MS 544-11-SEC2-2001 GCP

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CODE OF PRACTICE FOR STRUCTURAL USE

OF TIMBER :

PART 11 : RECOMMENDED SPAN TABLES

AND THEIR CALCULATIONS :

SECTION 2 : CEILING JOISTS

ICS : 91.080.20

Descriptors : permissible clear span, solid timber joist, design limitations, bearing length, timber size, joist spacing, sample calculations, span tables

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and accreditation body.

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with relevant interests, as may be appropriate to the subject in hand. These

standards where appropriate are adoption of international standards. Approval of

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ways.

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For further information on Malaysian Standards, please contact:

Department of Standards Malaysia

OR

SIRIM Berhad

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1, Persiaran Dato' Menteri

Persiaran Perbandaran

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Tel: 60 3 5519 8033

Tel: 60 3 5544 6000

Fax: 60 3 5519 2497

Fax: 60 3 5510 8095

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Page Committee representation…………..……… ii Foreword……….. i v 1 Scope……….. 1 2 Referenced documents……….... 1 3 Definitions ………..…… 1 4 Symbols……….. 2 5 Design considerations………..…… 4 6 Permissible spans………. 8 7 Bearing length……….. 12

8 Information to be given in span tables………. 12

Tables A1 Recommended average densities of timber for purpose of calculation……..…... 14

C1 Permissible clear spans for ceiling joists SG 1..………...….. 17

Figures 1 Roof construction (Typical example)………....….… 5

2 Bearing length, permissible effective and permissible clear span………... 13

Appendices A Recommended average densities of timber for purpose of calculation…………...… 14

B Sample calculations for a ceiling joists……….………. 15

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Committee representation

The Building and Civil Engineering Industry Standards Committee (ISC D) under whose supervision this Malaysian Standard was developed, comprises representatives from the following organisations :

Association of Consulting Engineers Malaysia Chartered Institute of Building Malaysia

Construction Industry Development Board Malaysia Department of Standards Malaysia

Jabatan Bekalan Elektrik dan Gas Jabatan Bomba dan Penyelamat Malaysia Masters Builders Association Malaysia

Ministry of Housing and Local Government (Housing Department) Ministry of Works (Public Works Department)

Pertubuhan Akitek Malaysia

The Institution of Engineers, Malaysia Universiti Teknologi Malaysia

The development of this Malaysian Standard is under the supervision of the following representatives of the CIDB Standards Committee:

Ir. Mohamad bin Mohd Nuruddin

Megat Kamil Azmi bin Megat Rus Kamarani Puan Zainora binti Zainal

Puan Hanishahani binti Othman

General Manager, Technology Development Division Senior Manager, Standard and Quality Unit

Manager, Standard and Quality Unit The Secretary of CIDB Standards Committee

The Technical Committee on Structural Use of Timber which developed this Malaysian Standard consists of representatives from the following organisations:

Dr. Abdul Rashid bin Hj. Ab. Malik (Chairman) Puan Hanishahani binti Othman (Secretary) Tuan Hj. Ir. Mohd. Shukari bin Midon Encik Zainuddin bin Kader

Puan Dang Anom binti Md. Zin Prof. Madya Dr. Sabaruddin bin Mohd/ Dr. Badorul Hisham bin Abu Bakar Prof. Ir. Dr. Zainai bin Mohamed/ Dr. Abd. Latif bin Saleh

Prof. Madya Ir. Dr. Mohd. Zamin bin Jumaat Dr. Mohd. Ariff bin Jamaludin

Encik Nor Zamri bin Mat Amin Ir. Yap Chin Tian

Tuan Hj. Mohamad Omar bin Mohamad Khaidzir

Forest Research Institute Malaysia

Construction Industry Development Board Malaysia Forest Research Institute Malaysia

Public Works Department Housing Department Universiti Sains Malaysia Universiti Teknologi Malaysia Universiti Malaya

Universiti Putra Malaysia

Malaysian Timber Industry Board Malaysia Malaysian Wood Industry Association Forest Research Institute Malaysia

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Committee representation (Working Group)

The Working Group on the Recommended Span Tables and Their Calculations which prepared this Malaysian Standard consists of the following representatives:

Tuan Hj. Ir. Mohd. Shukari bin Midon (Chairman) Encik Hamdan bin Husain (Secretary)

Puan Hanishahani binti Othman

Forest Research Institute Malaysia Forest Research Institute Malaysia

Construction Industry Development Board Malaysia Dr. Mohd Ariff bin Jamaludin

Prof. Madya Ir. Dr. Mohd. Zamin bin Jumaat Encik Mohd. Nor Zamri bin Mat Amin Ir. Yap Chin Tian

Dr. Badorul Hisham bin Abu Bakar Encik Chu Yue Pun

Encik David Yeoh Eng Chuan

Encik Rahim bin Husain/Puan Haliza binti Abd. Aziz Tuan Hj. Mohamad Omar bin Mohamad Khaidzir

Universiti Putra Malaysia Universiti Malaya

Malaysian Timber Industry Board Malaysia Malaysian Wood Industry Association Universiti Sains Malaysia

Forest Research Institute Malaysia Politeknik Shah Alam

Public Works Department Forest Research Institute Malaysia

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FOREWORD

This Malaysian Standard was developed by the Working Group on the Recommended Span Tables And Their Calculations established at the Construction Industry Development Board Malaysia (CIDB) under the authority of the Building and Civil Engineering Industry Standards Committee.

CIDB is the Standards-Writing Organisation (SWO) appointed by SIRIM Berhad to develop standards for the construction industry.

In the preparation of this standard reference was made to BS 5268 : Part 7 : 1989, ‘Recommendations for the calculation basis for span tables. Section 7.3 : Ceiling joists’. MS 544 consists of the following parts and sections, under the general title Code of practice for structural use of timber:

Part 1 : General

Part 2 : Permissible stress design of solid timber

Part 3 : Permissible stress design of glued laminated timber Part 4 : Timber panel products

Section 1 : Structural plywood Section 2 : Marine plywood

Section 3 : Cement bonded particleboard Section 4 : Oriented strand board (OSB) Part 5 : Timber joints

Part 6 : Workmanship, inspection and maintenance Part 7 : Testing

Part 8 : Design, fabrication and installation of prefabricated timber for roof trusses Part 9 : Fire resistance of timber structures

Section 1 : Method of calculating fire resistance of timber members Part 10 : Preservative treatment of structural timbers

Part 11 Recommendation for the calculation basis for span tables Section 1 : Domestic floor joists

Section 2 : Ceiling joists Section 3 : Ceiling binders Section 4 : Domestic rafters

Part 12 : Structural laminated veneer timber for structural application.

Compliance with a Malaysian Standard does not of itself confer immunity from legal obligations.

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CODE OF PRACTICE FOR STRUCTURAL USE OF TIMBER :

PART 11 : RECOMMENDED SPAN TABLES AND THEIR

CALCULATIONS :

SECTION 2 : CEILING JOISTS

1. Scope

This Section of MS 544 : Part 11 recommends a calculation basis for permissible clear span for ceiling joists with access at a maximum spacing of 610 mm centre-to-centre. It does not cater for the design of the ties of trussed rafters, whether prefabricated or otherwise.

The uniform and concentrated loads recommended in Uniform Building By-Law (UBBL) : 1984 are considered.

This Section of MS 544 : Part 11 is applicable to the species, strength groups and grades of timber given in MS 544 : Part 2 for both single and continuous span ceiling joists as shown in Figure 1.

2. Referenced documents

The following referenced documents contain provisions which, through reference in this text, constitute provisions of this Malaysian Standard. For dated references, where there are subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this Malaysian Standard are encouraged to investigate the possibility of applying the most recent editions of the referenced documents. For undated references, the latest edition of the publication referred to applies.

MS 544 : Part 1 to Part 8, Code of practice for structural use of timber. Uniform Building By-Laws 1984. (G.N.5178/85) (UBBL).

BS 5268 : Part 3 : Roof truss system.

Malaysian Grading Rules for Sawn Hardwood Timber : 1984.

3. Definitions

For the purpose of this Section of MS 544 : Part 11, the definitions given in MS 544 : Part 1 and the following apply.

3.1 Bearing length

Length at each end of the joist in contact with the support.

3.2 Effective span

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3.3 Grade stress

Stress that can safely be permanently sustained by material of a specific section size and of a particular strength group and grade.

3.4 Load-sharing system

Assembly to pieces of members that are constrained to act together to support common load.

3.5 Permissible clear span

Permissible unsupported span of a joist, measured between the faces of the support at its two ends.

NOTE. Permissible clear span is equal to permissible effective span less the notional bearing length. 3.6 Permissible effective span

Lowest value of effective span found from the calculations for bending strength, shear strength and deflection.

3.7 Permissible stress

Stress that can safely be sustained by a structural member of a particular cross section under the particular conditions of service and loading.

NOTE. For the purpose of this Section of MS 544 : Part 11, it is the product of the grade stress and the appropriate modification factors for depth, service and loading.

3.8 Point load

Concentrated load referred to in UBBL : 1984 that is regarded as acting at a point for calculation purpose.

3.9 Notional bearing length

Bearing length required for the calculation of permissible clear spans.

3.10 Strength group

Grouping of solid timber based on particular values of grade stress.

4. Symbols

For the purposes of this Section of MS 544 : Part 11, the following symbols apply:

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b breadth of joist;

E modulus of elasticity;

F total load per metre length;

Fd dead load per square metre applied by mass of ceiling materials, insulation etc.(excluding joist self weight);

F j self weight of joist per metre length;

Fp point load;

h depth of joist;

I second moment of area;

K modification factor (always with a subscript);

L effective span;

Ladm permissible effective span;

Lcl permissible clear span;

M bending moment;

s spacing of joists, centre-to centre;

δ deflection;

Z section modulus;

ρ density;

σ stress; and

τ shear stress.

The following subscripts are used: a) Type of force, stress etc:

c compression; and

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b) Significance: adm permissible; cl clear; g grade; and max maximum. c) Geometry:

// parallel (to the grain); and ⊥ perpendicular (to the grain).

It is recommended that where more than one subscript is used, the categories should be separated by commas.

Subscripts may be omitted when the context in which the symbols are used is unambiguous except in the case of modification factor K.

5. Design considerations

5.1 General

The design calculations recommended by this Section of MS 544 : Part 11 are based on engineers’ bending theory and are consistent with the recommendations of MS 544 : Part 1 – Part 7. The design method ensures that the permissible bending and shear stresses, as given in MS 544 : Part 2, are not exceeded and that the deflection due to bending and shear does not exceed the recommended limit of 0.003 times the span.

NOTE. A sample calculation is given in Appendix B. Tables C1 to C7 in Appendix C contain specimen span tables. 5.2 Qualifying assumptions

Although the calculations given in this Section envisage systems of ceiling joists at maximum spacing of 610 mm centre-to-centre, it is assumed that lateral load distribution is not adequate to allow stresses to be increased for `load sharing'. For members acting alone, i.e. without load sharing, the use of minimum modulus of elasticity is recommended in MS 544 : Part 2. However, for ceiling joists long experience has indicated that satisfactory performance can be achieved by the use of mean modulus of elasticity, and this practice is adopted in the equations for limiting deflection.

For roof pitches greater than 20 degree the axial tension induced by rafter thrust when the ceiling joist is used to tie complementary rafter feet together may be ignored except that it should be considered in connection design. The importance of obtaining tensile continuity when the ceiling joist is acting as a tie is emphasised.

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The uniformly distributed dead and imposed loads are as given in UBBL : 1984 for ceiling joists. Ceilings with access are assumed. The 0.9 kN concentrated load is applied only once to the ceiling joist and not simultaneously in any other position. The design calculations given in this Section do not allow for water tank loads. Additional design calculation should be made if the ceiling joists were intended to carry water tank loads.

Lateral support should be provided in accordance with 11.8 of MS 544 : Part 2.

The bearing length required at each end of the joist, calculated in accordance with 6.5, may not be sufficient for practical construction purposes.

5.3 Loading

The design calculations provide for ceilings with access and consist of the following.

a) Imposed load

0.25 kN/m2 uniformly distributed, together with a concentrated load of 0.9 kN which, in accordance with UBBL : 1984, taken as a point load for calculation purposes.

The point load is assumed to act in the position which produces maximum stress or deflection.

The imposed distributed load should be considered as a long term load. The imposed point load should be considered as a short term load, as given in MS 544 : Part 8 and Table 7 of BS 5268 : Part 3.

b) Dead load

Dead load per square metre Fd (in kN/m 2

) to provide for the mass of ceiling materials, insulation etc. Weights of materials are given in UBBL : 1984.

c) Self weight

Self weight per metre length Fj (in kN/m) to provide for the mass of the joists. The

timber densities (in kg/m3), given in Appendix A should be used.

5.4 Design loads

Two loading conditions should be considered :

a) a point and uniform imposed load condition, the loading consisting of a point imposed load plus uniformly distributed imposed load, dead load and self weight. This loading should be considered as short term; and

b) a uniform imposed load condition, the loading consisting of uniformly distributed imposed load, dead load and self weight. This loading should be considered as long term.

For the point and uniform imposed and dead loads and self weight (in kN/m) Fp = 0.9 kN

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(

d

)

j 1000 F s F 0.25+



+











(

d

)

j 1000 F s F 0.25 F= +



+











(

d

)

j p 1000 0.25 2 1000 F s F L F x F = + +



+











(

F

)

s F 1.25 L F x F













₊       + + = d j p 1000 0.25 2 1000

(

d

)

j p 1000 0.25 1.6 1000 F s F L F x F= + +



+











acting together with uniform imposed and dead loads and self weight (in kN/m)

(1) For the uniform imposed load condition, F (in kN/m) is given by the equation

(2) where,

s is the joist spacing (in mm);

Fd is the dead load (in kN/m2); and

Fj is the self weight of joist (in kN/m).

The value of Fj (in kN/m) may be found from the equation

Fj = 9.80665 x 10-9ρbh (3)

where,

ρ is the timber density (in kg/m3);

b is the joist breadth (in mm); and

h is the joist depth (in mm).

For the calculation of spans under loading incorporating a point load, the combined effect of uniform and point loads may be obtained using the equivalent uniformly distributed load F. F (in kN/m) is given by the following equations.

In bending strength calculations

(4)

In shear strength calculations

(5)

where the factor 1.25 is inserted to allow for continuity (see 6.1). In deflection calculations:

(6) In equations (4) to (6)

Fp = 0.9 kN

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(

d

)

j 2 6 g m, 6 8 1000 0.25 1800 1.5 bh L F s F L K x x 2





















₊ + + = σ Z M = adm m, σ

(

d

)

j ₂ 6 g m, 6 8 1000 0.25 1.0 bh L F s F K x x 2













_











₊ + = σ

6. Permissible spans

6.1 General

The permissible effective span of a timber joist subjected to the applied loads given in 5.3 should be the shortest effective span resulting from calculations for bending strength, shear strength and deflection, as given in 6.2, 6.3 and 6.4.

The permissible clear span should be calculated as the permissible effective span less the notional bearing length, calculated in accordance with 6.5.

Ceiling joists may be single-span beams, i.e. supported only at both ends, or they may be supported within their length by binders or supporting walls. Both configurations are covered by the design equations which recognise that the greatest deflection and bending stress occur in the single-span case while the shear stress is greater for multi-span cases.

6.2 Limitation of bending stress

From MS 544 : Part 2 the permissible bending stress σm,adm (in N/mm 2

) is given by the equation

σm,adm = σm,g K1K6 (7)

where,

σm,g is grade bending stress (in N/mm 2

) (see MS 544 : Part 2);

K1 is the load duration modification factor, 1.0 for long term or 1.5 for short term (see Table 5 of MS 544 : Part 2); and

NOTE. There is no medium term load case.

K6 is the section depth modification factor (see 11.6 of MS 544 : Part 2).

Expanding the equation

(8)

leads to the following equations.

Point and uniform imposed load condition

(9) Uniform imposed load condition

(10)

(15)

(

)

1350 - x 1.5 0 1000 0.25 4 3 6 g m, 2 2 j d 2 + =       ₊       + L K bh L F s F bh σ

(

)

- x 1.0 x 0 1000 s 0.25 4 3 6 g m, 2 j d 2 _ =     ₊       +F F L K bh σ bh FL 2 2 3 adm

=

τ

(

)

bh L F s F x L

x

























₊ ₊ + = d j g 1000 0.25 0.625 900 2 3 1.5

τ

(

)

bh L F s F 1000 0.25 x 0.625 x 2 3 1.0 x _d _j g       ₊ ₊ = τ

(

)

1350 x1.5 0 1000 0.25 2 0.625 x 3 g j d + − =       ₊       + τ bh L F s F bh (11)

Uniform imposed load condition

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6.3 Limitation of shear stress

From MS 544 : Part 2 the permissible shear stress

τ

adm (in N/mm 2

) is given by the equation

τ

adm =

τ

g K1 (13)

where,

τg is the grade shear stress (in N/mm 2

)(see MS 544 : Part 2); and

K1 is the load duration modification factor, 1.0 for long term or 1.5 for short term (see Table 5 of MS 544 : Part 2);

NOTE. There is no medium term load case.

Assuming the ceiling tie member is installed to act as continuous over two spans and expanding the equation

(14)

leads to the following equations.

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(16)

NOTE. These equations lead to the following polynomials in L.

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(

)

1.0 0 1000 s 0.25 2 0.625 x 3 g j d + − = +

























x L F F bh

τ

I E L F 1 EI FL4 p 3 max 48 384 5 + = δ

(

)

EI L F s F L F 4 384 5 1000 0.25 1.6 x 1000 j d p max

























=

+ + +

δ

(

)

3 4 bh E L x F s F L L 12 384 5 1000 0.25 1440 0.003 _d _j

























₊ + + =

(

)

225 0.003 0 1000 0.25 32 5 j d + + = +

























- L Ebh L F s F Ebh 2 3 3 3

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6.4 Limitation of deflection

From 11.7 of MS 544 : Part 2, the recommended deflection limitation δmax (in mm) for general

application is given by the equation

δmax = 0.003L (19)

The design equation limiting deflection* is: Point and uniform imposed load condition

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where, E is the mean modulus of elasticity

or, inserting the expressions for equivalent uniformly distributed load

(21)

where, Fp = 0.9 kN

with a deflection limitation of 0.003L. Point and uniform imposed load condition

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NOTE. This equation leads to the following polynomial in L.

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* The deflection due to bending excludes shear deflection because the equation is based on apparent E which has taken into consideration the shear effect.

(17)

(

d

)

j adm adm g , c, 1000 0.25 x 0.626 900 1.5 x F s F L L ba

























₊ + + = ⊥

σ

(

)

2 1000 0.25 900 1.5 x _d _j adm adm g , c, L F s F L ba

























₊ + + = ⊥

σ

6.5 Permissible clear spans

The calculation of clear span requires the deduction of a notional bearing length from an effective span.

The calculation of the notional bearing length to be deducted from the permissible effective span to produce the clear span is made after finding Ladm, the smallest of the effective spans

for a given cross section, as limited by:

a) bending stress under uniform imposed load; b) shear stress under point and uniform imposed load; c) shear stress under uniform imposed load; and d) deflection under point and uniform imposed load.

From MS 544 : Part 2 the permissible compression perpendicular to the grain stress σc,⊥,adm

(in N/mm2) is given by the equation.

σc,⊥,adm = σc,⊥,g K1 (24)

where,

σc,⊥,g is the grade compression perpendicular to the grain stress ((in N/mm 2

) (see Table 4 of MS 544 : Part 2)); and

K1 is the load duration modification factor, 1.0 for long term or 1.5 for short term (see Table 5 of MS 544 : Part 2).

NOTE. There is no medium term load case.

The notional bearing length a (in mm) required at each end should be found from the equation

σc,⊥,adm ba = Support reaction (25)

where, b is the breadth of joist (in mm).

Inserting appropriate expressions for the support reaction, equation (25) gives: Point and uniform imposed load condition with bending stress or deflection governing

(26)

Point and uniform imposed load condition with shear stress governing

(18)

(

)

2 1000 0.25 1.0 x _d _j adm g , c, L F s F ba

























₊ + = ⊥

σ

(28)

In equations (26) to (28)

a is the notional bearing length (in mm);

b is the breadth of the joist (in mm); and

Ladm is the permissible effective span (in mm).

The equation corresponding to the loading condition governing the permissible effective span should be solved for a and half the value of a should be deducted from each end of the span (total deduction a, see Figure 2) to give the permissible clear span. Lcl (in mm) is given by the

equation.

Lcl = Ladm - a (29)

NOTE. As the manner of support varies for ceiling joists, the calculation of bearing length assumes support on the underside of the joist and when preparing the span tables in Appendix C the same deduction has been applied to cater for all types of support.

7. Bearing length

Although correct for the calculation of clear span the procedure given in 6.5 for the calculation of bearing length may not ensure that the permissible compression perpendicular to the grain stress is not exceeded for all loading cases.

The design of some members may be governed by a loading case which does not represent the greatest total load of all loading cases. For example, the governing design case may include a concentrated load, but another less critical loading case may consist of a greater total load uniformly distributed along the span.

8. Information to be given in span tables

There are many possible formats for span tables. A typical format suitable for ceiling joists at predetermined centres and for quoted loading is given in Appendix C.

This Section of MS 544 : Part 11 does not recommend formats for different components but whatever format is used the following information should be given in the heading or in the main body or in the footnotes of the span tables, or in an introduction to the tables:

a) the loading;

b) details of the arrangement of the members;

c) the member sizes and their maximum permissible deviations and/or the standards that define these quantities;

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d) stress grade or strength group and/or the standards that define these properties;

e) a statement specifying any requirements additional to those given in the stress grading rules, e.g. whether wane is prohibited at bearings;

f) a statement that the spans have been calculated in accordance with the

recommendations of MS 544 : Part 2 and MS 544 : Part 11 : Section 2;

g) a statement specifying any structural requirements that may be necessary to comply with the qualifying assumptions made in 5.2, e.g. lateral support requirements, accommodation of lateral thrust at supports; and

h) the permissible clear spans.

a L cl a

a / 2 a / 2

L adm

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Appendix A

(normative)

Recommended average densities of timber for purpose of calculation

Table A1. Recommended average densities of timber for purpose of calculation Units in kg/m3

Recommended average densities Strength Group Dry Wet SG1 1050 1200 SG2 950 1100 SG3 850 1000 SG4 750 900 SG5 650 800 SG6 550 700 SG7 450 600

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Appendix B

(normative)

Sample calculations for a ceiling joists

The object is to find the permissible clear span, given the following data as applicable to particular design case.

Timber Strength group SG4, Dry (see Table 4 of

MS 544 : Part 2)

Dimensions Joist breadth, b Joist depth, h Joist spacing, s

= 47 mm = 72 mm = 600 mm

Loading Dead load, F d

Imposed load = 0.25 kN/m2 = 0.25 kN/m2 together with 0.9 kN point load (see 5.3 (b)) (see 5.3 (a)) (see 5.3 (a))

Grade stress and density MS 544 : Part 2

Common grade bending stress, σm,g Common grade shear stress, τg Mean modulus of elasticity, E

Common grade compression perpendicular to the grain stress (with wane permitted),

σc,⊥,g Density, ρ = 10.5 N/mm2 = 0.99 N/mm2 = 11000 N/mm2 = 1.54 N/mm2 = 750 kg/m3 Table 4 Table 4 Table 4 Table 4 Appendix A (MS 544 : Part 11) Modification factors

Uniform load, load duration K1 Point load, load duration, K1 Depth, K6 = 1.0 long term = 1.5 short term = 1.0 (300/h) 0.11 Table 4 Table 4 Clause 11.6

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Permissible stresses and recommended deflection limitation MS 544 : Part 11 : Section 2

Permissible bending stress,

σm,adm (in N/mm2) = σm,gK1K6

= 15.75 N/mm2 for point

and uniform load or = 10.50 N/mm2 for uniform load (long term)

Clause 6.2

Permissible shear stress,

stress τadm (in N/mm2) = τgK1

= 1.49 N/mm2 for point and uniform load or = 0.99 N/mm2 for uniform load (long t term)

Clause 6.3

Recommended deflection limitation

δmax (in mm) = 0.003L Clause 6.4

Permissible compression perpendicular to

the grain stress, σc ,_⊥,adm (in N/mm2) = σc,_⊥,g K1

= 2.31 N/mm2 for point and uniform load or = 1.54 N/mm2 for uniform load (long term)

Clause 6.5

Application of the design equations from 6.2 to 6.4 leads to the following solutions for effective span, L :

a) Limitation of bending stress, point and uniform

imposed load L = 2070 mm (equation (11))

b) Limitation of bending stress, uniform imposed load L = 7394 mm (equation (12))

c) Limitation of shear stress, point and uniform

imposed load L = 12,066 mm (equation (17))

d) Limitation of shear stress, uniform imposed load L = 10,999 mm (equation (18)) e ) Limitation of deflection, point and uniform imposed

load L = 1399 mm (equation (23))

The permissible effective span Ladm is therefore

Ladm = 1399 mm

The appropriate equation is selected from 6.5 to calculate the notional bearing length, a, as 7 mm.

The permissible clear span Lcl for the joist is then

(23)

Specimen span tables for ceiling joists

Table C1. Permissible clear spans for ceiling joists SG 1

Dead load supported by joist

0.25 kN/m2 0.50 kN/m2

Centre to centre spacing of joists (in mm Dry Nett Size (mm) 400 450 600 400 450 600 Wet Nett Size (mm) 35x72 1613 1597 1552 1552 1532 1478 38x75 95 2331 2302 2222 2222 2187 2095 100 120 3142 3095 2972 2972 2919 2779 125 140 3801 3740 3580 3580 3510 3331 150 165 4629 4549 4341 4341 4251 4023 175 190 5454 5356 5100 5100 4990 4712 200 215 6274 6157 5854 5854 5725 5398 225 47x72 1837 1817 1763 1763 1738 1673 50x75 95 2636 2600 2507 2507 2465 2356 100 120 3527 3474 3332 3332 3269 3109 125 140 4245 4176 3994 3994 3915 3713 150 165 5140 5051 4820 4820 4720 4466 175 190 6024 5917 5638 5638 5518 5213 200 215 6897 6771 6447 6447 6307 5954 225 60x140 4630 4555 4357 4357 4270 4050 63x150 165 5576 5481 5234 5234 5126 4853 175 190 6505 6392 6098 6098 5971 5647 200 215 7415 7286 6948 6948 6803 6431 225 72x190 6862 6747 6446 6446 6315 5979 75x200 215 7797 7666 7324 7324 7175 6794 225 NOTES :

1. For species in this strength group see Table 3 of MS 544 : Part 2.

2. The permissible clear spans as given, are of the minimum value between the dry and wet size calculation.

3. All permissible stress calculations in this span tables are based on common grade stresses and minimum modulus of elasticity. 4. The tables are computed on the basis that the specification include wane at bearing.

5. The spans have been calculated in accordance with the recommendations of MS 544: Part 11 : Section 1. Lateral support should be provided in accordance with 11.8 of MS 544 : Part 2.

6. The material should be stress graded in accordance with Malaysian Grading Rules 1984.

17

MS

(24)

2

0.25 kN/m2 0.50 kN/m2

Centre to centre spacing of joists (in mm Dry Nett Size (mm) ₄₀₀ ₄₅₀ ₆₀₀ ₄₀₀ ₄₅₀ ₆₀₀ Wet Nett Size (mm) 35x72 1533 1518 1477 1477 1458 1408 38x75 95 2221 2194 2120 2120 2087 2000 100 120 3001 2957 2841 2841 2791 2659 125 140 3637 3579 3427 3427 3361 3191 150 165 4437 4361 4163 4163 4077 3859 175 190 5238 5143 4898 4898 4793 4526 200 215 6035 5922 5630 5630 5505 5190 225 47x72 1748 1729 1679 1679 1657 1596 50x75 95 2515 2482 2394 2394 2355 2253 100 120 3375 3324 3190 3190 3131 2979 125 140 4070 4004 3831 3831 3756 3563 150 165 4939 4853 4631 4631 4535 4291 175 190 5800 5696 5426 5426 5310 5016 200 215 6651 6529 6213 6213 6078 5735 225 60x140 4448 4376 4185 4185 4102 3891 63x150 165 5369 5277 5038 5038 4934 4670 175 190 6277 6167 5880 5880 5756 5441 200 215 7168 7041 6710 6710 6567 6205 225 72x190 6634 6521 6225 6225 6097 5769 75x200 215 7552 7423 7085 7085 6938 6564 225 NOTES :

(25)

0.25 kN/m2 0.50 kN/m2

(26)

4

0.25 kN/m2 0.50 kN/m2

20

MS

(27)

0.25 kN/m2 0.50 kN/m2

Centre to centre spacing of joists (in mm Dry Nett Size (mm) ₄₀₀ ₄₅₀ ₆₀₀ ₄₀₀ ₄₅₀ ₆₀₀ Wet Nett Size (mm) 35x72 1151 1142 1116 1116 1104 1071 38x75 95 1688 1670 1621 1621 1599 1539 100 120 2306 2276 2196 2196 2160 2067 125 140 2816 2776 2668 2668 2621 2497 150 165 3467 3412 3267 3267 3203 3040 175 190 4126 4055 3870 3870 3790 3586 200 215 4787 4700 4475 4475 4378 4133 225 47x72 1321 1310 1277 1277 1262 1222 50x75 95 1925 1903 1844 1844 1817 1745 100 120 2615 2579 2484 2484 2442 2332 125 140 3180 3133 3006 3006 2951 2807 150 165 3896 3832 3664 3664 3591 3405 175 190 4615 4534 4324 4324 4234 4004 200 215 5332 5235 4983 4983 4875 4601 225 60x140 3504 3450 3307 3307 3245 3084 63x150 165 4273 4202 4016 4016 3935 3729 175 190 5040 4952 4723 4723 4623 4372 200 215 5802 5697 5425 5425 5308 5012 225 72x190 5366 5273 5031 5031 4926 4659 75x200 215 6159 6050 5765 5765 5642 5330 225 NOTES :

(28)

6

0.25 kN/m2 0.50 kN/m2

22

MS

(29)

0.25 kN/m2 0.50 kN/m2

MS 544-11-SEC2-2001 GCP

CODE OF PRACTICE FOR STRUCTURAL USE

OF TIMBER :

PART 11 : RECOMMENDED SPAN TABLES

AND THEIR CALCULATIONS :

SECTION 2 : CEILING JOISTS

ICS : 91.080.20

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for distribution and sale of Malaysian Standards.

For further information on Malaysian Standards, please contact:

Department of Standards Malaysia

OR

SIRIM Berhad

Tingkat 21, Wisma MPSA

1, Persiaran Dato' Menteri

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40675 Shah Alam

40911 Shah Alam

Selangor D.E.

Selangor D.E.

Tel: 60 3 5519 8033

Tel: 60 3 5544 6000

Fax: 60 3 5519 2497

Fax: 60 3 5510 8095

CONTENTS

FOREWORD

CODE OF PRACTICE FOR STRUCTURAL USE OF TIMBER :

PART 11 : RECOMMENDED SPAN TABLES AND THEIR

CALCULATIONS :

SECTION 2 : CEILING JOISTS

1.

Scope

2.

Referenced documents

3.

Definitions

4.

Symbols

5.

Design considerations

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