Joseph A. Yura

Winter's bracing approach revisited

Winters classic bracing paper is reviewed and his method for full bracing is extended to cases when less than full bracing is used. Full bracing, as redefined in this paper, permits the column or beam to support load levels corresponding to an unbraced length of KL where L is the distance between braces and K is an effective length factor taken as 1.0. Using Winters rigid bar model, an approximate buckling load for members with less than full bracing is developed that compares very favourably with an exact solution. It is also shown that Winters model rigid bar model can be extended to cases where the brace spacing is unequal.

Bracing requirements of inelastic columns

Various types of braces are used to prevent buckling of structures and increase buckling strength. While bracing requirements of elastic structures are well explained, those of inelastic structures are not fully developed. Experimental and analytical studies were conducted to determine bracing requirements of inelastic columns. In the experimental study, columns with a brace at mid height were loaded to their maximum limit with the brace stiffness at the mid height as the main variable. The tangent modulus of the columns which governs the inelastic buckling loads was kept constant. An analytical study was also performed to compare with the experimental results. The columns were modeled and analyzed by the finite element program, ABAQUS. It was found through the experimental and analytical studies that the bracing requirements for inelastic columns depend on the number of braces, the buckling load, and the length of a column but not on the material state. The results show that Winters simplified method to determine full brace requirements can be applied to inelastic members as well as elastic members.

Stability bracing of beams by shear diaphragms

Light gage metal sheeting is commonly used in the building and bridge industries for concrete formwork. In addition to supporting the concrete, the metal forms also improve the lateraltorsional buckling capacity of the beam or girder they are fastened to since they behave as a shear diaphragm and restrain the warping deformation of the top flange. However, the stability bracing requirements for shear diaphragms are not well established. This paper discusses the strength and stiffness requirements of diaphragm bracing of beams. The bracing behavior was investigated by conducting parametrical finite element investigations. The diaphragms in the study were connected along two edges to the top flanges of adjacent girders. Design expressions are presented for the stiffness and strength requirements of the diaphragm.

The use of a rolled wide-flange as a bridge support bearing

Publisher Summary The research presented in this chapter describes the results of tests pertaining to the use of the rolled wide-flange section as a bridge support beating. The beating must support the compressive load associated with the bridge live and dead loads. In the longitudinal direction, the cap girder is subject to rotation caused by the longitudinal girders. If the connection restrains the rotation, moments and forces will be produced in the cap girder, the connections, and in the pier. The resisting moment is proportional to the rotational stiffness of the connection. The center of rotation of a cap girder that is free to rotate is about the neutral axis of the longitudinal girders. Since the beatings are located near the bottom flange of the cap girder and are not coincident with the center of rotation, a horizontal displacement is produced at the bearings. Furthermore, a comparison of the connection using the rocker beating and the connection with the wide-flange bearing is also highlighted in this chapter.