Numerical Study on Confinement Effect and Efficiency of Concentrically Loaded RACFRST Stub Columns

Abstract

The mechanical behaviors of recycled aggregate concrete (RAC) are upgraded by outer steel tube confinement, and the performance of recycled aggregate concrete-filled steel tubular (RACFST) columns is similar to that of the traditional concrete-filled steel tube (CFST) columns. The purpose of this study is to investigate the behaviors of recycled aggregate concrete-filled rectangular steel tubular (RACFRST) stub columns under axial loading. Three-dimensional finite element (FE) models were established, which utilized a triaxial plastic-damage constitutive RAC model considering the replacement ratio of recycled aggregates. The finite element analysis results indicated that the lessened ultimate bearing capacity of RACFRST stub columns compared with their traditional concrete infilled counterparts was mainly due to the weakened confinement effect and confinement efficiency. A simplified formula of the bearing capacity of concentrically loaded RACFRST stub columns was proposed. The cross-sectional stress nephogram was reasonably simplified by the limited state of infilled concrete. The basics of proposed formula were the equilibrium condition and the superposition method. Finally, the formula for the bearing capacity of RACFRST stub columns was evaluated by comparing its accuracy and feasibility to some design formulae proposed by specialists and some design codes of different regions.

Study on Eccentric Compression Mechanical Characteristics of Basalt Fiber-Reinforced Recycled Aggregate Concrete-Filled Circular Steel Tubular Column

“…The research group's previous findings indicate that error modification can be performed by multiplying the coefficient ψ [37], and the procedure for calculating the correction coefficient is provided in Equation ( 14). ψ = (0.028m BF − 0.26)γ 2 + (−0.03m BF + 0.32)γ + −0.01m 2 BF + 0.036m BF + 1.046 (14) Therefore, the calculation method for he C-BFRRACFST short column's axial compression bearing capacity is illustrated in Equation (15).…”

“…In the area of RACFST, Liu et al [15] examined the constraining impact of steel tubes on RAC in RACFST columns. The findings demonstrate that the steel tube constraint improves the mechanical characteristics of RAC, and the performance of RACFST columns was comparable to that of concrete filled steel tube columns (CFST).…”

Confinement Effect and Efficiency of Concentrically Loaded RACFCST Stub Columns

“…In the normal behavior setting, the “Pressure-Overclosure” was set to “hard” contact mode, and the separation after contact was allowed. The penalty function was set as the tangential behavior of the contact attribute, in which the friction coefficient was 0.5 [ 7 ]. A tie constraint may couple two separate surfaces so that no relative motion occurs between them.…”

“…However, compared with structural concrete utilizing natural aggregates, RAC has some drawbacks verified by experimental studies such as the low strength and elastic modulus, high shrinkage and creep, inferior durability, and large scatter of its tested mechanical properties [ 4 , 5 , 6 , 7 , 8 ]. Those defects stem from the high porosity, the residual adherent mortar, and different sources of waste concrete, which hindered their application in engineering practice.…”

Prediction of Axial Compressive Load–Strain Curves of Circular Concrete-Filled Steel Tube Columns Using Long Short-Term Memory Network

“…Moreover, the mutual protection of the steel tube and in-filled concrete gives CFST columns better fire [9], impact [10], and corrosion [11,12] resistances. Because of the above-mentioned advantages, composite structural columns based on similar concepts, such as recycled aggregate concrete-filled steel tube [13], concrete-filled aluminum alloy tube [14], lightweight concrete-filled steel tube [15], stirrup-confined concrete-filled steel tube [16,17], and concrete-filled dual steel tube columns [18], have been proposed in recent years to satisfy different design objectives for low carbon, good appearance, light weight, high strength, etc.…”