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New Building Code Provisions and their Implications for Design and Construction in California (Abstract)

by David Bonneville

Bonneville, David (2007). New Building Code Provisions and their Implications for Design and Construction in California (Abstract). SMIP07 Seminar on Utilization of Strong-Motion Data, p. 117 - 118.

Abstract

The recently published 2007 California Building Code (CBC) represents the most significant change in seismic design and construction in California in a decade. The 2007 CBC requirements are adopted from the 2006 International Building Code (IBC), which in turn adopts seismic provisions essentially by reference from ASCE 7-05 - Minimum Design Loads for Buildings and Other Structures. The ASCE 7-05 requirements are presented in an entirely new format, which is more logical and which places the more commonly used sections in earlier chapters and the more specialized or advanced topics (e.g., response history procedures, and requirements for isolated or damped systems) in later chapters.

· Ground Motion is defined by a design spectrum based on spectral values maps adopted from the 2003 NEHRP Provisions. The updated maps reflect recent USGS research, resulting in refinements in spectral values in many locations, compared to the 2000 NEHRP, and more importantly for California, significant changes in ground motion compared to the UBC zone maps with accompanying near fault adjustments. The design spectrum also introduces a new long-period branch, following the constant velocity branch, which will affect very long period structures.

· A Seismic Design Category (SDC) is assigned to each structure as a means of capturing both the seismic hazard, in terms of Mapped Acceleration Parameters (spectral values), Site Class (defining the soil profile), and the Occupancy Category, which is based on its importance or hazardous material contents. The SDC affects analysis, design and detailing requirements as well as the structural system that is allowed to be used and its height. The traditional UBC approach was to capture such requirements strictly based on zone.

· Requirements for Nonstructural Components and for Nonbuilding Structures are substantially modified and expanded. Nonstructural Components are assigned the same SDC as the building to which they are attached; however, a given building, and therefore its components, may contain more than one occupancy category, and thus more than one SDC. Components are also assigned their own Importance Factor, based on either importance or hazardous materials content. There are also special Certification requirements for equipment that must remain operable after an earthquake or that contains hazardous materials. Nonbuilding Structures are addressed in a separate chapter, covering those that are similar to buildings and those that are not. The former are addressed in a manner similar to buildings, with factors for response modification, overstrength and displacement amplification. The later contains expanded requirements for tanks and vessels.