Post on 05-Apr-2018
transcript
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Chapter:5Masonry Design
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Learning Outcome:
Student will be able:
To explain design concept for un-
reinforced masonry wall. To design load bearing brick wall and wall
panel.
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Introduction- Masonry Design
Standard use: BS 5628: Part 1.
Eurocode 6
Main Materials: Bricks
Blocks
Mortars
Primary Usage: Load Bearing wall
Non-Loadbearing wall
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Other traditional usage:
Road, Tunnels,
Bridges,
Retaining Walls and Sewerage Systems
Or almost the whole village:
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The 2000 Years Old Aqueduct of
Segovia, Spain
30 meters high and 800 meters long
166 Arches and 120 Pillars
Constructed entirely of Granite Blocks
No cement or mortar
Use to functions as an elevated water
channel From Rio Frio into the city.
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Replace by reinforced concrete due to superior
strength and cost.
Recaptured market through aesthetic value
Structural, thermal and acoustic (sound proof)
properties.Fire and weather resistance
Faster and cheaper
Maintenance free and durable
Can be Reinforced and Prestressed
Resist lateral (wind) and vertical loading
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BS 5628: Code of Practice for Use
of Masonry
Part 1: Structural Use of Unreinforced
Masonry
Part 2: Structural Use of Reinforced and
Pre-stressed Masonry
Part 3: Materials and Components, Design and
Workmanship
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Materials
Bricks or Blocks
Mortar or Grout
Wall ties (BS 1243 or DD140) Damp-proof
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Masonry Design - Unreinforced
Load bearing walls resist vertical loading
With or without stiffening piers
Panel walls resist lateral loading
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Wall of 25 meters range in Tawau, Sabah
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Symbols t - actual thickness of wall
h - height of panel between restraints
L - length of wall between restraints
A - cross-sectional area of loaded wall
Z - sectional modulus
tef - effective thickness of wall
hef effective height of wall (Cl. 28.3.2)
K - effective thickness coefficient (Table 5, BS) depend on spacing of piers and tp/t. ex - eccentricity of loading at top of wall
- slenderness ratio (SR), hef /tef
- capacity reduction factor (Table 7, BS 5628) depend on =hef /tef and ex.
Fk - Total characteristic loads
Gk - characterictic dead load (BS 648: Schedule of Weights for Building Materials)
Qk - characteristic imposed load (BS 6399: Design Loadings for Buildings, Part 1)
Wk - Characteristic wind load (CP3: Chap. V: Wind Loads)
f - partial safety factor for load (Clause 22, BS 5628)
m - partial safety factor for materials: 2.5 3.5 (Table 4, BS 5628)
fk - characteristic compressive strength of masonry (Table 2 & Clause 23.1, BS 5
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Design of vertically loaded masonry
walls
Ultimate Design Load,N < Design Load Resistance, NR.
N = fFk: choose greater of: N = 1.4Gk + 1.6Qk.
N = 1.2 (Gk + Qk + Wk)
Design strength of masonry = fk/m. See Table 1 & Table 2, BS 5628
Table 5.5 & 5.8 (Note)
Brickwork Table 2 (a) If HorizontalA < 0.2m2, fk,mod = fk (0.7 + 1.5A): [clause 23.1.1,
BS 5628]
If thickness of wall,t = width of brick, fk,mod = fk (1.15): [clause
23.1.2, BS 5628]
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Table 1
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Table 2
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Figure 5.9
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Blockwork Table 2 (b, c, d)
Shape factor = height/least horizontal lengthofblock (h/tb) (Figure 5.9)
Use interpolation between table for shape
factor between 0.6 (Table 2b) and 2.0 (Table 2c).
If HorizontalA < 0.2m2, fk,mod = fk (0.7 +
1.5A)
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Slenderness ratio (SR), =hef/tef
Effective height (hef)
= L - if support provide simple resistance to lateralmovement (bearing less than t/2 or 90mm)
= 0.75 L if support provide enhanced resistance to lateral
movement (Min bearing greater than t/2 and 90mm)
Effective thickness (tef)
= t for single leaf wall
= tK if stiffened with piers: (K from Table 5, BS 5628)
= max of (2/3(t1 + t2), t1, t2) for unstiffened cavity wall
= max of (2/3(t1 + Kt2), t1, Kt2) for stiffened cavity wall
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Eccentricity of Vertical Loading, ex
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Design Vertical Load Resistance of
Walls, NR
NR = stress x area = (fk/m)(t x 1)
NR = t (fk/m)
N < NR fFk < t (fk/m)
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Design procedure for vertically loaded
walls.
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Example 1: Design of a load bearing
brick wall.
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Solution
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Solution