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.

Probabilistic Theory of Plastic Mechanism Control for Steel Moment Resisting Frames

2019 ◽  
Vol 76 ◽  
pp. 95-107 ◽  
Author(s):  
Vincenzo Piluso ◽  
Alessandro Pisapia ◽  
Paolo Castaldo ◽  
Elide Nastri
Keyword(s):  
Probabilistic Theory ◽  
Steel Moment Resisting Frames ◽  
Moment Resisting Frames ◽  
Plastic Mechanism ◽  
Moment Resisting ◽  
Mechanism Control

The effect of stiffener on behavior of reduced beam section connections in steel moment-resisting frames

2015 ◽  
Vol 15 (4) ◽  
pp. 827-834 ◽  
Author(s):  
M. Tahamouli Roudsari ◽  
F. Abdollahi ◽  
H. Salimi ◽  
S. Azizi ◽  
A. R. Khosravi
Keyword(s):  
Steel Moment Resisting Frames ◽  
Reduced Beam Section ◽  
Moment Resisting Frames ◽  
Moment Resisting ◽  
Beam Section

scholarly journals Reduced Beam Section (RBS) Moment Connections-Analytical Investigation Using Finite Element Method

2018 ◽  
Vol 4 (6) ◽  
pp. 1240 ◽  
Author(s):  
Christos Sofias ◽  
Dimitra Tzourmakliotou
Keyword(s):  
Cross Sections ◽  
Computational Cost ◽  
Analytical Investigation ◽  
Moment Connections ◽  
Reduced Beam Section ◽  
Moment Resisting ◽  
Group A ◽  
Beam Section ◽  
Structural Parts ◽  
Group B

Reduced Beam Section (RBS) moment resisting connections are among the most economical and practical rigid steel connections developed in the aftermath of the 1994 Northridge and the 1995 Kobe earthquakes. Although the RBS connection effectiveness was widely investigated using US design and construction practices, only limited data exist from European research. Recommendations of RBS applications in steel frames were prescribed in EC8, Part3. However the reliability of these recommendations is under consideration due to above mentioned poor existing data. This paper examines numerous different contours of radius cut-out (Group A) and provides recommendations for the design and detailing of radius cut Reduced Beam Section (RBS) moment connections.  Furthermore, it examines and compares different beam cross sections of European steel profiles (Group B) while the sizing of the RBS cut is kept at a constant ratio. Analytical approach was conducted investigating the adopted by EC8, Part 3 key parameters for the design. The main objective of the applied RBS geometry is to protect the connection and its components (endplate, column flange, bolts, welds) from either plastification or failure. Although the computational cost for optimization with ABAQUS is very large, the results of this study ensures on one hand that the performances of the structural parts can be effectively improved by shape optimization and an the other hand that adjustment in the geometry of the radius cut is needed for safe application to European profiles.

Fracture Moment Strength of Reduced Beam Section with Bolted Web Connections

2007 ◽  
Vol 348-349 ◽  
pp. 717-720
Author(s):  
Ki Hoon Moon ◽  
Sang Whan Han ◽  
Ji Eun Jung
Keyword(s):  
Moment Connections ◽  
Moment Capacity ◽  
Design Procedures ◽  
Reduced Beam Section ◽  
Moment Resisting ◽  
Current Design ◽  
Beam Section ◽  
The Moment ◽  
Rbs Connections ◽  
Experimental Researches

Reduced Beam Section (RBS) moment connections are developed for Special Moment Resisting Frames (SMRF). According to the beam web attachment the column flange RBS connections are classified into Reduced Beam Section with Bolted web connections (RBS-B), and the Reduced Beam Section with Welded web connections (RBS-W). Beam flanges are welded to the column. Regardless of different web attachment details in RBS-B and RBS-W connections current design procedures (FEMA 350) assumes that they could develop plastic moment of the beam gross section. In current design procedures, RBS-B connections should provide the sufficient strength that can reach the plastic moment capacity of the connected beam. However, some experimental researches reported that the beams in RBS-B connections fractured before the connection reached its plastic moment capacity. Such undesirable fracture shows that RBS-B connections have less strength than RBS-W connections. And if RBS-B connections designed in current design procedures, it might fail in a brittle manner and not satisfy SMRF due to undesirable fracture. Thus, this study develops a new set of equations for accurately computing the moment strength of RBS-B connections. The proposed strength equation accurately predicts connection moment capacity for RBS-B connections.

Effect of Column-Base Flexibility on the Seismic Response and Safety of Steel Moment-Resisting Frames

2013 ◽  
Vol 29 (4) ◽  
pp. 1537-1559 ◽  
Author(s):  
Farzin Zareian ◽  
Amit Kanvinde
Keyword(s):  
Nonlinear Response ◽  
Moment Frames ◽  
Steel Moment Frames ◽  
Steel Moment Resisting Frames ◽  
Four Frames ◽  
Plastic Mechanism ◽  
Fixed Base ◽  
Moment Resisting ◽  
Ductility Capacity ◽  
Column Base

The effect of column-base flexibility on the response of steel moment frames is assessed through parametric simulation. The response of four frames (2-, 4-, 8-, and 12-story), designed as per current codes, is investigated through static push-over simulations and sophisticated nonlinear response-history simulations, including collapse simulation. For each frame, a range of base fixities is interrogated, including realistic values that are calculated from the designed connections. The results indicate that a reduction in base fixity alters the force distribution and the plastic mechanism, significantly reducing ductility capacity and strength, as well as collapse resilience, while increasing member forces. For the 4-, 8-, and 12-story frames, this trend suggests that the expected response of such frames is worse than is implied by simulations and design approaches that assume a fixed-base condition. However, the trend is beneficial for the 2-story frame, which is analyzed and designed assuming a pinned base.

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.

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