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COMPARISON OF ESTIMATION OF REINFORCED CONCRETE
STRUCTURE WORKING COSTS BASED ON THE CONCEPT OF
COMPUTER-AIDED DESIGN (CAD) AND BUILDING INFORMATION
MODELING (BIM)
Intan Rahmani, Bambang Herumanta
Departemen Teknik Sipil,Sekolah Vokasi, Universitas Gadjah Mada, Yogyakarta, Indonesia
Email: Intanrahmani@mail.ugm.ac.id, Bambangherumanta@mail.ugm.ac.id
ARTICLE INFO
ABSTRACT
Date received: 04 July 2022
Revision date : 13 July 2022
Date received : 24 July 2022
The cost estimation process is an important aspect of project
management. In line with industry 4.0 development, a new
concept called building information modeling (BIM) was
introduced. However, in the Indonesia construction sector itself,
the application of the BIM concept is still not optimal. Many
construction actors still using conventional concept using
computer aided design (CAD) drawing in estimating project
cost. This case study aims to compare the project cost
estimation between conventional calculation based on CAD
drawing dan calculation with the BIM concept. This case study
was designed with quantitative approach where the unit price
analysis will refer to The PUPR regulation no 1 of 2022. From
the result, it was found that the project cost estimation using
conventional calculation based on CAD drawing was
Rp.39.249.184.000 meanwhile the project cost estimation based
on BIM concept was Rp.38.978.799.000 It can be concluded
that the calculation using the BIM concept result a lower cost
estimation of RP.270.385.000 or worth 0,69% compared to the
cost estimation based on conventional calculation.
Keywords: Cost estimation,
Computer Aided Design (CAD),
Building Information Modeling
(BIM), Conventional method,
regulation
This work is licensed under CC BY-SA 4.0
INTRODUCTION
The cost estimation process is one of the important aspects in project
management, because it is one part of the triple constraint. In estimating
implementation costs, the volume of work is the most influencing factor. In construction
projects in Indonesia, there are still many construction actors who use conventional
methods to calculate the volume of work. This conventional method is carried out with
the help of AutoCAD and Microsoft Excel which is guided by the Standard Method of
Measurement (SMM). However, the application of this conventional method is
considered less effective because it takes a long time to process and human errors
Comparison of Estimation of Reinforced Concrete Structure Working Costs Based on The
Concept of Computer-Aided Design (CAD) And Building Information Modeling (BIM)
Indonesian Journal of Multidisciplinary Science, Vol (10), July 2022
1238
often occur so that it will affect the level of accuracy in estimating the implementation
costs.
In line with the development of the Industry 4.0 era which also affects the
construction sector, new methods that are more effective and efficient in calculating the
volume of work and costs of a construction project have been started. This method is
called Building Information Modeling (BIM), which is a project simulation consisting of a
3D model of a project component that can be linked with all the required information
and is connected to project planning, construction or operations, and decommissioning
(Kymmell, 2008). The use of BIM in the Indonesian construction sector is also listed in
the PUPR Ministerial Regulation No. 22 of 2018 concerning the Construction of State
Buildings.
BIM has begun to be used in the Indonesian construction world, but its use is
still very low and limited. Most construction workers already know and recognize several
BIM software such as Autodesk Revit, ArchiCAD, Tekla, StaadPro, and so on. However,
the use of BIM software is generally only used at level one, namely for conceptual
design work with 3D modeling without any interdisciplinary data exchange (Pantiga &
Soekiman, 2021).
The use of BIM can make construction work more transparent and the
coordination process can run faster and easier. From the architect's and engineer's
perspective, the use of BIM can make it easier if there are changes to the work
components. Meanwhile, from the Owner's side, the use of BIM can help to make
decisions regarding the costs to be incurred from all work (Saputra, 2019).
Revit was introduced by Autodesk in 2002 after Autodesk acquired the Revit
program from a startup company. Revit is a separate platform from AutoCAD, with a
different basic code and file structure. Revit integrates architectural, structural, and MEP
work. Revit can be run on Windows OS and on Macs (Eastman, Eastman, Teicholz,
Sacks, & Liston, 2011).
The use of Autodesk Revit can prevent and minimize errors due to human errors
that usually occur when performing calculations using conventional methods using
AutoCAD and Ms Excel (Novita & Pangestuti, 2021).
Autodesk Revit can directly calculate the volume of work that has been modeled.
The results of the calculation of the volume of concrete from Revit have accurate
results on the structural components of columns and beams, because the volume of the
column is calculated based on elevation to elevation while the beam calculation is
calculated based on the clear span of the beam from the inside of the column. But for
the calculation of the slab structural components, Revit directly calculates the volume of
concrete according to the modeled slab without reducing the overlap of the concrete
volumes of columns and beams. The use of Revit to calculate the volume of work has a
Comparison of Estimation of Reinforced Concrete Structure Working Costs Based on The
Concept of Computer-Aided Design (CAD) And Building Information Modeling (BIM)
Indonesian Journal of Multidisciplinary Science, Vol (10), July 2022
1239
faster time, because the results of the volume calculation can be seen immediately after
modeling. This will also simplify calculations in the event of a design change, without
the need to calculate from scratch (Laorent, Nugraha, & Budiman, 2019).
The application of Building Information Modeling (BIM) in building construction
projects in Indonesia has not been widely carried out, this has prompted the author to
conduct research that discusses the comparison of cost estimates between conventional
methods and the concept of Building Information Modeling (BIM).
METHOD
Research Stages
The object of this research is the Gateway Park LRT City Apartment project
which is located on Jl. Kapin Raya, Pondok Gede, Bekasi City. This research consists of
several stages of analysis which are further elaborated in the research flow chart as
below:
Figure 1. Research Flowchart
Comparison of Estimation of Reinforced Concrete Structure Working Costs Based on The
Concept of Computer-Aided Design (CAD) And Building Information Modeling (BIM)
Indonesian Journal of Multidisciplinary Science, Vol (10), July 2022
1240
Research Design
This research was designed with a quantitative approach consisting of
conventional methods using computer-aided design (CAD)-based drawings and building
information modeling (BIM) concepts to compare cost estimates for reinforced concrete
structures.
In the BIM concept, the work volume will be generated automatically from the
material takeoff quantity after 3D modeling is completed. The calculation of the unit
price analysis (AHS) will refer to the Minister of Public Works and Public Housing
Regulation No. 1 of 2022 concerning Guidelines for Compiling an Estimated Cost of
Construction Works in the Public Works and Public Housing Sector. The price of
materials, labor, and tools will be adjusted to the project location.
Data Collection Methods
The data used in this study include 2 types of data, namely primary data and
secondary data. Primary data is data obtained directly from the main source consisting
of working drawings, technical specifications, work volume. While the secondary data
used consists of material unit price, labor unit price, tool unit price, work unit price
analysis coefficient.
RESULT AND DISCUSSION
Comparison of Work Volume of Reinforced Concrete Structures
The difference in the calculation of concrete volume between Conventional
concepts with Computer Aided Design (CAD) and Building Information Modeling (BIM)
concepts is caused by:
a. In calculating the volume of conventional concrete beams, floors with typical beam
plans, the volume of concrete is considered the same without taking into account any
reduction in the size of the column or corewall
b. In the calculation of the volume of conventional slab concrete, the slab area is
calculated from As to As, while in the calculation of the BIM concept, the slab is
modeled to cover the ends of the column/beam
c. Meanwhile, for the volume of concrete columns, elevator separator columns, and
corewalls, there is no difference in volume between conventional calculations and
calculations with BIM
The difference in the calculation of the reinforcement volume between the
Conventional concept with Computer Aided Design (CAD) and the Building Information
Modeling (BIM) concept is caused by:
Comparison of Estimation of Reinforced Concrete Structure Working Costs Based on The
Concept of Computer-Aided Design (CAD) And Building Information Modeling (BIM)
Indonesian Journal of Multidisciplinary Science, Vol (10), July 2022
1241
a. In calculating the volume of beam reinforcement, Revit will automatically adjust the
amount of stirrup reinforcement and the length of the main reinforcement if there is a
reduction in the column or corewall
b. There is a difference in the length of reinforcement between CAD drawings and Revit
3D modeling as can be seen in Figure 2 and Figure 3
Figure 2. Details of AutoCAD 2D Reinforcement
Figure 3. Details of Autodesk Revit 3D Reinforcement
Recapitulation of the volume of concrete and reinforcement from the results of
conventional calculations and the BIM concept can be seen in Table 1.
Table 1. Recapitulation of the Volume Comparison of Concrete and
Reinforcement
Based on Table 1, the volume of concrete work from conventional calculations is
9775.19 m3 while the results of Autodesk Revit 2022 calculations are 9868.91 m3 so
that there is a difference of 93.72 m3 or 0.959% where the Autodesk Revit 2022
calculation results in a higher volume of concrete work. large compared to the results of
conventional calculations. The volume of reinforcement work from the results of
conventional calculations and Autodesk Revit 2022 is 1,649,853 kg and 1,615,230 kg so
that there is a difference of 34,623 kg or 2,099% where the calculation with Autodesk
Comparison of Estimation of Reinforced Concrete Structure Working Costs Based on The
Concept of Computer-Aided Design (CAD) And Building Information Modeling (BIM)
Indonesian Journal of Multidisciplinary Science, Vol (10), July 2022
1242
Revit 2022 results in a smaller volume of reinforcement work compared to the
conventional calculation results.
Comparison of Cost Estimation of Reinforced Concrete Structures
The preparation of the Work Unit Price Analysis (AHSP) refers to the PUPR
Ministerial Regulation No. 1 of 2022 concerning Guidelines for Compiling an Estimated
Construction Work Cost for the Public Works and Public Housing Sector. Prices for
materials, labor, and tools are adjusted for the Jakarta location. The recapitulation of
the unit price of work can be seen in Table 2.
Table 2. Recapitulation of Work Unit
Work
Unit Price (Rp)
1 m3 Concrete Casting fc'
45 Mpa Using Ready Mixed
and Concrete Pump
1,934,600
1 m3 Concrete fc' 35 Mpa
Using Ready Mixed and
Concrete Pump
1,844,800
1 m3 Concrete fc' 30 Mpa
Using Ready Mixed and
Concrete Pumps
1,799,900
Reinforcement Plates for
Steel and Concrete Semi-
Mechanical Method
12,608
of columns, beams, ring
balks, and sloof
12,916
The calculation of the estimated cost is done by multiplying the volume of work by the
unit price of work in Table 2. The estimation of costs for conventional and BIM concept
work can be seen in Table 3.
Tabel 1. Estimasi Biaya
Total Harga
Konvensional
BIM
Comparison of Estimation of Reinforced Concrete Structure Working Costs Based on The
Concept of Computer-Aided Design (CAD) And Building Information Modeling (BIM)
Indonesian Journal of Multidisciplinary Science, Vol (10), July 2022
1243
2,644,522,421
2,615,255,882
2,644,522,421
2,615,250,347
2,570,855,446
2,542,130,042
2,534,346,460
2,504,436,374
2,504,005,815
2,480,220,041
2,508,119,500
2,480,712,603
2,438,626,423
2,426,108,802
2,438,626,423
2,426,582,916
2,292,488,332
2,278,601,685
2,291,213,027
2,279,671,669
2,278,273,634
2,263,688,253
2,231,175,950
2,211,949,589
2,194,845,650
2,173,986,729
2,191,864,010
2,174,591,823
2,154,712,244
2,137,231,011
2,086,558,561
2,076,273,804
1,244,427,022
1,292,107,104
39,249,183,339
38,978,798,672
39,249,184,000
38,978,799,000
The difference or difference in cost estimates between conventional calculations
and BIM calculations is Rp. 270,385,000 where the estimated costs with BIM
calculations produce a smaller cost estimate of 0.69% compared to conventional cost
estimates. This cost estimation difference occurs due to differences in the results of
calculating the volume of concrete and reinforcement work between conventional
methods based on CAD drawings and BIM methods using Autodesk Revit.
CONCLUSION
Based on the results of the analysis and discussion, the following conclusions can
be drawn:
1. The estimated cost of implementation with conventional calculations is Rp.
39,249,184,000 (thirty-nine billion two hundred forty-nine million one hundred and
eighty-four thousand rupiah)
2. Estimated cost implementation with the calculation of the BIM concept is Rp.
38,978,799,000 (thirty eight billion nine hundred seventy eight million seven hundred
ninety nine thousand rupiah)
3. The difference between the estimated implementation costs with conventional
calculations and the calculation of the BIM concept is Rp. 270,385 .000 (two hundred
Comparison of Estimation of Reinforced Concrete Structure Working Costs Based on The
Concept of Computer-Aided Design (CAD) And Building Information Modeling (BIM)
Indonesian Journal of Multidisciplinary Science, Vol (10), July 2022
1244
seventy million three hundred eighty five thousand rupiah), where the estimated cost
with the BIM concept is 0.69% lower than the estimated cost of conventional
calculations.
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