Stress Analysis And Reinforcement Effect Of The End Anchorage Joint Of Portal Frame

Since the 21 st century,with the rapid development of national economy,the level of industrialization in China has been constantly improved.A large number of steel structure factory buildings have been built.Especially,due to portal frames' short construction period and large span,the portal frame,as a kind of light steel,have been widely used in the factory building expansion.Due to the influence of national policies,the change of the use function of the factory building and so on,part of the portal steel frames are needed to install solar energy and other subsidiary equipment in the process of use,which lead to the increase of roof load,inadequate bearing capacity of steel beam,large deformation of components.These problems do not meet the functional requirements which portal steel frames need to be reinforced.The technology of external prestressing reinforcement is a convenient,cheap and reliable reinforcement method.In order to avoid the damage to the original structure of steel beam by welding,drilling and other connection methods,two types of new assembled end anchorage joints for external prestressing reinforcement of portal frame are proposed in this paper.The prestressed steel strand is anchored at the end of the steel beam with the new anchorage joints by means of site assembly without causing any damage to the original structure,which has the advantages of convenient construction,time-saving and labor-saving.And these devices can be applied to the actual reinforcement of steel beams.The strain and mid-span deflection of steel beams under prestressing of steel strands are studied by the field reinforcement test.We can use the ANSYS finite element analysis software to simulate and analyze the end node,and analyse the displacement of the node,equivalent stress,contact state,friction and other force characteristics.And it provides a reference for the optimization of this node.Through the simulation analysis,it should be pointed that there are relatively large local stresses in the contact part between the anchorage device and the steel beam,as well as in the fixed rod of the anchorage device,which should be considered in the design.In addition,there is a stress concentration where the flange meets the web and it is easy to be torn,which provides abasis for the further optimization of the end anchor joint.Midas Gen finite element analysis software is used to simulate and analyze the reinforcement test under various working conditions,and the portal frame was compared with the portal frame under experimental conditions.The results show that the application of external prestressing can reduce the bending moment and deflection of the beam and increase the bearing capacity of the steel beam.The external prestressing strand has about 5% loss of prestress.The new assembled external prestressing anchorage device proposed in this paper is safe and effective,and can be used as anchoring joints in steel beam reinforcement.