Influence Of Local Buckling Research Articles

Seismic Behavior of UHPC-Filled Rectangular Steel Tube Columns Incorporating Local Buckling

This paper presents a numerical study on the static behavior and cyclic behavior of UHPC-filled steel tube (UHPCFST) columns. A novel fiber element model is developed based on the effective distribution width method to consider the influence of local buckling. The parameters of the descending branch of the stress–strain curve of constrained concrete have been modified and proposed according to the existing experimental results. Thereafter, the impact parameter analysis of the seismic performance of UHPCFST columns under the pseudo static load is conducted, and the strength of steel and UHPC, width–thickness ratio, length–diameter ratio and axial compression ratio are considered. The results indicate that the proposed fiber element model can accurately predict the static and cyclic nonlinear behaviors of the UHPCFST columns. The bearing capacity and the post-peak ductility of UHPCFST columns can be overestimated, such as neglecting the local buckling of the steel tube, which will lead to the insecurity of structures.

Slenderness-based design criteria to allow for the plastic analysis of tubular beams

The present paper focuses on the rotational capacity of H.S.S. steel sections; in particular, the influence of local buckling is accounted for by means of a new generalized cross-sectional slenderness parameter, which is used to characterize the cross-sectional rotational capacity, and, by extension, the available deformation capacity.Careful shell modelling of hollow section beams in bending was used, the numerical models being previously carefully validated against more than 50 bending tests. Extensive F.E. studies were consecutively performed, including many parameters such as various material grades, load and support arrangements, length-to-height ratios, etc. Specific attention was paid to the introduction of initial geometrical (local) imperfections, as they were shown quite influential on the rotation capacity.The paper then analyses the numerical results and points out the various influences of height-to-width ratio, shear, moment gradient, yield stress and length-to-height ratio on the available rotational capacity. In a second step, the rotational capacity demand vs. stability criterion is detailed, and related to the proposed generalized cross-sectional slenderness, which is shown to be more appropriate than the b/t ratios usually proposed in design codes. Finally, code-ready recommendations for new ways of allowing for plastic analysis in practical design following the proposed approach are given.

Strength of trunk pipelines with critical damages

High internal pressure combined with external loading (bending/tension) and aggressive environment, along with the potential presence of local damages makes the assessment of strength and structural integrity of long-distance pipelines a formidable challenge. The paper considers the influence of local buckling (hereafter referred to as crimp) on the reduction of the static strength of pipelines. The reduction of plasticity and the increase of yield limit due to aging; decrease of the operation temperature; residual tensile stresses acting in the inner part of the pipe at the crimp top during plastic crimp formation; and residual tensile stresses caused by welding are assessed. The account of the influence of these damaging factors allows one to evaluate the reduction of the load carrying capacity of damaged pipelines. Threat of occurrence of damages in the form of crimps is either ignored or only partially taken into account by the existing procedures for pipeline strength analysis. The paper is aimed at filling this gap by analyzing strength of pipelines with crimps. Changes of the pipeline geometry, mechanical properties of the material, and stress concentration due to crimp formation are considered; results of calculations and tests are presented.

Strength of Thin-Walled Box Girders Curved in Plan

This paper presents a numerical method for predicting the influence of local buckling in component plates and distortional phenomenon on the ultimate strength of thin-walled, welded steel box girders curved in plan. A modified stress-strain curve allowing for local buckling of plate components is proposed. The effect of distortion is considered through incorporating additional strain in the reference stage of the incremental process in the nonlinear flexure analysis. Theoretical predictions obtained using the proposed method are compared to experimental test results. Nonlinear behavior of the test girders is illustrated and reasonable agreement between tests and theory is observed.

Local Buckling of Bracing Members in Semi-submersible Drilling Unit (2 nd Report)

An Idealized Structural Unit model of a tubular bracing member is developed considering the influence of local buckling which takes place after the ultimate strength is attained. That is, (1) The simplified method which was proposed in the 1 st report for a tubular member subjected to eccentric axial thrust is expanded so that the ultimate strength can be evaluated under general end loads and distributed lateral load. This method is applied to determine the ultimate strength of a member in the framework of the Idealized Structural Unit Method (ISUM) analysis.(2) An approximate method is proposed to determine the internal forces at a cross section after the ultimate strength is attained. Using these internal forces, strain distribution is determined. The occurence of local buckling is checked based on this strain at every load increments.(3) After the local buckling has started, its influence is reflected upon the full plastic strength interaction relationship through plastic nodal displacements of the element. A formulation to derive the elastic-plastic stiffness matrix is described considering the influence of local buckling.Several examples are analyzed applying the newly developed element. The calculated results are compared with those by the finite element method analysis and experiment, and its validity and usefulness are demonstrated.

Static/Dynamic Analysis of Locally Buckled Frames

The static and dynamic behavior of plane frames composed of thinwalled steel members is presented. Frame analysis includes post‐local‐buckling and/or first‐order geometric nonlinearities. Post‐local‐buckling behavior is included using the effective width concept which includes both axial and bending stresses. Direct iteration is used to calculate the effective cross section properties for members that have locally buckled. An “exact” elastic stiffness matrix, finite element geometric stiffness, consistent mass and Rayleigh damping matrix formulation is used to discretize the dynamic equilibrium equations. The nonlinear dynamic equations are solved using a modified Newton‐Raphson iteration strategy coupled with Newmark's time integration scheme. Static and dynamic analyses of a two‐bay, two‐story frame are considered. Static problem results are presented to demonstrate the accuracy of the formulation and the influence of local buckling and/or first‐order geometric nonlinearities. Dynamic simulations are ba...