The replacement of old equipment in multi-residential apartment buildings with bearing-wall structural systems requires demolition and reconstruction. Several issues arise when performing such tasks, including the degradation of the urban environment, the wasting of resources, and the generation of construction waste. As a potential solution to these issues, a hybrid composite structural system for use in an apartment building was proposed. This system provides a level of architectural flexibility that is not offered by a conventional bearing-wall structure. The architectural flexibility extends the service life of apartment buildings by reducing the need for demolishing and reconstructing bearing-wall apartment buildings. In addition, the alternative system maximizes the efficiency of material use through the optimized relocation of structural steel, cast-in-place concrete, and precast concrete, thereby reducing material quantities and minimizing CO2 emissions. When compared to a conventional bearing-wall apartment, the hybrid composite system consisting of structural steel, cast-in-place concrete, and precast concrete is expected to improve energy efficiency during construction. In this work, the results of analytical and experimental investigations of a hybrid composite beam to be used in multi-residential apartment buildings are presented. The beam was found to yield enhanced energy efficiency when compared to a conventional bearing-wall apartment. The developed analytical prediction method based on the strain compatibility theory was validated by experiment. (c) 2011 Elsevier B.V. All rights reserved.