Analysis Of Static And Dynamic Characteristics Of Prefabricated Beam-assisted Construction Facilities

With the improvement of China's modern integrated transportation system development plan,the transportation industry is now flourishing.Higher requirements for the technological innovation of prefabricated beam-assisted construction facilities because of the large-scale construction of prestressed concrete bridge.This article is based on the data of Tibet S5 Line Lhasa to Zedang Fast Track Project of Heilongjiang Longjian Road and Bridge First Engineering Co.,Ltd.In the process of pouring prefabricated T-beam,precast beam bottom formworks have disadvantages.In view of issues such as simple structure,single size,low reuse rate and not conducive to promotion.A kind of new precast beam bottom formwork with adjustable geometry,high reuse rate and good compatibility with side formwork deformation has been independently developed.By evaluating the lifting process of the prefabricated T-beams in the B5 bid section project of Gucheng Fuyu section of bei'an-fuyu expressway,it can be found that there are many problems with the traditional crane.The traditional cranes are large in size,complex in structure,and involve a complicated disassembly and assembly process.As such,there are great difficulties in transportation and installation,and is not flexible enough for using in construction projects in multiple places.Because of above reasons,a kind of small gantry crane,which can be transported without the use of a large car,and be quickly disassembled and installed,is developed independently.The research on the whole structure of two precast beam-assisted construction facilities are as follows:Vertical and horizontal loads are produced in the prefabricated concrete Tbeams with four span specifications of 40 m,35m,30 m and 25 m.The selection of the structural components of the precast beam bottom formworks for the different span specifications is completed.The three-dimensional solid model of the precast beam bottom formworks is established using Solid Works software.The static characteristics of the precast beam bottom formworks are analyzed using ANSYS Workbench.It is verified that the precast beam bottom formworks meet the requirements of static strength and rigidity.In order to avoid the damage caused by the resonance of the structure under external excitation,modal analysis of the precast beam bottom formwork is carried out.Based on the calculation results of the first six-order modes,the response behavior of the structure under dynamic load is analyzed,and the natural frequency of the precast beam bottom formwork of each span is determined.Based on the horizontal inertia load generated during the process of lifting the prefabricated T-beams,the structural components of the lifting machine are determined.The three-dimensional solid model of the gantry crane is established.The static characteristics of the gantry crane during the lifting process of the prefabricated T-beams with four span specifications of 40 m,35m,30 m and 25 m are analyzed using ANSYS.The singularity problem in strength analysis is solved.The structural members are optimized.The final results showes that the gantry crane structure satisfies the requirements of static strength,stiffness and stability.Based on the theory of dynamic analysis,the dynamic characteristics of the gantry crane are also analyzed.The first six-order modes and natural frequencies of the gantry crane are obtained by modal analysis.Through transient analysis,the vibration response of the gantry crane in the off ground and stable lifting stages of the prefabricated Tbeam is also studied.The results show that the gantry crane vibration response of prefabricated T-beam off-ground stage is higher than steady rise stage.The out-ofplane vibration response of the gantry crane structure is greater than in-plane.The research results of this paper can provide theoretical reference for the design and application of portable precast beam bottom formworks and gantry cranes.