Study On Shear Strength Of Reinforced Concrete Continuous Deep Beam

The reinforced concrete continuous deep beams are widely used in pratical engineering as the transfer menbers at discontinued region of vertial loads. The continuous deep beams can been used as the transfer girder connects up and below floors with different column spaces in building structure, and the cap beam connects superstructures with substructures in bridge structures.Continuous deep beams behave differently from either simply supported deepbeams or continuous shallow beams. By ignoring these differences during design, one may get significant unexpected cracking. Continuous deep beams develop a distinct tied arch or truss behaviour not found in shallow continuous beams. In the simply supported deep beam, most of the force is carried by the tuss system consists of the distinct direct compression struts and the buttom longitudinal reinforcement; in continuous deep beams, besides the positive moment truss system as the same in simple deep beams, there’s a negtive truss system consists of the compression struts and the top longitudinal reinforcement. The two systems behave together and form the truss system of the continuous deep beams. What’s more, the continuous deep beams are statically indeterminate structures, so they’re sensitive to applied deformation and different settlement of the supports. The result of those is that the strength models and design methods, based on shallow beams or simply span deep beams, are not necessarily appropriate for continuous deep beams.For evaluating the safty of code models for the shear strength of continuous deep flexural members, a shear tests database is built in this paper by collecting and filtering the test results in literatures and research reports. The strut-and-tie model(STM) adopted by ACI 318-11 and the shear strength equation for deep flexural members in GB 50010-2010 are analyzed and evaluated based on the database, and the results indicate that both the STM and Chinese code overestimated the shear strength of continuous deep flexural members. For Chinese code, by set the upper and lower limits to 3 and 0.25 respectively, its equation can estimate the shear strength of continuous deep flexural members safely; for STM in American code, its safety is improved by modifing the effective coefficient of concrete in strut.The influence of web reinforcement on the shear mechanism is very complicated. however, the test results scattered, and the systematic experimental studies were rare. In order to make up for the shortages of experimental analysis, nonlinear finite element method(FEM) is adopted in this paper for modeling the shear behavior of reinforced concrete continuous deep beams. The finite element models are built up by ATENA software, and they are justified by comparing with the test results. On this basis, another 76 modeling members vary in web reinforcement ratios and shear span-to-depth ratios are analyzed to study the influence of web reinforcement on shear strength of continuous deep beams. And the results of the finite element analysis are compared to the Chinese code equation, strut-and-tie model(STM) and the recently proposed Three-Parameter Kinematics Theory(3PKT), which shows that the Chinese code overestimated the contribution of horizontal web reinforcement on the shear strength, and both STM and 3PKT have insufficiencies.