Xian Xi Tang

Applications of Fiber Bragg Grating in Strain Measurement of Concrete Bridge

In order to verify the role of fiber bragg grating strain gauge in strain measurement of concrete bridge, and the influence of concrete and steel strain properties by fatigue loading, the relevant experimental researches were carried out. The results indicated that the Fiber Bragg grating strain gauge could reflect the strain regularity of concrete and steel well; for the fiber grating strain rosettes inside the concrete, the pasting equipments of fiber gratings had a certain impact of the measurement effect. The fatigue loading had a certain impact of the properties of concrete and steel, in conditions of the same number of fatigue, the greater the stress amplitude the more obvious the effects. The results analysis shown that, fiber grating strain measurement innovated the means and methods of strain measurement in detailed structure of the concrete bridge, for the strain measurements of concrete bridge under fatigue loading, the FBG could still play very good effect.

Concrete Crack Control in Monolithic Concrete Bed Construction of High-Speed Railway in Northwest Area of China

There were some reasons which cause the concrete cracks in monolithic concrete bed construction of high-speed railway. In this paper, combined with the specific situation of monolithic concrete bed construction of high-speed railway in northwest area of China, the states and causes of two kinds of cracks in monolithic concrete bed of high-speed railway were analyzed, the concrete cracking control measures were discussed from the concrete mixture ratio, construction technology and maintenance measures and other aspects, and the corresponding views were put forward. The study results had the important guiding significance on crack controls of concrete structure during the construction process of northwest area.

Experimental Study on Strain Performance of Tensile Reinforcement under Fatigue Loads

As for the study on the strain performance of tensile reinforcement under the fatigue loads with amplitude of certain values, two groups of reinforced concrete slab bridge specimen were made. The fatigue test was carried out on one group of specimen, and the corresponding static load test was carried out on another group of specimen, the experimental study on the strain performance of tensile reinforcement was carried on bottom of the mid span of slabs. The results of the study shown that, under the fatigue loads at a certain amplitude, the strain performance of the tensile reinforcement tend to be stable with the increase of number of fatigue cycle, the strain value showed certain linear relationship with static load applied. When the fatigue amplitude increased, the change rule of strain with static load value applied was approximately linear, but the strain value increased more than the fatigue amplitude less under the same static load. It could be seen through the comparison of load - strain curve of the static load specimen, after effect of compressive fatigue with certain amplitude, the strain change with load applied was close to linear change, which has great relationship with the effect on concrete and reinforcement plastic deformation by fatigue load. The test results had the vital significance of further research on reinforcement performance under the action of fatigue loads.

Experimental Study on the Development Regularity of Slab Concrete Cracks under Fatigue Loads

As for the study on the development regularity of slab concrete cracks under the fatigue loads with amplitude of certain values, two groups of reinforced concrete slab bridge specimen were made. The fatigue test was carried out on one group of specimen, and the corresponding static load test was carried out on another group of specimen, the experimental study on the development regularity of concrete cracks at bottom of slab were carried out. The results of the study shown that, under the fatigue loads at a certain amplitude, the development trend of cracks caused by loading at the bottom of slabs changed more under fatigue loads. The reasons caused the changes of development regularity of concrete cracks were analyzed. The experimental results has the vital significance of further research on the development regularity of concrete bridges under the action of fatigue loads.

Applications of Fiber Grating in Temperature Measurement of Hydration Heat of Concrete

In order to verify the application effect of fiber grating strain gauge in concrete hydration heat measurement, the relevant experimental researches were carried out. First, according to the formulas of concrete condensation hardening adiabatic temperature rising, the regulation of temperature changes in the concrete condensation hardening process was calculated. Then the observation results of concrete condensation hardening temperature by fiber grating were analyzed, and the variation regulation observed was summarized, and the variation regulation was verified by temperature sensors embedded in the corresponding positions. The results of the study shown that, the measured data by fiber grating can reflect the temperature change rule of concrete well. Therefore, it was feasible to measurement the temperature change regulation by fiber grating.

Analysis of Cracks in Concrete Beam Impacted by Construction Technology

There were many factors which caused cracks in the concrete beam, but some factors were often not be attention enough. In this paper, Combined with three kinds of crack occurrence in construction of concrete plate, the reasons leading to crack by construction technology were analyzed in detail, which including the construction process, curing conditions and controls of cover thickness, and the solution were given also. The result of analysis had guiding roles of crack controlling in concrete structure construction.

Analysis of Importance of Concrete Bridge Configurations Based on AHP

The applicability and durability proportions of the main structures in concrete bridge were determined based on AHP, and the influence degree of different influencing factors on applicable and durable structures of concrete bridge were also analysised, which laid the foundations of applicable and durable configurations study of concrete bridge.

Experimental Study of Ultimate Bearing Capacity of Hinged Plates with Different Configuration Hinge Joints

To study the role of vertical shear stress on the ultimate bearing capacity of hinge plates under fatigue loading, and different configurations of hinge joints on ultimate bearing capacity of hinged plates, three groups of hinged plate experiments were studied. Two groups of hinge plates with shallow hinge joint configurations were tested with static loading and fatigue loading respective, a group of hinge plates with deep hinge joint configurations were tested with fatigue loading directly. The ultimate bearing capacity analysis of hinge plates was carried out through mid-span deflection differences of hinged plates on both sides of hinge joints and transverse strains on top and bottom of hinge joints. Shown from the experimental results, for the hinge plates with shallow hinge joints, the ultimate bearing capacity under static load was 342.9kN, and under fatigue load was 340kN, but the ultimate bearing capacity under fatigue load of hinge plate with deep hinge joints was 610kN. Therefore, the vertical shear stress is not the main factor which cause the hinge joints destruction of hinge plates; hinge joints configurations, especially the depth of the hinge joints have great impact of ultimate bearing capacity of hinge plates; in the strengthen checking of hinge joints while hinge plates design, checking the vertical shear strength only is not comprehensive, various factors should be taken into account.

Numerical Analysis of Reasonable Hinge Joints Size of Reinforced Concrete Hinged Plates

In order to study the stress distribution in hinge joints of different depth and the effects of hinged plate by hinge joints depth, 5 group ANSYS finite element models of concrete simply supported hinged plates were built, hinge joints stress of models have been compared under the center load and side load, analysis has been made on the hinge joints of maximal stress. The analysis results indicated that with the increase of the depth of hinge joints, the transverse tensile stress, vertical shear stress and longitudinal tension stress were all showed regular distributions, and with the increase of the depth of hinge joints from 10cm to 26cm, the maximum reduction value of transverse tensile stress in hinge joints was 3.25MPa, the reduction range was 51.9%; the maximum reduction value of vertical shear stress was 1.06MPa, the reduction range was 77.9%; longitudinal compressive stress decreased gradually, and longitudinal tensile stress increased; the maximum reduction value of hinged plates deflection difference was 0.16mm, the reduction range was 36.4%; the transverse tensile stress of hinged plates’ bottom increased. Therefore, increasing the depth of hinge joints was the most effective way to increase the transverse stiffness of slab girder and to prevent hinge joints damage. At the same time, the tensile reinforcements setting in transverse and longitudinal at the bottom of hinge joints and the tensile reinforcements setting in transverse at the bottom of slab girder should be strengthened.