Since manufacturing an outdoor and large-sized billboard takes a lot of time, the working time required may be directly affected by weather changes, such as winds and rain. Moreover, without accurate planning, unforeseen situations may occur and even cause work delays. This report reviewed how to enhance work efficiency including fabrication and installation process of the billboard

Considering Working Environment
Jaesung General hospital requested World Housing, the manufacturer of rooftop billboards to manufacture and install its rooftop billboard. World Housing president, Hwang In-beom, said that the hospital did not want to disturb the patients, and we planned to pre-fabricate and assemble all components as many as possible on our companies, and had to bring them to the hospital. Since there was no other choice but to use a crane in lifting all materials required for the project to the worksite of the hospital's eight-floor housetop, the manufacturer assembled the reflective display, frame, and other components as lightweight as possible so that they could be lifted by a crane. After the completion of assembling them, the company transported all components to the worksite. It took a whole day to convey those components, while it took only about two hours to lift eight tons of assembled components from the ground to the housetop of the hospital. The H-beam frame was lifted by the housetop tower elevator for the H-beam work before other components were arranged appropriately on the housetop.

Lifting by a Crane For Working Efficiency
The company initially planned to install the rooftop billboard by a crane after fabricating large-format digital graphics and assembling all components lifted on the rooftop of the hospital. The company, however, could not find out a crane that was capable of lifting the eight-ton structure, and thus, assembled a structural frame that could be supported by a 25-ton crane. A 100-ton crane was considered, but a 50-ton crane was finally regarded cost effective. Mr. Hwang of World Housing explained, “Each structure could be moved by men. Unlike assembly work, though, a lift by a crane was more beneficial in terms of cost and time savings." It was important to determine which installation process were the most efficient in terms of cost and timesavings. Likewise, one should make an accurate calculation on equipments for reducing work time, thus reducing labor costs, and, consequently, total work costs. It was more critical, though, to accurately identify manpower, equipment, structural obstructions such as surrounding buildings and electric poles, road traffic situations, and climate changes like rainfall and strong winds, during the planning stage.

The Safety is most critical
Considering the nature of the location where housetop billboards were installed, outdoor billboards should be more stably and firmly installed than the other outdoor advertisements. They should be able to withstand even typhoons. Large-scale housetop billboards could lead to secondary disasters. Thus, Sign codes require billboards to be structurally safe to withstand winds of over 34 m/s. To guarantee such structural safety, billboards require reinforcement-oriented designs and installations. Chemical anchor technology used in manufacturing sub-structural H-beams could enhance the strength of adhesives, thus withstanding massive loads. Also, adhesives could enhance the concrete's chemical safety and lower water absorption. Due to its strengths, chemical anchor technology is used not only in ordinary construction, but also in underwater construction. The construction presented here used bolts in all joints. Major areas were joined by bolts, and then welded. The working area where bolts could not be used were all welded. Such bolts working make the project boost efficiency and helped shorten the installation time. Woo Sun-hun, president of Sunbong Planning, which also worked with the project, explained, "With bolts, oxygen canisters are no longer necessary, thus boosting efficiency. It is difficult for workers to conduct welding on the construction site at a time, but other workers can do bolt work at a time."