Abstract
Six fullscale loading tests for slim floors comprising
prestressed hollow core slabs and spine beams have been
carried out. In these tests, the observed shear
resistance of the slabs was only 40 to 70% of the shear
resistance observed in the reference tests in which slab
units were supported on rigid bearings. In one floor
test, yielding of the beam preceded the shear failure of
the slabs. In five tests, the slab units underwent a
shear failure before the yielding of the beam. According
to the conventional calculation models, the beams should
have failed first in all tests.
At failure, the deflection of the supporting beams was
relatively small, typically 1/400 to 1/250 of the span of
the beam. However, a three dimensional finite element
simulation and the observed failure mode, web shear
failure, confirm that the reduction in shear resistance
is due to transverse deformation in the hollow core units
caused by the deflection of the beams.
A calculation model for the analysis of the web shear
failure of the slabs is proposed. In the model, the
maximum principal stress in the web is calculated from
three non zero stress components and compared with the
tensile strength of the concrete. Two of the stress
components, namely the axial stress and vertical shear
stress, are calculated as in the conventional model. The
third one, the transverse horizontal shear stress, is
calculated using a linear composite beam model.
The loadbearing capacity of floors can be enhanced by
reducing the deflection of the beams, for example, by
making the beams stiffer or continuous. Another approach
is to reduce the transverse shear deformation of the slab
ends, for example, by filling the voids with concrete or
by providing the floor with a reinforced concrete
topping.
Original language  English 

Qualification  Doctor Degree 
Awarding Institution 

Supervisors/Advisors 

Award date  24 May 1995 
Place of Publication  Espoo 
Publisher  
Print ISBNs  9513847667 
Publication status  Published  1995 
MoE publication type  G4 Doctoral dissertation (monograph) 
Keywords
 prestress
 hollow core slab
 concrete structures
 precast concrete
 design
 prefabrication
 slim floor
 shear
 composite structures
 flexible support
 loading test
 composite beam
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Pajari, M. (1995). Shear resistance of prestressed hollow core slabs on flexible supports: Dissertation. VTT Technical Research Centre of Finland.