A Research On The Structure And Their Aseismatic Characteristics Of Ancient Chinese Timber Buildings

Through documentary research and field investigation,this paper is aiming at clarifying the origin,evolution and development on the quintessence of ancient Chinese building structure,the major timber structure,as well as its aseismatie mechanism and strengthening methods,forming a full-scale exploration,so as to reveal the general structural aseismatic methods and concept, hoping to be helpful to the better and longer preservation of existing monumental relics.The Chinese tradition timber structures had been developing for almost ten thousand years, this is closely associated with Chinese culture which is pro-nature and pro-life,and pay special attention to present practical value of construction.By the pseudo-static test of the column model,it was show that,under the seismic action, the stresses and the strains of structural components were mostly in the range of elasticity,and the principal aseismatic capacity of a timber structure doesn't spring from ductility and energy dissipation of its components.The pseudo-static test of mortise-tenon joint models was carded out and,on the basis of the moment-rotation hysteretic loops,the corresponding moment-rotation model of the mortise-tenon joints under the horizontal reversal action was established,moreover,the "nonlinear coefficient NL"that can evaluate quantitively the capacity dissipated or reduced energy of mortise-tenon joint was introduced,and the NLs corresponding four test pieces of mortise-tenon joint models were calculated respectively,the values were all situated between 0.0011 and 0.0065;otherwise,the"effective stiffness K_B" was also introduced,in addition,the K_B corresponding four test pieces of mortise-tenon joint models were calculated respectively. The test results show that,under seismic action,all mortise-tenon joints will cause the whole Chinese timber structure to perform an overall plastic deformation,which leading to looser connecting of the whole structure,and consequently greatly reducing the possible deforming damage from the seismic effects.The static and seismic tests of the bracket sets models showed that,under the horizontal reversal action,the deflection stiffness of bracket sets is always descend no matter when the action is increasing or decreasing;on the basis of the force-displacement hysteretic loops, the bilinear force-displacement relation of the bracket set,as well as seismic isolating model (that is vibration isolator),were established respectively,furthermore the "nonlinear coefficient NL" that can evaluate quantitively the capacity of the energy dissipation and vibration isolation of the bracket set was introduced,consequently the NLs corresponding four test pieces of the bracket sets were calculated respectively,too,and the calculated results were all situated between 0.235 and 0.392,which is 1～2 order of magnitude as big as that of mortise-tenon joint;thus theoretically,it is confirmed that the p'u z'uo floor is principal vibration reduction and shock isolation structural floor.Otherwise,in normal condition,the vertical load acting upon the p'u z'uo structural floor is only about 1/7 times as big as the extreme load of the structure.It is show that there is enough and to spare strength reserve in the structural components of a bracket sets.In accordance with the standards of(Song dynasty)the Ying-tsao fa-shih,the model of central bay skeleton of palace structural prototype with second class ts'ai was made,and corresponding vibrating table test was carried out,moreover,by aseismatic strengthening of the mortise-tennon joints of the test model(that is the mortise-tennon joints having been bound up with steel belts),and under the same condition,the vibrating table test was carried out again, corresponding dynamic response of the model was examined,so as to evaluate the aseismatic strengthened effect of the model,the test results showed that the principal aseismatic way of ancient Chinese timber structures is shock isolation,and the action of shock isolation,in general, is activated in the 7～8 seismic basic intensity.It's a very important guarantee for the structure of curved roof with great volume and weight to sustain completeness and integrity of whole structure under the seismic action.Having been strengthen,the integral characteristic and the aseismatic capacity of whole timber structure were improved.A 3-D FEA method with virtual semi-rigid joint elements was put forward,and to be used to analyse dynamic characteristics of ancient Chinese timber structure,the corresponding computational results showed that the analysis method is practicable.In a word,ancient Chinese timber structure system is a highly organic,scientific and mature,and its development is independent of western structural system,and its principal aseismatic concept is "overcome rigidity by flexibility,energy dissipation and shock isolation", it's intrinsic constituent part of Chinese culture,should be protected scientifically and effectively, and preserved for a longer time in history.