Moment-rotation response of nominally pinned beam-to-column joints for frames of pultruded fibre reinforced polymer: Fid-Bau Portal

Moment-rotation response of nominally pinned beam-to-column joints for frames of pultruded fibre reinforced polymer

Qureshi, Jawed / Mottram, J. Toby

Highlights • Moment-rotation behaviour of pinned joints in pultruded frames is characterised. • Joint stiffness is more variable than moment resistance. • Both initial stiffness and moment classify the joints as nominally pinned. • A single specimen measurement of stiffness is unsuitable for use in frame analysis. • FRP web cleats can crack before the mid-span deflection of a beam exceeds span/340.

Abstract This paper presents the test results to characterise the moment-rotation response of nominally pinned joints in frames of pultruded shapes. Mimicking conventional steel construction the major-axis beam-to-column joints are formed using pultruded FRP web cleats having steel bolting. There are two joint configurations with either a single row of three or two bolts per cleat leg. Testing is conducted on nominally identical specimens to statistically quantify the key joint properties. The average stiffness of all joints at damage onset is found to be 50% more variable than the average moment resistance. The presence of 70% difference between the minimum and maximum initial stiffness measured makes a single specimen measurement for stiffness unsuitable for frame analysis. The initial stiffness of the two joint configurations classifies them to be nominally pinned. No appreciable difference in characteristics for the three and two bolt configurations is found; the middle-bolt is unnecessary as two bolts give same results. The most important finding is that delamination cracks, at the top of the FRP cleats, could initiate before the mid-span vertical deflection of a simply supported beam with uniformly distributed load exceeds span/340.