Estimated Construction Quantity With The Building Information Modeling (BIM) Method In Building Construction Projects (Case Study: Manhattan - Medan Building, Indonesia)

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**Estimated Construction Quantity with the Building Information Modeling (BIM) Method in Building Construction Projects: A Case Study of the Manhattan Building in Medan, Indonesia**

Introduction

The estimation of quantity in construction projects is a continuous process that is heavily influenced by the stage of design development and the presentation of data documentation from the project concerned. In many cases, the pre-construction quantity estimation value is different from the value of the construction costs that arise during the implementation. This situation is often a challenge for construction industry players, especially for projects that have no anticipation of quantity uncertainty. The Building Information Modeling (BIM) method was introduced as a solution to overcome this problem, with a case study of the Manhattan Building which has an area of ​​more than 115,000 m² and uses a reroature contract.

The Importance of Accurate Quantity Estimation in Construction Projects

Accurate quantity estimation is crucial in construction projects as it directly affects the project's budget, timeline, and overall success. Inaccurate quantity estimation can lead to cost overruns, delays, and even project abandonment. The BIM method offers a solution to this problem by providing a digital model of the project that can be used to estimate quantities with high accuracy. The BIM model can be used to track changes, updates, and revisions to the project design, ensuring that the quantity estimation is always up-to-date and accurate.

The BIM Method: A Solution to Quantity Estimation Challenges

The BIM method is a digital modeling technique that allows architects, engineers, and contractors to create a virtual model of the project. This model can be used to estimate quantities, track changes, and manage the project's progress. The BIM method offers several benefits, including:

  • Improved accuracy: The BIM model can be used to estimate quantities with high accuracy, reducing the risk of errors and cost overruns.
  • Increased efficiency: The BIM model can be used to track changes, updates, and revisions to the project design, ensuring that the quantity estimation is always up-to-date and accurate.
  • Better decision-making: The BIM model can be used to make informed decisions related to cost management and resource allocation.

Case Study: The Manhattan Building in Medan, Indonesia

The Manhattan Building in Medan, Indonesia, is a large-scale construction project that uses a reroature contract. The project has an area of ​​more than 115,000 m² and requires accurate quantity estimation to ensure its success. The BIM method was used to estimate quantities for the project, and the results were compared with the existing quantity estimates.

Data Collection and Analysis

Data collection for the case study was carried out starting from the initial stage (preliminary), the tender stage, clarification 01, to clarification 02 or the contract phase. The data was then compared with the results of the BIM model to determine the difference in quantity that exist today. To validate data, a non-parametric statistical test was used, Wilcoxon Sign Rank Test paired, which aims to measure the significance of the significant changes between two data groups, namely between the estimated quantity and BIM modeling data.

Results and Discussion

The results of the analysis showed a strong correlation and significant changes to the application of the BIM system. The difference between the ratio between BIM data and the definitive calculation that has been developed is 0.47%. This finding proves that the BIM model can represent the physical condition of the project that was built. In addition, for the comparison of BIM data with existing data, the biggest difference occurs at the preliminary stage which reaches minus 74.41%, indicating the potential for quantity reduction. Meanwhile, the difference between BIM data and the largest employment contract conditions reached 11.24%, which shows the possibility of adding quantity.

Analysis of the Application of BIM in the Estimated Construction Quantity

The application of BIM in quantity estimates offers a number of significant benefits. First, the use of an integrated digital model allows project planners and implementers to have better access to actual and real-time information about building design and specifications. Thus, this information can be used to make more appropriate decisions related to cost management and resources.

Second, the BIM model not only increases the accuracy of the quantity estimation, but can also reduce the risk of errors that may occur in manual calculations. In the context of the Manhattan Building project, the reduction in the difference in quantity estimation at the preliminary stage is a strong indicator that the BIM system is able to present more valid and accurate data.

Third, by reducing uncertainty in the estimated quantity, contractors can carry out better planning related to the budget and resources. This has the potential to save time and costs and increase the efficiency of project implementation. In addition, the Wilcoxon statistical test process conducted in the quantity estimation data also provides further clarity on the extent to which the change is significant, and how it can be relied upon in future decision making.

Conclusion

Overall, the application of the BIM method in the estimated quantity of construction not only shows more accurate results but also offers a more efficient way to manage construction projects. The case study of the Manhattan Building provides empirical evidence of the effectiveness of this method, with results that indicate a positive and significant correlation between the estimated quantity and the BIM model. Thus, the adoption of BIM technology in the construction industry in Indonesia, especially for large projects, is a very relevant and useful step.

Recommendations

Based on the findings of this study, the following recommendations are made:

  • Adoption of BIM technology: The adoption of BIM technology in the construction industry in Indonesia, especially for large projects, is a very relevant and useful step.
  • Training and education: Training and education programs should be provided to construction industry professionals to ensure that they have the necessary skills and knowledge to use BIM technology effectively.
  • Data management: Data management systems should be implemented to ensure that data is accurate, up-to-date, and easily accessible.
  • Collaboration: Collaboration between stakeholders is essential to ensure that the BIM model is accurate and up-to-date.

Limitations of the Study

This study has several limitations, including:

  • Case study: The study is based on a single case study, which may not be representative of all construction projects.
  • Data collection: The data collection process may be subject to errors or biases.
  • Analysis: The analysis of the data may be subject to limitations and assumptions.

Future Research Directions

Future research directions include:

  • Large-scale studies: Large-scale studies should be conducted to validate the findings of this study.
  • Comparison with other methods: Comparison with other methods, such as traditional quantity estimation methods, should be conducted to determine the effectiveness of BIM technology.
  • Development of BIM standards: Development of BIM standards and guidelines should be conducted to ensure that BIM technology is used consistently and effectively across the construction industry.