The Effect Of Uneven Settlement Of Foundation On Shear Wall Structure By Back Analysis Method On The Basis Of Modified Two-spring Element

Tianjin Binhai New Area is characterized by the soft soil area. Because thebearing load of the foundation in soft soil area is much lower, the uneven settlementhappens more easily. Great additional internal force and additional distortion wouldappear in upper structure because of uneven settlement of foundation, which willeffect normal function use and even beat the capacity of upper structure. Shellelement is used to simulate shear wall in ANSYS software, although which has highnumerical precision computation complexity and difficulties in the sampling processof each parameter have limited its application. Based on the two-spring macro wallelement, a new modified type of two-spring element is proposed to decrease thenumber of degrees of freedom and improve the calculation speed. An example ofthree common shear wall forms showed that compared with shell element, themodified two-spring element can yield good accuracy and can be used in theelastic-plastic static analysis of high rise shear wall building structures.An example of a certain project in Tianjin Binhai New Area is taken to discussthe effect of uneven settlement of the foundation on upper structure, on the base ofmodified two-spring element. Surface equation was fit to meet the practical settlementsituation, according to the boundary conditions of the measured data of building’ssettlement. The fitted surface equation of settlement has been put on the undersurfaceof finite element model to analyze the changes and distribution of internal force of theupper structure. The amplification of additional internal force and additional distortionon upper structure has been analyzed with the increment of settlement and differencein settlement by putting different settlement on the undersurface of finite element. Itprovided a basis for structural design and structure reinforcement, comparing internalforce caused by wind load with additional internal force caused by uneven settlement.An example showed that the additional internal force on shear wall structuredecreased with the increase of altitude, which means the maximum of additionalinternal force occurred on the ground floor, and the additional internal force of shearwall on the edge of buildings were bigger than it on the interior of buildings. Theadditional shear force and additional bending moments increased with the increase ofsettlement and difference of settlement, in which the additional bending momentsincreased more remarkably.