Applied Mechanics and Materials Vols. 275-277

Abstract: Super concrete dam is threatened by dynamic brittle damage. In this paper, the fuzzy stochastic damping function was established for the seismic damping computation. According to the simulation results, there lives high level of fuzzy stochastic damage stress at the abutments and slope concrete sections of Xiluodu arch dam. Particularly, the stress level in downstream direction and transverse direction is higher than that in vertical direction.

Abstract: The retrofitting technique of externally wrapped by fiber reinforced polymer (FRP) can significantly enhance the deformability or ductility of deficient concrete columns. This paper develops a new advanced ultimate strain model for circular columns confined with FRP jacket based on a most updated and comprehensive test database where more than 800 axial compression test results of FRP confined circular concrete columns were collected newly. This work began with a careful review on some existing ultimate strain models after which an in-depth comparison between models predictions and experimental test results was conducted. The comparisons revealed that more or less defects of the existing models were detected and there existed large errors of their predictions as a much larger amount of columns than that used in the models derivations were evaluated. It is therefore necessary and of significance to refine a new advanced ultimate model in the paper.

Abstract: Considering the concrete as a three-phase composite material composed of aggregate, interface and cement matrix, an octagon unit cell is constructed based on ellipse, and the numerical solution of concrete chloride diffusion coefficient considering the aggregate shape is obtained using the finite element method. The validity of the proposed algorithm is preliminary verified after compared with the available test results, and the effect of interfacial crack opening angle and aggregate shape on the concrete chloride diffusion coefficient is quantitatively evaluated. Through numerical calculation, it is found that the chloride diffusion coefficient of concrete increases with the increase of interfacial crack opening angle and decreases with the increase of aggregate shape coefficient.

Abstract: Two-stage design method for base isolation structures includes simplified estimation and time history analysis. Simplified estimation is used in preliminary design stage for estimating the weight and the first period of an isolated structure, the upper structure is simplified as a SDOF system. According to the expected response reduction goals and response spectrum, the first period of the isolated structure, stiffness of isolation device and number of isolation bearing can be induced. Time history analysis is employed in detail design stage, for determination and optimization of isolation device based on current standards. The author has made it realized based on the old Seismic Code. As there are some changes of provision on base isolation analysis in new code, including the value of bearing stiffness and safety factor, etc., the method mentioned above should be updated. Numerical investigation shows that for regular multi-storey frame structures, the difference of the maxium ratio of floor shear between the old and new Seismic Code increase with fortification intensity.

Abstract: The corrosion resistance of post-tensioned prestress grout is considered an important indicator to structural safety and durability, based on some current specification on slurry anti-corrosion requirements of prestressing tendons at home and abroad, through laboratory accelerated corrosion test this paper mainly analyzes the diffusion way of harmful substances in the slurry, the relationships between rust time and prestressing tendons protective layer thickness, and then according to selected materials with different proportions have different corrosion time, take QL + ZQ is the best choice in anti-corrosion.

Abstract: This paper analyzes the load transfer characteristics of pipe roof over the excavating face, and the analytical solution of tunnel face stability is established by the method of three-dimensional analysis. Through the calculation of the load transfer of the pipe roof, it indicates that the released load of excavation is passed to the supporting structure and soil which is not excavated by the effect of the pipe roof, and the magnitude of load and coverage of impact are in connection with excavating footage as well as subgrade reaction. The three-dimensional analytical solution of tunnel face stability is used to analyze a project case of Airport Road underpass in Hangzhou. The results show that the tunnel face stability is not guaranteed when excavated on a large section while the stability is enhanced when excavated on separated pilot headings.

Abstract: Through repair and reinforcement of breaking reinforced concrete beams by epoxy resin and carbon cloth, and its experiment, the crack and deformation and bearing capacity as well as ductility of such beams are obtained. Experimental results show that the ultimate bearing capacity of beams after reinforcement increased by 210%, the structure ductility fell by 170%, structural failure form is similar to failure in normal cross section.

Abstract: Numerical simulations are done for stretch forming of uniaxial geogrid. And influence of different punching radius on the stress and strain of geogrid are studied. It shows that the maximum stress and strain in tensile process appear at the corner of the circle and straight edge. And the biggest stress is decreased with the radius. At the same time, radius increases reduce the deformation along the stretching direction on some extent. Based on this, a new optimization method for geogrid stretch forming is proposed. The shapes and sizes of punching can change the stress and strain distribution in the geogrid, which can reduce the probability of defect in the process of stretch forming.

Abstract: In this paper, the elasto-plastic dynamic analysis on dynamic failure behaviors of steel double-layer grids supported by tridimensional truss columns used in a gymnasium with the function of earthquake victims shelter under disaster earthquake is carried out under EL-centro wave with SAP2000, and the appraisal results on their anti-failure performances are presented under strong earthquake action based on the plastic-hinge theory. In the analyses, the geometric and material nonlinear effects are considered simultaneously based on the plastic-hinge theory. The plastic development level of the rod, the deformed shape and the failure type and the ductility are estimated by plastic hinge principle. The results show that the failure model of the structure under the earthquake wave action is the complicated combination of strength failure and elasto-plastic dynamic local buckling in deferent areas of the structure; When the structure reached its failure critical limit, the development of the plastic hinges is not sufficient and only 5.11% of the rods enter into their plastic stage; Its critical failure peak acceleration of EL earthquake wave when applied in the combination of three directions is 705gal and can be served as earthquake victims shelter in the area of 8 degree seismic fortification; Its displacement ductility coefficient is 2.39,which shows the structure owns good energy dissipation capacity.

Abstract: To reduce the construction cost of the domestic promotion of the new prefabricated concrete shear wall structure system which is promoted in our country. To analyze the factors which can affect the load-carrying capacity and seismic performance of shear wall, including the axial compression ratio, the concrete strength, the reinforcement ratio and some other factors. Among all these factors, the axial compression ratio is the main factor influencing the seismic performance and the section ductility [1]. This paper adopts the ANSYS finite element analysis program, operating a nonlinear analysis on the performance of the precast shear wall when it is with one-way loading, studying the axial compression ratio's effect on the bearing capacity and deformability of the precast shear wall. According to the finite element analysis, when the axial compression ratio is between 0.2 to 0.4 and as it rises, the specimen's bearing capacity and stiffness will increases while deformability and ductility will decrease. Through the finite element analysis, we can provide reliable theory basis for the performance of the precast shear wall when it is with one-way loading.