The National Building Code of Canada (NBCC) and the American Society of Civil Engineers' ASCE 7 Standard are two widely adopted guidelines for seismic design. Both standards aim to ensure the safety and performance of structures during seismic events, but their approaches to nonstructural components and systems differ. This article discusses the distinctions between NBCC and ASCE 7 in terms of nonstructural components and systems, focusing on the fundamental principles that guide the design and construction of these elements.
Definition and Classification of Nonstructural Components and Systems
NBCC: The NBCC does not provide an explicit definition or classification of nonstructural components and systems. The standard primarily focuses on the primary force-resisting systems and does not provide detailed guidance on the design and construction of nonstructural elements.
ASCE 7: ASCE 7 defines nonstructural components as those parts of a structure that do not contribute to its primary force-resisting system. The standard provides a comprehensive classification of nonstructural components and systems, including architectural, mechanical, electrical, and plumbing elements, as well as storage and other equipment.
The following is the basic equation for determining the component seismic force (Fp) for nonstructural components: | The following is the basic equation for determining the component seismic force (Fp) for nonstructural components as per NBCC: |
Fp = apI_pW_p Where: Fp: Component seismic force ap: Component response acceleration (depends on the component's fundamental period, damping ratio, and attachment method) I_p: Component importance factor (ranges from 1.0 for standard components to 1.5 for essential components) W_p: Component weight (dead load) To calculate the component response acceleration (ap), you need to use the following equation: ap = SDS(Rp/I_p) Where: SDS: Design spectral response acceleration at short periods, adjusted for the site class Rp: Component response modification factor (depends on the component's ability to dissipate energy through inelastic deformation) | Fp = 0.5IeWp(Sds/Rp) Where: Fp: Component seismic force Ie: Component importance factor (ranges from 1.0 for standard components to 1.5 for essential components) Wp: Component weight (dead load) Sds: Design spectral response acceleration at short periods, adjusted for the site class Rp: Component response modification factor (depends on the component's ability to dissipate energy through inelastic deformation) |
Design Requirements for Nonstructural Components and Systems
NBCC: The NBCC includes limited provisions for nonstructural components and systems, mainly addressing the anchorage and bracing of specific elements, such as exterior walls and mechanical equipment. However, the standard does not provide detailed guidance on the design and construction of nonstructural components and systems.
ASCE 7: ASCE 7 provides more extensive design requirements for nonstructural components and systems, addressing aspects such as anchorage, bracing, and detailing. The standard takes into account factors such as component importance, seismic design category, and the structure's occupancy, ensuring that nonstructural components can withstand the demands of seismic events without compromising safety or performance.
Seismic Performance Categories for Nonstructural Components and Systems
NBCC: The NBCC does not explicitly define seismic performance categories for nonstructural components and systems. The standard primarily focuses on the overall stability and performance of the structure during seismic events.
ASCE 7: ASCE 7 establishes seismic performance categories for nonstructural components and systems based on factors such as the structure's importance, occupancy, and seismic design category. These categories determine the design requirements and performance expectations for nonstructural components, ensuring that they can effectively resist seismic forces and minimize damage during earthquakes.
Inspection and Maintenance of Nonstructural Components and Systems
NBCC: The NBCC does not provide specific guidance on the inspection and maintenance of nonstructural components and systems. The standard focuses on ensuring the overall stability and performance of the structure during seismic events.
ASCE 7: ASCE 7 provides more detailed guidance on the inspection and maintenance of nonstructural components and systems, emphasizing the importance of regular assessments to ensure that these elements remain in good condition and can effectively resist seismic forces. The standard also highlights the need for proper maintenance and repair of nonstructural components to minimize the risk of damage and ensure continued performance during seismic events.
Conclusion
Understanding the differences between NBCC and ASCE 7 in nonstructural components and systems is essential for engineers working on seismic design projects. The distinctions in definition and classification, design requirements, seismic performance categories, and inspection and maintenance can significantly impact the design and performance of nonstructural elements during seismic events. By recognizing these differences, engineers can select the most appropriate standard for their projects and ensure the safety and performance of structures in earthquake-prone regions.