KEYWORDS: Chemical elements, Finite element methods, Bridges, Mechanics, Fused deposition modeling, 3D modeling, Nondestructive evaluation, Damage detection, Vibrometry, Computing systems
This work addresses the development of a new four-noded rectangular Mindlin plate bending element (MP4C) with a
crack which consists of three degrees of freedom at each corner node. The crack in the element is assumed to be not
closed and non-propagating. The crack affects the elastic strain energy and the flexibility matrix of the element, whereas
the mass matrix remains unchanged. The complete element stiffness matrix is constructed as the inverse of the combined
flexibility matrix of both non-cracked and cracked elements. To evaluate the behavior of the proposed cracked Mindlin
plate element, numerical examples are provided. They are based on developing user subroutines in the commercial finite
element software ABAQUS. The finite element analysis results using the developed plate element are in excellent
agreement with those reported in previous work. The cracked plate element developed in this paper provides a simple
and robust approach to model the real service conditions in plate-like structures.
This paper presents the results of a study to determine the effect of temperature on modal variability on a curved post-tensioned box girder bridge with three continuous spans. The bridge has been monitored during the past 6 years using 16 accelerometers, 12 thermocouples and 6 tilt meters. Monitoring is based on normal vehicle loading. There is concern that changes due to temperature variations may mask changes due to structural damage. A thorough understanding of this uncertainty is necessary so that changes in vibration response resulting from damage can be discriminated from changes that are due to temperature variability. This paper presents the results of a study to evaluate the ambient vibration information over a full year period in which data was collected continuously. The effects of temperature change on the bridge's modal frequencies are analyzed and interpreted. This correlation between the natural frequencies and temperature is essential to establishing a structural health monitoring approach that can provide for indications that damage has occurred.
KEYWORDS: Bridges, Composites, Finite element methods, Nondestructive evaluation, Temperature metrology, Sensors, Temperature sensors, Sun, Data modeling, Climate change
The University Of Connecticut, with support and assistance from the Connecticut Department of Transportation, has been involved in the design and implementation of long-term monitoring systems on a network of bridges critical to the State of Connecticut's highway infrastructure. This paper presents a report on the development, implementation and evaluation of the monitoring of a steel box-girder bridge. The bridge is a multi-span, continuous, box girder bridge made up of two steel box-sections that are composite with the deck slab. The bridge is supported on a series of tall concrete columns, one per support. Field investigations have shown that the columns have been subject to cracks that are thought to be due to torsion. Two spans in a three-span continuous segment are currently being monitored using 8 accelerometers, 8 temperature sensors and 6 tilt meters. An extensive analysis has been conducted to evaluate the test data. There have been large temperature gradients due to both annual climate changes and due to the position of the sun with respect to the bridge. The data has also been used to develop a basis for long-term nondestructive evaluation. This is based primarily on the development of a vibration signature. The field data has also been compared with results from an extensive finite element analysis. The longterm goal of this project has been to characterize the bridge behavior and then to use this in the nondestructive evaluation of the performance over multi-year periods.
The Connecticut Department of Transportation (ConnDOT) has undertaken a major initiative to install permanent remotely- accessible monitoring systems on seven in-service highway bridges. These systems will consist of either a Roadway Weather Information System (RWIS), or Structural Monitoring System (SMS), or both, depending on the structure type and/or location. The RWIS provides weather related information regarding the pavement on and off the structure and ambient weather conditions at the bridge site. Systems like this are commercially available and in use throughout the country assisting transportation agencies in performing winter maintenance operations. The SMS is the product of cooperative research at the University of Connecticut and ConnDOT. The University has specified, installed and operated a prototype vibrational-based monitoring system on tow in-service bridges during separate year-long studies. The planned SMS, modeled after the prototype, includes accommodations for a variety of sensors including strain, tilt, structural temperature and vibration. The ultimate goal of this work is to develop a generic platform for a remote bridge monitoring system which can be adapted to any bridge with any combination of sensors and sensor types. Such a system would benefit both the safety and management of these structures. Current activity along with background information are discussed.
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