Zur Zuverlässigkeit der Bemessung gegen Durchstanzen bei Einzelfundamenten

The safety and reliability of structures is influenced by the uncertainties of actions and resistances. The random character of the structural variables can be considered via probabilistic approaches and the failure probability can be calculated as a measure for safety. The concept of limit states allows the deduction of the partial safety factors considering the random character of actions and resistances. The main methods of structural reliability analyses are presented and applied to determine the safety of punching design equations for footings. Around the columns large moments and vertical shear forces arise in the footings. These forces can cause a local shear failure, which is called punching shear failure. In general, design codes do not distinguish between the punching shear strength of flat slabs and footings. Although experimental investigations clearly indicate that the shear span-depth ratio significantly affects the punching shear behaviour of footings, this effect is not considered in most design codes. A test data bank was established and different design provisions were critically reviewed. In addition, probabilistic methods were used to thoroughly investigate the existing safety level. A total of 22 reinforced concrete footings were tested to investigate the punching shear behaviour of footings. Ten specimens were realistically supported on sand in cooperation with the Institute of Geotechnical Engineering. Whereas the remaining footings were supported on the column stub and a uniform surface load was applied. The present tests indicated that the shear span-depth ratio significantly affects the punching shear behaviour. The angle of the failure shear crack is steeper in punching tests on compact footings than observed in tests on more slender footings. The shear strength decreases with increasing shear span-depth ratio. Shear reinforcement can substantially increase the punching capacity of footings. However, it is less effective with decreasing shear span-depth ratio. Nonlinear numerical analyses were conducted to study the main parameters affecting the punching shear strength of footings systematically. In the simulations, different failure modes were observed. The load-bearing behaviour of the compact footings can be described by a strut and tie model. The compression struts are inclined and expand like a conical shell from the edges of the column towards the bottom of the footing. Hence, the punching cone primarily develops due to splitting failure of the inclined compression struts. In more slender footings the ultimate load is achieved when the highly stressed compression zone at the column faces crushes. Based on the experimental and numerical investigations, the model according to AN-DRÄ was adapted to footings without shear reinforcement. For footings without shear reinforcement, the empirical design rule of Eurocode 2 was modified with a factor taking into account the shear slenderness. The reliability of the final equation was verified via semi-probabilistic calculations. In addition, a design proposal for footings with shear reinforcement was derived. For eccentrically loaded footings with and without shear reinforcement, the proposed design equations can be combined with a sector model.

Grantor dc:publisher

Lehrstuhl und Inst. für Massivbau [u.a.]

Year dc:date

2009

Author dc:creator

• Ricker, Marcus

Contributors dc:contributor

• Hegger, Josef

• info:eu-repo/classification/ddc/620
• Durchstanzen
• Stahlbeton
• Fundament
• Einzelfundament
• Boden-Bauwerk-Wechselwirkung
• Reliabilität
• Eurocode 2
• Tragverhalten
• Finite-Elemente-Methode
• Beton
• Ingenieurwissenschaften
• Schubschlankheit
• Durchstanzbewehrung
• Fundamente
• Zuverlässigkeitstheorie
• footings
• punching shear
• reinforced concrete
• shear span to depth ratio
• soil-structure interaction

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-113715%22

OAI record oai:identifier

https://publications.rwth-aachen.de/oai2d?verb=GetRecord&metadataPrefix=oai_dc&identifier=oai%3Apublications.rwth-aachen.de%3A51424