Research On Prediction And Damage Evaluation Of Masonry Building Caused By Tunnelling

Shield tunnel can lead to the settlement and damage risk of the superstructure.Based on settlement and damage of a masonry structure caused by shield tunnel as the engineering example,equivalent stiffness calculation considering opening of the building facade was put forward based on the stiffness calculation of variable cross-section cantilever beam,and based on Winkler foundation under the Timoshenko beam theory,a soil-structure interaction model was established to predict of settlements of building tunneling induced.Finally,the principal tensile strain distribution of the model building was determined based on the Timoshenko beam stress analysis,and then the damage degree of building was evaluated.The main research results are as follows:(1)Based on the case analysis of the damage of a masonry structure caused by shield tunnel of changsha metro line 4,the correlation among building settlement,deformation and damage is revealed.The results show that the large settlement results in the oblique crack at the highest slope of the settlement curve of the vertical wall of the masonry structure,the hollowing and falling off of the plaster layer were discovered,and the opening and closing of some doors and windows were limited.The area where the main tensile strain of the wall is greater than 0.05% can reveal the internal relationship between the deformation behavior of the wall and the damage performance,and the direction of cracks is perpendicular to the direction of the main tensile strain.(2)Based on the calculation of the equivalent stiffness of the cantilever beam with variable section,the method determining the equivalent stiffness of the wall with openings was proposed,the effect of the opening rate on the equivalent stiffness of buildings with different length,height and α value(opening properties,related to opening size and opening spacing)is also studied.The results show that the method determining the stiffness of beams with variable section can accurately calculate the reduction effect of opening rate on the wall’s equivalent stiffness,and the reduction on the wall’s stiffness and the opening rate is basically linear.The effect of the opening rate on the bending stiffness and shear stiffness of the wall is less affected by the length or height of the wall,but the effect is more obviously affected by αvalue.When α is small,the opening rate reduces the bending stiffness and shear stiffness of the wall greatly,and when α is large,the reduction of opening rate to the bending stiffness and shear stiffness of the wall is small.(3)Based on the Winkler elastic foundation model and the Timoshenko beam building model,the theory of soil-building interaction was put forward to determine the buildingsettlement caused by shield tunnel.The parametric analysis shows that the elasticity modulus of building materials,the number of building floors and the buried depth of the tunnel are negatively correlated with the maximum settlement value and the maximum settlement slope,while the soil compression modulus and the soil loss rate are positively correlated with the maximum settlement value and the maximum settlement slope.(4)Based on the deformation law of Timoshenko beam,the cloud picture of the main tensile strain of the building wall was obtained through the calculation of bending moment and shear force,the results show that the method can accurately predict the damage degree and damage area of the building.At the same time,different traditional evaluation methods were used to evaluate the buildings relying on the project.The comparison shows that the evaluation method based on Timoshenko beam building model can accurately calculate the distribution of main tensile strain and damage area of the wall tunneling induced,and the area close to doors and windows appears strain concentration that around 2 to 3 times of calculated results,the damage degree based on the level of damage prediction consistent with the actual damage survey.Compared with other traditional damage assessment methods,which are difficult to accurately evaluate the actual damage level and damage distribution of the building,this method can more accurately evaluate the damage of the building and reflect the internal distribution of damage.