Designers' Guide to Eurocode 5: Design of Timber Buildings: En 1995-1-1

ISBN-13: 9780727731623 / Angielski / Twarda / 2013 / 220 str.

Jack Porteous

Opis

This series of Designers Guides to the Eurocodes provides comprehensive guidance in the form of design aids, indications for the most convenient design procedures and worked examples. The books also include background information to aid the designer in understanding the reasoning behind and the objectives of the codes. All of the individual guides work in conjunction with the Designers Guide to EN 1990 Eurocode: Basis of Structural Design. The part of Eurocode 5 covered by this guide, EN 1995-1, addresses the common rules and rules for buildings, including structural fire design. This Designers Guide looks specifically at timber buildings, including full explanation and commentary on the code with examples, and direction to the National Annex documents."

Spis treści

Introduction - background to the Eurocode programme - status and field of application of the Eurocodes - national Standards implementing Eurocodes - links to EN’s - additional information specific to EN1995-1-1 - UK National Annex Chapter 1 - scope of EC5 Part 1 - normative reference - the language of the Euronorms - principal symbols and reference structure - member Axes Code section Chapter 2 2.1 Basic requirements 2.1 - a brief introduction to limit state design EN1990 - the limit states - partial factors - combination factors 2.2 Limit state design in timber 2.2 - first/second order analysis - serviceability limit states - (EN 1990) - influence of creep on deflection 2.3 Basic variables 2.3 - (EN1991) - comment on imposed/snow/wind actions - load-duration classes (sec 3.1.3) (relation to BS 5268) - service classes - Kmod and Kdef 2.4 Verification by the partial factor method 2.4 - relationship between characteristic / design values - design resistances Chapter 3 – Material properties - general factors which modify strength and stiffness for each material form: - basic material specification reference - depth factors - (Characteristic values for design purposes are given in the relevant EN for each material) 3.1 The general modification factors 3.1 - for strength (table 3.1) - for deflection (table 3.2) 3.2 Solid timber 3.2 - specification reference EN 14081.1 - the size factor - strength and stiffness properties - the strength classes (EN 338) - species/grade combinations (EN 1912) 3.3 Glued laminated timber 3.3 - specification reference EN14080 - the size factor 3.4 Laminated veneer timber (LVL) 3.4 - specification reference EN14374 - size factors (bending/tension) 3.5 Wood based panels 3.5 - specification 3.6 Adhesives 3.6 - types - conditions of use 3.7 Metal fasteners and connectors 3.7 - specification - types - corrosion protection Chapter 4 - Durability 4.1 Basic principles 4.1 material either: - durable in service class, or - treated to achieve durability 4.2 Methodology 4.2 (based on BS 8417, using EN references) - service factors (eg: replaceability) - service life - natural durability of selected timber - determine need for preservation - the range of preservatives - environmental issues Chapter 5 – Basis of structural analysis 5.1 General rules 5.1 - appropriateness of model - elastic/plastic behaviour - allow for deformations/joint slip 5.2 Member rules 5.2 5.3 Connections 5.3 5.4 Assemblies 5.4 - rules for models - plane frames and arches - second order check for slender structures Chapter 6 – Ultimate limit states Basic expressions for the strength verification of members in tension/compression/bending/shear. 6.1 Design of cross sections subject to stress in one direction 6.1 - tension/compression parallel to grain - tension perpendicular to grain - compression perpendicular to grain: low basic values in EN 338 clause is a series of equations to increase strength for local loading (clause likely to be amended) - bending - expressions for bending about two axes (no lateral/torsinal instability: see below) - shear - (rolling shear) - rules for concentrated loads close to support - torsion 6.2 Cross-sections subject to combined stress 6.2 - compression at an angle to the grain - bending/tension - bending/compression 6.3 Stability of members 6.3 - general explanation - columns: compression/bending - beams: bending/compression - effect of load distribution - (rules for stable beams from BS 5268) 6.4 Varying cross-sections 6.4 - single tapered beams - double, curved, pitched beams - (reductions due to ‘slope of grain’, tension forces) 6.5 Notched members 6.5 - general - beams notched at the support 6.6 System strength 6.6 - enhancement factors for linked members Chapter 7 – Serviceability limit states 7.1 The deflection of elements and assemblies 7.1 - the serviceability limit state - EN 1990 references - beams (load combinations) - creep deflection - assemblies (effect of joint slip) 7.2 Limiting values for deflection of beams 7.2 - the components of deflection - limiting values - EN 1990 - EC5 - EC5 UKNA 7.3 Vibrations 7.3 - principles of design - residential floors Chapter 8 – Connections with metal fasteners 8.1 The range of fasteners - nails, bolts etc (illustrated: commercial types) - applications: pros/cons - strength comparison (eg: single lapped joint 250mm wide) - (stiffness comparison) 8.2 Connection design - calculations complex (many variables) - but critical, as strength often less than members - for these reasons, suggest two-stage approach: - initial design (sometimes conservative) (may be sufficient for non-critical joints) - depending on results: - proceed to detailed design, or - re-configure joint to increase capacity Initial design: - determine member actions: values/directions/duration of load) - determine member thickness (d1, d2)/strength classes/service class - draw joint configuration - choose fastener type/diameter/spacings - determine single fastener capacity from, eg: load tables - calculate fastener group capacity Detailed design: - see following sections 8.3 Design of nailed connections 8.3 8.3.1 Nail types/properties - round/square/annular grooved - gun application - Pre-drilling: disadvantages 8.3.2 Joint layout - member sizes, arrangement - service class - strength classes (giving density) EN338 - trial fastener layout (spacing rules) 8.3.1.2(5) - (based on assumed fastener diameter) 8.3.3 Nail strengths - calculate yield moment My,r,k 8.3.1.1(4) - determine t1, t2, hence t1/t2 8.3.1.1(1) - (check min, pointside penetration) 8.3.4 Member properties - thicknesses (check t1, t2 above) - calculate characteristic embedment strength fhik 8.3.1.1(5) - calculate characteristic withdrawal strength FaxRk 8.3.2.2(4) - (note possible modification for 12d > tp> 8d) 8.3.2(1) - (note possible modification for service class) 8.3.2(8) 8.3.5 Calculation of fastener group strength 8.2.2(1) - enter equations with values above - (limit rope effect to max percentage) - (notes in relation to steel members) - Determine FvRk as min value - Calculate nef for loads parallel to grain 8.3.1.1(8) - Calculate fastener group strength 8.3.6 Axially loaded nails - general rules - withdrawal / pull through strength - load combinations 8.4 Stapled connections 8.4 -mainly based on nail rules - (brief coverage, as not greatly used in UK) 8.5 Bolted connection 8.5 8.5.1 Bolt types/properties 8.5.2 Joint layout (scope of this and following sub sections as nails) 8.5.3 Bolt strengths 8.5.4 Member properties 8.5.5 Calculation of bolt group strengths 8.5.6 Axially loaded bolts 8.6 Dowelled connections 8.6 - mainly based on bolt rules 8.7 Screwed connections 8.7 8.7.1 Screw types/properties 8.7.2 Joint layout (scope of this and following sub sections as nails) 8.7.3 Screw strengths 8.7.4 Member properties 8.7.5 Calculation of fastener group strength 8.7.6 Axially loaded screws 8.8 Connections made with punched metal plate fasteners 8.8 8.8.1 Plate types/properties 8.8.2 Plate capacity - brief coverage, as plates generally designed by fabricators using commercial software) 8.9 Split ring and shear plate connectors 8.9 8.9.1 Connector types/properties 8.9.2 Connector capacities - (brief, as little used in commercial design) Chapter 9 Components and assembles 9.1 Components 9.1 - glued thin webbed beams - basis of design - stresses in the flanges/webs - stability of the compression flange - buckling of the web - glued thin-flanged beams - basis of design - effective flange width - flange stresses - mechanically jointed beams/columns - basis of design (see Annex B/C) 9.2 Assemblies 9.2 - trusses - simple rules - metal plate fasteners - roof and floor diaphragms - ‘horizontal diaphragm: simple analysis - wall diaphragms (two methods are included in the code, but neither are thought to be satisfactory. A third method is currently under development) (see also Chapter 13) - bracing - single members in compression - system bracing Chapter 10 Structural detailing and control Detailing rules in construction which are necessary for the design rules in the previous chapters to apply - materials - glued joints - connections with mechanical fasteners - dowels - screws - assembly/transport/erection - control - diaphragm structures Chapter 11 – Annexes A,B,C - Annex A: block/plug shear failure (rarely critical) - Annex B/C: mech-jointed beams/built-up cols, (deals with the effect of slip in the joints) Chapter 12 – Fire Design Fire design is covered comprehensively in EC5 Part 1-2. This chapter outlines the approach to the design of structural timber members in fire conditions. - Basic requirements:  Period of fire resistance  (spread of flame – a non-structural requirement given in National Regulations) - In the UK, the period of fire resistance is likely to be:  None (for, eg, roofs not stabilising walls)  1/2hr or 1hr,, with controls on deflection after that time - Sacrificial design of exposed timber members  Charring rates  Check on residual profile - Protection of timber members  Non-combustible materials, eg, plasterboard  Part 1-2 gives analytical method  In UK, much reliance is made on tests for standard arrangements, eg suspended floors. Chapter 13 – Multi-storey timber frames Frame details - as TRADA publication / panel construction Overview of design criteria: - strength and stability - (thermal performance) - (acoustic performance) - (form of cladding) - (moisture movement of frame) - the effect of the above on structural design Vertical loading: - roof / floor design - transfer through floor X - wall design Lateral loading: - principally wind loads - failure modes:  sliding  racking (shear)  overturning  relative importance related to height and height/width ratio - Sliding resistance:  achieved by friction/fasteners  racking resistance  two methods in Section 9  possible third method - Inter-relation between racking and overturning - Overturning resistance: - Methodology (based on B55268- Part 6.1)  establish wind loads in two principal directions  identify stiff cross-walls in plan form  design walls for racking  apportion wind load to wall in proportion to racking resistance  make analysis of overturning about lee-ward edge, for each wall, using ECO loading combinations  wall satisfactory, or requires tie-down  local effects (Chapter 14 – Limit state design) (Chapter 15 – Research background)