Hyunsu Lim

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 Formwork Layout Model based on Genetic Algorithm

The recent increase in the number of irregularly shaped tall building has caused a continuous increase in the formwork costs. To reduce the cost of forms, modular forms are widely used since they are cheap and reusable. However, they cannot be applied around columns which are irregularly arranged. This study introduces a formwork layout model using a genetic algorithm to reduce formwork material costs. The proposed model seeks an optimum formwork layout to maximize the proportion of modular forms by arranging 12 types of modular forms with the columns, for which the positions and sizes of are changeable. From a casestudy, the model showed a decrease in the ratio of non-modular forms covering the area by about 11.9%, and the rental cost of forms can be reduced by 10.4% compared to the previous heuristic method. The model can be used in the structural planning stage by a structural engineer to reduce the cost of formwork, and increase the efficiency of the column layout.

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.

Simulation-based Planning Model for Table Formwork Operation in Tall Building Construction

Operation planning for table formwork using a crane-independent lifting system (CLS) is a crucial factor affecting productivity for formwork in tall building construction. Inappropriate heuristic operation plans are likely to increase work duration because of temporarily displaced stacks of table forms, and may also increase costs because of excessive use of equipment. The authors propose a simulation-based operation planning model for table formwork for efficient operations in tall building construction. By optimizing the shifting sequence of table forms and the location of the CLS in a case study, the proposed model reduced working hours for table forms by 6.62% from the working hours derived by a heuristic approach. Furthermore, the derived alternatives reduced working hours by a maximum of 45%, depending on the number of trolleys used. This study can be utilized for informed decision-making by construction workers in tall building construction while selecting the optimal operation plan for table forms by considering project cost and schedule.

Establishment of Cooperation Evaluation System between Domestic Large Enterprises and Small/Medium-Sized Enterprises for Invigorating Joint Overseas Expansion

Joint overseas expansion could contribute domestic large enterprises and small/medium-sized enterprises to expand overseas construction market by complementing each others vulnerabilities and weaknesses. To invigorate it, not only does mutual effort between both parties matter, but also providing motivation such as institutional incentives and compensations are important for inducing large enterprises to voluntarily expand overseas construction with small/medium-sized enterprises. However, institutional systems exist only to promote win-win growth limited to domestic construction except for overseas construction. Therefore, the purpose of this study is to establish cooperation evaluation system between domestic large enterprises and small/medium-sized enterprises for invigorating joint overseas expansion by evaluating large enterprises cooperation efforts, and offering incentives to some enterprises gaining a good grade. The developed system could contribute to effectively promote win-win growth by providing institutional guidelines. In other words, The government could induce large enterprises cooperation efforts to some parts which small/medium-sized enterprises need, and large enterprises could selectively and intensively support insufficient cooperation part based on the evaluation result.

A Preliminary Study for Dynamic Construction Site Layout Planning Using Harmony Search Algorithm

Construction site layout planning is a dynamic multi-objective optimization problem since there are various temporary facilities (TFs) employed in the different construction phase. This paper proposes the use of harmony search algorithm (HSA) to solve the problem that assigning TFs to inside of the building. The suggested algorithm shows a rapid convergence to an optimal solution in a short time. In addition, comparative analysis with Genetic Algorithm (GA) is conducted to prove the efficiency of the proposed algorithm quantitatively.