4. DATOS CLÍNICOS 1 Indicaciones terapéuticas
4.8 Reacciones adversas Resumen del perfil de seguridad
where fs for the tabular values was taken as fy, the yield stress of steel, but can take any value depending on the force in the bar at the point considered.
Table 4.5: Anchorage bond lengths (mm)
*f
y=250 N/mm
2In mortar In concrete
Bar size (mm)
32 1740 1300 1450 1040
*based on bar attaining full yield stress (÷ γms)
Table 4.6: Anchorage bond lengths (mm)*
f
y=460 N/mm
2In mortar In concrete
Bar size (mm)
Plain Deformed Plain Deformed
8 800 600 665 480
10 1000 750 835 600
12 1200 900 1000 720
16 1600 1200 1330 960
20 2000 1500 1670 1200
25 2500 1875 2080 1500
32 3200 2400 2670 1920
*based on bar attaining full yield stress (÷ γms)
Design of reinforced masonry 77
26.7 Laps and joints
26.8 Hooks and bends 26.9 Curtailment and anchorage
It is necessary for a number of reasons to continue bars beyond the point where they are no longer required to resist bending:
1. to allow for variations in load distribution in which case the shape of the bending moment diagram will be different to that calculated
2. to allow for tolerances in the placement of reinforcement
3. if the presence of stirrups would cause stress in the reinforcement at that point to increase to that corresponding to the moment at a section roughly an effective depth (for 45° cracks) away from that point
4. cracks of above average size may well occur at the points where the bars stop, which may locally reduce the shear strength
The minimum extension beyond the theoretical cut-off point is the greater of the effective depth or 12×the bars size to cater for points 1 to 3, whilst the extra provisions (a) to (c) deal with 4. Provisions (a) and (c) control the size of the crack at the cut-off point and (b) ensures that there is a reserve of shear strength. Provision (c) will be the easiest to apply and is recommended for general use. Provision (b) will often apply where low shear stresses are present and any nominal links provided automatically supply excess shear strength. Extra links can be added to comply with (b) but this is not recommended since extra shear calculation will be necessary and the amount and complexity of the reinforcement involved will generally be more than if the main reinforcement is extended to comply with (a) or (c). It should be noted that Clause 26.6 requires that no bars be cut-off less than an appropriate anchorage length from the last point at which it is assumed to be fully stressed. This will, on occasion, override the requirements discussed above.
No guidance is given in respect of curtailment of compression reinforcement or tension reinforcement which extend into compression zones beyond points of contraflexure. Provisions (a) to (c) can safely be ignored here but bars should extend the greater of 12 bar diameters or an effective depth beyond the point at which they are theoretically no longer required. For anchoring bars at simple supports using hooks or bends, reference should be made to Clause 26.8.
References
1. BRITISH STANDARDS INSTITUTION. CP 110: Part 1:1972 The structural use of concrete.
BSI, London. pp. 156.
2. POWELL, B and HODGKINSON, H R. The determination of the stress/strain relationship of brickwork. British Ceramic Research Association, Technical Note TN 249. 1976.
3. NEWSON, M J. A preliminary investigation of the stress/strain relationship for concrete blockwork. Cement and Concrete Association, Slough, 1983. pp. 30.
4. BEARD, R. A theoretical analysis of reinforced brickwork in bending. Proceedings British Ceramic Society, No. 30, 192.
5. ROBERTS, J J and EDGELL, G J. The approach to bending. Paper presented to Symposium on Reinforced and Prestressed Masonry, Cafe Royale, London, 8 July 1981. Institution of Structural Engineers. pp. 12–16.
6. BRITISH STANDARDS INSTITUTION. BS 5628: Part 1:1978 Unreinƒorced masonry, BSI, London. pp. 40.
7. RATHBONE, A J. The behaviour of reinforced concrete blockwork beams. Cement and Concrete Association, Slough, 1980. Publication No. 42.540.
8. RATHBONE, A J. The shear behaviour of reinforced concrete blockwork beams. Paper presented to Symposium on Reinforced and Prestressed Masonry, Cafe Royale, London, 8 July 1981. Institution of Structural Engineers. pp. 17–28.
9. SUTER, G T and KELLER, H. Shear strength of grouted reinforced masonry beams.
Proceedings 4th International Brick Masonry Conference, 1972.
10. TELLET, J and EDGELL, G J. The structural behaviour of reinforced brickwork pocket type retaining walls. British Ceramic Research Association, TN 353, 1983.
11. SINHA, B P and DE VEKEY, R C. Factors affecting the shear strength of reinforced grouted brickwork beams and slabs. Proceedings, 6th IBMAC, Rome 1982.
12. BRITISH STANDARDS INSTITUTION. CP 111:1970 Structural recommendations for loadbearing walls. BSI, London. pp. 40.
13. BRITISH CERAMIC RESEARCH ASSOCIATiON/Structural Ceramics Advisory Group.
Design guide for reinforced and prestressed clay brickwork, Special Publication SP 91, 1977.
14. ANDERSON, D E and HOFFMAN, E S. Design of brick masonry columns. Designing, Engineering and Constructing with Masonry Products. Gulf, Houston, Texas, 1969.
15. CEB/FIP. MANUAL ON BENDING AND COMPRESSION. CEB/FIP, Construction Press, Harlow, 1982. pp. 111.
16. BRITISH STANDARDS INSTITUTION. BS 8110:1985 Code of Practice for concrete. BSI, London.
17. ROWE, R E, et al. Handbook on the Unified Code for structural concrete (CP 110:1972).
Viewpoint Publications, London, pp. 153.
18. DAVIES, S R and ELTRAIFY, L A. Uniaxial and biaxial bending of reinforced brickwork columns. Proceedings 6th IBMAC, 1982.
19. HENDRY, A W. Structural brickwork (Chapter 2). Macmillan Press, London, 1981.
20. SCRIVENER, J C. Shear tests on reinforced brick masonry walls. British Ceramic Research Association, Technical Note TN 342, 1982.
21. HODGKINSON, H R and WEST, H W H. The shear strength of some damp-proof course materials. British Ceramic Research Association, Technical Note TN 326, 1981.
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