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This paper experimentally studied the shear behavior of corroded post-tensioned prestressed concrete beams with full grouting. The effects of insufficient grouting in shear span on the shear behavior were also investigated. Eight beams were fabricated and divided into two groups: four beams with full grouting and four beams with insufficient grouting. Three beams in each group were subjected to accelerated corrosion. All beams were tested to failure in four-point loading. Experimental data on shear cracking, load-deflection response, shear strength and failure modes were presented. Results showed that strand corrosion accelerated the formation and propagation of diagonal crack. Insufficient grouting decreased the number of diagonal cracks. Strand corrosion degraded the post-cracking stiffness and shear strength. Insufficient grouting aggravated the propagation of diagonal crack and the degradation of post-cracking stiffness. The shear strength of corroded beam with 31.7% corrosion loss decreased by 15.44% as compared to that of the uncorroded beam. Strand corrosion loss less than 31.7% did not change the shear compression failure mode in fully grouted beams. The failure modes of locally ungrouted beams changed from shear compression failure to rupture of wires as the corrosion loss exceeded 39.6%.

The results of an experimental and analytical study of the shear behavior of damaged or under-strength concrete beams strengthened with carbon fiber reinforced plastics (CFRP) grid and polymer cement mortar (PCM) shotcrete describes in this paper. The aim of this study is to evaluate shear performances of reinforced concrete beams retrofitted by using PCM shotcrete and CFRP grid. Four concrete beams reinforced internally with steel and externally with both PCM and CFRP grid (longitudinal direction used CR-10 and transversal direction used CR-6) applied to the specimens were tested under three-point bending. The shear failure is initiated by a major diagonal crack within the beam shear span. This diagonal crack extended horizontally at the level of the CFRP grid. Results show that PCM shotcrete with CFRP grid is very effective for shear strengthening. Increases in strength of 140% for PGB over the RCB as control, un-retrofitted beams were noted.

Purpose During service period, due to the overload or other non-load factors, diagonal cracks of the pre-stressed concrete beam are seriously affecting the safety of the bridge structure. The purpose of this paper is to quickly realize the shear bearing capacity and shear stiffness through maximum width of the diagonal cracks and make correct judgments. Design/methodology/approach Through the shear failure test of four test beams, collecting data of diagonal cracks and shear stiffness loss value. According to the deformation curve of the shear stiffness, and combined with the calculation formula of the maximum width of diagonal cracks, the formula for calculating the effective shear stiffness based on the maximum width of diagonal cracks is deduced, then the results are verified by test data. Data regression method is used to establish the effective shear stiffness loss ratio calculation formula, the maximum width of diagonal cracks used as a variable factor, and the accuracy of this formula is verified by comparing the shear failure test results of pre-stressed hollow plates. Findings With the increase in width of the diagonal crack, the loss rate of shear stiffness of the concrete beams is initially fast and then becomes slow. The calculation formulae for shear stiffness based on the maximum width of the diagonal cracks were deduced, and the feasibility and accuracy of the formulae were verified by analysis and calculation of shear test data. Originality/value A method for quickly determine the shear stiffness loss of structures by using maximum width of the diagonal cracks is established, and using this method, engineers can quickly determine effective shear stiffness loss ratio, without complex calculations. So this method not only ensures the safety of human life, but also saves money.

Shear strength is a widely investigated parameter for reinforced concrete structures. The corrosion of reinforcement results in shear strength reduction. Corrosion has become one of the main deterioration factors in reinforced concrete beam. This paper proposes a shear strength model for beams with inclined bars based on a limit equilibrium method. The proposed model can be applied to both corroded and uncorroded reinforced concrete beams. Besides the tensile strength of longitudinal steel bars, the shear capacity provided by the concrete on the top of the diagonal crack, the tensile force of the shear steel at the diagonal crack, the degradation of the cross-sectional area and strength of the reinforcements induced by corrosion are all considered. An experimental work on two groups accelerated corroded beams was performed. Good agreements were found between the proposed theoretical predictions and experimental observations.

The objective of this paper is to study the shear behavior of reinforced concrete (RC) beams cast with lava light weight aggregate (LWA). Six shear deficient beams were designed, constructed and cast with Normal weight concrete (NWC) and lightweight concrete (LWC). All the normal weight concrete (NWC) and light weight concrete (LWC) beam specimens were tested under one point loading, however LWC specimens were tested after 28 and 56 days. Load versus mid-span deflection response along with the failure modes was recorded until the failure of the specimens. The experimental results shows that all beam failed due diagonal crack and the specimens tested at 56 days achieved comparable shear strength to that of NWC beams. In-addition, the shear strength reduction factor was in the range of 0.78-0.94.

The test results on eight two-span deep beams made of self-compacting concrete (SCC) are presented and discussed in this paper. The main parameters investigated were the shear span-to-depth ratio, and the amount and configuration of steel reinforcement. All beams failed due to a major diagonal crack formed between the applied mid-span load and the intermediate support separating the beam into two blocks: the first one rotated around the end support leaving the other block resting on the other two supports. Both concrete compressive strength and web reinforcement had a major effect in controlling the shear capacity of the beams tested. For the shear span-to-depth ratio considered, the vertical web reinforcement had more influence on the shear capacity of the specimens than the horizontal web reinforcement. The shear provisions of the ACI 318M-11 are unconservative for most of the beams tested. Comparisons of test results with the strut-and-tie model (STM) suggested by ACI 318M-11, EC2 and CSA23.4-04 showed that the predictions are reasonable for continuous deep beams made with low and medium compressive strength. Although the equation suggested by ACI 318M-11 is very simple, its prediction is more accurate than the STM suggested by different design codes.

An appraisal of crimped and hooked-end steel fibres as minimum shear reinforcement in reinforced concrete beams made with two concrete grades is presented. Beams conventionally detailed with minimum shear reinforcement were used as control specimens. The fibre reinforced beams also showed varying degrees of multiple cracking at peak loads. The shear strength of the fibre reinforced beams though lower than those of the conventionally detailed beams were higher than a lower bound value recommended in the literature as well as predictions from ACI 318. Effect of concrete grade on normalised shear strength was insignificant. Between the two deformed fibre types, depending upon the aspect ratio, the beams reinforced with the hooked-end fibres had up to 38% higher shear strengths than those containing the crimped fibres. The validity of the ACI 318 flexural performance criteria for deformed fibres proposed to be used as minimum shear reinforcement has been examined and a simple mechanics-based shear strength model for fibre reinforced concrete has been proposed. The proposed model together with seven shear strength models selected from the literature have been evaluated for their predictive efficacy.

In this study, an experimental study is performed to investigate the effects of section height ( h ), ratio of shear span to effective depth ( a / d ) and compressive strength of concrete ( f c ' ) parameters on diagonal cracking and crack width behavior of RC deep beams after making comprehensive literature research. Effect of shear reinforcement on this behavior is also investigated. Eleven different RC deep beam specimens with or without shear reinforcement are tested under a 3-point loading with a simple support condition. Firstly, the test results reveal that the load carrying capacity of the specimens increases with an increase in section height. Very minor increments in mid-displacements are determined as well. Small increments are experienced in crack widths as h increases. Secondly, an increase in the shear strength of the tested members is obtained as a / d decreases. A small decrease in displacement values is observed with a brittle behavior as well. Moreover, diagonal crack widths increase along with an increment in a / d ratio. Thirdly, an increment of f ck makes a significant contribution to the shear strength of RC deep beams. However, it results in a decrease in maximum diagonal crack widths. Lastly, shear reinforcement makes a very significant contribution to shear strength due to confining struts.

Many researchers have performed experimental and theoretical studies on the shear behavior of steel fiber reinforced concrete (SFRC) beams with conventional reinforcement, few studies involve the shear behavior of SFRC beams with high-strength reinforcement. In this paper, the shear test of eleven beams with high-strength reinforcement was carried out, including eight SFRC beams and three reinforced concrete (RC) beams. The load-deflection curve, concrete strain, stirrup strain, diagonal crack width, failure mode and shear bearing capacity of the beams were investigated. The test results show that steel fiber increases the stiffness, ultimate load and failure deformation of the beams, but the increase effect of steel fiber decreases with the increase of stirrup ratio. After the diagonal crack appears, steel fiber reduces the concrete strains of the diagonal section, stirrup strains and diagonal crack width. In addition, steel fiber reduces crack height and increases crack number. Finally, the experimental values of the shear capacities were compared with the values calculated by CECS38:2004 and ACI544.4R, and the equation of shear capacity in CECS38:2004 was modified to effectively predict the shear capacities of SFRC beams with high-strength reinforcement.

The deflection of reinforced concrete (RC) beams with low span-effective depth ratios can be attributed equally to shear and flexural deformations. Although truss models can be used to evaluate shear deformation, their prediction accuracy is strongly dependent on how the diagonal crack angle is estimated. This paper presents the results from an experimental test of nine RC beams that failed in shear and had low span-effective depth ratios (i.e., a / h 0 3 ). It then proposes a multi-angle truss model for predicting ultimate shear deformation while considering the effect of the bending moment variation along the span on diagonal crack angles. An empirical formula is also presented to predict the shear stiffness degradation of RC beams up to the ultimate state through regression analyses. Numerical results show that the proposed multi-angle truss model can be used to predict the shear deformation of RC beams with low span-effective depth ratios with reasonable accuracy.

This research presents an experimental study related to the shear behavior of simply supported reinforced concrete beams reinforced with Glass Fiber Reinforced Polymer (GFRP) bars. Four concrete beams reinforced with GFRP bars and four control concrete beams reinforced with steel bars were tested until failure. In order to realize the occurrence of shear failure, all tested beams were designed with longitudinal reinforcement only and without shear reinforcement. The test variables used in this study were the concrete strength, f'c, and longitudinal reinforcement ratio, ρ. The crack patterns, location of the diagonal crack and angle of the diagonal crack were also observed during the test. The shear design equations obtained from the codes and references were used to evaluate the data obtained from the test. Finally, based on the data obtained from experimental and theoretical analysis, comments and recommendation on the shear strength equations were suggested.

In the paper, the method of a numerical simulation concerning diagonal crack propagation in concrete beams was presented. Two beams reinforced longitudinally but without shear reinforcement were considered during the Finite Element Method analysis. In particular, a nonlinear method was used to simulate the crack evaluation in the beams. The analysis was performed using the commercial program ANSYS. In the numerical simulation, the limit surface for concrete described by Willam and Warnke was applied to model the failure of concrete. To solve the FEM-system of equations, the Newton-Raphson method was used. As the results of FEM calculations, the trajectories of total stains and numerical images of smeared cracks were obtained for two analyzed beams: the slender beam S5 of leff = 1.8 m and the short beam S3k of leff = 1.1 m. The applied method allowed to generate both flexural vertical cracks and diagonal cracks in the shear regions. Some differences in the evaluation of crack patterns in the beams were observed. The greater number of flexural vertical cracks which penetrated deeper in the beam S5 caused the lower stiffness and the greater deformation in the beam S5 compared to the short beam S3k. Numerical results were compared with the experimental data from the early tests performed by Słowik [3]. The numerical simulation yielded very similar results as the experiments and it confirmed that the character of failure process altered according to the effective length of the member. The proposed numerical procedure was successfully verified and it can be suitable for numerical analyses of diagonal crack propagation in concrete beams.

To investigate the influence of shear span ratio for the shear behavior of reinforced concrete beam with HRBF500 high strength rebars as stirrups, an experiment was carried out, which included 8 simply supported beams with HRBF500 rebars as stirrups. Under concentrated loads, the crack, deflection, strain of rebars, bearing capacity and failure mode are observed under different shear span ratios. Some comparisons are made between test results and calculated outcome. It shows that the shear span ratio has very important influent on the shear behavior of reinforced concrete beam with HRBF500 high strength bars as stirrups. Formula in code for design of concrete structures can be used to calculate its shear capacity with enough safety.

The aim of the paper is to investigate the shear failure mechanism and shear capacity in longitudinally reinforced concrete beams without transverse reinforcement. It has been found that the shear span-to-depth ratio and a beam size are important parameters which significantly affect the failure mode in the investigated members. The “size effect”, which is described in professional literature as a decrease of shear strength with the increase of the members depth, is not evaluated sufficiently enough. The effective length-to-depth ratio which has been identified in this paper, also has a considerable influence on the contributions of the shear resistance mechanism and thus the ultimate shear capacity. In the paper it has been shown that members characterized by the same shear span-to depth ratio but different effective length-to-depth ratio can fail in a different way.

This study reports the findings of an experimental investigation into the behavior of an inclined shear plane in reinforced concrete, such as a diagonal crack in the web of a beam, strengthened with externally bonded carbon fiber–reinforced polymer (CFRP) fabric. A modified push-off test of novel geometry was developed for this study. This test generates a diagonal failure plane subject to combined shear and tension. Both unwrapped and wrapped tests were conducted, allowing the load sharing and load-displacement behavior of the reinforced concrete, and the reinforced concrete with externally bonded CFRP fabric, to be investigated. Fully wrapped and U-wrapped CFRP fabric configurations were tested. Results indicate that for the arrangement tested, concrete, steel, and CFRP contributions to resistance are not independent, and that effective anchorage lengths given in the United Kingdom and United States guidance for U-wrapped CFRP may not be adequate in some cases.

According to tests of 8 T concrete beams with HRB500 steel bars as stirrup, the shear behavior of beams was researched under uniform load, and the influencing factors of diagonal crack width were analyzed, such as the different concrete strength, stirrup spacing and the welded wire fabric. Experimental results show that concrete beams with HRB500 steel bars as stirrup show similar behavior to the beams with conventional stirrup, and the stirrups yield can be achieved which meets the requirement of shear behavior in structure. In addition, the welded wire fabric can be used as one of the new kinds of reinforcement to control diagonal crack width.

Experimental investigation and numerical simulation have been performed in order to analyze shear capacity and the character of diagonal crack propagation in concrete beams reinforced longitudinally but without transverse reinforcement. The early investigation showed that the shear failure mechanism varied significantly, particularly as a function of a shear span-to-depth ratio. In this paper the scale effect is discussed, as test results indicate a strong influence of the member size as well. In analyzed beams the static scheme, concrete grade and longitudinal reinforcement were the same, whereas the effective length l eff , varied from 0.8 to 1.8 m. Significant differences were observed in the character of cracking and failure process between short beams of l eff = 0.8 and 1.0 m and longer beams of l eff > 1.0 m. To analyze the scale effect on the failure process in the beams, numerical simulation has been performed. In particular, a fracture mechanics study has been used to simulate the crack evaluation in two beams of different length but of the same shear span-to-depth ratio. Numerical results were compared with the experimental data.

This paper deals with flexural concrete members reinforced longitudinally but without transverse reinforcement. The conducted experimental investigations have shown that beams without web reinforcement may fail without attaining their full flexural capacity and then shear governs their failure. In the paper, there are presented recent results of the author’s own experiments, which aimed at disclosing some aspects of the propagation of cracks in longitudinally reinforced concrete beams without stirrups. The experimental program has been designed to investigate the influence of the shear span-to-depth ratio on diagonal crack propagation and load carrying capacity of tested beams. The obtained test results were compared with numerical results made on the basis of Finite Element Method. In the performed numerical simulation the same longitudinally reinforced concrete beams as in the test were considered. During the numerical analysis, the special attention was paid on a tensile stress distribution and on changes of diagonal crack propagation in dependence of the shear span-to-depth ratio in calculated beams.

The resisting shear strengthening technology of existing reinforced concrete bridges as an important research topic in the field of old bridges, play an important significance to improve the mechanical properties of old bridges and reduce security incidents. Based on comparative test analysis on two basic beams and twelve reinforced concrete beams strengthened with external pre-stressed wire rope, the influence of the shear strengthening effect was studied systematically caused by the original beam design parameters and the spacing of wire rope, in the meantime the strengthening mechanism was analyzed. Research results showed that the shear capacity of the strengthened beams was improved, because the development of cracks was not only effectively limited, but also stirrup strain was reduced, and yield load was put off. Along with the increasing of the ratio of original beams longitudinal reinforcement and the ratio of stirrup ,and the concrete grade, as well as the decreasing of spacing of external wire rope, the stirrups strain were decreasing and the shear capacity of strengthened beams increased. With the spacing of external wire rope decreasing, the diagonal crack resistance of the strengthened beams increased. The research results can provide reference for the design and research on shear strengthening of bridges.

Based on cyclic loading experiment of nine beams in the two groups, the relationship among the average web stress, initial diagonal crack width and shear capacity of RC beams was studied. Experimental result shows that the decline of the shear strength of the RC beams due to cyclic loading can be characterized by the width of diagonal crack. Under the same load amplitude, the larger crack width is, the greater the decline of the bearing capacity is. Besides, under the same number of cycles, the greater the load amplitude is, the larger the crack width is, the greater the decline in the bearing capacity of beams is. In addition, according to the experimental phenomena and the shear compression failure mechanism of beam, a formula for shear capacity after cyclic loading is derived for engineering use.

Reinforced concrete with steel fibers (RSF) is one type of a hybrid structure that can improve the shear-load capacity of conventional reinforced concrete (RC) structures. This paper studies the synergetic effect of shear-reinforcing bars and steel fibers on the shear-resistance of RSF beams and columns, based on the shape and the distribution of diagonal cracks. A series of bending and lateral cyclic-loading tests were conducted to consider the effect of loading and support conditions on the shear-resistance mechanism. As a result, the optimum ratio of steel fibers to shear-reinforcing bars for the shear-load capacity is determined for the RSF linear members.

Twelve reinforced concrete continuous deep beams having web openings within interior shear spans were tested to failure. All beams tested had the same geometrical dimensions. The main variables investigated were the opening size and amount of inclined reinforcement around openings. An effective inclined reinforcement factor combining the influence of the opening size and amount of inclined reinforcement on the structural behavior of the beams tested is proposed. It was observed that the load distribution, diagonal crack width, and load capacity of beams tested were greatly dependent on the effective inclined reinforcement factor which ranged from 0 to 0.171 for the test specimens. The higher this factor, the smaller the diagonal crack width and its development rate. A higher load capacity also developed in beams having effective inclined reinforcement factor above 0.077 than in the corresponding solid deep beams. A numerical technique based on the upper bound analysis of the plasticity theory is proposed to evaluate the load capacity of continuous deep beams having openings within interior shear spans. Predictions obtained from the proposed formulas are in good agreement with test results.

The objective of this study is to experimentally and analytically estimate the influence of web openings in reinforced concrete deep beams. Thirty-two reinforced high-strength concrete deep beams with or without openings were tested under two-point top loading. Test variables included concrete strength, shear span-to-depth ratio, and the width and depth of the opening. Test results indicated that the strengths at diagonal crack and at peak were closely related to the angle of the inclined plane joining the support and the corner of the web opening. Also, the influence of concrete strength on the ultimate shear strength remarkably decreased in deep beams with openings rather than solid deep beams. From comparisons of predictions and test results, the equations proposed by Kong and Sharp, and Tan, Tong and Tang would be suitable for reinforced high-strength concrete deep beams with openings and θ 3 ≥ 3 0 ∘ .

Recently, Appendix A of ACI 318∼02 Code introduced the Strut-and-Tie Model(STM) procedure in shear design of deep flexural members. The STM procedure is widely used in the design of concrete regions where the distribution of longitudinal strains is significantly nonlinear, such as deep beams, beams with large openings, corbels, and dapped-end beams. Experimental study included five high-strength reinforced concrete deep beams with different detailing schemes for the horizontal and vertical reinforcement. The specimens were designed as simply supported beams subjected to concentrated loads on the top face and supported on the bottom face. At failure, all specimen exhibited primary diagonal crack running from the support region to the point load. Specimens which had mechanical anchorages(terminators) gives better representation of the load-carrying mechanism than the specimen had standard 90-degree anchorage at failure in deep flexural members. Based on the test results, shear design procedures contained in the ACI 318-99 Code, Appendix A of the ACI 318-02 Code, CSA A23.3-94 Code and CIRIA Guide-2 were evaluated. The Shear design of ACI 318-99 Code, Appendix A of the ACI 318-02 Code and CIRIA Guide-2 shown to be conservative predictions from 10% to 36% in the shear strength of the single-span deep beam which was tested. ACI 318-99 Code was the lowest standard deviation.

Thirteen reinforced concrete beams with square and rectangular sections were tested to investigate ultimate capacity under bi-axial shear loading and the ultimate bi-axial shear capacities of concrete and shear reinforcement are defined separately. The test results show that the ellipse formula underestimates bi-axial shear capacity of concrete and overestimates bi-axial shear capacity of shear reinforcement of specimens with rectangular section in which a model to calculate shear reinforcement capacity is formulated based on diagonal crack configuration. It is found that the estimations of bi-axial shear capacity of shear reinforcement of rectangular reinforced concrete beams give the values in the range of 0.88-1.27 of the tests.

An experimental study was performed to examine the effect of section depth on the strength and serviceability of reinforced concrete deep beams. Full-scale tests were conducted on simply supported beams with the following cross sections: 21 x 23 in. (533 x 584 mm), 21 x 42 in. (533 x 1067 mm), and 21 x 75 in. (533 x 1905 mm). Tests were performed on each section type at the following shear span-depth ratios (a/d): 1.2, 1.85, and 2.5. Diagonal cracking loads, diagonal crack widths, and shear at failure were recorded for each test. The strength results indicated that the shear capacity of a deep beam is governed by the strength of the nodal regions, which are not directly proportional to the member depth. When deep beams are designed with strut-and-tie models, the strength of the nodal regions are addressed explicitly and no depth effect on the shear capacity of the member is apparent.

The effect of loading path on the behavior of RC members is investigated. The shear capacity of RC members under coupled axial tension-shear is discussed. Three main effects of axial tension are (1) early yielding of main bar due to initial stress; (2) axial tensile stress accelerates the formation of diagonal crack and (3) pre-cracks caused by axial tension blunt the localization of diagonal cracks. The increase or decrease in shear capacity is possible depending on the relative effect of these three factors. JSCE design code seems to recognize only the first factor without explicit coverage of the second and the third ones. Comparative study of experimental results, JSCE and FEM predictions is conducted.

The shear failure of non-shear-reinforced concrete beams with normal shear span ratios is observed to be governed in general by the formation of a critical diagonal crack. Under the hypothesis that the cracking of concreteintroduces potential yield lines which may be more dangerous than the ones found by the usual plastic theory, a physical explanation is given for this phenomenon and a way to estimate the shear capacity of reinforced concrete beams, based on the theory of plasticity, is described. The theoretical calculations are shown to be in fairly good agreement with test results jrom a large number of experiments carried out by previous investigators.

This paper describes how four reinforced concrete T-beams were tested in order to study their behavior when strengthened for shear using near-surface mounted (NSM) bars. The objectives were to study the effects of the type of bars used (carbon fiber-reinforced polymer (CFRP) and conventional reinforcing steel) and the effects of the load level at which the bars are installed. It was observed that the CFRP bars bonded at zero load increased the shear capacity by up to 92%, while those bonded when the precracked beam was under load increased the capacity by 77%. For the steel bars, these values were 75% and 57%, respectively. The CFRP strengthened regions showed a slightly more favorable response than those strengthened with conventional steel bars. Strengthening provided an improved control of the diagonal crack width. In the beams with closer spacing of NSM bars, the increase in shear strength allowed the beam to fail after considerable flexural deformations.

This paper concerns the phenomenon of cracking in reinforced concrete elements subjected to combined torsion and shear. The theoretical model developed by Rahal and Collins is described in de tail. This model is the only one which is capable of predicting the full response (e.g.: steel and concrete strains, deformations, curvatures) rectangular reinforced concrete sections subjected to combined torsion and shear throughout their post cracking loading history. The assumptions of Modified Compression Field Theory are also described because the model of Rahal and Collins is based on this theory. It also contains a concept of the new method which is capable of determining the width of cracks in reinforced concrete elements subjected to combined torque moment and shear force. The method is based on the model suggested by Rahal and Collins.

Test results of eight reinforced concrete continuous deep beams are reported. The main parameters considered were shear span-to-depth ration, amount and type of web reinforcement, and amount of main longitudinal reinforcement. Vertical web reinforcement had more influence on shear capacity than horizontal web reinforcement. Failure is initiated by a major diagonal crack in the intermediate shear span between the edges of the load and intermediate support plates. Comparisons between test results and current codes of practice, namely the ACI Building Code (318-89) and CIRIA Guide 2, show little agreement.

The structural rehabilitation of reinforced concrete beams in shear was studied with particular attention paid to resin injection. Other shear-repair techniques that were examined include post-tensioning in shear, bar bonding, and stitching. Emphasis was placed on the influence of damage across the repair stage. A series of model beams, unreinforced in shear, were loaded in the laboratory until a major diagonal tension crack developed on both shear spans. Individual beams were unloaded to a set proportion of that load, repaired, and again loaded to failure. Scaled field-size beams were also tested. The repair strength achieved for resin-injected reinforced cocnrete beams was shown to be influenced by the condition of the major diagonal crack after initial damage. This conclusion was supported by surface-strain measurements, load-deflection data, and crack measurements.