Behavior Of Long-span Cable-stayed Bridge Research Articles

Temperature behavior of long-span cable-stayed bridges by using unified analysis

Varying temperatures significantly affect long-span cable-stayed bridges. However, previous studies on the temperature behavior of bridges were either limited by finite sensors, failing to capture the accurate relation between the temperature and responses, or constrained to a “divide-and-conquer” strategy, requiring considerable manual intervention. This study develops a unified approach to the investigation of thermal behaviors of cable-stayed bridges by integrating heat-transfer analysis and structural analysis based on the same refined global 3D finite element model. A navigation channel bridge of Hong Kong‒Zhuhai‒Macao Bridge is used as the testbed. First, the heat-transfer analysis is conducted based on thermal boundary conditions carefully determined from real-time ambient temperature, wind, and solar radiation, which are tailored for each surface to reflect the influence of the geometric configuration and temperature difference. Then, the detailed temperature distribution results are automatically converted to thermal loads, and thermal elements are changed to structural elements to calculate the temperature-induced responses. Results show that temperature has a significant effect on the structural responses of the bridge. The calculated temperatures and temperature-induced responses are in good agreement with their measured counterparts, verifying the effectiveness of the proposed unified approach to investigating the temperature behavior of cable-stayed bridges.

Experimental Study on Transverse Seismic Behavior of Long-Span Cable-Stayed Bridge with Two Inverted Y-Shaped Reinforced Concrete Towers

ABSTRACT The transverse seismic behavior of a long-span cable-stayed bridge with two inverted Y-shaped reinforced concrete towers is investigated in this study. To accomplish this, a 1/35-scale model of a cable-stayed bridge with a span of 1088 m was designed, constructed, and tested until failure on four shake tables; the test was conducted at Tongji University, China. A site-specific artificial wave was applied in the transverse direction. Moreover, the input peak ground acceleration was increased from 0.1 g to 1.3 g until the test model failed. The transverse displacement, force, rebar strain, and curvature responses of the bridge model are obtained and studied. The test results showed that the transverse displacement response of the tower was significantly affected by high-order modes. This resulted in the maximum seismic displacement of the tower at the middle – upper level of the middle column except for the tower top. The ratio of the transverse seismic forces acting on the towers significantly exceeded that of the forces acting on the piers. In the final test case, severe damage, including concrete crushing and rebar exposure, occurred at the bottom of the middle column – the most critical part of the tower – leading to the inclination of the tower. Damage to the cables or deck was not observed. The finite element model captured the elastic transverse seismic behavior of the test model.

Monitored structural behavior of a long span cable-stayed bridge under environmental effects

An accurate numerical analysis of the behavior of long-span cable-stayed bridges under environmental effects is a challenge because of complex, uncertain and varying environmental meteorology. This study aims to investigate in-situ experimental structural behavior of long-span steel cable-stayed bridges under environmental effects such as air temperature and wind using the monitoring data. Nissibi cable-stayed bridge with total length of 610m constructed in the city of Adıyaman, Turkey, in 2015 is chosen for this purpose. Structural behaviors of the main structural elements including deck, towers (pylons) and cables of the selected long span cable-stayed bridge under environmental effects such as air temperature and wind are investigated by using daily monitoring data. The daily variations of cable forces, cable accelerations, pylon accelerations and deck accelerations with air temperature and wind speed are compared using the hottest summer (July 31, 2015) and the coldest winter (January 1, 2016) days data.

Wind-induced vibration of long-span cable-stayed bridges during construction considering an initial static equilibrium state

This study deals with the dynamic behavior of long-span cable-stayed bridges under various wind effects. The novelty of this study is the consideration of an initial static equilibrium state subjected only to the self-weight of the bridge at various construction stages under complex buffeting winds. In particular, the dynamic response of a bridge prior to closure of the superstructure at the main and side spans are studied using a newly developed finite element program. The numerical results obtained for an existing three-span cable-stayed bridge model are compared to data from laboratory scaled-model testing. The parametric studies are focused on the various effects of wind speed on the dynamic behavior of cable-stayed bridges when the initial static equilibrium states at different construction stages are considered.

THE INFLUENCE OF BROKEN CABLES ON THE STRUCTURAL BEHAVIOR OF LONG-SPAN CABLE-STAYED BRIDGES

The influence of broken cables on the structural behavior of long-span cable-stayed bridges is examined considering all the nonlinear characteristics of a long-span cable-stayed bridge. The results show the influences of the broken cable on the structural behavior, such as the internal force, displacement, and the ultimate load-bearing capacity, are clear when an outside cable breaks. The results of the present study should assist in deciding when to replace cables in long-span cablestayed bridges.

Aerodynamic Behavior of Long-Span Cable-Stayed Bridges

In this paper, we study the behavior of the aerodynamic fan-shaped scheme of cable-stayed bridges under wind load. A numerical analysis is developed, based upon time integration of the motion equations of the discretized structure. The main structural nonlinearity arising from the stress–strain stay's constitutive equation is taken into account together with the nonlinear effects that arise assuming a nonstationary model for aerodynamic loads. A Newmark's type algorithm is used to discuss first the problem of free oscillations in still air, and to determine next the critical wind speeds, both in the case of A-shaped and of H-shaped towers. For the latter case, the overall discrete model is validated by comparison with analytical results obtained by a continuous model, already developed [5, 7]. The performance improvement of the structural behavior obtained by using A-shaped towers is numerically investigated by using the discrete model proposed here.

Ultimate Behavior of Long-Span Cable-Stayed Bridges

The study described here investigates the nonlinear static and ultimate behavior of a long-span cable-stayed bridge up to failure and evaluates the overall safety of the bridge. Both geometric and material nonlinearities are involved in the analysis. The geometric nonlinearities come from the cable sag effect, axial force-bending interaction effect, and large displacement effect. Material nonlinearities arise when one or more bridge elements exceed their individual elastic limits. The example bridge is a long-span cable-stayed bridge of a 605 m central span length with steel box girder and reinforced concrete towers under construction in China. Based on the limit point instability concept, the ultimate load-carrying capacity analysis is done starting from the deformed equilibrium configuration due to bridge dead loads. The effects of the steel girder hardening and the girder support conditions on the ultimate load-carrying capacity of the bridge have been studied. The results show that the geometric nonlinearity has a much smaller effect on the bridge behavior than material nonlinearity. The overall safety of a long-span cable-stayed bridge depends primarily on the material nonlinear behavior of individual bridge elements. The critical load analysis based on the bifurcation point instability concept greatly overestimated the safety factor of the bridge. The ultimate load-carrying capacity analysis and overall safety evaluation of a long-span cable-stayed bridge should be based on the limit point instability concept and must trace the load-deformation path of the bridge from applied loads to failure.