A finite-element approach for the analysis of pin-bearing failure of composite laminates

In this paper, a numerical home-made finite element model for the failure analysis of bolted joints between fiber-reinforced composite laminates is presented. The model is based on an incremental displacement-based approach, it is hinged on the laminate theory and on a progressive material degradation governed by the failure of composite constituents. The model has been applied to a pin-plate system comprising a mono-directional fiber-reinforced laminated plate, and numerical results in terms of the bearing failure load have been successfully compared with available experimental data. Aim of this paper is to evaluate the effectiveness of Rotem's and Huang's failure criteria in predicting the pin-bearing failure of bolted joints. The selected criteria act at different material scale: the former operating at the laminate level, while the latter at the constituent's scale. Proposed results seems to suggest that failure criteria accounting for micro-structural stress-strain localization mechanisms (for instance, Huang's criterion) give a more accurate estimate in terms of pin-bearing failure load

A finite-element approach for the analysis of pin-bearing failure of composite laminates

In this paper, a numerical home-made finite element model for the failure analysis of bolted joints between fiber-reinforced composite laminates is presented. The model is based on an incremental displacement basedapproach, it is hinged on the laminate theory and on a progressive material degradation governed by the failure of composite constituents. The model has been applied to a pin-plate system comprising a monodirectional fiber-reinforced laminated plate, and numerical results in terms of the bearing failure load have been successfully compared with available experimental data. Aim of this paper is to evaluate the effectiveness of Rotem’s and Huang’s failure criteria in predicting the pin-bearing failure of bolted joints. The selected criteria act at different material scale: the former operating at the laminate level, while the latter at the constituent’s scale. Proposed results seems to suggest that failure criteria accounting for micro-structural stress-strain localization mechanisms (for instance, Huang’s criterion) give a more accurate estimate in terms of pin-bearing failure load

In-plane shear capacity response of FRCM-strengthened masonry walls

This paper aims at investigating the in-plane shear response of FRCM-strengthened masonry walls. To this end, available results of experimental tests are collected, accounting for the masonry substrate made with bricks and mortar joints and several FRCM materials applied with different strengthening configurations. The contribution of the composite material to the masonry wall shear capacity is evaluated. The influence of some geometrical and mechanical parameters on the shear strength of the retrofitted walls is assessed. Available analytical design formulations are implemented to the database and commented

Basalt-based FRP composites as strengthening of reinforced concrete members: Experimental and theoretical insights

This work aims to investigate the effectiveness of BFRP composites as strengthening material for beam-like concrete structural elements. The non-linear flexural response of beams strengthened with BFRPs is investigated. An analytical approach, based on the evaluation of the cross-section moment-curvature relationship, that also considers the tension stiffening phenomenon, is developed and applied to a number of study cases. Neverthless, typical failure modes involve also the FRP-concrete end-debonding. This latter occurs as a brittle mechanism that jeopardises the ductility demand required in the structural design concept, becoming a critical issue. In this framework, results of a wide experimental program based on push-pull double shear tests on BFRP-concrete specimens are presented, by proposing suitable correction coefficients for improving the effectiveness of some available technical design rules when BFRP are adopted

A numerical failure analysis of multi-bolted joints in FRP laminates based on basal fibers

AbstractThis paper aims to model the progressive damage of multi-bolted joints connecting structural elements made up of FRP (fiber- reinforced polymers) composite laminates and comprising different fiber materials (namely, based on basalt, carbon and glass), as well as different stacking sequences. Differences in failure mode and ultimate-load values are numerically investigated. A numerical home-made finite element model has been conceived, implemented, and validated by means of available experimental data. The numerical model is based on an incremental displacement-based approach and on a plane-stress bi-dimensional for- mulation. The stress analysis has been performed by accounting for micro-structural stress-strain localization mechanisms, and describing the progressive damage process by implementing a failure criterion operating at the constituents’ scale (namely, the Huang's criterion). Proposed results have highlighted that bolted joints based on basalt-FRP laminates and defined by a double- bolted configuration exhibited bearing failure loads comparable to those computed for glass-FRP and carbon-FRP laminates. In the case of single-bolted joints, the use of carbon-FRP laminates allowed to obtain the best mechanical properties, although joints based on basalt-FRP laminates numerically-experienced mechanical response and strength features always comparable with those of glass-FRP

Guide for the Design and Construction of Externally Bonded Fibre Reinforced Inorganic Matrix Systems for Strengthening Existing Structures

The FRCM (Fibre-Reinforced Cementitious Matrix/Mortar) composites are nowadays used in structural rehabilitation interventions, more and more frequently, instead of classic FRP fibre reinforced composites (Fibre Reinforced Polymer), made with long glass, carbon or aramid fibres immersed in polymeric matrices (such as epoxy resins). In international literature the first are also called TRC (Textile Reinforced Concrete), TRM (Textile Reinforced Mortars), FRM (Fabric Reinforced Mortar) or even IMG (Inorganic Matrix-Grid Composites). In the following, since the acronym FRCM has been adopted in already approved Italian ministerial documents, it is preferred to continue using the same acronym. FRCM composites are the result of coupling nets, made with the same fibres mentioned above, or with others which have appeared more recently on the building materials market, with an inorganic matrix based on lime or cement mortar. Innovative fibres include basalt, PBO (Polyparaphenylene benzobisoxazole) and steel. In particular, this last material, very common in the construction field, is proposed again for use in FRCMs, in a version with highly enhanced mechanical performance, thanks to a particular processing process. The inorganic matrix has numerous advantages over the organic FRP matrix, especially for applications to masonry structures, given its greater affinity with this type of substrate. At the moment some guidelines are available in the international field for the qualification of FRCMs and for the design of structural reinforcement interventions carried out with such materials. In this connection the US acceptance criteria (ACI 434 - Acceptance Criteria for Masonry and Concrete Strengthening Using Fiber-Reinforced Cementitious Matrix (FRCM) Composite Systems, issued by ICC Evaluation Service, 2018) and the design guidelines (RILEM TC 250-CSM & ACI 549 - Guide to Design and Construction of Externally Bonded Fabric-Reinforced Cementitious Matrix (FRCM) and Steel Reinforced Grout (SRG) Systems for Repair and Strengthening Masonry Structures, pending approval) can be mentioned. In recent years, the scientific interest in the innovative applications of FRCMs for structural rehabilitation, on the one hand, and the special nature of the widely varied Italian building heritage on the other, have attracted the interest of numerous researchers operating in the fields of Structural Mechanics, Construction, Structural Rehabilitation and Seismic Engineering. It is clear that the drafting of an Italian Guideline for the design and construction of strengthening interventions with FRCMs could no longer be postponed; above all, the drafting of a wide ranging document usable for the different types present in the national building heritage, from the masonry to the concrete constructions, as well as for the many FRCM products currently present on the national market that are different in nature of the matrix and the net reinforcement. The CNR, through its Advisory Committee on Technical Recommendations for Construction, promptly felt this need and made efforts to satisfy it by setting up a Working Group in June 2016 with the task of drawing up a Guideline for the design and construction of externally bonded fibre reinforced inorganic matrix systems for strengthening existing structures. In July 2017, the CNR Advisory Committee approved a first draft of this Technical Document on a proposal from the Working Group. Subsequently, the Working Group expanded to include all interested Italian researchers already scientifically committed to the topic, and benefited from the invaluable contribution of the FRCM manufacturers. It was thus possible to draw up the present version of the Technical Document, broader than the initial draft and characterized by more advanced applications and more sophisticated approaches which are at the frontier of current international research on the topic of structural reinforcement with FRCM