Advanced Materials Research Vols. 368-373

Abstract: Adequately consider the mechanisim of concrete and steel of the beam after perish, this paper preclude the bending bearing capacity function of the old RC beam reinforced with CFRP sheet. The experiment which proposed on 4 beams which have been used over 40 years in Mianyang get the result that it is match the function. This paper also analyse the fracture morphology of the reinforced beam and the effective of the reinforcement. The conclusion this paper have aquire is that the old beam which reinforce with CFRP sheet can satisfy the engeneering.

Abstract: Hyperbolic paraboloidal latticed shell, with a span of 93.6m, is adopted in the gymnasium of China University of Petroleum. Single-layer shell of the inner 9 circles adopts crossed web bars to increase its stiffness and bearing capacity, and double-layer shell of the outer 3 circles is used to bear horizontal action. Elastic support is employed to simulate hydraulic support of the shell, beam element to chords, and truss element to crossed web bar. Thus unloading program, from inside to outside and multiple cycles, is raised. To master the influence of unloading on the shell’s security, vibrating string extensometer and total station are used to monitor stress and vertical displacement of key points. By comparing theoretical data with monitoring results, it is proved that the shell’s stress and deformation comply with the design requirements, and indicated the success of unloading.

Abstract: In order to evaluate safety performance of reinforced concrete poles accurately, 6 reinforced concrete pole specimens were selected randomly for the bending test. The mechanical behavior and failure mechanism of all specimens were studied, failure modes were revealed, and important experiment data were also obtained, such as cracking loading, ultimate loading, crack development shape, crack width and so on. Based on the experiment data, moment-crack width relationship curve and moment-deflection relationship curve were obtained. Research results showed that failure modes of specimens were similar to “less-reinforced beams”, based on limit state design method in normal use, security surplus factor is 1.27 before collapse damage.

Abstract: The structural damages, which result from the inadequate bearing capacity or the asymmetric support of foundation, are one of the crucial works in the conservation of historical masonry constructions. A new underpinning technique, applying the principle of pipe-jacking, is presented in this paper, which can build a new foundation system having sufficient rigidity under the bearing wall of the upper building. The technique has been successfully used in the conservation practices of masonry constructions, but the basic problems involved in the technique has not yet studied. Based on the field test, the principle of the underpinning by manual pipe-jacking , the mutual effect mechanism between box girders and soil, the calculation of jacking force and its influence factors are investigated in detail, and the empirical formula of calculating jacking force is also presented.

Abstract: First establish a dynamic model of tower crane in the load lifting process, the lifting load is solved.Then establish the FEM model of the tower crane under the normal and the damage condition. Get the dynamic displacement of the normal and the damage status under the lifting dynamic load. Propose a damaged diagnosis method by the displacement rate. The results of the study show that this method can not only diagnose the structural damage status, but also determine the positions of structural damage. This will be a new search on tower crane structural health diagnosis.

Abstract: A dynamic test of two unbonded fully prestressed concrete beams has been conducted. The results indicate that the natural frequency of beams increases with the prestress force, which is opposite to the analytical arguments for homogeneous and isotropic beams subject to axial force. This paper explains the change in frequencies by discussing the change in the elastic modulus. A modified formula is also proposed, and the experimental data agree well with the theoretical analysis.

Abstract: This paper introduces an example on AE monitoring and ultrasonic wave velocity measurement of concrete (C20). Experiment on AE characteristic of the full failure process of concrete is carried out on the pressing machine. AE sensors can be surface mounted. A system (the 8-channels, high-speed acquiring and analyzing AE signal), called HUS (Hyperion Ultrasonic System), was employed to acquire and record AE characteristics. AE signals were recorded during loading (fracture propagation) subject to the uniaxial compressive loading until failure. Using a simplex location algorithm allows AE event location from first arrival times to be determined by the AE sensors. The mechanical properties of concrete and acoustic emission characteristic, including the full stress-strain curves, AE counts, and AE rate and ultrasonic wave velocity, were obtained. The relations among AE counts, AE rate, stress levels, ultrasonic wave velocity and time are analyzed in detail. This paper reports AE observations made with an array of this new high-fidelity. Crack initiation and crack propagation due to the uniaxial compressive loading were monitored for AE activity and compared with visual observation. Meanwhile, stress changing influence the wave velocity of concrete; with the initial crack expands, up to the rock sample failure, the wave velocity falls gradually. Some insight into the percentage of AE events that must actually be detected to describe the health of concrete sample was gained.

Abstract: Based on optimal designed objective function method, on the constraint condition of control point level and the objective function of the least total yield, optimal analysis of well-group precipitation design to the subway section has been done, and some targets have been gotten, such as the total yield, precipitation sphere of influence, reasonable arrangement of dewatering well and single-well water yield. At the same time assign for the single-well yield using COMSOL Multiphysics, and then simulate and evaluate the precipitation effect, predict the sphere of influence to surroundings caused by engineering dewatering and also the settlement regularity of the soil. It turns out that the combination of the above two methods can solve the optimal precipitation well to reach a better effect, reduce the cost and affect less environment.

Abstract: In order to reasonably analyze the influence of rheological properties on the soil deformation behavior of tunnel in soil, this paper establishes visco-elastic-plastic numerical calculation model for analysis of tunnel in soil deformation based on ANSYS software by relying on physical construction. The results show that creep deformation accounts for 24% of total deformation of the tunnel, so it is necessary to make visco-elasto-plastic analysis on tunnel in soil. If the numerical simulation results are basically the same with the trend of temporal curve of measured data, and the data obtained is relatively close, then the established model is correct.

Abstract: An engineering case is taken to analyze data of buildings settlement caused by foundation pit excavation. The predicted value was calculated and compared with the measured data to discuss the settlement of buildings nearby foundation pit. It is proved that sedimentation rate and settlement are relative to depth of the foundation pit and distance between buildings and foundation pit. This paper suggests to monitoring variation during construction in order to ensure safety of structural support and surroundings.