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Experimental Study on Wood-Adhesive-Steel-Bolts Hybrid Connections with Slotted-in Steel Plates

Kawecki Bartosz

Advances in Science and Technology. Research Journal

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2024

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Vol. 18, no 4

76--88

EN

Structural connections are one of the most important parts influencing the overall performance of a wooden structure. The way of design of these can lead both to increasing and decreasing internal stresses occurring in the load-carrying elements and structure’s total deformations. Typical mechanical joints in wooden structures are defined as plastic hinges or, at best, semi-rigid. The innovative hybrid one proposed in the paper with adhesive added between elements can be much stiffer than typical connection, which can lead to assuming rigid joint and significant reduction in stresses and deformations of a structure. The research comprised 30 specimens in three groups (10 per each group: reference - without adhesive, hybrid with one-component PUR - polyurethane adhesive and hybrid with one-component PVAc – polyvinyl acetate adhesive) tested on the MTS 809 testing machine up to failure. An innovative idea was to connect elements initially by applying an accurately predicted tightening torque value to bolts. This resulted in obtaining enough clamping pressure between elements for adhesive curing, with none other equipment. The load was applied in parallel-to-grain wood direction. The results showed that utilising hybrid connection caused, both for PUR and PVAc adhesive, a huge increase in stiffness. When comparing to the reference no-adhesive, bolted connection, this was 2365% stiffer (nearly 24 times). Load-carrying capacity was higher too, however, the increase was not that significant and was at the level of 14.4% and 27.1%, for PUR and PVAc adhesives, consecutively. Worth noting is that the hybrid connection could continue to work after adhesive failure with 60% higher stiffness than the reference one and its load-carrying capacity was only 10% lower than the reference. Hybrid connections of this type can potentially serve as structural joints because of the innovative concept of combining components. Steel plates can be covered with adhesive and then inserted between wooden parts. Next, the tightened bolts can work as clamps producing enough pressure for adhesive curing, enabling the joint to be assembled directly on the construction site. Despite the mentioned advantages, before providing the connections’ design methods, the idea needs to be tested towards various effects influencing wooden structures. Incorporating numerical modelling can be extremely important too.

2

Badania eksperymentalne spalania belek z kompozytu drewno-CFRP w skali rzeczywistej

Kawecki Bartosz, Pieńko Michał, Lipecki Tomasz

Materiały Budowlane

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2023

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nr 7

29--32

PL

W artykule przedstawiono wyniki porównawcze miejscowego spalania 24 belek w skali rzeczywistej, obciążonych statycznie, wykonanych z kompozytu drewno-CFRP oraz drewna klejonego. Wytężenie próbek wynosiło 90%, w klasie drewna klejonego GL24h. Mierzone były czas spalania do momentu zniszczenia belki, przyrost ugięcia i temperatura elementu. Podsumowując otrzymane wyniki, zauważalny jest trend pozwalający stwierdzić, że taśmy CFRP stosowane wewnątrz przekroju mogą zwiększać odporność ogniową belek, jednak muszą być chronione przez drewno w czasie oddziaływania ognia.

EN

The paper presents comparative results of the local combustion of 24 full scale beams, statically loaded, made of wood-CFRP composite and glue laminated timber. An effort of the samples was 90%, in the class of glue laminated timber GL24h. The combustion time until beams’ failure, deflection increment and element temperature were measured. Summarising the gathered results, a trend allowing to conclude that CFRP tapes used inside the cross-section can increase the fire resistance of the beams is noticeable, but they must be protected by the wood during fire exposure.

3

Numerical Modelling and Experimental Testing on Polyurethane Adhesively Bonded Joints Behaviour in Wood-Wood and Wood-Carbon Fibre Reinforced Polymer Layouts

Kawecki Bartosz

Advances in Science and Technology. Research Journal

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2023

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Vol. 17, no 2

36--52

EN

Scientists do a variety of laboratory tests on timber and wood-containing composites. An example is adhesively bonded joints in such materials. Despite a wide range of empirical research, consideration of adhesive layers or surfaces in a structure is commonly done in a very simplified manner - they are often modelled as a perfect connection between adherends. It means the cohesive stiffness and opportunity of progressive delamination are neglected. This may lead to an overestimation of the structural load-bearing capacity. The article presents wood-wood and wood-CFRP adhesively bonded joints’ investigations, based on own experimental testing technique (covering a current one as a Digital Image Correlation), analytical double-lap model for adhesives and advanced numerical Finite Element approach. The aim of the paper is to give the guidelines for complex, non-linear modelling of connections in glue laminated timber and wood-CFRP composites that can be utilised for many purposes.

4

Guidelines for FEM modelling of wood-CFRP beams using ABAQUS

Kawecki Bartosz

Archives of Civil Engineering

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2021

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Vol. 67, nr 4

175--191

EN

The article presents detailed guidelines for the nonlinear modelling of wood-CFRP beams with full cross-section using the Finite Element Method (FEM). Reviewing the literature has shown that behaviour of such composites is a current research topic, undertaken by many scientists. Complex numerical models made in the Simulia ABAQUS software are the basis for modelling recommendations. Properties of the materials consider the orthotropy and plasticity of wood and CFRP tapes, and the stiffness of adhesive layers with delamination. Results of laboratory experiments, got for a statistically significant number of specimens, confirm the model assumptions. This research paper provides a rich source of knowledge and experiences for scientists and engineers, who deal with mechanics of wood-CFRP composites. The uniqueness of the presentation lies in the detailed description of the complex numerical model. Specification comprises the steps necessary to do complete and successful calculations. The model is suitable for analysing the behaviour of wood-CFRP composites in different reinforcement configurations.

PL

Artykuł przedstawia szczegółowe wytyczne do nieliniowego modelowania belek o pełnym przekroju wykonanych z kompozytu drewno-CFRP z wykorzystaniem Metody Elementów Skończonych (MES). Przegląd literatury pokazał, że zachowanie takich kompozytów jest aktualnym tematem badawczym, podejmowanym przez wielu naukowców. Podstawą zaproponowanych rekomendacji są złożone modele numeryczne wykonane w programie Simulia ABAQUS. Parametry materiałowe uwzględniają ortotropię plastyczność drewna i taśm CFRP, jak również sztywność warstw klejowych i możliwość ich delaminacji. Założenia modelu zostały potwierdzone badaniami laboratoryjnymi przeprowadzonymi na ważnej statystycznie liczbie próbek. Powyższe opracowanie zapewnia bogate źródło wiedzy i doświadczeń dla inżynierów i naukowców zajmujących się mechaniką kompozytów drewno-CFRP. Unikalność artykułu polega na dokładnym opisie złożonego modelu numerycznego, który przedstawia kroki niezbędne do wykonania kompletnych obliczeń.