Seismic Resilience Assessment Of Existing Buildings In Hohhot City And Its Improvement Measures

China is one of the countries in the world with many earthquake disasters,and the damage caused by earthquake disasters to cities is much higher than other disasters.A scientific and reasonable assessment of the seismic resilience of urban building clusters and improvement of the seismic resistance of vulnerable buildings is the most effective way to reduce casualties and property losses.At present,Hohhot City has not yet conducted seismic resilience assessment of existing buildings within the built-up area,and lacks reports on the results related to seismic resilience assessment of existing building clusters,which affects the progress and enthusiasm of the local "Seismic Strengthening Project for Houses in Earthquake Prone Areas".Therefore,it is a very urgent task to conduct seismic resilience assessment of building clusters in Hohhot city and analyze the benefits of strengthening and enhancing vulnerable buildings.In this paper,we take the reinforced concrete,brick and mortar,brick and wood and civil engineering building groups in Hohhot,a city with earthquakeprone housing seismic strengthening,as the research object,and evaluate the seismic resilience of buildings in terms of damaged area,economic loss,repair time and cost,and human casualties with reference to the evaluation index of building seismic resilience in China,and assess the cost required for the reinforcement of four types of structural types of vulnerable buildings,comparing the before and after reinforcement The study also assesses the cost of reinforcement for four types of vulnerable buildings and compares the economic and social benefits of reinforcement before and after.First,the seismic damage of the buildings in the study area under the given seismic level is evaluated,and the damage level of the buildings in the study area under the seismic action and their damage area are derived.The results of the resilience assessment,such as direct economic loss,casualties,repair time and repair cost,are also calculated by combining local population data,project price and construction team size.Then,based on the assessment results,the seismic strengthening costs required for the vulnerable buildings in the study area are predicted with reference to the parameters of the building seismic strengthening cases.Finally,the economic and social benefits of seismic resilience enhancement were derived by comparing the damaged floor area,direct economic loss,casualties,repair or reconstruction time and cost before and after the reinforcement of the subject buildings.The main findings are as follows:（1）The seismic resilience of urban buildings is average when the seismic intensity of urban area is 8 degrees.The damaged area of urban buildings is about 119,698,300 square meters,the direct economic loss after the earthquake is 144.250 billion yuan,the building repair time is 5.63 years,the repair cost is63.925 billion yuan,and the number of casualties in daytime earthquakes is48,800,including 10,900 deaths,the number of casualties is much higher when earthquakes occur at night than during the day.Damage varies by region.（2）The cost of seismic reinforcement required for damaged buildings in the study area is 44.415 billion yuan,of which the reinforcement cost required for medium-damaged buildings accounts for more than half of the total cost,or about 57%.The reinforcement costs required for different structural buildings are also different,with reinforced concrete buildings requiring 4.498 billion yuan,brick and wood buildings requiring 7.941 billion yuan,civil and wood buildings requiring 9.957 billion yuan,and brick and concrete buildings requiring 22.019 billion yuan.The highest reinforcement cost is required in Saihan District and the lowest in Yuquan District among the four regions.（3）The social and economic efficiency obtained in the study area was higher when the pre-earthquake vulnerable buildings were improved in seismic resilience capacity by means of seismic strengthening.Firstly,the damaged area of the subject buildings was significantly reduced,especially the destroyed and severely damaged floor area decreased significantly,between 83% and100%.However,the damage levels and their area changes differed for different structural buildings,with a decrease in the area of both moderate and minor damage for steel buildings,but an increase of 33%in the area of moderate damage for brick buildings,an increase in the area of minor damage for brick and wood buildings,and an increase in the area of moderate and minor damage for civil buildings.Secondly,after the object buildings were reinforced,the direct economic loss was reduced by 62.640 billion yuan,the repair time and repair cost were reduced by 60%,and the number of deaths and casualties were reduced by 66%and 52%when encountering the same earthquake intensity.The area of building damage,direct economic loss,repair time,repair cost and casualties were reduced in all four regions,but the reduction was different.If we consider the cost of reinforcement,the total economic benefits can exceed18 billion yuan.It can be seen that seismic strengthening of vulnerable buildings is one of the means of effective seismic resilience enhancement.The paper also proposes non-engineering means to enhance the seismic resilience of buildings.The promotion of seismic strengthening of houses in earthquakeprone areas is an important task to ensure the safety of local citizens’lives and sustainable socio-economic development.