Moment-rotation mechanical model of timber beam-stone wall joints in Zang-style historic building
In Zang-style historic buildings,timber beams and stone wall openings were simply lapped together.These timber beam-stone wall joints were weakly connected,resulting in a high risk of damage during earthquakes.The study focused on the timber beam-stone wall joints in Zang-style historic buildings,analyzed their construction process and force mechanisms.The force state determination conditions during forward and reverse rotation were provided.A moment-rotation mechanical model for the timber beam-stone wall joints was established.The accuracy of the mechanical model was validated by comparing with the finite element model.The results show that there is a direct gap between the top of the timber beam and the opening of the wall during construction.The rotation process of the timber beam-stone wall joint is divided into three parts:free rotation state(the timber beam head rotates freely in the hole with a small amplitude),critical state(the top and bottom surface of the timber beam head are in contact with the wall opening),and extrusion state(elastic deformation of the top surface and bottom surface of the timber beam,wood inlay yield on the top surface of the timber beam head,and timber inlay compression yield on the bottom surface of the timber beam head).According to the proposed mechanical model of the timber beam-stone wall joints,the bending moment rotation angle relationship of the actual joints can be calculated quickly.The theoretical calculated results of the bending moment angle curve of the beam-wall joints is in good agreement with the finite element simulation results,with an initial stiffness error less than 30%and a peak capacity error less than 10%.