Behaviour of reinforced concrete dapped-end beams

Abstract

The test results of 24 reinforced concrete dapped-end beams are reported. The main variables studied were the compressive strength of concrete, the shear span-to-depth ratio and the horizontal load. The test results indicate that the shear strength of dapped-end beams increases with an increase in concrete compressive strength. The shear strength of dapped-end beams also increases with decreases in shear span-to-depth ratio and horizontal load. The smaller the shear span-to-depth ratio of dapped-end beams, the greater their stiffness and ultimate load. Both the stiffness and the ultimate load of dapped-end beams increase with increasing concrete compressive strength, but decrease with an increase in horizontal load. The extension of the softened strut-and-tie model for predicting the shear strength of dapped-end beams with a shear span-to-depth ratio greater than unity is examined in this paper. The shear strength predicted by the proposed model, the strut-and-tie model of the American Concrete Institute (ACI) and the approach of the Precast/Prestressed Concrete Institute (PCI) are compared with available test results. The comparison shows that the proposed model and the strut-and-tie model can predict the shear strength of reinforced concrete dapped-end beams more accurately than the PCI approach.

Editorial: Research into structural concrete

“…The paper by Motamed et al (2012) considers the influence of horizontal web reinforcement on shear resistance. The article focuses on the contribution of dowel action which is not widely considered in shear design.The paper by Lu et al (2012) considers the behaviour of reinforced concrete dapped-end beams for which a softened strutand-tie model is shown to give reasonable predictions of shear strength. In this context, it is interesting to note that neither Eurocode 2 nor the draft Model Code 2010 relate the concrete compressive strength in struts to their orientation or the strain in the ties as suggested by Collins et al (2008).…”

“…The paper by Lu et al (2012) considers the behaviour of reinforced concrete dapped-end beams for which a softened strutand-tie model is shown to give reasonable predictions of shear strength. In this context, it is interesting to note that neither Eurocode 2 nor the draft Model Code 2010 relate the concrete compressive strength in struts to their orientation or the strain in the ties as suggested by Collins et al (2008).…”

Contribuição ao projeto de dentes de concreto para ligações em estruturas de concreto pré-moldado

“…(3) Escoamento da armadura de suspensão inclinada; Em um estudo realizado por Lu et al (2003), doze dentes com relação / 1, 0  ad foram ensaiados para avaliar o efeito de alguns parâmetros na capacidade resistente. Os parâmetros estudados foram a resistência à compressão do concreto, a quantidade de armadura principal do dente e a relação / ad .…”

“…Os parâmetros estudados foram a resistência à compressão do concreto, a relação / ad e a força horizontal. Assim como Lu et al (2003)…”

“…Nesta comparação entre resultados experimentais e analíticos, os modelos experimentais 4 e 10 de Lu et al (2003), 1 e 7 de Lu, Lin e Yu 2012 em que b é a largura do dente,  é o coeficiente de atrito com valor igual 1, 4 , sendo  o coeficiente que leva em conta a densidade do concreto, que vale 1,00, para concreto de densidade normal, e 0,75, para concreto de densidade baixa.…”