scholarly journals Ductility demand for uni-directional and reversing plastic hinges in ductile moment resisting frames

1999 ◽  
Vol 32 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Richard Fenwick ◽  
Raad Dely ◽  
Barry Davidson
Keyword(s):  
Plastic Hinge ◽  
Time History ◽  
Simple Relationship ◽  
Plastic Hinges ◽  
Ductility Demand ◽  
Displacement Ductility ◽  
Moment Resisting Frames ◽  
Moment Resisting ◽  
Negative Moment ◽  
Unidirectional Plastic

In a major earthquake the beams in moment resisting frames may develop either reversing or unidirectional plastic hinges. The form of plastic hinge depends upon the ratio of the moments induced by the gravity loading to those induced by the seismic actions. Where this ratio is low the plastic hinges form at the ends of the beams and the sign of the inelastic rotation changes with the direction of sway. These are reversing plastic hinges, and the magnitude of the rotation that they sustained is closely related to the inter-storey displacement. However, when the moment ratio exceeds a certain critical value, unidirectional plastic hinges may form. In this case negative moment plastic hinges develop at the column faces and the positive moment plastic hinges form in the beam spans. As the earthquake progresses the positive and negative inelastic rotations accumulate in their respective zones so that peak values are always sustained at the end of the earthquake. With this type of plastic hinge no simple relationship exists between inter-storey drift and inelastic rotation. Several series of time history analyses have been made to assess the relative magnitudes of inelastic rotation that are imposed on the two forms of plastic hinge. It is found that with design level earthquakes typically the unidirectional plastic hinge is required to sustain 21/ 2 to 4 times the rotation imposed on reversing plastic hinges, with the curvature ductilities ranging up to 140. These values are appreciably in excess of the values measured in tests using standard details. This indicates that in structures where unidirectional plastic hinges may form, the design displacement ductility and or the allowable inter-storey drift should be reduced below the maximum values currently permitted in the New Zealand codes. The problems associated with the formation of unidirectional plastic hinges can be avoided by adding positive moment flexural reinforcement in the mid regions of the beams. By this means the potential positive moment plastic hinges can be restricted to the beam ends.

scholarly journals A Review on the Plastic Hinge Characteristics of Beam-Column Joints in RC Moment Resisting Frames

2021 ◽  
Author(s):  
Surya SS ◽  
R Sajeeb
Keyword(s):  
Plastic Hinge ◽  
High Strength ◽  
Joint Interface ◽  
Careful Study ◽  
Plastic Hinges ◽  
Moment Resisting Frames ◽  
Extreme Loads ◽  
Moment Resisting ◽  
Column Joint ◽  
Joint Behavior

The behavior of beam-column joints plays a crucial role in the performance of Reinforced Concrete (RC) moment-resisting frames in earthquake-prone areas. In beam-column joints with high strength concrete and shear reinforcement in joints, the plastic hinge is formed at the beam-column joint interface, which is an undesirable failure mode. Predicting the behavior of plastic hinges subjected to large inelastic deformations caused by extreme loads such as earthquake plays an important role in assessing maximum stable deformation capacities of framed concrete structures. The present paper reviews the plastic hinge characteristics of beam-column joints of RC moment-resisting frames. A careful study and understanding of joint behavior are essential to arrive at a proper judgment of the design of joints. Various types of joints and the influence of bond strength characteristics, forces acting on joints, reinforcement detailing, and the concept and formation of plastic hinges in the joints are thoroughly reviewed.

Predicted Ductility Demands for Steel Moment Resisting Frames

1989 ◽  
Vol 5 (2) ◽  
pp. 409-427 ◽  
Author(s):  
Charles W. Roeder ◽  
James E. Carpenter ◽  
Hidetake Taniguchi
Keyword(s):  
United States ◽  
Seismic Design ◽  
The United States ◽  
Structural Systems ◽  
Ductility Demand ◽  
Steel Moment Resisting Frames ◽  
The Past ◽  
Moment Resisting Frames ◽  
Column System ◽  
Moment Resisting

Recent changes to the United States seismic design provisions permit the use of weak column-strong beam steel moment resisting frames. This design concept has not been used in the past, because it results in plastic hinges in the columns during moderate or extreme earthquakes. This paper shows the results of inelastic dynamic response calculations on a weak column frame and a comparable strong column system. The results show that the ductility demand is much greater for the weak column strong beam framing system with some acceleration records. The required ductility is then compared for the different structural systems and both are compared to the results of experiments. The comparison suggests that the weak column system may not be able to develop the required ductility. The results of this paper should help define the viability and limits in applicability of the weak column system.

Behaviour of dual eccentrically braced steel frames with short and long seismic links

2019 ◽  
Author(s):  
Ivan Lukačević ◽  
Tomislav Maleta ◽  
Darko Dujmovic
Keyword(s):  
Energy Dissipation ◽  
Plastic Hinge ◽  
Seismic Energy ◽  
High Strength ◽  
Elastic Behaviour ◽  
Braced Frame ◽  
Moment Resisting Frames ◽  
Collapse Mechanisms ◽  
Moment Resisting ◽  
Flexible Part

<p>Dual structures obtained by combining moment resisting frames with innovative bracing systems such as replaceable shear panels or seismic links have significant advantages among conventional solutions. The major advantages of such systems are energy dissipation in the specific locations and re-centring capability which significantly reduces repair costs. On the other hand, design of such systems is driven with specific requirements such as combining different steel grades to ensure elastic behaviour of the flexible part of the system. This paper deals with comparative behaviour analyses of two dual systems combining moment resisting multi-storey frames with eccentric bracing systems. The steel frame consists of three bays with central braced frame and two adjacent moment resisting frames. The bracing system contains either long or short seismic link. Seismic energy dissipation of these systems is completely different. Long seismic links are characterised with a classical plastic hinge in which energy is dissipated through bending while in case of short seismic links seismic energy is dissipated through shear. Multi-linear plastic diagrams for both links have been defined and pushover analyses are performed. The behaviour of the analysed systems based on collapse mechanisms, overstrength ratio, target displacement and possible solutions for re-centring capabilities are discussed. Analysed system with short seismic links despite more complicated modelling and requirements for high strength steel in MRFs, results in higher overstrength ratio regarding the system with long seismic links. It is also far easier to dismantle system with short seismic links, due to the bolted connection of links with the adjacent members.</p>

Seismic fragility of steel moment-resisting frames in Vancouver and Montreal designed in the 1960s, 1980s, and 2010

2015 ◽  
Vol 42 (11) ◽  
pp. 919-929 ◽  
Author(s):  
Lucía Valentina Díaz Gómez ◽  
Oh-Sung Kwon ◽  
Mohammad Reza Dabirvaziri
Keyword(s):  
Numerical Models ◽  
Fragility Curves ◽  
Time History ◽  
Steel Moment Resisting Frames ◽  
Moment Resisting Frames ◽  
Nonlinear Time History Analyses ◽  
Moment Resisting ◽  
The 1960S ◽  
Steel Mrfs ◽  
Nonlinear Time History

Typical steel moment-resisting frames (MRF) of six-storey buildings in Vancouver and Montreal were designed for three different provisions of the National Building Code of Canada (1960s, 1980s, and 2010). Numerical models were developed in OpenSees to understand the seismic performance of the structures. These models accounted for strength and stiffness degradation through appropriate representations of the beam–column connection behaviours, which were calibrated against experimental results available in the literature. The behaviour of the buildings was evaluated through pushover and nonlinear time history analyses. The pushover analysis results showed that the 1960s and 2010 steel MRFs of both cities exhibited strong-column-weak-beam failure mode. The 1980s steel MRFs of both cities showed soft-storey mechanism. Fragility curves were developed for the steel MRFs based on the seismic demands evaluated using nonlinear time history analyses, which can be used for regional seismic impact assessment studies in the future.

scholarly journals AN INVESTIGATION OF THE EFFECTIVENESS OF THE FRAMING SYSTEMS IN STEEL STRUCTURES SUBJECTED TO BLAST LOADING

2014 ◽  
Vol 20 (6) ◽  
pp. 767-777 ◽  
Author(s):  
Amy Coffield ◽  
Hojjat Adeli
Keyword(s):  
Failure Modes ◽  
Plastic Hinge ◽  
Blast Loading ◽  
Steel Structures ◽  
Response Analysis ◽  
Plastic Hinges ◽  
Braced Frame ◽  
Concentrically Braced Frame ◽  
Moment Resisting ◽  
Applied Element Method

The effectiveness of different framing systems for three seismically designed steel frame structures subjected to blast loading is investigated. The three faming systems considered are: a moment resisting frame (MRF), a concentrically braced frame (CBF) and an eccentrically braced frame (EBF). The blast loads are assumed to be unconfined, free air burst detonated 15 ft (4.572 m) from one of the center columns. The structures are modeled and analyzed using the Applied Element Method, which allows the structure to be evaluated during and through failure. Failure modes are investigated through a plastic hinge analysis and member failure comparison. Also, a global response analysis is observed through comparison of roof deflections and accelerations. A conclusion of this research is that braced frames provide a higher level of resistance to the blast loading scenario investigated in this research. Both the CBF and EBF had a smaller number of failed members and plastic hinges compared to the MRF. They also had smaller roof deflection and acceleration. The CBF yielded the fewest number of plastic hinges but the EBF had a slightly fewer number of failed members.

Amplified Seismic Loads in Steel Moment Frames

2016 ◽  
Vol 847 ◽  
pp. 222-232
Author(s):  
Bora Aksar ◽  
Selcuk Dogru ◽  
Bulent Akbas ◽  
Jay Shen ◽  
Onur Seker ◽  
...  
Keyword(s):  
Lateral Displacement ◽  
Ground Motions ◽  
Time History ◽  
Load Level ◽  
Steel Buildings ◽  
Moment Frames ◽  
Axial Loads ◽  
Steel Moment Resisting Frames ◽  
Moment Resisting Frames ◽  
Moment Resisting

This study focuses on exploring the seismic axial loads for columns in steel moment resisting frames (SMRFs) under strong ground motions. For this purpose, the increases in axial loads are investigated at the maximum lateral load level and the corresponding lateral displacement. The results are presented in terms of maximum amplification factors (Ω0) of all frame columns under the selected ground motions and axial load-moment levels in columns. four typical steel moment resisting frames representing typical low, medium and high rise steel buildings are designed based on the seismic design requirement in ASCE 7-10 and AISC 341-10 . An ensemble of ground motions range from moderate to severe are selected to identify the seismic response of each frames. Two sets of ground motions corresponding to 10% and 2% probability of exceedance are used in nonlinear dynamic time history analyses.

Seismic performance of ductile and nominally ductile reinforced concrete moment resisting frames. II. Analytical study

1998 ◽  
Vol 25 (2) ◽  
pp. 342-352 ◽  
Author(s):  
André Filiatrault ◽  
Éric Lachapelle ◽  
Patrick Lamontagne
Keyword(s):  
Reinforced Concrete ◽  
Dynamic Analysis ◽  
Dynamic Modelling ◽  
Time History ◽  
Reduction Factor ◽  
Major Influence ◽  
Shake Table ◽  
Analysis Model ◽  
Moment Resisting Frames ◽  
Moment Resisting

This paper is the second of two companion papers on the evaluation of the level of protection offered by ductile and nominally ductile reinforced concrete structures. In the first paper, experimental results obtained from shake table tests of two half-scale reinforced concrete moment resisting frames were reported. The first structure was designed as a ductile frame (force reduction factor R = 4) according to current Canadian standards; and the second structure incorporated only nominally ductile details (R = 2). This second paper deals with the dynamic modelling of the two structures. A simple nonlinear time-history dynamic analysis model is presented and its predictions are compared with the shake table test results. It is shown that inelastic deformations in beam-column joints have a major influence on the seismic response of the structures. Approximate modelling of these joint deformations, based on equivalent rotational springs, can provide a good correlation between numerical and experimental results.Key words: dynamic analysis, moment resisting frames, earthquakes, reinforced concrete, seismic.

scholarly journals Seismic Damage Detection of Moment Resisting Frame Structures Using Time-Frequency Features

2018 ◽  
Vol 2018 ◽  
pp. 1-18 ◽  
Author(s):  
Dongwang Tao ◽  
Qiang Ma ◽  
Shanyou Li
Keyword(s):  
Damage Detection ◽  
Plastic Hinge ◽  
Superposition Principle ◽  
Seismic Damage ◽  
Transformation Matrix ◽  
Gabor Wavelet ◽  
Plastic Hinges ◽  
Time Frequency ◽  
Moment Resisting Frame ◽  
Moment Resisting

To detect seismic damage of moment resisting frame (MRF) structures, a data-driven method using the fractal dimension (FD) of time-frequency feature (TFF) of structural seismic dynamic responses at measured stories is extended and refined. The TFF is defined as the real part of Gabor wavelet transform of translational interstory displacement, and FD is used to give a quantitative value to describe the calculated TFF. Static condensation method is first used to reduce the degrees-of-freedom (DOFs) of MRF and to express the rotational displacements using translational displacements. For linear MRF, the FDs of TFFs at all stories are the same using the definition of TFF and modal superposition principle. For damaged MRF with plastic hinges at the ends of beams and columns, the force analogy method is implemented to establish transformation matrix from plastic hinge rotations to translational interstory inelastic displacements. Due to the sparseness of the transformation matrix, plastic hinges only generate interstory inelastic displacements, which are low-frequency contents, in the vicinity of plastic hinges. Correspondingly, the FDs of TFFs of interstory displacements with inelastic component are different from the FDs of TFFs of the interstory displacements that do not contain inelastic component. A numerical simulation on a 16-story MRF was conducted. The simulation included 10 cases such as no damage or linear structure, plastic hinges in single-story beams, plastic hinges in single-story columns, plastic hinges in single-story beams and columns, and plastic hinges in multiple story beams and columns. The robustness to measurement noise was also investigated. The seismic damage detection results demonstrated that the proposed method was capable of locating the stories where the plastic hinges occurred.

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