Hunhee Cho

Safety and productivity analysis on alternative steel column-girder joint for automated construction

The automated construction method has been regarded as an alternative way to decrease the dependency of skilled laborers and to improve the constructional condition for ensuring safety and increasing productivity of relevant processes. For applying an automated construction system and for the realization of its expected effectiveness, unavoidable changes in conventional details of materials and sub-components might be needed. Now, in Korea, a project to research an automated construction system for steel structures is ongoing, and an alternative detail for the column-girder joint has been suggested as a partial progress result. In this study, performances of the suggested detail were analyzed on the points of collision stress and installation time that are measured in the pilot project. From the result, the application of the specified detail can be considered to satisfy this requirement, related to the allowable stress of the structural steel, and to result in an effective improvement in productivity.

Improvement of estimating method for construction management service fee by case study

The objective of this paper is to suggest the improvement of estimating system for construction management (CM) service fee through the analysis of the previous literatures and criteria and case study. In order to do this, this paper considered the relevance of existing criteria to estimate the CM service fee, the condition of input ratio of engineering resources in the real cases, and current utilization strategy of nonresident technical engineers. Based on the analysis, the following problems were identified; a) the different estimating system for CM fee and construction supervision fee, b) impractical estimating system for the CM fee, and c) inappropriate allocation of human resources for CM. Consequently, this paper suggested the following 4 items for the improvement of the existing system; (1) modification of the current structure of CM fee calculation, (2) rationalization of current level of the CM fee which is required to be raised approximately 5.4 percent compared to design or supervision fee, (3) securement of elasticity of the input ratio of engineering resources from the inception phase, and (4) development of the utilization strategy of nonresident engineers based on the technical requirement of the jobsite. Thus, it is anticipated that this research would affect the compensation package of CM in order to make the estimation process of CM service fee more efficient and to revitalize CM as business.

Customer Earned Value: Performance Indicator from Flow and Value Generation View

AbstractThe earned value method (EVM) is considered an advanced project control technique that provides a quantitative measure of work performance. However, the EVM is effective only under the assumption that every activity is independent. Literature shows that the EVM lacks the value generation view even working against the reliability of workflow. The goal of this research is to propose a project metric system to supplement the EVM in terms of the workflow and value generation. The researchers suggest a new metric of customer earned value (CEV), which is defined as the budgeted amount of work completed and is used by the successors on a network. Through a hypothetical case study, this research investigates how the work-in-process between trades and schedule performance in each trade behave under different uncertainties. The result suggests that the proposed metrics can provide project managers with more relevant managerial information on project progress as well as on the level of collaboration. The pro...

Performance assessment model for robot-based automated construction systems

An adjusted assessment model based on benefit-cost analysis (BCA) is proposed for evaluating the economic efficiency of automated construction technologies. In contrast to conventional BCA, the model does not compare monetary values, but the differences in benefits and costs between traditional and automated construction methods. To verify the usefulness of the model, it was applied to a real-scale building construction project that used a fully automated building construction system, and the face validity of the model was confirmed. The results indicate that the model can support decision makers in identifying valuable benefit factors and in assessing the cost effectiveness of the system.

A Study on the Improvement of Erection Bar Detailing in Domestic Building Construction

The erection bar is defined as the assistant bar used to fix the position of the reinforcing steel as the reinforcing steel is placed on site. As the erection bar do not bear the structural load and is not showed in the structural drawings, it is not managed importantly. But as chair bars in mat footing is used in large quantities to support the upper main bars, the detailing standards need to be suggested. and some erection bar is placed by experience of the fabricator and placer. Therefore, in this study, a survey about the erection bars was conducted to the reinforcement detailer, the fabricator and placer of domestic construction industry. 11 placing drawings is analyzed to find out the problems of detailing and the quantities of the erection bars. According to the analysis of the survey, the erection bar details in placing drawings were not standardized, and some erection bars are omitted in placing drawings. The improvement in the erection bar detailing was sought by analyzing the results of the survey.

Automated Lifting System Integrated with Construction Hoists for Table Formwork in Tall Buildings

AbstractIn tall-building construction, the equipment-driven table formwork method is a useful alternative for improving productivity of horizontal formwork with less skilled labor. The lifting system significantly affects the productivity and costs of table formwork operation. This study proposes a new system integrated with the construction hoists for automating the lifting process of table formwork. The system targets crane-independent transportation for productivity improvements while overcoming the limitations of the existing independent lifting system, which include high initial cost and extra work for assembly and operation. In a case study, the proposed system showed 49.4% improved productivity over a tower crane, and equipment costs were 73.8% lower than those of the existing independent system. The simplified structure of the system through integration with the hoist could minimize the additional time and cost inputs for its assembly and operation. The proposed system could provide more flexible ...

A Study on the Improvement of Reinforcing Bar Detailing

The reinforcing steel process is composed of the development of placing drawing, cutting and bending, and the placement and fabrication of the reinforcement, and is participated in by reinforcement detailer, the fabricator and placer. Because the reinforcing steel process-from estimating and rebar detailing, to production, material tracking, billing, and general accounting-is conducted by many participant, reinforcement details based on building code and reinforcing bar detailing standards are essential. The process, however, holds some problems. Building code has been revised recently, and the utilization of placing drawings was proved to be low, and the reinforcement estimating in early stage of the process is below what is required for placement. Therefore, in this study, a survey was conducted to the reinforcement detailer, the fabricator and placer of domestic construction industry. According to the analysis of the survey, the reinforcement details on site was not standardized. The improvement in reinforcing steel detailing standards was sought by analyzing the results of the survey including reinforcement constructability.

The Analysis on the Unsafe Acts of Laborers at Domestic Construction Sites

According to the increase of foreign laborers at domestic construction sites, its necessary to research in terms of the unsafe acts of both Korean and foreign laborers in order to prevent construction disasters. The objective of this study is to clarify the characteristics and the improvement priority of the unsafe acts using IPA(Importance-Performance Analysis). The result of this study showed which items of unsafe acts are identify difference between Korean and foreign laborers. Moreover, the result of IPA also showed items of unsafe acts that needed the immediate improvement for each one. Especially there are two items, i.e. equipment malfunction and wrong handling of hand tools, which both Korean and foreign laborers think simultaneous those needs improvement. The results can be

Optimization of Luffing-Tower Crane Location in Tall Building Construction

The luffing-tower crane (T/C) is a key facility used in the vertical and horizontal transportation of materials in a tall building construction. Locating the crane in an optimal position is an essential task in the initial stages of construction planning. This paper proposes a new optimization model to locate the luffing T/C in the optimal position to minimize the transportation time. A newly developed mathematical formula is suggested to calculate the transportation time of luffing T/C correctly. An optimization algorithm, the Harmony Search (HS) algorithm, was used and the results show that HS has high performance characteristics to solve the optimization problem in a short period of time. In a case study, the proposed model offered a better position for T/C than the previous heuristic approach.

Automatic data processing system for integrated cost and schedule control of excavation works in NATM tunnels

AbstractA type-based system is widely used for cost and schedule control in the NATM (New Austrian Tunnelling Method) tunnel. This study raises several limitations of the type-based system: a broad level of control, a distributed approach to cost and schedule data, ad hoc management, and difficulty in deriving meaningful data. Integrated cost and schedule control promises a myriad of benefits on both information flow and construction management. Nevertheless, the integrated approach still seems to be a long way from common use in the construction industry because it requires considerable overhead effort to acquire, track, and analyze the integrated data. The objective of this study is to propose a new method to automate the required processes for implementing cost and schedule integration. We propose an operational-level automatic data processing system for cost and schedule integration. The proposed system consists of a real-time location system for detecting equipment locations, a wireless mesh network ...