The paper discusses the problems connected with long-term exploitation of reinforced concrete post-tensioned girders. The scale of problems in the world related to the number of cable post-tensioned concrete girders built in the 1950s and still in operation is very large and possibly has very serious consequences. The paper presents an analysis and evaluation of the results of measurements of the deflection and strength and homogeneity of concrete in cable–concrete roof girders of selected industrial halls located in Poland, exploited for over 50 years. On the basis of the results of displacement monitoring in the years 2009–2020, the maximum increments of deflection of the analyzed girders were determined. Non-destructive, destructive, and indirect evaluation methods were used to determine the compressive strength of concrete. Within the framework of the indirect method recommended in standard PN-EN 13791, a procedure was proposed by the authors to modify the so-called base curve for determining compressive strength. Due to the age of the analyzed structural elements, a correction factor for the age of concrete was taken into account in the strength assessment. The typical value of the characteristic compressive strength is within the range 20.3–28.4 MPa. As a result of the conducted tests, the concrete class assumed in the design was not confirmed, and its classification depended on the applied test method. The analyzed girders, in spite of their long-term exploitation, can be still used for years on the condition that regular periodical inspections of their technical condition are carried out. The authors emphasize the necessity for a permanent and cyclic diagnostic process and monitoring of the geometry of girders, as they are expected to operate much longer than was assumed by their designers. In many cases in construction practice, it may not be possible to carry out a precise assessment of the technical condition of buildings and their components using traditional, commonly used methods. Such situations will concern buildings and structures with a large number of structures very sensitive to environmental conditions, for which the assumed technical life has already significantly exceeded their current service life. It will not be practicable to replace these elements with new ones due to the large number of buildings constructed with such and similar technologies. An example of such facilities are industrial halls built using prefabricated elements made in prestressed concrete technology.Post-tensioning techniques have been widely applied in construction to design bridge piers and decks, building slabs, and long-span girders . Post-TeTension presses (jacks) are used to prestress the structure. The space between the tendons and the walls of the cable tunnel is filled with an injection material  of sufficient strength to protect the steel of the tendons against corrosion and to transfer the prestressing forces to the structure.With a few exceptions, these structures have a segmental structure, joined directly on site during assembly by means of welded joints, filled with mortar. In spite of the impression made by their seemingly massive external appearance, these elements are quite “delicate” and have a long service life (approx. 50–75 years), hence the serious problem of their safe use; i.e., maintenance in an appropriate technical condition has already become a topic of discussion ,7,8,9.The beginnings of tests on prestressed reinforced concrete structures date to the second half of the 20th century .There are not many studies in the literature of specific standard guidelines for the testing and maintenance of these girders apart from a few technical manuals or handbooks, e.g., ,13,14,15Hence, the need has arisen to propose an appropriate and reliable methodology for testing materials via non-destructive testing (NDT) ,29,30,31Monitoring the long-term behaviour of civil structures is of great importance for damage prevention and design improvement . TechnicThe application of an appropriate approach to the monitoring of structures, as proposed, e.g., in ,35 and iThis paper presents selected problems of the evaluation of the technical condition of cable post-tensioned concrete girders. In particular, the path of their quick monitoring is presented. The results of deflection measurements and tests of compression strength and uniformity of concrete were evaluated. The subject of consideration was selected roof girders of two industrial halls located in southern Poland.The structures proposed for the case study are divided into two groups: typified and non-typified  cable post-tensioned concrete girders (type: KBO—monolithic one-piece girders and KBOS and KBS—girders assembled on the building site from prefabricated elements) with spans ranging from 15 to 27 m. Their shape is an arched upper chord, “broken” into ~3 m long sections, and a straight lower chord (tie beam), which are connected by vertical posts . The top2 or a roof area of more than 2000 m2 require inspection twice a year.The subject of the study are the girders built-in in two halls located in southern Poland: Hall A—17 girders with a span of 27 m , two layers of insulating fiberboards with a total thickness of approx. 2.5 cm, and a levelling layer of cement mortar with a thickness of approx. 1.5–2.0 cm. Subsequent thermo-modernization was carried out on the existing roof covering, which also increased the permanent load on the roof. This modernization consisted in laying hard mineral wool up to 20 cm thick and covering it with two layers of weldable roofing paper. Installations  were suspended from the lower girder strips, and roof windows (skylights) with a steel structure and single reinforced glass filling c were reDiagnostic tests allow evaluation of the condition of reinforced concrete prestressed girder structures, and the degree of deterioration of individual elements, and determination of the characteristics of concrete and reinforcement, and the causes of damage, and prediction of the durability of the structure . In the In this paper, the authors will present selected measures, including: visual inspection of girders , geodetic investigation of girder deflections, and selected concrete tests. These are elements of the developed simple and effective monitoring of the state of the girders, which the authors have been using for over ten years. It is a method of cyclic, precise updating of the measured deformations combined with macroscopic examination of all elements. In particular, the examination of the quality and class of concrete connections of prefabricated elements and the extent of corrosion according to the pathway are presented in The use of a proven and reliable fast-track procedure  is necessary when a large number of girders are involved in a single structure or assembly (there can be up to 150 girders in a single object). The tests performed should be supported by an appropriate computational algorithm. From a financial perspective, this may not be cost-effective unless it is done automatically or when changes are significant. This is especially the case if you use an already known algorithm of calculation.The ultimate limit state is the design and check for the safety of a structure and its users by limiting the stress that materials experience. It would be difficult to determine these values in a simple (measured) way without performing verifiable strength calculations, analyzing the actual static schemes of the structure as well as its verticality, and the flatness and deformation of the girders (taking into account imperfections) and their current properties and parameters, in this case, mainly concrete. The assessment of the serviceability limit state of buildings in intensive use and their structures consists, among others, in comparing the actual values of deformation of their geometry with the permissible values in relation to previous testing seasons. For this purpose, generally available measuring instruments or devices are used.2 on the whole surface of the roof) as part of thermomodernization work of hall B and in the case of hall A replacement of the carpentry of the roof windows (subtraction of approx. 0.5 kN/m on the whole surface of the skylights) already represent a requirement to check the capacity of the girder.Technical inspections should be carried out immediately any changes in the appearance of even a single girder are noticed. Additional load on the roof  on the elements and the extent and weight of suspended installations , information boards and other loads,cracks and defects in the glazing of skylights or replacement of their constituent elements with heavier ones,use of the building in accordance with its original purpose,thermal and humidity parameters of the building envelope and thermal and humidity conditions of the internal environment,possible influence of dynamic loads on the whole structure of the building, e.g., connected with the production technology of the plant.A visual inspection of the girders includes a preliminary assessment of the structural condition. During a visual inspection carried out as part of the periodic technical inspection, particular attention should be paid to:In the case of regular inspection by visual methods, e.g., by UAV, it is possible to use the very accurate and fast DIC  optical method for the analysis of the state of preservation of the material . The complete measurements and tests are used for the overall assessment of the elements and to assign them to a specific class:Classification of the technical condition of the girder/girders to classes III and IV necessitates conducting extensive technical and material tests and carrying out urgent repair recommendations. For the technical condition of an object/element classified to classes I and II, on-going maintenance work and subsequent inspections in the current cycle (according to the established schedule) are required, as well as repair and removal of defects.The compressive strength of concrete is a basic parameter which proves its quality and durability. Achieving the desired quality of concrete involves appropriate design of concrete mixes ,54, propThe evaluation of concrete strength in existing building structures can be carried out in accordance with standard PN-EN-13791 , which oDemonstration of compliance of the compressive strength of concrete in a structure, that is, concrete already embedded in the structural element , but without the use of “standard” samples. The indirect methods are used here, that is, those that do not “destroy” the structure, and at the same time are cheaper than traditional sampling.Evaluation of the quality of concrete in the case of non-compliance of the compression strength conditions, which was carried out with the use of standard samples or when execution errors are found during the execution of work.Evaluation of the technical condition of existing structures when they are to be modernized or redesigned.The standard recommendations for strength assessment in structures according to PN-EN-13791  concern The PN-EN 13791 standard  providesrebound number (sclerometric method)—PN-EN 12504-2 ,pull-out force (“pull-out” method)—PN-EN 12504-3 ,ultrasonic wave speed (ultrasonic method)—PN-EN 12504-4 .The development of non-destructive testing (NDT) of materials in civil engineering is mainly concerned with the detection of flaws and defects in concrete elements and structures . In indiIn practice, many different methods using different measuring instruments are used. Characteristics of NDT methods of concrete are presented in In the case study presented in this paper, sclerometric and ultrasonic tests were used. These methods are used often and successfully to evaluate the quality of concrete in existing structures ,66. The In the case of the direct method (destructive method/DT), tests are carried out on samples cut out of the structure through core drilling. A description of the testing is given in the tooling standard PN-EN 12504 series  concerniSpecimens should be drilled in the structure, from those places where section weakening is least likely to affect the load-bearing capacity of the structure, then tested in the laboratory. Nondestructive testing should cover from 2% (for good homogeneity) to 100% (for poor homogeneity) of the girders in a given structure . ExampleAll analyzed girders were visually inspected for structural and material damage using a visual method  with a gimbal .Examples of cable post-tensioned concrete girder damage in Hall A identified as a result of the inspection shown in During the operation of Hall A, damage occurred to the lower flange of the girder when the oversized structure was moved. The workers either did not notice this or ignored it. This coincided with the significant addition of loads during the replacement of a window skylight. The deflections of this girder were observed in the measurement results. At present, it is not known at what exact time (within one year) the damage shown in Was this a direct result of the exceptional load applied or did it propagate over time? Such situations may occur during the continuous operation of a production plant. During the following periodic inspection of the hall, the danger presented by a damaged bottom chord became apparent. Cracks, delamination, and deformation of the lower prestressed chord had completely changed its static scheme. Instead of compressing the concrete section, the tension of the cable caused it to be compressed by a large eccentric force that extended beyond the core of the chord section. It was only by chance that the damage to one girder, whose lower flange had lost its load-bearing capacity, did not lead to a widespread building disaster. After this event, two adjacent girders were carefully observed, for which deformation diagrams are shown in Figures 6–8.f in the middle of the span, monitored from 2009 to 2020 in Hall A was 25 mm, and in Hall B 32 mm. The results are summarized in In the analyzed Halls A and B, measurements of girder deflections have been carried out since 2009. The measurements were performed with the trigonometric levelling method, using an electronic total station (Leica TCRP 1203 R100). The height differences between three points on each cable post-tensioned concrete girder were measured. The points were marked with markers on the lower flanges of the concrete girders, two at the ends and one in the middle of the span. Measurements were taken with comparable accuracy ±1 mm. The reference level for measurements was the altitude level of the hall floor, the fixed benchmark of the national PL-KRON86-NH network with the value of + 105.50 m above sea level for Hall A, and +114.10 m above sea level for Hall B. Girder maximum deflection increments ΔCurrent procedures for testing reinforced and prestressed concrete structures using the sclerometric method are included in PN-EN 12504 . AccordiFor this reason, the recommendations of B-06250 , which akν < 12%. The hypothetical scaling curve was assumed in the form of Equation (1):cf—compressive strength of concrete,L—number of rebound.Testing of four roof girders was carried out with a Schmidt N-type sclerometer. In each structural element, measurements were made on lateral  surfaces at 15 measuring points. The scaling curve was determined by selecting a hypothetical scaling curve on the basis of reflection number tests and compressive strength (determined by the failure method). As a criterion for the selection of the hypothetical scaling curve, the condition was adopted that the value of the mean relative square deviation was kν = 23.6% > 12% was too high. Therefore, correction factor c was introduced, calculated as the ratio of the average strength of the samples taken in the press (c meanf) to the average strength of the specimens determined from the hypothetical scaling curve . This ratio was c mean:fc,h meanc = f = 1.15. The corrected scaling curve was therefore of the form of Equation (2).For this equation, the value kν = 10.5% < 12%. This curve could be used to determine the compressive strength of the concrete based on the reflection number L. The log of sclerometric measurements for one prestressed element  is shown in For this curve, i,min ≥ fck cube,1st criterion: fcmf≥ 1,2 ck cube,f2nd criterion: cmfck cube +≥ f 1.64·s3rd criterion: The characteristic compressive strength can be determined with formulas defined in :1st critckf ≤ 32.4 MPackf ≤ 36.0 MPa/1.2 = 30.0 MPackf ≤ 36.0 MPa—1.64·1.92 MPa = 32.8 MPa.Thus, according to , the minBased on sclerometric tests, the characteristic compressive strength value is 30.0 MPa. Using the recommendations from ,72, the k = 0.91 and relative standard deviation Based on the obtained value of homogeneity, the coefficient is rding to , the conThe homogeneity of hardened concrete from sclerometer tests for the four girders was determined and the results are given in k = 0.91 was very good and the quality of other considered beams .The scaling curve was determined by selecting a hypothetical scaling curve analogous to the ultrasonic method. The final corrected scaling curve was in the form of Equation (4).A detailed example log of the ultrasonic tests carried out for one of the girders  is summarized in ckf ≤ 30.2 MPack ≤f 34.2 MPa/1.2 = 28.5 MPack ≤f 34.2 MPa—1.64·2.11 MPa = 30.7 MPa.Based on the results of ultrasonic tests, the characteristic compressive strength of concrete can be estimated using the recommendations of standard . AccordiBased on ultrasonic tests, the characteristic compressive strength is 28.5 MPa.Using the recommendations of , the homk = 0.90 and relative standard deviation Based on the obtained value of homogeneity coefficient rding to  the concThe homogeneity of hardened concrete from ultrasonic tests for the four girders was determined from the recommendations in ,74. The k = 0.90 were very good and the quality of other considered beams  and sclerometric test results.The method recommended in  was usedc,cyl. It should be noted that the standard base curves were determined for fc,cube values determined on 150 mm cube specimens tested after 28 days of curing under laboratory conditions.To determine the correlation relationship between the compressive strength of concrete in the structure and the indirect test result, the correlation relationship of the strength obtained for cores drilled from the structure and the test results performed for nondestructive testing must be determined, thus obtaining pairs of test results. Determination of the correlation relationship involves fitting a straight line or curve via regression analysis of pairs of results obtained from the test program. The indirect method measurement result is considered a variable value and the determined compressive strength of concrete in the structure is a function of the variable. The standard  emphasizmv reflection numbers in a range specified as 43.8–48.0, a standard base curve [Since the study obtained average Lse curve  from Equf of the base curve depends on the mean value of the differences δfm(n) and the factor k1 associated with the number of measurements and is calculated from Equation (7).s—standard deviation of strength differences n ≥ 9.The evaluation of concrete strength consists in shifting the basic base curve (Equation (5)) to an appropriate level, determined by core drilling and non-destructive testing. The value of the shift of the basic ΔFrom Equation (6), the compressive strength of concrete (corresponding to the strength of concrete on 150 mm cubes) can be calculated anywhere in the structure, then the characteristic compressive strength of concrete dependent on the number of measurements can be determined. See Equation (8):cc(t) that takes into account the age of the concrete after 28 days of curing [t—age of structure (days),cs—cement class.The classification of concrete into a given strength class  is basedf curing   regulations applied to the sclerometric and ultrasound methods [n = 8, so on the basis of national experience [k1 as the value of statistics recommended in [γ = 0.75 and n = 8, and the statistic value read from [k1 = 3.27. The calculation of the base curves is shown in In the standard, the method of determining the shift parameter ∆ogous to , which s methods ,73. In tperience ,72,73 thended in . In the f of the base curve is ∆f = 4.9 − 3.27∙3.0 = −4.9 MPa, and the corrected equation of the base curve determined by Equation (5) will finally take the form (11):According to Equation (7), the value of the parameter ΔEquation (11) is valid only in the interval of rebound numbers 44.8 − 2 = 42.8 < L < 46.8 − 2 = 44.8, because a modified base curve has been defined for this interval.The purpose of the analyses was to determine the characteristic strength of concrete in the structure using the indirect method based on the modified base curve , so the n < 15 is presented as follows:1st criterion: 2nd criterion: The characteristic strength of concrete according to  was evalcc(t) = 1.438 was determined from Equations (9) and (10); hence, the strength of the concrete was 35.6 MPa/1.438 = 24.8 MPa.The characteristic strength of the concrete is 35.6 MPa. After assuming that class N cement was used to make the concrete and the age of the concrete was more than 50 years, the value of the coefficient considering the age of the concrete βL = 2.0% < 15%  and in hall B, 32 mm (about 33% of the maximum deflection). These values are high for this type of structure because of the lack of concerning amount of girder deformation since the beginning of the hall exploitation. The first measured deflections occurred in 2009 and these values were taken as a reference for later measurements and analyses. According to the authors, because of the age of the elements and incomplete measurement data, the constant measured deflection of the girders in the middle of the span should not exceed 35% of the permissible value. One of the aims of the research was to monitor the changes of displacement magnitude in the same points with changing sign, in similar conditions of the internal and external climate. The change of the ordinates of the measuring points exceeding the permissible values will indicate the overloading of the girder structure, the settling of supports, or the change of tension force in cables. It will become the reason for the detailed examination of this particular element  after its temporary protection.The authors have been observing cable post-tensioned concrete girders for several years, cyclically evaluating the material and geometric changes occurring in them. In the analyzed cases, the girder maximum deflection increment ΔOf course, such tests should not only concern roof structures, but also all other elements which are responsible for their proper support and ensure the spatial stiffness of the objects and their individual structures, and thus affect their deflections.The hidden defects of built materials as well as the ageing processes will determine their current technical condition, which will constantly change over time to their disadvantage. Periodic examinations, carried out on an ongoing basis, allow for the continued periodic use of the facilities, but at some point they should indicate the approaching end of their service life. Assessment of the parameters of the materials which make up these structures on its own will not be sufficient here, as it will be difficult or even impossible to reach all their locations. It will also not be possible here to assess the tension of cables due to their inaccessibility or to reliably assess the degree and extent of corrosion of steel cable strands (apart from single random tests) due to their number, as there are dozens or even hundreds of them in such halls. In the absence of developed testing methods for this type of structures, which are estimated to be even more than 60 years old, it is necessary to use those that monitor the maintenance of their geometric shapes not only in comparison with the permissible deformations but also through the analysis of these changes over time.The obtained values of the characteristic compressive strength were compared with the values of the characteristic strength calculated on the basis of the guidelines contained in Annex D of PN-EN 1990  concernikv—coefficient of variation of the sample; kv = cms/fnk—a factor that depends on the sample size and confidence level (at the minimum confidence level γ = 0.75 and n = 8 → nk = 5.07).According to Annex D, the procedure according to D.7.2 and D.7.3 can be directly applied to estimate the characteristic values. It is recommended that the estimation of test results should be carried out on the basis of statistical methods using existing  information about the type of distribution used and the associated parameters. Equation (12) can be used to estimate the characteristic value according to EN 1990 :fck = fckf = 35.9 MPa. The characteristic value of the compressive strength of concrete can also be determined according to EN 1990 [σ = 4.86 MPa, calculated from the relationship cm = fck +f 8 according to [The resulting characteristic compressive strength of concrete according to Equation (12) will be  EN 1990  in Annexrding to .s can be obtained using the Mellin function (Equation (13)):n—sample size,σ—population standard deviation.With an assumed a priori standard deviation of 4.86 MPa, the standard deviation estimator To determine the characteristic compressive strength of concrete according to , we use nk = 3.27, while the characteristic value of compressive strength according to Equation (14) for core samples will be ckf = 33.0 MPa.Under the assumption regarding the knowledge of standard deviation, the value of coefficient will be After considering the age parameter of concrete, the characteristic compressive strength for the core test is, 35.9/1.438 = 29.4 MPa and 33.0/1.438 = 27.0 MPa respectively.To determine the differences in the characteristic compressive strength values obtained by different methods, the values from each destructive and non-destructive method are summarized in a graph . In the ck(5)f − ck(5)s; f − s), is in the range of 20.3–28.4 MPa, and the relative variation of the compressive strength characteristic value measured by the coefficient of variation is 17% > 15%, which indicates the average variation of the compressive strength characteristic results obtained using different methods.The typical value  and also soft reinforcement, or from where the impediments to the use of the object are the least, hence the rationale for using primarily non-destructive methods. Such situations are often the result of a lack of prior visual inspection of the structure and assessment of potential obstructions. In the case under analysis, a total of rding to , non-desn = 3 is allowed by the standard and is justified when the tests concern a single element or a small fragment of the structure. When using the direct method, a minimum of 4–6 core holes should be made in single elements, and when the assessment concerns several elements  then a minimum of 9–18 holes should be made and a combination of indirect methods of testing should be used. Analyzing the obtained values of coefficients of variation for compressive strength, it can be stated that they are less than 15%, which indicates a very good homogeneity of compressive strength of hardened concrete. Very good homogeneity in compression is also evidenced by the obtained values of the homogeneity coefficient for non-destructive methods: sclerometric and ultrasonic.Sampling of n < 15 is available, the recommendations of the standard [The calculation procedures recommended in the standards proposed in this paper can enable the proper classification of concrete. It should be noted that using the criteria given in the standard , which astandard  should bstandard , the corn = 3) results in the necessity of additional tests. To exclude doubts arising at the stage of drawing conclusions, in situ tests should be attended by representatives of the interested parties, whose task it is to both confirm the location of the test points and visually evaluate the samples and, if possible, observe the test procedures.Implementation of European standards in the field of testing procedures  which could accelerate corrosion, mainly of invisible steel structures “covered” in the girder body.


Steel fiber reinforced concrete (SFRC) is currently the material of choice for a broad range of structural components. Through the use of SFRC, the entire, or a large portion of, conventional rebar reinforcement can be replaced, in order to improve the load-bearing behavior but also the serviceability and durability characteristics of engineering structures. The use of fiber reinforcement therefore plays a vital role in acute current and future construction industry objectives, these being a simultaneous increase in the service life of structures and the reduction of their environmental impact, in addition to resilience to extreme loads and environmental actions. Next to the extended use of SFRC, modern construction relies heavily on structural connections and assembly technologies, typically by use of bolt-type cast-in and post-installed concrete anchors. This paper addresses the influence of fiber reinforcement on the structural performance of such anchors in SFRC and, particularly, the load bearing behavior of single headed anchors under axial static loads in uncracked and cracked concrete. Along with a presentation of background information on previous studies of SFRC with a focus on anchor concrete breakout failure, the experimental investigations are described, and their results are presented and elaborated on by consideration of various research parameters. A comparison with current design approaches is also provided. The conclusions are deemed useful for structural engineering research and practice. Steel fiber reinforced concrete (SFRC) is currently the material of choice for a broad range of structures such as industrial floors , prefabricated elements, thin shells, segmental and sprayed as well as cast final tunnel linings, special foundations and slabs on grade, watertight and containment structures , and protection and defense structures. Furthermore, its use is also confirmed for many commonplace concrete component design situations, replacing the entire or a large portion of conventional rebar reinforcement in order to improve their load-bearing behavior as well as their serviceability and durability characteristics ,9,10,11.The main function of the fiber reinforcement is to improve the concrete crack formation and propagation, which is mostly related to an increased tensile strength and ductility of the material. Other basic material properties of fiber concrete, such as compressive strength or Young’s modulus, are only marginally influenced. In current practice, fibers used to improve the structural resistance of concrete are typically made of steel, where both the peak and residual tensile retention at various crack openings can be improved. This implies that tensile stresses and crack propagation are arrested by the fibers locally until (i) the fiber itself ruptures, (ii) the fiber is pulled-out from the concrete matrix, or (iii) the crack develops solely in the matrix between the distributed fibers. It is thus important to highlight that this overall response of SFRC is strongly influenced by the fiber dosage, but also by the fiber material and bond strength. The bond strength of the fiber depends, in turn, on its shape and end form and the matrix strength properties , and concrete splitting or side blow out of an adjacent free edge . Respectively, in shear, anchors may fail under steel rupture of the anchor , pry-out failure (due to generation of a fracture surface on the counter-loading direction as a consequence of levering response of the anchor rod), and concrete edge failure or breakout, particularly for anchorages close to a free edge of the concrete. A combination of the above failure modes is also possible. For a detailed description of the failure modes, see . The ultk = To estimate the mean capacity of a single headed anchor in plain uncracked concrete without edge influence, the well-established Concrete Capacity Design (CCD) method according to 18 can be used, as expressed in Equation (1), where n et al.  estimaten et al.  proposes3. The mean concrete cylinder compressive strength . Cattaneo et al. [3, respectively. The tests indicated an increase in concrete edge failure resistance under shear of up to 98%, and a mild to negligible increase in tensile and inclined tests. The same research group in [efh of 50, 75, and 100 mm in concrete with cf of 30, 75, and 90 MPa, without fibers and with steel hooked-ended fiber dosages of 50 and 70 kg/m3. The fibers had an L/D of 30/0.38 mm of unreported strength (but presumably >3000 MPa). Tests in SFRC with smaller embedment showed an increase in cone breakout resistance in the range of 10 to 20%, while a transition to steel and pull-out failure of the anchor also indicated a relatively higher (non-governing) concrete cone failure load for fiber concrete. Nilforoush et al. [efh = 220 mm in two concrete batches with strengths in the range from 40 to 80 MPa, including hooked-end fibers with L/D of 60/0.92 (of unreported strength) and a dosage of 80 kg/m3. All tests led to concrete cone failure, while some tests without fibers also exhibited splitting, and tests with fibers exhibited radial cracking. The tests showed an increase at failure load of 25% for normal and 40% for high strength concrete. Dengg et al. [efh between 40 and 70 mm, in special concrete mixes of compressive strength below 30 MPa with recycled, schist aggregate from tunnel excavation. The mixes included 30 kg/m3 of hooked-end steel fibers of L/D = 50/0.75 mm and material strength 1450 MPa with or without additional polypropylene fibers, yet this did not significantly influence the resistance against concrete cone failure. Hlavicka et al. [3). Delhomme et al. [efh = 40 mm failing with combined bond–pull-out failure in concrete with a special ultra-high-performance concrete with an fc > 165 MPa and a hybrid steel fiber dosage of 160 kg/m3, i.e., with L/D of 13/0.1 mm + 20/0.3 mm. Although the material strength is not specified, it is presumably > 2000 MPa. For concrete related failure nodes, the tests do indicate increased load capacity and a transition of failure modes from concrete cone to pull-out or steel rupture modes due to increased tensile strength of the concrete substrate. Schwenn et al. [efh = 40 mm in concrete with a 150 MPa strength using fibers of L/D = 6/0.2 mm and a 2800 MPa strength, at 150 kg/m3 dosage. A comparison of their concrete cone resistance, with the existing predictive equation as per 18, indicates an expected resistance increase in the range of 40 to 55%. Tóth et al. [3 hooked-end fibers with L/D of 35/0.75 and strength of 1200 MPa. The tests were carried out on M16 epoxy bonded threaded rods with τ = 35 MPa and efh = 70 mm, and they included tension on single and triple groups and shear tests toward a free edge (with edge distances of c1 = 60 and 85 mm). Concrete cone and concrete edge failure for tension and shear tests, respectively, were observed, with a definite increase in capacity compared to plain concrete. The improvement in the displacement behavior of the anchors that leads to an enhanced performance was highlighted. It was shown that a better re-distribution of anchor forces within an anchor group leads to an even higher group resistance than that of single anchors in a corresponding concrete mix. The ultimate tension load for single anchors was found to be increased by 50% for a 30 kg/m3 dosage, but only by 30% for a 50 kg/m3 dosage. This study also closely addressed the aspect of fiber orientation homogeneity, since the casting boundaries lead to a de-facto parallel alignment of the fibers close to the formwork and free surfaces of the specimen. In particular, this layer of non-homogeneous fiber orientation was proposed to be 1.7 times the fiber length. Ayoubi et al. [3, concluding with a clear increase in concrete breakout capacity (up to approx. 20%) and, consequently, also a transition from breakout in plain concrete to fastening steel failure in SFRC. Vita et al. [3, failing exclusively by cone breakout. The tests mainly focused on the influence of 0.3 mm cracks on the overall performance of the anchors, but from reference tests on uncracked concrete, it is seen that an approx. 12% increase in ultimate loads was observed for a dosage uptake from 40 to 80 kg/m3. Tests by Kocur et al. [3, respectively. Of the studies described above, only [In probably the first ever investigation on anchors in SFRC, Holschemacher et al.  reports u et al.  carried z et al. , which ty et al.  tested Mo et al.  carried group in  presentsg et al.  tested ve et al.  also pren et al.  presentsh et al.  defines i et al.  presentsr et al.  on M16 ave, only ,31,35 have, only  presentsve, only . Current3. The formula’s applicability is limited to anchors extending outside the non-homogeneous fiber orientation zone (1.7 times the fiber length) and for hooked-ended steel fibers with a dosage between 30 and 80 kg/m3. The applicability of the formula is extended by the same authors in [3 and for straight and corrugated steel fibers, with a minimum material strength of 1000 MPa and lengths between 35 and 60 mm, but always larger than three times the maximum aggregate diameter. Vita et al. [With respect to design and specification in concrete fastenings, currently, there is no coverage by product specification for use in SFRC, and this application finds its place either by use of project specific testing of anchors (design by testing) or by the simplifying assumption that fibers do not contribute to the strength of concrete breakout. Regarding design equations, Tóth et al.  based onthors in  for fibea et al.  for concTo date, product specifications and design standards do not cover fastenings in SFRC. However, as presented above, strong research interest is drawn to this topic. While various significant research efforts have focused on normal and high-performance concrete with different anchor types and fiber characteristics individually, an insight into the influence of fibers with different characteristics under otherwise comparable conditions is currently scarce. This article aims to extend the results from  in this 3). Both the tests and the concreting were carried out in the experimental hall of the TU Dortmund University (Institute for Building Research). As seen in For the concrete mix, CEM I 52.5 N Portland Cement and natural aggregates with a maximum size of 16 mm were used. The distribution for all concrete mixes was at 45, 20, and 25% for a sieve pass of 0/2, 2/8, and 8/16 mm, respectively. This composition is also in close agreement with the certification testing guide for mechanical anchors . The oveThe fibers used were of three main types of the product with the market name Dramix 3D 65/60BG, 4D 65/60BG and 5D 65/60BG, all by the same manufacturer, NV Bekaert SA, which are filaments of cold drawn wire with different hook-end shapes and material strength and deformability. Μain properties of the fibers used are shown in efh = 100 mm. The anchor head was formed by screwing the hex nut and stabilizing the washer on top of it by hot glue, creating a head bearing external diameter of 30 mm. The rod was taped along its remaining embedment to prevent inrush of concrete and bonding along the threads , as well as concrete cubes with a 150-mm dimension, were also obtained, and they are presented herein as part of efh (300 mm) from each other and the free edges, in order to allow for complete development of a possibly broader breakout body due to the fibers. The embedment depth and the minimum distances from free edges were in agreement with [The cube and anchor tests were performed 28 to 30 days after concreting of the respective specimen, while cored samples were tested within 4 weeks thereafter. The testing dates are also shown in ent with  to achieAdditional arrangements were required for the cracking of the concrete. Three PVC tubes were cast at each crack plane, perforating the concrete specimen, to host wedges applied to induce cracking. A trapezoidal metal sheet was added, crossing concentrically the location of the anchors. In addition, PVC tubes were used at crack intersections by rebars, to locally eliminate the reinforcement bond. The wedges were then hammered in place until the desired crack width was achieved in the entire length of the concrete specimen. Crack inducers assured that the cracks intersected concentrically with the anchors. The entire system was kept in place throughout the testing of the anchors to avoid the closure of the initial crack. During the testing, the crack might slightly increase only in the immediate area of the anchor, therefore, the crack was not measured continuously during testing.A drawing of the concrete specimen is given in efh from the anchor. In order to obtain the anchor displacement, two Linear Variable Displacement Transformers (LVDT) by Messotron GmbH & Co KG with market name WTH 20 l R/M, were placed at the pull-out fork adapter diametrically of the anchor in order to statistically process and reduce any displacement measurements errors. The load speed was set to 0.2 mm/min, and only after reaching 70% of the maximum load in the descending load-displacement branch, the speed would be increased to 1 mm/min. In general, the tension tests on single bonded anchors were carried out based on the recommendations given in , and thefc is the recorded cube compressive strength. The results of all the experiments in terms of ultimate loads are summarized in 3), but the dispersions in cracked concrete do not seem to follow a distinct pattern depending on any of the investigation parameters. However, a relatively high scatter of results, namely 10.9%, was observed for TS–5D–25–05–60. This may suggest that the test series in higher strength concrete with a 5D fiber dosage of 25 kg/m3 is associated with a deviation from the overall pattern of the tests, possibly due to a concrete batch quality issue, yet this is not substantiated by a closer review of the test procedure and the statistical interpretation of the results herein. Further, all test series have been subjected to the Grubb’s test and no outlier has been identified within each probe set of four tests. The coefficients of variation for the material tests were up to 11% 13% for cube and cylinder compression testing, respectively. It should be mentioned that the compressive strength of both types specimen is in the same order due to the influence from smaller dimensions of the cylinder discussed in [The coefficient of variation in all anchors tested in uncracked concrete remains below 10%, except for one test series (TS-5D-25-00-60), which exhibits a coefficient of variation of 13.3%. In the case of anchors in cracked concrete, the coefficient of variation is higher but still remains in reasonable margins. The highest coefficient of variation was 20.2% in the test series TS–4D–40–03–60 in cracked concrete. The highest dispersions in the tests for uncracked concrete (variation coefficients of 0.133 and 0.094) appeared for the lowest tested fiber dosages (25 kg/mussed in  and the ussed in ).3 still remain close to reference values. The results from the rebar reinforcement concrete also indicate a minor increase in the load bearing capacity of the anchors at a comparable increment, with that of 3D fibers at 25 kg/m3. Moreover, it is shown that the fiber type also strongly influences the performance of the anchors, since tests in concrete with 3D fibers almost consistently exhibit a lower normalized resistance to breakout as compared to concrete with the higher-performance 4D and 5D fibers. As seen, there is a substantial increase in the mean expected load by the inclusion of steel fiber reinforcement, reaching nearly 70% for TS–5D–80–00–60. The efficiency of 4D and 5D fibers as compared to 3D fiber reinforcement is also clearly evident for all cases, excluding TS–5D–25–00–60. At the same time, the contribution of fiber reinforcement to the anchor capacity is very similar for both types of 4D and 5D fibers.cr) of 0.3 and 0.5 mm are clustered to different reinforcement types and offset in the graph. Furthermore, the results of the rebar reinforcement configurations have not reached the desired crack width of 0.5 mm with the wedge system used in the tests. Instead, the crack width in this case only ranged between 0.015 mm and 0.15 mm. By comparison of the SFRC values with the reference strength, it becomes evident that the crack width and the fiber type pose a certain influence on the performance of anchors in cracked concrete. As with uncracked concrete, the results for 3D fibers lead to a minor increase to the performance of the anchors. In SFRC, wider cracks lead to lower anchor failure loads. However, the values in cracked SFRC remain, in their majority, higher than in cracked unreinforced concrete. The results from the rebar reinforced concrete have a very different behavior in relation with the crack width. As seen, the anchor performance immediately reduces even for very small crack widths (0.015 mm) and reaches that of the reference tests.cr, with wcr being the crack width, which can describe the mean load reduction with respect to the crack width for the results presented herein. In this case, a decisive influence of the fiber type is not present. For the rebar reinforced concrete, the reduction in the load bearing capacity of the anchors is approximately 30%, regardless of the crack width. It is also shown that anchors with surface rebar reinforcement do not follow the reduction pattern of the anchors on SFRC. 3 of 3D fiber reinforcement (b) are exemplarily presented. The overall influence of the fiber reinforcement on the performance of single anchors can be discerned. The results here are not normalized since all curves in each graph come from the same concrete specimen. The cube compressive strength is almost equal for the unreinforced specimen and the fiber reinforced specimen, with 33.5 MPa and 33.2 MPa, respectively. In the upper graph, the results of both uncracked and cracked with 0.5 mm crack are overlaid and, in the lower graph, this is the case for results of uncracked concrete and crack widths of 0.3 mm and 0.5 mm. Comparing the two figures, it can be seen that fiber reinforcement increased the load bearing capacity and the ductility of the anchors. The initial stiffness of the system is in the same order of magnitude for all anchors, although it gradually decreases with crack opening. Particularly for the fiber reinforced specimens, the load displacement development remains consistently in the linear elastic region for at least 70% of the peak load, whereas unreinforced elements exhibit instabilities earlier on in the load progression. All unreinforced specimens fail at a displacement in the spectrum of 2.0–4.0 mm, but a large number of tests in fiber reinforced specimens exceed this range and, in some cases, reach displacements of 6.0 mm. By observing the load displacement curves, it is evident that the nonlinear behavior of the anchors for cracked and uncracked concrete initiates in the domain of 60 to 65% of the peak load. Finally, the fiber reinforced concrete probes show a slightly higher ductility (area below the load-displacement curve) compared to the unreinforced probes, while in some fiber reinforced probes, a firmly ductile behavior is observed through several cases of nearly flat post-peak load retention. In cf = 61.3 MPa. In 3 of 5D fibers, i.e., the configuration with the highest fiber content, and the cube concrete compressive strength is in 53.1 MPa. As shown in the upper graph, the surface reinforcement has increased the ductility significantly in both cracked and uncracked concrete, through activation of the compressive struts in concrete and tensile force retention in the reinforcement, which restrained the development of the concrete breakout body. For the same reason, the aimed crack width was not achieved in the rebar reinforced configuration, and the crack ranged between just 0.015 mm and 0.15 mm instead. However, the resulting load displacement curves barely indicate a difference in ultimate load or ductility, depending on the crack widths. On the other side, it is evident in the bottom graph that the use of 5D fibers with the same total material weight as the rebar have increased the load bearing capacity remarkably and with a certain ductility. The initial stiffness of the anchors in rebar reinforced concrete decreases with crack opening, similarly to unreinforced concrete, as discussed in the previous paragraph, but this is not the case for the 5D fiber reinforced concrete, where a clear distinction of initial anchor stiffness subject to crack opening cannot be identified. Furthermore, the elastic region of the load displacement curve in the concrete with 5D fibers is maintained for a load level of up to 50% of the peak load, which is proportionally smaller as compared to the 3D fiber specimen presented above. Finally, the fiber reinforced concrete probes show some ductility (area below the load-displacement curve) compared to the unreinforced probes, while in some fiber reinforced probes a firmly ductile behavior is observed through a nearly horizontal post-peak load-displacement retention. 3 and goes up to approximately 70% for 5D fibers at a dosage of 80 kg/m3, with variation coefficients in a commonplace order of magnitude for concrete related failure modes of fastenings. Additionally, 4D and 5D fibers provide a similar rate of increase. While 3D fibers can still contribute to the concrete breakout capacity, it is to a lesser degree for otherwise the same fiber dosage and concrete strength. Therefore, for the configurations tested applying the same anchor design approach for SFRC as for concrete without fibers is on the safe side.The addition of fibers clearly leads to increase in the load-bearing resistance at mean values. This increase begins with 10% for 3D fibers at a dosage of 25 kg/m3 and 40 kg/m3, respectively.The fiber dosage is shown to be a very influencing fiber-related characteristic for the fastening resistance, which agrees with most previous research investigations discussed in the introduction. The type of fibers used has also a very strong influence on the anchor load-bearing resistance. Comparing fibers with hooked-ends and the same length and diameter, but with different material strength and end-anchorage shape, the load increase by use of 3D fibers was in the range of 5 and 15%, while 4D and 5D fibers led to an overall resistance increase in the range of 10 and 40% for fiber dosages of 25 kg/mFiber reinforced concrete has indicated a beneficial behavior in cracked concrete. The load bearing capacity of anchors in cracked fiber reinforced concrete was higher than in unreinforced concrete. A relation of the fiber type and the anchor performance in cracked concrete is evident. The 3D fibers have the least influence, while 4D and 5D fiber have a similar effect. Considering solely the SFRC specimens tested herein, the mean load reduction of anchors in cracked SFRC in relation to the crack width can be described by an analogy to the crack width, which is in reasonable agreement with the few previous studies discussed in the introduction.3. There is no contribution of the rebar to the load capacity in cracked concrete, and there is no apparent correlation between the crack width and the load reduction. Nonetheless, in both cracked and uncracked concrete the ductility of the anchors has increased remarkably.The surface rebar reinforcement does not influence the load bearing capacity significantly. The resistance increment for a favorably arranged reinforcement presented herein is similar to that of 3D fibers with 25 kg/mBoth typical surface reinforcement and fiber reinforcement in concrete influence the ductility of single anchors. There is notable increase in the ductility of the anchors behavior in the case of concrete cone failure mode for both types of reinforcement. For the same overall steel reinforcement quantity, high performance fibers provide a significantly higher load bearing capacity over that of rebar reinforcement.3 advocates for an applicability limit at or close to this lower bound fiber dosage. The reduction multiplier of 0.7 for the prediction of the load capacity in concrete anchors located in a 0.3 mm crack, as proposed by [The adequacy of currently proposed design approaches in ,35,38 isThis study reveals new knowledge in regard to the performance of SFRC structures and, in particular, to the load-bearing performance of single anchors in uncracked and cracked SFRC. Although some studies have been presented in the past and a design proposal is being developed, previous research has not comparatively examined the influence of fibers with different performance characteristics, neither has it posed applications in SFRC in comparison with applications of equivalent rebar reinforcement. The experimental investigations presented herein cover cast-in place headed anchors with varying fiber types, dosages, concrete strengths, and crack widths. Deriving from these studies, the following conclusions can be drawn:


Background: The main objective of this study was to use citation networks to analyze the relationship between different publications on the impact of cytokines at an ocular level and their authors. Furthermore, the different research areas will be identified, and the most cited publications determined. Methods: A search was performed in the Web of Science (WoS) database using the following keywords: “cytokine”, “inflammatory”, and “eye disease” for the period from 1990 to October 2021. The Citation Network Explorer and the CiteSpace software were then used to analyze the different publications. Results: 3127 publications with 8955 citations generated on the web were found. The largest number of publications on this topic emerged in 2018 and the authors with the largest number of publications addressing this area of research were Peizeng Yang (1.4%), Aize Kijlstra (1.3%), and Stephen C. Pflugfelder (1.2%). Conclusions: the citation network has provided a comprehensive and objective analysis of the main studies on the influence of cytokines in ocular inflammatory diseases. Eye inflammation is a common clinical problem, encompassing all parts of the eye. Thanks to numerous studies conducted on both human and animal subjects, a more consistent view of the role played by cytokines in inflammatory eye disease has emerged. The presence of cytokines  in ocular tissue obtained from patients with intraocular inflammation (uveitis) has been confirmed. Likewise, cytokines have been shown to induce inflammation in experimental animal models following intraocular injection , and granulocyte macrophage-colony stimulating factor (GM-CSF)). Several features that are unique to the eye’s immunology, such as immunosuppression which is associated with anterior chamber-associated immune deviation (ACAID), could be the result of the effects of cytokines. Along this same line, common complications of ocular inflammation, including retinal (macular) edema, keratic precipitates, and neovascularization may be interceded by cytokines. By obtaining a full understanding of the role of cytokines in the development of inflammatory eye disease, it will be possible to lay the foundations for therapies that can revoke the effects of these significant mediators of the inflammatory response .Due to its extreme vascularity, the uvea, the middle layer of the eye, takes the brunt of most serious ocular inflammations. Uveitis comprises a complex group of diseases, which result from diverse etiologies and pathogenic mechanisms. Studies into this group of diseases have provided increasing insight into the role played by cells and biologically active molecules in the immunopathogenesis of these diseases. Uveitis is one of the leading causes of visual impairment and blindness in most countries. However, uveitis remains an idiopathic disease in most cases despite extensive investigation . RecentlTears also play an essential role in maintaining corneal and conjunctival integrity. They provide a tightly regulated, optimal extracellular environment, which proves critical to its numerous functions, including anti-microbial defense, wound healing, and inflammatory responses such as allergies. Elevated levels of inflammatory cytokines have also been reported in tears from various ocular disease states .Ocular allergy and dry eye diseases (DED) are two common, relevant, symptomatic, and not mutually exclusive conditions that affect the ocular surface. These two conditions share certain clinical and biochemical features. Recent advances in our understanding of the pathogenesis of ocular allergy and DED have made it possible to identify several pathways of interaction between these two conditions. A growing body of evidence supports the role of ocular allergy as a risk factor for DED. Ocular allergy, particularly severe forms of keratoconjunctivitis, can have an impact on different key mechanisms of the DED vicious cycle, including tear film instability, ocular surface inflammation, cytokines secretion, and neurosensory abnormalities .By using citation network analysis, it is possible to search for scientific literature on a specific subject. This means that a single publication can provide links to additional and relevant publications, and through the creation of groups, it is also possible to prove, both qualitatively and quantitatively, the relationship that exists between the articles and authors . FurtherConsidering the increasing number of publications that address cytokines, and the role they play in the development of different inflammatory eye diseases, this study aimed to determine the different fields of research, as well as to identify which was the most cited publication. In addition, the relationships between both the different publications and the research group were analyzed using CitNetExplorer software 1.0.0 , Leiden University, Leiden, The Netherlands). The main purpose of this software is to analyze how scientific literature is developed within a research field.The WoS database was used to search for the different publications, once the following keywords: “cytokine”, “inflammatory”, and “eye disease” had been established. These specific keywords were chosen as they were in line with the main study objectives, and they are also the most used words across all the fields of research.Given that there were common articles amongst the results obtained, the Boolean operators NOT and AND, and the “*” characters were used to search for the singular and plural forms of the words. As a result, the words used in the first search were (“cytokine*” AND “inflammat*” AND “ocular” AND “disease*”), the words used in the second search were (“cytokine*” AND “inflammat*” AND “eye” AND “disease*” NOT “ocular”), and the words used in the third search were (“cytokine*” AND “inflammat*” AND “eye*” AND “pathology*” NOT “ocular” NOT “disease*”). The search covered the period from 1990 to October 2021.While conducting bibliographic searches, whether directly in external databases or in library catalogs, the WoS offers the possibility for these references to be added to the researcher’s library.With regards to the citation index, the following tools were used in this study: the Social Sciences Citation Index, the Science Citation Index Expanded, and the Emerging Sources Citation Index.On the other hand, given that authors and organizations use different citation methods, the data was standardized using the CiteSpace software 1.0.0 ). The data was searched and downloaded on the 10th of October 2021.The publications were first analyzed using the Citation Network Explorer software 1.0.0 ). This software is used to analyze and visualize the citation networks of scientific publications. Citation networks can be downloaded directly from the WoS, and it is also possible to manage different citation networks containing thousands of inter-related publications and citations. As a result, researchers can use a citation network that contains thousands of publications as the basis for their study, before moving on to focus only on the most relevant ones. By doing so, they can create a small subnetwork of 100 publications, which all cover the same topic.By using citation score metrics, it was possible to conduct a quantitative analysis of the most commonly cited publications within a specific time interval. This allowed for the quantification of both internal connections that exist within the WoS database and external connections, in which other databases were considered .The CitNetExplorer software 1.0.0 ), is comprised of several techniques used to analyze the different citation networks. The following formula, which was developed by Van Eck in 2012, was used to achieve the clustering function .Vc1 ,…,The clustering function is used to assign each publication to a group, so the most inter-related publications tended to be found in the same group based on the citation networks .Finally, the identifying core publication’s function was used to analyze the main publications. This function is used to identify the publications considered as the core of a citation network (publications with a minimum number of connections with other core publications). This makes it possible for irrelevant publications to be eliminated. The number of connections is established by the researchers, which means that the higher the value of this parameter, the lower the number of core publications . In thisAdditionally, the drilling down function was also used given that it allows for a deeper analysis of each group at different levels.Furthermore, the CiteSpace software 5.6.R2  was used to perform scientometric analysis. In the scientometric analysis process, certain parameter indicators were also used to carry out a specific assessment: The H-Index , the degree (number of connections), the centrality (importance of nodes within a research collaboration network), and the half-life (continuity of an investigation from a time perspective) ,12,13.The first articles on the influence of cytokines at the ocular level were published in 1990; therefore, the selected search period was from 1990 to October 2021. Following the WoS search, 3127 publications were found according to title, abstract, and keywords, as well as 8955 citation networks.As shown in Of all publications, 87.2% of them were articles, 11.7% were reviews, and 2.9% were proceedings papers.With regard to the language of the publications, 98.5% were in English, 0.6% were in French, and 0.5% were in German. As shown in Research on this topic is multidisciplinary. However, the fields of ophthalmology (37.2%) and immunology (11.1%)  are partAs shown in Among the institutions with the highest number of publications  were NorOn the other hand, the most used keywords were “inflammation” (127 publications), “cytokine” (125 publications), and “dry eye disease” (118 publications). The most cited publication was the article written by Liddelow et al. , which wWithin the 20 most cited articles, 15 of them discussed the relevance of the cytokines in the tear fluid of patients with dry eye disease. In turn, two of them attempted to identify the presence of cytokines in ocular allergies , and thrThe clustering function was used to assign each publication into a group, so publications that were close to each other within the citation network were in the same group. This means that each group was comprised of strongly linked publications in terms of their citation connections. As such, it was possible to interpret that each group represents a specific topic within the scientific literature. To distinguish between the groups, each group was assigned a different color and the connections between the groups are shown using colored lines.Nine groups were identified in this analysis, five of them containing a significant number of publications. The four remaining groups only represented 3.4% of all the publications on cytokines and ocular inflammatory diseases.In Group 1, 765 publications and 3758 citations were found throughout the whole network. The most cited publication was the article by Solomon et al. , which wThe articles in this group addressed the relevance of cytokines in the tear fluid of patients suffering from dry eye .Nature Medicine in 2007. In this study, the authors showed the participation of T helper type 17 cells (TH17) in uveitis and scleritis. In addition, they provided validation of a uveitis model, experimental autoimmune uveoretinitis (EUA). Thus, the authors concluded that TH1 cells can reduce uveitis by antagonizing the TH17 phenotype through the induction of interleukin IL-27 mediated by IFN-γ in the target tissue. On the other hand, interleukin IL-2 favors the expansion of TH17, which helps to explain the efficacy of IL-2R antibody therapy in uveitis. Likewise, it suggests that the antagonism of TH17 by IFN-γ and/or IL-27 could be used for the treatment of chronic inflammation.In Group 2, 611 publications and 1829 citations were found across the whole network. The most cited publication was the article by Amadi-Obi et al. , which wTherefore, the articles in this group analyzed the presence of cytokines and chemokines in uveitis .Progress in Retinal and Eye Research in 2009. This study showed how para-inflammation is also present in aging retinas and can contribute to age-related retinal pathologies. Thus, at the retinal/choroidal interface, the activation of complement activity in Bruch’s membrane, retinal pigment epithelial cells, and the accumulation of microglia in the subretinal space show para-inflammation. With age, para-inflammatory changes were also observed in the choroidal tissue, evidenced by an increase in the thickness of the choroid, a greater number of CD45 + CRIg + macrophages, morphological abnormalities in choroidal melanocytes, and fibrosis in the choroidal tissue.In Group 3, 534 publications and 1252 citations were found across the whole network. The most cited publication was the article by Xu et al. , which wThe publications in this group aimed to analyze intraocular cytokine levels and the prevalence of intraocular antiretinal antibodies in patients with retinitis pigmentosa, age-related macular degeneration, uveitis, glaucoma, and cataracts, before going on to correlate the results with the clinical manifestations .Progress in Retinal and Eye Research in 2004. In this study, it was demonstrated that, in pseudomonas aeruginosa, the sustained production of IFN gamma driven by IL-12 in dominant Th1-sensitive strains, such as C57BL/6 (B6), contributed to the destruction and perforation of the cornea, while IL-18 driven IFN gamma production in the absence of IL-12 was associated with bacterial death and less corneal destruction in Th2-responsive dominant strains, such as BALB/c.In Group 4, 254 publications and 751 citations were found across the whole network. The most cited publication was the article by Hazlett et al. , which wThe articles in this group analyzed the role of cytokines in anterior segment pathologies .CellBiology and Metabolism in 1996. In this study, the authors demonstrated that leukoregulin, a 50 kDa product of activated T lymphocytes, dramatically increased PGE2 synthesis in cultured human orbital fibroblasts and increased PGHS-2 expression in dermal fibroblasts. Orbital and dermal fibroblasts expressed high levels of mRNA and protein of PGHS-1, the other abundant form of cyclooxygenase. On the other hand, unlike the expression of PGHS-2, leukoregulin did not alter the levels of PGHS-1 in orbital or dermal fibroblasts, suggesting that PGHS-1 does not participate in cytokine-dependent prostanoid production in human fibroblasts. These findings clarified the relevant pathogenetic mechanism for the intense inflammation associated with Graves’ ophthalmopathy.In Group 5, 124 publications and 353 citations were found across the whole network. The most cited publication was the article by Wang et al. [Therefore, the articles in this group analyzed the influence of cytokines and chemokines in Graves’ disease .A total of 1299 publications with four or more citations were found, and the citation network was 6732, representing 40.4% . TherefoBibliometric studies are quantitative analysis methods. They use mathematical and statistical tools to measure the interrelationships and impacts of publications within a specific area of research. These methods allow an overview of large amounts of academic literature and can be used to identify influential studies, authors, journals, organizations, and countries over time. Moreover, through citation network analysis, the different research areas can be identified more intuitively using mapping social networks that include co-word, co-authorship, and co-citation analysis. It also allows examining the relationships between research groups, institutions, and even countries. In general, the citation network analysis provides a clear diagram of the most cited publications in a research area . The anaThe main databases, such as Scopus or WoS, allow citation networks to be created. However, their use is limited when conducting a systematic review of all the existing literature on a subject, given that they do not provide a general overview of the existing connections between the citations of a group and their publications. For this reason, CitNetExplorer software 1.0.0 ) and CiteSpace software 5.6.R2  were used to visualize, analyze, and explore the citation networks of scientific publications, as they provide a more in-depth analysis than databases such as WoS or Scopus when creating citation networks .The main objective of this study was to analyze the existing literature about the influence that cytokines have on inflammatory eye diseases. To do so the WoS database was used. With a search range dating back to 1900, it is one of the most extensive databases. Nonetheless, it should be noted that the WoS only accepts international journals that have passed a scrupulous selection process.Therefore, once the existing bibliography had been downloaded from the WoS, it was possible to use the CitNetExplorer software 1.0.0 ) and CiteSpace software 5.6.R2  to collect and analyze all the available literature on the impact of cytokines on ocular disease. By performing citation network analysis, it was also possible to assess the links between the fields of study and the different research groups, using the clustering function. This function allows for publications to be grouped according to the connections that exist between the citations. The drilling down function was also used to conduct a more in-depth analysis of each group’s bibliography. The core publication’s function identifies the main publications, that is to say, those with a minimum number of citations (more than 4 citations). Therefore, by using these functions, it was possible to completely analyze and study the research that has been done on the specific field of research. The methodology was based on previous citation network studies that have been conducted recently in other fields of study ,40,41,42One of the first publications on cytokines in eye diseases was published by Rosenbaum et al.  in 1991.The countries with the highest number of publications were the United States, China, and Japan. This may be related to the fact that fungal keratitis is one of the main causes of cough in the United States and industrialized countries. For this reason, countries with a higher income and therefore better infrastructures are currently working on this research topic, resulting in a higher number of publications. Similarly, the upward trend in the number of publications from countries such as the United States or Great Britain has been linked to a range of factors, for example, the fact that these are English-speaking countries and the possible affiliations that may exist between the different research groups within the scientific community ,47. In tAt the same time, and according to other bibliometric studies, Harvard University was among the institutions with the most publications. This once again confirmed the importance of this research field in the United States.However, in our study, Enriquez de Salamanca, the author with the highest number of publications, is Spanish, emphasizing the importance of highlighting the increased interest in this field of research by Spanish researchers, often working in collaboration with researchers from other countries.Investigative Ophthalmology & Visual Science stood out. This journal ranked tenth in the ophthalmology category with an impact factor of 3.47. This was because this open access journal had the highest number of citations and publications in the field of ophthalmology in recent years. In addition, the journal with the highest impact factor was Frontiers in Immunology, 7.56. However, it is worth considering that although the impact factor is a critical index of a journal’s importance, it is not an absolute measure index. The main difference between these indices is that the latter is based on the impact of the research results, in addition to the intellectual and physical contributions made by the authors [Regarding journals with a high number of publications,  authors .Regarding the years, despite the significant increase in the number of publications in recent years, the publications with the greatest impact and with the highest number of citations were published before 2010. Among the top 20 publications, the one published by Wang et al.  showed tOne of the most relevant studies was that carried out by Solomon et al., in which the authors investigated the pro- and anti-inflammatory forms of interleukin-1 in the tear fluid and conjunctiva of patients with dry eye disease. They demonstrated that the conjunctival epithelium appeared to be one source of the increased concentration of IL-1 in the tear fluid of patients with dry eye disease and that IL-1 played a key role in the pathogenesis of keratoconjunctivitis sicca. It is important to note that two subsequent articles by Massingale et al.  and by ERegarding the influence of cytokines on ocular allergies, one of the reference studies was published by Cook et al. in 2001 . The autCytokine [Another relevant study was published by Wakefield et al. in 1992 in Clinical Endocrinology [Finally, the last group, Group 5 of our citation network, analyzed the influence of cytokines and chemokines in Graves’ disease. The article by Metcalfe et al. published in rinology  in 1994,In conclusion, this study offers a comprehensive and objective analysis of the main papers on the influence of cytokines on inflammatory eye diseases. In this study, five main groups were found on the influence of cytokines on inflammatory eye diseases . Cytokines in tears was the most researched topic. Furthermore, by using the WoS database and the Citation Network Explorer software 1.0.0 ), it was possible to visualize, analyze, and explore the most cited articles and citation networks that exist to date.There has been a growing number of citation network studies because it is the only method of analysis that provides a global overview of the different fields of study on a specific topic. Moreover, the CitNetExplorer software 1.0.0 ) makes analyzing all studies on a topic possible, allowing for more detailed research to be conducted. This might change how research is conducted in different fields of study.


Promoting evidence-based antibiotic prescribing through successful antimicrobial stewardship (AMS) programmes is critical to preserving the effectiveness of antibiotics for common infections in primary care. This requires a coordinated multidisciplinary effort. Such pharmacist–prescriber partnerships have been effective in high-income countries (HICs). Yet, evidence generated in such countries is not always applicable because of different social determinants of health.A multidisciplinary workshop was conducted with pharmacists and clinicians  on community-based antibiotic stewardship, the purpose of which was to explore how and where such partnerships might work in publicly funded primary care clinics in the greater Cape Metro region.Participants perceived that promoting effective AMS was a priority for South African primary healthcare. However, it was clear that there are many hurdles to overcome working in settings that are relatively resource-poor. Prescribing guidelines needed to be harmonised. Participants felt that staff training on the principles of AMS should be mandatory. Research was urgently needed to better understand their community’s understanding of antibiotic use and AMS, and to champion outreach projects in the community.Important stakeholder perspectives in the community were highlighted to promote a multidisciplinary approach to AMS initiatives in primary care. These will need to be addressed to optimise antibiotic prescribing in the community. Overprescribing and inappropriate prescribing of antibiotics are the principal modifiable drivers of antibiotic resistance.4 and practical steps to address the governance framework needed at each level of the health system.5 This will become increasingly important in the transition to the country’s anticipated National Health Insurance (NHI) where pharmacists are likely to expand their role for primary healthcare services to increase access.6South Africa has shown much progress with major shifts in policy towards combatting antibiotic resistance. The country has a blueprint for the steps to be taken by healthcare practitioners and others to enact antibiotic stewardship at all levels of healthcare7Pharmacists and clinicians are being increasingly engaged in antibiotic stewardship partnerships to improve clinicians’ antibiotic prescribing. Antibiotic stewardship programmes aim to promote evidence-based antibiotic prescribing and typically involve educational programmes, the implementation of evidence-based guidelines, and audit and feedback for prescribers.8 In primary care, a recent review showed that such partnerships can be effective in decreasing the antibiotic prescribing rate  and increasing guideline-adherent antibiotic prescribing .9 Included studies, however, were all conducted in high-income countries (HICs). None were conducted in Africa. Yet, evidence generated in HICs is not always applicable because of differences in the social determinants of health.10Although the ‘practitioner–pharmacist’ collaboration model exists, this is more commonly found in hospitals than in community-based primary care. In hospitals, pharmacists play an active role in improving the appropriateness of antibiotic prescribing practice through the provision of expert advice, education and training, liaison with regards to formulary, the provision of resistance data, raising awareness of guideline adherence and policy-guided antibiotic prescribing.We therefore set out to explore the feasibility of a pharmacist–prescriber network in publicly funded primary care facilities to optimise antibiotic prescribing by frontline clinicians. We specifically wanted to know how and where such pharmacist–prescriber interventions might work in primary care clinics in the greater Cape Metro region and to identify the opportunities and barriers of good stewardship at primary care facilities in the region.We advertised and ran a local AMS workshop, held in October 2019 in Bellville, Cape Town. We invited any practising frontline pharmacists, nurses involved in prescribing, and doctors working in Community Health Centres (CHCs) or Community Day Centres (CDCs). Health professionals working solely in hospitals were excluded. We did not pre-specify a participant’s level of seniority or experience, but rather took an inclusive ‘bottom-up’ approach, focussing on a participant’s unique perspective on prescribing at their CHC or CDC, and their potential to contribute meaningfully to the workshop.Participants were divided into smaller groups to facilitate a balanced discussion of four topics see  and thenBOX 1Group workshop questions on community antimicrobial stewardship.What stewardship strategies can be implemented at primary care facilities? Give examples.What are the barriers of stewardship at primary care level and how can they be overcome?What are the enablers of stewardship in primary care facilities?What social  and behavioural aspects should be addressed to advance stewardship?Source: Reproduced and adapted with permission from Professor Philip Howard, British Society for Antimicrobial Chemotherapy.We confirm that ethical clearance was not needed/required for this study.Thirty-three participants contributed to the workshop  see . ParticiThe participants valued the use of readily available local and national prescribing guidelines. However, they pointed out that there were often conflicting prescribing regimens. Local communication circulars were often at odds with guidelines and some clinics were using guidelines that had been superseded. There were also concerns raised that private pharmacists at the community pharmacy level were often overlooked in current AMS initiatives yet have an important role to play.Although a timely audit and feedback were important, participants thought that time constraints, poor record-keeping and inadequate dissemination to the entire team made them question the value of prescribing audits. Participants perceived that the attitudes of patients towards prudent antibiotic use was at times unhelpful. This was compounded by inadequate time to discuss a non-antibiotic strategy, provide relevant health promotion (e.g. hand hygiene) or safety-netting of antibiotic use. Participants acknowledged that strong local leadership and good clinical governance were key. They suggested that all patient-facing clinic staff in the community should be required to have standard training in AMS.Participants wanted all clinic staff to show a unified front in applying an evidence-based approach to antibiotic prescribing and build patient trust in healthcare facilities. Thus, research was urgently needed to better understand their community’s understanding of antibiotic use and AMS. They felt that community healthcare workers might be best placed to champion AMS outreach projects. They also wanted additional initiatives on how best to engage patients about antibiotic use through relevant promotional media and health campaigns tailored to the local community.This workshop provided critical perspectives from stakeholders in publicly funded healthcare facilities to promote a multidisciplinary approach to AMS initiatives in primary care. We found that despite the enormous hurdles to overcome in the public health sector, there was an awareness and collaborative spirit to make AMS a priority.www.fidssa.co.za/SAASP/Edu_Material). This should also be extended to those health professionals still in training and private community pharmacies.Clinically, our findings support the need for clinics to ensure that the latest prescribing guidelines are being used and to communicate this to all staff – for example, setting up a suitable information-sharing platform (work WhatsApp group). All staff need to demonstrate their competencies in AMS by completing freely available AMS training modules (e.g. For policymakers, local and national prescribing guidelines need to be congruent with each other. They should also consider developing guidelines for common infection syndromes where antibiotics might not provide any additional benefit. Engaging patients in the discussion about antibiotic use, its harms and benefits for common infection syndromes and so forth needs to be incorporated into future health campaigns, bringing relevant information to the local community. Patients should receive clear information, ideally reinforced with leaflets or text messages, about the likely duration of symptoms, self-care, and the likely benefits and harms of antibiotics.Future research should focus on establishing studies to prospectively collect antibiotic prescribing data in primary care. This would require novel collaborations between pharmacists and prescribers to collaborate and collect prescribing data and link these to clinical indications. Currently, these data are retrospective and not linked to clinical indications. This is a major evidence gap but essential to describe the problems experienced about access to, and excess of, antibiotics for acute infection syndromes. Such descriptive studies are key to informing larger trials that can support the improved use of antibiotics.Our multidisciplinary workshop raised important stakeholder perspectives on potential AMS initiatives in primary care. Strategies that can optimise antibiotics can help to provide consistency in healthcare delivery, reduce inequality in healthcare provision, and ensure the continued effectiveness of antibiotics for common infections.