Study On Collapse-resistant Capacity And Reliability Of Reinforced Concrete Frame Structure System

It has happened many times of mega earthquake in the global world after entering the 21^st century.As for our country,the 2008 Sichuan earthquake and the 2010 Yushu earthquake have induced serious casualties and property damage.When earthquake happens,the collapse of buildings is the main reason for the casualties and property damage.RC?Reinforced concrete?Fame System is often used in the multi-story and high-rise building structures,such as the residential,school buildings,stores,which may gather a large number of people when earthquake happening.Previous earthquake catastrophes in the history show that RC Frame structure system doesn't have enough collapse-resistant capacity under extreme/mega earthquake.Therefore this thesis will focus on the collapse-resistant capacity and reliability of the RC frame structure system,and conduct a series of investigation.The key issues are relevant technology of collapse simulation using ABAQUS/Explicit platform,collapse simulation of different RC frame structure with different fortification intensity under different intensity ground motion,collapse-resistant reliability analysis of RC frame structure under random ground motions.The main achievements throughout this study list in the following summaries.?An analysis method of the collapse simulation using ABAQUS/Explicit platform for RC frame structure subjected to the earthquake is successfully proposed.In order to solve the problem that the concrete damaged plasticity constitutive model integrated in ABAQUS/Explicit can't use in the three dimension fiber beam element,a concrete damaged empirical plasticity constitutive model is integrated into the ABAQUS/Explicit via the material subroutine VUMAT provided by the ABAAQUS/Explicit.An obvious advantage of the concrete damaged empirical plasticity constitutive model is that it can make a good balance between calculation efficiency and precision.?The progressive collapse process of the RC frame structure with different fortification intensity under mega earthquake with different intensity is successfully simulated under ABAUQS/platform by making advantage of the concrete damaged empirical constitutive model.And the collapse mode and the evolution law of the damage mechanic is also investigated.The results show that RC frame structure with6-degree,7-degree fortification intensity can resist the fortification intensity or 0.5-degree,1-degree higher than fortification intensity mega earthquake ground motion.While the RC frame structure with 8-degree fortification intensity can't resist the fortification intensity mega earthquake ground motion.What is more,the RC frame structure with 8-degree fortification intensity exists different collapse failure mode under 9-degree fortification intensity mega earthquake ground motion,which is mainly in vertical progressive collapse while the RC frame structure with 6-degree,7-degree fortification intensity are mainly in lateral progressive collapse.Besides,by observing the evolution of damage factors of concrete and steel,the frame columns fail faster than the frame beams under strong earthquakes ground motion,which indicates that the RC frame structure according to the current design code does not realize the mechanism of"strong columns and weak beams".?The reliability of the RC frame structure with 6-degree fortification intensity is investigated based on the probability density evolution method and the engineering physical random ground motion model.And the result shows that the RC frame structure with 6-degree fortification intensity can remain high reliability and will hardly collapse?the reliability is almost 1?under the sample earthquake ground motions which is equivalent to 7-degree to 8-degree fortification earthquake ground motion.On the other hand,the RC frame structure with 6-degree fortification intensity performs low reliability under the sample earthquake ground motions which is larger than the 9-degree intensity earthquake ground motions.Using the vertical displacement as the collapse failure,when the failure boundary is 1m,the collapse-resistant reliability is about 0.2016;when the failure boundary is 1.5m,the collapse-resistant reliability is about 0.2686,which indicates that the reliability of RC frame designed according to the code to resist extreme earthquake is insufficient.