• Title/Summary/Keyword: codes-of-practice

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Interactive strut-and-tie-model for shear strength prediction of RC pile caps

  • Chetchotisak, Panatchai;Yindeesuk, Sukit;Teerawong, Jaruek
    • Computers and Concrete
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    • v.20 no.3
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    • pp.329-338
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    • 2017
  • A new simple and practical strut-and-tie model (STM) for predicting the shear strength of RC pile caps is proposed in this paper. Two approaches are adopted to take into account the concrete softening effect. In the first approach, a concrete efficiency factor based on compression field theory is employed to determine the effective strength of a concrete strut, assumed to control the shear strength of the whole member. The second adopted Kupfer and Gerstle's biaxial failure criterion of concrete to derive the simple nominal shear strength of pile caps containing the interaction between strut and tie capacity. The validation of these two methods is investigated using 110 RC pile cap test results and other STMs available in the literature. It was found that the failure criterion approach appears to provide more accurate and consistent predictions, and hence is chosen to be the proposed STM. Finally, the predictions of the proposed STM are also compared with those obtained by using seven other STMs from codes of practice and the literature, and were found to give better accuracy and consistency.

Effect of mitigation strategies in the severe accident uncertainty analysis of the OPR1000 short-term station blackout accident

  • Wonjun Choi;Kwang-Il Ahn;Sung Joong Kim
    • Nuclear Engineering and Technology
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    • v.54 no.12
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    • pp.4534-4550
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    • 2022
  • Integrated severe accident codes should be capable of simulating not only specific physical phenomena but also entire plant behaviors, and in a sufficiently fast time. However, significant uncertainty may exist owing to the numerous parametric models and interactions among the various phenomena. The primary objectives of this study are to present best-practice uncertainty and sensitivity analysis results regarding the evolutions of severe accidents (SAs) and fission product source terms and to determine the effects of mitigation measures on them, as expected during a short-term station blackout (STSBO) of a reference pressurized water reactor (optimized power reactor (OPR)1000). Three reference scenarios related to the STSBO accident are considered: one base and two mitigation scenarios, and the impacts of dedicated severe accident mitigation (SAM) actions on the results of interest are analyzed (such as flammable gas generation). The uncertainties are quantified based on a random set of Monte Carlo samples per case scenario. The relative importance values of the uncertain input parameters to the results of interest are quantitatively evaluated through a relevant sensitivity/importance analysis.

Fuzzy Inference Based Design for Durability of Reinforced Concrete Structure in Chloride-Induced Corrosion Environment

  • Do Jeong-Yun;Song Hun;Soh Yang-Seob
    • Journal of the Korea Concrete Institute
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    • v.17 no.1 s.85
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    • pp.157-166
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    • 2005
  • This article involves architecting prototype-fuzzy expert system for designing the nominal cover thickness by means of fuzzy inference for quantitatively representing the environment affecting factor to reinforced concrete in chloride-induced corrosion environment. In this work, nominal cover thickness to reinforcement in concrete was determined by the sum of minimum cover thickness and tolerance to that defined from skill level, constructability and the significance of member. Several variables defining the quality of concrete and environment affecting factor (EAF) including relative humidity, temperature, cyclic wet and dry, and the distance from coast were treated as fuzzy variables. To qualify EAF the environment conditions of cycle degree of wet-dry, relative humidity, distance from coast and temperature were used as input variables. To determine the nominal cover thickness a qualified EAF, concrete grade, and water-cement ratio were used. The membership functions of each fuzzy variable were generated from the engineering knowledge and intuition based on some references as well as some international codes of practice.

The effects of topography on local wind-induced pressures of a medium-rise building

  • Hitchcock, P.A.;Kwok, K.C.S.;Wong, K.S.;Shum, K.M.
    • Wind and Structures
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    • v.13 no.5
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    • pp.433-449
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    • 2010
  • Wind tunnel model tests were conducted for a residential apartment block located within the complex terrain of The Hong Kong University of Science and Technology (HKUST). The test building is typical of medium-rise residential buildings in Hong Kong. The model study was conducted using modelling techniques and assumptions that are commonly used to predict design wind loads and pressures for buildings sited in regions of significant topography. Results for the building model with and without the surrounding topography were compared to investigate the effects of far-field and near-field topography on wind characteristics at the test building site and wind-induced external pressure coefficients at key locations on the building facade. The study also compared the wind tunnel test results to topographic multipliers and external pressure coefficients determined from nine international design standards. Differences between the external pressure coefficients stipulated in the various standards will be exacerbated when they are combined with the respective topographic multipliers.

Triage Nurses' Work Experiences in Emergency Department: A Qualitative Research (응급실 중증도 분류 간호사의 업무 경험: 질적 연구)

  • Park, Yu Jin;Kong, Eun-Hi;Park, Young A
    • Journal of muscle and joint health
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    • v.25 no.3
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    • pp.176-186
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    • 2018
  • Purpose: The purpose of the study was to describe work experiences of triage nurses working at emergency departments in Korea. Methods: A qualitative descriptive research method was used. Twenty-one nurses of emergency department participated in the first interview and 16 of them participated in the second interview. Data were collected through in-depth interviews and field notes. Qualitative content analysis was utilized to analyze the data. Results: Forty-eight codes, 12 categories, and six themes emerged from the data analysis: caring on the frontline, burden as an initial evaluator, handling things alone, lack of others' understanding, becoming an expert, and needs for improvement. Participating triage nurses faced many challenges and difficult situations in emergency departments. They felt burden and loneliness as initial evaluator. Also, they felt pride in their work and struggled to become a professional. Conclusion: This study is the first qualitative study that has focused on exploring the experiences of triage nurses in emergency departments in Korea. The results provide description and in-depth understanding of working experiences of triage nurses. The results provide valuable fundamental data for regulation, clinical practice, education, and research for triage nurses in Korean emergency departments.

Effective Length of Reinforced Concrete Columns in Braced Frames

  • Tikka, Timo K.;Mirza, S. Ali
    • International Journal of Concrete Structures and Materials
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    • v.8 no.2
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    • pp.99-116
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    • 2014
  • The American Concrete Institute (ACI) 318-11 permits the use of the moment magnifier method for computing the design ultimate strength of slender reinforced concrete columns that are part of braced frames. This computed strength is influenced by the column effective length factor K, the equivalent uniform bending moment diagram factor $C_m$ and the effective flexural stiffness EI among other factors. For this study, 2,960 simple braced frames subjected to short-term loads were simulated to investigate the effect of using different methods of calculating the effective length factor K when computing the strength of columns in these frames. The theoretically computed column ultimate strengths were compared to the ultimate strengths of the same columns computed from the ACI moment magnifier method using different combinations of equations for K and EI. This study shows that for computing the column ultimate strength, the current practice of using the Jackson-Moreland Alignment Chart is the most accurate method for determining the effective length factor. The study also shows that for computing the column ultimate strength, the accuracy of the moment magnifier method can be further improved by replacing the current ACI equation for EI with a nonlinear equation for EI that includes variables affecting the column stiffness and proposed in an earlier investigation.

A Study on Bridge Live Loads and Traffic Modes (도로교 차량하중 및 통행특성에 관한 연구)

  • Kim, Sang Hyo;Park, Hung Seok
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.12 no.4
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    • pp.107-116
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    • 1992
  • The structural integrity of bridges is mainly damaged by overloaded heavy vehicles. The increasing volumes of overloaded heavy vehicles has been indicated as serious state. As results several countries have revised their bridge load codes. However, because of variety of truck types and their weights it is difficult to develop rational standard truck loads. In addition the common practice that only one design configuration of standard truck is adopted to design variety of bridges causes further difficulties. The objective of the study is to investigate the statistical characteristics of vehicle loadings based on survey data collected, in which some major factors, such as vehicle configurations, vehicle weights, traffic modes, etc., are incorporated. The vehicle load effects due to single presence of heavy truck are also tested with several short-span bridges and probabilistic characteristics of current design practices are evaluated.

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Practical second-order analysis and design of single angle trusses by an equivalent imperfection approach

  • Cho, S.H.;Chan, S.L.
    • Steel and Composite Structures
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    • v.5 no.6
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    • pp.443-458
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    • 2005
  • Steel angles are widely used in roof trusses as web and chord members and in lattice towers. Very often angle members are connected eccentrically. As a result, not only an angle member is under an axial force, but it is also subject to a pair of end eccentric moments. Moreover, the connection at each end provides some fixity so neither pinned nor the fixed end represents the reality. Many national design codes allow for the effects due to eccentricities by modifying the slenderness ratio and reducing the compressive strength of the member. However, in practice, it is difficult to determine accurately the effective length. The concept behind this method is inconsistent with strength design of members of other cross-sectional types such as I or box sections of which the buckling strength is controlled by the Perry constant or the initial imperfection parameters. This paper proposes a method for design of angle frames and trusses by the second-order analysis. The equivalent initial imperfection-to-length ratios for equal and unequal angles to compensate the negligence of initial curvatures, load eccentricities and residual stresses are determined in this paper. From the obtained results, the values of imperfection-to-length ratios are suggested for design and analysis of angle steel trusses allowing for member buckling strength based on the Perry-Robertson formula.

Neuro-fuzzy optimisation to model the phenomenon of failure by punching of a slab-column connection without shear reinforcement

  • Hafidi, Mariam;Kharchi, Fattoum;Lefkir, Abdelouhab
    • Structural Engineering and Mechanics
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    • v.47 no.5
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    • pp.679-700
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    • 2013
  • Two new predictive design methods are presented in this study. The first is a hybrid method, called neuro-fuzzy, based on neural networks with fuzzy learning. A total of 280 experimental datasets obtained from the literature concerning concentric punching shear tests of reinforced concrete slab-column connections without shear reinforcement were used to test the model (194 for experimentation and 86 for validation) and were endorsed by statistical validation criteria. The punching shear strength predicted by the neuro-fuzzy model was compared with those predicted by current models of punching shear, widely used in the design practice, such as ACI 318-08, SIA262 and CBA93. The neuro-fuzzy model showed high predictive accuracy of resistance to punching according to all of the relevant codes. A second, more user-friendly design method is presented based on a predictive linear regression model that supports all the geometric and material parameters involved in predicting punching shear. Despite its simplicity, this formulation showed accuracy equivalent to that of the neuro-fuzzy model.

Load Bearing Capacity of CLT - Concrete Connections with Inclined Screws (경사못이 적용된 CLT-콘크리트 접합부의 하중전달능력)

  • Kim, Kyung-Tae;Kim, Jong-Ho
    • Journal of the Architectural Institute of Korea Structure & Construction
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    • v.34 no.4
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    • pp.3-13
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    • 2018
  • Load bearing capacity of dowel type fasteners loaded perpendicular to the shear plane is determined based on Johansen's yield theory (Johansen, 1949). In case of inclined screws whose axis is no longer perpendicular, the ultimate load of connection increases because of additional axial withdrawal capacity. To calculate load bearing capacity for inclined screws, KBC2016 and Eurocode5 provide design equations using the combination of two effects; axial and bending strength. Although their equations have been validated for a long time, there is still minimal information how to apply them for concrete-CLT joints. Since there are not many test data available, engineers have to make certain assumptions and thus results may look inconsistent in practice. In this paper, authors would like to describe the current approach and assumptions indicated by KBC2016 and Eurocode 5 and how they match the experimental results in terms of shear strength of CLT-concrete connections. To fulfill the objective, several push-out tests were performed on nine different test specimens. Each specimen has different penetration angles and depths. By analyzing load-displacement curves, the maximum shear strength, stiffness, and ductility were obtained. Shear strength values were compared with the current design codes and theoretical equations proposed in this paper. Observations on stiffness and ductility were briefly discussed.