Challenges in Analysis of 100 Year Old River Crossing Structures

The first transmission line in the United States was constructed in 1889. The U.S. has since designed and installed 240,000 miles of high voltage transmission lines. Most of this infrastructure was developed prior to the 1960s, and some of the tallest river crossing towers (greater than 400’ in height) were constructed in the early 1900s and are still in active service today. While analyzing structures of this magnitude with a design origin from the early 20^th century, the original design criteria and drawings needed for analysis may not be available. Connections may have used rivets, steel, and bolt strength may not be specified, and section sizes used may be obsolete. This paper will present ways to overcome these challenges, reference historical design resources, and provide analysis recommendations. Furthermore, there have been significant changes in the design and analysis of lattice structures over the last 120 years. To understand these advancements, this paper presents a study comparing the latest design standards with those from the 1900s and the 1960s.