Mobile QR Code QR CODE

Journal of the Korea Concrete Institute

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




๊ฐ•์„ฌ์œ , ์ธ์žฅ๊ฐ•๋„, ํ˜•์ƒ๋น„, ์ธ์„ฑ
Steel fiber, Tensile strength, Aspect ratio, Toughness

1. ์„œ ๋ก 

๊ฐ•์„ฌ์œ ์˜ ํ˜ผ์ž…์€ ์ผ๋ฐ˜ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ทจ์„ฑ์  ํŒŒ๊ดด๋ฅผ ์˜ˆ๋ฐฉํ•˜๊ณ , ์ธ์žฅ๊ฐ•๋„ ๋ฐ ์—๋„ˆ์ง€์†Œ์‚ฐ ๋Šฅ๋ ฅ์„ ์ฆ์ง„์‹œํ‚จ๋‹ค. ๋˜ํ•œ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ „๋‹จ๊ฐ•๋„ ๋ฐ ๊ตฌ์†๋ ฅ ํ–ฅ์ƒ์—๋„ ํšจ๊ณผ์ ์ด๋ฉฐ, ๋”ฐ๋ผ์„œ ์ฒ ๊ทผ์ฝ˜ํฌ๋ฆฌ ํŠธ ๋ถ€์žฌ์˜ ์ „๋‹จ์ฒ ๊ทผ(Aoude et al., 2012; Minelli and Plizzari, 2013; Sahoo and Kumar, 2015) ๋ฐ ๊ตฌ์†์ฒ ๊ทผ(Aoude et al., 2009; Germano et al., 2016; Jang et al., 2018)์„ ๊ฐ•์„ฌ์œ ๋ณด๊ฐ• ์ฝ˜ํฌ๋ฆฌํŠธ (Steel Fiber-Reinforced Concrete, SFRC)๋กœ ๋Œ€์ฒดํ•˜๋Š” ์—ฐ๊ตฌ๊ฐ€ ๊ตญ๋‚ดโ€ค์™ธ์—์„œ ํ™œ๋ฐœํ•˜๊ฒŒ ์ง„ํ–‰๋˜๊ณ  ์žˆ๋‹ค.

์—ญํ•™์ ํŠน์„ฑ ์ค‘ ํœจ ์ธ์„ฑ์ง€์ˆ˜๋Š” SFRC์˜ ์ฃผ์š”ํ•œ ํŠน์„ฑ์œผ๋กœ ์•Œ๋ ค ์ ธ ์žˆ์œผ๋ฉฐ(Jhonston, 1982; Banthia and Trottier, 1995; Nataraja et al., 2000), ACI318-14(2014)์—์„œ๋Š” ์ฒ ๊ทผ์ฝ˜ํฌ๋ฆฌํŠธ ๋ณด์˜ ์ตœ์†Œ ์ „๋‹จ๋ณด๊ฐ•๊ทผ ๋Œ€์ฒด๋ฅผ ์œ„ํ•œ SFRC์˜ ์„ฑ๋Šฅ์„ ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ๊ณผ ํœจ ์ธ์„ฑ์ง€์ˆ˜๋ฅผ ํ†ตํ•ด ๊ทœ์ •ํ•˜๊ณ  ์žˆ๋‹ค. ์ƒ๊ธฐ์˜ ํœจ ์ธ์„ฑ์ง€์ˆ˜๋Š” 3๋“ฑ๋ถ„ ์  ํœจ ์‹คํ—˜์„ ํ†ตํ•ด ์–ป์€ ํ•˜์ค‘-์ฒ˜์ง ๊ณก์„ ์˜ ๋ฉด์ ์— ๊ทผ๊ฑฐ ํ•œ ํœจ ์ธ์„ฑ์„ ์ดˆ๊ธฐ๊ท ์—ด๊ฐ•๋„๋กœ ๋ฌด์ฐจ์›ํ™”ํ•˜๋Š” ๋ฐฉ๋ฒ•์œผ๋กœ ์‚ฐ์ •๋œ๋‹ค. ๋ณธ ์—ฐ๊ตฌ์—์„œ๋„ ASTM C1609(2012)์—์„œ ์ œ์‹œ๋œ ๋ฐฉ๋ฒ•์— ๋”ฐ๋ผ SFRC์˜ ํœจ ์ธ์„ฑ์ง€์ˆ˜๋ฅผ ํ‰๊ฐ€ํ•˜์˜€์œผ๋ฉฐ, ์ดˆ๊ธฐ๊ท ์—ด๊ฐ•๋„์˜ ๊ฒฝ์šฐ ์„ ํ–‰์—ฐ๊ตฌ(Jang et al., 2015)๋ฅผ ํ†ตํ•ด ๊ฒ€์ฆ๋œ ๋ฐฉ์‹์œผ๋กœ ์‚ฐ์ •ํ•˜์˜€ ๋‹ค. SFRC์˜ ์••์ถ•์ธ์„ฑ ํ‰๊ฐ€๋Š” ํœจ ์ธ์„ฑ์— ๋น„ํ•ด ์—ฐ๊ตฌ์‚ฌ๋ก€๊ฐ€ ์  ์œผ๋‚˜, SFRC์˜ ๊ตฌ์†๋ ฅ์„ ๋‚˜ํƒ€๋‚ด๋Š” ์œ ์šฉํ•œ ์ง€ํ‘œ๋กœ ํ™œ์šฉ๋  ์ˆ˜ ์žˆ์œผ๋ฉฐ, ์••์ถ•์‘๋ ฅ-๋ณ€ํ˜• ๊ณก์„  ์˜ˆ์ธก์„ ์œ„ํ•œ ํ™œ์šฉ์„ฑ์ด ๋†’๋‹ค. ์••์ถ• ์ธ์„ฑ ๋˜ํ•œ ํœจ ์ธ์„ฑ๊ณผ ์œ ์‚ฌํ•˜๊ฒŒ ํ•˜์ค‘-๋ณ€์œ„ ๊ณก์„ ์˜ ๋ฉด์ ์œผ๋กœ ํ†ต ํ•ด ์‚ฐ์ •๋˜๋ฉฐ, ์••์ถ•๊ฐ•๋„๋ฅผ ํ†ตํ•ด ๋ฌด์ฐจ์›ํ™” ํ•˜๋Š” ๋ฐฉ์‹์œผ๋กœ ์••์ถ• ์ธ์„ฑ์ง€์ˆ˜๋ฅผ ์‚ฐ์ •ํ•œ๋‹ค(Nataraja et al., 1999). ๋”ฐ๋ผ์„œ ๋ณธ ์—ฐ๊ตฌ์— ์„œ๋Š” ๋‹ค์–‘ํ•œ ๊ฐ•์„ฌ์œ ๊ฐ€ ์‚ฌ์šฉ๋œ SFRC์˜ ์••์ถ• ๋ฐ ํœจ ์ธ์„ฑ์ง€์ˆ˜๋ฅผ ํ‰๊ฐ€ํ•˜๊ณ , ๋‘ ํŠน์„ฑ์˜ ๊ด€๊ณ„๋ฅผ ์—ฐ๊ตฌํ•˜๊ณ ์ž ํ•œ๋‹ค.

SFRC์˜ ์—ญํ•™์ ํŠน์„ฑ์€ ์ฃผ๋กœ ๊ฐ•์„ฌ์œ  ํ˜ผ์ž…๋ฅ ์— ๋”ฐ๋ผ ๊ฒฐ์ •๋˜ ๋ฉฐ, ๊ฐ•์„ฌ์œ ์˜ ํ˜•์ƒ๋น„๋„ ์ค‘์š”ํ•œ ์š”์ธ์œผ๋กœ ์•Œ๋ ค์ ธ ์žˆ๋‹ค(Yazฤฑcฤฑ et al., 2007). ๋˜ํ•œ ๊ธฐ์กด์—ฐ๊ตฌ๊ฒฐ๊ณผ์— ๋”ฐ๋ฅด๋ฉด ๋†’์€ ์ธ์žฅ๊ฐ•๋„์˜ ๊ฐ•์„ฌ์œ ๋ฅผ ์‚ฌ์šฉํ•  ๊ฒฝ์šฐ ๊ณ ๊ฐ•๋„ SFRC์˜ ์„ฑ๋Šฅ์„ ํฌ๊ฒŒ ๊ฐœ์„ ํ•  ์ˆ˜ ์žˆ๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค(Kรถksal et al., 2012; Jeong et al., 2018). ๋”ฐ๋ผ์„œ ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ์ธ์žฅ๊ฐ•๋„ 1,600 MPa๊ธ‰ ๊ณ ๊ฐ•๋„ ๊ฐ•์„ฌ์œ  ๋ฅผ ์‚ฌ์šฉํ•œ ์‹คํ—˜์„ ๊ณ„ํšํ•˜์˜€๋‹ค.

๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ๊ฐ•์„ฌ์œ ์˜ ํ˜•์ƒ๋น„ ๋ฐ ์ธ์žฅ๊ฐ•๋„๊ฐ€ ๋ณดํ†ต๊ฐ•๋„ ๋ฐ ๊ณ ๊ฐ•๋„ SFRC์˜ ์—ญํ•™์ ํŠน์„ฑ์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์„ ํ‰๊ฐ€ํ•˜๊ณ ์ž ํ•˜๋ฉฐ, ์ด๋ฅผ ์œ„ํ•ด ๊ตญ๋‚ด์—์„œ ์ƒ์‚ฐ๋œ ์ด 4์ข…๋ฅ˜์˜ ๊ฐ•์„ฌ์œ ๋ฅผ ์‚ฌ์šฉ ํ•œ ์„ค๊ณ„๊ธฐ์ค€ ์••์ถ•๊ฐ•๋„ 35 ๋ฐ 60 MPa๊ธ‰ SFRC์˜ ์••์ถ• ๋ฐ ํœจ ๊ฑฐ ๋™์„ ํ‰๊ฐ€ํ•˜์˜€๋‹ค.

2. ์‹ค ํ—˜

2.1 ์‹คํ—˜๊ณ„ํš

2.1.1 ๋ณ€์œ„์ œ์–ด์†๋„์— ๋”ฐ๋ฅธ SFRC์˜ ์••์ถ•๊ฑฐ๋™ ํ‰๊ฐ€

ํ˜„ํ–‰ KS F 2405(2010)์—์„œ๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์••์ถ•๊ฐ•๋„๋ฅผ ํ‰๊ฐ€ ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ๋งค์ดˆ 0.6ยฑ0.4 MPa์˜ ์ฆ๊ฐ€์†๋„์˜ ํ•˜์ค‘์ œ์–ด ๋ฐฉ์‹ ์„ ์‚ฌ์šฉํ•˜๋„๋ก ๊ทœ์ •ํ•˜๊ณ  ์žˆ๋‹ค. ํ•˜์ง€๋งŒ ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” SFRC์˜ ์ตœ๋Œ€ํ•˜์ค‘ ์ดํ›„ ๊ฑฐ๋™์„ ํšจ๊ณผ์ ์œผ๋กœ ํ‰๊ฐ€ํ•˜๊ธฐ ์œ„ํ•ด ๋ณ€์œ„์ œ์–ด ๋ฐฉ์‹์„ ์ ์šฉํ•˜์˜€๋‹ค. ๊ธฐ์กด๋ฌธํ—Œ์˜ ์‹คํ—˜๊ฒฐ๊ณผ์— ๋”ฐ๋ฅด๋ฉด, ๋ณ€์œ„์ œ ์–ด ๋ฐฉ์‹์˜ ์ ์šฉ์€ SFRC์˜ ํ›„๋ฐ˜๋ถ€ ์••์ถ•๊ฑฐ๋™ ํ‰๊ฐ€์— ํšจ๊ณผ์ ์ธ ๊ฒƒ์œผ๋กœ ๋ณด๊ณ ๋˜์—ˆ๋‹ค. ํ•˜์ง€๋งŒ ์—ฐ๊ตฌ์ž๋“ค ๋งˆ๋‹ค ๋ถ„๋‹น 0.05โˆผ1.2 mm ์‚ฌ์ด์˜ ์ƒ์ดํ•œ ๋ณ€์œ„์ œ์–ด ์†๋„๋ฅผ ์ ์šฉํ•˜๊ณ  ์žˆ์–ด ๋ณ€์œ„์ œ์–ด ์†๋„์— ๋”ฐ๋ฅธ SFRC์˜ ์••์ถ•ํŠน์„ฑ ํ‰๊ฐ€๊ฐ€ ์š”๊ตฌ๋œ๋‹ค(Barros and Figueiras, 1999; Bencardino et al., 2008; Chen et al., 2014; Ou et al., 2012; Carneiro et al., 2014; Ahn et al., 2015; Lee et al., 2015). ์ด์— ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ๋งŒ๋Šฅ์žฌ๋ฃŒ์‹คํ—˜๊ธฐ ๋ณ€์œ„์ œ์–ด ์†๋„๋ฅผ ๋ถ„๋‹น 0.05, 0.1, 0.3, 0.5, 1.0 mm๋กœ ์ ์šฉํ•˜์—ฌ ์ผ์ถ•์••์ถ• ์‹คํ—˜์„ ์‹ค์‹œํ•˜์—ฌ, ๋ณ€์œ„์ œ์–ด ์†๋„์— ๋”ฐ๋ฅธ SFRC์˜ ์••์ถ•ํŠน์„ฑ์„ ํ‰๊ฐ€ํ•˜ ์˜€๋‹ค. ๋ณธ ์‹คํ—˜์„ ์œ„ํ•ด Table 1์— ๋‚˜ํƒ€๋‚ธ ์„ค๊ณ„๊ธฐ์ค€ ์••์ถ•๊ฐ•๋„ 35 MPa์ธ SFRC๋ฅผ ์‚ฌ์šฉํ•˜์˜€์œผ๋ฉฐ, Table 2์˜ ํ˜•์ƒ๋น„ 64 ๋ฐ ์ธ์žฅ ๊ฐ•๋„ 1,200 MPa์˜ ํ›„ํฌํ˜• ๊ฐ•์„ฌ์œ ๋ฅผ ์‚ฌ์šฉํ•˜์˜€๋‹ค.

Table 1

Mixture proportions of SFRC

JKSMI-23-3-43_T1.jpg
Table 2

Mechanical properties of steel fiber

JKSMI-23-3-43_T2.jpg

2.1.2 ์„ฌ์œ ์ข…๋ฅ˜์— ๋”ฐ๋ฅธ SFRC์˜ ์—ญํ•™์ ํŠน์„ฑ ํ‰๊ฐ€

๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” SFRC ์••์ถ•๊ฐ•๋„ ๋ฐ ๊ฐ•์„ฌ์œ ์˜ ์ข…๋ฅ˜์— ๋”ฐ๋ฅธ ์—ญ ํ•™์ ํŠน์„ฑ์„ ํ‰๊ฐ€ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ Table 1๊ณผ ๊ฐ™์ด ์„ค๊ณ„๊ธฐ์ค€ ์••์ถ•๊ฐ• ๋„ 35 ๋ฐ 60 MPa์˜ ๋ฐฐํ•ฉ์„ ๊ณ„ํšํ•˜์˜€๋‹ค. ์‚ฌ์šฉ๋œ ๊ฐ•์„ฌ์œ ์˜ ํŠน์„ฑ ์„ Table 2์— ๋‚˜ํƒ€๋‚ด์—ˆ์œผ๋ฉฐ, ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ํ˜•์ƒ๋น„ ๋ฐ ์ธ์žฅ๊ฐ• ๋„๋ฅผ ๋ณ€์ˆ˜๋กœ ๊ตญ๋‚ด์—์„œ ์ƒ์‚ฐ๋œ ์ด 4์ข…๋ฅ˜์˜ ํ›„ํฌํ˜• ๊ฐ•์„ฌ์œ ๋ฅผ ์‚ฌ ์šฉํ•˜์˜€๋‹ค. ๊ฐ•์„ฌ์œ ์˜ ํ˜ผ์ž…๋ฅ ์€ ๋ฏธ๊ตญ ์ฝ˜ํฌ๋ฆฌํŠธ ๊ตฌ์กฐ์„ค๊ณ„๊ธฐ์ค€ (ACI318-14, 2014)์—์„œ ์ œ์‹œ๋œ ์ „๋‹จ๋ณด๊ฐ•๊ทผ ๋Œ€์ฒด๋ฅผ ์œ„ํ•œ SFRC ์˜ ์ตœ์†Œ ํ˜ผ์ž…๋ฅ ์ธ 0.75%๋กœ ์„ค์ •ํ•˜์˜€๋‹ค. SFRC์˜ ๋ฐฐํ•ฉ๋ช…์€ 35-NS64์™€ ๊ฐ™์€ ํ˜•ํƒœ๋กœ ์„ค์ •ํ•˜์˜€์œผ๋ฉฐ ์•ž๋ถ€๋ถ„ ์ˆซ์ž๋Š” SFRC ์˜ ์„ค๊ณ„๊ธฐ์ค€ ์••์ถ•๊ฐ•๋„๋ฅผ ์˜๋ฏธํ•˜๊ณ , ์ค‘์•™์— NS ๋ฐ HS๋Š” ๊ฐ๊ฐ ๋ณดํ†ต๊ฐ•๋„ ๋ฐ ๊ณ ๊ฐ•๋„ ๊ฐ•์„ฌ์œ ๋ฅผ ๋‚˜ํƒ€๋‚ธ๋‹ค. ๋งˆ์ง€๋ง‰ ์ˆซ์ž๋Š” ๊ฐ•์„ฌ ์œ ์˜ ํ˜•์ƒ๋น„๋ฅผ ์˜๋ฏธํ•˜๋ฉฐ, ๊ฐ•์„ฌ์œ ๊ฐ€ ๋ณด๊ฐ•๋˜์ง€ ์•Š์€ ์ผ๋ฐ˜์ฝ˜ํฌ ๋ฆฌํŠธ์˜ ๊ฒฝ์šฐ 35-CON ๋ฐ 60-CON์œผ๋กœ ํ‘œ๊ธฐํ•˜์˜€๋‹ค.

2.2 ์‹คํ—˜๋ฐฉ๋ฒ•

Fig. 1(a)๋Š” ์••์ถ•๊ฑฐ๋™ ํ‰๊ฐ€๋ฐฉ๋ฒ•์„ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์œผ๋กœ, 2,000 kN ์šฉ๋Ÿ‰์˜ ๋งŒ๋Šฅ์žฌ๋ฃŒ์‹œํ—˜๊ธฐ๋ฅผ ์‚ฌ์šฉํ•˜์—ฌ ์‹คํ—˜์„ ์‹ค์‹œํ•˜์˜€๋‹ค. KS F 2403(2014)์— ์ค€ํ•˜์—ฌ ์••์ถ•๊ณต์‹œ์ฒด๋ฅผ ์ œ์ž‘ํ•˜์˜€์œผ๋ฉฐ, ์ตœ๋Œ€๊ธธ์ด 60 mm์˜ ๊ฐ•์„ฌ์œ ์˜ ๋ถ„์‚ฐ์„ฑ ํ™•๋ณด๋ฅผ ์œ„ํ•˜์—ฌ ์ง€๋ฆ„ 150 mm, ๋†’์ด 300 mm์˜ ์›์ฃผํ˜• ๊ณต์‹œ์ฒด๋ฅผ ์‚ฌ์šฉํ•˜์˜€๋‹ค. ์••์ถ•๋ณ€ํ˜•์ธก์ •์„ ์œ„ํ•ด ์ค‘์•™๋ถ€ 100 mm ๊ตฌ๊ฐ„์— ์ปดํ”„๋ ˆ์†Œ๋ฏธํ„ฐ(compressormeter)๋ฅผ ์„ค์น˜ ํ•˜์˜€์œผ๋ฉฐ, 2๊ฐœ์˜ ์„ ํ˜•๋ณ€์œ„๊ณ„๋ฅผ ์‚ฌ์šฉํ•˜์—ฌ ๋ณ€ํ˜•์„ ์ธก์ •ํ•˜์˜€๋‹ค.

Fig. 1

Test set-up for mechanical properties

JKSMI-23-3-43_F1.jpg

ํœจ ๊ฑฐ๋™ ํ‰๊ฐ€๋ฐฉ๋ฒ•์€ Fig. 1(b)์— ๋‚˜ํƒ€๋‚ธ ๋ฐ”์™€ ๊ฐ™์ด, ASTM C1609(2012)์— ์ค€ํ•˜์—ฌ 200 kN์˜ ๋งŒ๋Šฅ์žฌ๋ฃŒ์‹œํ—˜๊ธฐ๋ฅผ ์‚ฌ์šฉํ•˜ ์—ฌ ๊ฒฝ๊ฐ„ 450 mm์˜ 3๋“ฑ๋ถ„์  ๊ฐ€๋ ฅ๋ฐฉ์‹์œผ๋กœ ์‹คํ—˜์„ ์ง„ํ–‰ํ•˜์˜€๋‹ค. ํœจ ๊ณต์‹œ์ฒด์˜ ๋‹จ๋ฉด์€ ์„ฌ์œ ์˜ ๋ถ„์‚ฐ์„ฑ์„ ๊ณ ๋ คํ•˜์—ฌ 150ร—150 mm ๋กœ ๊ณ„ํšํ•˜์˜€์œผ๋ฉฐ, ์ดˆ๊ธฐ๊ท ์—ด ์ดํ›„ ๊ฐ•์„ฌ์œ  ๋ณด๊ฐ•ํšจ๊ณผ๋ฅผ ํ‰๊ฐ€ํ•˜ ๊ธฐ ์œ„ํ•˜์—ฌ ๊ฒฝ๊ฐ„์˜ 1/150 ๋ฐ 1/300 ์ฒ˜์ง๊นŒ์ง€์˜ ํœจ ์ธ์„ฑ ๋ฐ ํœจ ์ธ ์„ฑ์ง€์ˆ˜๋ฅผ ํ‰๊ฐ€ํ•˜์˜€๋‹ค. ํ•˜์ค‘-์ฒ˜์ง ๊ด€๊ณ„ ์ธก์ •์„ ์œ„ํ•ด ์‹คํ—˜์ฒด์— ์š”ํฌ(Yoke)๋ฅผ ์„ค์น˜ํ•˜์˜€์œผ๋ฉฐ, 2๊ฐœ์˜ ์„ ํ˜•๋ณ€์œ„๊ณ„๋ฅผ ์„ค์น˜ํ•˜์—ฌ ์ค‘์•™๋ถ€์˜ ์ƒ๋Œ€์ฒ˜์ง์„ ์ธก์ •ํ•˜์˜€๋‹ค.

3. ์‹คํ—˜๊ฒฐ๊ณผ ๋ฐ ๋ถ„์„

3.1 ๊ฐ€๋ ฅ์†๋„์— ๋”ฐ๋ฅธ SFRC์˜ ์••์ถ•๊ฑฐ๋™

Fig. 2๋Š” ๊ฐ€๋ ฅ์†๋„์— ๋”ฐ๋ฅธ SFRC์˜ ์••์ถ•๊ฑฐ๋™์„ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์œผ ๋กœ, 35-NS64 ๋ฐฐํ•ฉ์„ ๋Œ€์ƒ์œผ๋กœ ๊ฐ€๋ ฅ์†๋„๋ณ„ ๊ฐ 1๊ฐœ์˜ ๊ณต์‹œ์ฒด๋ฅผ ์ œ์ž‘ํ•˜์—ฌ ์‹คํ—˜์„ ์‹ค์‹œํ•˜์˜€๋‹ค. Table 3์€ ๋ณ€์œ„์ œ์–ด์†๋„์— ๋”ฐ ๋ฅธ SFRC์˜ ์‹คํ—˜๊ฒฐ๊ณผ๋ฅผ ์ •๋ฆฌํ•˜์—ฌ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์œผ๋กœ, ๋ณ€์œ„์ œ์–ด์† ๋„๊ฐ€ ๊ฐ์†Œํ•จ์— ๋”ฐ๋ผ ์••์ถ•๊ฐ•๋„๊ฐ€ ๋ฏธ์†Œํ•˜๊ฒŒ ๊ฐ์†Œํ•˜๋Š” ์–‘์ƒ์„ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ๋˜ํ•œ ๋ณ€์œ„์ œ์–ด ์†๋„ 1.0 mm์—์„œ ํ•˜์ค‘์ œ์–ด ๋ฐฉ์‹ ๊ณผ ์œ ์‚ฌํ•œ ์••์ถ•๊ฐ•๋„๊ฐ€ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ํƒ„์„ฑ๊ณ„์ˆ˜์˜ ๊ฒฝ์šฐ ๋ณ€์œ„์ œ์–ด ์†๋„ 0.05 mm ์‹คํ—˜์ฒด์—์„œ ๋‹ค์†Œ ๋‚ฎ๊ฒŒ ํ‰๊ฐ€๋˜์—ˆ์œผ๋‚˜, ๋‹ค๋ฅธ ์‹ค ํ—˜์ฒด์—์„œ๋Š” ์œ ์‚ฌํ•˜๊ฒŒ ํ‰๊ฐ€๋˜์—ˆ๋‹ค.

Fig. 2

Effects of loading rate on compressive behavior

JKSMI-23-3-43_F2.jpg
Table 3

Effect of loading rate on compressive properties of SFRC

JKSMI-23-3-43_T3.jpg

Fig. 3์€ ๋ณธ ์—ฐ๊ตฌ์˜ ์ตœ๋Œ€๊ฐ•๋„ ์ดํ›„ ์••์ถ•๊ฑฐ๋™ ํ‰๊ฐ€๋ฐฉ๋ฒ•์„ ๋‚˜ ํƒ€๋‚ธ ๊ฒƒ์œผ๋กœ, ์••์ถ•์ธ์„ฑ๊ณผ ์••์ถ•์ธ์„ฑ์ง€์ˆ˜ ์‚ฐ์ •๊ธฐ๋ฒ•์„ ๋‚˜ํƒ€๋‚ธ ๋‹ค. JSCE-SF5 (1984) ๋ฐ Nataraja et al.(1999)์˜ ์—ฐ๊ตฌ์—์„œ ์ œ์‹œ ๋œ ๊ธฐ๋ฒ•์„ ๊ทผ๊ฑฐ๋กœ ์‚ฐ์ •ํ•˜์˜€์œผ๋ฉฐ, ๋ณ€ํ˜• 0.009 ๋ฐ 0.015๊นŒ์ง€์˜ ์ธ์„ฑ ๋ฐ ์ธ์„ฑ์ง€์ˆ˜๋ฅผ ์‚ฐ์ •ํ•˜์˜€๋‹ค. ์ด๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ทนํ•œ๋ณ€ํ˜• ๋ฅ ๋กœ ์•Œ๋ ค์ง„ 0.003์˜ ๊ฐ๊ฐ 3 ๋ฐ 5๋ฐฐ๊นŒ์ง€์˜ ๋ณ€ํ˜•์„ ๋‚˜ํƒ€๋‚ธ๋‹ค. ์••์ถ•์ธ์„ฑ์ง€์ˆ˜๋Š” ์••์ถ•์ธ์„ฑ์„ ์••์ถ•๊ฐ•๋„๋กœ ๋ฌด์ฐจ์›ํ™” ํ•˜์—ฌ ์‚ฐ์ • ํ•˜์˜€์œผ๋ฉฐ, ์‚ฐ์ •์‹์„ ๊ฐ๊ฐ ์‹ (1) ๋ฐ (2)์™€ ๊ฐ™์ด ๋‚˜ํƒ€๋‚ผ ์ˆ˜ ์žˆ๋‹ค.

Fig. 3

Compressive toughness of SFRC

JKSMI-23-3-43_F3.jpg

(1)
T R c , 3 = T c , 3 0.9 ฯ€ r 2 f c u

(2)
T R c , 5 = T c , 5 0.9 ฯ€ r 2 f c u

์—ฌ๊ธฐ์„œ, TRc,3 ๋ฐ TRc,5๋Š” ๊ฐ๊ฐ ๋ณ€ํ˜• 0.009 ๋ฐ 0.015๊นŒ์ง€์˜ ์•• ์ถ•์ธ์„ฑ์ง€์ˆ˜, Tc,3 ๋ฐ Tc,5๋Š” ๊ฐ๊ฐ ์••์ถ•ํ•˜์ค‘-๋ณ€์œ„ ๊ณก์„ ์—์„œ ๋ณ€ํ˜• 0.009 ๋ฐ 0.015๊นŒ์ง€์˜ ์••์ถ•์ธ์„ฑ (Nโ€คmm), ฯ€๋Š” ์›์ฃผ์œจ, r์€ ์‹คํ—˜ ์ฒด์˜ ๋ฐ˜์ง€๋ฆ„ (mm), fcu๋Š” ์••์ถ•๊ฐ•๋„ (MPa)๋ฅผ ๋‚˜ํƒ€๋‚ธ๋‹ค. ์••์ถ•์ธ ์„ฑ ๋ฐ ์ธ์„ฑ์ง€์ˆ˜ ํ‰๊ฐ€๊ฒฐ๊ณผ๋Š” Table 3์— ๋‚˜ํƒ€๋‚œ ๋ฐ”์™€ ๊ฐ™์ด, ๊ฐ€๋ ฅ ์†๋„๊ฐ€ ์ฆ๊ฐ€ํ•จ์— ๋”ฐ๋ผ ์••์ถ•์ธ์„ฑ์ด ๋†’๊ฒŒ ํ‰๊ฐ€๋˜์—ˆ๋‹ค. ์ด๋Š” Fig. 3์— ๋‚˜ํƒ€๋‚œ ๋ฐ”์™€ ๊ฐ™์ด ๊ฐ€๋ ฅ์†๋„์— ๋”ฐ๋ผ ์ดˆ๊ธฐ์„ ํ˜•๊ตฌ๊ฐ„ ์ดํ›„ ๋™ ์ผํ•œ ๋ณ€ํ˜•์—์„œ ์‘๋ ฅ์ด ์ฆ๊ฐ€ํ•˜๊ธฐ ๋•Œ๋ฌธ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ๋ฐ˜๋ฉด ์•• ์ถ•์ธ์„ฑ์ง€์ˆ˜์˜ ๊ฒฝ์šฐ ๋ฌด์ฐจ์›ํ™”๋กœ ์ธํ•ด ๊ฐ€๋ ฅ์†๋„์— ๋”ฐ๋ฅธ ์ฐจ์ด๊ฐ€ ๋ฏธ์†Œํ•˜๊ฒŒ ๋‚˜ํƒ€๋‚ฌ๋‹ค.

3.2 ๊ฐ•์„ฌ์œ  ํŠน์„ฑ์— ๋”ฐ๋ฅธ SFRC์˜ ์••์ถ•๊ฑฐ๋™

Fig. 4๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ ๋ฐ SFRC ์••์ถ• ๊ณต์‹œ์ฒด์˜ ๋Œ€ํ‘œ์ ์ธ ํŒŒ๊ดด ์–‘์ƒ์„ ๋น„๊ตํ•˜์—ฌ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์œผ๋กœ, ์ผ๋ฐ˜ ์ฝ˜ํฌ๋ฆฌํŠธ์—์„œ๋Š” ๊ท ์—ด ์ดํ›„ ์ทจ์„ฑ์ ์ธ ํŒŒ๊ดด ๋ฐ ๋ฐ•๋ฆฌํ˜„์ƒ์ด ๋ฐœ์ƒํ•œ ๋ฐ˜๋ฉด ๊ฐ•์„ฌ์œ ๋ฅผ ๋ณด ๊ฐ•ํ•œ ๊ฒฝ์šฐ์—๋Š” ์„ฌ์œ  ๊ฐ€๊ต์ž‘์šฉ์œผ๋กœ ์ธํ•ด ๊ท ์—ด์ง„์ „ ๋ฐ ์ฝ˜ํฌ๋ฆฌ ํŠธ ๋ฐ•๋ฆฌ๊ฐ€ ์™„ํ™”๋˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ๋ฐฐํ•ฉ๋ณ„ ๊ฐ 3๊ฐœ์˜ ๊ณต์‹œ ์ฒด์— ๋Œ€ํ•œ ์‹คํ—˜์„ ์‹ค์‹œํ•˜์˜€์œผ๋ฉฐ, ํŽธ์ฐจ๊ฐ€ ํฐ ์‹คํ—˜์ฒด๋ฅผ ์ œ์™ธํ•œ ์‹คํ—˜์ฒด์˜ ์••์ถ•ํŠน์„ฑ์„ ์ •๋ฆฌํ•˜์—ฌ Table 4์— ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. Fig. 5 ๋Š” ์‚ฌ์šฉ๋œ ๊ฐ•์„ฌ์œ ์˜ ์ธ์žฅ๊ฐ•๋„ ๋ฐ ํ˜•์ƒ๋น„์— ๋”ฐ๋ฅธ SFRC์˜ ๋Œ€ํ‘œ ์ ์ธ ์••์ถ•์‘๋ ฅ-๋ณ€ํ˜• ๊ณก์„ ์„ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์œผ๋กœ, ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” 60 MPa๊ธ‰ ๊ณ ๊ฐ•๋„ SFRC๋ฅผ ๊ณ ๋ คํ•˜์—ฌ ์‚ฌ์ „์—ฐ๊ตฌ ์ค‘ ๊ฐ€์žฅ ๋‚ฎ์€ ์†๋„ ์ธ 0.05 mm/min์„ ์ ์šฉํ•˜์—ฌ ์‹คํ—˜์„ ์‹ค์‹œํ•˜์˜€๋‹ค. ํ•˜์ง€๋งŒ Fig. 5(a)์— ๋‚˜ํƒ€๋‚œ ๋ฐ”์™€ ๊ฐ™์ด ์„ค๊ณ„๊ธฐ์ค€ ์••์ถ•๊ฐ•๋„ 35 MPa๊ธ‰ SFRC ์˜ ํ›„๋ฐ˜๋ถ€ ๊ฑฐ๋™์€ ๋น„๊ต์  ์ž˜ ํ‰๊ฐ€๋˜์—ˆ์œผ๋‚˜, Fig. 5(b)์™€ ๊ฐ™์ด 60 MPa๊ธ‰ SFRC์˜ ๊ฒฝ์šฐ ์ตœ๋Œ€๊ฐ•๋„ ์ดํ›„ ์ทจ์„ฑ์ ์ธ ํŒŒ๊ดด์–‘์ƒ์„ ๋‚˜ํƒ€๋‚ด๋ฉฐ ํ›„๋ฐ˜๋ถ€ ๊ฑฐ๋™ ํ‰๊ฐ€๊ฐ€ ์–ด๋ ค์šด ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ์ด๋Š” ์••์ถ•๊ฐ•๋„ ์‹œ ๋งŒ๋Šฅ์žฌ๋ฃŒ์‹œํ—˜๊ธฐ์˜ ์ตœ๋Œ€ํ•˜์ค‘๊ณผ ๋ฐ€์ ‘ํ•œ ๊ด€๋ จ์ด ์žˆ ๋Š” ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋˜๋ฉฐ, ๊ฐ•์„ฌ์œ ์˜ ๊ธธ์ด๋กœ ์ธํ•ด ๊ณต์‹œ์ฒด์˜ ์ง€๋ฆ„์„ ์ž‘๊ฒŒ ํ•  ์ˆ˜ ์—†๋Š” ๊ฒฝ์šฐ ์Šคํ”„๋ง ๋“ฑ์˜ ์ถ”๊ฐ€์ ์ธ ๋ณด๊ฐ•์š”์†Œ๋ฅผ ํ™œ์šฉ ํ•˜์—ฌ ๊ณ ๊ฐ•๋„ SFRC์˜ ์••์ถ•์ธ์„ฑ ํ‰๊ฐ€๋ฅผ ์‹ค์‹œํ•ด์•ผํ•  ๊ฒƒ์œผ๋กœ ์‚ฌ ๋ฃŒ๋œ๋‹ค.

Fig. 4

Failure mode of SFRC under compressive loading

JKSMI-23-3-43_F4.jpg
Fig. 5

Compressive behavior of SFRC

JKSMI-23-3-43_F5.jpg
Table 4

Effect of steel fiber properties on compressive behavior of SFRC

JKSMI-23-3-43_T4.jpg

๊ฐ•์„ฌ์œ ์˜ ๋ณด๊ฐ•์—ฌ๋ถ€ ๋ฐ ์„ฌ์œ ์ข…๋ฅ˜์— ๋”ฐ๋ฅธ SFRC์˜ ํƒ„์„ฑ๊ณ„์ˆ˜ ๋ฐ ์••์ถ•๊ฐ•๋„์˜ ๋ณ€ํ™”๋Š” ๋ฏธ์†Œํ•œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋˜๋ฉฐ, ์˜ˆ์ƒ๋œ ๋ฐ”์™€ ๊ฐ™์ด ์••์ถ•๊ฐ•๋„๊ฐ€ ์ฆ๊ฐ€ํ•จ์— ๋”ฐ๋ผ SFRC์˜ ํƒ„์„ฑ๊ณ„์ˆ˜๊ฐ€ ์ฆ๊ฐ€ํ•˜ ๋Š” ์–‘์ƒ์„ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ๋ฐ˜๋ฉด ์ตœ๋Œ€ํ•˜์ค‘ ์ดํ›„ ํ›„๋ฐ˜๋ถ€ ๊ฑฐ๋™์—์„œ ๊ฐ•์„ฌ์œ ํšจ๊ณผ๊ฐ€ ๋†’๊ฒŒ ๋‚˜ํƒ€๋‚ฌ์œผ๋ฉฐ, ์••์ถ•์ธ์„ฑ์ง€์ˆ˜์˜ ๊ฒฝ์šฐ ๊ฐ•์„ฌ์œ  ๋ฅผ ๋ณด๊ฐ•ํ•จ์— ๋”ฐ๋ผ ํฌ๊ฒŒ ์ฆ๊ฐ€ํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ๋˜ํ•œ ์ธ์žฅ ๊ฐ•๋„๊ฐ€ ๋†’์€ ๊ฐ•์„ฌ์œ ๋ฅผ ์‚ฌ์šฉํ•  ๊ฒฝ์šฐ ๋†’์€ ์••์ถ•์ธ์„ฑ์ง€์ˆ˜๋ฅผ ๋‚˜ ํƒ€๋‚ด์—ˆ์œผ๋ฉฐ, ๋ณดํ†ต๊ฐ•๋„ ๊ฐ•์„ฌ์œ ๋ฅผ ์‚ฌ์šฉํ•œ ๊ฒฝ์šฐ์—์„œ๋Š” ํ˜•์ƒ๋น„๊ฐ€ ์ฆ๊ฐ€ํ•จ์— ๋”ฐ๋ผ ์••์ถ•์ธ์„ฑ์ง€์ˆ˜๊ฐ€ ์ฆ๊ฐ€ํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค.

3.3 ๊ฐ•์„ฌ์œ  ํŠน์„ฑ์— ๋”ฐ๋ฅธ SFRC์˜ ํœจ ๊ฑฐ๋™

ASTM C1609(2012)์— ๋”ฐ๋ฅธ SFRC์˜ ํœจ ์ธ์„ฑ ์‚ฐ์ •๊ธฐ๋ฒ•์„ Fig. 6์— ๋‚˜ํƒ€๋ƒˆ์œผ๋ฉฐ, ์‹คํ—˜์ฒด ์ง€๊ฐ„์˜ 1/300 ๋ฐ 1/150 ์ฒ˜์ง๊นŒ์ง€ ์˜ ์ธ์„ฑ์ง€์ˆ˜๋ฅผ ๊ฐ๊ฐ ์‹ (3) ๋ฐ (4)์— ๊ทผ๊ฑฐํ•˜์—ฌ ์‚ฐ์ •ํ•˜์˜€๋‹ค.

Fig. 6

Flexural toughness of SFRC

JKSMI-23-3-43_F6.jpg

(3)
T R f , 300 = 300 T f , 300 f 1 b h 2

(4)
T R f , 150 = 150 T f , 150 f 1 b h 2

์—ฌ๊ธฐ์„œ, TRf,300 ๋ฐ TRf,150์€ ๊ฐ๊ฐ ๊ฒฝ๊ฐ„์˜ 1/300 ๋ฐ 1/150 ์ฒ˜์ง ๊นŒ์ง€์˜ ํœจ ์ธ์„ฑ์ง€์ˆ˜, Tf,300 ๋ฐ Tf,150์€ ํœจ ํ•˜์ค‘-์ฒ˜์ง ๊ณก์„ ์—์„œ ๊ฒฝ๊ฐ„์˜ 1/300 ๋ฐ 1/150 ์ฒ˜์ง๊นŒ์ง€์˜ ํœจ ์ธ์„ฑ (Nโ€คmm), f1์€ ์ดˆ๊ธฐ ๊ท ์—ด ํœจ ๊ฐ•๋„ (MPa), b๋Š” ์‹คํ—˜์ฒด์˜ ๋„ˆ๋น„ (mm), h๋Š” ์‹คํ—˜์ฒด์˜ ๋†’์ด (mm)๋ฅผ ๋‚˜ํƒ€๋‚ธ๋‹ค.

๋ฐฐํ•ฉ๋ณ„ ๊ฐ 3๊ฐœ์˜ ๊ณต์‹œ์ฒด๋ฅผ ์ œ์ž‘ํ•˜์—ฌ ํœจ ์„ฑ๋Šฅ์„ ํ‰๊ฐ€ํ•˜์˜€์œผ ๋ฉฐ, ์ดˆ๊ธฐ๊ท ์—ด ์ดํ›„ ๊ธ‰๊ฒฉํ•œ ํŒŒ๊ดด๊ฐ€ ๋ฐœ์ƒํ•œ ์ผ๋ถ€ ์‹คํ—˜์ฒด๋ฅผ ์ œ์™ธ ํ•œ ์ดˆ๊ธฐ๊ท ์—ด๊ฐ•๋„, ์ตœ๋Œ€ ํœจ ๊ฐ•๋„, ํœจ ์ธ์„ฑ, ํœจ ์ธ์„ฑ์ง€์ˆ˜์˜ ํ‰๊ท  ๋ฐ ํ‘œ์ค€ํŽธ์ฐจ๋ฅผ ์ •๋ฆฌํ•˜์—ฌ Table 5์— ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. Fig. 7์€ ๊ฐ•์„ฌ ์œ ์˜ ์ข…๋ฅ˜์— ๋”ฐ๋ฅธ ๋Œ€ํ‘œ์ ์ธ SFRC์˜ ํœจ ๊ฑฐ๋™์„ ์••์ถ•๊ฐ•๋„ ์ˆ˜์ค€ ์— ๋”ฐ๋ผ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค. ๊ทธ๋ฆผ์— ๋‚˜ํƒ€๋‚œ ๋ฐ”์™€ ๊ฐ™์ด ์„ค๊ณ„๊ธฐ์ค€ ์•• ์ถ•๊ฐ•๋„ 35 MPa์˜ SFRC์˜ ๊ฒฝ์šฐ ๊ฐ•์„ฌ์œ ๋ฅผ ๋ณด๊ฐ•ํ•จ์— ๋”ฐ๋ผ ์ดˆ๊ธฐ ๊ท ์—ด๊ฐ•๋„ ๋ฐ ํœจ ๊ฐ•๋„๊ฐ€ ํ–ฅ์ƒ๋˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ์œผ๋ฉฐ, ๊ฐ•์„ฌ์œ  ์˜ ํ˜•์ƒ๋น„ ๋ฐ ์ธ์žฅ๊ฐ•๋„์— ๋”ฐ๋ฅธ ์ดˆ๊ธฐ๊ท ์—ด์˜ ๋ณ€ํ™”๋Š” ๋ฏธ์†Œํ•œ ๊ฒƒ ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ์„ค๊ณ„๊ธฐ์ค€ ์••์ถ•๊ฐ•๋„ 60 MPa์˜ SFRC์˜ ๊ฒฝ์šฐ ๊ฐ•์„ฌ์œ ์˜ ํ˜•์ƒ๋น„๊ฐ€ ์ฆ๊ฐ€ํ•จ์— ๋”ฐ๋ผ ์ดˆ๊ธฐ๊ท ์—ด๊ฐ•๋„๊ฐ€ ์ฆ๊ฐ€ํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ์œผ๋ฉฐ, ๊ณ ์ธ์žฅ๊ฐ•๋„ ๊ฐ•์„ฌ์œ ๋ฅผ ์‚ฌ์šฉํ•  ๊ฒฝ์šฐ ํœจ ๊ฐ• ๋„๊ฐ€ ํฌ๊ฒŒ ํ–ฅ์ƒ๋˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค.

Table 5

Effect of steel fiber properties on flexural behavior of SFRC

JKSMI-23-3-43_T5.jpg
Fig. 7

Flexural behavior of SFRC

JKSMI-23-3-43_F7.jpg

ํœจ ์ธ์„ฑ์ง€์ˆ˜ ํ‰๊ฐ€๊ฒฐ๊ณผ ๋ณดํ†ต๊ฐ•๋„ ์˜์—ญ์—์„œ๋Š” ๊ฐ•์„ฌ์œ ์˜ ํ˜•์ƒ ๋น„๊ฐ€ ์ฆ๊ฐ€ํ•จ์— ๋”ฐ๋ผ ํœจ ์ธ์„ฑ์ง€์ˆ˜๊ฐ€ ์ฆ๊ฐ€ํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ ์œผ๋ฉฐ, ์ธ์žฅ๊ฐ•๋„์— ๋”ฐ๋ฅธ ์˜ํ–ฅ์€ ๋ฏธ์†Œํ•œ ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ๋ฐ˜๋ฉด ๊ณ ๊ฐ•๋„ SFRC์˜ ๊ฒฝ์šฐ ๋†’์€ ์ธ์žฅ๊ฐ•๋„์˜ ๊ฐ•์„ฌ์œ ๋ฅผ ์‚ฌ์šฉํ•  ๊ฒฝ์šฐ ํœจ ์ธ์„ฑ์ง€์ˆ˜๊ฐ€ ์ฆ๊ฐ€ํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ์ด๋Ÿฌํ•œ ๊ฒฝํ–ฅ์€ ๊ฐ• ์„ฌ์œ ์˜ ํŒŒ๊ดด์–‘์ƒ๊ณผ ๋ฐ€์ ‘ํ•œ ๊ด€๋ จ์„ ๊ฐ–๋Š” ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

Fig.8์— ๋‚˜ํƒ€๋‚œ ๋ฐ”์™€ ๊ฐ™์ด ๋ณดํ†ต๊ฐ•๋„ SFRC์˜ ๊ฒฝ์šฐ์—๋Š” ๋ชจ๋“  ๊ฐ•์„ฌ์œ ์—์„œ ๋ถ€์ฐฉํŒŒ๊ดด๊ฐ€ ๋ฐœ์ƒํ•˜์ง€๋งŒ ๊ณ ๊ฐ•๋„ SFRC์—์„œ ๋ณดํ†ต ๊ฐ•๋„ ๊ฐ•์„ฌ์œ ๋ฅผ ์‚ฌ์šฉํ•  ๊ฒฝ์šฐ ์ฝ˜ํฌ๋ฆฌํŠธ์™€ ๊ฐ•์„ฌ์œ ์˜ ๋ถ€์ฐฉ๋ ฅ ์ฆ ์ง„์œผ๋กœ ์ธํ•ด ๊ฐ•์„ฌ์œ ์˜ ๋ถ€์ฐฉํŒŒ๊ดด์™€ ํŒŒ๋‹จ์ด ํ•จ๊ป˜ ๋ฐœ์ƒํ•˜์˜€์œผ ๋ฉฐ, ์ด๋กœ ์ธํ•ด ํœจ ์ธ์„ฑ์ง€์ˆ˜๊ฐ€ ๊ฐ์†Œํ•œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

Fig. 8

Failure mode of steel fibers

JKSMI-23-3-43_F8.jpg

3.4 ์••์ถ•์ธ์„ฑ๊ณผ ํœจ ์ธ์„ฑ์˜ ์ƒ๊ด€์„ฑ

Jang and Yun(2018)์˜ ์—ฐ๊ตฌ์—์„œ๋Š” ํœจ ์ธ์„ฑ์ง€์ˆ˜์— ๋น„ํ•ด ์ƒ ๋Œ€์ ์œผ๋กœ ํ‰๊ฐ€๊ฐ€ ์–ด๋ ค์šด SFRC์˜ ์••์ถ•์ธ์„ฑ์ง€์ˆ˜ ์˜ˆ์ธก์„ ์œ„ํ•ด ํœจ ์ธ์„ฑ์ง€์ˆ˜์— ๊ทผ๊ฑฐํ•œ ์˜ˆ์ธก๋ฐฉ์‹์„ ์ œ์•ˆํ•˜์˜€๋‹ค. Fig. 9๋Š” ๋ณธ ์—ฐ ๊ตฌ์˜ ์‹คํ—˜๊ฒฐ๊ณผ์™€ Jang and Yun(2018)์˜ ์‹คํ—˜๊ฒฐ๊ณผ๋ฅผ ๊ทผ๊ฑฐ๋กœ ์••์ถ•์ธ์„ฑ์ง€์ˆ˜์™€ ํœจ ์ธ์„ฑ์ง€์ˆ˜์˜ ๊ด€๊ณ„๋ฅผ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค. ์˜ˆ์ƒ๋œ ๋ฐ”์™€ ๊ฐ™์ด ํœจ ์ธ์„ฑ์ง€์ˆ˜๊ฐ€ ์ฆ๊ฐ€ํ•จ์— ๋”ฐ๋ผ ์••์ถ•์ธ์„ฑ์ง€์ˆ˜๊ฐ€ ํ–ฅ์ƒ ๋˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ํšŒ๊ท€๋ถ„์„์„ ํ†ตํ•ด ๊ธฐ์กด์—ฐ ๊ตฌ ์ œ์•ˆ์‹์˜ ๊ณ„์ˆ˜๋ฅผ ์ˆ˜์ •ํ•˜์—ฌ, ์‹ (5) ๋ฐ (6)์„ ์ œ์•ˆํ•˜์˜€๋‹ค.

Fig. 9

Correlations of compressive and flexural ratio

JKSMI-23-3-43_F9.jpg

(5)
T R c , 3 = 0.71 T R f , 300 3

(6)
T R c , 5 = 0.63 T R f , 150

Fig. 9์— ๋‚˜ํƒ€๋‚ธ ๋ฐ”์™€ ๊ฐ™์ด ๋ณธ ์—ฐ๊ตฌ์˜ ์ œ์•ˆ์‹์€ ์ง€๊ฐ„์˜ 1/300 ์ฒ˜์ง๊นŒ์ง€์˜ ํœจ ์ธ์„ฑ์ง€์ˆ˜๋ฅผ ๊ทผ๊ฑฐ๋กœ ๊ทนํ•œ๋ณ€ํ˜•๋ฅ ์˜ 3๋ฐฐ๊นŒ ์ง€์˜ ์••์ถ•์ธ์„ฑ์ง€์ˆ˜๋ฅผ ์˜ˆ์ธกํ•  ์ˆ˜ ์žˆ์œผ๋ฉฐ, ์ง€๊ฐ„์˜ 1/150 ์ฒ˜์ง๊นŒ ์ง€์˜ ํœจ ์ธ์„ฑ์ง€์ˆ˜๋ฅผ ๊ทผ๊ฑฐ๋กœ ๊ทนํ•œ๋ณ€ํ˜•๋ฅ ์˜ 5๋ฐฐ๊นŒ์ง€์˜ ์••์ถ•์ธ ์„ฑ์ง€์ˆ˜๋ฅผ ์˜ˆ์ธกํ•  ์ˆ˜ ์žˆ๋‹ค. ๋˜ํ•œ ์ œํ•œ๋œ ์‹์€ ์ „๋ฐ˜์ ์œผ๋กœ ๋ณธ ์—ฐ ๊ตฌ ๋ฐ ๊ธฐ์กด์—ฐ๊ตฌ์˜ ์‹คํ—˜๊ฒฐ๊ณผ๋ฅผ ์ž˜ ์˜ˆ์ธกํ•˜๋Š” ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

4. ๊ฒฐ ๋ก 

๋ณธ ์—ฐ๊ตฌ์—๋Š” ๊ฐ•์„ฌ์œ ์˜ ํ˜•์ƒ๋น„ ๋ฐ ์ธ์žฅ๊ฐ•๋„์— ๋”ฐ๋ฅธ SFRC์˜ ์—ญํ•™์ ํŠน์„ฑ์„ ํ‰๊ฐ€ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์‹ค์‹œ๋˜์—ˆ์œผ๋ฉฐ, ์••์ถ• ๋ฐ ํœจ ๊ฑฐ ๋™๊ณผ ์ธ์„ฑ์ง€์ˆ˜์— ๋Œ€ํ•œ ํ‰๊ฐ€๋ฅผ ์‹ค์‹œํ•˜์˜€๋‹ค. ๋ณธ ์—ฐ๊ตฌ์˜ ์‹คํ—˜๊ฒฐ ๊ณผ ๋ฐ ๋ถ„์„์„ ํ†ตํ•ด ์–ป์€ ๊ฒฐ๋ก ์„ ์š”์•ฝํ•˜๋ฉด ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

  • 1) ๊ฐ€๋ ฅ์†๋„๊ฐ€ ๊ฐ์†Œํ•จ์— ๋”ฐ๋ผ ์••์ถ•๊ฐ•๋„ ๋ฐ ์••์ถ•์ธ์„ฑ์ด ๊ฐ ์†Œํ•˜๋Š” ๊ฒฝํ–ฅ์„ ๋‚˜ํƒ€๋‚ด์—ˆ์œผ๋‚˜, ์••์ถ•์ธ์„ฑ์ง€์ˆ˜์˜ ๊ฒฝ์šฐ ๊ฐ€๋ ฅ์†๋„ ์— ๋”ฐ๋ฅธ ์˜ํ–ฅ์ด ๋ฏธ์†Œํ•œ ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. 35 MPa๊ธ‰ SFRC์˜ ๊ฒฝ์šฐ ํ˜ผ์ž…๋ฅ  0.75%์—์„œ ํ›„๋ฐ˜๋ถ€ ๊ฑฐ๋™์ด ๋ช…ํ™•ํ•˜๊ฒŒ ํ‰๊ฐ€๋˜์—ˆ๋‚˜, 60 MPa SFRC์˜ ๊ฒฝ์šฐ ์ตœ๋Œ€ํ•˜์ค‘์ดํ›„ ์ทจ์„ฑ์  ํŒŒ๊ดด๊ฐ€ ๋‚˜ํƒ€๋‚˜๋ฉด ์„œ ํ›„๋ฐ˜๋ถ€ ๊ฑฐ๋™ ํ‰๊ฐ€๊ฐ€ ์–ด๋ ค์šด ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ๋”ฐ๋ผ์„œ ๊ณ ๊ฐ• ๋„ SFRC์˜ ์••์ถ•ํ‰๊ฐ€ ๊ธฐ๋ฒ•์— ๋Œ€ํ•œ ์ถ”๊ฐ€์ ์ธ ์—ฐ๊ตฌ๊ฐ€ ์š”๊ตฌ๋œ๋‹ค.

  • 2) ๊ฐ•์„ฌ์œ ์˜ ํ˜ผ์ž…์—ฌ๋ถ€์™€ ์—ญํ•™์ ํŠน์„ฑ์ด ํƒ„์„ฑ๊ณ„์ˆ˜ ๋ฐ ์••์ถ•๊ฐ• ๋„์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์€ ๋ฏธ์†Œํ•œ ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ์œผ๋‚˜, ํ˜•์ƒ๋น„ ๋ฐ ์ธ ์žฅ๊ฐ•๋„๊ฐ€ ๋†’์€ ๊ฐ•์„ฌ์œ ๋ฅผ ์‚ฌ์šฉํ•  ๊ฒฝ์šฐ ์••์ถ•์ธ์„ฑ ๋ฐ ์••์ถ•์ธ์„ฑ ์ง€์ˆ˜๊ฐ€ ๋†’์•„์ง€๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ํœจ ๊ฑฐ๋™ํ‰๊ฐ€ ๊ฒฐ๊ณผ ๊ณ ๊ฐ•๋„ ๊ฐ•์„ฌ์œ ์˜ ํšจ์œจ์„ฑ์€ ๊ณ ๊ฐ•๋„ SFRC์—์„œ ๋†’๊ฒŒ ๋‚˜ํƒ€๋‚ฌ์œผ๋ฉฐ, ์ด๋Š” ๊ฐ•์„ฌ์œ ์˜ ํŒŒ๊ดด์–‘์ƒ๊ณผ ๋ฐ€์ ‘ํ•œ ๊ด€๋ จ์„ ๊ฐ–๋Š” ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

  • 3) ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ์ƒ๋Œ€์ ์œผ๋กœ ํ‰๊ฐ€๊ฐ€ ์–ด๋ ค์šด SFRC์˜ ์••์ถ• ์ธ์„ฑ์ง€์ˆ˜๋ฅผ ์˜ˆ์ธกํ•˜๊ธฐ ์œ„ํ•˜์—ฌ SFRC์˜ ์••์ถ• ๋ฐ ํœจ ์ธ์„ฑ์ง€์ˆ˜์˜ ์ƒ๊ด€์„ฑ์„ ๋ถ„์„ํ•˜์˜€์œผ๋ฉฐ, ์ด๋ฅผ ํ†ตํ•ด ์ œ์•ˆ์‹์„ ๋„์ถœํ•˜์˜€๋‹ค. ์ œ ์•ˆ์‹์€ ํ–ฅํ›„ ๊ธฐ๋‘ฅ ๋ฐ ์ปคํ”Œ๋ง ๋ณด ๋ถ€์žฌ์—์„œ SFRC์˜ ๊ตฌ์†ํšจ๊ณผ ๊ฒ€์ฆ์„ ์œ„ํ•ด ์œ ์šฉํ•˜๊ฒŒ ์‚ฌ์šฉ๋  ์ˆ˜ ์žˆ์„ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

๊ฐ์‚ฌ์˜ ๊ธ€

์ด ๋…ผ๋ฌธ์€ 2016๋…„๋„ ์ •๋ถ€(๊ต์œก๋ถ€)์˜ ์žฌ์›์œผ๋กœ ํ•œ๊ตญ์—ฐ๊ตฌ์žฌ ๋‹จ ์ง€์—ญ๋Œ€ํ•™์šฐ์ˆ˜๊ณผํ•™์ž์ง€์›์‚ฌ์—… (No. 2016R1D1A3B020081 79)์˜ ์ง€์›์„ ๋ฐ›์•„ ์ˆ˜ํ–‰๋œ ๊ฒฐ๊ณผ์ž…๋‹ˆ๋‹ค.

References

1. 
ACI Committee 318 (2014), Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary, American Concrete Institute.Google Search
2. 
Ahn, K. L., Jang, S. J., Jang, S. H., Yun, H. D. (2015), Effects of Aggregate Size and Steel Fiber Volume Fraction on Compressive Behaviors of High-Strength Concrete, Journal of the Korea Concrete Institute, 27(3), 228-235 (in Korea, with English abstract).DOI
3. 
Aoude, H., Cook, W. D., Mitchell, D. (2009), Behavior of Columns Constructed with Fibers and Self-Consolidating Concrete, ACI Structural Journal, 106(3), 349-357.DOI
4. 
Aoude, H., Belghiti, M., Cook, W. D., Mitchell, D. (2012), Response of Steel Fiber-Reinforced Concrete Beams with and without Stirrups, ACI Structural Journal, 109(3), 359-367.DOI
5. 
ASTM C1609 (2012), Standard Test Method for Flexural Performance of Fiber-Reinforced Concrete (Using Beam With Third-Point Loading), American Society for Testing and Materials.Google Search
6. 
Banthia, N., Trottier, J. F. (1995), Test Methods for Flexural Toughness Characterization of Fiber Reinforced Concrete: Some Concerns and a Proposition, ACI Materials Journal, 92, 48-57.DOI
7. 
Barros, J. A., Figueiras, J. A. (1999), Flexural Behavior of SFRC: Testing and Modeling, Journal of materials in civil engineering, 11(4), 331-339.DOI
8. 
Bencardino, F., Rizzuti, L., Spadea, G., Swamy, R. N. (2008), Stress-Strain Behavior of Steel Fiber-Reinforced Concrete in Compression, Journal of Materials in Civil Engineering, 20(3), 255-263.DOI
9. 
Carneiro, J. A., Lima, P. R. L., Leite, M. B., Toledo Filho, R. D. (2014), Compressive Stressโ€“Strain Behavior of Steel Fiber Reinforced-Recycled Aggregate Concrete, Cement and concrete composites, 46, 65-72.DOI
10. 
Chen, G. M., He, Y. H., Yang, H., Chen, J. F., Guo, Y. C. (2014), Compressive Behavior of Steel Fiber Reinforced Recycled Aggregate Concrete After Exposure to Elevated Temperatures, Construction and Building Materials, 71, 1-15.DOI
11. 
Germano, F., Tiberti, G., Plizzari, G. (2016), Experimental Behavior of SFRC Columns Under Uniaxial and Biaxial Cyclic Loads, Composites Part B: Engineering, 85, 76-92.DOI
12. 
Jang, S. J., Ahn, K. L., Yun, H. D. (2015), Effects of Aggregate Size and Fiber Volume Fraction on Flextural Properties of Steel Fiber Reinforced Concrete (SFRC), Architectural Institute of Korea, 31(2), 45-54. (in Korea, with English abstract)DOI
13. 
Jang, S. J., Jeong, G. Y., Yun, H. D. (2018), Use of Steel Fibers as Transverse Reinforcement in Diagonally Reinforced Coupling Beams with Normal-and High-Strength Concrete, Construction and Building Materials, 187, 1020-1030.DOI
14. 
Jang, S. J., Yun, H. D. (2018), Combined Effects of Steel Fiber and Coarse Aggregate Size on the Compressive and Flexural Toughness of High-Strength Concrete, Composite Structures, 185, 203-211.DOI
15. 
Jeong, G. Y., Jang, S. J., Kim, Y. C., Yun, H. D. (2018), Effects of Steel Fiber Strength and Aspect Ratio on Mechanical Properties of High-Strength Concrete, Journal of the Korea Concrete Institute, 30(2), 197-205 (in Korea, with English abstract).DOI
16. 
Johnston, C. D. (1982), Definition and Measurement of Flexural Toughness Parameters for Fiber Reinforced Concret, Cement, Concrete and Aggregates, 4(2), 53-60.DOI
17. 
JSCE-SF5 (1984), Method of Tests for Compressive Strength and Compressive Toughness of Steel Fiber Reinforced Concrete, Japan Society of Civil Engineers.Google Search
18. 
Kรถksal, F., Sahin, Y., Sahin, M. (2012), Effect of Steel Fiber Tensile Strength on Mechanical Properties of Steel Fiber Reinforced Concretes, Special Publication, 289, 1-15.Google Search
19. 
KS F 2403 (2014), Standard Test Method of Making and Curing Concrete Specimens, Korean Standards Association (in Korean).Google Search
20. 
KS F 2405 (2010), Standard Test Method for Compressive Strength of Concrete, Korean Standards Association (in Korean).Google Search
21. 
Lee, S. C., Oh, J. H., Cho, J. Y. (2015), Compressive Behavior of Fiber-Reinforced Concrete with End-Hooked Steel Fibers, Materials, 8(4), 1442-1458.DOI
22. 
Minelli, F., Plizzari, G. A. (2013), On the Effectiveness of Steel Fibers as Shear Reinforcement, ACI Structural Journal, 110(3).DOI
23. 
Nataraja, M. C., Dhang, N., Gupta, A. P. (1999), Stress-Strain Curves for Steel-Fiber reinforced Concrete under Compression, Cement and concrete composite, 21(5-6), 383-390.DOI
24. 
Nataraja, M. C., Dhang, N., Gupta, A. P. (2000), Toughness Characterization of Steel Fiber-Reinforced Concrete by JSCE Approach, Cement and Concrete Research, 30(4), 593-597.DOI
25. 
Ou, Y. C., Tsai, M. S., Liu, K. Y., Chang, K. C. (2011), Compressive Behavior of Steel-Fiber-Reinforced Concrete with a High Reinforcing Index, Journal of Materials in Civil Engineering, 24(2), 207-215.DOI
26. 
Sahoo, D. R., Kumar, N. (2015), Monotonic Behavior of Large-Scale SFRC Beams without Stirrups, Engineering Structures, 92, 46-54.DOI
27. 
Yazฤฑcฤฑ, ลž., ฤฐnan, G., Tabak, V. (2007), Effect of Aspect Ratio and Volume Fraction of Steel Fiber on the Mechanical Properties of SFRC, Construction and Building Materials, 21(6), 1250-1253.DOI