The contributions of the three review panelists for this publication are gratefully acknowledged. John A. Martin, Jr., structural engineer, is the president of John A. Martin and Associates in Los Angeles, California. He is responsible for the firm's structural design and production services to clients and is a Fellow of the American Concrete Institute.

Based on experience from the design of 20 concrete ductile core wall buildings using performance-based design concepts and a sample design for a high-rise concrete core wall building performed for the Los Angeles Tall Buildings Structural Design Council, several important issues to be considered before embarking on a detailed analysis have been identifi ed. Nonlinear response history analysis for large, complicated structures can consume many hours of engineering effort. It is always advisable to understand as much as possible about the anticipated building behaviour before beginning this analysis. Performance objectives should be clearly identifi ed for both frequent and maximum considered earthquakes. In particular, acceptable performance at serviceability levels should be understood, as current building codes do not provide much guidance. Factors such as anticipated demand on the lateral system, building height, soil type and seismic hazard should all be considered before running computer models, so appropriate cracking assumptions can be made. Even the design spectra themselves can be indicators of anticipated higher mode effects that may govern design.

With the 2014 update of the U.S. Geological Survey (USGS) National Seismic Hazard Model (NSHM) as a basis, the Building Seismic Safety Council (BSSC) has updated the earthquake ground motion maps in the National Earthquake Hazards Reduction Program (NEHRP) Recommended Seismic Provisions for New Buildings and Other Structures, with partial funding from the Federal Emergency Management Agency. Anticipated adoption of the updated maps into the American Society of Civil Engineers Minimum Design Loads for Building and Other Structures and the International Building and Residential Codes is underway. Relative to the ground motions in the prior edition of each of these documents, most of the updated values are within a ±20% change. The larger changes are, in most cases, due to the USGS NSHM updates, reasons for which are given in companion publications. In some cases, the larger changes are partly due to a BSSC update of the slope of the fragility curve that is used to calculate the risk-targeted ground motions, and/or the introduction by BSSC of a quantitative definition of “active faults” used to calculate deterministic ground motions.

SUMMARYA 64-story, performance-based design building with reinforced concrete core shear walls and unique dynamic response modification features (tuned liquid sloshing dampers and buckling-restrained braces) has been instrumented with a monitoring array of 72 channels of accelerometers. The responses of the building to ambient motions from ground or wind were recorded and analyzed to identify modes and associated frequencies and damping. Not unexpectedly, the low-amplitude dynamic characteristics are considerably different than those computed from design analyses. Nonetheless, these computed values serve as a baseline against which to compare future strong shaking responses. Such studies help to improve our understanding of the effectiveness of the response modification features at various levels of shaking, to evaluate the predictive capabilities of the design analysis tools and to improve similar designs in the future.

This manuscript, the first in a four-part series, describes the response history analysis approach developed for Chapter 16 of the ASCE/SEI 7 Standard and critical issues related to the specification of ground motions. Our approach provides new procedures for demonstrating adherence to collapse safety goals for new buildings (≤10% collapse probability at the MCER shaking level), creating nonlinear structural models, selecting and applying ground motions to the structural model, interpreting computed structural responses, and enforcing acceptance criteria to achieve the collapse safety goal. The ground motion provisions provide the option of using target spectra having more realistic spectral shapes than traditional uniform hazard spectra. Ground motions are developed using a two-stage procedure emphasizing spectral shape in their selection, followed by scaling or matching them to the target, with a modest penalty for matching. Horizontal component motions are applied to the structural model with random components to avoid bias associated with the maximum-component definition of the target spectrum.