Research On The Optimization Of Closure Of Continuous Rigid Frame Bridge With Asymmetric Construction

The continuous rigid frame bridge for the advantages of convenient construction, reasonable force, and economical cost has been widely used in domestic bridge construction. As to continuous rigid frame bridge built in the mountain valley areas, due to the landform limits, main-side span ratio has to be different from common bridges, the bridge span is often set to asymmetric forms, which will cause the number of beam segments on both sides of T-Frame is unequal, such continuous rigid frame bridge is often different from continuous rigid frame bridge with the symmetrical span, the closure methods are therefore different.Xiaowan Bridge which is a typical continuous rigid frame bridge with asymmetric construction located in Puxuan Highway in Yunnan Province, using MIDAS/Civil,this paper contrasts and analyzes its two asymmetric construction methods and its reasonable closure plan. The main contents and results are as follows:⑴In order to finish the construction of the asymmetric beam segments on sidespan, two construction methods concerning four aspects including the deformation of main girder, the internal force of main girder,the internal force of piers and horizontal displacement at pier top are contrasted and analyzed.⑵Four aspects including the deformation of main girder, the internal force of main girder, the internal force of piers and horizontal displacement of pier top are compared between two different closure sequences.⑶Considering the effect of temperature difference, the temperature has a strong impact on stress and displacement of the girder. Set the rise of system temperature an example, the differences of the effect of the temperature difference between different closure sequences are analyzed.⑷The shrinkage and creep of concrete has an effect on the bridge construction process and the final bridge state. The effect of the shrinkage and creep of concrete to the stress and deformation of main girder, and the difference of the action when the bridge has different closure sequence are analyzed. The results of comparison and analysis show that the closure sequence which closures side span first and mid span second is more favorable and should be selected.⑸Normally, before the continuous rigid frame bridge begins to closure, it is necessary to conduct incremental launching. The calculation method of closure jacking force using finite element model is expounded. By calculating the displacement of pier top caused by temperature difference and concrete shrinkage and creep, displacement which need to be controlled during the incremental launching is obtained, jacking force is calculated as well. A linear relationship between jacking force and temperature difference is found. A practical calculation formula is fitted out using MATLAB, thus jacking force can be calculated.There are many continuous rigid frame bridges with asymmetric construction at home and abroad, but the related literatures is seldom. Through this paper, which a detailed comparative analysis of the asymmetric construction continuous rigid frame bridge is conducted, the results obtained can provide a good reference for the design and construction of similar bridges.