Abstract
Structural robustness of simple beam-to-column joints in pultruded frames is assessed through tension pull tests. The tying capacity and failure modes are determined from static tests on two batches of specimens for six joints. Tying resistance is an important joint property for maintaining structural integrity in frames in case of accidental loads. No tests have been previously reported to investigate this key structural property for the design of Pultruded Fibre Reinforced Polymer (PFRP) structures. The tension pull tests consist of a PFRP Wide Flange (WF) section bolted to a stiff steel baseplate by a pair of PFRP web cleats, and at the other end the tensile load is applied. One batch of three specimens has a WF 254×254×9.53mm section with 100×9.53mm cleats of equal leg-angle material and the other has a WF 203×203×9.53mm with angles of size 75×9.53mm. Tension versus displacement curves are plotted to establish linear-elastic response, damage onset, non-linear response and ultimate tensile strength. Damage initiation is characterised by audible acoustic emissions. The load–displacement curve remains linear elastic up to 0.35 to 0.4 of the maximum (ultimate) tension force and damage happens at 0.6 of the ultimate value. Failure is from excessive delamination cracking emanating in the region of a cleat's fillet radius. A model to predict tying resistance is proposed, and successfully calibrated against experimental results. The most important finding of this study is that a pair of 9.53mm thick PFRP leg-angle web cleats should possess an adequate tying capacity for design against disproportionate collapse.
Highlights
Pultruded Fibre Reinforced Polymer (PFRP) shapes that mimic steel sections have been employed in structural engineering applications for over 40 years
Testing is split into the two batches for the 254 × 254 × 9.53 mm Wide Flange (WF) section with equal leg-angle cleats of 100 × 9.53 mm and for 203 × 203 × 9.53 mm WF section with cleats of size 75 × 9.53 mm
The most important finding is that a pair of 9.53 mm thick PFRP web cleats will possess the required minimum tying resistance of 4.5 kN in accordance with proposed guidance in Section 2.9 of an ASCE prestandard [14]
Summary
Pultruded Fibre Reinforced Polymer (PFRP) shapes that mimic steel sections have been employed in structural engineering applications for over 40 years. The minimum horizontal tying, in a steel framed building, is provided by ensuring that all steel beam-to-column joints are designed to sustain a tensile force of 75 kN. Because building height shall not exceed 4–5 storeys, the tying force method is the appropriate approach with PFRP structures It relies on development of catenary action to redistribute actions in the event of a column loss. Tying: Horizontal and vertical Ties Bridging: A structure designed to bridge over a loss of an untied member by notionally removing each untied element, and checking the area at risk of collapse is limited to: a. Developed to predict the tensile capacity is a new closed-form expression based on geometry and the transverse flexural strength of the cleat (PFRP) material
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