Karl Frank - US grants

Equipment will be utilized which will allow the development of a large force, 4.5 million and l.5 million pounds dynamic, tension element research facility. The specific equipment includes a hydraulic power supply and high performance servovalve and a data acquisition and specimen surveillance system. The equipment will provide a state-of-the-art facility to investigate and evolve new generation cables and other tension elements used in structures. Further, this equipment will be used to improve the capabilities of the large capacity tension loading research facility. The eqipment will allow faster cyclic testing and enhanced data acquisition and specimen surveillance. The equipment will allow intelligent data acquisition through computer control throughout the test. The equipment will also monitor specimen performance, such as individual wire fracture in a multistrand cable, to provide additional understanding of the cable or specimen performance. The equipment will allow basic research in this area to be performed to further enhance our understanding of cable and cable anchorage behavior under fatigue loading.

9416287 Engelhardt The January 1994 Northridge Earthquake caused unprecedented damage at beam-to-column connections in steel moment resisting frames. The failures occurred largely at the standard welded flange - bolted web type of steel moment connection. These failures reflected nonductile behavior, and has raised serious questions on current methods and standards of design. The research undertaken in this project will experimentally evaluate the performance of reinforced moment connections. Two reinforcing schemes will be investigated. Both involve the addition of reinforcing plates at the connection. The reinforcing plates substantially increase the flexural capacity of the connection, and at the same time, reduce stress levels on the beam flange welds. The lower weld stresses will significantly reduce the sensitivity of the connection to welding quality. Such reinforced connection details have shown promising performance in limited past tests. However additional large scale verification of these details is needed, and will be provided by this research project. Most tests will be conducted using beam steels with high yield strength and high yield to tensile strength ratio, in order to provide a severe test of the reinforced connections. However, some tests will also be conducted using beam steels with a controlled low value of yield and yield to tensile strengths. These tests will demonstrate the role of steel strength characteristics in the observed connection failures, and investigate the possibility of improved connection performance through control of steel material properties. The results of this testing program will provide urgently needed data for structural engineers and building code officials involved with design of new steel moment frames, as well as the repair or retrofit of existing steel moment frames. This is a Northridge Earthquake project. ***

0000027
The objective of this research project is to develop a wireless sensor to detect cracks in welded steel connections. The 1994 Northridge earthquake caused extensive damage to the connections of structural steel, special moment-resisting frames. Critical welds fractured in more than 200 buildings throughout the epicentral area; however, the damage was difficult and expensive to detect because the steel members are covered with fireproofing. Removal of the architectural cladding and fireproofing for inspection is expensive, time consuming, and disrupted the normal activities of the building occupants.

The proposed sensor relies on RF technology. The sensor is a resonant circuit, similar in design to adhesive Electronic Article Surveillance stickers that are used to control inventory in retail stores around the country. The sensors will be attached to the structural steel frame during construction, and are passive. The frequency characteristics of the sensor will change when a crack in the weld material or base metal beneath the sensor reaches a given size. A wireless transmitter/receiver will be used to interrogate the sensor and obtain information about the presence of cracks without removing any of the architectural finishes or fireproofing. The proposed crack detection sensor is attractive because it is inexpensive, robust, easy to install, and maintenance free.

The research has been divided into eleven tasks need to transfer this technology into structural evaluation. Critical issues that must be addressed include selection of appropriate components for manufacturing of the sensor (polymer film, wire coil, and adhesive layer) determination of required surface treatment for the steel, evaluation of optimal sensor placement based on the configuration of the welded connection, determination of optimal coil geometry, and development of a wireless transmitter/receiver to generate a frequency sweep to interrogate multiple sensors.

This project is supported under the 3rd -Year Competition under NSF 98-36 "US - Japan Cooperative Research in Urban Earthquake Disaster Mitigation"

ABSTRACT

Acquisition of a High-Temperature Testing Facility for Materials and Structural Components

As a result of the tragic events of September 11, 2001, building design professionals in the US are
increasingly being asked to design buildings, bridges and other structures for hazards that were not considered just five years ago. One of these newly-recognized hazards is fire. The formal investigation of the collapse of the World Trade Center (FEMA 2002) identified a number of critical concerns within the engineering community because insufficient information was available to predict the response of structures during a fire. Engineers need to conduct more research to understand how structural components and systems behave at elevated temperatures. The equipment requested in this proposal will be an important resource for meeting the basic research needs.

The proposed facility includes four primary components: (1) three closed-loop test frames, (2) two high temperature furnaces, (3) a digital control system, and (4) a hydraulic power supply. The facility was designed to test a variety of specimens ranging from small-scale material coupons to full-scale structural connections, a variety of loading histories ranging from static to impulsive, and a variety of thermal profiles from isothermal to temperature gradients and simulated fire histories. Basic material tests can be performed in the small load frame to evaluate the behavior and suitability of existing and new materials for use in buildings exposed to fires. New materials such as FRP and thermo-mechanically processed steel can be evaluated. The two larger load frames and large furnace provide the ability to test structural assemblages and connections. The proposed facility is unique within the US and provides unparalleled capabilities for high-temperature testing. The facility is not restricted to conducting standard code-based
fire tests. The proposed facility will provide the basis for the development of rational design
specifications and introduction of new building materials to reduce the hazards in a fire.

The broader impacts of the proposed facility extend far beyond the acquisition of equipment. The
proposed facility will greatly enhance the educational capabilities within the Departments of Civil and Mechanical Engineering and will complement on-going efforts within the College of Engineering to develop a multidisciplinary research thrust in the area of fire-structure interaction. Research results will be integrated into graduate and undergraduate courses in Architectural, Civil, and Mechanical Engineering. Undergraduate students in the structural design courses will be introduced to large-scale testing and research opportunities through laboratory demonstrations that compare the behavior of structural components at room and elevated temperatures. Faculty members associated with the proposed facility currently serve on specification committees for steel, concrete, masonry, wood, and fire protection which provide an avenue for the dissemination of the research results to the engineering community and ultimately into the design specifications and model building codes used in throughout the US.