Load configuration, geometry and web reinforcement effects on failure modes of sandwich deep beams

Abstract

In this article, an experimental investigation is carried out to understand the behaviour of sandwich deep beams. The shear strength, load transfer mechanism, integral action and failure modes are reported. Primary variables of this study include distribution of web reinforcement, beam geometry and type of loading. Twelve full-scale beams were tested with simply supported end conditions classifying them into two groups. Each series consists of six beams with rectangular and I-shaped cross-sectional geometry. Two types of loading, i.e. concentrated and uniformly distributed loads, were adopted to understand the influence of distribution of horizontal reinforcement along the depth of beam in the web. Using both types of cross-sections, two beams were tested under uniformly distributed loads, and all the remaining beams were subjected to concentrated load with two different shear span-to-depth ratios (a/d). Observations of the study with respect to strength and serviceability include initial cracking load, ultimate load, crack width, transverse deflection and out-of-plane deformations. The test results indicated that confined or unconfined I-beams in the web failed due to punching shear under concentrated or distributed loads. The modes of failure of rectangular beams with web confinement were diagonal splitting and shear-compression, whereas the unconfined beams failed in flexure. Shear strength expression for conventional deep beams is refined for sandwich beams, and the predicted shear strength agrees well with the experimental results.