Si-Yuan Zhao

Experimental Investigation into Flexural-Torsional Ultimate Resistance of Steel Circular Arches

AbstractThis paper deals with experimental investigations into flexural-torsional ultimate resistance of in-plane-pinned circular steel arches. Three I-section arches with the same span but different rise-to-span ratios were tested under different loading conditions. A test rig comprising loading frames and lever beams was used to apply symmetrical three-point loads over the full span and unsymmetrical two-point loads over half the span to the arch rib. These concentrated loads are directed toward fixed points during flexural-torsional buckling of the arches. The arches are supported in such a way that their ends in plane are pinned and out of plane are semirigidly restrained. Geometric imperfections are measured before loading. The test results show that when the test arches reach their load-carrying capacity, plastic zones form in the arch rib, and the out-of-plane flexural-torsional deformation is significant. It is found that the pinned arches buckle in an asymmetric double-wave S-shaped flexural-tors...

Flexural-Torsional Buckling and Ultimate Resistance of Parabolic Steel Arches Subjected to Uniformly Distributed Vertical Load

AbstractThis paper focuses on the flexural-torsional buckling and ultimate resistance of parabolic steel arches with box sections subjected to full-span uniformly distributed vertical load by using finite-element numerical analyses. First, analyses on prebuckling internal forces and flexural-torsional buckling loads are performed and compared with the existing theories. They show that parabolic arches under uniformly distributed vertical load are actually subjected to combined axial compressive and in-plane bending actions, rather than pure compression in the classic theory. Because the bending moment is substantial for shallow arches, the classic theory with the assumption of pure compression does not predict exactly the flexural-torsional buckling load. Second, the flexural-torsional ultimate resistance of parabolic arches is explored based on extensive finite-element numerical results, resulting in a design method based on a modified slenderness. The rise-to-span ratio is found to have a great effect o...

Out-of-Plane Elastic Buckling of Circular Arches with Elastic End Restraints

Circular arches subjected to in-plane loading are restrained with discrete lateral bracings to improve their out-of-plane stabilities in many cases. The arch segment between two adjacent bracings may buckle out of plane if the effective length of the arch segment is sufficiently large. During out-of-plane buckling, adjacent arch segments may provide elastic restraints which increase the out-of-plane stability of the arch segment significantly. This paper is concerned with out-of-plane elastic buckling of circular arch segments with elastic end restraints. The analytical method for deriving the out-of-plane buckling loads of circular arches with equal rotational restraints or equal warping restraints at both ends is formulated. For the convenience of structural designers, simple approximate formulas for predicting the out-of-plane buckling loads of these arches are developed by the curve-fitting method. As for circular arches with unequal rotational restraints, the approximate formula for the buckling load of the arch with equal rotational restraints is modified with a reduction factor. Comparisons with the finite-element results and the analytical solutions show that the predictions by approximate formulas are sufficiently accurate.

Threshold Stiffness of Discrete Lateral Bracing for Out-of-Plane Buckling of Steel Arches

AbstractSteel arches are often restrained by elastic lateral braces to improve their out-of-plane stability. Because in real structures, the braces are not infinitely elastic and the strength consideration can have an effect on the stiffness requirement of the braces, it is important for the lateral braces to have sufficient stiffness and to be configured properly. This paper presents an investigation of the threshold stiffness and arrangement of discrete lateral braces required for preventing steel arches from buckling out of their plane. An energy approach is used to derive the elastic threshold stiffness for discrete lateral braces, and the effect of out-of-plane geometric imperfections on the elastic threshold stiffness of the lateral bracing is also studied. The number of lateral braces and the length of the arch segment between adjacent braces are also derived analytically by comparing the in-plane buckling loads of the entire arch and the out-of-plane buckling loads of the arch segment between adja...

Ultimate Resistance Design of Shuttle-Shaped Steel Tubular Latticed Columns

AbstractAs a new type of nonprismatic built-up columns, the shuttle-shaped steel tubular latticed (SSTL) column is widely used in engineering structures. However, there are no methods available to test its ultimate resistance design and little research about its behavior. This article investigates the elastic buckling behavior of three-tube SSTL columns only with horizontal web members and subject to an axial load, and it is found that the SSTL column may buckle in a symmetric flexure-dominated mode or an antisymmetric shear-dominated mode, depending on distributions of sectional flexural stiffness and shear stiffness along the column length. The formulas for predicting elastic buckling loads are derived by accounting for the effects of sectional shear deformations. With the elastic buckling loads obtained, formulas for the effective slenderness and the normalized effective slenderness are proposed. The resistance design procedure for SSTL columns only with horizontal web members is developed in associati...