Size effect in circular concrete-filled steel tubes with different diameter-to-thickness ratios under axial compression

The bearing capacities of concrete-filled steel tubes are normally derived through experiments with small-scale specimens, but it is uncertain whether such derivations are appropriate for the much larger components used in practical engineering. This study therefore investigates the effect of different diameters (219, 426, 630, and 820 mm) on the axial compression of short concrete columns in steel (Q235) tubes. It is found that the peak nominal stress decreases with increasing specimen size and that the axial bearing capacity is determined by three separate components: the cylinder compressive strength of the concrete, the improvement in strength due to the confining effect of the steel tube, and the longitudinal strength of the steel tube. At peak load, increases in the specimen diameter reduce the hoop stresses in the steel tube, thereby reducing the strengthening effect of confinement. Vertical stress in the steel tube is increased with diameter; therefore, the axial bearing capacity of the steel tube is directly related to the specimen size. Size effect coefficients for these three aspects of bearing capacity are defined and used to develop a size-dependent model for predicting the axial bearing capacity of large, concrete-filled steel tubes. The model is then validated against experimental data.

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Concrete-filled steel tubes subjected to axial compression: Life-cycle based performance

Journal of Constructional Steel Research ◽

10.1016/j.jcsr.2020.106063 ◽

2020 ◽

Vol 170 ◽

pp. 106063

Author(s):

Lin-Hai Han ◽

Chao Hou ◽

You-Xing Hua

Keyword(s):

Life Cycle ◽

Axial Compression ◽

Steel Tubes ◽

Concrete Filled Steel Tubes

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Behavior of CFRP-confined reactive powder concrete-filled steel tubes under axial compression

Advances in Structural Engineering ◽

10.1177/1369433220974781 ◽

2020 ◽

pp. 136943322097478

Author(s):

Song Li ◽

Chu-Jie Jiao

Keyword(s):

Bearing Capacity ◽

Axial Compression ◽

Local Buckling ◽

Steel Tube ◽

Experimental Results ◽

Reactive Powder Concrete ◽

Test Results ◽

Steel Tubes ◽

Reactive Powder ◽

Concrete Filled Steel Tubes

Reactive powder concrete-filled steel tubes (RPCFSTs) have become an important research target in recent years. In engineering applications, RPCFSTs can provide superior vertical components for high-rise and tower buildings, thereby enabling developers to provide more floor space. However, this type of composite structure is prone to inelastic outward local buckling. The use of carbon fiber reinforced polymer (CFRP) wrapping to suppress such local buckling has shown great potential in limited test results. This paper presents experimental results concerning the axial compression of CFRP-confined reactive powder concrete-filled circular steel tubes (CF-RPCFSTs). We included 18 specimens in our experimental investigation, varying the number of CFRP layers, steel tube thickness, and RPC strength. According to our test results, CF-RPCFSTs exhibit compression shear failure and drum-shaped failure. The CFRP wrap can effectively enhance bearing capacity and postpone local buckling of the steel tube. In addition, three-layer CFRP-confined RPC-filled thin-wall steel tubes are suitable for engineering. We also propose a model to calculate the bearing capacity of CF-RPCFSTs. Compared to the existing model of CFRP-confined concrete-filled steel tubes, the results obtained using the proposed model are in good agreement with our experimental results.

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