The growth of world population will be the challenge of the century regarding the carbon footprints. The human activities produce both direct and indirect carbon emission that is contributing to the climate change. The construction industry itself contributes around 30 percent of total carbon emissions in the world. Thus, the challenge is to solve the problem of meeting the increasing needs and expectations of a growing population while at the same time modifying the current production and consumption patterns to achieve a more sustainable development model. Based on this, the need for the sustainable structural element is inevitable. Extending the exploitation life of the structural element is one of the solutions that should be looked. Reusing instead of recycling the structural element is one of the ways to extend the exploitation life which can reduce the carbon emission. Therefore the innovation in the structural design to reduce the carbon emission is important. The purpose of this thesis is to study the feasibility of a conceptual design of demountable structural system. On the first part of the thesis, it investigated the structural behaviour of a composite floor beam that consists of steel beam, prefabricated concrete deck and a single embedded nut bolt shear connector in the SLS condition. To accommodate fabrication tolerance and construction process, the bolt shear connector must have enough clearance. Various bolt-hole gap in bolt shear connector is applied to see the effect on structural performance of composite floor beam in SLS. The study of demountable composite floor beam is performed by mean of analytical calculations and finite element analysis. It is found that the bolt-hole gap clearance influences the deflection of composite floor beam due to partial interaction between prefabricated concrete deck and steel beam which leads to incomplete interaction of composite floor beam. The bigger hole clearance, the higher deflection occurs on composite floor beam. The second part of the thesis explores the conceptual design of plug and play beam-column connection. The purpose of developing a plug and play beam-column connection is to reduce the construction time so that it is easy to be mounted and demounted. Two conceptual designs have been developed and were evaluated through FEA. The resistance of those two conceptual designs is found to be higher than fin-plate connection while the rotational stiffness of this plug-play connection can be classified as a nominally pinned joint. The last part of the thesis aims to see the possibility of having a non-symmetrical column splice connection on the column. This is interesting for the architect as it provides aesthetic benefit for the façade. The non-symmetrical column splice connection located on the corner is evaluated by FEA. The connection is a combination of end-plate and cover plate splice column connection. Due to unsymmetrical nature of the connection, the resistance and failure mode of the connection is different in a different orientation of the loading.