High Strength Circular Steel Tubes Research Articles

Parametric Applicability Assessment of High-Strength Steel Tubes of Noise Tunnel Structures for Weight Reduction

This study addresses the material nonlinear behaviors of noise tunnel structures composed of high-strength circular steel tubes for weight reduction. A finite element elastic and plastic analysis is performed for different types of flange connections of noise tunnels. The plastic behaviors of flange connections are also investigated considering increased road widths. To reduce the weight of noise tunnel structures, this study uses four types of steel associated with various geometries of the entire structure. From an economic point of view, the parametric results obtained in this study show that the proper use of high-strength steels makes a positive contribution to the design of lighter noise tunnels. Keywords: Noise Tunnel, Nonlinear Analysis, High Strength Steel, Flange Connection

Experimental and numerical study on the stability capacity of Q690 high-strength circular steel tubes under axial compression

This paper presents experimental investigation on the local and overall buckling capacity of Q690 high-strength circular steel tubes under axial compression. Coupon tests are undertaken to obtain the Young’s modulus, Poisson’s ratio, tensile yield stress and ultimate tensile strength of Q690 steel material. Forty-two specimens under axial compression are tested to evaluate the buckling behavior and the failure mode. Test results indicate that most of the existing design standards are conservative for the design of Q690 steel tubes. The distribution model of residual stress is measured by cutting ring method. Then, a finite element model based on modified column deflection curve method (CDC) is built to assess the effects of initial imperfection and residual stress on the stability capacity of the steel tubes. Finally, design methods and recommendations are provided for estimating the stability capacity of high-strength circular steel tubes.

Nonlinear analysis of circular concrete-filled steel tubular short columns under eccentric loading

This paper presents an effective theoretical model for the nonlinear inelastic analysis of circular concrete-filled steel tubular (CFST) short columns under eccentric loading. Accurate material constitutive relationships for normal and high strength concrete confined by either normal or high strength circular steel tubes are incorporated in the theoretical model to account for confinement effects that increase both the strength and ductility of concrete. The predicted ultimate bending strengths and complete moment–curvature responses of circular CFST columns under eccentric loading are compared with existing experimental results to examine the accuracy of the theoretical model developed. The fundamental behavior of circular CFST beam–columns with various diameter-to-thickness ratios, concrete compressive strengths, steel yield strengths, axial load levels and sectional shapes is studied using the verified theoretical model. Based on extensive numerical studies, a new design model for determining the ultimate pure bending strengths of circular CFST beam–columns is proposed. The theoretical model and formulas developed are shown to be effective simulation and design tools for the nonlinear inelastic behavior of circular CFST beam–columns under eccentric loading.

Nonlinear analysis of circular concrete-filled steel tubular short columns under axial loading

The confinement effect provided by the steel tube in a circular concrete-filled steel tubular (CFST) short column remarkably increases the strength and ductility of the concrete core. The reliable prediction using nonlinear analysis methods for circular CFST columns relies on the use of accurate models for confined concrete. In this paper, accurate constitutive models for normal and high strength concrete confined by either normal or high strength circular steel tubes are proposed. A generic fiber element model that incorporates the proposed constitutive models of confined concrete is created for simulating the nonlinear inelastic behavior of circular CFST short columns under axial loading. The generic fiber element model developed is verified by comparisons of computational results with existing experimental data. Extensive parametric studies are conducted to examine the accuracy of various confining pressure models and the effects of the tube diameter-to-thickness ratio, concrete compressive strengths and steel yield strengths on the fundamental behavior of circular CFST columns. A new design formula accounting for concrete confinement effects is also proposed for circular CFST columns. It is demonstrated that the generic fiber element model and design formula adequately predict the ultimate strength and behavior of axially loaded circular CFST columns and can be used in the design of normal and high strength circular CFST columns.

Rational design analysis of stub columns fabricated using very high strength circular steel tubes

The mechanics of the compressional behaviour of stub columns fabricated from Grade 350 steel plates welded to very high strength (VHS) circular tubes are investigated in this paper. In the investigations comparisons of experimental load-axial shortening curves are made with the results of a postulated design analysis set up to examine the complete load-shortening behaviour of such members. Ramberg-Osgood type stress–strain equations are set up for the plate and tube materials. A procedure is described to evaluate the loads in individual plate and tube elements as the axial shortening is increased until the 0.2% proof strain for the VHS tube material is attained. Upon reaching this strain it is assumed that failure ensues as the result of a simple plastic mechanism occurring in the tubes. Comparisons of the load-axial shortening curves given by this analysis and experimental results indicate good agreement.

Section slenderness limits of very high strength circular steel tubes in bending

This paper investigates the bending behavior of very high strength (VHS) circular steel tubes. The tested VHS tube has a normal yield stress of 1350 MPa and an ultimate strength of 1500 MPa. A total of 12 specimens, with the normal diameter ranging from 31.8 to 75 mm and the tube thickness between 1.6 and 2.0 mm, were tested. Large bending deflection was achieved for VHS tubes with the diameter to thickness ratio up to 24. Full plastic moment was reached for tubes with the section slenderness of 197 or less. New plastic slenderness limits of 117 and 153 were proposed based on the beam plastic rotation capacity of 4 and 3. A yield slenderness limit of 264 was proposed for VHS tubes.