Structural Timber Design

Structural Timber Design Timber construction has been one of the most innovative areas of the building industry for several years. The speed with which new products are introduced into practical application is almost breathtaking compared to the other construction materials in the building industry. As a result, timber construction is continuously increasing its market share in commercial buildings and hall structures, and even in multi-storey construction for residential and office buildings. This book provides essential knowledge and skills required for the design, detailing, and construction of timber structures. Special emphasis is placed on the specific features of timber and wood-based materials compared to other construction materials. This concerns the numerous advantages, as e.g. the comparatively low weight, the good workability of the high-performance material and the large variety of assembling technologies, but also the challenges resulting from the material anisotropy and from the susceptibility to natural pests. In each chapter the essential phenomena are explained first and then brought into connection with code regulations. This aims to support the basic understanding of the interrelations and dependencies in timber engineering, which is the fundamental basis of creative engineering.

Table of Contents:
List of Fact Sheets xi Preface xiii About the Author xv Symbols and Abbreviations xvii 1 Timber as a Structural Material 1 1.1 Building with Timber: Advantages and Challenges 1 1.2 Mechanical Properties of Solid Timber 2 1.2.1 Influence of the Fibre Direction 3 1.2.2 Strength Values of Solid Timber 3 1.2.3 Deformation Properties of Solid Timber 5 1.2.4 Influence of Load Duration and Humidity 8 1.3 Wood-based Products 10 1.3.1 Solid Structural Timber and Glued Solid Timber 10 1.3.2 Glued Laminated Timber 11 1.3.3 Cross-laminated Timber 13 1.4 Wood-based Materials 14 1.4.1 Laminated Veneer Lumber 14 1.4.2 Plywood 14 1.4.3 Oriented Strand Boards 15 1.4.4 Particle Boards 15 1.4.5 Fibreboards 16 References 17 Standards and Technical Building Regulations 17 2 Structural Design of Beam-type Members 19 2.1 Basics of Structural Design 19 2.1.1 Action Combinations 21 2.1.2 Modification Factors and Deformation Factors 22 2.2 Bending 23 2.3 Shear 25 2.4 Torsion and Rolling Shear 26 2.5 Buckling 27 2.5.1 Lateral Flexural Buckling: k c Method 29 2.5.2 Lateral Torsional Buckling: k m Method 32 2.5.3 Torsional Flexural Buckling 38 2.5.4 Calculation According to the Second-Order Theory 39 2.6 Tension and Bending 40 2.7 Serviceability Limit State 41 2.7.1 Deformations 41 2.7.2 Vibrations 43 References 44 Standards and Technical Building Regulations 44 3 Stresses Perpendicular to the Grain 45 3.1 Introduction 45 3.2 Compression 45 3.2.1 Compression Perpendicular to the Grain 45 3.2.2 Compression Stresses at an Angle to the Grain 48 3.3 Tension Perpendicular to Grain 51 3.3.1 Overview 51 3.3.2 Notches 52 3.3.3 Tension-Loaded Connections Perpendicular to the Grain 54 3.3.4 Holes in Glulam Beams 57 Reference 59 4 Dowel-type Connections 61 4.1 Introduction 61 4.2 Connections with Dowel-type Fasteners 62 4.2.1 Overview 62 4.2.2 Deformation Behaviour 62 4.2.3 Basics of the Calculation of Shear-Loaded Connections 65 4.2.4 Shear-Loaded Timber–Timber Connections 68 4.2.5 Shear-Loaded Timber–Timber Connections: Simplified Calculation 71 4.2.6 Shear-Loaded Steel–Timber Connections 71 4.2.7 Shear-Loaded Steel–Timber Connections: Simplified Calculation 74 4.3 Dowels and Bolts 75 4.4 Nails and Staples 77 4.4.1 Overview 77 4.4.2 Construction Rules for Connections with Nails 81 4.4.3 Construction Rules for Staples 84 4.4.4 Load-Bearing Capacity 86 4.5 Connections with Screws 89 4.5.1 Overview 89 4.5.2 Conceptual Design of Connections with Screws 90 4.5.3 Load-Bearing Capacity 93 4.5.4 Application Examples and Execution 96 4.6 Block Shear 97 4.7 Reinforcement of Dowelled Connections 99 4.8 Connections with Cross-laminated Timber (CLT) 101 References 104 Standards and Technical Building Regulations 105 5 Other types of connections 107 5.1 Shear Connectors 107 5.1.1 Mechanism 107 5.1.2 Connector Types and Construction Rules 107 5.1.3 Load-Bearing Capacity 112 5.2 Carpentry Connections 116 5.2.1 Overview 116 5.2.2 Halving Joints 121 5.2.3 Step Joints 124 5.2.4 Mortise and Tenon 127 5.2.5 Deformations: Slip Moduli 130 5.3 Hinged and Moment-Resistant Connections 131 5.3.1 Structural Detailing and Calculation Modelling 131 5.3.2 Method of Sections 136 5.4 Adhesive-Bonded Connections 139 5.4.1 Overview 139 5.4.2 Adhesive Bonding of Structural Elements 141 5.4.3 Connections and Repair 145 5.5 Reinforcement Against Tension Forces Perpendicular to the Grain 148 5.5.1 Notches 148 5.5.2 Connections Perpendicular to the Grain 151 5.5.3 Holes in Glulam Beams 152 References 154 Standards and Technical Building Regulations 155 6 Structural Elements: Beam-Type Members 157 6.1 Glulam Beams 157 6.1.1 Bending Stresses 159 6.1.2 Tension Stresses Perpendicular to the Grain 166 6.2 Trusses 170 6.3 Composite Elements 172 6.3.1 Beams, Slab and Roof Elements 172 6.3.1.1 Application of the γ-method 172 6.3.1.2 Thin-webbed Beams: Single Web and Box type 176 6.3.1.3 Thin-flanged Beam: Effective Width 178 6.3.1.4 Box-Type Section with Interlayer 181 6.3.2 Timber–concrete Composites (TCC) 182 6.3.3 Columns 187 6.3.3.1 Overview 187 6.3.3.2 Spaced Columns with Continuously Connected Shafts 189 6.3.3.3 Spaced Columns with Packs and Gussets 190 6.3.3.4 Lattice Columns with Glued or Nailed Joints 192 6.4 Bracing: Design and Detailing 192 6.4.1 Overview 192 6.4.2 Roof Structures 195 6.4.3 Beams and Columns 198 6.5 Modelling of Beam-Type Elements 206 References 208 Standards and Technical Building Regulations 208 Product Information (Examples) 209 7 Structural Elements – Plane 211 7.1 Light-frame Elements 211 7.1.1 Overview 211 7.1.2 Wall Elements 213 7.1.3 Slab Elements – Diaphragms 216 7.1.4 Connections and Anchoring 218 7.2 Cross-laminated Timber (CLT) 220 7.2.1 Production, Load-bearing Characteristics and Strength 220 7.2.2 Plates 224 7.2.2.1 Bending and Shear Stiffness 224 7.2.2.2 Uniaxial Load Bearing 227 7.2.2.3 Biaxial Load Bearing 229 7.2.2.4 Single Loads 229 7.2.2.5 Deflections 232 7.2.3 Wall Panels 233 7.2.3.1 In-plane Stiffness 233 7.2.3.2 In-plane Shear 234 7.2.3.3 Axial and Combined Stresses 235 7.2.4 Detailing and Load Transfer 237 7.3 Modelling of Plane Elements 240 7.3.1 CLT Plates 240 7.3.2 Shear Walls 241 7.3.2.1 Light-frame Wall Elements 241 7.3.2.2 CLT Wall Elements 243 7.4 Interaction of Diaphragms and Bracing Walls 244 References 247 Product Information (Examples) 248 8 Dynamic Behaviour of Timber Structures 249 8.1 Dynamics and Vibration 249 8.1.1 Structures Under Dynamic Impact 249 8.1.2 Natural Frequencies of Simple Systems 252 8.2 Vibration of Slabs 256 8.3 Structures Under Earthquake Impact 259 8.3.1 Earthquake Impact and Energy Dissipation 260 8.3.2 Conceptual Design and Calculation 263 8.3.2.1 Force-based Approach (Lateral Force Method) 266 8.3.2.2 Performance-based Design (Non-linear Static Analysis) 266 8.3.2.3 Response History Analysis (Non-linear Dynamic Analysis) 267 8.3.3 Response Spectra Procedure – Equivalent Load 267 8.3.4 Verification of Wall and Slab Elements 278 References 281 Standards and Technical Building Regulations 282 9 Durability and Fire Protection 283 9.1 Durability 283 9.1.1 Overview 283 9.1.2 Durability of Wood Species 286 9.1.3 Constructive Measures Against Biological Attack 286 9.1.4 Encapsulated Construction 290 9.1.5 Wood Treatment 291 9.2 Resistance to Corrosion 293 9.3 Fire Protection 294 9.3.1 Overview 294 9.3.2 Terminology and Legal Regulations 295 9.3.3 Building Classes 296 9.3.4 Classification and Requirements for Structural Elements and Materials 297 9.4 Calculation of Fire Resistance Time 300 9.4.1 Effective Cross section Method 300 9.4.2 Connections 303 References 305 Standards and Technical Building Regulations 305 10 Conceptual Design 307 10.1 Multi-storey Timber Buildings 307 10.1.1 Overview 307 10.1.2 Design Criteria 307 10.2 Roof Structures 311 10.2.1 Overview 311 10.2.2 Criteria for Conceptual Design 312 10.2.3 Primary and Secondary Load-bearing Elements 315 10.2.4 Beams and Columns 316 10.2.5 Arches, Cables and Domes 318 10.3 Bridges 322 10.3.1 Overview 322 10.3.2 Design Criteria 325 10.3.3 Actions 331 10.3.4 Load Transfer 333 10.3.5 Maintenance 335 References 336 Standards and Technical Building Regulations 338 11 Supplementary Theoretical Background 341 11.1 Strength and Size Effect 341 11.2 Fracture Mechanics: Brittle Failure 344 11.2.1 B- and D-regions 344 11.2.2 Linear-elastic Fracture Mechanics: Energy-based Fracture Criterion 345 11.2.3 Application of Fracture Mechanics 349 11.3 Theory of Plasticity 350 11.3.1 Overview 350 11.3.2 Application of the Upper Bound Theorem 351 11.3.3 Application of the Lower Bound Theorem 352 11.3.4 Capacity Design 353 11.4 Calculation Methods for Composite Beams: γ-procedure 353 11.5 Volkersen’s Theory for Adhesive Bonded Connections 358 11.6 Calculation According to Second-order Theory 361 References 365 Index 367

About the Author :
Werner Seim is a professor for Timber Engineering and Building Rehabilitation at the University of Kassel, Germany, and also an engineer with more than 35 years of experience in design and assessment of timber structures. He holds a Civil Engineering Degree from the University of Stuttgart, received his PhD in 1994 at the Karlsruhe Institute for Technology KIT and conducted postdoctoral studies 1998 at the University of California UCSD, San Diego. His research is focussed on bracing systems for high-rise buildings, timber-concrete-composites and re-use of structures. He is member of several national and international scientific committees. He was invited as a Visiting Professor to UBC Vancouver, EPF Lausanne and FCBA Bordeaux. His commitment to teaching was rewarded in 2020 with the Hessian State Prize. Werner Seim ist Professor für Holzbau und Bauwerkserhaltung an der Universität Kassel, Deutschland, und Ingenieur mit mehr als 35 Jahren Erfahrung im Bereich des Holzbaus und der Bauwerkserhaltung. Er studierte Bauingenieurwesen an der Universität Stuttgart, promovierte 1994 am KIT (Karlsruher Institut für Technologie) und absolvierte 1998 ein Postdoc-Studium an der UCSD (University of California, San Diego). Seine Forschungsschwerpunkte sind Aussteifungssysteme für Hochhäuser, der Holz-Beton-Verbund sowie die Bewertung und Wiederverwendung von Tragelementen. Er ist Mitglied in mehreren nationalen und internationalen wissenschaftlichen Ausschüssen. Er wurde als Gastprofessor an die UBC Vancouver, die EPF Lausanne und das FCBA Bordeaux eingeladen. Sein Engagement in der Lehre wurde 2020 vom Land Hessen mit einem Preis für exzellente Lehre gewürdigt. Als Ingenieur erhielt er im Jahr 2006 den Holzbaupreis des Landes Baden-Württemberg.