Study On Seismic Design Method Of Long-Span Steel Grid Structure Building Based On Failure Mode With Function Of Disaster Earthquake Refuge

To deal with the earthquake disasters is an eternal theme of human survival and sustainable development on Earth. Today, disaster earthquakes still continue to destroy cities and villages, to leave a huge life lost and property damage and even trauma to humans. As the result, how to build earthquake resistance and disaster mitigation system in cities and towns and even rural area is still an important issue for human need to solve while the development of urban expansion can be seen anywhere. Based on the current situation of the earthquake resistance and disaster mitigation system in China, this paper from the beginning of investigation and analysis on catastrophic earthquake, proposes to build an earthquake resistance and disaster mitigation system of "catastrophic earthquake refuge and relief stronghold system", and focus on researching on the seismic performance design methods applied to the long-span grid structure buildings with the function of disaster earthquake refuge and relief stronghold. The main content of the study and the main conclusions obtained are as follows: First, the seismic parameters of the catastrophic earthquake in China since1920are been investigated statistically, the results showed that6to9degrees regions in our current fortification intensity, the intensity of the catastrophic earthquake in history was more than9degrees and some even reached12degrees, which corresponds to the peak of ground motion between620gal～3200gal, therefore the disaster earthquake that its intensity is higher than the level of fortification earthquake intensity may be occur at any time in cities and towns with large population. Response to future disaster earthquake the town emergency relief and refuge issues, the idea of the catastrophic earthquake fortification for the building with the function of earthquake refuge and relief stronghold is proposed in the paper. And a set of the disaster ground motion design parameters taken for current fortification intensity system in China is presented. Then the seismic fortification objective for the public building with earthquake refuge and relief stronghold function is adjusted to:"full operation under fortified earthquake, normal operation under rare earthquake, basic run under catastrophic earthquake", according to the requirements of these kinds of buildings.Through the analysis of the domestic and international disaster earthquake emergency rescue practices, large span public buildings are proposed to serve as the carrier as a relief stronghold and refuge shelter. It is easy for them to give the function of refuge and relief on the basis that meets their public serve function. According to the fact that public buildings generally use a large-span steel grid structure system, this paper focus on the study on the content and method of the seismic performance design of these building structures with the function of relief stronghold and refuge shelter, especially on failure criteria and failure bearing capacity assessment method for the structure as a whole (including the upper and lower part of the structure) under disaster earthquakes.To discuss the failure behaviors of the large-span steel grid structure system under earthquake, select spatial arch trusses, which commonly used in large-span public buildings, as the research object. Experimental and modeling investigation on three spatial arch truss models under cyclic loading vertically on the node of their middle span is carried out to study failure mechanism, the main findings are as follow:①Their failure process is that the weakest section firstly enter into the elastic-plastic state, then minor cracks appear on the end of the web bar with the maximum tensile force in their weakest section, last the web rods gradually tear from lower chord to lead for the truss to form geometrical mechanism and collapse.②the development of plasticity is limited to the local areas in which the inner forces of their bars are great, therefore their overall plastic deformation is generally small; The overall hysteresis curves are distorted, slender and not full, so their energy consumption performance is normal; but the hysteresis curves of the rods having entered into elastic-plastic state are full, their energy consumption performance is good.③After entering into the elastic-plastic state, reciprocating loading results in plastic cumulative damage, finally lead to low-cycle fatigue failure; the stress concentration, the three-way tensile stress state in the interfingering lines among the lower chord and4web rods, and weld defects will push the low cycle fatigue failure.④three different model test results did not show regularity with span ratio, its main reason is that the weak parts of the three models are all in the interfingering line joints in the loading area; The comparison finds that the failure patterns of the interfingering line joints in structural model tests here and independent interfingering line joint tests carried out by other scholars is basically the same, but the former is more comprehensive⑤The overall plastic development process, cracking location, the truss model’s overall hysteresis curve, hysteresis behaviors of the rods are generally consistent in their test and simulation, and it shows that rod’s centralized plastic hinge model used in simulation can bring the basic well description of plastic development of the rod in the test.The design cases of a large span public building of spatial arch truss structural system and a sports practice gymnasium of double-layer grids is carried out by the design method presented in this paper. The results show that structure system seismic performance design case studies, the results showed that:it is easy for engineers to understand and master the seismic performance design method based on failure modes under enough and suitable earthquake waves. It is easy to find the "weak part" of the structural system when the seismic design method above is applied. By strengthening the weak parts and optimize the design, it can be higher cost-effective to improve structural system seismic capacity to achieve its requirements of disaster earthquake fortification.