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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