Project Highlights

• 100-year-old historic bell tower structure
• Repair of limestone facade, parapets, and pinnacles

Overview

Over the years, water had infiltrated into cracked and broken stones of this 1914 Indiana Limestone-clad bell tower. More than 1200 stones, backed up with Chaska walls and interior piers, make up the decorative top. Repair of the damaged structure required dismantling, replacement, and reconstruction of the limestone facade panels and decorative carved limestone-laced parapets and pinnacles topping the 150 foot bell tower. The cracked and broken stones indicated bearing failure of the stone, caused by internal steel tension rods that were imparting a too large compressive force on the stones. The thermal expansion and contraction of steel is about three times the rate of stone. During cold winter months, the eight foot long steel tension rods contracted sufficiently to bear down on the stones and break them at the stone-to-stone bearing points, creating high compressive forces within the stone. A new modern tension rod system was installed, including disc springs that expand and contract linearly, imparting a gradual clamping force that can be controlled. The disc springs were designed to maintain a sufficiently low compressive stress, while allowing the full thermal contraction of the tension rods during cold a Minnesota winter.