Structural Connectors Catalog 2015-2016

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128 (800) 521-9790 Many factors are evaluated before an allowable load is derived for a structural connector. One important factor is the testing. This testing will then be compared with the calculations per the governing code to determine the capacity of the connector when properly installed. The information being presented here is to provide the user and or specifier of structural hardware with the facts regarding testing done by Alpine on its structural wood connectors. Those interested should obtain and review a copy of AC13, ACCEPTANCE CRITERIA FOR JOIST HANGERS AND SIMILAR DEVICES, published by ICC and available on their web site. There are a number of critical factors to look for when reviewing a test for legitimacy; 1) Typically a test assembly will have 2 wood connectors assembled with the relevant wood members in a symmetrical pattern (see Figure 1). This arrangement will require that the load applied by the test machine be divided by 2 to achieve an allowable load for each connector. 2) The 1/8 inch gap between the ends of the member simulating the joist and the sides of the member simulating the header is critical. This gap is important to minimize any friction between joist/ hanger and header which would give an unrealistic value to the typical connection. The 1/8 inch gap must be maintained throughout the test duration because as one side of the assembly deflects the opposite side will contact the header at the bottom giving an unrealistic value. Alpine will typically use a piece of 1/8 inch Teflon between the end of the joist/hanger and the header to both maintain the 1/8 inch gap as well as reduce the friction. 3) Both ASTM-D1761 and AC13 specify that the load bearing block used on top of the joist simulator be 1/2 the span of the joist. This block length will insure that the effects of bending in the solid sawn joist member will be reflected on the connectors tested capacity. 4) A critical element to a proper test is the preload. Preloads are applied to the test assembly to seat the wood and connectors in a realistic manner to simulate actual installed conditions. Current criteria requires that the preload be between 5 and 20 percent of the ultimate load. The preload should always be indicated on any properly conducted test. Once the preload has been applied the load is removed and the dial indicators are reset before loading begins. Excessive preload will yield unrealistic values for the connector because they will pre-deflect the connectors to a point above any actual field installation. 5) One of the criteria used to evaluate a connector's capacity, based on testing, is the amount of load required to deflect the joist simulator 1/8 inch in relation to the header simulator. This measurement is usually accomplished with the use of dial indicators accurate to .001 inch placed at each Figure 1 TESTING

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