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Journal of the Korea Concrete Institute

J Korea Inst. Struct. Maint. Insp.
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  • Korea Citation Index (KCI)

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ECC ๊ธฐ๋‘ฅ, ๋ฐ˜๋ณต์ด๋ ฅ๊ฑฐ๋™, ํšก๋ฐฉํ–ฅ ๋‚ด๋ ฅ, ์—๋„ˆ์ง€ ์†Œ์‚ฐ๋Šฅ๋ ฅ
ECC column, Cyclic behavior, Load carrying capacity, Energy dissipation capacity

1. ์„œ ๋ก 

์ตœ๊ทผ๋“ค์–ด ๊ตญ๋‚ด ๋ฐ ๊ตญ์™ธ์—์„œ ๊ฑด์„ค๋˜๊ณ  ์žˆ๋Š” ๊ตฌ์กฐ๋ฌผ๋“ค์€ ๊ณ  ์ธตํ™”, ๋Œ€ํ˜•ํ™” ๋˜๊ณ  ์žˆ์–ด ์ด์— ๋”ฐ๋ฅธ ๊ฑด์„ค ์žฌ๋ฃŒ๋“ค์˜ ๋ฐœ์ „์ด ๊ธ‰ ๊ฒฉํ•˜๊ฒŒ ์ง„ํ–‰๋˜๊ณ  ์žˆ์œผ๋ฉฐ ๊ฑด์„ค์žฌ๋ฃŒ๋“ค ์ค‘ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋ณ€ํ™”์™€ ๋ฐœ์ „์ด ๊ธ‰์ง„์ „ ๋˜๊ณ  ์žˆ๋‹ค. ๊ธฐ์กด ์ฝ˜ํฌ๋ฆฌํŠธ๋Š” ์ทจ์„ฑ(brittle)์ ์ธ ์„ฑ์งˆ๋กœ ์ธํ•˜์—ฌ ์ธ์žฅ ๋ฐ ํœจ์„ฑ๋Šฅ์ด ๋‚ฎ์€ ํŠน์„ฑ์„ ๊ฐ€์ง€๊ณ  ์žˆ์œผ๋ฉฐ ์ด๋Ÿฌํ•œ ๊ฒฐํ•จ์„ ๊ฐœ์„ ํ•˜๊ธฐ ์œ„ํ•œ ์ฝ˜ํฌ๋ฆฌํŠธ ์žฌ๋ฃŒ๋กœ ์ตœ๊ทผ ๊ตญ๋‚ด์™ธ์— ์„œ ํ™œ๋ฐœํžˆ ์—ฐ๊ตฌ๋˜๊ณ  ์žˆ๋Š” ๊ณ ์ธ์„ฑ ์‹œ๋ฉ˜ํŠธ ๋ณตํ•ฉ์ฒด(Engineered Cementitious Composite; ์ดํ•˜ ECC)๊ฐ€ ์žˆ๋‹ค.

๊ตญ๋‚ด์—์„œ๋Š” ์ตœ์ ์˜ ์‹œ๋ฉ˜ํŠธ๊ณ„ ๋ณตํ•ฉ์žฌ๋ฃŒ ๋ฐ ์ด๋ฅผ ์ ์šฉํ•œ ๊ตฌ ์กฐ๋ฌผ ์ ์šฉ์— ๋Œ€ํ•œ ์—ฐ๊ตฌ๊ฐ€ ์ง„ํ–‰๋œ๋ฐ” ์žˆ์œผ๋ฉฐ(Kim, 2006; Kim, 2014 and Lee, 2012), ECC ์žฌ๋ฃŒ๋Š” ์‹œ๋ฉ˜ํŠธ๊ณ„ ๋ณตํ•ฉ์žฌ๋ฃŒ์— ๋งˆ ์ดํฌ๋กœ์—ญํ•™์„ ์ ์šฉํ•œ ์„ฌ์œ ์™€ ๋งคํŠธ๋ฆญ์Šค๊ฐ„์˜ ์ธ์žฅ๋ณ€ํ˜•๋ฅ  ๊ฒฝํ™” ๊ฑฐ๋™ํŠน์„ฑ ๋ฐ ์•ˆ์ •์ƒํƒœ ๊ท ์—ด์ด๋ก ์„ ๊ธฐ๋ฐ˜์œผ๋กœ ๊ฐœ๋ฐœ๋˜์—ˆ๋‹ค(Li, 1991; Li, 1992 and Marshall, 1988). ECC๋Š” ์‹œ๋ฉ˜ํŠธ ๋ณตํ•ฉ์ฒด ์— ์ตœ์ดˆ ๊ท ์—ด์ด ๋ฐœ์ƒํ•  ๊ฒฝ์šฐ ํ˜ผ์ž…๋œ ๋‹จ์„ฌ์œ ๊ฐ€ ๊ฐ€๊ต์ž‘์šฉ์„ ํ•˜ ๋ฉด์„œ ์ฆ‰์‹œ ํŒŒ๊ดด์— ๋„๋‹ฌํ•˜์ง€ ์•Š๊ณ  2์ฐจ, 3์ฐจ ๊ท ์—ด์„ ์œ ๋„ํ•  ์ˆ˜ ์žˆ๋„๋ก ์„ค๊ณ„๋œ ์žฌ๋ฃŒ์ด๋‹ค(Kim, 2005; Li, 2001 and Shwan, 2015). ์ด๋Ÿฌํ•œ ํŠน์„ฑ์— ๊ธฐ์ธํ•˜์—ฌ ECC๋Š” ๋งˆ์ดํฌ๋กœ ์—ญํ•™๊ณผ ์•ˆ ์ •์ƒํƒœ๊ท ์—ด์ด๋ก ์„ ๋ฐ”ํƒ•์œผ๋กœ ์‹œ๋ฉ˜ํŠธ ๋งคํŠธ๋ฆญ์Šค์— 2 % ์ดํ•˜์˜ ๋‹จ์„ฌ์œ ๊ฐ€ ํ˜ผ์ž…๋˜์–ด 1์ถ• ์ธ์žฅ ํ•˜์—์„œ ๋‹ค๋ถ„์‚ฐ ๊ท ์—ด(multiple cracking) ํŠน์„ฑ์„ ๊ฐ€์ง€๊ณ  ๋‹ค์ˆ˜์˜ ๊ท ์—ด์ด ๋ฐœ์ƒ๋œ ํ›„์—๋„ ๋ณ€ํ˜•๋ฅ  ์˜ ์ฆ๊ฐ€์™€ ํ•จ๊ป˜ ์‘๋ ฅ์ด ์ฆ๊ฐ€ํ•˜๋Š” ๋ณ€ํ˜•๋ฅ  ๊ฒฝํ™”(strain-hardening) ๊ฐ€ ๋ฐœ์ƒํ•œ๋‹ค. ์ด๋Ÿฌํ•œ ํŠน์„ฑ์œผ๋กœ ์ธํ•˜์—ฌ Fischer(2002, 2003)๋Š” ๋ฐ˜๋ณต๊ฐ€๋ ฅ ์กฐ๊ฑด์—์„œ ECC๊ฐ€ ๋ณด๊ฐ•๋œ ์ฒ ๊ทผ์ฝ˜ํฌ๋ฆฌํŠธ ๊ธฐ๋‘ฅ์˜ ์‹ค ํ—˜๊ฒฐ๊ณผ ๋‚ด๋ ฅ ๋ฐ ์—ฐ์„ฑ๋Šฅ๋ ฅ์˜ ํ–ฅ์ƒ, ๋ถ€์žฌ๋‹จ๋ฉด์˜ ๊ฐ์†Œ ๋“ฑ ๋‚ด์ง„ ์„ฑ๋Šฅ ํ–ฅ์ƒ์„ ํ™•์ธํ•œ ๋ฐ” ์žˆ์œผ๋ฉฐ Salahuddin(2014)์€ ๋ณด-๊ธฐ๋‘ฅ ์ ‘ํ•ฉ๋ถ€์— ECC๋ฅผ ๋ณด๊ฐ•ํ•˜๋Š” ์—ฐ๊ตฌ๋ฅผ ์ง„ํ–‰ํ•˜์—ฌ ๊ทนํ•œ๊ฐ•๋„ ๋ฐ ์— ๋„ˆ์ง€ ์†Œ์‚ฐ๋Šฅ๋ ฅ ํ–ฅ์ƒ ๋“ฑ์˜ ์—ฐ๊ตฌ๊ฒฐ๊ณผ๋ฅผ ๋ณด๊ณ ํ•œ ๋ฐ” ์žˆ๋‹ค.

๋”ฐ๋ผ์„œ ์ด ์—ฐ๊ตฌ์—์„œ๋Š” ์„ฌ์œ -๋งคํŠธ๋ฆญ์Šค ๊ฒฝ๊ณ„๋ฉด์˜ ๋ถ€์ฐฉํŠน์„ฑ๊ณผ ์•ˆ์ „์ƒํƒœ ๊ท ์—ด์ด๋ก ์„ ์ ์šฉํ•˜์—ฌ ์ œ์ž‘ํ•œ ECC๋ฅผ ์ฒ ๊ทผ์ฝ˜ํฌ๋ฆฌํŠธ ๊ธฐ๋‘ฅ์— ์ ์šฉํ•˜์—ฌ ์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค. ์ด๋ฅผ ํ† ๋Œ€๋กœ ์ง€์ง„ํ•˜์ค‘ ๊ณผ ๊ฐ™์€ ํšก๋ ฅ์ด ์ž‘์šฉํ•  ๊ฒฝ์šฐ ๋‚ด๋ ฅ๊ณผ ์—ฐ์„ฑ๋Šฅ๋ ฅ์„ ํ–ฅ์ƒ์‹œํ‚ค๊ณ  ๊ธฐ๋‘ฅ ๋ฐ ๊ต๊ฐ๊ณผ ๊ฐ™์€ ์ฒ ๊ทผ์ฝ˜ํฌ๋ฆฌํŠธ ๊ตฌ์กฐ๋ฌผ์˜ ์•ˆ์ „์„ฑ์„ ์ฆ์ง„ ์‹œํ‚ค๊ณ ์ž ํ•จ์ด ์ด ์—ฐ๊ตฌ์˜ ๋ชฉ์ ์ด๋‹ค. ๋˜ํ•œ ๊ธฐ๋‘ฅ์˜ ์†Œ์„ฑํžŒ์ง€ ์ฝ˜ํฌ๋ฆฌํŠธ๋ฅผ ์ž„์˜์˜ ๋†’์ด๊นŒ์ง€ ECC๋กœ ๋Œ€์ฒดํ•œ ๊ธฐ์กด์˜ ์—ฐ๊ตฌ (Cho, 2014)์™€๋Š” ๋‹ฌ๋ฆฌ, ์ด ๋…ผ๋ฌธ์€ ๋ณด๋‹ค ํ•ฉ๋ฆฌ์ ์œผ๋กœ ECC ๋Œ€ ์ฒด ๋ฒ”์œ„๋ฅผ ๊ฒฐ์ •ํ•˜๊ณ ์ž ํ•˜๋Š” ์—ฐ๊ตฌ์˜ ์„ ํ–‰ ์‹คํ—˜์œผ๋กœ์„œ ๊ธฐ๋‘ฅ ์ „ ์ฒด๋ฅผ ECC๋กœ ๋งŒ๋“  ์‹คํ—˜์ฒด์˜ ๊ฑฐ๋™์„ ํŒŒ์•…ํ•˜๋Š” ๋ฐ์— ์—ฐ๊ตฌ์˜ ์ฃผ์•ˆ์ ์ด ์žˆ๋‹ค.

2. ์‹คํ—˜ ๊ฐœ์š”

2.1 ์‚ฌ์šฉ์žฌ๋ฃŒ

๊ธฐ๋‘ฅ ์‹คํ—˜์ฒด์˜ ๋‚ด์ง„์„ฑ๋Šฅ์„ ํ‰๊ฐ€ํ•˜๊ธฐ ์œ„ํ•ด ๋ณธ ์—ฐ๊ตฌ์—์„œ ์‚ฌ ์šฉํ•œ ECC๋Š” ์‹œ๋ฉ˜ํŠธ๊ณ„ ๋ชจ๋ฅดํƒ€๋ฅด ๋งคํŠธ๋ฆญ์Šค์— 2 % ์ดํ•˜์˜ ํ•ฉ ์„ฑ ์„ฌ์œ ๋ฅผ ํ˜ผ์ž…ํ•จ์œผ๋กœ์จ ์ผ๋ฐ˜ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ทจ์„ฑ์ ์ธ ์„ฑ์งˆ์„ ๊ฐœ์„ ํ•˜์—ฌ ์ธ์žฅ๋ณ€ํ˜•๋ฅ  2 % ์ด์ƒ์„ ๊ฐ–๋Š” ๊ณ ์ธ์„ฑ ์žฌ๋ฃŒ์ด๊ณ  ์ธ ์žฅ๋ณ€ํ˜•์ด ๋ฐœ์ƒํ•  ๋•Œ ๋‹ค์ˆ˜์˜ ๋ฏธ์„ธ ๊ท ์—ด(multiple micro cracks) ์ด ๋ฐœ์ƒํ•˜๋ฉฐ ๊ท ์—ดํญ์„ 100 ฮผm ์ดํ•˜๋กœ ์ œ์–ดํ•˜๋Š” ์šฐ์ˆ˜ํ•œ ๊ท  ์—ด ์ œ์–ด ํŠน์„ฑ์„ ๊ฐ–๊ณ  ์žˆ๋Š” ํŠน์„ฑ์ด ์žˆ๋‹ค. ๋ณธ ์—ฐ๊ตฌ์—์„œ ์ ์šฉํ•œ ECC์—๋Š” ์‹œ์ค‘์—์„œ ํŒ๋งคํ•˜๋Š” ๋ฐ€๋„ 3.15 g/cm3์˜ ๋ณดํ†ต ํฌํ‹€ ๋žœ๋“œ์‹œ๋ฉ˜ํŠธ(OPC)๋ฅผ ์‚ฌ์šฉํ•˜์˜€๊ณ , ECC์˜ ์ผ๋ฐ˜์ ์ธ ๊ณจ์žฌ๋กœ ์‚ฌ ์šฉํ•˜๋Š” ๊ทœ์‚ฌ(ํ‰๊ท ์ž…๊ฒฝ 130 ฮผm) ๋Œ€์‹  ์ˆœํ™˜์žฌ๋ฃŒ์ค‘ ํ•˜๋‚˜์ธ ํ”Œ ๋ผ์ด์• ์‹œ๋ฅผ ํ˜ผํ™”์žฌ๋ฃŒ๋กœ ๊ฒฐ์ •ํ•˜์—ฌ ๋ฐฐํ•ฉ์— ์‚ฌ์šฉํ•˜์˜€๋‹ค. ์„ฌ์œ ๋กœ ๋Š” Table 1์— ๋‚˜ํƒ€๋‚ธ๋ฐ”์™€ ๊ฐ™์ด ๋ฐ€๋„ 1.30 g/mm3, ์ง๊ฒฝ 39 ใŽ› ์ธ 12 mm ์˜ ํ‘œ๋ฉด์ฒ˜๋ฆฌ๋œ PVA ๋‹จ์„ฌ์œ ๋ฅผ ํ˜ผ์ž…ํ•˜์—ฌ ์ฝ˜ํฌ ๋ฆฌํŠธ์˜ ์ทจ์„ฑ์ ์ธ ์„ฑ์งˆ์„ ํ–ฅ์ƒ์‹œํ‚ค๊ณ ์ž ํ•˜์˜€๋‹ค. ๋˜ํ•œ, ECC๋ฐฐ ํ•ฉ์œผ๋กœ๋Š” Table 2์— ํ‘œ๊ธฐํ•œ ๋ฐ”์™€ ๊ฐ™์ด ๋ฌผ-๊ฒฐํ•ฉ์žฌ๋น„(W/B) 88 %, ํ”Œ๋ผ์ด์• ์‹œ/๊ฒฐํ•ฉ์žฌ๋น„(FA/B) 280 %, PVA์˜ ํ˜ผ์ž…๋ฅ  2 % ๋กœ ํ•˜์—ฌ ๋ฐฐํ•ฉ์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค. ์ ์šฉํ•  ECC ๋ฐฐํ•ฉ์€ ๊ธฐ์กด์˜ ๊ทœ ์‚ฌ๋ฅผ ์‚ฌ์šฉํ•˜๋Š” ECC๋ฐฐํ•ฉ๊ณผ ์œ ์‚ฌํ•œ ๋‹ค์ค‘๊ท ์—ด ํŠน์„ฑ์„ ๊ตฌํ˜„ํ•˜ ๊ธฐ ์œ„ํ•˜์—ฌ ํ”Œ๋ผ์ด์• ์‹œ์˜ ์น˜ํ™˜์œจ์„ ๋†’์—ฌ ๊ฒฐํ•ฉ์žฌ์™€ ์ถฉ์ „์žฌ์˜ ์—ญํ• ์„ ํ•  ์ˆ˜ ์žˆ๋„๋ก ํ•˜์˜€๋‹ค. ์‹œ๋ฉ˜ํŠธ ๋งคํŠธ๋ฆญ์Šค์— ํ”Œ๋ผ์ด์• ์‹œ ์˜ ์น˜ํ™˜์œจ์„ ๋†’์ž„์œผ๋กœ์„œ ๋งคํŠธ๋ฆญ์Šค์˜ ๊ฐ•๋„ ๊ฐ์†Œ๋กœ ์ธํ•œ ํŒŒ๊ดด ์ธ์„ฑ์„ ๋‚ฎ์ถ”์–ด ๋‹ค์ค‘๊ท ์—ด ํŠน์„ฑ์„ ๋ถ€์—ฌํ•˜๋„๋ก ํ•˜์˜€๋‹ค.

Table 1.

Properties of PVA fiber

Ingredient Density (g/mm 3) Length(mm) Diameter(ฮผm) Tensile strength(MPa) Youngโ€™s modulus(GPa) Elongation (%)
Polyviny lalcohol (PVA) 1.30 12 39 1,600 40 3-113
Table 2.

Mix proportion of ECC

W/C(%) FA/C(%) Unit:kg/m3
W OPC FA PCSP HPMC Defoamer PVA(vol.%)
88 280 362 411 1152 4.936 0.165 0.041 2

๋˜ํ•œ, ์‹œ๋ฉ˜ํŠธ ๋งคํŠธ๋ฆญ์Šค์˜ ์œ ๋™์„ฑ์„ ์ฆ๊ฐ€์™€ ๋ฐฐํ•ฉ ์‹œ ํ˜ผ์ž… ์„ฌ์œ ์˜ ๋ถ„์‚ฐ์„ฑ ํ–ฅ์ƒ์„ ์œ„ํ•˜์—ฌ ์นด๋ฅด๋ณธ์‚ฐ๊ณ„ ๊ณ ์„ฑ๋Šฅ ๊ฐ์ˆ˜์ œ (PCSP)๋ฅผ ์‚ฌ์šฉํ•˜์˜€์œผ๋ฉฐ, ์‹œ๋ฉ˜ํŠธ, ํ”Œ๋ผ์ด์• ์‹œ, ์„ฌ์œ  ๋“ฑ ํ˜ผํ•ฉ ์žฌ๋ฃŒ์˜ ์žฌ๋ฃŒ๋ถ„๋ฆฌ ๋ฐฉ์ง€๋ฅผ ์œ„ํ•˜์—ฌ ์…€๋ฃฐ๋กœ์˜ค์ฆˆ๊ณ„ ๋ถ„๋ฆฌ์ €๊ฐ์ œ (HPMC)์™€ ๊ณต๊ธฐ๋Ÿ‰ ์กฐ์ ˆ์„ ์œ„ํ•˜์—ฌ ์†Œํฌ์ œ(defoamer)๋ฅผ ํ˜ผํ™” ์ œ๋กœ ์‚ฌ์šฉํ•˜์˜€๋‹ค.

2.2 ECC์˜ ์ธ์žฅ์„ฑ๋Šฅ ํ‰๊ฐ€

๊ธฐ๋‘ฅ์‹คํ—˜์ฒด์— ์ ์šฉํ•œ ECC์˜ 1์ถ•์ธ์žฅ ์„ฑ๋Šฅ์„ ํ‰๊ฐ€ํ•˜๊ธฐ ์œ„ ํ•˜์—ฌ Fig. 1๊ณผ ๊ฐ™์ด ์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค. ๋‹จ๋ถ€์˜ ํŒŒ๊ดด๋ฅผ ๋ฐฉ์ง€ ํ•˜๋ฉด์„œ ์ง์ ‘์ธ์žฅ ์‹คํ—˜์ฒด์— ๊ท ์ผํ•œ 1์ถ• ์ธ์žฅํ•˜์ค‘์ด ๊ฐ€ํ•ด์ง€๋„ ๋ก dog-bone ํ˜•ํƒœ์˜ ์ธ์žฅ ์‹คํ—˜ํŽธ์„ ์ œ์ž‘ํ•˜์—ฌ ์ง์ ‘์ธ์žฅ ์‹คํ—˜ ์„ ์‹ค์‹œํ•˜์˜€๋‹ค. ์‹คํ—˜์ฒด๋Š” ํƒ€์„ค ํ›„ 28์ผ๊ฐ„ ์ˆ˜์ค‘์–‘์ƒ์„ ์‹ค์‹œํ•˜ ์—ฌ 24์‹œ๊ฐ„ ๊ฑด์กฐ๋ฅผ ๋งˆ์นœ ํ›„ 20t ์šฉ๋Ÿ‰์˜ UTM์„ ์ด์šฉํ•˜์—ฌ 1์ถ• ์ธ์žฅ์„ ๊ฐ€๋ ฅํ•˜์˜€์œผ๋ฉฐ, ์‹คํ—˜์ฒด ์ค‘์–‘๋ถ€ 80 mm ์ขŒ์šฐ ๋Œ€์นญ์ธ ๊ตฌ๊ฐ„์— 10 mm ๋ณ€์œ„๊ณ„(LVDT)๋ฅผ ์„ค์น˜ํ•˜์—ฌ ํ•˜์ค‘๊ณผ ํ•จ๊ป˜ ์‹ค ํ—˜์ฒด์— ๋ฐœ์ƒํ•˜๋Š” ์‹ค์‹œ๊ฐ„์˜ ๋ณ€์œ„๋ฅผ ์ธก์ •ํ•˜์˜€๋‹ค. ํ•˜์ค‘๊ณผ ๋ณ€์œ„ ๋Š” ์ธ์žฅ์‘๋ ฅ๊ณผ ๋ณ€ํ˜•๋ฅ ๋กœ ๊ฐ๊ฐ ํ™˜์‚ฐํ•˜์˜€์œผ๋ฉฐ ์ธ์žฅ์‘๋ ฅ-๋ณ€ํ˜•๋ฅ  ๊ด€๊ณ„๋ฅผ Fig. 2์— ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ์ตœ์ ๋ฐฐํ•ฉ์„ ๋ฐ”ํƒ•์œผ๋กœ ์ œ์ž‘๋œ ๊ณ ์ธ์„ฑ ์„ฌ์œ ๋ณตํ•ฉ์ฒด์ธ ECC๋Š” 1์ถ•์ธ์žฅ์—์„œ ๋šœ๋ ทํ•œ ๋ณ€ํ˜•๋ฅ  ๊ฒฝ ํ™”๊ฑฐ๋™์ด ๋ฐœ์ƒํ•˜์˜€์œผ๋ฉฐ, ๊ท ์—ดํญ์ด ์•„์ฃผ ์ž‘์€ ๋‹ค์ˆ˜์˜ ๋ฏธ์„ธ๊ท  ์—ด์ด ๋ฐœ์ƒํ•˜์˜€๋‹ค. ์‹คํ—˜์ฒด์˜ ํŒŒ๊ดดํ˜•ํƒœ๋Š” 1์ถ•์ธ์žฅ์‘๋ ฅ์ด ์ฆ๊ฐ€ ํ•˜์—ฌ ์‹คํ—˜์ฒด์˜ ๊ท ์—ด๊ฐ•๋„์— ๋„๋‹ฌํ•˜๋ฉด์„œ ์ฒซ ๊ท ์—ด์ด ๋ฐœ์ƒํ•˜์˜€ ์œผ๋ฉฐ ์ธ์žฅ๊ฐ•๋„๊ฐ€ ์ฆ๊ฐ€ํ•˜๋Š” ๋ณ€ํ˜•๊ตฌ๊ฐ„์—์„œ๋Š” ์•ˆ์ •์ƒํƒœ์˜ ๋ฏธ์„ธ ๊ท ์—ด์ด ์‹คํ—˜ํŽธ ์ „์ฒด์— ๋ถ„์‚ฐ๋˜๋ฉด์„œ ๋ณ€ํ˜•๋ฅ  ๊ฒฝํ™”๊ฑฐ๋™์ด ๊ด€์ฐฐ ๋˜์—ˆ๋‹ค. ์ดํ›„, ์‘๋ ฅ์ด ์‹คํ—˜์ฒด์˜ ์ตœ๋Œ€ ์ธ์žฅ๊ฐ•๋„๋ฅผ ์ดˆ๊ณผ๋  ๋•Œ ๋ฐœ์ƒ๋œ ๊ท ์—ด์— ์‘๋ ฅ์ด ์ง‘์ค‘๋˜์–ด ๊ท ์—ด์˜ ํญ์ด ์ปค์ง€๋ฉด์„œ ํŒŒ๊ดด ๋˜๋Š” ๊ฑฐ๋™์„ ๋‚˜ํƒ€๋‚ด์—ˆ์œผ๋ฉฐ ์‚ฌ์šฉ ์žฌ๋ฃŒ์˜ ํŠน์„ฑ์€ Table 3์— ํ‘œ ๊ธฐํ•˜์˜€๋‹ค. ์‹คํ—˜๊ฒฐ๊ณผ๋ฅผ ํ† ๋Œ€๋กœ ์ง์ ‘์ธ์žฅ ์‹คํ—˜์ฒด์˜ ์ตœ๋Œ€ ๋ณ€ํ˜• ๋ฅ ์€ 3.0 ~ 3.5 %๋ฅผ ๋ณด์—ฌ ํ‰๊ท  3.2 %์˜ ๋ณ€ํ˜•๋ฅ ์„ ๋‚˜ํƒ€๋‚ด์—ˆ ์œผ๋ฉฐ ์ด๊ฒƒ์€ ์ผ๋ฐ˜ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ธ์žฅ ๋ณ€ํ˜•๋ฅ  0.01 %์— ๋น„ํ•˜์—ฌ ์•ฝ 300๋ฐฐ ์ด์ƒ์˜ ์ธ์žฅ ๋ณ€ํ˜•์„ฑ๋Šฅ์— ํ•ด๋‹น๋œ๋‹ค.

Fig. 1.

ECC coupons and uniaxial tension test

JKSMI-19-75_F1.jpg
Fig. 2.

Measured tensile stress-strain curves of ECC

JKSMI-19-75_F2.jpg
Table 3.

Material properties of ECC

Material Compressive strength (MPa) First cracking strength (MPa) Ultimate tensile strength(MPa) Maximim tensile strain (%)
ECC 20 2.2 3.1 3.2

๋˜ํ•œ, ECC๋Š” ์ดˆ๊ธฐ๊ท ์—ด ์ดํ›„ ๋ฏธ์„ธํ•œ ๋‹ค์ˆ˜ ๊ท ์—ด์ด ๋ฐœ์ƒํ•จ๊ณผ ๋™์‹œ์— ๋ณ€ํ˜•๋ฅ  ๊ฒฝํ™”๊ฑฐ๋™์„ ๋‚˜ํƒ€๋‚ด๋ฏ€๋กœ ์ผ๋ฐ˜ ์ฝ˜ํฌ๋ฆฌํŠธ์— ๋น„ ํ•˜์—ฌ ์ธ์žฅ ์กฐ๊ฑดํ•˜์—์„œ ๊ท ์—ด์ด ๋ฐœ์ƒํ•˜๋”๋ผ๋„ ์ €ํ•ญํ•  ์ˆ˜ ์žˆ๋Š” ๋Šฅ๋ ฅ์ด ํ–ฅ์ƒ๋˜์–ด ECC๋ฅผ ๊ธฐ๋‘ฅ์‹คํ—˜์ฒด์— ์ ์šฉํ•  ๊ฒฝ์šฐ ๋†’์€ ์— ๋„ˆ์ง€ ์†Œ์‚ฐ๋Šฅ๋ ฅ์„ ๋ฐœํœ˜ํ•  ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

3. ๊ธฐ๋‘ฅ ์‹คํ—˜์ฒด ์ œ์ž‘ ๋ฐ ์‹คํ—˜ ๋ฐฉ๋ฒ•

3.1 ๊ฐœ์š”

์ด ์—ฐ๊ตฌ์—์„œ ์„ค๊ณ„ํ•œ ์‹คํ—˜์ฒด์˜ ํ˜•์ƒ ๋ฐ ์ œ์›๋Š” Fig. 3, Table 4์— ํ‘œ๊ธฐํ•˜์˜€๋‹ค. ๊ธฐ๋‘ฅ ์‹คํ—˜์ฒด๋Š” ์ด ๋†’์ด 2,640 mm ์ด๋ฉฐ, ๊ธฐ ๋‘ฅ ๋‹จ๋ฉด์น˜์ˆ˜ 300 mm ร— 300 mm, ๊ฐ€๋ ฅํŒ์ด ๋ถ€์ฐฉ๋˜๋Š” ๊ธฐ๋‘ฅ ๋จธ๋ฆฌ 400 mm ร— 400 mm ์ด๊ณ , ๊ธฐ๋‘ฅ๊ณผ ์—ฐ๊ฒฐ๋œ ๊ธฐ์ดˆ๋ถ€ ์น˜์ˆ˜ ๋Š” 900 mm ร— 900 mm ร— 700 mm๋กœ ์ œ์ž‘ํ•˜์˜€๋‹ค.

Fig. 3.

Details of test column(unit : mm)

JKSMI-19-75_F3.jpg
Table 4.

Two types of column specimens

Specimens Concrete compressive strength (MPa) Rebar yield strength (MPa) ECC Fiber vol. fraction (Vf) Longitudinal bars /tie bars
RC 20 387 - 8-D13 /D10@100
ECC 20 387 PVA2.0% 8-D13 /D10@100

๋ฐ˜๋ณต๊ฐ€๋ ฅ ์‹คํ—˜์„ ์œ„ํ•˜์—ฌ RC ์‹คํ—˜์ฒด์™€ ECC ์‹คํ—˜์ฒด๋ฅผ ์ œ ์ž‘ํ•˜์˜€๋‹ค. RC์‹คํ—˜์ฒด๋Š” ECC์‹คํ—˜์ฒด์™€ ๋น„๊ตํ•˜๊ธฐ ์œ„ํ•œ ๊ธฐ์ค€์‹ค ํ—˜์ฒด๋กœ์„œ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์••์ถ•๊ฐ•๋„๋Š” 20 MPa, ์ฃผ์ฒ ๊ทผ์€ 8๊ฐœ์˜ D13 ์ฒ ๊ทผ์„ ์‚ฌ์šฉํ•˜์˜€์œผ๋ฉฐ ๋ ์ฒ ๊ทผ์€ D10 ์ฒ ๊ทผ์„ ๊ธฐ์ดˆ๋ถ€๋กœ๋ถ€ ํ„ฐ 100 mm ๊ฐ„๊ฒฉ์œผ๋กœ ๋ฐฐ๊ทผํ•˜์—ฌ ์‹คํ—˜์ฒด๋ฅผ ์ œ์ž‘ํ•˜์˜€๋‹ค.

ECC์‹คํ—˜์ฒด์˜ ๊ฒฝ์šฐ ๊ธฐ์ดˆ๋ถ€๋Š” ์ผ๋ฐ˜ ์ฝ˜ํฌ๋ฆฌํŠธ 20 MPa๋ฅผ ์  ์šฉํ•˜์˜€๊ณ  ๊ธฐ์ดˆ๋ถ€์™€ ์—ฐ๊ฒฐ๋œ ๊ธฐ๋‘ฅ๊ณผ ๊ธฐ๋‘ฅ๋จธ๋ฆฌ ๋ถ€๋ถ„์€ ํ‰๊ท  ์ธ ์žฅ๋ณ€ํ˜•๋ฅ  3.2 %, ์žฌ๋ น 28์ผ ๊ธฐ์ค€ ์••์ถ•๊ฐ•๋„ 20 MPa์˜ ECC ๋ฅผ ์‚ฌ์šฉํ•˜์˜€๋‹ค.

3.2 ์‹คํ—˜์ฒด ์ œ์ž‘ ๊ณผ์ •

์‹คํ—˜์ฒด ์ œ์ž‘์„ ์œ„ํ•˜์—ฌ Fig. 4์™€ ๊ฐ™์ด ํ˜„์žฅ์—์„œ ๊ฑฐํ‘ธ์ง‘์„ ์ œ์ž‘ํ•œ ํ›„ ์ฒ ๊ทผ๋ง์„ ์กฐ๋ฆฝํ•˜์—ฌ ๊ฑฐํ‘ธ์ง‘ ๋‚ด๋ถ€์— ๊ณ ์ •ํ•˜์˜€๋‹ค. ์ฃผ ์ฒ ๊ทผ๊ณผ ๋ ์ฒ ๊ทผ์˜ ๋ณ€ํ˜•๋ฅ ์„ ์ธก์ •ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์กฐ๋ฆฝ๋œ ์ฒ ๊ทผ๋ง ์— ์ŠคํŠธ๋ ˆ์ธ ๊ฒŒ์ด์ง€๋ฅผ ์ขŒ์šฐ๋กœ ๋ถ€์ฐฉํ•˜์˜€๋‹ค. RC์‹คํ—˜์ฒด๋ฅผ ์ œ์ž‘ ํ•  ๋•Œ์—๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ ์ถฉ์ „์„ ์šฉ์ดํ•˜๊ฒŒ ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ๊ตต์€๊ณจ์žฌ ์˜ ์ตœ๋Œ€์น˜์ˆ˜ 20 mm, ์Šฌ๋Ÿผํ”„ 150 mm ๊ทœ๊ฒฉ์˜ ์ฝ˜ํฌ๋ฆฌํŠธ๋ฅผ ์‚ฌ ์šฉํ•˜์˜€๋‹ค. ECC ์‹คํ—˜์ฒด์˜ ๊ฒฝ์šฐ ๊ธฐ์ดˆ๋ถ€๋Š” RC ์‹คํ—˜์ฒด์™€ ๋™์ผ ํ•œ ์ฝ˜ํฌ๋ฆฌํŠธ๋ฅผ ์ ์šฉํ•˜์˜€๊ณ  ๊ธฐ๋‘ฅ๋ถ€์—๋Š” ์ „์ฒด๋ฅผ ECC๋กœ ํƒ€์„ค ํ•˜์˜€๋‹ค. ECC์˜ ๊ฒฝ์šฐ ์ฝ˜ํฌ๋ฆฌํŠธ์™€ ๋งˆ์ฐฌ๊ฐ€์ง€๋กœ ํ˜„์žฅ์—์„œ ๋ฐฐํ•ฉ ๋ฐ ํƒ€์„ค์„ ์ง„ํ–‰ํ•˜์˜€์œผ๋ฉฐ ์ฝ˜ํฌ๋ฆฌํŠธ ๋ฐ ECC ํƒ€์„ค ํ›„ ๊ฑด์กฐ์ˆ˜ ์ถ• ๊ท ์—ด์„ ๋ฐฉ์ง€ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์–‘์ƒํฌ๋ฅผ ๋ฎ์–ด ์ผ์ •ํ•œ ์Šต๋„๊ฐ€ ์œ  ์ง€๋˜๋„๋ก ์Šต์œค์–‘์ƒํ•œ ํ›„ ์žฌ๋ น 28์ผ์— ์‹คํ—˜์„ ์ˆ˜ํ–‰ ํ•˜์˜€๋‹ค.

Fig. 4.

Column specimen preparation

JKSMI-19-75_F4.jpg

3.3 ์‹คํ—˜ ๋ฐฉ๋ฒ•

๋ฐ˜๋ณต๊ฐ€๋ ฅ์‹คํ—˜์€ Fig. 5์™€ ๊ฐ™์ด ์ง„ํ–‰ํ•˜์˜€์œผ๋ฉฐ ๊ธฐ๋‘ฅ ๊ธฐ์ดˆ ๋ถ€ ๋ถ„์„ ์ •์ฐฉ์‹œํ‚ค๊ธฐ ์œ„ํ•œ ๋ฐฉ๋ฒ•์œผ๋กœ ์ง๊ฒฝ 50 mm์˜ ์›ํ˜• ๊ฐ•๋ด‰์„ ์‹คํ—˜์ฒด์˜ ๊ธฐ์ดˆ๋ถ€๋ถ„์— ๋ณผํŠธ๋กœ ์กฐ์ด๊ณ  ๊ธฐ์ดˆํŒ๊ณผ ๊ธฐ๋‘ฅ ๋จธ๋ฆฌ ๋ถ€ ๋ถ„์˜ ์ˆ˜์ง๊ณผ ์ˆ˜ํ‰์„ ์œ ์ง€ํ•˜๋„๋ก ์ •์ฐฉํ•˜์˜€๋‹ค. ์‹คํ—˜์ฒด์— ์ถ•ํ•˜ ์ค‘์„ ์žฌํ•˜ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ 300 kN ์šฉ๋Ÿ‰์˜ ์•ก์ธ„์—์ดํ„ฐ๋ฅผ ์‹คํ—˜์ฒด ์ƒ๋ถ€์— ๊ณ ์ •ํ•˜์˜€์œผ๋ฉฐ ์••์ถ•๋ ฅ์„ ๋ฐ›๊ณ  ์žˆ๋Š” ์ƒํ™ฉ์—์„œ ํšก๋ฐฉํ–ฅ ํ•˜์ค‘์„ ๊ฐ€๋ ฅํ•˜๊ธฐ ์œ„ํ•ด 500 kN ์šฉ๋Ÿ‰์˜ ์•ก์ธ„์—์ดํ„ฐ๋ฅผ ์‚ฌ์šฉํ•˜ ์˜€๊ณ  ๊ฐ€๋ ฅํŒ๊ณผ ๊ธฐ๋‘ฅ ์ƒ๋‹จ๋ถ€๋ฅผ ๋ณผํŠธ์™€ ๋„ˆํŠธ๋กœ ๊ณ ์ •ํ•˜์˜€๋‹ค. ์‹ค ํ—˜ ์‹œ์ž‘ ์‹œ ์ถ•๋ฐฉํ–ฅ ์•ก์ธ„์—์ดํ„ฐ๋ฅผ ์ด์šฉํ•˜์—ฌ ์‹คํ—˜์ฒด์— ์ถ•์••์ถ• ๊ฐ•๋„์˜ 10 %๋ฅผ ์ผ์ •ํ•˜๊ฒŒ ์ถ•ํ•˜์ค‘์œผ๋กœ ์žฌํ•˜ํ•œ ํ›„ ์‹คํ—˜์„ ์ง„ํ–‰ ํ•˜์˜€๋‹ค.

Fig. 5.

Test setup for cyclic loading on column

JKSMI-19-75_F5.jpg

ํšก๋ฐฉํ–ฅ ํ•˜์ค‘ ํ˜•ํƒœ๋Š” ๊ธฐ๋‘ฅ์‹คํ—˜์ฒด์˜ ๋†’์ด์— ๋Œ€ํ•œ ์ˆ˜ํ‰๋ฐฉํ–ฅ ๋ณ€์œ„์˜ ๋น„์ธ drift ratio๋ฅผ ์ฆ๊ฐ€์‹œํ‚ค๋Š” ๋ฐฉ๋ฒ•์œผ๋กœ ํšก๋ฐฉํ–ฅ ํ•˜์ค‘ ์„ ๊ฐ€๋ ฅํ•˜์˜€๋‹ค. ๊ฐ ๋‹จ๊ณ„๋ณ„ drift ratio๋Š” Fig. 6๊ณผ ๊ฐ™์ด ๋งคํšŒ 2 ์‹ธ์ดํด์”ฉ ์ •๊ฐ€๋ ฅ๊ณผ ๋ถ€๊ฐ€๋ ฅ์˜ ๋ฐ˜๋ณตํ•˜์ค‘์„ ๋ณ€์œ„์ œ์–ด ๋ฐฉ์‹์œผ๋กœ ์žฌํ•˜ํ•˜์˜€์œผ๋ฉฐ ์ด 24 ์‹ธ์ดํด์˜ ๋ฐ˜๋ณตํ•˜์ค‘์„ ์žฌํ•˜ํ•˜์˜€๋‹ค.

Fig. 6.

Cyclic lateral loading history by displacement control

JKSMI-19-75_F6.jpg

4. ๊ธฐ๋‘ฅ ์‹คํ—˜๊ฒฐ๊ณผ ๋ฐ ๋ถ„์„

4.1 ๊ท ์—ด ๋ฐ ํŒŒ๊ดด์–‘์ƒ

Fig. 7์€ ๋ฐ˜๋ณตํ•˜์ค‘ ์žฌํ•˜์— ๋”ฐ๋ฅธ RC์™€ ECC์‹คํ—˜์ฒด์˜ ์‹คํ—˜ ์ข…๋ฃŒ ํ›„ ๊ท ์—ด ๋ฐ ํŒŒ๊ดด์–‘์ƒ์„ ๋‚˜ํƒ€๋‚ด๊ณ  ์žˆ๋‹ค. ๊ธฐ์ค€ ์‹คํ—˜์ฒด์ธ RC ์‹คํ—˜์ฒด์˜ ๊ฒฝ์šฐ drift ratio 0.25 %(4.4 mm)์—์„œ ์ดˆ๊ธฐ ํœจ ๊ท ์—ด์ด ๋ฐœ์ƒํ•˜์˜€๊ณ  ํ•˜์ค‘์ด๋ ฅ์ด ์ฆ๊ฐ€ํ•จ์— ๋”ฐ๋ผ ํœจ๊ท ์—ด์˜ ๊ฐœ ์ˆ˜๊ฐ€ ์ ์ฐจ ์ฆ๊ฐ€ํ•˜์˜€๋‹ค. ์ดํ›„ drift ratio 1 % (17.4 mm)์— ๋„ ๋‹ฌํ•  ๋•Œ๊นŒ์ง€ ๊ท ์—ด์˜ ๋ฐœ์ƒ ์—†์ด ์‹คํ—˜์ฒด์— ๋ฐœ์ƒํ•œ ๊ธฐ์กด ๊ท ์—ด์˜ ํญ์ด ์ฆ๊ฐ€ํ•˜๋Š” ์–‘์ƒ์„ ๋ณด์˜€์œผ๋ฉฐ drift ratio 1.5 %(26.1 mm) ์— ๋„๋‹ฌํ•œ ํ›„ ์ถ”๊ฐ€์ ์ธ ํœจ ๊ท ์—ด์ด ๋ฐœ์ƒํ•˜๋ฉด์„œ ๊ธฐ์ดˆ-๊ธฐ๋‘ฅ ์ ‘ ํ•ฉ๋ถ€์—์„œ ์ฝ˜ํฌ๋ฆฌํŠธ ํ”ผ๋ณต์˜ ๋ฐ•๋ฆฌ๊ฐ€ ์‹œ์ž‘๋˜์—ˆ๋‹ค. drift ratio 2 %(34.8 mm)์—์„œ ์ตœ๋Œ€ ๋‚ด๋ ฅ์— ๋„๋‹ฌ ํ•œ ์ดํ›„ ์†Œ์„ฑํžŒ์ง€ ๊ตฌ๊ฐ„ ์—์„œ ๋ฐœ์ƒํ•œ ์ „๋‹จ๊ท ์—ด์˜ ์ง„์ „๊ณผ ํ•จ๊ป˜ ๋ฐ•๋ฆฌ๋˜๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์–‘์ด ํฌ๊ฒŒ ์ฆ๊ฐ€ํ•˜์˜€์œผ๋ฉฐ, drift ratio 2.5 %(52.2 mm)์—์„œ ๊ธ‰ ๊ฒฉํ•œ ํ•˜์ค‘๊ฐ์†Œ๊ฐ€ ๋ฐœ์ƒํ•˜๊ธฐ ์‹œ์ž‘ํ•˜์—ฌ 20 ์‹ธ์ดํด์— ๋„๋‹ฌํ•œ drift ratio 3 %(52.2 mm)์—์„œ ์‹คํ—˜์„ ์ข…๋ฃŒํ•˜์˜€๋‹ค.

Fig. 7.

Crack patterns of columns

JKSMI-19-75_F7.jpg

ECC ์‹คํ—˜์ฒด์˜ ๊ฒฝ์šฐ RC ์‹คํ—˜์ฒด์™€ ๋™์ผํ•˜๊ฒŒ drift ratio 0.25 %(4.4 mm)์—์„œ ์ดˆ๊ธฐ ํœจ ๊ท ์—ด์ด ๋ฐœ์ƒํ•˜์˜€๋‹ค. ์ดํ›„ drift ratio 1.75 %(30.5 mm)๊นŒ์ง€ ํ•˜์ค‘์˜ ์ฆ๊ฐ€์™€ ํ•จ๊ป˜ ์‹คํ—˜์ฒด์—์„œ ๋‹ค์ค‘ ๋ฏธ์„ธ๊ท ์—ด์ด ์ ์ง„์ ์œผ๋กœ ๋ฐœ์ƒํ•˜์˜€๊ณ  ๊ธฐ๋‘ฅ์˜ ์ตœ๋Œ€ ํ•˜์ค‘ ์€ drift ratio 3.0 %(52.2 mm)์—์„œ ์ตœ๋Œ€๋‚ด๋ ฅ์— ๋„๋‹ฌํ•˜์˜€์œผ ๋‚˜ RC ์‹คํ—˜์ฒด์™€ ๋‹ฌ๋ฆฌ ๊ธฐ์ดˆ-๊ธฐ๋‘ฅ ์ ‘ํ•ฉ๋ถ€์—์„œ์˜ ์ฝ˜ํฌ๋ฆฌํŠธ ๋ฐ• ๋ฆฌ๋Š” ๊ด€์ฐฐ๋˜์ง€ ์•Š์•˜์œผ๋ฉฐ drift ratio 4.0 %(69.6 mm)์— ๋„๋‹ฌ ํ›„ 24 ์‹ธ์ดํด์—์„œ ์‹คํ—˜์„ ์ข…๋ฃŒํ•˜์˜€๋‹ค. ์ตœ๋Œ€๋‚ด๋ ฅ์— ๋„๋‹ฌํ•œ ์ด ํ›„ ๊ธ‰๊ฒฉํžˆ ํ•˜์ค‘์ด ๊ฐ์†Œํ•œ RC ์‹คํ—˜์ฒด์™€๋Š” ๋‹ฌ๋ฆฌ ECC ์‹คํ—˜์ฒด ๋Š” ์ตœ๋Œ€๋‚ด๋ ฅ ์ดํ›„์— ์ˆ˜ํ‰๋ณ€์œ„์˜ ์ฆ๊ฐ€์—๋„ ๋‚ด๋ ฅ์ด ์œ ์ง€๋˜๋ฉด ์„œ ์„œ์„œํžˆ ๊ฐ์†Œํ•˜๋Š” ํŠน์„ฑ์„ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค.

4.2 ๋ฐ˜๋ณต์ด๋ ฅ๊ฑฐ๋™

Fig. 8, Fig. 9๋Š” ๋ฐ˜๋ณต๊ฐ€๋ ฅ์‹คํ—˜์„ ํ†ตํ•ด ์ธก์ •ํ•œ ์‹คํ—˜์ฒด๋ณ„ ํ•˜ ์ค‘-๋ณ€์œ„ ๋ฐ˜๋ณต์ด๋ ฅ๊ฑฐ๋™ ๋ฐ ํฌ๋ฝ๊ณก์„ ์„ ๋„์‹œํ•œ ๊ทธ๋ž˜ํ”„์ด๋ฉฐ Table 5๋Š” ๋‹จ๊ณ„๋ณ„ ํ•˜์ค‘ ๋ฐ ๋ณ€์œ„, ์—ฐ์„ฑ๋น„๋ฅผ ๋‚˜ํƒ€๋‚ธ ํ‘œ์ด๋‹ค. ๊ธฐ ์ค€์‹คํ—˜์ฒด์ธ RC์‹คํ—˜์ฒด์˜ ๊ฒฝ์šฐ ์ˆ˜ํ‰๋ณ€์œ„ 4.2 mm, 14.2 kN์˜ ํ•˜์ค‘์—์„œ ์ดˆ๊ธฐ ํœจ ๊ท ์—ด์ด ๋ฐœ์ƒํ•œ ์ดํ›„ 17.2 mm, 23.6 kN์— ์„œ ์ธ์žฅ๋ถ€ ์ฃผ์ฒ ๊ทผ์ด ์ตœ์ดˆ ํ•ญ๋ณต์— ๋„๋‹ฌํ•˜์˜€๋‹ค. ์ตœ์ดˆ ํ•ญ๋ณต์  ์ดํ›„ ํ•˜์ค‘์˜ ์ฆ๊ฐ€์™€ ํ•จ๊ป˜ ์ ์ง„์ ์œผ๋กœ ์ˆ˜ํ‰๋ณ€์œ„๊ฐ€ ์ฆ๊ฐ€ํ•˜์—ฌ 33.1 mm ๋ณ€์œ„์—์„œ 34.8 kN์˜ ์ตœ๋Œ€ํ•˜์ค‘์„ ๋‚˜ํƒ€๋ƒˆ๋‹ค. ์ตœ๋Œ€ํ•˜ ์ค‘ ์ดํ›„ ๋‚ด๋ ฅ์ด ๊ฐ์†Œํ•˜๋ฉด์„œ ์ˆ˜ํ‰ ๋ณ€์œ„๊ฐ€ ์ฆ๊ฐ€ํ•˜์˜€์œผ๋ฉฐ ์ตœ๋Œ€ ์ˆ˜ํ‰๋ณ€์œ„์—์„œ ๋ฐœ์ƒํ•œ ํœจ ๊ท ์—ดํญ์˜ ์ฆ๊ฐ€ ๋ฐ ์••์ถ•๋ถ€ ์ฝ˜ํฌ๋ฆฌํŠธ ์˜ ๋ฐ•๋ฆฌ๊ฐ€ ์ง„ํ–‰๋˜๋ฉด์„œ ๋‚ด๋ ฅ์ €ํ•˜๋กœ ์ธํ•˜์—ฌ ์‹คํ—˜์„ ์ข…๋ฃŒํ•˜์˜€ ๋‹ค. RC์‹คํ—˜์ฒด์˜ ์—ฐ์„ฑ๋น„๋Š” 1.92๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ECC ์‹คํ—˜์ฒด๋Š” ์ˆ˜ํ‰๋ณ€์œ„ 4.4 mm, 16.6 kN์˜ ํ•˜์ค‘์—์„œ ์ดˆ๊ธฐ ํœจ๊ท ์—ด์ด ๋ฐœ์ƒ ํ•˜์˜€๋‹ค. ์ดˆ๊ธฐ ๊ท ์—ด์ด ๋ฐœ์ƒํ•œ ์ดํ›„ ๋‹ค์ค‘ ๋ฏธ์„ธ๊ท ์—ด์˜ ๋ฐœ์ƒ๊ณผ ํ•จ๊ป˜ ์ˆ˜ํ‰๋ณ€์œ„ ์ฆ๊ฐ€์— ๋”ฐ๋ฅธ ํ•˜์ค‘์ด ์ ์ง„์ ์œผ๋กœ ์ฆ๊ฐ€ํ•˜์˜€์œผ ๋ฉฐ ๋ณ€์œ„ 21.4 mm, 29.4 kN์˜ ํ•˜์ค‘์—์„œ ์ฒ ๊ทผ์ด ํ•ญ๋ณตํ•˜์˜€๋‹ค. ์ฒ ๊ทผ์˜ ํ•ญ๋ณต ์ดํ›„ ๊ท ์—ดํญ์˜ ์ฆ๊ฐ€ ์—†์ด ๋ฏธ์„ธ๊ท ์—ด์ด ์ตœ๋Œ€ ๋‚ด๋ ฅ (๋ณ€์œ„ 52.5 mm, 41.0 kN)์— ๋„๋‹ฌํ• ๋•Œ๊นŒ์ง€ ์ง€์†์ ์œผ๋กœ ๋ฐœ์ƒํ•˜ ์˜€๋‹ค. RC ์‹คํ—˜์ฒด์— ๋น„ํ•˜์—ฌ ์ตœ๋Œ€๋‚ด๋ ฅ์€ ์•ฝ 18%, ์—ฐ์„ฑ๋น„(2.45) ๋Š” ์•ฝ 28 % ํ–ฅ์ƒ๋œ ๊ฒฐ๊ณผ๋ฅผ ๋ณด์ด๋ฉด์„œ ๊ตฌ์กฐ์ ์œผ๋กœ ๋ณด๋‹ค ์šฐ์ˆ˜ ํ•œ ๊ฑฐ๋™์„ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค.

Fig. 8.

Load-displacement relation curves

JKSMI-19-75_F8.jpg
Fig. 9.

Envelope curves of RC and ECC columns

JKSMI-19-75_F9.jpg
Table 5.

Test results of RC and ECC specimen

specimens Initial cracks Yieldingofbar Max.load Ductility ratio
Disp. (mm) Load (kN) Disp. (mm) Load (kN) Disp. (mm) Load (kN)
RC 4.23 14.2 17.19 23.6 33.06 34.8 1.92
ECC 4.35 16.6 21.44 29.4 52.49 41.0 2.45

4.3 ์—๋„ˆ์ง€ ์†Œ์‚ฐ๋Šฅ๋ ฅ

๋ฐ˜๋ณตํ•˜์ค‘์— ์˜ํ•œ ์—๋„ˆ์ง€ ์†Œ์‚ฐ๋Šฅ๋ ฅ์€ ์ง€์ง„์ด ๋ฐœ์ƒํ•  ๊ฒฝ์šฐ ๊ตฌ์กฐ๋ฌผ์˜ ๋‚ด์ง„์„ฑ๋Šฅ์„ ํ‰๊ฐ€ํ•  ์ˆ˜ ์žˆ๋Š” ์ค‘์š”ํ•œ ์š”์†Œ์ด๋‹ค. ์ด๋Ÿฌ ํ•œ ์—๋„ˆ์ง€ ์†Œ์‚ฐ๋Šฅ๋ ฅ์„ ํ‰๊ฐ€ํ•˜๊ธฐ ์œ„ํ•ด Fig. 11์— ๋„์‹œํ•œ ๋ฐ”์™€ ๊ฐ™์ด ์‹คํ—˜ ์ข…๋ฃŒ๊นŒ์ง€ ํ•˜์ค‘-๋ณ€์œ„ ๋ฐ˜๋ณต์ด๋ ฅ๊ณก์„ ์˜ ๋ฉด์ ์„ ๊ณ„์‚ฐ ํ•˜์—ฌ ์—๋„ˆ์ง€ ์†Œ์‚ฐ๋Ÿ‰์„ ์‚ฐ์ถœํ•˜์˜€๋‹ค.

Fig. 11.

Energy dissipation capacity of RC and ECC columns

JKSMI-19-75_F11.jpg

RC ์‹คํ—˜์ฒด์™€ ECC ์‹คํ—˜์ฒด์˜ ์—๋„ˆ์ง€ ์†Œ์‚ฐ๋Ÿ‰์€ ๊ฐ๊ฐ 29.52 kNยทm์™€ 60.27 kNยทm๋กœ ์‚ฐ์ถœ๋˜์—ˆ๋‹ค. ECC ์‹คํ—˜์ฒด์˜ ์—๋„ˆ์ง€ ์†Œ์‚ฐ๋Ÿ‰์€ ๊ธฐ์ค€์‹คํ—˜์ฒด์ธ RC ์‹คํ—˜์ฒด์˜ 204.2 %์— ํ•ด๋‹น๋˜์–ด ECC๋กœ ๋ณด๊ฐ•ํ•  ๊ฒฝ์šฐ ์ผ๋ฐ˜์ฝ˜ํฌ๋ฆฌํŠธ๋ฅผ ์‚ฌ์šฉํ•œ ๊ฒฝ์šฐ๋ณด๋‹ค ์•ฝ 2 ๋ฐฐ ์šฐ์ˆ˜ํ•œ ์—๋„ˆ์ง€ ์†Œ์‚ฐ๋Šฅ๋ ฅ์„ ๋ฐœํœ˜ํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚˜ ๋‚ด์ง„ ์„ฑ๋Šฅ๋„ ํฌ๊ฒŒ ํ–ฅ์ƒ๋  ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

5. ๊ฒฐ ๋ก 

์ฒ ๊ทผ์ฝ˜ํฌ๋ฆฌํŠธ ๊ธฐ๋‘ฅ์˜ ์ฝ˜ํฌ๋ฆฌํŠธ ๋Œ€์ฒด์žฌ๋กœ ๊ณ ์ธ์„ฑ ์„ฌ์œ ๋ณตํ•ฉ ์ฒด์ธ ECC๋ฅผ ์‚ฌ์šฉํ•œ ์‹คํ—˜์ฒด์˜ ๋ฐ˜๋ณต์ด๋ ฅ๊ฑฐ๋™์„ ์‹คํ—˜์ ์œผ๋กœ ํ‰๊ฐ€ํ•˜๊ณ  ์ด๋ฅผ RC ์‹คํ—˜์ฒด์˜ ๊ฑฐ๋™๊ณผ ๋น„๊ตํ•˜๋Š” ์—ฐ๊ตฌ๋ฅผ ์ˆ˜ํ–‰ํ•œ ๊ฒฐ๊ณผ, ๋‹ค์Œ๊ณผ ๊ฐ™์€ ๊ฒฐ๋ก ์„ ์–ป์—ˆ๋‹ค.

  1. ECC ์‹คํ—˜์ฒด์˜ ์„ฑ๋Šฅ์„ ํ‰๊ฐ€ํ•œ ๊ฒฐ๊ณผ RC ์‹คํ—˜์ฒด์— ๋น„ํ•˜ ์—ฌ ์šฐ์ˆ˜ํ•œ ํšก๋ฐฉํ–ฅ ๋ณ€ํ˜•๋Šฅ๋ ฅ๊ณผ ๋‚ด๋ ฅ์ด ๋‚˜ํƒ€๋‚ฌ๊ณ  ์ด๋Š” ๋ณ€ํ˜•๋ฅ  ๊ฒฝํ™” ๊ฑฐ๋™์œผ๋กœ ๋Œ€ํ‘œ๋˜๋Š” ECC์˜ ๋†’์€ ์—ฐ์„ฑ์— ๊ธฐ์ธํ•˜๋Š” ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

  2. ๊ธฐ์กด์˜ ์ฒ ๊ทผ์ฝ˜ํฌ๋ฆฌํŠธ ๊ธฐ๋‘ฅ ์‹คํ—˜์ฒด์™€ ๋น„๊ตํ•  ๊ฒฝ์šฐ ECC ์‹คํ—˜์ฒด๋Š” ์•ฝ 18 % ํ–ฅ์ƒ๋œ ๋‚ด๋ ฅ ์ฆ์ง„ํšจ๊ณผ๋ฅผ ๋ณด์˜€๋‹ค. ๋˜ํ•œ 1.92์˜ ์—ฐ์„ฑ๋น„๋ฅผ ๋ณด์ธ RC ์‹คํ—˜์ฒด์™€ ๋น„๊ตํ•  ๊ฒฝ์šฐ ECC ์‹คํ—˜์ฒด๋Š” 2.45์˜ ์—ฐ์„ฑ๋น„๋ฅผ ๋ณด์—ฌ ์•ฝ 28 % ํ–ฅ์ƒ๋œ ๋†’์€ ์—ฐ์„ฑ ๊ฑฐ๋™๋Šฅ๋ ฅ์„ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค.

  3. ์ฒ ๊ทผ์ฝ˜ํฌ๋ฆฌํŠธ ๊ธฐ๋‘ฅ์˜ ์ฝ˜ํฌ๋ฆฌํŠธ๋ฅผ ECC๋กœ ๋Œ€์ฒดํ•  ๊ฒฝ์šฐ, ์—๋„ˆ์ง€ ์†Œ์‚ฐ๋Šฅ๋ ฅ์ด ๊ธฐ์กด ์ฒ ๊ทผ์ฝ˜ํฌ๋ฆฌํŠธ ๊ธฐ๋‘ฅ๋ณด๋‹ค ์•ฝ 2 ๋ฐฐ๋กœ ์ฆ๊ฐ€ํ•˜์—ฌ ๋ณด๋‹ค ์šฐ์ˆ˜ํ•œ ๋‚ด์ง„์„ฑ๋Šฅ์„ ๋‚˜ํƒ€๋‚ผ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

  4. ์ด ๊ฒฐ๊ณผ๋Š” ์ฒ ๊ทผ์ฝ˜ํฌ๋ฆฌํŠธ ๊ธฐ๋‘ฅ์—์„œ ์ฝ˜ํฌ๋ฆฌํŠธ์— ๋Œ€ํ•œ ECC์˜ ๋Œ€์ฒด ๋ฒ”์œ„๋ฅผ ๋ณด๋‹ค ํ•ฉ๋ฆฌ์ ์œผ๋กœ ๊ฒฐ์ •ํ•˜๋Š” ํ›„์† ์—ฐ๊ตฌ์˜ ์ค‘์š”ํ•œ ๊ธฐ์ดˆ์ž๋ฃŒ๋กœ ํ™œ์šฉ๋  ๊ฒƒ์ด๋‹ค.

๊ฐ์‚ฌ์˜ ๊ธ€

๋ณธ ์—ฐ๊ตฌ๋Š” ๊ตญํ† ํ•ด์–‘๋ถ€ ๊ฑด์„ค๊ธฐ์ˆ ์—ฐ๊ตฌ์‚ฌ์—…์˜ ์—ฐ๊ตฌ๋น„ ์ง€์›(11 ๊ธฐ์ˆ ํ˜์‹ F04)์— ์˜ํ•ด ์ˆ˜ํ–‰๋˜์—ˆ์Šต๋‹ˆ๋‹ค.

References

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