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  1. ์„œ์šธ๊ณผํ•™๊ธฐ์ˆ ๋Œ€ํ•™๊ต ๊ฑด์ถ•๊ณผ ๋Œ€ํ•™์›์ƒ (Graduate Student, Department of Architecture, Seoul National University of Science and Technology, Seoul 01811, Rep. of Korea)
  2. ์„œ์šธ๊ณผํ•™๊ธฐ์ˆ ๋Œ€ํ•™๊ต ๊ฑด์ถ•ํ•™๋ถ€ ๊ต์ˆ˜ (Professor, School of Architecture (Architectural Engineering Program), Seoul National University of Science and Technology, Seoul 01811, Rep. of Korea)



์ฒ ๊ทผ์ฝ˜ํฌ๋ฆฌํŠธ ๊ธฐ๋‘ฅ, ๋‚ดํ™”์„ฑ๋Šฅ, ์œ ํ•œ์š”์†Œํ•ด์„, ํŽธ์‹ฌํ•˜์ค‘, ๋‹จ๋ถ€ํšŒ์ „๊ตฌ์†๋„
reinforced concrete columns, fire resistance, finite element analysis, eccentric load, end-rotation constraint

1. ์„œ ๋ก 

๋‚ดํ™”๊ตฌ์กฐ๋Š” ใ€Œ๊ฑด์ถ•๋ฒ• ์‹œํ–‰๋ นใ€์ œ2์กฐ์— ๋”ฐ๋ผ ํ™”์žฌ์— ๊ฒฌ๋”œ ์ˆ˜ ์žˆ๋Š” ์„ฑ๋Šฅ์„ ๊ฐ€์ง„ ๊ตฌ์กฐ๋กœ์„œ ใ€Œ๊ฑด์ถ•๋ฌผ ํ”ผ๋‚œ๏ฝฅ๋ฐฉํ™”๊ตฌ์กฐ ๋“ฑ์˜ ๊ธฐ์ค€์— ๊ด€ํ•œ ๊ทœ์น™ใ€์œผ๋กœ ์ •ํ•˜๋Š” ๊ธฐ์ค€์— ์ ํ•ฉํ•œ ๊ตฌ์กฐ๋ฅผ ๋งํ•˜๋ฉฐ, ใ€Œ๊ฑด์ถ•๋ฒ•ใ€์ œ50์กฐ ๋ฐ ใ€Œ๊ฑด์ถ•๋ฒ• ์‹œํ–‰๋ นใ€์ œ56์กฐ์— ๋ช…์‹œ๋œ ์šฉ๋„ ๋ฐ ๊ทœ๋ชจ์˜ ๊ฑด์ถ•๋ฌผ์€ ๋‚ด๋ ฅ๋ฒฝ, ๊ธฐ๋‘ฅ, ๋ฐ”๋‹ฅ, ๋ณด ๋“ฑ์˜ ์ฃผ์š”๊ตฌ์กฐ๋ถ€์™€ ์ง€๋ถ•์„ ๋ฐ˜๋“œ์‹œ ๋‚ดํ™”๊ตฌ์กฐ๋กœ ํ•˜์—ฌ์•ผ ํ•œ๋‹ค. ๋‚ดํ™”๊ตฌ์กฐ์˜ ๋ชฉ์ ์€ ํ™”์žฌ ์‹œ ์ผ์ • ์‹œ๊ฐ„ ๋™์•ˆ ํ•ด๋‹น ๊ตฌ์กฐ๋ถ€๊ฐ€ ๊ทธ ๊ฐ•๋„์™€ ์„ฑ๋Šฅ์„ ์œ ์ง€ํ•  ์ˆ˜ ์žˆ๋„๋ก ํ•˜๊ธฐ ์œ„ํ•จ์ด๋ฉฐ, ์—ฌ๊ธฐ์„œ ์ผ์ • ์‹œ๊ฐ„์ด๋ž€ ์šฉ๋„ ๋ฐ ๊ทœ๋ชจ์— ๋”ฐ๋ผ ์‚ฌ๋žŒ๋“ค์ด ์•ˆ์ „ํ•œ ๊ณณ๊นŒ์ง€ ๋Œ€ํ”ผํ•  ์ˆ˜ ์žˆ๋„๋ก ํ•˜๋Š” 1~3์‹œ๊ฐ„ ์ •๋„๋ฅผ ์˜๋ฏธํ•œ๋‹ค(ใ€Œ๊ฑด์ถ•๋ฌผ ํ”ผ๋‚œ๏ฝฅ๋ฐฉํ™”๊ตฌ์กฐ ๋“ฑ์˜ ๊ธฐ์ค€์— ๊ด€ํ•œ ๊ทœ์น™ใ€์˜ ๋ณ„ํ‘œ 1 ์ฐธ์กฐ). ๋‚ดํ™”๊ตฌ์กฐ ์„ค๊ณ„ ์‹œ ๊ธฐ์กด์—๋Š” ์‚ฌ์–‘์  ๋‚ดํ™”๊ตฌ์กฐ์„ค๊ณ„๋ฒ• ๋ฐ ๋‚ดํ™”๊ตฌ์กฐ ์ธ์ •์ œ๋„๊ฐ€ ๋งŽ์ด ํ™œ์šฉ๋˜์—ˆ์œผ๋‚˜, ์ตœ๊ทผ์—๋Š” ์ฐจ๋ณ„์ ์ธ ์„ฑ๋Šฅ๋ชฉํ‘œ, ์„ฑ๋Šฅ์š”๊ฑด, ์„ฑ๋Šฅํ‰๊ฐ€๋ฅผ ์ ์šฉํ•  ์ˆ˜ ์žˆ์–ด ASCE 7-22 Appendix E. Performance-based Design Procedures for Fire Effects on Structures(ASCE 2023) ๋ฐ ASCE Manual No. 138 Structural Fire Engineering Design(LaMalva 2018) ๋“ฑ์—์„œ ์ œ์‹œํ•˜๊ณ  ์žˆ๋Š” ์„ฑ๋Šฅ๊ธฐ๋ฐ˜ ๋‚ดํ™”๊ตฌ์กฐ์„ค๊ณ„๋ฒ•๋„ ์ ์ฐจ ํ™œ์šฉ์ด ๋Š˜๊ณ  ์žˆ๋‹ค(Khoury 2000; Wang et al. 2012; Ahn 2019). ์ด๋Ÿฌํ•œ ์„ฑ๋Šฅ๊ธฐ๋ฐ˜ ๋‚ดํ™”๊ตฌ์กฐ์„ค๊ณ„๋ฅผ ์œ„ํ•ด์„œ๋Š” ํ™”์žฌ ์‹œ ๋ถ€์žฌ์˜ ๊ตฌ์กฐ๊ฑฐ๋™์— ๋Œ€ํ•œ ์ดํ•ด๊ฐ€ ์„ ํ–‰๋˜์–ด์•ผ ํ•˜๋ฉฐ(Wittasek 2022), ์ด๋ฅผ ์œ„ํ•ด ์ผ๋ฐ˜์ ์œผ๋กœ ๊ตฌ์กฐ๋ถ€์žฌ ๋˜๋Š” ์ผ๋ถ€ ๊ตฌ์กฐ๋ถ€์— ๋Œ€ํ•œ ๊ณ ๊ธ‰์ˆ˜์น˜ํ•ด์„์ด ์ฃผ๋กœ ํ™œ์šฉ๋˜๊ณ  ์žˆ๋‹ค(Ahn 2019).

ํ•œํŽธ ์ฝ˜ํฌ๋ฆฌํŠธ๋Š” ๊ฐ•์žฌ์— ๋น„ํ•ด ๋‚ฎ์€ ์—ด์ „๋„์œจ(Thermal Conductivity) ๋ฐ ๋†’์€ ๋น„์—ด(Specific Heat) ๋“ฑ์œผ๋กœ ์ธํ•˜์—ฌ ์ƒ๋Œ€์ ์œผ๋กœ ํ™”์žฌ์— ๊ฐ•ํ•œ ๊ฒƒ์œผ๋กœ ์•Œ๋ ค์ ธ ์žˆ์œผ๋‚˜(Kodur and Phan 2007; Kodur 2014; Buch and Sharma 2017), ์ฒ ๊ทผ์ฝ˜ํฌ๋ฆฌํŠธ(RC) ๋ถ€์žฌ ์—ญ์‹œ ๊ณ ์˜จ์˜ ํ™”์žฌํ™˜๊ฒฝ์— ๋…ธ์ถœ๋˜๋ฉด ์ฝ˜ํฌ๋ฆฌํŠธ ๋ฐ ์ฒ ๊ทผ์˜ ํƒ„์„ฑ๊ณ„์ˆ˜์™€ ๊ฐ•๋„ ๋“ฑ ์žฌ๋ฃŒ์˜ ์—ญํ•™์  ํŠน์„ฑ์ด ์ €ํ•˜๋˜๋ฉฐ, ๊ธ‰๊ฒฉํ•œ ๊ฐ€์—ด ์‹œ ๋‚ด๋ถ€ ์ˆ˜์ฆ๊ธฐ์••์˜ ํญ๋ฐœ๋กœ ์ธํ•œ ํญ๋ ฌํ˜„์ƒ์ด ๋ฐœ์ƒํ•˜๋Š” ๋“ฑ ๋‹จ๋ฉด ๊ตฌ์„ฑ ๋ฐ ํ™”์žฌ ๋…ธ์ถœํ™˜๊ฒฝ ๋“ฑ์— ๋”ฐ๋ผ ๋ถ€์žฌ์˜ ๋‚ดํ™”์„ฑ๋Šฅ์ด ํฌ๊ฒŒ ์˜ํ–ฅ๋ฐ›๋Š”๋‹ค(Lie 1989; Kodur and Phan 2007; Raut and Kodur 2011; Shin et al. 2011; Kodur and Raut 2012; Buch and Sharma 2019; Lee and Kim 2023; Troung et al. 2024). ํŠนํžˆ ๋ชจ๋ฉ˜ํŠธ๊ณจ์กฐ ๋“ฑ์—์„œ ์ฃผ์š”ํ•œ ํšก๋ ฅ์ €ํ•ญ์š”์†Œ๋กœ ์‚ฌ์šฉ๋˜๋Š” ๊ธฐ๋‘ฅ์€ ์ƒ๋Œ€์ ์œผ๋กœ ๋†’์€ ์ถ•๋ ฅ์„ ๋ฐ›๊ณ  ์žˆ์œผ๋ฉฐ ํ†ต์ƒ ํœจ๊ณผ ์ถ•๋ ฅ์„ ๋™์‹œ์— ๋ฐ›๊ณ  ์žˆ์œผ๋ฏ€๋กœ, ์—ด์‘๋ ฅ(Thermal Stress)๊ณผ ๋”๋ถˆ์–ด ๊ธฐ์ž‘์šฉํ•˜๊ณ  ์žˆ๋Š” ๋†’์€ ์ˆ˜์ค€์˜ ๊ธฐ๊ณ„์  ์‘๋ ฅ(Mechanical Stress)์œผ๋กœ ์ธํ•ด ํ™”์žฌ ์‹œ ๊ตฌ์กฐ์†์ƒ์ด ๋” ๊ธ‰๊ฒฉํžˆ ๋ฐœ์ƒํ•  ์ˆ˜ ์žˆ์œผ๋ฉฐ(์ถ•๋ ฅ์— ๋”ฐ๋ฅธ 2์ฐจ ํšจ๊ณผ ๋ฐ ์ฒ ๊ทผ์˜ ์ขŒ๊ตด ๋“ฑ) ๊ทธ์— ๋”ฐ๋ฅธ ํ”ผํ•ด๋„ ๋ณด์™€ ๊ฐ™์€ ์ˆ˜ํ‰๋ถ€์žฌ์— ๋น„ํ•ด ํ›จ์”ฌ ์ค‘๋Œ€ํ•  ์ˆ˜ ์žˆ๋‹ค.

์ด๋Ÿฌํ•œ RC ๊ธฐ๋‘ฅ์˜ ๋‚ดํ™”์„ฑ๋Šฅ์„ ํ‰๊ฐ€ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ๋‹ค์–‘ํ•œ ์‹คํ—˜ ๋ฐ ํ•ด์„์—ฐ๊ตฌ๊ฐ€ ์ˆ˜ํ–‰๋˜์—ˆ๋‹ค(Lie and Woollerton 1988; Dotreppe et al. 1997; Kodur and Sultan 1998; Wu et al. 2007; Ali et al. 2010; Chinthapalli and Agarwal 2020). ํ•˜์ง€๋งŒ ์‹คํ—˜์„ธํŒ… ๋“ฑ์˜ ์ œ์•ฝ์กฐ๊ฑด์œผ๋กœ ์ธํ•˜์—ฌ ๋Œ€๋ถ€๋ถ„ ์ค‘์‹ฌํ•˜์ค‘์„ ๋ฐ›๋Š” ๊ฒฝ์šฐ๋ฅผ ๋Œ€์ƒ์œผ๋กœ ํ•˜๊ณ  ์žˆ์œผ๋ฉฐ(Kodur and Sultan 1998; Ali et al. 2010; Chinthapalli and Agarwal 2020), ํ™”์žฌ ์‹œ ์ธ์ ‘ ๋ถ€์žฌ์˜ ์ƒ๋Œ€๋ณ€ํ˜•์œผ๋กœ ๋ฐœ์ƒํ•  ์ˆ˜ ์žˆ๋Š” ๋‹จ๋ถ€ ๊ตฌ์†์กฐ๊ฑด์˜ ๋ณ€ํ™” ๋“ฑ์„ ๊ณ ๋ คํ•˜์ง€ ์•Š์•˜๋‹ค(Dotreppe et al. 1997; Wu et al. 2007). ์ฐธ๊ณ ๋กœ ์ถ•๋ฐฉํ–ฅ ๋ณ€ํ˜•์˜ ๊ตฌ์†๋„๊ฐ€ ๋ถ€์žฌ์˜ ๋‚ดํ™”์„ฑ๋Šฅ์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์— ๊ด€ํ•œ ์—ฐ๊ตฌ๊ฐ€ ์ผ๋ถ€ ์žˆ์œผ๋ฉฐ(Lie and Woollerton 1988; Tan and Nguyen 2013), ์ถ•๋ฐฉํ–ฅ ๋ณ€ํ˜•์„ ์™„์ „ํžˆ ๊ตฌ์†ํ•˜๋”๋ผ๋„ ๋ถ€์žฌ์˜ ๋‚ดํ™”์„ฑ๋Šฅ์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์€ ํฌ์ง€ ์•Š์€ ๊ฒƒ์œผ๋กœ ๋ณด๊ณ ๋œ ๋ฐ” ์žˆ๋‹ค(Lie and Lin 1986). ํ•˜์ง€๋งŒ ๋ถ€์žฌ ๋‹จ๋ถ€์˜ ํšŒ์ „๊ตฌ์†๋„๋Š” ๋ถ€์žฌ์˜ ๋‚ดํ™”์„ฑ๋Šฅ์— ํฐ ์˜ํ–ฅ์„ ๋ฏธ์น  ์ˆ˜ ์žˆ์œผ๋ฏ€๋กœ(Mahmoud 2021) ์ถ”๊ฐ€์—ฐ๊ตฌ๊ฐ€ ํ•„์š”ํ•˜๋‹ค. ํ•œํŽธ ๊ธฐ์กด ์—ฐ๊ตฌ๊ฒฐ๊ณผ๋ฅผ ๋ฐ”ํƒ•์œผ๋กœ Eurocode 2, ACI 216.1, AS 3600 ๋“ฑ ํ•ด์™ธ์˜ ๋‚ดํ™”์„ค๊ณ„๊ธฐ์ค€์—์„œ๋Š” RC ๊ธฐ๋‘ฅ์˜ ๋‚ดํ™”์„ฑ๋Šฅ ์˜ˆ์ธก์‹(Resistance, $R$ ๋˜๋Š” Fire Resistance Period, $FRP$ ๋“ฑ ๋‚ดํ™”์„ฑ๋Šฅ์‹œ๊ฐ„์œผ๋กœ ์ฃผ์–ด์ง)์„ ์ œ๊ณตํ•˜๊ณ  ์žˆ๋‹ค. ํ•˜์ง€๋งŒ ๋Œ€๋ถ€๋ถ„ ์‹คํ—˜๊ฒฐ๊ณผ์— ๊ธฐ๋ฐ˜ํ•œ ๊ฒฝํ—˜์‹์ด๊ณ  ๋ถ€์žฌ์น˜์ˆ˜์™€ ๊ด€๋ จ๋œ ๋ณ€์ˆ˜๋งŒ์œผ๋กœ ๋‚ดํ™”์„ฑ๋Šฅ์‹œ๊ฐ„์„ ์˜ˆ์ธกํ•˜๊ณ  ์žˆ์–ด ๊ทธ ์ ์šฉ๋ฒ”์œ„๋ฅผ ๋ฒ—์–ด๋‚œ ๊ฒฝ์šฐ์— ๋Œ€ํ•ด์„œ๋Š” ํ•ฉ๋ฆฌ์ ์ธ ๊ฒฐ๊ณผ๋ฅผ ๋„์ถœํ•˜์ง€ ๋ชปํ•  ์ˆ˜ ์žˆ๋‹ค(Kodur and Raut 2012). ๋˜ํ•œ ์„ค๊ณ„๊ธฐ์ค€์˜ ๊ณ ๋ ค์‚ฌํ•ญ๊ณผ ๋‹ฌ๋ฆฌ, RC ๋ถ€์žฌ์˜ ๋‚ดํ™”์„ฑ๋Šฅ์‹œ๊ฐ„์€ ๋‹จ๋ฉด์น˜์ˆ˜, ํ”ผ๋ณต๋‘๊ป˜, ์„ธ์žฅ๋น„, ์ถ•๋ ฅ๋น„ ๋ฟ๋งŒ ์•„๋‹ˆ๋ผ ํ™”์žฌ๋…ธ์ถœ๋ฉด, ํ•˜์ค‘ํŽธ์‹ฌ๋ฅ , ์ฝ˜ํฌ๋ฆฌํŠธ ํˆฌ๊ณผ์„ฑ(Permeability), ์ฝ˜ํฌ๋ฆฌํŠธ ํ•จ์ˆ˜์œจ, ํ™”์žฌ ์‹œ๋‚˜๋ฆฌ์˜ค ๋“ฑ์—๋„ ํฐ ์˜ํ–ฅ์„ ๋ฐ›๋Š”๋‹ค(Raut and Kodur 2011). ํŠนํžˆ ๊ธฐ๋‘ฅ์˜ ๊ฒฝ์šฐ, ์‹ค์ œ ํ™”์žฌ์ƒํ™ฉ์„ ๋ฐ˜์˜ํ•˜์—ฌ ๋น„๋Œ€์นญ์ ์ธ ํ™”์žฌ๋…ธ์ถœ ๋ฐ ํŽธ์‹ฌํ•˜์ค‘ ๋“ฑ๋„ ๊ณ ๋ คํ•  ์ˆ˜ ์žˆ๋Š” ๋ฐฉ์•ˆ์ด ํ•„์š”ํ•˜๋‹ค.

์ด์— ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ๋‹ค์–‘ํ•œ ์„ค๊ณ„์กฐ๊ฑด์„ ๊ฐ€์ง„ RC ๊ธฐ๋‘ฅ์˜ ๋‚ดํ™”์„ฑ๋Šฅ์‹œ๊ฐ„์„ ์˜ˆ์ธกํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์ถ•๋ ฅ๋น„, ํŽธ์‹ฌํ•˜์ค‘ ๋ฐ ๋‹จ๋ถ€ํšŒ์ „๊ตฌ์†๋„์˜ ์˜ํ–ฅ์„ ๊ณ ๋ คํ•œ 3์ฐจ์› ์œ ํ•œ์š”์†Œํ•ด์„ ๋ชจ๋ธ๋ง ๊ธฐ๋ฒ•์„ ๊ฐœ๋ฐœํ•˜์˜€๋‹ค. ๊ฒ€์ฆ์„ ์œ„ํ•˜์—ฌ ๊ฐœ๋ฐœ๋œ ์ˆ˜์น˜ํ•ด์„ ๋ชจ๋ธ๋ง ๊ธฐ๋ฒ•์„ Lie and Woollerton (1988)์˜ ์ค‘์‹ฌ/ํŽธ์‹ฌ ์žฌํ•˜๊ฐ€์—ด์‹คํ—˜์ฒด์— ์ ์šฉํ•˜์˜€์œผ๋ฉฐ, ๊ฐ€์—ด์‹œ๊ฐ„์— ๋”ฐ๋ฅธ ์˜จ๋„ ๋ถ„ํฌ, ์ถ•๋ฐฉํ–ฅ ๋ณ€ํ˜•, ๊ทธ๋ฆฌ๊ณ  ๋‚ดํ™”์„ฑ๋Šฅ์‹œ๊ฐ„ ๋“ฑ์˜ ๊ด€์ ์—์„œ ์‹คํ—˜๊ฒฐ๊ณผ์™€ ๋ฉด๋ฐ€ํžˆ ๋น„๊ตํ•˜์˜€๋‹ค.

2. ์œ ํ•œ์š”์†Œํ•ด์„ ๋ชจ๋ธ๋ง ๊ธฐ๋ฒ•

2.1 ์žฌํ•˜๊ฐ€์—ด์‹คํ—˜์ฒด

๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” Lie and Woollerton (1988)์˜ ์‹คํ—˜์ฒด๋ฅผ ๊ธฐ๋ฐ˜์œผ๋กœ ์œ ํ•œ์š”์†Œํ•ด์„ ๋ชจ๋ธ๋ง ๊ธฐ๋ฒ•์„ ๊ฐœ๋ฐœํ•˜์˜€๋‹ค. Lie and Woollerton (1988)์€ ์ด 41๊ฐœ์˜ RC ๊ธฐ๋‘ฅ์— ๋Œ€ํ•ด ์ค‘์‹ฌ/ํŽธ์‹ฌ ์žฌํ•˜๊ฐ€์—ด์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•˜์˜€์œผ๋ฉฐ, ๋‚ดํ™”์„ฑ๋Šฅ์— ์˜ํ–ฅ์„ ๋ฏธ์น˜๋Š” ๋‹ค์–‘ํ•œ ์„ค๊ณ„์กฐ๊ฑด(ํ•˜์ค‘๋น„, ๊ณจ์žฌ ์ข…๋ฅ˜, ๋‹จ๋ถ€ํšŒ์ „๊ตฌ์† ์กฐ๊ฑด, ์ฒ ๊ทผ๋น„ ๋“ฑ)์„ ์‹คํ—˜๋ณ€์ˆ˜๋กœ ๊ณ ๋ คํ•˜์˜€๋‹ค. ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ์ด ์ค‘ ์ค‘์‹ฌ๊ฐ€๋ ฅ ์‹คํ—˜์ฒด 5๊ฐœ, ํŽธ์‹ฌ๊ฐ€๋ ฅ ๋ฐ ๋‹จ๋ถ€ํšŒ์ „๊ตฌ์† ์กฐ๊ฑด ์‹คํ—˜์ฒด 5๊ฐœ ๋ฐ ์˜จ๋„ ๊ฒ€์ฆ ์‹คํ—˜์ฒด 1๊ฐœ๋ฅผ ๋Œ€์ƒ์œผ๋กœ ๋ชจ๋ธ๋ง ๊ธฐ๋ฒ•์„ ๊ฐœ๋ฐœํ•˜์˜€๋‹ค. ๋ณธ ํ•ด์„์—ฐ๊ตฌ์— ์‚ฌ์šฉ๋œ ์‹คํ—˜์ฒด์˜ ์ƒ์„ธ ๋ฐ ์‹คํ—˜๋ณ€์ˆ˜๋Š” ๊ฐ๊ฐ Fig. 1 ๋ฐ Table 1๊ณผ ๊ฐ™๋‹ค. ๊ธฐ๋‘ฅ์˜ ๋‹จ๋ฉด์€ $B\times D=$305 mmร—305 mm์ด๋ฉฐ, ์–‘๋‹จ๋ถ€ ์—”๋“œํ”Œ๋ ˆ์ดํŠธ๋ฅผ ํฌํ•จํ•œ ๊ธฐ๋‘ฅ์˜ ์ด ๊ธธ์ด๋Š” $L=$3,810 mm์ด๋‹ค. ์ฝ˜ํฌ๋ฆฌํŠธ๋Š” ๊ทœ์‚ฐ์งˆ ๊ณจ์žฌ๋ฅผ ์‚ฌ์šฉํ•˜์˜€์œผ๋ฉฐ, ์••์ถ•๊ฐ•๋„๋Š” $f_{ck}=$34.5 MPa์˜€๋‹ค. ์ฝ˜ํฌ๋ฆฌํŠธ ํ•จ์ˆ˜์œจ์€ ์‹คํ—˜ ์‹œ ์•ฝ 5 %๋กœ ์ถ”์ •๋˜์—ˆ๋‹ค(Lie and Woollerton 1988). ์ฃผ์ฒ ๊ทผ์œผ๋กœ D25($d_{b}=$25.4 mm) ์ฒ ๊ทผ์„ ๋ชจ์„œ๋ฆฌ์— ์ด 4๊ฐœ ๋ฐฐ์น˜ํ•˜์˜€์œผ๋ฉฐ(์ฒ ๊ทผ๋น„ $\rho =$2.19 %), ์ฃผ์ฒ ๊ทผ์˜ ํ”ผ๋ณต๋‘๊ป˜๋Š” 48 mm๋กœ ใ€ŒKDS 14 20 50ใ€์— ๋”ฐ๋ฅธ RC ๊ธฐ๋‘ฅ์˜ ์š”๊ตฌ์ƒ์„ธ(์ตœ์†Œํ”ผ๋ณต๋‘๊ป˜ 40 mm์™€ ํšก์ฒ ๊ทผ ์ง€๋ฆ„์˜ ํ•ฉ)์™€ ์œ ์‚ฌํ•œ ์ˆ˜์ค€์ด์—ˆ๋‹ค. ์ฃผ์ฒ ๊ทผ์˜ ํ•ญ๋ณต๊ฐ•๋„ ๋ฐ ์ธ์žฅ๊ฐ•๋„๋Š” ๊ฐ๊ฐ $f_{y}=$444 MPa ๋ฐ $f_{u}=$730 MPa์˜€๋‹ค. ํšก์ฒ ๊ทผ์œผ๋กœ D10($d_{b}=$9.53 mm, $f_{y}=$427 MPa, $f_{u}=$671 MPa) ์ฒ ๊ทผ์„ 280 mm ๊ฐ„๊ฒฉ์œผ๋กœ ๊ธฐ๋‘ฅ์˜ ์ „ ๊ธธ์ด์— ๊ฑธ์ณ ๋ฐฐ์น˜ํ•˜์˜€๋‹ค. ์ค‘์‹ฌ๊ฐ€๋ ฅ ์‹คํ—˜์ฒด๋Š” ์–‘๋‹จ๋ถ€๋ฅผ ๊ณ ์ •๋‹จ์œผ๋กœ ์ง€์ง€ํ•˜์˜€์œผ๋ฉฐ, ํŽธ์‹ฌ๊ฐ€๋ ฅ ์‹คํ—˜์ฒด์˜ ๊ฒฝ์šฐ ๊ธฐ๋‘ฅ ์–‘๋‹จ๋ถ€์— ๋ธŒ๋ž˜ํ‚ท์„ ๋‘๊ณ  ํšŒ์ „๋‹จ์œผ๋กœ ์ง€์ง€ํ•˜์˜€๋‹ค. ์ฐธ๊ณ ๋กœ, ํ†ต์ƒ ํŽธ์‹ฌ๊ฐ€๋ ฅ์˜ ๊ฒฝ์šฐ ๋‹จ๋ถ€์—์„œ ํŽธ์‹ฌ๊ฑฐ๋ฆฌ $e_{0}$๋ฅผ ๋‘๊ณ  ์ถ•๋ ฅ์„ ๊ฐ€ํ•˜๋Š” ๋ฐฉ์‹์ด์ง€๋งŒ, Lie and Woollerton (1988)์€ ์ค‘์‹ฌํ•˜์ค‘๊ณผ๋Š” ๋ณ„๋„๋กœ ํŽธ์‹ฌํ•˜์ค‘์„ ๋‹จ๋ถ€์— ์ž‘์šฉ์‹œํ‚ค๋Š” ๋ฐฉ์‹๋„ ์‚ฌ์šฉํ•˜์˜€๋‹ค. ๊ทธ ์ด์œ ๋Š” ๋‹จ๋ถ€ํšŒ์ „๊ตฌ์†๋„๊ฐ€ ๋ถ€์žฌ์˜ ๋‚ดํ™”์„ฑ๋Šฅ์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์„ ์กฐ์‚ฌํ•˜๊ธฐ ์œ„ํ•จ์ด๋ฉฐ, ๋‹จ๋ถ€ํšŒ์ „์— ๋Œ€ํ•ด ์™„์ „๊ตฌ์†(Fixed), ์ž์œ ํšŒ์ „(Pinned) ๋ฐ ๋ถ€๋ถ„๊ตฌ์†(Partial Restraint)์„ ๊ตฌํ˜„ํ•˜๊ธฐ ์œ„ํ•ด ์‹คํ—˜ ์ค‘ ํŽธ์‹ฌํ•˜์ค‘์˜ ํฌ๊ธฐ๋ฅผ ๋ณ€ํ™”์‹œ์ผฐ๋‹ค(Lie and Woollerton 1988; Lie 1989). ์ฐธ๊ณ ๋กœ III-7, III-8, III-9, III-10์€ ํŽธ์‹ฌํ•˜์ค‘ ์žฌํ•˜๋ฅผ ์œ„ํ•œ ๋ธŒ๋ž˜ํ‚ท์ด ์žˆ๋Š” ์‹คํ—˜์ฒด๋กœ์„œ, ๊ธฐ๋‘ฅ์˜ ๋‹จ๋ฉด๋„์‹ฌ์— ์ค‘์‹ฌํ•˜์ค‘์„ ๊ฐ€ํ•˜๊ณ  ๋„์‹ฌ์œผ๋กœ๋ถ€ํ„ฐ 508 mm ๋–จ์–ด์ง„ ์œ„์น˜์— ์ถ”๊ฐ€๋กœ ํŽธ์‹ฌํ•˜์ค‘์„ ๊ฐ€ํ•˜์˜€๋‹ค. III-14๋Š” ๋ธŒ๋ž˜ํ‚ท ์—†์ด ๋‹จ๋ฉด๋„์‹ฌ์œผ๋กœ๋ถ€ํ„ฐ 25 mm ๋–จ์–ด์ง„ ์œ„์น˜์—๋งŒ ํŽธ์‹ฌํ•˜์ค‘์„ ๊ฐ€ํ•˜์˜€๋‹ค.

Fig. 1 Details of test specimens used for numerical modeling (units: mm)
../../Resources/KCI/JKCI.2024.36.5.427/fig1.png
Table 1 Summaries of test specimens

Speci-

men

Test

parameter

Cross-

section

[mm]

Column

length

[mm]

Longi.

reinf.

ratio

[%]

End- condition

Concentric

load

$P_{c}$ [kN]

Eccentric

load

$P_{e}$ [kN]

Initial end

eccen-

tricity

($e_{0}/D$)

Nominal

strength

$P_{n},\: M_{n}$

[kN, kN๏ฝฅm]

Axial

load

ratio

($P/f_{ck}A_{g}$)

Failure

time

[hr:min]

I-1

Control

305ร—305

3,760

2.19

Fixed-fixed

-

-

0

3479, 0

-

Not failed

I-2

Concentric

Fixed-fixed

1,333

-

0.42

2:50

I-3

Concentric

Fixed-fixed

800

-

0.25

3:38

I-4

Concentric

Fixed-fixed

711

-

0.22

3:40

I-7

Concentric

Fixed-fixed

1,067

-

0.33

3:28

I-8

Concentric

Fixed-fixed

1,778

-

0.55

2:26

III-7*

Eccentric

Partial

rotation

1,022

49/32**

0.076

2883, 67

0.33

2:50

III-8*

Eccentric

Rotation

constraint

987

43/8**

0.070

2923, 62

0.32

3:45

III-9*

Eccentric

Rotation

constraint

889

43/22**

0.077

2880, 67.5

0.29

3:30

III-10*

Eccentric

Pinned-pinned

993

44/44**

0.071

2923, 63

0.32

2:47

III-14

Eccentric

Pinned-fixed

-

1178

0.081

2840, 71

0.37

3:03

Notes: *Columns with brackets, **Eccentric loads at the beginning and end of test

Fig. 2๋Š” ์‹คํ—˜์ฒด ๋‹จ๋ฉด์— ๋Œ€ํ•œ P-M ์ƒ๊ด€๊ณก์„ ์ด๋‹ค. Table 1์— ์ •๋ฆฌ๋œ ๋ฐ”์™€ ๊ฐ™์ด, ์ถ•๋ ฅ๋น„($P/f_{ck}A_{g}$, ์—ฌ๊ธฐ์„œ ์ด ์ถ•๋ ฅ $P$๋Š” ์ค‘์‹ฌ์ถ•๋ ฅ $P_{c}$์™€ ํŽธ์‹ฌ์ถ•๋ ฅ $P_{e}$์˜ ํ•ฉ)๋Š” ์•ฝ 0.22~0.55์˜ ๋ฒ”์œ„์— ์žˆ์—ˆ์œผ๋ฉฐ, ํŽธ์‹ฌ ์‹คํ—˜์ฒด์˜ ๊ฒฝ์šฐ ๋‹จ๋ถ€์˜ ์ดˆ๊ธฐํŽธ์‹ฌ์œจ($e_{0}/D$, ์—ฌ๊ธฐ์„œ ํŽธ์‹ฌ๊ฑฐ๋ฆฌ $e_{0}=M_{n}/P_{n}$)์˜ ํ‰๊ท ์€ ์•ฝ 0.075์ด์—ˆ๋‹ค. ์ฐธ๊ณ ๋กœ ํ†ต์ƒ์ ์ธ ๋ ์ฒ ๊ทผ ๊ธฐ๋‘ฅ์€ ์ถ•๋ ฅ๋น„ 0.44(๊ฐ•๋„๊ฐ์†Œ๊ณ„์ˆ˜ 0.65ร—์šฐ๋ฐœํŽธ์‹ฌ์„ ๊ณ ๋ คํ•œ ๊ณ„์ˆ˜ 0.8ร—๋“ฑ๊ฐ€์‘๋ ฅ๋ธ”๋ก ํฌ๊ธฐ๊ณ„์ˆ˜ 0.85) ์ดํ•˜๋กœ ์„ค๊ณ„๋˜๋ฏ€๋กœ, ์ผ๋ถ€ ์‹คํ—˜์ฒด์˜ ์ถ•๋ ฅ๋น„๋Š” ๋น„๊ต์  ๋†’์€ ์ˆ˜์ค€์ด์—ˆ๋‹ค.

Fig. 2 P-M interaction of test specimens and loading points
../../Resources/KCI/JKCI.2024.36.5.427/fig2.png

2.2 ํ•ด์„ ๋ชจ๋ธ๋ง

๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ๋ฒ”์šฉ ์œ ํ•œ์š”์†Œํ•ด์„ ํ”„๋กœ๊ทธ๋žจ์ธ Abaqus (2021)์—์„œ ์ œ๊ณตํ•˜๋Š” ์™„์ „ ์—ฐ๊ณ„ ์—ด-์‘๋ ฅ ํ•ด์„(Fully Coupled Thermo- mechanical Analysis)์„ ํ™œ์šฉํ•˜์˜€๋‹ค. ๊ธฐ์กด์˜ ๋‚ดํ™”ํ•ด์„์—ฐ๊ตฌ์—์„œ ์ฃผ๋กœ ์‚ฌ์šฉ๋˜์—ˆ๋˜ ์ˆœ์ฐจ์  ์—ด-์‘๋ ฅ ํ•ด์„(Sequentially Coupled Thermo-mechanical Analysis)์€ ์—ด ํ•ด์„ ๋ฐ ๊ธฐ๊ณ„์  ํ•ด์„์„ 2๋ฒˆ์— ๊ฑธ์ณ ์ˆ˜ํ–‰ํ•˜๋Š” ๋ฐฉ์‹์ด์ง€๋งŒ, ์™„์ „ ์—ฐ๊ณ„ ์—ด-์‘๋ ฅ ํ•ด์„์€ ์—ด์ „๋‹ฌ ํ•ด์„ ๋ฐ ๊ธฐ๊ณ„์  ํ•ด์„์„ ๋™์‹œ์— ์ˆ˜ํ–‰ํ•˜๋Š” ๋ฐฉ์‹์ด๋‹ค. ์™„์ „ ์—ฐ๊ณ„ ์—ด-์‘๋ ฅ ํ•ด์„์€ ์ˆœ์ฐจ์  ์—ด-์‘๋ ฅ ํ•ด์„์— ๋น„ํ•ด ํ•ด์„๊ณผ์ •์ด ๋” ๋ณต์žกํ•˜์ง€๋งŒ, ์žฌํ•˜๊ฐ€์—ด์‹คํ—˜์„ ๋” ์‹ค์ œ์ ์œผ๋กœ ๋ชจ์‚ฌํ•˜๋ฏ€๋กœ ๋”์šฑ ์ •ํ™•ํ•œ ํ•ด์„๊ฒฐ๊ณผ๋ฅผ ์–ป์„ ์ˆ˜ ์žˆ๋‹ค.

์—ด-์‘๋ ฅ ํ•ด์„์„ ์œ„ํ•ด์„œ๋Š” ์˜จ๋„๋ณ€ํ™”์— ๋”ฐ๋ฅธ ๊ตฌ์„ฑ์š”์†Œ(์ฝ˜ํฌ๋ฆฌํŠธ ๋ฐ ์ฒ ๊ทผ)์˜ ์žฌ๋ฃŒ๋ฌผ์„ฑ ๋ชจ๋ธ๋ง์ด ์ค‘์š”ํ•˜๋‹ค. ์—ญํ•™์  ํ•ด์„์„ ์œ„ํ•ด์„œ๋Š” ๊ตฌ์„ฑ์š”์†Œ์˜ ํƒ„์„ฑ๊ณ„์ˆ˜, ํฌ์•„์†ก๋น„, ์žฌ๋ฃŒ ๋น„ํƒ„์„ฑ ๊ฑฐ๋™ ๋“ฑ์ด ํ•„์š”ํ•˜๊ณ , ์—ด์ „๋‹ฌ(Heat Transfer) ํ•ด์„์„ ์œ„ํ•ด์„œ๋Š” ๊ตฌ์„ฑ์š”์†Œ์˜ ๋น„์—ด, ์—ด์ „๋„์œจ, ๋ฐ€๋„, ์—ดํŒฝ์ฐฝ๊ณ„์ˆ˜ ๋“ฑ์ด ํ•„์š”ํ•˜๋‹ค. ๋ณธ ์—ฐ๊ตฌ์˜ ๋ชฉ์ ์ด ์„ค๊ณ„๋ผ๋Š” ์ , ๊ทธ๋ฆฌ๊ณ  ๊ธฐ์กด ์‹คํ—˜์—ฐ๊ตฌ์—์„œ ์ถฉ๋ถ„ํ•œ ์ •๋ณด๊ฐ€ ์ œ๊ณต๋˜์ง€ ์•Š๋Š”๋‹ค๋Š” ์ ์„ ๊ฐ์•ˆํ•˜์—ฌ, ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” CEB-FIP ๋˜๋Š” Eurocode 2 ๋“ฑ์˜ ๋ชจ๋ธ์ฝ”๋“œ๋ฅผ ๊ธฐ๋ฐ˜์œผ๋กœ ์žฌ๋ฃŒ๋ฅผ ๋ชจ๋ธ๋งํ•˜์˜€๋‹ค.

๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” Abaqus์—์„œ ์ œ๊ณตํ•˜๋Š” CDP(Concrete Damaged Plasticity) ๋ชจ๋ธ์„ ์‚ฌ์šฉํ•˜์—ฌ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋น„์„ ํ˜• ๊ฑฐ๋™์„ ๋ชจ๋ธ๋งํ•˜์˜€๋‹ค. CDP ๋ชจ๋ธ์˜ ๋ณ€์ˆ˜๋Š” Sรผmer and AktaลŸ (2015)๋ฅผ ์ฐธ๊ณ ํ•˜๋˜, ์ƒ์˜จ ์‹คํ—˜์ฒด์— ๋Œ€ํ•œ ๋น„๊ต ๋ฐ ๋ณด์ •์„ ํ†ตํ•ด ๊ฒฐ์ •ํ•˜์˜€๋‹ค(Dilation Angle์€ 35ยฐ, Eccentricity๋Š” 0.1, $f_{b0}/f_{c0}$๋Š” 1.16, K๋Š” 0.67). ์ฐธ๊ณ ๋กœ, Viscosity Parameter๋Š” ์ˆ˜๋ ด๋„์˜ ์ฆ์ง„์„ ์œ„ํ•ด 0.0005๋ฅผ ์‚ฌ์šฉํ•˜์˜€๋‹ค. ์˜จ๋„์— ๋”ฐ๋ฅธ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์‘๋ ฅ-๋ณ€ํ˜•๋ฅ  ๊ด€๊ณ„ ๋ฐ ์—ด์  ๋ฌผ์„ฑ์น˜๋Š” Eurocode 2 Part 1-2(CEN 2004) ๋ฐ CEB-FIP (CEB 1993)๋ฅผ ๋”ฐ๋ž๋‹ค. ์ˆ˜๋ ด๋„์˜ ์ฆ์ง„์„ ์œ„ํ•ด ์ฝ˜ํฌ๋ฆฌํŠธ์˜ Tensile Damage Model์€ CEB-FIP์˜ Fracture Energy๋ฅผ ํ†ตํ•ด ๋ฐ˜์˜ํ•˜์˜€๋‹ค. ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋น„์—ด์€ ํ•จ์ˆ˜์œจ 5 %์— ํ•ด๋‹นํ•˜๋Š” ๊ฐ’์„ ์‚ฌ์šฉํ–ˆ์œผ๋ฉฐ, ์—ด์ „๋„์œจ์€ Upper Limit๊ณผ Lower Limit์˜ ํ‰๊ท ๊ฐ’์„ ์‚ฌ์šฉํ•˜์˜€๋‹ค. ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์—ด์ ๋ฌผ์„ฑ์€ ์˜จ๋„์— ๋”ฐ๋ผ ๋ณ€ํ•˜์ง€๋งŒ, ์‚ฌ์ „ํ•ด์„ ๊ฒฐ๊ณผ, ๋ฐ€๋„์˜ ๊ฒฝ์šฐ์—๋Š” ๊ทธ ๋ณ€ํ™”๊ฐ€ ์œ ์˜๋ฏธํ•œ ์ˆ˜์ค€์ด ์•„๋‹ˆ์–ด์„œ ํ•ด์„๊ฒฐ๊ณผ์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์€ ๋ฏธ๋ฏธํ•˜์˜€๋‹ค. ์˜จ๋„์— ๋”ฐ๋ฅธ ์—ดํŒฝ์ฐฝ๊ณ„์ˆ˜์˜ ๊ฒฝ์šฐ์—๋Š” ๊ณจ์žฌ ์ข…๋ฅ˜ ๋ฐ ํ•จ์ˆ˜์œจ์— ํฐ ์˜ํ–ฅ์„ ๋ฐ›์ง€๋งŒ, Eurocode 2 ๋ฐ ASCE ๋“ฑ์—์„œ ์ œ๊ณตํ•˜๋Š” ๋ชจ๋ธ์ด ์ถฉ๋ถ„ํžˆ ์ •ํ™•ํ•˜์ง€ ์•Š๋‹ค๋Š” ์—ฐ๊ตฌ๊ฒฐ๊ณผ๊ฐ€ ์žˆ๋‹ค(Ghannam 2019). ์ด์— ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ํ•ด์„์˜ ์ˆ˜๋ ด์„ฑ ๋“ฑ์„ ๊ฐ์•ˆํ•˜์—ฌ ๊ฐ„๋‹จํžˆ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋ฐ€๋„(2,300 kg/m3) ๋ฐ ์—ดํŒฝ์ฐฝ๊ณ„์ˆ˜(10ร—10-6 K-1)๋ฅผ ์˜จ๋„์— ์ƒ๊ด€์—†์ด ์ผ์ •ํ•œ ๊ฒƒ์œผ๋กœ ๊ฐ€์ •ํ•˜์˜€๋‹ค. Fig. 3์€ ๋ชจ๋ธ๋ง์— ์‚ฌ์šฉ๋œ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์žฌ๋ฃŒ๋ฌผ์„ฑ์„ ์ •๋ฆฌํ•˜์—ฌ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค.

Fig. 3 Concrete material properties at elevated temperature(CEN 2004)
../../Resources/KCI/JKCI.2024.36.5.427/fig3.png
Fig. 4 Steel material properties at elevated temperature(CEN 2005)
../../Resources/KCI/JKCI.2024.36.5.427/fig4.png

์ฒ ๊ทผ์˜ ์‘๋ ฅ-๋ณ€ํ˜•๋ฅ  ๊ด€๊ณ„ ๋ฐ ์—ด์  ๋ฌผ์„ฑ์น˜๋Š” Eurocode 3 Part 1-2(CEN 2005)๋ฅผ ๋”ฐ๋ž์œผ๋ฉฐ, ๋ณ€ํ˜•๋ฅ  ๊ฒฝํ™”(Strain Hardening)๋ฅผ ๋ฐ˜์˜ํ•˜์˜€๋‹ค. ์ฒ ๊ทผ์˜ ๋ฐ€๋„(7,850 kg/m3) ๋ฐ ์—ดํŒฝ์ฐฝ๊ณ„์ˆ˜(10ร—10-6 K-1) ์—ญ์‹œ ์˜จ๋„์— ์ƒ๊ด€์—†์ด ์ผ์ •ํ•˜๋‹ค๊ณ  ๊ฐ€์ •ํ•˜์˜€์œผ๋ฉฐ, ์‚ฌ์šฉ๋œ ์ฒ ๊ทผ์˜ ์žฌ๋ฃŒ๋ฌผ์„ฑ์€ Fig. 4์— ์ •๋ฆฌํ•˜์˜€๋‹ค.

์—ด๊ตํ™˜ ํ•ด์„์„ ์œ„ํ•ด ๋Œ€๋ฅ˜(Surface Film Condition) ๋ฐ ๋ณต์‚ฌ(Surface Radiation)์˜ ๊ฐ€์—ด๊ฒฝ๊ณ„์กฐ๊ฑด์€ Interaction์„ ํ†ตํ•ด ์ ์šฉํ•˜์˜€์œผ๋ฉฐ, ๊ฒฝ๊ณ„๋ฉด ๊ฐ€์—ด์กฐ๊ฑด์€ Eurocode 2์˜ ๊ถŒ์žฅ๊ฐ’์„ ์ ์šฉํ•˜์˜€๋‹ค: ๋Œ€๋ฅ˜์—ด์ „๋‹ฌ๊ณ„์ˆ˜(Film Coefficient)=25 W/m2๏ฝฅK, ๋ณต์‚ฌ๊ฒฝ๊ณ„์กฐ๊ฑด ๋ฐฉ์‚ฌ์œจ(Emissivity)=0.7, ์Šคํ…ŒํŒ-๋ณผ์ธ ๋งŒ ์ƒ์ˆ˜(Stefan- Boltzmann Constant)=5.6710ร—10-8 W/m2K4(Kang and Kim 2023).

์ฝ˜ํฌ๋ฆฌํŠธ, ์ฃผ์ฒ ๊ทผ, ๊ฐ•์žฌ(End-plates)์— ๋Œ€ํ•ด์„œ๋Š” ์—ด-์‘๋ ฅ ํ•ด์„์ด ๊ฐ€๋Šฅํ•œ ๊ฐ์†Œ์ ๋ถ„ Solid Mesh์ธ C3D8RT ์š”์†Œ๋ฅผ ์‚ฌ์šฉํ•˜์˜€๊ณ , ํšก์ฒ ๊ทผ์— ๋Œ€ํ•ด์„œ๋Š” ์—ด-์‘๋ ฅ ํ•ด์„์ด ๊ฐ€๋Šฅํ•œ Truss Mesh์ธ T3D2T ์š”์†Œ๋ฅผ ์‚ฌ์šฉํ•˜์˜€๋‹ค. Mesh Size๋Š” ํ•ด์„์˜ ์‹œ๊ฐ„ ๋ฐ ์ •ํ™•๋„๋ฅผ ๊ณ ๋ คํ•ด ๊ฒฐ์ •ํ•˜์˜€์œผ๋‚˜, ์ตœ๋Œ€ 50 mm ์ดํ•˜๋กœ ์ œํ•œํ•˜์˜€๋‹ค.

์ฒ ๊ทผ๊ณผ ์ฝ˜ํฌ๋ฆฌํŠธ๋Š” ์™„์ „๋ถ€์ฐฉ์„ ๊ฐ€์ •ํ•˜๊ณ  ๊ณ„๋ฉด์—์„œ์˜ ์—ด์  ์ €ํ•ญ์€ ๊ณ ๋ คํ•˜์ง€ ์•Š์•˜๋‹ค. ์ด์— ๋”ฐ๋ผ ์ฒ ๊ทผ๊ณผ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ธฐ๊ณ„์ /์—ด์  ์ƒํ˜ธ์ž‘์šฉ์€ Embedded Constraint๋กœ ๋ชจ๋ธ๋งํ•˜์˜€๋‹ค. ์ด ๊ฒฝ์šฐ ์ฒ ๊ทผ์— ์ž…๋ ฅ๋˜๋Š” ์˜จ๋„๋Š” ์ฒ ๊ทผ๊ณผ ๋งž๋‹ฟ์•„ ์žˆ๋Š” ์ฃผ๋ณ€ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์˜จ๋„์ด๋ฉฐ, Solid Element๋กœ ๋ชจ๋ธ๋ง๋œ ์ฃผ์ฒ ๊ทผ ๋‚ด๋ถ€์˜ ์—ด์ „๋‹ฌ์€ ์ฒ ๊ทผ์˜ ์—ด์  ๋ฌผ์„ฑ์น˜์— ๋”ฐ๋ฅธ๋‹ค. ๊ฐ•์žฌ์™€ ์ฝ˜ํฌ๋ฆฌํŠธ ๋ฐ ์ฃผ์ฒ ๊ทผ๊ณผ์˜ ์ƒํ˜ธ์ž‘์šฉ์€ Tie Constraint๋กœ ์ •์˜ํ•˜์˜€๋‹ค. ์ถ•๋ ฅ์€ ์ง‘์ค‘ํ•˜์ค‘ ๋ฐ Rigid Body Constraint๋กœ ๋‹จ๋ถ€์— ๋ชจ๋ธ๋งํ•˜์˜€์œผ๋ฉฐ, ํ•˜์ค‘ ์ž‘์šฉ์ ์˜ Boundary Condition์„ ํ†ตํ•ด ์‹คํ—˜์ฒด ๋‹จ๋ถ€ ๊ตฌ์†์กฐ๊ฑด์„ ๋ฐ˜์˜ํ•˜์˜€๋‹ค.

ํ•ด์„์€ ์ด ๋‘ ๋‹จ๊ณ„๋กœ ์ง„ํ–‰๋˜์—ˆ๋‹ค. ์‹คํ—˜์กฐ๊ฑด๊ณผ ๋™์ผํ•˜๊ฒŒ, Step 1์—์„œ๋Š” ์ถ•๋ ฅ(์ค‘์‹ฌํ•˜์ค‘ ๋ฐ ํŽธ์‹ฌํ•˜์ค‘)์„ ์ ์ง„์ ์œผ๋กœ ๊ฐ€ํ•œ ํ›„ ์ผ์ •ํ•˜๊ฒŒ ์œ ์ง€์‹œ์ผฐ๋‹ค. ์ดํ›„ Step 2์—์„œ ์—ด ํ•˜์ค‘์„ ๊ฐ€ํ•˜์˜€๋‹ค. ์‹คํ—˜์ฒด์˜ ์„ธ์žฅ๋น„($KL/r$)๋Š” 28.1~43.3์˜ ๋ฒ”์œ„์— ์žˆ์œผ๋ฉฐ ํ˜„ํ–‰ ์„ค๊ณ„๊ธฐ์ค€์ธ KDS 14 20 20(KCI 2022)์— ๋”ฐ๋ผ ์„ธ์žฅํ•œ ๊ธฐ๋‘ฅ(์žฅ์ฃผ)์œผ๋กœ ๋ถ„๋ฅ˜๋˜๋ฏ€๋กœ ํ•ด์„ ์‹œ ๊ธฐํ•˜ํ•™์  ๋น„์„ ํ˜•์„ฑ์„ ๊ณ ๋ คํ•˜์˜€๋‹ค. ๊ฐ€์—ด๋ฒ”์œ„๋Š” ์›๋ฌธ(Lie and Woollerton 1988)์— ์ •ํ™•ํ•œ ์ •๋ณด๊ฐ€ ์—†์–ด ํ•ด์„์—์„œ๋Š” ๊ธฐ๋‘ฅ ๊ธธ์ด์˜ 1/8~7/8๋กœ ๊ฐ€์ •ํ•˜์˜€์œผ๋ฉฐ(Fig. 5(a)), ASTM- E119์˜ ํ‘œ์ค€์‹œ๊ฐ„-๊ฐ€์—ด์˜จ๋„๊ณก์„ (Fig. 6)์— ๋”ฐ๋ผ 240๋ถ„๊ฐ„ 4๋ฉด์˜ ์˜จ๋„๋ฅผ ์ฆ๊ฐ€์‹œ์ผฐ๋‹ค. ์ฐธ๊ณ ๋กœ, ์‹ค์ œ ์‹คํ—˜์—์„œ ๊ฐ€์—ด๊ณผ ํ•จ๊ป˜ ํŽธ์‹ฌํ•˜์ค‘์„ ๊ฐ์†Œ์‹œํ‚จ ์‹คํ—˜์ฒด์˜ ๊ฒฝ์šฐ์—๋Š” ์›๋ฌธ์˜ ๋‚ด์šฉ์— ๋”ฐ๋ผ ํ•ด๋‹น ํŽธ์‹ฌํ•˜์ค‘์„ ์„ ํ˜•์ (0.1 kN/min)์œผ๋กœ ๊ฐ์†Œ์‹œ์ผฐ๋‹ค. ์—ด ํ•˜์ค‘์„ ํฌํ•จํ•œ ๋ชจ๋“  ํ•˜์ค‘์€ Amplitude๋ฅผ ํ†ตํ•ด ํ†ต์ œํ•˜์˜€๋‹ค.

Fig. 5 Location of thermocouples (T/C) and assumed range of fire exposure
../../Resources/KCI/JKCI.2024.36.5.427/fig5.png
Fig. 6 ASTM-E119 standard time-temperature curve
../../Resources/KCI/JKCI.2024.36.5.427/fig6.png

3. ์—ด-์‘๋ ฅ ํ•ด์„ ๊ฒฐ๊ณผ ๋ฐ ๊ฒ€์ฆ

์—ด-์‘๋ ฅ ํ•ด์„์˜ ๊ฒ€์ฆ์„ ์œ„ํ•˜์—ฌ, ํ•ด์„๊ฒฐ๊ณผ๋ฅผ ์‹คํ—˜๊ฒฐ๊ณผ์™€ ๋น„๊ตํ•˜์˜€๋‹ค. ์šฐ์„  ์—ด ํ•˜์ค‘์˜ ๊ฒ€์ฆ์„ ์œ„ํ•˜์—ฌ, ์˜จ๋„ ๋ถ„ํฌ๋ฅผ ๋น„๊ตํ•˜์˜€๋‹ค. ํ•ด์„๊ฒฐ๊ณผ๋Š” ์‹คํ—˜์ฒด ๋‚ด ์—ด์ „๋Œ€(Thermocouples) ์œ„์น˜(Fig. 5(b))์™€ ๋™์ผํ•œ ์œ„์น˜์—์„œ ์ถ”์ถœํ•˜์˜€๋‹ค. ์ฐธ๊ณ ๋กœ, ์‹คํ—˜์ฒด๋“ค์˜ ๋‹จ๋ฉด๊ตฌ์„ฑ ๋ฐ ๊ฐ€์—ด์กฐ๊ฑด์ด ๋™์ผํ•˜์—ฌ ๋‹จ๋ฉด ๋‚ด ์˜จ๋„ ๋ถ„ํฌ๊ฐ€ ์œ ์‚ฌํ•˜๋ฏ€๋กœ, ์—ฌ๊ธฐ์„œ๋Š” ๋Œ€ํ‘œ๋กœ ์‹คํ—˜์ฒด I-1์˜ ์˜จ๋„ ๋ถ„ํฌ๋งŒ ๋น„๊ตํ•œ๋‹ค.

Fig. 7์€ ์—ด-์‘๋ ฅ ํ•ด์„์„ ํ†ตํ•ด ์–ป์€ ๊ฐ€์—ด 60๋ถ„ ํ›„ ๋‹จ๋ฉด์˜ ์˜จ๋„ ๋ถ„ํฌ์ด๋‹ค. ์ „์ฒด์ ์œผ๋กœ ํ•ด์„๊ฒฐ๊ณผ๋Š” ์‹คํ—˜๊ฒฐ๊ณผ์™€ ์œ ์‚ฌํ•œ ์˜จ๋„ ๋ถ„ํฌ ๋ฐ ๋ณ€ํ™”๋ฅผ ๋ณด์˜€๋‹ค. ๋‹จ๋ฉด ๋‚ด ์œ„์น˜๊ฐ€ ๊นŠ์–ด์งˆ์ˆ˜๋ก ์˜จ๋„๊ฐ€ ๋‚ด๋ ค๊ฐ”์œผ๋ฉฐ, ์‹คํ—˜๊ณผ ํ•ด์„ ๋ชจ๋‘ ๊ธฐ๋‘ฅ ํ‘œ๋ฉด์—์„œ ์‹ฌ๋ถ€๊นŒ์ง€ ์•ฝ 815 ยฐC์˜ ์˜จ๋„ ์ฐจ์ด๊ฐ€ ๋ฐœ์ƒํ–ˆ๋‹ค. ๋‹ค๋งŒ ํ•ด์„ ๊ฒฐ๊ณผ, ์‹ฌ๋ถ€์—์„œ๋Š” ์•ฝ 2~5 ยฐC, ํ‘œ๋ฉด์—์„œ๋Š” ์•ฝ 3 ยฐC ์‹คํ—˜๊ฒฐ๊ณผ๋ณด๋‹ค ๋†’์€ ์˜จ๋„๋ฅผ ๋ณด์˜€๋‹ค. ํ•œํŽธ, 2๋ฐฉํ–ฅ์œผ๋กœ ๊ฐ€์—ด๋˜๋Š” ๋ชจ์„œ๋ฆฌ๋ถ€๊ฐ€ ๊ธฐ๋‘ฅ๋ฉด ์ค‘์•™๋ถ€๋ณด๋‹ค ํ‰๊ท ์ ์œผ๋กœ ๋” ๋†’์€ ์˜จ๋„ ๋ถ„ํฌ๋ฅผ ๋ณด์˜€๋‹ค: ํ‘œ๋ฉด์˜ ์˜จ๋„๋Š” ํ•ด์„์กฐ๊ฑด์— ๋”ฐ๋ผ ๋™์ผํ•˜๋‚˜, ๋ชจ์„œ๋ฆฌ์™€ ๋‹จ๋ฉด์˜ ๋„์‹ฌ์„ ์ž‡๋Š” ์„ ์„ ๋”ฐ๋ผ ์˜จ๋„ ๋ถ„ํฌ๋ฅผ ๋น„๊ตํ•˜๋ฉด, ์‹ฌ๋ถ€ ๊ทผ์ฒ˜๋Š” ์•ฝ 15 ยฐC, ํ‘œ๋ฉด๊ณผ ์‹ฌ๋ถ€ ์ค‘๊ฐ„์€ ์•ฝ 227 ยฐC ๋” ๋†’์•˜๋‹ค.

Fig. 7 Section temperature distribution at 60 mins
../../Resources/KCI/JKCI.2024.36.5.427/fig7.png
Fig. 8 Reinforcing bar temperature at elevated time
../../Resources/KCI/JKCI.2024.36.5.427/fig8.png

Fig. 8์€ ์‹œ๊ฐ„์— ๋”ฐ๋ฅธ ์ฃผ์ฒ ๊ทผ ๋ฐ ํšก์ฒ ๊ทผ์˜ ์˜จ๋„๋ณ€ํ™”์ด๋‹ค. ํ•ด์„๊ฒฐ๊ณผ, ๋Œ€๋ถ€๋ถ„ ์‹คํ—˜๊ณผ ์œ ์‚ฌํ•œ ์–‘์ƒ์œผ๋กœ ์˜จ๋„๊ฐ€ ์ ์ง„์ ์œผ๋กœ ์ฆ๊ฐ€ํ•˜๋Š” ์–‘์ƒ์„ ๋ณด์˜€๋‹ค. ๋‹ค๋งŒ T/C2(ํšก์ฒ ๊ทผ: Fig. 5 ์ฐธ์กฐ)์˜ ๊ฒฝ์šฐ ๊ฐ€์—ด์‹œ๊ฐ„ ๋‚ด ํ‰๊ท ์ ์œผ๋กœ ์•ฝ 80 ยฐC์˜ ์˜จ๋„ ์ฐจ์ด(ํ•ด์„์ด ๋” ๋†’๊ฒŒ ํ‰๊ฐ€)๊ฐ€ ๋ฐœ์ƒํ–ˆ์œผ๋ฉฐ, ์ตœ๋Œ€ ์•ฝ 115 ยฐC์˜ ์˜จ๋„ ์ฐจ์ด๊ฐ€ ๋ฐœ์ƒํ–ˆ๋‹ค. ๊ทธ ์™ธ์˜ ๊ฒฝ์šฐ์—๋Š” ์‹คํ—˜๊ณผ ํ•ด์„๊ฒฐ๊ณผ์˜ ์ฐจ์ด๋Š” ๋ฏธ๋ฏธํ–ˆ๋‹ค. ์‹คํ—˜ ๋ฐ์ดํ„ฐ์— ๋ช…์‹œ๋˜์–ด ์žˆ๋Š” ์ตœ์ข… ๊ฐ€์—ด์‹œ๊ฐ„์ธ 180๋ถ„ ๊ธฐ์ค€, ์ฒ ๊ทผ์˜ ํ‰๊ท ์˜จ๋„๋Š” ์•ฝ 682.2 ยฐC์˜€์œผ๋ฉฐ(์‹คํ—˜์—์„œ๋Š” ์•ฝ 681.4 ยฐC), ์ฃผ์ฒ ๊ทผ์˜ ์ตœ๋Œ€์˜จ๋„๋Š” ์•ฝ 734.1 ยฐC์˜€๋‹ค(์‹คํ—˜์—์„œ๋Š” ์•ฝ 710 ยฐC).

์—ด-์‘๋ ฅ ํ•ด์„๋ชจ๋ธ์˜ ๊ตฌ์กฐ๊ฑฐ๋™ ์˜ˆ์ธก์˜ ์ •ํ™•๋„๋ฅผ ํ‰๊ฐ€ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ, ์ถ•๋ฐฉํ–ฅ ๋ณ€ํ˜• ๋˜ํ•œ ์‹คํ—˜๊ฒฐ๊ณผ์™€ ๋น„๊ตํ•˜์˜€๋‹ค. ์šฐ์„  ์ •๋Ÿ‰์ ์ธ ๋น„๊ต๋ฅผ ์œ„ํ•ด, ์ตœ๋Œ€ ํŒฝ์ฐฝ๋Ÿ‰ ๋ฐ ํŒฝ์ฐฝ ์ดํ›„ ์ˆ˜์ถ•๊ณผ์ •์—์„œ ์ƒ์˜จ ๊ธฐ๋‘ฅ๊ธธ์ด๋ณด๋‹ค ๋” ์งง์•„์ง€๋Š” ์‹œ์ (Figs. 8๊ณผ 9์—์„œ x์ถ•๊ณผ์˜ ๊ต์ )์„ Table 2์— ๋น„๊ตํ•˜์˜€๋‹ค. ํ‰๊ท ์ ์œผ๋กœ ์‹คํ—˜๊ฒฐ๊ณผ์— ๋Œ€ํ•œ ํ•ด์„๊ฒฐ๊ณผ์˜ ๋น„์œจ์€ ์ตœ๋Œ€ ํŒฝ์ฐฝ๋Ÿ‰์˜ ๊ฒฝ์šฐ 0.64, ์ƒ์˜จ ๊ธฐ๋‘ฅ๊ธธ์ด ๋Œ€๋น„ ์ˆ˜์ถ• ์‹œ์ ์˜ ๊ฒฝ์šฐ 0.78์ด์—ˆ๋‹ค. ์ •๋Ÿ‰์ ์ธ ๊ด€์ ์—์„œ ๋ณด์•˜์„ ๋•Œ, ์ „์ฒด์ ์œผ๋กœ ํ•ด์„์€ ๊ธฐ๋‘ฅ์˜ ํŒฝ์ฐฝ์„ ๋‚ฎ๊ฒŒ ํ‰๊ฐ€ํ•˜๊ณ , ๊ธฐ๋‘ฅ์˜ ์ˆ˜์ถ• ์‹œ์ ์„ ์ด๋ฅด๊ฒŒ ํ‰๊ฐ€ํ•˜๋Š” ๊ฒฝํ–ฅ์„ ๋ณด์˜€๋‹ค.

๋”์šฑ ์ž์„ธํ•œ ๋น„๊ต๋ฅผ ์œ„ํ•˜์—ฌ, ๊ฐ€์—ด์‹œ๊ฐ„์— ๋”ฐ๋ฅธ ์ „์ฒด ์ถ•๋ณ€ํ˜• ์ด๋ ฅ์„ Fig. 9(์ค‘์‹ฌ๊ฐ€๋ ฅ)๊ณผ Fig. 10(ํŽธ์‹ฌ๊ฐ€๋ ฅ)์— ๋น„๊ตํ•˜์˜€๋‹ค. ์ค‘์‹ฌ๊ฐ€๋ ฅ์˜ ๊ฒฝ์šฐ(Fig. 9), ๋น„๋ก I-2์™€ I-8์ด ๊ธฐ๋‘ฅํŒฝ์ฐฝ์˜ ๊ด€์ ์—์„œ ๋น„๊ต์  ํฐ ์ฐจ์ด๋ฅผ ๋ณด์˜€์ง€๋งŒ, ์ „์ฒด์ ์œผ๋กœ ์‹คํ—˜๊ณผ ์œ ์‚ฌํ•˜๊ฒŒ ์—ดํŒฝ์ฐฝ์œผ๋กœ ์ธํ•œ ๋ณ€ํ˜• ๋ฐ ์žฌ๋ฃŒ๋ฌผ์„ฑ ๊ฐ์†Œ๋กœ ์ธํ•œ ์ˆ˜์ถ•์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์—ˆ๋‹ค. I-2 ๋ฐ I-8์˜ ๊ฒฝ์šฐ(์ถ•๋ ฅ๋น„=0.42 ๋ฐ 0.55), ๋ ์ฒ ๊ทผ ๊ธฐ๋‘ฅ์˜ ํ†ต์ƒ์ ์ธ ์„ค๊ณ„ ์ถ•๋ ฅ๋น„ ํ•œ๊ณ„(์•ฝ 0.44)์˜ ์•ฝ 95 % ๋ฐ 125 %๋ฅผ ๊ฐ€ํ•œ ์‹คํ—˜์ฒด์ด๋‹ค. ํ•ด์„๊ณผ ์‹คํ—˜์˜ ์ฐจ์ด๋Š” ๊ธฐ๋ณธ์ ์œผ๋กœ ์žฌ๋ฃŒ ๋ชจ๋ธ๋ง์˜ ์˜ํ–ฅ์„ ํฌ๊ฒŒ ๋ฐ›์ง€๋งŒ, ๋†’์€ ์ถ•๋ ฅ์ˆ˜์ค€ ์—ญ์‹œ ํฐ ์˜ํ–ฅ์„ ๋ผ์นœ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ์™œ๋ƒํ•˜๋ฉด ๋ณธ ์—ฐ๊ตฌ์—์„œ ๋Œ€์ƒ์œผ๋กœ ํ•œ ์‹คํ—˜์ฒด์˜ ๊ฒฝ์šฐ, ํŽธ์‹ฌํ•˜์ค‘์„ ๋ฐ›์œผ๋ฉฐ ์ƒ๋Œ€์ ์œผ๋กœ ์„ธ์žฅํ•œ RC ๊ธฐ๋‘ฅ์ด๊ธฐ ๋•Œ๋ฌธ์ด๋‹ค. ์ด ๊ฒฝ์šฐ 2์ฐจ ํšจ๊ณผ๊ฐ€ ๋ฐœ์ƒํ•˜๋Š”๋ฐ, ์ถ•๋ ฅ๋น„๊ฐ€ ๋†’์œผ๋ฉด ์•„์ฃผ ์ž‘์€ ํŽธ์‹ฌ๊ฑฐ๋ฆฌ(Eccentricity)/๋‹จ๋ถ€ํšŒ์ „๊ตฌ์†๋„์˜ ์ฐจ์ด ๋˜๋Š” ์•„์ฃผ ์‚ฌ์†Œํ•œ ์ดˆ๊ธฐ๋ถˆ์™„์ „์„ฑ(Initial Imperfection)์˜ ๊ฐœ์ž…๋งŒ์œผ๋กœ๋„ ์‹คํ—˜๊ฒฐ๊ณผ๊ฐ€ ํฌ๊ฒŒ ๋‹ฌ๋ผ์งˆ ์ˆ˜ ์žˆ๋‹ค. ํ•ด์„๊ณผ ์‹คํ—˜์—์„œ์˜ ์ฐจ์ด๋Š” ์ด๋Ÿฌํ•œ ๋†’์€ ์ถ•๋ ฅ์˜ ํšจ๊ณผ์— ์ฃผ๋กœ ๊ธฐ์ธํ•œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

Table 2 Comparison of test and analysis results

Loading

type

Specimen

Maximum

expansion

[mm]

Time at onset

of shortening

[mins]

Test

Analysis

Test

Analysis

Concentric

I-2

4.8

2.13

150

90.9

I-3

6.6

8.5

198.1

194.1

I-4

7.6

10.4

203.5

209.9

I-7

6

3.9

187.8

155.8

I-8

1.1

0.31

96.7

43.4

Eccentric

III-7

7.2

2.6

-

114.7

III-8

8.2

3.3

214.5

153.7

III-9

8.3

5.2

214.1

170.7

III-10

7.7

2.9

-

148.8

III-14

5.6

3.8

180.8

155.3

Fig. 9 Comparison of axial displacements (Concentrically loaded)
../../Resources/KCI/JKCI.2024.36.5.427/fig9.png
Fig. 10 Comparison of axial displacements (Eccentrically loaded)
../../Resources/KCI/JKCI.2024.36.5.427/fig10.png

ํŽธ์‹ฌ๊ฐ€๋ ฅ์˜ ๊ฒฝ์šฐ์—๋„(Fig. 10) ๋ณ€ํ˜•๋Ÿ‰์˜ ํฌ๊ธฐ ๋ฐ ๊ธฐ๋‘ฅ์ˆ˜์ถ• ์‹œ์ ์€ ๋‹ค์†Œ ์ฐจ์ด๊ฐ€ ์žˆ์—ˆ์ง€๋งŒ, ๊ฐ€์—ด์— ๋”ฐ๋ฅธ ํŒฝ์ฐฝ ๋ฐ ์ˆ˜์ถ•์˜ ์–‘์ƒ์ด ์‹คํ—˜๊ฒฐ๊ณผ์™€ ์œ ์‚ฌํ•˜์˜€๋‹ค. ์ฐธ๊ณ ๋กœ, Lie and Woollerton (1988)์€ ๊ธฐ๋‘ฅ์˜ ํ•ญ๋ณต์„ ์ถ•๋ณ€ํ˜• ๋ณ€ํ™”์œจ์ด 76 mm/min์„ ์ดˆ๊ณผํ•œ ์‹œ์ ์œผ๋กœ ์ •์˜ํ•˜์˜€๋‹ค. ํ•˜์ง€๋งŒ ์ผ๋ถ€ ์‹คํ—˜์ฒด์— ๋Œ€ํ•ด์„œ๋Š” ์ด ์กฐ๊ฑด์„ ๋งŒ์กฑํ•˜์ง€ ์•Š์•˜์Œ์—๋„ ์‹คํ—˜์„ ์กฐ๊ธฐ์ข…๋ฃŒํ•˜์˜€๋‹ค. ์›๋ฌธ์— ์ •ํ™•ํ•œ ์ด์œ ๋ฅผ ์ œ์‹œํ•˜์ง€๋Š” ์•Š์•˜์ง€๋งŒ, ์ƒ๋Œ€์ ์œผ๋กœ ๋†’์€ ์ถ•๋ ฅ๋น„, ํŽธ์‹ฌํšจ๊ณผ, ๋‹จ๋ถ€ํšŒ์ „๊ตฌ์†๋„ ๋“ฑ์„ ๊ณ ๋ คํ•˜์—ฌ ์•ˆ์ „์ƒ์˜ ์ด์œ ๋กœ ์กฐ๊ธฐ์ข…๋ฃŒํ•œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ์ด์— ๋”ฐ๋ผ III-7๊ณผ III-10์˜ ๊ฒฝ์šฐ, ์ƒ์˜จ ๊ธฐ๋‘ฅ๊ธธ์ด ๋Œ€๋น„ ์ˆ˜์ถ•์ด ๋ฐœ์ƒํ•˜์ง€ ์•Š์•˜์Œ์—๋„ ์‹คํ—˜์ด ์กฐ๊ธฐ์ข…๋ฃŒ๋˜์–ด, Table 2์— ์ƒ์˜จ๋Œ€๋น„ ๊ธฐ๋‘ฅ์ˆ˜์ถ• ์‹œ์ ์ด ๋ˆ„๋ฝ๋˜์–ด ์žˆ๋‹ค.

4. ํ† ์˜ ๋ฐ ๋‚ดํ™”์„ฑ๋Šฅ

4.1 ์˜จ๋„ ๋ถ„ํฌ

ํ•ด์„์— ๋”ฐ๋ฅธ ์‹ฌ๋ถ€์˜ ์˜จ๋„ ๋ถ„ํฌ๊ฐ€ ์‹คํ—˜๊ฒฐ๊ณผ๋ณด๋‹ค ๋‹ค์†Œ ๋†’์€ ๊ฒƒ์€ ์ฃผ๋กœ ์ฝ˜ํฌ๋ฆฌํŠธ ๋‹จ๋ฉด ๋‚ด ์ˆ˜๋ถ„์˜ ์˜ํ–ฅ ๋•Œ๋ฌธ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด ์ˆ˜๋ถ„์˜ ์˜ํ–ฅ์„ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋น„์—ด๋กœ๋งŒ ๋ฐ˜์˜ํ•˜์˜€์ง€๋งŒ, ์‹ค์ œ ์‹คํ—˜์—์„œ๋Š” ์ˆ˜๋ถ„๋ง‰ํž˜ํ˜„์ƒ(Moisture Clog Phenomenon: Harmathy 1965) ๋“ฑ์œผ๋กœ ์ธํ•ด ์‹ฌ๋ถ€๋กœ์˜ ์—ด์ „๋‹ฌ์— ์ฐจ์ด๊ฐ€ ๋ฐœ์ƒํ•  ์ˆ˜ ์žˆ๋‹ค: ์™ธ๋ถ€์—์„œ ์—ด์ด ๊ฐ€ํ•ด์ง€๋ฉด ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด๋ถ€์˜ ์ˆ˜๋ถ„์ด ๊ฐ€์—ด๋˜์–ด ์ˆ˜์ฆ๊ธฐ๊ฐ€ ๋˜๊ณ , ์ด๋Ÿฌํ•œ ๊ณ ์˜จ๊ณ ์••์˜ ์ˆ˜์ฆ๊ธฐ๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด ๋ฏธ์„ธ๊ณต๊ทน์„ ํ†ตํ•ด ์ƒ๋Œ€์ ์œผ๋กœ ์ €์˜จ์ €์••์ธ ์ฝ˜ํฌ๋ฆฌํŠธ ๋‚ด๋ถ€๋กœ ์ด๋™ํ•˜๋ ค ํ•˜์ง€๋งŒ, ์˜จ๋„ ์ฐจ์ด๋กœ ์ธํ•ด ์ผ๋ถ€๋Š” ๋‹ค์‹œ ์‘์ถ•๋˜๋ฉฐ, ์ด๋ ‡๊ฒŒ ์‘์ถ•๋œ ์ˆ˜๋ถ„์€ ๋‹ค์‹œ ๊ณต๊ทน์„ ๋ง‰๊ณ (ํฌํ™”์ธต ํ˜•์„ฑ) ๋น„์—ด๋„ ๋†’์•„ ์—ด์ „๋‹ฌ์„ ์ง€์—ฐ์‹œํ‚จ๋‹ค. ๋‹ค๋งŒ, ์ „์ฒด์ ์œผ๋กœ ํ•ด์„๊ฒฐ๊ณผ์˜ ์–‘์ƒ์ด ์‹คํ—˜๊ฒฐ๊ณผ์™€ ์œ ์‚ฌํ•˜๋‹ค๋Š” ์ ์„ ๊ฐ์•ˆํ•  ๋•Œ ์ œ์‹œ๋œ ์—ด-์‘๋ ฅ ํ•ด์„ ๋ชจ๋ธ์€ ์—ด ํ•˜์ค‘์„ ๋น„๊ต์  ์ •ํ™•ํ•œ ์ˆ˜์ค€์œผ๋กœ ์˜ˆ์ธกํ•œ๋‹ค๋Š” ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์—ˆ๋‹ค.

4.2 ์ถ•๋ฐฉํ–ฅ ๋ณ€ํ˜•

Fig. 9 ๋ฐ Fig. 10์„ ํ†ตํ•ด ๋ณ€ํ˜•๋Ÿ‰์˜ ํฌ๊ธฐ๋Š” ๋‹ค์†Œ ์ฐจ์ด๊ฐ€ ์žˆ์—ˆ์ง€๋งŒ, ๊ฐ€์—ด์‹œ๊ฐ„์— ๋”ฐ๋ฅธ ํŒฝ์ฐฝ ๋ฐ ์ˆ˜์ถ•์˜ ์–‘์ƒ์ด ์‹คํ—˜๊ฒฐ๊ณผ์™€ ์œ ์‚ฌํ•œ ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์—ˆ๋‹ค. ๊ฐ€์ •ํ•œ ์žฌ๋ฃŒ๋ฌผ์„ฑ ๋ฐ ๊ฐ€์—ด๋ฒ”์œ„, ์ƒ๋Œ€์ ์œผ๋กœ ๋†’์€ ์ถ•๋ ฅ๋น„ ๋ฐ ํŽธ์‹ฌํšจ๊ณผ, ๋‹จ๋ถ€ํšŒ์ „๊ตฌ์†๋„ ๋“ฑ ๋‹ค์–‘ํ•œ ์š”์ธ์ด ๋ณตํ•ฉ์ ์œผ๋กœ ๋ณ€ํ˜•๋Ÿ‰์— ์˜ํ–ฅ์„ ๋ฏธ์นœ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ๋‹ค๋งŒ ์ค‘์‹ฌ๊ฐ€๋ ฅ ๋ฐ ํŽธ์‹ฌ๊ฐ€๋ ฅ ๋ชจ๋‘, ์ถ•๋ณ€ํ˜•์˜ ๊ด€์ ์—์„œ ํ•ด์„์€ ์‹คํ—˜๊ณผ ์œ ์‚ฌํ•œ ์ด๋ ฅ์„ ๋ณด์ด๋ฉด์„œ๋„ ์ •๋Ÿ‰์ ์œผ๋กœ๋Š” ๋ณด์ˆ˜์ ์ธ ๊ฒฐ๊ณผ๋ฅผ ๋ณด์˜€๋‹ค. ์žฌํ•˜๊ฐ€์—ด์‹คํ—˜์˜ ๊ฒฝ์ œ์ , ์‹œ๊ฐ„์  ๋น„์šฉ๊ณผ ์—ด-์‘๋ ฅํ•ด์„ ๊ฒฐ๊ณผ์˜ ์˜ค์ฐจ์ •๋„๋ฅผ ๊ณ ๋ คํ•˜๋ฉด ์ œ์•ˆ๋œ ์ˆ˜์น˜ํ•ด์„ ๊ธฐ๋ฒ•์ด ๋‹ค์–‘ํ•œ ์„ค๊ณ„๋ณ€์ˆ˜ ๋ฐ ํ™”์žฌ ์‹œ๋‚˜๋ฆฌ์˜ค๋ฅผ ๊ณ ๋ คํ•ด์•ผ ํ•˜๋Š” ๋‚ดํ™”์„ค๊ณ„์˜ ๋ชฉ์ ์— ๋ถ€ํ•ฉํ•œ๋‹ค๊ณ  ํŒ๋‹จ๋œ๋‹ค. ์ฐธ๊ณ ๋กœ ํŽธ์‹ฌ๊ฐ€๋ ฅ ๊ธฐ๋‘ฅ์˜ ๊ฒฝ์šฐ, ๋‹จ๋ถ€ ๊ตฌ์†์กฐ๊ฑด์ด ๊ณ ์ •๋‹จ(III-8, 9)์ผ ๋•Œ๋ณด๋‹ค ํšŒ์ „๋‹จ(III-14)์ผ ๋•Œ ๋” ๊ธ‰๊ฒฉํ•œ ์ˆ˜์ถ• ์–‘์ƒ์„ ๋ณด์˜€์œผ๋ฉฐ, ๋‹จ๋ถ€ํšŒ์ „๊ตฌ์†๋„์˜ ์ฆ๊ฐ€์— ๋”ฐ๋ผ ๋‚ดํ™”์„ฑ๋Šฅ์ด ์ฆ๊ฐ€ํ•˜๋Š” ๊ฒฝํ–ฅ์„ ๋ณด์˜€๋‹ค. ๋‹ค๋งŒ, ํ•ด์„์ƒ III-10(์ž์œ ํšŒ์ „)์— ๋น„ํ•ด III-7(๋ถ€๋ถ„๊ตฌ์†)์˜ ๋‚ดํ™”์„ฑ๋Šฅ์‹œ๊ฐ„์ด ๋” ๋‚ฎ์€ ์ด์œ ๋Š” ์ƒ๋Œ€์ ์œผ๋กœ ๋‹จ๋ถ€ํšŒ์ „๊ตฌ์†๋„์— ๋น„ํ•ด ์ด ์ถ•ํ•˜์ค‘(์ค‘์‹ฌํ•˜์ค‘+ํŽธ์‹ฌํ•˜์ค‘)์˜ ์˜ํ–ฅ์ด ๋” ํฌ๊ธฐ ๋•Œ๋ฌธ์ด๋‹ค.

Fig. 11์€ ์ค‘์‹ฌ๊ฐ€๋ ฅํ•œ ๊ฒฝ์šฐ(I-7) ๊ฐ€์—ด์‹œ๊ฐ„์— ๋”ฐ๋ฅธ ๊ธฐ๋‘ฅ ๋‚ด ์‘๋ ฅ ๋ถ„ํฌ๋ฅผ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค. ์ถ•๋ ฅ์„ ์žฌํ•˜ํ•˜๊ณ  ๊ฐ€์—ด ์ „์—๋Š” ๋น„๊ต์  ๊ธฐ๋‘ฅ ์ „ ๋‹จ๋ฉด์— ์‘๋ ฅ์ด ๊ณ ๋ฅด๊ฒŒ ๋ถ„ํฌ๋œ ๋ฐ˜๋ฉด, ๊ฐ€์—ด ์ดˆ๊ธฐ์—๋Š” ์‹ฌ๋ถ€์— ๋น„ํ•ด ํšก์ฒ ๊ทผ ์™ธ๋ถ€์˜ ํ”ผ๋ณต ์ฝ˜ํฌ๋ฆฌํŠธ๋ถ€๊ฐ€ ์—ดํŒฝ์ฐฝ์œผ๋กœ ์ธํ•ด ์ƒ๋Œ€์ ์œผ๋กœ ๋” ํฐ ์‘๋ ฅ์„ ๋ฐ›๋Š”๋‹ค๋Š” ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜ ๊ฐ€์—ด์‹œ๊ฐ„์ด ๊ธธ์–ด์ง์— ๋”ฐ๋ผ ๊ณ ์˜จ์—์„œ์˜ ํ”ผ๋ณต ์ฝ˜ํฌ๋ฆฌํŠธ ๋ฐ ์ฃผ์ฒ ๊ทผ์˜ ์žฌ๋ฃŒ๋ฌผ์„ฑ ์ €ํ•˜๋กœ ์ธํ•ด, ์ตœ์ข…์ ์œผ๋กœ๋Š” ์‹ฌ๋ถ€ ์ฝ˜ํฌ๋ฆฌํŠธ๊ฐ€ ๋Œ€๋ถ€๋ถ„์˜ ํ•˜์ค‘์„ ๋ถ€๋‹ดํ•˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋‹ค.

Fig. 12๋Š” ์‹คํ—˜์ข…๋ฃŒ ์‹œ์ ์—์„œ ํŽธ์‹ฌ๊ฐ€๋ ฅํ•œ III-9 ๋ฐ III-14์˜ ๋น„ํƒ„์„ฑ ๋ณ€ํ˜•๋ฅ  ๋ถ„ํฌ๋ฅผ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค. ํŽธ์‹ฌ๊ฐ€๋ ฅํ•œ ๊ธฐ๋‘ฅ ๋˜ํ•œ ๊ฐ€์—ด์‹œ๊ฐ„์ด ๊ธธ์–ด์ง์— ๋”ฐ๋ผ ํ”ผ๋ณต ์ฝ˜ํฌ๋ฆฌํŠธ ๋ฐ ์ฃผ์ฒ ๊ทผ์˜ ์žฌ๋ฃŒ๋ฌผ์„ฑ ์ €ํ•˜๋กœ ์ธํ•ด ์‹ฌ๋ถ€ ์ฝ˜ํฌ๋ฆฌํŠธ๋กœ ํ•˜์ค‘์ด ์ „์ด๋˜๋Š” ์–‘์ƒ์„ ๋ณด์˜€์œผ๋ฉฐ, ์ข…๊ตญ์ ์œผ๋กœ๋Š” ์—ด์‘๋ ฅ๊ณผ ๋”๋ถˆ์–ด 2์ฐจ ํšจ๊ณผ๋กœ ์ธํ•œ ๊ธฐ๊ณ„์  ์‘๋ ฅ์ด ๋ณตํ•ฉ์ ์œผ๋กœ ์ž‘์šฉํ•˜์—ฌ ํŒŒ๊ดด์— ๋„๋‹ฌํ•˜์˜€๋‹ค. ์ฐธ๊ณ ๋กœ ํ†ต์ƒ์ ์ธ ํœจํŒŒ๊ดด์˜ ์–‘์ƒ๋ณด๋‹ค ์••์ถ•์ธก ํ”ผํ•ด๊ฐ€ ์ƒ๋‹นํ•จ์ด ํ™•์ธ๋˜์—ˆ๋Š”๋ฐ(Fig. 12), ์ด๋Š” ์••์ถ•์ธก์—์„œ๋Š” ์—ด์‘๋ ฅ(์—ดํ•˜์ค‘์— ์˜ํ•ด ๊ธฐ๋‘ฅ์€ ํŒฝ์ฐฝํ•˜๋ ค๊ณ  ํ•˜๋‚˜ ์–‘๋‹จ๋ถ€๊ฐ€ ๊ตฌ์†๋˜์–ด ์žˆ์–ด ์••์ถ•์‘๋ ฅ์„ ๋ฐ›์Œ)๊ณผ ๊ธฐ๊ณ„์  ์‘๋ ฅ(ํœจ์••์ถ•์‘๋ ฅ)์ด ์ค‘์ฒฉ๋˜๊ธฐ ๋•Œ๋ฌธ์ด๋‹ค. ์ด๋Ÿฌํ•œ ๊ฒฐ๊ณผ๋Š” Kodur and Banerji (2021)์˜ ํ•ด์„์—ฐ๊ตฌ์—์„œ๋„ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋‹ค.

Fig. 11 Stress distribution at various exposure time
../../Resources/KCI/JKCI.2024.36.5.427/fig11.png
Fig. 12 Plastic strain (PEMAG) distribution at the end of the test
../../Resources/KCI/JKCI.2024.36.5.427/fig12.png

4.3 ๋‚ดํ™”์„ฑ๋Šฅ์‹œ๊ฐ„

ํ˜„ํ–‰ ใ€Œ๊ฑด์ถ•๋ถ€์žฌ์˜ ๋‚ดํ™”์„ฑ๋Šฅ์‹œํ—˜๊ธฐ์ค€(KS F 2257-1)ใ€์— ๋”ฐ๋ฅด๋ฉด, ๋‚ดํ™”์„ฑ๋Šฅ์‹œ๊ฐ„์€ ๋ถ€์žฌ์˜ ํ•˜์ค‘์ง€์ง€๋ ฅ์œผ๋กœ ํ‰๊ฐ€ํ•˜๋ฉฐ, ์ˆ˜์ถ•๋Ÿ‰($L$/100 mm) ๋ฐ ๋ณ€ํ˜•๋ฅ (3$L$/1,000 mm/min)๋กœ ์ •์˜๋œ๋‹ค. ๋‹ค๋งŒ, ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” Lie and Woollerton (1988)์˜ ์ •์˜์™€ ๋™์ผํ•˜๊ฒŒ ๊ธฐ๋‘ฅ ์ถ•๋ณ€ํ˜• ๋ณ€ํ™”์œจ์ด 76 mm/min์„ ์ดˆ๊ณผํ•œ ์‹œ์ ์„ ๋‚ดํ™”์„ฑ๋Šฅ์‹œ๊ฐ„์œผ๋กœ ํŒ์ •ํ•˜์˜€์œผ๋ฉฐ, ์กฐ๊ธฐ์ข…๋ฃŒ๋œ ์‹คํ—˜์ฒด์— ๋Œ€ํ•ด์„œ๋Š” ์‹คํ—˜์ข…๋ฃŒ์‹œ์ ์„ ๋‚ดํ™”์„ฑ๋Šฅ์‹œ๊ฐ„์œผ๋กœ ๊ฐ€์ •ํ•˜์˜€๋‹ค. Table 3์€ ํ•ด์„๊ฒฐ๊ณผ๋ฅผ ์‹คํ—˜๊ฒฐ๊ณผ์™€ ๋น„๊ตํ•œ ๊ฒƒ์ด๋‹ค. ํ˜„ํ–‰ ๊ธฐ์ค€๊ณผ ๋น„๊ต๋ฅผ ์œ„ํ•˜์—ฌ, Eurocode 2(CEN 2004)์— ๋”ฐ๋ฅธ ๋‚ดํ™”์„ฑ๋Šฅ์‹œ๊ฐ„๋„ ํ•จ๊ป˜ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ํ‘œ์— ๋‚˜ํƒ€๋‚œ ๋ฐ”์™€ ๊ฐ™์ด, ํŽธ์‹ฌ๋ฅ  ๋ฐ ์ถ•๋ ฅ๋น„ ๋“ฑ์— ๋”ฐ๋ผ ๋‹ค์†Œ ์ฐจ์ด๊ฐ€ ์žˆ์ง€๋งŒ, ์ „์ฒด์ ์œผ๋กœ ์‹คํ—˜๊ฒฐ๊ณผ์— ๋Œ€ํ•œ ํ•ด์„์˜ ๋น„์œจ์€ ํ‰๊ท ์ด 0.99์ด๊ณ  ํ‘œ์ค€ํŽธ์ฐจ๋Š” 0.11 ์ˆ˜์ค€์ด์—ˆ๋‹ค. ํ•ด์„/์‹คํ—˜์˜ ๋น„๊ฐ€ 1.0์„ ๋„˜๋Š” ๋น„์•ˆ์ „์ธก์˜ ํ•ด์„๊ฒฐ๊ณผ๊ฐ€ ์ผ๋ถ€ ์žˆ์ง€๋งŒ, III-10์˜ ๊ฒฝ์šฐ์—๋Š” ํ•ด๋‹น ์‹คํ—˜์ด ์กฐ๊ธฐ ์ข…๋ฃŒ๋˜์—ˆ๊ธฐ ๋•Œ๋ฌธ์ด๋ฉฐ, I-4, I-7, I-8์˜ ๊ฒฝ์šฐ์—๋Š” ๋‚ดํ™”์„ฑ๋Šฅ์‹œ๊ฐ„์ด ์ •์˜๋œ ์‹œ์ ์— ๋”ฐ๋ฅธ ์ฐจ์ด์ผ ๋ฟ Fig. 9์—์„œ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋“ฏ์ด ํ•ด์„๊ฒฐ๊ณผ๊ฐ€ ๋” ๋ณด์ˆ˜์ ์ด์—ˆ๋‹ค. ํ•œํŽธ, ์‹คํ—˜๊ฒฐ๊ณผ์— ๋Œ€ํ•œ Eurocode 2์˜ ๋น„์œจ์€ ํ‰๊ท ์ด 0.71์ด๊ณ  ํ‘œ์ค€ํŽธ์ฐจ๋Š” 0.08 ์ˆ˜์ค€์ด์—ˆ์œผ๋ฉฐ, ํŠนํžˆ ํŽธ์‹ฌํ•˜์ค‘ ๋ฐ ๋‹จ๋ถ€ํšŒ์ „๊ตฌ์†๋„๊ฐ€ ์žˆ๋Š” ๊ฒฝ์šฐ ์˜ค์ฐจ๊ฐ€ ์ปค์ ธ ๋งค์šฐ ๋ณด์ˆ˜์ ์ธ ๊ฒฐ๊ณผ๋ฅผ ๋ณด์˜€๋‹ค. ์ด๋Ÿฌํ•œ ๊ฒฐ๊ณผ๋Š” ์ œ์‹œ๋œ ์œ ํ•œ์š”์†Œํ•ด์„ ๋ชจ๋ธ๋ง ๊ธฐ๋ฒ•์ด ํ˜„ํ–‰ ๊ธฐ์ค€๋ณด๋‹ค ๋” ์ •ํ™•ํ•œ ์˜ˆ์ธก์น˜๋ฅผ ์ œ๊ณตํ•  ์ˆ˜ ์žˆ๊ณ , ์ด์— ๋”ฐ๋ผ RC ๊ธฐ๋‘ฅ์˜ ๋‚ดํ™”์„ค๊ณ„ ์‹œ ์ถฉ๋ถ„ํžˆ ํ™œ์šฉ๋  ์ˆ˜ ์žˆ์Œ์„ ๋‚˜ํƒ€๋‚ธ๋‹ค.

Table 3 Comparison of fire resistance ratings obtained from test and analysis

Loading

type

Specimen

Fire resistance ratings [mins]

$t_{test}$

$t_{analysis}$

($t_{analysis}/t_{test}$)
$t_{EC2}$

($t_{EC2}/t_{test}$)

Concentric

I-2

165

160 (0.97)

133 (0.81)

I-3

218

210 (0.96)

161 (0.74)

I-4

220

240 (1.09)

167 (0.76)

I-7

208

211 (1.01)

146 (0.70)

I-8

146

150 (1.02)

111 (0.76)

Eccentric

III-7

170

136 (0.8)

122 (0.72)

III-8

225

210 (0.93)

123 (0.55)

III-9

225

224 (0.99)

129 (0.57)

III-10

167

206 (1.23)

123 (0.74)

III-14

183

173 (0.94)

130 (0.71)

5. ๊ฒฐ ๋ก 

๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ๋‹ค์–‘ํ•œ ์„ค๊ณ„์กฐ๊ฑด์„ ๊ฐ€์ง„ RC ๊ธฐ๋‘ฅ์˜ ๋‚ดํ™”์„ฑ๋Šฅ์„ ์˜ˆ์ธกํ•˜๊ธฐ ์œ„ํ•˜์—ฌ, 3์ฐจ์› ์œ ํ•œ์š”์†Œํ•ด์„ ๋ชจ๋ธ๋ง ๊ธฐ๋ฒ•์„ ๊ฐœ๋ฐœํ•˜์˜€๋‹ค. ๊ฒ€์ฆ์„ ์œ„ํ•˜์—ฌ ์ค‘์‹ฌ/ํŽธ์‹ฌ ์žฌํ•˜๊ฐ€์—ด์‹คํ—˜์ฒด์— ์ ์šฉํ•˜์˜€์œผ๋ฉฐ, ๊ฐ€์—ด์‹œ๊ฐ„์— ๋”ฐ๋ฅธ ์˜จ๋„ ๋ถ„ํฌ, ์ถ•๋ฐฉํ–ฅ ๋ณ€ํ˜•, ๊ทธ๋ฆฌ๊ณ  ๋‚ดํ™”์„ฑ๋Šฅ์‹œ๊ฐ„ ๋“ฑ์˜ ๊ด€์ ์—์„œ ๋น„๊ตํ•˜์˜€๋‹ค. ๋ณธ ์—ฐ๊ตฌ์˜ ๊ฒฐ๋ก ์„ ์š”์•ฝํ•˜๋ฉด ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

1) ํ˜„ํ–‰ ์„ค๊ณ„๊ธฐ์ค€์—์„œ ์ฃผ๋กœ ๊ณ ๋ คํ•˜๊ณ  ์žˆ๋Š” ๋ถ€์žฌ์น˜์ˆ˜ ๋ฟ๋งŒ ์•„๋‹ˆ๋ผ, ์ถ•๋ ฅ๋น„, ํŽธ์‹ฌํ•˜์ค‘ ๋ฐ ๋‹จ๋ถ€ํšŒ์ „๊ตฌ์†๋„ ๋“ฑ๋„ RC ๊ธฐ๋‘ฅ์˜ ํ™”์žฌ ์‹œ ๊ฑฐ๋™์— ์ค‘๋Œ€ํ•œ ์˜ํ–ฅ์„ ๋ฏธ์น˜๋ฏ€๋กœ, ์œ ํ•œ์š”์†Œํ•ด์„ ๋ชจ๋ธ๋ง ๊ธฐ๋ฒ• ๊ฐœ๋ฐœ ์‹œ ๊ณ ๋ คํ•˜์˜€๋‹ค.

2) Abaqus๋ฅผ ์ด์šฉํ•œ ์™„์ „ ์—ฐ๊ณ„ ์—ด-์‘๋ ฅ ํ•ด์„ ๋ฐฉ์‹์œผ๋กœ ๋ชจ๋ธ๋ง ๊ธฐ๋ฒ•์„ ๊ฐœ๋ฐœํ•˜์˜€์œผ๋ฉฐ, ์ค‘์‹ฌ ๋ฐ ํŽธ์‹ฌ ์žฌํ•˜๊ฐ€์—ด์‹คํ—˜์ฒด 10๊ฐœ์— ๋Œ€ํ•ด ๊ฒ€์ฆ์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค. ์ƒ๋Œ€์ ์œผ๋กœ ๋†’์€ ์ถ•๋ ฅ๋น„, ํŽธ์‹ฌํšจ๊ณผ, ๋‹จ๋ถ€ํšŒ์ „๊ตฌ์†๋„ ๋“ฑ์œผ๋กœ ์ธํ•ด ๋‹ค์†Œ ์ฐจ์ด๊ฐ€ ์žˆ์—ˆ์ง€๋งŒ, ์ „์ฒด์ ์œผ๋กœ ํ•ด์„์€ ๋ณด์ˆ˜์ ์ธ ๊ฒฐ๊ณผ๋ฅผ ๋ณด์˜€๋‹ค.

3) ๋‹จ๋ฉด๋‚ด ์˜จ๋„ ๋ถ„ํฌ์˜ ๊ฒฝ์šฐ, ์ „์ฒด์ ์œผ๋กœ ํ•ด์„๊ฒฐ๊ณผ๋Š” ์‹คํ—˜๊ฒฐ๊ณผ์™€ ์œ ์‚ฌํ•œ ์˜จ๋„ ๋ถ„ํฌ ๋ฐ ๋ณ€ํ™”๋ฅผ ๋ณด์˜€๋‹ค. ๋‹ค๋งŒ ์˜จ๋„์˜ ํฌ๊ธฐ๋Š” ํ•ด์„์ด ๋‹ค์†Œ ๋†’๊ฒŒ ํ‰๊ฐ€ํ•˜์˜€๋‹ค. ์žฌ๋ฃŒ ๋ชจ๋ธ๋ง ๋ฐ ๊ฐ€์—ด๋ฒ”์œ„ ๊ฐ€์ • ๋“ฑ๊ณผ ๋”๋ถˆ์–ด, ์‹คํ—˜ ์‹œ ์ˆ˜๋ถ„๋ง‰ํž˜ํ˜„์ƒ์œผ๋กœ ์ธํ•ด ์ฐจ์ด๊ฐ€ ๋ฐœ์ƒํ•œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

4) ๊ธฐ๋‘ฅ์˜ ์ถ•๋ฐฉํ–ฅ ๋ณ€ํ˜•์˜ ๊ฒฝ์šฐ, ๊ธฐ๋‘ฅ ๊ธธ์ด์˜ ํŒฝ์ฐฝ๋Ÿ‰ ๋ฐ ์ˆ˜์ถ•์‹œ์ ์˜ ๊ด€์ ์—์„œ ํ•ด์„์ด ๋ณด์ˆ˜์ ์œผ๋กœ ํ‰๊ฐ€ํ•˜๋Š” ๊ฒฝํ–ฅ์„ ๋ณด์˜€๋‹ค. ๋†’์€ ์ถ•๋ ฅ๋น„, ํŽธ์‹ฌํšจ๊ณผ ๋ฐ ๋‹จ๋ถ€ํšŒ์ „๊ตฌ์†๋„ ๋“ฑ ๋‹ค์–‘ํ•œ ์š”์ธ์ด ๋ณ€ํ˜•๋Ÿ‰์— ์˜ํ–ฅ์„ ๋ฏธ์นœ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

5) ๋‚ดํ™”์„ฑ๋Šฅ์‹œ๊ฐ„(๊ธฐ๋‘ฅ ์ถ•๋ณ€ํ˜• ๋ณ€ํ™”์œจ์ด 76 mm/min์„ ์ดˆ๊ณผํ•œ ์‹œ์ )์˜ ๊ฒฝ์šฐ, ์‹คํ—˜์— ๋Œ€ํ•œ ํ•ด์„์˜ ๋น„์œจ์€ ํ‰๊ท ์ด 0.99์ด๊ณ  ํ‘œ์ค€ํŽธ์ฐจ๋Š” 0.11 ์ˆ˜์ค€์ด์—ˆ๋‹ค. ์ด๋Ÿฌํ•œ ๊ฒฐ๊ณผ๋Š” ์ œ์‹œ๋œ ์œ ํ•œ์š”์†Œํ•ด์„ ๋ชจ๋ธ๋ง ๊ธฐ๋ฒ•์ด RC ๊ธฐ๋‘ฅ์˜ ๋‚ดํ™”์„ค๊ณ„์‹œ ์ถฉ๋ถ„ํžˆ ํ™œ์šฉ๋  ์ˆ˜ ์žˆ์Œ์„ ๋‚˜ํƒ€๋‚ธ๋‹ค.

๋ณธ ์—ฐ๊ตฌ๊ฒฐ๊ณผ๋ฅผ ๊ธฐ๋ฐ˜์œผ๋กœ ์ถ”ํ›„ ๋‹ค์–‘ํ•œ ์กฐ๊ฑด์— ๊ด€ํ•ด ๋ณ€์ˆ˜์—ฐ๊ตฌ๋ฅผ ์ˆ˜ํ–‰ํ•  ์˜ˆ์ •์ด๋ฉฐ, ์ด๋ฅผ ํ†ตํ•ด ์„ค๊ณ„๊ธฐ์ค€์˜ ๊ฐœ์„  ๋ฐ ์„ฑ๋Šฅ๊ธฐ๋ฐ˜ ๋‚ดํ™”๊ตฌ์กฐ์„ค๊ณ„์— ํ™œ์šฉํ•˜๊ณ ์ž ํ•œ๋‹ค.

๊ฐ์‚ฌ์˜ ๊ธ€

๋ณธ ์—ฐ๊ตฌ๋Š” ์ •๋ถ€(๊ณผํ•™๊ธฐ์ˆ ์ •๋ณดํ†ต์‹ ๋ถ€)์˜ ์žฌ์›์œผ๋กœ ํ•œ๊ตญ์—ฐ๊ตฌ์žฌ๋‹จ์˜ ์ง€์›์„ ๋ฐ›์•„ ์ˆ˜ํ–‰๋œ ์—ฐ๊ตฌ์ž„(No. NRF-2022R1A4A3026883, RS-2024-00455020).

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