Applied Mechanics and Materials Vols. 94-96

Abstract: Fracture ratio is one of important parameters for evaluation of rock mass quality. The fracture ratio of rock is analyzed by digital image analysis with matlab. In this paper, the width of different place on fracture of rock is gotten, which is more important than average width of fracture for analysis characteristic of fracture. The area of fracture is directly gotten from the binary image of fracture and it can avoid the error of area of fracture due to average width of fracture. So the fracture ratio of area is more exacter. The practice shows that the method of digital image analysis is a good method for investigation of fracture ratio of rock.

Abstract: In the process of solving rural drinking water safety,there are some problems need to attach great importance. Evaluation index system of rural drinking water safety includes water quality, quantity, convenience, and dependability. Figure 1 shows that Polluted water is the main reason of unsafe drinking water quality, 40.9% of unsafe drinking water quality, 28.8% of unsafe drinking water. Figure 2 shows that basically the discharge of waste water each year from 1998 to 2009 is increasing, the total discharge of waste water across China from 1997 to 2009 reached to 621.945 billion t. Table 2 shows that national industrial solid waste generation and utilization is increasing,but discharge decreasing, industrial solid waste, directly or indirectly polluted water environment, especially rural drinking water sources. The paper draws a conclusion that there are some problems of rural drinking water such as rural unsafe drinking water quality, lack of laws and regulations and effective management, serious rural water pollution.

Abstract: This paper briefly expounds the basic principle of structure isolation, reviews the development process of isolated technology. Adopting the common and base isolation system and inputting El-Centro as the earthquake wave, in this paper, comparative analysis of structure’s earthquake-resistant performance was conducted on a 6-layer custom steel structure residence in Changzhou area. The result shows that the gradually matured seismic isolated technology can be applied to steel structure as well, which means the seismic isolation steel structures possess the same characteristics as other seismic isolation structures. With the satisfaction of required bearing capacity, the structural reaction to earthquake has been effectively reduced and its safety has been guaranteed after considering the seismic isolation of steel structure residence; moreover, the storey accelerations reaction has also been greatly declined, meeting higher requirements towards comfortableness of residence structure. Meanwhile, by nonlinear dynamic analysis of simple Bouc-Wen hysteretic model, the requirement towards the biggest ductility was discussed and a brief analysis of the life cycle cost of this residence was worked out. The analysis result demonstrates that the seismic isolation layer has effectively controlled the vibration of superstructure, which would contribute to the reduction of seismic hazard.

Abstract: A two-step damage identification method based on elemental modal strain energies and natural frequencies has been presented for a beam-like structure. In the first stage, this method makes use of the change of elemental modal strain energy before and after damage to locate the potential damage regions. And in the second stage, a damage identification algorithm based on the frequency changes is developed to calculate the damage extent and further determine the actual damage locations. The performance of the proposed method is numerically demonstrated by a simply supported beam with two damage cases. Results indicate that the method can identify the damage location and quantify the damage severity accurately in a beam-like structure.

Abstract: Hefei Xinqiao International Airport Terminal is a steel structure consisting of long-span rigid frames, with 804m in length and about 161m in width at the widest part. The long-span frame consists of box columns, large curvature beams, tapered box beams and space trusses. The joints between space trusses and box beams named truss-to-box beam connections are the critical parts of the whole structure, because of the discontinuity in geometries and stiffness which result in high stress concentrations and complicated mechanical properties. GJ3-6, GJ3-5 and GJ3-1 of the airport terminal are modeled by ABAQUS. Structure internal forces at six load combinations of bearing capacity limit state are calculated. Lower chords of the landside connections sustain large tensions, while web members of the airside connections sustain large pressures. Since these truss bars are directly connected to cover plate of the box beam, better design details are recommended to reduce the stress concentrations caused by geometrical discontinuity.

Abstract: Abstract. This paper deals with the tensile behaviour of steel fiber reinforced concrete with respect to fibers content. A series of experimental tests were conducted to investigate uniaxial tensile ductility by using epoxy adhesive method. The specimen dimension was 100×100×200mm3 and the content of steel fiber was 20kg/m3, 40 kg/m3, 60 kg/m3 and 80 kg/m3, respectively. The test results showed that steel fiber can improve the tensile property effectively.

Abstract: In this paper, the elasto-plastic dynamic analysis on the steel spatial arch truss with 90m span and 0.4 rise-span ratio is carried out under earthquake EL-Centro wave with SAP2000. In the analyses, the geometric and material nonlinear effects are considered at the same time based on the plastic-hinge theory. Under the action of EL wave with the peak increasing gradually, its elasto-plastic dynamic responses have been obtained. All the results displays its failure mode under the earthquake action is elasto-plastic dynamic buckling; that its critical peak acceleration of EL earthquake wave when applied in X direction is 381gal, and is 583gal when applied in Z direction; The ratio of its maximal node horizontal and its structural height is 1/290, and its displacement ductility coefficient is 1.43 and the ratio of its bars with plastic hinge appearing when buckling is 3.00% when EL-Centro waves applied on structure in X direction; The ratio of its maximal node vertical and its structural span is 1/567, and its displacement ductility coefficient is 1.48 and the ratio of its bars with plastic hinge appearing when buckling is 2.50% when EL-Centro waves applied in Z direction.

Abstract: Under the action of tensile load obvious necking-down phenomena will accur in the metal test-piece. The tensile experiment about the metal test-piece has been studied, but the finite element simulation of the tensile necking-down phenomena has not been reported. The paper first studies the experiment of the mental test-piece, using the universal testing machine of WE-10A and WI-60T to load the mental test-piece and using IZ-910 infrared thermal imager to test the change process of infrared radiation temperature fields, then works out the finite element program to simulate the tensile necking-down phenomena of the metal test-piece with the elastic-plastic model. The experiment result shows that the infrared thermal effect of the metal test-piece in the process of loading is obvious, before the sample fracture will appear the omen of high temperature in the position where the future fracture will occur; in stress concentration the microcracks concentrate and the thermal figure is obvious; in the whole loading process the fracture starts from the local part, develops and evolutes gradually; with the stress change on the metal test-piece the infrared radiation tempreture of the test-piece surface changes, having the temperature-rising tendency in the total and the temperature rising trend in the local fracture position is obvious. This is because the metal test-piece material or the force is uneven and the stress concentration is formed, In the position of the stress concentration the deformation destruction firstly occurs. Because the energy is released in the process of deformation destruction, so the temperature change is obvious in the fracture position. After the experiment the obvious necking-down phenomena occurs in the test-piece. At the same time, in order to provide the theoretical basis for the experiment, with the finite element software of FEPG the finite element program is worked out, with the elastic-plastic model and the uneven material the fracture evolution process of the metal test-piece is simulated. Through the comparasion we can see that obvious necking-down phenomena appeared in the metal test-piece under the tensile load, the infrared information testing shows the temperature-rising is obvious in the position where necking-down phenomena occurs and the tensile necking-down phenomena of the metal test-piece is well simulated, which can provide helpful basis for the prediction and forecast of mental structure fracture.

Abstract: According to the formers' study of theory and experiment, to analyze the mechanical properties on compacting effect of lime compaction piles. The effects of collapsible loess reinforced by the lime pile have been analyzed. The theory of collapsible loess reinforced by lime pile has made useful exploration. Through the round hole expansion theory to lime piles under expansion compacting process, the elastic-plastic solution on compacting effect of lime compaction piles has been solved. The effective radius of expansion and the law of stress change between the piles can also be determined. Finally using the finite element method to verify the proposed method, and the results show that the proposed method is effective and can provide theoretical basis and guidance for the similar projects.

Abstract: Construction process analysis is the difficult problem of the cable dome. A new method lifting the strut layer by layer is presented. The structure is shaped by lifting struts layer by layer from outer to inner hoop. Besides, pulling cables are installed during the construction process, large deformation can be avoided effectively and the construction can be controlled easily. To compare new construction method of lifting struts layer by layer with traditional method of tensioning diagonal cables, construction process simulations of two kinds of methods are carried out in a numerical example using the nonlinear time-varying mechanics analysis program. Results show that the new method is feasible and can be used in the actual construction. At last, some suggestions for design and construction of cable dome are made in the paper.