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<br />Aside from the <br /> <br />material properties <br />to be considered: <br /> <br />of the brick walls, there are three <br /> <br />types of restraints <br />. Wall clips. <br />o Roof rafter and ceiling joists. <br />. Connection of studs to base plate. <br />Walls 1 and 2 had only the wall clips and stud connections to baseplate <br />restraints. Wall 3 had the additional restraints of roof rafters and ceiling <br />joists. <br />First, consider the restraint of the roof rafter and ceiling joist at its <br />connection to the top plate of the stud wall. The variables which can affect <br />the strength of this restraint include: <br />. Kinds of lumber used. <br /> <br />o Way the connection is nailed. <br /> <br /> <br />. Slope of roof rafter. <br /> <br /> <br />. Amount of dead load on top of the roof rafter producing friction at the <br /> <br />connection. <br /> <br />A test setup for roof rafter and ceiling joist restraints is presented in Fig- <br />ure 22. <br />The roof rafter slope and dead load made no noticeable difference in the <br />strength of the roof rafter and ceiling joist restraint. The connection was <br />nailed in the standard manner with reasonable positioning of nails into the <br />member. Later, tests were conducted with nails driven for maximum penetration <br />into the top plate as well as going through enough of the roof rafter and <br />ceiling joist. Connections with nails placed for maximum penetration were <br />slightly stronger, but as long as the nails were placed in a reasonable manner <br />the difference in the strength of the restraint was slight. The pine lumber <br />caused an increase in the slope of the load deflection curves (Figure 23). <br />The maximum restraint of this connection using spruce was about 1,200 to <br />1,500 lb (Figure 24). <br />The restraint due to wall ties was determined. There are several types <br />and thicknesses of wall ties (Figure 25) but the two most commonly used (22 <br />and 28 gage) were tested. The test setup is presented in Figure 26. The <br />clips have a wide variation in load deflection characteristics. In general, <br />the 22-gage clips have a maximum strength of 100 to 200 lb (Figure 27a). The <br />28-gage clips have a maximum strength of about 40 to 60 lb (Figure 27b). The <br />variation of the strength of the 28-gage clips is greater than that of the <br /> <br />15 <br />