Research On Seismic Behavior Of Hoop Head Tenon Joint Of Ancient Timber Structures In Canton

As a typical representative of folk buildings in Canton,the ancestral hall is a kind of building system which is between the senior palace and common house.As a result of the long-term erosion of the external environment,there are a large number of ancestral hall buildings were damaged to varying degrees and urgent need to be protected and repaired.The hoop head tenon joints are often used to connect the beams and columns in ancestral hall.Since the detail structure of the hoop head tenon joints have obvious regional characteristics and the size and the sustained load of joints are various in different ancestral hall examples.Up to now,the researches on the hoop head tenon joints of ancestral halls are insufficient,which brings great difficulties to the protection and repair of the ancestral hall in Canton.In order to study the seismic behavior of the hoop head tenon joints with different parameters,the following research works were carried out in this paper:(1)The cyclic loading tests on 8 unidirectional hoop head tenon joints were carried out to investigate the seismic behavior of joints.The main parameters included: height of beam(h),diameter of column(D),width of tenon(t)and axial compression load(F).The behaviors of hoop head tenon joints such as the experimental phenomena,hysteretic curves,skeleton curves,ductility,stiffness degradation and energy dissipation were obtained from low cyclic reversed loading test.It is shown that the rotational stiffness,ultimate bending moment and energy dissipation capacity of the joints increase with the increase of the beam height and column diameter.While it increases first and then decreases with the increase of the tenon width.The rotational stiffness,ultimate bending moment and energy dissipation capacity of the joints reach the maximum when the tenon width is 0.4D.The change of axial load within a certain range has little effect on the seismic behavior of joints.(2)The cyclic loading tests on 2 bidirectional hoop head tenon joints were carried out to investigate the influence of tenon width(t)on seismic behavior of joints.The results show that the increase of the tenon width increases the rotational stiffness and the ultimate bending moment of joints during forward loading,but it has little effect on the stiffness,the ultimate moment and the energy dissipation capacity of the joint during reverse loading.The hysteresis curve,the skeleton curve and the ring stiffness degeneration curve in the forward and reverse loading show obvious asymmetry because of the different mechanical characteristics of joints.The stiffness and the bearing capacity of the bidirectional hoop head tenon joints are smaller than unidirectional hoop head tenon joints of the same size.(3)Based on the test result of unidirectional hoop head tenon joints,further analysis by FEA software ABAQUS were also conducted.The results show that FEM simulates well in skeleton curves,hysteretic curves,failure modes and strain distribution with test results.The parametric analysis results showed that the rotational stiffness,yield moment and ultimate bending moment of joints increase linearly with the increase of the beam height and column diameter.While it increases first and then decreases with the increase of the tenon width.The ultimate bending moment of the joints reach the maximum when the tenon width is between 0.4D and 0.5D.The rotational stiffness,ultimate moment and ultimate rotation decreases with the increase of axial load if the axial load is greater than 200 kN.The relation of moment and rotation of hoop head tenon joint is obtained by means of regression analysis.(4)Based on the mechanism analysis of hoop head tenon joint,a moment-rotation calculation formula was deduced.The existed tests approved that the formula are accurate and the calculated result agrees well with the test result.According to the moment-rotation calculation formula,the factors affecting the rotational stiffness of joints were analyzed.The results show that the initial rotational stiffness and ultimate bending moment increase with the increase of beam height,column diameter,mortise width and the friction coefficients.Based on the theoretical calculation formula,a two-linear mechanical model defined with yield point and an ultimate point was proposed.The mechanical model can provide a theoretical evidence for the research on the seismic behavior and the protection and repair of ancient timber structures in Canton.