The assessment of unreinforced masonry structures is difficult to undertake in practice. A structural engineer is usually confronted with a standing, apparently competent, structure that seems to defy most of the rules of structural behavior, as incorporated in modern building codes. The engineer must then choose between reinforcing the structure according to a modern understanding of material strength and structural behavior or trying to make sense of the behavior and anticipated strength of the structure on a more fundamental level. A fundamental structural assessment, although it involves a considerable amount of effort in analysis and in furthering the understanding of masonry behavior, is the more rewarding. This course of action is consistent with the principles of historic preservation, as summarized in the Secretary of the Interior’s Standards for the Treatment of Historic Properties
. The following manual is intended to introduce a sympathetic structural engineer to some of the principles of unreinforced masonry and especially to provide some basic instructions in preparing a model of such a structure for analysis, using widely available, modern tools for structural analysis. In Section 2, the assessment of two dimensional arches is introduced. This section begins with an elaboration of the competing issues of code compliance and rational assessment as described in the introductory remarks above. Section 3 covers the assessment of three-dimensional masonry vaults using widely available structural analysis software. Case studies, illustrating the procedure recommended for the assessment of masonry structures are provided in Sections 4 through 6.
This manual was made possible through Grant MT-2210-04-NC-05 from the National Center for Preservation Technology and Training (NCPTT).