Effect of load history on shear strength of reinforced concrete I-Beams

Abstract

A series of 32 reinforced concrete I-beams was tested to investigate the effect of existing inclined cracks on shear strength. Testing of beams consisted of two stages. At the preliminary stage, load large enough to cause a formation of a developed crack pattern in the web was applied with the primary shear span-depth ratio. After that, the load with breaking shear span-depth ratio was applied until failure of the specimen. The load applied during the preliminary loading stage was maintained with a full or partial value by a lever, or removed. The test variables include shear span, shear reinforcement ratio and angle of stirrups inclination. Pre-cracking was found to decrease the ultimate shear strength of beams by a maximum of 16 percent depending on the angle of stirrups. A corresponding reduction factor is suggested to the formula of the Russian code for the design of bridges. The finite element simulation of beams was fulfilled by using the program OpenSees. The webs of beams were simulated with a 2D element built on the Cyclic Softened Membrane Model to take into account the deterioration of concrete due to the previous loading. The accuracy of the proposed FE model was verified with the aforementioned tests and the results of several other studies.