1. Cyclic Behavior of Column Base Plate Assembly Under Cyclic Loading
Research Assistant: Jackie Burda
Experimental investigation was conducted on six one-half scale column-base assemblies under constant axial load and large lateral cyclic deformations. The design of the column base-plate assembly utilized a limit state concept by limiting the inelastic activity to the base plate itself. The results of the investigation showed that the thickness of the base plate played an important role in the overall strength and stiffness on the column base assembly. It was also shown that thin base plates were able to dissipate more energy than thick plates. The failure mode for all tested specimens was the fracture of the weld between the column section and the base plate. The performance of the complete joint penetration weld outperformed the performance of the fillet weld under large cyclic deformations.
View of Test Set-up for Column-Base Plate Subassembly Experiment
2. Cyclic Behavior of Steel Moment Frame Connections Under varying Axial Load and Lateral Displacement
Research Assistant: Jose Zepeda
Full scale experiments were conducted on steel moment connections subjected to varying axial load and lateral displacements. The beam specimens consisted of reduced beam section, wind plates, and longitudinal stiffeners. The test specimens were subjected to varying axial forces and lateral displacements to simulate the effects on beams in Coupled Girder Moment Resisting Frame under lateral loading. The figure below shows the test set-up that was used in this investigation. The test results showed the specimens responded in a ductile manner since the plastic rotations exceeded 0.03 rad without significant drop in the lateral capacity. The presence of the longitudinal stiffener assisted in transferring the axial forces and delayed the formation of the web local buckling. These beam connections were used in the Mascone Center in San Francisco, CA.
View of the test set-up used for Testing Moscone Moment Connections
3. Cyclic Response of Steel Moment Connections for Large Beam Sections Using Haunch and Reduced Beam Section Concept
Research Assistant: Z. Cheng
Experimental investigation was conducted on full scale moment connections for large beam sections under large cyclic deformations. The moment connections utilized a hybrid concept that is particularly suitable for heavy beams and large columns that are normally used in tall buildings and long spans. The figure below shows the details moment connection. The connection was composed of a flange plate and a bottom tee haunch which is used to strengthen the beam at the face of the column. In addition a reduced beam section away from the column face was utilized to weaken the beam such that inelastic activity will be concentrated in this zone. The test results showed that these connections performed in a ductile manner and far exceeded the code specified values. These connections were used in the UCLA Hospital in LA, CA.
View of Moment Connection of the UCLA Hospital
4. Performance of an Unprotected Steel Structure Subjected to Repeated Fire at a Firefighter Training Facility
Post Doctorate Research Assistant: Lyle P. Carden
An evaluation of a single story unprotected steel structure exposed to repeated fire during the training of fire fighter is under taken. The figure below shows the training facility. Temperatures are monitored on the structure using resistance temperature detectors connected to a data acquisition system. Temperatures of up to 384 C are measured in the steel of the structure, which are below levels likely to cause much degradation in stiffness or strength. Uniform heating of the columns was shown to result in minimal stresses in the structure as the columns were relatively free to deform axially. However, it was found that differential temperature of the opposite sides of the members resulted in stains up to 16 times the yield strains.
View of Unprotected Steel Structure during Fire-fighter Training
