Torsional Stability Analysis Of Central Cable Plane PC Cable-stayed Bridge With Extra Wide At Construction Stage

The central cable-stayed PC bridge is a new type of cable-stayed bridge.With the outstanding advantages of attractive appearance and reasonable force,and the wide bridge deck can meet the increasing traffic demand,it is increasingly welcomed by bridge builders.However,due to the large lateral width of the deck,the main beam is more sensitive to laterally uneven loads during construction.In the cantilever construction phase of the main beam,the stiffness of the main beam is relatively weak,and there are many system transitions,which is an unfavorable phase of the bridge construction and operation cycle.At the same time,the layout of the cable surface in the center of the anchor deck cannot provide enough torsional stiffness.It is generally believed that the torsional stiffness is mostly provided by the main beam itself.This exacerbates the risk of torsional overturning of the main girder during the bridge construction period.The paper relies on a typical super-wide central cable-stayed cable-stayed bridge project in Guangdong Province to study the torsion overturning stability of the main beam during the entire construction period of such bridges.The main contents are as follows:1 Based on the design data and actual site conditions,the finite element model of the construction process of the ultra-wide cable-stayed bridge was established,and the most unfavorable phase of the partial load and disconnection of the construction during the entire construction period was calculated.2 Quantify the contribution of the cable stayed and the main beam to resist torsion under eccentric load.Under the maximum single and double cantilever state under partial load,the main beam's resistance torque is more than 3.5 times the cable's resistance torque,confirming the torsional stiffness of cable-stayed cable-stayed bridges is mainly provided by the main beam.The mechanism of the torsional characteristics of the wide cable-stayed bridge is more clearly revealed.3 In view of the above-mentioned most unfavorable stage,a number of working conditions were established to study the deformation and force characteristics of the structure under the action of partial load and breakage of the construction,and to compare and analyze the effect of lateral partial load and breakage on structural deformation and internal forces.Under the effect of eccentric load,the main beam still takes the bending as the main deformation,there is no negative reaction force of the bearing,and the structural elastic stability coefficient is greater than 4,the torsional effect does not affect the overall performance of the force.However,under the action of a single breakage cable,the structural elasticity stability coefficient is 3.77,which does not meet the requirements in the specification greater than 4,and the torsional stability is insufficient.4 The parametric analysis of the lateral cable distance of the cable stays and the steel pipe pile structure was carried out to study the effect of the cable tension and stability on the structure during the construction phase.Temporary consolidation of steel pipe piles is important for increasing torsional stability during cantilever construction of the main beam.Properly increasing the horizontal and vertical distances of the steel pipe pile arrangement can increase its effectiveness.