Issues on Design Shear Strength of RC Deep Beams
01 Jan 2019-pp 107-117
TL;DR: In this paper, a simple analytical expression is proposed for limiting the design shear strength of RC deep beams, by considering following facts: the effect of size, tension reinforcement and limitations on compressive strength of concrete result in either overestimation or high underestimation of beam shears with a/d ratio ranging between 1.0 and 2.0.
Abstract: In this paper, a simple analytical expression is proposed for limiting the design shear strength of RC deep beams, by considering following facts. The maximum shear strength equation of ACI code is same for both concentrated and uniformly distributed loading cases. The effect of \( \frac{a}{d} \) needs to be accounted for properly. Second, the effect of size, tension reinforcement and limitations on compressive strength of concrete result in either overestimation or high underestimation of shear strength of beams with a/d ratio ranging between 1.0 and 2.0. The proposed equation is validated with the test data of 413 deep beams segregated from literature and design provisions of various codes. The proposed model overestimates only, a meagre fraction, 5% of the collected data, whereas the ACI 318-14 code equation overestimates 18.4% of collected data.
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TL;DR: In this paper, the effect of detailing of web reinforcement as per current design codes on the strength and serviceability behavior of bottle-shaped struts has been experimentally investigated, particularly in the context of codal minimum reinforcement requirements, by testing eleven scaled deep beams.
Abstract: The effect of detailing of web reinforcement as per current design codes on the strength and serviceability behavior of bottle-shaped struts has been experimentally investigated, particularly in the context of codal minimum reinforcement requirements, by testing eleven scaled deep beams. The experimentally obtained efficiency factors of the bottle-shaped struts besides being significantly higher than the values given in the ACI 318-08 were also found to be sensitive to the amount of web reinforcement. The minimum web reinforcement requirements specified in current design codes were found to be adequate for controlling service load crack widths though the unreinforced bottle-shaped struts allowed in the ACI code were observed to violate the maximum crack width requirements. It has been shown that the transformation equation in the ACI code does not accurately represent the relationship between the strut efficiency factor and the amount of transverse reinforcement whereas a corrected version of the equation shows a clear dependence of the former on the latter.
18 citations
14 Oct 2008
TL;DR: This study validates the Strut-and-Tie Modeling approach for deep beams incorporating high strength steel reinforcement and shows that member capacity decreased as the shear-span-to-depth ratio increased, and as the longitudinal reinforcement ratio decreased.
Abstract: The Strut-and-Tie Method is a widely accepted design approach for reinforced concrete deep beams. However, there are differences between various design code implementations with respect to reinforcement tie influences on the capacity of adjacent concrete struts. Furthermore, each design code specifies different limits on the maximum permitted design stress for the ties. This study validates the Strut-and-Tie Modeling approach for deep beams incorporating high strength steel reinforcement. Laboratory tests of ten large-scale deep beams were conducted, where primary test variables included the shear-span-to-depth ratio, longitudinal reinforcement ratio and strength, and presence of web reinforcement. The results showed that member capacity decreased as the shear-span-to-depth ratio increased, and as the longitudinal reinforcement ratio decreased. The inclusion of web reinforcement significantly increased the member strength and ductility. It was possible to design members to efficiently exploit the high strength reinforcing steel when applying Strut-and-Tie modeling techniques according to CSA A23.3-04, ACI 318-05 and Eurocode 2 provisions.
18 citations
TL;DR: In this paper, a two-part study evaluating bent caps from 1950s reinforced concrete deck girder bridges, five realistic full-scale replicas of in-service bent caps with 1950s vintage details were constructed and tested under incremental cyclic loads.
Abstract: Many reinforced concrete deck girder bridges were built in the 1950s, and now some of their components are showing signs of distress. In this paper, part of a two-part study evaluating bent caps from 1950s reinforced concrete deck girder bridges, five realistic full-scale replicas of in-service bent caps with 1950s vintage details were constructed and tested under incremental cyclic loads. The test specimens were a subassemblage of pertinent bridge components at the bent cap region, including the integral columns, cap beam, and portions of the monolithic internal girders that frame into the cap. The results showed that the shear span-depth ratio, the anchorage of flexural steel, and web reinforcement were all salient parameters that affected ultimate shear capacity. The bond stress provided in AASHTO-LRFD and ACI 318-08 underestimated the available flexural anchorage because neither of these provisions takes into account the beneficial effect of active confining stress on bond strength. Shear compression was the failure mode in all of the specimens and the failure mode in all but one specimen was brittle.
10 citations