Research On Seismic Performance And Design Method Of Traditional-style Steel Structures

Chinese 5000-year cultural heritage has created a number of traditional cultural expressions with Chinese characteristics.In order to create new modern buildings with Chinese typical style and regional characteristics,traditional-style buildings constructed with modern building materials have emerged.Due to the high strength and good seismic performance of steel structure,the steel traditional-style buildings have a broad application prospect.At present,the researches on steel traditional-style architectural structures are not sufficient at home and abroad,so it is of great significance to conduct this kind of research.The major research contents and results of this paper are as follows:(1)Four traditional-style transition steel connections with a ratio of 1:1.5 were designed,and the reversed cyclic lateral test was carried out.The influences of axial compression ratio and the stiffness ratio of upper and lower columns on the seismic performance were investigated.Test results showed that when the structure entered the plastic stage,the heat affected zone between the circular cover plate and the rectangular steel pipe column cracked,and the crack extended along the fillet weld direction,resulting in the final damage.When the ultimate state was reached,the displacement angles of all the test pieces were between 1/35 and 1/45,which meets the steel elastoplastic displacement angle(1/50)in the Chinese seismic code,indicating strong deformation capacity.Based on the test results,an ideal bilinear backbone curve model suitable for this kind of structure was proposed.At the same time,in order to consider the damage accumulation during loading,the damage index was introduced to quantitatively describe the degradation effect of structural stiffness.Finally,the hysteresis rules and characteristic calculation formulas of traditional-style transition steel connections were proposed.(2)The elastic-plastic analysis of the transition connection in traditional style was carried out by ABAQUS finite element software,and the influence of initial imperfection and welding residual stress on the structure were considered.The simulation results showed that the finite element results were highly consistent with the experimental results.The yielding occurred first at the corners of tension flange of the rectangular steel tube on the loading side,and then the yielding range at the two corners of the tension flange section continued to increase.The monotonic loading results showed that the increase of the axial force will reduce the fracture possibility to some extent.The smaller the stiffness ratio of upper and lower columns is,the larger the stress triaxiality is,and the Mises stress is reduced correspondingly,and the fracture index increases and the fracture probability increases accordingly.(3)The pseudo-dynamic test on a steel traditional-style frame structure with a special-shaped joint was performed,the El Centro,Wenchuan and Lanzhou ground motions equivalent to the frequent earthquake of 8-intensity,moderate earthquake of 8-intensity and rare earthquake of 8-intensity were input.When the peak ground acceleration was less than 8-intensity,no macro damage occurred.Under the input peak acceleration of 400 gal Wenchuan wave,the maximum interlayer drift angle was 1/305,which satisfied the fortification objectives of “no collapse to rare earthquake”.In order to understand the final structural failure mechanism under horizontal cyclic loadings,a reversed cyclic horizontal loading test was performed.The test results showed that the Dou and Gong component first yielded and tearing failure along the interface between web and flange occurred,which served as the first anti-seismic defense line;the base metal at the beam end was finally pulled apart.The failure characteristics belonged to the beam-hinge mechanism.The ultimate displacement angle reached 1/20,showing excellent collapse resistance.(4)Based on the on-site tests of steel traditional-style frame structures,the dynamic time history and static pushover analysis of the steel frame were carried out.When the ground motion with a peak acceleration of 1000 gal was applied to the structure,the macroscopic damage in the exterior column occurred obviously.The yield deformation of the test piece mainly focused on Dou and Gong components,and the convex deformation of the beam end was more obvious.With the increase of the yield strength of the steel,the displacement ductility of the frame decreased,the bearing capacity and stiffness increased greatly.The axial compression ratio had a great influence on the ductility,bearing capacity,stiffness and failure mode of the steel traditional-style frame,different arrangement form of Dou-Gong component had a certain influence on the structural failure modes,and the presence of the Gong member moved the plastic hinge of the beam end to the outside region.(5)The seismic behavior of steel traditional-style structure was divided into four requirements,namely normal operation,basic operation,post-repair operation and life safety,which were in turn corresponding to intact,slightly damaged,medium damage and severe damage.At the same time,four performance objectives of seismic performance of steel traditional-style structure were established,i.e.highest goal,the higher target,medium target and basic target.The interlayer displacement angle limiting values corresponded to the four performance levels of the steel traditional-style frame structure were proposed.The displacement-based seismic design theoretical method was applied to the steel traditional-style structure,and the specific design steps were given,finally it was applied to a five-story traditional-style steel frame design example.