Damage Failure Mode Analysis Of The Layer Frame Structure

A third of territories in our country belongs to the mountainous region according to the geomorphic type. Layer frame structure is the widely used and most representative architectural form with structure in mountainous cities. Significant differences between structural behavior and the common ground frame structure are determined by different height of layer frame structure. There are few standards about mountainous frame structure design in the world, which leads to the obvious research lag of anti-seismic property in actual engineering. In particular, since Wenchuan Earthquake,huge differences were shown in several structures among damage the failure mode and expectations in structures designing. Moreover, many seismically active belts are located in mountainous land type. Research in mountainous layer frame structure under earthquake damage failure mode is imminent, with following question that effects of Near-fault ground motion on mountainous frame structure. Seismic response analysis of mountainous frame structure has long-term mainly relied on the simplified truss model,for the research of multidimensional structure theory and software development progressing slowly. It is necessary, therefore, to study seismic response to fine solid model.The recognized factor affecting frame structure damage failure mode- casting slab,was existed in a chapter choosing another spatial layer frame structure in 8 degree seismic regions(0.2g), with using finite element analysis software ABAQUS.We discussed and evaluated damage failure mode under strong shock of spatial layer frame structure of solid modeling based on structural concrete tension and compression damage coefficient and the time history curve of seismic response indexes, and analyzed effects of elastoplastic slab material?slab thickness?floor beam end slit on the damage failure mode of layer frame structure.This study chooses spatial layer frame structure in 8 degree seismic regions(0.2g)as an object, using non-linear structural analysis and performance evaluation software Perform-3D. We discussed and evaluated anti-seismic property under near-fault ground motions and far-field ground motions of spatial layer frame structure from the whole and the part levels. Also, we analyzed effects of changing column cross-sectional dimension?reinforcement ratio of the end beam?reinforcement ratio of the end column?cross-out of layer frame structure on damage failure mode under various seismic waves,and effects of adjacent-field velocity-pulses on mountainous frame structure.The main conclusions of this article are as follows:(1)Fine solid layer frame structure model constructed by ABAQUS showed damage failure mode of mixing hinge beams and columns under strong shock, whereas, the simplified truss model established by SAP2000 showed that damage failure mode of beams hinge is a major, indicating the former can effectively simulate the actual damage failure mode of layer frame structure under strong shock. Among fine solid models,damage failure mode for no-floor layer frame structure mainly relies on beams hinge,and on mixing hinge beams and columns for a- floor layer frame structure, showing the floor affecting the internal force distributions of layer frame structure, with slowing girders damage and accelerating columns damage. After setting the floor material as an elastic material, the calculation cannot reflect the sequence and structure of the plastic yield energy distribution in the shock, based on the assumption of elastic floor, with no reasonable descriptions of structure failure compared to that of elastic-plastic. Secondly we analyzed the influence of thickness of slab on layer frame damage failure modes. In this case, three thickness variation(80mm-100mm-120mm), although they were mixing hinge beams mode, increase in the thickness showed more beneficial to postpone girders damage, and to accelerate columns damage. For layer frame structure,if the joints of the cast-in-situ slab at the end of the beams are proper setted, the reinforcement will be reduced which is aroused by the slab for the beam flexural capacity. That's in favor of the "strong column and weak beam" failure modes. At the same time, the damage degree of the column becomes smaller, and from an overall perspective, the lateral displacement of layer frame structure is reduced.(2) Perform-3D based software was used to analyze the condition of changing 20 kinds of reinforcement ratio of the end beam, increase in reinforcement ratio of the end beam will lead to an increase in the destruction of columns, and it is easy to form mixing hinge beams damage failure modes. Changing 16 kinds of reinforcement ratio of the end column with condition analysis results showed decrease in column cross-sectional dimension was harmful to ‘Strong Column and Weak Beam'. In this study, we also analyzed 16 kinds of working conditions of cross-out of layer frame structure. From the perspective of hinge in beams and column, the design focus of layer frame structure and ground structure is completely different, and with increasing cross-out of structure, layer frame structure should be inclined to follow ground structure of the same floor to design, paying attention to the seismic performance of thebottom. Conversely, decrease in cross-out of layer frame structure, should be more inclined to follow ground structure of reducing under the ground to design.(3) Compared to the far field seismic,near-fault seismic containing the velocity pulses with a wealth of the low-frequency component, has a negative impact on the long period(more than 0.9s) structure; and far field seismic with the high-frequency component, damage the short period(less than 0.9s) structure. Near-fault seismic containing the velocity pulses could amplify earthquake responseof spatial layer frame structure(Overall response indicators and Partial response indicatorsof structure). From maximal inner story drift angle(over the plastic interlayer displacement angle 1/50 limit Chinese anti-regulation provisions)of spatial layer frame structure under near-fault seismic, considerations in the current standards for pulse effects near-fault seismic are not sufficient.