Seismic response of plane steel MRF with setbacks: Estimation of inelastic deformation demands

Karavasilis, Theodore L.; Bazeos, Nikitas; Beskos, D.E.

doi:10.1016/j.jcsr.2007.12.002

Cited by 65 publications

(43 citation statements)

References 8 publications

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“…As it can be observed, at low intensities (0.1-0.3 g) the highest drifts are clearly localized in the vicinity of the upper setback, but this tendency changes for increasing intensities, as it can be observed for the cases of 0.6 and 0.7 g, in which the highest drifts occur around the lower setback level and, finally, the lowest levels. This is close to the findings by Karavasilis et al (2008), who report an increasingly marked concentration of damage in the proximities of the setbacks with increasing intensity of ground motion. However, their results do not show the shift observed in the present study, but rather an earlier concentration of higher drifts around the upper setback, with a subsequent concentration in the lower setback as well, but keeping the drift magnitudes at around the same level for both setbacks.…”

Section: Resultssupporting

confidence: 90%

“…Even though the results obtained for the trial case study buildings appear to indicate that application of current DDBD procedures to the design of steel moment resisting frames with setbacks can be straight forward, subsequent consideration of the work of Karavasilis et al (2008) leads to believing that a revision of the higher mode reduction factors might be appropriate. In their study, based on results of NLTHAs run on 120 steel frames with setbacks, the authors developed an expression that allows the maximum inter-storey drift to be correlated with the maximum displacement at the top of the frame (i.e.…”

Section: Recommended Modifications To the Higher Mode Reduction Factormentioning

confidence: 95%

“…10, following the ideas of Mazzolani and Piluso (1996), to quantify the degree of irregularity of the frames. Karavasilis et al (2008) found that the estimation of the maximum inter-storey drift using these equations with the maximum roof displacement known leads to a median ratio of approximate to real maximum inter-storey drift of 1.00 and dispersion equal to 0.17 (it is important to notice that the authors express the central value and the dispersion of the approximation with the counted sample median and the standard deviation of the natural logarithm of the ratio of the predicted to the exact value, and that they exclude results associated with the elastic range of response). When applied to the results obtained for the NLTHAs of Frames A and B on a record by record basis (that is, calculating the approximate maximum inter-storey drift using Eq.…”

Section: Recommended Modifications To the Higher Mode Reduction Factormentioning

confidence: 99%

“…Setbacks are one of the most common types of irregularities that can be found, and yet their influence on the seismic response of moment resisting frames is not fully understood. The number of studies conducted on the topic has been increasing in the last years but, as skilfully summarized by Karavasilis et al (2008) and De Stefano and Pintucchi (2007), while some authors find concentration of damage in members located in the vicinity of the setbacks, others report the performance of this kind of structures not to be significantly different from that of regular ones.…”

Section: Introductionmentioning

confidence: 99%

“…The work of Karavasilis et al (2008) is of particular interest for the present study, for it investigates in depth the seismic response of steel frames with setbacks, based on the results of 30 ground motion records run at 4 performance levels for 120 frames. The study found that the localization of damage depends on the geometrical characteristics of the setbacks (which they represent by the calculation of two geometrical indices, after Mazzolani and Piluso 1996) and the intensity of the ground motion.…”

Section: Introductionmentioning

confidence: 99%

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Applicability of the direct displacement-based design method to steel moment resisting frames with setbacks

Nievas

Sullivan

2015

Bull Earthquake Eng

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While quite extensive research has been undertaken during the last decades to extend the direct displacement-based design (DDBD) method to a wide range of structural types and materials, it is recognized that there are still some areas requiring further study and development. Steel structures and, more specifically, steel moment resisting frames with setbacks are one of these and, therefore, this work aims to investigate the seismic response of such structures designed according to the DDBD procedure currently prescribed for regular frames and to elaborate specific recommendations based on the results obtained. The main aspects to be considered are the adequacy of the displacement profile and higher mode reduction factor to be used, as well as the suitable strength distribution required. In a trial application of the current DDBD procedure, two two-dimensional 12-storey frames with setbacks are designed, and the solutions obtained are used to develop models of the structures, which are then subject to a series of non-linear time-history analyses at increasing levels of intensity, using spectrum-compatible scaled accelerograms. The results obtained are contrasted with those of Karavasilis et al. (J Constr Steel Res 64:644-654, 2008), which were developed for steel frames designed via code methods. It is recognized that the DDBD method can benefit from the expressions developed by these authors, and recommendations for the adjustment of the DDBD higher mode reduction factors are subsequently proposed. The efficacy of the latter is evaluated by the design and verification at a range of diverse intensities of a set of two-dimensional frames of 6, 9 and 12 storeys, and satisfactory outcomes are obtained. These results have been fundamental in revealing the need for future research regarding the influence of the design spectral shapes, ductility demand and P-Delta instability in the dynamic amplification of drifts due to higher mode effects.

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Section: Resultssupporting

confidence: 90%

Section: Recommended Modifications To the Higher Mode Reduction Factormentioning

confidence: 95%

Section: Recommended Modifications To the Higher Mode Reduction Factormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Applicability of the direct displacement-based design method to steel moment resisting frames with setbacks

Nievas

Sullivan

2015

Bull Earthquake Eng

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A new evolutionary polynomial regression technique to assess the fundamental periods of irregular buildings

Marasco

Cimellaro

2021

Earthq Engng Struct Dyn

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The main seismic design codes propose simplified formulations to evaluate the fundamental period of regular structures based on the total height. Indeed, the fundamental period depends on several parameters directly connected to the mass and stiffness of the structure and on its geometrical characteristics, including also irregularities. This paper proposes a set of mathematical formulations to evaluate the longitudinal and transversal fundamental period of vibration of 3D Reinforced Concrete (RC) frames, which have various vertical and plan irregularities and for different mechanical and geometrical design parameters.Several types of Reinforced Concrete Bare Moment Resisting Frame (RC-BMRF) buildings have been designed according to the different versions of the Italian codes starting from 1916 to nowadays and then used as case studies. Modal analysis is performed on the entire building dataset to assess the fundamental periods in both longitudinal and transversal directions. Then, cluster analysis is carried out to classify the buildings based on similar design characteristics and construction details. Finally, a robust Evolutionary Polynomial Regression (EPR) technique is used to find the optimal polynomial forms of the natural period. Numerical results show a better performance of the proposed formulation compared with the existing methodologies available in the literature.

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Estimation of seismic drift and ductility demands in planar regular X‐braced steel frames

Karavasilis

Bazeos

Beskos

2007

Earthq Engng Struct Dyn

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This paper summarizes the results of an extensive study on the inelastic seismic response of X-braced steel buildings. More than 100 regular multi-storey tension-compression X-braced steel frames are subjected to an ensemble of 30 ordinary (i.e. without near fault effects) ground motions. The records are scaled to different intensities in order to drive the structures to different levels of inelastic deformation. The statistical analysis of the created response databank indicates that the number of stories, period of vibration, brace slenderness ratio and column stiffness strongly influence the amplitude and heightwise distribution of inelastic deformation. Nonlinear regression analysis is employed in order to derive simple formulae which reflect the aforementioned influences and offer a direct estimation of drift and ductility demands. The uncertainty of this estimation due to the record-to-record variability is discussed in detail. More specifically, given the strength (or behaviour) reduction factor, the proposed formulae provide reliable estimates of the maximum roof displacement, the maximum interstorey drift ratio and the maximum cyclic ductility of the diagonals along the height of the structure. The strength reduction factor refers to the point of the first buckling of the diagonals in the building and thus, pushover analysis and estimation of the overstrength factor are not required. This design-oriented feature enables both the rapid seismic assessment of existing structures and the direct deformation-controlled seismic design of new ones. A comparison of the proposed method with the procedures adopted in current seismic design codes reveals the accuracy and efficiency of the former.

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Seismic response of plane steel MRF with setbacks: Estimation of inelastic deformation demands

Cited by 65 publications

References 8 publications

Applicability of the direct displacement-based design method to steel moment resisting frames with setbacks

Applicability of the direct displacement-based design method to steel moment resisting frames with setbacks

A new evolutionary polynomial regression technique to assess the fundamental periods of irregular buildings

Estimation of seismic drift and ductility demands in planar regular X‐braced steel frames

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