ASCE 7-22 Table 1.5-1 outlines four Risk Categories (I, II, III, IV). For portable units:
Whether you are designing a modular classroom, a temporary event stage, a portable solar array, a construction job site trailer, or a military shelter, the concept of compliance is no longer optional—it is a legal and safety necessity. asce 7 22 portable
However, beware: If your portable unit is stacked (two-story portable office), the 7-22 code prohibits the free-rocking exception. Stacked portables must be treated as fixed-base structures with explicit seismic connections. Inside a portable building, everything moves: server racks, lockers, medical equipment, and furniture. ASCE 7-22 Section 13.2.1 now requires that portable structures with casters or wheels have all internal components independently braced for ( F_p = 0.6 S_DS W_p ) (up from 0.4 in 7-16). This is a 50% increase in internal bracing loads. ASCE 7-22 Table 1
ASCE 7-22 introduces based on updated maps (incorporating the 2018 NSHMP model). For portable structures: 4.1 The "Free Rocking" Exception Portable structures mounted on elastomeric pads or wheels are considered "self-centering" if their height-to-width ratio is < 0.5. For these units, ASCE 7-22 allows a reduced seismic response coefficient (R = 4) instead of the standard R = 1.5 for non-ductile portable buildings. Stacked portables must be treated as fixed-base structures
The release of brought a seismic shift (literally and figuratively) to the engineering world. While most engineers immediately focused on the changes to wind speeds, seismic maps, and tsunami loads, a growing sector of the industry has been asking a critical question: How do these new provisions apply to portable buildings?
The wind speed maps have been recalibrated. A Risk Category II portable building in Houston, TX, now requires design for 150 mph (instead of 140 mph in ASCE 7-16). If you are using an old "portable wind calculator" app—throw it away. Part 3: Wind Loads on Portable Structures (Chapter 26 & 29) This is the heart of the matter. A portable structure behaves differently than a permanent building because it has gaps, tow bars, exposed chassis, and—critically—no rigid connection to the earth. 3.1 Main Wind Force Resisting System (MWFRS) vs. Components & Cladding (C&C) For a portable unit, the MWFRS is the steel skid or chassis. The C&C includes the lightweight walls and roof.