scholarly journals Theory of Plastic Mechanism Control: State-of-The-Art

2014 ◽  
Vol 8 (1) ◽  
pp. 262-278 ◽  
Author(s):  
Alessandra Longo ◽  
Elide Nastri ◽  
Vincenzo Piluso
Keyword(s):  
Failure Modes ◽  
State Of The Art ◽  
Closed Form Solution ◽  
Form Solution ◽  
Collapse Mechanism ◽  
Concentrically Braced Frames ◽  
Moment Resisting Frames ◽  
Plastic Mechanism ◽  
Moment Resisting ◽  
Mechanism Control

In this paper, the state-of-the-art regarding the “Theory of Plastic Mechanism Control” (TPMC) is presented. TPMC is aimed at the design of structures assuring a collapse mechanism of global type. The theory has been developed in the nineties with reference to moment-resisting steel frames (MRFs) and progressively extended to all the main structural typologies commonly adopted as seismic-resistant structural systems. In particular, the outcome of the theory is the sum of the plastic moments of the columns required, at each storey, to prevent undesired failure modes, i.e. partial mechanisms and soft-storey mechanisms. The theory is used to provide the design conditions to be satisfied, in the form of a set of inequalities where the unknowns are constituted by the column plastic moments. Even though the set of inequalities was originally solved by means of an algorithm requiring an iterative procedure, now, thanks to new advances, a “closed form solution” has been developed. This result is very important, because the practical application of TPMC can now be carried out even with very simple hand calculations. In order to show the simplicity of the new procedure, numerical applications are herein presented in detail with reference to Moment Resisting Frames (MRFs) and dual systems both composed by Moment Resisting Frames and Eccentrically Braces Frames (MRF-EBFs) with inverted Y scheme and composed by Moment Resisting Frames and Concentrically Braced Frames (MRF-CBFs) with X-braced scheme and V-braced scheme. Finally, the pattern of yielding obtained is validated by means of both push-over analyses and incremental dynamic analyses. A comparison in terms of structural weight of the designed structures is also presented and the corresponding seismic performances are discussed.

scholarly journals Comparison Between Different Design Strategies For Freedam Frames: Push-Overs and Ida Analyses

2018 ◽  
Vol 12 (1) ◽  
pp. 140-153 ◽  
Author(s):  
Rosario Montuori ◽  
Elide Nastri ◽  
Vincenzo Piluso ◽  
Simona Streppone ◽  
Mario D’Aniello ◽  
...  
Keyword(s):  
Structural Damage ◽  
Code Design ◽  
Design Strategies ◽  
Moment Resisting Frames ◽  
Repair Costs ◽  
Plastic Mechanism ◽  
Moment Resisting ◽  
Mechanism Control ◽  
Traditional Structures ◽  
Structural Solutions

Background:Modern seismic code design rules are known to be based on capacity design principles. They try to assure the damage to occur in the ductile parts of the structure, such as beam ends while the other have to remain in elastic range. Therefore, in the aftermath of design earthquakes, plastic deformations at member or connection level will imply high repair costs. In the last decades, innovative structural solutions based on the so-called supplementary energy dissipation strategy allow increasing the dissipative capacity of structures through equipping it with special damping devices. In the case of substitution of dissipative zones with dissipative devices the strategy takes the name of substitutive strategy. This is the case of Moment Resisting Frames investigated in this paper, where traditional dissipa-tive zones, are equipped with innovative low damage frictional devices. However, the current version of codes does not provide any rules to design of MRFs equipped with this type of friction joints.Methods:Therefore, this paper reports two design approaches amply investigated and compared. The first one is based on the application of the Beam-to-Column Hierarchy Criterion (BCHC) while the second one exploits the Theory of Plastic Mechanism Control (TPMC). The comparison between them is herein discussed on the basis of the results of nonlinear static and dynamic analyses.Conclusions:Structures equipped with low damage frictional connections show larger drift demand than conventional Moment Resisting Frames. However, differently from traditional structures, the larger displacement demand of MRFs equipped with friction joints does not corre-spond to structural damage, thus allowing the reparability of the structure.

scholarly journals Evaluation of the Seismic Capacity of Existing Moment Resisting Frames by a Simplified Approach: Examples and Numerical Application

2021 ◽  
Vol 11 (6) ◽  
pp. 2594
Author(s):  
Rosario Montuori ◽  
Elide Nastri ◽  
Vincenzo Piluso ◽  
Paolo Todisco
Keyword(s):  
Collapse Mechanism ◽  
Eurocode 8 ◽  
Seismic Capacity ◽  
Numerical Application ◽  
Simplified Approach ◽  
Soft Storey ◽  
Moment Resisting Frames ◽  
Inelastic Analysis ◽  
Plastic Mechanism ◽  
Moment Resisting

The capacity of a structure can be assessed using inelastic analysis, requiring sophisticated numerical procedures such as pushover and incremental dynamic analyses. A simplified method for the evaluation of the seismic performance of steel moment resisting frames (MRFs) to be used in everyday practice has been recently proposed. This method evaluates the capacity of buildings employing an analytical trilinear model without resorting to any non−linear analysis. Despite the methodologies suggested by codes, the assessing procedure herein described is of easy application, also by hand calculation. Furthermore, it constitutes a suitable tool to check the capacity of the buildings designed with the new seismic code prescriptions. The proposed methodology has been set up through a large parametric analysis, carried out on 420frames designed according to three different approaches: the theory of plastic mechanism control (TPMC), ensuring the design of structures showing global collapse mechanism (GMRFs), the one based on the Eurocode 8 design requirements (SMRFs), and a simple design against horizontal loads (OMRFs) without specific seismic requirements. In this paper, some examples of the application of this simplified methodology are proposed with references to structures supposed to exhibit global, partial and soft storey mechanism.

Optimum Plastic Design of Moment Resisting Frames Using Mechanism Control

Structures ◽  
2018 ◽  
Vol 16 ◽  
pp. 254-268
Author(s):  
Mostafa Fathi Sepahvand ◽  
Jalal Akbari ◽  
Koichi Kusunoki
Keyword(s):  
Plastic Design ◽  
Moment Resisting Frames ◽  
Moment Resisting ◽  
Mechanism Control

VULNERABILITY REDUCTION OF STEEL MOMENT RESISTING FRAMES BY MEANS OF REDUCED BEAM SECTION

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Rosario Montuori
Keyword(s):  
Seismic Load ◽  
Steel Moment Resisting Frames ◽  
Reduced Beam Section ◽  
Load Combination ◽  
Plastic Mechanism ◽  
Moment Resisting ◽  
Final Design ◽  
Mechanism Control ◽  
Beam Section ◽  
The Cost

The idea and the developed example of this work are based on the attainment of seismic performance improvement by simply trimming the flanges of the beam-ends. This strategy is to be applied by considering both the results of the theory of plastic mechanism control and the rules assuring the yielding of reduced beam sections (RBS) when seismic loads are applied to the structure. The results of such strategy are not always effective. In fact, there are several conditions that are to be satisfied in order to obtain an actual seismic improvement. Notwithstanding, when these conditions are satisfied, the cost of intervention can be considered as negligible. For this reason, this strategy can be very interesting and the rules applied in this work can clarify which is the effect of RBS taking into account all the parameters playing a role in the final design, i.e. existing column sections, resistance and ductility of existing connections, vertical loads acting in seismic load combination, amount of the reduction of beam section and its distance from the connection.

Strength Demand Issues Relevant for the Seismic Design of Moment-Resisting Frames

2005 ◽  
Vol 21 (2) ◽  
pp. 415-439 ◽  
Author(s):  
Ricardo A. Medina ◽  
Helmut Krawinkler
Keyword(s):  
Seismic Design ◽  
Brittle Failure ◽  
Failure Modes ◽  
Shear Forces ◽  
Moment Resisting Frames ◽  
Weak Beam ◽  
Moment Resisting ◽  
Nonlinear Static ◽  
Current Code ◽  
Code Provisions

This paper deals with the evaluation of strength demands relevant for the seismic design of columns that are part of moment-resisting frames. Regular frames with fundamental periods from 0.3 sec. to 3.6 sec. and number of stories from 3 to 18 are investigated. An evaluation of the relationships between strength demands (e.g., story shear forces, story overturning moments, and moments in columns), ground motion intensity, fundamental period, and number of stories is the focus of this paper. The results from this study demonstrate that the magnitude and distribution over the height of maximum axial and shear forces in columns exposed to severe earthquakes often are not adequately estimated by current seismic design and analysis procedures (e.g., the nonlinear static pushover). Moreover, the potential of plastic hinging in columns is high for regular frames designed according to the strong-column/weak-beam requirements of current code provisions, and more stringent strong-column/weak-beam criteria appear to be called for. The presented results are intended to provide guidance for improvement of seismic design provisions to avoid brittle failure modes in columns of moment-resisting frames.

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