• Journal of the Earthquake Engineering Society of Korea
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• v.21 no.4
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• pp.163-170
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• 2017

The need for eco-friendly building materials such as engineered wood has increased to reduce carbon emissions. Although the range and height of engineered wood buildings are gradually increasing in North America and Europe, engineered wood is mainly used for low-rise residential buildings in Korea. In order to reduce carbon emissions more, therefore, it needs to expand the use of engineered wood by applying it to various buildings with different uses or more stories. With this background, the aim of this study is to investigate the applicability of engineered wood for 9-story office buildings. Since a 9-story building with engineered wood only is not allowed in KBC, an example building has RC ordinary shear walls as the lateral force resisting system while engineered wood is only used for gravity load resisting moment frames. Another example building is also used for comparison where both lateral and gravity load resisting systems are designed by RC. The applicability of engineered wood is investigated by comparing the seismic performance and the amount of carbon emission of both buildings. The result shows that the seismic performance of both buildings was not significantly different while the amount of carbon emission of the engineered wood building was much less then the RC building. Based on this result, engineered wood is sufficiently applicable to 9-story office buildings even though it still needs to pay attention to the shear design of reinforce concrete walls.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.192-194
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• 1993

In this paper, a silicon piezoresistive accelerometer of which the cantilevers have uniform thickness is designed and fabricated with SOI wafer. The accelerometer consists of a seismic mass and four cantilevers, and is fabricated mainly by the anisotropic etching method using EPW etchant. The fabrication processes are that of the frontside processes including the etching of the cantilevers and the doubleside alignment holes, the diffusion of the piezoresisters and patterning of the contact windows, and the metal connection process, and that of the backside processes including the etching of the shallow cavity and the seismic mass. Because of the uniformity of thickness, the performance of the accelerometer fabricated with SOI wafer is expected to be better than that of accelerometer fabricated by the time-controlled etching method.

• Advances in Computational Design
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• v.3 no.3
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• pp.233-267
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• 2018

Conventional seismic design of concentrically braced frame (CBF) structures suggests that the gusset plate connecting a steel brace to beams and/or columns should be designed as non-dissipative in earthquakes, while the steel brace members should be designed as dissipative elements. These design intentions lead to thicker and larger gusset plates in design on one hand and a potentially under-rated contribution of gusset plates in design, on the other hand. In contrast, research has shown that compact and thinner gusset plates designed in accordance with the elliptical clearance method rather than the conventional standard linear clearance method can enhance system ductility and energy dissipation capacity in concentrically braced steel frames. In order to assess the two design methods, six cyclic push-over tests on full scale models of concentric braced steel frame structures were conducted. Furthermore, a 3D finite element (FE) shell model, incorporating state-of-the-art tools and techniques in numerical simulation, was developed that successfully replicates the response of gusset plate and bracing members under fully reversed cyclic axial loading. Direct measurements from strain gauges applied to the physical models were used primarily to validate FE models, while comparisons of hysteresis load-displacement loops from physical and numerical models were used to highlight the overall performance of the FE models. The study shows the two design methods attain structural response as per the design intentions; however, the elliptical clearance method has a superiority over the standard linear method as a fact of improving detailing of the gusset plates, enhancing resisting capacity and improving deformability of a CBF structure. Considerations were proposed for improvement of guidelines for detailing gusset plates and bracing members in CBF structures.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.3 s.49
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• pp.85-100
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• 2006

This paper proposes an optimal design method of linear viscous dampers for the seismic performance of two adjacent structures with different heights. Accordingly, connection method using diagonal bracing between two floors and connection method between two structures are considered, and the effectiveness of the latter method is confirmed through the comparison of the frequency response functions with respect to damping capacity. Moreover, optimal damping to minimize the response of the adjacent structures in the frequency domain is found. The sensitivity of natural frequency and modal damping according to the damper capacity at each floor is obtained for the optimally designed system. From the sensitivity analysis, the modal damping is evaluated to be very sensitive to the damper installed at higher floor. Therefore, sensitivity-based damping distribution method is proposed. Diagonal bracing connection method, uniform distribution method and sensitivity-based distribution method are compared to each other in terms of seismic performance. The comparative results demonstrate that the proposed method is an effective seismic design method for the adjacent structures.

• Computers and Concrete
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• v.2 no.2
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• pp.147-164
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• 2005

This paper summarizes an experimental study on the seismic behavior of lower stories of a mid-rise reinforced concrete frame building. Two reinforced concrete frames with two stories and one span were tested and each frame represents lower two stories of an 11-story RC frame building. Both frames were designed in accordance with Japanese design guidelines and were identical except in the variation of axial force. The tests demonstrated that the overall load-displacement relations of the two frames were nearly the same and the first-story column shear was closely related to the column axial load. The columns and beams elongated during both of the tests, with the second-floor beam elongation exceeding 1.5% of the beam clear span length. The frame with higher axial loads developed more cracks that the frame under moderate axial load.

• Steel and Composite Structures
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• v.28 no.2
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• pp.123-138
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• 2018

Eccentrically braced frames (EBF) represent an optimal structural solution for seismic prone areas, being able to provide high dissipative capacity and good elastic stiffness, to withstand strong seismic events without significant loss of bearing capacity and to avoid damage to non-structural elements in case of low and moderate earthquakes. The accurate knowledge of the cyclic behaviour of the dissipative links, characterizing the whole performance of EBFs, is required to optimize the structural properties and to refine the design techniques adopted for multi-storey buildings' analysis. Reliable numerical models for the links, at the same time requiring a limited computational effort, are then needed. The present work shows the results of a wide experimental test campaign executed on real-scale one storey/one bay frames with horizontal and vertical links, together with the elaboration of a simple semi-analytical model for the quick representation of the cyclic behaviour of shear links.

• Earthquakes and Structures
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• v.10 no.3
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• pp.645-667
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• 2016

The 750 m long "De Bosset" bridge in the Cephalonia Island of Western Greece, being the area with the highest seismicity in Europe, was constructed in 1830 by successive stone arches and stiff block-type piers. The bridge suffered extensive damages during past earthquakes, such as the strong M7.2 earthquake of 1953, followed by poorly-designed reconstruction schemes with reinforced concrete. In 2005, a multidisciplinary project for the seismic assessment and restoration of the "De Bosset" bridge was undertaken under the auspices of the Greek Ministry of Culture. The proposed retrofitting scheme combining soil improvement, structural strengthening and reconstruction of the deteriorated masonry sections was recently applied on site. Design of the rehabilitation measures and assessment of the pre- and post-interventions seismic response of the bridge were based on detailed in-situ and laboratory tests, providing foundation soil and structural material properties. In-situ inspection of the rehabilitated bridge following the strong M6.1 and M6.0 Cephalonia earthquakes of January 26th and February 3rd 2014, respectively, revealed no damages or visible defects. The efficiency of the bridge retrofitting is also proved by a preliminary performance analysis of the bridge under the recorded ground motion induced by the above earthquakes.

• Steel and Composite Structures
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• v.44 no.1
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• pp.49-63
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• 2022

This study aims to develop ensemble machine learning (ML) models for estimating the peak floor acceleration and maximum top drift of steel moment frames. For this purpose, random forest, adaptive boosting, gradient boosting regression tree (GBRT), and extreme gradient boosting (XGBoost) models were considered. A total of 621 steel moment frames were analyzed under 240 ground motions using OpenSees software to generate the dataset for ML models. From the results, the GBRT and XGBoost models exhibited the highest performance for predicting peak floor acceleration and maximum top drift, respectively. The significance of each input variable on the prediction was examined using the best-performing models and Shapley additive explanations approach (SHAP). It turned out that the peak ground acceleration had the most significant impact on the peak floor acceleration prediction. Meanwhile, the spectral accelerations at 1 and 2 s had the most considerable influence on the maximum top drift prediction. Finally, a graphical user interface module was created that places a pioneering step for the application of ML to estimate the seismic demands of building structures in practical design.

• Steel and Composite Structures
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• v.53 no.2
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• pp.155-167
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• 2024

Identifying the location of earthquake-induced damage in buildings and mitigating its impact, especially in low-damage systems such as rocking frames, is a significant challenge for structural engineers. Therefore, it is crucial to investigate the sensitivity and type of damage of buildings exposed to severe earthquakes to concentrate damage in predefined locations that can be repaired easily. This paper explores the seismic responses of a Self-Centering Rocking Steel Braced Frame (SCR-SBF) under far-field and near-field ground motions. This earthquake-resistant system includes components such as post-tensioning cables to provide frame self-centering, eliminate residual drift in the system, and replaceable fuses to concentrate the earthquake-induced damage. While previous studies have examined far and near-field earthquakes, their comparative influence on the seismic behavior of structures with a rocking system remains unexplored. This paper presents a novel investigation into the sensitivity of SCR-SBF structures to far and near-field earthquakes. Considering the critical effects of shock and impulse loads on rocking systems, the study aims to assess the effects of near-field earthquakes and compare them to far-field earthquakes on these systems. For this purpose, different response parameters have been calculated under records of far- and near-field earthquakes at three specific ground acceleration levels by incremental nonlinear dynamic analysis. Additionally, the seismic behavior of the SCR-SBF and Steel-Braced Frame (SBF) are compared for near and far-field ground motions. The results show that SCR-SBF systems have better resilience and reduced local failures compared to SBF systems under far and near-field earthquakes, requiring tailored design strategies.

• Steel and Composite Structures
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• v.19 no.6
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• pp.1449-1466
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• 2015

Mixed structures consist of two parts: a lower part and an upper part. The lower part is usually made of concrete while the upper part is made of steel. Analyzing these structures is complicated and code-based design of them has many associated problems. In this research, the seismic behavior of mixed structures which have reinforced concrete frames and shear walls in their lower storeys and steel frames with bracing in their upper storeys were studied. For this purpose, seventeen structures in three groups of 5, 9 and 15 storey structures with different numbers of concrete and steel storeys were designed. Static pushover analysis, linear dynamic analysis and incremental dynamic analysis (IDA) using 15 earthquake records were performed by OpenSees software. Seismic parameters such as period, response modification factor and ductility factor were then obtained for the mixed (hybrid) structures using more than 4600 nonlinear dynamic analysis and used in the regression analysis for achieving proper formula. Finally, some formulas, effective in designing such structures, are presented for the mentioned parameters. According to the results obtained from this research, the response modification factor values of mixed structures are lower compared to those of steel or concrete ones with the same heights. This fact might be due to the irregularities of stiffness, mass, etc., at different heights of the structure. It should be mentioned that for the first time, the performance and seismic response of such structures were studied against real earthquake accelerations using nonlinear dynamic analysis, andresponse modification factor was obtained by IDA.