Researches On Double Span Traditional Timber Structures In Song Dynasty

Ancient building represented science, culture, politic, economic and art in historic period, and could reflected material and cultural progress. The senses of responsibility and mission of protecting and rescuing those human relics arouse the enthusiasm for historic building of researchers in architecture, art, archaeology and structure areas. In past 20 years, quite a few scholars were coming to study the seismic mechanism and mechanical performance hidden in Chinese ancient timber structure, and doing some excellent pioneering workings. Still, many problems were remained to be studied. Traditional multi-span timber structures remain largely unexplored until current days. It is recorded in the book of Construction Technique in Chinese Traditional Timber Structure written by Ma BingJian that the cross-section of traditional dovetail looks like an upside down trapezoid (wide on the top side, and narrow at the bottom side). This inverted trapezoid dovetail is expected to be studied. Besides, the mechanical model of semi-rigid connector for ordinary tenon with rectangular cross-section is still not built up. The analysis approaches used to wooden structures are not yet excellent.Fen-Xin-Dou palace built in Song Dynasty is double span wooden structure, and used for the main entrance of ancient buildings. Double-span timber structure is a special sort of multi-span timber structures, and its details are simpler than other multi-span structures. Research on the structure can lay the groundwork for subsequent studies of multi-span wooden structures.Based on Fen-Xin-Dou palace built in Song Dynasty, three scaled model with the ratio of 1:4 are built, and its connector is made as inverted trapezoid dovetail. According to the realistic connection condition at the bottom and top of column, the text makes rational assumptions about the boundary conditions and loaded modes for the test samples, and reports the results of pseudo-static tests of the three samples.The samples made of either steel or concrete, rather than timber, have larger capacities resisting lateral force and lower ductility. For these samples, the overall P-A effects induced by structural displacement are only the test values of actuator of 1/20～1/10 in test process, thus, we can neglect the overall P-△effects in analyzing test values, and the errors resulted by the simplification will be small. But the second order lateral force induced by overall P-△ effects of timber structure, with semi-rigid joggle joint, is 0.3～3.5 times of the test values of actuator. When lateral displacement of structure is relatively larger, the lateral force by P-△effects occupies the leading position, so, P-△effects should be concern in dealing with the test results of wooden samples.Both virtual load and D-value method based on equivalent portal frame are presented. Those methods take the non-linear effect and overall P-△effects into consideration, and are validated with a broader range of test results. They can be more incorporated into frame analysis with semi-rigid joints for predicting system response.Formulas are obtained, such as relationships between connectional moment and stiffness, between connectional moment and flexibility, between lateral displacement and relative angle of wedge joint, between lateral displacement and connectional stiffness in joints, and between lateral displacement and connectional flexibility in joints. Besides, both double-line and power functional model between connectional moment and relative angle in joints are decided. Based on multi-linear pivot hysteresis model, both revised bi-linear and multi-linear pivot hysteresis model are presented. The power function representation between connectional moment and relative angle in joints is validated with the results of a number of computer imitations, and is suited to estimate the responses of semi-rigid timber frame.Mode parameters of 3 double span wooden structures were tested. Besides, based on both methods of the amplitude-frequency peak value and of the real-frequency and imaginary-frequency peak value, fundamental frequencies and fundamental mode damping ratios of tested samples were estimated.