Tripoli1, Mubarak2, Nurisra3, Mahmuddin4
1,2,3,4
University of Syiah Kuala, Jl. Syekh Abdurrauf 10, Banda Aceh, Indonesia E-mail: [email protected]
Abstract. This paper discusses the implementation of Indonesian National Standard (SNI) 7394: 2008 on procedures for calculating the unit price of concrete work for the construction of building and housing. The standard provides a number of reinforced concrete constructions unit price (UP) analysis by specified the total number of reinforcing uses. Related to reinforced concrete beam work (Analysis No. 6.31), the reinforcement requirement is stated at 200 kg/m3 of concrete. Once the implementation considers various earthquake zoning, the question will arise about the extent to which the standard is feasible to apply. Therefore, this research aimed to analyse the possibility of UP standard implementation in accordance to certain earthquake zonation. This research is focused on the construction of reinforced concrete beam for buildings with function as educational, residential and office buildings. The data used are sourced from 21 buildings in two zones in Aceh Province, covering Zone 10 and Zone 15 based on earthquake map of SNI 1726: 2012. The analysis results indicate that the UP standard for reinforced concrete beam cannot be applied to all zoning. The UP standard is only possible on buildings constructed in Zone 10 or zonation with seismic spectral response 0.6-0.7g or lower.
1. Introduction
Cost estimation plays an important role in the implementation of construction projects. The activities covering the process of estimates or judgments, based on certain facts and assumptions, of the final cost of a project, product, or process [1]. The estimation is the process of preparing one of the most comprehensive documents in a project, which affects the overall project team and project related activities. The inaccuracy of the estimation will bring disadvantage to the parties involved. The cost estimation process usually begins with analysing the unit price (UP) of work. A number of standards are set by the government in accordance with the scope of work and type of construction [2]. In relation to reinforced concrete work, the unit price could be analysed by referring to SNI 7394: 2008 on the procedure for calculating the price of concrete work units for the construction of buildings and houses [3].
The building is a construction formed by several main components, namely structural components, non-structural components, and utility components [2]. Structural components are components that have the largest cost portion of a building. These components include construction of foundations,
columns, beams, floor plates, and roof structures. This construction can be made using concrete, steel, wood, or composite materials such as reinforced concrete. Associated with the beam, this construction is one of the structural components designed to hold and move the transverse load across space to the supporting element [4]. A beam is a part of a structure used as a floor slab holder and a column top binder. Reinforced concrete composite material commonly used for beam construction. This construction formed by two main components, namely concrete and steel for reinforcement.
A number of factors determine the planning of the reinforced concrete beam structure dimensions.
One important factor is related to earthquake loading. The planning standard used is SNI 1726: 2012 on earthquake resistance planning procedures for buildings and non-buildings [5]. This SNI describes the potential difference of earthquake risk in accordance to the earthquake-zoning map. This map shows the position of the entire zones of Indonesia based on different spectral response value of earthquake. The zoning indicated by difference colours which informed upper and lower values of spectral response limits in gravity (g). Spectral value is used as a reference to design the earthquake load in the planning of a building in Indonesia.
A number of studies related to the cost estimation and unit price of works in buildings in Aceh Province have been done. Generally, the research develops estimation model at the conceptual stage (pre-construction design) [6, 7, 8]. Associated with earthquake risk factors, research has been undertaken for modelling rehabilitation costs [9]. However, there is no special research discussing the issues related to the application of UP for the construction of reinforced concrete in a number of earthquake zoning. The existence of this study will provide answers to the extent to which SNI 7394:
2008 can be applied in relation to the zoning and function of certain buildings.
2. Methods
2.1. Location and object of research
Survey on this research was conducted on building projects built in Aceh Province. The research object's review is focused on building with simple and non-simple classification as defined in Ministry of Public Work Regulation No. 45/PRT/M/2007 [2]. The object of the building to be studied can be classified according to the function and location based on the earthquake zonation map of the year SNI 1726: 2012. The criteria location and object of research as follows:
• The object locations of the research used based on SNI 1726: 2012 earthquake zonation maps, namely Zone 10 (region with spectral response of 0.6-0.7 g) and Zone 15 (region with spectral response of 1.2-1.5 g ), as shown in Figure 1.
• The project used minimum of two storey buildings.
• The functions of the buildings studied are for offices (OFC), residence (RES), and education (EDU).
2.2. Data collection
The required data are as follows:
• Document of contract of building project constructed from 2012 until 2015, containing quantity and bill of quantity data, and drawings (site plan, plan, and building view).
• Indonesia earthquake zonation map SNI 1726: 2012.
2.3. Data processing and analysis
The process of data processing and analysis through the stages as follows:
• The data grouping is based on zoning division, covering 10 earthquake zones and seismic zone 15. Data of each earthquake zone are reclassified based on office function (OFC), residence (RES), and education (EDU).
• The requirement analysis of reinforcement material is done by calculating the need of reinforcement of the beam done based on the dimension of cross section, the type of
reinforcement (thread and plain), the reinforcement function (reinforcement, the main reinforcement and the intermediate reinforcement) and the reinforcement diameter used.
• The ratio of reinforcement use per m3 of concrete by comparing the total weight of the beam reinforcement volume with the volume of concrete in each building.
• Analysis of deviation of analysis result with AUP SNI standard.
Statistical analysis is used to determine the mean value (x) and standard deviation (σ ) of the results of the analysis of the ratios of each building (x) for the total number of buildings (n), with the following equation:
n x=
∑
x(1)
( )
1 n
x
x 2
−
=
∑
− σ(2)
Figure 1. Indonesia Earthquake Zoning Map of SNI 1726: 2012 3. Results and discussions
3.1. Description of the buildings
The building that is used for data is 21 buildings consist of 2 and 3 storey buildings, which are distributed at 28.6% in Zone 10, and 71.4% in Zone 15. Based on building function, the study object consists of 28.6% Office buildings and education, and the remaining 42.8% are residential buildings.
The analysis of beam constructions were only focussed on floor beam (primary beams and secondary beams), and excludes tie beam and roof beam. The full description is shown in Table 1.
3.2. The actual ratios of reinforcement use per 1 m3 of reinforced concrete beam
The actual beam reinforcement ratio is analysed based on the ratio of reinforcement use (in kg units) to the use of concrete (in units of m3). The average reinforcement ratios for Zone 10 were 194.41 kg/
m3 increased by 6.4% to 206.92 kg/m3 for Zone 15. This increase was consistent with the increase of
---- Observation Zones
the load due to the earthquake corresponding to the response value of the spectra in the two zones. The calculation results of beam reinforcement ratios can be seen in Table 2.
Tabel 1. Description of the buildings
Zone Building function Number of building Office Education Residence
10 2 2 2 6 (28.6%)
15 4 4 7 15 (71.4%)
Total 6 (28.6%) 6 (28.6%) 9 (42.8%) 21 (100.0%) Table 2. The actual reinforcement ratio of reinforced concrete beam
No Zone Name
3.3. Comparison of the actual ratios and SNI
SNI 7394: 2008 provides that for reinforced concrete beam work used reinforcement of 200 kg / m3 of concrete. The results of the analysis at Zone 10 show an average deviation of 5.59 kg or 2.80% below the value of the needs of the SNI reinforcement. This condition explains that this standard can still be applied to this zone. However, when viewed from the standard deviation values that arise, the use of this standard still needs to consider the possibility of deviation. The indication of such deviation is indicated by one building data with a positive deviation value greater than the standard deviation value. In Zone 15, the general deviation value indicates that the actual reinforcement ratio is greater than the value of the SNI bone needs ratio. The average deviation was 6.92 kg / m3 with a standard deviation of 15.67 kg / m3. This condition indicates that the UP application on SNI for this zone is not feasible because it has the potential to cause cost estimation with the amount below the actual requirement. The complete results of the ratio of actual reinforcement to the UP standard are shown in Table 3.
Table 3. The actual reinforcement comparing to SNI No Zone Name of building Building function
Reinforcement ratio Deviation Standard 10.52 5.26 7 15 EDU-3 Education 181.37 200.00 -18.63 -9.31 Deviation Standard 15.67 7.83 3.4. Comparison of Reinforcement Ratio Based on Building Function
The reinforcement ratio analysis needs to be done to examine more specifically the application of SNI related to the three building functions in each zone. Potential standard UP applications are possible for buildings with residential functions (Zone 10) and educational functions (Zones 10 and Zone 15).
With respect to the function of office buildings throughout the zone, the mean deviation indicates an actual ratio value greater than the UP standard. Similarly, it is seen in the residence function in Zone 15. The positive deviation value explains that in this function and zone, the use of HSB can meet the needs of reinforcement that should be required. In other words, the required reinforced material requirement index is still below the actual needs. When associated with the estimated cost value, the estimated amount generated by UP usage is potentially insufficient for the completion of construction.
An illustration of the comparison of the rebar ratio based on the building function is shown in Table 4.
Tabel 4. The deviation of reinforcement based on building function Building
Function
No of Building Average deviation of reinforcement per zone
4. Conclusions
Implementation of standard work unit price (UP) SNI 7394: 2008 for the construction of reinforced concrete beams can be concluded by considering the following two conditions:
• Implementation of the UP standard based on zoning is only possible for building buildings built in Zone 10 or areas with spectral responses below 0.6g. The reinforcing material requirement index on the UP standard of 200 kg / m3 of concrete for beam construction is still able to meet actual reinforcement usage in this zone.
• Implementation of UP standards based on building functions is possible on certain functions only. However, the application associated with the building function should not necessarily be used. Still, consideration of zonation-related implementation as a whole, given the standard deviation value indicated.
The results of the analysis on Zone 10 are based on relatively limited data, so that the accuracy of the research results is still possible to be improved by the addition of more adequate data. The implementation of standards in Zones 11 and Zone 12 has the potential to be done. This condition is seen from the results of the analysis at Zone 10 that indicates the margin ratio in the range of 183.89 - 200 kg/m3.
5. Acknowledgement
This research was granted for funding support from Hibah Penelitian Produk Terapan No.
55/UN11.2/PP/SP3/2017 of Fiscal Year 2017, Directorate General of Research and Development, Ministry of Research, Technology and Higher Education. The authors express high appreciation to all parties who have contributed in this research, especially to Ichwan and other research teams that involved from data collection to completion of the research.
6. References
[1] Aaron A L 1997 The Estimating Process The Engineer's Cost Handbook: Tools for Managing Project Costs ed R E Westney (New York: Marcel Decker) chapter 1 p 1–40
[2] Ministry of Public Work Regulation No. 45/PRT/M/2007 on the Technical Guidelines of State Building Development
[3] SNI 7394:2008 on Procedures for calculating the unit price of concrete work for the construction of buildings and housing
[4] Ching F D K 2014 Building construction illustrated Fifth ed. (New Jersey: John Wiley &
Sons)
[5] SNI 1726: 2012 on Procedures of earthquake resistant planning for buildings and non-buildings
[6] Mubarak 2010 Studi Harga Satuan Bangunan Gedung di Provinsi Nanggroe Aceh Darussalam Jurnal Teknik Sipil volume 1 p 43-52
[7] Mubarak & Tripoli 2011 Penggunaan variabel harga material untuk memprediksi harga satuan Prosiding Seminar API 2011
[8] Fachrurrazi, Husin S, Tripoli and Mubarak 2017 Neural network for the standard unit price of the building area Proc. Engineering 171 p 282 – 293
[9] Mahmuddin and Mubarak 2014 Housing Rehabilitation Budget Estimate due to Earthquake Disaster in Aceh Province using the Multiple Linear Regression Models Proc. 9th AIWEST-DR 2014 p 52 – 59