Study On External Prestressing Reinforcement Effect Of Portal Frame

Since the reform and opening up,the construction industry has developed by leaps and bounds with the needs of national economic development.Steel structures are increasingly being used in civil and industrial buildings because of their lighter weight and economic benefits.One of the typical forms of steel structure is the portal frame structure used in industrial plants.Sometimes,due to changes in the function of the building structure at a later stage of the industrial plant,additional equipment is required to increase the load,such as additional photovoltaic panels,etc.,resulting in the bearing capacity of the building structure not being able to meet the requirements,so it needs to be reinforced.In order to reinforce the portal frame,the strut and cable are arranged under the portal frame to form a chord-supported frame structure.By applying prestress on the cable,the external prestressed reinforcement system of the portal frame is established.In this paper,with the help of Midas/Gen finite element analysis software,the selection method of cable prestress is determined according to the principle that the deflection of portal frame strengthened by external prestress is close to that under initial load.In the external prestressed reinforcement system of portal frame,the effects of the connection mode of the two ends of the strut,the joint position of the anchor between the cable and the steel beam,the prestress,the strut arrangement,the number of strut,the length of strut and span on the reinforcement effect of portal frame are studied,and the internal force and deformation of portal frame structures with different spans are analyzed.The optimal number and length of struts for the reinforcement of portal frames with different spans are obtained.Finally,with the help of ABAQUS finite element analysis software,the modal analysis of portal frame strengthened by external prestressing is carried out.The influence of the number and height of struts on the dynamics characteristics of reinforced portal frame is mainly studied.It is concluded that the increase of the number of struts increases the natural frequency of the structure,but to a certain extent,stabilizing effect on the natural frequencies of the structure.The longer the strut length is,the greater the natural frequency of the structure is,and the more obvious the influence on the dynamic characteristics of the structure is.This study has practical reference value for the later application of portal frame structure reinforcement engineering,and lays a foundation for the later in-depth study of the dynamic analysis of portal frame structure.