Shear strength of reinforced concrete non-slender members subjected to point loads

For many years, shear strength of reinforced concrete members has been studied and researched. The main purpose of this thesis is development of simple equations to consider shear strength enhancement of non-slender members under point load. Shear strength is enhanced when loads are applied within a distance 2-2.5d of support. European codes, namely Eurocode 2 and Model Code 2010 allow sectional shear strength enhancement instead of more refined models to account for the strut action in non-slender members. Eurocode2 and fib Model Code 2010 take account of shear enhancement by decrease the shear force by one factor. Recent research has shown that this approach gives very poor results. In this thesis shear enhancement methods in Model Code 2010 will be evaluated using ACI-DAfStb databases for point loaded members with no vertical design and with shear reinforcement. Results will be presented along with recommendations. In the fib MC2010, when loads are performed near 2d distance of supports, the design shear force can be reduced by 𝑎𝑣/2𝑑, where 𝑎𝑣 is the clear shear span and 𝑑 is the effective depth. The accuracy and conservativeness of the shear enhancement method in the fib MC2010 are evaluated. Based on the results obtained, recommendations are made to enhance the certainty of the fib MC2010 sectional shear enhancement method. In the shear design of non-slender members, significant vertical compressive stresses occur by the loading and support conditions. Sectional models which ignore the beneficial effects of these vertical compressive stresses underestimate the shear strength of such members. In this thesis, a simple expression is derived to calculate the vertical compressive stress at middepth of point loaded non-slender beams and the influence of these compressive stresses is incorporated into the shear design procedures of fib Model Code 2010. It is concluded that sectional analysis with vertical compressive stresses yields better results than the sectional enhancement method in the fib MC2010.