Applied Mechanics and Materials Vols. 488-489

Abstract: In order to investigate the shear behaviors of RC beams after freeze-thaw cycles, static shear experiments of 45 RC beams after 0, 75, 100, 125, and 150 freeze-thaw cycles were made. The influences of different numbers of freeze-thaw cycles on the shear behaviors of RC beams with different stirrup spacing were studied. The results show that Freeze-thaw cycle, stirrup spacing of reinforced concrete beam has no significant effect on crack distribution and failure pattern; cracking load and ultimate load of shear beams decrease with the increasing of freeze-thaw cycles.

Abstract: In order to solve the difficulties in the deformation measurement of subway shield tunnel structure, a non-contact measurement method of close range photogrammetry technology based on movable base is put forward. A light metal frame is designed as the movable base, which is calibrated by the electronic total station. And the case study verified the feasibility of the measurement.

Abstract: A new GM(1,1) model is proposed in the paper thinking about of the influence of the traditional modeling accuracy bias of subjective modeling and noise interfere. Using the new model, the noisy part of monitoring data could be deleted and prediction error could be decreased. At the same time, the constraint conditions of minimum fitting error sum of squares of each variable during once accumulation is raised to build and optimize a prediction model with optimal initial values based on the Principle of Least Squares. Moreover, the new GM(1,1) model is established by improving the background value and gray value with consideration of systematical optimization. Finally through the practical case, the results show that the calculation result of using the new GM(1,1) model is smaller and the accuracy is higher than using the traditional model.

Abstract: How to exploiture and apply environmentally friendly and low carbon asphalt modifier is one of technicality problems which are exigent to solved in highway construction. Based on the introduction of vulcanizing process of eucommia ulmoides gum (EUG) and the physical and mechanical properties of vulcanized gum, and the explains of its desirable engineering characteristics as well as its engineering application foreground.,the new approach is presented to use modified asphalt which is a blend of vulcanized EUG and asphalt as new pavement materials of highway. With sweep electron microscope (SEM) and analysis on the improvements of the asphalt`s performance, the best crosslinking degree of asphalt modified vulcanized EUG was studied, and the result indicates that vulcanized EUG has a range of the best crosslinking degree. When the crosslinking degree of vulcanized EUG reaches the range, the vulcanized EUG can improve asphalt`s performances in both low temperature and high temperature, which means it is feasible to use vulcanized EUG for asphalt modifying.

Abstract: The photosynthesis effect of arbuscular mycorrhizal fungi (AMF) on mulberry was evaluated in karst rocky desertification area. Three-month-old sterile mulberry saplings were transplanted in karst rocky desertification area and were inoculated with Gigaspora rosea. Some growth parameters and photosynthesis indexes were measured to study the physiological responses after inoculating for 1 year. The results showed mulberries that were inoculated with AMF had greater height, larger stem diameter and leaf area, more leaf number per plant, more fibrous root number and biomass of shoots and roots, as well as higher chlorophyll content, net photosynthetic rate, transpiration rate, stomatal conductance compared with non-AMF plants. The research results confirmed that AMF markedly enhanced the absorptive ability of root system, promoted the vegetative growth, improved the photosynthetic capacity, and obviously increased mulberry survival rate in karst rocky desertification area. These results provided a theoretical base for the ecological restoration in karst rocky desertification area.

Abstract: Owing to the excellent tensile strength and corrosion-resistance of fiber reinforced unsaturated polyester composite, it is expected to solve the corrosion problem of building instead of steel bars in some special occasions. Bonding performance between concrete and FRP rebars was studied by pull-out test,the influences of the surface form, anchorage length and diameter of FRP rebar on bonding strength were discussed in detail.

Abstract: Based on a tunnel in western China as a project, with high water pressure, water-rich, karst features and other projects, launched grouting water research, the cement-silicate slurry mixing method for determining the mixing ratio to ensure the effectiveness and construction safety grouting key factors, as well as the specific implementation grouting effect evaluation method has important theoretical and practical value for the design and construction of similar tunnels provide a reference.

Abstract: Based on a municipal highway tunnel in western China, for the building of the tunnel surface dense, especially import Portal Jude Biao most shallow depth of less than 10m building project, we proposed borehole layout, charge and detonate Network Road design method, and the corresponding control points of drilling and blasting operations and blasting safety control measures and means to ensure that the duration and quality of construction, can provide some experience of similar projects and basis.

Abstract: Based on a tunnel in western China as a project, with high water pressure, water-rich, karst features and other projects, launched grouting water research, the cement-silicate slurry mixing method for determining the mixing ratio to ensure the effectiveness and construction safety grouting key factors, as well as the specific implementation grouting effect evaluation method has important theoretical and practical value for the design and construction of similar tunnels provide a reference.

Abstract: Welded tubular structures are widely used in many constructions, such as offshore platforms, which are all consisted of welded tubular members. There is a stress concentration at the intersection between chord and brace. When subjected to loads, a crack exists in the weld toe at the intersection. Then the propagation of the crack leads to failure of the joint. So the static strength of rectangular hollow section (RHS) T-joints with local chord reinforcement under in-plane bending load is investigated by using finite element method. To study the effect of the chord reinforcement of a RHS T-joint, overall 18 T-joint models with different chord reinforcements have been analyzed numerically. This paper presents the results of a detailed parametric study of the static strength of in-plane bending loaded tubular T-joints with reinforced chord. The study, carried out using non-linear finite elements, demonstrated the accuracy of the finite element analysis to investigate the effects of different geometric parameters which influence the static strength of the stiffened joints. It is found that the effect of the chord thickness near the intersection is significant in improving the ultimate capacity of T-joint models. The ultimate strength enhances as the length of the chord reinforcement becomes longer and the chord wall thickness becomes larger. The effect of the chord wall thickness on the static strength of T-joints are remarkable. However, increasing the length of the reinforced chord to improve the static strength of Tubular T-joint is relatively ineffective.