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The Structural behaviour of timber joints made with fully overlapping nails.

Porteous, Alexander (2003) The Structural behaviour of timber joints made with fully overlapping nails. PhD thesis, Napier University.

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    Abstract/Description

    An integrated programme of experimental and analytical work was carried out to evaluate the nonlinear
    semi-rigid characteristics of timber connections using fully overlapping nails subjected to short
    duration lateral loading and moment. The investigation is part of a continuing programme of research at
    Napier University into the behaviour of timberjoints using fully overlapping nails as the connecting Z -1
    mechanism.

    The effects of the factors and material properties that influence the behaviour of nailed joints were
    addressed in a structured and controlled way allowing semi-empirical models to be developed for the
    lateral load behaviour of rnulti-nailed timber joints using steel and plywood gusset plates. A quality
    control procedure was established for the testing programme and consistent standards were applied to
    the preparation and testing work. The semi-empirical models that were developed included for the
    effect of timber density: crussept late material effect- nail strength; number of nails: nail diameter; row
    spacing and the effect of the moisture content in the timber. They covered joints assembled with and
    without a gap between the timber and the gusset plates and for joints assembled with steel gusset plates,
    the effect of the predrill size used in the gusset plate was also investigated. The model results compared
    very well with the results from tests, accurately predicting the non-linear behaviour of the joints up to
    failure.

    An extensive analytical and experimental study was carried out to investigate the moment-rotation
    behaviour of these types ofjoints. Two linear arýd four non-linear models were developed for each type
    of joint and the efficiencies of the models were compared to detennine the one that best simulated the
    joint behaviour. The linear models consistently underestimated the capacity of the joint, giving
    conservative results. The best solutions were obtained by applying the torsion formula used for steel
    connections and incorporating the nail behaviour models developed for the non-linear lateral load
    joints. Account was taken of the non-linear behaviour of the connection and alternative models using
    fixed and moveable centres of rotation were developed. Very good comparisons were achieved between
    these models and the test results.

    A detailed comparison was made between the behaviour of the joints using the lateral load displacement
    models and Eurocode 5 (EC5) and it was concluded that EC5 rules did not accurately
    simulate the behaviour of this type of joint. It was concluded that the nail spacing rules in the code did
    not apply to fully overlapping nails. A limit state design method based on the principles used in EC5
    has been developed from the models for the design of joints using fully overlapping nails and subjected
    to lateral loading or moment.

    The semi-rigid behaviour of the joints was also investigated and it was concluded that to safely predict
    the response of structures assembled with fully, overlapping nails. the semi-rigid behaviour must be
    included for in the analysis procedure. Rigidity factors, end fixing moment reduction factors and the
    secant rotational stiffness coefficients for the joints were derived. It was also shown that where the
    analysis was limited to the serviceability limit state. a modified elastic method of analysis could be used
    and where it was beyond this state a non-linear method of analysis was required.

    Item Type: Thesis (PhD)
    Uncontrolled Keywords: Structural engineering; Timber connections; Timber joints; Overlapping nail joints; Mechanical behaviour; Rigidity; Empirical models; Lateral loading; Non-linear responses; Laboratory tests; Limit state design characteristics;
    University Divisions/Research Centres: Faculty of Engineering, Computing and Creative Industries > School of Engineering and the Built Environment
    Dewey Decimal Subjects: 600 Technology > 690 Building & construction > 694 Wood construction & carpentry
    600 Technology > 620 Engineering > 624 Civil engineering
    Library of Congress Subjects: T Technology > TH Building construction
    T Technology > TA Engineering (General). Civil engineering (General)
    Item ID: 2787
    Depositing User: Dr. David A. Cumming
    Date Deposited: 27 Jul 2009 12:25
    Last Modified: 12 Jan 2011 04:50
    URI: http://researchrepository.napier.ac.uk/id/eprint/2787

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