Hysteretic Behavior Of Full Scale Timber Structure Specimen With Dou-gong Sets And Four Columns In Song Dynasty By Pseudo-static Tests And Simulation Analysis

Many researches on the static characteristic of ancient timber structure were completed based on one pseudo-static test(PST)of reduced models.These tests therefore failed to reveal the degradation of hysteretic behaviour in such ancient timber-structures which have stood for almost a thousand years with accumulated damage arising from many earthquakes;meamwhile,the effect of size and the similarity relationship as related to the scaled structure remain unclear and deserve a further study.Based on previous research results,and by using a single-layer full-scale test model and corresponding numerical model with dou-gong sets and four columns,which showing most of the typical characteristics of Chinese ancient timber structure buildings,the hysteretic behaviour and its degradation laws were explored through two PSTs and numerical analysis under three levels of vertical load.The main results are as follows:(1)The similar relationship between the second material and the seventh material of Cai Fen system in ying zao fa shi were studied.(2)The ultimate state of the traditional timber structure was mainly controlled by lateral displacements.In the ultimate state,components were basically in an elastic state of stress except few pupaifangs,mortises at the column top,and dowels experiencing relatively larger deformation and some splitting.(3)The energy dissipation mechanism was discussed on the basis of the results from two pseudo-static tests.Based on the prerequisite of floating pedestals for column feet,the timber structure can swing freely;and being the key construction measures,mortise-tenon connections provide for the structure to produce larger lateral displacement.Because of the upper reasons,the components and connections is not damage or destruction when larger lateral displacement of the structure;in the meanwhile,the external input energy is converted to gravitational potential energy and elastic strain energy of components.(4)The characteristics of hysteresis behaviors were studied by the hysteresis curves from two pseudo-static tests.The yield load,peak load and ultimate load showed significant linear correlation with the applied vertical load;while the yielding,peak,and the ultimate displacements were only related to the column diameter.The lateral stiffness of the timber structure increased under increasing vertical load;while with increasing ductility coefficient,it degraded in accordance with a power function relationship.The elastic drift angle and elastic-plastic drift angle should be limited to 1/120 and 1/30,respectively.(5)Comparing the results of two pseudo-static tests(PST1 and PST2),the laws of hysteretic performance degradation were pointed out.The envelope curves’ trend of PST1 was simplified into a tri-linear relationship,while the PST2 was a bi-inear relationship.(6)The values obtained from the numerical simulation had bigger different to that from testing although the consistent law of hysteretic behaviors between them.