Experimental investigation on behavior of splicing glass fiber–reinforced polymer-concrete–steel double-skin tubular columns under axial compression

Splicing glass fiber–reinforced polymer (GFRP)-concrete–steel double-skin tubular column (DSTC) is to set connection component at the joint of two or more separated GFRP tubes, and then pour concrete in the double-tube interlayer to form a continuous composite member. In this paper, the splicing DSTC composite members based on steel bar connection were designed and tested under axial compression to determine its mechanical performance. The main parameters include the connection steel ratio, the hollow ratio, and the thickness of GFRP tube. The results show that the GFRP tube presents apparent constraint effect on the concrete at about 60% of the ultimate load. The failure of splicing specimen occurred in the non-splicing section at a certain distance from the splice joint, and the stirrups at the splice joint provide effective constraint effect on the internal concrete. The proposed DSTC splicing method based on steel cage connection can satisfy the strength requirements of splice joint. Nevertheless, the increase of axial steel bar ratio cannot improve the bearing capacity of the splicing column, and the steel ratio of 2.44% is suggested for the splice joint of DSTCs under axial compression. The axial bearing capacity of splicing DSTCs significantly increases with the increase of GFRP tube thickness, but the amount of stirrups should be increased properly when a larger tube thickness is used. Two models were selected to calculate the bearing capacity of splicing members and it is found that Yu’s model is more accurate in predicting splicing DSTCs.

Fiber element modeling of circular double-skin concrete-filled stainless-carbon steel tubular columns under axial load and bending

Circular concrete-filled double-skin steel tubular (CFDST) columns with external stainless-steel are high-performance composite columns that have potential applications in civil construction including the construction of offshore structures, bridge piers, and transmission towers. Reflecting the limited research performed on investigating their mechanical performance, this study develops a computationally efficient fiber model to simulate the responses of short and slender beam-columns accounting for the influences of material and geometric nonlinearities. Accurate material laws of stainless steel, carbon steel, and confined concrete are implemented in the mathematical modeling scheme developed. A new solution algorithm based on the Regula-Falsi method is developed to maintain the equilibrium condition. The independent test results of short and slender CFDST beam-column are utilized to validate the accuracy of the theoretical solutions. The influences of various column parameters are studied on the load-axial strain [Formula: see text] curves, load-lateral deflection [Formula: see text] curves, column strength curves, and interaction curves of CFDST columns. Design formulas are suggested for designing short and beam-columns and validated against the numerical results. The computational model is found to be capable of simulating the responses of CFDST short and slender columns reasonably well. Parametric studies show that the consideration of the concrete confinement is important for the accuracy of the prediction of their mechanical responses. Furthermore, high-strength concrete can be utilized to enhance their load-carrying capacity particularly for short and intermediate slender beam-columns. The strengths of CFDST columns computed by the suggested design model are in good agreement with the test and numerical results.

Numerical Simulation Investigation of a Double Skin Transpired Solar Air Collector

Transpired solar collectors (TSC) are one of the most popular solar thermal technologies for building façades. TSC use solar energy to heat the absorber surface, which transmits thermal energy to the ambient air. A variant of TSC, namely, a double skin transpired solar collector (DSTSC), has been analyzed in this paper, thus providing guide values and a technical point of view for engineers, architects, and constructors when designing such transpired solar collectors. Three important parameters were addressed in this study through numerical simulation: the influence of a separation plate introduced in a TSC, turning it into a DSTSC; the air layer thickness influence on the performance of the collector; and the influence of the used absorber materials for the separation plate material. Greater heat exchange efficiency was noticed for the DSTSC at every imposed airflow rate compared with the TSC. Regarding the thickness of the collector, the efficiency gradually increased when increasing the solar collector thickness until it reached a value of 20 cm, though not varying significantly at a thickness of 30 cm.