Punching shear reinforcement in crosswise arrangement – Effective or impermissible?

Stud rails used as punching shear reinforcement in flat slabs are arranged radially in Germany. A crosswise arrangement in the layout of the reinforcement elements, as it is common practice in North America for easier installation, is not permitted in
Germany. The areas in the corners of the cross joints remaining without shear rein-forcement decline the punching shear resistance compared to punching shear points with an all-over reinforcement arrangement.

The Filigran punching shear reinforcement consisting of welded three-dimensional reinforcement elements is used in semi-precast floor slabs along with lattice girders arranged in parallel to the same [1]. This arrangement ensures an ease of installation. However, not all inclined load-bearing struts of the punching shear reinforcement are directed ideally into the direction of the column.

The effectiveness of the Filigran punching shear reinforcement is enhanced by a crosswise arrangement with inclined reinforcement elements being directed towards the column. Such an orthogonal arrangement, in contrast to a radial arrangement, retains the ease of installation in respect of both the punching shear reinforcement and the upper bending tensile reinforcement. Larger areas without shear reinforcement are avoided by the installation of additional reinforcement elements next to the cross-shaped design (Fig. 1). Building component tests using this arrangement showed highest punching shear resistances [2]. The European Technical Assessment ETA-13/ 0521 [3] approves an enhanced punching shear reinforcement for this reinforcement arrangement by a factor of 2.1 in contrast to slabs without shear reinforcement. This easy-to-install version is particularly suitable when in-situ concrete is used.

References / Literatur
[1] Furche, J.; Bauermeister, U.: Elementbauweise mit Gitterträgern. In: Beton-Kalender 2021. Bergmeister, K.; Wörner, J.-D.; Fingerloos, F. (Hrsg.)
[2] Schmidt, P.; Furche, J.; Bauermeister, U.: Orthogonale Anordnung der Filigran-Durchstanzbewehrung. Beton- und Stahlbetonbau 114(2019), Heft 7, S. 495-504.
[3] ETA-13/0521, Europäische Technische Bewertung für Filigran-Durchstanzbewehrung FDB, Deutsches Institut für Bautechnik (DIBt).

Related articles:

Issue 2017-01 Filigran Trägersysteme

Joints optimized between precast concrete elements in areas of punching shear

Flat slabs are economically manufactured with precast slabs and topped with in-situ concrete. Accurate execution requires detailed planning. In areas of punching shear, the arrangement of the precast...


Filigran punching shear reinforcement newly assessed

The FDB Filigran punching shear reinforcement consists of spatial welded reinforcement elements with optimized geometry. The punching shear resistance of flat slabs is more than doubled by using FDB,...

Issue 2019-02 New experimental results on punching shear behavior of flat slabs with varying amount of punching shear reinforcement

Reduction of punching shear reinforcement

With introduction of Eurocode 2 in Germany, the punching shear design provisions for flat slabs were revised. In consequence of limited anchorage conditions of punching shear reinforcement elements in...


Punching shear reinforcement with increased bond resistance

Flat slabs with lattice girders as semi-precast construction system feature horizontal composite joints between the semi-precast concrete slabs and the in-situ concrete topping. Both the punching...

Issue 2021-02

Punching shear behavior of steel fiber reinforced flat slabs in combination with punching shear reinforcement

The guideline “Steel Fibre Reinforced Concrete” published by the German Committee for Reinforced Concrete (DAfStb) in 2012 regulates the punching shear design of steel fiber reinforced flat slabs...