Monitoring and Repair of the Milwaukee City Hall Masonry Tower

The Milwaukee City Hall was built between 1893 and 1898 and is located in downtown Milwaukee, one block east of the Milwaukee River. The $300\mathrm{ft}$ $\left(91.4\mathrm{m}\right)$ long building, nine stories high over its main portion, is a trapezoid in plan. On the south side, there is a $393\mathrm{ft}$ $\left(119.8\mathrm{m}\right)$ tall South Tower located above the main entrance to the building. On three sides, the South Tower rises from the street level to the 13th level and the roof above, and on the north side, it is connected to the rest of the building up to the ninth floor. The South Tower is a hybrid steel and masonry structure consisting of masonry perimeter walls and a central core, four-sided steel truss supporting the floors and roof. The building is a perimeter-load-bearing masonry structure supported on wood piles. The city of Milwaukee had been aware of distress, in the form of cracks and loose masonry, in the South Tower for a number of decades. In 2002, the city took action to investigate the causes and significance of distress, and to develop a repair program. The scope of our work included review of the available structural drawings and documents, inspection of the tower, measurement and monitoring of movements, monitoring of thermal response, structural analyses of the hybrid steel and masonry structure, and development of repair recommendations. The repair program presently is under construction. This paper describes the monitoring program, analyses of the causes for distress, and the implemented repair concepts for the observed distress in the South Tower of the Milwaukee City Hall.