내진강구조물의 용접재료 시험 규정의 변화

2019. 08. 28.

발표자 : 서 승 은

1994년 LA Northridge 지진 피해 내역

* 리히터 스케일 7 의 강진.

* LA 지역 강구조물 빌딩의 조사된 부재 중 32 % 에서 균열발생.

* 조사된 부재의 15.7 % 는 기둥-보 접합용접에서 균열 발생.

* Flange 이음 용접균열 중,

70 % - beam bottom flange 이음 용접부.

30 % - beam top flange 이음 용접부.

1994년 미국 Northridge 대지진 이후, 미국 Codes & Standards의 변화

ASTM A992 - 2002, 화학성분 검사에 V, Cb, Cu, Ni, Cr, Mo, N 성분의 상한 값 추가.

Ys/Tu 의 상한 값, 0.85 를 신설 함.

AISC 360-2005, 2016, Specification for Structural Steel Buildings,

AISC N690-2006, 2016, Specification for Safety-Related Steel Structures for Nuclear Facilities.

AISC 341-2005, 2016, Seismic Provisions for Structural Steel Buildings,

AISC 358-2005, 2016, Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications,AISC 327-2005, 2018, Seismic Design Manual, 3rd edition.

ASCE-7-2005, 2010, Minimum Design Loads for Buildings and Other Structures.

AWS D1.1-2002, 2015, Structural Welding Code - Steel,

AWS D1.8-2005, 2016, Structural Welding Code - Seismic Supplement,

AISC 341-16, Seismic Provisions for Structural Steel Buildings

A3.1 Material Specifications : The structural steel used in the SFRS described in Chapters E, F, G

and H shall meet one of the following ASTM Specifications :

- 강재 사양 : A36, A53, A500 Gr. B, C, A501, A529, A572 Gr. 42, 50, 55, A588,

A913 Gr.50, 60, 65, A992, A1011 HSLA Gr.55, A1043,

A3.3 Heavy Sections :

- For structural steel in SFRS, hot rolled shapes with flange thickness equal to or greater than

1-1/2 in. shall have a minimum Charpy V-Notch (CVN) toughness of 20 ft-lb @ 21℃.

- Plates with thickness equal to or greater than 2 in. shall have a minimum Charpy V-Notch (CVN)

toughness of 20 ft-lb @ 21℃.

A3.4 Consumables for Welding :

4a. Seismic Force-Resisting System Welds : All welds in members and connections in the SFRS

shall be made with filler metals meeting the requirements specified in clauses 6.1, 6.2 and 6.3 of

Structural Welding Code - Seismic Supplement (AWS D1.8)

4b. Demand Critical Welds : Welds designated as demand critical shall be made with filler metals

meeting the requirements specified in AWS D1.8 clauses 6.1, 6.2 and 6.3.

User Note : AWS D1.8 requires that all seismic force-resisting system welds are to be made with

filler metals classified using AWS A5 standards that achieve the following mechanical properties :

Filler Metal Classification Properties for Seismic Force-Resisting System Welds

PropertyClassification

70 ksi 80 ksi 90 ksi min.

Yield Strength, ksi 58 min. 68 min. 78 min.

Tensile Strength, ksi 70 min. 80 min. 90 min.

Elongation, % 22 min. 19 min. 17 min.

CVN Toughness, ft-lb *a 20 min. @ -18℃ *a 25 min. @ -30℃

*a. Filler metals classified as meeting 20 ft-lbf min. at a temperature lower than -18℃ also meet this requirement.

Mechanical Properties for Demand Critical Welds

PropertyClassification

70 ksi 80 ksi 90 ksi min.

Yield Strength, ksi 58 min. 68 min. 78 min.

Tensile Strength, ksi 70 min. 80 min. 90 min.

Elongation, % 22 min. 19 min. 17 min.

CVN Toughness, ft-lb *b, c 40 min. @ 20℃ 40 min. @ 10℃

*b. For LAST of +10℃. For LAST less than +10℃, see AWS D1.8 clause 6.2.2.*c. Tests conducted in accordance with AWS D1.8 Annex A meeting 40 ft-lb min. at a temperature lower than +20℃ also meet this requirement.

주 : a. 표시된 용접이음. 기둥 약한 축 방향으로 용접 이음되는 부재는 SFRS 부재가 아니다.

1. D1.8-DC 표시는 내진용접으로 설계된 용접을 의미한다.

2. D1.8 표시는 D1.8 규정에 의해 규제되는 용접을 의미하나, 내진용접으로 분류되지 않는다.

3. D1.1 표시는 D1.1 규정만 적용되는 용접을 의미한다.

그림 C-1.1 – RBS/기둥의 강한 축 방향과 빔 용접이음의 예

(C-1.2.1의 2, 3, 4 항 참조)

주 : a. 표시된 용접이음. 기둥 약한 축 방향으로 용접 이음되는 부재는 SFRS 부재가 아니다.

1. D1.8-DC 표시는 내진용접으로 설계된 용접을 의미한다.

2. D1.8 표시는 D1.8 규정에 의해 규제되는 용접을 의미하나, 내진용접으로 분류되지 않는다.

3. D1.1 표시는 D1.1 규정만 적용되는 용접을 의미한다.

그림 C-1.2 – Eccentric Brace/Link/Column 용접이음의 예

(C-1.4.1의 2, 3, 4 항 참조)

주 : a. 표시된 용접이음. 기둥 약한 축 방향으로 용접 이음되는 부재는 SFRS 부재가 아니다.

1. D1.8-DC 표시는 내진용접으로 설계된 용접을 의미한다.

2. D1.8 표시는 D1.8 규정에 의해 규제되는 용접을 의미하나, 내진용접으로 분류되지 않는다.

3. D1.1 표시는 D1.1 규정만 적용되는 용접을 의미한다.

그림 C-1.3 – WUF-W/기둥 강한 축 방향 용접이음의 예

AWS D1.8, clause 6.2.2 Lowest Anticipated Service Temperature Applications.

For Demand Critical welds in applications where the Seismic Force Resisting System is subject to

service temperatures below +10℃ following completion of the structure, the minimum CVN of

40 ft-lbf as prescribed by 6.2.1 shall be provided at a test temperature not more than 10℃ above

the LAST for 70 ksi and 80 ksi filler metals and at LAST for 90 ksi filler metals.

AWS D1.8, clause 6.7 Maximum Interpass Temperature

6.7.1 Standard Maximum Interpass Temperature :

- The max. interpass temperature shall not exceed 300℃, unless an alternate value is qualified

in accordance with 6.7.2.

- The max. interpass temperature shall be measured at a distance of 1 in. to 3 in. from the joint.

a. 최소 예열온도와 최소 층간온도는 A 위치에서 측정. 용접 경계선에서 최소 3 in. [75 mm] 또는 강재 두께 t 중

큰 거리에서 측정.

주 : 최대 층간온도는 B 위치에서 측정. 용접 경계선에서 1 in. - 3 in. [25 mm - 75 mm] 범위에서 측정.

그림 C-6.1 - 예열온도와 층간 온도의 측정 위치 (C-6.7.1 참조)

AWS D1.8, clause 6.8 Heat Input

6.8.1 Heat Input Limits : Acceptable heat input limits on WPSs for Demand Critical welds shall

include the following, at the Contractor's option :

(1) The heat input range qualified by testing in accordance with Annex A.

(2) For carbon steel FCAW electrodes classified with the supplemental designator "-D," the heat

input range prescribed in clause 17 of AWS A5.20-2005.

(3) The heat input range prescribed in AWS A5.20-2005 Clause 17 for the following 70 ksi or 80

ksi tensile strength filler metals when optionally tested to the requirements of the AWS A5.20

"-D" supplemental designator :

(a) Low alloy FCAW electrodes, classified to AWS A5.29 ;

(b) Carbon steel GMAW composite (metal cored) electrodes, classified to AWS A5.18, and

low alloy GMAW composite (metal cored) electrodes, classified to AWS A5.28 ;

(c ) Carbon steel SAW electrode/flux combinations, classified to AWS A5.17, and low alloy

SAW electrode/flux combinations, classified to AWS A5.23 ;

(5) The heat input range prescribed in AWS A5.36-2012 Clause 16 for carbon and low alloy steel

FCAW and GMAW-metal core electrodes classified with the supplemental designator "-D" :

Annex A - WPS Heat Input Envelope Testing of Filler Metals for Demand Critical Welds.

Table A.1 Heat Input Envelope Testing - Heat Input, Preheat, and Interpass Temperatures.

Suggested Heat InputMax. Preheat Temperature

Max. Interpass Temperature

Low Heat Input Test 30 kJ/in. ± 20% 40 ℃ 120 ℃

Suggested Heat InputMin. Preheat

Temperature *aMin. Interpass Temperature *a

High Heat Input Test 80 kJ/in. ± 20% 120 ℃ 240 ℃

*a. For the high heat input test, the test plate shall be heated to the minimum preheat, and then welding shall

begin. Welding shall continue without substantial, deliberate interruption until the minimum interpass temperature

is obtained. After the test plate has been heated to the min. interpass temperature, all subsequent weld pass

shall be made at a temperature not less than the min. interpass temperature.

Should the test plate temperature fall below the min. interpass temperature for any reason, the test plate shall

be heated to a temperature not less than the min. interpass temperature before welding resumes. If the required

interpass temperature is not achieved prior to interruption of the welding operations, welding shall not resume

untill the test assembly has been heated to the prescribed min. interpass temperature.

Table A.2 All Weld Metal Mechanical Properties

Nominal Electrode Classification Strength 70 ksi 80 ksi 90 ksi min.

Yield Strength, ksi, 0.2% offset method 58 min. 68 min. 78 min.

Tensile Strength, ksi 70 min. 80 min. 90 min.

Elongation, %, measured in a 2 in. gage length

22 min. 19 min. 17 min.

CVN Toughness when LAST is greater than or equal to +10℃, ft-lbf

40 min. @ +21℃ 40 min. @ +10℃

CVN Toughness when LAST is less than +10℃, ft-lbf

40 min. @ LAST + 10℃ 40 min. @ LAST

A5. Welding of Test Plate :

A5.1 Preheat and Interpass temperature ; The test assembly shall be heated to the specified

preheat temperature, measured at a location 1 in. from the center of the groove at the location

shown in Fig. A.1. When max. interpass temperature prescribed in Table A.1 is exceeded, the test

plate shall be allowed to cool until the prescribed temperature is achieved.

A5.2 Heat Input ; The test plate shall be welded with a combination of variables that will

generate the desired high or low level of heat input. The test plate shall be completed such that

the computed heat input value for each weld pass does not vary from desired heat input level by

more than ±20%.

A5.3 Warpage ; A completed test plate that is warped more than 5° from flat shall be discarded.

Welded test assemblies shall not be straightened.

A5.4 Thermal Treatment ; No thermal treatment of weldment or test specimens is permitted,

except that machined tensile test specimens may be aged at 95℃ to 105℃ for up to 48 hours,

then cooled to room temperature, before testing.

A7. Acceptance Criteria :

A7.1 The all-weld-metal tensile test specimens shall meet strength and ductility requirements as

prescribed in Table A.2, as applicable.

A7.2 CVN Toughness Requirements. The lowest and highest values obtained from five test

specimens from each test plate shall be disregarded. Two of the remaining three values shall

equal or exceed the specified CVN toughness of 40 ft-lbf energy level at the testing temperature.

One of the three may be lower, but not lower than 30 ft-lbf.

The average of the three shall not be less than the requirements of Table A.2. (40 ft-lbf).

Root Opening (R) Groove Angle (α)

Option 1 1/2 in. [12 mm] 45°

Option 2 5/8 in. [16 mm] 20°

*a ; For SAW, test plate thickness may be 1 in. [25 mm].

Figure A.1 – Heat Input Envelope Test Plate (see A4, A5.1, A6)

AWS A5.20 Procedure Requirements for "-D" Optional Supplemental Designator

OptionalSupplementalDesignator

Procedure Heat Input(Fast or SlowCooling Rate)

PreheatTemperature

℃

InterpassTemperature

℃

Heat InputRequirement for

Any Single Pass *a

Required AverageHeat Input forAll Passes *a

D

low(fast cooling rate)

20℃ ± 15℃ 90℃ ± 15℃

For electrode diameters 〈 2.4 mm

33 kJ/in. 30 +2, -5 kJ/in.

For electrode diameters ≥ 2.4 mm

44 kJ/in. 40 +2, -5 kJ/in.

high(slow cooling rate)

150℃ ± 15℃ 260℃ ± 25℃ 75 kJ/in. 80 +5, -2 kJ/in.

*a. Does not apply to first layer. The first layer may have one or two passes.

AWS A5.36 Procedure Requirements for "-D" Optional Supplemental Designator

OptionalSupplementalDesignator

Procedure Heat Input(Fast or SlowCooling Rate)

PreheatTemperature

℃

InterpassTemperature

℃

Heat InputRequirement for

Any Single Pass *a

Required AverageHeat Input forAll Passes *a

D

low(fast cooling rate)

50℃ max. 120℃ max

For electrode diameters 〈 2.4 mm

38 kJ/in. max. 24 kJ/in. - 36 kJ/in.

For electrode diameters ≥ 2.4 mm

44 kJ/in. max. 35 kJ/in. - 42 kJ/in.

high(slow cooling rate)

120℃ min. 240℃ min. 65 kJ/in. min. 65 kJ/in. - 85 kJ/in.

*a. Does not apply to first layer. The first layer may have one or two passes.

* Heat Input Envelope Testing - Heat Input, Preheat, and Interpass Temperatures 비교표

Suggested Heat InputMax. Preheat Temperature

Max. Interpass Temperature

Low Heat

Input Test

D1.8, Annex A 30 kJ/in. ± 20% 40 ℃ 120 ℃

A5.20, "-D" 30 +2, -5 kJ/in. 20℃ ± 15℃ 90℃ ± 15℃

A5.36, "-D" 24 kJ/in. - 36 kJ/in. 50℃ max. 120℃ max

Suggested Heat InputMin. Preheat Temperature

Min. Interpass Temperature

High Heat

Input Test

D1.8, Annex A 80 kJ/in. ± 20% 120 ℃ 240 ℃

A5.20, "-D" 80 +5, -2 kJ/in. 150℃ ± 15℃ 260℃ ± 25℃

A5.36, "-D" 65 kJ/in. - 85 kJ/in. 120℃ min. 240℃ min.