Test And Analysis Of Bending Bearing Capacity Of Prestressed CFRP Cloth Reinforced Damaged Timber Beams

Ancient architecture is an important component of China’s historical and cultural heritage,with high artistic,historical,cultural,and scientific value.After years of baptism,some of the existing wooden structure ancient buildings have been damaged to varying degrees,posing safety hazards when they continue to be used.Therefore,it is urgent to protect,reinforce,and repair the wooden structure ancient buildings.Considering the protection needs of ancient wooden structures,this article proposes a new type of prestressed CFRP fabric reinforcement scheme for damaged timber beams: prestressed CFRP fabric is applied to the CFRP fabric through a column end anchored CFRP fabric tension anchor device;And conduct experiments and finite element analysis on the flexural bearing capacity of damaged timber beams,CFRP cloth reinforced damaged timber beams,and prestressed CFRP cloth reinforced damaged timber beams,to verify the effectiveness,reliability,practicality,and convenience of the new prestressed CFRP cloth reinforced damaged timber beam scheme proposed in this article.(1)Conduct bending bearing capacity tests and finite element analysis on damaged timber beams.Firstly,conduct wood property tests on Citipine wood,a wood beam material,and analyze and calculate its various characteristic parameters.Artificial damage treatment was performed on the experimental timber beams,and then graded loading was used to test the bending bearing capacity of the damaged timber beams.The bending bearing capacity,load-deflection curve,and load-stress curve were measured.The test results showed that the damaged timber beams lost their bearing capacity after reaching their maximum bending bearing capacity,and the specimens brittle failure occurred at the tensile side crack,where the maximum strain value also appeared.A finite element analysis was conducted on a damaged timber beam,and the results of the finite element analysis were compared with the experimental results.It was found that the bending bearing capacity,maximum deflection at mid span,failure mode,and position of maximum stress obtained from the experiment were basically consistent with the results of the finite element analysis.(2)By pasting CFRP cloth on the tensile side of the timber beam,the damaged timber beam was reinforced and subjected to bending bearing capacity tests.The bending bearing capacity,load deflection curve,and load stress curve were measured.The results showed that compared with the damaged timber beam,the bending bearing capacity and ductility of the damaged timber beam reinforced with CFRP cloth were improved,with a bearing capacity increase of 20.6% and a mid span deflection increase of 31.0%.The finite element analysis software ANSYS was used to establish a finite element model of CFRP cloth reinforced damaged timber beams.The analysis showed that the model can better reflect the stress state of the damaged timber beams before and after reinforcement,and the finite element analysis results are in good agreement with the experimental results.(3)Propose a new scheme for strengthening damaged timber beams with prestressed CFRP fabric,design a column end anchored CFRP fabric tensioning and anchoring device,including tensioning and anchoring devices,and deepen the design to determine the dimensions of its components.The tensile bearing capacity of the screw in the tensioning device and the shear bearing capacity of the bolt in the anchoring device were verified.The tension test of CFRP fabric was conducted using a column end anchored CFRP fabric tension anchor device.The test results showed that this device can meet the tension requirements of CFRP fabric and achieve the preset tension level.Using finite element software to establish a U-shaped groove model in the tensioning device,the analysis results show that the component can meet the requirements of the tensioning device.(4)The flexural bearing capacity test was conducted on the damaged timber beams strengthened with prestressed CFRP sheets after tension testing.The flexural bearing capacity,load-deflection curve,and load-stress curve were measured.The results showed that compared with damaged timber beams,the flexural bearing capacity and ductility of the damaged timber beams strengthened with prestressed CFRP sheets were significantly improved,with an increase of 35.3% in flexural bearing capacity and 51.4% in mid span deflection.Establishing a finite element model of prestressed CFRP fabric reinforced damaged timber beams,comparing experimental results with finite element analysis results,it was found that CFRP fabric delayed or avoided the tensile brittle failure of timber beams;Reducing the impact of wood defects on the bending performance of timber beams;The failure mode changes from brittle failure at the crack on the tensile side of the timber beam to compression side failure.A comparison was made between the reinforcement effect of using CFRP cloth alone to reinforce damaged timber beams and using prestressed CFRP cloth to reinforce damaged timber beams.It was found that using prestressed CFRP cloth to reinforce damaged timber beams can more effectively improve their flexural bearing capacity.