Study On Structural Performance And Whole Process Simulation Test Of Curvilinear Partially Cable-stayed Bridge With Double-connected And Rigid Frame Girder

In order to meet the requirements of special terrain,route alignment,crossing obstacles and geological conditions,it is necessary to build concrete curvilinear cable-stayed bridges.At present,there are relatively few studies on concrete curvilinear partial cable-stayed bridges,and the research on double jointed concrete curvilinear partial cable-stayed bridge is fewer.In view of this,based on the investigation and statistics of the research results of some completed cablestayed bridges,this paper studies the composition,type,parameter design range and influence law of the key components of this type of structural system by using the nonlinear analysis method,the variation analysis of key design parameters,and the full bridge model test,taking the double rigid frame concrete curvilinear partial cable-stayed bridge as the prototype,Analyze the static and dynamic performance and seismic characteristics of the structure;Study the bearing capacity,mechanical characteristics and failure mode of the structure under different load modes;At the same time,the full-scale model simulation test of the whole bridge and the whole process from the construction stage to the operation state will be carried out.The main research contents and innovative achievements are as follows:1.Research on structural form and structural system of curvilinear partially cable stayed bridge.Investigate and analyze the common configurations and design characteristics of key components,compare and analyze the structural stress evolution process of the prestressed tendons of the main beam from being located in the beam(beam bridge),changing to being relatively flat outside the beam(partial cable-stayed bridge),and then changing to being relatively steep outside the beam(cable-stayed bridge),study the connection mode,interaction relationship and adaptability of tower beam pier and cables,and give the distribution rules and design suggestions of cable spacing and cable free zone length of tower beam.Based on the principle of load distribution of cable and beam of straight bridge,considering the spatial effect of curved structure,the calculation method of the stiffness ratio of cable and beam of partially curved cable-stayed bridge is established,and the modified formula of the load distribution ratio of cable and beam of partially curved cable-stayed bridge is given.It is proposed to limit the lateral displacement of tower top by setting prestress or adjusting tower stiffness;The influence of curve effect on the force of beam and tower is adjusted by the deviation of anchor points of beam and tower;Adjust the internal and external cable forces by offsetting the anchor point of the cable on the beam as a whole outwards;The anchor point on the tower shall be shifted to the outside to reduce the bending moment at the tower root and other technical measures.2.Research on structural performance of double-connected concrete curvilinear partially rigid frame cable-stayed bridge.Taking the physical engineering as the prototype,the structural effect under dead and live load is analyzed by reasonably changing the key design parameters such as side to middle span ratio,pier height to span ratio(height to span ratio),structural width to span ratio(width to span ratio),and horizontal curve design radius,and the influence of parameter changes on structural performance is studied to reveal the change rule of structural performance with key design indicators.The research shows that: the dead load of the double rigid frame concrete curvilinear partial cable-stayed bridge plays a decisive role in the structural stress,and the dead load index is the main control index in its design and calculation;Propose reasonable value range of height span ratio and side to middle span ratio;The design and engineering countermeasures to resist negative reaction of bearing under the conditions of small curve radius,small side to middle span ratio,large height to span ratio,etc.,and the sudden change of main beam torque on both sides of the tower under the conditions of large width to span ratio are given.3.Dynamic characteristics and anti-seismic performance analysis of doubleconnected concrete curvilinear partially rigid frame cable-stayed bridge.Through the dynamic analysis model established,the dynamic characteristics of the structure are analyzed,and the seismic response of the structure under longitudinal,transverse,vertical and combined actions is analyzed using the response spectrum theory.The order of vibration modes and the main vibration mode forms of the twin curvilinear concrete partial cable-stayed bridge with tower,pier and beam consolidation system are given,that is,the symmetric and anti symmetric vertical bending and transverse bending vibrations of the beam do not occur torsional vibration,which reflects the characteristics of large consolidation system stiffness and good torsional resistance of the twin structure;Vertical,horizontal and vertical earthquakes are mainly caused by vertical vibration,beam horizontal vibration accompanied by small vertical vibration and beam vertical vibration respectively.The internal forces of beams and towers increase under combined action,and the axial force,vertical shear force and bending moment of main beams increase significantly.The variation rules of structural internal forces and displacements under different actions are given,and the significant factors pointed out can be used for reference in seismic design and calculation.4.Research on bearing capacity of double-connected concrete curvilinear partially rigid frame cable-stayed bridge.Based on the elastic stability analysis of the structure,the space numerical method is used to+ λ The nonlinear bearing capacity,mechanical characteristics and failure modes of the structure under four load models in the construction stage and eight load models in the operation stage are studied in the live load mode.A nonlinear bearing capacity analysis method combining numerical method with plastic hinge theory is proposed.It is pointed out that the elastic stability of the structure is high,the stability of the cable structure is better than that of the cable free structure,whether in the construction or operation period,and the accidents such as the falling off or weightlessness of the hanging basket when the cable free cantilever is large should be prevented;The structural failure process is clarified,namely,four stages and three modes: normal operation stage initial loading section cracking;Cracking of box girder section-plastic hinge of the first section;Plastic hinge of the first section-plastic hinge of the second section;Plastic hinge of the second section-plastic hinge of the third section(corresponding to the ultimate bearing capacity state of structural failure).The research shows that the failure mode of the structure is related to the loading path,the bending failure of the main beam occurs first,the minimum live load safety factor is greater than 2,and the structural safety is good.According to the bridge bearing capacity of structural cracking,section plasticity and structural damage,the structural safety factors from small to large are: unfavorable midspan,maximum cable force,maximum negative bending moment,unfavorable side span.The load coefficients of section plasticity and damage are 2.4-6.6 and14.0-18.0 respectively.The safety of the bridge is good,and the safety of the stay cable is high.5.Model test and research of double-connected curvilinear partially rigid frame cable-stayed bridge.Relying on the physical engineering design,the full scale similar model of 1:40 steel tower,aluminum alloy curvilinear box girder and high-strength steel wire cable is made.The lever method is used for counterweight loading to simulate the key construction process,operation and overload status,and the full range model test of the double rigid frame curvilinear partial cable-stayed bridge is carried out.The model test research shows that the stress,displacement and cable force of the key components such as beams,towers and cables are within the reasonable design range during the key construction process and operation stage,the stress state of the internal and external structures of curvilinear beams is basically balanced,and the measured values of the shear lag effect and other parameters of the box section and their variation laws are basically consistent with the theoretical analysis,which verifies the reliability of the structural design of the double rigid frame curvilinear partial cable-stayed bridge,Have a certain overload capacity;At the same time,it is found that after construction loading and cable tensioning,the shear lag effect of the key section is significant,the displacement of the top of the main tower is uneven,the stress difference of the internal and external box girder structure,and the cable force distribution changes significantly in the side and middle spans,and puts forward technical countermeasures for structural design,construction,operation and maintenance.This study reveals the structural performance and bearing capacity of the double jointed rigid frame concrete curvilinear partial cable-stayed bridge,which provides a scientific basis for the structural design,construction and control,operation management and safety evaluation of such bridges.