M id A tlantic Real Estate Journal — Owners, Developers & Managers — July 2023 — 5C
www.marej.com
O wners , D evelopers & M anagers By Frank Cox, ECS Mid Atlantic Peeling Back the Layers: A Look at Structural Diagnostics
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n many ways, a building is like a cake. Its struc- ture consists of different ingredients and layers. When one ingredient differs from the recipe, the entire cake is compromised. This is also true for building structures, and pinpointing the issues can be challenging for those tasked with fixing them. Often, what starts out as a small crack can reveal a host of structural issues when the layers of the building are peeled back. “The building has good bones,” is a phrase often used to describe a building that is being slated for adaptive reuse. How do we know that the build- ing elements are structurally sound? That’s where structural diagnostics comes into play. Leveraging a combination of advanced diagnostic tools, laboratory testing and profes- sionals experienced with new design, construction, forensics and instrumentation, diagnos- ing a known or unknown issue can be performed—one layer at a time. Field diagnostic testing Structural diagnostics rou- tinely requires the use of non-destructive evaluation (NDE) equipment to evaluate a variety of building materi- als, including concrete; steel; masonry; wood; composites, such as fiber-reinforced or glass-reinforced polymers and soils beneath the building floor or foundation. NDE tools commonly used by structural diagnostic profes- sionals include ground-pene- trating radar (GPR), ultrasonic testing and a small hammer. Believe it or not, many struc- tural issues can be identified using a light sounding on a concrete surface using a small hammer. For example, a hollow sound is bad, whereas a ringing sound is good. GPR is used to locate the pres- ence of reinforcing steel or other embedded items within a con- crete structure or voids below slabs or pavements. A GPR scan is typically the first step to iden - tify gross deficiencies. Suspect areas on concrete structures identified to have deficiencies are then further investigated using tools such as ultrasonic echo tomography (UET). UET is used to evaluate the condition of hardened concrete by measuring time of an ultra- sonic shear-wave transmitting in the hardened concrete. UET tests such as ultrasonic pulse
velocity and impulse response can locate voids or honeycomb- ing in the concrete. A useful testing method for evaluating steel is half-cell po- tential testing. It determines the amount of corrosion of rebar embedded in concrete by measuring electrical resis- tance when current is passed through. Ultrasonic testing is also used as a non-destructive method to measure section loss on steel beams or other structural members. Laboratory testing Field diagnostic testing is most often followed by collect- ing samples for specialized
laboratory testing. Reasons to conduct lab tests include evaluating tensile strength and chemical analysis of steel, petrographic examination of concrete to determine the condition of concrete evidence of deleterious chemical reac- tions and chemical analysis of building materials to de- termine contamination from exposure to chemicals. The list of investigation tools and techniques is very long and employing them can give diagnostic pro- fessionals the information needed to evaluate a struc- ture or identify the extent of
damage or deterioration and make informed engineering design decisions. Structural diagnosis case study This structural-diagnosis project involved a donated building at the heart of a community-revitalization project. The intent was to adapt the building for use as a commercial kitchen space for residents and farmers to use to support the community. Stripped of all interior fin - ishes, this three-story build- ing began its life as a retail and warehouse space and has undergone many generational
changes, which was evident by different structural and non- structural components. Ex- posed reinforcing steel, chipped and spalled concrete and de- teriorated beams were found throughout, raising concerns about the structure’s integrity. Our evaluation began by taking concrete core samples from structural members to determine compressive strength of the concrete. Cores were taken from beams, col- umns and slabs. Additionally, ground penetrating radar was used to locate reinforcing steel within the structural members continued on page 10C
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