• Earthquakes and Structures
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• v.15 no.5
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• pp.565-581
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• 2018

This paper proposes a new analytical formulation for computing the seismic input at various levels of a structure in terms of floor response spectra. The approach, which neglects the dynamic interaction between primary structure and secondary element, is particularly useful for the seismic assessment of secondary and non-structural elements. The proposed formulation has a robust theoretical basis and it is based on few meaningful dynamic parameters of the main building. The method has been validated in the linear and nonlinear behavior of the main building through results coming from both experimental tests (available in literature) and parametric numerical analyses. The conditions, for which the Floor Spectrum Approach and its simplified assumptions are valid, have been derived in terms of specific interval ratios between the mass of the secondary element and the participant mass of the main structure. Finally, a practice-oriented formulation has been derived, which could be easily implementable also at code level.

• Journal of Korean Association for Spatial Structures
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• v.16 no.4
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• pp.91-100
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• 2016

A retractable-roof spatial structure is frequently used for a stadium and sports hall. A retractable-roof spatial structure allows natural lighting, ventilation, optimal conditions for grass growth with opened roof. It can also protects users against various weather conditions and give optimal circumstances for different activities. Dynamic characteristics of a retractable-roof spatial structure is changed based on opened or closed roof condition. A tuned mass damper (TMD) is widely used to reduce seismic responses of a structure. When a TMD is properly tuned, its control performance is excellent. Opened or closed roof condition causes dynamic characteristics variation of a retractable-roof spatial structure resulting in off-tuning. This dynamic characteristics variation was investigated. Control performance of a passive TMD and a smart TMD were evaluated under off-tuning condition.

• Journal of the Korean Society of Safety
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• v.24 no.2
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• pp.55-61
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• 2009

Seismic Safety Analysis of Intake Tower is very important because failure of intake tower may incur huge chaos on the modem society. Recently, there has been growing much concern about earthquake resistance of existing structures. This research demonstrates the dynamic fluid pressure calculation using added mass simulation. The actual safety evaluation has been conducted through not only the static analysis but also the dynamic analysis. According to the analysis results, the vibration incurred by earthquake may induce considerable damage to the hydraulic structure. Therefore, the appropriate design process out of exact calculation is quite necessary.

• Journal of the Korean Society of Safety
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• v.32 no.5
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• pp.47-53
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• 2017

In this study, we propose a new control system that effectively utilizes the interaction effect of control force through the connection of stiffness member for seismic performance enhancement of two adjacent structures equipped with active tuned mass damper (ATMD). The efficiency of the proposed control system is verified by comparing with the existing independent control system through the numerical simulations of the 10th- and 12th-story buildings. From the numerical results, it is confirmed that the proposed method can show similar or better control performance even with more economical control capacity than the existing independent control system. Another advantage is that the existing system does not exhibit the adaptive control performance in emergency of failure of one control device, whereas the proposed system can achieve successful adaptive control performance by economically and efficiently utilizing the interacting control effect through the connection member.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1997.04a
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• pp.225-232
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• 1997

A study of effects of design parameters on the seismic responses of base isolated structure is performed to reduce the seismic responses using a linear tw0-degree of freedom system and a lumped-mass model of a nuclear power p;ant(NPP). From the simplified 2 DOF system the optimal isolation frequency being less than 1/10th of the fundamental frequency of superstructure is obtained, and the isolator damping minimizing the peak acceleration depends on superstructure frequency. From the time history analyses for lumped mass model of NPP the optimal damping is calculated as 40% in containment building and 65% in reactor internal structure. Similar results are obtained in 2 DOF system

• Structural Engineering and Mechanics
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• v.85 no.1
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• pp.55-64
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• 2023

Energy-based seismic design and evaluation methods are promising to be involved in the next generation design codes. Accordingly, determining the distribution of earthquake input energy demand among floor levels is quite imperative in order to develop an energy-based seismic design procedure. In this paper, peak floor input energy demands are achieved from relative input energy response histories of several reinforced concrete (RC) frames. A set of 22 horizontal acceleration histories selected from recorded near-fault earthquakes and scaled in time domain to be compatible with the elastic acceleration design spectra of Turkish Seismic Design Code are used in time history analyses. The distribution of the computed input energy per mass values and the arithmetic means through the height of the considered RC frames are presented as a result. It is found that spatial distribution of input energy per mass is highly affected by the number of stories. Very practical yet consistent formulation of distributing the total input energy to story levels is achieved, as a most important contribution of the study.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2003.03a
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• pp.13-30
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• 2003

In this paper, a new systematic method will be introduced, in which a Rock-mass Prediction System(RPS) predicts the geological conditions and rock mass movements before tunnel excavation and the appropriate counter-measures are taken in the expected weak zones during tunnel construction. The Rock-mass Prediction System(RPS) consists of the LIM, a horizontal core drilling and a seismic exploration method(TSP/HSP). In the Rock-mass Prediction System(RPS), the seismic exploration method (TSP/HSP) gives information on the locations of the weak zones such as major faults and voids in wide-range, and the horizontal core drillings are utilized to find exact location and widths of the faults or voids near the weak zones which was predicted by the seismic exploration method (TSP/HSP). The LIM is used to find the hardness of the rock mass and small weak zones near the excavation face. The Rock-mass Prediction System (RPS) was successfully applied to the Sol-An Tunnel and the effectiveness of the system was verified.

• Structural Engineering and Mechanics
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• v.41 no.6
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• pp.711-734
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• 2012

The foundation of a tall building frame resting on settable soil mass undergoes differential settlements which alter the forces in the structural members significantly. For tall buildings it is essential to consider seismic forces in analysis. The building frame, foundation and soil mass are considered to act as single integral compatible structural unit. The stress-strain characteristics of the supporting soil play a vital role in the interaction analysis. The resulting differential settlements of the soil mass are responsible for the redistribution of forces in the superstructure. In the present work, the nonlinear interaction analysis of a two-bay ten-storey plane building frame- layered soil system under seismic loading has been carried out using the coupled finite-infinite elements. The frame has been considered to act in linear elastic manner while the soil mass to act as nonlinear elastic manner. The subsoil in reality exists in layered formation and consists of various soil layers having different properties. Each individual soil layer in reality can be considered to behave in nonlinear manner. The nonlinear layered system as a whole will undergo differential settlements. Thus, it becomes essential to study the structural behaviour of a structure resting on such nonlinear composite layered soil system. The nonlinear constitutive hyperbolic soil model available in the literature is adopted to model the nonlinear behaviour of the soil mass. The structural behaviour of the interaction system is investigated as the shear forces and bending moments in superstructure get significantly altered due to differential settlements of the soil mass.

• Earthquakes and Structures
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• v.8 no.5
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• pp.1255-1276
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• 2015

The importance of considering soil-structure interaction effect in the analysis and design of RC frame buildings is increasingly recognized but still not penetrated to the grass root level owing to various complexities involved. It is well established fact that the soil-structure interaction effect considerably influence the design of multi-storey buildings subjected to lateral seismic loads. The shear walls are often provided in such buildings to increase the lateral stability to resist seismic lateral loads. In the present work, the linear soil-structure analysis of a G+5 storey RC shear wall building frame resting on isolated column footings and supported by deformable soil is presented. The finite element modelling and analysis is carried out using ANSYS software under normal loads as well as under seismic loads. Various load combinations are considered as per IS-1893 (Part-1):2002. The interaction analysis is carried out with and without shear wall to investigate the effect of inclusion of shear wall on the total and differential settlements in the footings due to deformations in the soil mass. The frame and soil mass both are considered to behave in linear elastic manner. It is observed that the soil-structure interaction effect causes significant total and differential settlements in the footings. Maximum total settlement in footings occurs under vertical loads and inner footings settle more than outer footings creating a saucer shaped settlement profile of the footings. Each combination of seismic loads causes maximum differential settlement in one or more footings. Presence of shear wall decreases pulling/pushing effect of seismic forces on footings resulting in more stability to the structures.

• Structural Engineering and Mechanics
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• v.85 no.3
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• pp.381-391
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• 2023

The seismic performance of the tall building equipped with a tuned mass damper (TMD) considering soil-structure interaction (SSI) effects is well studied in the literature. However, these studies are performed on the nominal model of the seismic-excited structural system with SSI. Hence, the outcomes of the studies may not valid for the actual structural system. To address the study gap, the reliability theory as a useful and powerful method is utilized in the paper. The present study aims to carry out reliability analyses on tall buildings equipped with TMD under near-field pulse-like (NFPL) ground motions considering SSI effects using a subset simulation (SS) method. In the presence of uncertainties of the structural model, TMD device, foundation, soil, and near-field pulse-like ground motions, the numerical studies are performed on a benchmark 40-story building and the failure probabilities of the structures with and without TMD are evaluated. Three types of soils (dense, medium, and soft soils), different earthquake magnitudes (M_w = 7,0. 7,25. 7,5 ), different nearest fault distances (r = 5. 10 and 15 km), and three seismic performance levels of immediate occupancy (IO), life safety (LS), and collapse prevention (CP) are considered in this study. The results show that tall buildings built near faults and on soft soils are more affected by uncertainties of the structural and ground motion models. Hence, ignoring these uncertainties may result in an inaccurate estimation of the maximum seismic responses. Also, it is found the TMD is not able to reduce the failure probabilities of the structure in the IO seismic performance level, especially for high earthquake magnitudes and structures built near the fault. However, TMD is significantly effective in the reduction of failure probability for the LS and CP performance levels. For weak earthquakes and long fault distances, the failure probabilities of both structures with and without TMD are near zero, and the efficiency of the TMD in the reduction of failure probabilities is reduced by increasing earthquake magnitudes and the reduction of fault distance. As soil softness increases, the failure probability of structures both with and without TMD often increases, especially for severe near-fault earthquake motion.