Doctor of Philosophy (PhD)
Civil and Environmental Engineering
Temperature variation is an inevitable environmental loading type that affects bridges. Considering temperature effects during structural design is deemed essential for short, medium, and long span bridges. Temperature loading can be categorized into three components; uniform temperature, vertical temperature gradient, and transverse temperature gradient. Temperature variation causes additional movements, stresses, and internal forces that should be considered in the design of bridges. In this study, the temperature effects of vertical and transverse temperature gradients are investigated for continuous prestressed concrete bridges.
Thermal restraint moments induced by vertical temperature gradients on prestrssed concrete bridges are investigated by performing three-dimensional (3D) finite element (FE) analyses. Simplified formulas are proposed to estimate the thermally induced moment for design purposes. Parameters affecting the thermally induced moment are explored by conducting a parametric study including several bridge attributes.
Transient heat transfer analysis for a continuous prestressed concrete bridge case study; John James Audubon Bridge Segment #2, is carried out for two different days representing summer and winter seasons using TAITherm software to quantify the transverse temperature gradient. Results from the heat transfer analyses are validated using field temperature measurements. The local effect of the validated global temperature distribution on the bridge case-study components; girders and bearings, are explored. Thermally induced moments as well as shear stresses at supporting bearing pads are estimated based on 3D FE modelling for the bridge case study.
The current AASHTO Bridge Design Specifications is based on considering uncertainties inherent in the structural design process by proposing load and resistance factors. In this study, statistical uncertainties for vertical temperature gradient related to solar radiation Zone 2 are quantified using field data for John James Audubon Bridge. The probability distribution function for vertical temperature gradient is established. The best-fit probability distribution type for largest extreme value is investigated and extrapolated over 75-year return period. The statistical parameters for extrapolated largest extreme value are introduced. Furthermore, load factor for vertical temperature gradient is recalibrated for Service III limit state. First order reliability method, FORM, is used for recalibrating load factor for vertical temperature gradient based on available data for solar radiation Zone 2.
Elshoura, Ahmed Saad Elsayed Mohamed, "Temperature Gradient Effects on Behavior and Design of Prestressed Concrete Girder Bridges" (2021). LSU Doctoral Dissertations. 5504.