Numerical Study on Moment Resisting Frames under Monotonic and Cyclic Loads

2018 ◽  
Vol 763 ◽  
pp. 625-632 ◽  
Author(s):  
Beatrice Faggiano ◽  
Antonio Formisano ◽  
Generoso Vaiano ◽  
Federico M. Mazzolani
Keyword(s):  
Seismic Behavior ◽  
Numerical Study ◽  
Seismic Energy ◽  
Experimental Tests ◽  
Design Criteria ◽  
Cyclic Loads ◽  
Factors Affecting ◽  
Moment Resisting Frames ◽  
Moment Resisting ◽  
Set Up

Moment Resisting Frames (MRF) should ideally dissipate the seismic energy through the development of plastic hinges in the beams and at the column bases with the purpose to pursue a global failure mechanism. The current seismic design criteria, through hierarchy resistance and ductility requirements, are conceived to achieve this objective. However there are still some inaccuracies in the prediction of the structural performances, mainly under cyclic loadings, as much important as the number of bays and stories augments. The current paper would give a contribution for deepening key issues related to MRF seismic behavior, presenting the numerical simulation of some literature experimental tests conducted on simple portal MRF subjected to monotonic and cyclic loads both in presence and in absence of vertical loads. The refined Finite Element structural models of the study systems are developed through the software ABAQUS (v6.13-1). The models set up provide very good replications of both monotonic and hysteretic behaviors in terms of strength, stiffness, ductility and energy dissipation. They represent powerful analysis instruments to perform parametric studies, aiming at detecting the main factors affecting the seismic behavior of MRFs, thus leading towards appropriate design criteria.

Numerical Study on Concentric Braced X Frames under Monotonic and Cyclic Loads

2018 ◽  
Vol 763 ◽  
pp. 633-641 ◽  
Author(s):  
Beatrice Faggiano ◽  
Antonio Formisano ◽  
Generoso Vaiano ◽  
Federico M. Mazzolani
Keyword(s):  
Numerical Study ◽  
Elastic Field ◽  
Seismic Energy ◽  
Experimental Tests ◽  
Cyclic Loads ◽  
Braced Frames ◽  
Structural Behaviour ◽  
Factors Affecting ◽  
Strength And Stiffness ◽  
Set Up

Concentric Braced Frames (CBF) are designed for dissipating the seismic energy mainly through plastic deformations of diagonals in tension, while beams and columns, designed on the basis of the hierarchy resistance criterion, should resist the design loads in elastic field without undergoing buckling and yielding phenomena. For such structural systems there are still some uncertainties on the performances under cyclic loadings, due to the degradation of the strength and stiffness under tension for the occurrence of instability problems in compression. The current paper deepens such key issues, presenting the numerical simulation of some literature experimental tests conducted on CBX frames subjected to monotonic and cyclic loads both in presence and in absence of vertical loads. The refined FE structural models of the study systems are developed through the software ABAQUS v6.13-1. The models set up have provided a very good replication of both monotonic and hysteretic behaviours in terms of strength, stiffness, ductility and energy dissipation. They are powerful analysis instruments to perform parametric studies, aiming at detecting the main factors affecting the cyclic structural behaviour, thus leading towards appropriate design criteria.

scholarly journals Performances of moment resisting frames with slender composite sections in low-to-moderate seismic areas

2018 ◽  
Author(s):  
Hervé Degée ◽  
Yves Duchêne ◽  
Benno Hoffmeister
Keyword(s):  
Numerical Model ◽  
Global Analysis ◽  
Local Buckling ◽  
Experimental Tests ◽  
Hysteretic Behavior ◽  
Moderate Intensity ◽  
Moment Resisting Frames ◽  
Composite Frames ◽  
Moderate Seismicity ◽  
Moment Resisting

The aim of the recently completed European research program Meakado is therefore to study design options with requirements proportioned to the actual seismic context of constructions in areas characterized by a low or moderate seismic hazard, contrary to most researches aiming at maximizing the seismic performances. In this general framework, specific investigations have been carried out regarding typical beam profiles commonly used for multi-bay - multi-storey composite frames. In a first stage, experimental tests on class-3 composite beam-to-column connections were performed. The measurement results were evaluated with regard to the development of the hysteretic behavior with particular emphasis on the degradation. These test results have been used as reference for the calibration and validation of numerical model aiming at extending the scope of the experimental outcomes through appropriate parametric variations regarding the behavior of nodal connections as well as towards the global analysis and behavior of structures made of class 3 and 4 profiles. Numerical investigations of the global performance of composite frames with slender cross-sections are then performed resorting to the numerical model previously calibrated with respect to the experimental tests and additional simulations at node level. Results are compared to the performance of an equivalent frame made of compact steel profiles. Attention is paid to the effects of strength and stiffness degradation due to local buckling. The analysis of the results is specifically focusing on the comparison of the rotation capacity of the slender section with the actual rotation demand imposed by a moderate intensity earthquake. Based on the outcomes of these investigations, practical design recommendations are finally derived for multi-storey, multi-bay moment resisting frames with type b (full composite action) beam-to column connections located in low and moderate seismicity regions. 

scholarly journals Experimental Study on Seismic Retrofitting of Reinforced Concrete Frames Using Welded Concrete-Filled Steel Tubes

2020 ◽  
Vol 10 (20) ◽  
pp. 7061 ◽  
Author(s):  
Kyong Min Ro ◽  
Min Sook Kim ◽  
Young Hak Lee
Keyword(s):  
Reinforced Concrete ◽  
Seismic Performance ◽  
Seismic Energy ◽  
Maximum Load ◽  
Steel Tube ◽  
Seismic Retrofitting ◽  
Reinforced Concrete Frame ◽  
Concrete Frame ◽  
Moment Resisting Frames ◽  
Moment Resisting

Buildings constructed with non-seismic details are at risk of damage and collapse when an earthquake occurs due to a lack of strength, stiffness, and ductility. For reinforced concrete (RC) moment-resisting frames, seismic retrofitting methods that can enhance strength or ductility should be applied. However, such strategies have many disadvantages related to constructability, serviceability, securing integrity, and cost. In this paper, a welded concrete-filled steel tube (WCFST) system was examined in order to resolve the problems of the existing seismic retrofitting methods for RC moment-resisting frames. To evaluate the seismic performance of the proposed system, two specimens, one with non-seismic details and another reinforced with a WCFST seismic system, were manufactured for the cyclic loading tests. As a result of the experiments, the specimen retrofitted with the WCFST system showed maximum load, effective stiffness, and energy dissipation capacity values approximately 3, 2, and 2.5 times greater, respectively, than those obtained from the existing reinforced concrete frame specimen. The experimental results indicate that the proposed WCFST system is expected to be effective at improving the seismic performance by enhancing both the strength of the existing reinforced concrete frame structures and the dissipation of the seismic energy.

scholarly journals A Hybrid BEM-CFD Virtual Blade Model to Predict Interactions between Tidal Stream Turbines under Wave Conditions

2020 ◽  
Vol 8 (12) ◽  
pp. 969
Author(s):  
Nicolo’ Lombardi ◽  
Stephanie Ordonez-Sanchez ◽  
Stefania Zanforlin ◽  
Cameron Johnstone
Keyword(s):  
Numerical Study ◽  
Experimental Tests ◽  
Full Scale ◽  
Small Scale ◽  
Ansys Fluent ◽  
Narrow Channels ◽  
Tidal Turbine ◽  
Performance Deterioration ◽  
Set Up ◽  
Blade Model

Tidal turbine array optimization is crucial for the further development of the marine sector. It has already been observed that tidal turbines within an array can be heavily affected by excessive aerodynamic interference, thus leading to performance deterioration. Small-scale experimental tests aimed at understanding the physical mechanisms of interaction and identifying optimal distances between machines can be found in the literature. However, often, the relatively narrow channels of laboratories imply high blockage ratios, which could affect the results, making them unreliable if extrapolated to full-scale cases. The main aim of this numerical study was to analyze the effects of the blockage caused by the laboratory channel walls in cases of current and also current surface waves. For this purpose, the performance predictions achieved for two turbines arranged in line for different lateral offsets in case of a typical laboratory scale were compared to the predictions obtained for a full scale, unconfined environment. The methodology consisted in the adoption a hybrid Blade Element Momentum–Computational Fluid Dynamics (BEM-CFD) approach, which was based on the Virtual Blade Model of ANSYS-Fluent. The results indicate that (1) the performance of a downstream turbine can increase up to 5% when this has a lateral separation of 1.5D from an upstream device in a full-scale environment compared to a misleading 15% calculated for the laboratory set-up, and (2) the relative fluctuations of power and thrust generated by waves are not significantly affected by the domain dimensions.

scholarly journals Robustness Assessment of Steel Moment Resisting Frames

2017 ◽  
Vol 11 (1) ◽  
pp. 420-433 ◽  
Author(s):  
David Cassiano ◽  
Carlos Rebelo ◽  
Luís Simoes da Silva
Keyword(s):  
Seismic Design ◽  
Progressive Collapse ◽  
Design Criteria ◽  
Steel Moment Resisting Frames ◽  
Moment Resisting Frames ◽  
Long Span ◽  
Moment Resisting ◽  
Structural Plastic ◽  
Steel Mrf ◽  
Pushdown Analysis

Nowadays, many buildings with steel Moment Resisting Frames (MRF) are built in seismic zones when seismic codes are at its early stages of development, and as such, these structures are often designed solely to resist lateral wind loads without providing an overall ductile mechanism. On the other hand, current seismic design criteria based on hierarchy of resistance allow enhancing the structural ductility and controlling the structural plastic behaviour. Therefore, seismic design criteria might also be beneficial to improve the structural robustness. In order to investigate this issue for steel MRF, a parametric study based on pushdown analysis and on the Energy Balance Method is described and discussed in the present paper. With this regard, the following cases are examined: (i) MRF not designed for seismic actions and (ii) MRF designed for seismic actions. The investigated parameters are (i) the number of storeys, (ii) the interstorey height, (iii) the span length, (iv) the building plan layout and (v) the column loss scenario. Results show that the low-rise and long span structures are the most prone to progressive collapse and that the elements in the directly affected zone of the wind designed 8 storey structures respond in the elastic range. Structures designed according to the capacity design principles were found to be less robust than wind designed structures that are characterized by strong beams and weak columns. The number of elements above the removed column and size of beam cross section were found to be key parameters in arresting progressive collapse.

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>

Study of the seismic behavior of rigid and semi-rigid steel moment-resisting frames

2021 ◽  
Vol 186 ◽  
pp. 106910
Author(s):  
Abed Rigi ◽  
Behtash JavidSharifi ◽  
Mohammad Ali Hadianfard ◽  
T.Y. Yang
Keyword(s):  
Seismic Behavior ◽  
Steel Moment Resisting Frames ◽  
Moment Resisting Frames ◽  
Moment Resisting
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