Research For Static Model Test Of Long-span Prestressed Metro Station With Closely Spaced Frame

Metro station gives priority to adopting three-span two-layer island type structure with open(cover)cut method at present,and the column spacing of platform floor changes from 5 meters to 10 meters.The applicability and comfortability of the structure need to be improved,since space and span are both limited.It cannot perfectly fulfill the requirement of long span and the demand of constructing new type rail transit,which is resource-saving,environmentally friendly,technically innovated,safe and convenient.Recently,China has started planning and practicing long-span metro stations without columns,whose maximum span has reached 15.8 meters to solve a series of problems brought by the small span.Prestressing technology has been applied by Shanghai Academy of Building Research to control the crack and seepage in metro station,which has been successfully tested at Zhongshan Park station of Shanghai No.2 Metro Line.This dissertation focuses on studying long-span prestressed metro station structure with closely spaced frame through finite element calculation,design optimization and static model test based on the existing engineering practice and research of long-span metro station without column.Its mechanical performance and failure characteristics under static loads are obtained.The model test is divided into two groups,A and B,whose sizes are 1/8 of prototypes.The top and the foundation of model A are beam slab structures with unidirectional force.Hidden columns are set in side walls at corresponding positions of main beams,and vertical haunches are set in top beams.The top beam of model B gets haunches in the full length,whose bottom surface is elliptical,while model A only has haunches at the support.The foundation of model B has changed from beam slab foundation into slab foundation with hidden beams compared with model A.Based on the existing calculation and test conditions,the main results are as follows:(1)The performance of model structure achieves the expectation,bearing capacity,tensile stress and deflection can meet the control standard.Calculation results of stress,displacement and effective pre-stress are in good agreement with experimental results,so the design and calculation method of model structure is reasonable and feasible.(2)The arching effect of haunch and foundation type has great influence on the structural performance.The arching effect of vertical haunch has an evident strengthening effect on the top beam,while the horizontal thrust of arching effect will have an adverse impact on the substructure,which should be paid adequate attention in design.The performance of slab foundation with hidden beams is significantly better than that of beam slab foundation with the same thickness to span ratio.(3)The effective prestress of circumferential prestressed tendon should be controlled in practical engineering,while the structural performance review of various unfavorable conditions should be carried out.The deformation of foundation can be controlled through prestressing the bottom plate(beam),and the foundation can be broadened outside appropriately to adjust the phenomenon that subgrade reaction concentrates under sidewalls.In summary,when the surrounding environment does not have tensioning conditions,the internal tensioning prestressing technology can be adopted to realize the long-span design of metro station.