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.

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 Rigid-Plastic Analysis of Seismic Resistant T-Frame considering Moment-Shear Interaction

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Ghader Bagheri ◽  
Payam Ashtari ◽  
Farhad Behnamfar
Keyword(s):  
Energy Dissipation ◽  
Collapse Mechanism ◽  
Rigid Plastic ◽  
Soft Storey ◽  
Collapse Mechanisms ◽  
Plastic Mechanism ◽  
Plastic Analysis ◽  
Seismic Resistant ◽  
Global Collapse ◽  
The Moment

To select a seismic resistant system, in addition to strength and stiffness, ductility and energy dissipation are important to be considered. Structures have nonlinear behavior under the influence of moderate and strong earthquakes. One of the primary aims in designing seismic resistant structures is to prevent the formation of undesirable collapse mechanisms such as the collapse in only a few storeys of the structure that leads to low energy dissipation. In order to achieve a global collapse mechanism, modern seismic codes provide simple rules for design, which is called the hierarchy criteria. Although these simple criteria could prevent the formation of a soft storey mechanism, they could not lead to an optimal global collapse mechanism. In these mechanisms, the energy dissipation zones include all the yielding zones such as beams, while all other parts of the structure have remained in the elastic range. TRF (T-resisting frame) is an innovative lateral resistant system introduced for architectural reasons and to provide more energy dissipating capability. This system has several collapse mechanisms due to the moment, shear, or moment-shear behavior of its members. In this paper, within the framework of the theory of plastic mechanism control, the rigid-plastic analysis of the TRF system to achieve the desired collapse mechanism is used by considering the moment-shear interaction. According to these analyses, which are performed on a single storey frame, simple hierarchy criteria are developed to create the desired collapse mechanism. Also, these criteria prevent undesired collapse mechanisms in order to have more energy dissipation and more ductility. Finally, the validity of the proposed criteria has been verified by the pushover analysis.

From Design to Earthquake Loss Assessment of Steel Moment-Resisting Frames

2018 ◽  
Vol 763 ◽  
pp. 124-130 ◽  
Author(s):  
Luís Macedo ◽  
Antonio Silva ◽  
José Miguel Castro
Keyword(s):  
Seismic Design ◽  
Eurocode 8 ◽  
Loss Assessment ◽  
Behaviour Factor ◽  
Steel Moment Resisting Frames ◽  
Performance Factors ◽  
Moment Resisting Frames ◽  
Moment Resisting ◽  
Earthquake Loss ◽  
Steel Mrfs

Steel moment-resisting frames (MRFs) are well known for their ductile and stable hysteretic behaviour. For this reason, they are an attractive and effective structural system for seismic resistance. Current seismic design codes, namely Eurocode 8, provide system performance factors that should be used in the seismic design under different ductility classes. However, recent research studies have shown that the use of the code-prescribed performance factors lead to stiffer and heavier structural solutions that are not consistent with the performance-based design assumptions. A new methodology, Improved Force-Based Design (IFBD), has recently been proposed with the aim of a more rational determination of the adopted value of the behaviour factor, q, instead of using the upper bound reference values provided by the design code. This paper investigates if the obtained values of q for both EC8 and IFBD concerning steel MRFs are not only adequate, but also provide sufficient margins against collapse under maximum considered earthquake (MCE) ground motions. To this end, the methodology proposed in FEMA P695 was used. Additionally, the expected direct economic seismic losses are computed according to the PEER-PBEE methodology.

A Simplified Approach for Seismic Performances Estimation for Steel Moment Resisting Frames

ce/papers ◽  
2021 ◽  
Vol 4 (2-4) ◽  
pp. 2335-2340
Author(s):  
Elide Nastri ◽  
Rosario Montuori ◽  
Vincenzo Piluso ◽  
Paolo Todisco
Keyword(s):  
Simplified Approach ◽  
Steel Moment Resisting Frames ◽  
Moment Resisting Frames ◽  
Moment Resisting
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