To investigate collapse prevention mechanism of innovative PEC（Partially Encased Composite）column-steel beam composite frame system

the test specimen of inter-story substructure of crimping PEC column（weak axis）-reduced-section steel beam composite frame with end plates and pretension high-strength penetrating bolts connection were taken as an object

the software ABAQUS was adopted to simulate its collapse mechanism under quasi-static lateral cyclic loading.Based on the analysis data

the specimen′s performance was analyzed

including load-carrying capacity

degradation of lateral stiffness

connection mechanical performance

shear distribution

deformation mode

force-transfer of joint and failure mechanism.The results indicate that the specimen has high strength and initial lateral-resisting stiffness;the inter-story shear is evently sustained by PEC columns and the deformation is induced by shearing;all joints exhibit partial self-centering function resulting from pre-tension penetrating bolts

and reduced-section steel provides rotational capacity and energy-dissipation capacity;the collapse is primarily induced by plastic hinge in reduced cross-section of steel beam

and connection rotation and interstory drift both surpass the limit（1/50）of design-basis earthquake for structure

and the specimen has ductility and collapse prevention capacity.