Bulk Material Shiploader Structure Inspection and Fatigue Analysis

Abstract: Dry bulk materials such as petroleum coke are common export commodities at ports on the Texas Gulf coast. At one port, petroleum coke is loaded onto moored vessels using a radial shiploader operating on a turntable. The primary structure of the shiploader is two structural steel plate girders, which are 11.5 feet deep and have an overall length of approximately 211 feet. A shuttle and boom assembly moves along rails on the girders to extend and retract the boom during vessel loading. During a rail replacement project in early 2022, corrosion-induced section loss was observed on the top flanges of both girders, raising questions regarding the possibility of increased stresses in the girders and reduced fatigue life. Due to a lack of record documentation on girder loading due to shuttle/boom movement and bulk material loading operations, a structural evaluation approach was developed involving instrumentation of the girders to measure the distribution of stress amplitudes and cycles during vessel loading events. The sensor data were compared to structural models and used to calculate the remaining fatigue life of the girders accounting for the corrosion section loss.
The project is a case study of using instrumentation and monitoring along with advanced analysis to provide the information needed to manage and extend the remaining service life of a key structural asset for this port facility. The findings enabled the port to confidently continue to use the structure and develop an inspection and maintenance plan to manage the future structural condition of the shiploader. The paper will summarize the investigation approach including instrumentation and data analysis, present the findings of the girder fatigue evaluation using the measured stress response, and summarize the recommendations to manage the risk associated with the current condition of the shiploader.

How does this project / topic contribute to the advancement of the industry and profession?: As port infrastructure ages, questions often arise as to the structural adequacy and remaining life of maritime assets, including shiploaders. In some cases, a visual investigation is not sufficient to determine whether an observed condition has compromised safety or reduced the remaining life, and more in-depth assessment is needed. This project demonstrates that in-depth assessment including instrumentation and monitoring and advanced analysis can provide the condition information needed by the port operations, engineering, and asset management teams to information to manage aging port infrastructure.

Does the project / topic implement new and innovative techniques, materials, technologies, and delivery methods?: The project implemented structural instrumentation and remote monitoring technology along with fatigue analysis procedures that are used in some bridge engineering and condition assessment situations. This project represents an adaptation of those approaches to a maritime shiploader structure.

What was the most challenging aspect of your project / topic and how did you handle it to ensure success?: The environment on the Gulf coast presents heat, humidity, and chloride exposures that are challenging for the operation of instrumentation and data acquisition equipment. The added shiploader operational conditions of exposure to petroleum coke dust and washing down of the shiploader also had to be addressed in the design and installation of the instrumentation and monitoring systems to ensure reliable data collection over a period of several months. These conditions were addressed through the use of weather-resistant enclosures, redundant instrumentation, and remote monitoring to detect and respond to issues that arose during the project.

Who is the target audience for this paper?: Port engineering, operations, and asset management personnel, and consulting structural engineers and inspectors.