Experimental study on seismic performance of pocket base connections for steel latticed columns

The applications of pocket base connections for steel latticed columns were increasing in single-story industrial workshops, but basic research on this type of column base was insufficient. Quasi-static tests of four pocket base connections for steel latticed columns were carried out to investigate their seismic behavior. The influences of grouting material type, volume stirrup ratio, stud and base plate on the seismic behavior of column bases have been analyzed. Results exhibited three failure modes of pocket base connections for steel latticed columns, including the cracking of the secondary pouring surface, the pullout of the tensile chord, and the buckling of the compressive chord. The bearing capacity of the specimens with the first two failure modes was lower, while the specimen with compressive chord buckling had a higher bearing capacity and a plumper hysteretic curve. Compared with the specimens with tensile chord pullout and secondary pouring surface cracking, the bearing capacity of the one with compressive chord buckling was increased by 324% and 25%, respectively. Based on the experimental results and relevant analysis, it is demonstrated that pocket base connections for steel latticed columns should be arranged with studs in the embedded part or with a base plate at the bottom of the chord. When the embedment ratio is reduced to 2.0, which is lower than the requirement of the current Chinese seismic standard, excellent seismic performance can be also achieved if the cementitious grout is used in the secondary grouting and the volume stirrup ratio of the pocket foundation is increased.