Experimental study on deformation limits of RC beams

Abstract:

To establish deformation limits of reinforced concrete(RC) beams, study on the method for classification of RC beams, definition of performance states and determining the deformation limit of specific performance state was conducted. As for the classification of RC beams, parameters affecting the failure modes of RC beams were investigated using collected test data for 103 RC beams tested under low frequency cyclic loading. A method was proposed to classify the failure modes into flexure-controlled and shear-controlled based on shear span ratio and moment shear ratio of beams. As for the performance states of RC beams and their deformation limits, the performance states of RC beams were divided into seven levels with reference to the current Chinese codes for seismic design, and the method for determining the deformation limits of these levels was put forward, which is based on three key performance points (point of yielding, point of losing 20% load capacity, point of losing bearing capacity) of the force-drift ratio backbone curves. With the test data of 103 RC beams, regression analysis of deformation limits was performed on multiple sets of parameters, key parameters and formula of deformation limits of the three key performance points were found for the flexure-controlled and shear-controlled RC beams. Deformation limits of flexure-controlled and shear-controlled RC beams were then put forward. To further verify the proposed deformation limits, quasi-static test of 9 RC beams was conducted, test deformation limits of three key performance points were obtained and compared to the proposed performance limits. The results show that the accuracy, discreteness and failure probability of the proposed RC beam deformation limits are all within reasonable range.