07-30-2012, 06:02 AM
NRCC Guidelines for Seismic Evaluation of Existing Buildings
Author: D.E. Allen, principal investigator, | Size: 8.3 MB | Format: PDF | Quality: Original preprint | Publisher: NRCC (National Research Council of Canada) | Year: December 1993 | pages: 166 | ISBN: ISBN 0-660-15382-3
These Guidelines are a technical manual that offers guidance to engineers in the seismic evaluation of existing buildings. These Guidelines are addressed to well-qualified structural engineers, but who are not necessarily experts in earthquake engineering. The objective of the Guidelines is to identify typical structural deficiencies that have been observed in past earthquakes to lead to failure and falling of structural components and to partial or total collapse, with an attendant injury or loss of life. The methodology and criteria of the Guidelines are based on life safety, not property damage, and therefore satisfy the basic life-safety objective of the National Building Code. They do not, however, comply with specific requirements of the National Building Code, which are appropriate for the design of new buildings. The Guidelines present a set of questions that are designed to uncover weaknesses of the particular building being evaluated. The questions are in the form of Evaluation Statements that relate to various vulnerability areas in the structural system that require specific consideration. The Evaluation Statements are written so that a positive or 'true' response to a statement implies that the building is adequate in that area. If a building passes all applicable statements with 'true' responses, it can be passed without further evaluation, i.e., it is deemed not to be a life-safety hazard. For statements that are 'false,' additional evaluation is required. A 'false' statement does not necessarily imply that a complete structural evaluation is necessary, or that the building is automatically deficient; it simply flags an area of concern for the evaluating engineer and implies that a life-safety hazard may exist. If any such potential life-safety hazards are identified, an appropriate detailed analysis is recommended, with acceptance criteria suggested for each element of concern. Through this procedure, not iv only are weak links in the structural system identified, but the presence of the life-safety hazard is also assessed. These Guidelines provide a methodology that can be applied nation-wide to all existing buildings that are suspected of posing a potentially serious risk of loss of life and injury in case of a damaging earthquake. This procedure covers both structural and nonstructural elements and requires the review of construction documents, the general condition of the building, and calculations. The Guidelines include checklists, diagrams, and sketches that help to guide the user. These Guidelines are organized to be compatible with the NEHRP Handbook of Techniques for Seismically Rehabilitating Existing Buildings (FEMA, 1992-2). The NEHRP document identifies and describes seismic rehabilitation techniques for a broad spectrum of building types and building components, including both structural and non-structural elements. To aid the reader in the process of moving from evaluation to rehabilitation, the Guidelines and the NEHRP document on upgrading techniques are both organized to address building systems and components. Building components are organized into the following subsystems: vertical elements resisting horizontal loads (i.e., moment resisting frames, shear walls, and braced frames); horizontal elements resisting lateral loads (i.e., diaphragms); foundations; connections between subsystems; and non-structural building components. The NEHRP document has, however, not been adapted to be compatible with Canadian practice. The Guidelines provide the tools to identify seismically hazardous buildings. It is not a directive or a requirement, but rather a practical technical approach that can be used to identify seismic deficiencies in existing buildings.
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