Chao Dou

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...

In-Plane Failure Mechanism and Strength of Pin-Ended Steel I-Section Circular Arches with Sinusoidal Corrugated Web

AbstractThis paper investigates the global in-plane failure and local web shear failure mechanism and strength of steel I-section circular arches with a sinusoidal corrugated web. In reference to a flat web that can resist both the shear and axial forces, the sinusoidal corrugated web can resist the shear force only. As a result, the sinusoidal corrugated web may fail in an elastic-plastic shear buckling mode. This study considers pin-ended circular steel arches with a sinusoidal corrugated web under a uniform radial load or a uniform vertical load to elucidate numerically their different failure modes. It is found that local web failure occurs suddenly without warning, and all aspects pertaining to the local web shear failure are investigated thoroughly with an equation for the ultimate shear-carrying capacity of nonuniformly sinusoidal corrugated webs being proposed. It is also found that the effects of the shear deformations of corrugated web on global in-plane buckling and the strength of steel arches...

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...

Effects of Geometric Imperfections on Flexural Buckling Resistance of Laterally Braced Columns

AbstractThis paper deals with the effects of geometric imperfections on flexural inelastic buckling resistance of axially loaded columns with equally spaced lateral braces and presents a simplified way of forming the critical geometric imperfection for finite-element analyses, which leads to rational results for buckling resistances. First, laterally braced columns with geometric imperfections formed by the traditional single half sine wave or the eigenbuckling modes were analyzed by FEM to illustrate the effect of different imperfection shapes. Second, geometric imperfections of columns acquired from measurements in laboratory tests were adopted, and the statistical characteristic and probability distribution of initial deflections along the column length were obtained; then, extensive numerical results from finite-element analyses were obtained through random imperfection simulations. Last, the comparison was made between statistical results based on the random imperfections and those based on eigenbuck...

Flexural-Torsional Buckling Resistance Design of Circular Arches with Elastic End Restraints

AbstractThis paper presents the flexural-torsional buckling resistance and design of steel circular arches subjected to uniform compression with elastic end bending restraints by using finite element (FE) numerical analyses. Firstly, effects of geometric and mechanical parameters such as initial imperfections, section types, material properties, slenderness, rise-to-span ratios, and end restraints on flexural-torsional buckling resistances of arches are investigated and are found to be eliminated to a large extent by introducing the normalized slenderness. Then, on the basis of extensive numerical results, a design method is proposed to predict the flexural-torsional buckling resistances of circular arches in uniform compression with elastic end restraints by the column curves according to the normalized slenderness and a specific section type, namely curve ‘a’ for hollow sections, curve ‘b’ for welded box sections, and curve ‘c’ for welded I-sections. Next, the flexural stiffness of an arch is studied, t...

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.

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...

Study on failure mechanism and end construction influences of double rectangular tube assembled buckling-restrained brace

The double rectangular tube assembled buckling-restrained brace is a new type of buckling energy consumption buckling-restrained brace. Because of its external restraining members, which are bound by high-strength bolts, its mechanical mechanism is more complicated and its failure modes are more varied. In this study, the double rectangular tube assembled buckling-restrained brace composition and three types of end constructions are introduced in detail. The influences of different design parameters on the performance of double rectangular tube assembled buckling-restrained brace are studied by numerical analysis methods; the possible failure modes and the influence of the end strengthening construction of double rectangular tube assembled buckling-restrained brace are also investigated, and a number of suggestions are proposed to improve this design. This study shows that the pinned double rectangular tube assembled buckling-restrained brace has four types of typical failure modes, namely, overall buckling failure, external end local pressure-bearing failure, bending failure of the extended strengthened core region and bolt threading failure. Rational design can prevent a buckling-restrained brace from losing its load-bearing capacity. In addition, compared with the end strengthening scheme with an external hoop, the end strengthening scheme with a strengthened bench can improve the load-bearing capacity of the double rectangular tube assembled buckling-restrained brace more effectively, and a reasonable design can also save materials.