Analysis and modelling of the seismic behaviour of high ... - Ingegneria

3. SEISMIC BEHAVIOUR OF BOLTED END PLATE BEAM-TO-COLUMN STEEL JOINTS
deformation. A nominally pinned joint shall be designed so that it cannot develop
significant moments, which might adversely affect members of the structure, and
should be able to transmit the forces calculated in the design and accept the
resulting rotations. A joint that does not meet the criteria for a rigid joint or a
nominally pinned joint shall be classified as a semi-rigid joint.
Depending on the strength, a joint can be classified as full-strength, nominally
pinned or partial strength by comparing its moment resistance with the moment
resistances of the connected members. The design resistance of a full-strength
joint shall not be inferior to the members connected. A full-strength joint should be
so rigid that, under the design loads, the rotations at the necessary plastic hinges
do not exceed their rotation capacities. A nominally pinned joint shall be capable of
transmitting the calculated design forces, without developing significant moments,
which might adversely affect members of the structure. The rotation capacity of a
nominally pinned joint should be sufficient to enable all the necessary plastic
hinges to develop under design loads. The design resistance of a partial-strength
joint shall be not be less than that necessary to transmit the calculated design
forces and moments, but may be less than that of connected members. The
rotation capacity of a partial-strength joint, which occurs at a plastic hinge location,
shall not be inferior to the capacity needed to enable all the necessary plastic
hinges to develop under the design loads.
A vital requisite of any design approach incorporating joint response as a key
parameter, is the capability of enabling adequate approximation of the whole
beam-to-column joint response in terms of stiffness, strength and rotation capacity.
As regard to this aspect, many of the traditional methods were developed with the
sole purpose of determining the connection resistance capacity. Furthermore, the
complexity of the stress state in the nodal zone makes the range of application of
most methods rather limited (Nethercot & Zandonini, 1988). An attempt to
overcome these difficulties, and to provide a general and comprehensive tool is
given by the so-called component model, which identifies the various elemental
joint components, and builds up the overall response of the joint on the individual
response of these components (Eurocode 3, 2001). The advantages of this
approach, schematically shown in Figure 3.2, are multi-faceted: (i) the attention of
research and design is focussed on the elemental components, whose behaviour
is easier to be determined (either experimentally or numerically) and modelled; (ii)
the range of applicability is potentially unlimited, and actually bounded only by the
range of geometrical and/or mechanical data, on which the component model is
based; (iii) the response of the joint can be controlled in design through the control
of the critical component(s), i.e., of the component(s) governing the key aspect of
the behaviour for the limit state considered.
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