Fracture design criteria for special moment -resisting frames
Abstract
The objective of this thesis is the development of fracture design criteria for welded flange-bolted web (WFBW) connections in special moment-resisting frames (SMRFs). To achieve this, strength limit-states and loading effects at a critical location have been investigated. The strength limit-states have been assessed by a method of “back-calculation” using experimental results. The load effects have been evaluated by a series of parametric studies. These studies provide the effect of key parameters on the stress states at the critical location when a beam has reached a plastic rotation of 3% radians. Based on this study, several conclusions were drawn: (1) the region most susceptible to joint-fracture (also called “the critical location”) in a welded flange-bolted web connection is located at the interface between the column and the beam flange at the weld root, (2) the strength limit-state can be expressed as a linear function of the octahedral normal and shear stresses, and (3) the local stress state at the critical location can be estimated by factoring up the nominal stress of beam flange by a stress amplification factor. This amplification factor can be expressed as a function of geometric and material properties. On the basis of these conclusions, a fracture design and analysis procedure has been developed using the proposed strength limit-states and the load effects. The load effects have been calculated using the stress amplification factors and the nominal stresses at the beam-column interface. With these load effects, the use of the strength limit-state for joint-fracture provides a practical procedure for the prediction of the susceptibility of welded flange-bolted web connections in special moment-resisting frames to joint-fracture. This criterion supplements the special requirements for welded flange-bolted web connections provided in the AISC Seismic Provision.
Degree
Ph.D.
Advisors
Sotelino, Purdue University.
Subject Area
Civil engineering
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