| With thousands of years of inheritance and development,traditional Chinese dwellings exhibit strong regional cultural characteristics and irreplaceable historical value.Columnand-tie timber structure is one of the important structural forms of traditional Chinese dwellings,and the infill wall that in the structure was severely damaged under the earthquake.However,the influence of infill walls on the seismic performance of entire timber structures had not been studied in depth.Therefore,the seismic performance of column-and-tie timber structure with infill walls and the function of the infill wall were studied scientifically,which could provide a reference for the reasonable design and effective protection/repair of column-and-tie timber structure.The main researching contents and the results of this paper are as follows:(1)A 1/2 scaled two-story and two-span column-and-tie timber structure with infill walls was designed and produced.A shaking table test was performed for obtaining the dynamic characteristics of the structure,and consequently,the damage characteristics,seismic responses and energy dissipation behaviors of the scaled model under four selected seismic ground motions of varying intensity were studied.The results indicate that the pull-out of the mortise and tenon joints,the slippage of the column feet,the extrusion deformation between the infill wall and timber frame,and the break of wooden dowels were the main damage of column-and-tie timber structure with infill walls.The initial natural frequencies in the X and Y directions of the structure were 3.36 Hz and 1.41 Hz,respectively.The damping ratio was between 9.3% and 22.6%.The acceleration amplification factors of the structure were basically less than 1,indicating that the structure had excellent seismic reduction effects.When the PGA reached 0.4g,the maximum story drift of the structure was 1/33,which met the story drift limit of 1/30 for timber frames,revealing that the column-and-tie timber structures had good deformation performance and collapse resistance performance.(2)The seismic performances of column-and-tie timber structures with(Model 2)or without(Model 1,preliminary test)infill walls were analyzed and compared.The results showed that the lateral stiffness of whole structure increased because of the existence of the wooden walls.The natural frequency of model 2 was greater than that of model 1.Moreover,the story drift of model 2 was less than that of model 1 with the same input.When the PGA reached 0.22 g,the maximum story drift of model 1 and model 2 were1/47 and 1/59,respectively.The lateral deformation of model 2 decreased due to the existence of the wooden walls.The wooden walls were the first fortification line for the earthquake to dissipate seismic energy,and the energy dissipation of model 2 was greater than that of model 1 with the same input.Moreover,the calculation of horizontal seismic action is affected by infill wall,which is suggested that the function of the infill wall should be considered in the seismic analysis of traditional timber structures.(3)Modal analysis and nonlinear dynamic analysis of model 1 were carried out by using Open Sees,and the natural frequency and seismic responses were obtained.When the finite element results of model 1 agreed well with experimental ones,and then truss element was added to simulate the wooden wall,thus,the finite element analysis of model2 was carried out.The relative errors between calculated value and test value of the fundamental natural frequency in the X and Y directions of model 2 were 6.5% and 11.3%,respectively.And the relative errors of maximum acceleration response and displacement response were basically less than 30%,indicating that the finite element model was reasonable and effective.Moreover,the natural frequency and seismic response of the two structures were investigated when the column foot was articulated or rigid connection,and complete fixation of the column foot on the cornerstone was not recommended in strengthening the structure.(4)The natural frequency and seismic response of column-and-tie timber structures with wooden walls,brick walls or mud walls were analyzed and compared.Taking the model infilled with brick wall as an example,the change law of natural frequency and seismic response with the wall thickness and the influence of layout of infill walls on the seismic performance of the structure were studied.The results indicate that the natural frequency of the model infilled with mud wall was minimum.The lateral deformation significantly decreased due to the effect of brick wall.Moreover,little difference of the shear force was present between the model filled with brick walls and the model filled with mud walls with the same thickness,and the base shear of the model filled with masonry walls was about 2 to 6 times that of the model filled with wooden walls.In addition,the natural frequency and base shear of the model filled with brick walls increased with the increase of the wall thickness,and the acceleration response and displacement response had little change.Furthermore,compared with the model full filled with brick walls,the fundamental natural frequency of the model that only the first floor filled with brick walls in the X and Y directions were reduced 15.3% and 10.6%,respectively.The displacement response of the model that only the first floor filled with brick walls was 1 to 3 times that of model full filled with brick walls.It is suggested that the infill walls should be made of lightweight and high strength materials,and the layout of the wall should be continuous and uniform.(5)The seismic response of column-and-tie timber structures with different material infill walls were analyzed and compared under the long period ground motion and ordinary ground motion.The results showed that under the long period ground motion,the maximum acceleration response of the structure with the same material infill wall was the 1 to 1.5 times that under ordinary ground motion,and the maximum displacement response was significantly greater than that under ordinary ground motion.For the model filled with brick walls and the model filled with mud walls,the relative displacement of column foot was close to or exceeded the critical value of the sliding collapse of the column foot under the seismic action with a PGA of 0.22 g,and it is suggested to increase the diameter of the cornerstone appropriately.Moreover,the shear force of the structures under the long period ground motion was basically greater than that under ordinary ground motion.It was indicated that the harmfulness of long period ground motion on seismic response of column-and-tie timber structures were more severe than that of ordinary ground motion. |
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