Title:
Repairing and Upgrading of a Heavy-Duty R/C Slab
Author(s):
Pietro G. Gambarova, Francesco Lo Monte, Seyed M.S. Mousavi, Pietro L. Torregiani, and Mattia Zecchillo
Publication:
Symposium Paper
Volume:
326
Issue:
Appears on pages(s):
104.1-104.10
Keywords:
finite-element analysis (of slabs); mixed restraints (in slabs); reinforced-concrete slabs; stiffening beams (in slabs); structural fire design (of R/C slabs); yield-lines method
DOI:
10.14359/51711087
Date:
8/10/2018
Abstract:
A heavy-duty almost square R/C slab is studied in this paper based on two tests performed under the service loads, after adding a stiffening R/C beam along the only free edge. The very linear behavior exhibited during the tests was the starting point: (a) to perform a FE analysis to investigate the role of the mixed restraints; (b) to identify the most probable failure mechanisms – under distributed and concentrated loading - within the kinematic theorem of Limit Analysis (Yield-Line Method); (c) to quantify the extra strength provided by the stiffening beam; and (d) to study the bearing capacity in fire.
Slab sides are close to 8 m [27 ft] and the thickness is 35 cm [13.8 in.]. Two adjoining sides rest on walls, while the third side is partially supported and the fourth side - initially free – has been stiffened by casting an R/C beam along the extrados.
The mixed restraints show that (a) not always the yield lines and the failure mechanisms dictated by intuition are the most probable; (b) stiffening a free edge may not be required at the serviceability or ultimate limit states, but by the checks in fire; and (c) stiffening a free edge tends to shift the failure mechanism towards slab-localized mechanisms, because of the greater heat sensitivity of thin slabs compared with solid beams.