Study On The Influence Of Column Foot Damage On Mechanical Properties Of Fourth Grade Timber Frame

As a traditional architectural form,timber structure has a history of thousands of years in China.The few existing timber structure buildings have also become an important cultural heritage in China.Due to the influence of natural environment,human activities and other factors,most of the existing timber structures were damaged to varying degrees.The research repair and protection of the damaged timber frame is the responsibility of every ancient architecture researcher,and it is also an urgent work to be carried out.This paper used ABAQUS finite element analysis software establishing the fourth grade timber frame model by referring to the "Yingzaofashi" of Song Dynasty.The horizontal monotonic loading overturning simulation test and the dynamic simulation test under the action of simple harmonic wave were carried out.The effects of column foot damage and uneven settlement of foundation were analyzed.The specific research results were as follows:(1)The damage of column foot leads to the decrease of peak load,ultimate load,ultimate displacement and stiffness of the timber frame,and the reduction range increases with the increase of damage degree.The damage of column foot affects the energy conversion during the movement of the timber frame.The increase of column foot damage increases the proportion of elastic strain energy and friction energy consumption.The proportion of gravity potential energy decreases with increasing column foot damage,and a maximum reduction of6.15% is obtained.(2)Under reverse loading(loading towards the settlement end),the peak load,ultimate load and stiffness of the timber frame are reduced,and the reduction range decreases with the increase of settlement.While the ultimate displacement increases with the increase of settlement.The foundation settlement also has an impact on the energy conversion during the movement of the timber frame.With the increase of settlement,the proportion of elastic strain energy decreases,and the proportion of friction energy consumption increases,with the maximum increase of 7.5%.The proportion of gravity potential energy decreases with the increase of settlement.(3)When the amplitude of simple harmonic acceleration is 50 gal,the acceleration of column top is greater than that of column bottom,and the amplification factor is greater than1.While when it is 100 gal or 150 gal,the amplification factor is less than 1.Thus,the damping effect of the timber frame is better when the acceleration amplitude is large.The relative displacement of column top increases with the increase of input harmonic frequency.The inter story displacement angle of the timber frame increases with the increase of damage degree,and the maximum displacement angle is 1/8(0.5Hz-150 gal,50mm).(4)With the increase of foundation settlement,the acceleration amplification factor of the column top of the timber frame decreases,and the minimum amplification factor is 0.11.The inter story displacement angle of the timber frame increases with the increase of foundation settlement,and the angle may be up to 1/17(50gal-0.5Hz,100mm),which far exceeding the limit of 1/30.However,the structure has not been overturned,indicating that the timber frame has good deformation capacity.