Full-range behaviour of prestressed concrete bridges with corrugated steel webs

Abstract

Bridge engineers and researchers have been looking for efficient structural forms under the performance-based concept to satisfy various attributes, including serviceability, safety, economy, constructability, durability, etc. Prestressed concrete bridges with corrugated steel webs have emerged as one of the promising bridge forms due to their remarkable advantages such as efficient prestressing of concrete, high buckling strength of steel webs and lightness. In 1986, the first bridge of this type, Cognac Bridge, was built in France. Its successful application and significant advantages over conventional prestressed concrete bridges have prompted researchers and construction companies in various countries to get involved in this new form of composite structure. However, the full-range behaviour of the bridges covering both the service and failure stages is rather complicated, and has not been systematically studied.

In view of the different behaviour of components and the large shear deformation of corrugated steel webs with negligible axial stiffness, the assumption that plane sections remain plane is no longer valid and therefore the classical Euler-Bernoulli and Timoshenko beam models may not be applicable. To study the structural behaviour of prestressed concrete bridges with corrugated steel webs, numerical and experimental investigations were carried out. A sandwich beam theory was developed to investigate both the static and dynamic behaviour numerically. In addition, a modified Timoshenko beam model was developed for linearly elastic analysis of static service behaviour, which provides a convenient alternative for design purpose. In the development of numerical models, special emphasis was placed on the modelling of corrugated steel webs, external prestressing tendons, diaphragms, and interaction between web shear deformation and local flange bending. The numerical models were verified by tests.

Using the numerical models proposed, the static service behaviour, dynamic properties and long-term behaviour were studied. Some parametric studies were carried out to further explore their structural behaviour.

The sectional ductility, deformability and strength were evaluated by nonlinear analysis taking into account the actual stress-strain curves and path-dependence of materials. The numerical results obtained were compared with experimental results for verification. A parametric study was then undertaken to clarify the effects of various parameters.

In the design of this type of bridges, both the ultimate load and ductility should be examined, which requires the estimation of full-range structural behaviour. The sandwich beam model was extended for analysis of the full-range behaviour considering geometric and material nonlinearities. With a nonlinear kinematical theory, complete description of the nonlinear interaction between the external tendons and the bridge was obtained. The numerical model proposed was also verified by experiments.

The failure mechanisms were studied experimentally and numerically for more accurate evaluation of safety-related attributes such as ultimate load, ductility and deformability. The formation of plastic hinge and its size were also studied thoroughly in view of their importance in the prediction of full-range behaviour. A simplified method to predict the full-range behaviour was also proposed based on the concept of equivalent plastic hinge length.

Based on the study, some design recommendations were provided.