Punching through

from Wikipedia, the free encyclopedia

The load L acting over a large area on the plate F must be diverted via the column C. If the load is too great, the plate will fail in a frustoconical section. The support punches through the plate.

In the construction industry, punching through is a punctiform shear force failure of a reinforced concrete or prestressed concrete slab. There is a risk of punching through under load if a slim, flat component is supported by a bearing with a small circumference (usually point bearing), e.g. B. with a flat slab on a support , or in the opposite case, if a point load is to be introduced into a plate, z. B. with a support that stands on a flat foundation. The plate fails in a truncated pyramid or truncated cone-shaped section around the support. The support "punches through the plate". There may also be the risk of local, partial punching through, which is initially only a local failure, e.g. B. when a flat ceiling is mounted on one wall end.

Failure and rating

Star-shaped punching shear reinforcement in a slab reinforcement for connecting the column below

When point loads are introduced into a plate, large local shear stresses arise in it. The punching is therefore a shear stress failure of the concrete and must be taken into account in the design . Can be a planned plate not absorb the transverse forces from the point-shaped or line-shaped introduction computationally alone with the concrete load-bearing capacity, in the plate in the region of the mullion or wall terminal is a punching reinforcement arranged to allow a sufficient capacity. Various systems are available for this reinforcement . The European design standard for reinforced concrete DIN EN 1992-1-1 (Eurocode 2) regulates the use of push bars or bent longitudinal bars. For special punching shear reinforcements, national approvals or European technical assessments (abbreviation from English: ETA) are created. This also indicates the maximum increase in punching shear resistance. In the German version of the design standard, an increase factor of 1.4 is standardized for stirrups. A factor of 1.96 is explained for double headed bolts (headed bolt strips or dowel strips). The filigree punching shear reinforcement, which is used in partially prefabricated filigree ceilings as well as in in-situ concrete ceilings, has an increase factor of 2.1. The dimensioning and verification of the punching shear resistance is usually carried out using the appropriate software from the manufacturer. Another way to prevent punching shear problems is to change the geometry of the connection. A local reinforcement of the ceiling or widening of the column head ensures that the loads can be introduced into the slab over a larger area and the transverse force load decreases accordingly.

In Europe, the consideration of punching through when dimensioning a reinforced concrete slab is regulated in Part 1-1 of Eurocode 2 .

literature

  • Eurocode 2: Dimensioning and construction of reinforced concrete and prestressed concrete structures - Part 1-1: General rules and rules for building construction; German version EN 1992-1-1: 2004 + AC: 2010 , edition January 2011, section 6.4, p. 103 ff.

Individual evidence

  1. a b Jürgen Grünberg (Ed.): Reinforced concrete and prestressed concrete structures according to DIN 1045: Parts 1 to 3 (July 2001) Explanations and applications . Springer, 2002, ISBN 3-540-43155-1 , pp. 177 ff .
  2. a b EC2-1-1
  3. http://www.pcae.de/main/progs/details/beton/4h_stanz/beton_stanz_details_nachweise.htm