Afsheen Khan is a Senior Structural Engineer and Project Manager at PICCO. Her main areas of practice include natural stone cladding connections and backup system engineering, structural engineering, residential structural engineering, light gauge steel and connections.
The following is a reprint of her article, originally published in The Natural Stone Institute's March/April 2021 issue of The Cutting Edge publication, exclusively for members.
As a Structural Engineer working on stone cladding projects, I cannot emphasize enough the importance of stone testing for a safe and efficient design. When specifying natural stone, it is crucial to understand the material’s inherent characteristics to make an appropriate choice for the application. As the specifier, the design professional is responsible for material selection based on aesthetics, but also strict performance criteria. Material properties and expected application performance is best sourced through physical testing and professional analysis.
Most natural stones are anisotropic, which means physical properties like strength, durability, and resistance to natural eroding produce variable values when tested in different directions, or when the material is used in different ways. Hence, it is imperative to get the stone tested for appropriate ASTM standards so that appropriate safety factors can be applied.
The Natural Stone Institute lab has been the preferred testing facility for PICCO Engineering since they opened. With the latest in testing equipment and a highly knowledgeable staff, The NSI lab supports our project needs seamlessly with prompt and high-quality services.
PICCO Engineering recently completed a project using Blanc Absolute marble quarried in Spain. This marble was used in a large art installation with some pieces weighing over 6,000lbs. The seismic forces govern design when dealing with such heavy weights, and we needed to acquire kerf test results, with specific edge distances for our connection design. We contacted Chuck Muehlbauer to inquire about the required ASTM C1354 (Strength of Individual Stone Anchorages in Dimension Stone) for kerfs, pins, and epoxied threaded rod pull out tests. Chuck provided a detailed list of the NSI lab services available, namely, ANSI A326.3, ASTM C97, ASTM C170, ASTM C99, ASTM C880, ASTM C1354, ASTM C1353, ASTM C666 (and similar) for natural stone.
We contacted our client and requested the required quantity and sizes of stone samples from Spain be shipped to the NSI lab in Oberlin, OH. Testing was expedited due to our schedule needs and a detailed test report was provided. A list of the apparatus used and photos of the samples, before and after the tests, were also included. Based on the test results, we were able to specify an appropriate safety factor and design efficient and robust connections for stone anchorage.
There was constant coordination with the Natural Stone Institute during testing, which made the lab a key contributor to overall project success.
“As Natural Stone Institute members, we are lucky to have a professional, high quality testing lab accessible and eager to support our projects. Working with the lab and their team has been a pleasure and we look forward to future collaborations with the Natural Stone Institute.”
See the original article posted in our Press section: piccogroup.com/press