Butt joints design procedure

P(2) Instead of butt joints a strap, scarf or lap joint configuration shall be used (see Figure 5.41). The joint design is then undertaken according to the procedures for strap or scarf joints respectively. When using strap configurations the adherend ends shall also be bonded. 

The choice of joint design should also take account of the fact that the lifetime of the chosen sealant may well be less than that of the building and that at some future date the sealant will have to be replaced. If such an operation is likely, a design of joint must be used that allows defective sealant to be removed and the joint surfaces cleaned and prepared before reapplication of fresh sealant. Because this procedure is fairly straightforward in the butt joint, this is the solution most frequently adopted by designers. In the discussion of some other aspects of joint design that follows, it is assumed that the butt joint is the option chosen. 

Prevention can be accomplished by proper design and operating procedures. Nonabsorbant gasketting material should be used at flanged joints, while fully penetrated butt-welded joints are preferred to threaded joints. 

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