Current seismic design provisions such as ASCE 7-10 provide criteria for selecting ground motions for conducting response history analysis. This study is the sequel of a companion paper (I – Ground Motion Selection) for assessment of the ASCE 7-10 criteria. To assess of the ASCE 7-10 criteria, nonlinear response history analyses of twelve single degree of freedom (SDF) systems and one multi-degree of freedom (MDF) system are conducted in this study. The results show that the target seismic demands for SDF can be predicted using the mean seismic demands over seven and ten ground motions selected according to the proposed method within an error of 30% and 20%, respectively
For estimating the seismic demand of buildings, most seismic design provisions permit conducting linear and nonlinear response history analysis. In order to obtain reliable results from response history analyses, a proper selection of input ground motions is required. In this study, an accurate algorithm for selecting and scaling ground motions is proposed, which satisfies the ASCE 7-10 criteria. In the proposed algorithm, a desired number of ground motions are sequentially scaled and selected from a ground motion library without iterations.
High voltage electric power transmitter GIS(Gas Insulated Switchgear) above 72.5kV needs to satisfy domestic Korean peninsular standard(ES-6110-0002) in KEPCO with respect to normal and special operation conditions which include internal gas pressure, dead weight, wind and seismic load. Some other requirements not described in Korean standard can be applied from other international standards such as IEC(International Electronical Committee) 62271-203 and 62271-207. The GIS is a kind of pressure vessel structure made of aluminum and filled with SF6 gas of internal pressure 0.4~0.5MPa. Finite element analysis of GIS is performed with such operational loads including seismic loading and the stability and reliability is determined according to ASME BPVC(Boiler and Pressure Vessel Code) SEC. VIII standard where the allowable stress level of the pressure vessel is suggested. The result shows that the stress of GIS is satisfied the allowable stress level and the safety factor is about 2.3 for Korean peninsular standard.
In Korea, the occurrence frequency of earthquakes has recently increased, compared with the past. So, the various damages for cultural properties due to earthquake can be expected, and especially fortress structure is vulnerable to earthquake. Therefore, the resonable seismic characteristics evaluation is required to secure the safety for fortress structure with the various construction and configuration types. Also, we should consider the various applied load conditions as design variables. To this end, this study classifies fortress structures according to the construction and configuration types, and then applies the discrete element method to model and analyze fortress structures. Finally, the seismic characteristics is evaluated through slip condition due to the analysis results considering the various design variables.
This study aims to establish a seismic resistance performance evaluation method that makes sure to secure the seismic resistance performance of the existing mid-low story reinforced concrete structures. This study focuses on the development of the seismic resistance performance evaluation method for the overall seismic resistance performance evaluation on the buildings by applying fuzzy theory. This seismic resistance performance evaluation method considers the mutual relations among the type of force, the type of member, the type of story, and the states of deterioration of the buildings. The total seismic resistance performance index from this method was calculated by the intensity weight of each evaluation item, fuzzy measure, fuzzy integration. Moreover, the evaluation methodology was established in this study to identify the performance level of the Immediate Occupancy, Life Safe, Collapse Prevention by applying the fuzzy theory.
The paper presents an experimental evaluation of RC columns retrofitted by TRC(Textile fabric Reinforced Concrete). TRC were made using textile fabric fiber and self leveling mortar. A total of three specimens was constructed and was performed cyclic loading test. One specimen was a non-retrofitted column, while others were retrofitted with textile fabric and sheet type fiber. By comparing with non-retrofitted specimen, the maximum strength and ductility of retrofitted RC column was improved compared to non-retrofitted RC column.
Nonlinear analysis for seismic performance evaluation of existing building usually takes 4~5 times more than linear analysis based on KBC code. To obtain accurate results from the nonlinear analysis, there are a lot of things to be considered for nonlinear analysis modeling. For example, reinforcing layout, applied load and seismic details affect behavior of structural members for the existing building. Engineer-oriented computerized system was developed for engineers to evaluate effective seismic performance of existing buildings with abiding by seismic design principles. Using the engineer-oriented program, seismic performance evaluation of reinforced concrete building was performed. Nonlinear hinge properties were applied with real time multiple consideration such as section layout, section analysis result, applied load and performance levels. As a result, the building was evaluated to satisfy LS(Life Safety) performance level. A comparison between engineer-oriented and program-oriented results is presented to show how important the role of structural engineer is for seismic performance evaluation of existing buildings.
Seismic design of braced frames that simultaneously considers economic issues and structural performance represents a rather complicated engineering problem, and therefore, a systematic and well-established methodology is needed. This study proposes a multi-objective seismic design method for an inverted V-braced frame with suspended zipper struts that uses the non-dominated sorting genetic algorithm-II(NSGA-II). The structural weight and the maximum inter-story drift ratio as the objective functions are simultaneously minimized to optimize the cost and seismic performance of the structure. To investigate which of strength- and performance-based design criteria for braced frames is the critical design condition, the constraint conditions on the two design methods are simultaneously considered (i.e. the constraint conditions based on the strength and plastic deformation of members). The linear static analysis method and the nonlinear static analysis method are adopted to check the strength- and plastic deformation-based design constraints, respectively. The proposed optimal method are applied to three- and six-story steel frame examples, and the solutions improved for the considered objective functions were found.
This research describes the impact of vertical earthquake components on the performance of typical non-ductile bridges. To achieve this goal, this research chooses a non-seismically designed reinforced concrete bridge typically found in the California area. Particularly, their columns with inadequate design have a higher possibility of shear failure. To consider this failure, the column model reflects shear-axial interaction effect and is verified by comparing simulated results and experimental data available in literature. Two computational bridge models having column shear model subjected to constant and varying axial load are then built to conduct inelastic dynamic analyses. The responses are employed to construct probabilistic seismic demand models for two bridge models. This results indicate that the consideration of shear-axial interaction effect increases the seismic demand of all bridge components in non-ductile bridges, resulting in their increased seismic vulnerability.
Recent decades, maintenance and reconstruction have been paid attention to old buildings. Especially, it has been recognized that seismic retrofit measures are necessary for non-reinforced masonry buildings which are used for prevailing building constructions. However, such applications can be limited due to its excessive costs, long-period, and inherent difficulty in securing construction spaces. For this reason, different reinforcement methods have been proposed by previous researchers in the economic manner. This study carried out an adhesive retrofit material upgrading low workability and excessive costs of existing reinforcement methods and, in turn, verified the level of seismic reinforcement throughout experimental studies. In order for the objectives, masonry walls with an aspect ratio of 1.0 were designed and manufactured. Also, effective parameters which are affected by openings, adhesive material types, the number of reinforcement layers, and lateral load levels were established. Experimental results showed that MW specimens without openings were collapsed for low-seismic resistances resulting from rocking failure modes, while strength and displacement capacities were improved for reinforced openings. Also, R-MWO-3F specimens with opening which was enhanced for three layers of stiffener showed displacement, ductility capacities, and energy dissipating capacities in the stable manner, even satisfying the collapse prevention level proposed in the current seismic codes.
This report offers an economically reasonable seismic reinforcement to non-seismic mid/low reinforced concrete structures. Installed a slit in between the reinforced concrete frame and masonry infilled wall then inserted twist bar to prevent inversion and attached to the lower/upper beam. Confirmed the seismic reinforcement effect through static loading test. Total of 4 specimens were produced for the test, a masonry infilled wall without seismic reinforcement and with seismic slit or twist bar applied. As a result, applying the seismic slit and twisted bar was economically reasonable and seismic reinforcement effect was confirmed by showing stable failure, increase of maximum strength and yield displacement, increase of accumulated energy dissipation.
After the Gyeong-ju 9.12 earthquake, we found the necessity of seismic design of nonstructural element is important to reduce damages in view of properties and economic losses. This study focused on the investigation of damages including both properties and human beings. It was found that most of the damages are leaking of water pipe line, rupture of glasses, spalling of roof finishing, cracks of building, and falling from roof. It was also found that the seismic design force of nonstructural elements is taking account into the natural periods, amplification factors, response modification factors to forsee inelastic behaviors. From this studies, it is recommended that more studies are necessary on the seismic design force of nonstructural element.
After an earthquake occurred in the Gyeongju, 2016, many low-story buildings have been questioned in terms of the seismic performance since mostly they have been exempted from the seismic design requirement since 1988. In this study, a 3-story moment resisting frame (MRF) building was analyzed and evaluated the seismic performance. Due to the insufficient seismic performance required for the seismic performance levels, three different seismic retrofit schemes were proposed and their seismic performances were re-evaluated. While steel brace and open shear wall retrofit systems mainly focused on the strength retrofit, the VES damper retrofit system is mainly to enhance the energy dissipation capacity of the system and resultes in the increased ductility. The original building and 3 retrofitted buildings were evaluated using the nonlinear static and nonlinear dynamic analyses and suggestions were proposed. Through the analysis of nonlinear time history and push-over using MIDAS/Gen program, damages of the building in terms of top story and average story drift and effect of reinforcement were analyzed.
This paper investigates seismic performance of a small-sized single story building in Korea. Nonlinear pushover anlaysis is performed to verify shear failure of RC short columns eventually led to performance degradation. Also, nonlinear time history analysis is performed using the same earthquakes from Gyeongju. Similar failure mode was obtained as in the report where a sudden rupture of the RC columns happened.
This paper investigates seismic damage potential of recent September 12 M5.8 Gyeongju earthquake from diverse earthquake engineering perspectives using the accelerograms recorded at three stations near the epicenter. In time domain, strong motion durations are evaluated based on the accelerograms and compared with statistical averages of the ground motions with similar magnitude, epicentral distance and soil conditions, while Fourier analysis using FFT is performed to identify damaging frequency contents contained in the earthquake. Effective peak ground accelerations are evaluated from the calculated response spectra and compared with apparent peak ground accelerations and the design spectrum in KBC 2016. All these results are used to consistently explain the reason why most of seismic damage in the earthquake was concentrated on low-rise stiff buildings but not quite significant. In order to comparatively appraise the damage potential, the constant ductility spectrum constructed from the Gyeongju earthquake is compared with that of the well-known 1940 El Centro earthquake. Deconvolution analysis by using one accelerogram speculated to be recorded at a stiff soil site is also performed to estimate the soil profile conforming to the response spectrum characteristics. Finally, response history analysis for 39- and 61-story tall buildings is performed as a case study to explain significant building vibration felt on the upper floors of some tall buildings in Busan area during the Gyeongju earthquake. Seismic design and retrofit implications of M5.8 Gyeongju earthquake are summarized for further research efforts and improvements of relevant practice.
In this paper, some popular intensity measures of earthquakes including magnitude, MMI, and PGA as well as their empirical relationships are briefly reviewed since they have been widely used without prudence by mass media, the public, and even the government when asking or expressing the seismic capacity of buildings. The basic concept of current seismic design is also presented in order to facilitate relevant discussions. It is emphasized that expressing the building seismic capacity simplistically in terms of seismological quantities or terminologies like magnitude and MMI is inherently irrational, may be misleading the stakeholders, and should be avoided. Alternative expressions, more rational and consistent with current seismic design philosophy and practice, are recommended.
Secure operation of hospitals during and right after earthquake is essential. Past lessons from earthquake damages have shown that most of the injured and the death occurred within 30 minutes after earthquake and the portion of nonstructural damage has become significant. However, hospital buildings in Korea have not prepared fully to address such rising issues. This paper is to study what type of damage patterns are related to hospital buildings and how to develop a preparedness plan to keep hospitals operational at all earthquakes if possible. This paper first reviews on past earthquake damages reported as critical to hospital buildings while classifying them into four groups: (1) structural element; (2) architectural-nostructural element; (3) medical equipments and contents; and (4) utility facility. Upon such classification, some detailed concerns can be specified under each group explicitly. Then a hierarchy for hospital building is also developed for the classified groups, which enables us to identify required things for the enhancement of seismic performance of hospital building that consists of heterogeneous elements. To upgrade the level of seismic performance for existing hospital buildings, the concept of performance-based approach can be adopted to address the heterogeneous problems in a systematic and stepwise manner. Finally a conceptual framework for the seismic risk assessment for hospital building is proposed toward the seismic enhancement of hospital buildings using performance-based approach.