EUROCODE 6 Design of masonry structures

Transcription

1 Dissemination of information for training Brussels, 2-3 April EUROCODE 6 Design of masonry structures

2 Dissemination of information for training Brussels, 2-3 April Laterally Loaded Masonry

3 Introduction Dissemination of information for training Brussels, 2-3 April U.K. Walls slender in comparison to most of Europe Design EC6: Pt. 1.1 Calculation methods EC6: Pt. 3 - Empirical guidance and - Simplified calculation - methods 3

4 Dissemination of information for training Brussels, 2-3 April Effective thickness (t ef ) (Dependant on layout t Characteristic lateral load W k wind load Section modulus Z = (bt ef 2 )/6 h Unit type Unit strength Unit dimensions Mortar type Partial safety factor for load (γ f ) Degree of Control Of Construction (γ m ) Checks: Shear strength Slenderness limits Irregular shapes Openings Hollow blocks DPC s Cavity walls height length Aspect ratio (h/l) Support conditions Design moment of Design resistance M = (Zf kp )/γ m l Characteristic flexural strength when failure parallel to bed joints (f kb ) Orthogonal ratio μ = fkb/fkp (Modified due to self weight) moment per unit height m = αw k γ f l 2 Characteristic flexural strength when failure perpendicular to bed joints (f kp ) Bending moment coefficient (α) 4

5 Dissemination of information for training Brussels, 2-3 April Load Type Permanent Actions G k Variable Actions Q k1 Additional Variable Actions Combinations of Actions Combinations of Actions Permanent plus Variable (leading only) Unfavourable γ F Favourable γ F Unfavourable γ G Favourable γ G Q ki Favourable γ Qi Ψo Permanent plus Variable (wind) Permanent plus Variable (leading) plus Variable (additional) wind x0.5 NOTE Wind may be either a leading or additional variable load. 5

6 Clause 18 of BS5628 Part 1 Dissemination of information for training Brussels, 2-3 April

7 Clause 18 of BS5628 Part 1 Dissemination of information for training Brussels, 2-3 April

8 Design To EC6 Part 1.1 Dissemination of information for training Brussels, 2-3 April (Flexural strength approach - Clauses & 6.3.1, Annex E & Annex F) f xk1 f xk2 h h Characteristic flexural - strength Applied moments Moments of resistance Design procedure Shear design Slenderness limits LL 8

9 Characteristic Flexural Strength Dissemination of information for training Brussels, 2-3 April f xk1 (About an axis parallel to bed joints) f xk2 (About an axis perpendicular to bed - joints) Table NA.6 of UK National Annex (strengths) Annex E of EC6 Pt. 1.1 (panel coefficients) Annex F of EC6 Pt. 1.1 (size limitations) 9

10 Applied Bending Moment Dissemination of information for training Brussels, 2-3 April Preliminaries Orthogonal strength ratio μ = f xk1 /f xk2 Panel aspect ratio = h/l Bending moment coefficient obtained - using μ and h/l from Annex E of EC6 Pt

11 Applied Bending Moments Dissemination of information for training Brussels, 2-3 April Vertically spanning walls M Ed1 = αw Ed h 2 m = design moment per unit length wall W Ed = design lateral (wind) load unit area h = height between horizontal supports α = bending moment coefficient With simple supports, α = (1/8) 11

12 Applied Bending Moments Dissemination of information for training Brussels, 2-3 April Horizontally spanning walls M Ed2 = αw Ed L 2 M Ed2 = design moment per unit height wall W Ed = design lateral (wind) load unit area L = length between vertical supports α = bending moment coefficient With simple supports, α = (1/8) With fixed supports, α = (1/16) 12

13 Applied Bending Moments Dissemination of information for training Brussels, 2-3 April Two way spanning walls M Ed1 = α 1 W Ed L 2 M Ed1 = design lateral (wind) load unit area L = length between vertical supports α 1 = bending moment coefficient And α 1 = µ α 2 13

14 Moment Of Resistance Dissemination of information for training Brussels, 2-3 April M Rd = f xd z or (f xd1 + σ d )z where: M Rd = Design moment of resistance f xd = Design flexural strength about - relevant direction of bending (NA.6) f xd1 = Design flexural strength with - plane of failure parallel to bed - joints z = Section modulus (bt 2 /6) σ = d Design vertical dead load ( 0.2f d ) 14

15 Moment Of Resistance Dissemination of information for training Brussels, 2-3 April Walls with Piers - Assessing z Take outstanding length of flange from face of pier as lesser of: h/10 for vertically spanning walls h/5 for cantilever walls half the clear distance between piers And h is clear height of wall 15

16 Design Procedure Dissemination of information for training Brussels, 2-3 April Assume support conditions 2. Assume strength and thickness of - unit required 3. Find orthogonal strength ratio - μ = f xk1 /f xk2 4. Find panel aspect ratio = h/l 5. Find moment coefficient, α (Annex E) 6. Determine bending moment applied to panel as: M Ed = αw Ed l 2 16

17 Design Procedure Dissemination of information for training Brussels, 2-3 April Check flexural capacity of wall, M Rd as: M Rd = f xd z self weight may - be included 8. If M Rd M Ed then wall acceptable If not, return to 1) or 2) and modify Shear and panel dimensions still to be checked. 17

18 Shear Strength Of Panels Dissemination of information for training Brussels, 2-3 April Shear must be controlled such that: V Rd V Ed 18

19 Shear Strength Of Panels (Clauses & 6.2) Dissemination of information for training Brussels, 2-3 April Design shear strength of masonry (V Rd ) f vk = (f vko + 0.4σ d ) 0.065f b where, σ d is design compressive stress, if any And V Rd = (f vk /γ m ) A w Design shear applied (V Ed ) V Ed = W Ed A w where W Ed is design (wind) load per unit area A w is effective cross-sectional area of wall. - Use 45 o spread lines 19

20 BS5628 Clause 21 Dissemination of information for training Brussels, 2-3 April

21 BS5628 Clause 21 Dissemination of information for training Brussels, 2-3 April

22 BS 5628 Clause 21 Dissemination of information for training Brussels, 2-3 April

23 BS 5628 Clause 21 Dissemination of information for training Brussels, 2-3 April

24 EC6 NA Table NA.5 Dissemination of information for training Brussels, 2-3 April

25 EC6 NA.2.5 & NA.2.6 Dissemination of information for training Brussels, 2-3 April For filled and unfilled perpend joints respectively 25

26 Cavity Walls To EC6 Pt. 1.1 Dissemination of information for training Brussels, 2-3 April Design strength = sum of design lateral - strength of each wall M Rd = M Rd1 + M Rd2 OR Design applied load W Ed apportioned to - each leaf on a stiffness basis (W Ed1 ; W Ed2 ) 26

27 Eurocode 6 Part 1.1 Annex E Dissemination of information for training Brussels, 2-3 April

28 BS 5628 Pt.1 Slenderness Limits Dissemination of information for training Brussels, 2-3 April Panel simply supported top and bottom Height 40t ef Free standing wall Height 12t ef 28

29 Eurocode 6 Part 1.1 Annex E Dissemination of information for training Brussels, 2-3 April

30 Eurocode 6 Part 1.1 Annex E Dissemination of information for training Brussels, 2-3 April

31 Eurocode 6 Pt. 1.1 NA.2.8 Dissemination of information for training Brussels, 2-3 April

32 Values characteristic flexural strength from EC6 Dissemination of information for training Brussels, 2-3 April

33 Values characteristic flexural strength from EC6 Dissemination of information for training Brussels, 2-3 April

34 EC6 NA Table NA.6 Dissemination of information for training Brussels, 2-3 April

35 EC6 NA Table NA.6 (Detail) Dissemination of information for training Brussels, 2-3 April

36 BS 5628 Pt.1 Slenderness Limits (Clause 32.3 controls slenderness) Dissemination of information for training Brussels, 2-3 April Panel supported on three sides (i) Two or more sides continuous: height x length 1500t ef 2 (ii) All other cases: height x length 1350t ef 2 No dimension to exceed 50t ef 36

37 BS 5628 Pt.1 Slenderness Limits Dissemination of information for training Brussels, 2-3 April Panel supported on four sides (i) Three or more sides continuous: height x length 2250t ef 2 (ii) All other cases: height x length 2025t ef 2 No dimension to exceed 50t ef 37

38 Eurocode 6 Pt. 1.1 Figure F.1 Dissemination of information for training Brussels, 2-3 April

39 Eurocode 6 Pt. 1.1 Figure F.2 Dissemination of information for training Brussels, 2-3 April

40 Eurocode 6 Pt. 1.1 Figure F.3 Dissemination of information for training Brussels, 2-3 April

41 Dissemination of information for training Brussels, 2-3 April Comparison of serviceability limits for Laterally Loaded Panels 2.7m high & 100mm thick Description Maximum panel length Maximum panel length BS 5628 EC6 Walls restrained top and bottom but not ends 4m 3m 41

42 Dissemination of information for training Brussels, 2-3 April Comparison of serviceability limits for Laterally Loaded Panels 2.7m high & 100mm thick Description Panels supported on four edges Maximum panel length Maximum panel length BS 5628 EC6 5m 12m 42

43 Dissemination of information for training Brussels, 2-3 April Comparison of serviceability limits for Laterally Loaded Panels 2.7m high & 100mm thick Description Maximum panel length Maximum panel length BS 5628 EC6 Panels supported on three edges 5m 12m 43

44 Dissemination of information for training Brussels, 2-3 April Comparison of serviceability limits for Laterally Loaded Panels 2.7m high & 100mm thick Description Maximum panel length Maximum panel length BS 5628 EC6 Panels supported on three edges 5m 5,2m 44

45 Dissemination of information for training Brussels, 2-3 April Enhancing Lateral Load Performance

46 Bed joint reinforcement used to enhance lateral load resistance Dissemination of information for training Brussels, 2-3 April Use partial safety factors from BS 5628 Part 1 Can use mortar designation (iii) c.s.a. reinforcement at least 14mm 2 at vertical centres not exceeding 450mm. 46

47 Limiting Dimensions in BS 5628 Dissemination of information for training Brussels, 2-3 April Number of sides Types of support supported 3 Two or more sides continuous 1800 t 2 ef 4 Three or more sides continuous 2700 t 2 ef All other cases 1600 t 2 ef All other cases 2400 t 2 ef N.B No dimension to exceed 60 t ef 47

48 Four design methods in BS5628 Dissemination of information for training Brussels, 2-3 April Design as horizontally spanning wall 2. Design with reinforced section carrying extra load only 3. Design using modified orthogonal ratio 4. Design based on cracking load 48

49 Four design methods Dissemination of information for training Brussels, 2-3 April Design as horizontally spanning wall 2. Design with reinforced section carrying extra load only 3. Design using modified orthogonal ratio 4. Design based on cracking load 49

50 Wall types Dissemination of information for training Brussels, 2-3 April Type a Type b Type c Type d walls restrained along 4 edges walls restrained along all edges, except for 1 vertical edge walls restrained along all edges, except at top edge walls restrained along the top and bottom edges only 50

51 Figure B.1 Dissemination of information for training Brussels, 2-3 April