Creep in Timber Structures

About this book

This book presents the current state of the art about creep in wood, timber and timber structures. It brings together up to date information from research and practice about the interaction between moisture changes and mechanical loading, which may lead to excessive deflections or joint movements in timber structures. Modelling of this interaction is a relatively recent development, with important applications in timber engineering, which will have consequences for national and international structural codes of practice. The book has been prepared by RILEM Technical Committee TC 112 'Creep in Timber Structures'. The importance of deflection requirements in design of timber structures is first explained, and basic knowledge of time-dependant deformations, creep and predictive models is reviewed. The next chapters discuss the sensitivity of creep to different environments, deformation kinetics, mechano-sorptive creep, time-dependent slip of joints and creep testing of wooden structural components. The last two chapters summarize the variation of moisture in timber and creep analysis of timber structures. Priority research needs are identified and an appendix reviews national building code creep factors.

Contents

The Importance of deflection requirements in the design of timber sturctures - S Thelandersson. Introduction. Glulam beams. Timber beams. Sensitivity Studies. Conclusion. Basic knowledge - P Morlier and L C Palka. Modelling of time-dependent deformations. Some general observations about creep in wood. Some basic questions. Predictive models for creepin wood and wood-based materials. References. Sensitivity of creep to different constsnt environments - C Le Govic. Notation. Introduction. Viscoelasticity of solid polymers. Experimental phenomena. Linear creep models. Thermaoactivated models. Representation of creep by non-linear models. Conclusions. References. Deformation kinetics - T A C M van der put. Introduction. Theory of molicular deformation kinetics. Conclusions from the application of the theory. References. Present knowledge of mechano-sorptive creep of wood - D G Hunt. Introduction. Testing methods. Characteristics of mechano-sorptive creep and requirements of a model. Structural theories and constitutive equations. Conclusions and recommendations for future research. References. Time-dependent slip of joints in timber engineering _ P Morlier. Introduction. Wood connector rheology. Literature review. Tests unker vonstant loading and constant environment. Tests under varying loading and vrying environment. Vreep modelling. Conclusions. References. Creep of wooden structural components: testing methods - C Le Govic. Introduction. Speciments and materials. Mechanical test. Load history. Climatic conditions and internal variables. Deflection measurements. Conclusion. References. Variation of moisture content in timber structures - S Thlandersson. Introduction. Climatic exposure. Long-term variation of MC. Distribution of MC within sections. Short-term variations. Influence of moisture variations on criip of timber beams. Summary and conclusions. References. Creep analysis of timber structures - A Ranta-Maunus. Code method. Linear viscoelastic analysis. Mechano-sorptive creep analysis. Residual stresses and long-term strength of wood. Reasearch needs. References. Conclusion: priority research needs - P Morlier. Fundamental. Characterization. Constitutive equations. Structural analysis. Timber construction. References. Appendix: National building code creep factors - C Le Govic. Introduction. Comparison of natinal codes. Concluding remarks. Index.

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