Research On Construction Control Of Long-span PC Continuous Beam Bridge By Cantilever Casting

With the rapid development of China's highway and railway, more long span bridges were needed to span great rivers and bays. PC continuous beam bridge emerged as required and has been developed fleetly in recent years. The PC continuous beam bridge can meet the carrying capacity of long span bridge, This kind of structure is fit for the comfortable steer .It characterized the wholeness of structure, good aseismatic ability and load-bearing ability, construction rapidness, brief bridge style, easy to maintain and convenient for segmental construction using the cantilever technique. The PC continuous beam bridge have taken an increasingly great proportion in bridges constructed and those under construction at city and county. there are a few the construction methods of the PC continuous beam bridge .Among these methods , cantilever installation and cantilever casting have been used widely. Especially since cantilever casting method was born in 1953, The PC continuous beam bridge has been developed rapidly. In our country, this construction method is adopted in the construction of the long span PC continuous beam bridge constructed widely . This construction method results in the complex change of the internal forces and displacements in the bridge. For ensuring bridge construction quality and construction safety, the construction control is indispensable. In fact, construction control of bridge had been used previously, such as steel trussed girder. But when self-erecting construction is maked application for PC bridge ,some problems are appear. Except the heterogeneity and instability of concrete material, the construction of PC bridge are effected by some uncertain factor ,such as temperature ,humidity and time. For the adoption of the self-erecting construction each segmental concrete interacts, and this interaction is different. So these influencing factor are bound to result in the offdesign of the internal forces and displacements along with the change of concrete laying process. For ensuring construction quality, the strict construction control should be carried out in the whole bridge construction. It to say that the construction control is quality assurance of bridge construction. The task of the bridge's construction control is controlling the process of bridge construction to ensure internal force and deformation of bridge being the safe range, and make sure the state of constructed bridge adhereing to design specification. The deformation control is most important. This paper mainly combined the project sponsored by JiLin Province Communication Department to research the computing method of deformation control, the adjustment and forecast of deflection's error, which using the data of the Tao-Lai-Zhao songhua river bridge. The chapter one the developing process, structural form and foreground of application of PC continuous beam bridge are introduced in detail, the basic principle and construction process of cantilever casting are stated particularly, the necessity of long span concrete bridge construction is summarized. The main work that had been done was put forth in this chapter. The chapter two the chief content and influencing factor of long span concrete bridge construction are mainly introduced, accumulated experience for same style bridge construction. The viewpoint that deformation control is important in stage of concrete bridge cantilever construction was put forth.This chapter summarized present state of bridge's construction control and chief control method at home and abroad in detail and the problem of exiting method, lay a foundation for the research on construction control method. The chapter three vertical control method of cantilever casting construction is mainly studied. Combining FEM , on account of concrete creep strain the compution of node deflection was analyzed. By means of QJX that is a general bridge analyse software, the constructed segments of Tao-Lai-Zhao songhua river bridge was computed to benefit the latter works. In chapter four, the exiting construction control method was improved. The sensitivity of design parameter was analyzed, It is put forth that using the principle of susceptiveness to make identification and adjustment of design parameter to adjust the error between the computing deflection and actual measured deflection of each cantilever construction segment. So the bridge can be healed propitiously. This method is simple and feasible for technical staff, and can identify the chief parameter influencing structural state of bridge quickly, and make adjustment to reduce the error and to ensure favourable result of construction control. The chapter five the new method which can forecast error of each construct segment cantilever accumulate deflection is bring forward. The method is based on the mathematics statistics and least square method. Using this method the constructor can take steps to reduce construction error in advance. The method is a powerful tool that can ensure the construction quality. Based on the previous five chapter's works, in the chapter six the works that had been done is summarized. Drew the conclusion as follows:(1)The construction controls of PC continuous beam bridge should starts with the deformation control , configuration stress control and configuration stability control and the most important is deformation control. (2)The key problem that deformation control is the control of cantilever casting because of the heterogeneity of the concrete material, result in the erratically of deflection in the construction period. It is very important that how to adjust and predict the accumulation of the deflection to make the control obtaining the good result and assurance construction of the bridge gathering together . (3)By means of an sensitive analysis method the construction bridge of design parameter can be adjusted. The sensitivity analysis can be carried on to the design parameter first to confirm the main design parameter which influence bridge structure, then compute its sensitivity, aiming at carring on the parameter adjustment. (4)This sensitive analysis method is more simple and handle than other method and the accuracy is higher, and make that calculated value is equal to the measure one to adjust the error of the deflection, making the deformation control to obtain the good result and assuring construction of the bridge gathering together smoothly. (5)The method of deflection prediction is base on the mathematics statistics and least-square theories. Through calculation and analyse, the forecast error adjustment rate attains 50% above, under the condition that bridge construction control's indetermination factors are quite a few, the validity and practicability of this method is stick out a mile. Using the...