BS 4978:1988
Superseded
A superseded Standard is one, which is fully replaced by another Standard, which is a new edition of the same Standard.
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Specification for softwood grades for structural use
Hardcopy , PDF
15-08-1996
English
30-11-1988
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Foreword
Committees responsible
Specification
0. Introduction
1. Scope
2. Definitions
3. Stress graded timber
Section two. Visual stress grading
4. Measurement of characteristics
5. Grade requirements
6. Marking
7. Re-marking
Section three. Visual stress grades for laminating
8. Requirements for laminating grades
Section four. Machine stress grading
9. Requirements for machine grading
10. Marking
11. Re-marking
Section five. The acceptance of stress grading machines
12. General
13. Requirements for all systems
14. Additional requirements for 'machine controlled'
systems
15. Additional requirements for 'output controlled'
systems
Appendices
A. Determination of the knot area ratio in cases of
dispute
B. The control and supervision of stress grading
operations
C. Determination of slope of grain
D. Species marking
E. Determination of settings for grading machines in
'machine controlled' systems
F. Determination of settings for grading machines in
'output controlled' systems
G. Testing for quality control of grading in 'output
controlled' systems
Tables
1. Permissible limits for the SS and GS visual stress
grades
2. Visual requirements for machine grades
3. Values of species constants
Figures
1. Edge, face and margin areas
2. Knot projection
3. Typical knot area ratios and the resulting grades
4. Measurement of rate of growth
5. Amounts of wane
6. Fissures
7. Measurement of bow, spring, twist and cup
8. Swivel handled scribe for determination of slope of
grain
9. Use of scribe
10. Measurement of slope of grain
11. A graph of variables A and B for use in the
determination of cusum control constants for mean
modulus of elasticity
12. Cusum control form (in control)
13. Cusum control form (out of control)
14. Cusum chart of data from figures 12 and 13
Specifies 2 methods of grading softwood namely, visual and machine stress grading. Permissible limits of characteristics for: (a) 2 visual stress grades - General Structural (GS) and Special Structural (SS); (b) 3 laminating grades - LA, LB and LC. Requirements for machine stress grades; Machine General Structural (MGS), Machine Special Structural (MSS), M50 and M75 and Strength Classes are specified. Also includes performance requirements for machines which grade softwood.
| Committee |
B/518
|
| DevelopmentNote |
BS DRAFT 93/104870 DC REFERS TO AMD 3
|
| DocumentType |
Standard
|
| Pages |
48
|
| PublisherName |
British Standards Institution
|
| Status |
Superseded
|
| SupersededBy | |
| Supersedes |
| Standards | Relationship |
| ISO 2299:1973 | Similar to |
| ISO 2301:1973 | Similar to |
| ISO 1030:1975 | Similar to |
| ISO 2300:1973 | Similar to |
| BS 2830:1994 | Specification for suspended access equipment (suspended chairs, traditional steeplejack\'s seats, work cages, cradles and platforms) for use in the building, engineering construction, steeplejack and cleaning industries |
| BS 8103-3:1996 | Structural design of low-rise buildings Code of practice for timber floors and roofs for housing |
| BS 6579-7:1989 | Safety fences and barriers for highways Specification for components for untensioned corrugated beam safety fence |
| BS 5975:1996 | Code of practice for falsework |
| BS 5234-2:1992 | Partitions (including matching linings) Specification for performance requirements for strength and robustness including methods of test |
| ISO/IEC Guide 28:2004 | Conformity assessment Guidance on a third-party certification system for products |
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