Authored by Armin B Mehrabi2*
Abstract
Aging and decay of transportation facilities, and the higher long-term cost of passive maintenance has led to the need for development of proactive management systems for bridge maintenance, repair and rehabilitation. This paper proposes a framework for Bridge Decision Support Framework (BDSF) as a form of proactive asset management system. A BDSF allows the asset manager to perform economic analyses on a bridge in order to establish priorities and make preliminary selection of preservation, repair or rehabilitation options. Among various bridge systems, segmental bridges using internal and external post-tensioning have faced great challenges due to issues related to the durability of the posttensioning tendons. Although some reserve capacity has been designed into these bridges, failure of tendons can have profound effect in the safety and structural integrity. These experiences have stressed the need for a proactive and predictive BDSF. A major component of such system is the ability to accurately plan inspection and condition assessment of the bridge, and to provide appropriate mitigation strategies preventing major damages to progress beyond manageable levels. Employing BDSF allows consideration of a variety of rehabilitation scenarios and strategies under different criteria when different decision makers are involved. The BDSF proposed in this paper considers a bridge as a system comprising of subsystems, each with distinct structural role and performance. Special emphasis is placed on post-tensioning tendons as critical subsystem. This paper attempts to identify subsystems for a post-tensioned bridge, their position in the structural integrity of system, respective properties and deterioration potentials.
Keywords: Bridges; Post-tensioned bridges; Post-tensioning tendons; Reliability; Risk-based maintenance; Condition assessment; Maintenance; Decision Making; Rehabilitation; Corrosion; Deterioration.
Introduction
As important links within the overall transportation infrastructure, all bridges experience deterioration during their service life, and bridges using post-tensioning tendons, hereafter referenced as PT bridges, are not an exception. In fact, PT bridges have experienced alarmingly fast deterioration causing major concerns among bridges owners. Figure 1 shows a dissected tendon with incomplete grouting and severe corrosion of steel strands, a finding that applies to many contemporary bridges. Addressing bridge deterioration requires regular inspections, maintenance and repair actions targeted at improving the condition of the bridge and bridge elements and reducing the risk of failure. Because damage in PT tendons is in most cases not readily evident (FDOT) and the high costs associated with maintenance operations, the proper decision support framework for maintenance activities is needed to avoid (a) unexpected structural failures, and (b) unnecessary spending on maintenance and repair activities. Aging and decay of transportation facilities, and the higher long-term cost of passive maintenance has led to the need for development of proactive management systems for bridge maintenance, repair and rehabilitation. A framework for Bridge Decision Support Framework (BDSF) is proposed here as a form of proactive asset management system.
Innovation in bridge maintenance and rehabilitation is the key to the health and wellness of bridges as a valuable national asset. A major component of maintenance and rehabilitation is the ability to accurately plan inspection and condition assessment of the bridge, and to provide appropriate mitigation strategies [1]. Employing a decision support framework is common in maintenance management since it can satisfy the needs of planning and assessment while at the same time has the ability to carry a variety of rehabilitation scenarios and strategies under different criteria when different decision makers are involved [2]. This paper attempts to investigate the application of a reliability-based maintenance decision making for PT bridges. A framework for decision support is devised for a general PT bridge in basic design phase and includes several modules under multiple tasks. This framework can be customized for each bridge with respect to bridge characteristics. This framework is applicable to all types of bridges, however, some of the modules in this framework are developed further using practical approaches for specific PT-type bridges. The proposed methodology attempts to take advantage of timedependent variation of bridge reliability based on deterioration models to represent an effective and practical framework. Through implementation of adaptive modules structural simulation can be updated and made more accurate. The framework takes advantage of life-cycle-cost analysis and risk assessment process for effective and meaningful decision making for maintenance.
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