Study On The Dynamic Response Of The Eight-grade Timber Frame With Damaged Joints

In the long years,due to the erosion of wind and rain,man-made damage,plus its unique material properties and a series of factors,the vast majority of existing ancient wood structure buildings,the overall structure damage and local node damage has been very serious,the situation is in danger.From the point of view of joint damage,this paper explores and analyzes the dynamic response of wood structures with damaged joints under external dynamic excitation,which can be used as a reference for the study and protection of dynamic response of ancient wooden structures.The model in this paper follows the relevant regulations on the size of wooden structures in the Song Dynasty Construction Formula,using ABAQUS finite element analysis software to establish an eight-grade single-span wooden frame model.And in the case of simple harmonic excitation,the dynamic response of the intact and damaged models are studied separately.The natural frequency of the single-span timber frame of intact 8th grade material was studied,and the natural frequency experiments of the simple harmonics with amplitudes of500 G and 750 G under different input frequencies were carried out.The results showed that:the natural frequency and simple harmonics There is no obvious law between the natural frequencies and the simple harmonic frequencies;under the same wooden frame model and the same weight,the intersection interval of the natural frequency ranges of the two amplitudes is 0.798Hz～1.796Hz;it is determined that the simple harmonic frequencies of the follow-up study are 1Hz.A study on the dynamic response of a single-span timber frame with eight grades of intact material shows that the acceleration image of the structure shows a pattern of resonance;the acceleration of the column top has a lagging phenomenon compared with the phase of the input acceleration;for acceleration In terms of the size,compared with weak external power,the wooden frame can exert its superior performance in resisting power under strong external power;the acceleration at the bottom of the column is closely matched with the input acceleration;and the subsequent research amplitude is determined to be 750 G.Through the study on the dynamic response of the tenon-and-mortise joints of the eight-grade single-span timber frame with different gaps,the main conclusions are: different gaps have different effects on the dynamic response of the timber frame,and the end gap has a greater impact on the phase lag.The side seams and end-side seams have a greater effect on reducing the maximum relative displacement of the wooden frame,and the side seams and end-side seams have a greater effect on reducing the acceleration of the column top.On the whole,the end-to-side joints combine the ability of the two types of joints to affect the dynamic response of the timber frame.The dynamic response experiments of wooden frames with only column foot damage were analyzed.It was found that the top acceleration of the single elastic modulus and the gradual elastic modulus of the two film layers decreased as the elastic modulus decreased.The top acceleration of the single elastic modulus and the gradual elastic modulus are not affected by the thickness of the film.The effect of thin film layer on the dynamic response of wooden frame is weaker than that of mortise and tenon joints with gaps.Through the experiment of dynamic response of multi-node damaged wooden frame,it is found that the acceleration response of the top of the multi-node damaged wooden frame decreases gradually with the increase of the degree of damage,and the acceleration response of the top of the multi-node damaged wooden frame is smaller than that of the single node damaged wooden frame.For the relative displacement and inter-storey displacement Angle,the inter-storey displacement Angle fluctuates between 1/30-1/40 in any multi-node and single-node damage condition,and does not exceed the collapse limit of the timber frame,which is sufficient to indicate that the timber frame has a very good ability to resist dynamic deformation and displacement regardless of intact or damaged.