抗地震破坏的焊接结构性能研究

Not only the steel structure is widely used in the industrial fields, but also it is wide spread in the high rise building because of its light weight, good earthquake resistant performance, high degree of the industrialization and high speed of installation. However, in the recent earthquake of Northridge in America and Kobe in Japan, brittle fracture occurred in the beam-to-column connection, which is relevant to the factors of welding. So, it is very important to direct the research of improving the earthquake resistant behavior for steel structure. .The earthquake damage of welded connection has provoked the interest of the international welding specialist. The research of design, materials selecting and manufacturing of welded connection have been performed in Japan and America. The IIW made up a special work group to research the earthquake resistant performance of welded steel structure. The research concentrated in the stress distribution and fracture toughness requirement of welded connection. The research of seismic resistant steel structure in my country concentrated in the performance of the whole structure. There is no research concentrated in the poor segment--welded connection of steel structure. So, aiming to the details of welded connection to perform the research of connection design, accumulative damage has important significance..During the earthquake, the seismic energy is dissipated through the plastic deformation of the welded connection. The hysteric energy is one of the criteria to evaluate the earthquake resistant behavior of the steel structure. Acted by the seismic energy, the connection is to display various degree of accumulative damage..So, the main purpose of this project is to aim the hysteric energy and damage of the connection to perform extensive research..A method to calculate seismic response of structure is given. At first seismographic records are transformed to load spectrum by spectrum analysis method, and then modal superposition is used to compute seismic response of whole structure. Two typical accelerogram records of El Centro earthquake and Tianjin earthquake are taken to compute structure response..In order to assess earthquake-resistant behavior of typical type-H beam-to-column connection in China, Stress distribution of connection is first computed with three-dimensional FEM under moment to simulate load condition on earthquake, and stress concentration at the root of flange weld is also analyzed. As backing bar for grooved weld on beam flange exists, artificial crack is formed because of lack-of-fusion at the root of flange weld. Stress intensity factors (KI) at the root of flange weld are computed from the viewpoint of fracture mechanics. The computation shows that stress intensity factor on bottom flange weld is obviously higher than that on top flange weld..Based on the assumption that surface cracks exist at the root of flange weld, linear-elastic fracture mechanics is used to evaluate required toughness of original connection and reinforced connection forms, among which are ones of with cover on flange, with stiffened rib inside beam and with upstanding rib above flange. Keep the size of basic geometry of original connection constant, optimum designs of some detailed geometry of flange weld, such as thickness of backing bar, height of flange weld and shape of weld access hole are carried out. Effects of these factors on carrying capacity of structure are analyzed and some conclusions are drawn fellow: (1) With the decrease of thickness of backing bar, Stress intensity factors of surface crack increase. (2) No matter which changes made on shape of weld access hole, effect of ameliorating stress concentration is not better than that with no weld access hole. (3) The less extra height of flange weld when joint strength is enough to keep safety, the better..The simulation of the cyclic large deformation test is directed by using the large programming package of ANSYS. The cyclic load, whose amplitude is gradually increased, simulates the seismic loading. There are

采用有限元法建立梁－柱焊接节点的力学模型，研究焊接钢结构梁－柱节点，在地震载荷作用下的力学行为和特征，并辅以相应的实验和计算方法，如局部法，并试图开发一种能模拟动载及应变时效等因素影响的试验方法，寻求设计及制造工艺方面为焊接钢结构抗震设计与制造提供理论和试验依据。