Seismic Design, Assessment and Retrofitting of Concrete Buildings

Hysteretic behavior of exterior post-tensioned flat plate connections

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 d...

http://nees.ucla.edu/wallace/Abstracts%20and%20Presentations/Kang,%20Thomas/Journal-Cyclic_Behaviour_macr_2006_58_10.pdf

Cyclic behaviour of interior post-tensioned flat plate connections

Punching Shear Retrofit Method Using Shear Bolts for Reinforced Concrete Slabs under Seismic Loading

Summary
Shaking table tests were conducted on a scaled reinforced concrete waffle–flat plate structure. It represented a conventional construction design under current building codes in the Mediterranean area. The test structure was subjected to a sequence of four seismic simulations of increasing magnitude. Each simulation was associated with a seismic hazard level characterized by the mean return period PR. The test structure performed well for the simulations associated with PR = 95, 475 and 975 years but collapsed under the maximum considered earthquake of PR = 2475 years. Damage concentrated at column bases, where the maximum chord rotation reached 93% of the ultimate capacity, and at the transverse beams of the exterior plate-to-column connection that failed in torsion. It is shown that most (from 85% to 90%) of the energy input by the earthquake that contributes to damage is dissipated by the plate. The capacity curve of the tested structure estimated from the experimental base shear vs. top displacement relationship allowed us to compute the overstrength (1.4). It is close to the maximum established by European code EN 1998-1 (1.5). Based on a detailed study of the test results, potential updates to current codes and design recommendations are suggested. Copyright © 2015 John Wiley & Sons, Ltd.

Shaking table tests of a reinforced concrete waffle–flat plate structure designed following modern codes: seismic performance and damage evaluation

Design algorithms expressed in current building codes and practiced in design offices focus attention on earthquake induced lateral forces, and away from earthquake induced lateral displacements. These procedures have led to development of structural systems in which a portion of the structural frame is designed to resist the total seismic design force while a substantial remainder of the structure is proportioned assuming it resists only gravity loads. This approach is commonly applied to design of slab-column systems in regions of high seismicity. For such systems, a displacement-oriented approach has advantages. Applications of the approach are described.

J P Moehle

Papers

Seismic design considerations for flat-plate construction