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Grigorian M.,MGA Structural Engineers Inc. | Grigorian C.E.,URS Corporation
Engineering Structures | Year: 2012

This study was prompted by the need to elaborate on the lateral displacements of steel moment frames at incipient collapse. The paper presents relatively simple solutions for assessing lateral displacements of basic flexural modules, as component parts of high-rise frames, at the onset of plastic failure due to combined gravity, and lateral forces magnified by P-delta effects. These solutions are then utilized in conjunction with plastic collapse load interaction diagrams to develop families of generic displacement interaction curves for different boundary conditions. Effects of plastic hinge offsets on the ultimate performance of moment frames, has been discussed in some detail. The paper presents a number of novel concepts and formulae that have not appeared in the literature before. The results of research leading to the preparation of this article have been summarized in the conclusions. It has been shown how these findings may complement the existing literature on the subject. © 2012 Elsevier Ltd. Source


Grigorian M.,MGA Structural Engineers Inc.
Journal of Bionic Engineering | Year: 2014

Currently, there are only three classical and a handful of emerging design methodologies available to structural engineers worldwide. None of these methodologies can explain the design concepts involved in the realization of natural structures such as trees, nor can they fully address the design needs of contemporary engineering structures. The recently developed Performance Control (PC) incorporates both the essence of the classical concepts and the newer procedures and addresses the observed performance of the structure during its known history of loading. PC attempts to mimic nature by applying the known theories of structures to the design of case-specific frameworks, rather than investigating their results for compliance against prescriptive criteria. Parametric examples have been provided to illustrate the applications of the conceptual design similarities between trees and manmade moment frames. It has been shown that an understanding of the structural performance of trees can enhance the structural design of moment frames, and that bioinspired PC can lead to minimum weight moment frames under lateral loading. The analogous performances of the natural and manmade structures may help explain the structural response of trees to similar loading scenarios. © 2014 Jilin University. Source


Grigorian M.,MGA Structural Engineers Inc. | Grigorian C.E.,URS Corporation
Canadian Journal of Civil Engineering | Year: 2012

This paper proposes a simple, relatively new elastic-plastic design method for earthquake resisting frames that enables the engineer to directly control the essential aspects of the future behavior of certain structural forms, through basic statics and imposition of predetermined modes of behavior. The method is particularly applicable to the preliminary design of low to mid-rise buildings where the fundamental period of vibrations dominates the response of the system to seismic loading. The focus of this paper is directed towards simplified but accurate manual design rather than sophisticated structural analysis. The premise of the proposed solution is that the constituent elements of the system can be selected in such a way as to cause both the elastic as well as the plastic drift functions to follow linearly varying straight line profiles during all phases of loading. Frameworks designed by this method act not only as structures of uniform response (UR), i.e., uniform strength and stiffness, where the demand/capacity ratios of its members remain the same, both before and after formation of plastic hinges, but they also result in unique solutions, satisfying the prescribed yield criteria, the boundary support, as well as the of static equilibrium conditions. Source


Grigorian M.,MGA Structural Engineers Inc. | Grigorian C.E.,URS Corporation
Journal of Constructional Steel Research | Year: 2012

Plastic Design Analysis (PDA) is a recently developed, case specific procedure that aims at direct displacement based lateral design of steel moment frames. PDA is a byproduct of the classical Plastic Analysis and Design (PAD) method of approach. While PAD can only estimate the ultimate loading at failure, PDA has been developed to address such important design issues as the P-delta effects, sequential hinging and lateral displacements at incipient collapse. This is achieved by, first relating the global stiffness of the sub frames of the structure to the most critical target drift and then providing as much capacity as demand imposed on the elements of the frame. Such schemes embrace envelopes of several initial designs within which member sizes could be rearranged for any purpose while observing the prescribed performance conditions. In the interim, a practical method of forecasting the sequence of formation of the plastic hinges is introduced. PDA, as introduced in this article, is based on several complimentary design concepts and novel formulae that have not appeared in the literature before. © 2012 Elsevier Ltd. All rights reserved. Source


Grigorian M.,MGA Structural Engineers Inc. | Grigorian C.E.,URS Corporation
Journal of Structural Engineering (United States) | Year: 2012

Performance control (PC) is the ability to design a structure in such a way as to expect predetermined modes of response at certain stages of loading, extents of damage, and/or drift ratios. The primary purpose of this paper is to complement the existing literature on performance-based plastic design of moment frames. PC is, in fact, a new analytic performance-based elastic-plastic design method for ductile structures under seismic loading. It empowers the engineer to control the design rather than investigate design-related numerical output. Failure mechanisms and stability conditions are enforced rather than tested. Unlike traditional closed-form procedures, PC enables the designer to control the response of the structure at preselected performance stages such as before and at first yield, any fraction of the failure load, or specified drift ratios up to and including incipient collapse. It offers a simple design solution to a rather complex problem. © 2012 American Society of Civil Engineers. Source

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