International Journal of Civil Engineering and Technology (IJCIET)
Volume 10, Issue 04, April 2019, pp. 1770–1787, Article ID: IJCIET_10_04_186
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJCIET&VType=10&IType=4
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
© IAEME Publication Scopus Indexed
Seungho Cho
Research Professor, Institute of Construction Technology, Seoul National University of
Science and Technology, Seoul, 01811, Republic of Korea
Jongsik Lee
Professor, Department of Architectural Engineering, Songwon University, Gwangju, 61756,
Republic of Korea, Corresponding Author
ABSTRACT
Excessive arrangement of re-bars in the construction of high rise and long span structure is been considered one of the main reasons that deteriorate the quality of the structural member. To overcome this quality degradation problem that arise from the excessive arrangement of the re-bars, the strengths of the steel materials used in structural members has been increasing steadily in the recent years in consideration of stability and durability of buildings. As a consequence, while using of high-strengths re-bar in the construction of highrise and long-span structures is not only bring an ease to re-bar arrangement but also improve the constructability, reduce the construction periods and more simplified connection details can be obtained. The purpose of this research is to investigate the reduction ratio and applicability of the high-strength reinforcing bars (SD500, SD600) to three types of structural systems (rahmen structure, bearing wall system and flat plate system). The results of this study summaries that the reduction ratio of the high-strength bars on the horizontal members was higher than the vertical members in general. This is because, in the case of the vertical members, the reduction of the amount of the re-bar was governed by the minimum required ratio and spacing rather than the member strengths itself. Among the horizontal members, beam and foundation showed a similar decrease in each structure. On the other hand, in case of slabs, the reduction ratio of the re-bar was large according to the type of the structure. For the mixed-used residential complex building the decreasing ratio of the re-bar was significant when slabs strengths were large. But, in the case of apartment buildings re-bar ratio decreasing was highly governed by the minimum requirement and the spacing of the re-bar, while the amount of the rebar was rather increased due to the restriction of crack spacing in the case of office buildings. Based on the above findings, the use of high strengths reinforcing bars reduces the amount of reinforcement work and shortens the construction period due to the reduced reinforcing bars. Ultimately, the economizing effect is greater if considering the qualitative effects such as the improvement of the workability and the quality improvement of the structure due to the proper spacing of the re-bars. http://www.iaeme.com/IJCIET/index.asp 1770 editor@iaeme.com

Comparison of High Strength Re-Bar Usage by Type of Building Structure in Korea
Key words: High-strengths Rebar, Rebar Quantity Analysis, Rigid Frame System,
Bearing Wall System, Flat Plate System.
Cite this Article: Seungho Cho and Jongsik Lee, Comparison of High Strength Re-
Bar Usage by Type of Building Structure in Korea, International Journal of Civil
Engineering and Technology 10(4), 2019, pp. 1770–1787. http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=4
Excessive arrangement of re-bars in the construction of the high-rise and long span structure has been widely considered to deteriorating the quality of the structural members. As a matter of solution with the withstanding problem with excessive re-bar arrangements in the high-rise buildings to improve the safety and durability, a use of high strengths re-bar is recommending and increasing [1]. The high-strength reinforcing bars can be expected to reduce the sectional area of the members and reduce the amount of the reinforcing bars, and additionally allow a margin to the spacing of the re-bars in the structural members. Thus, the improvement of the workability can be expected by avoiding the excessive complicated arrangement of the re-bars at the construction connections [2]. The structural concrete design code specified that the strengths of the main reinforcement re-bar should not exceed 550MPa. And, the strengths of the shear reinforcement should not be exceeding 400MPa. In the local structural concrete design code, SD400 reinforcing bars are generally used. However, due to the increase of the high-rise and long-span structures, it became necessary to establish a standard for high strength steel reinforcement which is revised and cited in 2012. KCI (Korean Concrete
Institute) [3] has upgraded the re-bar strengths to SD600 which was SD550 before the revision been made in 2012 [4]. However, there are few cases where SD600 reinforcing bars are applied and SD500 reinforcing bars are being used in a limited manner. The study on the productivity and economical efficiency of the re-bar works in Korea has been carried out from various perspectives. Representative study is as follows. Kim, S.K., et al. (1991) developed an algorithm for reducing the loss rate of re-bar during site work processing [5]. Joo, J.K., et al.
(2003) proposed a work model for improving the productivity of re-bar works [6]. Kim, J.Y., et al. (2008) analyzed the actual application of the joining method of SD500 re-bar in construction site in Korea and developed an economic evaluation model to judge the economical efficiency of super high strength re-bar joints. In addition, the economic evaluation model was used to provide the criteria for the selection of the re-bar joining method and to provide the decision-making method for the joining method of the re-bar works
[7]. In this way, existing studies on re-bar work are mainly focused on minimizing the work processing loss, improving the re-bar work method and studying for the improvement of the re-bar work using IT technology [8]. In addition, there is a lack of data to quantitatively determine the increase or decrease of rebar quantity when using SD500 and SD600 rebar.
Therefore, in this study, SD500 and SD600 reinforced bars are applied to the already constructed rahmen structure, the bearing wall structure, and the flat plate structure for the purpose to analyze the increase or decrease of the reinforcing bars according to the strengths of the re-bars.
In order to understand the changes in the amount of reinforcing steel according to the use of high strength reinforcing bars, office buildings in the form of a rahmen structure which resists vertical and horizontal loads simultaneously, apartment buildings in the form of bearing wall http://www.iaeme.com/IJCIET/index.asp 1771 editor@iaeme.com

Seungho Cho and Jongsik Lee system, mixed use residential building complex in the form of flat plat system has been selected as typical reinforced concrete structures and analyzed the amount (in terms of pure quantity + development-Splice bar) of reinforcing steel increased or decreased due to the use of high strengths steel bars. SD400, SD600, and SD600 were used as the strength of the main re-bar and SD400 & SD500 were used for the strength of the shear reinforcement. When calculating the amount of re-bar for SD600, SD500 was used for the strength of the shear reinforcement and SD600 was used for the strength of the main re-bars. For the comparison of the amount of reinforcing steel by strengths, SD400, SD500 and SD600 were applied to all diameter bars, SD400 was applied to D10 and D13, SD400, SD500 and SD600 were applied to larger of diameter D16, SD500 was applied to D10 and D13 re-bars, SD500 and SD600 were applied to larger of diameter D16 for the purpose of analysis. The members analyzed in each building are shown in Table 1.
Items
Office Complex building
Apartment
Mixed use building
(Residentialcommercial)
Table 1 List of Members Analyzed
Slab Beam &
Girder
Column Wall Retaining wall
Footing
Main Shear Main Shear
Reba r
Reba r
Reba r
Reba r
Main Shear Main Shear
Reba r
Reba r
Reba r
Reba r
Main Shear Main Shear
Reba r
Reba r
Reba r
Reba r
〇 × 〇 〇 〇 〇 〇 〇 × × 〇 ×
〇
〇
×
×
〇
〇
〇
〇
×
〇
×
〇
〇
〇
〇
〇
〇
×
×
×
〇
〇
×
×
Table 2 shows the outlines of the structure applied to the analysis, and the structural plan vies is shown in Figure 1 ~ Figure 3. The horizontal loads applied to the structures are shown in
Table 3.
Purpose
Office Complex
Building
Number of stories
(ground / basement)
25/1
Apartment
Mixed use
Building
(Residentialcommercial)
25/1
43/1
Table 2 Structural Summary
Structural Type Footing type Concrete Compressive
Strength
Rigid
Frame
Bearing Wall Bearing Capacity of Soil (Mat
Footing) f ck
=24 MPa
(11F-RF: Vertical Member
B1-RF: Horizontal Member,
Footing) f ck
=27 MPa
(B1-10F: Vertical Member)
Flat plate
Bearing Capacity of Soil (Mat
Footing) f ck
=27~40 MPa
(Vertical Member) f ck
=27~30 MPa
(Horizontal Member, Footing)
Bearing Capacity of Soil (Mat
Footing) f ck
= 30~50 MPa
(Vertical Member) f ck
= 30~36 MPa
(Horizontal Member, Footing) http://www.iaeme.com/IJCIET/index.asp 1772 editor@iaeme.com

Comparison of High Strength Re-Bar Usage by Type of Building Structure in Korea
Purpose
Table 3 Horizontal Load
Seismic Load Wind Load
Site
Coeffi cient
Importance
Factor
Ground Response
Modification
Coefficient
Terrain
Category
Design Wind
Speed
Gust
Influence factor
A 1.5 Sc 5.0 B 30m/sec 2.2 Office Complex
Building
Apartment A
Mixed use Building
(Residentialcommercial)
A
1.5
1.5
Sc
Sc
4.5
5.0
B
B
30m/sec
30m/sec
2.2
2.2
(a) Typical FL Framing Plan (b) Basement FL Framing Plan
Figure 1.
Framing Plan of Office Complex Building http://www.iaeme.com/IJCIET/index.asp 1773 editor@iaeme.com

Seungho Cho and Jongsik Lee
(a) Typical FL Framing Plan (b) Basement FL Framing Plan
Figure 2.
Framing Plan of Apartment
(a) Typical FL Framing Plan
(b) Basement FL Framing Plan
Figure 3.
Framing Plan of Mixed use Building (Residential-commercial) http://www.iaeme.com/IJCIET/index.asp 1774 editor@iaeme.com

Comparison of High Strength Re-Bar Usage by Type of Building Structure in Korea
(1) Member Design: Structural Concrete Design Code (KCI 2012, Chapter 5) [3].
(2) Applied Load: Architectural Structural Design Code (KBC 2009, Seismic & Wind Load)
[9].
2.3.1. Analysis of Related Specifications on Main Re-bar
2.3.1.1. Slab
(1) Ratio of Shrinkage & Temperature Reinforcement
SD500 (20%↓), SD600(33.3%↓) decrease
Maximum spacing of re-bar : less than three times the slab thickness, or less than 450mm
(2) Spacing limit followed for Crack Control (1-way slab)
(3) Reinforcement due to vertical load
2.3.1.2. Wall: core portion of the wall
(1) Vertical re-bar: equal spacing is the primary principle (no end reinforcement re-bar).
(2) Vertical re-bar (less than D16): 0.12% (larger than D16) : 0.15%
Horizontal re-bar (less than D16): 0.2% (larger than D16): 0.25%
Spacing Limit

Vertical re-bar: Horizontal length of wall/5, or three times of wall thickness, or 450mm
Horizontal re-bar: Horizontal length of wall/3 or three times of the wall thickness, or 450mm
(3) Since the minimum re-bar limit for wall is not dependent on f y
the ratio of reinforcement is the same as for SD400 re-bar when using high-strength re-bar

The efficiency of using high strength steel bars decreases with the amount of minimum steel reinforcement.
2.3.1.3 Footings
(1) Design based on flexural member.
(2) All structures foundation type: bearing type mat foundation
2.3.1.4 Deflection
The deflection increases slightly when high strengths rebars are used due to the decrease of cracked second moment of inertia, although f y
has no direct effect on deflection. In this study, most of the members of each structure has satisfied the deflection limit and therefore, consideration on deflection has been omitted when calculating of the re-bar ratio/quantity. http://www.iaeme.com/IJCIET/index.asp 1775 editor@iaeme.com

Seungho Cho and Jongsik Lee
2.3.1.5 Crack
(1) Spacing of re-bar for crack control
( ) ( ) ( )
Here, : least distance from surface of reinforcement or pre-stressing steel to the tension face(mm), : stress of reinforcement closest to the tension face at service load(MPa) .
(2) In case of larger beam cross section, especially when the width of the beam is larger than usual, minimum spacing limit of the main rebar to prevent the crack with high strengths
SD500 and SD600 has no significance in terms of reducing the re-bar ratio. Therefore, smaller diameter of SD500 and SD600 has been considered in the analysis.
(3) Slab crack spacing limit:
SD400

235mm
[ ]
SD500

186mm
[ ]
SD600

146mm
[ ]
(4) Beam crack spacing limit:
SD400

170mm
[ ]
SD500

136mm
[ ]
SD600

71mm
[ ]
2.3.1.6. Development and Splice
(1) Development Lengths
① Development length of the deformed bar in compression:
√
② Development length of deformed bar in tension:
√ ( )
③ Development length of deformed bar in tension with standard hook: http://www.iaeme.com/IJCIET/index.asp 1776 editor@iaeme.com

Comparison of High Strength Re-Bar Usage by Type of Building Structure in Korea
√
Here, : nominal diameter of the re-bar, mm, : Factor used to modify development length based on reinforcement location, : Factor used to modify development length based on reinforcement coating, : Modification factor of lightweight concrete, : Factor used to modify development length based on reinforcement size, : Value regarding spacing between bars or cover thickness, : Transverse reinforcement index.
(2) Slab member (1-way slab)

Calculation based on beam.
(3) Footing member

Calculation based on beam.
2.3.2. Analysis of Related Specifications on Shear Reinforcement
The shear design of the wall is almost the same as that of a conventional beam shear design.
However, there is a difference between the horizontal and vertical reinforcement spacing and also the vertical shear reinforcement spacing is different when the shear span ratio is very small.
(1) Shear strengths should be calculated from the following 2 equations and the minimum value should be used in shear design.
√
[ √
( √ )
]
Here, : Factor for lightweight concrete : overall thickness or height of the member(mm), : effective depth of the member(mm), : Factored axial force normal to cross section
(considering effect of creep and shrinkage on tension) occurring simultaneously with Vu; to be taken as positive (+) for compression and negative (-) for tension, the wall(mm).
: Horizontal length of
(2) If , arrangement of the horizontal shear reinforcement should be calculated by
Here, spacing
: Area of shear reinforcement parallel to flexural tension reinforcements with
(mm
2
), : Spacing of shear reinforcements in wall, mm
(3) Minimum reinforcement and bar arrangements
If, is smaller than ⁄ : reinforcement shall be provided in accordance with
④ or reinforcement should be placed according to wall
① through
If,
④
is greater than ⁄ : reinforcement shall be provided in accordance with ① through
① Ratio of area of horizontal shear reinforcement to total vertical area of concrete , shall not be less than 0.0025
② Spacing of horizontal shear reinforcement, , shall not exceed the smallest of l w
/5 , 3h and
450 mm http://www.iaeme.com/IJCIET/index.asp 1777 editor@iaeme.com

Seungho Cho and Jongsik Lee
③ Ratio of area of vertical shear reinforcement to area of horizontal section, , shall not be less than the greater of the value from the following equation and 0.0025
( ) ( )
The value of need not be greater than the required area of horizontal shear reinforcement.
④ Spacing of vertical shear reinforcement, , shall not exceed the smallest of l w
/3 , 3h and
450mm.
In order to analyze the amount of rebar quantity or ratio by member and strengths, pure quantity of reinforcement & required rebar for development and splice length were calculated by the actual member strengths governed by SD400, SD500 and SD600. The re-bar considered in the analysis were ① Slab used D10 reinforcing bar for SD400, SD500, SD600,
② The main reinforcing bar for beam used D22 for SD400, D19 for SD500 and D16 for
SD600. Also, as a shear reinforcement D10 for SD400 and D13 for SD500 has been used. ③
The main re-bar used for column were D25 for SD400 and D22 for SD500 & SD600. Also, as a tie-hoop D10 for SD400 & SD500 has been used. ④ for wall D10, D13, D16, D19 were used as vertical reinforcement for all cases of SD400, SD500, SD600. The horizontal re-bar used were D10 for SD400 and D13 for SD500. ⑤ Finally, for footing D29 for SD400, D25
& D29 for SD500, D22 & D25 for SD600 were used. Also, the re-bar reduction ratio due to the member strengths and amount of reinforcing bar increased due to the required development & splice length were calculated to find out the optimum decreasing quantity of re-bar when they were used as high-strengths. Besides that, SD500 was applied to the strengths of shear reinforcement when calculating the amount of rebar for SD600. To analyze the total re-bar quantity by considering re-bar strengths ① When all reinforcing bars were applied with SD400, SD500 and SD600, respectively, ② D10 & D13 were applied to SD400 and those of D16 or above were applied to SD400, SD500 & SD600 respectively, ③ D10 &
D13 were applied to SD500 and D16 or above were applied to SD500 & SD600 and finally they were compared numerically.
Table 4 & Figure 4 are showing the quantity of re-bar for all the re-bar applied to SD400,
SD500 and SD600 respectively. Office building showing a reduction ratio of 12.4% for
SD500 & 15.4% for SD600 while comparing with standard SD400. On the other hand, apartment complex showing a ratio of 5.1% reduction for SD500 & 9.7% for SD600 compared to SD400. In addition, mixed use building (residential-commercial complex) amounted a reduction ratio of 11.7% for SD500 and 19.8% for SD600 compared to base rebar with SD400.
Table 5 & Figure 6 are showing the ratio of re-bar for D10 & D13 applied to SD400 and
D16 or above applied to SD400, SD500 & SD600 respectively. Office building showing a rebar reduction ratio of 13.2% for D10 & D13 to SD400 and D16 or above re-bar to SD500 while comparing with the standard SD400. Also, a reduction of 18.2% has been resulted for
D10 & D13 applied to SD400 and D16 or above to SD600. On the other hand, for the apartment building, a non-significant value of 1% reduction for D10 & D13 applied to SD400 and D16 or above applied to SD500 were calculated. Besides, another non-significant value of
1.9% reduction were calculated for D10 & D13 applied to SD400 and D16 or above to
SD600. In addition, mixed use building (residential-commercial complex) has shown a re-bar http://www.iaeme.com/IJCIET/index.asp 1778 editor@iaeme.com

Comparison of High Strength Re-Bar Usage by Type of Building Structure in Korea reduction of 8.1% for D10 & D13 applied to SD400 and D16 or above to SD500. A significant reduction of 14.1% has been calculated for D10 & D13 applied to SD400 and D16 or above to SD600 while comparing with the typically used SD400 re-bar.
Table 6 and Figure 6 showing a resulted output value of re-bar quantity or ratio for D10 &
D13 applied to SD500 and D16 or above to SD500 & SD600. Office building has shown a rebar reduction of 12.4% for SD500 while comparing with standard SD400. Also, for office building a significant reduction of 17.3% for D10 & D13 applied to SD500 and D16 or above to SD600 has been accounted. On the other hand, apartment building showing a less re-bar reduction ratio of only 5.1% for SD500 when comparing to base SD400. Additionally, a reduction of 5.9% for D10 & D13 applied to SD500 and D16 or above to SD600 has been observed in the apartment building. In addition, a re-bar reduction of 11.7% for SD500 compared to base SD400 has been observed for mixed use (residential-commercial) building.
Also, for mixed use building a large re-bar reduction of 17.6% has been shown for D10 &
D13 applied to SD500 and D16 or above to SD600.
Table 4 Total Rebar Quantity [unit : ton] (All Rebar is applied to SD400, SD500, SD600)
Items Rebar quantity Slab Column Wall Footing Total
SD400 Pure quantity 233.36
Beam /
Girder
654.09 381.21 192.15 284.36 Office
Complex
Building
Develop. / splice
Subtotal
10.26
243.62
(100%)
SD500 Pure quantity 250.35
Develop. / splice
13.60
Subtotal 263.95
(108.3%)
SD600 Pure quantity 291.35
Develop. / splice
18.77
Subtotal 310.12
(127.3%)
Apartment SD400 Pure quantity 139.83
Develop. / splice
Subtotal
6.77
146.60
(100%)
SD500 Pure quantity 122.05
Develop. / splice
Subtotal
7.18
129.23
(88.2%)
SD600 Pure quantity 122.05
Develop. / splice
8.57
172.88
826.97
(100%)
533.92
120.7
654.62
(79.2%)
464.38
98.10
562.48
(68.0%)
38.76
16.38
55.14
(100%)
37.70
20.50
58.20
(105.6%)
31.37
12.77
95.27
476.48
(100%)
346.59
89.15
435.74
(91.5%)
335.31
102.40
437.71
(91.9%)
13.31
205.46
(100%)
185.78
14.55
200.33
(97.5%)
182.48
15.13
197.61
(96.2%)
236.41
16.66
253.07
(100%)
229.03
18.52
247.55
(97.8%)
221.67
19.52
74.84
359.20
(100%)
232.12
63.29
294.41
(82.0%)
214.05
69.14
283.19
(78.8%)
24.85
5.55
30.40
(100%)
20.75
4.67
25.42
(83.6%)
17.88
4.36
1,745.17
(100%)
366.56
(100%)
2,111.73
(100%)
1,548.76
(88.8%)
301.29
(82.2%)
1,849.05
(87.6%)
1,487.57
(85.2%)
303.82
(82.8%)
1,786.64
(84.6%)
439.82
(100%)
45.36
(100%)
485.21
(100%)
409.53
(93.1%)
50.87
(112.2%)
460.4
(94.9%)
392.97
(89.3%)
45.22
(99.7%) http://www.iaeme.com/IJCIET/index.asp 1779 editor@iaeme.com

Seungho Cho and Jongsik Lee
Subtotal 130.62
(89.1%)
44.14
(80.1%)
SD400 Pure quantity 1,873.07 182.68 Residentialcommercial
Complex building
Develop. / splice
214.28
Subtotal 2,087.35
(100%)
269.33
452.01
(100%)
SD500 Pure quantity 1,551.04 164.75
852.75
386.32
1,239.06
(100%)
731.78
Develop. / splice
221.21
Subtotal 1,772.25
(84.9%)
279.85
444.60
(98.4%)
SD600 Pure quantity 1,330.20 151.38
344.79
1,076.57
(86.9%)
637.01
Develop. / splice
226.28
Subtotal 1,556.48
(74.6%)
275.99
427.37
(94.6%)
308.71
945.72
(76.3%)
241.19
(95.3%)
708.22
75.85
784.07
(100%)
668.84
78.55
747.39
(95.3%)
656.36
87.48
743.84
(94.9%)
22.24
(73.2%)
141.22
43.63
184.85
(100%)
112.40
37.88
150.28
(81.3%)
96.82
36.53
133.35
(72.1%)
438.19
(90.3%)
3,757.94
(100%)
989.41
(100%)
4,747.34
(100%)
3,228.81
(85.9%)
962.28
(97.3%)
4,191.09
(88.3%)
2,871.77
(79.4%)
934.99
(94.5%)
3,806.76
(80.2%)
Figure 4.
Comparison of rebar quantity according to the yield strength charge (All rebar is applied
SD400, SD500, SD600) http://www.iaeme.com/IJCIET/index.asp 1780 editor@iaeme.com

Comparison of High Strength Re-Bar Usage by Type of Building Structure in Korea
Table 5 Total rebar quantity [unit : ton] (D10 and D13 is applied SD400, D16 or above is applied
SD400, SD500, SD600)
Footing Total Items Rebar quantity Slab Beam / girder
Column Wall
233.36 654.09 381.21 192.15 Office
Complex building
SD400 Pure quantity
Develop. / splice
10.26 172.88 95.27 13.31
Subtotal 243.62
(100%)
826.97
(100%)
476.48
(100%)
205.46
(100%)
233.36 550.19 333.21 187.68 SD400
+
SD500
Pure quantity
Develop. / splice
10.26 120.70 89.15 13.17
Subtotal 243.62
(100%)
670.89
(81.1%)
422.36
(88.6%)
200.85
(97.8%)
233.36 480.65 321.93 185.15 SD400
+
SD600
Pure quantity
Develop. / splice
10.26 98.10 102.4 12.49 subtotal 243.62
(100%)
Apartment SD400 Pure quantity
139.83
Develop. / splice
6.77
578.75
(70.0%)
38.76
16.38
424.33
(89.1%)
197.64
(96.2%)
236.41
16.66
Subtotal 146.6
(100%)
139.83 SD400
+
SD500
Pure quantity
Develop. / splice
6.77
Subtotal 146.6
(100%)
139.83 SD400
+
SD600
Pure quantity
Develop. / splice
6.77
55.14
(100%)
38.76
20.5
59.26
(107.5%)
38.76
24.11
253.07
(100%)
230.17
18.76
248.93
(98.4%)
226.22
18.07
Subtotal 146.6
(100%)
62.87
(114.0%)
244.29
(96.5%)
Residentialcommercial
Complex
SD400 Pure quantity
1,873.07 182.68 852.75
Develop. / 214.28 269.33 386.32
708.22
75.85
284.36 1,745.17
(100%)
74.84 366.56
(100%)
359.20
(100%)
2,111.73
(100%)
232.12 1,536.56
(88.0%)
63.29 296.57
(80.9%)
294.41
(82.0%)
1,832.13
(86.8%)
214.05 1,435.14
(82.2%)
69.14 292.39
(79.8%)
283.19
(78.8%)
24.85
5.55
30.4
(100%)
20.75
4.67
25.42
(83.6%)
1,727.53
(81.8%)
439.85
(100%)
45.36
(100%)
485.21
(100%)
429.51
(97.6%)
50.7
(111.8%)
480.21
(99.0%)
17.88
4.36
422.69
(96.1%)
53.31
(117.5%)
22.24
(73.2%)
476.00
(98.1%)
141.22 3,757.94
(100%)
43.63 989.41 http://www.iaeme.com/IJCIET/index.asp 1781 editor@iaeme.com

Seungho Cho and Jongsik Lee building splice
Subtotal 2,087.35
(100%)
452.01
(100%)
1,239.06
(100%)
784.07
(100%)
1,716.7 169.96 723.35 684.53 SD400
+
SD500
Pure quantity
Develop. / splice
215.28 279.85 344.79 80.36
Subtotal 1,931.98
(92.6%)
449.81
(99.5%)
1,068.14
(86.2%)
764.36
(97.5%)
1,604.74 156.59 628.58 665.85 SD400
+
SD600
Pure quantity
Develop. / splice
214.37 275.99 308.71 89.43
Subtotal 1,819.11
(87.2%)
432.58
(95.7%)
937.29
(75.7%)
755.28
(96.3%)
184.85
(100%)
(100%)
4,747.34
(100%)
112.40 3,406.94
(90.7%)
37.88 958.16
(96.8%)
150.28
(81.3%)
96.82
4,364.57
(91.9%)
3,152.58
(83.9%)
36.53
133.35
(72.1%)
925.03
(93.5%)
4,077.61
(85.9%)
Figure 5.
Comparison of rebar quantity according to the yield strength charge (D10 and D13 is applied SD400, D16 or more is applied SD400, SD500, SD600) http://www.iaeme.com/IJCIET/index.asp 1782 editor@iaeme.com

Comparison of High Strength Re-Bar Usage by Type of Building Structure in Korea
Table 6 : Total rebar quantity [unit : ton] (D10 and D13 is applied SD500, D16 or more is applied SD500,
SD600)
Items Rebar quantity Slab Footing Total
233.36
Beam / girder
Column Wall
654.09 381.21 192.15 Office
Complex building
Residentialcommercial
Complex building
SD400 Pure quantity
Develop. / splice
SD500
SD500
+
Subtotal
Pure quantity
Develop. / splice
Subtotal 263.95
(108.3%)
Pure quantity
SD600
Develop. / splice
Apartment SD400
SD500
SD500
+
Subtotal
Pure quantity
Develop. / splice
Subtotal
Pure quantity
Develop. / splice
Subtotal 129.23
(88.2%) pure quantity
SD600 develop. / splice subtotal 129.23
SD400 Pure quantity
Develop. / splice
10.26
243.62
(100%)
250.35
13.60
250.35
13.60
263.95
(108.3%)
139.83
6.77
146.60
(100%)
122.05
7.18
122.05
7.18
(88.2%)
172.88
826.97
(100%)
98.10
16.38
55.14
(100%)
37.70
20.50
58.20
(105.6%)
37.7
24.67
62.37
(113.1%)
95.27
435.74
(91.5%)
102.40
13.31
533.92 346.59 185.78
120.7
654.62
(79.2%)
200.33
(97.5%)
464.38 335.31 183.25
562.48
(68.0%)
38.76
476.48
(100%)
89.15
437.71
(91.9%)
205.46
(100%)
14.55
14.85
198.06
(96.4%)
236.41
16.66
253.07
(100%)
229.03
18.52
247.55
(97.8%)
224.54
18.10
242.64
(95.9%)
1,873.07 182.68 852.75 708.22
214.28 269.33 386.32 75.85
284.36 1,745.17
(100%)
74.84 366.56
(100%)
359.20
(100%)
2,111.73
(100%)
232.12 1,548.76
(88.8%)
63.29 301.29
(82.2%)
294.41
(82.0%)
1,849.05
(87.6%)
214.05 1,447.34
(82.9%)
69.14 298.09
(81.3%)
283.19
(78.8%)
1,745.39
(82.7%)
24.85
5.55
30.40
(100%)
20.75
4.67
25.42
(83.6%)
17.88
439.85
(100%)
45.36
(100%)
485.21
(100%)
409.53
(93.1%)
50.87
(112.2%)
460.4
(94.9%)
402.17
(91.4%)
4.36
22.24
(73.2%)
54.31
(119.3%)
456.48
(94.1%)
141.22 3,757.94
(100%)
43.63 989.41 http://www.iaeme.com/IJCIET/index.asp 1783 editor@iaeme.com

Seungho Cho and Jongsik Lee
Subtotal 2,087.35
(100%)
SD500 Pure quantity
452.01
(100%)
1,239.06
(100%)
784.07
(100%)
1,551.04 164.75 731.78 668.84
Develop. / splice
221.21 279.85 344.79 77.55
Subtotal 1,772.25
(84.9%)
444.60
(98.4%)
1,076.57
(86.9%)
747.39
(95.3%)
1,439.08 151.38 637.01 660.63 SD500
+
Pure quantity
SD600
Develop. / splice
220.3 275.99 308.71 82.15
Subtotal
* SD400 is for a comparison
1,659.38
(79.5%)
427.37
(94.6%)
945.72
(76.3%)
745.78
(95.1%)
184.85
(100%)
(100%)
4,747.34
(100%)
112.40 3,228.81
(85.9%)
37.88 961.28
(97.2%)
150.28
(81.3%)
96.82
4,191.09
(88.3%)
36.53
133.35
(72.1%)
2,984.92
(79.4%)
923.68
(93.4%)
3,911.6
(82.4%)
Figure 6: Comparison of rebar quantity according to the yield strength charge (D10 and D13 is applied SD500,
D16 or more is applied SD500, SD600.)
In the present study an analytical study with different structural system (rahmen structure for office building, bearing wall type structure for apartment building, flat plate structural system for mixed use commercial-residential complex building) that resist vertical and horizontal http://www.iaeme.com/IJCIET/index.asp 1784 editor@iaeme.com

Comparison of High Strength Re-Bar Usage by Type of Building Structure in Korea load simultaneously has been done for the purpose to figure out the rebar quantity using the high strengths re-bar. Followings are the summarized results of this research study.
(1) In case of high strength steel SD500 & SD600, the strengths of reinforcing material are increased by 25% and 50% compared to that of SD400. However, when designing according to the contents of concrete structure design standard, the ratio of reduction of reinforcing bar by stress is 20% for SD500 and 33% for SD600. In the context of flexural member and 1-way structure, the ratio of re-bar reduction by minimum reinforcement ratio was 20%, and 30% respectively. On the other hand, an increase of 25% due to required splice bar and a 50% increase due to required development length was observed.
(2) In case of SD500 a reduction ratio of 12.4% for office building, 5.1% for apartment building and 11.7% for mixed used residential-commercial building has been observed when comparing to the SD400 re-bar. Also, in addition, in case of SD600 a reduction ratio of 15.4% for office building, 9.7% for apartment building and 19.8% for mixed used residentialcommercial building has been observed compared to the SD400 re-bar.
(3) The difference in the re-bar reduction in terms of structural system are as follows:
① in the case of the rahmen structural type office building, the ratio of re-bar of the vertical member to the horizontal member is about 35:65. Considering this practical phenomenon, a re-bar reduction of 18.0~20.8% with high strengths re-bar of SD500 for beam and footing has been observed. In addition to that, a range of reduction between 21.2~32.0% has been observed while using SD600. On the other hand, among the flexural member, slab has shown increasing of rebar ratio due to its minimum rebar spacing required for crack control. A slab member with SD500 has shown 8.3% increase of re-bar and 27.3% increase for SD600.
② The effect of reducing the quantity of rebar in the apartment was small due to the small reduction effect of wall that accounted for more than 50% of the total rebar quantity. In other words, the effect of decreasing the quantity of rebar on the wall is small because there is no effect of decreasing the volume on the horizontal wall, which accounts for about 50% of the total quantity of rebar of the wall. Also another reason why the rebar reduction ratio in the apartment was not significant was due to the minimum ratio and spacing required for the vertical re-bar above a certain floor.
③ in the mixed use residential-commercial complex, the slab, which is a horizontal member, accounts for about 40% of the total volume of the building. The vertical member is the same section from the lowest to the uppermost layer of the residential building, and the rebar quantity is determined by the minimum reinforcement ratio rather than the strengths of the member above a certain number of layers. The splice also has to be in all layers, and the effect of reducing the quantity of re-bar due to the use of high-strengths steel bars was small. On the other hand, reduction effect was larger than other members for footings.
(4) To compare the amount of re-bar by strength ① When all reinforcing bars were applied with SD600 ② When D10 & D13 were applied with SD400 and D16 or above were applied with SD500 ③ When D10 & D13 were applied with SD500 and D16 or above were applied to SD600. The calculated results were compared in terms of quantity.
① as a result of comparison with office buildings, the effect of reducing the quantity of rebar was more favorable in the order ③ , ② , ① . This is probably because the slab is a oneway system and the stress is small which is governed by the spacing of re-bar for the purpose to control crack that leads the increase of re-bar quantity.
② as a result of comparison with apartments, the effect of reducing the amount of re-bar was more favorable in the order of ① , ③ and ② . This is because the amount of steel reinforcement decreased by the slab was larger than the steel re-bar decreased by the wall. http://www.iaeme.com/IJCIET/index.asp 1785 editor@iaeme.com

Seungho Cho and Jongsik Lee
However, in case ① , the shear reinforcement is limited to SD500, so it is considered that the application of ③ is effective because of difficulties in field management when reinforcing bars of different strengths are used for the same diameter. Also as the wall stresses were relatively small for the flat-type apartments, the re-bar reduction ratio has shown a smaller value. Therefore, while the shape of the apartment is atypical and the higher the level, ③ will be more favorable to reduce the quantity of the steel re-bars. ③ as a result of comparison between the residential-commercial complex, the effect of decreasing the re-bar quantity was more favorable in order of ① , ③ , ② . However, the decrease in the amount of re-bar in ① is not much different from that in ③ . In addition, the shear reinforcement is limited to SD500 in ① which is considered to be effective.
(5) The decrease of the quantity of the steel bars was larger in horizontal member than that of the vertical members. In the case of vertical member, the re-bar reduction is highly governed by the minimum ratio and spacing of the re-bar require above a certain floor level. Among the horizontal members, beam and foundation showed a similar decrease in each structure, but slabs showed a large difference in the reduction rate of rebar depending on the type of structure. For the residential-commercial buildings, the decreasing rate was large when the slab resistance was large. In the case of apartment buildings, the reduction ratio was relatively small due to the minimum reinforcement and the minimum spacing. But, in the case of office buildings, the amount of rebar was rather increased due to the restriction of crack spacing.
(6) The use of high strength reinforcing bars reduces the amount of reinforcement work and shortens the construction period due to the reduced reinforcing bars. The economizing effect could be expected greater if considering the qualitative effects such as the improvement of the workability and the quality improvement of the structure due to securing the proper spacing.
This research was supported by Basic Science Research Program through the National
Research Foundation of Korea(NRF) funded by the Ministry of
Education(2017R1D1A3B03028597).
[1] Kim, J. Y. and Kim, D.W. A Study on the Economic Evaluation Model of Splice of
Reinforcement Bar(SD500), Journal of The Korean Institute of Building Construction,
8(1), 2008, pp. 71-76.
[2] Hong, G. H. Flexural Performance Evaluation of Reinforced Concrete Beams with High-
Strength Reinforcing Bars, Journal of the Architectural Institute of Korea, Structure &
Construction, 27(1), 2011, pp. 103-110.
[3] KCI, Structural Concrete Design Code and Commentary, Korea Concrete Institute, 2012.
[4] Moon, D. Y. Flexural Behavior of Concrete Beams Reinforced with High-Strength Steel
Bars, Journal of Korean Society of Disaster & Security, 13(6), 2013, pp. 107-113.
[5] Kim, S. K. and Kim, M. H. A Study on the Development of the Optimization Algorithm to
Minimize the Loss of Reinforcement Bars, Journal of the Architectural Institute of Korea,
Structure & Construction, 7(3), 1991, pp. 385-390.
[6] Joo, J. K., Kim, T. H. and Kim, S. K. A Work Model for Enhancing the Productivity of
Rebar Work, Journal of the Architectural Institute of Korea, Structure & Construction,
19(12), 2003, pp. 189-196.
[7] Kim, J. Y. and Kim, D. W. A Study on the Economic Evaluation Model of Splice of
Reinforcement Bar (SD500), Journal of the Korea Institute of Building Construction, 8(1),
2008, pp. 71-76. http://www.iaeme.com/IJCIET/index.asp 1786 editor@iaeme.com

Comparison of High Strength Re-Bar Usage by Type of Building Structure in Korea
[8] Kim, J. Y. and Kim, G. H. A Study on Economic Evaluation Method of Coupler Splice for
High Strength (SD500) Reinforcement, Korea Journal of Construction Engineering and
Management, 8( 2), 2007, pp. 136-145.
[9] AIK, Korean Building Code Structural 2009, Architectural Institute of Korea, 2010.
[10] ACI, ACI Detailing Manual 2004, Publication SP-66(04), American Concrete Institute,
2004.
[11] ACI Committee 318, Building Code Requirements for Structural Concrete (ACI 318-08) and Commentary (ACI 318R-08), American Concrete Institute, 2008.
[12] Joint ACI-ASCE Committee 352, Recommendations for Design of Beam-Column
Connections in Monolithic Reinforced Concrete Structures (ACI 352R-02), American
Concrete Institute, Farmington Hills, MI, p. 37, 2002.
[13] Chun, S. C., Lee, S. H. and Oh, B.H. Simplified Design Equation of Lap Splice Length in
Compression, International Journal of Concrete Structures and Materials, 4(1), 2010, pp.
63-68. http://www.iaeme.com/IJCIET/index.asp 1787 editor@iaeme.com