Code modelling of reinforced-concrete deep beams

Abstract

Code provisions for shear design of deep beams have commonly developed from limited test results. There are also very few studies on the validity of shear-carrying capacities of concrete and shear reinforcement in code provisions including strut-and-tie models. The present study investigates the effect of different parameters on the shearcarrying capacities of concrete and shear reinforcement in four code provisions: ACI 318-99 and CIRIA Guide 2 for empirical formulae, and ACI 318-05 and Eurocode (EC) 2 for strut-and-tie models. A comprehensive database having a total of 448 simple and 73 continuous deep beam test results was compiled and compared with the code provisions. Different statistical parameters to measure the safety and accuracy of code provisions are also presented for various web reinforcement arrangements. Code provisions generally fail adequately to capture the effect of different parameters on the shear capacities of concrete and shear reinforcement in deep beams, indicating that shear capacities predicted from empirical code provisions and the strut-and-tie model of ACI 318-05 are more unconservative in continuous deep beams than in simple deep beams, while the strut-and-tie model of EC2 is more unconservative in simple deep beams than in continuous deep beams. In addition, a higher unconservatism appears in strut-and-tie models than in empirical formulae.

Strut-and-Tie Model Based on Crack Band Theory for Deep Beams

“…In general, longitudinal reinforcement keeps within the elastic state when the structural failure of deep beams are governed by compressive crushing of concrete struts. 19 In addition, many investigations 2,11,16 showed that vertical and horizontal shear reinforcements do not commonly reach the yield strength when shear span-to-overall depth ratio is less than approximately 1.0 and more than 1.0, respectively. …”

“…2 As the height of the top nodal zone is assumed to be 0.8 t w from the concrete effective stresses in the nodal zones, the distance between top and bottom nodes is calculated from the following equation:…”

“…As a result, the increase of shear capacity according to the decrease of shear span-to-depth ratio is more significant in deep beams than slender beams. It has been also pointed out 2,3 that the empirical shear provisions of ACI 318-99 4 based on diagonal cracking shear strength of slender beams fail to provide a rational approach to explain the shear transfer mechanisms of concrete web and shear reinforcement, which lead to unconservative shear design of deep beams.…”

“…2,3 Although most codes of practice 3,9 recommend the use of a minimum amount of shear reinforcement in two orthogonal directions in each face for bottle-shape strut, no specific guidelines on the shear transfer mechanism of shear reinforcement are provided.…”

Prediction of combined effects of fibers and nanosilica on the mechanical properties of self-compacting concrete using artificial neural network

“…Artificial neural networks (ANN)were previously used to predicting the concrete properties (Flood et al, 2001;Pannir selvam et al, 2008;Perera et al, 2010;Yang et al, 2008;Guang and Zong, 2000;Goh ATC, 1995;Sanad and Saka, 2001;Jamal et al, 2007;Arslan, 2009;Arslan et al, 2007).From a literature study it could be find that there is no investigation on the combined effects of fibers and nano-silica on the mechanical Properties of SCC using ANN.…”