BEHAVIOR OF REINFORCED HIGH STRENGTH CONCRETE DEEP BEAMS WITH WEB OPENINGS

Abstract

In order to study the shear behavior of reinforced High-Strength Concrete (1-ISC) and Normal-Strength Concrete (NSC) simply supported and continuous deep beams with and without web openings an experimental and analytical investigation has been conducted. The test results have been used to examine the applicability of the shear design requirements of four international codes (ACI 318-02, ECCS-200 I, NZS 3101-98 and EC-2). The test program included nineteen reinforced concrete simply supported deep beams and fourteen reinforced concrete continuous deep beams. The main parameters examined were the size and position of opening, the design concrete compressive strength, the magnitude of transverse reinforcement ratio and span-to-depth ratio. The results indicated that the presence of web openings (of height equal to 20% and 40% of the total web height, respectively) in the load path leads to a reduction in the ultimate shear strength of HSC continuousdeep beams by about 38% and 45%, respectively, and a reduction in the ultimate shear strength of 1-!SC simple deep

beams by about 25% and 58 % when compared with a similar beam without opening. The predictions of the ultimate shear strength of HSC and NSC continuous deep beams with web openings according to the ACI 318-02, ECCS-2001, NZS 3101-98 and EC-2 may lead to unsafe design when the opening intercept the load path and the opening height is equal to or greater than 20% of the web height. When the height of opening is deducted from the beam depth the predictions of the ACI 318-02 and ECCS-200 I for shear strength are safe. In order to predict the complete response of reinforced concrete deep beams such as,

displacements, strains and stresses distributions, ultimate shear loads and failure modes, and cracking patterns, a three dimensional nonlinear finite element model using the computer program ANSYS [5] is utilized. Strut-and-Tie models for all tested simple deep beams have been suggested based on experimental results of crack patterns, modes of failure, internal stresses trajectors obtained from the finite element analysis. The obtained results are compared with experimental tests on simple reinforced concrete deep beams with openings subjected to different boundary conditions and various influencing parameters.