Applied Crane Load Modeling Study for the Design of Container Terminal Crane Beam and Support Piles

Abstract: Container terminals are the center of the U.S. economy, having immense economic impact on all major global ports. Increasing shipping demands have led to larger cranes with large wheel loads being required. The application of crane loading in wharf design depends on the engineer’s judgment with code guidance. The Port of Long Beach Wharf Design Criteria (POLB WDC v.5), a commonly used reference in designing container terminals, states crane beams and supporting substructures shall be “analyzed using beam on elastic foundation,” or BOEF.
Crane beam and pile demands are typically obtained by applying the crane wheel loads as a moving distributed load, moving point load, or uniform load on a BOEF using computer software, such as SAP2000. Additionally, some design approaches exclude BOEF and instead evaluate structural demands considering axial restrained boundary conditions. Large variations in demands between either load application has not been anticipated if all design considerations remain constant. A study was performed to evaluate various crane wheel load applications for a new container terminal in the Port of Long Beach. Six cases of crane load application considering the two boundary conditions were modeled in SAP2000.
Five cases were analyzed considering BOEF with fully modeled piles with upper bound or lower bound pile tip tz-springs. A single case considered the same beam supported on piles with axial restrained ends. The total crane load, dead loads, and adjacent live loads were appropriately applied. A Load and Resistance Factor Design load combination was considered for analyzing the crane beam and an Allowable Stress Design load combination was used for the pile demands.
The base case considered one crane with a moving distributed load projected to the BOEF centerline. The second case considered a uniformly distributed load applied over the beam’s length. The third case replicated the base case with distributed load projected to the BOEF centerline; however, two back-to-back cranes were modeled with a spacing of 12 feet considered between cranes. The fourth case consisted of one crane with moving point loads representing each wheel applied at the BOEF surface. The fifth case considered the uniformly distributed load of the second case; however, the load was applied along the same length of the base case distributed load rather than the entire length. Finally, the sixth case replicated the base case except the pile tip had axial restrained boundary conditions rather than tz-springs.
The beam flexural, beam shear, and pile axial demands of each case were compared. Results were surprisingly varied amongst the six cases, apart from the base case and the third case which provided near similar results. Structural demand percent differences deviated from the base case demands anywhere between 10 percent to 180 percent. Careful consideration should be given to the analysis method when determining structural demands. If uniformly distributed load is applied on the entire beam with or without BOEF, the design would be unconservative. This paper will discuss the analysis cases, methodology, results, and recommendations for a proper crane beam on piles analysis for wharves.

How does this project / topic contribute to the advancement of the industry and profession?: The purpose of the paper is to serve as a resource for design engineers and owners. This study highlights the sensitivity of the analysis approach on crane beams and the structural performance of the wharf. The publication of this information will benefit the community to enhance port decision engineering when designing container wharves.

Does the project / topic implement new and innovative techniques, materials, technologies, and delivery methods?: The topic presents awareness of decision engineering for structural analysis.

What was the most challenging aspect of your project / topic and how did you handle it to ensure success?: Modeling is the most challenging aspect of this topic. Ensuring the consistency of the constant variables in the application amongst the six models is crucial to providing more accurate statistical results for the differing variables, which is the focal point of the paper. In addition, it was a challenge to properly capture the various design approaches considered, not only internally but those used in the global industry.

Who is the target audience for this paper?: Designers/structural engineers and port authorities