This paper discusses the development of a new structural composite hybrid system that is able to replace a conventional residential structural system in which space is partitioned using concrete walls. The new structural system consists of structural tees and wide flange steel beams, with the bottom flange and/or portion of the web partially encased in pre-cast concrete, which is then mechanically anchored by headed stud shear connectors both to the bottom flange and the web of the structural tees. In composite frame built apartments, materials known to be heavy carbon dioxide (CO2) emitters can then be either excluded or reduced with consequent reduction in CO2 emissions. This study has investigated 36 selected multi-residential apartment buildings of linear shape to compare the CO2 emissions of the new composite hybrid and conventional multi-residential apartments. The CO2 emissions resulting from the composite hybrid apartments were reduced to approximately 75—80% in comparison to the emissions occurring from the construction of conventional load-bearing wall apartments. This was achieved by reducing the main sources responsible for CO2 emission.

Apartments with load-bearing wall construction are used extensively in Korea, but have the disadvantage of a short life, causing serious economic losses in terms of construction waste, materials and energy consumption. This paper presents the findings on multi-residential apartments that utilise a hybrid composite frame as a viable alternative for the energy efficiency associated with construction materials. The hybrid composite frame consists of a structural tee, reinforcement steels and pre-cast concrete. The use of the hybrid composite frame reduces the overall amount of energy consumption. In addition, multi-residential apartments utilising a hybrid composite frame have advantages such as flexibility in planning and easier repair and remodelling. This study investigates tower-shape, multi-residential apartments of various heights and floor areas to compare the energy efficiency of the hybrid composite system with that of the bearing wall system. The multi-residential apartments that utilise the hybrid composite frame are analysed in terms of both reduced principal materials and reduced energy consumption compared with apartments of a load-bearing wall structure. Rapid demand for long life and multi-residential apartment construction is expected.

The bearing wall apartments which occupy the majority of multi-residential apartment buildings built in Korea, are known for having limited architectural plan flexibility, posing challenges in terms of maintenance and remodeling. The economic losses and environmental issues resulting from the reconstruction of bearing wall apartments are now accumulating to the extent that they are becoming a national concern. Multi-residential apartment buildings, which are now the dominant form of residence in Korea, must accommodate diverse customer needs and changes in life style. A new concept of Rahmen structure with architectural flexibility is Green Frame. GF multi-residence housing is expected to reduce construction costs and shorten the construction schedule by overcoming the shortcomings of conventional bearing wall apartments. This goal is consistent with the national policies that target the reduction of resource and energy consumption. In addition, GF will be established as a core contributor to achieving a reduction in CO 2 emissions, which will enable the sustainable growth of domestic construction industry, and address the low-carbon green growth drive implemented by the government.