Abstract

This paper presents a comparative approach between a digital documentation workflow of a hyperbolic paraboloid heritage building using contemporary tools versus a traditional documentation technique. This documentation was undertaken to better understand the building’s structure, its evolution, and to assess the performance of this modern concrete structure for future seismic and damage analysis. Furthermore, this paper discusses the challenges related to producing a Heritage Building Information Model (HBIM) of this building using point cloud data in Autodesk’s Revit BIM-authoring software. This project states the importance of a parallel study between the traditional and the contemporary documentation methods; which led to discoveries about the current state of the extrados in the hyperbolic parabola after several earthquakes. Upon analyzing the HBIM and comparing it to the historical drawings, we discovered a gap between the moisture barrier membrane and the concrete shell. Visualizing the building in 3D provides a deeper and more accurate understanding of the currentstate of this pavilion and is one of many advantages of using digital technologies. The insights provided by digital documentation techniques and analyzing the historical images of the pavilion showed that the curvature of the pavilion had changed over time. The results that we found imply two hypotheses. First, the profile of the curvature had been modified due to earthquakes, and second that the modification was due to improper maintenance of the pavilion, namely, multiple additions of the membrane layers. This could not have been detected by solely relying on traditional documentation techniques.

Abstract

When completed in 1961, the roof of St. Charles Church became the largest unbalanced hyperbolic paraboloid structure in the world and the only shell structure in Spokane, WA. Situated on an 8-acre site on the north side of the city, St. Charles is a modernist structure designed through partnership of Funk, Molander & Johnson and architect William C. James. This asymmetric structure is over 45.72m (150ft) and utilizes folded edge beams that taper from 1067mm (42in) at the base to a 76.2mm (3in) thickness at the topmost edge using regular strength reinforcing steel and concrete. The novelty of the shell structure serves both architectural and structural design criteria by delivering a large, uninterrupted interior sanctuary space in materially and economically efficient manner. Having previously completed an initial analysis of the structure, now, 60 years later, a complete structural forensic evaluation of the shell has been conducted using full point cloud laser scanning to generate a complete in-situ model. The in-situ geometry and historic loads are described and deflections as first steps in a full structural forensic study. Results of the current in-situ geometry are compared to the design geometry of original construction documents.