Delamination Plan Of Urban Underground Space And Research On Fire Resistance Of Concrete Components

With the acceleration of urbanization in China,the limited ground space of the city had already cannot met the increasing land demand of people,which led to the utilization and exploration of underground space.Efficient and reasonable utilization of underground space provides huge space resources for the reconstruction of urban center,simultaneously there are some hidden dangers.For example,in the macro aspect,the research on the layered planning of urban underground space and in the micro aspect,the research on the fire resistance of reinforced concrete components in urban underground space.On the one hand,there is no unified division standard for the lower space level in each city of our country,and there is less detailed research on the vertical planning of underground facilities.Relevant researches can have contributions to the management of urban underground space as well the orderly and sustainable development and utilization of resources.On the other hand,in this paper,the fire resistance of reinforced concrete structures in urban underground space is mainly studied on the beams,slabs,columns and other structural components in the throat area of subway.For the complex building with the combination of Metro throat area and property development,according to the current code,there is no clear fire protection requirements for such buildings.Based on the research status at home and abroad and the above problems,this paper uses the methods of field investigation,analytic hierarchy process,numerical simulation and so on to carry out the specific works as follows:(1)By investigating the status quo of 49 cities planning in China,and dividing the underground space according to the type of the city,combining with the domestic existing facilities,the relevant norms and the characteristics of various facilities,the suitable depth of underground facilities was studied.This study can lay a foundation for the study of the layered norms of urban underground space.(2)Based on the principle of the best comprehensive benefit of urban underground space development,the analytic hierarchy process model is established.Combined with the results of experts scoring,the weight ranking of various underground facilities was obtained which can solve the vertical conflict of various underground facilities in the process of underground space development.(3)Based on the relevant researches and parameter selection experiences of domestic and foreign scholars on thermal and thermodynamic properties,the material parameters suitable for the fire resistance of reinforced concrete beams,slabs and columns in underground space were proposed.Based on ABAQUS finite element software,the numerical analysis models of reinforced concrete beams,slabs and columns were established,and the correctness and applicability of the models were verified by comparing with the actual engineering results.Through fitting analysis and calculation,the calculation formula of different thickness and relative deflection of protective layer of reinforced concrete beam under high temperature was established,and the reasonable thickness of protective layer of reinforced concrete beam was determined.Based on the analysis of the fire resistance of reinforced concrete slab with different thickness of protective layer under high temperature,combined with the influence of different thickness of protective layer under high temperature on the rigidity and bending capacity of slab section,the reasonable thickness of protective layer of reinforced concrete slab was determined.By analyzing the fire resistance of reinforced concrete columns with different thickness of protective layer under high temperature,changing the ultimate bearing capacity and the degree of stirrup densification,the reasonable thickness of protective layer of reinforced concrete columns was determined and the method of quickly judging its safety was proposed.The relevant research results provide a reference for the fire resistance design of reinforced concrete members in underground engineering.