All ETDs from UAB

Advisory Committee Chair

Nasim Uddin

Advisory Committee Members

Ashraf Z Al-Hamdan

Ian E Hosch

Jason Kirby

Talat Salama

Document Type

Dissertation

Date of Award

2012

Degree Name by School

Doctor of Philosophy (PhD) School of Engineering

Abstract

Bridge weigh-in-motion system (B-WIM) testing is a popular technology in bridge applications. The B-WIM system can track extensive information about loading conditions to which bridges are subjected, and engineers can evaluate the responses of bridges and assess their performance relative to the safety index and serviceability. Currently, the USA, significant numbers of bridges are considered defective and are eligible for retrofits and replacement. Optimized safety evaluation of old and defective bridges is urgent in response to reduced government funding for infrastructure improvements. To conduct safety evaluations of existing bridges without interrupting traffic, the B-WIM system is the first choice for application. FAD (Free-of-Axle-Detector) or NOR (Nothing-On-Road) B-WIM system works well, but only if the system detects axle locations. In the USA, there are challenges for some beam-and-slab bridges. If the vehicle wheels are too close to the girders, the strain of the slab often has an unusually small variation so that axle detection sensors miss the required peak at the transverse position. In the first manuscript, we describe a study with alternative strategies for sensor types and sensor installation locations for beam-and-slab bridges using finite element (FE) analysis. The sensor layouts are identified and two new sensors are investigated. The new developed strategies of sensor layout will improve the performance of B-WIM system Most of the commercially available B-WIM systems are based on an algorithm developed by Moses (1979). The performance of this method is acceptable for estimating gross vehicle weight (GVW), but it can be unsatisfactory for estimating single axle loads. In order to improve the accuracy to an acceptable level, two algorithms are proposed. The second and third manuscripts present the measurement of axle weights and GVWs of moving heavy vehicles based on these algorithms. As determined in a case study of a bridge on US-78, both algorithms significantly improved the accuracy of measurements of axle weights in comparison with the commercial B-WIM system. Existing bridges may be functionally obsolete or have deficient structures based on older design codes or features. These bridges are not unsafe for normal vehicle traffic, but they can be vulnerable to specific traffic conditions, such as when five-axle semi-trailer trucks face an emergency situation or there is a disaster. To analyze the capacity of bridges, we propose, in manuscript 4, use of a simulation model based on B-WIM experimental data derived during extreme events. The results provide an improved understanding of the possible deficiencies of this bridge, and an appropriate retrofit is suggested. Finally, the dynamic amplification factor (DAF) is a significant parameter for design new of bridges and for evaluation of existing bridges. AASHTO guidelines provided very conservative values. So, improved methods for determination of DAF values need to be developed to evaluate the safety of existing bridges. This manuscript presents a simulation method to evaluate the DAF of existing bridges by use of the B-WIM data. The accurate results are obtained based on site-specific data.

Included in

Engineering Commons

Share

COinS