The use of new developed high-strength steel in concrete members can reduce steel bar congestion and construction costs. This research aims to study the behavior of concrete columns reinforced with new developed high-strength steel under eccentric loading. Ten reinforced concrete columns were fabricated and tested. The test variables were the transverse reinforcement amount and yield strength, eccentricity, and longitudinal reinforcement yield strength. The failure patterns were compression and tensile failure for columns subjected to small eccentricity and large eccentricity, respectively. The same level of post-peak deformability and ductility could only be obtained with a lower amount of transverse reinforcement when high-strength transverse reinforcements were used in columns subjected to small eccentricity. The high-strength longitudinal reinforcement improved the bearing capacity and post-peak deformability of the concrete columns. Furthermore, three different equivalent rectangular stress block (ERSB) parameters for predicting the bearing capacity of columns with high-strength steel are discussed based on test and simulated results. It is concluded that the China Code GB 50010-2010 overestimates the bearing capacity of columns with high-strength steel, whereas the bearing capacities computed using the America Code ACI 318-14 and Canada Code CSA A23.3-04 agree well with the test results. Over the last decade, the use of high-strength steel bars in the construction industry has prompted extensive research in this area. High-strength steel bars have the advantage of lowering reinforcement congestion and construction costs, especially in high-rise and special buildings. The use of high-strength steel as longitudinal reinforcement can enhance concrete members’ load capacity; moreover, its use for stirrups may decrease the transverse reinforcement amount required to ease concrete placement. In recent years, the continuous development of steel smelting technology has produced new high-strength steel . The new developed high-strength steel has a linear pre-yield behavior, obvious yield plateau and comparatively good ductility, while ultra-high-strength reinforcing bars have a high yield strength, but no yield plateau and poor ductility. The typical stress–strain relationships of different reinforcing bars are presented in There have been many investigations on the performance of high-strength steel  used in concrete beams ,2,3, beaMany researchers ,16,17 haThe available literature related to the use of new developed high-strength steel mainly focuses on the seismic behavior of concrete beams, columns, beam–column joints, and walls, while studies on the eccentric compressive behavior of columns reinforced with new developed high-strength steel are scare. This study investigated the behavior of new developed high-strength steel used in concrete columns under eccentric loading. Ten large-scale concrete square columns with high-strength steel were designed to explore the effect of using new developed high-strength steel. In addition, this paper compares the different analytical models used to predict the axial load-bending moment interaction curves of high-strength steel reinforced square concrete columns.lρ) was 1.97%. The columns were confined by well-shaped compound hoops with 135° bend anchorages. The transverse reinforcement spacing in the test region was 70 mm or 105 mm, and the corresponding transverse reinforcement ratios (shρ) were 1.91% and 1.28%, respectively. The two haunched heads were fabricated with dense transverse reinforcements of 50 mm to prevent local compression failure at the column ends. The geometric sizes and reinforcing bars of the columns are illustrated in Ten concrete columns were designed and fabricated with a square section (350 × 350 mm) and a column height of 1500 mm. The test region of columns with height of 700 mm and two column ends (each 400 mm in height) were haunched. The concrete cover thickness of the columns was 20 mm. The test regions of columns were constructed using 12 longitudinal reinforcements with a diameter of 16 mm, and the percentage of longitudinal reinforcements (os as defined by Eq. (18.7.5.3). These limitations lead to a maximum transverse reinforcement spacing of 87.5 mm for the columns. Four specimens, EC3, EC5, EC8, and EC10, do not meet the ACI 318-14 requirement on maximum transverse reinforcement spacing. All columns were separated into two groups. The first group consisted of five concrete columns . Columns from the first group were loaded under a nominal eccentricity of 80 mm (e/h = 0.23). In the second group, a total of five concrete columns  were examined under a nominal eccentricity of 180 mm (e/h = 0.51). The detailed test variables are presented in This test aims to study the three main variables that affect the eccentric compressive behavior of concrete columns: (1) the effect of using high-strength transverse reinforcement and its spacing; (2) the effect of using high-strength longitudinal reinforcements; (3) the effect of eccentricity. Clause 18.7.5.3 in America Code ACI 318-14  specifieColumns EC2 and EC6 were reinforced with D8 high-strength transverse reinforcements and had the same transverse reinforcement configuration as columns EC1 and EC5, which were reinforced by ordinary transverse reinforcements, to investigate the effects of transverse reinforcement yield strength. The ratio of the configured high-strength stirrup amounted to the amount specified by ACI 318-14 , which wColumns EC4, EC5, EC9, and EC10 were confined by the same transverse reinforcement configuration as columns EC2, EC3, EC7, and EC8, respectively, but differed in longitudinal reinforcement yield strength. Columns EC4, EC5, EC9, and EC10 were fabricated with high-strength longitudinal reinforcements as to be compared with columns EC2, EC3, EC7, and EC8 which were reinforced with ordinary longitudinal reinforcements. The comparison of the behavior of these columns aims to understand the influences of high-strength longitudinal reinforcement.fc’ according to the China Code GB 50010-2010 Code, as shown in All columns were cast using the same batch of concrete mix. The materials involved were Portland cement, river sand, coarse aggregate, tap water for mixing and curing, fly ash, and mineral powder to improve the workability of the material. The ratio of sand to coarse aggregate was 0.36 and the water–bind ratio was 0.32. A small amount of superplasticizer was mixed in to increase concrete fluidity. Six plain concrete cubes with a width of 150 mm were fabricated and tested on the day that the columns were loaded to obtain average concrete compressive strength D16 HRB400 and D16 HRB600 reinforcing bars served as longitudinal reinforcements. The HRB400 and newly developed HRB600 represent the minimum specified yield strength of 400 MPa and 600 MPa, respectively. All columns were confined by D8 HRB400 or HRB600 transverse reinforcements. Tensile tests of the steel samples were conducted to obtain the properties of each type of reinforcing bar. The details of the reinforcing bars are given in All columns were subjected to eccentric loading using a 10,000 kN capacity electro-hydraulic servo machine , as shown in e = 80 mm) failed at the mid-height, as demonstrated in The columns subjected to a small-eccentric compressive loading  also failed at the mid-height of the columns, as given in The columns subjected to large-eccentric compressive loading , and 5.5 mm for columns subjected to large eccentricity (e = 180 mm). After the yield point, the plastic hinge was generated near the mid-height and the stiffness of columns decreased. This behavior continued until the concrete cover underwent crushing and spalling, which caused a sudden decrease of approximately 5% to 10% of the maximum load. The average lateral displacement was 9.0 mm when the first peak load was reached. The applied load increased again until a second peak appeared for the strongly confined columns only , and the corresponding lateral displacement ranged from 13.1 mm to 13.95 mm. For columns loaded to small eccentricity (e = 80 mm), the post-peak deformability was less than that of the columns subjected to large eccentricity (e = 180 mm), and the post-peak behavior was similar to that of the columns under the concentric compression loading. The transverse reinforcements provided a lateral confinement effect to the core concrete, and increased the post-yield deformation capacity of the columns. Therefore, the transverse reinforcement amounts, and yield strength had a significant effect on the confinement effect of concrete and dominated the post-peak behavior of the columns. For the columns loaded to large eccentricity (e = 180 mm), the post-peak behavior was similar to that of the flexural members, and they failed in ductility behavior. The compression zones of the critical cross-section for the columns were relatively small and the transverse reinforcements did not develop lateral confining pressure. Therefore, the effects of the transverse reinforcement amounts and yield strength on the behavior of the columns were minor.The lateral displacements versus the applied load curves for the columns are illustrated in x is the longitudinal coordinate variable, as shown in L is the height of column; and δ is the lateral displacement at the x position, as given in The lateral deformations recorded by the five LVDTs are illustrated in A comparison of the sine-shaped model with experimental lateral deformation is shown in maxP). The first longitudinal reinforcement yielding appeared on the compression side of the columns subjected to small eccentricity (e = 80 mm), while it happened on the tension side of the columns subjected to large eccentricity (e = 180 mm). The steel yielding appeared at 0.779 maxP on average, ranging from 0.712 to 0.831 maxP, for the columns reinforced with ordinary longitudinal reinforcements and at 0.904 maxP on average, ranging from 0.845 to 0.938 maxP, for the columns with high-strength longitudinal reinforcements. At maximum load, the average ratios  of the measured strain to yield strain in compressive longitudinal reinforcements for the columns ranged from 4.00 to 10.95, which indicate that the compressive longitudinal reinforcements could yield despite the use of high-strength longitudinal reinforcements. However, the average ratios  of the measured strain to yield strain in the tensile longitudinal reinforcements ranged from 0.67 to 1.86 for the columns subjected to small eccentricity and ranged from 1.50 to 5.24 for the columns subjected to large eccentricity, which indicate that the tensile high-strength longitudinal reinforcements could not yield  for the columns loaded to small eccentricity. The average strains  of the transverse reinforcement on the compression side ranged from 1.03 to 2.03 of yield strain of the transverse reinforcements for columns subjected to small eccentricity, which is similar to the behavior of the columns subjected to concentric compression loading. It indicates that transverse reinforcements have an obvious confinement effect on the concrete. However, the average strain  of the transverse reinforcements on the compression side ranged from 0.39 to 0.79 of yield strain for the columns loaded to large eccentricity, which shows that the confinement effect of the transverse reinforcement on the core concrete was not significant due to the low stress of the transverse reinforcements. The average strains  of the transverse reinforcements on the tension side ranged from 0.02 to 0.39 of yield strain of transverse reinforcement for all the columns, which is much less than the yield strain. This is due to the stress release of the transverse reinforcements caused by the cracking of the concrete on the tension side.maxP and corresponding mid-height lateral displacement Δmax, calculated maximum loads PACI, PGB and PCSA using the ACI 318-14 [y and the displacements Δ0.85P corresponding to 0.85 of the maximum load. The maximum loads of the columns were calculated using the equivalent rectangular stress block (ERSB) parameters stated in ACI 318-14, GB 50010-2010, and CSA A23.3-04. There are differences in the calculation of maximum loads in the above three codes. ACI 318-14 defines ERSB width and depth using parameters α and β, respectively. Factor α is given as 0.85. The concrete ultimate compression strain is taken as εcu = 0.003. Factor β defined by ACI 318-14 is given as follows:I 318-14 , GB 5001I 318-14  and CanaI 318-14  Codes, rα and β parameters. Factor α and β should be taken as 1.0 and 0.80 for concrete strength grade up to and including C50 (cube concrete strength cuf’ = 50 MPa), respectively. For the concrete strength grade of C80 (cube concrete strength cuf’ = 80 MPa), factor α and β can be taken as 0.94 and 0.74, respectively. While for the concrete strength grade between C50 and C80, parameters α and β should be determined using the linear interpolation method. The concrete ultimate compression strain is taken as εcu = 0.0033.The ERSB in the China Code (GB 50010-2010) is explained using the α and β as follows: The Canada CSA A23.3-04 Code defines the ERSB, using factors εcu = 0.0035.The specified concrete compressive strength ranges from 20 MPa to 80 MPa. The ultimate compression strain is taken as maxP to PACI was 1.03 on average, ranging from 0.91 to 1.15, the ratio of maxP to PGB was 0.91 on average, ranging from 0.83 to 0.99, and the ratio of maxP to PCSA was 1.04 on average, ranging from 0.93 to 1.15. The theoretical loads of the columns obtained according to GB 50010-2010 Code were larger than the experimental maximum loads. The theoretical loads calculated using ACI 318-14 and CSA A23.3-04 Codes were close to the experimental results, and the standard deviations of mean ratios were 0.074 and 0.071, respectively. The average ratio of experimental maximum load to theoretical load obtained using codes decreased with the increase of nominal eccentricity. In the theoretical calculations of the columns with high-strength steel, the ERSB parameters given in ACI 318-14 and CSA A23.3-04 Codes were more suitable than the GB 50010-2010 Code.As shown in λ [μ [λ is defined as the ratio of mid-height lateral displacement at ultimate load to mid-height lateral displacement at peak load. The ultimate load was determined by the load corresponding to 85% of the maximum load on the descending branch [μ is defined as the ratio of ultimate lateral displacement to notional yield displacement. The yield displacement was given as the displacement at the yield point of load-displacement curves, which can be determined by the method proposed by Park et al.  than columns subjected to large eccentricity (e = 180 mm). This is due to the lower amount of core concrete confined by transverse reinforcement for columns subjected to large eccentricity, which results in the low effect of confinement. According to the load-displacement curves of the columns illustrated in λ and ductility μ, respectively, compared with column EC1, which had 1.91% of the ordinary transverse reinforcement. These results indicate that increasing transverse reinforcement yield strength has beneficial effects on the post-peak deformability and ductility of columns subjected to small eccentricity. However, column EC7 with 1.91% of the high-strength transverse reinforcements showed 15% and 19% decreases in deformability λ and ductility μ, respectively, compared with column EC6 with 1.91% of the ordinary transverse reinforcements. This is because the transverse reinforcements cannot yield despite the use of high-strength transverse reinforcement in columns (refer to measured strains in shρ = 1.27%) to columns EC1 and EC6 (shρ = 1.91%), respectively. Columns EC3 and EC8 exhibited 14% and 7% decreases in maximum load maxP compared with columns EC1 and EC6, respectively. This is attributed to the smaller mechanical ratio (shfyhρ/cf’) proposed by Canbay et al. [λ and ductility μ, respectively, compared with EC1, although it contained a lower transverse reinforcement amount. However, column EC8 exhibited 26% and 29% decreases in deformability λ and ductility μ, respectively, compared with column EC6. These results show that the same level of deformability and ductility can only be achieved with lower amounts of transverse reinforcements when high-strength transverse reinforcements are used in columns subjected to small eccentricity. That is, the beneficial effects of using high-strength transverse reinforcements to solve steel congestion in the columns can be achieved for columns subjected to small eccentricity. Therefore, the confinement effect of high-strength transverse reinforcements was not effective in columns subjected to large eccentricity. The effects of transverse reinforcement yield strength on the eccentric compressive behavior of the columns are shown in y et al. . Column maxP compared with columns EC2, EC3, EC7, and EC8, respectively. These results demonstrate that the high-strength longitudinal reinforcements can increase the bearing capacity of the columns. That is, the beneficial effects of using high-strength longitudinal reinforcements to solve steel congestion in columns with large amounts of reinforcement can be achieved. Columns EC4 and EC5 exhibited similar ductility μ  compared with columns EC2 and EC3, respectively. While columns EC9 and EC10 increased by 103% and 47% in ductility μ compared with columns EC7 and EC8, respectively. These results indicate that the benefits of using high-strength longitudinal reinforcements for improving ductility can be achieved in columns subjected to large eccentricity. In addition, columns EC4, EC5, EC9, and EC10 showed 65%, 37%, 39%, and 65% increases in deformability λ compared with columns EC2, EC3, EC7, and EC8, respectively, which indicates that the high-strength longitudinal reinforcements can clearly improve post-peak deformability of the columns.The influence of longitudinal reinforcement yield strength on the behavior of the columns is illustrated in fc’, eccentricity e, and slenderness ratio λ on the bending moment of the columns with high-strength steel. These included investigating concrete strengths of fc’ = 20 MPa, 40 MPa, and 50 MPa under eccentricities of e = 80 mm, 160 mm, 240mm; eccentricities of e = 40 mm, 80 mm, 120 mm, 160 mm, 200 mm, 240 mm, 280 mm, and 320 mm under concrete strength fc’ = 30 MPa; slenderness ratios λ = 6, 9, 12, and 15 under eccentricities e = 80 mm, and 240mm. The finite element model is based on nonlinear beam-column elements with fiber sections. Herein, the fiber section includes 52 fibers for the unconfined cover, 144 fibers for the confined core, and one fiber for each longitudinal reinforcing bar. Concrete 02 and reinforcing steel material models in Opensees were used to simulate the concrete and steel constitutive of the columns, respectively. The Concrete 02 takes into account the tensile properties of the concrete and the stiffness degradation in unloading compared with other concrete constitutive models. Furthermore, the test results in the literature [The behavior of the columns with varying design parameters cannot be fully covered experimentally. Hence, numerical models were established using Software OpenSees to extensively investigate the effect of concrete strength terature  were alsM of the columns reported in P-Δ effect). The actual e/h for each series of columns was approximately equal and hence any change in bending moment capacity was due to the test variables. As shown in e/h increased. The average ratios of the experimental and simulation bending moment capacity (M) to bending moment capacity (MACI) computed using the ACI 318-14 Code, M/MACI was 1.10; the bending moment capacity (MGB) according to GB 50010-2010 Code, M/MGB was 0.98; and the bending moment capacity (MCSA) calculated according to the CSA A23.3-04 Code, M/MCSA was 1.07. The bending moment capacity calculated according to the ACI 318-14 and CSA A23.3 Codes were less than those of the experimental and simulation results, which indicates that the calculated results are conservative. While the bending moment capacities calculated by GB 50010-2010 Code were bigger than the experimental and simulation results, which shows that the GB 50010-2010 Code overestimates the bending moment capacity.As a result of the nature of eccentric loading, the axial load produced a large bending moment at the mid-height of the column. The bending moment capacity P and bending moment M of the columns can be calculated in terms of the relevant formulas from the GB50010-2010, ACI318-14, and CSA A23.3-04 Codes. For different eccentricities, the axial load-bending moment (P–M) curves are shown in P–M interaction curves calculated using the GB 50010-2010 Code give an upper bound, and the P–M interaction curves obtained using the ACI 318-14 Code almost coincide with the CSA A23.3-04 curves. The results remain on the unsafe side of the P–M curve obtained using the GB 50010-2010 Code, whereas the experimental and simulation points are close to those of the ACI 318-14 and CSA A23.3-04 curves. The ACI 318-14 and CSA A23.3-04 Codes give the safest predictions. The GB 50010-2010 Code overestimates the capacity for the columns with high-strength steel. In general, capacities calculated using the ACI 318-14 and CSA A23.3-04 Codes agree well with the test results.According to the detailed parameters of the columns given in the test, the axial load For small-eccentrically loaded concrete columns reinforced with high-strength steel, the failure was located in the middle part with concrete crushing on the compression side and compression failure occurring. For large-eccentrically loaded concrete columns with high-strength steel, the tensile cracks extended through the entire cross-section of the columns with several major cracks in the tensile zones and concrete crushed on the compression side, which is a typical tensile failure mode.Increasing the amount of transverse reinforcements improved the deformability and ductility of the columns with high-strength steel. In addition, the confinement effect of transverse reinforcements was more effective in columns subjected to small eccentricity than columns subjected to large eccentricity.The same level of deformability and ductility could be achieved with a lower amount of transverse reinforcement when high-strength transverse reinforcements were used in columns subjected to small eccentricity. However, increasing the transverse reinforcement yield strength failed to improve post-peak deformability and ductility of the columns subjected to large eccentricity due to the inadequate confinement of the high-strength transverse reinforcement.High-strength longitudinal reinforcements improved the bearing capacity and post-peak deformability of columns under eccentric loading, but the benefits of using high-strength longitudinal reinforcements for improving ductility can only be achieved in columns subjected to large eccentricity.In general, the equivalent rectangular stress block (ERSB) parameters stated in the GB 50010-2010 Code overestimate the bearing capacity of columns with high-strength steel, whereas the bearing capacities computed using the ACI 318-14 and CSA A23.3-04 Codes better agree with the test results.This study aimed to investigate the eccentric compressive behavior of RC columns with new developed high-strength steel. The transverse reinforcement amount and yield strength, eccentricity, and longitudinal bar yield strength were the test variables. In total, 10 concrete columns were tested under eccentric loading. According to the experimental and analytical results, some conclusions were obtained:


The bond between carbon fiber reinforced polymer (CFRP) and concrete is significantly and adversely affected by thermal cycles in air and water. In the present study, the effects of thermal cycles in air or water on the bond performance between CFRP and concrete were examined. A single-lap shear test was adopted to evaluate the performance of the CFRP–concrete bond. A number of 270 thermal cycles in air increased the interfacial fracture energy of the CFRP plate– and CFRP sheet–concrete by 35% and 20%, respectively while 270 thermal cycles in water reduced the interfacial fracture energy of the CFRP plate– and CFRP sheet–concrete by 9% and 46%, respectively. Thermal cycles in water caused the failure mode to change from concrete cohesive failure to primer–concrete interfacial debonding. The failure modes of CFRP–concrete exposed to thermal cycles in air still occurred in concrete. A reduction factor for the CFRP–concrete structure for thermal cycles in water was proposed. Externally bonded carbon fiber reinforced polymer (CFRP) has become a popular technology for the rehabilitation of concrete structures. The technology depends on the integrity of the CFRP–concrete interfacial bond. A numerical and experimental study was adopted to investigate the short-term performance of FRP−concrete ,2,3. AltTg) of construction adhesives are relatively low, generally ranging from 45 to 82 °C [Tg) and curing time. Compared to CFRP sheet–concrete at 20 °C, the interfacial fracture energy at −10 °C decreased by 15%, whereas a 12% increase of interfacial fracture energy was reported at 40 °C (below Tg) [−6, 35 × 10−6, and 1 × 10−6 (1/°C), respectively [The high and low temperatures induced by thermal cycles affect the interfacial failure of CFRP–concrete bonds . The glaelow Tg) . The coeectively ,9. The mThe moisture level plays a very important role in the effect of thermal cycles on the deterioration of CFRP–concrete performance ,11,12. O88.6 MPa .Thermal cycles in air or water may cause variation in the CFRP–concrete failure modes under shear. Water immersion was reported to shift the failure modes of debonding from concrete cohesive fracture to interfacial debonding . The detAs discussed, the presence of water moisture causes the differences in the performance of CFRP–concrete between thermal cycles and freeze–thaw cycles. The present study investigates the effects of thermal cycles in air or water on the bond behavior of a CFRP–adhesive–concrete system. The CFRP type and thermal cycles in air and water were considered in the present study. The evolution of the constituent materials and the interfacial bond between CFRP and concrete was studied under the conditions of thermal cycles in air and water. This paper also sheds light on the effect of water moisture on the bond failure mechanism at the interface region by degradation at the interface.A pultruded CFRP plate and sheet were adopted in the present study. The fiber volume fraction of the pultruded CFRP plates was 67%, and its dimensions were 1.4 mm in thickness and 25 mm in width. The nominal thickness of the CFRP sheet was 0.167 mm. The fiber volume fraction of the sheet with a wet layup was 30%. The tensile test of the CFRP plate/sheet was carried out according to the ASTM D3039 method . The concrete consisted of water, cement, sand, and gravel with a mass ratio of 0.43: 1.0: 1.29: 2.75. Concrete blocks (100 mm × 100 mm × 400 mm and 100 mm × 100 mm × 100 mm) were prepared and cured at 95% relative humidity (RH) for 3 months. The concrete compressive strength of 100 mm × 100 mm × 100 mm cubes was 55.4 MPa . A modif′ in MPa . The elaUsing Equation (1), the effective bond lengths were determined to be 195 mm and 112 mm for CFRP plate–concrete and CFRP sheet–concrete, respectively. The sufficient bond lengths of 300 mm and 150 mm were applied for CFRP plate–concrete and CFRP sheet–concrete, respectively.The CFRP strain along the centerline of the CFRP was measured with electrical resistance foil strain gauges spaced at 30 mm. The stain gauges of type BE 120-3AA  were used. Six and eleven strain gauges were placed along the centerline of the CFRP sheet and CFRP plate, respectively, as shown in t, tr is the thickness of the epoxy and adhesive (2 mm for the studied samples), and D and The epoxy and adhesive with thermal cycles in air was assumed to be independent of moisture. The water uptake of the epoxy and adhesive was considered in water conditions. The moisture uptake of the epoxy and adhesive as a function of the square root of the exposure duration is shown in The equilibrium moisture content of the adhesive is 1.5 times greater than that of the epoxy. The moisture uptake depends on the chemical structures of the epoxy system . To characterize the moisture diffusion in CFRP, the diffusivity coefficient and the equilibrium moisture content of the CFRP sheet can be determined by :(3)DFRP=The variation of the mechanical properties of the epoxy and adhesive sample exposed to thermal cycles in air and water is listed in The thermal cycles in air increase the elastic modulus of the epoxy and adhesive by 13% and 6%, respectively, whereas the thermal cycles in water reduce the elastic modulus of the epoxy and adhesive by 9% and 14%, respectively. The increase in elastic modulus is caused by the increases in the cross-link density of the epoxy and adhesive owing to postcuring. It has been reported that the enhancement of the elastic modulus has positive effects on the CFRP–concrete interfacial fracture energy .The failure modes of all specimens are listed in Thermal cycles in air result in peeled-off concrete. The failure modes are similar to those of the control specimens. Thermal cycles in air increase the bond between the primer and the concrete. This means that the internal stress induced by 270 thermal cycles in air insignificantly influences the interfacial bond.In the case of thermal cycles in water, the failure modes shift from concrete cohesive failure to interfacial debonding between the primer and the concrete. This phenomenon has been reported in the case of CFRP–concrete in water ,32. The A and B can be fitted by the A is the maximum strain in the FRP with a sufficiently long bond length. The average maximum strain ε=fGf=PuA and B are determined using Equation (5), and Pu is determined using Equation (6). The values of A and B, the ultimate load capacity, and the interfacial fracture energy are listed in In the case of the control specimens, the interfacial fracture energy of the CFRP plate–concrete is 55% larger than that of CFRP sheet–concrete. It has been reported that the interfacial fracture increases with FRP stiffness (Eftf) . In the 2 (concrete) deteriorates significantly owing to the disruption of hydrogen bonding and the reduction of van der Waals forces [s forces ,33.Compared to a 9% reduction in the interfacial fracture energy of CFRP plate–concrete exposed to thermal cycles in water, the thermal cycles in water reduce the interfacial fracture energy of the CFRP sheet–concrete by 41%. The thickness and fiber volume fraction of the CFRP plate are 4.2 and 2 times those of the CFRP sheet, respectively. This means that the saturation time of the CFRP sheet is less than that of the CFRP plate, which indicates that the deterioration of the interfacial bond in CFRP sheet–concrete is more severe than that of CFRP plate–concrete. The increase in the interfacial fracture energy of CFRP plate–concrete is more than that of CFRP sheet–concrete under thermal cycles in air conditions. Thermal cycles in air induce the internal stress fatigue owing to the deformation of the adhesive and the primer. The deformation of the CFRP does not vary under the thermal cycles in water owing to very low thermal expansion coefficient of CFRP. The thickness of the adhesive layer (including primer and adhesive) provides the gradient of the deformation between CFRP and concrete. The 0.2 mm thickness of the adhesive layer in CFRP sheet– concrete results in greater internal stress. A and B [s are the bond stress (MPa) and the corresponding slip, respectively. The bond stress–slip relationship can be expressed as a function of A and B :(8)τ=A2BThe bond stress–slip curves determined by Equation (8) are shown in Le) was determined by strain distribution along the CFRP. The detailed determination was described in Ref. [The effective bond length . In the case of CFRP sheet–concrete exposed to thermal cycles in water, a 23% reduction in the effective bond length of CFRP sheet–concrete results from the deterioration of the interfacial bond between primer and concrete. As discussed above, the mechanism of the influence on the CFRP–concrete bond varies with the exposure environment. y = 1. This means that the thermal cycles in air increase the interfacial fracture energy. The fracture energy decreases by 15% with increasing thermal cycles in air from 90 to 365. This means that the short duration of thermal cycles has a positive influence on the fracture energy. The fatigue of the internal stress induced by the thermal cycles in air plays a role in the fracture energy with increasing thermal cycles.Only one dataset on the effects of thermal cycles in air on CFRP–concrete was found to correlate with the present study. The collected data from Subramaniam et al. (2008), Xian et al. (2018), and Gamage et al. 2015) were adopted for correlation analysis with the present study of thermal cycles in water  were ado,34. CanoThe normalized fracture energy of both CFRP sheet–concrete and CFRP plate–concrete seems to reduce to a constant value. It has been reported that the bond binding energy due to Van der Waals interaction is reduced by 2/3, whereas the interlocking interaction does not vary with unlimited immersion time ,36. It wThermal cycles increase the interfacial fracture energy. The increase in the fracture energy of CFRP sheet–concrete is smaller than that of CFRP plate–concrete.The failure modes of both CFRP sheet–concrete and CFRP plate–concrete are still concrete cohesive failure. The thermal cycles in water change the failure mode of both CFRP sheet–concrete and CFRP plate–concrete from concrete cohesive failure to interfacial debonding between the adhesive layer and concrete.The degradation of the interfacial bond mainly results from water moisture with 270 thermal cycles in water. The internal stress induced by thermal cycles in air has insignificant effects on the interfacial fracture energy.A reduction factor (0.7) for a CFRP–concrete structure for thermal cycles in water was proposed.This report investigated the influence of thermal cycles in air and in water on the bond behavior between a CFRP plate/sheet and concrete. Based on the experimental results, the following can be concluded:2 (concrete) and epoxy exposed to thermal cycles in water.Based on the preceding conclusions, it is clear that the parameter of thermal cycles in water is one of the key environmental durability issues, which affects the bond between CFRP and concrete. Therefore, relevant consideration should be made during the design stage to ensure the safety and longevity of the structure. The proposed reduction factor only considered the specific range of compressive strength. In future research, the high concrete compressive strength should be taken into account in the reduction factor. Besides, a molecular dynamics model has been modeled to investigate the mechanism of the deterioration of the bond between SiO


Medication adherence in people living with HIV (PLWH) is a key element in reducing morbidity and mortality. Quantitative and qualitative assessment of research activity helps identify research gaps as well as efforts implemented to improve adherence behaviors in PLWH. The aim of the current study was to assess and analyze literature on HIV/AIDS–related medication adherence using bibliometric methods.SciVerse Scopus was used to accomplish the purpose of the current study. The study period included all times up to 2017. The analysis was restricted to documents published in academic journals.h-index of 136, and an average of 4.4 authors per documents. The volume of literature on HIV/AIDS-related medication adherence constituted 1.3% of the overall HIV/AIDS literature. There was a significant  correlation between the growth of publications in AIDS-related stigma and medication adherence. The regions of America (567.9) had the highest research output per one million infected people (567.9) followed by the European region (314.3), Western Pacific Region (70.7), Eastern Mediterranean region (31.4), South East Asia (34.0), and Africa (19.3). Geographical distribution of publications showed an active contribution of certain countries in the Southern and Eastern region of Sub-Saharan Africa. Harvard University  was the most active institution. The top cited documents focused on the impact of adherence on disease outcome and the impact of text messages on improving medication adherence.Search strategy retrieved 3021 documents with an average of 32.5 citations per document, an Research on medication adherence in PLWH showed regional variations. International research collaboration with high burden regions such as Sub-Saharan Africa needs to be strengthened to achieve the global target of ending AIDS as a public health threat by 2030.The online version of this article (10.1186/s12913-018-3568-x) contains supplementary material, which is available to authorized users. Human Immunodeficiency Virus (HIV) and its clinical manifestation of “Acquired Immunodeficiency Syndrome (AIDS)” are considered major global public health challenge , 2. It iPrevention and control of HIV infection largely depend on adherence to recommended treatment , 9. PoorThe need to assess research trends in medication adherence in PLWH is important for researchers, health policymakers, and clinical practitioners. Such importance is due to the crucial role of adherence in improving survival of infected people and minimizing the spread of infection given that medication adherence varies with different societies and different world regions , 24. AssIn this study, a bibliometric methodology was implemented. Bibliometric analysis is not the same as systematic reviews or scoping reviews. In bibliometric analysis, one single database is used to provide baseline information and to identify research gaps for future studies and funding purposes , 30. SciSciVerse Scopus, an online database containing abstracts and citations of more than 23,000 journals in various fields , was useh-index) [The quality of retrieved publications was assessed using Hirsh-index (h-index) . Author h-index) . ArcGIS h-index) . The anah-index) . For theh-index) . Prevaleh-index) . All datThe search strategy retrieved 3021 journal documents. The same search strategy retrieved approximately 232,000 documents on HIV/AIDS. Therefore, the literature on medication adherence in PLWH constituted 1.3% of total literature on HIV/AIDS published during the same study period. Retrieved documents were mostly research articles  and review articles . The types of documents encountered in the retrieved literature were shown in Table Analysis of the most frequent keywords, excluding those pertaining to HIV/AIDS and adherence, were shown in Fig. Publications on HIV/AIDS-related medication adherence started as early as 1992. The number of publications increased with time and reached a maximum of approximately 200 documents per year in the last five years of the study period. Table h-index of 136. Table Retrieved publications received 98,175 citations, an average of 32.5 citations per document, and an Analysis of the retrieved documents indicated that authors in the region of Americas made the largest contribution , followed by those in the European region , the region of Africa 497; 16.5%), the region of South East Asia , the Western Pacific region , and the Eastern Mediterranean region . Figure 97; 16.5%n = 1733). Two countries in the top ten active list were from African region; one from Latin America, one from South East Asia, and the remaining were from Northern America and Western Europe. No significant correlation was found between the number of publications and the prevalence rate of HIV/AIDS. When the research output was standardized by calculating the percentage of publications on medication adherence relative to overall HIV/AIDS research activity in HIV/AIDS field, Uganda ranked first followed by Brazil and South Africa in.The list of these top ten active countries was shown in Table Harvard University  was the most active institution followed by University of California, San Francisco , and Johns Hopkins University . The top ten active institutions/organizations included seven academic institutions and three research/clinical organizations.Table International collaboration in the field of HIV/AIDS-related medication adherence research was visualized for countries with a minimum productivity of 40 publications Fig. . The mapAIDS Care  followed by AIDS and Behavior journal . Six journals in the top active list were published from the USA, three from the UK, and one from the Netherlands.In total, 634 different journals participated in publishing the retrieved documents; 39 of them were in the field of HIV/AIDS. The top ten active journals included eight journals in the field of HIV/AIDS, one in the field of infectious diseases, and one journal with multidisciplinary scope (Table n = 92) followed by Professor Safren, S.A. .The average number of authors per document was 4.4. Table . The top cited article received 599 citations, an average of 75 citations per year since the time of publication [Highly cited articles on HIV/AIDS-related medication adherence were identified. The top cited articles for the period from 1992 to 2007 were shown in Additional file 2lication .p-value of < 0.01. Figure Stigma research activity in HIV/AIDS showed parallel growth to that of medication adherence with a correlation coefficient of 0.912 and a The Lancet and the article discussed the role of short mobile messages in improving adherence to AIDS therapy in Kenya [In total, 149 (4.9%) documents about the role of mobile and phone technology in adherence to AIDS therapy were retrieved. These documents were published during the period from 2003 to 2017. The documents received 3643 citations, an average of 24.4 citations per document. The highest citation was achieved by an article published in in Kenya . This stin Kenya .This study aimed to analyze literature on HIV/AIDS-related medication adherence and present the results in bibliometric maps and tables. The results of this study showed a noticeable growth in this field relative to the overall HIV/AIDS research output indicative of the importance of this topic in the global fight against HIV/AIDS particularly in countries with limited resources or those with high social stigma against HIV infected people. The growth of publications in HIV/IDS-related medication adherence could be attributed to several factors. First, the natural increase in global research and publications on HIV/AIDS in general, secondary to international calls to decrease the global health burden of HIV/AIDS . HoweverHIV/AIDS is a global public health problem, with the problem in Africa considered to pose the greatest challenge, given a variety of barriers including poor access to medications, unsafe sex behaviors, stigma, and poverty. As a result, many African countries have significant numbers of PLWH , 65. TheResults indicated that keywords such as stigma, depression, and drug abuse were most frequently encountered author keywords in HIV/AIDS-related medication adherence literature. Stigma has been reported, particularly in low and middle – income countries, to be a real and important barrier to medication adherence –71. The h-index was 136 indicates that a large number of citations and a large number of readers showed interest in this field. For example, the h-index for publication on antimicrobial resistance of uropathogens [h-index obtained in this study was also higher than that reported for health topics unrelated to infectious diseases [h-index relative to other non-infectious diseases is the fact that non-adherence in HIV/AIDS patients might have more deleterious and acute effects than that for other chronic diseases such as diabetes. For example, medication non-adherence in diabetes could be replaced with diet restriction and exercise, which is not the case in HIV/AIDS. Furthermore, non-adherence in patients with HIV/AIDS might lead to a serious resistance problem to anti-viral drugs, which is not the case with anti-diabetic medications [The finding that the athogens , multidrathogens , and antathogens  was lowediseases , 79, 80.ications –86. Mediications –90.The most active journals in adherence to AIDS therapy were those in the specific field of AIDS. There are more than 70 journals in the specific field of AIDS/HIV indexed in Scopus. These journals created a scientific forum for researchers and clinicians to discuss hot topics in the field of AIDS. The involvement of these journals in publishing research in AIDS-related medication adherence is an indication of the high importance of this topic to the scientific community. However, most of these journals were published in Northern America and Europe, which might explain the large contribution of researchers from developed countries to publications appearing in these journals. Most institutions in the active list were also from high-income countries in Americas and Europe. It seems that academic institutions in the USA receive good funding for research pertaining to AIDS/HIV in general and to aspects pertaining to issues with serious impact on public health in particular. The presence of large numbers of PLWH in the USA is another potential reason for the high involvement of US researchers and institutions in AIDS-related medication adherence.h-index, which is not an ideal method to measure quality because self-citations might influence the values of citations and give a false impression of high impact. Despite these limitations, this study is the first to discuss literature on adherence to AIDS therapy in a bibliometric methodology. The findings of the current study should direct the efforts of researchers, human right activists, clinicians, and health policymakers to encourage research that point out barriers to medication adherence in world regions with a high burden of infected people. Furthermore, international health agencies need to direct and allocate funds and financial support to research in which technology could be used to overcome barriers to adherence. Social and human right activists need to speak out on the role of stigma and discrimination in medication adherence and such should implement social policies to minimize stigma and, therefore, enhance adherence. Clinicians in their practice settings should use mobile technology as a method of following up and communication with PLWH. This is extremely important in world regions where stigma and decimation as a real barrier to medication adherence. Clinicians should pressure the pharmaceutical industry and international health organization to provide AIDS therapy with minimum cost to low resourced regions. The Pharmaceutical industry could also help in improving adherence by manufacturing combination products with a minimum frequency of dosing and minimum possible cost. Nurses could also play a key role in improving adherence. Nurses in AIDS clinics should provide people with HIV full information regarding the importance of medication adherence in AIDS and the potential hazards of non-adherence to prescribed therapy. The fight against AIDS is a global and collective effort and people from the entire clinical spectrum, including clinical researchers, need to play a positive role in this regard.Medication adherence in PLWH is a global health issue and publication in this field is growing. It was the goal of this study to retrieve all relevant literature. However, not all journals, particularly those issued in Africa, are indexed in Scopus. Therefore, it is possible that some publications were missed. Furthermore, the title search gives accurate data but might cause some loss of publications in which the keywords were mentioned in abstract and not in the title. In this study, quality of publications was measure by citation analysis and h-index of retrieved literature was relatively high indicative of the importance of the topic to researchers and clinicians. Research on medication adherence in PLWH is a key component for the plan to minimize the global health burden of HIV/AIDS particularly in the presence of effective anti-HIV therapies that were proven to increase survival of PLWH. International research collaboration needs to be strengthened, particularly with countries where HIV/AIDS burden is high and national resources are scarce.The results of this study showed (1) an increase in the number of publications with time and that this increase was parallel to that of AIDS-related stigma literature; (2) the region of Africa had the least research productivity in HIV/AIDS-related medication adherence when productivity was adjusted by the number of PLWH; (3) depression and stigma were one of the most frequent author keywords in HIV/AIDS-related medication adherence literature; finally (4) the Additional file 1:Research strategy with keywords used and implemented to retrieve literature in HIV/AIDS – related medication adherence (DOC 32 kb)Additional file 2:Top 10 cited documents on HIV/AIDS-medication adherence (DOCX 38 kb)


Rigid polyurethane foams (RPUFs) were successfully modified with different weight ratios  of APIB-POSS and AEAPIB-POSS. The resulting foams were evaluated by their processing parameters, morphology , mechanical properties , viscoelastic behavior , thermal properties  and application properties . The results showed that the morphology of modified foams is significantly affected by the type of the filler and filler content, which resulted in inhomogeneous, irregular, large cell shapes and further affected the physical and mechanical properties of resulting materials. RPUFs modified with APIB-POSS represent better mechanical and thermal properties compared to the RPUFs modified with AEAPIB-POSS. The results showed that the best results were obtained for RPUFs modified with 0.5 wt% of APIB-POSS. For example, in comparison with unfilled foam, compositions modified with 0.5 wt% of APIB-POSS provide greater compression strength, better flexural strength and lower water absorption. Rigid polyurethane foams (RPUFs) are highly cross-linked, three dimensional polymers with closed-cell structures which account for about 23% of all polyurethane (PU) production . Due to Tg increased by 6 °C. Widya and Macasko [Beside the favorable properties of resulting materials, improving the mechanical properties of RPUFs is the foundation for their further potential applications. To successfully employ them in building application, it is critical that foams are combined with other materials or elements that provide mechanical strength and low thermal conductivity. A review of the related literature indicates that applying nanomaterials contributes a better improvement to mechanical properties and heat resistance ,14,15,16 Macasko  incorpor Macasko  investigAlongside traditional substances, an interesting group of reactive nanofillers are polyhedral oligomeric silsesquioxanes (POSSs). POSSs are unique organic–inorganic nanobuilding blocks, with a rigid siliceous core with silicon (Si) atoms on the vertices and oxygen (O) atoms on the edges ,18. OrgaThe effects of open-cage nanostructure disilanoisobutyl POSS (DSI-POSS) on the properties of rigid PU foams were studied by Hebda et al. . The hybThe aim of this research is to develop and test PU foams modified with closed-cage nanostructure aminopropyl isobutyl-POSS (APIB-POSS) and aminoethylaminopropylisobutyl-POSS (AEAPIB-POSS). The influence of different amounts of POSSs on thermal properties , dynamic mechanical properties , physico-mechanical properties , and morphology of obtained PU composites was examined in the current work. The results obtained in the present work indicate that the addition of APIB-POSS and AEAPIB-POSS in the range of 0.5–5 wt% influences the morphology of analyzed foams and consequently their further mechanical and thermal properties.N,N-Dimethylcyclohexylamine), flame retardant (Tris(2-chloro-1-methylethyl)phosphate), and chain extender  [RPUFs were synthesized from the same polyurethane-modified polyisocyanurate rigid foam formulation based on petrochemical components provided by Purinova Sp. z o.o. at Bydgoszcz, Poland (Izopianol 30/10/C and Purocyn B). Izopianol 30/10/C used in the reaction is a fully formulated mixture containing a mixture of polyester polyol , catalyst (anediol) . Purocynanediol) . Aminopranediol) ,36,37,38RPUFs were manufactured using a two-step method. In the first step, the component A, containing a polyol (Izopianol 30/10/C) and selected POSS, was prepared by mechanical stirring. The POSS reactive additive was introduced into the polyol in an amount of 0.5, 1.5 and 5 mass% of the polyol weight (wt%) and dispersed by the mechanical stirrer. In the second step, pMDI (Purocyn B) as component B was added to component A and the PU system was mixed using a mechanical stirrer for 10 s. After this time, the mixture was poured into an open mould where free foaming occurred in the vertical direction. RPUFs were conditioned at room temperature for 24 h. After this time, samples were cut with a band saw into appropriate shapes (determined by obligatory standards) and their physico-mechanical properties were investigated.−1 in ambient temperature.The absolute viscosities of polyol and isocyanate were determined corresponding to ASTM D2930  using a rotary Viscometer DVII+ . The torque of samples was measured as a range of shear rate from 0.5 to 100 sThe apparent density of foams was determined accordingly to ASTM D1622 . The densities of five specimens per sample were measured and averaged.The morphology and cell size distribution of foams were examined from the cellular structure images of foam which were taken using JEOL JSM-5500 LV scanning electron microscopy . All microscopic observations were made in the high-vacuum mode and at the accelerating voltage of 10 kV. The samples were scanned in the free rising direction. The average pore diameters, walls thickness and pore size distribution were calculated using ImageJ software .−1 up to 600 °C with the sample mass of about 10 mg. The initial decomposition temperatures, T10%, T50% and T80% of mass loss were determined.The thermal properties of the synthesized composites were evaluated by TGA measurements performed using the STA 449 F1 Jupiter Analyzer . About 10 mg of the sample was placed in the TG pan and heated in argon atmosphere at a rate of 10 K minσ10%) of foams was determined accordingly to the ASTM D1621  using Zwick Z100 Testing Machine  with a load cell of 2 kN and a speed of 2 mm min−1. Samples of the specified sizes were cut with a band saw in the direction perpendicular to the foam growth direction. Then, the analyzed sample was placed between two plates and the compression strength was measured as a ratio of load causing 10% deformation of the sample cross-section in the parallel and perpendicular direction to the square surface. The result was the average of five measurements per each sample.The compressive strength  results for each sample were expressed as a mean value. The average of five measurements per each type of composition was accepted.A three-point bending test was carried out using Zwick Z100 Testing Machine  at room temperature, according to ASTM D7264 . The tested samples were bent with a testing speed of 2 mm min−1, using a frequency of 1 Hz and applied deformation at 0.1%. Dynamic mechanical analysis (DMA) was determined using an ARES Rheometer . Torsion geometry was used with samples of that had a thickness of 2 mm. Measurements were examined in the temperature range 20−250 °C at a heating rate of 10 °C minSurface hydrophobicity was analyzed by contact angle measurements using the sessile-drop method with a manual contact angle goniometer with an optical system OS-45D  to capture the profile of a pure liquid on a solid substrate. A water drop of 1 μL was deposited onto the surface using a micrometer syringe fitted with a stainless steel needle. The contact angles reported are the average of at least 10 tests on the same sample.Water absorption of the RPUFs was measured according to ASTM D2842 . Samples were dried for 1 h at 80 °C and then weighed. The samples were immersed in distilled water to a depth of 1 cm for 24 h. Afterwards, the samples were removed from the water, held vertically for 10 s, the pendant drop was removed and then blotted between dry filter paper  at 10 s and weighed again. The average of five specimens was used.ol is the length of sample before thermostating and l is the length of sample after thermostating. The average of five measurements per each type of composition was reported.Changes in the linear dimensions were looked into with accordance to the ASTM D2126 . The samples were conditioned at temperatures of 70 °C and −20 °C for 14 days. The change in linear dimensions was calculated in % from Equation (2).One of the most important parameters for industrial processing of polyols is their rheological behavior. The dispersion of the POSS’s particles in the PU matrix was evaluated by optical microscopy. The viscosity of the reactive mixture was measured first, since it is a critical parameter affecting the foaming process . Increasn) was calculated from the slopes. All results are presented in The rheological properties of polyol premixes are shown as the viscosity versus shear rate in Tmax) slightly increases. It is believed that a higher temperature of the reaction of the modified compositions is connected with a higher reactivity of the components of the reaction mixture [1)) providing more heat evaporation to the system, and consequently a higher temperature of the modified system compared with the PU-0 foam. It should also be pointed out that amine groups of the POSS can act as a catalyst and promote the polymerization reaction between polyol and isocyanate, which is an exothermic reaction [The results presented in  mixture . The prereaction ,44,45. Treaction , who tes−3. The apparent density for RPUFs increases from 40 to 43 kg m−3 and from 40 to 44 kg m−3 with an increase of APIB-POSS and AEAPIB-POSS content of 0.5 and 5 wt%, respectively. This effect can be explained by the analysis of the role of filler particles on nucleation and cell growth. The POSS particles act as nucleation sites promoting the formation of bubbles, and this is an increasing trend with nanoparticles content, but, at the same time, the growth process of the resulting cells is hindered by an increase of the gelling reaction speed, which is revealed in the greater viscosity. This results in bubble collapse and higher density foams. Moreover, it should be pointed out that another factor affecting the density of RPUFs is higher density of POSS (ca. 1.2 g cm−3) compared to the PU foam matrix. This resulted in the increase of the apparent density of studied composites, wich is also in agreement with the results reported in the literature [Apparent density is an important parameter that influences the properties and performances of RPUFs. The values of density of prepared foams are presented in terature ,48.2 gases escaping from the foam structure and thus, to a prolonged start and gel time. Compositions modified with the addition of POSS are also characterized by a shorter tack-free time, indicating that POSS particles act as a curing accelerator. The total characteristic times measured for the POSS-modified compositions are higher than those measured for the PU-0, but still in the range of operation conditions for preparing RPUFs [The foaming process was determined by measuring the characteristic processing times, such as cream, extension and tack-free time. The results presented in ng RPUFs ,52. Contng RPUFs  who deteImageJ software from SEM images and the median values are summarized in The morphology of the RPUFs is shown in As observed from the micrograph of the PU-0 a, the ceAnother important parameter that impacts performance characteristics is the compressive strength, and the change in its value are presented in Such changes in the mechanical properties of composite samples can be explained in terms of characteristic features of their structure. As presented in Moreover, the reason for the decreasing mechanical strength at a high filling rate might also be related to the non-uniform dispersion of particles and polyol mixture. A high tendency to aggregate filler particles, noticeable in the structure, leads to a weakened interfacial adhesion between the filler and effective active surface. In consequence, RPUFs are characterized by a microphase separation of the structure, which leads to the failure of samples in an unexpected manner at random locations in the samples. The non-uniform concentration of the filler in some regions contributed to the embrittlement effect of polymer structures, inhibiting the enhancement of the mechanical properties of RPUFs. By increasing the content of the POSS, the negative effects of the filler such as disruption of the formation of hydrogen bonds and reaction stoichiometry, the probability of the agglomeration of nanoparticles due to the increase of viscosity and inappropriate distribution of nanoparticles is increased. Therefore, the particles interaction with PU macromolecules is decreased and the mechanical properties are weakened. The poor interfacial adhesion between some particles, especially the loose ones as discussed above, the polymer matrix and the uneven dispersion of the filler may lead to the above results, as proven by other authors ,59,60,61−2 and from 0.39 to 0.32 kJ m−2 as shown in With the increasing concentration of APIB-POSS and AEAPIB-POSS fillers from 0.5 to 5 wt%, the impact strength decreases from 0.46 to 0.31 kJ mfσ) shows that the same trend can be observed in both properties . As shown in δ peak is often assumed to be due to a broader distribution in molecular weight between crosslinking points or heterogeneities in the network structures [RPUFs prepared with different weight percentages of APIB-POSS and AEAPIB-POSS were analyzed by DMA. The most interesting observation from this analysis is the displacement of the peak in the tanructures .E′), however, with the increasing content of the filler in the PU matrix, the value of the storage modulus significantly decreases  phase and hard-segment domains which act as macroscopic cross links. The higher E′ for RPUFs with 0.5 wt% of APIB-POSS and AEAPIB-POSS indicates more restricted mobility compared to the RPUFs with higher concentrations (1.5 and 5 wt%) of fillers; thus, the introduction of POSS over a certain optimal level, in this kind of RPUFs, produces more flexible materials. This might be connected with the fact that the PU matrix itself is highly crosslinked and an excess of POSS particles may actually disrupt this crosslinking, even if it is multifunctional. It has also been observed, that during the synthesis of the foams the viscosity of the system increased with the addition of the POSS  and derivative thermogravimetry (DTG), as illustrated in Typically, the thermal degradation of RPUFs consists of three stages. The first step of decomposition is connected with the dissociation of the urethane bond at a temperature between 150 and 330 °C  ,65. The It has been noticed  that thePolihedral oligomeric silsesquioxanes functionalized by amino groups significantly affected the hydrophobicity of the foams . Regardiθ) of the RPUF composites with various weight percentages of APIB-POSS and AEAPIB-POSS also confirm this trend , foaming parameters, and morphology of RPUFs was examined. The presented results indicate that the addition of APIB-POSS and AEAPIB-POSS in the range of 0.5–5 wt% influences the morphology of analyzed foams and consequently, their mechanical and thermal properties. It was noticed that RPUFs modified with APIB-POSS are characterized by smaller and more regular polyurethane cells. This suggests better compatibility between the PU foam matrix and APIB-POSS, compared to the AEAPIB-POSS filler. This results in a significant improvement of the physico-mechanical properties and thermal stability of composites with APIB-POSS. For example, compared to the AEAPIB-POSS-modified RPUFs, composition with 0.5 wt% of the APIB-POSS showed greater compressive strength (351 kPa), higher flexural strength (0.458 MPa) and less water uptake (11% after 24 h). The results obtained in this study confirm that the addition of APIB-POSS and AEAPIB-POSS over a certain optimal level has a negative effect on cell morphology. The addition of both fillers in an amount of 5 wt% led to samples with reduced compression modulus, compressive strength, thermal transitions, and storage modulus with respect to the RPUFs containing 0.5 and 1.5 wt% of the fillers, mainly due to detrimental changes induced by the fillers.


Antimicrobial resistance is a growing global problem that causes increased deaths as well as increased suffering for people. Overall, there are two main factors that drive antimicrobial resistance: the volumes of antimicrobials used and the spread of resistant micro-organisms along with the genes encoding for resistance. Importantly, a growing body of evidence points to contagion  being the major, but frequently under-appreciated and neglected, factor driving the increased prevalence of antimicrobial resistance. When we aggregate countries into regional groupings, it shows a pattern where there is an inverse aggregate relationship between AMR and usage. Poor infrastructure and corruption levels, however, are highly and positively correlated with antimicrobial resistance levels. Contagion, antibiotic volumes, governance, and the way antibiotics are used are profoundly affected by a host of social and economic factors. Only after we identify and adequately address these factors can antimicrobial resistance be better controlled. Staphylococcus aureus and E. coli. In India with E. coli, because of very high antibiotic resistance rates, it appears that that about half of all community-onset urinary tract infections are, for practical purposes, untreatable  per person), education, and community infrastructure are known to affect health outcomes ,29 and lSome social enablers of the spread of AMR are difficult to define concepts that challenge conventional modes of data analysis; however, their relevance is transparently obvious. An important example is corruption of a society’s administrative governance. If corruption is poorly controlled, it is much more likely that there will be antibiotic use that is undocumented and so antibiotic volumes used, and their effects, will not be reflected in official figures. With increased corruption there will also be poorer controls on the many ways that resistant bacteria can spread into the environment and/or between animals and people. Inspection, measurement and enforcement of regulations regarding waterways and drinking water will also be compromised. Health regulations for the preparation, transportation, packaging, and storage of food will not be enforced in communities that are administered corruptly. Clearly, there are many factors that must be addressed if one wants to control AMR other than just focusing on usage volumes, the types of antibiotic used and usage patterns. There is a desperate need to better understand and quantify the magnitude of, and how social, economic and policy environments enable the spread of AMR. We need to put in place appropriate policy priorities to address these issues. In Europe, socioeconomic determinants, such as population income, demographic structure, density of general practitioners, and their remuneration method, have all been shown to impact outpatient antibiotic use. Richer countries in Europe use more outpatient antibiotics compared to countries with a lower ability to pay. This effect of income has also been shown to be a factor in developing countries. Additionally, supply-side factors and incentives attached to payment schemes  are likely to be important and need to be considered in government interventions . Antibiotics usage and corruption levels in regions of Europe have been studied at a sub-national level by Rönnerstrand and Lapuente . They loA previous study looked at the importance of governmental, social, and economic factors as drivers of AMR compared to what are usually considered the main driving factors—antibiotic usage and levels of economic development . Only 28In our recent study we found that globally poor administrative governance and corruption are strongly correlated with high levels of AMR , a resulAMR continues to rise globally and is associated with increased deaths as well as increased suffering for people. However, there are many things we can do to improve the situation. These are best captured within “One Health”, although it will be important that the “One Health” concept does not predominately focus on antibiotic use and levels in the human, agriculture, and environmental sectors, but adequately addresses “contagion” and includes social and economic determinants. Global evidence shows a pattern where poor infrastructure and corrupt administrative governance are associated with lower levels of antibiotic consumption yet higher prevalence of AMR. Even in high income countries, where the focus has been mainly on antibiotic consumption as the most important factor contributing to AMR. However, antibiotic usage volumes explain only a small portion of the observed AMR levels. Contagion, rather than antibiotic usage volumes, is the major factor contributing to the variations in antibiotic resistant levels across countries. Contagion is, in turn, affected by many social determinates and economic factors. This new insight has major policy implications. Interventions focusing on decreasing antibiotic consumption alone are not likely to be sufficient, especially in LMICs, because contagion is likely the dominant factor affecting the prevalence of higher levels of AMR.We need to improve all the economic and social factors that contribute to “contagion” and so then make spread less likely to occur. This needs to include better sanitation, better access to clean water, better housing, less crowding, safer foods, less transmission in hospitals by adopting better infection control and prevention practices, as well as improving administrative governance . We also need an increase in public expenditure on health if we are to better tackle AMR on a global scale. Better approaches that take into account cultural contexts are required to better facilitate successfully approaches to what and how antibiotics are used in people and restrictions on use that are needed. It is also important that these approaches extend to management of food animals, especially for critically important antibiotics. Future research and policy formulation must much better recognise and address the importance of cultural, social, and economic determinates that drive contagion, because it is the complex amalgam of these factors that enable and facilitate the spread of AMR.


The preparation of hybrid nanocomposite materials derived from polyhedral oligomeric silsesquioxane (POSS) nanoparticles and polyimide (PI) has recently attracted much attention from both academia and industry, because such materials can display low water absorption, high thermal stability, good mechanical characteristics, low dielectric constant, flame retardance, chemical resistance, thermo-redox stability, surface hydrophobicity, and excellent electrical properties. Herein, we discussed the various methods that have been used to insert POSS nanoparticles into PI matrices, through covalent chemical bonding and physical blending, as well as the influence of the POSS units on the physical properties of the PIs. Nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), and thermogravimetric analysis (TGA) confirmed the chemical composition and structure of these PI-g-PMA-POSS nanocomposite films.Wei et al.  prepared2 reacted with various aromatic tetracarboxylic dianhydrides to obtain POSS-PIs nanocomposites octasilsesquioxane (OG-POSS), 4,4′-carbonyldiphthalic anhydride (BTDA), and 4,4′-oxydianiline diamine (ODA)  83]. Th. Th83]. Li et al. prepared a series of octa(aminophenyl)silsesquioxane (OAPS) covalently cross-linked sulfonated PIs (SPIs)  84]. Th. Th84]. 2 at 30 °C, and its blending with various percentages of OAPS; subsequently, thermal imidization of the PAA/OAPS nanocomposites at 300 °C to obtain the POSS-PI nanocomposites. Thermal studies revealed that the glass transition temperature, char yield, thermal stability, and flame-retardant properties of the POSS-PI hybrid nanocomposite were all greater than those of the pristine PI. Adıguzel et al. [Alagar et al. synthesized PI/POSS hybrid) materials through a two-step method  85]. Fi. Fi85]. l et al.  preparedIn this Review, we discussed various preparation types of PIs containing POSS NPs that displayed attractive characteristics, including low dielectric constants, low water absorption, and methanol permeability; excellent mechanical and electrical properties; and high thermal stability, surface hydrophobicity, flame retardance, chemical resistance, proton conductivity, and thermo-redox stability compared with those of their pristine PI precursors. The insertion of these POSS units into the PI precursors has been performed through either physical blending or covalent bonding. The preparation of organic/inorganic hybrid materials containing POSS and PI remains an interesting topic in academic and industrial science because of their potential applications in fuel cells and gas separation membranes, as insulator materials in microelectronics, and in the aerospace industry.


The need for a sustainable development and improved whole life performance of concrete infrastructure has led to the requirement of more durable and sustainable concrete bridges alongside accurate predictive analysis tools. Using the combination of Self-Compacting Concrete (SCC) with industrial by-products and fiber-reinforced polymer (FRP), reinforcement is anticipated to address the concerns of high carbon footprint and corrosion in traditional steel-reinforced concrete structures. This paper presents a numerical investigation of the structural behavior of basalt fiber-reinforced polymer (BFRP)-reinforced SCC deck slabs in a real bridge, named Thompson Bridge, constructed in Northern Ireland, U.K. A non-linear finite element (FE) model is proposed by using ABAQUS 6.10 in this study, which is aimed at extending the previous investigation of the field test in Thompson Bridge. The results of this field test were used to validate the accuracy of the proposed finite element model. The results showed good agreement between the test results and the numerical results; more importantly, the compressive membrane action (CMA) inside the slabs could be well demonstrated by this FE model. Subsequently, a series of parametric studies was conducted to investigate the influence of different parameters on the structural performance of the deck slabs in Thompson Bridge. The results of the analyses are discussed, and conclusions on the behavior of the SCC deck slabs reinforced by BFRP bars are presented. It has been widely recognized that the durability of concrete bridge deck slabs is reduced as a consequence of the corrosion of the reinforcements ,2,3. BecIn an existing bridge, the bridge deck slabs of a typical beam–slab composite bridge have inherent strength provided by the lateral restraint of beam-to-slab boundary conditions. Bridge deck slabs subjected to wheel load are restrained against horizontal expansion because of the presence of an inherent in-plane restraint, which is the compressive membrane action (CMA) or arching action see  10,11].,11.10,11Currently, to improve the whole life performance of concrete infrastructures and drive sustainable development, the traditional reinforced concrete structures are planned to be replaced by sustainable construction with adequate material by means of design optimization. Self-Compacting Concrete (SCC) with an additional mineral provides an engineering material which has attracted wide attention from researchers and engineers because of its advantages ,15,16. PUntil now, the investigation of FRP-reinforced concrete using SCC in construction has been widely developed. However, the study of FRP-reinforced SCC structures, particularly in concrete deck slabs, is significantly limited. To investigate the feasibility of using BFRP-reinforced SCC structures in the construction industry, we carried out a field test and a study on SCC deck slabs reinforced with BFRP bars in a real bridge, named Thompson Bridge, in Northern Ireland, U.K. . BecauseThe aim of this paper was to study the behavior of SCC deck slabs with BFRP reinforcing bars under the wheel load. To extend our understanding of the ultimate state and failure mechanisms of Thompson Bridge deck slabs, a numerical investigation through the 3D finite element model was used in this paper ,20,21. IThompson Bridge is a replacement bridge on the A509 trunk road in County Fermanagh, Northern Ireland. The length and width of Thompson Bridge are 32 and 11.85 m, respectively, and the thickness of the entire deck slab is 200 mm . It cons2. The details of the material properties of the reinforcement are shown in BFRP is a new type of synthetic material, which is fabricated through the pultrusion molding process using basalt fiber as a reinforcement material and resin as a matrix material. BFRP bars have higher tensile strength and lower elastic modulus compared with steel bars see . BesidesThe test program was designed to evaluate the influence of the reinforcement type and compressive membrane action on the structural behavior of the bridge deck slab. The test regions 1 to 4 of the bridge deck slab reinforced by BFRP had a reinforcement percentage of 0.6%, and the test regions 5 and 6 incorporated steel reinforcement with a reinforcement percentage of 0.7% see . As showThe effective span of the test regions 2, 3, and 5 between the W-beams and of the test regions 1, 4, and 6 between W-beams and W-beams are 1400 and 1600 mm, respectively. A typical test arrangement is shown in All the test areas were loaded in increments of 5 kN, and the deflection and microstrain values were recorded at each increment. The bridge deck slabs were preloaded twice, in increments of 12.5 kN or 25 kN to 50 kN before the formal loading. A test load of over twice the current maximum wheel load (150 kN) given by Europe Code was applied incrementally in the formal loading. The deflection and microstrain values were recorded at each load increment.The results of the maximum vertical deflections under full test load are compared in The results for the microstrain in the test regions 1 and 2 of the BFRP-reinforced deck slab are given in A commercial finite element analysis software named ABAQUS 6.10 was used as a tool of numerical investigation for failure mode and ultimate capacity of the Thompson Bridge deck slabs. It is accurate to predict the ultimate bearing capacity and failure mechanism of a FRP-reinforced concrete structure with the finite element method ,23. The In the finite element model, a truss element is adopted to simulate the reinforcement material inside the concrete structures. A bridge deck slab with lateral restraint has a perfect bond between bars and concrete under two-way reinforcement, and the bond-slip is generally not considered in the finite element model, so an embedded constraint was used in the bridge deck between the SCC and the reinforcement bars, in which the reinforcement material was designated as the embedded element, and the concrete was used as the host element. The loading surface of wheel load was modelled using a steel plate with the dimensions 300 mm × 300 mm × 60 mm. Because of the convergence difficulties in standard static solution of the FE analysis, a dynamic and explicit method was used for the numerical solution of the FE model in this study. To effectively simulate the descending section of the failure stage of the bridge slab, a method of displacement loading was adopted in the finite element model. An accurate result required that the mesh size depended on the maximum aggregate size of concrete, and the element size of the bridge slab in the thickness direction of 20 mm was adopted in the model.The model uses the yield function proposed by Lubliner et al.  and thenα, β, and γ were calculated on the basis of Equations (2)–(4), respectively; .The parameters lane see .(2)α= shows the stress–strain relationship proposed by Saenz  for conca lacked .(6)σc=EThe tension–softening curve of concrete was suggested by Hordijk  under unThe reduction of the elastic modulus was assumed in the concrete damaged plasticity model, and a scalar degradation variable The tensile cracking and compressive crushing are the main failure mechanisms of concrete in the concrete damaged plasticity model. The stiffness degradation variable Equations (10) and (11) can be deduced from the stress–strain relationships of compression and tension see , respectBy substituting  loading .The stress–strain relationships of FRP and steel reinforcement are represented in The comparison between the load–deflection displacement responses of the bridge deck slabs from the experimental test and the numerical analysis are shown in On the basis of the validation numerical analysis results, it can be concluded that the proposed finite element model is suitable for analyzing the structural behavior and failure mechanism of bridge deck slabs in the study. These finding are discussed in the following sections.The Von Mises stress clouds of bridge deck slabs are shown in The ultimate bearing capacity of the SCC deck slabs in Thompson Bridge was predicted see  by the fIn this parametric study through FE analysis, four structural variables, namely, reinforcement ratio, reinforcement type, concrete compressive strength, and depth of bridge deck slab, were involved. The influence of the four structural variables on the ultimate state of the bridge deck slab will be discussed separately.The effects of different types of reinforcement, such as Glass Fiber Reinforced Polymer (GFRP) rebar, BFRP rebar, Carbon Fiber Reinforced Polymer (CFRP) rebar, and steel rebar, on the structural performance of the concrete deck slabs in the numerical simulation is presented in The influence of the depth of the bridge deck slab on the ultimate bearing capacity was investigated see . It was The results of the field test in Thompson Bridge showed that the deflections and strain values of BFRP-reinforced concrete deck slabs under a wheel load of 400 kN were within an acceptable service range. However, it is worth mentioning that BFRP-reinforced SCC deck slabs exhibited better structural behaviors that that is predicted by current design codes, due to the contribution of the compressive membrane action to the structural behaviors of restrained deck slabs.The results of the proposed FE model for BFRP-reinforced SCC deck slabs in Thompson Bridge showed good agreement with the field test results.The FE analysis results indicated that BFRP-reinforced SCC deck slabs used in Thompson Bridge exhibited Compressive Membrane Action (CMA), as clearly obtained in the FE analysis.The ultimate load-carrying capacity of the SCC deck slabs with BFRP-reinforced was predicted to be approximately 1000 kN by the FE model, which far exceeds the design ultimate loads. Because of the influence of CMA, the SCC deck slabs reinforced with BFRP bars had a similar reinforcement percentage as those reinforced with steel bars. In addition, the predicted failure mode of the SCC deck slabs reinforced with BFRP bars under wheel load was determined to be the punching failure by the FE model.The parametric analysis by the FE model demonstrated that the reinforcement ratio and reinforcement type have an insufficient effect on the structural behavior of the bridge deck slabs. This is attributed to the contribution of CMA inside the laterally restrained deck slabs. However, the concrete compressive strength and the depth of the bridge deck slabs play a significant role in the structural mechanical properties of the bridge deck slabs under ultimate and service state.The FE investigation results indicates that the BFRP-reinforced SCC deck slabs showed similar structural behavior as the steel-reinforced normal concrete (NC) deck slabs in terms of compressive membrane action. However, because of the use of a high volume of an industrial by-product (fly ash) in the SCC mixture of this study, the sustainability and durability of SCC can be improved compared to traditional NC. Additionally, using the benefits of the compressive membrane action it is possible to configure a very low reinforcement ratio of BFRP bars in concrete deck slabs. On the basis of the corrosion-free property of the BFRP bars, these findings indicate that the combination of the compressive membrane action, BFRP, and SCC can produce low-carbon footprint, durable, and economical infrastructures.This paper reveals an FE study of the structural behavior of BFRP-reinforced SCC deck slabs under wheel loads in a real bridge, namely, the Thompson Bridge. From this study, the following conclusions can be drawn:


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