Alignment Control For Bridges Constructed In Stages

The method and technology of bridge constructed in stages have become one of the most notable achievements in civil engineering. Although this method has many obvious advantages, significant errors of final internal force and line shape exist between structures constructed in stages and the overall construction method. In order to solve this problem, the analysis theory of bridge constructed in stages was proposed. This dissertation addresses five parts based on the analysis theory of bridge constructed in stages:Part I:This part reviews the history of bridge constructed in stages, and describes the construction techniques, classifications, analysis methods and the approaches to determine the intermediate state of bridge constructed in stages. The equilibrium equation of the structures formed by stages is also introduced in detail. The theoretical equation shows that the internal force and line shape in the final state of the structures depend on three conditions: the loads, the structural system and the unstressed parameters of structural elements. This theory was mainly applied to the cable-supported bridge at the beginning of its development.Part II:This part introduces the composition of bridge alignment. According to the analysis theory of the bridge constructed by stages, when the unstressed parameters of structural elements are employed in the control of bridge alignment, the three spline interpolation method is used to calculate the unstressed curvatures due to the alignment of the bridge described a series of discrete height point. The detailed derivation process is staged and the examples are also adopted to prove the accuracy of the results.Part III:This part introduces the node height of the main girder into the basic equilibrium equation of bridge formed by stages and derives the alignment control equation of the main girder. The parameters for the precast segments are obtained by employing unstressed parameters as the control parameters of bridge alignment. Based on these parameters, the dissertation gives the segment contour shape and its mathematical equations. For the main girder cast-in-place construction, the alignment control equation can be applied directly and then get the elevation of formwork which meets the final bridge state.Part â…£:This part introduces the bridge alignment control considering the time dependent effect of materials. According to the analysis theory formed by stages, the formulas of calculating the variations of unstressed parameters due to the shrinkage and creep are obtained by the numerical simulation method or alignment control equation. This change is taken as a correction for the original unstressed parameters and the final corrected unstressed parameters is used in the alignment control of bridge.Part V:The part mainly focuses on the temperature effect in the construction process, According to the analysis theory of bridge formed by stages, the mathematical expression in the relative altitude of the girder segment is obtained. Based on this expression, one or several reasonable and effective approach is proposed for correcting the construction response due to temperature changes in the process, and then the accuracy of the results by these methods is validated by the specific examples, and the advantages and limitations are also discussed.