Matharu, Navroop S. (2014) Aspects of bolted connections in pultruded fibre reinforced polymer structures. PhD thesis, University of Warwick.

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Abstract

This thesis presents an extensive test programme for bolted connections using SuperStructural Pultruded Fibre Reinforced Polymer (PFRP) materials with an emphasis on characterising strengths for the pin-bearing failure mode and linking coupon results to bearing failure in lapshear bolted connections. The motivation for the research is to address key gaps in knowledge that are known to be hindering the preparation of recognised design guidelines for PFRP (frame) structures, which upon becoming available shall broaden exploitation in civil engineering works.

Prominent among these knowledge gaps has been the need to have statistically verified pinbearing and bolted connections strengths that are with connection configurations complying with current design practice. Thread in bearing, as found in practice, is investigated together, for the first time, with the plain shaft situation. Both as-received and environmental (hot-wet aging) conditioned PFRP materials are characterized to study long-term behaviour. A nonstandard pin-bearing strength test methodology, developed at The University of Warwick, is used to provide targeted test results for a comprehensive test matrix of 150 batches having 5 or 10 nominally identical specimens per batch.

A key contribution from the pin-bearing strength characterisation is that the in-house test method (WUTS) is shown to be suitable for the determination of pin-bearing strengths for flange and web materials, for bolting with or without thread and sizes from M10 to M20, and with a PFRP material orientated at 0o, 45o or 90o to the direction of pultrusion. Thread in bearing does not always have an adverse effect, and it is found that both thread pitch and material orientation have a significant contribution on the measured pin-bearing strength. It is recommended, for the situation when thread is in bearing, a reduction factor of 0.7 is applied to the characteristic plain pin-bearing strength value in the bearing strength equations. Accelerated aging regimes and long-term strength prediction modelling has shown a mean pinbearing strength reduction of up to 25% over 7.8 years, at UK service temperature of 10.5 °C. This value is found to lie within the bounds set by an American Load and Resistance Factor Design (LRFD) Pre-standard and gives confidence to the mandatory design requirements.

The thesis also reports on a series of strength tests following the methodology for pin-bearing characterization with single and double lap-shear bolted connections having configurations for single and two-rows, and for single and multi-bolts. Reported are a series of open-hole tension tests carried out to characterise the by-pass load situation in multi-rowed connections. A reduction factor of 0.6 between single and double lap configuration is found, with the possibility of multiple mixed failure modes, including block shear. The SuperStructural material has a tri-axial stitched fabric mat reinforcement (usually in pultrudates the mat is a continuous filament mat) which is influencing the strength of bolted connections. Using the procedure in Eurocode 1990, a partial factor of 1.3 for pin-bearing resistance has been calibrated by combining the WUTS and lap-shear bolted connection tests results. Results from an open-hole tension study have shown that the correlation coefficient proposed in the 1970s by Hart-Smith does not satisfactorily relate the isotropic stress concentration factor to the orthotropic stress concentration factor.

The findings and recommendations from the 1500 individual and 230 batch strength test results presented in this thesis have been successful in addressing or partially addressing a number of the key gaps in knowledge.

Item Type:	Thesis (PhD)
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Library of Congress Subject Headings (LCSH):	Fiber-reinforced plastics -- Joints, Fibrous composites, Bolted joints
Official Date:	September 2014
Dates:	Date Event September 2014 Submitted
Institution:	University of Warwick
Theses Department:	School of Engineering
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Mottram, J. Toby (James Toby), 1958-
Sponsors:	Engineering and Physical Sciences Research Council (EPSRC) - EP/H042628
Format of File:	pdf
Extent:	xviii, 289 leaves : illustrations (colour), charts (colour)
Language:	eng

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