| The straddle-type monorail belongs to the form of urban rail transit with small and medium capacity.Because of its unique technical advantages,it has a very broad prospect in the future of urban rail transit in China.However,the existing straddle-type monorail transporttation in China mainly adopts PC(Prestressed Concrete)track beams with a simple support system at present.The small span leads to poor structural permeability and a large amount of later operation and maintenance.Therefore,the PC track beams with continuous rigid frame system is used to improve the ability of straddle-type monorail to cross over the curved section.Since there are few studies on continuous rigid frame curve PC track beams and no lines opened in China.So,the design of continuous rigid frame curve PC track beam bridges are studied in this paper.The main research work and results of this paper include:1)The analysis of the structural design of the track beam structure is completed,and the general layout is determined as three spans and one joint.The track beam adopts a rectangular section with a width of 0.69 m,and the substructure adopts a T-shaped standard pier.And the two design methods of the track beam structure are compared,and the limit state method is tried to design the structure.The construction method of simply supported variable continuous rigid frame is determined,and the structural system conversion process is analyzed.In addition,this paper analyzes the mechanical characteristics of the straddle type monorail curve PC track beam,and the check index of the track beam is proposed.2)In this paper,many factors affecting the mechanical properties of continuous rigid frame curved beam bridge are analyzed,and the curve radius,beam section height,side to mid span ratio and pier stiffness are determined as the key design parameters of the track beam bridge.Then,the influence of design parameters on the mechanical properties of the track beam bridge is calculated and analyzed by using the control variable principle and the finite element software.The research results can guide the design of the track beam bridge.3)The prestressing effect of curved track beams is studied,and the longitudinal shape of prestressing tendons are determined.Through finite element analysis,it is found that the prestress has a greater effect on the torque of the curved track beam section,and the smaller the radius of the curve,the greater the adverse impact on the structure.So it is necessary to pay attention to the torsional design of the structure.4)The influence of sensitive parameters such as temperature effect,prestressing effect and concrete loading age on the structure and shape of the bridge during the bridge construction has been studied.The results show that the closure of the track beam should be avoided in the period with large temperature change;the tension stress should be strictly controlled during the construction and the loss of the prestress should match the design value;the age of the prefabricated track beam has a greater impact on the vertical displacement of the stru-cture,it is suggested that the age should be more than 7 days.5)The three-span continuous rigid frame rail girder bridge is designed,and the stress characteristics during the conversion of the track beam system are analyzed.Finally,the safety of the track beam structure during the system conversion and the static and dynamic performance of the structure during the operation period are checked,the results meet the requirements of the code. |
