In the rapidly evolving urban landscape, parking buildings are vital components of a wide variety of facilities, and—as their functional importance grows—so does the complexity of designing and building them, especially in earthquake-prone regions.
Updates to seismic codes significantly affect how structures are designed, budgeted, and constructed. These regulations, implemented to improve public safety, reshape the structural systems selected in the design process and influence many other considerations from material costs to project schedules. For facility owners and other stakeholders, navigating this evolving landscape requires informed decision-making and early collaboration with designers and contractors who understand the seismic implications.
Seismic Code Updates and Their Impact
Seismic design requirements become more rigorous with the development of each new code. Earthquakes around the globe inform the design industry of the successes and failures of various design and construction methodologies, leading to refinements and new requirements within the code. While seismic design is required throughout the United States, it is no more prominent and critical than in the highly seismic Pacific region of the country such as California, Oregon, and Washington.
Designers must also consider the influence of site-specific factors: the soil type (which controls how much the ground will shake), adjacency to other buildings (which impacts lateral force system preference), the intended use of the structure (public access, hospital-related, or commercial parking), and regional construction practices and labor experience. Each of these factors can affect the seismic strategy and lead to a different structural solution.
Shear Wall vs. Moment Frame Systems
Design teams typically evaluate two main options when selecting a seismic force-resisting system: shear walls and moment frames.
Shear wall systems are prominently used throughout the country as the primary lateral system within parking buildings. Their relative stiffness compared to moment frames result in structures with reduced sway during an earthquake. This stiffness, while beneficial in some respects, results in higher lateral forces throughout the structure, increased stresses, and higher demands on foundations. In some regional markets, these implications may be of minor consequence. However, in regions of high seismicity, the implications of stress concentrations and foundation demand may result in higher initial construction cost and long-term maintenance when compared to moment frame solutions.
Moment frame lateral systems, by contrast, are inherently less stiff than a shear wall system. The lateral system is typically broadly distributed around the perimeter of the structure rather than the concentrated locations common with shear walls. This inherent flexibility and distribution of the lateral system results in a lower seismic demand on the structure, minimizes internal stresses, and results in a reduction on foundation dimensions—benefits most prevalent in high-seismic regions, leading them to be the prominent system of choice in the California market. Additionally, moment frame beams are commonly designed and detailed to serve also as the perimeter crash barrier of a parking building, further increasing the economy of the system.
The selection of the most appropriate lateral system for a parking building must evaluate the building’s use, seismic demand, market conditions, and regional construction practices.
The Value of Early Contractor Involvement
The sooner a contractor is brought into project conversations, the better positioned the project is for success. Early engagement between owners, stakeholders, designers, and contractors enables collaborative development that takes local codes and regulations, site conditions, owner priorities, and construction means and methods into account.
For example, contractors provide critical input on how the different seismic systems can impact construction timelines, labor requirements, and overall budget. Contractors can help weigh the upfront investment of a seismic restraint system against the features it might offer in foundation sizing, constructability means and methods, or construction phasing. Additionally, understanding which structural approach aligns best with local trade expertise can lead to better bids and fewer surprises during construction.
Early collaboration also prevents costly redesigns. By addressing seismic requirements and constructability issues at the outset, facility owners avoid rework and delays that stem from late-stage changes or code misalignment. It’s not just about choosing a structure that meets code—it’s about choosing one that meets code efficiently.
Balancing Functionality, Resilience, and Cost
Parking buildings must meet a wide range of owner expectations, from performance and safety to cost and aesthetics. Owners and other stakeholders are therefore tasked with making appropriate cost, construction speed (schedule certainty), and parking efficiency (structural optimization) decisions on their projects.
This is where collaborative planning and clear trade-off analysis become invaluable. For example:
- Seismic resilience vs. cost: Shear walls may provide stiffness but carry high costs under updated code. A moment frame might offer more distributed force resistance at a lower overall cost.
- Material efficiency vs. constructability: Some systems might reduce material quantities but require more complex sequencing or labor-intensive formwork.
- Aesthetic goals vs. structural strategy: Facade skin systems and natural ventilation requirements may influence where shear walls or frames can be located, requiring architectural and structural teams to work in sync.
Market familiarity is also critical. Even in regions where precast construction has long been the standard, shifting project demands—such as seismic resilience, future adaptability, and speed-to-market—are prompting owners to reassess assumptions and explore more adequate solutions. Contractors familiar with local preferences can advise owners toward solutions that comply with code and also align with available labor and supplier capabilities.
Building Smarter: A Collaborative Path Forward
As seismic codes continue to evolve, they challenge project teams to think more strategically and collaboratively. While the structural codes continue to adapt to increased safety performance requirements, it’s important to remember that the earlier teams work together, the better the outcome.
For owners, balancing various parking building requirements on their projects means more than meeting structural codes. It requires balancing structural systems’ requirements with constructability, aesthetic, budget, and schedule constraints. The best way to achieve this is by engaging knowledgeable contractors early, partnering closely with designers, and making informed decisions that account for site-specific demands and long-term use.
Fernando Sanchez is a integrated design director focused on parking buildings at McCarthy Building Cos. Inc., and Darren King is the principal in charge at structural engineering firm Culp & Tanner.