PROBLEMS AND COUNTERMEASURES

OF THE QUALITY OF FABRICATED

STEELWORK IN THAILAND

By

Assoc. Prof. Taweep Chaisomphob

Sirindhorn International Institute of Technology

IntroductionThe 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.

Propose of this study

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.

The propose of this study as following:

• To establish the construction checklist for inspecting the quality of

fabricated steel structures

• To inspect and evaluate PEB imported from foreign country

• To help Authorities and the third party better understand their role

Three-dimension view of PEB

Components of PEBConnecting by bolting at

construction sites

Data CollectionWe 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.

• Company A is visited and collected data in foreign country

• Company B, C, D are visited and collected data in the branch

of Thailand

DesignFor the design method, most of the companies use the

Allowable Strength Design (ASD) and loading conditions as

follows:

• Dead load consists of the weight of all material of

construction incorporated into the building.

• Roof Live Loads, for built-up frames minimum uniformly

distributed live load on roof is 0.57kN/m2 according to

MBMA.

• Collateral loads are included in roof live loads that arise

due to sprinklers, ducts, lighting fixtures and ceilings

• 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/h.

FabricationFlow chart of fabrication process

These components are connected by bolted at the site of

construction. As shown in figure below. The fabricated steel parts

are the components of rafters and columns which will be ready to

be imported to Thailand.

Rafter Components Column Components

Material SpecificationFrom 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.

Material Company A Company B Company C Company D

1.Built-up

member

ASTM A572 Gr

50

ASTM A572

Gr 50Q 345 (GB)

Q 345 (GB) or

ASTM A 572

Gr.50

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

SS400ASTM A36

JIS SS 400 or

ASTM A36

3.Anchor boltASTM 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)

Result and DiscussionFive 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 show in

below.

Description of visited sites

Site No. Type Description of SiteDimension of PEB

X (m) Y (m)

1 Garment FactoryFabricated by company A

Erected in the foreign country 60 10

2 Warehouse Fabricated by company A

Erected in the foreign country 60 6

3 WarehouseFabricated by company B

Erected in Thailand 60 14.4

4 WarehouseFabricated by company C

Erected in Thailand 48 8

5 WarehouseFabricated by company D

Erected in Thailand 30 9.8

Picture during construction Site 1 to 5

13

Site 1

14

Overview of construction site

Site 1

15

Rafter componentAnchor bolt using double nut and 1 washer

Site 2

16Overview of construction site

Site 2

17Rafter and column connected by bolt

Anchor Bolts 3 nuts & 2 Washers

Site 3

18Overview of construction site

Site 3

19

Lifting rafter for installation Erection rafter and purlin

Site 4

20Overview of construction site

Site 4

21Rafter and column connected by bolt

Component of rafter, purlin and roof after installation

Site 5

22Overview of construction site

Site 5

23

2 Rafter and 1 column connecting by boltAnchor bolt using double nut and 1 washer

Results of personnel interviewFor 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

Results of personnel interview

For the erection process

• Check all bracing in position and tightened

• Check bolts tightened to correct tension

• Check dimensions and locations of column and rafter

• Check misdrilled screws

• Check all roof penetrations for weather tightness

Inspection resultIn 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

• Nominal Dry Film Thickness (NDFT)

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.

Welding Defects

• Some steel structures have defects of welding on the steel surface, especially

incomplete fusion, spatter, porosity, and undercut.

• The evaluation of the weld defects was classified as unacceptable by

according to DPT 1561 (Department of Public Works and Town & Country

Planning, Thailand)or equivalent to AWS D1.1/D1.1M .

Examples of the welding defects

Incomplete fusion

Undercut

Spatter

28

Porosity

Imperfect weld

Examples of the welding defects

29

Examples of the defects of anchor bolt• Defects of anchor bolt at some sites, which was evaluated that the bolt

were unacceptable are shown below

Remaining screw length less than

position of nut

Single nut30

Defects of Fabrication ProcessThe 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.

Defects of Fabrication ProcessIt was evaluated that the built-up section was not

good because fabrication process is not up to the

fabrication standard according to MBMA For example, the

distortion of area in steel structure as shown in below.

Steel thickness• The results of steel thickness measurement are compared with

the thickness specified in the as-built drawing.

• The measured steel thickness is more than the thickness

specified in the drawing, and the results are acceptable.

Ultrasonic Thickness Gauge33

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

ColumnWeb 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

ColumnWeb 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

ColumnWeb 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

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.4

ColumnWeb 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

RafterWeb 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

ColumnWeb 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

RafterWeb 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

Coating thickness• Coating thickness at some sites is less than the required

thickness.

• Quality control on coating process must be properly

implemented at the fabrication factory.

Coating Thickness Gauge

36

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

ColumnWeb

8087 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

ColumnWeb

80100.4 107.2 102.8 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

ColumnWeb

660935 883 1052 1224 979 1014.6 132 54% OK

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

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.4

ColumnWeb

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

RafterWeb 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

ColumnWeb

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

RafterWeb 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

Conclusions and Recommandations• Four PEB international companies which are the manufacturers of

fabricated steel structures imported to Thailand.

• Five construction sites, including two sites in a foreign country and three

sites in Thailand, were visited.

• The inspections of each site are welding defect, steel thickness and coating

thickness.

• Some sites, there are some defects in the fabricated parts before and after

the parts are delivered to Thailand. for example, welding defects were

unacceptable mainly because of undercut and porosity.

• Erection of the steel structure at the site is not good, and hence there is

some defects in anchor bolts. Coating thickness was unacceptable because

of less values than the required thickness.39

Suggestion of SolutionsThe 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.

Fabricators AccreditationThe structural steel fabricators accreditation scheme is also important.

The Structural Steel Fabricators Accreditation Scheme by Singapore

Structural Steel Society (SSSS) 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

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 will include six main items as

follows: Material selection, Fabrication, Welding, Welding

Inspection, Coating and Erection

THANK YOU

FOR

YOUR ATTENTION43