• Smart Structures and Systems
• /
• v.4 no.2
• /
• pp.221-232
• /
• 2008

This paper represents the final results of a research program sponsored by the European Commission through project WIND-CHIME ($\underline{W}$ide Range Non-$\underline{IN}$trusive $\underline{D}$evices toward $\underline{C}$onservation of $\underline{HI}$storical Monuments in the $\underline{ME}$diterranean Area), in which the possibility of using advanced seismic protection technologies to preserve historical monuments in the Mediterranean area is investigated. In the current research, the dynamic characteristics of two outstanding Mamluk-Style minarets, which similar minarets were reported to experience extensive damage during Dahshur 1992 earthquake, are investigated. The first minaret is the Qusun minaret (1337 A.D, 736 Hijri Date (H.D)) located in El-Suyuti cemetery on the southern side of the Salah El-Din citadel. The minaret is currently separated from the surrounding building and is directly resting on the ground (no vaults underneath). The total height of the minaret is 40.28 meters with a base rectangular shaft of about 5.42 ${\times}$ 5.20 m. The second minaret is the southern minaret of Al-Sultaniya (1340 A.D, 739 H.D). It is located about 30.0 meters from Qusun minaret, and it is now standing alone but it seems that it used to be attached to a huge unidentified structure. The style of the minaret and its size attribute it to the first half of the fourteenth century. The minaret total height is 36.69 meters and has a 4.48 ${\times}$ 4.48 m rectangular base. Field investigations were conducted to obtain: (a) geometrical description of the minarets, (b) material properties of the minarets' stones, and (c) soil conditions at the minarets' location. Ambient vibration tests were performed to determine the modal parameters of the minarets such as natural frequencies and mode shapes. A $1/16^{th}$ scale model of Qusun minaret was constructed at Cairo University Concrete Research Laboratory and tested under free vibration with and without SMA wire dampers. The contribution of SMA wire dampers to the structural damping coefficient was evaluated under different vertical loads and vibration amplitudes. Experimental results were used along with the field investigation data to develop a realistic 3-D finite element model that can be used for seismic risk evaluation of the minarets. Examining the updated finite element models under different seismic excitations indicated the vulnerability of such structures to earthquakes with medium to high a/v ratio. The use of SMA wire dampers was found feasible for reducing the seismic risk for this type of structures.

• Journal of the Society of Disaster Information
• /
• v.14 no.4
• /
• pp.450-457
• /
• 2018

Purpose: The evaluation of seismic performance of critical structures has been emerging a key issue in Korea, since a magnitude 5.8 earthquake, the worst in Koran history, struck Gyeongju, southern area in Korea on september 12th, 2016. In particular, the catastrophic failure of nonstructural components such as sprinkler piping systems can cause significant economic loss or loss of life during and after an earthquake. The nonstructural components can be more fragile than structural components in seismic behavior. Method: This study presents the seismic performance evaluation of fire protection piping system, using coupled building-piping system installed with Triple Friction Pendulum Bearings (TPBs). Kobe (Japan), Kocaeli (Turkey), and GyeongJu (Korea) were selected to consider the uncertainty of ground motions in this study. Result: In the simulation results, it was observed that the reduction of maximum displacements of the piping system with the TPBs' system was significant: Kobe, Kocaeli, and Gyeongju cases were 49%, 14.4% and 21.5%, respectively. Conclusion: Therefore, using seismically isolated system in a building-piping system can be more effective to reduce the seismic risk than a normally installed building-piping systems without TPBs in strong earthquakes.

• Earthquakes and Structures
• /
• v.14 no.5
• /
• pp.425-436
• /
• 2018

The design of seismically isolated structures considering the stochastic nature of excitations, base isolators' design parameters, and superstructure properties requires robust reliability analysis methods to calculate the failure probability of the entire system. Here, by applying artificial neural networks, we proposed a robust technique to accelerate the estimation of failure probability of equipped isolated structures. A three-story isolated building with susceptible facilities is considered as the analytical model to evaluate our technique. First, we employed a sensitivity analysis method to identify the critical sources of uncertainty. Next, we calculated the probability of failure for a particular set of random variables, performing Monte Carlo simulations based on the dynamic nonlinear time-history analysis. Finally, using a set of designed neural networks as a surrogate model for the structural analysis, we assessed once again the probability of the failure. Comparing the obtained results demonstrates that the surrogate model can attain precise estimations of the probability of failure. Moreover, our proposed approach significantly increases the computational efficiency corresponding to the dynamic time-history analysis of the structure.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.03a
• /
• pp.58-69
• /
• 2010

Turkey Eurasia Tunnel Project is large scale road construction project of which the total length is 14.6km. The subsea shield TBM tunnel will be constructed under Bosphorus strait and the project site is in poor condition as composite ground, high water pressure and earthquake. The design procedure of subsea tunnel was introduced with tender design materials. That procedure contains tunnel type, TBM type and the principal design items considering geological condition such as high water pressure, composite ground and seismic area. This paper states the progress for geotechnical investigation, seismic analysis and TBM tunnel design. Analysis for geotechnical investigation is in progress, aseismatic design is going on stability study for liquefaction and structure. In addition, the performance of shield TBM to be considered such as advance rate and improvement of TBM was reviewed. The plan of fire safety was also reviewed with respect to fire protection.

• Structural Engineering and Mechanics
• /
• v.75 no.2
• /
• pp.229-237
• /
• 2020

The steel slit shear wall (SSSW), made by cutting vertical slits in a steel plate, is increasingly used for the seismic protection of building structures. In the domain of thin plate shear walls, the out-of-plane buckling together with the potential fracture developed at slit ends at large lateral deformation may result in degraded shear strength and energy dissipation, which is not desirable in view of seismic design. To address this issue, the present study proposed a new type of SSSW made by intentionally introducing initial out-of-plane folding into the originally flat slitted plate. Quasi-static cyclic tests on three SSSWs with different amplitudes of introduced out-of-plane folding were conducted to study their shear strength, elastic stiffness, energy dissipation capacity and buckling behavior. By introducing proper amplitude of out-of-plane folding into the SSSW fracture at slit ends was eliminated, plumper hysteretic behavior was obtained and there was nearly no strength degradation. A method to estimate the shear strength and elastic stiffness of the new SSSW was also proposed.

• Structural Engineering and Mechanics
• /
• v.46 no.4
• /
• pp.487-504
• /
• 2013

In the present work a new friction device, with a set of single or double rotational friction flanges and a link element, is described and tested. The mechanism may be applied for the strengthening of existing r/c or steel buildings as well as in new constructed buildings. The device has selectable variable behavior in different levels of displacement and an interlock mechanism that is provided by the link element. The link element may be designed to lock at preselected level of displacement, offering in this way an extra safety reserve against strong earthquakes. A summary of the existing literature about other similar mechanisms is initially presented in this paper. The proposed mechanism is presented and described in details. Laboratory experiments are presented in detail and the resulted response that proves the efficiency of the mechanism at selectable levels of strength capacity is discussed. Drawings of the mechanism attached to a r/c frame with connection details are also included. Finally a dynamic analysis of two r/c frames, with and without the proposed mechanism attached, is performed and the resulted response is given. The main conclusion is that the proposed mechanism is a cheap and efficient devise for the improvement of the performance of new or existing framed buildings to seismic loads.

• Earthquakes and Structures
• /
• v.13 no.2
• /
• pp.193-200
• /
• 2017

To overcome the difficulty of performing multi-point response spectrum analysis for engineering structures under spatially varying ground motions (SVGM) using the general finite element code such as ANSYS, an approach has been developed by improving the modelling of the input ground motions in the spectral analysis. Based on the stochastic vibration analyses, the cross-power spectral density (c-PSD) matrix is adopted to model the stationary SVGM. The design response spectra are converted into the corresponding PSD model with appropriate coherency functions and apparent wave velocities. Then elements of c-PSD matrix are summarized in the row and the PSD matrix is transformed into the response spectra for a general spectral analysis. A long-span high-pier bridge under multiple support excitations is analyzed using the proposed approach considering the incoherence, wave-passage and site-response effects. The proposed approach is deemed to be an efficient numerical method that can be used for seismic analysis of large engineering structures under SVGM.

• Journal of Korean Association for Spatial Structures
• /
• v.21 no.3
• /
• pp.51-60
• /
• 2021

As earthquakes continue to occur in Korea in recent years, seismic evaluation and retrofit of existing school buildings have been carried out. Many domestic school buildings were built using or referring to standard drawings. Therefore, if the overall structural characteristics of a school building can be known first based on standard drawings, it can be provided as valuable data for detailed seismic evaluation. For this reason, this study investigated the weak structural components and failure modes by comparing the strength of beams, columns, and joints constituting standard school buildings constructed in the 1980s. The evaluation was performed for different types of standard drawings and different material strengths. The results showed that the joint was mainly the weakest due to the eccentricity, and the failure modes were partially changed depending on the material strength.

• Structural Engineering and Mechanics
• /
• v.82 no.3
• /
• pp.325-341
• /
• 2022

Previous major earthquakes indicated that the earthquake induced ground motions are typical non-stationary processes, which are non-stationary in both amplification and frequency. For the convenience of aseismic design and analysis, it usually assumes that the ground motions at structural supports are stationary processes. The development of time-frequency analysis technique makes it possible to evaluate the non-stationary responses of engineering structures subjected to non-stationary inputs, which is more general and realistic than the analysis method commonly used in engineering. In this paper, the wavelet-based stochastic vibration analysis methodology is adopted to calculate the non-stationary responses of multi-support structures. For comparison, the stationary response based on the standard random vibration method is also investigated. A frame structure and a two-span bridge are analyzed. The effects of non-stationary spatial ground motion and local site conditions are considered, and the influence of structural property on the structural responses are also considered. The analytical results demonstrate that the non-stationary spatial ground motions have significant influence on the response of multi-support structures.

• Earthquakes and Structures
• /
• v.27 no.1
• /
• pp.57-67
• /
• 2024

To assess the seismic performance of Plate-Shell Integrated Concrete Liquid-Storage Structure (PSICLSS), a scaled test model was constructed. This model incorporated a hybrid isolation system, which combined shape memory alloy (SMA), lead-cored rubber isolation bearing (LRB) and sliding isolation bearing (SB). By conducting shaking table test, the dynamic responses of both non-isolated and hybrid-isolated PSICLSS were analyzed. The results show that the hybrid isolation system can effectively reduce the acceleration and displacement responses of the structure. However, it also results in an increase in local hydrodynamic pressure and liquid sloshing height. Under extreme earthquake action, the displacement of isolation layer is small. When vertical ground motion is taken into account, the shock absorption rate of horizontal acceleration decreases. The peak hydrodynamic pressure increases significantly, and the peak hydrodynamic pressure position also changes. The maximum displacement of isolation layer increases, the residual displacement decreases.