A Static Behavior Analysis Of Large-span Column-free Subway Station Structure

With the development of China’s economy,the upsurge of underground space development has been set off in major cities.Among them,the construction of subway is one of the important contents of urban underground construction.As an important underground transportation hub,subway stations are facing tremendous travel pressure.As a new structural type,long-span non-column subway station is increasingly favored by engineering circles because of its advantages such as large available space,transparent vision and large flow of people.Taking a subway station in Guangzhou as a prototype,the finite element analysis method is used to study the mechanical behavior of long-span subway station with two different structural types: broken-line arch plate and circular arc arch plate.According to the mechanical characteristic that the arch would produce large horizontal thrust,the fine finite element analysis is carried out on the top frame of the station,in order to provide reference for the design of long-span non-column subway station.The main contents are as follows:(1)Based on analytical solution and finite element simulation method,the force distribution law of subway station roof under two-dimensional and three-dimensional conditions is analyzed,and based on the current code,the frame beams and columns are rereinforced.Two-dimensional and three-dimensional situations,the stress law of the station roof is consistent,and it is considered that when the rise-span ratio of broken-line slab is 0.08,the truncation length ratio is 0.6,and the rise-span ratio of circular arch slab is 0.14,the stress distribution of the roof is reasonable;Based on the elastic results and the current code,the relevant sections and reinforcement of the frame are adjusted,which paves the way for the later work of fine finite element modeling and comparison with the code formula.(2)The applicability of CDP model in ABAQUS is verified by two examples,and the fine finite element model of station top frame in ABAQUS is established.After the analysis of two frames with different failure mechanisms,it is pointed out that the calculation of beams under the combined action of bending and torsion under the current code is too conservative,and "strong beams and weak columns" may appear in actual design,which provides an optimized idea for parametric research in the future(3)Parametric analysis of frames under different horizontal loads is carried out,and the influence of the ratio Ω of horizontal load to vertical load on the failure mechanism of frames under different structures is further studied.After calculation,it is concluded that under the current code,although the failure mechanism of the structure tends to change to beam failure,it is still the failure of column foot in essence,and the design goal of "strong column and weak beam" cannot be realized easily.In order to explore the true bearing capacity of the beam,this paper takes measures to increase and strengthen the column section steel and steel bars and weaken the beam section steel.Through finite element calculation,it can be concluded that the failure mode of the frame constructed according to this method is that the beam is destroyed before the column,and the "strong column and weak beam" effect in seismic design is preliminarily realized.