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Moment-resisting Frames (moment-resisting + frame)
Selected AbstractsIncremental dynamic analysis for estimating seismic performance sensitivity and uncertainty ,EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 2 2010Dimitrios Vamvatsikos Abstract Incremental dynamic analysis (IDA) is presented as a powerful tool to evaluate the variability in the seismic demand and capacity of non-deterministic structural models, building upon existing methodologies of Monte Carlo simulation and approximate moment-estimation. A nine-story steel moment-resisting frame is used as a testbed, employing parameterized moment-rotation relationships with non-deterministic quadrilinear backbones for the beam plastic-hinges. The uncertain properties of the backbones include the yield moment, the post-yield hardening ratio, the end-of-hardening rotation, the slope of the descending branch, the residual moment capacity and the ultimate rotation reached. IDA is employed to accurately assess the seismic performance of the model for any combination of the parameters by performing multiple nonlinear timehistory analyses for a suite of ground motion records. Sensitivity analyses on both the IDA and the static pushover level reveal the yield moment and the two rotational-ductility parameters to be the most influential for the frame behavior. To propagate the parametric uncertainty to the actual seismic performance we employ (a) Monte Carlo simulation with latin hypercube sampling, (b) point-estimate and (c) first-order second-moment techniques, thus offering competing methods that represent different compromises between speed and accuracy. The final results provide firm ground for challenging current assumptions in seismic guidelines on using a median-parameter model to estimate the median seismic performance and employing the well-known square-root-sum-of-squares rule to combine aleatory randomness and epistemic uncertainty. Copyright © 2009 John Wiley & Sons, Ltd. [source] Seismic performance of a 3D full-scale high-ductility steel,concrete composite moment-resisting structure,Part I: Design and testing procedureEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 14 2008A. Braconi Abstract A multi-level pseudo-dynamic (PSD) seismic test programme was performed on a full-scale three-bay two-storey steel,concrete composite moment-resisting frame built with partially encased composite columns and partial-strength connections. The system was designed to provide strength and ductility for earthquake resistance with energy dissipation located in ductile components of beam-to-column joints including flexural yielding of beam end-plates and shear yielding of the column web panel zone. In addition, the response of the frame depending on the column base yielding was analysed. Firstly, the design of the test structure is presented in the paper, with particular emphasis on the ductile detailing of beam-to-column joints. Details of the construction of the test structure and the test set-up are also given. The paper then provides a description of the non-linear static and dynamic analytical studies that were carried out to preliminary assess the seismic performance of the test structure and establish a comprehensive multi-level PSD seismic test programme. The resulting test protocol included the application of a spectrum-compatible earthquake ground motion scaled to four different peak ground acceleration levels to reproduce an elastic response as well as serviceability, ultimate, and collapse limit state conditions, respectively. Severe damage to the building was finally induced by a cyclic test with stepwise increasing displacement amplitudes. Copyright © 2008 John Wiley & Sons, Ltd. [source] Seismic performance of a 3D full-scale high-ductile steel,concrete composite moment-resisting frame,Part II: Test results and analytical validationEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 14 2008A. Braconi Abstract This paper presents the results of a multi-level pseudo-dynamic seismic test program that was performed to assess the performance of a full-scale three-bay, two-storey steel,concrete composite moment-resisting frame built with partially encased composite columns and partial-strength beam-to-column joints. The system was designed to develop a ductile response in the joint components of beam-to-column joints including flexural yielding of beam end plates and shear yielding of the column web panel zone. The ground motion producing the damageability limit state interstorey drift caused minor damage while the ultimate limit state ground motion level entailed column web panel yielding, connection yielding and plastic hinging at the column base connections. The earthquake level chosen to approach the collapse limit state induced more damage and was accompanied by further column web panel yielding, connection yielding and inelastic phenomena at column base connections without local buckling. During the final quasi-static cyclic test with stepwise increasing displacement,amplitudes up to an interstorey drift angle of 4.6%, the behaviour was ductile although cracking of beam-to-end-plate welds was observed. Correlations with numerical simulations taking into account the inelastic cyclic response of beam-to-column and column base joints are also presented in the paper together. Inelastic static pushover and time history analysis procedures are used to estimate the structural behaviour and overstrength factors of the structural system under study. Copyright © 2008 John Wiley & Sons, Ltd. [source] Multiobjective heuristic approaches to seismic design of steel frames with standard sectionsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 11 2007M. Ohsaki Abstract Seismic design problem of a steel moment-resisting frame is formulated as a multiobjective programming problem. The total structural (material) volume and the plastic dissipated energy at the collapse state against severe seismic motions are considered as performance measures. Geometrically nonlinear inelastic time-history analysis is carried out against recorded ground motions that are incrementally scaled to reach the predefined collapse state. The frame members are chosen from the lists of the available standard sections. Simulated annealing (SA) and tabu search (TS), which are categorized as single-point-search heuristics, are applied to the multiobjective optimization problem. It is shown in the numerical examples that the frames that collapse with uniform interstorey drift ratios against various levels of ground motions can be obtained as a set of Pareto optimal solutions. Copyright © 2007 John Wiley & Sons, Ltd. [source] A Distributed Object-Oriented Finite-Element Analysis Program ArchitectureCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 5 2001Hung-Ming Chen This article presents a distributed object-oriented design for a nonlinear finite-element analysis using the message-passing paradigm and a single-program, multiple-data scheme. The architecture is an extension of an existing sequential object-oriented architecture. The design recognizes the costly communication startup time penalty by attempting to minimize the frequency of communications. This is facilitated by distributing not only the elements in the model but also their associated nodes and mapping between the degrees of freedom and the analytical equations of equilibrium. The proposed object design was implemented and tested on a nonlinear static pushover analysis of three moment-resisting frames. [source] Rigid-plastic models for the seismic design and assessment of steel framed structuresEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 14 2009C. Málaga-Chuquitaype Abstract This paper demonstrates the applicability of response history analysis based on rigid-plastic models for the seismic assessment and design of steel buildings. The rigid-plastic force,deformation relationship as applied in steel moment-resisting frames (MRF) is re-examined and new rigid-plastic models are developed for concentrically-braced frames and dual structural systems consisting of MRF coupled with braced systems. This paper demonstrates that such rigid-plastic models are able to predict global seismic demands with reasonable accuracy. It is also shown that, the direct relationship that exists between peak displacement and the plastic capacity of rigid-plastic oscillators can be used to define the level of seismic demand for a given performance target. Copyright© 2009 John Wiley & Sons, Ltd. [source] Pure aluminium shear panels as dissipative devices in moment-resisting steel framesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 7 2007G. De Matteis Abstract The use of energy dissipation systems for the seismic control of steel structures represents a valid alternative to conventional seismic design methods. The seismic devices currently employed are mostly based on the metallic yielding technology due to the large feasibility and efficiency they can provide. Within this context, in the current paper an innovative solution based on the adoption of low-yield-strength pure aluminium shear panels (SPs) for seismic protection of steel moment-resisting frames is proposed and investigated. In order to prove the effectiveness of the system, a wide numerical study based on both static and dynamic non-linear analyses has been carried out, considering a number of different frame-to-shear panel combinations, aiming at assessing the effect of the main influential parameters on the seismic response of the structure. The obtained results show that the contribution provided by aluminium SPs is rather significant, allowing a remarkable improvement of the seismic performance of the structure in terms of stiffness, strength and ductility, with the possibility to strongly limit the damage occurring in the members of moment-resisting frames. In particular, it is clearly emphasized that the stiffening effect provided by SPs allows a more rational design procedure to be adopted, since the serviceability limit state check does not lead to unavoidable and uneconomical increase of the size of main structural members. Copyright © 2007 John Wiley & Sons, Ltd. [source] Evaluation of residual drift demands in regular multi-storey frames for performance-based seismic assessmentEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 13 2006Jorge Ruiz-García Abstract This paper summarizes results of a comprehensive analytical study aimed at evaluating the amplitude and heightwise distribution of residual drift demands in multi-storey moment-resisting frames after earthquake excitation. For that purpose, a family of 12 one-bay two-dimensional generic frame models was subjected to an ensemble of 40 ground motions scaled to different intensities. In this investigation, an inelastic ground motion intensity measure was employed to scale each record, which allowed reducing the record-to-record variability in the estimation of residual drift demands. The results were statistically processed in order to evaluate the influence of ground motion intensity, number of stories, period of vibration, frame mechanism, system overstrength, and hysteretic behaviour on central tendency of residual drift demands. In addition, a special emphasis was given to evaluate the uncertainty in the estimation of residual drift demands. Results of incremental dynamic analyses indicate that the amplitude and heightwise distribution of residual drift demands strongly depends on the frame mechanism, the heightwise system structural overstrength and the component hysteretic behaviour. An important conclusion for performance-based assessment is that the evaluation of residual drift demands involves significantly larger levels of uncertainty (i.e. record-to-record variability) than that of maximum drift demands, which suggests that this variability and corresponding uncertainty should be explicitly taken into account when estimating residual drift demands during performance-based seismic assessment of frame buildings. Copyright © 2006 John Wiley & Sons, Ltd. [source] Seismic performance and new design procedure for chevron-braced framesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 4 2006Edoardo M. Marino Abstract The paper is concerned with the seismic design of steel-braced frames in which the braces are configured in a chevron pattern. According to EuroCode 8 (EC8), the behaviour factor q, which allows for the trade-off between the strength and ductility, is set at 2.5 for chevron-braced frames, while 6.5 is assigned for most ductile steel moment-resisting frames. Strength deterioration in post-buckling regime varies with the brace's slenderness, but EC8 adopts a unique q value irrespective of the brace slenderness. The study focuses on reevaluation of the q value adequate for the seismic design of chevron-braced frames. The present EC8 method for the calculation of brace strength supplies significantly different elastic stiffnesses and actual strengths for different values of brace slenderness. A new method to estimate the strength of a chevron brace pair is proposed, in which the yield strength (for the brace in tension) and the post-buckling strength (for the brace in compression) are considered. The new method ensures an identical elastic stiffness and a similar strength regardless of the brace slenderness. The advantage of the proposed method over the conventional EC8 method is demonstrated for the capacity of the proposed method to control the maximum inter-storey drift. The q values adequate for the chevron-braced frames are examined in reference to the maximum inter-storey drifts sustained by most ductile moment-resisting frames. When the proposed method is employed for strength calculation, the q value of 3.5 is found to be reasonable. It is notable that the proposed method does not require larger cross-sections for the braces compared to the cross-sections required for the present EC8 method. Copyright © 2005 John Wiley & Sons, Ltd. [source] Earthquake behavior of structures with copper energy dissipatorsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2004Juan C. De la Llera Abstract The earthquake behavior of structures with supplemental copper dampers is evaluated in this study. The investigation is divided into two parts: (i) an experimental work with seven pairs of hourglass copper dampers of different aspect ratios and side profiles; and (ii) a parametric study of 6-, 12-, and 25-story planar structures with elastic as well as inelastic behavior in the primary structure and copper dampers. The copper used in this study is electrolytic tough pitch (ETP) copper C11000; probably the most commonly used of all coppers; ductile, with a low-yield, and highly resistant to corrosion. Experimental results demonstrate that all copper plates reached stable angular distortions of the order of ,=25%, which implies transverse distortions in the devices larger than 40mm. The behavior of the devices is highly dependent on the aspect ratio of the plate, h/t, and a recommendation is made to use plates in the range 11 h/t,18. Plates beyond this range exhibit either large stress and strain concentrations in the neck of the device or a strong influence of axial deformations in their cyclic behavior. The inelastic earthquake response of structures with such devices shows that drift reduction factors of the order of 30 to 40% can be achieved with reasonably economic designs. It is also shown that the efficiency of these devices depends on the soil conditions and flexibility of the primary structure. Finally, it is concluded that supplemental copper dampers are a good alternative for drift reduction in a wide range of structural layouts, ranging from coupled shear-wall systems to moment-resisting frames, and for impulsive as well as non-impulsive ground motions. Copyright © 2003 John Wiley & Sons, Ltd. [source] Localization analysis in softening RC frame structuresEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 2 2003Ali R. Khaloo Abstract This paper discusses the sensitivity of softening reinforced concrete frame structures to the changes in input ground motion and investigates the possibility of localizations for this type of structure in static and dynamic analysis. A finite element model is used in which the sections resisting force are calculated using a proposed differential hysteretic model. This model is especially developed for modelling softening behaviour under cyclic loading. To obtain parameters of the differential model the moment,curvature of each section is evaluated using a microplane constitutive law for concrete and bi-linear elasto-plastic law for reinforcements. The capability of the procedure is verified by comparing results with available experimental data at element level, which shows good accuracy of the procedure. The effect of possible changes in ground motion is assessed using a non-stationary Kanai,Tajimi process. This process is used to generate ground motions with approximately the same amplitude and frequency content evolution as those of base ground motion. The possibility of localization in static and dynamic loading is investigated using two structures. A measure for the possibility of localization in code-designed structures is obtained. This study indicates that localization may occur in ordinary moment-resisting structures located in high seismic zones. Localization may result in substantial drift in global response and instability due to P,, effect. Also, it is shown that the structure becomes very sensitive to the input ground motion. It is concluded that allowance by some design codes of the use of ordinary moment-resisting frames in regions with high seismicity should be revised or improvements should be made in the detailing requirements at critical sections of these structures. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||