Mobile QR Code QR CODE : Journal of the Korean Society of Civil Engineers

  1. ์ „๋‚จ๋Œ€ํ•™๊ต ํ† ๋ชฉ๊ณตํ•™๊ณผ ๊ต์ˆ˜ (Chonnam National University)
  2. ์ˆœ์ฒœ์ œ์ผ๋Œ€ํ•™๊ต ํ† ๋ชฉ์กฐ๊ฒฝ๊ณผ ์กฐ๊ต์ˆ˜ (Suncheon Jeil College)


ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ, ๋ถ€์ฐฉํŠน์„ฑ, ํ”ผ๋ณต๋‘๊ป˜, ์ตœ๋Œ€๊ท ์—ด๊ฐ„๊ฒฉ, ์‚ฌ์šฉํ•œ๊ณ„์ƒํƒœ
Average crack spacing, Bond characteristics, Cover thickness, Maximum crack spacing, Serviceability limit states

  • 1. ์„œ ๋ก 

  • 2. ๊ท ์—ด๊ฐ„๊ฒฉ ๊ธฐ๋ณธ์‹

  •   2.1 ๋ถ€์ฐฉํŠน์„ฑ ๋ชจ๋ธ๋ง

  •   2.2 ํ”ผ๋ณต๋‘๊ป˜์˜ ์˜ํ–ฅ

  •   2.3 ์ฝ˜ํฌ๋ฆฌํŠธ ๊ฐ•๋„์˜ ์˜ํ–ฅ

  • 3. ๊ท ์—ด๊ฐ„๊ฒฉ ์ƒ๊ด€๊ด€๊ณ„

  • 4. ๊ท ์—ด๊ฐ„๊ฒฉ ์ œ์•ˆ์‹ ๋น„๊ต

  • 5. ๊ฒฐ ๋ก 

1. ์„œ ๋ก 

๊ท ์—ด๊ฐ„๊ฒฉ์€ ๊ท ์—ดํญ์œผ๋กœ ๋Œ€ํ‘œ๋˜๋Š” ์ฒ ๊ทผ์ฝ˜ํฌ๋ฆฌํŠธ ํœจ๋ถ€์žฌ์˜ ์‚ฌ์šฉํ•œ๊ณ„์ƒํƒœ ์„ค๊ณ„์™€ ์‚ฌ์šฉ์„ฑ๋Šฅ ๋ฐ ๋‚ด๊ตฌ์„ฑ๋Šฅ ๊ฒ€์ฆ์— ์ค‘์š”ํ•œ ์—ญํ• ์„ ํ•œ๋‹ค. ํœจ๋ชจ๋ฉ˜ํŠธ ๋˜๋Š” ์ธ์žฅ๋ ฅ์„ ๋ฐ›๋Š” ์ฒ ๊ทผ์ฝ˜ํฌ๋ฆฌํŠธ ๋ถ€์žฌ์—์„œ ๊ท ์—ดํญ์€ ์ฒ ๊ทผ๊ณผ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋ณ€ํ˜•๋Ÿ‰ PICE99C.gif, PICE9AD.gif์˜ ์ฐจ์ด์™€ ๊ท ์—ด๊ฐ„๊ฒฉ PICE9AE.gif์˜ ๊ณฑ์œผ๋กœ์„œ, ์—ญํ•™์ ์œผ๋กœ๋Š” ๊ท ์—ด๊ฐ„๊ฒฉ ๋‚ด์—์„œ ๋ถ€์ฐฉ์— ์˜ํ•ด ํ•ฉ์„ฑ๋œ ์ฒ ๊ทผ๊ณผ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋ณ€ํ˜•๋ฅ  PICE9BE.gif, PICE9BF.gif ์ฐจ์ด์— ๋Œ€ํ•œ ๋ˆ„์ ํ•ฉ์œผ๋กœ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ์ •์˜ํ•œ๋‹ค.

PICE9D0.gif (1)

๊ท ์—ดํญ์„ ๊ฒฐ์ •ํ•˜๋Š” ๋‘ ๋ณ€์ˆ˜์˜ ์ ˆ๋Œ€์ ์ธ ํฌ๊ธฐ๋กœ ๋น„๊ต๋ฅผ ํ•˜๋ฉด, ์ฒ ๊ทผ๊ณผ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋ณ€ํ˜•๋ฅ  ์ฐจ์ด๋ณด๋‹ค๋Š” ๊ท ์—ด๊ฐ„๊ฒฉ์˜ ์˜ํ–ฅ์ด ์ง€๋ฐฐ์ ์ด๋ผ๊ณ  ํ•  ์ˆ˜ ์žˆ๋‹ค. ์ด์™€ ๊ฐ™์ด ๊ท ์—ด๊ฐ„๊ฒฉ์€ ๊ท ์—ดํญ์˜ ํฌ๊ธฐ๋ฅผ ๊ฒฐ์ •ํ•˜๋Š”๋ฐ ์ค‘์š”ํ•œ ์—ญํ• ์„ ํ•˜๊ธฐ ๋•Œ๋ฌธ์— ๊ฐ•๋„์„ค๊ณ„๋ฒ•์„ ๊ธฐ๋ฐ˜์œผ๋กœ ํ•˜๋Š” Korea Concrete Institute(2012)(์ดํ•˜ KCI 12)๊ณผ ํ•œ๊ณ„์ƒํƒœ์„ค๊ณ„๋ฒ•์„ ๊ธฐ๋ฐ˜์œผ๋กœ ํ•˜๋Š” Korea Road and Transportation Association(KHBDC)(2016)(์ดํ•˜ KHBDC)์—์„œ๋Š” ๊ฐ๊ฐ ๊ท ์—ด๊ฐ„๊ฒฉ์„ ์‚ฐ์ •ํ•  ์ˆ˜ ์žˆ๋Š” ์‹์„ ๊ทœ์ •ํ•˜๊ณ  ์žˆ๋‹ค. ์ฝ˜ํฌ๋ฆฌํŠธ๊ตฌ์กฐ๊ธฐ์ค€์—์„œ๋Š” ๋ถ€๋ก โ…ข ๊ท ์—ด์˜ ๊ฒ€์ฆ์—์„œ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ PICE9E1.gif์œผ๋กœ, ๋„๋กœ๊ต์„ค๊ณ„๊ธฐ์ค€(ํ•œ๊ณ„์ƒํƒœ์„ค๊ณ„๋ฒ•)์—์„œ๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ๊ตํŽธ์—์„œ ์ตœ๋Œ€๊ท ์—ด๊ฐ„๊ฒฉ PICE9E2.gif์œผ๋กœ ๊ฐ๊ฐ ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

PICE9E3.gif ; KCI 12     (2a)

PICE9F3.gif ; KHBDC       (2b)

์—ฌ๊ธฐ์„œ, PICE9F4.gif๋Š” ์ตœ์™ธ๋‹จ ์ธ์žฅ์ฒ ๊ทผ์˜ ํ‘œ๋ฉด๊ณผ ์ฝ˜ํฌ๋ฆฌํŠธ ํ‘œ๋ฉด ์‚ฌ์ด์˜ ์ตœ์†Œ ํ”ผ๋ณต๋‘๊ป˜(mm), PICE9F5.gif์€ ๋ถ€์ฐฉํŠน์„ฑ์— ๋”ฐ๋ฅธ ๊ณ„์ˆ˜๋กœ์„œ ์ดํ˜•์ฒ ๊ทผ์€ 0.8, ์›ํ˜•์ฒ ๊ทผ์€ 1.6์ด๊ณ , PICEA06.gif๋Š” ํ•˜์ค‘ ํ˜•ํƒœ์— ๋”ฐ๋ฅธ ๊ณ„์ˆ˜๋กœ์„œ ํœจ๋ชจ๋ฉ˜ํŠธ๋ฅผ ๋ฐ›๋Š” ๋ถ€์žฌ๋Š” 0.5, ์ง์ ‘์ธ์žฅ๋ ฅ์„ ๋ฐ›๋Š” ๋ถ€์žฌ๋Š” 1.0์ด๋ฉฐ, PICEA07.gif๋Š” ์ธ์žฅ์ฒ ๊ทผ์˜ ์ง€๋ฆ„(mm), PICEA17.gif๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์œ ํšจ์ธ์žฅ๋ฉด์  PICEA28.gif์„ ๊ธฐ์ค€์œผ๋กœ ํ•œ ์ฒ ๊ทผ๋น„(=PICEA29.gif)์ด๋‹ค. ์ฝ˜ํฌ๋ฆฌํŠธ ์œ ํšจ์ธ์žฅ๋ฉด์ ์€ Fig. 1์— ๋ณด์ธ ๊ฒƒ๊ณผ ๊ฐ™์ด ๋ถ€์žฌ ๋‹จ๋ฉด์˜ ํญ๊ณผ ์œ ํšจ์ธ์žฅ๊นŠ์ด PICEA2A.gif์˜ ๊ณฑ์œผ๋กœ ์ •์˜ํ•˜๋Š”๋ฐ, ์—ฌ๊ธฐ์„œ ์œ ํšจ์ธ์žฅ๊นŠ์ด๋Š” ํœจ๋ชจ๋ฉ˜ํŠธ๋ฅผ ๋ฐ›๋Š” ๋ถ€์žฌ์—์„œ๋Š” PICEA3B.gif์™€ PICEA3C.gif ์ค‘ ์ž‘์€๊ฐ’์œผ๋กœ ํ•˜๊ณ , ์ง์ ‘์ธ์žฅ๋ ฅ์„ ๋ฐ›๋Š” ๋ถ€์žฌ๋Š” PICEA3D.gif์™€ PICEA4D.gif ์ค‘ ์ž‘์€๊ฐ’์œผ๋กœ ํ•œ๋‹ค.

Fig. 1.

Effective Concrete Tension Area

Figure_KSCE_38_2_02_F1.jpg

๊ทธ๋Ÿฐ๋ฐ, ์ฝ˜ํฌ๋ฆฌํŠธ๊ตฌ์กฐ๊ธฐ์ค€์—์„œ๋Š” ๊ท ์—ดํญ ์‚ฐ์ •์‹œ์— ๊ท ์—ดํญ ํ‰๊ฐ€๊ณ„์ˆ˜ PICEA4E.gif๋ฅผ ํ•จ๊ป˜ ๊ทœ์ •ํ•˜๊ณ  ์žˆ๋Š”๋ฐ, ์ด ๊ณ„์ˆ˜์— ์˜ํ•˜๋ฉด ํ‰๊ท  ๊ท ์—ดํญ์„ ๊ณ„์‚ฐํ•  ๋•Œ 1.0, ์ตœ๋Œ€ ๊ท ์—ดํญ์„ ๊ณ„์‚ฐํ•  ๋•Œ 1.7์„ ์ ์šฉํ•˜๋„๋ก ํ•œ๋‹ค. ๋”ฐ๋ผ์„œ, ์ตœ๋Œ€ ๊ท ์—ดํญ ๊ณ„์ˆ˜์ธ 1.7์„ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ Eq. (2a)์— ๊ณฑํ•˜์—ฌ ์ •๋ฆฌํ•˜๋ฉด ์ตœ๋Œ€๊ท ์—ด๊ฐ„๊ฒฉ์ธ Eq. (2b)๊ฐ€ ๋œ๋‹ค. ๋”ฐ๋ผ์„œ ํ˜„ํ–‰ ๋„๋กœ๊ต์„ค๊ณ„๊ธฐ์ค€(ํ•œ๊ณ„์ƒํƒœ์„ค๊ณ„๋ฒ•)๊ณผ ์ฝ˜ํฌ๋ฆฌํŠธ๊ตฌ์กฐ๊ธฐ์ค€์€ ๋™์ผํ•œ ๊ฐœ๋…์˜ ๊ท ์—ด๊ฐ„๊ฒฉ ์‚ฐ์ •์‹ ๋ฐ ๊ท ์—ด๊ฐ„๊ฒฉ ์ƒ๊ด€๊ด€๊ณ„๋ฅผ ๊ทœ์ •ํ•˜๊ณ  ์žˆ๋‹ค๋Š” ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋‹ค.

Abrishami and Mitchell(1996), Broms(1965), Forth and Beeby (2014), Lee and Kim(2009) ๋“ฑ์˜ ์—ฐ๊ตฌ๊ฒฐ๊ณผ์— ๋”ฐ๋ฅด๋ฉด ๊ท ์—ด๊ฐ„๊ฒฉ์€ ์ฒ ๊ทผ๊ณผ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋ถ€์ฐฉํŠน์„ฑ ๋ฐ ํ”ผ๋ณต๋‘๊ป˜์˜ ์˜ํ–ฅ์„ ๋ฐ›๋Š”๋‹ค๊ณ  ์•Œ๋ ค์ ธ ์žˆ๋Š”๋ฐ, ์ด๋Ÿฌํ•œ ์‚ฌ์‹ค์€ Eq. (2)์—์„œ๋„ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋‹ค. ์ฆ‰, ์šฐ๋ณ€์˜ ์ฒซ ๋ฒˆ์งธ ํ•ญ์—์„œ ํ”ผ๋ณต๋‘๊ป˜์˜ ์˜ํ–ฅ์„ ๋ฐ˜์˜ํ•˜๊ณ  ์žˆ์œผ๋ฉฐ, ๋‘ ๋ฒˆ์งธ ํ•ญ์—์„œ ์ฒ ๊ทผ์˜ ํ‘œ๋ฉด ํ˜•ํƒœ์— ๋”ฐ๋ฅธ ๊ณ„์ˆ˜ PICEA4F.gif๊ณผ ๋ถ€์ฐฉ์ „๋‹ฌ๊ธธ์ด ํ•ด์„์— ๋”ฐ๋ฅธ PICEA60.gif์™€ ์ƒ์ˆ˜์— ์˜ํ•ด ๋ถ€์ฐฉํŠน์„ฑ์„ ๋ฐ˜์˜ํ•œ๋‹ค๊ณ  ํ•  ์ˆ˜ ์žˆ๋‹ค. ๊ทธ๋Ÿฐ๋ฐ, ์ด ์‹๋“ค์€ CEB-FIP Model Code 1990(1990) ๋ฐ EUROCODE 2 (2002) ๊ทœ์ •๊ณผ ๋™์ผํ•œ ๊ฒƒ์ด๋ฉฐ, ์‹ค์ œ ์‹คํ—˜์—์„œ ์ธก์ •๋œ ๊ท ์—ด๊ฐ„๊ฒฉ๊ณผ ๋น„๊ตํ•˜์˜€์„ ๋•Œ ์ƒ๋‹นํ•œ ์ฐจ์ด๊ฐ€ ๋ฐœ์ƒํ•œ๋‹ค๊ณ  ๋ณด๊ณ ๋˜๊ณ  ์žˆ๋‹ค(Lee and Kim, 2009).

์ด ์—ฐ๊ตฌ๋Š” ํ˜„ํ–‰ ์„ค๊ณ„๊ธฐ์ค€์—์„œ ๊ทœ์ •ํ•˜๊ณ  ์žˆ๋Š” ๊ท ์—ด๊ฐ„๊ฒฉ ์‚ฐ์ •์‹์˜ ์ฃผ์š” ๋ณ€์ˆ˜์ธ ํ”ผ๋ณต๋‘๊ป˜์™€ ๋ถ€์ฐฉํŠน์„ฑ์˜ ์˜ํ–ฅ์„ ์žฌ๋ถ„์„ํ•˜์—ฌ ์ •ํ™•์„ฑ์„ ๊ฐœ์„ ํ•˜๋Š” ๊ฒƒ์„ ๋ชฉ์ ์œผ๋กœ ํ•œ๋‹ค. ์ด๋ฅผ ์œ„ํ•˜์—ฌ ๊ตญ๋‚ดโ€ค์™ธ ์—ฐ๊ตฌ์ž๋“ค์ด ์ˆ˜ํ–‰ํ•œ ๋‹ค์–‘ํ•œ ํ”ผ๋ณต๋‘๊ป˜, ์ฒ ๊ทผ๋น„ ๋ฐ ์ฝ˜ํฌ๋ฆฌํŠธ ์••์ถ•๊ฐ•๋„๋ฅผ ๋ณ€์ˆ˜๋กœ ๊ฐ–๋Š” ์ง์ ‘์ธ์žฅ์‹คํ—˜ ์ž๋ฃŒ์˜ ๋ถ„์„๊ณผ ์„ค๊ณ„๊ธฐ์ค€์—์„œ ์ œ์‹œํ•˜๋Š” ๋ถ€์ฐฉํŠน์„ฑ ๊ฐ’์„ ๋ฐ˜์˜ํ•œ ๋ถ€์ฐฉ์ „๋‹ฌ๊ธธ์ด ๋ชจ๋ธ๋ง์„ ํ†ตํ•˜์—ฌ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ ์‚ฐ์ •์‹์„ ์ˆ˜์ •ํ•˜์˜€๋‹ค. ๊ทธ๋ฆฌ๊ณ , ์‹คํ—˜์—์„œ ์ธก์ •๋œ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ๊ณผ ์ตœ๋Œ€๊ท ์—ด๊ฐ„๊ฒฉ์˜ ์ƒ๊ด€๊ด€๊ณ„ ๋ถ„์„์„ ํ†ตํ•˜์—ฌ ์ตœ๋Œ€๊ท ์—ด๊ฐ„๊ฒฉ ๊ณ„์ˆ˜๋ฅผ ์ƒˆ๋กญ๊ฒŒ ๋„์ถœํ•˜์˜€๋‹ค.

2. ๊ท ์—ด๊ฐ„๊ฒฉ ๊ธฐ๋ณธ์‹

2.1 ๋ถ€์ฐฉํŠน์„ฑ ๋ชจ๋ธ๋ง

๊ท ์—ด๊ฐ„๊ฒฉ์€ ์ฒ ๊ทผ๊ณผ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ํ•ฉ์„ฑ์ž‘์šฉ์˜ ๊ทผ๊ฐ„์ด ๋˜๋Š” ๋ถ€์ฐฉํŠน์„ฑ์œผ๋กœ๋ถ€ํ„ฐ ๊ธฐ๋ณธ์‹์ด ์œ ๋„๋œ๋‹ค. Fig. 2(a)์— ๋ณด์ธ ๊ฒƒ๊ณผ ๊ฐ™์€ ์ง์ ‘์ธ์žฅ๋ถ€์žฌ์— ์ธ์žฅ๋ ฅ PICEA61.gif๊ฐ€ ์ž‘์šฉํ•˜๋ฉด, ์ธ์žฅ๊ฐ•๋„ PICEA72.gif์— ๋„๋‹ฌํ•œ ์ฝ˜ํฌ๋ฆฌํŠธ ๋‹จ๋ฉด์—์„œ ์ฒซ ๊ท ์—ด์ด ๋ฐœ์ƒํ•˜๊ณ , ์ด ๊ท ์—ด๋ฉด์—์„œ๋Š” ์ฒ ๊ทผ์ด ์ธ์žฅ๋ ฅ์„ ๋ชจ๋‘ ๋ถ€๋‹ดํ•œ๋‹ค. ๊ท ์—ด์ด ๋ฐœ์ƒํ•œ ์ดํ›„์—๋Š” ์ฒ ๊ทผ๊ณผ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋ถ€์ฐฉํŠน์„ฑ์— ๋”ฐ๋ผ ๊ท ์—ด๊ฑฐ๋™์ด ๋ณต์žกํ•˜๊ฒŒ ๋œ๋‹ค. ์ฒ ๊ทผ์œผ๋กœ๋ถ€ํ„ฐ ์ฝ˜ํฌ๋ฆฌํŠธ๋กœ ์ „๋‹ฌ๋˜๋Š” ๋ถ€์ฐฉ์‘๋ ฅ PICEA73.gif์— ์˜ํ•ด ์ฝ˜ํฌ๋ฆฌํŠธ๊ฐ€ ์ž‘์šฉํ•˜์ค‘์˜ ์ผ๋ถ€๋ฅผ ๋ถ„๋‹ดํ•˜๋Š”๋ฐ, ๊ทธ ํฌ๊ธฐ PICEA74.gif๋Š” ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

PICEA84.gif (3)

Fig. 2.

Bond Stress and Strain Distribution of Axially Loaded RC Tension Members; (a) RC Tension Members (b) Strain Distribution of Crack Formation Stage (c) Bond Stress Distribution (d) Strain Distribution of Stabilized Cracking Stage

Figure_KSCE_38_2_02_F2.jpg

์ด์™€ ๊ฐ™์€ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ธ์žฅ๋ ฅ ๋ถ„๋‹ด์— ์˜ํ•ด Fig. 2(b)์™€ ๊ฐ™์ด ์ฒ ๊ทผ์˜ ์‘๋ ฅ๊ณผ ๋ณ€ํ˜•๋ฅ ์€ ๊ท ์—ด๋ฉด์—์„œ ์ตœ๋Œ€๊ฐ€ ๋˜๊ณ , ๊ท ์—ด๋ฉด์œผ๋กœ๋ถ€ํ„ฐ ๊ฑฐ๋ฆฌ์— ๋”ฐ๋ผ ์ ์ฐจ ๊ฐ์†Œํ•˜์—ฌ ์ฝ˜ํฌ๋ฆฌํŠธ์™€ ์ฒ ๊ทผ์˜ ๋ณ€ํ˜•๋ฅ ์ด ๊ฐ™๊ฒŒ ๋˜๋Š”๋ฐ ๊ท ์—ด๋ฉด์œผ๋กœ๋ถ€ํ„ฐ ์ด ๊ฑฐ๋ฆฌ๋ฅผ ๋ถ€์ฐฉ์ „๋‹ฌ๊ธธ์ด(bond transfer length) PICEA85.gif๋ผ๊ณ  ํ•œ๋‹ค. ์ž‘์šฉํ•˜์ค‘์ด ๊ณ„์† ์ฆ๊ฐ€ํ•˜๋ฉด ๋ถ€์ฐฉ์ „๋‹ฌ๊ธธ์ด๋ฅผ ๋„˜์–ด์„  ์œ„์น˜์—์„œ ์ƒˆ๋กœ์šด ๊ท ์—ด์ด ๊ณ„์† ๋ฐœ์ƒํ•˜๋Š”๋ฐ, ์ด๋Š” ๊ท ์—ด๋ฉด์œผ๋กœ๋ถ€ํ„ฐ ๋ถ€์ฐฉ์ „๋‹ฌ๊ธธ์ด๊นŒ์ง€๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ๋กœ ์ „๋‹ฌ๋˜๋Š” ์ธ์žฅ๋ ฅ์ด ์ƒ๋Œ€์ ์œผ๋กœ ๋‚ฎ์•„ ์ธ์žฅ๊ฐ•๋„์— ๋„๋‹ฌํ•˜์ง€ ๋ชปํ•˜๊ธฐ ๋•Œ๋ฌธ์ด๋‹ค. ๋”ฐ๋ผ์„œ ๊ท ์—ด๊ฐ„๊ฒฉ์ด ๋ถ€์ฐฉ์ „๋‹ฌ๊ธธ์ด์˜ 2๋ฐฐ ๋ฏธ๋งŒ์ด ๋  ๋•Œ๊นŒ์ง€ ๊ณ„์†์ ์œผ๋กœ ๊ท ์—ด์ด ๋ฐœ์ƒํ•˜๊ฒŒ ๋˜๋Š”๋ฐ, ์ด๋•Œ๋ฅผ ๊ท ์—ดํ˜•์„ฑ๋‹จ๊ณ„(crack formation stage)๋ผ๊ณ  ํ•œ๋‹ค. ์ดํ›„ ์ƒˆ๋กœ์šด ๊ท ์—ด์ด ๋” ์ด์ƒ ๋ฐœ์ƒํ•˜์ง€ ๋ชปํ•˜๊ณ  ๊ท ์—ดํญ๋งŒ ํ™•์žฅ๋˜๋Š” ์ƒํƒœ๊ฐ€ ๋˜๋Š”๋ฐ, ์ด๋Ÿฌํ•œ ์ƒํƒœ๋ฅผ ๊ท ์—ด์•ˆ์ •ํ™”๋‹จ๊ณ„(stabilized cracking stage)๋ผ๊ณ  ํ•œ๋‹ค.

์•ž ์ ˆ์—์„œ ์„ค๋ช…ํ•œ ๋ฐ”์™€ ๊ฐ™์ด ์‚ฌ์šฉํ•œ๊ณ„์ƒํƒœ ์„ค๊ณ„ ๋ฐ ์‚ฌ์šฉ์„ฑ๋Šฅ ๊ฒ€์ฆ์€ ์ผ๋ฐ˜์ ์œผ๋กœ ๊ท ์—ด์•ˆ์ •ํ™”๋‹จ๊ณ„์—์„œ ์ด๋ค„์ง€๋Š”๋ฐ, ์ด๋•Œ์˜ ๋ถ€์ฐฉ์ „๋‹ฌ๊ธธ์ด๋กœ๋ถ€ํ„ฐ ๊ท ์—ด๊ฐ„๊ฒฉ์ด ๊ฒฐ์ •๋œ๋‹ค๊ณ  ํ•  ์ˆ˜ ์žˆ๋‹ค. ์ฆ‰, ์ตœ์†Œ๊ท ์—ด๊ฐ„๊ฒฉ์€ ๋ถ€์ฐฉ์ „๋‹ฌ๊ธธ์ด PICEA86.gif๊ฐ€ ๋˜๊ณ , ์ตœ๋Œ€๊ท ์—ด๊ฐ„๊ฒฉ์€ 2PICEA97.gif๊ฐ€ ๋˜๋ฉฐ, ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ์€ ์‚ฐ์ˆ ์ ์œผ๋กœ ๋‘ ๊ฐ„๊ฒฉ์˜ ์ค‘๊ฐ„๊ฐ’์œผ๋กœ ๊ฐ„์ฃผํ•  ์ˆ˜ ์žˆ๋‹ค. Fig. 2(c)์— ๋ณด์ธ ๋ฐ”์™€ ๊ฐ™์ด ๋ถ€์ฐฉ์ „๋‹ฌ๊ธธ์ด๋Š” ์ฒ ๊ทผ๊ณผ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋ถ€์ฐฉํŠน์„ฑ์œผ๋กœ๋ถ€ํ„ฐ ์ •์˜ํ•  ์ˆ˜ ์žˆ๋Š”๋ฐ, ์‹ค์ œ ๋ถ€์ฐฉ์‘๋ ฅ ๋ถ„ํฌ๋Š” ์ฒ ๊ทผ๊ณผ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ฒฝ๊ณ„๋ฉด์—์„œ ๋ฐœ์ƒํ•˜๋Š” ๋ฏธ๋„๋Ÿผ ํŠน์„ฑ๊ณผ ๋ถ€์ฐฉ๊ฐ•๋„์— ๋”ฐ๋ผ ๋น„์„ ํ˜• ํ˜•ํƒœ๋กœ ๋ณต์žกํ•˜๊ฒŒ ๋‚˜ํƒ€๋‚œ๋‹ค. ์ด ์—ฐ๊ตฌ์—์„œ๋Š” ๊ณ„์‚ฐ์˜ ๋‹จ์ˆœํ™”๋ฅผ ์œ„ํ•ด CEB-FIP Model Code 1990 (MC 90) ๋ฐ EUROCODE 2 (EC 2)์—์„œ ๋„์ž…ํ•˜๊ณ  ์žˆ๋Š” ํ‰๊ท ๋ถ€์ฐฉ์‘๋ ฅ ๊ฐœ๋…์„ ์ด์šฉํ•˜์—ฌ ๋ถ€์ฐฉ์ „๋‹ฌ๊ธธ์ด PICEA98.gif๋ฅผ ๋ชจ๋ธ๋งํ•˜์˜€๋‹ค. ๋ถ€์ฐฉ์ „๋‹ฌ๊ธธ์ด ๋‚ด์— ๋ถ„ํฌํ•˜๋Š” ๋ถ€์ฐฉ์‘๋ ฅ์˜ ํ‰๊ท ๊ฐ’์„ PICEA99.gif์ด๋ผ๊ณ  ํ•˜๋ฉด, Eq. (3)์— ์˜ํ•ด ์ฒ ๊ทผ์œผ๋กœ๋ถ€ํ„ฐ ์ฝ˜ํฌ๋ฆฌํŠธ๋กœ ์ „๋‹ฌ๋˜๋Š” ๋ถ€์ฐฉ๋ ฅ์˜ ํ•ฉ์ด ์ฝ˜ํฌ๋ฆฌํŠธ ์ธ์žฅ๊ฐ•๋„์— ๋„๋‹ฌํ•˜์˜€์„ ๋•Œ ๊ท ์—ด์ด ๋ฐœ์ƒํ•œ๋‹ค๊ณ  ํ•  ์ˆ˜ ์žˆ๋‹ค. ์ด๋ฅผ ์ˆ˜์น˜์ ์œผ๋กœ ํ‘œํ˜„ํ•˜๋ฉด ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

PICEAA9.gif (4)

์—ฌ๊ธฐ์„œ, PICEAAA.gif๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ ์ธ์žฅ ๋ฉด์ (mm2), PICEAAB.gif๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ ์ธ์žฅ๊ฐ•๋„(MPa), PICEABC.gif๋Š” ์ฒ ๊ทผ์˜ ์ง€๋ฆ„(mm)์ด๋‹ค.

Eq. (4)๋ฅผ ๋ถ€์ฐฉ์ „๋‹ฌ๊ธธ์ด PICEABD.gif์— ๋Œ€ํ•ด์„œ ์ •๋ฆฌํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์š”์†Œ ์ „์ฒด ๋‹จ๋ฉด์ ์— ๋Œ€ํ•œ ์ฒ ๊ทผ ๋‹จ๋ฉด์ ์˜ ๊ธฐํ•˜ํ•™์  ๋น„๋กœ์„œ ์ •์˜๋˜๋Š” ์ฒ ๊ทผ๋น„ PICEABE.gif๋ฅผ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ๋ณ€ํ˜•ํ•  ์ˆ˜ ์žˆ๋‹ค.

PICEACF.gif (5)

์ฒ ๊ทผ ์ง€๋ฆ„ํ•ญ์œผ๋กœ ๋ณ€ํ˜•์‹œํ‚จ Eq.(5)๋ฅผ Eq. (4)์— ๋Œ€์ž…ํ•˜์—ฌ ์ •๋ฆฌํ•˜๋ฉด ๋ถ€์ฐฉ์ „๋‹ฌ๊ธธ์ด PICEAD0.gif๋ฅผ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ๋‚˜ํƒ€๋‚ผ ์ˆ˜ ์žˆ๋‹ค.

PICEAE0.gif (6)

๊ทธ๋Ÿฐ๋ฐ, ํ‰๊ท ๋ถ€์ฐฉ์‘๋ ฅ PICEAE1.gif์€ ์ผ๋ฐ˜์ ์œผ๋กœ ์ฝ˜ํฌ๋ฆฌํŠธ ์••์ถ•๊ฐ•๋„์˜ ์ œ๊ณฑ๊ทผ์— ๋น„๋ก€ํ•œ๋‹ค๊ณ  ์•Œ๋ ค์ ธ ์žˆ๋Š”๋ฐ, ์ด๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ธ์žฅ๊ฐ•๋„ PICEAE2.gif ํ•ญ์œผ๋กœ๋„ ์„ค๋ช…์ด ๊ฐ€๋Šฅํ•˜๋‹ค๋Š” ๊ฒƒ์„ ์˜๋ฏธํ•œ๋‹ค. ์ด๋Ÿฌํ•œ ๋ฐฐ๊ฒฝ์—์„œ MC 90์—์„œ๋„ ํ‰๊ท ๋ถ€์ฐฉ์‘๋ ฅ์„ ์ฝ˜ํฌ๋ฆฌํŠธ ์ธ์žฅ๊ฐ•๋„ ํ•ญ์œผ๋กœ ์ •์˜ํ•˜๊ณ  ์žˆ๋Š”๋ฐ, ์ด ์—ฐ๊ตฌ์—์„œ๋Š” MC 90์—์„œ ๊ทœ์ •ํ•˜๊ณ  ์žˆ๋Š” ๊ท ์—ด์•ˆ์ •ํ™”๋‹จ๊ณ„์—์„œ์˜ ํ‰๊ท ๋ถ€์ฐฉ์‘๋ ฅ PICEAF3.gif๋ฅผ ์ด์šฉํ•˜์—ฌ ๋ถ€์ฐฉ์ „๋‹ฌ๊ธธ์ด Eq. (6)์„ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ๊ฐ„๋‹จํ•˜๊ฒŒ ์ •๋ฆฌํ•˜์˜€๋‹ค.

PICEAF4.gif (7)

ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ PICEB33.gif์€ Eq. (7)๋กœ ์ •์˜๋˜๋Š” ๋ถ€์ฐฉ์ „๋‹ฌ๊ธธ์ด์˜ 1.0๋ฐฐ์—์„œ 2.0๋ฐฐ ์‚ฌ์ด์˜ ๊ฐ’์ด ๋˜๋ฉฐ, ์ž‘์šฉํ•˜์ค‘ ํŠน์„ฑ ๋ฐ ์ฒ ๊ทผ ํ‘œ๋ฉด์˜ ์˜ํ–ฅ๋„ ๊ณ ๋ คํ•ด์•ผ ํ•œ๋‹ค. ๋”ฐ๋ผ์„œ ์ด ์—ฐ๊ตฌ์—์„œ๋Š” ๋ถ€์ฐฉ์ „๋‹ฌ๊ธธ์ด PICEB34.gif์˜ 1.5๋ฐฐ๋กœ ๊ฐ„์ฃผํ•˜๊ณ , ์ฒ ๊ทผ ๋ฐ ํ•˜์ค‘ ํŠน์„ฑ์€ ํ˜„ํ–‰ ์„ค๊ณ„๊ธฐ์ค€์—์„œ ๊ทœ์ •ํ•˜๋Š” ๊ณ„์ˆ˜๋“ค์„ ๊ทธ๋Œ€๋กœ ์ ์šฉํ•˜์—ฌ ๋ถ€์ฐฉํŠน์„ฑ์„ ๊ณ ๋ คํ•œ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ PICEB45.gif์„ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ์ •์˜ํ•˜์˜€๋‹ค.

PICEB46.gif (8)

์—ฌ๊ธฐ์„œ, PICEB47.gif๋Š” Eq. (1)์—์„œ ์ •์˜ํ•œ ๊ฒƒ๊ณผ ๊ฐ™์ด ์œ ํšจ์ฒ ๊ทผ๋น„๋กœ์„œ Eq. (7)์˜ ์œ ๋„์— ์ ์šฉ๋œ ์ง์ ‘์ธ์žฅ๋ถ€์žฌ๊ฐ€ ์•„๋‹Œ ํœจ๋ถ€์žฌ์—์„œ ๋‹จ๋ฉด ๊นŠ์ด์— ๋”ฐ๋ผ ์ธ์žฅ์‘๋ ฅ์ด ๋ณ€ํ•˜๋Š” ์˜์—ญ์— ์ ์šฉํ•  ์ˆ˜ ์žˆ๋„๋ก ์ธ์žฅ ์˜์—ญ์„ ๋“ฑ๊ฐ€์˜ ์ˆœ์ˆ˜ ์ธ์žฅ๋ถ€์žฌ๋กœ ๋ณ€ํ™˜ํ•œ ๊ฒƒ์ด๋‹ค.

ํ•œํŽธ, Eq. (8)์€ ์ด์ „ ์„ค๊ณ„๊ธฐ์ค€์ธ ์ฝ˜ํฌ๋ฆฌํŠธ๊ตฌ์กฐ์„ค๊ณ„๊ธฐ์ค€(2007)๊ณผ ๋„๋กœ๊ต์„ค๊ณ„๊ธฐ์ค€(ํ•œ๊ณ„์ƒํƒœ์„ค๊ณ„๋ฒ•)(2012)์—์„œ ๊ทœ์ •ํ–ˆ๋˜ ์ตœ๋Œ€๊ท ์—ด๊ฐ„๊ฒฉ๊ณผ ๊ฐ™์€ ํ˜•์‹์ธ๋ฐ, ์ด๋“ค ๊ธฐ์ค€์€ MC 90๊ณผ EC 2-Part โ…ก์—์„œ ๊ทœ์ •ํ•˜๋Š” ๊ท ์—ด๊ฐ„๊ฒฉ์„ ์ฑ„ํƒํ•œ ๊ฒƒ์ด๋‹ค.

PICEB58.gif (9)

2.2 ํ”ผ๋ณต๋‘๊ป˜์˜ ์˜ํ–ฅ

์•ž ์ ˆ์—์„œ ์ œ์‹œํ•œ ๋ถ€์ฐฉํŠน์„ฑ๊ณผ ํ•จ๊ป˜ ๊ท ์—ด๊ฐ„๊ฒฉ์— ์˜ํ–ฅ์„ ๋ฏธ์น˜๋Š” ์ฃผ์š” ๋ณ€์ˆ˜๋กœ ์ฝ˜ํฌ๋ฆฌํŠธ ํ”ผ๋ณต๋‘๊ป˜๊ฐ€ ์žˆ๋‹ค. Kim(2000), Yun(1999), Lee(2001), Lee(1998), Hong(1999), Abrishami and Mitchell(1996), Deluce et al.(2014), Fields and Bishoff(2004), Goto(1971), Lorrain et al.(1998), Perera and Mutsuyoshi(2011) ๋“ฑ์ด 91๊ฐœ์˜ ์‹คํ—˜์ฒด์—์„œ ์ธก์ •ํ•œ ๊ท ์—ด๊ฐ„๊ฒฉ์„ ํ”ผ๋ณต๋‘๊ป˜์— ๋”ฐ๋ผ ๋„ํ•ดํ•œ Fig. 3์„ ์‚ดํŽด๋ณด๋ฉด, ํ”ผ๋ณต๋‘๊ป˜๊ฐ€ ๋‘๊บผ์›Œ์งˆ์ˆ˜๋ก ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ์ด ๋น„๋ก€ํ•˜์—ฌ ์ฆ๊ฐ€ํ•˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋‹ค.

Fig. 3.

Average Crack Spacing vs Cover Thickness from Various Test Results

Figure_KSCE_38_2_02_F3.jpg

์ด์™€ ๊ฐ™์€ ์‚ฌ์‹ค์„ ๋ฐ˜์˜ํ•˜์—ฌ ํ˜„ํ–‰ ์„ค๊ณ„๊ธฐ์ค€์—์„œ๋„ Eq. (2)์™€ ๊ฐ™์ด ์ฝ˜ํฌ๋ฆฌํŠธ ํ”ผ๋ณต๋‘๊ป˜๋ฅผ ๊ท ์—ด๊ฐ„๊ฒฉ์˜ ๋ณ€์ˆ˜๋กœ ํ•˜๊ณ  ์žˆ๋‹ค. ๊ทธ๋Ÿฐ๋ฐ, Fig. 4์— ๋ณด์ธ ๋ฐ”์™€ ๊ฐ™์ด ์ด ์‹์„ ์ด์šฉํ•˜์—ฌ ๊ณ„์‚ฐํ•œ ์ตœ๋Œ€ ๋ฐ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ์€ ์‹ค์ œ ์‹คํ—˜ ๊ฒฐ๊ณผ์™€ ์ƒ๋‹นํ•œ ์ฐจ์ด๊ฐ€ ์žˆ์Œ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋‹ค. ๋˜ํ•œ ๊ท ์—ด๊ฐ„๊ฒฉ์„ ์ฃผ์š” ๋ณ€์ˆ˜๋กœ ํ•˜๋Š” ๊ท ์—ดํญ ๊ณ„์‚ฐ์— ์žˆ์–ด์„œ๋„ ์ด์— ๋น„๋ก€ํ•˜์—ฌ ์˜ค์ฐจ๊ฐ€ ๋ฐœ์ƒํ•  ์ˆ˜ ์žˆ๋‹ค.

Fig. 4.

Comparison of Measured and Predicted Crack Spacing

Figure_KSCE_38_2_02_F4.jpg

์ด ์—ฐ๊ตฌ์—์„œ๋Š” ๊ท ์—ด๊ฐ„๊ฒฉ ๊ณ„์‚ฐ์˜ ์ •ํ™•์„ฑ์„ ๋†’์ผ ์ˆ˜ ์žˆ๋„๋ก ๋ถ€์ฐฉํŠน์„ฑ์ด ๋ฐ˜์˜๋œ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ Eq. (8)์— ๋Œ€ํ•ด์„œ ํ˜„ํ–‰ ์„ค๊ณ„๊ธฐ์ค€์˜ ๊ทœ์ •๊ณผ ๋™์ผํ•˜๊ฒŒ ํ”ผ๋ณต๋‘๊ป˜ PICEB59.gif์˜ ์˜ํ–ฅ์„ ๊ณ ๋ คํ•  ์ˆ˜ ์žˆ๋„๋ก ํ”ผ๋ณต๋‘๊ป˜ ๊ณ„์ˆ˜ PICEB69.gif๋ฅผ ๋„์ž…ํ•˜์—ฌ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ์ˆ˜์ •ํ•˜์˜€๋‹ค.

PICEB6A.gif (10)

Eq. (10)์˜ ๊ณ„์ˆ˜ PICEB7B.gif๋ฅผ ๊ฒฐ์ •ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ๊ตญ๋‚ดโ€ค์™ธ ์—ฐ๊ตฌ์ž๋“ค์ด ์ง์ ‘์ธ์žฅ์‹คํ—˜์„ ํ†ตํ•ด ์ธก์ •ํ•œ ๊ท ์—ด๊ฐ„๊ฒฉ ์‹ค์ธก ์ž๋ฃŒ๋“ค์„ ํ”ผ๋ณต๋‘๊ป˜๋ฅผ ๋ณ€์ˆ˜๋กœ ํ•˜์—ฌ ํ†ต๊ณ„ ๋ถ„์„์„ ์‹ค์‹œํ•˜์˜€๋‹ค. ๋ถ„์„์— ์‚ฌ์šฉ๋œ ์‹คํ—˜ ์ž๋ฃŒ๋“ค์€ ํšก๋ฐฉํ–ฅ๊ท ์—ด์ด ๋‹ค์ˆ˜ ๋ฐœ์ƒํ•˜์—ฌ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ ๋ฐ ์ตœ๋Œ€๊ท ์—ด๊ฐ„๊ฒฉ์˜ ๋ช…ํ™•ํ•œ ๊ตฌ๋ณ„์ด ๊ฐ€๋Šฅํ•˜๋‹ค๊ณ  ๊ฐ„์ฃผํ•  ์ˆ˜ ์žˆ๋Š” ๊ธธ์ด๊ฐ€ 1,000mm ์ด์ƒ์ธ ์‹คํ—˜์ฒด์—์„œ ์ธก์ •๋œ ๊ฐ’๋“ค์ด๋‹ค.

์•ž ์ ˆ์—์„œ ๋ฐํžŒ ๋ฐ”์™€ ๊ฐ™์ด ๊ท ์—ด๊ฐ„๊ฒฉ์€ ๋ถ€์ฐฉํŠน์„ฑ๊ณผ ํ”ผ๋ณต๋‘๊ป˜๋ฅผ ํฌํ•จํ•œ ๋งŽ์€ ๋ณ€์ˆ˜์˜ ์˜ํ–ฅ์„ ๋ฐ›์œผ๋ฏ€๋กœ,์ด ์—ฐ๊ตฌ์—์„œ๋Š” ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ์„ ๊ธฐ์ค€์œผ๋กœ ํ•˜์—ฌ ํ”ผ๋ณต๋‘๊ป˜์˜ ์˜ํ–ฅ์„ ๋ถ„์„ํ•˜์˜€๋‹ค. ๋ถ„์„์— ์‚ฌ์šฉ๋œ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ๋“ค์€ Fig. 3์˜ ๋ถ„์„์— ์ด์šฉ๋œ ์—ฐ๊ตฌ์ž๋“ค์˜ ์‹คํ—˜์ž๋ฃŒ๋กœ์„œ, ์ด๋“ค์ด ์ˆ˜ํ–‰ํ•œ ์ง์ ‘์ธ์žฅ์‹คํ—˜์„ ํ†ตํ•ด 120๊ฐœ์˜ ์‹คํ—˜์ฒด์—์„œ ์ธก์ •๋œ ๊ฒƒ์ด๋‹ค.

์‹ค์ธก๋œ 120๊ฐœ์˜ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ์„ ์ด์šฉํ•˜์—ฌ ํ”ผ๋ณต๋‘๊ป˜ ๊ณ„์ˆ˜ PICEB7C.gif๋ฅผ ๊ฒฐ์ •ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ Eq. (10)์„ PICEB7D.gif์˜ ํ•ญ์œผ๋กœ ์ •๋ฆฌํ•œ ํ›„, ํ”ผ๋ณต๋‘๊ป˜ PICEB8E.gif๋ฅผ ๋ณ€์ˆ˜๋กœ ํ•˜์—ฌ ๊ฐ ์‹คํ—˜์ฒด ๋ณ„ ๊ฐ’๋“ค์„ Fig. 5์— ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ์ด ๊ทธ๋ฆผ์„ ์‚ดํŽด๋ณด๋ฉด, ๋ถ„์„์— ์‚ฌ์šฉ๋œ ์‹คํ—˜์ฒด๋“ค์ด ์—ฐ๊ตฌ์ž๋ณ„๋กœ ์žฌ๋ฃŒ๊ฐ•๋„, ์ฒ ๊ทผ๋น„ ๋ฐ ๋‹จ๋ฉด์ œ์› ๋“ฑ์ด ์„œ๋กœ ๋‹ค๋ฅธ ๊ด€๊ณ„๋กœ ํ”ผ๋ณต๋‘๊ป˜์— ๋”ฐ๋ฅธ ๊ณ„์ˆ˜๊ฐ’์˜ ๋ถ„์‚ฐ๊ณผ ํ‘œ์ค€ํŽธ์ฐจ๊ฐ€ ๋น„๊ต์  ํฌ๊ฒŒ ๋ฐœ์ƒํ•จ์„ ์•Œ ์ˆ˜ ์žˆ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜, ์ด๋“ค ์‹คํ—˜์ฒด์— ์ ์šฉ๋œ ๋ณ€์ˆ˜๋“ค์€ ์ฝ˜ํฌ๋ฆฌํŠธ ์„ค๊ณ„๊ธฐ์ค€์••์ถ•๊ฐ•๋„ PICEB9E.gif๊ฐ€ 20~100MPa, ์ฒ ๊ทผ ํ•ญ๋ณต๊ฐ•๋„ PICEBBE.gif๊ฐ€ 400~600MPa ๋ฐ ์ฒ ๊ทผ๋น„ PICEBCF.gif๊ฐ€ 1~3%์˜ ๋ฒ”์œ„์— ์žˆ์œผ๋ฏ€๋กœ ํ˜„์‹ค์ ์ธ ์„ค๊ณ„ ์กฐ๊ฑด์— ๋Œ€๋ถ€๋ถ„ ๋ถ€ํ•ฉํ•œ๋‹ค๊ณ  ํ•  ์ˆ˜ ์žˆ๋‹ค. ๋”ฐ๋ผ์„œ ๋ถ„์„์„ ํ†ตํ•ด ๊ฒฐ์ •๋œ ํ‰๊ท ๊ฐ’์ธ 1.71์„ ์ด ์—ฐ๊ตฌ์—์„œ ์ œ์•ˆํ•˜๋Š” ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ ํ”ผ๋ณต๋‘๊ป˜ ๊ณ„์ˆ˜ PICEBD0.gif๋กœ ์‚ฐ์ •ํ•˜์˜€๋‹ค.

Fig. 5.

Coefficient of Cover Thickness in Average Crack Spacing

Figure_KSCE_38_2_02_F5.jpg

2.3 ์ฝ˜ํฌ๋ฆฌํŠธ ๊ฐ•๋„์˜ ์˜ํ–ฅ

์ฝ˜ํฌ๋ฆฌํŠธ ์••์ถ•๊ฐ•๋„๊ฐ€ ์ปค์งˆ์ˆ˜๋ก ๋ถ€์ฐฉ์‘๋ ฅ์ด ๊ท ์—ด๋ฉด ๋˜๋Š” ๋‹จ๋ถ€์ชฝ์œผ๋กœ ์ง‘์ค‘๋˜๋ฉด์„œ ๋ถ€์ฐฉ์ „๋‹ฌ๊ธธ์ด๊ฐ€ ์ƒ๋Œ€์ ์œผ๋กœ ๊ฐ์†Œํ•˜๊ธฐ ๋•Œ๋ฌธ์— ๊ท ์—ด๊ฐ„๊ฒฉ์ด ๋ณดํ†ต๊ฐ•๋„ ์ฝ˜ํฌ๋ฆฌํŠธ์™€ ๋น„๊ตํ•˜์—ฌ ์ƒ๋Œ€์ ์œผ๋กœ ์ค„์–ด๋“ ๋‹ค๊ณ  ์•Œ๋ ค์ ธ ์žˆ๋‹ค(Kim et al., 2001). ์ด๋Ÿฌํ•œ ์‚ฌ์‹ค์„ ํ™•์ธํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ๊ท ์—ด๊ฐ„๊ฒฉ ๋ถ„์„์— ์‚ฌ์šฉ๋œ ์‹คํ—˜์ž๋ฃŒ๋“ค์„ ์ฝ˜ํฌ๋ฆฌํŠธ ์••์ถ•๊ฐ•๋„๋ฅผ ๋ณ€์ˆ˜๋กœ ํ•˜์—ฌ Fig. 6์— ์ •๋ฆฌํ•˜์˜€๋‹ค. ์ด ๊ทธ๋ฆผ์„ ์‚ดํŽด๋ณด๋ฉด ์ฝ˜ํฌ๋ฆฌํŠธ ์••์ถ•๊ฐ•๋„๊ฐ€ ์ปค์งˆ์ˆ˜๋ก ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ์ด ๊ฐ์†Œํ•˜๋Š” ๊ฒฝํ–ฅ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์œผ๋ฉฐ, ์ด๋Ÿฌํ•œ ์‚ฌ์‹ค์€ (ํ‰๊ท )๊ท ์—ด๊ฐ„๊ฒฉ์˜ ์ •ํ™•ํ•œ ์˜ˆ์ธก์„ ์œ„ํ•ด์„œ ์ฝ˜ํฌ๋ฆฌํŠธ ์••์ถ•๊ฐ•๋„์˜ ์˜ํ–ฅ๋„ ๊ณ ๋ คํ•ด์•ผ ํ•œ๋‹ค๋Š” ๊ฒƒ์„ ํ™•์ธํ•˜๋Š” ๊ฒฐ๊ณผ๋ผ๊ณ  ํ•  ์ˆ˜ ์žˆ๋‹ค. ํŠนํžˆ ๊ตฌ์กฐ๋ฌผ ์„ค๊ณ„ ์‹œ ๊ณ ๊ฐ•๋„์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ ์šฉ์ด ํฌ๊ฒŒ ์ฆ๊ฐ€ํ•˜๊ณ  ์žˆ์œผ๋ฉฐ ์‚ฌ์šฉ์„ฑ ๋ฐ ๋‚ด๊ตฌ์„ฑ์ด ๊ฐ•์กฐ๋˜๊ณ  ์žˆ๋Š” ์ตœ๊ทผ์˜ ์„ค๊ณ„ ๋™ํ–ฅ์— ์˜ํ•œ๋‹ค๋ฉด, ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์••์ถ•๊ฐ•๋„์˜ ์˜ํ–ฅ์„ ๊ณ ๋ คํ•œ ๊ท ์—ดํญ ๊ฒ€์ฆ์€ ๋”์šฑ ์ค‘์š”ํ•˜๋‹ค๊ณ  ํ•  ์ˆ˜ ์žˆ๋‹ค.

์ด ์ ˆ์—์„œ๋Š” ์œ„์—์„œ ์„ค๋ช…ํ•œ ์ฝ˜ํฌ๋ฆฌํŠธ ๊ฐ•๋„์˜ ์˜ํ–ฅ์„ ์ถ”๊ฐ€์ ์œผ๋กœ ๋ฐ˜์˜ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ, Eq. (10)์˜ ๋‘ ๋ฒˆ์งธ ํ•ญ์— ๋‹จ์œ„ ๊ฐ•๋„(unit strength) 1MPa์„ ๊ณ ๋ คํ•œ ์ฝ˜ํฌ๋ฆฌํŠธ ์„ค๊ณ„๊ธฐ์ค€์••์ถ•๊ฐ•๋„ PICEBD1.gif์— ๋Œ€ํ•ด์„œ ์ง€์ˆ˜ํ•จ์ˆ˜ ํ˜•ํƒœ์˜ ๋ฌด์ฐจ์› ์ฝ˜ํฌ๋ฆฌํŠธ ๊ฐ•๋„๊ณ„์ˆ˜ PICEBE2.gif๋ฅผ ๋„์ž…ํ•˜์—ฌ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ์ˆ˜์ •ํ•˜์˜€๋‹ค.

PICEC12.gif (11)

์ฝ˜ํฌ๋ฆฌํŠธ ๊ฐ•๋„๊ณ„์ˆ˜ PICEC13.gif๋ฅผ ๊ฒฐ์ •ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ Fig. 6์˜ ๋ถ„์„์— ์‚ฌ์šฉ๋œ ์‹คํ—˜์ž๋ฃŒ๋“ค์„ ๊ทธ๋Œ€๋กœ ์ด์šฉํ•˜์˜€๋‹ค. ๋จผ์ € Eq. (11)์„ ๋ณ€ํ˜•ํ•˜์—ฌ PICEC23.gif์— ๋Œ€ํ•ด์„œ ์ •๋ฆฌํ•œ ํ›„, ์ด๋“ค ์‹คํ—˜์ž๋ฃŒ์— ์˜ํ•œ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ๊ณผ ํ”ผ๋ณต๋‘๊ป˜ ๋ฐ ๊ณ„์ˆ˜ PICEC24.gif, PICEC25.gif๋ฅผ ๋Œ€์ž…ํ•˜์—ฌ ๊ณ„์‚ฐํ•˜์˜€๋‹ค. ๊ทธ๋ฆฌ๊ณ , Fig. 7์— ์ •๋ฆฌํ•œ ๊ฒƒ๊ณผ ๊ฐ™์ด ์ด ๊ฐ’๋“ค๋กœ๋ถ€ํ„ฐ ์ฝ˜ํฌ๋ฆฌํŠธ ์„ค๊ณ„๊ธฐ์ค€์••์ถ•๊ฐ•๋„์— ๋”ฐ๋ฅธ ์ง€์ˆ˜๋ฅผ ๊ฐ๊ฐ ๊ณ„์‚ฐํ•œ ํ›„, ์ด ๊ฐ’๋“ค์˜ ํ‰๊ท ๊ฐ’์„ ์‚ฐ์ •ํ•˜์˜€๋‹ค.

Fig. 6.

Average Crack Spacing vs Concrete Compressive Strength from Various Test Results

Figure_KSCE_38_2_02_F6.jpg
Fig. 7.

Coefficient of Concrete Compressive Strength in Average Crack Spacing

Figure_KSCE_38_2_02_F7.jpg

Fig. 7์— ๋ณด์ธ ๋ถ„์„๊ฒฐ๊ณผ์— ์˜ํ•˜๋ฉด, ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ ๊ณ„์‚ฐ์„ ์œ„ํ•œ ์ฝ˜ํฌ๋ฆฌํŠธ ๊ฐ•๋„๊ณ„์ˆ˜ PICEC36.gif๋ฅผ ๊ฒฐ์ •ํ•˜๋Š” ์ง€์ˆ˜ PICEC37.gif๋Š” ํ‘œ์ค€ํŽธ์ฐจ 0.218, ๋ถ„์‚ฐ 0.047๋ฅผ ๊ฐ–๋Š” ํ‰๊ท ๊ฐ’ โ€“0.12๋กœ ๊ฒฐ์ •๋˜์—ˆ๋‹ค. ์ด ๊ฐ’์€ ์•ž ์ ˆ์—์„œ ์ˆ˜ํ–‰ํ•œ ํ”ผ๋ณต๋‘๊ผ ๊ณ„์ˆ˜ PICEC38.gif๋ณด๋‹ค ํ†ต๊ณ„์  ์˜ค์ฐจ๊ฐ€ ์ƒ๋‹นํžˆ ๊ฐ์†Œํ•˜์˜€๋‹ค. ๊ทธ๋ฆฌ๊ณ , ์„œ๋กœ ๋‹ค๋ฅธ ์ข…๋ฅ˜์˜ ์ฒ ๊ทผ ํ•ญ๋ณต๊ฐ•๋„, ํ”ผ๋ณต๋‘๊ป˜ ๋ฐ ์ฒ ๊ทผ๋น„๋ฅผ ํฌํ•จํ•œ ์‹คํ—˜๊ฒฐ๊ณผ์˜ ๋ถ„์„์œผ๋กœ๋ถ€ํ„ฐ ์–ป์–ด์ง„ ๊ฒฐ๊ณผ์ž„์„ ๊ณ ๋ คํ•˜๋ฉด ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ ๊ณ„์‚ฐ์„ ์œ„ํ•œ Eq. (11)์— ์ ์šฉํ•˜๋Š”๋ฐ ๋ฌด๋ฆฌ๊ฐ€ ์—†์„ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

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3. ๊ท ์—ด๊ฐ„๊ฒฉ ์ƒ๊ด€๊ด€๊ณ„

์•ž ์ ˆ์—์„œ ์œ ๋„ํ•œ ๊ท ์—ด๊ฐ„๊ฒฉ์€ ์ฒ ๊ทผ๊ณผ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ํ‰๊ท ๋ณ€ํ˜•๋ฅ  ๋ฐ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ์œผ๋กœ๋ถ€ํ„ฐ ๊ณ„์‚ฐ๋˜๋Š” ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ PICEC69.gif์ด๋‹ค. ๊ทธ๋Ÿฐ๋ฐ, ์‚ฌ์šฉ์„ฑ๋Šฅ ๊ฒ€์ฆ ๋ฐ ์‚ฌ์šฉํ•œ๊ณ„์ƒํƒœ ์„ค๊ณ„๋ฅผ ์œ„ํ•ด์„œ๋Š” ์ตœ๋Œ€๊ท ์—ดํญ์„ ์ด์šฉํ•˜๋Š” ๊ฒƒ์ด ์ผ๋ฐ˜์ ์ด๋ฏ€๋กœ ์ตœ๋Œ€๊ท ์—ด๊ฐ„๊ฒฉ์„ ๊ฒฐ์ •ํ•˜๋Š” ๊ฒƒ๋„ ์ค‘์š”ํ•˜๋‹ค๊ณ  ํ•  ์ˆ˜ ์žˆ๋‹ค. ์ด ์—ฐ๊ตฌ์—์„œ๋Š” ์ตœ๋Œ€๊ท ์—ด๊ฐ„๊ฒฉ์— ๋Œ€ํ•œ ๋ณ„๋„์˜ ๊ณ„์‚ฐ์‹์„ ์ œ์‹œํ•˜์ง€ ์•Š๋Š” ๋Œ€์‹ ์— ์ฝ˜ํฌ๋ฆฌํŠธ๊ตฌ์กฐ๊ธฐ์ค€(2012)์—์„œ ๊ทœ์ •ํ•˜๋Š” ๊ท ์—ดํญ ํ‰๊ฐ€์ง€์ˆ˜ ๊ฐœ๋…์ฒ˜๋Ÿผ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ์„ ์ด์šฉํ•˜์—ฌ ์ตœ๋Œ€๊ท ์—ด๊ฐ„๊ฒฉ์„ ์‚ฐ์ •ํ•  ์ˆ˜ ์žˆ๋„๋ก ํ•˜์˜€๋‹ค. ์ด๋ฅผ ์œ„ํ•˜์—ฌ ์•ž ์ ˆ์˜ ๋ฐฉ๋ฒ•๊ณผ ๋™์ผํ•˜๊ฒŒ ์—ฌ๋Ÿฌ ์—ฐ๊ตฌ์ž๋“ค์ด ์ˆ˜ํ–‰ํ•œ ์ง์ ‘์ธ์žฅ์‹คํ—˜์—์„œ ์–ป์–ด์ง„ ์ตœ๋Œ€ ๋ฐ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ ์‹คํ—˜์ž๋ฃŒ๋ฅผ ์ด์šฉํ•˜์—ฌ ์ƒ๊ด€๊ด€๊ณ„ ๋ถ„์„์„ ์‹ค์‹œํ•˜์—ฌ Fig. 8์— ์ •๋ฆฌํ•˜์˜€๋‹ค. ์ƒ๊ด€๊ด€๊ณ„ ๋ถ„์„์— ์‚ฌ์šฉ๋œ ์‹คํ—˜์ž๋ฃŒ๋Š” ํ•œ ์‹คํ—˜์ฒด์—์„œ ์ตœ๋Œ€ ๋ฐ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ์„ ๋ชจ๋‘ ์ธก์ •ํ•œ Kim(2000), Lee(1998), Hong(1999), Abrishami and Mitchell(1996), Lorrain et al.(1998) ๋“ฑ์˜ ์ด 79๊ฐœ์ด๋‹ค.

Fig. 8์— ์ •๋ฆฌํ•œ ์‹ค์ธก ๊ท ์—ด๊ฐ„๊ฒฉ์˜ ์ƒ๊ด€๊ด€๊ณ„ ๋ถ„์„ ๊ฒฐ๊ณผ์— ์˜ํ•˜๋ฉด, ์ตœ๋Œ€๊ท ์—ด๊ฐ„๊ฒฉ์€ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ์˜ 1.5๋ฐฐ๋กœ ๋ฐœ์ƒํ•˜๊ณ  ์žˆ์Œ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋‹ค. ๊ทธ๋ฆฌ๊ณ , ์ด ์ƒ๊ด€๊ด€๊ณ„๋Š” ๋ถ„์‚ฐ 0.065, ํ‘œ์ค€ํŽธ์ฐจ 0.255๋กœ์„œ ๋น„๊ต์  ์ •ํ™•ํ•œ ์˜ˆ์ธก์ด ๊ฐ€๋Šฅํ•˜๋‹ค๊ณ  ํ•  ์ˆ˜ ์žˆ์œผ๋ฏ€๋กœ, ์ด ์—ฐ๊ตฌ์—์„œ๋Š” ์ตœ๋Œ€๊ท ์—ด๊ฐ„๊ฒฉ๊ณผ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ์˜ ๊ด€๊ณ„๋ฅผ ๊ฒฐ์ •ํ•˜๋Š” ์ƒ๊ด€๊ณ„์ˆ˜๋ฅผ 1.5๋กœ ์ ์šฉํ•˜์˜€๋‹ค.

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Fig. 8.

Correlation Coefficient of Maximum and Average Crack Spacing

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4. ๊ท ์—ด๊ฐ„๊ฒฉ ์ œ์•ˆ์‹ ๋น„๊ต

์ด ์—ฐ๊ตฌ์—์„œ๋Š” ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ์˜ ์ •ํ™•ํ•œ ์˜ˆ์ธก์„ ์œ„ํ•˜์—ฌ ๋ถ€์ฐฉํŠน์„ฑ๊ณผ ํ”ผ๋ณต๋‘๊ป˜ ๋ฐ ์ฝ˜ํฌ๋ฆฌํŠธ ๊ฐ•๋„์˜ ์˜ํ–ฅ์„ ๊ณ ๋ คํ•œ Eq. (11)๊ณผ ์ด๋ฅผ ์ด์šฉํ•˜์—ฌ ์ตœ๋Œ€๊ท ์—ด๊ฐ„๊ฒฉ์„ ์˜ˆ์ธกํ•  ์ˆ˜ ์žˆ๋Š” ์ƒ๊ด€๊ด€๊ณ„ Eq. (13)์„ ์ œ์•ˆํ•˜์˜€๋‹ค. ์ด ์‹๋“ค์— ๋Œ€ํ•ด์„œ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ์œผ๋กœ ๊ทœ์ •ํ•˜๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ๊ตฌ์กฐ๊ธฐ์ค€(2012)(KCI 12)๊ณผ ์ตœ๋Œ€๊ท ์—ด๊ฐ„๊ฒฉ์œผ๋กœ ๊ทœ์ •ํ•˜๋Š” ๋„๋กœ๊ต์„ค๊ณ„๊ธฐ์ค€(ํ•œ๊ณ„์ƒํƒœ์„ค๊ณ„๋ฒ•)(2016)(KHBDC)์˜ ๊ท ์—ด๊ฐ„๊ฒฉ ์‹๊ณผ ๋น„๊ต๋ฅผ ์‹ค์‹œํ•˜์˜€๋‹ค. ์•ž ์ ˆ์˜ ๋ถ„์„์— ์‚ฌ์šฉ๋œ ์‹คํ—˜์ž๋ฃŒ๋“ค์„ ๋Œ€์ƒ์œผ๋กœ ํ•˜์—ฌ ํ˜„ํ–‰ ์„ค๊ณ„๊ธฐ์ค€ ๋ฐ ์ด ์—ฐ๊ตฌ์˜ ์ œ์•ˆ์‹์œผ๋กœ ์˜ˆ์ธกํ•œ ๊ท ์—ด๊ฐ„๊ฒฉ๊ณผ ์‹คํ—˜์„ ํ†ตํ•ด ์ธก์ •ํ•œ ๊ท ์—ด๊ฐ„๊ฒฉ์˜ ๋น„๋ฅผ ๊ฐ๊ฐ ๊ณ„์‚ฐํ•œ ํ›„, ์ด๋“ค์˜ ํ‰๊ท ๊ฐ’ ๋ฐ ํ‘œ์ค€ํŽธ์ฐจ์™€ ๋ถ„์‚ฐ์„ ๋ถ„์„ํ•˜์—ฌ Figs. 9 and 10์— ๊ฐ๊ฐ ์ •๋ฆฌํ•˜์˜€๋‹ค.

Fig. 9.

Comparison of Proposed Model and Code Provision in Average Crack Spacing

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Fig. 10.

Comparison of Proposed Model and Code Provision in Maximum Crack Spacing

Figure_KSCE_38_2_02_F10.jpg

ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ์„ ๋ถ„์„ํ•œ Fig. 9๋ฅผ ์‚ดํŽด๋ณด๋ฉด, ์ฝ˜ํฌ๋ฆฌํŠธ๊ตฌ์กฐ๊ธฐ์ค€์˜ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ ๊ทœ์ •์€ ์‹คํ—˜๊ฐ’์˜ ์•ฝ 1.4๋ฐฐ ์ •๋„ ๊ณผ๋Œ€ํ‰๊ฐ€ํ•˜๊ณ  ์žˆ๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ์œผ๋ฉฐ, ๋ถ„์‚ฐ๊ณผ ํ‘œ์ค€ํŽธ์ฐจ ๋˜ํ•œ ํฌ๊ฒŒ ๋‚˜ํƒ€๋‚˜๊ณ  ์žˆ์Œ์„ ์•Œ ์ˆ˜ ์žˆ๋‹ค. ์ด์™€ ๋‹ค๋ฅด๊ฒŒ ์ด ์—ฐ๊ตฌ์—์„œ ์ œ์•ˆํ•œ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ Eq. (11)์€ ์ฝ˜ํฌ๋ฆฌํŠธ๊ตฌ์กฐ๊ธฐ์ค€๊ณผ ๋น„๊ตํ•˜์—ฌ ์ƒ๋Œ€์ ์œผ๋กœ ์ž‘์€ ๋ถ„์‚ฐ๊ณผ ํ‘œ์ค€ํŽธ์ฐจ์— ์˜ํ•ด ์‹คํ—˜๊ฐ’์„ ์•ฝ 1.2๋ฐฐ ์ •๋„ ํฌ๊ฒŒ ์˜ˆ์ธกํ•˜์ง€๋งŒ, ์ •ํ™•์„ฑ์€ ํ˜„ํ–‰ ๊ธฐ์ค€์˜ ๊ทœ์ •๋ณด๋‹ค ๊ฐœ์„ ๋˜์—ˆ๋‹ค๊ณ  ๊ฐ„์ฃผํ•  ์ˆ˜ ์žˆ๋‹ค.

๋‹ค์Œ์œผ๋กœ ์ตœ๋Œ€๊ท ์—ด๊ฐ„๊ฒฉ์„ ๋ถ„์„ํ•œ Fig. 10์„ ์‚ดํŽด๋ณด๋ฉด, ๋„๋กœ๊ต์„ค๊ณ„๊ธฐ์ค€(ํ•œ๊ณ„์ƒํƒœ์„ค๊ณ„๋ฒ•)์˜ ์ตœ๋Œ€๊ท ์—ด๊ฐ„๊ฒฉ ๊ทœ์ •์€ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ๊ณผ ๋งˆ์ฐฌ๊ฐ€์ง€๋กœ ์‹คํ—˜๊ฐ’์„ ์•ฝ 1.5๋ฐฐ ์ •๋„ ๊ณผ๋Œ€ํ‰๊ฐ€ํ•˜๊ณ  ์žˆ์œผ๋ฉฐ, ๋ถ„์‚ฐ๊ณผ ํ‘œ์ค€ํŽธ์ฐจ ๋˜ํ•œ ํฌ๊ฒŒ ๋‚˜ํƒ€๋‚˜๊ณ  ์žˆ์Œ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋‹ค. ์ด์™€ ๋‹ค๋ฅด๊ฒŒ, ์ด ์—ฐ๊ตฌ์—์„œ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ๊ณผ์˜ ์ƒ๊ด€๊ด€๊ณ„๋กœ์„œ ์ œ์•ˆํ•œ ์ตœ๋Œ€๊ท ์—ด๊ฐ„๊ฒฉ Eq. (13)์€ ์ƒ๋Œ€์ ์œผ๋กœ ์ž‘์€ ๋ถ„์‚ฐ๊ณผ ํ‘œ์ค€ํŽธ์ฐจ๋กœ์„œ ์‹คํ—˜๊ฐ’์˜ ์•ฝ 1.1๋ฐฐ ์ •๋„๋กœ ๋„๋กœ๊ต์„ค๊ณ„๊ธฐ์ค€(ํ•œ๊ณ„์ƒํƒœ์„ค๊ณ„๋ฒ•) ๋ณด๋‹ค ๋น„๊ต์  ์ •ํ™•ํ•˜๊ฒŒ ์˜ˆ์ธกํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค.

์ด์ƒ๊ณผ ๊ฐ™์€ ๋ถ„์„์— ๋”ฐ๋ฅด๋ฉด ๊ท ์—ด๊ฐ„๊ฒฉ ์ œ์•ˆ์‹์€ ํ˜„ํ–‰ ์„ค๊ณ„๊ธฐ์ค€์˜ ๊ทœ์ •๊ณผ ๋น„๊ตํ•˜์—ฌ ๋ถ„์‚ฐ๊ณผ ํ‘œ์ค€ํŽธ์ฐจ๊ฐ€ ๊ฐœ์„ ๋œ ์˜ˆ์ธก์ด ๊ฐ€๋Šฅํ•˜์ง€๋งŒ, ํ‘œ์ค€ํŽธ์ฐจ์™€ ํ‰๊ท ์˜ ๋น„๋กœ ์ •์˜๋˜๋Š” ๋ณ€๋™๊ณ„์ˆ˜์—๋Š” ๋ณ€ํ™”๊ฐ€ ์—†๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ์ด๋Ÿฌํ•œ ์ด์œ ๋Š” ํ˜„ํ–‰ ์„ค๊ณ„๊ธฐ์ค€์—์„œ ๊ทœ์ •ํ•˜๋Š” ๊ท ์—ด๊ฐ„๊ฒฉ ์‹์˜ ๋ณ€์ˆ˜๋ฅผ ๊ทธ๋Œ€๋กœ ์œ ์ง€ํ•˜๋ฉด์„œ, ๋‹ค์–‘ํ•œ ๋ณ€์ˆ˜๋ฅผ ํฌํ•จํ•˜๋Š” ์‹คํ—˜์ž๋ฃŒ์˜ ๋ถ„์„์— ์˜ํ•œ ํ”ผ๋ณต๋‘๊ป˜์™€ ์ฝ˜ํฌ๋ฆฌํŠธ ๊ฐ•๋„์˜ ์˜ํ–ฅ์— ๋Œ€ํ•œ ๊ณ„์ˆ˜๋ฅผ ์ˆ˜์ • ๋˜๋Š” ์ถ”๊ฐ€ํ•˜์˜€๊ธฐ ๋•Œ๋ฌธ์ด๋ผ๊ณ  ํŒ๋‹จ๋œ๋‹ค. ๋˜ํ•œ, ์•ˆ์ „์ธก ์„ค๊ณ„๋ฅผ ๋ณด์žฅํ•˜๋Š” ํ˜„ํ–‰ ์„ค๊ณ„๊ธฐ์ค€๋ณด๋‹ค ๊ท ์—ด๊ฐ„๊ฒฉ์„ ๊ณผ์†Œํ‰๊ฐ€ํ•˜๊ฒŒ ๋˜์ง€๋งŒ, ์‚ฌ์šฉํ•œ๊ณ„์ƒํƒœ ๊ฒ€์ฆ ์ค‘ ๊ท ์—ดํญ ๊ณ„์‚ฐ์˜ ์ •ํ™•์„ฑ๊ณผ ์„ค๊ณ„ ๋‹จ๋ฉด์˜ ์ตœ์ ํ™”์— ๋”ฐ๋ฅธ ๊ฒฝ์ œ์„ฑ ๋“ฑ์„ ๊ฐœ์„ ํ•  ์ˆ˜ ์žˆ์„ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

5. ๊ฒฐ ๋ก 

์ฒ ๊ทผ์ฝ˜ํฌ๋ฆฌํŠธ ๋ถ€์žฌ์˜ ๊ท ์—ดํญ ๊ณ„์‚ฐ์— ์ค‘์š”ํ•œ ์—ญํ• ์„ ํ•˜๋Š” ๊ท ์—ด๊ฐ„๊ฒฉ์— ๋Œ€ํ•ด์„œ ๋ถ€์ฐฉํŠน์„ฑ์— ์˜ํ•œ ๊ธฐ๋ณธ์‹์„ ์œ ๋„ํ•˜๊ณ , ์—ฐ๊ตฌ์ž๋“ค์ด ์ˆ˜ํ–‰ํ•œ ์ง์ ‘์ธ์žฅ์‹คํ—˜ ๊ฒฐ๊ณผ๋กœ๋ถ€ํ„ฐ ํ”ผ๋ณต๋‘๊ป˜ ๋ฐ ์ฝ˜ํฌ๋ฆฌํŠธ ๊ฐ•๋„์˜ ์˜ํ–ฅ์„ ๋ถ„์„ํ•˜์—ฌ ๋‹ค์Œ๊ณผ ๊ฐ™์€ ๊ฒฐ๋ก ์„ ์–ป์—ˆ๋‹ค.

(1)์ฒ ๊ทผ๊ณผ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ํ‰๊ท ๋ถ€์ฐฉ์‘๋ ฅ๊ณผ ํ‰ํ˜•์กฐ๊ฑด์„ ์ด์šฉํ•˜์—ฌ ์œ ๋„ํ•œ ๋ถ€์ฐฉ์ „๋‹ฌ๊ธธ์ด์˜ 1.5๋ฐฐ๋ฅผ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ์œผ๋กœ ์ •์˜ํ•˜๊ณ , ํ˜„ํ–‰ ์„ค๊ณ„๊ธฐ์ค€์˜ ๊ท ์—ด๊ฐ„๊ฒฉ ๊ทœ์ •๊ณผ ๋™์ผํ•˜๊ฒŒ ํ”ผ๋ณต๋‘๊ป˜์˜ ์˜ํ–ฅ์„ ๊ณ ๋ คํ•  ์ˆ˜ ์žˆ๋„๋ก ๊ธฐ๋ณธ์‹์„ ๊ตฌ์„ฑํ•˜์˜€๋‹ค.

(2)์—ฌ๋Ÿฌ ์—ฐ๊ตฌ์ž๋“ค์ด ์ˆ˜ํ–‰ํ•œ ์ง์ ‘์ธ์žฅ์‹คํ—˜ ๊ฒฐ๊ณผ์— ์˜ํ•˜๋ฉด ๊ท ์—ด๊ฐ„๊ฒฉ์€ ํ”ผ๋ณต๋‘๊ป˜๊ฐ€ ๋‘๊บผ์›Œ์งˆ์ˆ˜๋ก ์ฆ๊ฐ€ํ•˜๊ณ , ์ฝ˜ํฌ๋ฆฌํŠธ ์••์ถ•๊ฐ•๋„๊ฐ€ ์ปค์งˆ์ˆ˜๋ก ๊ฐ์†Œํ•˜์˜€์œผ๋ฉฐ, ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ๊ณผ ์ตœ๋Œ€๊ท ์—ด๊ฐ„๊ฒฉ์€ ์ผ์ •ํ•œ ์ƒ๊ด€๊ด€๊ณ„๊ฐ€ ์žˆ์Œ์„ ํ™•์ธํ•˜์˜€๋‹ค.

(3)์‹คํ—˜๊ฒฐ๊ณผ์˜ ํ†ต๊ณ„๋ถ„์„์„ ํ†ตํ•˜์—ฌ ํ”ผ๋ณต๋‘๊ป˜์™€ ์ฝ˜ํฌ๋ฆฌํŠธ ์••์ถ•๊ฐ•๋„์˜ ์˜ํ–ฅ์„ ๊ณ ๋ คํ•  ์ˆ˜ ์žˆ๋Š” ๊ณ„์ˆ˜๋ฅผ ๋„์ž…ํ•˜์—ฌ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ ๊ณ„์‚ฐ์‹์„ ์ œ์•ˆํ•˜์˜€๊ณ , ๊ท ์—ด๊ฐ„๊ฒฉ์˜ ์ƒ๊ด€๊ด€๊ณ„ ๋ถ„์„์„ ํ†ตํ•˜์—ฌ ํ‰๊ท ๊ท ์—ด๊ฐ„๊ฒฉ์œผ๋กœ๋ถ€ํ„ฐ ์ตœ๋Œ€๊ท ์—ด๊ฐ„๊ฒฉ์„ ๊ณ„์‚ฐํ•  ์ˆ˜ ์žˆ๋Š” ์ƒ๊ด€๊ณ„์ˆ˜๋ฅผ ํ•จ๊ป˜ ์ œ์•ˆํ•˜์˜€๋‹ค.

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