Project Objective

The specific objectives of the proposed research are: * Identify effective and economic sensing devices that can be utilized for instrumentation, * Elastomeric bearings, * To develop possible instrumentation schemes for implementing the concept of "smart bearings", and * To conduct feasibility study for producing instrumented bearings.

Project Abstract

The proposed research will critically review and analyze various cost-effective (existing as well as emerging) sensing techniques for use in smart bridge bearings. These sensing technologies will reviewed on the basis of cost-effectiveness, implementability, maintenance, technical expertise required for acquisition and analysis of data, and reliability of the technology in field conditions. The central focus of the proposed research will be to identify technologies that are cost-effective, low maintenance and robust for field conditions. The final outcome of the proposed research will be the demonstration of feasibility of the "smart bridge bearing" concept and its detailed implementation plan. The proposed research will result in specific recommendations for production and development of the smart bearings to meet the stated functional objectives.

Task Descriptions

The specific objectives of the proposed research are to identify available as well as emerging smart sensing technologies that can be integrated with bridge bearings for continuous real-time monitoring of, bearing reactions and displacements. The proposed research effort will involve the following three tasks:

Task 1: Identifying Effective and Economic Sensing Devices The bearing reactions are caused by the relative movement between the girders and the piers, and they essentially consist of vertical compression, horizontal shear and bending moment. These reactions can either be measured directly using load cell type of transducers, by the measurement of vertical, horizontal and rotational displacements, and a mathematical relation between these displacements and reactions, or by using piezo based sensors that can directly measure these reactions. The main goal of this task is to identify appropriate sensors that, have potential for applications. Sensors for use in infrastructure applications, such as highway bridge monitoring, have to satisfy very strict criteria that will ensure robustness and long-term performance. In addition, criteria such as ease of implementation, availability of commercial technology, level of expertise required for interpreting the results, low maintenance, etc., playa very important role in identifying an appropriate technology. To identify effective and economic sensing devices that have potential for applications to bridges, the proposed task will be accomplished through: (a) an extensive literature review, (b) information and specifications about the advanced sensors that are commercially available, (c) field surveys from several companies and experienced engineers to obtain feedback about the experience with the use of these advanced sensors, and (d) the development of objective criteria for evaluating the suitability of sensors for applications in actual bridges. The information gathered will be compiled and sensors that have the most promise will be selected for further evaluation at the end of this task. Practical feasibility of these sensors will be further evaluated in consultation with technical experts in bridge testing and monitoring. The final outcome of this task will be a detailed technical know-how about different sensing devices that can be used for measuring bearing reactions and movements.

Task 2: Developing Possible Instrumentation Schemes for implementing Smart Bearings The main goal of this task will be to investigate instrumentation schemes to obtain consistent and reliable information about bridge bearing reactions. For example, piezo based sensors could be used to determine the vertical bearing reactions. To integrate these sensors with the bridge bearings, they can be designed in the form of a plate that can either be integrated with the bearing itself or be placed between the girders and the bearings. Similarly the movements of the bearings (including rotations) could be monitored using conventional strain gage based and capacitive sensors, eddy current displacement sensors or resistive foil strain gages. These sensors can also easily be integrated with the bridge bearings itself at the time of manufacturing of bearings. An appropriate technology that will be- able to transmit measured data to a display on the bearing surface or to a remote data processing center will also be investigated. The design of an instrumentation scheme will depend on several factors, such as the possible range of movement expected in abridge bearing, the typical reaction forces generated at a bearing, and the environmental field conditions experienced by a typical bearing. Data about these factors will be collected in collaboration with the NYSDOT and a statistical analysis will be conducted to determine an optimal operational range of these factors. This information will be utilized to determine instrumentation scheme that will provide the necessary information about the reaction and movements of a bearing during the field implementation of sensors.

Task 3: Feasibility study for producing instrumented bearings The focus of this task is on practical aspects of implementing different instrumentation schemes developed in the previous task. This task deals with identifying the different costs associated with producing, installing, and collecting data from the smart bearings in abridge. Estimates of the necessary gage costs, expenses related to installing the gages, monitoring equipment costs, manpower needed to monitor the equipment and other related expenses will be prepared. An economic and feasible instrumentation plan will be prepared through extensive consultations with commercial companies specializing in the manufacturing of sensors and bridge bearings.

Task 4: Final Report At the end of this project, a conclusive and comprehensive report on the three tasks proposed above will be produced as per the publication guidelines of NYSDOT. In addition to the final report, quarterly reports on the progress of work on different tasks identified in this proposal will also be submitted to the NYSDOT for review.

Budget

$94,083

Student Involvement

This project will involve several graduate and doctoral students in data collection, presentations, literature documentations and report preparation.

Relationship with Other Research Activities

None

Technology Transfer Activities

None

Benefits of the Project

1. Comprehensive report that will summarize information from scientific journal articles, internet postings, manufacturers? brochures, and field surveys on the availability, capabilities, drawbacks, and costs associated with the different existing and emerging sensors with potential for integration with bridge bearings will be developed at the end of Task I of this project.

2. Blue prints and detailed technical drawings identifying the instrument selection, placement and data collection from a bearing will be submitted at the end of task II of this project.

3. Feasibility study of an instrumented "smart bearing" in the field condition in an actual bridge will be produced at the end of Task III of this project.

4. A comprehensive report summarizing the findings of this study and recommendations for implementation will be produced at the end of Task IV of this project.

Key Words

Bridge bearings, Bridge bearing pads