The Influences Of Joint And Slab On The Progressive Collapse-resisting Performance Of RC Frames

After the event of 11 September 2001, more and more researchers in the engineering fields have started to focus on establishment of rational methods for the assessment and enhancement of progresssive collapse-resisting capacity of the structures under the extreme loads caused by the events such as explosion, impact and fire. Most of these methods, eigher quantitative or qualitative, place an emphasis on improving structural integrity. Because the joint and slab of RC frames play an important role in internal force transmission and redistribution after the local damage of structural elements caused by abnormal loads. So it is necessary to study the influences of joint and slab on the progressive collapse-resisting capacity of the structures.The evaluation of influences of structural joint and slab on the progressive collapse-resisting performance of reinforced concrete (RC) frames is conducted by employing the structures designed in accordance with the Chinese building codes.(1) The influences of joint on the progressive collapse-resisting performance of RC frames have been studied and the quantitative results are given. It is also confirmed through the parametric analyses that the diameter and strength of the steel bars have great influences on the progressive collapse-resisting performance of the structure, with little such impact resulting from the shear deformation of concrete and the concrete compressive strength in joint area. In addition, the analysis of the failure mode of members considering the influence of joints has shown the flexural failure remains the dominant failure mode of the members, and no members appear shear failure.(2) The influences of slab on the progressive collapse-resisting performance of RC frames have been studied and the quantitative results given. It is also confirmed through the parametric analyses that the reinforcement ratio of slab have great influences on the progressive collapse-resisting performance of the structure, with little such impact resulting from the concrete tensile strength and the concrete compressive strength of the slab. The effect of the thickness of the slab on the progressive collapse-resisting performance depends on the reinforcement ratio, as shown from the results, if there is a relatively small value of reinforcement ratio of slab, it would be unfavorable for the progressive collapse-resisting performance to increase the thickness of the slab, while as the ratio increases, augmenting the thickness of the slab tends to show a favorable effect on the progressive collapse-resisting performance.