Remediation of settlements in a steel structure due to adjacent excavations

Marmaray Project is a 13.6 km long Bosphorus crossing railway system in Istanbul connecting Asia and Europe by a 1.4 km immersed tube tunnel for the first time and also comprises refurbishment of 63 km long existing railway systems which makes it one of the major transport projects in the world. During excavations of one of three new underground stations of the project at Yenikapi district, an ancient Byzantine port was discovered and the archaeological excavations are still being performed on a plot of land measuring 58,000 square-meters. Excavation-induced local ground settlements occurred in an existing steel structure adjacent to this excavation area. In this study, these settlements and their effects on the steel structure were investigated. To investigate the behavior of the structure under local settlements, 3D computer models using 3D beam elements and gap elements were carried out by using the commercially available software SAP2000. The effects induced on the structure by local settlements were simulated using gap elements at the column bases. As a result, a strengthening scheme was proposed to remediate the negative effects caused by settlements.