MCEER HIGHWAY PROJECT
FHWA CONTRACT DTFH61-98-C-00094

Seismic Vulnerability of the Highway System

Task D2-2: Develop and Evaluate Prototype Intelligent Passive Systems

Subject Area: Earthquake Protective Systems 
Research Year 2 

Principal Investigator(s) and Institution(s)

George C. Lee, University at Buffalo

Objective

Earthquake protection systems are becoming a valuable tool for engineers designing bridges to be more seismically resistant. However, present practice is utilizing technologies that do not adapt their performance to the magnitude of an earthquake. As a result, these technologies may be detrimental to the performance of a bridge during earthquakes less than the design earth-quake. Furthermore, there may already exist intelligent materials and technologies that if appropriately designed for highway bridges could significantly improve the performance of these types of technologies.

This task will focus on a continued effort on the design and construction of prototypes of intelligent earthquake protection system(s). Furthermore, the prototype(s) will be subjected to appropriate experimental evaluation testing to verify its performance and determine its applicability to the highway system.

Approach

Using the information presently being obtained from Task D2-1, reviewing the state of art for intelligent bearings, this task will develop and evaluate at least one intelligent passive earthquake protective system. A preliminary design for a passive seismic isolation bearing has already been developed. The bearing utilizes multiple steel rollers which in the event of an earthquake are permitted to roll on a sloped surface. Preliminary proof of concept testing was conducted on the bearing and encouraging results were obtained.

One concern that this task has been established to address is the fact that passive systems are usually customized for optimum performance at the design earthquake only. Consequently, performance at more frequent (or smaller) events or under multi-directional ground motions would be less than optimal and may even be adverse. The purpose of developing this new passive system is to improve the performance of the present-day sliding isolation bearings. The roller bearing will be further modified and evaluated by theoretical analysis and numerical simulation (see below).

Evaluation testing will be conducted to verify and document its performance. Some of the evaluation testing will be based on the Guidelines for the Testing of Seismic Isolation and Energy Dissipating Devices that was developed by the Highway Innovative Technology Evaluation Center (HITEC) with funding from FHWA and Caltrans. 

This document describes, in detail, a testing procedure necessary to prove that isolation bearings perform as designed and to document the relevant performance characteristics of a bearing. The HITEC guidelines document focuses on standard bearings without "intelligence" and has been designed for market-ready technologies. Since this task will focus on evaluating an experimental "intelligent" bearing, a HITEC type evaluation is not appropriate at this time. However, the intent and purpose of the HITEC testing procedures will be the basis for much of the prototype evaluation. Consequently, at a minimum, the following will be considered during evaluation testing:

  • Variations in performance based on varying compressive loads
  • Variations in performance based on varying frequencies
  • Durability of the prototype based on fatigue and wear and environmental aging
  • Performance at the various temperature extremes that bridges may be exposed to
  • Durability of the prototype when subjected to a moderate number of strong motion cycles
  • Margin of safety (i.e. what occurs when the device is subjected to displacements beyond its design capacity)

Additionally, if time and funding permit, the P.I. would like to explore using different protective coatings for A-36 carbon steel rollers in order to increase the life of this isolation bearing.

Products

Following completion of this task, a report will be furnished that will document the design of any prototypes, the results of the evaluation testing, and further recommendations for improvements to the prototype(s). The report will also recommend methods to integrate the technology in the highway system, if appropriate. Furthermore, consistent with the progress of subtask D2-1 and D2-3, adding "intelligence" to this new bearing will be recommended by using selected semi-active control technologies.

In addition, a manuscript on theoretical consideration of bridge based isolation design will be prepared for possible journal publication.

Technical Challenges

The primary challenge of this task is to develop a earthquake protection system that has characteristics that will make it desirable to the state DOTs and other highway agencies so it will be incorporated into the U.S. bridge system. The ideal technology will be simple, easy to install, inexpensive, durable and offer much better performance as compared to current bridge isolation bearings.

8/14/01

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