Shear Lag Analysis due to Flexure of Prismatic Beams with Arbitrary Cross-Sections by FEM

This paper presents the use of a finite element method (FEM) to analyze the shear lag effect due to the flexure of beams with an arbitrary cross-section and homogeneous elastic material. Beams are constrained by the most common types of supports, such as fixed, pinned, and roller. The transverse, concentrated, or distributed loads act on the beams through the shear center of the cross-section. The presented FEM transforms the 3D analysis of the shear lag phenomenon into separated 2D cross-sectional and 1D beam modeling. The characteristics of the cross-section are firstly derived from 2D FEM, which uses a 9-node isoparametric element. Then, a 1D FEM, which uses a linear isoparametric element, is developed to compute the deflection, rotation angle, bending warping parameter, and stress resultants. Finally, the stress field is obtained from the local analysis on the 2D-cross section. A MATLAB program is executed to validate the numerical method. The validation examples have proven the efficiency and reliability of the numerical method for analyzing shear lag flexure, which is a common problem in structural design.

Analysis and Study on Bending Vibration Frequency of New Corrugated Steel Web Composite Box Girder

In order to accurately analyze the bending vibration frequency of the new composite box girder, the effects of web folding effect, shear lag, and shear deformation are comprehensively considered in this paper, and the elastic control differential equation and natural boundary conditions of the composite box girder are established by using the Hamilton principle. A one-span composite box girder with corrugated steel webs is used as a numerical example. The effects of height span ratio, width span ratio, web thickness, cantilever plate length, and fold effect on the vertical vibration frequency of the new composite box girder are analyzed. The results show that the analytical solution is in good agreement with the finite element solution. When considering the shear lag and fold effect, the vibration frequency of composite box girder decreases. With the increase in order, the influence of shear lag and fold effect on its frequency becomes stronger. The changes of height span ratio and web thickness of composite box girder have a great influence on its folding effect, while the changes of width span ratio and cantilever plate length have little influence on it. The conclusion can provide a reference for the design of medium section new composite bridge in practical engineering.

STUDY ON SPATIAL STRESS EFFECT OF PC CONTINUOUS THIN-WALLED BOX GIRDER BRIDGE

In order to study the influence of spatial stress effect and shear lag effect on the cracking of PC continuous thin-walled box girder bridge, a spatial model was established by using ANSYS finite element software to analyze the internal stress distribution of the bridge. The test results are compared with the analysis results of spatial model and plane link system model through the load test of real bridge. The results show that the longitudinal stress is evenly distributed along the width direction, which means that the spatial stress effect and the shear lag effect have little influence on the downdeflection of the bridge. The shear lag coefficient at the longitudinal axis of midspan bottom plate and the intersection of bottom plate and web are larger than other positions, which is most likely to produce cracks caused by stress concentration, and should be strengthened here in practical engineering. The results of load test show that the results of spatial finite element analysis are more reliable than those of plane link system calculation, and the design and construction based on the results of spatial finite element analysis is safer.