FILIGRAN TRÄGERSYSTEME

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 shear resistance and the load-bearing capacity of the composite joint have to be ensured for these floor slabs. Using the Filigran punching shear reinforcement not only increases the punching shear resistance, but also the maximum resistance of the composite joint.  A faultless composite joint in the highly loaded punching shear area is the prerequisite for an equivalent load-bearing capacity of semi-precast Filigran floor slabs.

In addition to a rough precast component surface, the use of composite reinforcement increases the joint resistance. The Filigran punching shear reinforcement adopts this function as well. The verification by calculation of the composite joint is based on the principle of the Eurocode 2 design standard for reinforced concrete. This verification includes a maximum load-bearing capacity independent of the embedded reinforcement quantity. The Technical Report TR 508 specifies this upper limit with an increase factor for Filigran punching shear reinforcement. The maximum stress vRdi  in the composite joint is dependent on the roughness factor n of the composite joint in accordance with Eurocode 2 and the concrete strength fcd. When Filigran punching shear reinforcement is used, the increase factor kmax,i is specified as kmax,i = 1.6 in the European Technical Assessment ETA-13/0521.

  The increase factor for the maximum load-bearing capacity of the composite joint was verified in punching shear tests carried out on semi-precast floor slabs with horizontal composite joints. The high bond resistances are attributed to the stiff anchorage of the Filigran punching shear reinforcement on both sides of the composite joint as well as the fine distribution of the composite reinforcement within the punching shear area.

The increased maximum load-bearing capacity of the composite joint ensures the utilization of the maximum punching shear resistance in semi-precast floor slabs similar to cast-in-situ concrete slabs. When using the Filigran punching shear reinforcement a resistance of 2.1times of a slab without punching shear reinforcement applies as maximum load-bearing capacity for both cast-in-situ concrete slabs and Filigran floor slabs. Any verification required can easily be provided by the ProFi design program. This program is available for free download at www.filigran.de. The program also provides the verification of the composite joint beyond the punching shear area. Moreover, lower bond stresses occur in the joint.

CONTACT
Filigran Trägersysteme GmbH & Co. KG
Zappenberg 6
31633 Leese/Germany
+49 5761 92250
REFERENCES/LITERATUR:
» ETA-13/5021: Europäische Technische Bewertung ETA-13/0521 für die Filigran-Durchstanzbewehrung. Deutsches Institut für Bautechnik (DIBt).
» TR 058: Increase of punching shear resistance of flat slabs or footings and ground slabs –lattice girders – Calculation methods. European Organisation for Technical Assessment (EOTA).
x

Related articles:

Issue 10/2018 FILIGRAN TRÄGERSYSTEME

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,...

more
Issue 11/2021 Monday, 15th November → Innovation workshop (6)

New European Assesment for punching shear reinforcement

Flat slabs made of reinforced concrete are supported directly on columns. The total height of the slab construction is reduced and the formwork effort is simplified because beams are done away with....

more
Issue 02/2014 New design tools for practice

Punching shear –

While DIN EN 1992-1-1 and the national annex of Germany treat punching shear design for in-situ concrete slabs and centrically loaded footings in great detail [1, 2], joints between semi precast...

more
Issue 12/2013

Flat floors with semi-precast elements in accordance with Eurocode 2

Flat floors composed of precast slabs with lattice girders and a structural concrete topping require specifically designed punching shear reinforcement systems and structural rules and guidelines for...

more
Issue 02/2016 Experimental investigations, applications and recommendations

“Construction of slab-column-connections in semi-precast slabs”

Semi-precast slabs become more and more important as flat slabs due to the high degree of prefabrication. Their structural design is important in terms of safety owing to the high shear stress and...

more