Transcript Impacts of application of IBS score regulations of CIDB on

Impacts of IBS score
regulations of CIDB on the
concrete volumes required for
building projects in Malaysia
Sami Mustafa M. E. Ahmed, Noor Amila Wan Abdullah Zawawi and Zulkipli B. Ghazali
Improvement of construction industry will contribute to the economy of Malaysia
because it is one of the five sectors used to calculate the national GDP.
This fact is encouraging the Construction Industry Development Board (CIDB) of
Malaysia to prepare many development plans like Roadmap 2003-2010, CIMP 20062015, and Roadmap 2011-2015.
Adoption of the Industrialized Building System (IBS) is the step stone for all these
plans. CIDB has created an indicator to assess the degree on industrialization for
applied building system; IBS score. Furthermore, CIDB has specified the minimum
values of this score for the building projects of government and private sector.
This paper discusses the effects of adjusting these values on the structural design of
an office building.
The CIDB method of calculating the IBS score, the moment distribution method of
structural analysis and BS8110 code of design will be used to analyze the selected
case study.
400
425
425
425
425
250
Beam1
C3
C2
C2
250
400
400
Beam2
Beam6
C2
C2
C2
C2
C2
400
C2
C2
D
C2
C3
450
C2
Beam4
C1
C1
C1
C1
C1
C1
C2
C1
Beam5
C1
C1
C
C2
Beam3
300
C2
C1
C1Beam4
C1
C1
C1
C1
C2
C1 Beam5 C1
C1
C2
B
450
C3
C2
C2
C2
C2
C2
C2
C2
C2
C2
C2
C3
A
Beam1
1
2
3
4
5
6
7
6: Construction joint
8
9
10
11
1. Column : the section of C1 is 25×50 cm and of C2 and C3 is 25×45cm. The
reinforcement for all types is 6φ16mm and St.R8@150mm. C2 and C3 are the same in
super structure level but their short columns have different sections.
45
45
50
25
25
25
2. Beams : sections of all beams are the same; 250×500 cm. The average reinforcement
for all beams is 8φ16mm (with consideration of cutoff points) and St.R8@150mm.
Section (a) is used at the middle and near support of beams equal or less than 3m.
Section (b) is used at the middle and (c) near the support for the other beams.
50
50
50
25
25
25
3. Slabs : the thickness of slab is 130mm. The reinforcement of top and bottom is
φ10@150 b/w.
(Columns) section of 300×300mm with reinforcement of 4φ20mm and St.R10@225
mm is found to be suitable for all columns after the structural analysis is revised.
(Slabs) For span of 5m length, a half precast slab of depth 7.5cm and to be topped up by
concrete of 12.5cm depth; the total depth will be 20cm. The main reinforcement for top
and bottom layers is φ10-100c/c, and the secondary for both layers is φ10-250c/c. The
width of each panel is either 600 or 1200 or 2400 mm.
(Beams)
For A and D from 1 to 6, a section of 300×500 with 7φ16 mm and St.R10@200 is
proposed.
For A and D from 6 to 11, a section of 300×550 with 6φ16 and St.R10@200 is sufficient.
For B and C from 1 to 6, a section of 350×500 with 8φ16 and St.R10@150 is considered.
For B and C from 6 to 11, a section of 350×500 with 7φ16 and St.R10@ 150 is suggested.
For external (1 & 11) and construction joint (6) beams, a section of 350×450 with 7φ160 and
St.R10@250 is proposed for the length from A to B and from C to D.
A section of 350×600 with 5φ12 & 2φ16 and St.R10@200 is considered for the length
from B to C.
For other beams in this direction from A to B and C to D, a section of 300×450 with 7φ16
and St.R10@250 is proposed, and
A section of 300×550 with 4φ12 & 2φ16 and St.R10@200 is found to be sufficient for the
length from B to C.
(Walls)
A block could be considered as an alternative for the brick and it will increase the IBS score.
IBS score reflects the degree of industrialization of composite building system.
IBS score = S1+S2+S3
Where:
S1= 50×Ʃ (Qs/Qst) ×Fs ;Fs factor of the structural system from Table 1
S2= 20×Ʃ (Ws/Wst)×Fw ; Fw is factor of the wall system from Table 2
S3 is factor for compatability with MS1064 and repeatioions (floor height, horizontal and
vertical).
Qs/Qst: the percentage of the construction area of which a particular system is used; out
of the total construction area of the building include roof
Qw/Qwt: the ratio of a particular wall system (external or internal) used out of the total wall
length of the building
Table 1 Factor of structural system (Fs)
Beam
system
Column
system
Floor system
precast
RFS*
Precast
Precast
1.0
0.7
0.6
1.0
Precast
RFS*
0.9
0.6
0.5
0.8
Precast
TFS*
0.8
0.5
0.4
0.7
RFS*
RFS*
0.7
0.5
0.3
0.6
TFS*
TFS*
0.6
0.3
0.0
0.0
RFS*
Precast
0.9
0.6
0.5
0.8
TFS*
Precast
0.8
0.5
0.4
0.7
There are four types of roof considered;
Prefab timber roof truss (PTR, Fs=1.0),
Prefab metal roof truss (PMR, Fs=1.0),
Pre-cut metal roof truss (PCM, Fs=0.5) and
Timber roof trusses (TMT, Fs=0.0).
TFS*
No-floor
Table 2 Factor of wall system (Fw)
No
1
Wall System
Precast concrete panel (PCP)
Fw
1.0
2
3
4
5
In-situ concrete with RFS*
In-situ concrete with TFS*
Block-work system (BWS)
Pre-assemble brick wall/ block wall (PBB)
0.5
0.0
0.5
1.0
6
Common brick wall (CBW)
0.0
Table 3 compatability with MS1064 and repeatioion (S3)
IBS score
Description
Unit
Percentage of usage
50% to
75% to
<75%
<=100%
Utilization of standard components based on MS 1064
1
Beams
Nos
2
4
2
Columns
Nos
2
4
3
Walls
m
2
4
4
Slabs
M2
2
4
5
Doors
Nos
2
4
6
Windows
Nos
2
4
Repetition of structural Layout
a) For building > 2 storeys
1
Floor to floor height Nos
1
2
2
Vertical repetition
Nos
1
2
3
Horizontal repetition Nos
1
2
b) For building 1 or 2 storeys
1
Horizontal repetition Nos
3
6
Switching from conventional columns which require 5.62 m3 of concrete per meter length
to equivalent precast columns of concrete volume of 4.32m3 per meter length will reduce
the volume of concrete by 1.305 m3 per meter length per each floor.
The concrete volume for conventional beams=
0.25×0.5× (4× (23+17) +12×12) =43 m3 per floor.
The concrete used for IBS beams=
23×2×(0.3×0.5+0.35×0.5)+17×2×(0.3×0.55+ 0.35×0.5)+
9×4×0.3×0.45+3×4×0.35×0.6+ 9×8×0.3×0.45+3×8×0.3×0.55 =47.57 m3 per floor.
The total increase in concrete volume due to switching from conventional to IBS beams is
13.71 m3.
The difference in slab depth between the two systems is 12.5 cm; the concrete volume of
the half precast slab is greater by 75m3 per floor. Additional 225m3 of concrete will be
required if all slabs will be switched from conventional to IBS.
Results analysis (1)
The drawings show that there is no slab in the ground floor; Fs equals 1 when pre-cast
columns and beams are used. The roof is to be casted by using TFS; Fs=0.
If a combination of TFS slab and pre-casted beam and columns for the roof and the first and
second floors, the Fs of table 1 will equal to 0.6. Hence the contribution of the structural
part will be 28.2 to the IBS score. This contribution plus the 28% of the other two tables
will yield 56.2%. This score satisfies the regulation of CIDB for private projects (not less
than 55%). The cost of this satisfaction on the bases of concrete volume equals to (13.7111.745) =2m3 which is approximately 8% of the total volume of the concrete.
The slab volumes remain at the lower value; 43m3 per floor. The factor of wastes for in-situ
casted concrete is estimated by 3% [6]. However, the same factor for precast concrete can
be considered 0% due to possibility of recycling. Hence the actual difference can be
forecasted by only 5%.
Results analysis (2)
Another scenario will be examined to satisfy the regulation regarding governmental
buildings, the slabs are casted by using RFS and columns and beam are pre-cast.
The contribution of table 1 equals 50× (1/4+0.7×2/4)=30%.
The total IBS score is 58% which is less than CIDB requirements. That means at least
one floor slab (including roof) must be precast concrete.
The contribution of the structural part for a case of (No floor, TFS, and precast roof
slab) equal 40% which less than 42% required to satisfy CIDB requirements.
Using RFS for floor slabs will improve this value to be 42.5% and the total IBS score of
70.2% which is accepted by CIDB for government building projects. Any other scenario
of improvement will propose using precast slab and this will increase the required
volume of concrete.
Conclusion and recommendations
The current regulations will encourage private sector to use precast column and beams
because a margin of 3% in concrete volume may be accepted as a cost for the higher
quality and time saving.
Designer and contractor of government buildings have to expect that most of their
future projects will include precast slab as well as precast columns and beams.
Using of Block work instead of brickwork will contribute by 10% to the IBS score.
It is recommended that more studies related to the use of some optimization techniques
like the Artificial Intelligence Algorithms (AIA) will lead to better understanding for
the impact of IBS score on the construction industry of Malaysia.