Research On Construction Control And Model Test Of Cantilevering Casting Construction Of Long-Span RC Arch Bridge

With the continuous development of transportation in China, the spans of bridges are becoming longer and the strength of concrete is increasing. Using the cantilevering casting method to construct reinforced concrete arch bridge is economical, and it has the advantages such as convenient construction, favorable unity, less maintenance and easier repair when there is no precast space in the construction site or it is difficult to transport the prefabricated parts. Considering the traffic construction condition of the western in our country, where most roads need to pass through the Mountain and Clough, the long-span reinforced concrete arch bridge has obvious advantages in the economy and technique, compared with the other types of bridges, and it has great practical significance to study a new technic of constructing reinforced concrete arch bridge in mountainous area. Because the technic of constructing reinforced concrete arch bridge by cantilevering casting is used firstly in our country, in the thesis, some research work surrounding the issue of the technic based on collecting and studying correlative information at home and abroad, has been done in the following:1. Based on collecting and studying correlative information at home and abroad, referring to the construction control methods and calculation theory of cable-stayed bridges, continuous beams and the others constructed by cantilevering casting, the origin and types of construction error are analyzed, the mothed of eliminating error is put forward. The construction control method of constructing reinforced concrete arch bridge by cantilevering casting is researched and the construction control system applied to construct reinforced concrete arch bridge by cantilevering casting is established.2. The stress balanced method is applied to determine the reasonable construction state of reinforced concrete arch bridge constructed by cantilevering casting and relevant expressions are intrduced to determine the reasonable dimension of cable force during the course of construction. The program of the stress balance method is developed based on MATLAB program language. The technique of "birth and death element" is applied to the simulation analysis for the construction process of reinforced concrete arch bridge by cantilevering casting. What's more, the command file about the simulation analysis is programmed based on the development tool APDL language in ANSYS, which makes simulation analysis rule and simple. The method of determining anchorage cable force in the course of reinforced concrete arch bridge constructed by cantilevering casting is intrduced.3. It is intrduced that the internal force of the reinforced concrete arch in the finished state can be improved by adjusting cable force before the closure of the reinforced concrete arch rib at the crown. An optomization model is established to optimize the cable force, and the optomization program method is developed by the multi-objective, multi-restriction optimization algorithm, based on MATLAB program language. Taking the NO.1 Baishagou Bridge as example, the cable force optimization before the closure of the arch rib at the crown and the sequence of removing the cables after the closure of the arch rib at the crown are discussed.4. The sensitivity of the parameters which induces error in the process of construction by cantilevering casting is analyzed in order to reduce error of design parameters in the NO.1 Baishagou Bridge and the main design parameters are confirmed. Based on this, the real value of parameters is identified by least square method and the error of desien parameters can be eliminated in the process of construction control.5. Taking BaiShaGou 1~# bridge as example, which lies on the highway from XiChang to PanZhiHua, a model test of cantilevering cast construction of reinforced concrete arch bridge is done, which simulates roundly the course of cantilevering cast construction and tests the displacements, stresses of the master sections of the reinforced concrete arch rib, forces in the tiebacks. A finite element calculation mode was made for optimization of cable force by the stress balanced method and the cable force adjustment before the closure of the rib at the crown. The test resultes show that the test and calculated results of displacements of the reinforced concrete arch, stresses of the master sections and cable forces reasonable agreement. The method of the cable force optimization is rational and the construction technic of cantilevered casting of reinforced concrete arch bridge is feasible. Finally, the ultimate bearing resistance is tested and it shows that the main arch made by cantilevering cast construction has a high coefficient of safety.