Study On Key Construction Techniques Of Reinforced Concrete Arch Bridge In Mountain Area

The reinforced concrete box arch bridge has the characteristics of good integrity,high material utilization efficiency and low maintenance cost of the main arch structure.When the arch bridge strides over the U-shaped valley,which forms a further distance between the arch ring and the valley bottom,cast-in-place method of the steel arch centering provides a feasible method for this kind of arch bridge construction.In the construction of the box arch bridge in mountainous areas of southwest China,the cast-in-place method of the steel arch centering is widely used,and the construction span is usually less than 150 m.The stability and deformation extent of the arch centering during the construction process determines the construction safety and pouring quality of the arch ring.This paper summarizes the development history of the reinforced concrete arch bridge in the past 40 years,concludes the characteristics and precautions of the construction method for the arch centering,and moreover,studies some problems in the construction of the deck arch bridge in mountains areas.In this paper,the accuracy of the calculation formula of the main cable of the cable crane in the assembly of the arch centering,the influence on the overall stability caused by the parallel connecting of the arch centering,the local stability of the arch centering chords,the instability of the reinforcing bar in the pouring of the arch ring,as well as the method for determining the length of sectional pouring,are studied orderly.The research results aim to provide reference for professional technicians engaged in bridge design and construction.The main work includes several parts as follows:(1)The mechanical characteristics and engineering application of arch bridge in mountains areas in China are introduced,and the historical development of different stages and achievements of the deck arch bridge are reviewed.Besides,the advantages and disadvantages of the five construction methods of the deck arch bridge are briefly described.(2)Summarize the key steps in the utilization of the cast-in-place method of the steel arch centering,introduce the types and generality of the commonly used steel arch centering in China,and therefore,conclude the core technology and precautions in the utilization of the cast-in-place method of the steel arch centering.(3)Define the load factor and use the dimensionless form to express the cable force and deformation.With the span ratio of the main cable within the range of 1/10~1/18 and the load coefficient within the range of 1 ~ 4,the difference in calculation results of the catenary theory and the parabola theory is then compared and analyzed.(4)Study the influence on the overall stability caused by the lateral bracing of the arch centering,and analyze the contribution of the different lateral bracing to the stability of the arch centering.The calculation method of the reinforcing bar stability in the construction is studied,and the necessity of setting isolation trenches in the pouring is proved by the calculation result.(5)Define the deformation evaluation index of the arch centering,determine the optimization conditions of sectional loading sequence of the arch centering,and calculate the deformation of the arch centering by using the gap truss element.The segmentation principle of the cast-in-place method in 7 sections of the steel arch centering and its deformation criterion are put forward,which can be applied to practical projects by programming.