| ABSTRACT:Externally prestressed box girder with corrugated steel webs, which uses corrugated steel webs instead of concrete webs, is a new composite structure. This type of structure has a great deal of advantages, such as light self-weight, excellent anti-seismic performance, high effective prestressing system,short construction period and higher economic effectiveness. On the base of practicality, the former research achievement and design experience in the world are summarized. The key problems in the practical design of this type of girder are holded and studied intensively using the method of theoretical analysis and experimental verification. Suggestions are given and verified by field test of an actual birdge.In view of the structure of externally prestressed box girder with corrugated steel webs, the influence of sectional curvature of externally prestressed box girder with corrugated steel webs is considered through formula of addition bending moment built by shear slip strain of shear key. The influence of stress increment of external tendons on the deformation of girders is calculated respectively based on the plastic hinge method and deformation assumption method. The result is verified by experiment. It shows that the sectional curvature is increased when considering shear slip of shear key; the calculated results using formula deduced in this article approach to measured results, which can give reference to same type projects.In view of the evident torsion and distortion deformation of box girder with corrugated steel webs, considering the distortion caused by torsion of box girder, the formula of eccentricity magnifying coefficient of box girder with corrugated steel webs is given. The availability of the formula is verified by experimental results. It is shown that the eccentricity magnifying coefficient of box girder with corrugated steel webs is obviously larger than the experiential value of eccentricity magnifying coefficient of concrete box girders. The formula of eccentricity magnifying coefficient deduced has high consistency with the experimental results, which shows that the formula can be used as a reference to the the design of other box girder with corrugated steel webs.In view of the evident shear lag and shear deformation of box girder with corrugated steel webs, using the variational principle method, the deflection formula of box girder with corrugated steel webs is deduced. Comparing with the results of the experimental results and the finite element model, the effectiveness of the formula is verified and the influence degree of each affecting factor is analyzed. The analysis results show that theoretical calculation formula has high consistency with the results of the experimental and the finite element analysis, which can be used to calculate the deflection in the design and construction. The shear lag has influence on the distribution of the normal stress; the shear deformation has no influence on it. Considering the shear lag effect, the deflection value can increase 1.3%.The deflection value can increase 44.7% when considering shear deformation. So shear deformation can not be ignored in the actual design.Based on the research results of this paper, combining the former research achievement and design experience, the key problems in the practical design of this type of girder such as selection of the structural parts, internal force calculation and deformation checking etc. and the effectiveness of design guidance is verified by field test of an actual birdge. The design guidance can be used as guidance for the design of box girder with corrugated steel webs. |
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