Optimization and Design of the Hybrid FRP-Concrete Truss Girder Bridge System
Creators: name: Hosseini, Seyed Mahdi
Publisher: name: Science
Year: 2023
Subjects: subject: Truss girder bridge
subject: Hybrid bridge
subject: Genetic algorithm
subject: Optimization
subject: Confinement
subject: Fibre reinforced polymer
subject: Concrete-filled FRP tube
subject: Finite element modeling
subject: Steel double-headed studs
subject: Shear friction
subject: Engineering--Civil

description: An innovative hybrid Fibre Reinforced Polymer (FRP) truss girder bridge system has been developed, designed, and extensively tested by El-Badry at the University of Calgary. The use of double-headed studs and confined truss elements have made the bridge system unique with outstanding structural performance. The objective of this research is to optimize the weight and cost of the truss girder and its components using experimental, numerical, and analytical methods.First, the flexural design of the truss girder bridge system was calculated using a genetic algorithm (GA). A software code was developed in MATLAB to calculate the optimum properties and dimensions of the bridge components. A linear elastic method was used to solve the indeterminate bridge structure and apply the constraints. The system was optimized for the weight or the cost of the materials, and the results were compared. It was suggested that weight optimization be used for short spans and cost optimization be used for bridges as their span length increases. Also, span capacity diagrams were developed and activity of the constraints which shows critical and active constraints at the optimum solution was investigated. The vertical and diagonal truss elements were found to be the critical components in the structure; thus, they require extra attention when designing to prevent failure. By using the proposed equation for the shear connection and the code developed to calculate the optimum flexural design, it is possible to design the truss girder bridge system for any given length and width.Afterward, the use of steel double-headed studs as slab-to-girder connectors was investigated through a series of experiments. Four full-size slab-on-beam specimens were built and tested under quasi-static loading to study the behaviour of the steel double-headed studs with various arrangements and spacings. An analytical equation was proposed to calculate the shear capacity of the slab-girder joint reinforced with steel double-headed studs. The optimum inclination angle of the studs was then calculated and validated using experimental results. It was shown that using the studs as shear-connectors between the slab and the girder in an inclined position would improve the interface shear strength in the slab-girder system.Finally, to improve the accuracy of the optimization process, the feasibility of replacing the linear analysis that was used in the optimization process with nonlinear finite element modeling (FEM) was investigated. A model of the concrete-filled FRP tube (CFFT) as components of the truss girder was developed in ABAQUS. The model was validated using experimental and analytical results available in the literature. A sensitivity analysis was done on the CFFT to study the effects of various parameters including the dilation angle and the stress ratio on the behaviour of the model. The finite element (FE) model of the confined column was then used in modeling a segment of the truss girder using ABAQUS and the model was validated using experimental results available in the literature. It was shown that it is possible to develop a numerical model of the truss girder for use in the optimization process or do a parametric study. The results of a future parametric study could be used to find the effect of various parameters on the behaviour of the truss girder and to find the optimum design of the structure. The results could then be compared with the optimization results taken from the code developed in this thesis.