Advanced Materials Research Vols. 368-373

Abstract: This paper studied the main cracking reasons for small and medium-span continuous girder bridge with secondary concreting based on ANSYS. Some prevention measures to concrete crack caused by the inelastic subsidence were also proposed. In considering the global deformation of scaffold-beam, the inelastic deformation of scaffold, the hydration heat of cement, and the characteristics of early-age concrete, influence of inelastic subsidence of support foundation on concrete cracking were analyzed by time-varying transient analysis. It can be concluded that the value of inelastic deformation is the decisive factor for the concrete cracking. Field measurement results of several bridges validate the conclusion.

Abstract: In this paper, a new prediction model named RBNN-GM(1,1) (Radial Basis Neural Network-Grey Model) model was constructed and used for the analysis of building subsidence prediction for the Palms Together Dagoba in Famen Temple in Shaanxi Province in China. The constructed model can make full use of the advantages of few samples and little information predicting in Grey Theory and swift and self-learning in RBNN. The prediction results show that the combined model is more effective than the common grey model. The proposed combined model for building subsidence prediction may offer scientific rationale for estimating whether the building transmutation exceeds the criterion and provide reference for taking the corresponding safety measures.

Abstract: In structure design, for expressions with partial safety factors, partial safety factors and nominal value of loads are calculated based on the presupposition that the design reference period is 50 years. When the design reference period is not 50 years, it would cause unclear reliability of building structure by using expressions with partial safety factors following correlative codes yet. It may lead to hidden dangers in that way. In order to derive expressions with partial safety factors suitable for any design reference period, two useful methods are shown in this paper, modification of partial safety factors and modification of importance factor of structures. From results of analysis, we get the conclusions that it can assure the reliability index of the expression using the method of modification of partial safety factors, and the method of modification of importance factor of structures is very simple, but cannot assure the reliability index of the expression.

Abstract: At present, the main methods of analyzing the reasons why construction cost always got out of control are qualitative analysis based on the practical construction experiences in the construction cost management. And these analyses were easily affected by subjective factors. By introducing a complete decomposition model, the influencing factors of the incontrollable construction cost in the construction stage can be decomposed to the effect of quantity changes and the effect of unit price changes of each kind of construction. A quantitative analysis will be carried on subsequently to analyzing these effects to find the main effects of the whole construction cost changes. This model made the analysis more objective and scientific, and can accumulate the data for new or planned similar constructions. To illustrate, the decomposition on construction cost changes of a small civil project is carried out.

Abstract: The bending performance test on one ordinary reinforced concrete beam and six RC beams strengthened with basalt fiber sheets(BFRP) is carried out, and the bending performance of the RC beams strengthened with BFRP is analyzed. The experimental results show that BFRP improves the bending performance of the beam. Pasting one layer,two layers or three layers of BFRP, The ultimate strength RC beams were increased by 29%, 56% and 78%. Basalt fiber sheets and concrete beams can work better together and play an effective role in reinforcement.

Abstract: This paper introduces the status of long span bridge detection, the current detection system, the specifications and the main evaluation methods; analyzes the present existing problems of bridge test; and puts forward the development direction of large-span bridge test, i.e. seeking new detection system and modifying the original specifications and evaluation methods.

Abstract: Flood-induced piping and subsequent formation of sand boils can cause severe damage to river levees. And it is known that no piping failure occurs, without seepage exit. The paper represents an experimental study on the process and mechanism of seepage exit forming on top stratum at a weak zone in a double-layer dike foundation, using sandbox modeling. According to the practical observation, three series experiments were designed. The size, thickness and the physical and mechanical properties of the top stratum are considered. The results show that the failure mode is close related to the size of the weak zone. And the hydraulic gradient of seepage exit forming is greater than the value, computed by Terzaghi’s formula.

Abstract: This paper presents a nonlinear numerical analysis on the seismic behavior of concrete filled square steel tube (CFST) columns and steel beam planar frame with through bolt-endplate beam-column connection, by using the finite element analysis modeling with ABAQUS. Parametric studies were conducted to investigate the influence of axial load ratio and beam-to-column linear stiffness ratio on the seismic behavior of composite frames. The analysis results were in good agreement with the experiment results. The analysis results showed that CFST frame with through bolt-endplate beam-column connection had good seismic behavior. The increase of axial load ratio will degrade the horizontal load bearing capacity and increase the energy dissipation capability. The increase of beam-to-column linear stiffness ratio will increase the horizontal load bearing capacity and degrade the energy dissipation capability.

Abstract: Modal decomposition method is utilized to investigate Lamb wave scattering at step-like discontinuity. The structure is regard as a special delamination structure where one or two delamination layers are missing and only one delamination layer extended to infinite. Model decomposition technique is then combined with the boundary condition equations to get the scattering solution of the whole discontinuity region. The efficacy of the method is illustrated by calculation examples where the scattering of the second symmetric mode at step-discontinuity with different thickness are evaluated and Energy flux conservation is confirmed.

Abstract: Many of the wave propagation based structural health monitoring techniques rely on some knowledge of the structure in a healthy state in order to identify damage. Baseline measurements are recorded when a structure is pristine and are stored for comparison to future data. A concern with the use of baseline subtraction methods is the ability to discern structural changes from the effects of varying environmental and operational conditions when analyzing the vibration response of a system. The use of a standard baseline subtraction technique may falsely indicate damage when environmental or operational variations are present between baseline measurements and new measurements. A procedure was outlined for the method, including excitation and recording of Lamb waves, and the use of damage detection algorithms. In this paper, several tests are performed and the results are used to help develop the damage detection algorithms previously described, and to evaluate the performance of the instantaneous baseline SHM technique. Analytical testing is first performed by feeding known input signals into each damage detection algorithm and analyzing the output data. The results of the analytical testing are used to help develop the damage detection algorithms.