The research project is aimed to develop the scientific knowledge required for a better design of post-tensioned slab bridges.
It will also enhance the checking methods applicable in engineering practice for the analysis of existing bridges. In this latter case, it is especially important to have reliable calculation methods that account for all load-carrying reserves, to avoid unnecessarily strengthening, which can be both complicated and costly.
Part of the results may be included in the partial revision of the SIA 262 concrete design code, scheduled for 2008-2009.
This project includes all of these steps:
a) Theoretical study of the shear field and influence of stiffness on the distribution of shear force (effect of prestressing and armature in both directions). This will be done by studying the results of finite element with a non-linear behavior to bending.
b) Deriving an analytical law-load rotation for prestressed slabs. Preparation of a simplified version used in practice.
c) Performing a series of punching tests on 8 prestressed slabs in one direction or partially in both directions with the aim to validate the proposed load-rotation relationship and confirm the failure criterion for small deformations.
d) Performing a series of punching tests on 4 slabs with punching reinforcement consisting of reinforcing bars detected. Two tiles are not preloaded while the other two will have a longitudinal prestressing.
e) Validation of the theoretical model for the determination of the resistance to punching slabs with rebar identified.
f) Study of the effect of a compressive force on the puncture resistance of the tiles.
g) Derivation of a theoretical model for determining the puncture resistance of prestressed slabs.
h) Practice Derivation for the partial revision of the SIA 262 standard.
i) Report preparation and scientific articles.
The project provided following results:
- study of the actual behaviour of slabs - the actual behavior of slabs post-tensioned was studied in one or two directions, without or with only limited punching shear reinforcement
- theoretical model of slabs behaviour - developing a theoretical model, with a simplified version for practical applications, in a format compatible to that of the current SIA 262 design code
- validation of the theoretical model - series of experimental tests to validate the theoretical model, including the effect of post-tensioning and bent-up bars was provided