Creep performance of concrete-filled steel tubular (CFST) columns and applications to a CFST arch bridge

Meng-Gang Yang,C. S. Cai,Yong Chen 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.19 No.1

This paper first presents an experimental study of twelve specimens for their creep performance, including nine concrete-filled steel tubular (CFST) columns and three plain concrete columns, subjected to three levels of sustained axial loads for 1710 days. Then, the creep strain curves are predicted from the existing creep models including the ACI 209 model, the MC 78 model, and the MC 90 model, and further a fitted creep model is obtained by experimental data. Finally, the creep effects of a CFST arch bridge are analyzed to compare the accuracy of the existing creep models. The experimental results show that the creep strains in CFST specimens are far less than in the plain concrete specimens and still increase after two years. The ACI 209 model outperforms the MC 78 model and the MC 90 model when predicting the creep behavior of the CFST specimens. Analysis results indicate that the creep effects in the CFST arch bridge are significant. The deflections and stresses calculated by the ACI 209 model are the closest to the fitted model in the three existing models, demonstrating that the ACI 209 model can be used for creep analysis of CFST arch bridges and can meet the engineering accuracy requirement when lack of experimental data.

State of the Art of Creep of Concrete Filled Steel Tubular Arches

K. M. Shrestha,Bao-chun Chen,Yong-feng Chen 대한토목학회 2011 KSCE JOURNAL OF CIVIL ENGINEERING Vol.15 No.1

The state of the art of creep of Concrete Filled Steel Tubular (CFST) arch bridges including CFST members is presented in this paper. It is delineated that researches on creep of CFST is not mature and need much study compare to creep of plain concrete and reinforced concrete. In comparison with the plain concrete members, creep magnitude in CFST is relatively low but, the duration is longer. Creep has much influence on the deformation, stress redistribution between steel tube and core concrete and to reduce the buckling strength of CFST arches; how to implement the research results on actual arch bridge design is necessary part of research in pending. A good creep prediction model is the urgent essence of today’s design works with CFST element.

Experimental Studies on Circular CFST Frames with ALC Walls under Cyclic Loadings

Bo Wang,Jingfeng Wang,Xudong Gong,Bingkang Liu 한국강구조학회 2014 International Journal of Steel Structures Vol.14 No.4

To investigate the interaction and failure mechanism between aerated lightweight concrete (ALC) walls and concrete-filledsteel tubular (CFST) frames under seismic action, one specimen of circular CFST frame and four specimens of circular CFSTframes with ALC walls under cyclic loading were carried out. The test parameters included the panel thickness, the wallconnector type and the panel type. Test process and failure modes of the typed structures were investigated in detail. Hystereticcurves, ductility and energy dissipation etc were also analyzed. The test result showed that using reasonable measurement ofU-typed connector, hooked bolt, rocking connector and angle steel, circular CFST frames and ALC walls under seismicloadings can be in cooperative work and have good seismic performance.

Compressive strength of circular concrete filled steel tubular stubs strengthened with CFRP

Jialing Ou,Yong-Bo Shao 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.39 No.2

The compressive strength of circular concrete filled steel tubular (C-CFST) stubs strengthened with carbon fiber reinforced polymer (CFRP) is studied theoretically. According to previous experimental results, the failure process and mechanism of circular CFRP-concrete filled steel tubular (C-CFRP-CFST) stubs is analyzed, and the loading process is divided into 3 stages, i.e., elastic stage, elasto-plastic stage and failure stage. Based on continuum mechanics, the theoretical model of C-CFRP-CFST stubs under axial compression is established based on the assumptions that steel tube and concrete are both in three-dimensional stress state and CFRP is in uniaxial tensile stress state. Equations for calculating the yield strength and the ultimate strength of C-CFRP-CFST stubs are deduced. Theoretical predictions from the presented equations are compared with existing experimental results. There are a total of 49 tested specimens, including 15 ones for comparison of yield strength and 44 ones for comparison of ultimate strength. It is found that the predicted results of most specimens are within an error limit of 10%. Finally, simplified equations for calculating both yield strength and ultimate strength of C-CFRP-CFST stubs are proposed.

Global seismic performance of a new precast CFST column to RC beam braced frame: Shake table test and numerical study

Z.L. Li,S.Y. Xu,H.J. Liu 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.21 No.4

A new type of precast CFST column to RC beam braced frame is proposed in this paper. A series of shake table tests were conducted to excite a one-third scale six-story model for investigating the global seismic performance of this type of structure against earthquake actions. Particular emphasis was given to its dynamic property, global seismic responses and failure path. Correspondingly, a numerical model built on the basis of fiberbeam- element model, multi-layer shell model and element-deactivation method was developed to simulate the seismic performance of the prototype structure. Numerical results were compared with the measured values from shake table tests to verify the validity and reliability of the numerical model. The results demonstrated that the proposed novel precast CFST column to RC beam braced frame performs excellently under strong earthquake excitations; the "strong CFST column-weak RC beam" and "strong connection-weak member" anti-seismic design principles can be easily achieved; the maximum deflections of precast CFSTC-RCB braced frame satisfied the deflection limitations proposed in national code; the numerical model can properly simulate the dynamic property and responses of the precast CFSTC-RCB braced frame that are highly concerned in engineering practice.

Square CFST columns under cyclic load and acid rain attack: Experiments

Fang Yuan,Mengcheng Chen,Hong Huang 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.30 No.2

As China’s infrastructure continues to grow, concrete filled steel tubular (CFST) structures are attracting increasing interest for use in engineering applications in earthquake prone regions owing to their high section modulus, high strength, and good seismic performance. However, in a corrosive environment, the seismic resistance of the CFST columns may be affected to a certain extent. This study attempts to investigate the mechanical behaviours of square CFST members under both a cyclic load and an acid rain attack. First, the tensile mechanical properties of steel plates with various corrosion rates were tested. Second, a total of 12 columns with different corrosion rates were subjected to a reversed cyclic load and tested. Third, comparisons between the test results and the predicted ultimate strength by using four existing codes were carried out. It was found that the corrosion leads to an evident decrease in yield strength, elastic modulus, and tensile strain capacity of steel plates, and also to a noticeable deterioration in the ultimate strength, ductility, and energy dissipation of the CFST members. A larger axial force ratio leads to a more significant resulting deterioration of the seismic behaviour of the columns. In addition, the losses of both thickness and yield strength of an outer steel tube caused by corrosion should be taken into account when predicting the ultimate strength of corroded CFST columns.