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PROBLEMS AND COUNTERMEASURES OF THE QUALITY OF

FABRICATED STEELWORK IN THAILAND

BY

TAWEEP CHAISOMPHOB1, WATCHARAPHON SAEGOW2

AND EKARIN LUEANGVILAI3

SYNOPSIS:

Nowadays, pre-engineered steel buildings (PEB), which are imported from foreign countries,

become popular for the construction of factories and warehouses in Thailand. In most of the

PEB projects in Thailand, the fabricated parts imported from foreign countries, have not been

properly examined by the concerned Thai authorities or the third party. This study collects

information about imported PEB steel structures. The method consists of site visiting and

interviews of personnel in charge of design and construction of the imported PEB. In order to

perform a comparative study on the quality of fabricated structures, international inspection

standards for fabrication are adopted in this study. From the inspection results at five imported

PEB construction sites, some defects in the steel structures are found as follows: 1) welding

defects such as undercut, overlap and porosity, 2) defects in anchor bolt such as remaining

screw length less than position of nut, 3) defects in the fabricated part, due to error of

fabrication process such as distortion of area surrounding the holes and insufficient of coating

thickness. The proposed countermeasures for quality control of fabricated steel structures were

divided into two schemes as follows: (a) fabricator accreditation to classify the fabricator

according to their capabilities. (b) checklist for inspection the quality of fabricated steel

structures. These two schemes are the missions of Thailand Structural Steel Society (TSSS).

Keywords: Pre-Engineered steel Buildings (PEB), Steel Structures, Inspection and Defects

1 President, Thailand Structural Steel Society and Advisor, Metal Tube and Cold-forming

Steel Association, Sirindhorn International Institute of Technology, Thammasat University,

Pathum Thani, Thailand, E-mail: secretary.tsss@gmail.com 2 Graduate Student, Sirindhorn International Institute of Technology, Thammasat University,

Pathum Thani, Thailand

3 Structural Engineer, Expressway Authority of Thailand, Bangkok, Thailand

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1. Introduction

The fabricated steelwork has sparked concern over the quality of fabricated steelwork

in Thailand when sourced from foreign countries. Therefore, these companies may not be able

to fully control the quality of fabricated steelwork. This is true especially for the case of

imported steelwork. This situation has placed greater responsibility on Construction site

(typically Professional Engineers), as the technical expert relied upon by Building Control

Authorities and the third party to ensure steelwork for Thailand building projects meets the

requirements of the international standard such as welding standard or fabrication standard.

The Propose of this study is to help Authorities and the third party better understand their role.

In Fig.1, PEB as the latest trend in building construction are increasingly confirmed their

outstanding advantages in industrial and commercial projects such as factory, warehouse, cold

storage, showroom, office, supermarket, school, stadium. because of cost saving, fast erection,

perfect quality control and high durability.

In Fig.2, PEB are built by connecting three members to each other as follows:

1. Primary members (columns, rafters and bracing)

2. Secondary members (Z or C purlins and girts)

3. Roof and wall sheeting

Fig.1 Three-dimension view of PEB

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Fig.2 Components of PEB

The fabricated parts are done at the factory and then brought to the site in a knock down

system. These components are connected by bolted at the site of construction. As shown in

Fig.3. The fabricated steel parts are the components of rafters and columns which will be ready

to be imported to Thailand.

(a) Rafter Components (b) Column Components

Fig.3 Components of rafters and columns imported to Thailand

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2. Data Collection

In this study, we have visited four companies to collect data on PEB such as design,

fabrication, erection and also interviewed engineers who are responsible for design and

construction. These four companies are the international companies in which their fabrication

factories are located outside Thailand in this paper, they are named as company A, B, C and D.

After visiting the headquarter (Company A) of the foreign country and the branch of

other three companies (Company B, C, D) in Thailand.

For the design method, most of the companies use the Allowable Strength Design

(ASD) and loading conditions as follows:

1. Dead load consists of the weight of all material of construction incorporated into the

building.

2. Roof Live Loads, for built-up frames minimum uniformly distributed live load on

roof is 0.57kN/m2 according to MBMA [6].

3. Collateral loads are included in roof live loads that arise due to sprinklers, ducts,

lighting fixtures and ceilings.

4. Wind loads are governed by wind speed, roof slope, eave height and open wall

conditions of the building. PEB are designed for a minimum wind speed of a 110

km/hr.

2.1 Fabrication Process

The fabrication process of the components of PEB is shown in Fig.4. The first step

begins with preparation of raw material. Second step is cutting/drilling and punching by plasma

and flame method. Third step is tacking web and flange built up into H-Beam, after that auto

welding by a submerged arc welding process (SAW). Fourth step is fitting and final welding

by a gas metal arc welding process (GMAW) or Flux core arc welding process (FCAW). The

last step is blasting two surface profiles including SA2.0 and SA2.5 according to ISO 8501-1

[5], and coating with a quick drying primer.

Fig.4 Fabrication process of PEB

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2.2 Material Specification

From the results of collecting data at 4 companies, it was found that the international

standards such as USA and Japan are used for material selection of the frame structure as shown

in Table 1.

Table 1 Comparisons of material specifications

Material Company A Company B Company C Company D

1.Built-up member ASTM A572

Gr 50

ASTM A572

Gr 50 Q 345 (GB)

Q 345 (GB) or

ASTM A 572

Gr.50

2.X-Bracing rod ASTM A 36 JIS G3101 or

SS400 ASTM A36

JIS SS 400 or

ASTM A36

3.Anchor bolt ASTM A 36

(Gr. 4.6)

TCVN 1916-

1995

ASTM A36

(Gr. 4.6)

ASTM A36

(Gr. 4.6)

4.High strength bolt ASTM A 325

(Gr 8.8)

ASTM A490

(Gr 10.9)

ASTM A325

(Gr8.8)

ASTM A325

(Gr8.8)

3. Result and Discussion

3.1 Description of Visited Site

Five construction sites were visited: two construction sites in a foreign country (site

no.1, 2) and three construction sites in Thailand (site no. 3, 4, 5). The dimension and some

description of the visited sites are illustrated is Fig.5 and Table 2

Fig.5 Frame cross section

X

Y

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Table 2. Description of visited sites

Site

No. Type Description of Site

Dimension of PEB

X (m) Y (m)

1 Garment

Factory

Fabricated by company A Erected

in the foreign country 60 10

2 Warehouse Fabricated by company A Erected

in the foreign country 60 6

3 Warehouse Fabricated by company B Erected

in Thailand 60 14.4

4 Warehouse Fabricated by company C Erected

in Thailand 48 8

5 Warehouse Fabricated by company D Erected

in Thailand 30 9.8

3.2 Results of Personnel Interview

From results of interviewing the personnel responsible for construction site, the

inspection routine, for the fabricated parts imported from foreign countries, were divided into

two processes as follows:

For the fabrication process,

• Check welding defects

• Check sweep/camber/waviness of built-up member

• Check dimensions and locations of fit up components

• Check primer paint which has been tough up

• Check NDFT

For the erection process,

• Check all bracing in position and tightened

• Check anchor bolt and high strength bolts tightened to correct tension

• Check dimensions and locations of column and rafter

• Check misdrilled screws

• Check all roof penetrations for weather tightness

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3.3 Inspection Result

In the inspection and evaluation process, we adopted the inspection criteria based on

international standards such as welding standard and fabrication standard. Site inspection was

mostly carried out by using visual inspection (VT), bolt inspection, steel thickness and nominal

dry film thickness (NDFT), since this method does not affect on the surface of steel structures.

Interview the personnel at the site construction was done to obtain information about the

indirect and root causes of the problems and damage of steel structures imported from foreign

countries.

3.3.1 Welding Defects

From the inspection results, it was found that some steel structures have defects of

welding on the steel surface, especially incomplete fusion, spatter, porosity, and undercut,

which exceed the standard limit in DPT 1561 [1] which is equivalent to AWS D1.1/D1.1M [2].

The evaluation of the weld defects was classified as unacceptable. Examples of the welds that

were unacceptable for some sites are shown in Fig.6.

(a) Welding defects on rafter at site no. 4

(b) Welding defects on column at site no. 5

Fig.6 Welding defects found on column and rafter

undercut

imperfect

welding

porosity

spatter

incomplete

fusion

undercut

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3.3.2. Defects of Anchor Bolt

From the inspection results, it was found that there are the defects of anchor bolt at

some sites. It was evaluated that the bolt was unacceptable because the length of bolt beyond

nuts is too short, i.e. less than 3 threads, according to JASS 6 [3] as shown in Fig.7 (a). In

addition, single nut is used as shown in Fig.7 (b), but according to MBMA [6], double nut must

be adopted.

(a) Defect of anchor bolts (b) Defect of anchor bolt (single nut)

Fig.7 Defects of anchor bolt at site no. 2

3.3.3 Defects of Fabrication Process

The Fabricator’s design primary responsibility is to ensured that structural steelwork is

manufactured according to the requirements. However, from inspection results, it was found

that there are defects on steel structures at sites no.4. It was evaluated that the built-up section

was not good because fabrication process is not up to the fabrication standard according to

MBMA [6] For example, the distortion of area in steel structure as shown in Fig.8 (a) were the

bolting area is not properly formed, and the hole on steel surface as shown in Fig.8 (b).

(a) Poorly fabricated steelwork (b) Poorly fabricated steelwork

Fig.8 Defects of fabrication process at site no. 4

single nut remaining screw length less than

position of nut.

Poorly fabricated steelwork

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3.3.4 Steel Thickness and Coating Thickness

In this study, we measured steel thickness and coating thickness of a steel parts (column,

rafter) as shown in Fig.9. The inspection of steel thickness was done by using ultrasonic pulse-

echo testing (UT) according to ASTM E797 [7], and the inspection of coating thickness was

made by using NDFT according to ISO 19840 [4]. The results of steel thickness measurement

are compared with the thickness specified in the as-built drawing (Table 3), and the coating

thickness measurement results are compared with the required thickness (Table 4). From Table

3, it can be seen that the measured steel thickness is more than the thickness specified in the

drawing, and the results are acceptable. From Table 4, it was found that the coating thickness

at some sites are less than the required thickness. Therefore, the quality control on coating

process must be seriously performed at the fabrication factory.

Fig.9 Components of built-up steel section

Flange

Web

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Table 3 Result of Steel Thickness

Inspected part

Thick.

Specied

in the

drawing

(mm)

Measured Value (mm)

Average

(mm)

S.D.

(mm)

Difference

(%) Evaluation

x1 x2 x3 x4 x5

Site no.1

Column Web 6 5.98 5.9 6.5 6.2 6.7 6.7 0.13 1% OK

Flange 8 8.07 8.2 8.6 7.9 8.5 8.2 0.29 3% OK

Site no.2

Column Web 6 6 5.5 6 6.2 6.1 6.2 0.26 0% OK

Flange 8 8.6 8.2 8.7 8.9 8.2 8.5 0.32 7% OK

Site no.3

Column Web 10 11.7 11.6 11.4 11.2 12.6 11.6 0.34 16% OK

Flange 10 11.5 10.6 11.1 11.9 10.7 11.2 0.54 12% OK

Site no.4

Column Web 8 8.7 8.7 8.9 8.9 8.7 8.8 0.1 10% OK

Flange 10 10.8 10.5 10.5 10.6 11.5 10.8 0.4 8% OK

Rafter Web 8 9.8 9.1 9.3 9.4 9.2 9.2 0.16 15% OK

Flange 10 10.9 10.8 10.7 10.9 10.6 10.8 0.12 8% OK

Site no.5

Column Web 5 5.3 5.7 5.9 5.3 5.6 5.6 0.24 11% OK

Flange 10 10.3 11.7 10.9 10.4 10.9 10.8 0.57 8% OK

Rafter Web 5 5.7 5.7 5.9 5.5 6 5.7 0.27 14% OK

Flange 10 10.8 10.5 10.3 10.6 10.6 10.7 0.18 6% OK

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Table 4 Result of Coating Thickness

Inspected part

Thick.

specied

in the

drawing

(µm)

Measured Value (µm)

Average

(µm)

S.D.

(µm)

Difference

(%) Evaluation

x1 x2 x3 x4 x5

Site no.1

Column Web

80 87 88.4 90.2 85.7 100 90.3 5.7 13% OK

Flange 80.5 82 94.5 81.7 92.4 86.2 6.7 8% OK

Site no.2

Column Web

80 100.4 107.2 102.8 83 82 95.1 11.8 19% OK

Flange 102 89.2 102.2 91.4 95.4 96 6 20% OK

Site no.3

Column Web

660 935 883 1052 1224 979 1014.6 132 54% OK

Flange 510 666 636 640 603 611 60.7 -7% NG

Site no.4

Column Web

660

256.3 249.8 258.8 253.1 215.5 246.7 17.8 -63% NG

Flange 179.9 222.1 209.1 193.8 188.2 198.6 16.9 -70% NG

Rafter Web 263.4 236.6 230.3 239.3 218.5 237.6 16.5 -64% NG

Flange 202.4 185 230.8 218.8 210.7 209.5 17.3 -68% NG

Site no.5

Column Web

80

105 115.6 102.4 110 111.2 108.8 5.2 36% OK

Flange 91.1 101.1 100 95.4 96.3 96.8 4 21% OK

Rafter Web 80.2 85.4 90.5 90 88.5 86.9 4.3 9% OK

Flange 98.4 95.2 94.6 96.3 98.2 96.5 1.8 21% OK

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4. Conclusions

4.1 Conclusions

In this study, the defect or damage on the fabricated steelwork in Thailand. It was found

that, most of fabrication defects are found in welded. They are undercut, overlap and porosity.

Distortions due to fabrication process are also observed. Thickness of coating is insufficient.

Assembly defects are found such as improper bolts installation, caused from poor workmanship

in the construction process. These defects can be fixed directly by redoing the construction

process, such as re-weld, re-coat, and re-install. The defect from poorly coated steel could cause

a severe damage to the structure, corrosion damage on the steel surface. In order to guarantee

the safety and serviceability of steel structures in Thailand, the Thai authorities or the third

party should strictly check the quality of steel structures.

Finally, the implementation of a fabricator accreditation in conjunction with checklist

for inspection the quality of fabricated steel structures. These two countermeasures are essential

to ensure high quality and establish standard for steel construction in Thailand. Internationally

there has been various structural steel quality initiatives to reduce the compliance risk to all

parties associated with fabrication of structural steel. In addition, this paper aim of empowering

Construction Reviewers to more competent and fulfill their role in controlling quality, for

projects featuring structural steel.

4.2 Suggestion of Solutions

While many of the same issues apply to ensure and to demonstrate compliance of

structural steelwork from foreign countries, there are additional challenges that need to be

addressed, when structural steelwork is sourced internationally. A consideration often

associated with imported fabricated steelwork is the use of alternative steel of any standards

not recognized in the international level. The proposed countermeasures for quality control of

fabricated steel structures were divided into two schemes as follows:

1.) Fabricator Accreditation

2.) Checklist for Inspection the Quality of Fabricated Steel Structures.

4.2.1 Fabricators Accreditation

The structural steel fabricators accreditation scheme is also important. The Structural

Steel Fabricators Accreditation Scheme by Singapore Structural Steel Society (SSSS) [8] will

classify the fabricator according to their capability, financial status, skilled technical, human

resource and the standard of the fabrication plants. There will be three categories of fabricators

accreditation as follows:

1. Category S1: Large Company

2. Category S2: Medium Company

3. Category S3: Small Company

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4.2.2 Checklist for Inspection the Quality of Fabricated Steel Structures

Thailand needs to have a system in place to ensure quality of steel structures for inspect

the steel structure practically by using this system. So, we should have proposed guideline to

provides official with a tool to ensure quality and public safety involved steel structures.

The checklist for steelwork [9] will include six main items as follows:

1. Material selection

2. Fabrication

3. Welding

4. Welding Inspection

5. Coating

6. Erection

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References

[1] Thai Department of Public Works and Town & Country Planning, DPT 1561-51 to DPT

1565-51 Structural Steel welding inspection standard using Non-destructive testing, 2008.

[2] American Welding Society, AWS D1.1/D1.1M Structural Welding Code – Steel., United

State of America, Construction and Building Materials, 2010.

[3] Architectural Institute of Japan Japanese Architectural Standard Specification JASS 6

Structural Steelwork Specification for Building Construction, 1993.

[4] International Standard Organization. ISO 19840 Paints and varnishes -- Corrosion

protection of steel structures by protective paint systems -- Measurement of, and acceptance

criteria for, the thickness of dry films on rough surfaces, 2012.

[5] International Standard Organization. ISO 8501-1 – Rust grades and preparation of uncoated

steel substrates and steel substrates after overall removal of previous coatings, 2007.

[6] MBMA: Metal Building Manufacturers Association, Metal Building Systems Manual,

2016.

[7] ASTM E797 Standard Practice for Measuring Thickness by Manual Ultrasonic Pulse-Echo

Contact Method, 2015.

[8] Structural Steel Fabricators Accreditation Scheme. Singapore Structural Steel Society

(SSSS), Singapore, 13 Mar, 2016.

[9] Fussell, A., Cowie, K., Hicks S., Karpenko, M., Ensuring Compliance of Structural

Steelwork - Regardless of Origin. Steel Advisor QLT1001, Steel Construction New Zealand,

2016.

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