Issue #10

1. Code & Standards Watch

2. Research Snapshot

Strengthening strategies for unreinforced stone masonry walls using FRP and CFM composites
Unreinforced masonry continues to be a high-value target for research into retrofits for strength & ductility improvements.  This study put Fiber-Reinforced Polymer (FRP) and Carbon Fiber Mesh (CFM) applied reinforcement to the test in a head-to-head, full-scale in-plane shear test, with a control of unreinforced stone masonry to ground the conversation.

Both reinforcements added substantial strength to their respective samples, though only the CFM added noticeable ductility.  The FRP used in this study did’t feature the same woven texture that CFM does, and that woven texture appears to have acted as a series of connection nodes with tensile struts between, keeping cracks smaller, engaging the reinforcement earlier, and forcing a more controlled and reliable failure mode.  With three samples in each category, this study did well compared to the field for sample size, though still more suggestive than definitive, statistically speaking.

Key Takeaways: Both Fiber-Reinforced Polymer (FRP) and Carbon Fiber Mesh (CFM) epoxy-applied masonry reinforcements added substantial in-plane shear strength to these unreinforced stone walls, though only CFM added much ductility.  CFM is also generally cheaper to procure and easier to install, making it the emerging choice for the field.

3. Tools & Workflow

Autodesk launches “Autodesk for small business” initiative

4. Case Study of the Week

Numerical modeling of the out-of-plane dynamic response of masonry gable walls via a high-fidelity block-based finite element modeling approach – part II: post-diction and application to other structural configurations

A critical weak point of unreinforced masonry wall construction is gable end walls, the triangular projections of the end walls that extend up above the main walls on the longer, main runs.  The tendency here is for flexure and high tensile stresses to develop along that imaginary line where the adjacent walls terminate, toppling the walls and forfeiting much of the support they offer to the major roof planes.

This team put a selection of authors into competition as part of the ERIES SUPREME blind prediction competition, asking various authors to develop theoretical models, which were later put to the test against three real walls, some with pre-existing cracking.  After the physical testing, authors were offered the data and the opportunity to fine-tune their models.  

Key takeaways: Major influences on performance of unreinforced masonry gable end walls were stiffness of roofline connection and the amount of pre-existing damage.  All other tested & considered factors were totally dominated by these two.  If that roofline connection is flexible, the wall behaves like a rocking block, whereas a stiff roofline connection drives a cantilevered plate behavior instead.

5. Upcoming Free Live PDH

6. Quick Hits

👋 From the Editor

I’m Eric, the engineer behind the StructEd Bulletin.  I dig through stacks of journal articles and software patch notes to find useful information for practicing engineers and keep an eye on the scattered code updates & errata for you. I’m just getting started, so if you find this useful, the best way to support the newsletter is to share it with a colleague or post it on LinkedIn. It helps more than you’d think!

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