Butt strap joints

Riveted steel pipes (untuberculated)—(good = girth, riveted only normal = full riveted, taper, or cylinder joints poor = full riveted, butt-strap joints)... 

Figure 50 shows the adhesive shear stress distributions for a doublescarf joint and a double butt-strap joint and compares them with ordinary single- and double-lap joints. The double butt-strap joint gives the lowest stress concentration at its middle, but is then identical to the ordinary, parallel double-lap joint at the other end. For this reason, it is suggested that the straps should be bevelled or scarfed so that the stress concentration might approach that of the double-scarf joint. 

Fig. 80. Double-lap joints (a) to ASTMD 3165-73 (b) stresses in a doublelap joint (c) double butt-strap joint (dimensions in mm).

Another variation of the lap test is the true double lap illustrated in Fig. 80(b). Even in this case, as was shown in Chapter 2, we still have differential straining of the adherends and the loads are still non-colinear internally, even though the external forces balance. Such joints tend to fail at T where the adhesive is in transverse tension rather than at C where it is in compression. The double butt-strap joint shown in Fig. 80(c) is a form of double-lap joint and again it fails at T. Sometimes, if the gap between the two tension members is small, most of the load is carried directly across the stiff, butt faces. Premature failure ensues here but the joint is still able to carry a substantial load in excess of this. 

ISO 12215-6 (2008) International Standards Organisation. Part 6 Small Craft-HuU construction and Scantlings - Structural arrangements and details Jarry E, Shenoi RA (2006) Performance of butt strap joints for marine applications. Int J Adhes Adhes 26 162-176... 

Thermosetting resin pipe can be joined with mechanical joints or adhesive-bonded Joints. Mechanical joints are generally a variation of gasketed bell-and-spigot joints and may be either nonrestrained or self-restrained. Adhesive-bonded joints are typically bell-and-spigot or butt-and-strap. Butt-and-strap joints join piping components with multiple layers of resin-saturated glass reinforcement. 

A typical laminated joint is a butt joint on to which doublers are laminated, the result being a double-strap joint. The following features distinguish this laminated joint from the corresponding adhesively bonded double-strap joint ... 

Escher, G. A., and W. B. MacDonald Chemical and Mechanical Properties of Butt and Strap Joints, Proceedings of the 1975 Conference on Managing Corrosion with Plastics, National Association of Corrosion Engineers, Houston. 

Most of the adhesively bonded pipe joints used in engineering, such as adhesively bonded socket joints, butt-weld and strap joints and heat activated coupling joints etc., can be basically regarded as two pieces of composite pipes joined by a connection coupler via the bonding adhesive, as shown in Figure 5. In order to reduce the stress concentration influence on the joint system, the smart beam-like joint concept was extended to develop a novel adhesively bonded smart composite pipe joint system by integrating the smart piezoelectric... 

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. 

Figure J.l Common flat adhesive joint designs butt, plain lap, and single strap. (See Appendix K for joint design improvements on these.)...

The section on design of structural adhesive joints will describe and cite advantages and disadvantages of joint geometries, such as butt, lap, scarf, strap, and combined versions of these. A general design criterion will also be included. Another section of the chapter will pertain to fracture mechanics. General theories on fracture mechanics and test techniques used to characterize structural adhesives fracture behavior will be discussed. 

Most common joint is the lap or variations on the lap, for example, the tapered lap and scarf (preferred). Can also incorporate straps and self-locating mechanisms. Butt joints are not recommended on thin sections. 

---