• Title/Summary/Keyword: low-rise building

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Evaluation of Fatigue Performance of RC Deck Slabs by 80 MPa High-Strength Concrete (80 MPa급 고강도 콘크리트를 적용한 RC 바닥판의 피로 성능 평가)

  • Bae, Jae-Hyun;Hwang, Hoon-Hee;Yoo, Dong-Min;Park, Sung-Yong
    • Journal of the Korean Society of Safety
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    • v.32 no.4
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    • pp.66-72
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    • 2017
  • Recently, the use of high-strength concrete is increasing due to the trend of constructing high-rise and long span structures. The benefit of using the high-strength concrete is that it increases the durability and strength while it reduces the cross-sectional area of the bridge deck slabs. Moreover, it offers more safety as these bridge deck slabs applying high-strength requires strict structural performance verification. In this study, the fatigue performance of the bridge deck slabs applying 80 MPa high-strength concrete was verified through various experiments. The experimental results showed that the specimens satisfy the conditions of flexural strength, punching shear strength, deflection and cracking. In conclusion, the bridge deck slabs designed by 80 MPa high-strength concrete are enough safe despite of its low thickness.

Effects of wind direction on the flight trajectories of roof sheathing panels under high winds

  • Kordi, Bahareh;Traczuk, Gabriel;Kopp, Gregory A.
    • Wind and Structures
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    • v.13 no.2
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    • pp.145-167
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    • 2010
  • By using the 'failure' model approach, the effects of wind direction on the flight of sheathing panels from the roof of a model house in extreme winds was investigated. A complex relationship between the initial conditions, failure velocities, flight trajectories and speeds was observed. It was found that the local flow field above the roof and in the wake of the house have important effects on the flight of the panels. For example, when the initial panel location is oblique to the wind direction and in the region of separated flow near the roof edge, the panels do not fly from the roof since the resultant aerodynamic forces are small, even though the pressure coefficients at failure are high. For panels that do fly, wake effects from the building are a source of significant variation of flight trajectories and speeds. It was observed that the horizontal velocities of the panels span a range of about 20% - 95% of the roof height gust speed at failure. Numerical calculations assuming uniform, smooth flow appear to be useful for determining panel speeds; in particular, using the mean roof height, 3 sec gust speed provides a useful upper bound for determining panel speeds for the configuration examined. However, there are significant challenges for estimating trajectories using this method.

Comparison of Nonlinear Analysis Programs for Small-size Reinforced Concrete Buildings II (소규모 철근콘크리트 건축물을 위한 비선형해석 프로그램 비교 II)

  • Yoo, Changhwan;Kim, Taewan;Park, Hong-Gun
    • Journal of the Earthquake Engineering Society of Korea
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    • v.19 no.5
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    • pp.229-238
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    • 2015
  • For small-size reinforce-concrete buildings, Midas Gen, OpenSees, and Perform-3D, which are structural analysis programs that are most popularly used at present, were applied for nonlinear static pushover analysis, and then difference between those programs was analyzed. Example buildings were limited to 2-story frames with irregular shaped walls. Analysis result showed that there were more differences than for frames only and frames with rectangular walls, but it was not so significant. Nevertheless, the capacity curve were different in some buildings, which is attributed to shape and location of walls, and feature of the analysis program. Especially, selection of automatic or manual input in Midas Gen, or nonlinear wall elements in Perform3D can affect the capacity curve and performance of the buildings. Therefore, the program users should understand the feature of the program well, and then conduct performance assessment. The result of this study is limited to low-story buildings so that it should be noted that it is possible to get different results for mid- to high-rise buildings.

Comparison of Nonlinear Analysis Programs for Small-size Reinforced Concrete Buildings I (소규모 철근콘크리트 건축물을 위한 비선형해석 프로그램 비교 I)

  • Yoo, Changhwan;Kim, Taewan
    • Journal of the Earthquake Engineering Society of Korea
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    • v.19 no.5
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    • pp.219-228
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    • 2015
  • For small-size reinforce-concrete buildings, Midas Gen, OpenSees, and Perform-3D, which are structural analysis programs that are most popularly used at present, were applied for nonlinear static pushover analysis, and then difference between those programs was analyzed. Example buildings were limited to 2-story frames only and frames with one or more rectangular walls. Analysis results showed that there was not much difference for frames only based on capacity curves. There were some differences for frames with rectangular walls, but it was not so significant. The global behaviors represented by the capacity curve were not so different, but the feature of each analysis program appeared when the results were analyzed in more detail. Therefore, the program users should understand the feature of the program well, and then conduct performance assessment. The result of this study is limited to low-story frames only and frames with rectangular walls so that it should be noted that it is possible to get different results for frames with non-rectangular walls or mid- to high-rise buildings.

Wind loads on solar panels mounted parallel to pitched roofs, and acting on the underlying roof

  • Leitch, C.J.;Ginger, J.D.;Holmes, J.D.
    • Wind and Structures
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    • v.22 no.3
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    • pp.307-328
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    • 2016
  • This paper describes an investigation of the net wind loads on solar panels and wind loads on the underlying roof surface for panels mounted parallel to pitched roofs of domestic buildings. Typical solar panel array configurations were studied in a wind tunnel and the aerodynamic shape factors on the panels were put in a form appropriate for the Australian/New Zealand Wind Actions Standard AS/NZS 1170.2:2011. The results can also be used to obtain more refined design data on individual panels within an array. They also suggest values for the aerodynamic shape factors on the roof surface under the panels, based on a gust wind speed at roof height, of ${\pm}0.5$ for wind blowing parallel to the ridge, and ${\pm}0.6$ for wind blowing perpendicular to the ridge. The net loads on solar arrays in the middle portion of the roof are larger than those on the same portion of the roof without any solar panels, thus resulting in increased loads on the underlying roof structure.

A study of aerodynamic pressures on elevated houses

  • Abdelfatah, Nourhan;Elawady, Amal;Irwin, Peter;Chowdhury, Arindam
    • Wind and Structures
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    • v.31 no.4
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    • pp.335-350
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    • 2020
  • In coastal residential communities, especially along the coastline, flooding is a frequent natural hazard that impacts the area. To reduce the adverse effects of flooding, it is recommended to elevate coastal buildings to a certain safe level. However, post storm damage assessment has revealed severe damages sustained by elevated buildings' components such as roofs, walls, and floors. By elevating a structure and creating air gap underneath the floor, the wind velocity increases and the aerodynamics change. This results in varying wind loading and pressure distribution that are different from their slab on grade counterparts. To fill the current knowledge gap, a large-scale aerodynamic wind testing was conducted at the Wall of Wind experimental facility to evaluate the wind pressure distribution over the surfaces of a low-rise gable roof single-story elevated house. The study considered three different stilt heights. This paper presents the observed changes in local and area averaged peak pressure coefficients for the building surfaces of the studied cases. The aerodynamics of the elevated structures are explained. Comparisons are done with ASCE 7-16 and AS/NZS 1170.2 wind loading standards. For the floor surface, the study suggests a wind pressure zoning and pressure coefficients for each stilt height.

A Study on the improvement of Strength delay according to Low Temperature of Cold Weather Concrete (한중콘크리트의 저온에 의한 강도지연 개선연구)

  • Lee, Sang-Soo
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.7 no.1
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    • pp.51-59
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    • 2012
  • The cold weather concrete poured in the winter season can cause the problem of the Due to recent high-rise building is made. In this research, the nominal mix of the early strength in concrete tried to be set through the mixing proportion experiment for each empirical variable and each component strength properties for the early strength improvement tries to be examined. In the cold weather concrete experiment, the cement and high early strength (type3) cement improving in OPC than OPC was excellent. The polycarboxylic acid based compound was exposed to be excellent in the intensity revelation properties. Because the using of the fly ash was disadvantageous it was excluded from this experiment. It showed the optimum temperature for the intensity revelation up over $12^{\circ}C$.

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Evaluation of Seismic Performance of 2-Story Fire Protection Sprinkler Piping System (화재방호계통 복층구조 스프링클러 파이프라인 내진성능 평가)

  • Jeon, Jun-Tai;Jung, Woo-Young;Ju, Bu-Seog
    • Journal of the Society of Disaster Information
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    • v.10 no.3
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    • pp.458-464
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    • 2014
  • Fire protection (sprinkler) piping system is an essential element for the energy supply and for the protection against the seismic-induced fire during and after an earthquake. The primary objective of this study was to understand the seismic performance of complex two-story piping system installed in a low-rise building subjected to bi-directional and three-directional earthquakes. The result of current study revealed that the displacement of the piping system in accordance with floor level was significantly different due to acceleration-sensitivity but the effect of the piping system due to the vertical direction earthquake was not significant.

Seismic performance of a 10-story RC box-type wall building structure

  • Hwang, Kyung Ran;Lee, Han Seon
    • Earthquakes and Structures
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    • v.9 no.6
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    • pp.1193-1219
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    • 2015
  • The purpose of this study is to evaluate the seismic performance of high-rise reinforced concrete (RC) box-type wall structures commonly used for most residential buildings in Korea. For this purpose, an analytical model was calibrated with the results of the earthquake simulation tests on a 1:5 scale 10-story distorted model. This calibrated model was then transformed to a true model. The performance of the true model in terms of the stiffness, strength, and damage distribution through inelastic energy dissipation was observed with reference to the earthquake simulation test results. The model showed high overstrength factors ranging from 3 to 4. The existence of slab in this box-type wall system changed the main resistance mode in the wall from bending moment to tension/compression coupled moment through membrane actions, and increased the overall resistance capacity by about 25~35%, in comparison with the common design practice of neglecting the slab's existence. The flexibility of foundation, which is also commonly neglected in the engineering design, contributes to 30~50% of the roof drift in the stiff direction containing many walls. The possibility of concrete spalling and reinforcement buckling and fracture under the maximum considered earthquake (MCE) in Korea appears to be very low when compared with the case of the 2010 Concepcion, Chile earthquake.

An Efficient Method for Design and Implementation of Tweet Analysis System (효율적인 트윗 분석 시스템 설계 및 구현 방법)

  • Choi, Minseok
    • Journal of Digital Convergence
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    • v.13 no.2
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    • pp.43-50
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    • 2015
  • Since the popularity of social network services (SNS) rise, the data produced from them is rapidly increased. The SNS data includes personal propensity or interest and propagates rapidly so there are many requests on analyzing the data for applying the analytic results to various fields. New technologies and services for processing and analyzing big data in the real-time are introduced but it is hard to apply them in a short time and low coast. In this paper, an efficient method to build a tweet analysis system without inducing new technologies or service platforms for handling big data is proposed. The proposed method was verified through building a prototype monitoring system to collect and analyze tweets using the MySQL database and the PHP scripts.