Finite Element Analysis of the Mechanical Properties of Axially Compressed Square High-Strength Concrete-Filled Steel Tube Stub Columns Based on a Constitutive Model for High-Strength Materials

Abstract

With the development of new concrete technology, high-strength concrete has been used worldwide. In particular, more economic benefits can be achieved by applying high-strength concrete-filled steel tube (HSCFST) columns in the concrete core walls of super high-rise buildings. A constitutive relation with high applicability for high-strength materials with different strength grades is proposed. Based on this constitutive model, a brick element model of 181 sets of axially compressed square HSCFST members is established and experimentally verified. The effects of the concrete strength, diameter-to-thickness ratio, and steel yield strength on the axial compressive capacities of these members were investigated based on finite element calculation results. The results showed that with an increase in the concrete strength, the ultimate bearing capacities of CS-CC, HS-HC, HS-CC, and CS-HC stub column members increased by 60%, 24%, 44%, and 21% at most, respectively. Additionally, as the steel yield strength increased, the ultimate bearing capacities of CS-CC, HS-HC, HS-CC, and CS-HC stub column members increased by 8.8%, 5.1%, 8.5%, and 5.2%, respectively, Hence, material strength has the greatest impact on CS-CC and HS-CC. The confinement effect of the square steel tube on the concrete weakens as the strength grade of steel or concrete increases. Notably, the confinement effect of steel tube on the concrete is strongest in CS-CC and weakest in the CS-HC. In addition, the confinement coefficients of square HSCFST stub columns with different combinations of concrete and steel strengths were analyzed. Based on the superposition principle in the ultimate state, a practical axial compressive capacity calculation formula for three types of square HSCFSTs is established. Compared with existing major design code formulas, the proposed formula is more accurate and concise and has a clear physical meaning.

Experimental and Numerical Study on Hysteretic Behavior of Frictional Energy Dissipation Steel Truss

“…The normal behavior was set to "hard" contact. The frictional coefficient was calibrated to 0.25 for the brass-steel contacting surfaces and was tuned to 0.5 for the concrete-steel contacting surfaces [30,31]. the expected slip force f can be calculated based on Coulomb friction theory:…”

“…The normal behavior was set to “hard” contact. The frictional coefficient was calibrated to 0.25 for the brass-steel contacting surfaces and was tuned to 0.5 for the concrete-steel contacting surfaces [ 30 , 31 ]. the expected slip force f can be calculated based on Coulomb friction theory: where n is the number of high-strength bolts applying the pressure, which is 22 in this study; μ is the friction coefficient, calibrated as 0.25 at the steel–brass interface; r is the number of friction surfaces, which is 2 in this study; N is the bolt pre-tightening force, which is 20 kN in this study.…”

Artificial Neural Network Models for Determining the Load-Bearing Capacity of Eccentrically Compressed Short Concrete-Filled Steel Tubular Columns

“…The second approach is finite element modeling in a three-dimensional setting, taking into account the real deformation diagrams of concrete and steel, as well as the contact interaction between the shell and the concrete core. A significant number of publications are devoted to the issues of finite element modeling of the stress-strain state of CFST columns [10][11][12][13][14][15][16][17]. This approach provides good agreement with experimental data but requires great computational resources and time.…”

An Experimental Study of the Mechanical Properties of Partially Rehabilitated Cable Tunnels

“…It can be learnt from previous studies [ 25 , 26 , 27 ] that for a pipe ring structure, the dangerous sections are located at the crown, invert, and springlines of the pipe under surface load, where the cracks appear and propagate first [ 28 , 29 ]. As shown in Figure 2 b, the exposed area contains the dangerous section at the crown of the pipe, and it can be rehabilitated with the partial lining method, which suggests a potential structural enhancement by rehabilitating with this method [ 30 , 31 ]. To verify this hypothesis, several pre-cracked reinforced concrete pipe (RCP) models were cast as simulated tunnel sections, and different materials were applied for partial lining at the cracked area of the crown.…”