'Periodica Polytechnica Budapest University of Technology and Economics'
Abstract
Inspecting the IMS structural system tensioned together from precast reinforced concrete
elements, considerable corrosion, in some cases rupture of the reinforcing tendons was
found in the critical floor cross-sections. On the basis of the results of investigations
carried out on a typical floor panel, assuming a corrosion predictable from disclosures,
possibility of failure of the critical cross-section is 15 years after its construction by about
two orders of magnitude higher than prescribed in the Hungarian Standard. Complete
corrosion or rupture of the reinforcing tendons in either of the directions can lead to
progressive collapse of the floor due to the rearrangement of stresses. Its prevention calls
for structure strengthening.
Insufficient load bearing capacity of the floor structures - especially in the case
of multielement systems - can be most favourably guaranteed by supplementary post-
tensioning. Efficiency of the strengthening by post-tensioning depends essentially on the
distribution of the normal force originating from the stressing force applied -concentrically
in the block floor ribs - that can be regarded as monolithic in respect of the supplementary
stressing -, as well as on moments and reactions due to concentrated forces arising in
consequence of the polygonal cable arrangement and acting perpendicularly to the floor
plane.
For design the strengthening effect of subsequent steps of the post-tensioning and of
the location of force application, the role of columns in stiffening, influence of the possible
lattice models as well as the role of the 3.5 cm floor plate in stiffening and effect of joint
eccentricity joint of structural elements have been investigated