Papers by Author: Zhi Wu Yu

Abstract: The concrete residual compressive strength after different burning temperature and time by water cooling was experimentally studied. A detailed review of experimental phenomena in fire and the concrete failure characteristics in compressive test were given, and the relationship between the compressive strength and temperature, time were discussed. It is found that with the exposure of temperature and time increasing, the concrete residual compressive strength tends to decrease generally, but when the temperature is low or time is short, the concrete residual compressive strength tends to increase on the contrary. According to analysis of the experiment results, the formula for concrete residual compressive strength and temperature-time relationship after the fire was built.

Abstract: This paper presents an investigation of ultimate strength of square CFT stub columns with slender sections. The definition of square CFT stub columns with slender sections is discussed and a new strength model is proposed. Experimental results of 31 axially loaded square CFT stub columns published in the literature are then used to verify the proposed strength model. Results show that the proposed strength model provides a direct, compact, and efficient representation of the ultimate strength of square CFT stub columns with slender sections.

Abstract: Nonlinear finite element model is established for the square interior constrained concrete filled steel tube column based on the research of the element type and material constitutive relation with finite element software ANSYS to find out the influence of the thickness of the steel tube, location of studs and geometry of the stirrups on the compression capacity of the short column, The results show that the compression capacity of the short column has something to do with the thickness of the steel tube and the studs, but the stirrups can eventually enhance a lot for the compression capacity as the validity is confirmed for the coherence of the results stepped from the finite element model and in test.

Abstract: Since 90s of last century, foreign scholars propose a floor response spectrum method for seismic analysis of pipeline system multiply supported on buildings, which is named as Cross-Oscillator Cross-Floor Response Spectrum (CCFS) method. The CCFS method is simple in calculation and its results are reliable. Firstly, basic assumptions in expression derivation of CCFS method are studied, such as not introducing support degrees of freedom of building, adopting displacement model and assuming white noise as earthquake excitation etc. All of these assumptions will lead to some shortcomings. Then, the defect root of CCFS method is explained by specific theoretical derivation process, and it is pointed out that utilizing CCFS method for calculating displacement of boundary degrees of freedom of pipeline system relative to building may lead to inaccuracy of results, and the white noise assumption for earthquake excitation will also certainly produce some errors. Finally, the defect of CCFS method is verified by numerical example. The conclusions can provide an important reference for reasonable application of CCFS method in seismic analysis of multiply supported pipeline system on buildings.

Abstract: The paper discusses the strain of high-strength concrete (HSC) at peak compressive strength for a wide range of compressive strength. A large volume of selected experimental data has been collected from existing literature and then analyzed. Particular emphasis has been given to studying the effects of concrete compressive strength and the types of coarse aggregate on the strain of HSC at peak compressive strength. The adequacy and applicability of the existing models for predicting the strain of HSC at peak compressive strength has been critically examined, and a new empirical model is proposed to cover concrete strength up to 125 MPa. The new empirical model seems to perform much better when applied to the published experimental data on normal weight concrete over a wide strength range.

Abstract: This paper presents an investigation of ultimate strength of square CFT stub columns with compact sections. The beneficial composite action between the steel tube and the filled concrete is taken into account and a new analytical model for predicting the axial capacity of square CFT stub columns with compact sections is proposed. Experimental results of 89 axially loaded square CFT stub columns published in the literature are then used to verify the proposed strength model. Results show that the proposed strength model provides a direct, compact, and efficient representation of the ultimate strength of square CFT stub columns made with not only normal strength but also with high strength steel tubes and concrete.