Key Engineering Materials Vol. 648

Abstract: Concrete cracks monitoring of a practical bridge was discussed in order to investigate the practical application of structural health monitoring (SHM) technique. Some detail information of the SHM system of a practical bridge were introduced and some key issues for building this monitoring system was discussed. Strain of bridge beam generated near the concrete cracks was applied to assess the change of width of cracks, and the monitoring data were analyzed. The condition of this practical was evaluated from the point of view of the change trend of concrete cracks.

Abstract: A cave is formed when surface water and groundwater effect on soluble rocks through chemical and mechanical damage. That is called karst phenomenon. It will affect the stability and stress distribution of the surrounding rock. Part of the tunnel construction process will affect the stress distribution of the surrounding rock greatly. Some caves are unavoidable, which could make structures insecurity and instability. At the same time, the construction process will become complicated. Caves will increase the risk and uncertainty of the whole project as well. Therefore, the development of scientific and efficient measures to ensure the quality and safety of the construction project becomes extremely important. In this paper several safety precautions would be introduced based on the specific case of tunnel construction. And experience will be given in order to benefit the construction of similar problems.

Abstract: Long-span bridge across the river in cold areas, is often impacted by the drift ice in spring, thus having some severe effects on the stability and vibration of the bridge structure. With a long-span prestressed concrete T-rigid frame bridge as studied object, based on the display analysis function of the LS-DYNA software, this paper represents the simulating process of the contact and collision between the drift-ice and T-rigid frame bridge pier, and the influence of various factors was analyzed, such as model boundary condition, contact types of river ice and pier, algorithm and element connection transition area. Thus the reasonable calculation model of the collision force caused by drift-ice to pier was determined. The result has important theoretical and practical value to ensure the safety of the bridge in cold area, as well as to reduce the project cost.

Abstract: Structural health monitoring systems used in bridges contain sensors providing a large amount of monitored data, such as stress, deflection and et.al. In this paper, firstly, based on monitored everyday extreme stress data, time-variant proof load effects of structural members were defined, and based on the time-dependent proof load effects, the time-dependent performance functions of structural member’s proof modes were built; and then based on the monitored data, the Bayesian dynamic models (BDMs) of extreme stresses were built, and based on the predicted extreme stress with BDMs, the time-variant performance functions of structural member’s failure modes were given; and then based on the time-dependent performance functions of failure modes and proof modes and correlation coefficients between them, with the conditional probability method, the time-dependent reliability indices of structural members were updated and predicted; finally an actual engineering was provided to illustrate the application of the proposed models and methods.

Abstract: Based on the requirement for fatigue damage evaluation of long-span bridges, and existing research literatures, the vehicle type, vehicle weight and time duration are taken as characteristic parameters of random vehicle load. Taking the Second Nanjing Yangtze River Bridge as an example, the characteristics of traffic load are obtained by traffic investigation and the data from existing research results. In the paper the method and process for vehicle load spectrum simulation which includes data acquisition of random traffic load, statistical analysis and Monte Carlo simulation is proposed. The simulation program of random traffic flow is verified using the measured data. The proposed method can provide a reference for random traffic load simulation.

Abstract: Damage accumulation and resistance decrease inevitably happen to bridge structures due to the effects of earthquakes, impact loads, wind load and corrosion during their service time. Once the damages of the key components accumulate to a certain level, they would spread promptly, causing the sudden destruction of the whole structure if not found and dealt with in time. So the structural damages would not only shorten the operation life of structure but also threaten the human lives and financial safety. Therefore, the technology of damage diagnosis of bridge structure holds supreme significance. This paper summarized the current research situation of the existing bridge diagnosis methods and analyzed the characteristics of each method through the reading and studying of the related material both domestically and internationally. Among those methods, only the diagnosis method based on load tests is the most direct and effective one for current bridge diagnosis, the diagnosis results of which shows higher reliability. And the structural dynamic characteristic method based on dynamic load tests could beautifully avoid the disadvantages of the static load tests, becoming the main development direction of rapid diagnosis of bridge. Furthermore, lastly it elaborated the analysis of the key problems of breaking through the development bottleneck of current rapid diagnosis methods of bridge, creating a solid foundation for the future research.

Abstract: The hot-rolling-whole-molded and comb-type-designed bridge expansion devices are widely used in the urban and highway bridges, owning the characteristics of large expansion allowance and small burial depth. Whereas using traditional craft to install comb-type expansion joint, such phenomenon like settlement, water seepage, bumping and noise in driving would happen with slow construction. Through continuous improvement for many years, Jinan Urban Construction Group has developed a full construction technology of installing comb expansion joint based on fixation stent by using tailor-made location frame to integrally move the anchor bolt group into the groove for firm weld with embedded steel, matching with moving lifting tool. Through this construction technology, the efficiency of construction is improved, the construction period is shortened, and the smoothness of asphalt after installing comb plate would meet the design requirements, also such quality defects like bumping and abnormal sound would be precluded. hot-rolling-whole-molded and comb-type-designed bridge expansion devices

Abstract: It is well known that a lot of concrete filled steel tubular (CFST) arch bridges were built in China. Thus it became a main bridge type. Its architectural design shows much novelty, while the structural design is always conducted based on the finite element (FE) model analysis. Meanwhile there is no professional code for design and construction of this type of bridge. To overcome these disadvantages, scaled model tests are preferable to evaluate the mechanical behavior and provide guidelines for design and construction of prototype bridges. In this paper, an irregular CFST arch bridge as the prototype was introduced and a 1/16 scaled bridge model was designed and constructed according to the similarity theory. The experimental study on the scaled model was aimed to simulate the construction stages and mechanical behavior under moving loads. The test results are used to make comparison with the construction monitoring and bearing-capacity load test of the prototype. The analysis shows that the experimental results of the scaled model are close to the measured results of the prototype. The scaled model test was proved to be valuable for the pre-camber setup of the arch rib and the tension optimization of the suspenders and for the operation safety.

Abstract: As more and more arch bridges built with the construction method of cantilever erection, the strength and entirety of the bridge shall worry the designers. This paper studies an arch bridge with a 65-meter span, gives the static loading test plan and the dynamic test plan, analyzes the testing data of the displacement and strain, explains the methods of static and dynamic load test in detail, and gives a conclusion about the bearing capacity and dynamic properties of bridge. This can be referred by the similar bridge.