PITA FY2014 Projects

Tensile Properties Of Modern Steel Cables At Elevated Temperatures

PI:Spencer Quiel, Civil and Environmental Engineering

University:Lehigh University

Co-PI(s):

Industry Affiliate(s):Wirerope Works

Summary:In the wake of recent events, fire resistance has become an increasing concern for the bridge construction industry. Cold-drawn steel used for bridge cables experiences a more rapid deterioration of strength and stiffness at high temperature than hot-rolled mild structural steel, making cold-drawn elements even more susceptible to fire-induced damage. Most of the fire-related experimental testing for cold-drawn steel wire in the last 50 years was performed in the 1960’s and addressed the performance of steel strands in post-tensioned and prestressed concrete structures. Reliance on this data for bridge cables has two potential pitfalls. First, the existing data has been developed for heating rates consistent with prestressed and post-tensioned concrete construction, which are typically slower than heating rates applicable to bridge cables. Second, the metallurgic formulation and maximum strength of common steel cable types has changed since these tests were performed, and the new properties may potentially alter the material deterioration at high temperature.

The PI is proposing an experimental study to perform tensile testing of several types of steel bridge cables both during and after exposure to high temperature. In keeping with the PITA mission, this project is a collaboration between the ATLSS Center at Lehigh University and Wirerope Works, Inc. of Williamsport, PA. The proposed study will include three components: (1) tensile testing at constant temperature and transient stress, (2) tensile testing at transient temperature and constant stress, and (3) metallographic analysis of the specimens to observe the effects of heating and the failure modes. The results of this study will provide updated material models of bridge cables under fire and encourage increased student participation and interest in structural-fire engineering.