Advanced Materials Research Vols. 368-373

Abstract: On account of the fracture status of shaft joint in complex stratum, we analyze the reasons causing damage, then put forward restoration plans, such as, controlling water and consolidate the weak stratum by grouting, and strengthen the shaft supporting. We also propose to enhance supporting shaft thickness reasonably through shaft calculation, checking, and numerical simulation. In addition, bolting support with metal mesh and cable system should be adopted in the combined support of weak surrounding rock, double bolt plates should be used to enhance the links between shaft and surrounding rock, and the support effect should also be monitored.

Abstract: In order to make much detail monitor and more practical evaluation on structural safety and durability for long-span continuous rigid frame bridge, the condition for prestressing reservation in service stage turns out to be a necessary key index. By means of obtained stress value on prestressing tendons, discrimination on subordinated mode and recognition on nominal coefficients of prestress losses are implemented. Furthermore, unified evaluation on effective prestress of post-tensioned PC bridges are realized at anytime of the whole service life, which include different geometric patterns of prestressed reinforcement, different types of structure and different structural formation systems. Simultaneously, recognition on two types of nominal coefficients for prestress losses is realized and regularities of practical distribution can be simulated. The practical utility of a long-span continuous rigid frame bridge show that the general principle for effective prestress can be demonstrated. Therefore, key parameters for health monitoring on existing long-span continuous rigid frame bridge are provided and the results lay the foundation for further control.

Abstract: In this paper, a total of six reinforced concrete beams including four beams strengthened with externally prestressed CFRP rods and two unstrengthened beams have been tested under monotonic and cylic loads in order to investigate the influence of a novel technique on the flexural static and fatigue behavior of the specimens. The experimental results show that the static and fatigue performance of strengthened members have been improved in terms of that the flexural capacity is greatly enhanced, the fatigue life is increased and the stress range of the internally tensile reinforcing bars is decreased as compared with the unstrengthened ones. It indicates that the developed technique can enhance the flexural capacity as well as improve the fatigue performance of RC members.

Abstract: A bearing capacity evaluation model of prestressed concrete bridge is established based on analytic hierarchy process. In order to determine the bearing capacity of the existing bridge condition, fuzzy evaluation method is used to evaluate material damage degree of bridge structures, in which of experience of experts can be used sufficiently. The method is evident and useful, which can reflect the prestressed concrete bridge in service effectively, improve the existing structure model and optimize the bearing capacity of synthetic evaluation. At the same time, the result is verified reasonably by an engineering example.

Abstract: Static load test is now recognized as a reliable bridge inspection method. However, this method has to interrupt transportation and consume manpower and material greatly. Firstly, this paper introduced the mathematic relation between static calibration coefficient and dynamic calibration coefficient, which are achieved by dynamic/static load tests with different load efficiencies—by comparing them, the proposed equation are verified. Quantitative assessment of bridge is achieved by combining dynamic load inspection method.

Abstract: Based on a secondary load, the formula of calculating the cross-section stress and stiffness of the reinforced concrete simply supported beam by CFRP reinforcing in normal use is derived. Through the comparison and analysis of the load test data before and after the concrete simply supported beam in-service is reinforced, it is showed that CFRP can be coordinated with the concrete in normal use so that the carrying capacity of concrete beam is increased by about 17% to 19%, the stiffness is increased by about 50%, and it is consistent with the formula calculated results.

Abstract: The combination of a single row of artificially-dug-up piles and pre-stressed anchor rope was adopted to the foundation pit as the retaining structure,and anchor-plate retaining structure and rubble retaining wall were used as the bracing system for the complicated building slope. In the process of excavation, monitoring has been done to see if any horizontal displacement, deformation of deep soil and crack width take place or any technical data and code dispatch from the demand. Monitoring results show that deformation in some parts of the tops of support structure is larger than the designed warning value some times and the deformation continue to increase in the process of the excavation, and this result in twice dangerous situations in the support structure of the slope. In this paper, the geologic construction of the slope and the situations of the designed support structure and monitoring condition were depicted. The mechanism of the instability of the slope was explained on the basis of comprehensive analysis of deformation monitoring datas. It is concluded that the over-excavation, explosive excavation, rainfall and so on were the factors affecting the stability of the slope. Corresponding emergency measures and reinforcement measures,such as unloading and pre-stress rope, were proposed, which were proved to be highly effective.

Abstract: The sustainable development of Xi’an was analyzed based on statistical data from 1996—2008 using economic theory to find the principle factors influencing the development of Xi’an and to identify the formula of contribution rate to the growth of Xi’an by each factors. The regression analysis is used to obtain the value of contribute rate. The result show that the largest contribution is from accumulation of physical capital, and the contribution from technological advances is increasing year by year. The labor factor and human capital investment make little contribution to Xi’an growth. Capital allocation and scale economic do negative effect to economic growth.

Abstract: Based on nonlinear elastic theory and Hamilton’s principle, a generalized element stiffness matrix, which incorporates the effects of flexural as well as axial stresses induced by initial load, is given. A finite element method for dynamic analysis considering the effect of initial load is presented, with corresponding computer programs produced to facilitate the analysis. The formula is validated through a comparison in results with the analytical solution. The effects of key physical factors, including the type and magnitude of initial load, and stiffness parameters such as sectional inertia moment, inertia radius and span, on the dynamic characteristics of the beams with various restraint conditions are discussed with the effect of initial flexural stress considered. The results suggest that the natural frequency of the beam would be enhanced due to the existence of flexural stress induced by initial load and such as effect relates to the magnitude of initial load and stiffness parameters of the beam.

Abstract: A new type of construction employing shaped steels as boundary elements and layered braces of RC(Reinforced Concrete) short-pier shear wall is put forward. The braces are in X shape and are erected in a multi-storied form. They are embedded in the boundary zone and the web of SRC (Steel Reinforced Concrete) short-pier shear wall respectively to make it possible to improve the bearing capacity and ductility of this shear wall and to improve its seismic performance. Three half-scale specimens of the SRC short-pier shear wall are tested under reversed cyclic loading. High design axial load radio of 0.5 is used. The failure processes and modes of the specimens are observed. The law about bearing capacity and displacement ductility of the specimens influenced by the layered braces structures is revealed. The experimental results show that the displacement ductility is closely related to the amount of stories of braces. The specimens with layered braces structures have better ductility and larger bearing capacity, and therefore the layered braces structures effectively improve the seismic performance of the SRC short-pier shear wall.