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

2018 ◽  
Vol 272 ◽  
pp. 53-63 ◽  
Author(s):  
Ondrej Keseli ◽  
Juraj Bilčík ◽  
Ivan Hollý
Keyword(s):  
Punching Shear ◽  
Slab Thickness ◽  
Shear Reinforcement ◽  
Lower Face ◽  
Existing Structures ◽  
Flat Slabs ◽  
Parking Garages ◽  
Upper Face ◽  
Deformation Level ◽  
The Moment

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.

scholarly journals Performance of Shear Reinforcement against Punching Shear Loads

2019 ◽  
Vol 9 (2) ◽  
pp. 841-850
Keyword(s):  
Numerical Study ◽  
Shear Capacity ◽  
Punching Shear ◽  
Slab Thickness ◽  
Test Results ◽  
Shear Reinforcement ◽  
Concentrated Load ◽  
Flat Slab ◽  
Flat Slabs ◽  
Strength Formula

This research targets to maximize the ductility and strength of the reinforced concrete flat slabs. However, to be efficient, the shear reinforcement must be anchored well in the tension and compression zones of the slab. The test results on the slab-column connection models which provided with shear reinforcement are introduced in this study. The benefits of using shear reinforcement are to reduce the slab thickness, and to minimize both the cost and the total weight of the structure. Twelve flat slab specimens have been tested to study the effect of different types of steel RFT on the punching shear of the flat slab. The experimental parameters include no shear reinforcement which study the advantage of using tension RFT ONLY against punching shear, no shear reinforcement which study the advantage of using compression RFT against punching shear, shear RFT (Vertical Stirrups) which study the effect of using shear RFT with constant distribution 0.5d, and a new distribution of shear stirrups which study the effect of using new different width & spacing of vertical stirrups. The twelve specimens were loaded with concentrated load at the mid span until failure. The general behavior of the deformation of the tested slab specimens was examined and recorded (cracking, deflection, and strain in both steel and concrete). A comparison established between the experimental and the numericaltheoretical results obtained from applying the punching shear strength formula given in design codes, and finite element modeling analysis; ABAQUS 2017 software package was used for this analysis. A total of six building codes were examined with regard to their provisions concerning the punching shear. A comparison had been made between the research test results and the codes equations to improve the methods of the analysis about the flat slabs. This study aimed to improve the punching shear capacity of flat slab which leads to more accurate results compared with the codes predictions. To achieve this aim, an experimental and numerical study was carried out for this investigation.

Punching Shear Capacity of Steel Fiber Reinforced Concrete Slab- Column Connections

2019 ◽  
Author(s):  
Josef Landler ◽  
Oliver Fischer
Keyword(s):  
Reinforced Concrete ◽  
Steel Fiber ◽  
Fiber Type ◽  
Fiber Content ◽  
Fiber Reinforced Concrete ◽  
Steel Fibers ◽  
Punching Shear ◽  
Slab Thickness ◽  
Shear Reinforcement ◽  
Fiber Reinforced

<p>To design flat slabs directly supported on columns, the punching shear resistance of the slab is a main factor. It can be increased in the vicinity of the slab-column connection with punching shear reinforcement, like bent up bars or shear studs, to bear the high reaction forces. However, the usage of punching shear reinforcement requires the knowledge of special design rules and often leads to problems and deficiencies in construction.</p><p>Fiber reinforced concrete seems to be a promising alternative to conventional punching shear reinforcement. To investigate the load bearing behavior of the slab-column connection using fiber reinforced concrete, a total of eight punching shear tests were performed. The specimens were realized with a typical top and bottom flexural reinforcement, but without punching shear reinforcement. Varied parameters were the slab thickness with 250 mm and 300 mm and the fiber content V<sub>f</sub> with 0.5 Vol.-% and 1.0 Vol.-%. To investigate the influence of modern fiber types, normal- and high-strength steel fibers with normal- and double-hooked-ends were used.</p><p>In all eight experimental tests, the intended punching shear failure was achieved. The capable load using fiber reinforced concrete increased by 20 % to 50 % compared to the reference tests without steel fibers, depending on the fiber type and the fiber content V<sub>f</sub>. Additionally, this load increase was accompanied by a significant improvement in ductility. The post-cracking behavior was noticeably influenced by the used steel fiber type. An influence of the slab thickness or steel fiber type on the shear strength contributed by the fiber reinforced concrete could not be determined.</p>

Enhanced reliability assessment of punching shear resistance models for flat slabs without shear reinforcement

2021 ◽  
Vol 226 ◽  
pp. 111319
Author(s):  
Marcus Ricker ◽  
Tânia Feiri ◽  
Konstantin Nille-Hauf ◽  
Viviane Adam ◽  
Josef Hegger
Keyword(s):  
Reliability Assessment ◽  
Shear Resistance ◽  
Punching Shear ◽  
Shear Reinforcement ◽  
Flat Slabs

A Method to Predict the Punching Shear Strength of Flat Slabs with Shear Reinforcement Using a Strut-and-Tie Model

2017 ◽  
Vol 738 ◽  
pp. 25-35
Author(s):  
Lukáš Lyčka ◽  
Petr Štěpánek
Keyword(s):  
Shear Failure ◽  
Complex Problem ◽  
Punching Shear ◽  
Shear Reinforcement ◽  
Model Code ◽  
Strut And Tie ◽  
Flat Slabs ◽  
Model Code 2010 ◽  
Strut And Tie Model ◽  
Critical Aspects

The use of flat slabs in constructions due to its many functional and economic advantages is wide-spread. Behavior of flat slabs in shear and flexure is a fairly complex problem. Therefore, the punching shear failure belongs to one of the most critical aspects in the design of concrete buildings.The purpose of this paper is to describe a framework of the proposed method for predicting the punching shear of flat slabs with shear reinforcement. Most of the current codes in force are mainly based on empirical formulation. The proposed method is based on a strut-and-tie model and therefore could be considered as an analytical approach. For the purpose of demonstrating the effectiveness of the proposed method, the method is compared with some of the main methods currently in use, such as Eurocode EC2, ACI 318 and Model Code 2010. The comparison consists of results of more than 90 experiments on flat slabs with shear reinforcement, gathered from publications from all around the world.

Punching Shear in Post-Tensioned Flat Slabs with Shear Reinforcement: Codes and Tests

2016 ◽  
Vol 113 (2) ◽  
Author(s):  
Alessandra L. Carvalho ◽  
Guilherme S. Melo ◽  
Ronaldo B. Gomes
Keyword(s):  
Punching Shear ◽  
Shear Reinforcement ◽  
Flat Slabs ◽  
Post Tensioned

Strut-and-Tie Model for Predicting the Punching Shear of Flat Slabs with Shear Reinforcement

2017 ◽  
Vol 259 ◽  
pp. 178-183
Author(s):  
Lukáš Lyčka ◽  
Petr Štěpánek
Keyword(s):  
Physical Models ◽  
Punching Shear ◽  
Empirical Equations ◽  
Shear Reinforcement ◽  
Model Code ◽  
Strut And Tie ◽  
Flat Slabs ◽  
The World ◽  
Model Code 2010 ◽  
Strut And Tie Model

The purpose of this paper is to describe a framework of the proposed method for predicting the punching shear of flat slabs with shear reinforcement. The proposed method is based on a strut-and-tie model. Current methods of predicting the punching shear strength of flat slabs could be divided into these categories: models based on empirical equations, physical models, analytical methods and finite element methods. Most of the current codes in force would be best described as empirical formulations. Physical model for prediction of punching shear is described in Model Code 2010. Proposed method for flat slabs with shear reinforcement is based mainly on a strut-and-tie model and therefore could be considered as an analytical method.For the purpose of demonstrating the effectiveness of the proposed method, the method is compared with some of the main methods currently in use, such as Eurocode EC2, American code ACI 318 and Model Code 2010. The comparison consists of results of more than 98 experiments of punching shear on the flat slabs with shear reinforcement, gathered from publications from all around the world.

scholarly journals Study on reliability of punching shear of flat slabs without shear reinforcement according to NBR6118

2017 ◽  
Vol 10 (2) ◽  
pp. 276-297
Author(s):  
M. L. CARVALHO ◽  
C. R. SILVA ◽  
F. R. STUCCHI
Keyword(s):  
Probabilistic Model ◽  
Reliability Index ◽  
Shear Force ◽  
Limit State ◽  
Punching Shear ◽  
Slab Thickness ◽  
Ultimate Limit State ◽  
Flat Slabs ◽  
Frequent Use ◽  
Ultimate Limit

Abstract The frequent use of flat slabs in building constructions highlights the importance of improving the study of slab-column joints, particularly regarding the verification of the ultimate limit state of punching shear, given the complexity of this phenomenon. This article applies concepts of the Theory of Reliability in order to evaluate the safety of the formulation established by NBR6118: 2014 standard to check punching shear in flat slabs with centered columns. Twelve probabilistic model analysis for C and C' equations were developed, considering the influence that the variation of the slab thickness, the ������ and the shear force eccentricity have on reliability index �� and failure rate ����. Results indicated that formulation of C boundary is reasonably safe, although C'boundary revealed �� index below expectations.

Sign in / Sign up

Export Citation Format

Share Document