Nondestructive Evaluation: Structural Performance of Masonry
Masonry is one of the world’s most durable construction materials. Masonry structures can remain in service for hundreds or even thousands of years. Masonry structures often outlive their designers, their original design documents, and their original functions. When historic masonry structures are evaluated for preservation, adaptive use, or additions, there are numerous questions that may arise about the construction and the condition of the brick, stone, concrete block, and mortar. One of the first questions typically asked by the design or investigation team is “How is it performing?” It is important to understand observed distress, such as cracks, corrosion, and surface erosion. Often the cause and/or extent of distress can play a major role in rehabilitation work and in determining what other types of nondestructive evaluation are required. Another common question about masonry is “How strong is it?” In order to conduct a structural evaluation, an engineer must have at least some information about the strength of the masonry. A related question often asked next is “How was it constructed?” Masonry characteristics such as ties, voids, headers, and embedded items are often hidden from view, but these items are critical to understanding how the assembly will perform. Finally, in some cases it is important to ask “What is it doing right now?” It can be vital to understand what types of loads and stresses the masonry is currently experiencing, especially in order predict future performance under new or different loads. Other questions regarding moisture permeability, acoustic properties, or thermal behavior of masonry may also arise. This Practice Point focuses on these fundamental questions by providing a summary of current nondestructive-evaluation tools available for the assessment of historic masonry. While case studies and descriptions of specific nondestructive test methods are fairly common, this article provides an overview of numerous techniques, both listing the technologies available and helping in the selection of an appropriate method. A wide range of evaluation methods are available for use, and many claims are made regarding the accuracy of Practice Points NUMBER 09
Numerical analysis of the flat-jack test on masonry walls
Simulation numerique de cet essai a l'aide d'un programme de calcul par elements finis non lineaires realise sur des murs en maconnerie prealablement soumis a des essais experimentaux. Les domaines de rupture de la maconnerie varient en fonction de l'angle compris entre les joints de mortier et les directions principales de contrainte. Le critere de rupture a donc ete adopte de facon a approximer l'ensemble de ces domaines obtenus experimentalement par Page et coll.
Traceability strategy for gear-pitch-measuring instruments: development and calibration of a multiball artifact
There is a strong demand to ensure the traceability of gear-measuring instruments (GMIs). We propose a multiball artifact (MBA) for the evaluation of pitch-measuring accuracy. The aim of the MBA is to transfer the minimum uncertainty from a calibrated value at the National Metrology Institute of Japan (NMIJ) to a measured value of GMIs at a shop floor. The MBA is composed of equally spaced high-accuracy balls around an axis. The pitch-measuring accuracy of GMIs is evaluated by measuring the angular pitch deviation of the balls instead of the angular pitch deviation of a gear. We calibrated the angular pitch deviation using a coordinate measuring instrument (CMM) at the NMIJ and adapting a multiple-orientation technique. We proposed a calibration strategy of the angular pitch deviation. The calibration value of the pitch deviation for the MBA at the NMIJ was obtained with a measurement uncertainty (U95) of 0.2 µm. We evaluated the pitch-measuring accuracy of a GMI using the calibrated MBA. Each value of U95 for the cumulative and single pitch deviations for the left and right flanks was less than or equal to 0.5 µm. The small uncertainty was transferred from the NMIJ to the GMI.