May Technical Speaker 2

Stability Analysis of the USS Salem Wharf Under Gravity Loads

Dr. Mina Dawood, Ph.D., P.Eng. - Associate Professor, Department of Civil and Environmental Engineering at the University of Houston

The USS Salem Wharf Structure is located in Quincy, MA and was built in 1959 to expand a regional ship building yard. It has been since re-purposed and currently serves to moor the USS Salem, a decommissioned US Navy havey cruiser and floating museum. In its current use, the wharf is subjected to substantially smaller gravity loads than it was initially designed to support. Recent inspections of the over 700 ft. long structure revealed significant but highly localized corrosion in many of the supporting steel piles. In the most severe cases the corrosion approached nearly complete loss of the pile cross section. The lack of specific guidelines for calculating the capacity of such severely corroded piles made the reliable assessment of the remaining capacity of the structure challenging. Preliminary (overly conservative) calculations suggested that the structure could not support its own self-weight, although it was still standing. This was believed to be due to several factors that are not considered in the simplified preliminary calculations including: the relatively high post-buckling capacity of the steel piles and the high stiffness of the superstructure which permitted load redistribution from buckling piles to adjacent piles. To more fully understand the response of the wharf to gravity loads, a detailed finite element analysis was conducted. The finite element model was also used to conduct a parametric study of the wharf to investigate the influence of key parameters on the stability of the structure. This detailed analysis was made possible due to the availability detailed information regarding the geometry of the corroded piles which was obtained from an extensive underwater investigation. The analysis results suggest that in addition to its self-weight, the structure could support a uniformly distributed load of up to 185 psf, even if the superstructure was assumed to be heavily cracked. The findings highlight the importance and value of detaild structural inspections and advanced analysis techniques in characterizing the performance of existing structures.

Mina Dawood, Ph.D., P.Eng. is an Associate Professor in the Department of Civil and Environmental Engineering at the University of Houston (UH). He joined UH after completing his MS and Ph.D. degrees and a post-doctoral fellowship at North Carolina State University. Dr. Dawood's research focuses on evaluating the behavior of metallic and composite structures and structural systems. His research if focued on two primary areas:

(i) evaluating the remaining capacity or service life of existing deteriorated infrastructure, and 

(ii) developing new approaches to repairing deteriorated infrastructure using advanced materials, including fiber reinforced polymers (FRP), structural adhesives, and shape  memory alloys (SMA), with an emphasis on the repair and rehabilitation of steel structures.  

Dr. Dawood  has authored or co-authored 25 journal papers, 31 conference papers, and 3 book chapters.