Cyclic Testing of Steel-Latticed Members for the San Francisco–Oakland Bay Bridge

To evaluate the cyclic behavior of a type of as-built steel-latticed member for the seismic retrofit of the San Francisco–Oakland Bay Bridge, cyclic testing of three half-scale specimens was conducted at the University of California-San Diego. For eccentrically loaded specimens, local buckling in the end panel caused significant degradation in compressive strength. Net-section fracture of flange angles near rivet holes in which laces were connected also was observed. Bifurcation-type global buckling was observed for the concentrically loaded specimen, causing a drastic drop in compressive strength. The buckling strength could be reliably predicted when the shearing effect and the appropriate effective length were considered. The ductility capacity of these specimens ranged from 2.0 to 2.4. All three specimens were able to reach and exceed the strength predicted by the load and resistance factor design (LRFD) interaction curve by about 6 percent, but this “overstrength” was slightly lower than that typically found in wide flange-beam columns. On the basis of the test results, a modified axial force-moment interaction relationship was proposed.