Flexibility of, and load distribution in, multi-bolt lap joints subject to in-plane axial loads.
Abstract:ESDU 98012 introduces a Fortran program, ESDUpac A9812, that computes the bolt loads and flexibilities, and joint extension and flexibility of a multi-bolt, single row, lap joint loaded in either axial tension or compression. The analysis allows for joints in which the bolts are of different sizes and are not at a regular pitch and in which the thickness and/or width of the joined plates vary between bolt pitches. The analysis may be applied to symmetric double lap joints and joints with multiple rows of bolts provided the rows are identical. The details of the idealisations adopted are explained, and worked examples illustrate the program input and output formats used. The program requires the joint geometry and material properties and the flexibilities of each of the bolts under shear loading. A theory for the calculation of these flexibilities is also described and may be used when they are not available. The program also requires the effective stiffnesses of the plates and an empirical relationship between effective stiffness and plate modulus and bolt diameter is given. However, it is suggested that, if possible, the effective stiffness of the plate to be used should be determined experimentally, and a suitable test procedure is provided. Detailed notes on the major parameters that influence the bolt loads and joint flexibility are included along with figures that illustrate those influences. The joint stiffness value calculated will be particularly useful to represent such a joint when using finite element analysis to determine the gross load distribution through a structure.
|Data Item ESDU 98012|
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|Figure 1||Variation of fb in one plate with t and lambda for 6.35 and 12.7 mm diameter bolts|
|Figure 2||Variation of fb with Aps for the 6.35 mm diameter bolts of Figure 1 at plate thicknesses of 10 and 25 mm and with lambda = 1 x 104 kN mm/rad|
|Figure 3||Effective width of plate between identical bolts (see Section 220.127.116.11)|
|Figure 4||Effect of varying N on individual bolt loads in a single lap symmetric joint of constant length with equally spaced bolts, loaded in tension|
|Figure 5||Effect of varying N on individual bolt loads in a single lap asymmetric joint of constant length with equally spaced bolts, loaded in tension|
|Figure 6||Effect of varying N on maximum bolt loads and flexibilities for single lap joints of constant length (single row of bolts equally spaced, joint properties and geometry constant along length)|
|Figure 7||Effect of varying N on individual bolt loads in a single lap symmetric joint of constant pitch with joint length varying, loaded in tension|
|Figure 8||Effect of varying N on individual bolt loads in a single lap asymmetric joint of constant pitch with joint length varying, loaded in tension|
|Figure 9||Effect of varying N on maximum bolt loads and flexibilities for single lap joints of fixed pitch and varying joint length, single row of bolts, joint properties and geometry constant along length)|