Advanced Materials Research Vols. 243-249

Abstract: This paper aims to study the influence of aggregate shape and size on the tensile strength, compressive strength and fracture energy in mesoscopic modeling of concrete. For this purpose, several numerical models under three loading cases, uniaxial tension, uniaxial compression and bending resistance test are analyzed utilizing the software ABAQUS/Explicit. The mechanical responses and cracking behaviors well match the realistic situations of experiments. Various stress-strain curves and fracture patterns are presented and compared, which indicate that the aggregate size has very small effect on the tensile strength, compressive strength and fracture energy, and the effect of aggregate shape is a little more significant than that of the size.

Abstract: Lateral pressure is a key parameter to silos’ design. It has an important effect on the safety and efficiency of silos. The lateral pressure ratios that recommended by some overseas design codes and literatures have been analyzed. These ratios didn’t take into account the elasticity of silo wall, one of which is 28% smaller than the measure value, but another goes up to super pressure ratio. A new lateral pressure ratio is derived by considering the elasticity of silo wall, which is relevant to Passion ratio of stored material and relative stiffness coefficient . The coefficient of usual metal silo varies from 0.01 to 0.2, so it has significance to consider the wall elasticity.

Abstract: Both reference [1~2] method and partitioned design method (GB 50010-2002) were adopted to design complex shear walls, and some factors such as axial compression ratio, reinforcing ratio, section dimension, concrete strength grade and effective flange width were considered, then their limited loading capacity would be compared with each other when axial force was considered as a fixed value. It was found that there were some defects of complex shear wall partitioned design method. And its applied conditions were suggested, which included section restricted condition and limited value of axial compression ratio. When these conditions couldn’t be satisfied, the adjusted reinforcement partitioned design method of reference [3] was suggested. If the uneconomical problem of partitioned design method could not be accepted, whole section design method of reference [1~2] would be suggested.

Abstract: Equivalent static wind loads (ESWL) are the bridge between engineer in the structure design field and researcher in wind engineering field. In this paper, a practical high-rise building with 204 meters high was tested in wind tunnel, and then ESWL was calculated by load-response correlation (LRC) method based on the results of wind tunnel. Some results are useful for design of building structures.

Abstract: Studies on the characteristics of the mean wind load acting on the cantilevered roofs are carried out systematically by CFD (Computational Fluid Dynamics) numerical simulation. The influences of some factors, including the incoming flow condition, inclination angle of roofs and the ventilation rate above grandstand, on mean wind loading are investigated. It is found that the terrain type and grandstand type are not significantly influence the mean wind loads on the roof structure; The wind force acting on roof is increased with roof pitch; Sub-roof venting is found to reduce uplifts by no more than 12%; Introducing a similar shaped grandstand upstream is found to significantly decrease the wind loading. Based on these results, an empirical equation for the calculation of mean wind loading is derived for the reference of designers.

Abstract: The part-through circumferential crack is a typical crack form in pipe structure, which often lead to the structure failure. Firstly, the local flexibility equations of a pipe with a part-through circumferential crack are derived by using linearly elastic fracture mechanics. Secondly, an adaptive Simpson quadrature-revisted was used to numerically calculate the local flexibility coefficients. Finally, the model test were performed to validate the local flexibility for a part-through circumferentially cracked pipe. The results show that the natural frequencies of cracked pipe obtained by the model test agree well with the theoretical values from the proposed equations of the local flexibility. It is demonstrated the feasibility of the proposed method for vibtaion analysis and damage identification of a cracked pipe.

Abstract: The mathematical model of optimal design for prestressed structures is established and a two-level algorithm based on hybrid variables is proposed. At the first level, the prestressed forces are chosen to be the design variables and the optimal design for prestressed forces based on continuous variable is carried out. At the second level, the cross-sectional areas are chosen to be the design variables and the discrete sizing optimization is carried out under fixed prestressed forces, the local constrains are satisfied with one-dimensional search algorithm, the integral constrains are satisfied with the relative difference quotient algorithm, and the efficiency of the relative difference quotient algorithm is greatly improved by introducing the assumption of statically determinant structures. The numerical example shows the correctness and effectiveness of the method.

Abstract: The textile reinforced concrete (TRC) member has no distinct failure symptom when it arrives at its ultimate load. At the same time, ordinary steel-reinforced concrete (RC) elements have large dead weight and can not efficiently restrict the expansion of the main crack of structures. In order to overcome the above disadvantages, a new architecture reinforced with a combination of the textile and steel bar was presented in this study. The analytical formulae of the proper beam using this new structure were derived, including the load-carrying capacity at different stages and load vs. mid- span deflection relationship during the entire loading process. The theoretical values were compared with the experimental values. It is shown that the theoretical values coincide with the experimental values well and the feasibility of the formulae is verified.

Abstract: The modal analysis is performed on the single beam string structure in a practical project in this paper. Then the response history analyses, under the four different earthquake-induced ground motions in the single direction, are implemented on the structure. The analysis results indicate that it is very necessary to install out-of-plane bracings for the single beam string structure. In the design of similar structures, the section dimensions of the struts can be appropriately reduced due to the average stresses of the struts being smaller, and cross beams near the middle of structures are be given attention. And the analysis results provide a reference for the seismic analysis and design of similar structures.

Abstract: Because channel quality defects of post-tensioned prestressed concrete construction cannot be discovered on time, an electric heating method is put forward to produce effective detection. The results of the numeric simulation on the temperature field of a prestressed concrete component show that the electric heating infrared detection method, for its energy consumption, efficiency and safety, is feasible for detecting the channel quality of prestressed concrete component, but the electric current needs to be controlled to avoid high temperature which affects the physical and mechanical properties of the strand and the concrete.