All ETDs from UAB

Advisory Committee Chair

Nasim Uddin

Advisory Committee Members

Ashraf Al-Hamdan

Jason Kirby

Christopher Waldron

Ian Hosch

Document Type

Dissertation

Date of Award

2015

Degree Name by School

Doctor of Philosophy (PhD) School of Engineering

Abstract

The main objective of this dissertation is to simulate dynamic heavy vehicle bridge interaction using advanced numerical models of heavy vehicle and bridges for the Next Generation Bridge Weigh in Motion (B-WIM) system. The traditional B-WIM system uses a simplified approach where the bridge is considered as a beam and the heavy vehicle is considered as a stable mass moving with constant speed. On the contrary, the moving heavy vehicle consists of a series of complex parts such as tire assembly, springs and dampers, rigid bodies, and types of materials. Along with the complexities of the heavy vehicle, the bridge itself consists of several components such as slab, girders, reinforcements, diaphragms and the parameters associated with them such as road surface irregularities, effect of geometries and sizes, and types of material. Moreover, the contacts between heavy vehicle and bridges, friction coefficients, various types of constraints, heavy vehicle mass distribution, and the heavy vehicle's position over the bridge, also play crucial roles in determining the bridge response during dynamic heavy vehicle bridge interaction. All these parameters form a series of complex differential equations which cannot be addressed with the simplified approaches currently being used in the traditional B-WIM system. Another great challenge of the B-WIM is axle detectability. The traditional B-WIM system fails to detect the axles when subjected to multiple heavy vehicles passing on the bridge at the same time. In order to address these issues properly the sophisticated 3 dimensional finite element model (3D FEM) of the heavy vehicle with spring and damper systems has been developed and is used when studying the heavy vehicle bridge interaction, in order to predict accurate bridge responses for heavy vehicles. The 3D FEM of heavy vehicles thus incorporates complex parts such as spring and dampers, heavy masses of various components, pneumatic tires, etc. Along with the components of the heavy vehicle, the 3D FEM of US Girder bridges was developed which accounts for various components of the bridge such as variable sizes of girders, slab and camber slopes and various material properties. Using 3D FEMs of heavy vehicles and US girder bridges, numerical simulations are carried out on heavy vehicle bridge interactions for determining, validating, and comparing the responses of the bridges with the experimental results obtained from the B-WIM test. The simulated outputs, for weighing sensors located underneath the girders, and free of axle detector (FAD) sensors located underneath the slab, are obtained using the 3D FEM of dynamic heavy vehicle bridge interaction, and validated with the experimental strain results. Once the 3D FEMs were field calibrated, a detailed parametric analysis was carried out of the effectiveness of B-WIM system in identifying the responses of the bridge, including: effects of multiple heavy vehicles on the dynamic amplification factor (DAF) and the effect of skew bridges on the DAF. Along with the bridge responses, the parametric analysis of dynamic vehicle bridge interaction was also carried out for optimization of the FAD sensors in order to obtain vehicle parameters including the number of axles, the distance between the axles, vehicle velocity and the effects of the number of vehicles on axle detectability. Moreover, simplified 3 dimensional finite element models (3D SFEM) of vehicles and the bridges were developed using the spatial system and verified with the experimental test results in order to reduce computational time and be of use for the real time bridge response assessments. The effect of variable surface roughness profiles on the bridge DAF as well as the accuracy of axle detectability was analyzed by use of the 3D SFEM. Along with the surface roughness effects, the dynamic vehicle bridge interaction was also analyzed for obtaining DAFs in all possible loading scenarios including single vehicle and multiple vehicles over the bridges, variable vehicle positioning over the bridges and variable velocities and their effects on the DAF, etc. Results from all the above listed scenarios will be used for obtaining ideal DAFs for possible vehicle loadings, providing guidelines for sensor placement and determination of bridge capacity. Moreover, by replacing the simplified model currently being used in commercial B-WIM system, with High Fidelity FEMs developed through dissertation, the proposed next generation B-WIM system aims to achieve step change accuracy, both in identifying heavy vehicle type, and load. Finally, based on results for all possible scenarios, bridge capacity information can be obtained along with critical worst possible scenarios and together they can achieve a high level of accuracy in bridge safety assessments.

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