Column Behavior in PR Construction: Experimental Behavior

Abstract

Previous studies of the strength of steel columns are reviewed, with particular attention being given to the role of the column as part of a frame. The concept of partially restrained (PR) construction in the draft LRFD Specification is shown more appropriately to describe the behavior of frames incorporating most of the normal forms of field bolted connections. Despite several recent theoretical studies of end‐restrained columns, complementary experimental data against which the analyses may be checked and refined are virtually nonexistent. A series of full‐scale tests on I‐shaped, nonsway subassemblages comprising a column attached via various types of semirigid connections to 4 beams is described. Both direct column load and independent beam loading were used with the response of the column, connections, and beams being monitored. The subassemblage was constrained to eliminate out‐of‐plane action. Preliminary study of the results clearly demonstrates the large amounts of end restraint transmitted by even the most flexible connections. When this is taken into account in determining column strength through a modification to the SSRC G‐factor approach, acceptable estimates of the test values may be obtained from the normal interaction formulas approach to beam‐column design.