Papers by Keyword: Punching Shear

Abstract: The new generation of Eurocodes for concrete structures, specifically the draft standard FprEN 1992-1-1:2023, introduces an innovative application of non-prestressed Fibre Reinforced Polymer (FRP) reinforcement (Annex R). This standard represents the first standardized method for the application of FRP reinforcement, an area that has been lacking in European standards to date. Composite reinforcement using glass (GFRP) or carbon fibre (CFRP) provides a perspective alternative in specific applications where it can replace traditional steel or stainless steel reinforcement. The main advantages are high corrosion resistance and electromagnetic neutrality. This allows for application in structures exposed to a high level of environmental impact. However, composite reinforcement with glass fibres exhibits sensitivity to alkaline environments and has a lower modulus of elasticity compared to steel reinforcement. Due to the linear elastic stress-strain diagram for FRP reinforcement, the design of structures with FRP reinforcement requires a different approach than traditional concrete reinforcement. The standard FprEN 1992-1-1:2023 provides specific approaches for the design of concrete elements using FRP reinforcement, considering various types of loading. In the context of design resistance to punching shear, the standard offers a specific relationship that determining the punching shear resistance for using longitudinal FRP reinforcement. In situations where it is necessary to consider punching shear reinforcement, the shear reinforcement should not be made from FRP. The transition to the new Eurocode brings significant changes in the method of design punching shear resistance compared to the current standard ČSN EN 1992-1-1. The aim is to verify the accuracy of the newly introduced relationships for punching shear through a real experiment with steel and FRP longitudinal reinforcement. The experiment will also research the effect of the adding FRP stirrups on the overall resistance under local loading conditions.

Abstract: One of the most effective and common ways of an increasing the punching shear capacity of the flat slabs is using of shear reinforcement. An important limit during the design is the determination of the maximum punching shear resistance. The fact that the calculation of such an important value is still clearly empirical has met with criticism from many experts in recent years. Consequently, a new design model for the calculation of the maximum punching shear resistance, based on the critical shear crack theory was developed. The second generation of the Eurocode 2 (prEC2) introduces a more accurate and sophisticated design model for the determination of the upper limit of the punching shear capacity and considers several parameters. The main aim of this paper is to describe the new methodology of calculation of the maximum punching shear strength and the parameters that could influence it. The paper deals also with an assessment of the suitability of new model by comparing it with experimental results, that have been selected from a database of specimens that failed by punching at the level of V_R,max.

Abstract: To validate the accuracy of ANSYS V.19, an experimental model based on a previous study was used to determine the typical values of crack pattern, ultimate load, and deflection. The model was a flat slab with an internal column with dimensions of 1000 × 1000 × 100 mm³. Four groups used a slab with an edge column in parametric research. The first group studied the opening size relative to the column face. The second group of specimens studied opening sizes close to column corners. The third group consisted of four specimens: two had openings in front of the column face and two in front of the column corner to study how opening distance affected flat slab behaviour. The fourth group examined the optimum opening arrangement in slabs with two openings around the column. The findings showed that flat slab openings at the column corner had higher ultimate load capacity than those at the column face; however, increasing opening dimensions beyond the column dimension decreases punching shear capacity. If the column needs two openings, place them on opposite faces or near the corners; this minimizes ultimate load reduction.

Abstract: Due to the importance of the joists slab system as an excellent solution for increasing span demands in different building types, investigating its properties becomes essential for different researchers. The effects of numerous parameters on the structural behaviour of the joists slab system, whether it was a waffle, ripped, or composite sections were reviewed in this paper from past studies. This study aims to determine the most effective parameters for the joist's system loading capacity. The main conclusions were that the slab thickness and joist height were the critical parameters for increasing the load capacity and stiffness of the slab. Furthermore, a small opening in the slab was more efficient in reducing the punching shear effect than larger openings. While providing stiffening rips around the opening was more effective in rose load bearing and reducing deflection than strengthening by carbon fibre sheets.

Abstract: This article aims to verify the possibility of strengthening existing flat slabs against punching by concrete overlay and the effectiveness of this type of strengthening. The method of strengthening by concrete overlay was verified on a theoretical level using the currently valid Eurocode 2 and other standards. A non-linear analytical model was developed in Atena 3D software, and the results of this model were compared with previous results from calculations according to the valid standards. The article also contains previous research results of Hugo Fernandes, who dealt with a similar type of strengthening method and this research was also based on experimental study. An important aspect is the detailing of the interface between the two concrete layers namely the roughening the existing surface or the use of studs, which ensure a minimum longitudinal displacement of the two layers. Two non-linear model approaches were presented. The results based on nonlinear analysis show that when using a simple model of two macroelements and defining the parameters of one interface, the punching shear resistance is higher than the actual resistance, in this case by of about 13% on the dangerous side.

Abstract: 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.

Abstract: In the international and national practice of design, a different type of slab on the various types of grade are becoming increasingly common. For such structural elements, shrinkage and temperature influences in combination with low tensile stress, mainly in early age, leads to the risk of cracking in reinforced concrete structures, and as result, a reduction of its durability. The present article describes some of the possible ways of usage of the post-tensioned flat slabs and the rational design procedures to provide their structural reliability. The theoretical background of the punching resistance checking, in the case when the piles support the foundation post-tensioned slabs, presented. For ground floor slabs, an iterative method is given for determining design compression pre-stresses distribution in slab sections, taking into account the restrained effect created by the friction shear stresses in contact between the slab and the base. Besides, the article presents some practical implementations of the post-tensioned slabs as an artificial base in the presence of weak soils and as a large-size ground floor (slab-on-grade) without any joints.

Abstract: This study evaluates the influence of utilizing silica fume as a stabilizer to the filler on the behavior of asphalt mixes. The investigation of the properties of asphalt mixes was conducted by using different percentages of Silica Fume (0, 3, 6, and 9% by filler weight). Results indicate that, the OAC is 4.7% and it achieves the best results in the Marshall tests. Marshall Stability is increased by about 27.5% and the flow is decreased by about 20.2 %. In this study the implementation of 9% of silica fume in the asphalt concrete mix showed a considerable excess in the resistance to moisture damage of 28% when compared to the original mix. A great decrease in the tensile strength of asphalt concrete mixes, in a range from (4-15)% could be noticed following the moisture damage process for both the reference and silica fume adjusted mixes. Six percent of it was the optimum percent that had developed the tensile characteristics of the hot asphalt concrete mixes. The moisture sensibility of the asphalt concrete was reduced with an increase in the silica fume content. Following the moisture damage process, Silica fume of 9% was the optimum percent that had developed the punching shear characteristics of asphalt concrete. It exhibited a positive effect of 20%, while 6-9% of silica fume exhibited a positive effect of 5-9% on the development of the tensile characteristics of asphalt concrete.

Abstract: —Ribbed slab is an ideal structure for architects and contractors. It has an attractive soffit appearance and also giving economical value when it is come in weight and material saving. Placing and finishing of concrete slab normally influence about 30% - 35% of overall cost of flooring system. Ribbed slab or also known as one-way joist slab system consist of regularly spaced concrete joist or ribs spanning in one direction, a reinforced concrete slab cast integrally with the ribs and beam span between the columns, perpendicular to the ribs. However the complexity of the structure itself has become an issue due to honeycomb and poor workmanship. To overcome this problem, the use of Self-Compacting Steel Fiber Reinforcement Concrete (SCFRC) could improve the workmanship quality and to minimize the occurrence of honeycomb in concrete. Steel fiber in concrete improved the resistance of reinforced structural members cracking, deflection and other serviceability condition. Thus, this alternative approach will be the main focus in this study.Punching shear strength in reinforced concrete slabs subjected to concentrated loads has received a lot of emphasis due to its importance in the structural system, this failure may take place due to in conservative design of slab overloading and deterioration of strength in concrete and reinforcement. The continuous improvement of the technology of SCFRC and the better knowledge on the mechanical behavior of this SCFRC ribbed slab are contributing to a larger field application of SCFRC. Determination of punching shear strength has received considerable attention by the engineering profession in recent years.

Abstract: This paper deals with behavior and capacity of punching shear resistance for ribbed slabs produce from self-compacting fiber reinforced concrete (SCFRC) by application of nonlinear finite element method. The analysis will be achieved by using ABAQUS software. The nonlinear finite element analysis by ABAQUS will be compare with the experimental results. Results and conclusions may be useful for establishing recommendation and need to be acknowledged.