EXPERIMENTAL RESEARCH OF SHEAR STRENGTH MODELS FOR REINFORCED CONCRETE MEMBERS

The question of systematically calculating the shear strength of reinforced concrete (R.C.) elements in flexure-shear reversals with or without axial load has been central to the development of performance based design.The multitude of models in the international literature, some of which have been adopted by the Seismic Codes of Assessment or Design (such as ACI 318-2011, FEMA 273 and 356, ASCE/SEI 41-07, EC8-III (2005)) hints to the limited extent of the current level of understanding of this problem; the success of these models in reproducing strength values is very good when flexural failures dominate the response, but their performance, as measured by the amount of scatter between experiment and analysis, increasingly deteriorates when used to estimate shear capacity in shear driven modes of failure.The most important shear strength models [ACI 318-2011, FEMA 273 and 356, as modified by ASCE/SEI 41-07, EC8-III ( 2005)] are tested against two experimental databases comprising elements from the international literature.The first database consists of approximately 550 elements detailed according to the modern provisions whereas the second consists of 40 poorly detailed elements (inadequate transverse reinforcement with brittle details, inadequate lap splices in critical regions, low concrete and steel strengths etc.).Furthermore a parametric study was conducted with regards to the displacement ductility, the normalized axial load, the aspect ratio, the transverse reinforcement and other important design parameters.The results are presented in the form of graphs, in order to highlight the deficiencies of each model whereas the scatter observed illustrates the need for additional investigation to improve the shear strength estimates.