Assess and Improve Finite Element/Fracture Models for Various Connection Configurations and Types 

Principal Investigators: Sashi Kunnath, Sherif El-Tawil 
University of Central Florida 

    This task will focus on a typical FR bolted-welded connection, attempting to establish how key geometric parameters such as beam and column flange thickness (tcf and tbf), beam depth (db), column web thickness (twc), continuity plate thickness (tcp) or absence of continuity plate, size and geometry of weld access hole, size and stiffness of shear plate (thickness, tsp, and depth dsp), and doubler plate thickness (tdp or absence of doubler plate) affect connection ductility and potential for cracking. The parameter study will consider variations in the material properties of the steel in the beam and column with particular emphasis on the ratio of the yield stress to the ultimate tensile stress, and the relative strength of the steel in the beam and the column. Shear yielding of the panel zone must also be evaluated in the analytical study, to clearly establish whether inelastic analysis predictions suggest increased (or decreased) potential for cracking if there is variation in the degree of panel zone yield deformation. Analytical models will focus on strong axis connections, but a limited series of calculations for a weak axis column orientation are also required. A standard pre-Northridge connection with backing bars removed will be the basis of the computer models, but the model should be designed with sufficient versatility to simulate alternate conditions such as the addition of top and bottom backing bars or supplemental welding between the beam and the erection plate. The results must include local stress and strain distribution, distribution of yielding and the general potential for cracking. It must be emphasized that this phase is not directed toward crack propagation. It is concerned with potential for cracking through issues such as the development of hydrostatic states of stress or other stress states or material conditions that would facilitate cracking if a weld flaw or other irregularity is introduced. 
 
The detailed breakdown of the technical activities in this task are provided in the workstatement available here.