Dynamics of structures

Developments and advanced applications of concrete-filled steel tubular (CFST) structures: Members

External confinement of concrete by means of high-strength fiber composites can significantly enhance its strength and ductility as well as result in large energy absorption capacity. The confinement mechanism may include fiber-wrapping of existing columns as a retrofitting measure or encasement of concrete in a fiber reinforced plastic (FRP) tube for new construction. Proper design of such hybrid columns, however, requires an accurate estimate of the performance enhancement. Current design methods use simple extension of the models developed for conventional reinforced concrete columns. Results from a series of uniaxial compression tests on concrete-filled FRP tubes are compared with the available confinement models in the literature. The present study indicates that these models generally result in overestimating the strength and unsafe design. The study also shows a unique characteristic of confinement with fiber composites in that, unlike steel, FRP curtails the dilation tendency of concrete, as it re...

Behavior of Concrete Columns Confined by Fiber Composites

A model for the axisymmetric growth and coalescence of small internal voids in elastoplastic solids is proposed and assessed using void cell computations. Two contributions existing in the literature have been integrated into the enhanced model. The first is the model of Gologanu-Leblond-Devaux, extending the Gurson model to void shape effects. The second is the approach of Thomason for the onset of void coalescence. Each of these has been extended heuristically to account for strain hardening. In addition, a micromechanically-based simple constitutive model for the void coalescence stage is proposed to supplement the criterion for the onset of coalescence. The fully enhanced Gurson model depends on the flow properties of the material and the dimensional ratios of the void-cell representative volume element. Phenomenological parameters such as critical porosities are not employed in the enhanced model. It incorporates the effect of void shape, relative void spacing, strain hardening, and porosity. The effect of the relative void spacing on void coalescence, which has not yet been carefully addressed in the literature. has received special attention. Using cell model computations, accurate predictions through final fracture have been obtained for a wide range of porosity, void spacing, initial void shape, strain hardening, and stress triaxiality. These predictions have been used to assess the enhanced model. (C) 2000 Elsevier Science Ltd. All rights reserved.

An extended model for void growth and coalescence - application to anisotropic ductile fracture

Proper material constitutive models for concrete-filled tube (CFT) columns are proposed and verified by the nonlinear finite element program ABAQUS against experimental data. The cross sections of the CFT columns in the numerical analysis are categorized into three groups, i.e., circular section, square section, and square section stiffened by reinforcing ties. Via the numerical analyses, it is shown that for circular CFT columns, the tubes can provide a good confining effect to the concrete especially when the width-to-thickness ratio D/t is small (say D/t 30). The confining effect of square CFT columns with reinforcing ties is enhanced by the use of reinforcing ties especially when the tie spacing is small and the tie number (or tie diameter) is large.

https://ir.nctu.edu.tw:443/bitstream/11536/27503/1/000185407600004.pdf

Nonlinear analysis of axially loaded concrete-filled tube columns with confinement effect

Uniaxial stress–strain relationship of concrete confined by various shaped steel tubes

An experimental study on the strength and deformation of concrete‐filled square box stub‐columns is presented. Six specimens of concrete‐filled composite columns were tested under cyclic compressive loads. For comparison, four specimens of steel columns were also loaded to failure. The ultimate strength, ductility, and collapse behavior of the two types of columns were compared. In the comparison, the effect of width‐thickness ratio and stiffener rigidity on the behavior of the columns was examined. The study showed that high strength and high ductility can be expected from the concrete‐filled composite column. In the case of concrete‐filled composite columns, an empirical reduction factor that accounts for the effect of the size of the filled‐in concrete prism and the concrete strength class was introduced in evaluating the compressive strength of the concrete, and the local buckling strength of the plate panel in composite columns was then compared with available empirical design formulas for a thin‐wal...

Strength of Concrete‐Filled Thin‐Walled Steel Box Columns: Experiment

This is a reconnaissance report on the damage to bridges during the 2008 Wenchuan, China, earthquake. Site investigation was conducted by the authors on August 10–14, 2008. Presented is a detailed discussion of the damage to 12 bridges as well as possible damage mechanisms. Characteristics of two near-field ground accelerations and Chinese seismic bridge design practices are also presented. An investigation of the damage finds insufficient intensity of seismic design force, inadequate structural detailing for enhancing the ductility capacity, and an absence of unseating prevention devices.

Reconnaissance Report on Damage of Bridges in 2008 Wenchuan, China, Earthquake

Strength analysis of concrete-filled thin-walled steel box columns

The purpose of this experimental study is to investigate the influences of the filled-in concrete on the strength, ductility and energy absorption capacity of the column. A total of 12 concrete-filled steel box column specimens modeling steel bridge piers were tested under a constant compressive axial load and cyclic lateral loads. In designing the specimens, the plate width-thickness ratio, slenderness ratio and length of the filled-in concrete were chosen as main parameters. Moreover, the effect of the diaphragm over the concrete, on the column behavior was also examined. The collapse characteristics of tested specimens were presented in detail to provide some useful information for understanding of their inelastic behavior under cyclic loading. Test results were also discussed in the light of improvement of ductility and energy-absorption capacity of steel bridge piers. It is concluded that concrete-filled steel box columns can be effectively used as bridge substructures in strong earthquake areas.

Hanbin Ge

Papers

Uniaxial stress–strain relationship of concrete confined by various shaped steel tubes

Strength of Concrete‐Filled Thin‐Walled Steel Box Columns: Experiment

Reconnaissance Report on Damage of Bridges in 2008 Wenchuan, China, Earthquake

Strength analysis of concrete-filled thin-walled steel box columns

Cyclic Tests of Concrete-Filled Steel Box Columns