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Laboratory tests of reinforced concrete beams without shear reinforcement have shown that the shear strength (in terms of average shear stress) decreases as the size (depth) of the member increases. This paper discusses the results of experimental research performed to test the hypothesis that the effective depth influences the shear strength of reinforced concrete flexural members that do not contain web reinforcement in the range of overall depth between 12 to 36 in. (610 to 900 mm) where ACI 318-08 does not require skin reinforcement. The results of tests on eight simply supported reinforced concrete beams without shear and skin reinforcement are described, discussed, and correlated herein. The longitudinal reinforcement ratio was approximately 1.25%. The target concrete compressive strength was 10, 000 psi (70 MPa). The beam width varied between 8 and 24 in. (203 and 610 mm). All of the beams were simply supported and monotonically loaded in increments at midspan up to destruction. The shear span-depth ratio was maintained at 3.0. Test results show a reduction in shear strength with increasing effective depth; however, significant differences in behavior were observed between the 12 in. (305 mm) specimens and the larger specimens in terms of the amount of flexural cracking, crack progression, load-displacement, and load-strain measurements despite holding other traditionally considered influential parameters constant. These differences suggest that the reduction in shear strength was influenced not only by a size effect but also by differences in behavior and mode of shear transfer at failure (beam action versus arch action). For the beams tested in this study, flexural crack spacing did not scale with beam size. The change in ACI 318-08 restricting isolated beams without minimum shear reinforcement to heights not greater than 10 in. (250 mm) is supported by the findings of this study.

Results from 16 tests of reinforced concrete columns subjected to different displacement histories are presented. It is concluded that the drift capacity of a reinforced concrete column depends not only on the properties of the column and the applied axial load, but also on the displacement history. A numerical model to calculate drift capacity as a function of displacement history is presented.

An evaluation of the collapse of a large portion of the Daikai subway station during the 1995 Kobe earthquake is presented based on results from nonlinear finite element analyses. The numerical studies focused on two main aspects: 1) evaluation of soil-structure interaction and drift demands imposed on the Daikai Subway Station, and 2) evaluation of the drift capacity of the reinforced concrete (RC) columns that collapsed during the Kobe earthquake. Results from this study indicate that the estimated drift and shear stress demands in the critical columns of the Daikai station— approximately 1.1% and 2.2 MPa, respectively—were sufficient to cause failure of the central RC columns of the Daikai station due to poor transverse reinforcement detailing combined with moderate axial load demands. On the other hand, the central RC columns of an adjacent running tunnel structure survived the earthquake motions with limited damage due to lower drift and shear stress demands (0.8% and 1.0 MPa, respectively), and the use of an enhanced transverse reinforcement detailing. The use of the Elwood-Moehle column collapse model led to the prediction of a reasonable range of drifts at which collapse was expected in the RC columns of the Daikai station.

This paper gives results from monotonic testing of 4 reinforced concrete deep beams. The behavior of the deep beams is described in terms of cracking patterns, load-versus-deflection response, failure mode, and strains in steel reinforcement and concrete. Despite different failure modes, failure loads and corresponding ultimate deflections were similar in all 4 specimens. Yielding of both longitudinal and transverse reinforcement occurred prior to failure. Based on the test results, the shear design procedures contained in the ACI 318-99 Code and Appendix A of the ACI 318-02 Code were evaluated. Both design procedures yielded conservative predictions of the shear strength of the single-span deep beams.

This paper summarizes the results from a research project that evaluated the durability of short-span bridges constructed with full-span prestressed concrete form panels in northern climates where deicing salt usage is extensive. A full-scale bridge specimen was constructed and subjected to 48 weeks of durability exposure cycling to determine the potential for delamination and assess the resistance to chloride-induced reinforcement corrosion. The exposure cycling greatly accelerated the penetration of chlorides, producing concentrations in the deck that exceeded those from bridges that had been in service for nearly 40 years. The results from this study showed that long-term composite behavior can be achieved in these structures by applying a raked finish to the top surface of the prestressed panels. Corrosion measurements revealed the need to modify the positive moment connections at interior piers to provide a more durable structure.

To evaluate the structural performance of concrete bridge decks and slabs with epoxy-coated reinforcement and subjected to repeated loading, investigators tested 34 slab specimens of two types of cross section with splices and transverse steel. Evaluations were performed by comparing the performance of specimens with uncoated bars to that of otherwise identical companion specimens with epoxy-coated bars under repeated loading and at ultimate load condition. Test variables included concrete compressive strength, bar size and deformation pattern, coating thickness, splice length, and applied stresses. During the repeated loading portion of the tests, specimens with epoxy-coated reinforcement had fewer but wider cracks than those with black reinforcement, while differences in deflections were not significant. Average bond stress ratios were 0.78 with #7 bars and 0.75 with #11 bars at failure. The strength results support the use of a single development length modification factor for beams with spliced epoxy-coated reinforcement.

This paper examines the performance of epoxy-coated stirrups in reinforced concrete beams under bending and shear. A review of previous studies in bond and detailing of stirrups is provided. The results of an experimental program are described. From these results, several conclusions are reached, supported by ultimate failure load, deflection, stirrup strain, crack pattern, and crack width data. All beams reinforced with epoxy-coated stirrups and those with uncoated stirrups failed at higher than calculated shear capacities from those in American Concrete Institute (ACI) 318-89 and the proposed American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) 1993 Bridge Specifications.

Twenty three beams with splices placed in a constant moment region were subjected to repeated loading and then tested to failure to compare the service and ultimate load behavior of beams with coated and uncoated reinforcement. The repeated loading consisted of one million or 5 million cycles in the service load range. Splittng cracks formed at a lower load in beams with epoxy-coated reinforcement than in beams with uncoated reinforcement. Deflections, crack widths, and reinforcement stresses were larger in beams with epoxy-coated reinforcement during service loading. The differences were reduced with repeated loading. The differences are attributed to a larger friction component of the bond mechanism with uncoated reinforcement.

The paper presents results of recent tests of concrete members reinforced with epoxy-coated bars. Evaluation of the bond strength, member defelections, and crack width and spacing are included. Recommendations for further research are made.

A limited truss model design approach with variable angle of inclination diagonals and a concrete contribution for beams with web reinforcement is proposed as a viable and economic design tool. Computed values were compared with a wide range of test results of reinforced and prestressed concrete beams failing in shear. The modified truss model approach was shown to be conservative and in good agreement with test results. A diminishing concrete contribution is proposed to supplement the strength of the variable angle truss model for reinforced concrete beams.