MS 544-part11-sec1-2001 GCP

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CODE OF PRACTICE FOR STRUCTURAL USE

OF TIMBER :

PART 11 : RECOMMENDED SPAN TABLES

AND THEIR CALCULATIONS :

SECTION 1 : DOMESTIC FLOOR JOISTS

ICS : 91.080.20

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

© Copyright

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MS 327 : PART 2 : 1997

DEVELOPMENT OF MALAYSIAN STANDARDS

The Department of Standards Malaysia (DSM) is the national standardisation

and accreditation body.

The main function of the Department is to foster and promote standards,

standardisation and accreditation as a means of advancing the national

economy, promoting industrial efficiency and development, benefiting the health

and safety of the public, protecting the consumers, facilitating domestic and

international trade and furthering international cooperation in relation to standards

and standardisation.

Malaysian Standards are developed through consensus by committees which

comprise of balanced representation of producers, users, consumers and others

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

standards where appropriate are adoption of international standards. Approval of

a standard as a Malaysian Standard is governed by the Standards of Malaysia

Act 1996 (Act 549). Malaysian Standards are reviewed periodically. The use of

Malaysian Standards is voluntary except in so far as they are made mandatory by

regulatory authorities by means of regulations, local by-laws or any other similar

ways.

The Department of Standards appoints SIRIM Berhad as the agent to develop

Malaysian Standards. The Department also appoints SIRIM Berhad as the agent

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

Persiaran Perbandaran

P.O. Box 7035, Section 2

40675 Shah Alam

40911 Shah Alam

Selangor D.E.

Tel: 60 3 5519 8033

Tel: 60 3 5544 6000

Fax: 60 3 5519 2497

Fax: 60 3 5510 8095

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MS 544 : PART 11 : SECTION 1 : 2001

CONTENTS (continued)

Page

Appendices

A Recommended average densities of timber for purpose of calculation……...…….. 13 B Sample calculation for a domestic floor joists…..……….…………...…….. 14 C Specimen span tables for domestic floor joists…..……….………..…. 16

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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 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 Master 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. Mohamed bin Mohd Nuruddin General Manager, Technology Development Division Encik Megat Kamil Azmi bin Megat Rus Kamarani Senior Manager, Standard and Quality Unit

Puan Zainora binti Zainal Manager, Standard and Quality Unit Puan Hanishahani binti Othman The Secretary of CIDB Standards Committee

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

Dr. Abdul Rashid bin Hj. Ab. Malik (Chairman) Forest Research Institute Malaysia

Puan Hanishahani binti Othman (Secretary) Construction Industry Development Board Malaysia Tuan Hj. Mohd Shukari bin Midon Forest Research Institute Malaysia

Encik Zainuddin bin Kader Public Works Department Puan Dang Anom binti Md. Zin Housing Department Prof. Madya Dr. Sabaruddin bin Mohd./ Universiti Sains Malaysia Dr. Badurol Hisham bin Abu Bakar

Prof. Dr. Zainai bin Mohamed/

Dr. Abd. Latif bin Saleh Universiti Teknologi Malaysia Prof Madya Ir. Dr. Mohd Zamin bin Jumaat Universiti Malaya

Dr. Mohd Ariff bin Jamaludin Universiti Putra Malaysia

Encik Mohd Nor Zamri bin Mat Amin Malaysian Timber Industry Board Malaysia Ir. Yap Chin Tian Timber Trade Federation Malaysia Tuan Hj. Mohamad Omar bin Mohamad Khaidzir Forest Research Institute Malaysia

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MS 544 : PART 11 : SECTION 1 : 2001

Committee representation (Working Group)

The Working Group on Recommendations For The Calculation Basis For Span Tables which developed this Malaysian Standard consists of the following representatives:

Tuan Hj. Mohd Shukari bin Midon (Chairman) Forest Research Institute Malaysia Encik Hamdan bin Husain (Secretary) Forest Research Institute Malaysia Encik Zainuddin bin Kader/

Cik Sarina bin Husain Public Works Department

Puan Hanishahani binti.Othman Construction Industry Development Board Malaysia Ir. Yap Chin Tian Timber Trade Federation Malaysia

Prof. Madya Ir. Dr. Mohd Zamin bin Jumaat Universiti Malaya Dr. Mohd. Ariff bin Jamaludin Universiti Putra Malaysia

Encik Chu Yue Pun Forest Research Institute Malaysia Encik Mohd Nor Zamri bin Mat Amin Malaysian Timber Industry Board Encik David Yeoh Eng Chuan Politeknik Shah Alam

Tuan Hj. Mohamad Omar bin Mohamad Khaidzir Forest Research Institute Malaysia Dr. Badurol Hisham bin Abu Bakar Universiti Sains Malaysia

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FOREWORD

This Malaysian Standard was developed by the Working Group on Recommendations For The Calculation Basis For Span Tables 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 construction industry.

In the development of this standard, reference was made to BS 5268 : Part 7 : 1989 “Recommendations for the calculation basis for span tables. Section 7.1 : Domestic floor 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 1 : DOMESTIC FLOOR JOISTS

1. Scope

This Section of MS 544 : Part 11 recommends a calculation basis for the permissible clear span for simply supported domestic floor joists of solid timber. The recommendations apply to joists at a maximum spacing of 610 mm centre-to-centre, this being the maximum spacing of which the `load-sharing' assumption may be adopted as described in MS 544 : Part 2. The method of calculation makes no allowance for any contribution of the flooring to the load resistance of the joists where such action can be provided by adequate attachments between the elements as in a stressed skin panel floor. Only uniform loading is considered whereas concentrated or line loads applied by partition, trimmers and other similar causes are excluded.

This Section of MS 544 : Part 11 is applicable to the species, strength and grades of timber given in MS 544 : Part 2.

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).

3. Definitions

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

3.1 Bearing length

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MS 544 : PART 11 : SECTION 1 : 2001

3.2 Effective span

Span from centre-to-centre of the minimum bearing lengths at each end.

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 a common load.

3.5 Notional bearing length

Bearing length required for the calculation of permissible clear spans.

3.6 Permissible clear span

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

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

3.7 Permissible effective span

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

3.8 Permissible stress

Stress that can safely be sustained by structural material under a particular condition.

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 section size, service and loading.

3.9 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. The symbols used are:

a distance (notional bearing length);

(11)

E modulus of elasticity;

F total load per metre length;

Fd dead load per square metre applied by mass of ceiling and flooring materials

(excluding joist self weight);

F j self weight of joist per meter length;

G shear modulus;

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 m bending. b) Significance : adm permissible; cl clear; g grade; and

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MS 544 : PART 11 : SECTION 1 : 2001

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 to Part 7 and the shear stresses as given in MS 544 : Part 2 are not exceeded and that the deflection does not exceed the recommended limit of 0.003 times the span or 14 mm (see 11.7 of MS 544 : Part 2) whichever is smaller.

NOTES:

1. A sample calculation is given in Appendix B.

2. Tables C1 to C7 in Appendix C contain specimen span tables.

5.2 Qualifying assumptions

The calculations given in this Section apply to systems of at least four domestic floor joists, at a maximum spacing of 610 mm centre-to-centre and having adequate flooring to provide lateral load distribution. Because load sharing take place the load sharing modification factor

K2 and the mean modulus of elasticity should be used.

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 purpose.

5.3 Loading

The design calculations provide for domestic floor loads which consist of the following.*

a) Imposed load

i) for an effective span equal to or greater than 2400 mm, the imposed load is 1.5 kN/m2 uniformly distributed;

(13)

(

d

)

j 1000 1.5 F s F F = +



+











j d 1000 F s F L 3600 F = +



+























ii) for an effective span less than 2400 mm, the imposed load is 3.6 kN per metre width of floor (measured perpendicular to the span) uniformly distributed over the span.

NOTE. This imposed load of 1.5 kN/m2_{entirely fulfils the recommendations of UBBL : 1984. The maximum imposed}

load of 3.6 kN per metre width is a more onerous load applied to ensure that very small joist sizes do not result from the calculations for small spans.

The imposed load should be considered as a long term load.

b) Dead load

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

) to provide for the mass of ceiling and flooring materials, puggings, 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

The total load per metre length of span, F, is found in different ways depending on whether the span is less than or greater than 2400 mm.

For spans equal to or greater than 2400 mm, F (in kN/m) is given by the equation

(1)

For spans equal to or less than 2400 mm, F (in kN/m) is given by the equation

(2)

where,

s is the joist spacing (in mm);

L is the effective span (in mm);

Fd is the dead load (in kN/m 2

); and

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

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MS 544 : PART 11 : SECTION 1 : 2001

Z M adm g, m,

=

σ

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

Fj = 9.80665 x 10 -9_ρbh

(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).

NOTE. The value of F is regarded as being in N/mm in the equations given in Clause 6, where all values are in newtons and millimetres because MS 544 : Part 2 gives stresses in N/mm2

.

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.

6.2 Limitation of bending stress

From MS 544 : Part 2, the permissible bending stress

σ

m, adm (in N/mm

2

) is given by the equation

σ

m, adm =

σ

m, g K1K2K6 (4)

where,

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

) (see MS 544 : Part 1);

K1 is the load duration modification factor, 1.0 for long term (see Table 5 of MS 544 :

Part 2);

K2 is the load sharing modification factor, 1.1 (see Clause 10 item (a) of MS 544 : Part

2); and

K6 is the section depth modification factors 1.0 (see.11.6 of MS 544 : Part : 2).

Expanding the equation

(15)

bh FL 2 2 3 adm

=

τ

(

d

)

j 2 ₂ 6 g m, 6 8 1000 1.1 x x 1.0 x bh L F s F 1.5 K       ₊       + = σ 2 2 j d 6 g m, 6 8 1000 1.1 x x 1.0 x bh L F s F L 3600 K       ₊             ₊ = σ

(

)

x 1.0 x x 1.1 0 1000 1.5 4 3 6 g m, 2 j d 2 _ =     ₊       +F s F L - K bh σ 0 1.1 x x 1.0 x 1000 2700 1000 4 3 6 g m, 2 2 j d 2 _ =     +       ₊       s _L_- _K bh L F s F bh σ

leads to the following equations: Effective span, L ≥ 2400 mm

(6)

Effective span, L ≤ 2400 mm

(7)

NOTE. These equations lead to the following polynomials in L. L ≥ 2400 mm

(8)

L ≤ 2400 mm

(9)

6.3 Limitation of shear stress

From MS 544 : Part 2, the permissible shear stress τadm (in N/mm 2

) is given by the equation:

τadm = τg K1 K2 (10)

where,

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

) (see MS 544 : Part 2);

K1 is the load duration modification factor, 1.0 for long term (see Table 5 of MS 544 :

Part 2); and

K2 is the load duration modification factor, 1.1 [see clause 10 Item (a) of MS 544 : Part

: 2].

Expanding the equation

(16)

MS 544 : PART 11 : SECTION 1 : 2001

(

)

bh L F s F 2 1000 1.5 2 3 1.1 x 1.0 _j g d

























₊ + = x

τ

bh L F s F L 1000 2 3600 2 3 1.1 x 1.0 _d _j g





































₊ ₊ = x

τ

(

)

x 1.0 x 1.1 0 1000 1.5 4 3 g j d +

-

= +

























_τ

L F s F bh 0 1.1 x 1.0 x 1000 2700 1000 4 3 j d + +



-

=



































g

τ

s bh L F s F bh

leads to the following equations: Effective span L ≥ 2400 mm

(12)

Effective span L ≤ 2400 mm

(13)

NOTE. These equations lead to the following polynomials in L. L ≥ 2400 mm

(14)

L ≤ 2400 mm

(15)

6.4 Limitation of deflection

From MS 544 : Part 2, the recommended deflection limitation δmax (in mm) is given by the

equation

δmax = 0.003L (16)

(17)

EI FL4 max 384 5 =

δ

(

)

_



_















_











₊ + = 384 5 x 1000 1.5 4 j d max EI L F s F

δ

(

)

_



_















₊













=

+ ₃ 4 j d 12 384 5 1000 1.5 0.003

x

bh E F s F L

L

              _₊            ₊ = EI L F s F L 3600 4 j d max 384 5 x 1000 δ

























































₊ ₊ = ₃ 4 j d 12 384 5 x 1000 3600 0.003 bh E L F s F L L

(

)

-0.003 0 1000 1.5 32 5 3 j d 3 _ =     ₊       +F s F L Ebh

The design equation limiting deflection is

(17)

NOTE. In addition to the deflection due to bending, the shear deflection can be significant and has been taken into account.

where, E is the mean modulus of elasticity

or, inserting the expressions for equivalent uniformly distributed load, for an effective span L ≥ 2400 mm

(18)

and for an effective span L ≤ 2400 mm

(19)

With a deflection limitation of 0.003L for an effective span L ≥ 2400 mm

(20)

and for an effective span L ≤ 2400 mm

(21)

A further design equation is required for the 14 mm limitation on deflection of spans greater than or equal to 2400 mm: this is similar to equation (20) but with '0.003L' replaced by ‘14'. The deflection of spans less than 2400 mm will be limited to less than 14 mm by equation (21).

NOTE. The three design equations lead to the following polynomials in L.

Limitation 0.003L L ≥ 2400 mm

(18)

MS 544 : PART 11 : SECTION 1 : 2001

0 0.003 -1000 32 118000 1000 32 5 3 2 j d 3 3 = + +

_



_



























s Ebh L F s F Ebh L

(

)

-14 0 1000 1.5 32 5 j d 3 4 = + +

























F s F Ebh L

and for an effective span L ≤ 2400 mm

(23)

Limitation 14 mm L ≥ 2400 mm

(24)

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 L adm, the smallest of the effective spans

for a given cross section, as limited by: a) bending stress, L ≥ 2400 mm; b) bending stress, L ≤ 2400 mm; c) shear stress, L ≥ 2400 mm; d) shear stress, L ≤ 2400 mm;

e) deflection, limitation 0.003L, L ≥ 2400 mm; f) deflection, limitation 0.003L, L ≤ 2400 mm; and g) deflection, limitation 14 mm.

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 K1K2 (25)

where,

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

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

K1 is the load duration modification factor, 1.0 for long term

(19)

2 adm adm , c, FL ba

=

⊥

σ

(

)

2 1000 1.5 1.1 x 1.0 _d _j adm g , c,

x

ba F s F L

























₊ + = ⊥

σ

2 1000 3600 1.1 x 1.0 _d _j adm adm g , c,

x

F s F L L ba

































₊

+ = ⊥

σ

K2 is the load sharing modification factor, 1.1 (see clause 10 item (a)

of MS 544 : Part 2).

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

(26)

where,

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

Ladm is the permissible effective span (in mm).

Inserting the expressions for F, equation (26) gives for an effective span L ≥ 2400 mm

(27)

for L ≤ 2400 mm

(28)

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 1) to give the permissible clear span. Lcl (in mm) is given by the

equation

Lcl = Ladm - a (29)

7. Bearing length

Although correct for the calculation of clear span the procedure given in 6.5 for the calculation of notional 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 may consist of a greater total load uniformly distributed along the span.

(20)

MS 544 : PART 11 : SECTION 1 : 2001

8. Information to be given in span tables

There are many possible formats for span tables. A typical format suitable for domestic floor joist at predetermined centers 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;

d) the 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;

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

(21)

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

(22)

MS 544 : PART 11 : SECTION 1 : 2001

Appendix B

(normative)

Sample calculation for a domestic floor joists

The objective is to find the permissible clear span, given the following data as applicable to a 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 = 1.5 kN/m2 or = 3.6 kN/m width of floor (see 5.3 (b))

(L

≥≥ 2400 mm,

see 5.3 (a))

(L ≤ 2400 mm, see 5.3 (a))

The following data are given in MS 544 : Part 2 : 2000

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 (dry), 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

MS 544 : Part 2

Load duration, K1 Load sharing, K2 Depth, K6 = 1.0 long term = 1.1 = 1.0 Table 17 Clause 10 Clause 11.6

Permissible stresses and recommended deflection limitation MS 544 : Part 11 : Section 1

Permissible bending stress,

σm,adm (in N/mm2) = σm,gK1K2

= 11.55 N/mm2

Clause 6.2 Permissible shear stress,

τadm (in N/mm2) = τgK1K2

= 1.09 N/mm2

Clause 6.3 Recommended deflection limitation

δmax (in mm) = 0.003L

or = 14 mm Clause 6.4 Permissible compression perpendicular to the

grain

Stress, σc,⊥,adm (in N/mm2) = σc,⊥,g K1K2

= 1.69 N/mm2

(23)

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 L = 1868 mm (equation (8))

or L = 1544 mm (equation (9));

b) Limitation of shear stress L = 4571 mm (equation (14))

or L = 15,744 mm (equation (15)); c ) Limitation of deflection (0.003L) L = 1510 mm (equation (22))

or L = 1248 mm (equation (23)); d) Limitation of deflection (14 mm) L = 2003 mm (equation (24)).

NOTE. Solutions to all seven design equations have been provided in (a) to (d) for illustrative purposes but in practice fewer solutions would be required for any individual permissible span calculation. Some solutions are invalid; for example the solution of equation (9) is invalid because it exceeds 2400 mm.

The permissible effective span Ladm is therefore,

Ladm = 1248 mm

The appropriate equation is selected from 6.5 (i.e. in this case for L <2400 mm) to calculate the notional bearing length, a, as 15 mm.

The permissible clear span Lcl for the joists is then,

LcI = Ladm – a

(24)

(25)

(normative)

Specimen span tables for domestic floor joists

Table C1. Permissible clear spans for domestic floor joists SG 1

Dead load supported by joist

0.25 kN/m2 0.50 kN/m2 1.25 kN/m2

Centre to centre spacing of joists (in mm) Dry Nett Size (mm) 400 450 600 400 450 600 400 450 600 Wet Nett Size (mm) 35x72 1683 1593 1391 1610 1526 1337 1453 1382 1219 38x75 95 2446 2341 2055 2327 2213 1951 2055 1958 1738 100 120 3077 2964 2702 2949 2840 2587 2662 2561 2318 125 140 3578 3448 3145 3431 3305 3013 3099 2983 2715 150 165 4200 4049 3697 4029 3882 3542 3642 3507 3194 175 190 4776 4646 4245 4623 4457 4069 4183 4029 3671 200 215 5224 5085 4755 5067 4930 4593 4702 4548 4147 225 47x72 1925 1825 1599 1834 1742 1531 1645 1566 1386 50x75 95 2686 2588 2348 2575 2480 2220 2311 2206 1964 100 120 3375 3253 2971 3237 3119 2846 2927 2818 2567 125 140 3920 3781 3456 3762 3627 3312 3405 3280 2989 150 165 4596 4435 4058 4414 4257 3891 3999 3853 3515 175 190 5106 4973 4655 4955 4824 4467 4589 4424 4038 200 215 5581 5437 5094 5418 5276 4938 5039 4903 4559 225 60x140 4220 4074 3730 4055 3912 3578 3677 3544 3234 63x150 165 4869 4744 4376 4727 4586 4200 4314 4160 3801 175 190 5387 5251 4924 5233 5098 4776 4872 4742 4364 200 215 5882 5736 5384 5717 5572 5224 5328 5188 4853 225 72x190 5600 5462 5130 5444 5307 4979 5077 4944 4619 75x200 215 6110 5963 5606 5943 5797 5443 5549 5406 5064 225 NOTES :

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

2. The shown permissible clear spans are of the mean value between the dry and wet nominal size calculation.

3. All permissible stress calculations in this span tables are based on common grade stresses and mean modulus of elasticity. 4. The tables are computed on the basis that the specification does not exclude wane at bearing.

5. The spans have been calculated in accordance with the recommendations of MS 544 : Part 2 and 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. 7. The nett sizes has taken into consideration their maximum permissible deviations .

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MS 544 : PART 11 : SECTION 1 : 2001

0.25 kN/m2 0.50 kN/m2 1.25 kN/m2

17

MS

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0.25 kN/m2 0.50 kN/m2 1.25 kN/m2

(28)

MS 544 : PART 11 : SECTION 1 : 2001

0.25 kN/m2 0.50 kN/m2 1.25 kN/m2

19

MS

(29)

0.25 kN/m2 0.50 kN/m2 1.25 kN/m2

(30)

MS 544 : PART 11 : SECTION 1 : 2001

0.25 kN/m2 0.50 kN/m2 1.25 kN/m2

21

MS

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0.25 kN/m2 0.50 kN/m2 1.25 kN/m2