Incremental dynamic analysis (IDA) is a parametric analysis method that has recently emerged in several different forms to estimate more thoroughly structural performance under seismic loads. It involves subjecting a structural model to one (or more) ground motion record(s), each scaled to multiple levels of intensity, thus producing one (or more) curve(s) of response parameterized versus intensity level. To establish a common frame of reference, the fundamental concepts are analysed, a unified terminology is proposed, suitable algorithms are presented, and properties of the IDA curve are looked into for both single-degree-of-freedom and multi-degree-of-freedom structures. In addition, summarization techniques for multi-record IDA studies and the association of the IDA study with the conventional static pushover analysis and the yield reduction R-factor are discussed. Finally, in the framework of performance-based earthquake engineering, the assessment of demand and capacity is viewed through the lens of an IDA study. Copyright © 2001 John Wiley & Sons, Ltd.

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Incremental dynamic analysis

(1991). Applied Linear Regression Models. Journal of Quality Technology: Vol. 23, No. 1, pp. 76-77.

Applied Linear Regression Models

Minimum Design Loads for Buildings and Other Structures provides requirements for general structural design and includes means for determining dead, live, soil, flood, wind, snow, rain, atmospheric ice, and earthquake loads, as well as their combinations, which are suitable for inclusion in building codes and other documents. This Standard, a revision of ASCE/SEI 7-05, offers a complete update and reorganization of the wind load provisions, expanding them from one chapter into six. The Standard contains new ultimate event wind maps with corresponding reductions in load factors, so that the loads are not affected, and updates the seismic loads with new risk-targeted seismic maps. The snow, live, and atmospheric icing provisions are updated as well. In addition, the Standard includes a detailed Commentary with explanatory and supplementary information designed to assist building code committees and regulatory authorities. Standard ASCE/SEI 7 is an integral part of building codes in the United States. Many of the load provisions are substantially adopted by reference in the International Building Code and the NFPA 5000 Building Construction and Safety Code. Structural engineers, architects, and those engaged in preparing and administering local building codes will find this Standard an essential reference in their practice. Note: New orders are fulfilled from the second printing, which incorporates the errata to the first printing.

Minimum Design Loads for Buildings and Other Structures

Estimation of fragility functions using dynamic structural analysis is an important step in a number of seismic assessment procedures. This paper discusses the applicability of statistical inferenc...

Efficient analytical fragility function fitting using dynamic structural analysis

Introduced in this paper are several alternative ground-motion intensity measures (IMs) that are intended for use in assessing the seismic performance of a structure at a site susceptible to near-source and/or ordinary ground motions. A comparison of such IMs is facilitated by defining the “efficiency” and “sufficiency” of an IM, both of which are criteria necessary for ensuring the accuracy of the structural performance assessment. The efficiency and sufficiency of each alternative IM, which are quantified via (i) nonlinear dynamic analyses of the structure under a suite of earthquake records and (ii) linear regression analysis, are demonstrated for the drift response of three different moderate- to long-period buildings subjected to suites of ordinary and of near-source earthquake records. One of the alternative IMs in particular is found to be relatively efficient and sufficient for the range of buildings considered and for both the near-source and ordinary ground motions.

Structure-specific scalar intensity measures for near source and ordinary earthquake ground motions

Summarized in this paper are the major findings from analytical studies of nine steel moment frame buildings conducted under Phase 1 of the SAC Steel Project. The buildings range in height from two to seventeen stories and most of them experienced damage to welded beam-column connections during the Northridge earthquake of 1994. Elastic response spectrum, inelastic static pushover, and elastic and inelastic time-history analyses were conducted using ground motion data representative of the Northridge earthquake to establish the loading/deformation demands that the buildings experienced. The primary performance indices obtained from the analyses were demand-to-capacity ratios, interstory drift ratios, and inelastic hinge rotations. Maximum ratios of elastic member force demands to plastic strengths ranged between 1.0 and 2.0; maximum inelastic hinge rotations were 0.005–0.010 rad; and maximum interstory drift ratios were from 1 to 2%. These damage indices increased by 50%–150% under more severe ground motions recorded during the Northridge earthquake at the Sylmar site. Accuracy of the analyses is shown to be sensitive to a number of modeling parameters including finite joint size, joint panel behavior, composite beam action, strain hardening, second-order (P-Δ) effects, and three-dimensional response. Overall, there was only modest correlation between the frame performance indices and the observed connection damage, due largely to the fact that significant aspects of the connection fracture behavior are not captured in the frame analyses.

Summary of SAC Case Study Building Analyses

Incorporating a rocking mechanism into steel frames, concrete shear walls, or masonry piers has been shown to reduce the amount of seismic base shear that a lateral resisting system is required to resist Rocking structural systems have therefore been developed primarily for high seismic regions The benefits provided by allowing rocking are, however, also advantageous in moderate seismic zones This paper summarizes previous research on the seismic behavior of steel-framed rocking systems and examines the application of the rocking mechanism to steel frames in moderate seismic zones by analyzing an example braced frame with and without allowing column uplift

Steel-Framed Rocking Structural Systems for Moderate Seismic Zones

Generalized modified modal superposition procedure for seismic design of rocking and pivoting steel spine systems

Building code seismic design provisions for steel and composite moment frames and their implications on seismic performance are examined through comparative trial designs of three six-story buildings. Using nonlinear analyses, static and dynamic contributions to inelastic force reduction are identified and compared to code-specified assumptions. The trial design study demonstrates that static overstrength is significantly larger for space frame systems compared to perimeter frames, whereas the force reduction attributable to inelastic dynamic response is fairly constant between the frame types. The trial designs are shown to meet the minimum performance implied by building code provisions, primarily due to the large static overstrength resulting from minimum stiffness requirements imposed through seismic drift limits. The study suggests that more consistent reliability can be achieved by disaggregating the R-factor into its component static and dynamic parts and that the default values of static and dynamic inelastic response factors should be reduced from those implied by current R-factors. INTRODUCTION Over the past fifteen years composite moment frames, consisting of reinforced concrete columns and steel beams (so called RCS systems) have been used in the US and Japan. The recently published Intemational Building Code, IBC (1), and AISC Seismic Provisions (2__) include seismic design requirements for RCS systems. Essentially, these standards treat composite systems as extensions of traditional steel or reinforced concrete systems. For instance, seismic response modification and displacement amplification factors (i.e., R and Cd factors) are based largely on consensus opinions from comparable factors for conventional steel and reinforced concrete systems (3_). Judgments of this sort are necessitated by the lack of information regarding the behavior of composite systems and clear methodologies for calculating seismic design coefficients (R and Cd) from first principles. This paper begins with an overview of IBC seismic design provisions for composite RCS moment frames and then presents data from nonlinear Incremented Dynamic Analyses (IDA) to evaluate the adequacy of the provisions including an assessment of the code-specified R and Cd factors. The overall goal is to help establish the reliability of composite systems designed using current standards and to provide better technical underpinnings to the empirical foundation of current code provisions. IBC EQUIVALENT LATERAL FORCE STATIC PROCEDURE FOR SEISMIC DESIGN The Equivalent Lateral Force procedure of the IBC specifies a design base shear, V~, given by the following equation:

Gregory G. Deierlein

Papers

Summary of SAC Case Study Building Analyses

Steel-Framed Rocking Structural Systems for Moderate Seismic Zones

Generalized modified modal superposition procedure for seismic design of rocking and pivoting steel spine systems

Seismic Design of Composite Moment Frame Buildings—Case Studies and Codes Implications

State of the Art in Computational Simulation for Natural Hazards Engineering