1 PROBLEMS AND COUNTERMEASURES OF THE QUALITY OF FABRICATED STEELWORK IN THAILAND BY TAWEEP CHAISOMPHOB 1 , WATCHARAPHON SAEGOW 2 AND EKARIN LUEANGVILAI 3 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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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: [email protected] 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).