Papers by Author: Ri Gao

Abstract: In order to determine the distribution of wind load on the roof, wind tunnel test and numerical simulation are both carried out. Then the distribution of mean wind pressure under different wind directions is obtained and the features of mean wind pressure are also analyzed. The datas show that wind pressure distribution of the roof is predominantly negative pressure; only a small area of windward side is positive pressure distribution. The peak of negative pressure appears at the roof ridge or windward long eaves, and varies as changes of wind direction. Meanwhile, the comparison between the results of the numerical simulation and wind tunnel test shows that the distribution law of both is almost the same, but in some areas that flow separation is serious, the error is larger. Then the reasons for the error are discussed.

Abstract: To enhance the earthquake resistance capacity of long-span continues bridge, theory and design of a new seismic isolating system are proposed based on the utilization of improved carbon structural steel material. Pseudo-static test result of the damping tenon, one essential energy dissipation component, proved the system’s excellent characteristic of consuming earthquake energy. Comparative experiments of three models reflect the working stability of the damping tenon confronted with different stimulation. Finite Element simulation further validates accuracy of the experiment and helps analyzing the material’s elastic and plastic developing status due to different load steps. Finally, this new seismic isolating system is recommended to long-span continues girder bridge designed on the basis of high level earthquake resistant standard.

Abstract: In this paper, completes the selection of preliminary Reactive Powder Concrete (RPC) wind barriers, and on the basis of the theories of the computational fluid dynamics ( CFD), relying on the model-building and analysis platform of FLUENT, 3D models of trains under crosswind with and without wind barriers are built. From the calculation results of the pressure distribution,path lines and aerodynamic forces of model trains under 3D turbulence flows ,the stability of trains under crosswind is analysed ,and the effects of the wind barriers on traffic safety of trains are discussed.The results show that rationa1 design of the wind barriers is able to improve the traffic safety of trains.

Abstract: The safety of aged steel structures, especially those with cracking members, has aroused a great deal of attention. In this paper, the application of fracture mechanics for evaluating the ultimate load-carrying of steel material is proposed. Three-point bending tests of three specimens with the mode-I fracture are done to get the ultimate load-carrying capacity, when specimens are destroyed. Fracture ductility KIC, and the steel allowable stress [σ] with certain crack length are formulated. Magnetic method for measuring cracks of steel members is adopted for an aged steel truss bridge, and material composition of specimens is tested, and field nondestructive load test involved static and dynamic test are carried into execution. By comparing the results of the calculation and those of the field test, some conclusions are obtained, which are likely to contribute to safety evaluation of aged steel structures, or contribute to designing similar bridges.

Abstract: A literature review was carried out to identify advances in research on workability of fresh concrete via both experimental tests and modeling, especially high performance concrete and self-compacting concrete. As to the relationship between fluidity of concrete and that of paste, future research can be conducted in two aspects, i.e. one is the influence of the quantity of paste in concrete, and another is the influence of fluidity of paste affected by a couple of factors. Most literature proved that the flow of concrete depends both on positive effect and negative effect, the former promote fluidity, such as dispersing, filling and lubricating, and the latter restricts fluidity, such as formation of particle coagulation, an increase of wettable surface of solid particles and mechanical interlock.

Abstract: A literature review was carried out to identify advances in research on workability of fresh concrete via both experimental tests and modeling, especially high performance concrete and self-compacting concrete. It is concluded that, in order to achieve better understanding of fresh concrete, especially self-compacting concrete (SCC) and high-performance concrete (HPC), a clear methodology of research should be established as the first step. It is suggested that there is no unique workability test method suitable for all the range of fluidity of fresh concrete, and a specific method should be identified for a proper range of fluidity. As to the relationship between fluidity of concrete and that of paste, future research can be conducted in two aspects, i.e. one is the influence of the quantity of paste in concrete, and another is the influence of fluidity of paste affected by a couple of factors.

Abstract: Reactive powder concrete (RPC) is a new kind of ultra-high strength and upper ductility concrete first developed in 1990’s in France. In this paper, the RPC mixture proportion is optimized and its mechanical properties, such as compressive strength, flexural strength, elastic modulus, and its durability, are tested and discussed. Based on the optimal mixture proportion, four simply supported plain RPC beams (without reinforcement bars) are made and tested. The mechanical properties of plain RPC beams, including section deformation, load-displacement relationship, failure forms, crack distribution, crack extension, and ultimate flexural capacity, are discussed. It is concluded that RPC is an excellent material with high strength and durability. Steel fiber is important both to control the crack extension and to enhance the ductility of RPC beams.