Investigation Of Life Cycle Carbon Emission Assessment And Low-carbon Design Method Of High-rise Buildings

China is currently the country with the largest carbon dioxide emissions in the world.Its carbon emissions from the construction sector account for more than 50% of the national carbon emissions.To alleviate the increasingly severe environmental problems caused by global greenhouse gas emissions,and to achieve the "carbon peak by 2030" and "carbon neutral by 2060" goals,energy conservation and emission reduction in the construction sector are of vital importance.According to the analysis of national statistical data,in China’s construction sector,the annual carbon emissions from the building material production phase and the building operation phase are larger than those from other phases.In recent years,researchers focus on the low energy or near zero energy consumption technologies,promoting the development and the applications of those technologies.The carbon emissions from the operational phase have been reduced continuously.The ratio of carbon emissions from building material production phase to the entire life cycle is still very large,of which the structural materials account for the most.Therefore,how to control and reduce the emissions from structural materials is the key to achieve the goals mentioned above.In previous studies,only a few considered the impact of the main structures on the carbon emissions from a building during its life cycle.Normally,this type of research was based on a small number of case studies and could only draw some conclusions qualitatively.They cannot provide effective technical support for low carbon structural design.Regarding high-rise buildings,there is no research systematically studying low-carbon design technology for different structural systems and building functions.In addition,the life cycle assessment model proposed by the existing research needs to be enhanced according to the characteristics of building sector and the structural design.The enhanced model can evaluate the carbon emissions from high-rise buildings in a more precise and convenient manner.Based on the research background mentioned above,this research focuses on the carbon emission assessment methods and low-carbon design technology of the high-rise building with various functions and different structural systems.The research content and conclusions are stated as follows:(1)To propose an enhanced analysis method of life-cycle carbon emissions estimation for high-rise buildings.Based on the characteristics of structural systems,main structural materials,and actual engineering experience,the scope of the assessment method is expanded,and an enhanced model is proposed.According to the current industry technologies in China,refined carbon emission coefficients for structural materials are provided.This part mainly focuses on the phases of building material production,building construction and building demolition.(2)To study on the characteristics of carbon emissions from high-rise structures and propose a prediction model.For buildings with various functions and structural systems,this research conducts systematic parametric analysis;compares and analyzes the carbon emissions of each structural system in each life cycle phase and reveals the carbon emissions characteristics of high-rise structures(24.0m～100.0m).With the consideration of the parametric analysis results and the actual engineering data,a carbon emission prediction model is proposed.It can be used for carbon emission prediction and design scheme comparison at the early stage of the building design.This study found that without considering the recycling of structural materials,the carbon emissions by structural materials from concrete structure systems and steel structure systems accounted for58.61%～76.92% and 52.16%～61.61% of the whole life cycle,respectively.The emissions from steel structures are generally greater than those of concrete structures.Increasing the recycling rate of structural materials and reducing the paints’ emissions are effective measures to reduce carbon emissions from steel structures.(3)To study on low-carbon design methods of high-rise structures at the building materialization stage.This study proposes four low-carbon design methods which are suitable for high-rise buildings.The design methods are increasing in the design life,improving in the seismic toughness,applying of high-strength materials and the combination of the above three technologies.The research is conduced based on the results from Part(2).Carbon reduction analysis was carried out for various structural systems.This study found that increasing the design life is an efficient low-carbon design method.Improving the seismic toughness can reduce carbon emissions to a certain extent(concrete structures 2.03%～17.12%,steel structure 2.09%～7.26%).The method of using high-strength materials can reduce the usage amount of materials to achieve a certain degree of carbon reduction(concrete structure does not exceed 8.50%,and the steel structure does not exceed 6.60%).Compared with any of the above-mentioned lowcarbon design methods,the combination of them is the most efficient.(4)To research on carbon reduction technologies during high-rise structure operation and the demolition stages.The research mainly focuses on an existing building during its design service life.Its structural bearing capacity is insufficient due to the change or improvement of the building function or the shortage of the durability of the building.Therefore,the structure needs to be enhanced to achieve "life extension";and in the building demolition phase,how to increase the direct reuse rate of high-rise steel structures is carried out.The research analyzes the carbon reduction benefits of two reinforcement technologies and proposes a method to increase the direct reuse rate of high-rise steel structures.