• Structural Engineering and Mechanics
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• v.33 no.2
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• pp.113-136
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• 2009

The seismic induced interaction between multistory structures with unequal story heights (inter-story pounding) is studied taking into account the local response of the exterior beam-column joints. Although several parameters that influence the structural pounding have been studied sofar, the role of the joints local inelastic behaviour has not been yet investigated in the literature as key parameter for the pounding problem. Moreover, the influence of the infill panels as an additional parameter for the local damage effect of the joints on the inter-story pounding phenomenon is examined. Thirty six interaction cases between a multistory frame structure and an adjacent shorter and stiffer structure are studied for two different seismic excitations. The results are focused: (a) on the local response of the critical external column of the multistory structure that suffers the hit from the slab of the adjacent shorter structure, and (b) on the local response of the exterior beam-column joints of the multistory structure. Results of this investigation demonstrate that the possible local inelastic response of the exterior joints may be in some cases beneficial for the seismic behaviour of the critical column that suffers the impact. However, in all the examined cases the developing demands for deformation of the exterior joints are substantially increased and severe damages can be observed due to the pounding effect. The presence of the masonry infill panels has also been proved as an important parameter for the response of the exterior beam-column joints and thus for the safety of the building. Nevertheless, in all the examined inter-story pounding cases the presence of the infills was not enough for the total amelioration of the excessive demands for shear and ductility of the column that suffers the impact.

• 한국터널공학회:학술대회논문집
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• 2005.04a
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• pp.233-247
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• 2005

Most tunnel lining material which has been used in the domestic is a concrete. But many problems as the construction period, the cost, and the crack occurrence for the design, construction, and management were happened in the concrete lining. For this reason, many research institutes like the Korea Highway Corporation recognize the necessity of an alternate material development and grow on the interest for that. So in this study, the seismic behaviour characteristics for the application of the Corrugated Steel Plate Lining in cut-and-cover tunnel are evaluated as several conditions for the backfill height, the cutting slope, and the relative density of backfill soil are changed. The compressive stress which is calculated in the Corrugated Steel Plate Lining by the seismic load is decreased as the backfill height increases and the cut slope grows gentle. Also, the moment shows the tendency of decrease according to the increase of the backfill height. But in the case of the relative density of the backfill soil is small, the moment increases according to the increase of the backfill height and affects the dynamic behaviour characteristic. So it is considered that the relative density of the backfill soil is also the important point. As the result in analyzing the seismic response characteristics of the reinforcement spacing of the Corrugated Steel Plate, the variation in the compressive force is hardly happened, but the moment and the shear force increase on the reinforcement spacing being narrow.

• Earthquakes and Structures
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• v.17 no.1
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• pp.115-129
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• 2019

The effectiveness of an innovative method for the earthquake-resistant rehabilitation of existing poorly detailed reinforced concrete (RC) structures is experimentally investigated herein. Eight column subassemblages were subjected to earthquake-type loading and their hysteretic behaviour was evaluated. Four of the specimens were identical and representative of columns found in RC structures designed in the 1950s-70s period for gravity load only. These original specimens were subjected to cyclic lateral deformations and developed brittle failure mechanisms. Three of the damaged specimens were subsequently retrofitted with innovative high-strength steel fiber-reinforced concrete (HSSFC) jackets. The main variables examined were the jacket width and the contribution of mesh steel reinforcement in the seismic performance of the enhanced columns. The influence of steel fiber volume fraction was also examined using test results of a previous work of Tsonos et al. (2017). The fourth earthquake damaged subassemblage was strengthened with a conventional RC jacket and was subjected to the same lateral displacement history as the other three retrofitted columns. The seismic behaviour of the subassemblages strengthened according to the proposed retrofit scheme was evaluated with respect to that of the original specimens and that of the column strengthened with the conventional RC jacket. Test results clearly demonstrated that the HSSFC jackets effectively prevented the development of shear failure mechanisms, while ensuring a ductile seismic response similar to that of the subassemblage retrofitted with the conventional RC jacket. Ultimately, an indisputable superiority in the overall seismic performance of the strengthened columns was achieved with respect to the original specimens.

• Structural Engineering and Mechanics
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• v.21 no.4
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• pp.469-494
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• 2005

In order to consider the modified seismic response of framed structures in the presence of masonry infills, proper models have to be formulated. Because of the complexity of the problem, a careful definition of an equivalent diagonal pin-jointed strut, able to represent the horizontal force-interstorey displacement cyclic law of the actual infill, may be a solution. In this connection the present paper, continuing a previous work in which a generalised criterion for the determination of the ideal cross-section of the equivalent strut was formulated, analizes some models known in literature for the prediction of the lateral cyclic behaviour discussing their field of validity. As a support of the discussion, the results of an experimental investigation involving single story-single bay infilled reinforced concrete. Frames under vertical and lateral loads with different kind of infill (actually not yet so much investigated) are presented. Finally, an improvement of a model known in the literature is proposed, taking the results of the experimental tests before mentioned into account.

• Structural Engineering and Mechanics
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• v.55 no.1
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• pp.205-228
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• 2015

The results of a numerical investigation pertaining to the hysteretic behaviour of concrete filled steel tubular (CFT) column to I-beam connections are discussed in detail. Following the verification of the numerical results against the available experimental tests, the nonlinear finite element (FE) analysis was implemented to evaluate the effects of different parameters including the column axial load, beam lateral support, shape and arrangement of stiffeners, stiffness of T-stiffeners, and the number of shear stiffeners. Pursuing this objective, an external CFT column to beam connection, tested previously, was selected as the case-study. The lateral forces on the structure were simulated, albeit approximately, using an incremental cyclic loading reversal applied at the beam tip. The results were compared in terms of hysteretic load-displacement curves, stress distributions in connection, strength, rotation, and energy dissipation capacity. It was shown that external T-stiffeners combined with internal shear stiffeners play an important role in the hysteretic performance of CFT columns to I-beam connections.

• Earthquakes and Structures
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• v.9 no.3
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• pp.503-539
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• 2015

A new constitutive model for the representation of the seismic behaviour of steel bars including hardening phenomena is presented. The model takes into account relative slip between bars and concrete, necessary for the estimation of the structural behaviour of r.c. elements and of the level of strain induced by earthquakes on bars. The present work provides the analytical formulation of the post-yielding behaviour of reinforcements, resulting in a continuous axial stress-slip relationship to be implemented in engineering software. The efficacy of the model is proved through the application to a cantilever column, for whose bars the constitutive law is derived.

• Earthquakes and Structures
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• v.11 no.3
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• pp.517-538
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• 2016

This paper presents a probabilistic fragility analysis for two groups of bridges: simply supported and integral bridges. Comparisons are based on the seismic fragility of the bridges subjected to accelerograms of two seismic sources. Three-dimensional finite-element models of the bridges were created for each set of bridge samples, considering the nonlinear behaviour of critical bridge components. When the seismic hazard in the site is controlled by a few seismic sources, it is important to quantify separately the contribution of each fault to the structure vulnerability. In this study, seismic records come from earthquakes that originated in strike-slip and reverse faulting mechanisms. The influence of the earthquake mechanism on the seismic vulnerability of the bridges was analysed by considering the displacement ductility of the piers. An in-depth parametric study was conducted to evaluate the sensitivity of the bridges' seismic responses to variations of structural parameters. The analysis showed that uncertainties related to the presence of lap splices in columns and superstructure type in terms of integral or simply supported spans should be considered in the fragility analysis of the bridge system. Finally, the fragility curves determine the conditional probabilities that a specific structural demand will reach or exceed the structural capacity by considering peak ground acceleration (PGA) and acceleration spectrum intensity (ASI). The results also show that the simply supported bridges perform consistently better from a seismic perspective than integral bridges and focal mechanism of the earthquakes plays an important role in the seismic fragility analysis of highway bridges.

• Journal of Korean Association for Spatial Structures
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• v.24 no.2
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• pp.31-41
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• 2024

This study aims to investigate the seismic response of a large span thin shell structures and assess their displacement under seismic loads. The study employs finite element analysis to model a thin shell structure subjected to seismic excitation. The analysis includes eigenvalue analysis and time history analysis to evaluate the natural frequencies and displacement response of the structure under seismic loads. The findings show that the seismic response of the large span thin shell structure is highly dependent on the frequency content of the seismic excitation. The eigenvalue analysis reveals that the tenth mode of vibration of the structure corresponds to a large-span mode. The time history analysis further demonstrates, with 5% damping, that the displacement response of the structure at the critical node number 4920 increases with increasing seismic intensity, reaching a maximum displacement of 49.87mm at 3.615 seconds. Nevertheless, the maximum displacement is well below the allowable limit of the thin shell. The results of this study provide insight into the behaviour of complex large span thin shell structures as elevated foundations for buildings under seismic excitation, based on the displacement contours on different modes of eigenvalues. The findings suggest that the displacement response of the structure is significant for this new application of thin shell, and it is recommended to enhance the critical displacement area in the next design phase to align with the findings of this study to resist the seismic impact.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.2
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• pp.1-12
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• 1998

The seismic behaviour of rotating machine-foundation systems subjected to six-component nonstationary earthquake ground accelerations is analyzed. The rotating machine-foundation system is idealized by using discs, rotating shaft, fluid-film journal bearings, pedestals, and space frame foundation. Thus, governing equations of motion for the rotating machine-foundation system are obtained by considering Gyroscopic effect, Coriolis effect, dynamic characteristics of fluid-film journal bearings, and translational and rotational motions of seismic rigid base. The influences due to Gyroscopic effects, Coriolis effects, and rotational motions of seismic base on the overall structural response are demonstrated by a numerical example. The results show that the inclusion of base rotations and Gyroscopic effects contributes significantly to the system response.

• Earthquakes and Structures
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• v.7 no.6
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• pp.1259-1281
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• 2014

This research has been conducted in order to investigate the effects of peak ground velocity (PGV) of near-field earthquakes on base-isolated structures mounted on Single Friction Pendulum (SFP), Double Concave Friction Pendulum (DCFP) and Triple Concave Friction Pendulum (TCFP) bearings. Seismic responses of base-isolated structures subjected to simplified near field pulses including the forward directivity and the fling step pulses are considered in this study. Behaviour of a two dimensional single story structure mounting on SFP, DCFP and TCFP isolators investigated employing a variety range of isolators and the velocity (PGV) of the forward directivity and the fling step pulses as the main variables of the near field earthquakes. The maximum isolator displacement and base shear are selected as main seismic responses. Peak seismic responses of different isolator types are compared to emphasize the efficiency of each one under near field earthquakes. It is demonstrated that rising the PGVs increases the isolator displacement and base shear of structure. The effects of the forward directivity are greater than the fling step pulses. Furthermore, TCFP isolator is more effective to control the near field effects than the other friction pendulum isolators are. This efficiency is more significant in pulses with longer period and greater PGVs.