. Broad-spectrum antibiotics do not necessarily result in lower rates of postoperative SSIs compared to narrower-spectrum agents. Therefore, cefazolin, a first-generation cephalosporin, or cefuroxime, a second-generation cephalosporin with a broader spectrum of activity and a similar half-life of approximately 2 h, are typically the preferred antibiotics of choice for surgical prophylaxis . Both ofplanted) ,85,86. Iplanted) . In the Staphylococci; (ii) when a patient is known to be colonized with MRSA; and (iii) in the case where a patient is at a high risk for MRSA colonization, especially when surveillance data are unavailable, such as recent hospitalization, residing in a nursing home, undergoing hemodialysis, or receiving immunosuppressive medications. In such cases, a beta-lactam antibiotic  may be added to vancomycin due to its effectiveness against Gram-negative bacilli. However, for patients with allergies to cephalosporins, alternatives such as gentamicin, ciprofloxacin, levofloxacin, or aztreonam can be considered [Achieving the right drug concentration at the surgical site, including weight-based dosing, is crucial for effective surgical prophylaxis. Vancomycin may be considered as an alternative to cephalosporins in specific circumstances ,88,89: . These strategies include the following principles:Effective collaboration between the AS Team and the Microbiology Lab is crucial for the successful implementation of AS initiatives and protocols . The seaRapid Bacterial Identification. Implementing PCR techniques alongside conventional cultures and stains can expedite the identification of bacterial isolates in various specimens such as rhinopharyngeal, bronchial, blood, CSF, and fecal samples, with results available in less than an hour [ an hour ,101,102.MALDI-TOF MS Bacterial Species Identification. This technique allows for precise identification of bacterial species in under 30 min. The impact of MALDI-TOF MS plus stewardship interventions in patients with bacteremia or candidiasis was evaluated by Huang et al. [p < 0.001), whereas during the intervention period, mortality was lower . Therefore, authors recommended that AS programs in combination with rapid diagnostics were beneficial in terms of the patient outcome. A major advantage is the determination of underlying resistance mechanisms at the level of ESBL and carbapenemase products, aiding in the decision to administer advanced antibiotics while awaiting susceptibility test results [g et al. . MALDI-T results ,101.Rapid Antibiotic Susceptibility Testing. Rapid diagnostics that enable tailoring of therapy on the same day blood cultures turn positive have been developed. Commercially available options like the Accelerate Pheno® system  and VITEK® REVEAL™  offer results in approximately 6 h and 4.5 h, respectively [ectively ,105,106.The Selective Reporting of Antibiotic Susceptibility Test. The IDSA recommends the practice of selective and cascade reporting of antibiotics rather than reporting results for all tested antibiotics [ibiotics . This apibiotics . Howeveribiotics ,109. ThiBiomarkers. Procalcitonin (PCT) is a valuable biomarker that becomes elevated during systemic inflammation and therefore can help differentiate between bacterial and viral infections. It plays a role in assessing the likelihood of a bacterial infection’s presence and, notably, guiding the cessation of antibiotic treatment [reatment . PCT, hoNext-Generation Sequencing. Next-generation sequencing (NGS) technologies have become increasingly available for use in the clinical microbiology diagnostic environment. There are three main applications of these technologies in the clinical microbiology laboratory: whole genome sequencing (WGS), targeted metagenomics sequencing, and shotgun metagenomics sequencing. These applications are being utilized for initial identification of pathogenic organisms, the detection of antimicrobial resistance mechanisms, and for epidemiologic tracking of organisms within hospital systems [ systems . In the  systems . NGS tec systems ,112.Several critical methods should be employed to facilitate this collaboration:Despite the discovery of attractive newer methodologies, it remains important for the AS Team to advocate for the continued use of Gram staining in appropriate specimens. Gram staining, with a turnaround time of less than 3 min, remains indispensable and irreplaceable even in the context of modern techniques. Furthermore, it is crucial for the Microbiology Lab to consistently assess the quality of specimens, which can lead to specimen rejection and the request for a new, appropriate specimen when necessary. This quality control process helps maintain the reliability and accuracy of diagnostic results.C. difficile infections and their prompt isolation. Moreover, nurses can contribute to educating healthcare staff on proper catheterization techniques for veins and the urinary bladder, inspecting compliance with surgical prophylaxis protocols, and promoting hand hygiene practices. It is worth noting that AS programs demonstrate greater efficacy when implemented alongside infection control (p = 0.030) and hand hygiene interventions (p < 0.0001) [In recognition of the pivotal role nurses play in patient care, hospital quality improvement, and the urgent need to expand AS efforts, the CDC, in collaboration with the American Nurses Association (ANA), convened a Workgroup comprising registered nurses. This initiative aimed to explore the role of nurses in AS and identify key areas where they could contribute significantly . The Wor 0.0001) . These r 0.0001) . ConsequApproximately 10–15% of hospitalized patients in the United States report being allergic to penicillin ,119. HowData regarding the plans and initiatives of AS Teams, which include antibiotic consumption and resistance, should be disseminated beyond just healthcare providers. It is imperative that this information reaches hospital leadership and key stakeholders, including the pharmacy department, medical staff, various committees, and the hospital board. To ensure effective communication and transparency, regular discussions should be scheduled at predefined intervals following the preparation of comprehensive reports on antibiotic tracking. The insights and conclusions drawn from activities like preauthorization and a prospective audit and feedback should be shared directly with prescribers. This direct feedback loop helps healthcare professionals understand the impact of their prescribing decisions and encourages better antibiotic stewardship practices. Additionally, AS Teams can consider alternative methods of disseminating data and conveying important messages to the hospital staff. This may involve utilizing internal communication channels such as staff newsletters and email notifications to ensure that the broader healthcare community is informed and engaged in the ongoing efforts to optimize antibiotic use and combat antibiotic resistance .C. difficile infections) and providing examples of how programs like PAF and “Restricted Formulary and Preauthorization” are applied enhance the education of hospital personnel. Creating hospital-specific messages for display on TV screens in lobbies, cafeterias, patients’ rooms, and computer screens in patient wards and regular evaluation of the program’s results at predefined intervals are essential. The AS Team should also apply a program on stewardship metrics in order for the results of the application of the program to be evaluated at regular time intervals [Education plays a crucial role in AS, especially for smaller hospitals where personalized AS training is essential. AS Teams, consisting of pharmacists and Infectious Diseases physicians, can serve as valuable sources of stewardship knowledge, providing education to nursing and pharmacy staff, as well as relevant students within the healthcare system . Online ntervals ,126. It ntervals ,22.In light of the significant surge in global antibiotic resistance, it has become abundantly clear that ASPs should be implemented across all hospital settings, regardless of their size or scientific orientation. These ASPs should encompass a comprehensive range of interventions led by a multidisciplinary team, with a dedicated Infectious Diseases physician serving as a leader, and should foster collaboration with hospital administrators. A substantial body of evidence has unequivocally demonstrated the efficacy of ASPs in mitigating antibiotic resistance, particularly against multidrug-resistant Gram-negative bacteria, including carbapenemase and ESBL producers, as well as in limiting the spread of antibiotic-resistant strains among hospitalized patients. Additionally, ASPs have demonstrated their ability to assist physicians in enhancing the quality of care and ensuring patient safety. One particularly promising approach within ASPs is the “prospective audit with communication and feedback” method, which enhances the efficacy, safety, and feasibility of Antimicrobial Stewardship while fostering positive relationships with medical staff. Furthermore, the concurrent implementation of hand hygiene practices has exhibited a synergistic effect and is strongly recommended for future planning. The dearth in support for advanced research in the field of Antimicrobial Stewardship underscores the need for high-quality studies conducted through international collaboration, which would be of paramount importance to public health. Nonetheless, the existing body of evidence and knowledge is more than sufficient to mandate the obligatory implementation of ASPs, making them a top priority and an imperative. The escalating threat of antibiotic resistance poses a grave and rapidly escalating menace to humanity, demanding immediate action.


Recently, polymer concrete (PC) has been widely used in many civil engineering applications. PC shows superiority in major physical, mechanical, and fracture properties comparing to ordinary Portland cement concrete. Despite many suitable characteristics of thermosetting resins related to processing, the thermal resistance of polymer concrete composite is relatively low. This study aims to investigate the effect of incorporating short fibers on mechanical and fracture properties of PC under different ranges of high temperatures. Short carbon and polypropylene fibers were added randomly at a rate of 1 and 2% by the total weight of the PC composite. The exposure temperatures cycles were ranged between 23 to 250 °C. Various tests were conducted including flexure strength, elastic modulus, toughness, tensile crack opening, density, and porosity to evaluate the effect of addition of short fibers on fracture properties of PC. The results show that the inclusion of short fiber lead to an increase in the load carrying capacity of PC by an average of 24% and limits the crack propagation. On the other hand, the enhancement of fracture properties of based PC containing short fibers is vanished at high temperature (250 °C), but still more efficient than ordinary cement concrete. This work could lead to broader applications of polymer concrete exposed to high temperatures. Polymer concrete (PC), one of the three types of polymer concrete type, is formed by completely substituting Portland cement with polymer binders. The two other types are polymer-impregnated concrete (PIC), which consists of a hardened Portland cement concrete impregnated with a low-viscosity monomer polymerized in situ, and the second one is the polymer cement concrete (PCC) which is produced by incorporating a monomer or polymer in a Portland cement concrete mix and polymerized after placing concrete .The polymer binder used in PC is acting through a polymerization process to bond the solid particles of concrete ,3. PC, wVarious types of resins have been used in the production of polymer concrete such as epoxy ,9, unsatSeveral studies have been undertaken to improve the PC performance throughout the insertion of flame retardant, coupling agent, and fibers, or by the replacement of the solid part by industrial by-products  ,21,22,23The inclusion of synthetic or natural fibers seems to be an effective option to overcome the PC shortcoming and increase the strength capacity, ductility, and toughness of PC ,28. G.MaMany models have been used to predict the crack propagation for different materials  such as The TPM developed by Jenq and Shah  and baseA review of recent literature showed a considerable number of studies on polymer PC. However, limited work has been conducted to investigate the mechanical and fracture properties of fiber reinforced polymer concrete, which undergoes extreme thermal exposure conditions. Hence, the main objective of this study is to evaluate the degradation and the retention of the residual mechanical characteristics and toughness of epoxy-based polymer concrete reinforced randomly with short carbon and polypropylene fibers after exposure to elevated temperatures. In this study, short fibers were added in a rate of 1 and 2% by the total weight of the PC composite. The exposure temperatures cycles used were ranged between 23 to 250 °C. Various tests were conducted including flexure strength, elastic modulus, toughness, tensile crack opening, density, and porosity to evaluate the effect of addition of short fibers on fracture properties of PC.A thermosetting two-component product (hardener and resin) was selected to prepare the polymer concrete. Commercialized epoxy resin under the reference EPONAL 371 obtained from Bostik SA (France) was used in this study. The epoxy was cross-linked with chemical modified polyamines hardener. It was mixed immediately before use for common applications. Advantageously, the curing of the selected thermosetting resin can be implemented at a temperature at 10–35 °C, but preferably at room temperatures (20–25 °C) as prescribed. The service temperature range of this epoxy has not been mentioned in technical data but the glass transition temperature was 82.51 °C, as measured using a differential scanning calorimetry machine TA Instruments Q100 DSC . The epoxy properties are presented in ® ECO-H6 was supplied by Torayca Company, Japan. These fibers  are chopped into short lengths in the interest to help dispersion in viscous fluids. The second type of fiber, labeled under the name of DUOMIX FIRE® (M6), was provided by Bekaert (Belgium) as fine monofilaments polypropylene. These fibers have a tubular shape and come in the form of clusters which can be easily dispersed during mixing. The main disadvantage of these types of fibers was lowering the workability of the mix for the same volume of polymer.Two kinds of fibers (carbon and polypropylene) were chosen to be embedded into the PC’s mixes . A carbo3. Preliminary investigations based on the compressible packing model (CPM) was conducted to obtain the proportions of aggregates that guaranteed the maximum compactness of solid grains while minimizing the amount of polymer needed to wet fully the aggregates and fill gaps between. Portland cement CEM I 52.5 N having a specific density of 3.13 g/cm3 and a specific surface equal to 3590 cm2/g as evaluated via Blaine apparatus was also used in this study.Sand graded from 0 to 4 mm and a gravel graded from 4 to 10 mm were used as fine and coarse aggregates, respectively. The specific gravity of the sand was 2.47, whereas the specific gravity of gravel was 2.53 g/cmIn this study, four PC mixes with fibers reinforcements and 13% of polymer, by weight of PC, were prepared. The PC samples were prepared according to a process described in the work of Elalaoui et al. [The content of polymer was kept constant for the all mixes. This content was selected as the optimal amount in the basis of previous studies ,33,34,352 as maximum) under vacuum conditions and under pressure ranging from 14 to 414 MPa.Several tests were conducted including compression and flexure strength, elastic modulus determined using the ultrasonic pulse velocity method (UPV), toughness, tensile crack opening, density, and porosity  to evaluate the effect of addition of short fibers on fracture properties of PC. The principle of MIP is to inject a no-wetting liquid such as mercury inside the pores of a small sample . The effect of adding fibers on the flexure strength, toughness, and mechanical residual properties of PC were investigated by performing three-point bending test beam (50 mm × 50 mm × 305 mm). These tests were conducted in a displacement-control mode with a constant rate of 1.0 mm/min and 1.25 mm/min for bending and compression, respectively, as per the procedure stated in RILEM PCM8 1995 .The midpoint deflection of beams was evaluated by the mean of a linear variable differential transformer (LVTD) rested on a steel L-shape bracket attached to specimens at mid-height as shown in the figure below .Concrete toughness was evaluated throughout pre-notched beams using a 250 kN closed loop INSTRON machine. The crack mouth opening displacement (CMOD) was measured by virtue of clip-gauge attached to a knife-edges installed at the bottom of the beams . The midFor the OCC mix, beam samples of 70 mm × 70 mm × 280 mm for bending test and cylinder samples of 150 mm × 300 mm for compression sample were casted. The OCC beams samples were loaded at rate of 0.05 MPa/s, whereas the cylinder samples was loaded at 0.5 MPa/s.The fracture toughness values of PC in mode-I, KIC, and the fracture energy GF were calculated using a two fracture parameters model ,38 whichIc using linear elastic fracture mechanics, LEFM. This value of KIc was found to be independent of the specimen size [The effective crack length and the peak load, are required to determine Kmen size .The stress intensity factor is given by means of Equation (1):The critical crack length is presented by Equation (3)0 and d0 are described in The geometrical parameters S, b, d, aThe fracture energy is calculated according to the following relation as postulated by the following LEFM equation:The prepared specimens were heated at a rate of 0.5 °C/min until target temperature was reached according to the predefined protocol. The temperature was maintained for 3 h before being decreases with the same heating rate till samples reached the ambient temperature being kept for 24 h until the specimens were tested. To ensure that the setting temperature (from 100 °C to 250 °C) is compatible with specimen temperature, two k-type thermocouples mounted on data logger were attached to one side and in the middle of samples for a continuous recording .A set of four specimens was allocated for each test type. The tests were conducted on concretes allowed to cure for 7 days at prescribed room temperature for both unreinforced and reinforced PC and 28 days age for OCC.The setting and recorded temperatures were close and only a difference not exceeding ±3 °C was reported .3 to 2.23 g/cm3. In fact, a marginal decrease was observed for the entire mixes. The same trend can be observed for the carbon group of mixes as the density decreased with higher fiber dosages. The maximum difference in densities recorded over the mixes was 3.2%, which shows that incorporation of fibers with small quantities did not significantly affect the concrete density. In addition, it was noted that the density of polypropylene fibers is lower than that of polymer. This could be due to the deficiency of uniform distribution during the mixing process and thereby in concrete bulk.The effect of addition of short fibers on the density PC mixed is shown in c as shown in The pore structures  were characterized by means of MPI and results are presented in The dynamic Young’s modulus The value of Poisson’s ratio is given by Equation (7):d represents the dynamic elasticity modulus (MPa), VL is the compressive P-wave velocity, VT is shear wave velocity (km/s), ν is Poisson’s ratio, and 3).In the Equation (5) to Equtaion (6), EThe results of the experimental program revealed that the static elastic modulus (Es) decreased slightly as the fiber content increased a,b. ThisBy adding fibers to PC, all mixes showed indistinctly an increase in the modulus with sample age and being stabilized after a period of 5 to 7 days . This caThe results of flexural and compressive strength of PC mixes are presented in However, the results show that flexural strength of PC made with carbon fibers increased with the increase in fibers content a. In aveThe decrease in the mechanical resistances is probably due to poor adhesion between the fibers and the matrix and to the high values of porosity. This decrease is a sign of decrease in transverse bonds in polymer, which decrease the stiffness and increase ductility of polymer concrete . In factIt can be concluded that the addition of fibers did not accomplish the expected reinforce or at least has the same strength characteristics as unreinforced PC . Hence, IC and the fracture energy GF as a function of the exposure temperature for both the PC system and the OCC. It can be seen that PC is more resistant to crack propagation than OCC. By increasing the exposure temperature, the toughness is improved up to 225 °C for both concrete before declining slightly at higher temperatures (250 °C). Such a variation has been similarly observed for the flexural strengths mainly in the case of plain PC as a result of action of two coexistent and competitive phenomena: (i) post crosslinking initiated by heat and (ii) thermo-oxidative degradation of the epoxy polymer [ polymer . This va polymer .The effect of carbon fiber introduction on the fracture properties of PC is studied and the results are depicted on It can be seen also that for reinforced PC mixes the load carrying capacity increases until 150 °C and then decreases for higher temperatures. Moreover, a significant change in the post-peak behavior was observed, the ductile behavior becomes less brittle ; similarEpoxy-based concrete possesses higher mechanical properties compared to ordinary cement concrete.For temperatures less than 250 °C, the epoxy polymer concrete is still more efficient than ordinary cement concrete.The addition of short carbon fibers content by a rate of 1% by weight to polymer concrete indicated that there was no indicative difference in the concrete density, the elastic characteristics, the compressive strength, and led to a decrease in the flexural strength. It also did not enhance the fracture properties at room temperature.When exposed to high temperatures of up to 150 °C, the 1% fiber introduction resulted in a load-carrying capacity increase. This enhancement of fracture properties is vanished for higher heating temperatures.Compared to the post cracking behavior at room temperature, the ductility of 1%-fibered polymer concrete increases when it is exposed to high temperatures, resulting in slower crack propagation.Carbon fibers introduction at content of 2% by weight of polymer-based concrete did not improve its mechanical and fracture properties. The same was observed for polypropylene fibers used with a fraction of 1% by weight.The effect of incorporating short carbon and polypropylene fibers combined with the exposure to high heating temperatures reaching 250 °C on the mechanical and fracture properties of epoxy polymer-based concrete is investigated in depth in this study and the following remarks were derived:Due to complexity and co-existence of many phenomena, deeper investigations are hence needed to explain their interaction that affect the properties of reinforced fiber polymer concrete. Curing conditions of samples and their effects in the fracture and thermo-mechanical properties seems to be interesting to be investigated and evaluated to build a complete and consistent knowledge about polymer concrete exposed to extreme in-service conditions.