Study On Spatial Behaviour Of Curved Continuous Rigid Frame Box-girder Bridge With High-pier

The study on prestressed concrete curved continuous rigid frame bridge with high pier& long span is just getting started in our country at present. Research on box-girder bridge includes both straight ones and curved ones, the research methods not only includes facet analysis with local space analysis, but also includes pure spatial behaviour analysis. But with regard to the pre-stressed structure of curved bridge, the method of pure spatial analysis is used lesser; the further spatial analysis based on grading and working conditions is much lacked. For the ordinary straight bridges, the adoption of planar program with local space analysis can meet the demand of design & calculation, while for the curved ones, it is necessary to use spatial calculation procedure. At present, study on analysis of internal force for high pier & long span curved continuous rigid frame bridge mainly focuses on analysis on shear lag, torsion and local space etc. This kind of study proceeds its analysis around single factor, the methods of single-factor analysis and its achievement are relatively mature, but as they are all the methods of "planar linkage system with local analysis" and "three-dimension element of incomplete space", they can't reach the simulation analysis of complete space.This paper is the theoretical support of the science & technology project on transportation construction of western China:"Study on Design & Construction Technology of High Pier & Long Span Curved Bridge". Making use of BridgeKF developed by the project team, this research raise the spatial solid analysis to the simple degree of girder element, and makes the automatic calculation of pre-stress, simulation of work progress by stages, automatic dynamically programming for live load; This article provides the modeling method based on the solid element analysis of BridgeKF. This article provide the technical tool and the method for further using it to study the high pier& box-girder continual rigid frame curved bridge's spatial behavior, and lay the foundation; By way of the massive numerical calculus analysis to prestressed concrete curved continuous rigid frame bridge structure with high pier & long span, this paper study on internal force change rule of this kind of bridge systematically, and build the rationale for the design and the construction of curved continuous rigid frame bridge with high pier& long span. The main work include:Based on the home and abroad achievements, a systemic research on spatial behaviour of curved continuous rigid frame box-girder bridge with high-pier is made. In order to accord with the habit of engineering design, after a pre-anlaysis of load, difference in temperature, enforced displacement, shrinkage and creep, dynamic programming, prestressing force and it's losses and simulation in the stage of construction, discuss in depth from the above 5 aspects, analysis of box girder torsion and shear lag of box girder, box girder transverse analysis, analysis of spatial of thin-wall pier and forced displacement of box girder:(1) Analysis of box girder torsion mainly studies the influence of bend radius to box girder torque, vertical bending moment, lateral bending moment, vertical shear force and the deformation analysis, emphasizes on torsion effect. (2) The study of shear lag mainly focuses on the law of influence of such factors as the radius, height of pier, ratio of span to height of girder, width-span ratio to the shear lag effect of curved bridge. (3) Transverse analysis emphasizes on the analysis of lateral stress of the box girder structure and lateral displacement of the pier cap, the major variables are dead load, bend radius, prestressing force and temperature change. (4) Analysis of thin-wall pier lays important research on influence of curved box girder to thin-wall pier, the key changing factors include dead load, bend radius, pre-stress and temperature. (5) Forced displacement lays important analysis on influence of the forced displacement of support and main pier to the upper box girder, the key changing factors include radius and dead load. The main innovative achievements include:1. By the analysis of torsion of curved continuous rigid frame box-girder bridge with high-pier with different radius, acquire the rule of influence of bend radius to the spatial internal force of box girder. Under the action of dead load, the most affected is torque, the second is lateral bending moment, the lesser is vertical bending moment and shear; the bend radius is smaller, the torque is larger, and the gap of displacement between inner board and out board is larger, when the bend radius is less than 800m, the growth trend of torque and displacement between inner board and out board is to get bigger. Under the action of live load, the most affected is lateral bending moment, the second is torque. While the bend radius is less than 800m (bending angle over 18.3°), the influence to various index of internal force intensifies.2. By the study of shear lag effect indicate curved continuous rigid frame box-girder bridge with high-pier, acquire the influence rule of radius, height of pier, ratio of span to height of girder, width-span ratio. Under the action of dead load, the influence of bend radius to the shear lag factor at the baseboard of box girder cap, with the decrease of radius, the response of shear lag effect at inside and outside. When the radius is more than 1200m, the influence of radius to the shear lag of box girder is negligible, when the radius is over 250m, if without regard to the influence of curvature, the error calculated by planar process according to straight bridge will be within 25%. In addition, shear lag is affected by some factors such as the height of pier, width-span ratio and the ratio of span to height of girder. The pier is higher, the effect of shear lag is more obvious, when the height is up to 40m, the influence to shear lag tends to be stable. The width-span ratio is larger, the effect of shear lag is sharper; the ratio of girder span to height is smaller, the effect of shear lag is sharper.3. Research of the lateral stress and displacement response of dead load, bend radius, pre-stress and temperature change shows:the lateral stress is much affected by bend radius; the radius is smaller, the lateral effect of baseboard of box girder cap is more obvious, and the displacement towards inside is larger. The lateral stress is relatively affected by width-span ratio and heating/cooling.4 Study on influence of dead load, bend radius, pre-stress and temperature change of curved continuous rigid frame box-girder bridge structure to thin-wall pier shows:The internal force of thin-wall pier is affected by its dead weight, upper pre-stress, bend radius, height of pier, cross section shape and temperature etc., the change of radius has much impact on side and vertical bending moment of pier; the pier is higher, the side and vertical bending moment are smaller. The displacement of central pier is mainly on lateral direction, and it reaches the maximum in case the cantilever is biggest. When the radius decreases, the lateral displacement increases.5 Research on influence of structure's forced displacement to the upper box girder shows: the subsidence of side-span support has great impact on the torque of side-span. When the support at the inner side of side-span sinks in lcm, the torque of side-span will be twice of the one of integrated bridge.The research result of this article is a guidance to studies on such fields as the internal force analysis and calculation, identification of factors influencing to internal force, structure design for high pier & long span curved continuous rigid frame bridge in our country, and can be for reference on high pier & long span pre-stressed rigid frame bridge design and construction.