Static tensile loading experiments and nonlinear finite element analysis were carried
out to study the mechanical properties and failure modes of diaphragm-through
joints of concrete-filled square steel tubular columns. Comparison between
experimental data and finite element analysis revealed that the FE predictions of
failure modes, load-displacement curves and bearing capacity agree with the test
results. It was found that the tensile load from the steel beam flange is mainly shared
by the square steel tube and the diaphragm. The plastic zone of the tube appears
around the intersections of the tube and the diaphragm whereas the diaphragm
plastic zone appears along the cross-section lines enclosed by the steel square tube.
Calculation models of yield lines on square steel tube and diaphragm are established
based on distribution pattern of plastic zone, and an analytical method for the design
of such joints is proposed as well. The experimentally obtained bearing capacities of
the tested specimens are in good agreement with the analytically computed
capacities.