Shear Buckling of Steel-Concrete Composite Plate Girders under Fire Exposure (SuCoFi)

• Applicant: Professor Dr. Markus Knobloch
• Subject Area: Structural Engineering, Building Informatics and Construction Operation
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 471334788

This research plan outlines the intended investigations to be performed by the Chair of Steel, Lightweight and Composite Structures at Ruhr-Universität Bochum, on the shear buckling behavior of steel-concrete composite plate girders subject to fire. The plan presents a background to web shear buckling, observations and methods at ambient temperature, previous and current research directed at elevated temperatures, and a comprehensive work package plan.Plate girders are structural elements frequently used in construction to withstand high loads and are often required to span long distances. They are typically used as transfer structures to provide column-free floor space for buildings, and as small to medium span bridges for vehicular and pedestrian traffic. Steel plate girders are fabricated by connecting narrow flanges and slender web plates with welded joints; and are used frequently in combination with a concrete slab that is connected to the girder with shear studs to form and act as a steel-concrete composite section. Due to the slender cross-sectional proportions, the webs of girders are highly susceptible to out-of-plane shear buckling. The structural performance of steel plate girder webs is well understood at ambient temperature, but only limited research has been conducted on the shear buckling behavior of composite plate girders at ambient and elevated temperatures. Such key structural components require special attention in predicting their performance when subjected to a fire hazard. Experiments on steel plate girders have shown a reduction in shear strength of up to 50% even for temperatures below 400°C, while numerical studies have indicated that additional thermal restraint forces may further deteriorate strength of girders and may change a flexural failure mode into a shear dominated mode.The SuCoFi project would provide the analytical, numerical and experimental contributions that are required to understand the fundamental behavior of steel-concrete composite plate girders loaded under fire conditions. The main steps and objectives are as follows:- Perform experiments on suitably sized composite plate girder specimens to provide an insight into their fundamental behavior in fire and to compare with observations made at ambient temperature.- Produce a robust FE-model that is validated with the data generated from the experiments, so that the failure mechanisms can be understand both qualitatively and quantitively.- Formulate an analytical model that can predict accurately the structural fire performance.The research is directly relevant to the structural and fire engineering scientific communities, where the high-quality test data and analytical models will have a crucial impact on structural fire research worldwide, and also to the construction industry, where the use of plate girders is commonplace and where the scientific knowledge on the fundamental behavior is needed to produce cost-effective and safe structures.

• DFG Programme: Research Grants