TxDOT Research Library - TxDOT Research Project

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Fatigue Resistance and Reliability of High Mast Illumination Poles (HMIPs) with Pre-Existing Cracks (CTR)

What Was the Need?

"Texas currently has about 5000 high mast illumination poles (HMIPs), varying in height from 100 to 175 ft. In recent years, a number of HMIP collapses have been reported in other states. These collapses have been attributed to fatigue failures at the HMIP shaft-to-base plate connection. No collapses of HMIPs have been reported in Texas, however, recent studies have shown that many galvanized HMIPs in Texas have pre-existing cracks at their shaft-to-base plate connection, most likely caused by the galvanization process before the poles were placed in service.

"TxDOT has identified three major issues/concerns with respect to HMIPs with pre-existing cracks. First, there is a lack of reliable experimental data about the fatigue life of pre-cracked HMIP base-connection details. Second, there is significant uncertainty regarding the natural wind response of HMIPs to the various major wind environments in Texas. Much of this uncertainty is related to the lack of measured data from comprehensive field studies. Third, due to this lack of data, the ‘safe/serviceable’ life of in-service TxDOT HMIPs with pre-existing cracks cannot be reliably predicted."

What's the Solution?

"The main objective of Project 0-6829 was to develop a probabilistic-based assessment of the remaining life of HMIPs of pre-existing cracks in Texas... While the predicted fatigue life of HMIPs with pre-existing cracks, based on a 5-percent probability of failure, varied from about 30 years to more than 300 years for various locations around the state, there were a number of locations where the fatigue life was on the order of 30 to 40 years... The research identified certain TxDOT districts with more severe wind conditions, and therefore shorter predicted fatigue lives for HMIPs with pre-existing cracks... As a result, the research team recommends that TxDOT develop a program of inspection to identify HMIPs with significant cracking at the base, and consider [repair or replacement] of the poles." --Project Summary Report

Project Number

0-6829

Status

Completed

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