The Analysis Of Continuous Variable Height Shear Lag Effect And Cantilever Plate Force

In the current bridge construction, there are various of structural forms of the bridge, in which box section is the most common section of the form. Box beam has a unique mechanical properties, such as the shear lag effect. Bridge construction in the past, some of them, precisely because of shear lag effect has led to the cracking or damage. So shear lag effect can not be ignored in the bridge construction. The picked out part both sides of the box beam in the roof, also called cantilever plate, which is very important to analysis for the internal force. When the length of long cantilever is more than 2.5m, should be detailed analysis. The negative moment of cantilever root in the force analysis of long cantilever plate, should be calculated according to specification. At the same time, the positive moment which is appearing in the inter-plate should not be despised.This paper studies the internal force distribution of variable height of continuous box girder cantilever. The study includes two aspects:1) The analysis of shear leg effect of variable height continuous box girder loading gravity load.2) The calculated and distribution of cantilever plate positive moment.For the analysis of shear lag effect, combined with previous theoretical results, using three limbs analogy method and solutions limb method, derive the normal stress expression of the variable height continuous box girder which section is single-box with double rooms, two side webs is oblique when it's loading gravity load. And in accordance with the actual project-SongPu bridge, calculate the normal stress value of a pivot section. With elementary theoretical value, calculate shear lag. And using ANSYS do Assisted simulation analysis, checking the availability of theoretical calculations of the value.For the analysis of cantilever plate Internal forces, with SongPu bridge, according to the design standard load "urban bridge design load standard" (CJJ77-98) 4.1.3, city-A vehicle load, and "reinforced concrete and prestressed concrete highway bridge design specification" (JTG D62-2004) 4.1.5, calculate the negative moment of the roots using Baider Bahkt method for long cantilever plate, which have edge beams, variable thickness, and its span more than 2.5m. And using ANSYS modeling, analysis the characteristics and rules of the cantilever plate positive moment when it's loading design standard load and linear uniformly distributed load. Finally, analysis the rules of cantilever plate positive moment when it's single wheel load. Try to solve, calculate wheel load maximum positive moment of cantilever plate.