Life Cycle Sustainability Assessment Of CFST Frames In Seismic Regions

In recent years,the intensification of climate change has led to a series of economic,social and environmental problems around the world,affecting the sustainable development of human society.For this reason,after the signing of the Paris Agreement,countries have developed carbon neutral implementation roadmaps to address the increasingly serious climate change issue.As the world’s largest developing country and carbon emitter,China has put forward a new challenge of reaching a carbon peak by 2030 and achieving carbon neutrality by 2060.The building sector is one of the three main areas of energy consumption(industry,transport and buildings)and is one of the main areas responsible for direct and indirect carbon emissions.New opportunities promote us to look at the development of the industry from a new perspective,but also new challenges,accelerating the upgrading of the construction industry is imminent.On the other hand,China is located in a seismic zone with frequent seismic activity.Concrete-filled steel tube(CFST)is being widely used in many areas of civil engineering due to its good performance,however,current research on Concrete-filled steel tube frame structures is mainly focused on the mechanical properties,with relatively little evaluation of the sustainability of the structure.For CFST frame structures,having the ability to cope with natural disasters while having good economic,environmental and social impacts during their life cycle is,firstly,in line with our country’s philosophy of people first and life first,to safeguard people’s lives to the greatest extent possible in the face of natural disasters,and secondly,in line with the country’s strategic policy of promoting green development,fostering harmony between humans and nature and implementing sustainable development.Based on a scientific theoretical system,this thesis provides a full life cycle sustainability assessment of CFST frame structures in seismic regions from multiple dimensions,while considering the safety-related structural seismic performance,which is of great practical significance to improve the application and promotion of CFST frames in seismic regions and to realize the sustainable development of the construction industry.In this thesis,CFST frame structures are analyzed and studied from the following aspects.(1)Firstly,OpenSees open source finite element software was briefly introduced and previous tests on CFST elements(columns)and CFST frame structures were simulated by building a model to verify the reasonableness of the model building.(2)The 6-story and 12-story concrete-filled steel tube frame structures designed by previous scholars were selected,and the recommended 22 seismic waves were used to conduct seismic vulnerability analysis based on IDA method.The results show that the CFST frame structure can better meet the requirements of "no damage in small earthquakes,repairable in medium earthquakes and not collapsing in large earthquakes",and can protect people’s lives in the face of natural disasters.(3)The Life Cycle Sustainability Assessment(LCSA)is applied to the characteristics of CFST frame structures,the life cycle scope and system boundary of steel pipe and concrete frame structures are clarified,and the life cycle inventory quantification method of CFST frames is discussed.Through the integration of LCA,LCC and S-LCA of CFST frame structures,a life cycle sustainability evaluation system for CFST frames is formed.By adopting a social Willingness to Pay(WTP)weighting,the LCA results and S-LCA results are transformed into economic indicators,and the results of the three dimensions of LCA,LCC and S-LCA are centrally reflected in monetary terms as the LCSA results.(4)Applying the above evaluation model,the three dimensions of the sustainability of the two selected CFST frame structures in the life cycle are quantitatively analyzed,and the sustainability quantitative results of the concrete-filled steel tubular frame structures are obtained.(5)According to the calculation model of life cycle disaster loss expectation of building structure under single disaster,the disaster loss expectation of life cycle sustainability is further discussed and calculated.