Cyclic behaviour of interior post-tensioned flat plate connections

Abstract

In high seismic regions, post-tensioned (PT) slab–column frames are commonly used to support gravity loads in conjunction with a lateral-force resisting system (LFRS) such as a core wall. The LFRS is designed to resist 100% of the design lateral forces as well as to limit lateral displacements to an acceptable level, whereas the slab–column frame must sustain the gravity loads under the expected (design) displacements. Given the relatively sparse data on the seismic performance of PT flat plate slab–column frames, cyclic tests of four interior PT slab–column connections were conducted. Primary test variables were the level of gravity shear at the slab–column connection and the slab tendon arrangement. Test results indicate that both the test variables strongly influence the cyclic behaviour of the PT connections, and that the use of slab bottom reinforcement at the slab–column connection was effective in resisting positive moment developed under lateral loading as well as improving the hysteretic energy dissipation capacity.

Effect of slab bottom reinforcement on seismic performance of post-tensioned flat plate frames

“…Coefficients for the pinching model are calibrated to simulate accurately the actual hysteretic behaviour obtained from previous experiments (Han et al, 2006a). Pinching coefficients of 0 .…”

“…The hysteretic behaviour of the PT slab-column connections reported by Han et al (2006aHan et al ( , 2006bHan et al ( , 2009) is simulated by using the numerical connection model developed by this study. Software OpenSees (2007) is used.…”

“…The detail information on these specimens is available in Han et al (2006aHan et al ( , 2006bHan et al ( , 2009). Figure 7 shows the hysteretic behaviour of slab-column connection specimens PI-D30, PI-D50, PI-D50X and PE-D50 obtained from the numerical analyses and experiments.…”

“…Previous studies (Han et al, 2006a(Han et al, , 2006b(Han et al, , 2009MartinezCruzado, 1993;Qaisrani, 1993) reported that a slab sagging moment could occur at PT slab-column connections under lateral force associated with design earthquake specified in current seismic design provisions; therefore, sufficient slab bottom reinforcement must be placed to avoid the formation of large cracks. Han et al (2009) demonstrated that slab bottom reinforcement passing through the column placed in accordance with ACI-ASCE 352 R.1 (ACI-ASCE Joint Committee 352, 1997) is effective in resisting unexpected sagging moments at PT slabcolumn connections.…”

Fracture Model for PT Flat Plate Connections under Seismic Loading

“…According to ACI 318-05 [1], minimum top bonded reinforcement is required to the PT gravity flat plate system, however, for these PT gravity systems, minimum bottom reinforcement is usually not required in the connection regions. But prior researches [2,3,4,5] indicate that slab bottom reinforcements influenced to lateral drift. The positive slab moment eventually develops on one side of the slab-column connection as the seismic demand is increased, therefore, sufficient bottom reinforcement should be provided to avoid the formation of large cracks.…”