Jongsung Won

Metrics for Quantifying the Similarities and Differences between IFC Files

Recently, several papers reported problems in data exchange using industry foundation classes (IFC). However, most comparisons were made based on a visual check, a manual count, and observation of properties that were selectively chosen. This study proposes a set of metrics for quantifying the similarities and differences between IFC files. The proposed metrics include the similarity rate, the matching rate, the globally unique identifier (GUID) preservation rate, the missing rate, and the addition rate. A long-term goal of this study is to develop a set of metrics for quantifying the information exchange rate between two IFC files. Automated identification of modified information versus newly generated information is an unsolved challenge. The proposed metrics were used in analyzing 88 IFC files generated from different systems to demonstrate the potential use of the proposed metrics.

Query Performance of the IFC Model Server Using an Object-Relational Database Approach and a Traditional Relational Database Approach

Most previous industry foundation classes (IFCs) servers were developed based on relational databases (RDBs), and many studies reported performance problems. This study developed the object-relational IFC (OR-IFC) server using the object-relational database (ORDB) approach to improve query performance by simplifying the mapping process of the inheritance structure and the aggregation concepts. In addition to the OR-IFC server, a RDB-based IFC server was also developed using mapping rules on the same database-management system as that on which the OR-IFC server was implemented to compare the performance of the ORDB- and RDB-based systems. The performance of the OR-IFC server and the RDB-based IFC server was evaluated using the Benchmark of Universal or Complex Kwery Ynterfaces benchmark method, and two test-case models with different sizes were used. The benchmark results clearly showed the query- performance improvement of the suggested OR approach. The OR-IFC server far outperformed the RDB-based server in every query related to object-oriented features such as inheritance, collection-type data, and referencing. DOI: 10.1061/(ASCE)CP.1943-5487.0000256.

Quantification of construction waste prevented by BIM-based design validation: Case studies in South Korea

Waste generated in construction and demolition processes comprised around 50% of the solid waste in South Korea in 2013. Many cases show that design validation based on building information modeling (BIM) is an effective means to reduce the amount of construction waste since construction waste is mainly generated due to improper design and unexpected changes in the design and construction phases. However, the amount of construction waste that could be avoided by adopting BIM-based design validation has been unknown. This paper aims to estimate the amount of construction waste prevented by a BIM-based design validation process based on the amount of construction waste that might be generated due to design errors. Two project cases in South Korea were studied in this paper, with 381 and 136 design errors detected, respectively during the BIM-based design validation. Each design error was categorized according to its cause and the likelihood of detection before construction. The case studies show that BIM-based design validation could prevent 4.3-15.2% of construction waste that might have been generated without using BIM.

No-Schema Algorithm for Extracting a Partial Model from an IFC Instance Model

AbstractThis paper proposes an algorithm for extracting a partial model from an Industry Foundation Classes (IFC) instance model without an IFC schema or a complete IFC model view definition (MVD). The methods developed in previous studies require either an IFC schema or MVD and software applications, such as an IFC model server or a building information modeling (BIM) authoring tool, to extract a partial IFC instance model. The algorithm proposed in this paper generates a partial model by recursively extracting IFC data instances in referential relations directly from an IFC instance model file, and it relies solely on the internal data structure of an IFC instance model, without an IFC schema or a MVD. The algorithm extracts physical and nonphysical data instances relevant to the user’s selection of building elements by recursively iterating through data instances based on the rules specified in the algorithm. A set of required building elements is not defined on the spot; rather, a set of building elem...

Development of Post-installable Pullout Bolts and a Loading Device for Evaluating Concrete Strength

The pullout test is a nondestructive testing method certified by the American Society for Testing and Materials (ASTM) and British Standards (BS). Research has shown that it is very reliable in terms of evaluating the concrete strength of reinforced concrete members. However, the pullout test is rarely performed on domestic construction sites due to the complex procedures and high costs involved. This study proposes a new pullout test composed of a post installable break-off bolt, an insert nut, and a pullout tester, which satisfy both economical and practical purposes on a construction site. Three different types of special fastening methods, a temporary fixed bolt, a plastic fixed panel, and a fixed bar, have been developed. A pullout tester is proposed that is driven by the circle force introduced into a handle composed of eight gears without a load cell and a hydraulic cylinder. The serviceability and reliability of these instruments were investigated through experiments at construction sites. Furthermore, the sample pullout test with a wall specimen was conducted to estimate the usefulness of the temporary fixed bolt type of fastening methods and pullout devices. Eventually, the developed instruments will be useful on construction sites if minor requirements are met.

Method for Composing a Portfolio for REITs Investment Using Markowitz`s Portfolio Model

Domestic construction companies are suffering from financing difficulties in the wake of the economic slump in Korea and abroad. During this economic slump, real estate investment trusts (REITs), facilitators for improving financing and stimulating construction businesses, have increasingly expanded since their introduction in 2001. However, in terms of growth speed and marketing size, Korean REITs are falling behind those of other nations. The purpose of this study is to suggest a method for composing a portfolio using the Markowitz portfolio selection model to stimulate REITs. The main contents are as follows. First, a comparative analysis was conducted of increased REIT profit with the application of the Markowitz model and the average REIT profit rate from July 3, 2007, to July 21, 2008, during the investment analysis periods. The results showed that the total profit rate from the Markowitz model was about 10% higher than the average REIT profit rate. Second, the sensitivity was analyzed according to the portfolios data-gathering and replacement cycle to measure the optimum cycle and yield. The six-month profit data collection period showed about 16% higher profits with the Markowitz model than with the REITs. The two-week portfolio change period resulted in about 11% higher profits with the Markowitz model than with the REITs