Numerical investigation of jacking method for asymmetric settlement rectification in tilted concrete buildings

In the town of Fereshteh, Tabriz, Iran, there is a growing concern regarding the tilting of recently constructed buildings. This uneven settlement issue can be primarily attributed to variations in loose fill material thickness, elevated groundwater levels, and the presence of loose sandy layers intermixed with clayey layers. The challenges posed by these tilted structures are further compounded when dealing with historically significant buildings, making demolition an undesirable and wasteful solution. Therefore, alternative restoration methods must be explored. This study focuses on the application of the jacking technique to rectify the tilt observed in reinforced concrete buildings ranging from four to eight stories in height. To simulate the rectification process, numerical modeling using the finite element method was employed. The strategic placement of jacks was critical, as they applied force until the foundation achieved equal vertical displacement on both sides or until the uneven settlement was reduced to an acceptable level. Ensuring the structural integrity of the building during this rectification process was of paramount importance to prevent cracking or collapse due to the forces exerted by the jacks. The investigation into internal forces within the structural elements revealed an interesting pattern. Elements on the first floor experienced significantly higher internal forces compared to their counterparts on upper floors. Stress concentration was notably observed at the intersection point of the columns and the foundation surface. This highlights the critical importance of positioning the jacks directly beneath the axis of the columns or bearing elements to ensure effective rectification. Based on the results obtained for the studied structures, it becomes evident that employing the jacking method becomes unfeasible when a section of the raft experiences a settlement exceeding 10 cm. This is due to the drastic change in stress distribution conditions within the structural components under such circumstances. However, the jacking method remains a viable and effective solution for settlements below this threshold, rectifying uneven structural settlements without causing harm to the structural elements.