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Structural joints for building frames of pultruded fibre reinforced polymers

Final Report Summary - PFRPSTRUJOIN (Structural joints for building frames of pultruded fibre reinforced polymers)

Project PFRPStruJoin conducted advanced, transformative and timely research for the preparation of scientifically founded design guidelines for mechanically fastened connections and joints in (building) frames of pultruded Fibre Reinforced Polymer (FRP) composite materials.

Research undertaken as part of the PFRPStruJoin project has produced the following important results:
1. A comprehensive literature review of the state-of-the-art experimental and analytical methodologies adopted in the construction industry for the design of mechanically fastened connections and joints in pultruded fibre reinforced polymer framed structures:
1.1 Results and conclusions obtained from the published literature relating to the effects of critical parameters, which included geometry, material properties, configuration, connecting components, fasteners, lateral restraint, etc. on the mechanical behaviour and failure modes were discussed in the light of addressing gaps in knowledge that need resolving to prepare design guidance that is reliable and robust.
1.2 Further research required to improve the design of composite mechanically fastened joints was identified as a result of this review.
2. Guidelines for a reliable failure analysis of composites in the context of the Finite Element (FE) method:
2.1 Modelling of intralaminar failure modes using continuum damage mechanics.
2.2 Modelling of interlaminar delamination using a cohesive zone approach.
2.3 Implementation of regularization techniques.
3. Validation of FE model for failure analysis of composites:
3.1 Double-cantilever and end-notched flexural specimens.
3.2 OHT specimen, which is a very challenging scientific problem because failure involves complex mechanisms such as fibre breakage, matrix cracking and delamination. In addition, the OHT strength and dominant failure modes can depend on geometrical parameters and mate-rial properties, such as hole diameter, stacking sequence and ply thickness.
4. Virtual testing of bolted connections of pultruded GFRP:
4.1 Development and validation of a nonlinear FE modelling methodology to predict the initiation and damage progression in notched FRP laminated plates subjected to increasing in-plane tension load.
4.2 Implications of geometric characteristics on net section and shear-out failures; based on the numerical results, design recommendations for minimum edge and end distances, and pitch and gauge spacing for bolts are given (support to revisiting current geometry requirements of the American Society of Civil Engineers pre-standard in 2010).
4.3 Tying resistance and structural robustness of bolted joints.

The programme of work added value to the strategy of the European committee CEN/TC250 to prepare a structural Eurocode, by way of research, for the construction material of FRPs. It furthermore contributed to the structural and technological change in the framework of the Europe 2020 Strategy and its flagship initiatives on (i) a “Resource Efficient Europe” towards a low carbon or green economy to achieve sustainable growth and (ii) “Innovation Union” under the action “Delivering the ERA” by promoting mobility of a researcher in Europe and knowledge transfer.