Punching shear and shear resistance of high performance fibre reinforced concrete
Event details
| Date | 16.12.2010 |
| Hour | 12:15 |
| Speaker | Prof. René Suter, University of applied sciences Fribourg |
| Location |
GC A3 31
|
| Category | Conferences - Seminars |
Modern admixtures as well as the addition of steel fibres allow producing concretes with exceptional mechanical rheological and durability characteristics. These high performance fibre reinforced concretes (HPFRC) are perfectly adapted to the design of new and innovative constructions. Currently in practice the use of high performance concretes is still limited to isolated cases despite the highly attractive characteristics of this material. The principal reasons are a poor knowledge on the behaviour of structural HPFRC elements and the lack of adequate design rules.
In order to contribute to a better knowledge on the structural behaviour of these concretes theoretical and experimental studies were carried out at University of applied sciences in Fribourg. This presentation will discuss the studies of shear behaviour of post-tensioned concrete beams and punching shear capacity of thin concrete slabs.
Full scale tests were carried out on seven precast and post-tensioned TT beams and on eight rectangular beams in order to analyse the contribution of steel fibres on the shear capacity. These tests showed that the addition of steel fibres increases the shear capacity by 10 % to 40%. According to these results it will be possible to replace stirrups by an adequate percentage of fibres.
Load tests were also carried out on twenty HPFRC slabs according to three parameters: the quantity of fibres the reinforcement ratio and the post-tensioning level. These tests highlighted the contribution of steel fibres on punching shear capacity which increases by 20% to 70 %. They also showed that the punching shear capacity is inversely proportional to the rotation of the slab. That means the more the reinforcement ratio or the post-tensioning level are important the more the risk of a failure by punching shear becomes determinant. The numerical analysis on the behaviour of the slabs is based on the failure criterion developed by Muttoni. Actually we are working on adapting this failure criterion for HPFRC slabs in order to establish directives for dimensioning.
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