Reinforcement Limits

Rubber consumption is dominated by tyre production. In these, conveyor belts, and pressure hoses, thin layers of either steel wire or polymeric fibre reinforcement take the main mechanical loads. These layers, with rubber interlayers, allow flexibility in bending, whereas the reinforcement limits the in-plane stretching of the product. The applications are dominated by natural rubber and styrene butadiene copolymer rubber (SBR). Other rubbers have specialised properties butyl rubbers have low air permeability, nitrile rubbers have good oil resistance, while silicone rubbers have high and low temperature resistance. Rubbers play a relatively small role in this book, but the rubbery behaviour of the amorphous phase in semi-crystalline thermoplastics is important. 

An advantage of these composites is the increased resistance to fibre damage during composite processing which results from the intrinsic ductility of metallic fibres and the possibility of exploiting their plastic deformation for composite toughness enhancement [100]. A penalty is paid due to the relatively low thermal capability and poor chemical resistance of the metallic fibre reinforcement, limiting the application temperature and environment. 

Extensive studies have been carried out in the past to determine the amount of steel required in reinforced slabs. The principle adopted was that an increase of the amount of steel reinforcement limits the severity of cracking that may appear and reduces the number of transverse joints. 

For applications in design problems, where the reinforcement requirements are established, the method of replacing areas is chosen rather flian a method that balances loads or stresses. An area at the opening for carrying primary loads and stresses is removed. Thus this required area must be replaced by another area adjacent to the opening that is not used for that purpose. It is desirable to replace that area required for primary loads by an adjacent reinforcement area. Within the reinforcement limits, the reinforcement areas are assumed to have the same load-carrying capabilities as the area removed for the opening. Consequently, when the reinforcement areas are equal to or exceed the required area, primary stresses have been restored to as near the unperforated plate as possible. 

Area available in nozzle wall waU extends inward for 61 in. as full reinforcing limit outward ... 

Total reinforcement available form head and nozzle within 100% reinforcement limit is... 

For code application, the number was rounded off to 2.5 7. With the wide range of r/t ratios, which are currently used in process vessel construction, some of the codes are setting this reinforcement limit in the vertical direction by... 

Example 11.3 A cylindrical pressure vessel that is 60-in. ID by 6-in. thick contains a nozzle that is 12-in. ID by 3-in. thick. What is the stress intensity factor at the reinforcing limit that is parallel to the surface of the vessel ... 

REINFORCEMENT LIMITS 349 Solution. The two horizontal limits are set by the larger of... 

If the new reinforcement limit in the vertical direction were based on r/t = 5 instead of r/t 10 that was used to obtain the present limit of 2.5r , what is this multiplying factor in terms of T for r/t = 5 ... 

When the reinforcement limits do not extend outside the zone of nominal wall thickness of the shell and nozzle, the area available for reinforcement may be calculated by the following formulas ... 

REINFORCEMENT LIMITS Umitations on Dimensions and Shape of Openings... 

It may be possible to obtain more refinement and a thinner or narrower plate by reevaJuating the vertical limits by setting = 0.312 in. and by including the outer fillet welds if they lie within the horizontal reinforcement limits. This recalculation may reduce the pad thickness and/or the pad width. However, a 14-in. by 5/16-in. pad is satisfactory. ... 

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