scholarly journals Cracking in Concrete near Joints in Steelconcrete Composite Slab / Zarysowanie Płyty Żelbetowej W Strefie Przywęzłowej Stropu Zespolonego

2015 ◽  
Vol 16 (1) ◽  
pp. 167-179
Author(s):  
Marcin Niedośpiał ◽  
Michał Knauff ◽  
Wioleta Barcewicz

Abstract In this paper results of the experimental tests of four full-scale composite steel-concrete elements are reported. In the steel-concrete composite elements, a steel beam was connected with a slab cast on profiled sheeting, by shear studs. The end-plates were (the thickness of 8 mm, 10 mm and 12 mm) thinner than in ordinary design. Joints between the column and the beams have been designed as semi-rigid, i.e. the deformations of endplates affect the distribution of forces in the adjacent parts of the slab. The paper presents the theory of cracking in reinforced concrete and steel-concrete composite members (according to the codes), view of crack pattern on the surface of the slabs and a comparison of the tests results and the code calculations. It was observed, that some factors influencing on crack widths are not taken in Eurocode 4 (which is based on Eurocode 2 with taking into account the phenomenon called „tension stiffening”).

Author(s):  
Rosângela Silva Pinto ◽  
Vanessa Carolaine Sousa ◽  
Luamim Sales Tapajós ◽  
Maurício de Pina Ferreira ◽  
Aarão Ferreira Lima Neto

abstract: This paper presents the results of seven experimental tests in reinforced concrete wide beams, aiming to investigate their performance when subjected to shear, using prefabricated truss stirrups as shear reinforcement, as well as a supplementary reinforcement to control cracks by delamination. The main analysed variables were: position of the supplementary reinforcement, inclination of the shear reinforcement, and spacing between stirrups. Results showed that strength increments of up to 142% were obtained using the prefabricated truss stirrups. Furthermore, the experimental results were compared with the theoretical shear strength estimates of the tested beams, following the recommendations of NBR 6118 (2014), Eurocode 2 (2004), and ACI 318 (2014), in order to evaluate the safety level of these codes when designing concrete elements subjected to shear with the reinforcement used in this paper.


2016 ◽  
Vol 38 (2) ◽  
pp. 37-46 ◽  
Author(s):  
Mateusz Kaczmarek ◽  
Agnieszka Szymańska

Abstract Nonlinear structural mechanics should be taken into account in the practical design of reinforced concrete structures. Cracking is one of the major sources of nonlinearity. Description of deflection of reinforced concrete elements is a computational problem, mainly because of the difficulties in modelling the nonlinear stress-strain relationship of concrete and steel. In design practise, in accordance with technical rules (e.g., Eurocode 2), a simplified approach for reinforced concrete is used, but the results of simplified calculations differ from the results of experimental studies. Artificial neural network is a versatile modelling tool capable of making predictions of values that are difficult to obtain in numerical analysis. This paper describes the creation and operation of a neural network for making predictions of deflections of reinforced concrete beams at different load levels. In order to obtain a database of results, that is necessary for training and testing the neural network, a research on measurement of deflections in reinforced concrete beams was conducted by the authors in the Certified Research Laboratory of the Building Engineering Institute at Wrocław University of Science and Technology. The use of artificial neural networks is an innovation and an alternative to traditional methods of solving the problem of calculating the deflections of reinforced concrete elements. The results show the effectiveness of using artificial neural network for predicting the deflection of reinforced concrete beams, compared with the results of calculations conducted in accordance with Eurocode 2. The neural network model presented in this paper can acquire new data and be used for further analysis, with availability of more research results.


1998 ◽  
Vol 7 (6) ◽  
pp. 096369359800700 ◽  
Author(s):  
E. Gutiérrez ◽  
G. Di Salvo ◽  
J.M. Mieres ◽  
L. Mogensen ◽  
E. Shahidi ◽  
...  

In this paper we outline the development of an all-in-one composite reinforcing formwork system for manufacturing reinforced concrete elements, in particular, we describe the main experimental tests carried out on an 8 metre beam using high strength concrete poured and bonded on a hybrid, glass/carbon fibre formwork.


2009 ◽  
Vol 1 (1) ◽  
pp. 23-39 ◽  
Author(s):  
Vidmantas Jokūbaitis ◽  
Linas Juknevičius

The width of normal cracks at the level of tensile reinforcement was calculated according to various methods using the data obtained from experimental tests on reinforced concrete beams (without reinforcement pre-stress), pre-cast reinforced concrete slabs and ribbed roof slabs. Th e numerical results were compared to actual crack widths measured during the experimental tests. Also, the crack widths of pre-stressed reinforced concrete beams were calculated according to various methods and compared with each other. Th e following conclusions were reached based on the analysis of numerical and experimental results: 1) Design stresses in tensile reinforcement calculated according to [STR] and [EC] design codes are very similar, although the calculation of such stresses is more logical and simple according to [EC]. Design stresses calculated according to [RU] are greater due to the estimation of the plastic deformations of concrete in the compressive zone. Th e method proposed by Rozenbliumas (Розенблюмас 1966) estimates tensile concrete above the crack peak, and thus allows a more accurate calculation of stresses in tensile reinforcement (Fig 3). Therefore, the latter stresses in pre-stressed RC beams may be decreased by 10–12 %, when height hct ≠ 0 (Fig 1, c) and ratio M/MRd varies between 0,65 and 0,75; 2) The widths of normal cracks in conventional RC beams (subjected to load that corresponds approx. 70 % of their carrying capacity) calculated according to [STR] and [EC] design codes are almost equal to the experimentally obtained crack widths. When beams and slabs are loaded by approximately 52 % of their carrying capacity, design crack widths wk [EC] are approximately 12 % less than wk [STR], although the design crack width wk [RU] is signifi cantly greater. Here, ratio β in the beams and slabs is equal to 2 and 3.3 respectively. Th erefore, the design code [RU] ensures higher probability that the crack width will not reach the limit value (for environmental class XO and XC1) equal in all design codes mentioned in this article; 3) In case of loaded prestressed reinforced concrete beams, the calculated increases of crack widths wk [EC], wk [RU] and w [5] are greater if compared to wk [STR] (Fig 6). Th e increased reinforcement ratio ρ has more signifi cant infl uence on the increases of crack widths calculated according to other design codes if compared to wk [STR]. Tensile concrete above the crack peak has signifi cant infl uence on the design crack width when pre-stressed RC beams are lightly reinforced (ρ ≤ 0,008); 4) During the evaluation of the state of fl exural RC members, expression (5) could be used for calculating the crack width or a position of the neutral axis when the heights of the crack and the tensile zone above the crack are known (calculated or measured experimentally). Design crack widths w (5) are very similar to the experimentally obtained results.


2011 ◽  
Vol 194-196 ◽  
pp. 1449-1452
Author(s):  
Gui Bing Li ◽  
Xiao Yan Sun ◽  
Yu Gang Guo

Many flexural or tensile reinforced concrete members must be crack-free or the crack widths must be within specified limit value at service load levels. Presently, there are a number of structure members cannot satisfy its designed serviceability, due to the degradation of structural materials (due to durability problems) or by an increase in design loads. The use of bonding CFRP sheets on the side surfaces for strengthening or repair existing RC beamsis proposed to investigate the first crack strength and the cracking characteristics of RC beams. In order to verify the effectiveness of this application, experimental tests on six strengthened beams and one control beamhad been carried out. Experimental results demonstrated that this appears a promising technique both on improving the first crackstrength and on suppressing the crack width.


2018 ◽  
Vol 230 ◽  
pp. 02014 ◽  
Author(s):  
Olena Krantovska ◽  
Mykola Petrov ◽  
Liubov Ksonshkevych ◽  
Sergii Synii ◽  
Pavlo Sunak

According to the results of experimental studies, empirical dependencies were obtained (obtained from the appropriate mathematical models). The advanced (refined) method of engineering calculation of express-estimation of the strength of sloping cross sections of elements of flexible reinforced concrete structures on the basis of comparative analysis of the obtained empirical dependencies and standard accepted methods in the world was developed (nine basic norms are taken: DSTU B.V.2.6-156:2010 (Ukraine), previously operating SNiP 2.03.01-84*, SNB 5.03.01-02 (Belarus), SR 63.13330.2012 (Russia), Eurocode 2, 2004 (European Union), ACI 318-M14 (USA), AIJ Code, 2007 (Japan), CSA 23.3-04 (Canada), DIN 1045-1 (Germany). The coefficient of variation of bearing capacity and accident ratio according to the results of calculations of standard methods are determined. Their comparative analysis is carried out and informative graphic figures are presented.


2021 ◽  
Vol 98 (6) ◽  
pp. 50-62
Author(s):  
S.O. KURNAVINA ◽  
◽  
I.K. MANAENKOV ◽  
I.V. TSATSULIN ◽  
◽  
...  

The Russian standards for earthquake resistant constructions suppose the development of plastic strains in reinforced concrete constructions under seismic effects. Their presence influences significantly on the stress-strain state, bearing capacity and mechanism of destruction of reinforced concrete constructions under alternation loads of high intensity. The methodology and main results of experimental tests connected with the evaluation of plastic deformations influence on the behavior of reinforced concrete bending elements when changing the force sign is represented. The information about the bearing capacity reduction when changing the force sign with the increase of plastic strains in the first semi cycle of loading is given. The coefficients of plasticity for reinforcement deformations limit values are obtained, corresponding to the beginning of compressed zone concrete destruction when changing the force sign and the plots of normal sections deformations distribution of experimental specimens under direct and reverse loading have been built.


2011 ◽  
Vol 3 (3) ◽  
pp. 112-122
Author(s):  
Rokas Girdžius ◽  
Gintaris Kaklauskas ◽  
Renata Zamblauskaitė ◽  
Ronaldas Jakubovskis

The deformation analysis of cracked reinforced concrete (RC) members is not straightforward and often controversial. The main difficulties arise from the complex structure of concrete matrix, different mechanical properties of concrete and reinforcement, the creep and shrinkage of concrete and tension stiffening. The latter effect is related to intact concrete and reinforcement interaction between cracks. Tension stiffening effect has a significant influence on the results of a shortterm deformation analysis of RC members. The present research is aimed at deriving tension-stiffening relationship in accordance with the provisions of the Eurocode 2 technique. Using the inverse technique proposed by the second author, tension-stiffening constitutive laws were derived from the moment-curvature diagrams of RC beams calculated by Eurocode 2. The diagrams were calculated for a number of RC sections having a different amount of tensile reinforcement, the grade of concrete, effective depth and a modulus of steel elasticity. For the above model parameters, 450 moment-curvature diagrams were generated. For each of them, tension-stiffening relationships were obtained. The performed regression analysis led to analytical tension – stiffening relationship, which takes into account the reinforcement ratio, modulus ratio and concrete grade. A simplified short-term deformation analysis method of flexural RC members has been also proposed. This method is based on a bi-linear moment-curvature diagram: elastic and cracked parts. For the cracked part of the moment-curvature diagram, coefficient γ was introduced, which deals with the degradation of stiffness after cracking. An analytical expression was proposed for calculating coefficient γ, which takes into account the effective depth of the beam, reinforcement ratio and modulus ratio. A statistical verification of the proposed models has shown that a good agreement between calculated and experimental results was obtained at service loadings.


2014 ◽  
Vol 13 (3) ◽  
pp. 111-118
Author(s):  
Michał Knauff ◽  
Marcin Niedośpiał

In this paper some aspects of the calculation of the width of cracks in joints of steel-concrete composite slabs are reported. The code concerning design of composite steel and concrete structures for the calculation of crack widths refers to the code of reinforced concrete structures. The application of the formula, which takes into account „tension stiffening”, seems to lead to surprising results - for the elements with small reinforcement ratio, the obtained stress is much greater than the stress calculated in classical way i.e. without tension stiffening. The authors present the derivation of this formula - the result corresponds to the formula in the code but in the paper an additional case is taken into account. Furthermore, the authors suggest to consider two types of areas as in the RC code. Type D (D from "discontinuity") should be analyzed in the close surrounding of the column and type B (B from Bernoulli) areas at some distance from the column.


Sign in / Sign up

Export Citation Format

Share Document