Resin connectors in timber

Di Maria, V., 2017. Resin connectors in timber. PhD, Nottingham Trent University.

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The use of Glued In Rod joints for wooden constructions is an efficient technology to connect and design members in new timber structures and to rehabilitate the damaged structural elements of historical buildings. The major issue concerning the use of adhesive anchors in timber is the lack of a standard regulation in the current Eurocode 5 for timber structures. Due to the gap in knowledge of this specific topic in engineering structural design, designers' choices are still supported by test analysis which enables knowledge, and the prediction, of the structural behaviour of Glued In Rod joints.

Over the last 30 years, research studies have suggested diverse and contradictory procedures for the prediction of the withdrawal capacity of adhesive anchors in timber whose application led to the relay of inconsistent information about the use of Glued In Rods in the timber engineering field.

The presented research work is aimed at clarifying the contradictory nature amongst existing design rules and at proposing a correct design procedure to assess the load bearing capacity of adhesive anchors in timber, whilst also taking into consideration the high product-dependency which Glued In Rod connections are characterised by. Moreover, the thesis investigates the development of new prototypes of resin connectors in timber through the identification of innovative technical solutions in order to achieve an improved structural performance of the studied adhesive joints.

An extensive experimental program has been carried out on 'traditional' and new prototypes of adhesive anchors in timber, identified respectively by smooth-cylindrical and rough-threaded internal boreholes in which 8 mm steel rods have been glued by the use of low and high viscosity epoxy resins. The tensile performance of more than 100 samples of single adhesive anchors made from solid timber and glulam has been tested by pull-compression tests in confined test regimes, in both cold states and at elevated temperatures.

Experimental findings suggest that in cold states and in restrictive manufacturing conditions, the adoption of the new prototype of Glued In Rods, characterised by the presence of a threaded and rough internal bonding surface, can simultaneously provide an increase of up to 12% in the withdrawal capacity and a decrease in the joint’s cost, due to a significant reduction (30-40%) in the use of epoxy resins when compared to 'traditional' Glued In Rods. Conversely, a change in the internal borehole's shape does not affect the thermal performance of the connections, highlighting that the structural performance of a Glued In Rod joint at elevated temperatures is highly dependent on the thermal properties (Heat Deflection Temperature) of the resin used to assemble the connection.

Regarding the design of the withdrawal capacity of Glued In Rods, a critical literature review revealed that previous design equations all stemmed from research studies based on the application of different methods and investigative methodologies for both the manufacturing and the testing phases; hence, they cannot be used to produce general statements on the structural behaviour of Glued In Rods. The thesis filled the gap in knowledge about the design of adhesive anchors in timber by proposing a simple and innovative design process mainly composed of two phases: the identification of a specific bond strength parameter which has to be determined by standard experiments and provided by adhesive manufactures, and the presentation of a mathematical equation which allows the calculation of the withdrawal capacity of a single adhesive anchor in timber by knowing the aforementioned bond strength parameter and joint's geometrical features.

This research thesis provides critical information about all the stages that the process of using Glued In Rod connections involves (manufacturing, testing, installation and design) identifying priority actions to be undertaken for the implementation of European technical guidelines and design methods for the use of adhesive anchors in the timber engineering field.

Item Type: Thesis
Creators: Di Maria, V.
Date: February 2017
Rights: This work is the intellectual property of the author. You may copy up to 5% of this work for private study, or personal, non-commercial research. Any re-use of the information contained within this document should be fully referenced, quoting the author, title, university, degree level and pagination. Queries or requests for any other use, or if a more substantial copy is required, should be directed to the owner of the Intellectual Property Rights.
Divisions: Schools > School of Architecture, Design and the Built Environment
Record created by: Linda Sullivan
Date Added: 19 Sep 2017 08:07
Last Modified: 20 Aug 2021 13:12

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