Study On Construction Control Technology Of Cantilever Pouring Concrete Arch Bridge

Cantilever pouring method is a common construction method for large-span concrete arch bridges in foreign countries.In recent years,there are five concrete arch bridges built with this method in China,and four of them are under construction.With the continuous maturation of construction technology and structural analysis theory of cantilever pouring concrete arch bridges,it is an inevitable trend to construct long-span concrete arch bridge by cantilever pouring method.When concrete arch ring is constructed by cantilever pouring,cable force is more sensitive to the stress and alignment of arch ring.Due to the small tensile strength of concrete,it can only be controlled by tensioning or adjusting cable force.Therefore,this thesis focuses on stress control analysis of cantilever pouring concrete arch bridge,takes the Yelang Lake bridge under construction as the object of study,which will be carried out as the following study work:(1)In view of the fact that the “improved stress balance method” take allowable tensile and compressive stress as the stress control limit,the formula is complex and the amount of calculation is large.It is proposed that only the allowable tensile stress of concrete is used as the stress control limit,and deduction of the theoretical formula for cable force feasible region algorithm is proposed,and the “improved algorithm for cable force feasible region with prediction mechanism” is proposed.(2)Based on a group of cables corresponding to one control section for segment of arch ring only ensures that stress of the control section is controlled,and the remaining section stress still has the problem of over-limitation.The idea of using multiple sections to control is proposed.In order to reduce the scale of the stress-influencing matrix,the “double control section method” is studied to select the main control section and the additional control section as stress control constraints in the stress-sensitive region.(3)In view of the different resistance of the concrete arch ring to tensile stress capability during the cantilever pouring stage,combination of “improved algorithm for cable force feasible region with prediction mechanism” and “double control section method” is proposed for cantilever pouring to judge the way of tensioning of cable during the cantilever pouring stage,and the influence of cantilever pouring on stress of concrete arch ring is studied.(4)The combination of “improved algorithm for cable force feasible region with prediction mechanism”and “double control section method” is generalized to stress control of concrete arch ring in the stage of stiffening skeleton outsourcing concrete pouring,and the influence of outer concrete pouring on stress of cantilever pouring concrete arch ring section and outer concrete is studied.