Applicability And Key Techniques Research Of Precast Segmental Bridges

Precast segmental concrete bridges have many advantages, such as accelerating construction, less environmental influence, improving construction quality, lower long-term cost. Though this technique is applied in several projects of China, its applicability hasn’t been researched. This paper analyzes matters which influence the design and construction of bridges, then formulate an approach to choose plan. In addition research on shear capacity of joints and bowing of match cast segments during hydration of concrete is carried out. The main work and results are as follows:(1) Description of span-by-span assembly and cantilever assembly and analyzing matters that limit their applicabilities.(2) Discussing advantages of precast segmental bridges in technique and cost. Listing matters such as length, span, ambient condition, transportation, cost, quality, and concluding suitable conditions for precast segmental bridges. Calculating life-cycle cost of different construction plans under different lengths.Formulating an approach including matters and coefficients to calculate applicabilities of construction plans. The formula expresses the ability per cost, so it could judge whether the plan suits the project. Two different examples using three construction methods are shown to verify whether the formula is practical.(3) Researching stress state in the base of shear key and get a hypothesis ofay. To verify the hypothesis, a simple FEM is modeled and the distribution ofτ is distinctive. With the equation consists of σy and τ, the shear capacity of dry joints under shear-off failure is figured out. Then shear capacities of epoxy joints and joins under shear-moment failure can be work out.By calculating the capacities of specimens made by Xiangming Zhou and comparing the results with the test and AASHTO formula, formulas by this paper are revised.(4) Setting up a FEM of match-cast segments to analyze the thermal gradient and deformation caused by hydration heat. Then studying factors such as w/l, type of cement, ambient condition to get their influences on the bowing deformation. In addition FEMs of a bridge with perfect segments and bowing segments are modeled to study the gap’s influence on the deformation and stress in a bridge.(5) Summarizing key parameters including materials, calculation methods of ultimate capacities, details of box girder, proportion of mixed post-tensioning, details of shear keys, anchorage teeth, deviators in precast segmental bridges.