Study Of Regulation Effect On Continuous Prestressed Glulam String Beam

Wood has the advantages of green,low-carbon and renewable,and has great potential in the field of construction.In recent years,China has vigorously developed prefabricated buildings,so the research group proposed a new type of continuous prestressed glulam string beam which can make full use of wood material properties and accord with the characteristics of prefabricated buildings.In traditional string beam,although the applied prestress changes the stress state of the beam,it also produces the reverse arch,which causes the tensile stress on the top of the glulam.Therefore,the value of the applied prestress must be limited.Based on the above reasons,this paper proposes a prestressing regulation method for continuous prestressed glulam string beam to ensure that the glulam doesn't fail in the process of applying prestress,so as to make full use of the material properties of high strength steel and glulam.In this paper,the bending test of 12 beams in 6 working conditions with different degree of control is carried out.Making use of load-deflection curve,load-strain curve and so on,the influence of prestress regulation on the failure mode,ultimate load and deformation ability of the continuous glulam beam is analyzed.The results show that in all beams,the beams whose failure mode are with compression failure on the top of the beam account for 58.33%of the total number of beams,the beams whose failure mode are with tear damage between the laminate account for 25%,and 16.7%of the beams are with failure mode of unstability.Compared with the beam without prestressing regulation,the ultimate load of the continuous prestressed glulam string beams increase by 13.60%?46.41%for the beams with regulation extent of 18%?42%estimated limit load.After completing the test research,the test beam is simulated by ABAQUS finite element software.The simulation results are compared with the test results to verify the feasibility of the finite element simulation.At the same time,under more working conditions,the influence of prestress regulation on the stress of steel wire and ultimate load of beam is studied.The results show that the stress of steel wire at the moment when the beam fail increases with the increase of beam regulation extent,which indicates that the high strength steel wire is fully used.When the regulation extent of the beam is 6%-42%of its estimated ultimate load,the ultimate bearing capacity of the beam is increased by 8.86%?45.74%.Combined with the test data,the indexes of steel wire stress and ultimate load are investigated,and it is concluded that the reasonable regulation extent of prestress is between 24%?36%of the ultimate load,and the optimal control degree is about 30%of the ultimate load.