• Nondestructive Testing of Steel Bridge Members Using the Time of Flight Diffraction Method
• Seismic Response of an Existing Reinforced Concrete Building

Top: Colorscale D-scan of plate with implanted fatigue crack. Bottom: Same crack identified with MT.	Nondestructive Testing of Steel Bridge Members Using the Time of Flight Diffraction Method Graduate Research Assistant: Rebecca Wuellner Faculty Advisor: José A. Pincheira Description: Many steel bridges in the U.S. have low fatigue resistant details. Fatigue cracks that go undetected can lead to larger cracks and in some cases cause structural failure. Typically, inspectors will conduct a visual inspection to determine if a structure is experiencing detrimental cracking. To supplement visual inspection, non-destructive testing (NDT) methods can be used. In this study, the Time of Flight Diffraction (TOFD) method is used to locate and size flaws in steel elements. This method uses the time of arrival of ultrasonic signals to calculate flaw location and depth. The objectives of the current study are to apply the TOFD method to the inspection of complex geometries, to determine if surface conditions typical to what might be encountered in the field affect the accuracy of the method, and to develop a set of guidelines for the use of the TOFD method in field inspections. To date, cracks have been identified and sized to within 5% of the reported values. Surfaces with light corrosion or paint do not affect the accuracy of the method. Procedures are currently being developed to use the TOFD method on various complex geometries, including T-welds and welded cover plates. More Information
Visualization of the deformed shape of the building during the 1994 Northridge earthquake. [31 KB JPG]	Seismic Response of an Existing Reinforced Concrete Building Graduate Research Assistants: Bugra Barin, Devanshu Kant, and Olga Reyes Faculty Advisor: José A. Pincheira Description: Older reinforced concrete buildings (those built prior to the 1970s) have performed poorly in recent earthquakes (1994 Northridge earthquake in California and 1995 Hyogo-Ken Nabu earthquake in Japan). Past research has shown that these types of buildings often lack adequate strength and ductility to withstand the forces and displacements imposed by strong earthquakes. For example, the columns in older buildings are often susceptible to brittle failures which can cause the partial or total collapse of the structure. Engineers are then faced with the decision to either improve the seismic resistance of the building in anticipation of future events or tear down the existing structure and construct a new building. To make such a decision, a detailed evaluation of the deficiencies of the building using realistic and validated behavioral models must be conducted. More Information