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

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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. 43
3. SEISMIC BEHAVIOUR OF BOLTED END PLATE BEAM-TO-COLUMN STEEL JOINTS A number of validation and calibration studies were carried out in the last decade, and design criteria and recommendations were developed and included in the Eurocodes 3 (2001) and Eurocode 4 (2002). 44 5 1 6 2 7 4 3 1. - Column web panel in shear 2. - Column web in compression 3. - Beam flange in compression 4. - Bolts in tension 5. - Column web in tension 6. - Column flange in bending 7. - End plate in bending Figure 3.2. Mechanical model of the EC3 - Design of joints A similar development, as to the novel importance of joints in design, took place in earthquake engineering. The possible role of joints in the energy dissipation mechanism was in fact recognised and the potential of semi-continuous frames in seismic areas investigated. Design approaches based on conceptual design were also proposed for steel as well as for composite frames. The limits of the traditional approaches in appraising the joint response become even more evident when cyclic loads are considered. A clear need for catching stiffness and strength deterioration, and possible pinching effects associated with buckling and fracturing of components and with the increase of lack-of-fit due to plastic deformations (in particular in bolted connections), makes the requirements to be met by prediction models more strict than in the case of static loading. The peculiar features listed above for the component method make it a fairly appealing solution for modelling joints also in seismic analysis. In particular, it should be stressed that it would allow to concentrate on the cyclic response of individual components, which can be investigated in a far more simple and economic way than the response of the whole joint. 3.3 Semi-rigid partial-strength extended end plate connection Extended end plate as well as flush end plate connections allow to realize joints covering a rather wide range of strength and stiffness. In many instances they also possess an adequate rotation capacity for plastic design. The complexity of the
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Dipartimento di Ingegneria Meccanic
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UNIVERSITÀ DEGLI STUDI DI TRENTO D
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3. SEISMIC BEHAVIOUR OF BOLTED END
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4. SEISMIC RESPONSE OF PARTIAL-STRE
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5. SEISMIC BEHAVIOUR OF RC COLUMNS
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6. SUMMARY, CONCLUSIONS AND FUTURE
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Analysis and modelling of the seismic behaviour of high ... - Ingegneria

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