Date of Graduation

2015

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

Hota V S GangaRao

Committee Co-Chair

Mark Skidmore

Committee Member

P V Vijay

Abstract

With the drive for high strength, lightweight component design, the desire for composite materials for structural applications has been increasing in recent years. High strength-to-weight ratio, high stiffness, high fatigue and impact resistance, corrosion resistance, and ease of fabrication are just a few of the advantageous properties of pultruded fiber reinforced polymer (FRP) composites. The various structural applications of pultruded materials typically require the joining of composites either to composites or to metals. Despite introducing high stress concentrations in the composite material, bolted joints are the most practical connection for civil engineering applications. Bolted connections in glass FRP composites have been studied for years; however, accurate prediction models to determine failure strength and failure modes of these bolted connections are still being developed and confirmed. The American Society of Civil Engineers (ASCE), in conjunction with the American Composites Manufacturers Association (ACMA) are working to develop the Pre-Standard for Load & Resistance Factor Design (LRFD) of Pultruded Fiber Reinforced Polymer (FRP) Structures. The eighth chapter of the pre-standard focuses on the design of bearing-type connections.;The study presented herein is intended to increase the understanding of bolted joints in pultruded composites, while analyzing the effectiveness of existing failure prediction methods. Specifically, bolted connections in cooling tower tie lines are investigated for their bearing failure. Two types of samples were tested: (1) full cooling tower tie lines, which represented a single bay in cooling tower designs, and (2) shorter column-to-tie connection samples, intended to specifically test the bolted connection strength. The connections between the column and tie were either singly bolted or doubly bolted. Researchers performed compression testing on over one hundred samples until the point of failure. Failed specimens were inspected for cracks and fracture patterns. The results were analyzed and compared to values found using the strength equations provided in the pre-standard, as well as other existing methods. Since all twenty-four column-to-tie connection samples presented as bearing failures, the evaluation of existing failure prediction methods focused on the pin-bearing strength. It was found that the failures in the bolt-loaded pultruded samples could be predicted reasonably well with the proposed formulae in the pre-standard.

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