Károly Péter Juhász

• Doctor of Engineering
• Principal Investigator at Budapest University of Technology and Economics

This paper describes the 3rd Blind Simulation Competition (BSC) organized by the fib WP 2.4.1 which aims to assess the predictive performance of models based on the finite element method (FEM) for analysis and design of fiber reinforced concrete (FRC) structures submitted to loading and support conditions that promote punching failure mode. Fiber r...

Fiber reinforced concrete (FRC) is a composite material whose post-crack response is highly dependent on the properties of the mixed fibers, as well as their position and orientation in the matrix and on the fracture surface. To determine the material parameters of fiber reinforced concrete, a relatively small, notched beam with a cross-section of...

The refurbishment of railway lines and the installation of new tracks necessitate the construction of numerous concrete manholes; therefore, the optimization of manholes should be investigated. To this end, the use of innovative materials in addition to advanced design methods with realistic modeling is required. In the case of conservatively desig...

A szálerősítésű beton egy kompozit anyag, ahol a betonban elkevert szálak elsődleges szerepe a beton duktilitásának a növelése. A kompozit anyag anyagtulajdonságai függenek a beton mátrix és az elkevert szálak mechanikai tulajdonságaitól, ugyanakkor a mátrix és a szálak kapcsolatától is. A szálerősítésű beton anyagparamétereinek meghatározására a l...

The demand for jointless industrial floors is increasing, but there are no relevant agreed-upon standards or design recommendations, particularly for floors made of synthetic fiber reinforced concrete. The primary challenge associated with jointless floors is controlling the cracking caused by the restrained movement of concrete due to shrinkage an...

Macro synthetic fibre reinforcement has become widely used in concrete structures, such as tramlines, tunnels, industrial floors and precast elements. With using synthetic fibres as a reinforcement in concrete structures the casting time and the labour work will decrease, while the ductility will increase. In most cases the steel reinforcement can...

There are several existing guidelines for determining the material parameters of fibre reinforced concrete (FRC). The most commonly used test methods for this determination are the four-point and three-point bending beam tests. Generally, owing to the relatively small size of specimens and the random locations of fibres, the standard deviation of t...

This article describes the second blind simulation competition (BSC) organized by the fib WG 2.4.1, which aims to assess the predictive performance of models based on the finite element method (FEM) for the analysis and design of fiber reinforced concrete (FRC) structures. Slabs supported on columns or piles have becoming competitive applications f...

La investigación experimental ha demostrado el extraordinario potencial de la adición de fibras cortas a los materiales cementiceos, ya que mejoran significativamente el comportamiento de estructuras de hormigón en los estados límite de servicio y último. Para la simulación del comportamiento no lineal del material en estructuras de hormigón reforz...

Experimental research has shown the extraordinary potential of the addition of short fibers to cement‐based materials by improving significantly the behavior of concrete structures for serviceability and ultimate limit states. Software based on the finite element method has been used for the simulation of the material nonlinear behavior of fiber‐re...

The characteristic values of the material parameters used for structural design are usually determined from the mean and standard deviation of the material test results, and the design values are calculated from the characteristic values using the appropriate safety factor. However, if the standard deviation of the test data is high, the characteri...

A szálerősítésű beton egy rövid szálas kompozit anyag, melynek tulajdonságai nagyban függnek a mátrixban elkevert szálak orientációjától. Kiindulásként a szálak egyenletes elkeveredését és ezáltal egyenletes orientációt feltételezünk, azonban a valóságban különböző hatások miatt ez nem teljesül. A szálak orientációjának egyenletestől való eltérése...

Fibre-reinforced concrete is a short-fibre composite material, whose properties are significantly dependent on the orientation of the mixed fibres. As a starting point, the fibres are assumed to be uniformly distributed and have a uniform orientation. However, in reality, they have a non-uniform distribution owing to various factors. Such deviation...

Fibre reinforced concrete belongs to the group of composite materials, where matrix means the concrete, and fibres mean the various shaped (straight, hooked, wavy, etc.) and material (steel, polypropylene, glass, etc.) fibres, which are short compared to the size of concrete elements. Fibres are mixed in fresh concrete which supposedly provides a p...

Quantity of the fibres intersecting the unit cross section is a relevant parameter. Firstly, the residual tension strength, which is the base of the material model of the fibre reinforced concrete, depends most on the number of fibres intersecting the cracked cross section. Secondly, by counting the fibres on the cross section of the broken test sp...

Fibre reinforced concrete has become a widely used material since the end of the 20 th century. The uniformly distributed steel or macro synthetic fibres in the concrete structures can give the concrete a residual flexural strength after the first cracks. The different behaviour of materials subjected to different loading rates is a well-known phen...

Fibre reinforced concrete has become a widely used material since the end of the 20th century. The uniformly distributed steel or macro synthetic fibres in the concrete structures can give the concrete a residual flexural strength after the first cracks. The different behaviour of materials subjected to different loading rates is a well-known pheno...

Nowadays macro synthetic fibres are able to compete with steel fibres despite their low Youngs Modulus. This is due to their different pull-out mechanism and a larger number of individual fibres per kilo compared to steel fibres. Macro synthetic fibres bond to the concrete along their full length, usually with an embossed surface, while steel fibre...

In this article a macro synthetic fibre reinforced precast concrete trackslab's design process will be presented. The analysis was done with using an advanced finite element software called ATENA (Cervenka et al 2013). Beside the static loads, the precast slab was also checked for dynamic and fatigue loads. The structure was verify for early ages,...

Shanghai metro extension is one of the most enormous TBM tunnel investigation nowadays in Republic of China. Because of the size of the investment several research connected to the project. The Customers tried to use the most economic concrete reinforcement, and joint element between the rings. The Tongji University made a real scale test about the...

Fibre Reinforced Concrete (FRC) is widely accepted in the tunnelling industry for use such as shotcrete, cast-in-situ linings or Tunnel Boring Machine (TBM) concrete linings. To calculate an FRC structure the generally accepted method is to measure the parameters of the FRC using the standard 3 point beam test, measuring the load, deflection and/or...

In recent years, fiber reinforced concrete has been increasingly used not only for industrial floors but for many other loadbearing structures as well. The different types of synthetic fibers have distinct effects on concrete: micro fibers to reduce plastic shrinkage cracking of concrete, and macro fibers to give higher fracture toughness. This pap...

The design of bolts in a segmental tunnel is presently not covered by a generally accepted design method, moreover the use and necessity of the bolts is subject to dispute, too. Some design guidance, such as British Tunnelling Society [2], French Underground Construction Society [1] and German Tunnelling Committee [5] state that the bolts are used...

FRP rebar has become considered more and more as an ordinary reinforcement in concrete structures, due to its main advantage of being corrosion-free. However, FRP bars can be bent only at the manufacturing stage and not on site, which makes the production of items such as stirrups difficult and uneconomical. As an alternative, shear reinforcement b...

The effect of the use of fibre for controlling early age shrinkage is well-known, although there is no generally accepted method to make calculations on it. One of the biggest advantages could be to increase the dilatations and/or joints distances with the use of the fibres. The effect of the fibre during hardening was measured in our laboratory at...

The standard test methods of FRC (Fiber Reinforced Concrete) are bending beam tests. Due to the random distribution of the fibers there could be a big dispersion in the results. This large dispersion could be decreased by increasing the number of specimens and/or the area of the representative cross section. In this article the possibility of decre...

A szálerősítésű beton egy kompozit anyag, amely betonból, mint a szálak ágyazóanyagából és a benne elkevert szálakból tevődik össze. A beton egy kétfázisú anyag, amely tovább bontható adaléka-nyag vázra és habarcsra (víz, cement és homok). A beton egy kvázirideg anyag, azaz a repedés után rendelkezik maradó húzószilárdsággal, amely a repedéstágassá...

The standard test methods of FRC (Fibre Reinforced Concrete) are bending beam tests. Due to the random distribution of the fibres there could be a big dispersion in the results. This large dispersion could be decreased by increasing the number of specimens and/ or the area of the representative cross section. In this article the possibility of decr...

The use of fibre reinforcement has become a popular alternative to traditional steel mesh in industrial floors for the control of early age shrinkage. However, there are no generally accepted standards for the design of the jointless floors, only guidelines. One of the most well-known guidelines for industrial floors is the British guideline: TR 34...

Macro synthetic fibre reinforcement’s popularity is continuously growing and finds new sectors in tunnel engineering also. The added macro fibres increase the fracture energy of the concrete, which can be modelled by the Modified Fracture Energy Method. This method can be implemented into advanced Finite Element Analysis Software like ATENA. This s...

Magyarország nagyvárosaiban az elmúlt 6-7 évben megújultak a városi villamosvonalak. Az uniós fejlesztések a mobilitást, a környezetvédelmet és az utazási komfort növelését, továbbá a személygépjármű-forgalom csökkentését irányozták elő. A tömegközlekedés, ezen belül a villamosvonalak fejlesztése, korszerűsítése létkérdés a nagyvárosi közlekedésben...

Talajon fekvő padlók tervezésénél a legbonyolultabb feladat a beton szilárdulásakor jelentkező zsugorodásra való méretezés. Még nehezebb a helyzet, ha a dilatációs távolságok nagyok – esetleg nincsenek is, mint a jelen esetben épült gördeszkapályánál. Komoly kihívást jelentett így mind tervezési, betontechnológiai és kivitelezési oldalról egyaránt....

Szegeden a 2-es villamosvonal teljes hosszában 2025 vfm hosszban CDM-QTrack rendszerben kiépített, kétvágányú füvesített, öntözött kialakítású, melyben 3 db füvesített kitérő és 2 db mikroszál-erősítésű beton pályalemezes kitérő lett kiépítve műanyag georács erősítéssel (TENSAR SS 100). A kis sugarú ívekben a pályagerendákba épített sínkenők üzemel...

Four large-scale, prismatic, T-shaped beams with 19 m span were produced without stirrups, but 2 with synthetic fibres and 2 with steel fibres. Four point bending tests were made to simulate the load bearing process of built-in beams. Three point shear tests were made in the uncracked ends of the beams to prove the shear resistance of FRC. The beha...

The authors were engaged to optimise a traditional rebar cage reinforced concrete segmental lining by means of finite element analysis (FEA) using macro synthetic fibres for the Shanghai metro extension. The aim of this study was to reduce or entirely replace the original steel reinforcement of the segmental lining, in order to make the precast pro...

Hazánkban is egyre elfogadottabbá válik a szintetikus szálerõsítésû betonok alkalmazása, habár a szintetikus mikro és makro szálak közötti alapvetõ különbségeket gyakran még a szakemberek sem ismerik. A különbség azonban jelentõs, mind a méretezés, mind a felhasználás tekintetében. Ebben a cikkben ezeket a fõbb különbségeket vesszük sorra: szabvány...

The Company EPC (elastoplastic concrete) has developed a series of new synthetic fibers: Barchip. It a good alternative to steel bars, because of its better durability, fire resistance and low carbon emission, etc.. EPC company desires that the synthetic Barchip can be applied in the subway tunnel construction in Shanghai. Therefore, this paper is...

Fibre manufacturers specify different parameters for measuring the performance of their fibres, e.g. Re3 number or σ-ε diagram. However, these parameters depend largely on the strength class of the concrete; most specifically on the fracture energy, which is in itself a variable from cement manufacturer to manufacturer, even within the same class....

A stadium with 20.020 people capacity will be built in Debrecen, Hungary. The slab part of the precast, multi-stairs grandstand is only 12 cm thin and prestressed; PFRC is used instead of mild stirrups. Six types of polymer fibres were tested and compared according to RILEM regulations with the same dosage. Two selected types were tested with diffe...

Kulcsszavak: beton, szálerősítésű beton, húzó-hajlító szilárdság, törési energia Keywords: concrete, fiber reinforced concrete, flexural tensile strength, fracture energy KIVONAT A beton és szálerősítésű beton húzó-hajlító szilárdságának meghatározására a jelenlegi irányelvek a törőerőt veszik alapul. Ez az ered-mény lineáris számításokhoz megfelel...

Kulcsszavak: beton, szálerősítésű beton, gerendateszt, teszteredmények kiértékelése Keywords: concrete, fibre reinforced concrete, beam test, evaluation of test results KIVONAT Szálerősítésű beton gerendák szabványos vizsgálata az 1 vagy 2 ponton terhelt kéttámaszú gerendateszt, melynek útvezérelt vizsgálat során a terhelő erőt, középponti relatív...

INTRODUCTION: The purpose of this paper is to bring to the attention of the audience the numerous cases around the world that have substituted steel mesh and steel fibres for structural synthetic fibres as their reinforcement option in different types of tunnels.

Macro fibres have been well accepted for the reinforcement of sprayed concrete in mining and tunnelling applications, and today are starting to be used in other structural elements either in combination with existing steel bars, reducing the size of the steel bars or replacing the steel altogether. Although the use of fibre-reinforced concrete in t...

Deflections of concrete structures are commonly investigated under service loads. For calculating the position of the neutral axis non-linear equations must be solved. There is not an accepted general method, because the functions, which have been used, are sophisticated and their convergence features are not known. This article presents a method...