Safety of the Models for Assessment of Punching Resistance of Flat Slabs with Openings Adjacent to the Columns

2020 ◽  
Vol 309 ◽  
pp. 186-192
Author(s):  
Ľudmila Kormosova ◽  
Jaroslav Halvonik ◽  
Lucia Majtánová
Keyword(s):  
Standard Method ◽  
Design Model ◽  
Column Height ◽  
Transverse Reinforcement ◽  
Flat Slab ◽  
Flat Slabs ◽  
Current Design ◽  
Effective Depth ◽  
Effective Part

The paper deals with the quality of the current EC2 (2004) model for predicting punching capacity of flat slabs without transverse reinforcement, supported by elongated columns and weakened by two openings placed adjacent to the column. The ratio column’s section height/effective depth of a slab was six. The reference punching capacities were obtained from non-linear analyses carried out on the flat slab fragments. Five different arrangements of the openings were tested with three models that take into account an effect of the openings on the punching resistance. Based on the investigation performed, it was observed that the length 3d of the effective part of a column perimeter along the column height h with the ratio h/d > 3 is very conservative. The whole control perimeter contributed to the punching capacity for all slab fragments tested. Current design model EC2 (2004) is safe in the case of predicting the punching capacity of flat slabs with openings adjacent to the columns if the standard method of reduction of the control perimeter lengths due to openings is used. The most consistent results provided method that is based on the Augustin's proposal for reduction of the control perimeter length.

scholarly journals Experimental Investigation of the Maximum Punching Resistance of Slab-Column Connections

2018 ◽  
Vol 26 (3) ◽  
pp. 22-28 ◽  
Author(s):  
Jaroslav Halvoník ◽  
Lucia Majtanová
Keyword(s):  
Experimental Investigation ◽  
Progressive Collapse ◽  
Transverse Reinforcement ◽  
Test Results ◽  
Structural System ◽  
Structural Behaviour ◽  
Shear Forces ◽  
Flat Slab ◽  
Direct Verification ◽  
Flat Slabs

Abstract Flat slabs represent a structural system with a typical concentration of shear forces near the vicinity of its local supports. A possible failure from punching is a dangerous phenomenon due to the brittleness and possible progressive collapse of a whole structure. An improvement in the structural behaviour of a slab-column connection provides transverse reinforcement. The amount of this reinforcement and thus its contribution to the resistance against punching has a limit, which is represented by the maximum punching capacity. This capacity can be assessed using the kmax factor or by direct verification of the strut capacity. The article deals with the results of a test campaign carried out on flat slab specimens with their transverse reinforcements designed in such a way that the crushing of the struts is the governing mode of any failure. The test results obtained allowed for an evaluation of the kmax factors and provide an answer as to whether it is possible to cover failures due to the crushing of struts by this factor.

scholarly journals Are the defined substrate-based methods adequate to determine the microbiological quality of natural recreational waters?

2009 ◽  
Vol 8 (1) ◽  
pp. 11-19 ◽  
Author(s):  
Marta Sofia Valente ◽  
Paulo Pedro ◽  
M. Carmen Alonso ◽  
Juan J. Borrego ◽  
Lídia Dionísio
Keyword(s):  
Standard Method ◽  
Membrane Filtration ◽  
Microbiological Quality ◽  
Recreational Waters ◽  
Total Coliforms ◽  
E Coli ◽  
Quality Of Water ◽  
Routine Monitoring ◽  
Rapid Tests

Monitoring the microbiological quality of water used for recreational activities is very important to human public health. Although the sanitary quality of recreational marine waters could be evaluated by standard methods, they are time-consuming and need confirmation. For these reasons, faster and more sensitive methods, such as the defined substrate-based technology, have been developed. In the present work, we have compared the standard method of membrane filtration using Tergitol-TTC agar for total coliforms and Escherichia coli, and Slanetz and Bartley agar for enterococci, and the IDEXX defined substrate technology for these faecal pollution indicators to determine the microbiological quality of natural recreational waters. ISO 17994:2004 standard was used to compare these methods. The IDEXX for total coliforms and E. coli, Colilert®, showed higher values than those obtained by the standard method. Enterolert® test, for the enumeration of enterococci, showed lower values when compared with the standard method. It may be concluded that more studies to evaluate the precision and accuracy of the rapid tests are required in order to apply them for routine monitoring of marine and freshwater recreational bathing areas. The main advantages of these methods are that they are more specific, feasible and simpler than the standard methodology.

On Bending of a Flat Slab Supported by Square-Shaped Columns and Clamped

1954 ◽  
Vol 21 (3) ◽  
pp. 263-270
Author(s):  
S. Woinowsky-Krieger
Keyword(s):  
Stress Distribution ◽  
Conformal Mapping ◽  
Complex Variable ◽  
Complex Variable Method ◽  
Variable Method ◽  
Flat Slab ◽  
Flat Slabs ◽  
At Will

Abstract A solution is given in this paper for the problem of bending of an infinite flat slab loaded uniformly and rigidly clamped in square-shaped columns arranged to form the square panels of the slab. The complex variable method in connection with conformal mapping is used for this aim. Although not perfectly rigorous, the solution obtained is sufficiently accurate for practical purposes and, besides, it can be improved at will. Stress diagrams traced in a particular case of column dimensions do not wholly confirm the stress distribution, generally accepted in design of flat slabs.

Background

2020 ◽  
pp. 20-40
Keyword(s):  
Expert System ◽  
Urban Regeneration ◽  
User Participation ◽  
Design Model ◽  
User Needs ◽  
Specific Context ◽  
Mass Housing ◽  
Living Environments ◽  
Methodological Aspects

Re-Coding Homes searches for flexibility in the standard layout of contemporary housing units very common in the big cities of Turkey. The project differentiates from other studies with its unique design model characterized by an expert system that generates complete home environments according to parameters defined by user needs. In this sense, certain methodological and contextual aspects were employed throughout the study. Among these, flexibility, modularity, adaptability, and user participation were discussed as methodological aspects that identify the design model. Urban regeneration and mass housing are investigated as contextual aspects that affect the overall quality of present living environments in the specific context of Istanbul.

Nonlinear FEM Analysis of Experimentally Tested Flat Slabs with Openings

2019 ◽  
Vol 292 ◽  
pp. 191-196 ◽  
Author(s):  
Tomáš Augustín ◽  
Ľudovít Fillo ◽  
Jaroslav Halvonik
Keyword(s):  
Model Calibration ◽  
Fem Analysis ◽  
Linear Analysis ◽  
Experimental Results ◽  
Nonlinear Fem ◽  
Flat Slabs ◽  
The World ◽  
The Face ◽  
Effective Depth ◽  
Reference Specimens

Experimental programs focused on the issues related to the flat slabs still attract the attention of the scientists around the world. At the Central Laboratories of STU in Bratislava, together 8 fragments of the flat slabs were tested, focusing on the influence of the openings on the punching resistance. The two reference specimens were without openings and the others had two symmetrically placed openings. The openings were moved from the face of the column in multiples of the effective depth (0d, 1d, 2d). For the assessment of the tests, the models introduced in the relevant standards and codes were applied. The experimental results were also used for NFEM model calibration. The paper will deal with comparison of the theoretical and experimental results as well as with non-linear analysis that was performed in the ATENA FEM program, with the goal to obtain the most realistic behaviour of the flat slabs with openings. The material properties used in the analysis were obtained from the laboratory tests.

Punching Analysis of a Flat Slab with a Change in Elevation

2015 ◽  
Vol 1106 ◽  
pp. 233-236
Author(s):  
Jan Nováček ◽  
Miloš Zich
Keyword(s):  
Nonlinear Model ◽  
Linear Models ◽  
Flat Slab ◽  
Flat Slabs

In recent years, construction of buildings with concrete flat slabs has developed widely. For these structures, correct punching design is crucial. Suitable punching check methods for most common details are provided in all standards. In some cases, however, it is necessary to use a detail that is not fully covered in effective codes. In the article, the change in elevation at a column line detail of a flat slab is analysed. Attention is paid to possible ways of inner forces interpretation and to their subsequent check in accordance with standards. Several linear models and one nonlinear model were created and compared against each other.

Reconstruction Effectiveness of Locally Supported Flat Slabs to Increase in Shear Resistance

2020 ◽  
Vol 309 ◽  
pp. 246-251
Author(s):  
Mária Bolešová ◽  
Katarína Gajdošová ◽  
Marek Čuhák
Keyword(s):  
Shear Stress ◽  
Numerical Models ◽  
Shear Resistance ◽  
Reconstruction Method ◽  
Detailed Calculation ◽  
Shear Reinforcement ◽  
Flat Slab ◽  
Advantages And Disadvantages ◽  
Flat Slabs ◽  
Eurocode 2

The most used horizontal load-bearing systems in concrete buildings are flat slabs. The effective and economic reconstruction of a locally supported flat slab of an existing building creates a complex task. Shear stress arises near the column and it becomes critical in design with increasing slab slenderness and requires a more detailed calculation. Increasing in the shear resistance of the flat slab can be achieved in various ways. Each method brings different effectiveness, advantages and disadvantages. The most widely used methods of the reconstruction are the increase in the size of the column (therein increasing the control perimeter for displaying the shear stress), the increase in the thickness of the flat slab or reinforcing the slab with shear reinforcement. Bolts and screw anchors (using different mounting angles) can be used as shear reinforcement. Each mentioned reconstruction method should be subjected to numerical calculations and verification of its efficiency. The parametric study presented in this paper is focused on the reconstruction techniques and their verification according to various numerical models. The results from Eurocode 2, fib Model Code 2010 and the new generation of Eurocode 2 are compared to show the differences between them. The aim of this paper is to bring a demonstration of the reconstruction methods that will increase in the shear resistance of the locally supported flat slabs and trying to choose the most effective one.

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 Cooling of the continental plate during flat-slab subduction

Geosphere ◽  
2021 ◽  
Author(s):  
Xiaowen Liu ◽  
Claire A. Currie ◽  
Lara S. Wagner
Keyword(s):  
Heat Flow ◽  
Numerical Models ◽  
Thermal Structure ◽  
Surface Heat ◽  
Surface Cooling ◽  
Flat Slab ◽  
Surface Heat Flow ◽  
Flat Slabs ◽  
Flat Slab Subduction ◽  
Subducting Plate

Most flat-slab subduction regions are marked by an absence of arc volcanism, which is consistent with closure of the hot mantle wedge as the subducting plate flattens below the continent. Farther inland, low surface heat flow is observed, which is generally attributed to cooling of the continent by the underlying flat slab. However, modern flat slabs have only been in place for <20 Ma, and it is unclear whether there has been sufficient time for cooling to occur. We use numerical models to assess temporal variations in continental thermal structure during flat-slab subduction. Our models show that the flat slab leads to continental cooling on timescales of tens of millions of years. Cool slab temperatures must diffuse through the continental lithosphere, resulting in a delay between slab emplacement and surface cooling. Therefore, the timescales primarily depend on the flat-slab depth with shallower slabs resulting in shorter timescales. The magnitude of cooling increases for a shallow or long-lived flat slab, old subducting plate, and fast convergence rates. For regions with flat slabs at 45–70 km depth (e.g., Mexico and Peru), shallow continental cooling initiates 5–10 Ma after slab emplacement, and low surface heat flow in these regions is largely explained by the presence of the flat slab. However, for the Pampean region in Chile, with an ~100-km-deep slab, our models predict that conductive cooling has not yet affected the surface heat flow. The low heat flow observed requires additional processes such as advective cooling from the infiltration of fluids released through dehydration of the flat slab.

scholarly journals Experiment of Pullout Expansion Anchor in Installation Cast in Place and Post Installed with Concrete Breakout Failure

2021 ◽  
Vol 23 (1) ◽  
pp. 37-45
Author(s):  
Amirul Huda ◽  
Henry Apriyatno
Keyword(s):  
Pullout Test ◽  
Test Results ◽  
Pullout Capacity ◽  
Concrete Compressive Strength ◽  
Strength Tests ◽  
Effective Depth ◽  
The Difference ◽  
Better Than ◽  
Ready Mix Concrete

Abstract: The use of anchors in construction is gaining popularity to connect steel and concrete constructions, and to transmit tensile loads acting onto the concrete. This research aims to find out the difference in the strength of anchor based on two methods of installations that are cast in place compared to post installed with the influence of effective depth, diameter of anchor and quality of concrete, and failure of concrete breakout. Expansion anchor used in this study is "Sanko" M12x100 and ready-mix concrete PT Bonindo Ungaran, fc 25 MPa with 6 pieces of test specimens of 300x300x150 mm. Each specimen has 4 anchors with a distance between the anchors of 100 cm, the distance between the anchors to the edge of the concrete 100 mm, and the depth of installation (hef) of 60 mm. The result of the study is the predicted value of the anchor pullout capacity with the failure of concrete breakout due to the theoretical pullout, namely 42,223 N, anchor pullout test results with cast in place method of 40,574 N and post installed method by 37,494 N. Tensile strength tests (material) of anchor (fy) 338 MPa, for flat concrete compressive strength strength of (f’c) 25,698 MPa. The results of the cast in place pullout test are larger and better than post installed (40574 N>37494 N). Failure that occurred in cast in place method is a failure of concrete breakout and post installed method has occurred slip. Failures that occur are relevant to the theory.

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