ESDU 85021:2012

Available as part of the ESDU Series on Structures, Stress and
Strength and Engineering Structures. For information on all ESDU
validated engineering data please contact us using the details on
the preceding page.

By using an idealised joint model, the concept of a
load/deflection diagram is developed to show the influence of
pretensioning through to joint separation. That analysis is then
built on to show how the load paths may be determined in a
practical joint, including the effects of prying apart when the
load is off-set from the fastener axis, dimensional tolerances on
squareness and flatness of the components, fastener yielding, level
of pretension, and changes in materials properties with
temperature. Guidance is included on estimating the stiffness
contribution made by each component of the joint and, in
particular, to assist in rapid calculation of the feet, graphs are
provided. Factors governing the selection of fastener size,
avoidance of separation, and fatigue loading of the fastener are
explained. Sketches illustrate the influence of bolt size and
material, hinge point position, washer and plate and foot
thicknesses, load, and other parameters on pretension values for
bolt yielding and joint separation. Two extensive practical worked
examples illustrate the use of the methods. A program based on the
methods presented, ESDUpac A8521, accompanies the Data Item. The
program treats any combination of material properties, washers of
different design on either end of the bolt, plates between the feet
or layered over the feet and under the bolt head or nut, and
non-standard features such as Belleville washers represented by
their stiffness.