Jeffrey Weidner

Structural Identification of a Deteriorated Reinforced Concrete Bridge

AbstractDisplacement coefficients and profiles have been proposed as objective indexes for bridge structural condition evaluation by many researchers. In this paper, experimental data of the following type were collected for structural identification (St-Id) of a deteriorated bridge: (1) static displacement and strain measurements taken under proof-load level and (2) multireference impact testing (MRIT) data from one of the spans of a three-span, cast-in-place reinforced concrete T-beam bridge (Smithers Bridge). The MRIT was used to generate the modal data for computation of the modal flexibility and displacement profiles. Several significant obstacles were encountered during the St-Id of the Smithers Bridge including high damping level (which led to difficulties in identifying and selecting the poles), finite-element (FE) model updating challenges, and correlation of the MRIT results with truck load test measurements. The first challenge was addressed through the use of the complex mode indicator functio...

Structural Identification of Bridges to Assess Safety and Performance

Structural identification (St-Id) offers wide ranging benefits to infrastructure owners by providing insight into the safety and performance of their bridges. St-Id generally refers to the construction of field calibrated models of a structural system by correlating simulated and measured responses. The Drexel Intelligent Infrastructure Institute (DI3) has applied St-Id to numerous bridges over the past decade. These applications have ranged from long span (arch, suspension, and truss) landmark bridges to undocumented short span reinforced concrete slab, t-beam, and arch bridges. Through these experiences, DI3 researchers have gained an appreciation of the benefits of St-Id related to decision-making, and the distinctions between applications to short and long span bridges. The application of any St-Id begins with the formulation of a specific objective that will drive the study along with the structure type, which may limit the experimental and analytical tools to be employed. St-Id, founded in the model of the scientific method, is applicable to a wide range of structures and can inform a range of objectives. Every bridge/owner combination presents a unique situation which will have its own characteristics, requirements and deliverables. There are several other factors that can affect the feasibility and reliability of any St-Id, and these include: (a) relevant responses used to assess safety and performance, (b) owner motivation and resources, (c) impact of structural and population scales, and (d) reliability of results and owner expectations. The objective of this paper is to highlight how a St-Id is defined by the constraints set forth through the owner, structural type (long or short span), and expected life of the structure, and how these constraints delineate what type of modeling, experimental methods and potential outcomes that are applicable. This comparison will be presented an illustrated through a discussion of two St-Id case studies: a concrete arch bridge and a long span truss bridge.