Declaring Independence
Building owners are turning to adaptive reuse of existing buildings to meet the market demand for alternative uses, such as life science, data, robotics, and other tech-related industries. These uses typically require upgrading the building’s mechanical, electrical, plumbing, and fire protection (MEP-FP) systems that use larger and heavier equipment than the building’s original structural design. As a result, this work can trigger costly structural upgrades for strength, serviceability, or both to comply with building code requirements.
When an alteration increases design gravity and lateral loads (wind or seismic) on structural elements beyond certain thresholds, the International Existing Building Code (IEBC) requires evaluating those elements. In general, if the demand-to-capacity ratio for gravity load resisting or lateral load resisting elements increases by more than 5% and 10%, respectively, the designer must show that those elements satisfy the gravity and wind load provisions of the International Building Code (IBC), and the reduced seismic provisions of the IEBC.
Many older and historic buildings do not have well-defined lateral load resisting systems (LLRS) or lack the gravity and/or lateral capacity to accommodate the additional loads, which makes reinforcing the existing structure per IEBC requirements challenging and sometimes cost-prohibitive. To address this issue, the authors have designed new independent equipment frames within the existing building footprint to carry most, if not all, of the new equipment. This strategy can meet the project goals without whole building strengthening or a detached horizontal addition. Avoiding the latter might save the project from additional zoning reviews and approvals processes by the Authorities Having Jurisdiction (AHJs). This article discusses the design considerations for these independent frames.
Publisher
STRUCTURE Magazine