Qing Quan Liang

A dual-function self-slitting recycled aggregate concrete squat composite shear wall with steel tubes (DF-SRAC-SCSW) is an efficient lateral load resisting system. In this system, the boundary elements are designed to provide both load-bearing capacity and self-slitting energy dissipation through the formation of controlled vertical slits under cyclic loading. This paper presents a numerical study on the seismic performance of squat composite shear walls constructed with recycled aggregate concrete and steel tubes. A three-dimensional finite element (FE) model is developed in ABAQUS, in which a proposed bond-slip constitutive model is used to simulate the bond-slip behavior between steel tubes and concrete. The validated FE model is employed to investigate the effects of axial compressive ratio, hoop spacing, yield strength of steel, steel content ratio, recycled concrete strength, shear span ratio, and steel tube arrangement on seismic performance. The results indicate that axial compressive ratio and shear span ratio are key factors governing seismic performance. Shear walls with high axial compressive ratios combined with low shear span ratios have a higher risk of brittle failure. Closely spaced hoops and higher steel content ratios improve confinement to the core RAC, thereby enhancing strength, stiffness, and energy dissipation. In addition, the number and distribution of steel tubes strongly influence seismic response, with a uniform distribution along the wall length providing the most favorable balance between strength, ductility, and energy dissipation. Design-oriented recommendations are proposed for DF-SRAC-SCSWs, offering practical guidelines for the seismic design of sustainable composite wall systems.

Concrete-filled double steel tubular (CFDST) columns possess higher fire resistance than concrete-filled steel tubular (CFST) and double-skin CFST (DCFST) columns. However, there is a lack of a simple and practical fire design method for such concrete-filled composite (CFC) columns. This paper proposes a unified method for the design of CFC columns exposed to fire, including CFDST, CFST, and DCFST columns. The unified method is developed based on the Rankine approach, in which the temperature-dependent sectional resistance, Euler buckling load, global buckling reduction, and loading eccentricity effect are consistently incorporated. A total of 474 finite element models were developed using Abaqus to simulate the fire behavior of CFDST columns. A new buckling curve for CFDST columns is derived from Rankine's theory. The buckling coefficients are calibrated by the finite element analysis results. A parameter is proposed to account for the influence of loading eccentricity on the column behavior. Furthermore, a MATLAB-based post-processing program is developed to monitor the temperature evolution of CFC columns. The average temperatures are calculated to approximate the temperature fields in a composite column. The accuracy of the proposed unified method is validated by 118 experimental results and 1040 finite element simulations of CFC columns exposed to fire. The unified method is shown to be an accurate and efficient tool for practical design of CFC columns under fire exposure.

Accelerated urbanization has intensified environmental concerns due to excessive natural resource consumption and construction waste generation. Circular concrete‐filled steel tube (CFST) columns incorporating manufactured sand recycled coarse aggregate (MS‐RCA) concrete have emerged as an innovative composite element offering notable environmental and economic benefits. To advance the use of MS‐RCA concrete in CFST structures, this paper presents experimental investigations into the behavior of 72 circular CFST stub columns constructed with MS‐RCA concrete. The effects of aggregate type, steel tube thickness, and stone powder content on structural response are examined. The results show that the failure modes of CFST columns with MS‐RCA concrete are characterized by local buckling and shear failure, similar to those of circular CFST columns with natural aggregate concrete. CFST columns with MS‐RCA have about 5.6% higher ultimate axial strength than those filled with natural sand‐RCA concrete. The inclusion of MS significantly enhances the ductility of CFST columns by an average of 34.6%, 25.4%, and 28.6% for steel tube thicknesses of 3.0, 3.5, and 4.0 mm, respectively. Moreover, for high‐strength concrete, the ultimate strength of columns filled with pebble MS‐RCA concrete is higher than that of those filled with limestone MS‐RCA concrete. Existing codes for CFST columns are evaluated and found to be highly conservative. Therefore, a new formula is proposed for CFST columns filled with MS‐RCA concrete and validated by experimental data. These findings confirm the viability of CFST columns with MS‐RCA concrete and highlight their potential to advance sustainable civil infrastructure.