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 resistance of reinforced concrete waffle flat slabs around the solid panel
This work presents a study on the behaviour of reinforced concrete waffle flat slabs with solid panels around internal columns and without moment transfer. Testes on 6 square waffle flat slab models were carried out, with 2400 mm in side length, 185 mm in height, 70 mm in top slab thickness, 115 mm in ribs height, 50 mm in ribs width, and 270 mm in ribs spacing, from center to center. The variables were the size of the solid panels (either 590 × 590 mm or 1130 × 1130 mm), ribs web steel ratio, type and layout. Except for one model that failed in flexure by crushing the ribs at the solid panel, all other models failed in shear by diagonal tension of the ribs. Test results were analyzed and compared with one another and with the estimations of existing expressions from codes and from other works available in the literature for punching shear of the solid panels around the column and ribs shear next to the solid panels. Finally, proposals for the design procedures for the slab region within the lines of zero moments and around the columns are given, regarding the definition of the solid panel size as a function of the ribs resistances towards shear and flexure.
Mechanics of deformable directed surfaces
Abstract The paper develops a simple, yet complete and consistent non-linear dynamic thermo-elastic shell theory based on the concepts of a two-dimensional directed continuum. The constitutive equations are postulated in a general form. Stress-strain relations are derived using the equation of energy balance and the two entropy production inequalities, which are rewritten in a special form. The linear theory is discussed in detail. The structure of the stress-strain relations is presented in the most general form and then specialized to concrete examples, in particular, to the classical shell theory, using their invariance properties with respective to certain symmetry groups. The elastic moduli are determined by demanding the coincidence of the frequency dispersion surfaces obtained using the two-dimensional theory with the lowest foils of the corresponding surfaces resulting from the three-dimensional theory of elasticity.