Doctor of Philosophy
Civil and Environmental Engineering
El Naggar, M. Hesham
This thesis investigates the structural behavior and soil-structure interaction mechanism of large-span soil-steel structures utilizing steel plates with the deepest corrugation profile, 500 mm X 237 mm. The world’s largest-span soil-steel bridge, with a span of 32.40 m, was constructed using 12 mm thick steel plates with the deepest corrugation profile and was instrumented extensively to monitor the displacements and straining actions of the steel structure. Lateral reinforcement steel mesh was attached to the steel structure and the ends of the structure were strengthened by circumferential reinforced concrete collars. Three-dimensional (3D) nonlinear finite element (FE) model was conducted and validated by the field measurements at different construction stages. The calculated deformations and straining actions captured the same trend of the field measurements. The numerical results indicated that two main critical zones of the steel structure, the crown and at the change of arc radii, were observed to experience high axial stresses, which should be considered carefully in the structural design. The numerical results also revealed that the deployed steel mesh reinforcement and concrete collars reduced the induced straining actions in cut ends and beveled ends of buried structures with up to 50%. Moreover, the effects of modeling technique on the predicted performance and straining actions were evaluated. The results demonstrated that incongruous numerical simulation could lead to difference in the results up to 60% with the anticipated results causing significant changes in the design of soil-steel structures. Furthermore, 3D FE model was conducted and validated by experimental data obtained from a fully monitored full-scale soil-steel structure with 10.0 m span and subjected to truck loading under service and ultimate loading conditions. The critical straining actions obtained from the steel structure at ultimate condition were used to evaluate the ultimate limit states provided by different design codes and standards. The results revealed that the ultimate capacity of the SSS was reached without conforming to all ultimate bounds provided by the current design codes. Finally, a limit state function was proposed to account for the structure instability that may occur to the steel structure under ultimate loading condition.
Summary for Lay Audience
Soil-steel structures are widely used nowadays as a solution for roadways, waterways and railways overpassing because of their relative low cost and ease of construction compared to conventional concrete and steel bridges. The buried steel structures are formed of corrugated steel plates with a wide range of sizes and shapes depending on the application. Recently, the world’s deepest corrugated profile, with a total depth of 237 mm, has been developed to achieve large spans up to 32 m. Current design guidelines for these large-span special-featured structures require comprehensive computational techniques to specifically simulate different structural elements and the soil-structure interaction. The current study stipulates guidelines and recommendations for simulating large-span soil-steel structures having special features that are used to strengthen the buried steel structure. The ultimate capacity of soil-steel structures is also investigated under the effect of maximum backfill height and topmost live loading. The performance of the steel structure is compared to the limit states prescribed in current design codes and standards. The results revealed that the current ultimate limit state requires additional parameters to account for the structure instability that may occur to the steel structure under ultimate loading condition. The current research proposes an ultimate limit state function that successfully predicted failure in the steel structure under all cases considered in the current analysis before failure occurred in the steel structure.
Embaby, Kareem, "Performance and Ultimate Limit State of Large-Span Soil-Steel Structures" (2022). Electronic Thesis and Dissertation Repository. 8583.
Available for download on Thursday, August 31, 2023