A new method for post-installed punching shear reinforcement

Walkner, Rupert; Spiegl, Mathias; Feix, Jürgen

doi:10.35789/fib.bull.0081.ch17

Cited by 3 publications

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“…Even the inclined layout of the anchors is statically effective and provides longer anchorage length for the anchors, it is very impractical to drill the inclined boreholes and avoid collision with longitudinal reinforcement. To overcome the aforementioned problems, the new strengthening system based on installation of the screw anchors in vertical direction is being investigated [8] and [9]. The main advantage of the system is that the screw anchor cuts the thread into the concrete during the installation so the connection between the anchor and the concrete is mechanical.…”

Section: Introductionmentioning

confidence: 99%

Screw Anchors Used as Post-Installed Shear Reinforcement in Flat Slabs

Keseli¹,

Bilčík²

2018

SSP

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More restrictive requirements of new codes, increasing of imposed loads connected with usage change of the existing structures, errors in design process or during execution can lead to necessity of the strengthening of the existing buildings. In paper, the new and modern strengthening system of flat slabs against punching shear using screw anchors is presented. Screw anchors are installed from lower face of the slab into vertically drilled boreholes. After the installation, the screw anchors operate as punching shear reinforcement. The advantages of the system are significant resistance and deformation capacity increment of the flat slab as well as easy and fast installation with no need to drill through the whole slab thickness and access the upper face of the slab. System is suitable for strengthening of office buildings, since removal of the flooring is not needed or in parking garages, where the water resistance is not disturbed by the system. Moreover, paper deals with special problems that are connected with design of the presented strengthening system e.g. considering of load (deformation) level of the slab at the moment of strengthening, performance of the screw anchors in cracked and non-cracked concrete and anchorage conditions improvement of the screw anchors by application of glue or mortar into the borehole prior the screw installation.

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Section: Introductionmentioning

confidence: 99%

Screw Anchors Used as Post-Installed Shear Reinforcement in Flat Slabs

Keseli¹,

Bilčík²

2018

SSP

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Concrete screws as a post‐installed punching shear reinforcement

Walkner

Spiegl

Feix

2020

Structural Concrete

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The strengthening of concrete structures is becoming more and more important. To achieve this need for strengthening measures, technically innovative, simple and economical systems for subsequent strengthening are required. At the University of Innsbruck, a system for subsequent strengthening of the punching shear zone through the installation of concrete screws has been developed. These screws are installed from the soffit side of the slab in vertically predrilled holes and are arranged concentrically around the support. This paper discusses the results of four test series, with a total of 21 specimens used to develop the system. The system, which can be very easily installed, demonstrates a significant increase of the shear punching capacity and a reduction in brittle failure modes. In addition, cyclic loading with typical levels of service load has no negative effect on the effectiveness of the system. Finally, the influence of the flexural reinforcement ratio on the effectiveness of the strengthening system was investigated.

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Concrete screws as a post‐installed punching reinforcement

Spiegl

Walkner

Feix

2021

Structural Concrete

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A major part of central European infrastructure buildings was designed decades ago and has different needs of strengthening. Increasing traffic volume, increasing axle loads, and a growth in transport volume as well as more restrictive design rules are the reasons why the support regions of existing bridges and flat slabs often show a lack of punching resistance today. At the University of Innsbruck, a system for subsequent strengthening by the use of concrete screws was developed. Various laboratory tests showed that the system leads to a significant increase of punching resistance with minimal efforts for its installation. This article deals with the development of a numerical model that can predict the punching loads of unstrengthened and screwstrengthened punching plates. Further the punching loads from the laboratory tests and the simulations are compared to the predictions of a design approach. The presented novel design approach is an advancement of the existing Eurocode 2 provisions and allows the influence of the screws on the punching resistance to be taken into account. The comparison shows that the numerical model predicts the punching resistances in an appropriate way and the design approach predicts them on the safe side. The presented design approach was included into the technical assessment for the concrete screws of the system reLAST as post-installed punching reinforcement system [Z-15.1-340 (2019)] in order to be applicable in practice.

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A new method for post-installed punching shear reinforcement

Cited by 3 publications

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Screw Anchors Used as Post-Installed Shear Reinforcement in Flat Slabs

Screw Anchors Used as Post-Installed Shear Reinforcement in Flat Slabs

Concrete screws as a post‐installed punching shear reinforcement

Concrete screws as a post‐installed punching reinforcement

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