This paper presents results of a formal survey of current North American practices for connections in wood construction and synthesizes the data with related knowledge and experience. The primary aim of the survey was to assess current practices for selecting, designing, and specifying connections that join lumber and other structural wood-based products to each other, or components made of other material. The survey instruments were broad based electronic questionnaires and follow-up discussions with selected respondents, experts and producers of engineered wood products. Different questionnaires were distributed to structural engineers in Canada and the US, and architects in Canada. Follow-up discussions were focussed on specific issues and removal of ambiguities in responses to questionnaires. It was found that traditional fasteners like bolts, nails, spikes and screws are most widely utilized. Connection selection, design and specification practices have not changed significantly owing to the introduction of modern engineered wood products into the market place. Major perceived deficiencies in engineering design information are: complexity of code rules, lack or scarcity of appropriate information related to screwed connections, non-factory gluing, practical difficulty of using split ring and shear plate connectors, and appropriateness of using power-driven nails when design codes only address use of hammer-driven nails. The findings of the surveys are helping with prioritization of research activities within Canada and proposed revision of the Canadian wood design code.
The application of linear elastic fracture mechanics is ideally suited to estimating the strength of notched timber elements because wood is quite brittle with respect to tension across the grain. Elements with notches more than a few millimetres deep behave in a brittle manner. Some of the early research in developing this practical application of linear elastic fracture mechanics is presented.In mathematical terms the stress field in the vicinity of a notch contains at least one and sometimes two stress singularities. The magnitudes of these singularities are defined by stress intensity factors. Crack initiation, associated with a predictable size effect, occurs when these factors reach critical values.This paper gives equations for the stress fields around an orthotropic notch root. It also provides a simple method for computing stress intensity factors and size effects in notched structural elements. Some examples of stress intensity factors for timber elements containing zero and non-zero angle notches are listed. Critical stress intensity factors for timber, related to density, are given for a series of notch types. Measured effects on strength arising from interactions between loading configurations are also presented.
This paper presents an overview of research conducted by the authors and others both experimentally and analytically in the area of blast wave interactions with buildings and structures in an urban landscape. Empirical tools for the assessment of blast wave resultants for simple-geometry situations are first presented before the confining effects of buildings along a street are discussed. Street layouts such a T-junctions and crossroads are then introduced and the way that blast wave characteristics are affected by street width and the height of buildings along the street is assessed. The influence of the location of the explosive charge within the street layout on the blast load experienced by buildings is also reviewed. It is likely that building facades closest to the explosion will fail and the effect on the loading experienced further from the detonation is therefore assessed. A complementary study of the loads developed inside a building whose facade has failed is also discussed. Apart from the blast loads on buildings in a street in which there is an explosion, buildings in adjacent streets will also experience blast loading. Studies concerned with the phenomena of 'channelling' and 'shielding' are presented and the extent to which both processes occur in any given situation discussed. The various studies reported throughout the paper indicate that simple tools are often inappropriate and the development of empirical rules for more complex geometries may not be reliable. This view is supported by studying blast wave propagation in a realistic cityscape comprising streets of different widths with several layout features all bounded by buildings of different size, shape and height. Such studies conclude that computational fluid dynamics analyses may sometimes be the only satisfactory approach for the engineer seeking a reliable assessment of blast loads experienced by buildings in an urban landscape.
review of repair schemes for reinforced concrete frame buildings is presented in this paper, within the context of global objectives of the intervention process. Local as well as global intervention measures are discussed and their technological application details outlined. The effect of the reviewed repair schemes on the member, sub-assemblage and system performance are qualitatively assessed. The important role of the foundation system in the rehabilitation process is outlined and measures that are consistent with the super-structure intervention methods are given. The paper concludes with a global assessment of the effect of repair methods on stiffness, strength and ductility, the three most important seismic response parameters, to assist researchers and practitioners in decision-making to satisfy their respective intervention objectives. The framework for the paper complies with the requirements of consequence-based Engineering, where the expected damage is addressed only when consequences are higher than acceptable consequences, and a cyclical process of assessment and re-assessment is undertaken until the community objectives are deemed to be satisfied.
Embedding strength is a key parameter most commonly adopted for designing laterally loaded timber joints fastened with dowel-type fasteners. This property, however, is non-unique for any given specimen of timber but is dependent upon several factors. Currently, there is a scarcity of literature that considers some of the major factors as a whole. In this review, an attempt is made to bring some of these factors together and then examine them in the context of historical test results. This is followed by new test results derived from idealized tests for application in designing double-sided punched metal plate fastened joints. It is shown that changes in combinations of factors can potentially lead to appreciable differences in the values of embedding strength obtained from tests. By accounting for the quantitative effect of some key factors, it is possible to explain differences between theoretically obtained embedding strength values and idealized test results. In addition, the proposed indirect method of obtaining effective embedding strengths for punched metal plate timber joints is validated through correlation of idealized test results with theoretical calculations.
