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Journal of the Korea Concrete Institute

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

  1. ์ •ํšŒ์›,LHํ† ์ง€์ฃผํƒ์—ฐ๊ตฌ์› ์ฑ…์ž„์—ฐ๊ตฌ์›
  2. ์ •ํšŒ์›,LHํ† ์ง€์ฃผํƒ์—ฐ๊ตฌ์› ์—ฐ๊ตฌ์œ„์›
  3. ์ •ํšŒ์›,๊ณต์ฃผ๋Œ€ํ•™๊ต ๊ฑด์ถ•๊ณตํ•™๊ณผ & ๋„์‹œ์œตํ•ฉ์‹œ์Šคํ…œ๊ณตํ•™๊ณผ



์ฒ ๊ทผ์ฝ˜ํฌ๋ฆฌํŠธ ๋ณด, ์œ ๊ณต, ์œ ๊ณต ๋ณด๊ฐ•๊ทผ, ์ „๋‹จ์„ฑ๋Šฅ, ์—๋„ˆ์ง€์†Œ์‚ฐ๋Šฅ๋ ฅ
RC beams, Web openings, Web opening reinforcement, Shear performance, Energy dissipation

1. ์„œ ๋ก 

์ธ๊ตฌ์‚ฌํšŒ๊ตฌ์กฐ์˜ ๋ณ€ํ™” ๋ฐ ์‚ฌ์šฉ์ž์˜ ์š”๊ตฌ์— ๋”ฐ๋ผ ๊ธฐ๋‘ฅ-๋ณด(์ดํ•˜ ๋ผ๋ฉ˜)๊ตฌ์กฐ ๊ณต๋™์ฃผํƒ์˜ ํ•„์š”์„ฑ์ด ๋Œ€๋‘๋˜๊ณ  ์žˆ๋‹ค. ๋ผ๋ฉ˜ ๊ตฌ์กฐ ๊ณต๋™์ฃผํƒ์€ ๊ธฐ์กด ๋ฒฝ์‹๊ตฌ์กฐ ๊ณต๋™์ฃผํƒ์— ๋น„ํ•˜์—ฌ ๊ฐ€๋ณ€์„ฑ๊ณผ ์žฅ์ˆ˜๋ช…ํ™” ๋“ฑ์— ์œ ๋ฆฌํ•œ ์žฅ์ ์ด ์žˆ์œผ๋‚˜, ์ธต๊ณ ๊ฐ€ ๋†’์•„์ง€๋Š” ๋‹จ์ ์žˆ๋‹ค. ์ด๋Ÿฌํ•œ ๋‹จ์ ์„ ๊ทน๋ณตํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ๋ผ๋ฉ˜๊ตฌ์กฐ ๊ณต๋™์ฃผํƒ์˜ ์ธต๊ณ ๋ฅผ ์ €๊ฐํ•˜๋ฉด์„œ๋„ ๊ฒฝ์ œ์„ฑ์„ ํ™•๋ณดํ•  ์ˆ˜ ์žˆ๋Š” ์ฒ ๊ทผ์ฝ˜ํฌ๋ฆฌํŠธ(์ดํ•˜ RC) ์œ ๊ณต๋ณด์— ๋Œ€ํ•œ ์—ฐ๊ตฌ๊ฐ€ ๋‹ค์ˆ˜ ์ง„ํ–‰๋˜์–ด ์™”๋‹ค(Nasser et al., 1967; Mansur 1983; Mansur et al., 1984; Lee 2015; Kim et al., 2021).

๋ผ๋ฉ˜๊ตฌ์กฐ ๊ณต๋™์ฃผํƒ์˜ ๋ณด์— ์ˆ˜ํ‰์œผ๋กœ ์œ ๊ณต์„ ๋ฐฐ์น˜ํ•  ๊ฒฝ์šฐ, ๊ธฐ๊ณ„์„ค๋น„ ๋ฐฐ๊ด€์„ ์ฒœ์ • ๋งˆ๊ฐ ๋‚ด๋ถ€์— ๊ด€ํ†ต์‹œ์ผœ ์ธต๊ณ  ํ™•๋ณด์™€ ์ฃผํƒ๊ณ„ํš ์ธก๋ฉด์—์„œ์˜ ์œตํ†ต์„ฑ์„ ์ œ๊ณ ํ•  ์ˆ˜ ์žˆ๋‹ค. ํŠนํžˆ, ์ธต๊ณ  ์ €๊ฐ์€ ๊ณต๋™์ฃผํƒ์˜ ๊ฒฝ์ œ์ ์ธ ์„ค๊ณ„ ์œ ๋„ ๋ฐ ์ž์ค‘ ๊ฐ์†Œ๋กœ ์ด์–ด์ ธ ๋‚ด์ง„์„ค๊ณ„ ์‹œ ์œ ๋ฆฌํ•˜๋‹ค.

RC ๋ณด์— ์œ ๊ณต์„ ๋ฐฐ์น˜ํ•  ๊ฒฝ์šฐ ์œ ๊ณต ์ฃผ๋ณ€์— ์‘๋ ฅ์ด ์ง‘์ค‘๋˜์–ด ์ฝ˜ํฌ๋ฆฌํŠธ์— ๊ท ์—ด์ด ๋ฐœ์ƒํ•˜๊ฒŒ ๋˜๋ฉฐ, ๋‹จ๋ฉด์†์‹ค์— ๋”ฐ๋ฅธ ํ•˜์ค‘์ €ํ•˜ ๋ฐ ์ฒ˜์ง์ด ์ฆ๊ฐ€ํ•˜์—ฌ ์‚ฌ์šฉ์„ฑ ์ธก๋ฉด์—์„œ ๋ฌธ์ œ๊ฐ€ ๋ฐœ์ƒํ•  ์ˆ˜ ์žˆ๋‹ค. ์ด๋Ÿฌํ•œ ๋ฌธ์ œ์  ๋ณด์™„์„ ์œ„ํ•˜์—ฌ ๊ธฐ์กด ์—ฐ๊ตฌ์ž๋“ค์€ RC ์œ ๊ณต๋ณด์— ๋Œ€ํ•œ ์—ฐ๊ตฌ๋ฅผ ํฌ๊ฒŒ 2๊ฐ€์ง€๋กœ ์ง„ํ–‰ํ•˜์˜€๋‹ค.

์ฒซ์งธ๋กœ ์œ ๊ณต๋ณด๊ฐ•๊ทผ์˜ ์ƒ์„ธ์— ๋Œ€ํ•œ ์—ฐ๊ตฌ์ด๋‹ค. RC ๋ณด์— ๋ฐฐ์น˜๋œ ์œ ๊ณต ์ฃผ์œ„์˜ ์ „๋‹จ๊ท ์—ด์„ ์ œ์–ดํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์ „๋‹จ๋ณด๊ฐ•๊ทผ์„ ์ถ”๊ฐ€๋กœ ๋ฐฐ์น˜ํ•˜๊ฑฐ๋‚˜ ๋Œ€๊ฐ์ฒ ๊ทผ์„ ๋ฐฐ์น˜ํ•˜๋Š” ๋ฐฉ๋ฒ•์„ ์ด์šฉํ•œ ์—ฐ๊ตฌ๋ฅผ ์ง„ํ–‰ํ•˜์˜€๋‹ค(Mansur 1988; Mansur et al., 2006).

๋‘ ๋ฒˆ์งธ๋Š” ์œ ๊ณต์˜ ๋ณ€์ˆ˜ ๋ฐ ํ•ด์„์  ์—ฐ๊ตฌ์ด๋‹ค. RC ๋ณด์— ๋ฐฐ์น˜๋˜๋Š” ์œ ๊ณต์˜ ํฌ๊ธฐ์™€ ํ˜•์ƒ, ์žฌ๋ฃŒ์˜ ๊ฐ•๋„, ์ „๋‹จ๊ฒฝ๊ฐ„๋น„, ํ•˜์ค‘ ํŒจํ„ด, ๋ณด ๋‹จ๋ฉด์˜ ๋น„๋Œ€์นญ์„ฑ ๋“ฑ์— ๋Œ€ํ•œ ์—ฐ๊ตฌ๊ฐ€ ์ง„ํ–‰๋˜์–ด ์™”๋‹ค(Hasnat and Aktanizzamam 1987; Tian et al., 1995; and Rishi, 2000; Torunbalci, 2000; Yang et al., 2006; Campione and Minafo 2012; Aykac et al., 2013).

๊ธฐ์กด ์—ฐ๊ตฌ๋ฅผ ๋ฐ”ํƒ•์œผ๋กœ ๋ฏธ๊ตญ ์ฝ˜ํฌ๋ฆฌํŠธ์„ค๊ณ„ ๊ธฐ์ค€(American Concrete Institute 2019)์€ ๊ธฐ์กด RC ๋ณด์˜ ์ „๋‹จ๊ฐ•๋„ ์‹์— ์œ ๊ณต์œผ๋กœ ์ธํ•˜์—ฌ ๋ฐœ์ƒ๋˜๋Š” ๋‹จ๋ฉด์†์‹ค์„ ๊ณ ๋ คํ•˜์—ฌ ๋ณด์˜ ์œ ํšจ๊นŠ์ด ($d$)๋ฅผ $d-d_{o}$๋กœ ๋Œ€์ฒดํ•œ ์ „๋‹จ๊ฐ•๋„ ์˜ˆ์ธก์‹์„ ์ œ์•ˆํ•˜๊ณ  ์žˆ๋‹ค.

์ผ๋ณธ ๊ฑด์ถ•ํ•™ํšŒ๋Š” 1980๋…„๋Œ€ ์œ ๊ณต ๋ณด ์œ„์›ํšŒ์˜ ์—ฐ๊ตฌ๊ฒฐ๊ณผ๋ฅผ ๋ฐ”ํƒ•์œผ๋กœ RC ์œ ๊ณต๋ณด ์ „๋‹จ๊ฐ•๋„ ์˜ˆ์ธก์‹์„ ์ œ์•ˆํ•˜์˜€์œผ๋ฉฐ, ์ผ๋ณธ์˜ ๊ฑด์ถ•ํ•™ํšŒ ์ œ์•ˆ์‹(Architectural Institute of Japan 2010)์€ ์ „๋‹จ์ฒ ๊ทผ์˜ ๊ธฐ์—ฌ๋ถ„๊ณผ ์œ ๊ณต๋ณด๊ฐ•๊ทผ์˜ ๊ธฐ์—ฌ๋ถ„์„ ํŠธ๋Ÿฌ์Šค ๊ธฐ๊ตฌ๋ฅผ ํ†ตํ•˜์—ฌ ๋ฐ˜์˜ํ•˜์˜€์œผ๋ฉฐ, ์œ ๊ณต์˜ ์ตœ๋Œ€ ํฌ๊ธฐ๋Š” ๋ณด๊ฐ•์„ ์ถฉ๋ถ„ํžˆ ํ•˜๋”๋ผ๋„ ๋ณด์˜ ์œ ํšจ๋†’์ด($d$)์˜ 1/3์„ ์ดˆ๊ณผํ•˜์ง€ ๋ชปํ•˜๋„๋ก ๊ทœ์ •ํ•˜๊ณ  ์žˆ๋‹ค.

Kim et al.(2018)์€ ๊ธฐ์กด RC ์œ ๊ณต ๋ณด์— ๋Œ€ํ•œ ์—ฐ๊ตฌ๋ฅผ ๋ณด์™„ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์ผ๋ฐ˜ ๋ ์ฒ ๊ทผ์— ๋น„ํ•˜์—ฌ ์‹œ๊ณต์„ฑ์„ ํ™•๋ณดํ•œ ๋งˆ๋ฆ„๋ชจ๊ผด ๋‚˜์„ ํ˜•ํƒœ์˜ ์œ ๊ณต๋ณด๊ฐ•๊ทผ์— ๋Œ€ํ•œ ์—ฐ๊ตฌ๋ฅผ ์ง„ํ–‰ํ•˜์˜€์œผ๋ฉฐ, ์ด๋ฅผ ํ†ตํ•˜์—ฌ ์œ ๊ณต์ฃผ๋ณ€์˜ ๊ท ์—ด์ œ์–ด๋Š” ์œ ๊ณต๋ณด๊ฐ•๊ทผ์˜ ํ˜•์ƒ์— ๊ด€๊ณ„๊ฐ€ ์žˆ์Œ์„ ๋ฐํ˜”๋‹ค. ๊ทธ๋Ÿฌ๋‚˜ ๋งˆ๋ฆ„๋ชจ๊ผด ์œ ๊ณต๋ณด๊ฐ•๊ทผ์€ ๋ณด ๋‚ด๋ถ€๊นŒ์ง€ ๋‚˜์„ ํ˜•์ƒ์œผ๋กœ ๋˜์–ด ์žˆ์–ด ๋‹จ๋ฉดํ˜•์ƒ์ด ๋ถˆ์—ฐ์†์ด๊ฑฐ๋‚˜ ๋‹ค๋Ÿ‰์˜ ์ฒ ๊ทผ์ด ๋ฐฐ๊ทผ๋˜๋Š” ๊ตฌ๊ฐ„์—์„œ๋Š” ์‹œ๊ณต์„ฑ์ด ์ €ํ•˜๋  ์šฐ๋ ค๊ฐ€ ์žˆ๋‹ค.

๋”ฐ๋ผ์„œ, ์ด ์—ฐ๊ตฌ์—์„œ๋Š” ๋‚˜์„ ํ˜• ์œ ๊ณต๋ณด๊ฐ•๊ทผ์— ๋น„ํ•˜์—ฌ ์‹œ๊ณต์„ฑ์˜ ํŽธ๋ฆฌ์„ฑ์„ ๋†’์ด๊ณ  ํšจ๊ณผ์ ์ธ ์ „๋‹จ์ €ํ•ญ์ด ๊ฐ€๋Šฅํ•˜๋„๋ก ์‚ฌ๊ฐํ˜•๊ณผ ํŒ”๊ฐํ˜•์ด ์ค‘์ฒฉ๋œ ํ˜•ํƒœ์˜ ๋ ์ฒ ๊ทผ ํ˜•์ƒ์˜ ๋‚˜์„ ํ˜• ๋ฐฐ๊ทผ๋ฐฉ๋ฒ•์„ ๊ณ ์•ˆํ•˜์˜€์œผ๋ฉฐ, ์ด๋ฅผ ์ ์šฉํ•œ RC ์œ ๊ณต ๋ณด์˜ ์ „๋‹จ์„ฑ๋Šฅ์„ ํ‰๊ฐ€ํ•˜์˜€๋‹ค.

2. ์‹คํ—˜๊ณ„ํš

2.1 ์‚ฌ์šฉ์žฌ๋ฃŒ

์ด ์—ฐ๊ตฌ์—์„œ๋Š” ์œ ๊ณต ๋ฐ ์œ ๊ณต๋ณด๊ฐ•๊ทผ์˜ ์ƒ์„ธ์— ๋”ฐ๋ผ ์ด 4์ฒด์˜ RC ๋ณด ๋ถ€์žฌ ์‹คํ—˜์ฒด๋ฅผ ์ œ์ž‘ํ•˜์˜€์œผ๋ฉฐ, Table 1๊ณผ ๊ฐ™์ด ์‚ฌ์šฉ๋œ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์••์ถ•๊ฐ•๋„๋Š” 24 MPa์ด๋‹ค. ์ฝ˜ํฌ๋ฆฌํŠธ ์••์ถ•๊ฐ•๋„ ์‹œํ—˜์€ KS F2405์— ๊ธฐ์ดˆํ•˜์—ฌ ์ˆ˜ํ–‰ํ•˜์˜€์œผ๋ฉฐ, ๊ทธ ๊ฒฐ๊ณผ ํ‰๊ท  21.0MPa์„ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. Table 2์™€ ๊ฐ™์ด ์‹คํ—˜์ฒด์˜ ์ฃผ์ฒ ๊ทผ์€ D25๋ฅผ ์‚ฌ์šฉํ•˜์˜€์œผ๋ฉฐ, ์ „๋‹จ๋ณด๊ฐ•๊ทผ์œผ๋กœ D10, ์œ ๊ณต๋ณด๊ฐ•๊ทผ์€ ๋ชจ๋‘ $\phi$6์„ ์‚ฌ์šฉํ•˜์˜€๋‹ค.

Table 1 Properties of concrete mix design

$f'_{c}$

(MPa)

$G_{\max}$

(mm)

W/C

(%)

s/a

(%)

Unit weight ($kg/cm^{3}$)

Slump

(mm)

W

C

S

G

AD

24

25

49.7

48.5

82

214

872

936

69.3

120

$f'_{c}$: Compressive of concrete, $G_{\max}$: Maximum size of aggregate , W/C: water/cement ratio, s/a: Fine aggregate ratio, AD : Admixture
Table 2 Mechanical properties of reinforcements

Reinforcement

Diameter

Yield strength

(MPa)

Tensile strength

(MPa)

Yield strain

Elastic modulus

(GPa)

Note

Web opening

$\phi$6

300

327

0.0015

200

Round reinforcement

Shear

D10

540

636

0.0027

200

Deformed reinforcement

Longitudinal

D25

610

749

0.0031

197

2.2 ์‹คํ—˜์ฒด ๊ณ„ํš

Table 2 ๋ฐ Fig. 1๊ณผ ๊ฐ™์ด ๋ชจ๋“  ์‹คํ—˜์ฒด๋Š” โ… ํ˜•์ƒ์œผ๋กœ ์‹คํ—˜ ๊ตฌ๊ฐ„์€ ๊ธธ์ด 2,000 mm, ํญ(b) 300 mm, ๊นŠ์ด(D) 375 mm๋กœ ๊ณ„ํšํ•˜์˜€์œผ๋ฉฐ, ์ „๋‹จ๊ฒฝ๊ฐ„๋น„(a/D)๋Š” 3.08์ด๋‹ค. ์–‘๋‹จ๋ถ€ ์Šคํ„ฐ๋ธŒ๋Š” ์‹คํ—˜์ฒด์™€ ๊ฐ€๋ ฅ์žฅ์น˜๋ฅผ ์—ฐ๊ฒฐํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ๊ณ„ํšํ•˜์˜€๋‹ค.

์‹คํ—˜๊ตฌ๊ฐ„์— ๋ฐฐ์น˜ํ•œ ์œ ๊ณต์˜ ์ง๊ฒฝ($\phi$)์€ ๋ณด ๋‹จ๋ฉด์˜ ๊นŠ์ด(D)์˜ 1/3(D/3=125 mm)์ด๋‹ค. ์‹คํ—˜์ฒด๋Š” ํœจ ํ•ญ๋ณต์ด์ „์— ์ „๋‹จํŒŒ๊ดด๋ฅผ ์„ ํ–‰ํ•˜๊ณ ์ž D25์˜ ์ฃผ์ฒ ๊ทผ์„ ์••์ถ•์ธก๊ณผ ์ธ์žฅ์ธก์— 4๋Œ€์”ฉ ์ด 8๋Œ€๋ฅผ ๋ฐฐ๊ทผํ•˜์˜€์œผ๋ฉฐ, ์ „๋‹จ๋ณด๊ฐ•๊ทผ์˜ ๊ฐ„๊ฒฉ์€ 150 mm์ด๋‹ค. ์‚ฌ์šฉ๋œ ์œ ๊ณต๋ณด๊ฐ•๊ทผ์€ Fig. 1(a)์™€ ๊ฐ™์ด ๊ธฐ์กด์— ๋„๋ฆฌ ์‚ฌ์šฉ๋˜๋Š” X์ž ํ˜•ํƒœ(์ดํ•˜ Bandํ˜•)์™€ Fig. 1(b)์™€ ๊ฐ™์ด ์ด ์—ฐ๊ตฌ์—์„œ ์ œ์•ˆํ•œ ํŒ”๊ฐ๊ณผ ์‚ฌ๊ฐ์˜ ํ˜•์ƒ์ด ํ˜ผ์šฉ๋œ ๋‚˜์„ ํ˜•(์ดํ•˜ ๋‚˜์„ ํ˜•)์ด๋‹ค.

Fig. 1 Details of specimens (Unit:mm)
../../Resources/ksm/jksmi.2021.25.5.76/fig1.png

2.3 ๊ฐ€๋ ฅ ๋ฐ ๊ณ„์ธก ๋ฐฉ๋ฒ•

์œ ๊ณต์œผ๋กœ ์ธํ•œ ์ฝ˜ํฌ๋ฆฌํŠธ ๋‹จ๋ฉด์†์‹ค์€ RC ๋ถ€์žฌ์— ๋‚ด๋ ฅ์— ํฐ ์˜ํ–ฅ์„ ๋ฏธ์น˜๋ฏ€๋กœ, ์ด ์—ฐ๊ตฌ์—์„œ๋Š” Fig. 2(a)์™€ ๊ฐ™์ด ์‹คํ—˜์ฒด์— ์—ญ๋Œ€์นญ ๋ชจ๋ฉ˜ํŠธ๋ฅผ ๊ฐ€๋ ฅํ•˜์—ฌ RC ๋ถ€์žฌ์— ๋ถˆ๋ฆฌํ•œ ์ง€์ง„ํ•˜์ค‘์„ ๋ชจ์‚ฌํ•˜์˜€๋‹ค. ๊ฐ€๋ ฅํ”„๋ ˆ์ž„ ์ƒ๋ถ€์— ์œ„์น˜ํ•œ ์—‘์ธ„์—์ดํ„ฐ๋ฅผ ์ด์šฉํ•˜์—ฌ ์‹คํ—˜์ฒด๋ฅผ ๊ณ ์ •ํ•˜๊ณ  ํšกํ•˜์ค‘์€ 1,000 kN ์šฉ๋Ÿ‰์˜ ์—‘์ธ„์—์ดํ„ฐ๋ฅผ ์ด์šฉํ•˜์—ฌ ๊ฐ€๋ ฅํ•˜์˜€๋‹ค. ๊ฐ€๋ ฅํ”„๋ ˆ์ž„ ์–‘์ชฝ ์˜†์— ์„ค์น˜๋œ ์ˆ˜ํ‰์œ ์ง€์žฅ์น˜๋ฅผ ์ด์šฉํ•˜์—ฌ ์‹คํ—˜๊ตฌ๊ฐ„์— ์—ญ๋Œ€์นญ ๋ชจ๋ฉ˜ํŠธ์™€ ์ผ์ •ํ•œ ์ „๋‹จ๋ ฅ์ด ์ž‘์šฉํ•˜๋„๋ก ํ•˜์˜€๋‹ค.

ํšกํ•˜์ค‘์€ ๋ณ€์œ„์ œ์–ด๋ฒ•์„ ์ด์šฉํ•˜์—ฌ Fig. 2(b)์™€ ๊ฐ™์ด ๋งค ํ•˜์ค‘ ๋‹จ๊ณ„๋ณ„๋กœ 2์‚ฌ์ดํด์”ฉ ๊ฐ€๋ ฅํ•˜์˜€๋‹ค. ์‹คํ—˜์€ ์ตœ๋Œ€ ๋‚ด๋ ฅ์˜ ์•ฝ 85% ์ดํ•˜๋กœ ํ•˜์ค‘์ด ์ €ํ•˜๋  ๋•Œ๊นŒ์ง€ ์ง€์†ํ•˜์˜€๋‹ค.

์‹คํ—˜์ฒด์˜ ํšก๋ฐฉํ–ฅ ๋ณ€์œ„๋Š” Fig. 2(c)์™€ ๊ฐ™์ด 300 mm ์šฉ๋Ÿ‰์˜ ๋ณ€์œ„๋ณ€ํ™˜๊ธฐ(LVDT)๋ฅผ 2๋Œ€๋ฅผ ์ด์šฉํ•˜์—ฌ ์ธก์ •ํ•˜์˜€์œผ๋ฉฐ, ์ธก์ •๋œ ์‹คํ—˜์ฒด์˜ ํšก๋ณ€์œ„๋ฅผ ์ด์šฉํ•˜์—ฌ ์‹ (1)๊ณผ ๊ฐ™์ด ๋ถ€์žฌ๋ณ€ํ˜•๊ฐ์„ ์‚ฐ์ •ํ•˜์˜€๋‹ค.

(1)
$\theta =\dfrac{\delta_{1}+\delta_{2}}{L}(\%)$

์ด ์—ฐ๊ตฌ์—์„œ๋Š” Fig. 1๊ณผ ๊ฐ™์ด ์‹คํ—˜์ฒด ์ฒ ๊ทผ์˜ ๋ณ€ํ˜•๋ฅ ์„ ์•Œ์•„๋ณด๊ธฐ ์œ„ํ•˜์—ฌ ์ฃผ์ฒ ๊ทผ๊ณผ ์ „๋‹จ๋ณด๊ฐ•๊ทผ, ๊ทธ๋ฆฌ๊ณ  ์œ ๊ณต๋ณด๊ฐ•๊ทผ์— ๊ฒŒ์ด์ง€๋ฅผ ๋ถ€์ฐฉํ•˜์˜€๋‹ค. ์ฃผ์ฒ ๊ทผ์€ ์ „๋‹จ์œ„ํ—˜๊ตฌ๊ฐ„ ๋ฐ ์‹คํ—˜๊ตฌ๊ฐ„์˜ ์ค‘์•™๋ถ€์— ๋ถ€์ฐฉํ•˜์˜€์œผ๋ฉฐ, ์ „๋‹จ๋ณด๊ฐ•๊ทผ์€ ์ „๋‹จ ๋ณด๊ฐ•๊ทผ์˜ ์ค‘์•™์ ์— ๊ฒŒ์ด์ง€๋ฅผ ๋ถ€์ฐฉํ•˜์˜€๋‹ค. ๊ธฐ์กด Bandํ˜• ์œ ๊ณต๋ณด๊ฐ•๊ทผ์€ ๋Œ€๊ฐ๋ถ€ ์ƒ๋ถ€์™€ ํ•˜๋ถ€์— ๊ฒŒ์ด์ง€๋ฅผ ๋ถ€์ฐฉํ•˜์˜€์œผ๋ฉฐ, ์ œ์•ˆ ์œ ๊ณต๋ณด๊ฐ•๊ทผ์€ ํŒ”๊ฐ๊ณผ ์‚ฌ๊ฐ ๋ถ€๋ถ„์— ๊ฐ๊ฐ ๊ฒŒ์ด์ง€๋ฅผ ๋ถ€์ฐฉํ•˜์˜€๋‹ค.

Fig. 2 Test setup of specimens
../../Resources/ksm/jksmi.2021.25.5.76/fig2.png

2.4 ์œ ๊ณต๋ณด๊ฐ•๊ทผ ์ƒ์„ธ

Fig. 1์— ๋‚˜ํƒ€๋‚ธ ๋ฐ”์™€ ๊ฐ™์ด ์ด ์—ฐ๊ตฌ์—์„œ ์ œ์•ˆ๋œ ๋‚˜์„ ํ˜• ์œ ๊ณต๋ณด๊ฐ•๊ทผ์€ ํŒ”๊ฐ๊ณผ ์‚ฌ๊ฐ์ด ์ผ์ฒดํ™”๋œ ๋ ์ฒ ๊ทผ ํ˜•์ƒ์œผ๋กœ ๊ธฐ์กด Band ํ˜•์ƒ์— ๋น„ํ•˜์—ฌ ์‹œ๊ณต์ด ๊ฐ„ํŽธํ•œ ์žฅ์ ์ด ์žˆ๋‹ค. ๋‚˜์„ ํ˜• ์œ ๊ณต๋ณด๊ฐ•๊ทผ ์ค‘ ์ˆ˜์ง์ฒ ๊ทผ์€ ์‹คํ—˜์ฒด์˜ ์œ ๊ณต๋ณด๊ฐ•๊ทผ์˜ ์—ญํ• ๊ณผ ํ•จ๊ป˜ ์ „๋‹จ๋ณด๊ฐ•๊ทผ์˜ ์—ญํ• ์„ ํ•ด ์ฃผ๋ฉฐ, ์›ํ˜•์— ๊ฐ€๊นŒ์šด ํŒ”๊ฐํ˜• ์ฒ ๊ทผ์€ ์œ ๊ณต ์ฃผ์œ„์— ๋ฐœ์ƒํ•˜๋Š” ์ „๋‹จ๊ท ์—ด์„ ์ œ์–ดํ•œ๋‹ค.

์‹คํ—˜์ฒด์— ๋ฐฐ๊ทผ๋œ ๋‚˜์„ ํ˜• ์œ ๊ณต ๋ณด๊ฐ•๊ทผ์˜ ์–‘์€ ์œ ๊ณต์œผ๋กœ ์ธํ•œ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ „๋‹จ๋ ฅ ์†์‹ค๋ถ„์„ ๋ณด์ „ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์‹ (2)์™€ ๊ฐ™์ด ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์†์‹ค์ „๋‹จ๋ ฅ ์ด์ƒ์œผ๋กœ ๋ฐฐ๊ทผํ•˜์˜€๋‹ค.

(2)
$V_{co}<V_{so}$

์—ฌ๊ธฐ์„œ $V_{co}$๋Š” ์œ ๊ณต์œผ๋กœ ์ธํ•˜์—ฌ ์†์‹ค๋˜๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ „๋‹จ๊ธฐ์—ฌ๋ถ„์ด๋ฉฐ, $V_{so}$๋Š” ์œ ๊ณต๋ณด๊ฐ•๊ทผ์˜ ๋ถ€๋‹ดํ•˜๋Š” ์ „๋‹จ๊ธฐ์—ฌ๋ถ„์ด๋‹ค.

$V_{co}$๋Š” ๋‹ค์Œ ์‹ (3)๊ณผ ๊ฐ™์ด ์ฝ˜ํฌ๋ฆฌํŠธ๊ตฌ์กฐ๊ธฐ์ค€(ํ•œ๊ตญ์ฝ˜ํฌ ๋ฆฌํŠธํ•™ํšŒ, 2017)์˜ ์‚ฐ์ •์‹์—์„œ ๋ณด์˜ ์ „๋‹จ๊ฐ•๋„ ๊ฐ์†Œ๋ฅผ ๊ณ ๋ คํ•˜์—ฌ ($d-d_{o}$)์‚ฌ์šฉํ•˜์˜€๋‹ค.

(3)
$V_{co}=\dfrac{1}{6}\sqrt{f_{ck}}b_{w}(d-d_{o})$

์—ฌ๊ธฐ์„œ $f_{ck}$๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์••์ถ•๊ฐ•๋„์ด๋ฉฐ, $b_{w}$๋Š” ๋ณด์˜ ํญ, $d$๋Š” ๋ณด์˜ ์œ ํšจ ๊นŠ์ด, $d_{o}$๋Š” ์œ ๊ณต์˜ ์ง๊ฒฝ์ด๋‹ค.

์œ ๊ณต ๋ณด๊ฐ•๊ทผ์ด ๋ถ€๋‹ดํ•˜๋Š” ์ „๋‹จ๋ ฅ $V_{so}$๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ๊ตฌ์กฐ๊ธฐ์ค€์˜ ์ „๋‹จ๊ฐ•๋„ ์‹์„ ์ด์šฉํ•˜์—ฌ ๋‹ค์Œ ์‹ (4)์™€ ๊ฐ™์ด ๊ตฌํ•  ์ˆ˜ ์žˆ๋‹ค.

(4)
$V_{so}=\dfrac{A_{vo}f_{yo}d}{s_{o}}$

์—ฌ๊ธฐ์„œ $A_{vo}$๋Š” ์œ ๊ณต๋ณด๊ฐ•๊ทผ ์ค‘ ์ˆ˜์ง์ฒ ๊ทผ์˜ ๋‹จ๋ฉด์ ์ด๋ฉฐ, $f_{yo}$๋Š” ์œ ๊ณต๋ณด๊ฐ•๊ทผ์˜ ํ•ญ๋ณต๊ฐ•๋„, $s_{o}$๋Š” ์œ ๊ณต ๋ณด๊ฐ•๊ทผ์˜ ์ˆ˜์ง์ฒ ๊ทผ ์‚ฌ์ด์˜ ๊ฑฐ๋ฆฌ์ด๋‹ค.

์ œ์•ˆํ•œ ๋‚˜์„ ํ˜•์˜ ์œ ๊ณต๋ณด๊ฐ•๊ทผ ์ค‘ ํŒ”๊ฐ ์ฒ ๊ทผ์€ ์œ ๊ณต์ฃผ์œ„์˜ ์ „๋‹จ๊ท ์—ด์˜ ์ œ์–ด ํšจ๊ณผ๊ฐ€ ์ฃผ๋œ ๋ชฉ์ ์œผ๋กœ, ์ „๋‹จ๋ ฅ $V_{so}$ ๊ณ„์‚ฐ ์‹œ ํŒ”๊ฐ ์ฒ ๊ทผ์˜ ๋‹จ๋ฉด์ ์€ ๊ณ ๋ คํ•˜์ง€ ์•Š์•˜๋‹ค.

3. ์‹คํ—˜ ๊ฒฐ๊ณผ

3.1 ์ „๋‹จ๋ ฅ-๋ถ€์žฌ๋ณ€ํ˜•๊ฐ ๊ด€๊ณ„

Fig. 3์—๋Š” ๊ฐ ์‹คํ—˜์ฒด์˜ ์ „๋‹จ๋ ฅ-๋ถ€์žฌ๋ณ€ํ˜•๊ฐ ๊ด€๊ณ„๋ฅผ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ๋ชจ๋“  ์‹คํ—˜์ฒด๋Š” ์‹คํ—˜์˜ ์ข…๋ฃŒ์ „๊นŒ์ง€ ์ฃผ์ฒ ๊ทผ์˜ ํ•ญ๋ณต์ด ๋‚˜ํƒ€๋‚˜์ง€ ์•Š์€ ์ „๋‹จํŒŒ๊ดด๋ฅผ ๋‚˜ํƒ€๋‚ด์—ˆ์œผ๋ฉฐ, ์ด๋ฅผ ์ „๋‹จ๋ ฅ-๋ถ€์žฌ๋ณ€ํ˜•๊ฐ ๊ทธ๋ž˜ํ”„์˜ ํ˜•์ƒ์„ ํ†ตํ•˜์—ฌ ํ™•์ธ ํ•  ์ˆ˜ ์žˆ๋‹ค. ์ด ์—ฐ๊ตฌ์—์„œ๋Š” ์ •๋ฐฉํ–ฅ(+) ํ•˜์ค‘์„ ๋Œ€์ƒ์œผ๋กœ ์ตœ๋Œ€ํ•˜์ค‘์„ ์‚ฐ์ •ํ•˜์˜€๋‹ค.

์œ ๊ณต์ด ์—†๋Š” S ์‹คํ—˜์ฒด๋Š” ๋ถ€์žฌ๋ณ€ํ˜•๊ฐ 2%์—์„œ ์ตœ๋Œ€ ์ „๋‹จ๋ ฅ 183.2 kN์— ๋„๋‹ฌํ•˜์˜€์œผ๋ฉฐ, ์ตœ๋Œ€ ์ „๋‹จ๋ ฅ ์ดํ›„ ํ•˜์ค‘ ์ €ํ•˜๋กœ ์‹คํ—˜์ด ์ข…๋ฃŒ๋˜์—ˆ๋‹ค. ์œ ๊ณต์€ ์žˆ์œผ๋‚˜ ์œ ๊ณต๋ณด๊ฐ•๊ทผ์ด ์—†๋Š” NW ์‹คํ—˜์ฒด๋Š” ๋ถ€์žฌ๋ณ€ํ˜•๊ฐ 1%์—์„œ ์ตœ๋Œ€ ์ „๋‹จ๋ ฅ์— ๋„๋‹ฌํ•˜์˜€์œผ๋ฉฐ ๊ทธ ๋•Œ์˜ ํ•˜์ค‘์€ 151.9 kN์„ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค.

์œ ๊ณต๋ณด๊ฐ•๊ทผ์˜ ํ˜•์ƒ์ด Bandํ˜•์ธ WB ์‹คํ—˜์ฒด๋Š” ๋ถ€์žฌ๋ณ€ํ˜•๊ฐ 2%์—์„œ ์ตœ๋Œ€ ์ „๋‹จ๋ ฅ 173.5 kN์— ๋„๋‹ฌํ•˜์˜€๋‹ค. WB์‹คํ—˜์ฒด๋Š” ์ตœ๋Œ€ํ•˜์ค‘ ์ดํ›„ ๊ฐ•์„ฑ์˜ ์ €ํ•˜๊ฐ€ ๋‚˜ํƒ€๋‚ฌ์œผ๋ฉฐ, ์ตœ๋Œ€ ์ „๋‹จ๋ ฅ ์ด์ „์— ์œ ๊ณต๋ณด๊ฐ•๊ทผ์ด ํ•ญ๋ณตํ•˜์˜€๋‹ค. ์œ ๊ณต๋ณด๊ฐ•๊ทผ ํ˜•์ƒ์ด ๋‚˜์„ ํ˜•์ธ WS ์‹คํ—˜์ฒด๋Š” ๋ถ€์žฌ๋ณ€ํ˜•๊ฐ 2%์—์„œ ์ตœ๋Œ€ ์ „๋‹จ๋ ฅ 208.5 kN์„ ๋‚˜ํƒ€๋‚ด์—ˆ์œผ๋ฉฐ, WB ์‹คํ—˜์ฒด์™€ ๋™์ผํ•˜๊ฒŒ ์ตœ๋Œ€ ์ „๋‹จ๋ ฅ ์ด์ „์— ์œ ๊ณต๋ณด๊ฐ•๊ทผ์ด ํ•ญ๋ณตํ•˜์˜€๋‹ค.

Fig. 3์—์„œ ๋‚˜ํƒ€๋‚ธ ๋ฐ”์™€ ๊ฐ™์ด ์ด ์—ฐ๊ตฌ์—์„œ ์ œ์•ˆ๋œ ์‚ฌ๊ฐ+ํŒ”๊ฐ์˜ ๋‚˜์„ ํ˜• ์œ ๊ณต๋ณด๊ฐ•๊ทผ์€ ๊ธฐ์กด Bandํ˜• ๋ฐ ์œ ๊ณต์ด ์—†๋Š” ์‹คํ—˜์ฒด์— ๋น„ํ•˜์—ฌ ์ตœ๋Œ€์ „๋‹จ๋ ฅ์ด ๋™๋“ฑ ์ด์ƒ์œผ๋กœ ๋‚˜ํƒ€๋‚˜ ์œ ๊ณต์˜ ์ „๋‹จ๋ณด๊ฐ•์— ํšจ๊ณผ์ ์ž„์„ ํ™•์ธํ•˜์˜€๋‹ค.

Fig. 3 Shear force โ€“ drift angle relationships
../../Resources/ksm/jksmi.2021.25.5.76/fig3.png

3.2 ์‹คํ—˜์ฒด ํŒŒ๊ดด ์–‘์ƒ

๊ฐ ์‹คํ—˜์ฒด์˜ ์ตœ์ข… ํŒŒ๊ดด ์–‘์ƒ์„ Fig. 4์— ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ๋ชจ๋“  ์‹คํ—˜์ฒด๋Š” ๋ถ€์žฌ๋ณ€ํ˜•๊ฐ 0.25~0.5%์‚ฌ์ด์— ๋ณด์˜ ์–‘๋‹จ๋ถ€ ์†Œ์„ฑํžŒ์ง€ ๊ตฌ๊ฐ„์—์„œ ํœจ ๊ท ์—ด์ด ๋ฐœ์ƒํ•˜์˜€๋‹ค. ์ดํ›„ ํ•˜์ค‘์ด ์ฆ๊ฐ€ํ•จ์— ๋”ฐ๋ผ ๊ท ์—ด์ด ์‹คํ—˜์ฒด ์ค‘์•™๋ถ€๋กœ ์ง„์ „๋˜๋Š” ๊ณตํ†ต๋œ ํŒŒ๊ดด์–‘์ƒ์„ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค.

S ์‹คํ—˜์ฒด๋Š” ์ตœ๋Œ€ ์ „๋‹จ๋ ฅ์„ ๋‚˜ํƒ€๋‚ธ ๋ถ€์žฌ๋ณ€ํ˜•๊ฐ 2.0% ์ดํ›„ ์‹คํ—˜์ฒด์˜ ๋ณต๋ถ€์— ์‚ฌ์ธ์žฅ๊ท ์—ด์ด ๋ฐœ์ƒํ•˜์˜€์œผ๋ฉฐ, ์ดํ›„ ์ฃผ์ฒ ๊ทผ์„ ๋”ฐ๋ผ ํ• ๋ ฌ๊ท ์—ด์ด ๋ฐœ์ƒํ•˜์—ฌ ์ตœ์ข… ํŒŒ๊ดดํ•˜์˜€๋‹ค.

์œ ๊ณต๋ณด๊ฐ•๊ทผ์ด ์—†๋Š” NW ์‹คํ—˜์ฒด๋Š” ํœจ ๊ท ์—ด ๋ฐœ์ƒ ์ดํ›„ ์œ ๊ณต์ฃผ๋ณ€์—์„œ ๋ฐฉ์‚ฌํ˜•์œผ๋กœ ์‚ฌ์ธ์žฅ๊ท ์—ด์ด ๋ฐœ์ƒํ•˜์˜€์œผ๋ฉฐ, ํ•˜์ค‘์ด ์ฆ๊ฐ€ํ•จ์— ๋”ฐ๋ผ ์œ ๊ณต์ฃผ๋ณ€์— ๋ฐœ์ƒํ•œ ๊ท ์—ด์˜ ์ˆ˜์™€ ํญ์ด ์ฆ๊ฐ€ํ•˜์˜€๋‹ค. ์ตœ๋Œ€ ์ „๋‹จ๋ ฅ ์ดํ›„ ์œ ๊ณต๊ณผ ์œ ๊ณต์‚ฌ์ด์˜ ๊ท ์—ด์ด ์—ฐ๊ฒฐ๋˜์–ด ๋ณต๋ถ€ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์••๊ดด๊ฐ€ ๋ฐœ์ƒํ•˜์—ฌ ์ตœ์ข… ์ „๋‹จํŒŒ๊ดดํ•˜์˜€๋‹ค.

Bandํ˜• ์œ ๊ณต๋ณด๊ฐ•๊ทผ์œผ๋กœ ๋ณด๊ฐ•ํ•œ WB ์‹คํ—˜์ฒด๋Š” ์ดˆ๊ธฐ ํœจ ๊ท ์—ด ๋ฐœ์ƒ์ดํ›„ ํ•˜์ค‘์ด ์ฆ๊ฐ€ํ•จ์— ๋”ฐ๋ผ ์œ ๊ณต์ฃผ๋ณ€์—์„œ ๊ท ์—ด์ด ๋ฐœ์ƒํ•˜์˜€์œผ๋ฉฐ, ์œ ๊ณต์„ ๊ด€ํ†ตํ•˜๋Š” ์‚ฌ์ธ์žฅ๊ท ์—ด์˜ ๋ฐœ์ƒ์œผ๋กœ ์ตœ์ข…ํŒŒ๊ดดํ•˜์˜€๋‹ค.

์ด ์—ฐ๊ตฌ์—์„œ ์ œ์•ˆํ•œ ๋‚˜์„ ํ˜•์˜ WS ์‹คํ—˜์ฒด๋Š” NW ๋ฐ WB ์‹คํ—˜์ฒด์™€ ์œ ์‚ฌํ•˜๊ฒŒ ํ•˜์ค‘์˜ ์ฆ๊ฐ€์— ๋”ฐ๋ผ ์œ ๊ณต์ฃผ๋ณ€์˜ ๊ท ์—ด์ด ๋ฐœ์ƒํ•˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•˜์˜€๋‹ค. ์ตœ๋Œ€ ์ „๋‹จ๋ ฅ ์ดํ›„ ์œ ๊ณต์„ ๊ด€ํ†ตํ•˜๋Š” ์‚ฌ์ธ์žฅ๊ท ์—ด์ด ๋ฐœ์ƒํ•˜์—ฌ ์ตœ์ข…ํŒŒ๊ดดํ•˜์˜€๋‹ค.

Fig. 4์˜ (b)~(d)์™€ ๊ฐ™์ด WS ์‹คํ—˜์ฒด๋Š” NW ๋ฐ WB ์‹คํ—˜์ฒด์™€ ๋น„๊ตํ•˜์—ฌ ์œ ๊ณต์ฃผ๋ณ€์— ๋ฐฉ์‚ฌํ˜•์œผ๋กœ ๋ฐœ์ƒํ•œ ๊ท ์—ด์˜ ์ˆ˜๊ฐ€ ๋งŽ์•˜์Œ์—๋„ ๋ถˆ๊ตฌํ•˜๊ณ  ์œ ์‚ฌํ•œ ๋™๋“ฑ์ด์ƒ์˜ ๋‚ด๋ ฅ๊ณผ ํŒŒ๊ดด์–‘์ƒ์„ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ์ด๋Š” ์ œ์•ˆ๋œ ์œ ๊ณต๋ณด๊ฐ•๊ทผ์ด ์‚ฌ๊ฐ๊ณผ ํŒ”๊ฐ์ด ํ˜ผ์šฉ๋œ ๋‚˜์„ ํ˜•์ƒ์œผ๋กœ ์œ ๊ณต์ฃผ๋ณ€์˜ ๊ท ์—ด์„ ์ž˜ ์ œ์–ดํ•˜์˜€์Œ์„ ๋ณด์—ฌ์ค€๋‹ค.

Fig. 4 Crack pattern of specimens
../../Resources/ksm/jksmi.2021.25.5.76/fig4.png

3.3 ์ฃผ์ฒ ๊ทผ์˜ ๋ณ€ํ˜•๋ฅ  ๋ถ„ํฌ

Fig. 5๋Š” ์‹คํ—˜์ฒด์˜ ์ฃผ์ฒ ๊ทผ์— ๋ถ€์ฐฉ๋œ ์ฒ ๊ทผ๊ฒŒ์ด์ง€์˜ ๊ฐ’์„ ํ•˜์ค‘๋‹จ๊ณ„๋กœ ๊ตฌ๋ถ„ํ•˜์—ฌ ๋‚˜ํƒ€๋‚ธ ๊ทธ๋ž˜ํ”„์ด๋‹ค. ์ฃผ์ฒ ๊ทผ์˜ ๋ณ€ํ˜•๋ฅ  ๋ถ„ํฌ๋Š” NW ์‹คํ—˜์ฒด๋ฅผ ์ œ์™ธํ•˜๊ณ  ๋ชจ๋‘ ์ •๋ฐฉํ–ฅ (+) ๊ฐ’์ด๋‹ค.

๋ชจ๋“  ์‹คํ—˜์ฒด ์ฃผ์ฒ ๊ทผ์˜ ๋ณ€ํ˜•๋ฅ ์€ ์‹คํ—˜ ์ข…๋ฃŒ ์‹œ ๊นŒ์ง€ ํ•ญ๋ณต ๋ณ€ํ˜•๋ฅ ($\varepsilon_{y}=0.0031$)์— ๋„๋‹ฌํ•˜์ง€ ์•Š์•˜๋‹ค.

์ด์™€ ๊ฐ™์€ ์ฃผ์ฒ ๊ทผ์˜ ๋ณ€ํ˜•๋ฅ  ๋ถ„ํฌ์™€ ์ „๋‹จ๋ ฅ-๋ถ€์žฌ๋ณ€ํ˜•๊ฐ(Fig. 3), ์‹คํ—˜์ฒด ํŒŒ๊ดด์–‘์ƒ(Fig. 4)๋ฅผ ์ข…ํ•ฉํ•˜์—ฌ ๋ณผ ๋•Œ, ์‹คํ—˜์ฒด๋Š” ์ „๋‹จํŒŒ๊ดด ํ•˜์˜€์Œ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์—ˆ๋‹ค.

Fig. 5 Strain of longitudinal reinforcement
../../Resources/ksm/jksmi.2021.25.5.76/fig5.png

3.4 ์ „๋‹จ๋ณด๊ฐ•๊ทผ์˜ ๋ณ€ํ˜•๋ฅ  ๋ถ„ํฌ

Fig. 6์€ ์‹คํ—˜์ฒด์˜ ์ „๋‹จ๋ณด๊ฐ•๊ทผ์— ๋ถ€์ฐฉ๋œ ๊ฒŒ์ด์ง€์˜ ๊ฐ’์„ ์ •๋ฐฉํ–ฅ(+)์˜ ํ•˜์ค‘๋‹จ๊ณ„๋กœ ๊ตฌ๋ถ„ํ•˜์—ฌ ๋‚˜ํƒ€๋‚ธ ๊ทธ๋ž˜ํ”„์ด๋‹ค.

์œ ๊ณต์ด ์—†๋Š” S ์‹คํ—˜์ฒด๋Š” ์‹คํ—˜ ์ข…๋ฃŒ ์‹œ ๊นŒ์ง€ ์‹คํ—˜์ฒด ์ „ ๊ตฌ๊ฐ„์˜ ์ „๋‹จ๋ณด๊ฐ•๊ทผ์ด ํ•ญ๋ณต๋ณ€ํ˜•๋ฅ ($\varepsilon_{y}=0.0027$)์— ๋„๋‹ฌํ•˜์ง€ ์•Š์•˜๋‹ค. NW ์‹คํ—˜์ฒด๋Š” ์ตœ๋Œ€ ์ „๋‹จ๋ ฅ ์ด์ „์— ์ค‘์•™๋ถ€์˜ ์ „๋‹จ๋ณด๊ฐ•๊ทผ์ด ํ•ญ๋ณตํ•˜์˜€์œผ๋ฉฐ, ํ•˜์ค‘์˜ ์ฆ๊ฐ€์™€ ํ•จ๊ป˜ ํ•ญ๋ณต๊ตฌ๊ฐ„์ด ์ฆ๊ฐ€ํ•˜์˜€๋‹ค. ์ด์™€๋Š” ๋ฐ˜๋Œ€๋กœ ์œ ๊ณต๋ณด๊ฐ•๊ทผ์ด ๋ฐฐ๊ทผ๋œ WB์™€ WS ์‹คํ—˜์ฒด๋Š” ์ตœ๋Œ€ ์ „๋‹จ๋ ฅ ์ดํ›„ ์ „๋‹จ๋ณด๊ฐ•๊ทผ์ด ํ•ญ๋ณตํ•˜์˜€์Œ์„ ํ™•์ธํ•˜์˜€๋‹ค. ์ด๋ฅผ ํ†ตํ•˜์—ฌ ์œ ๊ณต๋ณด๊ฐ•๊ทผ์€ ์ „๋‹จ๋ณด๊ฐ•๊ทผ์ด ๋ถ€๋‹ดํ•ด์•ผ ํ•  ํ•˜์ค‘์„ ๋ถ„์‚ฐ์‹œ์ผœ ์œ ๊ณต๋ณด์˜ ํ•˜์ค‘ ์ €ํ•ญ๋Šฅ๋ ฅ์„ ํ–ฅ์ƒ์‹œํ‚ด์„ ํ™•์ธํ•˜์˜€๋‹ค.

Fig. 6 Strain of transverse reinforcement
../../Resources/ksm/jksmi.2021.25.5.76/fig6.png

3.5 ์œ ๊ณต๋ณด๊ฐ•๊ทผ์˜ ๋ณ€ํ˜•๋ฅ  ๋ถ„ํฌ

Fig. 7์€ WB์™€ WS ์‹คํ—˜์ฒด์˜ ์œ ๊ณต๋ณด๊ฐ•๊ทผ์— ๋ถ€์ฐฉ๋œ ๊ฒŒ์ด์ง€ ๊ฐ’์„ ์ •๋ฐฉํ–ฅ(+)์˜ ํ•˜์ค‘๋‹จ๊ณ„๋กœ ๊ตฌ๋ถ„ํ•˜์—ฌ ๋‚˜ํƒ€๋‚ธ ๊ทธ๋ž˜ํ”„์ด๋‹ค.

WB ์‹คํ—˜์ฒด๋Š” ์œ ๊ณต์˜ ์‚ฌ์ธ์žฅ๊ท ์—ด์˜ ์˜ํ–ฅ์„ ์ž˜ ๊ณ„์ธกํ•  ์ˆ˜ ์žˆ๋Š” ์œ ๊ณต๋ณด๊ฐ•๊ทผ์˜ ๋Œ€๊ฐ ์œ„์น˜(์ƒ๋ถ€, ํ•˜๋ถ€)์— ๋ถ€์ฐฉ๋œ ๊ฒŒ์ด์ง€ ๊ฐ’์„ ์‚ฌ์šฉ ํ•˜์˜€์œผ๋ฉฐ, WS ์‹คํ—˜์ฒด๋Š” ์œ ๊ณต๋ณด๊ฐ•๊ทผ์˜ ์‚ฌ๊ฐ๊ณผ ํŒ”๊ฐ๋ถ€๋ถ„์— ๋ถ€์ฐฉ๋œ ๊ฒŒ์ด์ง€ ๊ฐ’์„ ์‚ฌ์šฉํ•˜์˜€๋‹ค.

Fig. 7(a)์™€ ๊ฐ™์ด WB ์‹คํ—˜์ฒด๋Š” ์ตœ๋Œ€ํ•˜์ค‘ ์ด์ „์— ์‹คํ—˜์ฒด์ค‘์•™๋ถ€์— ์œ„์น˜ํ•œ ์ƒ๋ถ€ ๋Œ€๊ฐ ์œ ๊ณต๋ณด๊ฐ•๊ทผ์ด ํ•ญ๋ณตํ•˜์˜€๋‹ค. ํ•˜๋ถ€ ๋Œ€๊ฐ ์œ ๊ณต๋ณด๊ฐ•๊ทผ์€ ํ•ญ๋ณต๋ณ€ํ˜•๋ฅ ๊นŒ์ง€ ๋„๋‹ฌํ•˜์ง€ ์•Š์•˜์ง€๋งŒ ์ƒ๋ถ€ ๋Œ€๊ฐ์œ ๊ณต๋ณด๊ฐ•๊ทผ๊ณผ ์œ ์‚ฌํ•œ ๋ณ€ํ˜•๋ฅ ๋ถ„ํฌ๋ฅผ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค.

Fig. 7(b)์™€ ๊ฐ™์ด WS ์‹คํ—˜์ฒด๋Š” ์ตœ๋Œ€ํ•˜์ค‘ ์ด์ „์— ์‹คํ—˜์ฒด ์ƒ๋ถ€์— ์œ„์น˜ํ•œ ์œ ๊ณต๋ณด๊ฐ•๊ทผ์˜ ์‚ฌ๊ฐ๋ถ€๋ถ„์ด ํ•ญ๋ณตํ•˜์˜€๋‹ค. ์ดํ›„ ์‚ฌ๊ฐ๋ถ€๋ถ„์˜ ์œ ๊ณต๋ณด๊ฐ•๊ทผ์€ ํ•˜์ค‘์˜ ์ฆ๊ฐ€์™€ ํ•จ๊ป˜ ๋ณ€ํ˜•๋ฅ ์ด ์ฆ๊ฐ€ํ•˜๋Š” ์–‘์ƒ์„ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. Fig. 6(d)์˜ ์ „๋‹จ๋ณด๊ฐ•๊ทผ ๋ณ€ํ˜•๋ฅ  ๋ถ„ํฌ์™€ ๋น„๊ตํ•˜์—ฌ ๋ณผ ๋•Œ, WS์˜ ์‚ฌ๊ฐ๋ถ€๋ถ„์€ ์‹คํ—˜์ฒด์˜ ํ•˜์ค‘์„ ์ „๋‹จ๋ณด๊ฐ•๊ทผ๊ณผ ๋‚˜๋ˆ„์–ด ๋ถ€๋‹ดํ•˜๋Š” ๊ฒƒ์„ ํ™•์ธ ํ•  ์ˆ˜ ์žˆ๋‹ค. ๋˜ํ•œ WS์˜ ํŒ”๊ฐ๋ถ€๋ถ„์˜ ๋ณ€ํ˜•๋ฅ  ๋ถ„ํฌ๋Š” ์‹คํ—˜์ข…๋ฃŒ ๊นŒ์ง€ ํ•ญ๋ณต๋ณ€ํ˜•๋ฅ ์— ๋„๋‹ฌํ•˜์ง€ ์•Š์•„ ์‚ฌ๊ฐ๋ถ€๋ถ„์— ๋น„ํ•˜์—ฌ ํ•˜์ค‘์„ ์ ๊ฒŒ ๋ถ€๋‹ดํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ์ด๋ฅผ ํ†ตํ•˜์—ฌ ์ œ์•ˆ๋œ ๋‚˜์„ ํ˜• ์œ ๊ณต๋ณด๊ฐ•๊ทผ์˜ ์‚ฌ๊ฐ๋ถ€๋ถ„์€ ์œ ๊ณต๋ณด์˜ ํ•˜์ค‘ ๋ฐ ๊ท ์—ด ์ œ์–ด, ํŒ”๊ฐ๋ถ€๋ถ„์€ ๊ท ์—ด์ œ์–ด์— ํšจ๊ณผ์ ์ธ ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ์•„์šธ๋Ÿฌ ์ด ์—ฐ๊ตฌ์—์„œ ์‹ (4) $V_{so}$์˜ ๊ณ„์‚ฐ์˜ ํƒ€๋‹น์„ฑ์„ ์ž…์ฆํ•˜์˜€๋‹ค.

Fig. 7 Strain of web opening reinforcement
../../Resources/ksm/jksmi.2021.25.5.76/fig7.png
Table 3 Properties of specimens

Specimens

b

(mm)

D

(mm)

Longitudinal reinforcement

Shear

reinforcement

Web

reinforcement

Diameter of

web opening

Number of opening

Note

S

300

375

(a/D=3.08)

(d=325 mm)

$f_{y}$=610MPa

8-D25

(506.7 ใŽŸ)

$f_{wy}$=540MPa

D10

(71.3 ใŽŸ)

-

-

-

-

125 mm

(D/3)

4

NW

WB

(Band)

$f_{yo}$=300 MPa

$\phi$6

(36 ใŽŸ)

125 mm

(D/3)

4

WS

(Spiral)

125 mm

(D/3)

4

4. ์‹คํ—˜๋ถ„์„

4.1 ์ „๋‹จ๊ฐ•๋„ ์˜ˆ์ธก

์‹คํ—˜์˜ ์œ ํšจ์„ฑ๊ณผ ์ด ์—ฐ๊ตฌ์—์„œ ์ œ์•ˆํ•œ ์œ ๊ณต ๋ณด๊ฐ•๊ทผ์˜ ๊ตฌ์กฐ์„ฑ๋Šฅ์„ ๊ฒ€์ฆํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์œ ๊ณต๋ณด์˜ ์ „๋‹จ๊ฐ•๋„์— ๊ด€ํ•œ Mansur et al.(1985)์˜ ์ œ์•ˆ์‹๊ณผ ์ผ๋ณธ ๊ฑด์ถ•ํ•™ํšŒ(Architectural Institute of Japan 2010)์˜ ์ œ์•ˆ์‹์„ ์‚ฌ์šฉํ•˜์—ฌ ์ „๋‹จ๊ฐ•๋„๋ฅผ ๋น„๊ตํ•˜์˜€๋‹ค.

Mansur et al.(1985)๋Š” RC์œ ๊ณต๋ณด์˜ ์ „๋‹จ๊ฐ•๋„๋ฅผ ํ•œ๊ตญ ์ฝ˜ํฌ๋ฆฌํŠธํ•™ํšŒ ๊ธฐ์ค€(KCI 2017) ๋ฐ ๋ฏธ๊ตญ ์ฝ˜ํฌ๋ฆฌํŠธํ•™ํšŒ ์„ค๊ณ„ ๊ธฐ์ค€(American Concrete Institute 2019)๊ณผ ๋™์ผํ•˜๊ฒŒ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ธฐ์—ฌ๋ถ„๊ณผ ์ „๋‹จ๋ณด๊ฐ•๊ทผ์˜ ๊ธฐ์—ฌ๋ถ„์œผ๋กœ ๋‚˜๋ˆ„์–ด ๋‹ค์Œ ์‹ (5)~(8)๊ณผ ๊ฐ™์ด ์ œ์•ˆํ•˜์˜€๋‹ค. Mansur et al.(1985)๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ „๋‹จ๊ธฐ์—ฌ๋ถ„ ํ•ญ์—์„œ ์œ ๊ณต์˜ ์œ„์น˜๋ฅผ ์ œ์™ธํ•˜๊ณ  ์œ ๊ณต์˜ ์ง๊ฒฝ $d_{o}$ ๋งŒํผ ๊ฐ์†Œ๋œ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋‹จ๋ฉด ์†์‹ค๋งŒ์„ ๊ณ ๋ คํ•˜์˜€๋‹ค.

(5)
$V=V_{c.M}+V_{s.M}$
(6)
$V_{c.M}=\dfrac{1}{6}\sqrt{f_{ck}}b_{w}(d-d_{o})$
(7)
$V_{s.M}=V_{sv}+V_{sd}$
(8.a)
$V_{sv}=\dfrac{A_{v}f_{yt}}{s}(d_{v}-d_{o})$
(8.b)
$V_{sd}=A_{d}f_{yd}\sin\alpha_{d}$

์—ฌ๊ธฐ์„œ $V_{c.M}$์€ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ „๋‹จ๊ฐ•๋„,$V_{s.M}$์€ ์ „๋‹จ๋ณด๊ฐ•๊ทผ ์ „๋‹จ๊ฐ•๋„, $A_{v}$๋Š” ์ˆ˜์ง ์ „๋‹จ๋ณด๊ฐ•๊ทผ์˜ ๋‹จ๋ฉด์ , $f_{yt}$๋Š” ์ˆ˜์ง ์ „๋‹จ ๋ณด๊ฐ•๊ทผ์˜ ํ•ญ๋ณต๊ฐ•๋„, $d_{v}$๋Š” ์ƒ๋ถ€์™€ ํ•˜๋ถ€ ์ฃผ์ฒ ๊ทผ์˜ ์ค‘์‹ฌ๊ฐ„ ๊ฑฐ๋ฆฌ, $A_{d}$๋Š” ๋Œ€๊ฐ ์ „๋‹จ๋ณด๊ฐ•๊ทผ์˜ ๋‹จ๋ฉด์ , $f_{yd}$๋Š” ๋Œ€๊ฐ ์ „๋‹จ๋ณด๊ฐ•๊ทผ์˜ ํ•ญ๋ณต๊ฐ•๋„, $\alpha_{d}$๋Š” ๋Œ€๊ฐ ์ „๋‹จ๋ณด๊ฐ•๊ทผ๊ณผ ์ฃผ์ฒ ๊ทผ ์‚ฌ์ด์˜ ๊ฐ๋„์ด๋‹ค.

์ผ๋ณธ๊ฑด์ถ•ํ•™ํšŒ(Architectural Institute of Japan 2010)์˜ RC์œ ๊ณต๋ณด ์ „๋‹จ๊ฐ•๋„ ์˜ˆ์ธก ์‹์€ ์‹คํ—˜์„ ๊ธฐ์ดˆ๋กœ ์œ ๊ณต๋ณด์˜ ํฌ๊ธฐ ํšจ๊ณผ, ์ธ์žฅ์ฒ ๊ทผ๋น„ ๊ณ„์ˆ˜, ์œ ๊ณต๋ณด๊ฐ•๊ทผ์˜ ์ฒ ๊ทผ๋น„ ๋“ฑ์„ ๊ณ ๋ คํ•˜์—ฌ ๋‹ค์Œ ์‹ (9)์™€ ๊ฐ™์ด ์ œ์•ˆํ•˜๊ณ  ์žˆ๋‹ค.

(9.a)
$V_{c}=\left[\dfrac{0.092k_{u}k_{p}(f_{ck}+18)}{\dfrac{a}{d}+0.12}\left(1-\dfrac{1.61d_{o}}{h}\right)\right]b_{w}d_{v}$
(9.b)
$V_{s}=0.85\sqrt{\rho_{w}f_{yv}}b_{w}d_{v}$
(9.c)
$\rho_{w}=\dfrac{A_{v}(\sin\alpha +\cos\alpha)}{b_{w}d_{v}}$

์—ฌ๊ธฐ์„œ $V_{c}$์€ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ „๋‹จ๊ฐ•๋„,$V_{s}$๋Š” ์ „๋‹จ๋ณด๊ฐ•๊ทผ์˜ ์ „๋‹จ๊ฐ•๋„, $k_{u}$๋Š” ๋‹จ๋ฉด์˜ ์œ ํšจ๊นŠ์ด์˜ ํฌ๊ธฐํšจ๊ณผ ๊ณ„์ˆ˜(0.72โˆผ1.0์‚ฌ์ด ๊ฐ’), $k_{p}$๋Š” ์ธ์žฅ์ฒ ๊ทผ๋น„์˜ ๊ณ„์ˆ˜๋กœ $2.36(A_{s}/b_{w}d_{v})^{0.23}$, $a$๋Š” ์ „๋‹จ๊ฒฝ๊ฐ„๋น„, $b_{w}$๋Š” ๋ณด ํญ, $d_{v}$๋Š” ์ƒ๋ถ€์™€ ํ•˜๋ถ€ ์ฃผ์ฒ ๊ทผ์˜ ์ค‘์‹ฌ๊ฐ„ ๊ฑฐ๋ฆฌ, $h$๋Š” ๋ณด ๋†’์ด, $d_{o}$๋Š” ์œ ๊ณต์˜ ์ง๊ฒฝ, $\rho_{w}$๋Š” ์œ ๊ณต ์ค‘์‹ฌ์—์„œ ์–‘ ์˜†์œผ๋กœ $d_{v}/2$๋ฒ”์œ„ ์•ˆ์— ์žˆ๋Š” ์œ ๊ณต๋ณด๊ฐ•๊ทผ์˜ ๋น„, $f_{yv}$๋Š” ์œ ๊ณต๋ณด๊ฐ•๊ทผ์˜ ํ•ญ๋ณต๊ฐ•๋„์ด๋‹ค.

Fig. 3๊ณผ Table 4์— ์‹คํ—˜๊ฒฐ๊ณผ์™€ ํ•ด์„๊ฒฐ๊ณผ๋ฅผ ๋น„๊ตํ•˜์—ฌ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. $V_{Man}$์˜ ์˜ˆ์ธก ์ „๋‹จ๊ฐ•๋„๋Š” ์‹คํ—˜๊ฒฐ๊ณผ์™€ ๋น„๊ตํ•˜์—ฌ ํ‰๊ท  1.05, ๋ณ€๋™๊ณ„์ˆ˜๋Š” 14%๋กœ ๋‚˜ํƒ€๋‚ฌ์œผ๋ฉฐ, $V_{AIJ}$๋Š” ์‹คํ—˜ ๊ฒฐ๊ณผ์˜ ๋น„๊ตํ•˜์—ฌ ํ‰๊ท  1.05, ๋ณ€๋™๊ณ„์ˆ˜๋Š” 10%๋กœ ๋‚˜ํƒ€๋‚˜ ์‹คํ—˜๊ฒฐ๊ณผ๋ฅผ ์ž˜ ์˜ˆ์ธกํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜ ๋‘ ์˜ˆ์ธก์‹ ๋ชจ๋‘ ์ œ์•ˆ ์œ ๊ณต๋ณด๊ฐ•๊ทผ์„ ๋ฐฐ๊ทผํ•œ ์‹คํ—˜์ฒด์˜ ์ „๋‹จ๊ฐ•๋„๋ฅผ ๊ณผ์†Œํ‰๊ฐ€ํ•˜๊ณ  ์žˆ์–ด ํ–ฅํ›„ ์ „๋‹จ๊ฐ•๋„ ์˜ˆ์ธก ์‹์— ์œ ๊ณต๋ณด๊ฐ•๊ทผ์˜ ํ˜•์ƒ์— ๋Œ€ํ•œ ์˜ํ–ฅ์„ ๋ฐ˜์˜ํ•ด์•ผ ํ•  ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

๋˜ํ•œ S ์‹คํ—˜์ฒด๋ฅผ ๊ธฐ์ค€์œผ๋กœ ํƒ€ ์‹คํ—˜์ฒด๋ฅผ ๋น„๊ตํ•˜์˜€์„ ๋•Œ, ์œ ๊ณต์„ ๋ณด๊ฐ•ํ•˜์ง€ ์•Š์€ NW ์‹คํ—˜์ฒด๋Š” 17% ๋‚ฎ์€ ์ „๋‹จ๊ฐ•๋„๋ฅผ ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ์ด๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋‹จ๋ฉด์†์‹ค์— ์˜ํ•œ ์ „๋‹จ๊ฐ•๋„์˜ ๊ฐ์†Œ๋กœ ํŒ๋‹จ๋œ๋‹ค. ์œ ๊ณต์„ ๋ณด๊ฐ•ํ•œ WB ์‹คํ—˜์ฒด๋Š” S ์‹คํ—˜์ฒด์™€ ๋น„๊ตํ•˜์—ฌ ์•ฝ 6%๋‚ฎ์€ ์ „๋‹จ๊ฐ•๋„๋ฅผ ๋‚˜ํƒ€๋‚ด์—ˆ์œผ๋ฉฐ, WS ์‹คํ—˜์ฒด๋Š” S ์‹คํ—˜์ฒด์— ๋น„ํ•˜์—ฌ ์ „๋‹จ๊ฐ•๋„๊ฐ€ 14% ์ฆ์ง„๋˜์—ˆ๋‹ค. ์ด๋ฅผ ํ† ๋Œ€๋กœ ์ œ์•ˆ ๋‚˜์„ ํ˜• ์œ ๊ณต๋ณด๊ฐ•๊ทผ์€ Bandํ˜• ์œ ๊ณต๋ณด๊ฐ•๊ทผ์— ๋น„ํ•˜์—ฌ ์œ ๊ณต์„ ํšจ์œจ์ ์œผ๋กœ ๋ณด๊ฐ•ํ•˜์˜€์Œ์„ ํ™•์ธํ•˜์˜€๋‹ค.

Table 4 Experimental results of tested specimens

Specimens

$V_{\exp}$

(kN)

$V_{Man}$

(kN)

$V_{AIJ}$

(kN)

$V_{\exp}/V_{S.\exp}$

$V_{\exp}/V_{Man}$

$V_{\exp}/V_{AIJ}$

S

183.2

215.3

164.2

1.00

0.85

1.12

NW

151.9

147.8

164.2

0.83

0.93

0.93

WB

173.5

165.7

178.5

0.94

0.97

0.97

WS

208.5

165.7

178.5

1.14

1.26

1.17

Ave.

1.05

1.05

C.O.V

14%

10%

$V_{\exp}$ : Test results, $V_{S.\exp}$ : Test result of S specimen, $V_{Man}$ :Analytical results of Mansur et al. ,$V_{AIJ}$ : Analytical results of AIJ

4.2 ์—๋„ˆ์ง€์†Œ์‚ฐ๋Šฅ๋ ฅ

RC ์œ ๊ณต๋ณด๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋‹จ๋ฉด์†์‹ค์ด ๋ฐœ์ƒํ•˜๋ฏ€๋กœ ์ง€์ง„๊ณผ ๊ฐ™์€ ๋ฐ˜๋ณตํ•˜์ค‘์— ์ €ํ•ญํ•˜๋ฉด์„œ ์—๋„ˆ์ง€๋ฅผ ์ถฉ๋ถ„ํžˆ ํก์ˆ˜ ํ•  ์ˆ˜ ์žˆ๋Š” ๋Šฅ๋ ฅ์„ ๊ฐ€์ ธ์•ผ ํ•œ๋‹ค. (Kim et al. 2019) ์‹คํ—˜์ฒด์˜ ์—๋„ˆ์ง€์†Œ์‚ฐ๋Šฅ๋ ฅ์„ ํ‰๊ฐ€ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ Fig. 3์˜ ์ „๋‹จ๋ ฅ-๋ถ€์žฌ๋ณ€ํ˜•๊ฐ ๊ณก์„ ์˜ ๋ชจ๋“  ๋ฉด์ ์„ ๋ˆ„์ ํ•˜์—ฌ ์‚ฐ์ •ํ•˜์˜€๋‹ค. ์ด ์—ฐ๊ตฌ์—์„œ๋Š” Fig. 8๊ณผ ๊ฐ™์ด ์—๋„ˆ์ง€์†Œ์‚ฐ๋ฉด์ ์„ ์ตœ๋Œ€ ์ „๋‹จ๋ ฅ ์ด์ „๊ณผ ์ดํ›„๋กœ ๋‚˜๋ˆ„์–ด, ์œ ๊ณต๋ณด๊ฐ•๊ทผ์ด ์ตœ๋Œ€ ์ „๋‹จ๋ ฅ ์ดํ›„ ์ง€์ง„ํ•˜์ค‘์— ์ €ํ•ญํ•˜๋Š” ๋Šฅ๋ ฅ์„ ํ‰๊ฐ€ํ•˜์˜€๋‹ค.

๋ชจ๋“  ์‹คํ—˜์ฒด์—์„œ ์ตœ๋Œ€ ์ „๋‹จ๋ ฅ ์ด์ „์— ์—๋„ˆ์ง€์†Œ์‚ฐ๋ฉด์ ์€ ์•ฝ 5kN โ€ค m ๋‚ด์™ธ๋กœ ์œ ์‚ฌํ•˜๊ฒŒ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ์ตœ๋Œ€ ์ „๋‹จ๋ ฅ ์ดํ›„์˜ ์—๋„ˆ์ง€์†Œ์‚ฐ๋ฉด์ ์€ WS ์‹คํ—˜์ฒด๊ฐ€ 334%, WB ์‹คํ—˜์ฒด๊ฐ€ 274% ์ฆ๊ฐ€ํ•˜์—ฌ ์ œ์•ˆ๋œ ๋‚˜์„ ํ˜• ์œ ๊ณต๋ณด๊ฐ•๊ทผ์ด Bandํ˜• ์œ ๊ณต๋ณด๊ฐ•๊ทผ์— ๋น„ํ•˜์—ฌ ํšจ๊ณผ์ ์œผ๋กœ ์ „๋‹จํ•˜์ค‘์— ์ €ํ•ญํ•˜์˜€์Œ์„ ํ™•์ธํ•˜์˜€๋‹ค. ๋”ฐ๋ผ์„œ ๋‚˜์„ ํ˜• ์œ ๊ณต๋ณด๊ฐ•๊ทผ์€ ์œ ๊ณต์„ ํšจ๊ณผ์ ์œผ๋กœ ๊ตฌ์†ํ•˜์—ฌ ์œ ๊ณต๋ณด์˜ ๋‚ด์ง„์„ฑ๋Šฅ์„ ํ™•๋ณด ํ•  ์ˆ˜ ์žˆ์„ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

Fig. 8 Energy dissipation of specimens
../../Resources/ksm/jksmi.2021.25.5.76/fig8.png

5. ๊ฒฐ ๋ก 

์ด ์—ฐ๊ตฌ์—์„œ๋Š” ์‹œ๊ณต์„ฑ๊ณผ ์•ˆ์ •์„ฑ์„ ํ™•๋ณดํ•œ ์‚ฌ๊ฐ๊ณผ ํŒ”๊ฐ์ด ํ˜ผ์šฉ๋œ ๋‚˜์„ ํ˜• ์œ ๊ณต๋ณด๊ฐ•๊ทผ์— ๋Œ€ํ•œ ์ „๋‹จ์„ฑ๋Šฅ์„ ํ‰๊ฐ€ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ

RC ์œ ๊ณต๋ณด๋ฅผ ๋Œ€์ƒ์œผ๋กœ ๋ฐ˜๋ณตํ•˜์ค‘ ๊ฐ€๋ ฅ ์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•˜์˜€์œผ๋ฉฐ, ๊ทธ ๊ฒฐ๊ณผ๋ฅผ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ์–ป์—ˆ๋‹ค.

1. ์ œ์•ˆ๋œ ๋‚˜์„ ํ˜•์˜ ์œ ๊ณต๋ณด๊ฐ•๊ทผ์„ ๋ฐฐ๊ทผํ•œ WS ์‹คํ—˜์ฒด๋Š” ์œ ๊ณต์ด ์—†๋Š” ์‹คํ—˜์ฒด์— ๋น„ํ•˜์—ฌ ์•ฝ 14% ์ „๋‹จ๊ฐ•๋„๊ฐ€ ์ฆ์ง„๋˜์—ˆ์œผ๋ฉฐ, ๊ธฐ์กด Bandํ˜• ์œ ๊ณต๋ณด๊ฐ•๊ทผ๊ณผ ๋น„๊ตํ•˜์˜€์„ ๋•Œ, ๋™๋“ฑ ์ด์ƒ์˜ ๊ตฌ์กฐ์„ฑ๋Šฅ์„ ํ™•๋ณดํ•œ ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค.

2. ์‹คํ—˜์ฒด์˜ ์ „๋‹จ๋ณด๊ฐ•๊ทผ ๋ฐ ์œ ๊ณต๋ณด๊ฐ•๊ทผ์— ๋ถ€์ฐฉ๋œ ๊ฒŒ์ด์ง€ ๋ณ€ํ˜•๋ฅ ์„ ๋น„๊ตํ•œ ๊ฒฐ๊ณผ ์ œ์•ˆ๋œ ๋‚˜์„ ํ˜• ์œ ๊ณต๋ณด๊ฐ•๊ทผ์˜ ์‚ฌ๊ฐํ˜• ๋ถ€๋ถ„์€ ์ „๋‹จ๋ณด๊ฐ•๊ทผ๊ณผ ๋”๋ถˆ์–ด ์ „๋‹จ์ €ํ•ญ์— ํšจ๊ณผ์ ์ž„์„ ํ™•์ธํ•˜์˜€์œผ๋ฉฐ, ํŒ”๊ฐ๋ถ€๋ถ„์€ ์œ ๊ณต์ฃผ์œ„์˜ ๊ท ์—ด ์ œ์–ด์— ํšจ๊ณผ์ ์ž„์„ ํ™•์ธํ•˜์˜€๋‹ค.

3. ์‹คํ—˜์ฒด์˜ ์ „๋‹จ๊ฐ•๋„๋ฅผ ๊ธฐ์กด RC ์œ ๊ณต๋ณด ์˜ˆ์ธก์‹์œผ๋กœ ๋น„๊ตํ•œ ๊ฒฐ๊ณผ, ์‹คํ—˜๊ฒฐ๊ณผ๋ฅผ ๋ชจ๋‘ ํ‰๊ท  1.05๋กœ ์ž˜ ์˜ˆ์ธกํ•˜์—ฌ ์‹คํ—˜์˜ ์œ ํšจ์„ฑ์ด ๊ฒ€์ฆ๋˜์—ˆ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜ ์ œ์•ˆ๋œ ๋‚˜์„ ํ˜• ์œ ๊ณต๋ณด๊ฐ•๊ทผ์ด ๋ฐฐ๊ทผ๋œ ์‹คํ—˜์ฒด์˜ ์ „๋‹จ๊ฐ•๋„๋ฅผ ๊ณผ์†Œํ‰๊ฐ€ํ•˜๊ณ  ์žˆ์–ด ํ–ฅํ›„ ์œ ๊ณต๋ณด ์ œ์•ˆ์‹์— ์œ ๊ณต๋ณด๊ฐ•๊ทผ์˜ ํ˜•์ƒ์— ๋Œ€ํ•œ ์˜ํ–ฅ์ด ๊ณ ๋ ค๋˜์–ด์•ผ ํ•  ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

4. ์‹คํ—˜์ฒด์˜ ์—๋„ˆ์ง€์†Œ์‚ฐ๋ฉด์ ์„ ์‚ฐ์ • ํ•œ ๊ฒฐ๊ณผ WS ์‹คํ—˜์ฒด๋Š” ์ตœ๋Œ€ ์ „๋‹จ๋ ฅ ์ด์ „์— ๋น„ํ•˜์—ฌ ์ตœ๋Œ€ ์ „๋‹จ๋ ฅ ์ดํ›„ ์—๋„ˆ์ง€์†Œ์‚ฐ๋ฉด์ ์ด 334% ์ฆ๊ฐ€ํ•˜์˜€๋‹ค. ๋”ฐ๋ผ์„œ ์ œ์•ˆ๋œ ๋‚˜์„ ํ˜• ์œ ๊ณต๋ณด๊ฐ•๊ทผ์€ ์œ ๊ณต์„ ํšจ๊ณผ์ ์œผ๋กœ ๊ตฌ์†ํ•˜์—ฌ ์ „๋‹จ๋ ฅ๊ณผ ๋‚ด์ง„์„ฑ๋Šฅ์„ ํ™•๋ณด ํ•œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

๊ฐ์‚ฌ์˜ ๊ธ€

์ด ์—ฐ๊ตฌ๋Š” ํ•œ๊ตญํ† ์ง€์ฃผํƒ๊ณต์‚ฌ(ํ† ์ง€์ฃผํƒ์—ฐ๊ตฌ์›)์—์„œ ์ง€์›ํ•œ โ€œLH RC ์œ ๊ณต๋ณด ๋ณด๊ฐ•์ƒ์„ธ ๊ฐœ๋ฐœ(2017)โ€ ๊ฒฐ๊ณผ์˜ ์ผ๋ถ€์ž…๋‹ˆ๋‹ค.

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