The Finite Element Analysis On Mechanical Behaviors Of Large Reinforced Concrete Hollow Beam

In order to avoid increasing construction period and construction costs of shaft towerswhich vertical shaft use freezing method construction, shaft towers require a transformationlayer. Due to the upper transfer large load and large span, the section size of transferbeam supporting pillars is very large. And box girder has good mechanical properties and thehigher utilization rate of cross section, therefore, the study of hollow transfer beam hasimportant engineering application value.This paper summarizes the mechanical properties and design method of the transferbeam supporting pillars and box girder, based on the transfer beam of Zhongtian HechuangEnergy Co., Ltd Menkeqing mine main shaft well tower, design the plain girder and thehollow beam who has the same steel consumption, use finite element software to analysisultimate bearing capacity, deflection and roof concrete compressive stress under the designload, cracking load, rebar yield load and the hollow beam failure mode of different crosssection parameters of the hollow beams, get the following conclusion:(1) when the hollowratio reaches43%, compared with plain girder, the deflection under the design loadincreases by30.36%, still less than80mm of specification limits; cracking load reducing by21.05%, the yield load of longitudinal reinforcement at bottom reduce by3.36%, ultimateload reduce by10.6%, design load for hollow beam is66.63%of the ultimate load;Failuremode changes from bending failure of plain girder into shear damage of hollow beam. So,hollow beam mechanical performance meet the requirements.(2)The increase of the platethickness can reduce the stress concentration near support, slow web plate concrete crushed atthe bottom of inclined cracks near support to avoid prematurely shear failure. Thickness oftop plate increases can reduce the stress concentration at loading point, improve the hollowbeam stiffness. Web thickness increase can improve the ability of hollow beam shear, lightenthe diagonal crack development, make the hollow beam by shear damage to bending failure.Under the condition of this paper, the best thickness of the floor, roof, web plate is500 mm.(3)Solid web part beam side can greatly reduce the diagonal crack propagation of thelower web, avoid the occurrence of premature shear damage, increase the ability of beamshear, and effectively restrain inclined cracks of bend shear zone. Solid web best length is2400mm.(4)Hollow beam with bearing can improve the stiffness of beam, improve theultimate bearing capacity, reduce the deflection, lower stress concentration phenomenon offloor, roof and web plate junction, improve the mechanical property of beam, at the same timemake the crack development relatively uniform.Through a series of finite element simulation of the large reinforced concrete hollowbeams, this paper presents some design suggestions of hollow transfer beam compared themechanical properties with plain girder, and laid a certain foundation for the development ofthe form of conversion components.