scholarly journals Application of critical shear crack theory on punching of flat slabs

2021 ◽  
Vol 1209 (1) ◽  
pp. 012060
Author(s):  
S Sarvaicova ◽  
V Borzovic
Keyword(s):  
Experimental Test ◽  
Shear Crack ◽  
Experimental Tests ◽  
Shear Capacity ◽  
Nonlinear Program ◽  
Flat Slab ◽  
Crack Theory ◽  
Flat Slabs ◽  
Significant Difference ◽  
Non Linear

Abstract This article deals with the punching capacity of a flat slab fragment supported by an internal atypically elongated column. Based on the results of this analysis and the application of Critical Shear Crack Theory, the reliability of two design models was determined. The CSCT model is a mechanical model where the shear force transferred by concrete in shear crack can be determined by accounting for the roughness and opening of a critical shear crack. The crack width is proportional to the slab rotation, which was obtained from a nonlinear program Atena and from experimental test and shear capacity was obtained by integrating the shear strength along the control perimeter. The aim of this analysis was to compare the application of CSCT in non-linear analysis and experimental test to point out the significant difference between obtained results, which shows the importance of experimental tests realization. Non-linear analyses provided unsafe results. Contrary the currently used EC2 model provided safe results when reduction of the control perimeter was applied. The best results were obtained in a combination of the CSCT model with measured rotations of the slab specimen.

Effect of Membrane Forces on Punching Shear Capacity of Flat Slabs

2021 ◽  
Vol 322 ◽  
pp. 136-141
Author(s):  
Aleksandar Vidaković ◽  
Lucia Majtánová ◽  
Jaroslav Halvonik
Keyword(s):  
Shear Crack ◽  
Three Dimensional ◽  
Structural Response ◽  
Experimental Tests ◽  
Shear Resistance ◽  
Shear Capacity ◽  
Punching Shear ◽  
Element Analysis ◽  
Flat Slabs ◽  
Non Linear

The paper presents the analysis of the membrane forces and moment redistribution effect on punching shear capacity of flat slabs on the area of the inner column. The previous experimental tests performed on the isolated slab specimens representing the slab-column connections are assessed by the method that uses the levels-of-approximation (LoA) approach, introduced in the fib Model Code 2010. LoA I to III are intended for design and the highest LoA IV, which uses non-linear finite element analysis (NLFEA) combined with the Critical Shear Crack Theory (CSCT) model is used for assessment and a better understanding of the punching shear phenomenon. Both, multi-layered (2D) shell and three-dimensional (3D) continuum elements were used to model the slab-column connection specimen and were found to accurately predict the structural response. The numerical model was then used to conduct a parametric study on the influence of slab continuity on punching shear resistance. The results from a non-linear analysis of continuous slab models are then compared with the punching shear resistance obtained from the code provisions. The paper will present the obtained results by the LoA method and recommendations concerning of NLFEA modelling of RC flat slabs.

Punching shear behaviour of flat slabs with different reinforcement schemes: openings and rectangularity effects

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Donia Salman ◽  
Rabab Allouzi ◽  
Nasim Shatarat
Keyword(s):  
Structural Engineering ◽  
Experimental Tests ◽  
Shear Capacity ◽  
Punching Shear ◽  
Shear Behaviour ◽  
Cross Sectional ◽  
Content Type ◽  
Flat Slabs ◽  
Reinforced Concrete Slabs ◽  
Rectangular Columns

PurposeThe main goal is to investigate the effect of size and location of opening and column size on the punching shear strength. Openings are often needed in order to install mechanical and electrical services. This process takes away part of the concrete volume which is responsible for resisting the shear forces and any unbalanced moment. Furthermore, the application of rectangular columns in flat slabs is commonly used in practice as they provide lateral stiffness to the building. They are also utilised in garages and multi-storey buildings where these elongated cross-sectional columns reduce the effective span length between adjacent columns.Design/methodology/approachThis research is a numerical-based investigation that is calibrated based on a thirteen previously tested and numerically calibrated slab specimens with no openings. A parametric study is conducted in this study to consider the effect of other parameters, which are the size and location of opening and the rectangularity ratio of column in order to evaluate their effect on the punching shear capacity. A total of 156 models are developed to study these factors. Additionally, the predicted shear carrying capacity of the simulated slabs is calculated using the ACI318–19 and Eurocode (EC2-04) equation.FindingsThe presence of openings reduced the punching shear capacity. The small opening's location and orientation have almost no effect except for one slab. For slabs of large openings, the presence of openings reduced the punching capacity. The punching capacity is higher when the openings are farther from the column. The numerically obtained results of slabs with rectangular columns show lower punching capacity compared to slabs of squared columns with the same length of the punching shear control perimeter. The punching capacity for all slabs is predicted by ACI318–19 and Eurocode (EC2-04) and it is found that Eurocode (EC2-04) provided a closer estimation.Originality/valueThe slabs considered for calibration were reinforced with four different punching shear reinforcement configurations, namely; ordinary closed rectangular stirrups, rectangular spiral stirrups, advanced rectangular spiral stirrups and circular spiral. Generally, there has been limited research on concrete flat slabs with openings in comparison with other subjects related to structural engineering (Guan, 2009) and no research on punching shear with openings of slabs reinforced with these reinforcement schemes. The available research focussed on the effects of openings on the flexural behaviour of reinforced concrete slabs includes Casadei et al. (2003), Banu et al. (2012) and Elsayed et al. (2009). In addition, experimental tests that examined slabs supported on rectangular columns are very limited.

scholarly journals PERILAKU PUNCHING SHEAR PADA HUBUNGAN KOLOM BULAT DENGAN FLAT SLAB AKIBAT BEBAN TEKAN AKSIAL

2019 ◽  
Vol 1 (1) ◽  
pp. 1-14
Author(s):  
Muhammad Zardi
Keyword(s):  
Concrete Strength ◽  
Load Condition ◽  
Maximum Load ◽  
Shear Capacity ◽  
Punching Shear ◽  
Shear Reinforcement ◽  
Eccentric Load ◽  
Flat Slab ◽  
Circular Column ◽  
Flat Slabs

The aim of the tests was to investigate the influence of concrete strength, the eccentricity of the column and the use of shear reinforcement in flat slabs on punching shear. The research specimens are 8 units of flat slabs. Flat slab size 1400 x 1400 mm2 with thickness of 120 mm. Flat slabs were connected with circular column with dimension 225 mm  of diameter and 200 mm of height. Flat slabs were made in to 2 variations of concrete strength, e.i. 30 MPa and 60 MPa, 2 variations of shear reinforcement, e.i. without shear reinforcement and with shear reinforcement and 2 variations of eccentricity that, e.i. without eccentricity and with eccentricity. Each treatment has 1 specimen. Each specimen has 6 cylinder specimens. Cylinder specimens used as a concrete strength control for main specimen (flat slab). The tests showed that the concrete strength had a strong influence on punching shear strength. This is shown by capacity increase of 42.78%; 54.00%; 46.59% and 0.02%. The value is ratio between the maximum load of the specimens with 60 MPa and 30 MPa at the same eccentricity and the same shear reinforcement. The eccentricity of column reduce the capacity of punching shear. This is shown by 3 specimens decrease in capacity of 3.70%; 36.75% and 7.30%. Only 1 specimen that increase in capacity of 9.27%. The value is ratio between the maximum load of the specimens with 40 mm eccentricity and 0 mm eccentricity at the same compressive strenght and the same shear reinforcement. The use of shear reinforcement does not always increase the punching shear capacity. There are 2 observations that increased capacity (52.07% and 65.37% at the centric load) and 2 observations decreased capacity (0.12% and 4.92% at the eccentric load). The value is ratio between the maximum load on the specimens using shear reinforcement with the specimens that do not use shear reinforcement at the same compressive strenght and the same eccentricity.The use of shear reinforcement increase punching shear capacity of flat slab at the centric load condition. The use of shear reinforcement decrease punching shear capacity of flat slab at the eccentric load condition.

scholarly journals Shear Behavior of RC Deep Beam Strengthened by V-Shaped External Rods

2020 ◽  
Vol 10 (1) ◽  
pp. 41-59 ◽  
Author(s):  
Pramod Rai ◽  
Kitjapat Phuvoravan
Keyword(s):  
Experimental Test ◽  
Shear Failure ◽  
Experimental Tests ◽  
Shear Behavior ◽  
Shear Capacity ◽  
Deep Beam ◽  
Nominal Strength ◽  
Rod System ◽  
Strengthened Beam ◽  
Strengthening Technique

This research investigated the shear strengthening technique of Reinforced Concrete (RC) deep beams using a V-shaped external rod system. Shear behavior, the stress in an external rod, and the shear capacity at the diagonal shear failure of a strengthened beam were focused mainly. Experimental tests of control and two strengthened beams were carried out to observe the effect of the external rod on shear behavior of RC deep beam. A theoretical approach to compute the stress in the external rod and the nominal strength of the strengthened beam in the diagonal shear failure were examined based on the experimental test results and verified using Finite Element Method (FEM) in ABAQUS. The computed nominal shear strength of the strengthened beam was 10% higher than the experimental test. The strengthening technique shifted the brittle shear failure to ductile shear failure and improved the performance of RC deep beam.

scholarly journals Design considerations on the influence of slab continuity on punching resistance of flat slabs

2020 ◽  
Vol 13 (6) ◽  
Author(s):  
Fernanda Gabriella Batista Santos Oliveira ◽  
Luis Fernando Sampaio Soares ◽  
Robert Lars Vollum
Keyword(s):  
Shear Crack ◽  
Floor Plate ◽  
Punching Shear ◽  
Fe Modelling ◽  
Flat Slab ◽  
Design Considerations ◽  
Flat Slabs ◽  
Shear Design ◽  
Eurocode 2 ◽  
Modelling Assumptions

abstract: This paper assesses the influence of slab continuity on the punching resistance of a realistically proportioned flat slab floor plate without shear reinforcement. The edge column punching resistance of a symmetric flat slab extending bays in each direction was assessed by means of NLFEA with TNO DIANA, MC2010 levels II, III, IV, Eurocode 2 and NBR 6118. Both Eurocode 2 and NBR 6118 are seen to give similar predictions for punching resistance, while MC2010, which is based on the Critical Shear Crack Theory and depends on how rotations are calculated and FE modelling assumptions, varies significantly with its levels of approximation with Level IV agreeing reasonably well with predictions from NLFEA. Direction for the critical rotations is shown to vary and can also be influenced by the reinforcement over the span. For EC2, NBR 6118 and MC2010 LoA II and III punching shear design are independent of span, unlike the results obtained with MC2010 LoA IV.

scholarly journals Strengthening flat slabs without shear reinforcement against punching shear by concrete overlay

2021 ◽  
Vol 1209 (1) ◽  
pp. 012056
Author(s):  
D Čereš ◽  
K Gajdošová
Keyword(s):  
Parametric Study ◽  
Shear Crack ◽  
Shear Resistance ◽  
Shear Capacity ◽  
Reinforcement Ratio ◽  
Punching Shear ◽  
Flat Slab ◽  
Model Code ◽  
Eurocode 2 ◽  
Model Code 2010

Abstract Research in this paper presents a theoretical study of increasing in punching shear capacity of the strengthened flat slab by concrete overlay. The parametric study is based on comparison of three different relevant standards design models and presents results how Eurocode 2 (EN 1992-1-1), Model Code 2010 and draft of second generation of Eurocode 2 (prEN 1992-1-1) take into account strengthening by concrete overlay. A reference specimen is represented by a fragment of a flat slab supported by circular column. Influence of concrete toppings depends on thickness and also on reinforcement ratio. In Eurocode 2 and new generation of Eurocode 2 the increase of punching shear resistance of the slab with concrete topping can be taken into account only by reinforcement ratio and thickness of the slab considering the perfect connection and bond between the original slab and new layer of concrete overlay. Model Code 2010 is based on Critical shear crack theory and the reinforcement ratio in concrete topping was considered in equation of moment of resistance and punching shear resistance is calculated by considering the rotation and deformation of the slab. Estimation of results by parametric study are compared by non-linear model from Atena software.

Review of the Punching Shear Behavior of Concrete Flat Slabs in Ambient and Elevated Temperature

2013 ◽  
Vol 4 (4) ◽  
pp. 259-280 ◽  
Author(s):  
Mehrafarid Ghoreishi ◽  
Ashutosh Bagchi ◽  
Mohamed Sultan
Keyword(s):  
Elevated Temperature ◽  
Shear Failure ◽  
Shear Behavior ◽  
Shear Capacity ◽  
Punching Shear ◽  
Ambient Conditions ◽  
Flat Slab ◽  
Flat Slabs ◽  
Analytical Studies ◽  
In Fire

There are a number of benefits associated with two-way concrete flat slab construction for office buildings, parking garages and apartments - for example, reduced formwork, prompt erection, flexibility of partitions, and minimal increase in story heights. However, concrete flat slabs could be quite vulnerable to punching shear failure in the event of a fire. The objective of the present article is to provide a state of the art review of the existing research and the issues associated with concrete flat slabs in fire and elevated temperature. There are a number of experimental and analytical studies on the punching shear behavior of concrete flat slabs in ambient conditions, available in the literature. Based on these studies, it is found that punching shear capacity in ambient condition is affected by many factors, which may not remain constant during a fire exposure. Only a limited number of studies on concrete flat slabs for punching shear failure in fire are available. This paper reviews the available experimental and analytical studies, standards and codes to address the research gap in estimating of punching shear strength of concrete flat slab-column connections without shear reinforcement.

Compressive Membrane Action Effects on Punching Strength of Flat RC Slabs

2016 ◽  
Vol 711 ◽  
pp. 698-705 ◽  
Author(s):  
Raffaele Cantone ◽  
Beatrice Belletti ◽  
Luca Manelli ◽  
Aurelio Muttoni
Keyword(s):  
Shear Crack ◽  
Experimental Tests ◽  
Punching Shear ◽  
Crack Model ◽  
Potential Contribution ◽  
Membrane Action ◽  
Flat Slabs ◽  
Codes Of Practice ◽  
Rc Slabs ◽  
Compressive Membrane Action

The design of reinforced concrete flat slabs in practice can be governed at failure by punching shear close to concentrated loads or columns. Punching shear resistance formulations provided by codes are calibrated on the basis of experimental tests on isolated slabs supported on columns in axisymmetric conditions. Nevertheless, the behavior of flat slabs can be different than isolated specimens due to the potentially beneficial contributions of moment redistributions and compressive membrane actions. Accounting for the significance of these effects, nonlinear finite element analyses are performed with the crack model PARC_CL implemented in Abaqus. This paper aims to investigate a series of punching shear tests on slabs with and without shear reinforcement, different reinforcement ratios and loading conditions accounting for the potential contribution to the enhancement of the punching strength due to compressive membrane action (CMA). The numerical results with a multi – layered shell modeling are then post – processed adopting the failure criterion of the Critical Shear Crack Theory (CSCT). The results pointed out the significant outcomes and differences between standard specimens and actual members showing how the current codes of practice may underestimate the punching capacity.

scholarly journals Fiber Reinforced Polymer Laminates for Strengthening of RC Slabs against Punching Shear: A Review

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 685 ◽  
Author(s):  
Osama Ahmed Mohamed ◽  
Manish Kewalramani ◽  
Rania Khattab
Keyword(s):  
Shear Strength ◽  
Shear Capacity ◽  
Fiber Reinforced Polymer ◽  
Punching Shear ◽  
Fiber Reinforced ◽  
Flat Plates ◽  
Flat Slab ◽  
Flat Slabs ◽  
Reinforced Polymer ◽  
Floor Systems

Reinforced concrete flat slabs or flat plates continue to be among the most popular floor systems due to speed of construction and inherent flexibility it offers in relation to locations of partitions. However, flat slab/plate floor systems that are deficient in two-way shear strength are susceptible to brittle failure at a slab–column junction that may propagate and lead to progressive collapse of a larger segment of the structural system. Deficiency in two-way shear strength may be due to design/construction errors, material under-strength, or overload. Fiber reinforced polymer (FRP) composite laminates in the form of sheets and/or strips are used in structurally deficient flat slab systems to enhance the two-way shear capacity, flexural strength, stiffness, and ductility. Glass FRP (GFRP) has been used successfully but carbon FRP (CFRP) sheets/strips/laminates are more commonly used as a practical alternative to other expensive and/or challenging methods such column enlargement. This article reviews the literature on the methodology and effectiveness of utilizing FRP sheets/strips and laminates at the column/slab intersection to enhance punching shear strength of flat slabs.

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.

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