| With the rapid development of high-rise buildings and underground space,the large and deep foundation pit projects are increasing day by day.Some traditional forms of support are limited by factors such as construction site,adjacent buildings and roads.The up-down method can not only solve the difficult problem of traditional construction method,but also shorten the construction period and improve the social and economic benefits.But up-down method as a new construction method the construction organization is relatively complex,process is various,not only need to consider the internal force and deformation of the conventional shun encountered in the practice,but also to consider the structural support system design parameter and the connection handle beam-column joints,column vertical displacement,adjacent supporting column of the differential settlement of the problems in the up-down method,etc.Based on the up-down method project of Yuzhou Yinhe PARK in Hefei,this paper discusses and calculates the design theory of the supporting columns,supporting piles and horizontal steel supports.The processing design of beam-column joint is emphasized.The finite element software MIDAS GTS NX is used to simulate the construction.The axial force and vertical displacement of lattice column and the axial force variation of horizontal steel support are analyzed.The influence on the structure is discussed by modifying the main design and construction parameters.Finally,the theoretical values,simulation values and field monitoring values are compared to discuss the rationality and feasibility of numerical simulation and theoretical calculation.The conclusions are summarized as follows:（1）The stability of the plate is the main factor in lattice column design.The spacings of the plates directly affect the stability of the lattice column as a whole and the stability of the split-limbs.（2）Pile tip resistance is an important part of bearing capacity.When calculating the vertical bearing capacity of bored pile,the resultant effect of pile tip resistance and pile side resistance should be considered.（3）As an important part of the horizontal support system in reverse construction,the horizontal steel support can be isolated first and then simplified into a two-dimensional plane structure for calculation and analysis.（4）In the construction,the first horizontal steel support takes the main role,and the second horizontal steel support takes the secondary role.The horizontal steel bracing must be constructed in time during the excavation of the foundation pit to avoid the instability of the whole foundation pit caused by excessive pressure of the supporting structure.（5）Under the same working condition,the axial force of lattice columns and horizontal steel supports in the middle of the foundation pit is larger than that of lattice columns and horizontal steel supports in the edge of the foundation pit.（6）The vertical displacement of lattice columns has space-time effect.The closer to the center of foundation pit,the vertical displacement of lattice columns is more affected by construction.Therefore,the space-time effect should be fully used in construction to strengthen construction management.（7）When the lattice column spacing increases,the loaded area of a single lattice column will increase,and the axial force will also increase.The loaded area of each lattice column should be considered in the design,and the spacing and number of lattice columns should be set reasonably.（8）The verticality of lattice columns should not be greater than 1/300.Even lattice column verticality in small offset,also can produce larger stress,and the state as the condition gradually aggravate,lattice column,therefore in the construction should strictly follow the regulations,take effective measures to ensure the verticality of lattice column,avoid verticality partial greater than large and lead to frame column cannot be outsourced,such as bearing capacity to reduce adverse situation.Figure[61] Table[20] Reference[60]... |
PDF Full Text Request