Seismic and Construction Challenges for Modern Fireboat Station 15 Compound at Port of Long Beach

Abstract: Over the past two decades, the shipping industry has been evolving whereas consolidation of the shipping lines has occurred and vessel sizes have increased dramatically. The Port of Long Beach (POLB) strives to achieve the goal of maintaining financial strength and security of assets. POLB has invested in new and upgraded terminal facilities to accommodate these larger vessels and higher container volumes. To ensure business continuity and provide adequate emergency response capabilities for the Port’s infrastructure, POLB has committed to upgrade the Port’s fire safety facilities. Fireboat Station No. 15 was designed as a LEED Gold (Leadership in Energy and Environmental Design) facility and is the most modern fire security compound consisting of a landside station building, a waterside boat bay building supported on a wharf to accommodate a larger fire boat, an access bridge and other miscellaneous structures.

The compound is an essential structure and required to be operational after a significant earthquake. Since the waterfront site is prone to liquefaction and large lateral slope movement, multiple seismic design and construction challenges had to be addressed efficiently by various methods, such as implementing ground improvement, using moment frames for the boat bay, adopting performance-based design, and seismically isolating different structures. Each structure encountered different challenges: 1) The footprint of the landside station building sits on existing buried rock dikes, which poses a challenge for pile installation. Therefore, jet grout columns were selected to improve the ground and support the building. 2) Since the boat bay building requires large horizontal span and high vertical clearance to house the state-of-the-art fireboat with leading-edge technology, ordinary steel moment frames were utilized in the transverse direction. 3) The seismic design of the boat bay wharf was enhanced by implementing performance based design per the POLB Wharf Design Criteria (WDC). The combination of inertial and kinematic loading was included to capture the response of piles due to the slope movement outside the ground improvement zone. 4) The single span access bridge consists of precast prestressed box beams supported on the wharf at the water side and the abutment at the landside. Both ends are seismically isolated from the wharf and abutment wall by inserting a sliding plate and elastomeric pads in between. The access bridge was designed per AASHTO LRFD Bridge Design Specifications.

This paper highlights the unique and challenging site and subsurface conditions, multiple seismic design challenges, effective approach to address safety, cost, code requirements and design procedures, and comparison between force-based and performance-based design criteria. Lessons learned include overcoming construction challenges from jet grouting improvement, pile driving, large span framing, and the intricacies of integrating all construction trades including land/marine work. Innovative engineering solutions and strategies to address the seismic design and construction challenges made this project successful so that POLB can provide the most robust waterborne safety and maximum landside firefighting coverage to protect the major commercial gateway for the nation.

How does this project / topic contribute to the advancement of the industry and profession?: This project demonstrated to the industry and professionals how various design philosophies and codes were applied to different components of the most modern fireboat station compound at the Port of Long Beach. It will protect and secure Port property and resources through 24/7 situational awareness and response and through the efficient application of technology, personnel, and intelligence. Jet grout, geogrids, performance based design, and combining both inertia and kinematic loadings, etc. were all weaved into this project.

Does the project / topic implement new and innovative techniques, materials, technologies, and delivery methods?: A 3D model was created to simulate the boat bay which combined a marine wharf and a building. While the building was designed per the force-based ASCE 7, the wharf was designed with performance-based design per Long Beach Wharf Design Criteria (WDC). Pushover analysis was used to check the ratio of displacement demand over capacity. Since the slope failure plane is located at a shallow depth, the wharf design combined both inertial and kinematic loadings in order to capture the response of piles. This combination was an enhanced analysis to WDC and it complied with the spirit of performance-based design.

What was the most challenging aspect of your project / topic and how did you handle it to ensure success?: The water-front site is prone to liquefaction and large lateral deformation. In addition, the site subsurface consists of buried rock dikes which posted multiple seismic design and construction challenges. Jet grout columns and geogrids were used to mitigate liquefaction and to provide stable building foundation. Lateral kinematic loading due to slope movement outside the ground improvement zone was combined with inertial loading to capture the wharf pile response. Construction challenges during jet grouting, pile driving, and large span framings were overcome effectively by the experienced design and construction management team.

Who is the target audience for this paper?: The structural engineers, geotechnical engineers, marine engineers, project managers, construction managers, terminal operators, shipping lines, and fire fighters would be interested in this topic.