Shear Predictions of Eurocode EC2
The shear strength of reinforced concrete members is a function of shear capacity of concrete (Vc), which in turn depends on influencing parameters including concrete compressive strength (f’c), ratio of tension reinforcement (), shear span to depth ratio (a/d), size effect or depth factor (ξ), size of the aggregate in relation to the minimum size of the member (aggregate interlock aspects).Over the last several decades, researchers have tested reinforced concrete beams (without web reinforcement) over a range of variables limited by the breadth and depth of their experimental investigations and on the basis of their experimental results, have proposed empirical equations for predicting the shear capacity of normal and high strength-high performance concrete in reinforced concrete beams. In this paper a relational database using ACCESS software is developed and is populated with experimental results of 2145 shear critical reinforced concrete beams without web reinforcement using both normal as well as high strength –high performance concrete. An evaluation was also conducted to assess the predictive accuracy of shear design equation of Euro Code EC2. The results indicate for beams of normal as well as high strength concrete, the Euro Code EC2 design equation is adequate to accurately predict the shear capacity of reinforced concrete beams over the range of variables considered in this study.
SHEAR STRENGTH PREDICTION FOR SEPERATE CATEGORIES OF SIMPLE BEAM TESTS
THE ULTIMATE SHEAR STRENGTH OF SIMPLE RECTANGULAR BEAMS UNDER CONCENTRATED LOAD IS NOT ONLY A FUNCTION OF THE COMMON DESIGN PROPERTIES OF COMPANION CONCRETE CYLINDER STRENGTH, STEEL RATIO (AREA OF LONGITUDINAL TENSILE STEEL/BEAM WIDTH X BEAM EFFECTIVE DEPTH TO STEEL), SLENDERNESS (SHEAR SPAN/BEAM EFFECTIVE DEPTH TO STEEL), AND WEB REINFORCEMENT STIRRUP RATIO X STIRRUP YIELD STRESS) BUT ALSO IS STRONGLY INFLUENCED BY THE BEAM SUPPORT CONDITIONS. THE ACCURATE PREDICTION OF TEST BEAM STRENGTH MUST NECESSARILY CONSIDER ALL OF THESE FACTORS AVAILABLE BEAM TEST DATA ARE SEPARATED INTO THE DISTINCT CATEGORIES OF DIFFERENT STRENGTH BEHAVIOR, AND SIMPLE EMPIRICAL EQUATIONS ARE DERIVED FOR EACH CATEGORY. BEGINNING WITH A PREVIOUSLY DEVELOPED EQUATION FOR SLENDER (SLENDERNESS LESS THAN (2.5) BEAM SHEAR STRENGTH, EQUATIONS ARE DEVELOPED FOR SHORT (SLENDERNESS LESS THAN 2.5) INDIRECT OR SIDE BRACKET LOADED BEAMS WITH OR WITHOUT VERTICAL STIRRUPS AND SHORT DIRECT, TOP AND BOTTOM PLATE LOADED BEAMS WITH OR WITHOUT VERTICAL STIRRUPS. GOOD ENGINEERING PREDICTION RESULTS WITH THESE EQUATIONS, AND A DEFINITE AMOUNT OF DOWEL ACTION IS DETECTABLE IN BEAMS, WITH VERTICAL STIRRUPS, HAVING TWO LAYERS OF LONGITUDINAL REINFORCEMENT. /ACI/
ARCH ACTION IN REINFORCED CONCRETE BEAMS--A RATIONAL PREDICTION OF SHEAR STRENGTH
A rational expression, developed to predict the shear strength of reinforced concrete beams, is derived from the relationship between shear and the rate of change of bending moment along a beam coupled with experimental findings for the arch action. Eight reinforced concrete simple span beams without web reinforcement were tested statically up to failure to investigate quantitatively the arch action. Variables included four shear span-to-depth ratios (2, 2.5, 3, and 4) and two longitudinal steel ratios (1% and 2%). On the basis of the experimental findings, an equation is proposed to predict the internal moment arm length, which then leads to a shear strength equation that combines beam action and arch action. The proposed ultimate shear strength equation, arising from analytical premises and then calibrated with experimental data, is a similar form to the American Concrete Institute (ACI) 318 equation derived mainly from an empirical approach. The proposed ultimate shear strength equation applied to existing test data and the results were compared with those predicted by the ACI 318 equation and the Zsutty's equation.