Evaluation of distress in supports of hyperbolic paraboloid shell

A church building structure, composed of a saddle-type hyperbolic paraboloid concrete shell roof supported by buttresses and brick masonry walls, was constructed in 1963. At one corner of the structure, the perimeter of the roof shell projects beyond the exterior building walls to form a canopy over the main entrance. This canopy is partially supported by two brick masonry fin walls that project outward from the main building walls. At the time of original design, closed-form methods (equations) were the only practical way of analyzing this shell structure. However, the configuration of the roof shell was not consistent with detailing requirements of the closed form methods. After 36 years of service, the fin walls had bowed significantly, were exhibiting wide cracks, had slipped laterally with respect to the roof shell, and were in danger of collapse. The writer led an investigation team that developed a finite element model of the church structure, studied the behavior of the church structure when subjected to applied loads and temperature changes, and developed repairs to restore structural integrity and serviceability.