Research On Bending Interfacial Properties Of Large-Span Crane Main Girder Strengthened With CFRP

With the vigorous development of industrial technology,steel structures are increasingly used in large-scale equipment.In the process of long-term service,they will inevitably suffer from various forms of damage and corrosion.The traditional steel structure reinforcement method costs much time and creates new damage to the structure while the new method of reinforcing steel with carbon fiber reinforced polymer(CFRP)material has the advantages of convenient construction,no residual stress and no increase in dead weight.However,its reinforcement method is still in the process of research.The paper aims at the reinforcement and repair of flexural bearing capacity of large-span steel girder of large shipbuilding gantry crane with corrosion and damage.The main work of this paper is as follows:Firstly,“Shell-Combine-Shell” finite element model is proposed to simulate carbon fiber reinforced steel main girder.After the finite element model of the original main beam is established,the force analysis of the adhesive layer is performed to derive the calculation method of the spring element real constant.Apply the displacement constraint equation between the nodes of CFRP and adhesive layer to simulate the actual situation.Finally,based on the simulation results,the reinforcement effect and the stress distribution of CFRP and adhesive layer are analyzed.Secondly,based on the classical similarity theory,establish the scale model for large-span steel main beam by using similar design methods with stress and displacement as study parameter.In the process of derivation,the equivalent simplification of the stiffeners in the scale model are taken into consideration to ensure the rationality and realizability of the scale model.Then 4 test beams is manufactured for subsequent experimental study.It provides a reference for the establishment of scale model for thin-walled and large-section box-type structure.Then,test scheme is designed to study the reinforcement effect of CFRP reinforced test beams,including CFRP reinforcement layers,environmental temperature,and hot and humid salinity corrosion.According to the experimental phenomenon,the test beams' flexural load capacity is increased when they reinforced with CFRP.Environmental temperature has a significant impact on the reinforcement effect.Strengthened test beams' failure form is CFRP stripped after test beams yield.Finally,the test data is analyzed and summarized.The load-deflection curve and load-stress curve of test beam mid-span under different CFRP layers strengthened,different environmental temperature,and hot and humid salinity corrosion are obtained.By comparing the experimental results with the simulation results,the rationality of the finite element model of “shell-combine-shell” proposed in this paper is verified.The defects that the stress and strain of the adhesive layer could not be measured during the test were compensated.