Study Of Construction Control For Long-span PC Continuous Rigid Frame Bridge

With the rapid development of highway in our country, more long span bridges were needed to span great rivers and bays. The prestressed concrete continuous rigid frame bridge has been growing up rapidly in recent years with its unique predominance of handy construction, economical cost, reasonable internal force, comfortable traveling and convenient for segmental construction using the cantilever technique. It almost has become the first selective bridge style when the main pan is in the range from 100 meters to 300 meters.The prestressed concrete continuous rigid frame bridge adopts the segmental construction technique (cantilever installation and cantilever model). During the process of the balanced cantilever construction, the bridge structure is influenced by various factors, such as the design parameter error margin, construction error margin, temperature change of concrete, concrete shrinkage and creep, and so on. Such factors result in the complex change of the displacements and internal forces in the bridge structure. To ensure the quality of construction and the safety of construction process, and make sure that the displacements and internal forces of bridge being in the safe range, and make sure that the state of constructed bridge adhering to design specification, it is necessary to execute construction control for bridge's construction.Bridge construction control establishes corresponding model based upon the modern control theory. The model is used for finding out the true value of parameter which is affected by the various error facts. The result is used in direction of bridge's construction.Bridge construction control methods generally include afterwards control method, forecasting control method and self-adapting control method. During the cantilever construction of the prestressed concrete continuous rigid frame bridge, the beam axis shape of formed blocks can not be regulated during the subsequent constructions; therefore we generality choose self-adapting control method.In order to achieve the purpose of construction control, we must adopt reasonable theory analysis and computation method to attain the ideal state of internal force and deflection in every stage of construction. Structural computation is the theory gist of bridge monitor control. Structural computation methods include forward analysis method, retrograde analysis, without stress state method and so on. To continual rigid frame bridge, forward analysis method's computation workload is small and its precision satisfies the requirement.During the process of bridge cantilever construction, since the comprehensive disturb of the structure design parameter error margin, construction error margin, measuring error margin, structural analysis error margin and so on, that actual state of the construction always does not completely fit with the ideal state of the structure. So we must make use of the theories and methods of necessity to analyze and adjust these error margins. We carry out forecast, estimation and control in the subsequent construction period. Common theory and method of the error margin adjustment include identifying and adjusting of structure design parameters, Kalman filtering method, grey system method and least square method.This paper mainly combined the project of changxin viaduct construction control sponsored by Jilin Province Communication Department. We carry out simulation analysis to the whole construction stages by the computation software Dr. Bridge. On the basis of these computations, we find out the parameter loca of structure in construction stage, and then amend the model by identifying and adjusting the specific actual measurand parameter which is gotten by field experiment. At the same time, this paper expand on that how to carry out forecasting control for the deflection change of main girder by founding GM(1,1) model of grey system theory. And through the monitor, feedback, estimate, carry out the line form adjustment and control, coming to the preconcerted target, and verify the usefulness of grey system method in structural state parameter of estimation and reaction.This paper introduced the rationale and the comparison of stress monitoring instrument for stress test, and point out the influencing factors of stress test in continual rigid frame bridge construction supervision. This paper expound the disposal scheme of changxin viaduct stress measuring point, tidy stress monitoring results, and compare the theoretical calculation to actual measuration, and then conclude the changing rule of box-girder testing section stress during the process of bridge construction. The stress monitoring results indicating that the stress satisfies design requirements during the process of bridge cantilever construction. The construction process is security.