Advanced Materials Research Vols. 243-249

Abstract: Through experiment study on full scale segmental model of Huaian bridge pylon, the stress distribution in the segmental model under the U shaped tendons and the horizontal load was measured. At the same time, the critical cracking load and the coefficient cracking safety class of the anchorage zone were obtained. At last, the theoretical analysis was compared with the experimental results, the theory agreed with the experiment well.

Abstract: The evaluations on the same factor from different experts, based on AHP, are not identical, and some even far cry, because the evaluation may be effected by the knowledge, experience and emotion of the experts. To remedy this shortage, this paper established a hierarchical analysis model based on entropy. In the model, entropy value represents the uncertainty of the results. And entropy weight reflects the contribution of every expert in the assessment. Then comprehensive combination weights of the factors are determined, reflecting the importance of every factor. Applying the method, the risk factors in some bridge construction were analyzed, and, the conclusion has important significance for correct risk countermeasures and smooth construction.

Abstract: A structure model of three-span continuous rigid frame bridge was constructed based on the finite element method. At first, the modal analysis was performed to get the natural frequencies and periods. The dynamic characteristics of the bridge structure were summarized, and some improvement measures are suggested to overcome the shortcoming for the bridge structure. Then, seismic response analysis was carried out based on the EL-Centro wave. The input excitations adopted the combination of vertical wave plus longitudinal wave, or vertical wave plus lateral wave. Based on the two excitation cases, some useful results were obtained, which include internal forces, displacements, accelerations time-history curves of the critical sections for the bridge structure. And some commentates about the time-history curves are given. At last, some helpful conclusions are drawn based on the calculation and analysis above. The calculation methods and results in this paper can provide some referenced information for the engineering design.

Abstract: To simulate the hysteretic behavior and propose the analytical model of steel reinforced concrete (SRC) columns under low cyclic loads, different fiber models which can reflect the mechanical behavior of materials are used in this paper. The unconfined concrete, partially confined concrete, highly confined concrete, structure steel and longitudinal reinforcement bars of the complex cross section can be established by OpenSees program which can define the different fibers for kinds of materials with their own stress-strain relations, respectively. Based on fiber models, the analytical model for simulating the hysteretic behavior of SRC columns is proposed. By comparing with the conventional simulation results, the results which are obtained from the proposed analytical model in this paper agree with the experimental results better.

Abstract: The objective of this study is to analyze the temperature and shrinkage stresses of the mid-span cross-section of a 20 meters box girder to find the reasons which cause the longitudinal cracks in the web and bottom of box girder. According to the results of damage inspeation, there are many longitudinal cracks in the web and bottom slab of box girders, especially the web of the edger beam, the crack is very clear. Ansys ver.10 software is used to analyze two dimensional finite element model of a typical cross section of a real bridge to calculate the temperature stresses caused by temperature difference between inside and out side of the box and the shrinkage stresses based on moisture diffusion. The results of analysis show that the outer surface of the web and bottom slab of the fabricated box girder will produce tensile stress at the effect of negative temperature difference. If the concrete reaches a certain age, the tensile stress does not cause creaks in the cross-section. The shrinkage stress changes with the moisture gradient in the box section. It will reach the maximum in 15 days and then decreases with the growth of the age. Shrinkage stress may cause cracking of the concrete surface because of the tensile strength is low in the early age.

Abstract: Being the most critical component among long-span PC bridges, prestress steel tendon’s current condition is closely related to structural safety and durability. For the sake of measuring it exactly to estimate the condition for prestressing reservation practically in service stage, an invented instrument named Stretching Force Tester is applied to monitor the effective prestressing force of strand. The precision of this technology is guaranteed by means of amending analogous boundary condition and minimizing test errors through the tool of double-stage differences. Based on comparatively sophisticated prestressing loss method in current code, an evaluation model on attenuation of effective prestress is built up. By means of obtained stress datum on strand, recognition on two types of nominal coefficients for prestress losses is realized and regularities of practical distribution can be simulated simultaneously. The experimental results of a large-scale beam model demonstrate accuracy and practical utility of the technology.

Abstract: On the basis of analyzing the necessary, such as the bridge monitoring data management, safety state evaluation, evaluation opinions and etc , this paper designs a remote monitoring and assessment system (BRMAS)with the parametric, intelligent and modular design thought, and applicates object-oriented software Microsoft VC++ to developt BRMAS system, which gives a system structure, function module and evaluation model. Through applying the design scheme and developed software into a highway bridge management, applications indicated that BRMAS system is very maneuverable, and realize the modern information management of bridges.

Abstract: The aseismatic performance of long span continuous rigid-frame bridge is an important but difficult research topic. To explore the impact of pier height and reinforcement ratio on long span continuous rigid-frame bridge’s aseismatic performance, Midas/Civil bridge Finite Element program is used to construct the three-dimensional model of a continuous rigid-frame bridge in this research. Fiber element and plastic hinge are used in pier simulation. Through the adjustment of pier height and ratio of reinforcement, the internal force, displacement and plastic rotation of bridge pier’s critical sections are analyzed under the action of seismic loading. Thereby, the impact of pier height and plastic hinge on such bridge’s aseismatic performance is obtained. It is shown that: maximum displacement, bending moment and plastic rotation increase at pier cap with pier height, indicating that pier height has strong impact on seismic response. And with increasing reinforcement ratio, the bending moment and yielding moment at pier cap and base both increase. Therefore, suitable pier height and reinforcement ratio should be selected for better aseismatic performance.

Abstract: For steel cable-stayed bridges which have been operating for many years, their static and dynamic parameters have been being changed because of corrosion and overloading. Therefore, an adjustable numerical model, describing and orienting all the various phases of the safety status of bridges, is needed for a theoretical guide of daily maintenance or periodical repair for them. In order to build such a model reflecting the different phases of working conditions of a bridge, a link between the model and the present condition of the targeted bridge should be erected by periodical field inspections for the structure. In this paper, backed on a practical engineering example, the Shengli cable-stayed bridge of Dongying, a finite element model (FEM) based on the periodical field inspection data was proposed, which could possess a strategy modified correspondingly according to parts or all of the results in the field inspections. Specifically, for the initial FEM, three important issues in the modeling of such a complicated bridge, such as simulation of boundary conditions, equivalence of orthotropic steel deck, and implementation of accurate cable tensions, were firstly studied. Then, the initial finite element model built was modified in terms of the optimization principle by minimizing the difference between the static deflections resulting from the field inspection and those calculated by the FEM before being modified. Lastly, dynamic results from the field inspection were compared with those from the optimized FEM to justify feasibility and reasonability of the developed three-dimension FEM which could reflect one or some certain properties of the structure we were emphatically paying attention to. This model-building and model-modifying method for the baseline FEM of the Shengli cable-stayed bridge also provided reference for the similar existing cable-stayed bridges.

Abstract: Xia-Zhang Sea-crossing Bridge was located in earthquake zone, the design of which was governed by earthquake. Based on seismic-isolation principles, seismic-isolation bearing system and damper system were studied to find out the effect of each seismic-isolation system on seismic performance of steel box arch bridge scheme. Seismic response could be effectively reduced by damper system, without changing the original constraint system of structure, which was recommended for longitudinal seismic system. Two liquid viscous dampers were suggested installing between pier and girder after parameter analysis, with damping coefficient of 4000kN/ (m/s) ^1.0 and damping index of 1.0.