Steel-concrete Elements Research Articles

A simplified method for thermal buckling verification in steel–concrete composite elements

This paper delivers a comprehensive analysis of the thermomechanical behavior of steel–concrete (SC) composite elements under elevated temperatures, up to 200 °C, as these can be encountered in accidental scenarios within nuclear power plant operations. The focus lies on the thermal buckling of external thin steel plates. We undertake an integrated approach, combining an experimental campaign and numerical simulations, to investigate thermal buckling phenomena. Using these findings, along with principles from thermoelasticity and thin plate theory, we establish an analytical model to guide preliminary SC element design. The efficacy of this model is ascertained through rigorous comparisons with experimental and numerical results. The paper concludes by demonstrating the model’s practical utility for thermal buckling verification through a relevant case study.

Results Of Experimental Research Of Steel-Concrete Composite Beam Under Cyclic Freezing-Thawing

One of the ways to improve the efficiency and quality of reinforced concrete structures is the development and implementation of new building structures, the use of which ensures a decrease in material consumption and cost. These effective structures include steel-concrete structures. An important problem when using steel-concrete structures is to ensure the joint work of steel and concrete, which is determined by the adhesion of materials. Reinforced concrete structures must meet the requirements for safety, serviceability and durability. The question of the operation of steel-concrete structures with external reinforcement in the form of a box section remains poorly understood. At the same time, the question of the influence of cyclic freezing and thawing on the adhesion strength between the metal shell and concrete remains open. In order to identify the features of the work of bent steel-concrete elements with external reinforcement at alternating temperatures, experimental studies were carried out, the results of which on strength and deformability are presented in this article. Investigations were carried out in two directions: first, the influence of the CFT on the change in the adhesion strength between the metal shell and concrete under compression; the second influence of CFT on the joint work of concrete and metal in bent steel-concrete elements.

Experimental analysis of shear-lag effect in reinforced concrete T-beams

The non-uniform distribution of normal stresses within wide flanges of beam sections is typically referred to as shear-lag effect. Shear lag is a result of the interaction of normal and tangential stresses or correspondingly by the influence of shear strains on longitudinal strains. In structural engineering, the shear-lag effect has been a concern in the flanges of thin-walled metallic structures or the slab of composite steel–concrete elements, among others. Though existing codes of practice provide a simplified way to address shear lag by means of the effective width concept, such provisions can be insufficient for concrete structures, for which a deeper knowledge on the real influence of shear lag is necessary due to the current trend to design wide concrete bridge girders, with geometric configurations of the cross-sections which can be sensitive to shear lag (i.e. box- or T-sections). Moreover, the influence of the behaviour of structural concrete (cracking, rheology, yielding of reinforcement) has not been dealt with in detail so far. In the present paper, an experimental campaign on two reinforced concrete T-beams is presented. The beams have been subjected to two types of tests: firstly, to time-dependent effects governed by concrete shrinkage and creep; secondly, to the application of increasing direct loads to cover the whole concrete behaviour (uncracked, cracked and ultimate stage). The strain distribution at the top slab of the T-sections has been studied with extensive strain measurements at different cross-sections. The experiments have shown a distinct intensity of shear-lag effect depending on the load type. Moreover, the shear-lag impact varies longitudinally for each cross-section. In case of direct load tests, it has been also found that the strain distribution on the top slab changes as a function of the load level, which indicates that the different behavioural stages of concrete affect the shear lag, especially cracking. The experimental results have been analyzed with the help of analytical and numerical models, which have allowed understanding the progressive modification of the strain distribution within the top slab and the shear-lag intensity.

Hybrid Column Designs for Industrial Buildings

The article analyzes the possible application of hybrid steel-concrete structures for industrial buildings, presents new developments in the structural forms of columns, supports, as well as ways to interface steel-concrete elements. The calculation of the steel-concrete step column is performed, the analysis of the reduction in steel consumption and other advantages of hybrid steel-concrete structures in comparison with traditional solutions of steel and reinforced concrete columns is made. The use of hybrid steel-concrete structures is effective mainly in compressed elements: columns, posts, supports, compressed parts of beams and trusses, crane beams, frame and arched structures.

Assessing the challenges of condition assessment of steel-concrete (SC) composite elements using NDE

Steel-concrete (SC) is a structural typology and construction method in which continuous steel plates are used on the surfaces of concrete walls or slabs, having dual role of formwork and longitudinal reinforcement. The continuous steel-plates on both sides of the concrete element improve economy by prefabrication, but hinder the use of traditional non-destructive evaluation (NDE) to assess the condition of the concrete. In this research, conventional NDE techniques were investigated with regards to their suitability for SC elements, with focus on detection of mechanical damage. Tests were performed on large-scale, mechanically damaged, SC elements. The deployed NDE methods were based on ultrasonic measurements using: the pulse echo technique; radiographic inspection; ultrasound 3D tomographer; impact-echo (IE); impulse-response (IR) and ground penetrating radar (GPR). It was assessed whether cracks of different sizes in the SC beams could be detected through the steel-plated surface. Perpendicular and oblique cracks of 0.1–2.5 mm width were studied. Resultsshow that ultrasonic testing and GPR were not suitable for testing through the steel surface, due to loss of the transmitted energy in the steel plates. Mechanical impact-based testing systems revealed promising results to detect cracks and de-bonding. Radiographic testing was successful in detecting the presence of cracks in cases when these had sufficient opening and length.

Micro and Macro Structural Investigations on Welded Joints of Composite Truss Steel Concrete Beams

The results of an experimental test campaign including micro and macro investigations on welded joints typically used in Composite Truss Steel‐Concrete beams are presented. The research was carried out with the aim of assessing the relevance of welding effects on the mechanical performance of different typologies of steel grades that can be used to realize the internal truss steel system, connected to the bottom steel plate used with the double structural and formwork function. Two different steel typologies were adopted for the steel truss: the “traditional” structural micro‐alloyed steel, normally used for composite steel‐concrete elements, and the typical reinforcing steel with TempCore® structure, achieved through the application of two‐phase thermomechanical treatment of quenching and tempering. The interest in the possibility of adopting reinforcing steel for the internal truss arises from its potential economic benefit, finding its justification in the intermediate condition in which this structural typology lies, between composite steel‐concrete and ordinary reinforced concrete buildings. Welding has a strong impact on such reinforcing steel material, resulting in relevant drops of ductility and brittle failure usually taking place in correspondence of the heat‐affected zone. So, it is advisable to refrain from using such steel grade, especially in constructions in seismic‐prone areas, where ductility is a major influencing and design factor.

MODERN APPROACHES TO RESIDUAL LIFE CALCULATION OF FLEXURAL STEEL CONCRETE ELEMENTS WITH CORROSION DAMAGE

The article is devoted to problems of ensuring durability of steel concrete elements of buildings. It is shown that durability depends on their residual and service life. Normalizing of the latter is generalized, not sufficiently substantiated and non-regulatory. Computational techniques to assess the construction durability are not yet available. Actual and informative is determining the residual life of steel concrete structures. It was noted that the reason for the reduction in the carrying capacity of steel concrete structures and, accordingly, the residual life is corrosion damage of concrete and reinforcement due to an aggressive environment. This paper analyzes the modern methods of calculating residual life of flexural elements with corrosion, identifies their advantages and disadvantages in building inspection. The residual life should be determined on the basis of field surveys, when the maximum corrosion damage is found in various design sections. The physical and statistical approach is the most promising and acceptable for assessing and predicting the residual life of flexural steel concrete elements. The value of the residual life is proposed to be established with regard to reliability coefficient. Considering the ever increasing cases of early loss of bearing capacity of steel concrete structures due to corrosion damage, it is advisable to include mandatory requirements in construction design standards of calculating on a new ultimate limit state.

Design of a high-rise building with hybrid steel-concrete structural elements

This paper presents the challenges encountered during the structural design of a high-rise building located in a seismic area. The construction is an office building, it has 20 stories including the basement levels and a narrow base. Some of the challenges are: providing an accurate structural system to resist the wind and earthquake actions and to design a proper foundation to avoid the overturning of the entire structure. Another important aspect is to limit the stories drift but at the same time provide an open space for the office area. Hybrid structures do not behave like reinforced concrete structures in the sense of Eurocode 2 nor like composite structures in the sense of Eurocode 4. For this reason and due to the lack of knowledge related to the problem of force transmission between steel and concrete the design of structures with hybrid steel-concrete elements can become very difficult. Several models are analysed comparing structural systems made of reinforced concrete, ones made of hybrid steel-concrete elements and several other types of systems.

On the New "Manual on Design of Composite Steel and Concrete Structures (in Elaboration of Formulary SP 266.13330.2016 "Composite Steel and Concrete Structures. Design Rules")"

The paper provides a brief overview of domestic and foreign guidelines (manuals) for the design of composite steel and concrete structures: steel-concrete slabs on profiled flooring, combined beams, and columns with rigid reinforcement. The necessity of creation of the actual manual corresponding to the modernlevel of development of construction science, normative documents and design practiceslinked to the new formulary SP 266.1325800.2016 is proved. It will facilitate the design, reduce labor expenditures and improve the reliability of composite steel and concrete structures. The new guidance provides general recommendations for the design of composite steel and concrete structures and the basic regulations for the calculations. The new guidance describes recommendations for modeling of composite steel and concrete structures and elements in the calculated complexes, the recommendations for calculation of combined beams fully concreting rectangular and T-section, partially concreting along with support slab on the lower flange of the beam, columns with rigid reinforcement, shear a connection of composite beams. Recommendations on the registration of creep, shrinkage and crack formation in the appointment of the modulus of elasticity are given. Recommendations on the use of diagrams of the state of concrete, reinforcement, and steel in the calculation of steel-concrete elements on a nonlinear deformation model are given. Recommendations on the use of the range of sheet flooring for steel-reinforced concrete slabs, as well as metal profiles as steel beams and rigid reinforcement in the cross sections of columns and combined beams, are presented. Recommendations on a design of units and details of composite steel and concrete structures are given, refined recommendations on buffer are presented. The examples of connection of steel beams with columns with rigid reinforcement are given. The examples of calculation of composite steel and concrete structures taking subject to the recommendations given in the Manual are presented.

Resistance of Steel – Concrete Composite Girders with Corrugated Web

The paper discusses the analysis of shear resistance of girders with corrugated web, combined with a concrete slab in a way that allows creation of a composite structure according to the definition of Eurocode 4. The results of the authors’ experimental tests of girders with a corrugated web connected to a concrete slab, and the results of tests on girders without a concrete slab were used. Experimental investigations concerned the effectiveness of SIN girder (i.e. with sinusoidal corrugation) WTA 500 / 300x15 strengthening with a concrete slab for shear resistance of the whole steel-concrete element and shear buckling resistance of the web. Load – displacements paths LDPs P(y) as well as the results of tensometric strain measurements of the web were analysed. The results of the composite girder tests were compared with the results of tests of SIN girder without a concrete slab with a similar static diagram and a similar failure mode due to the loss of the web stability. In addition, the first buckling load and slab contribution to shear force transferring were analysed. Based on the analysis of experimental results and available analytical models, the solution for estimating design shear buckling resistance in girders with corrugated web strengthened with a concrete slab was proposed. Using the proposed formula, the contribution of the web and concrete slab to the transfer of shear load for the whole series of girders with web heights hw = 500 mm to 1500 mm and thickness tw = 2 mm, 2.5 mm and 3 mm was shown. The proposed formula takes into account the mutual interaction between the local and global mode of shear stability of the web, which leads to the reduction in design shear buckling resistance. Additionally, improvement in the web boundary conditions as an effect of increased flange stiffness due to joining it to the concrete slab was taken into account. This paper also uses the results of tests concerning SIN girders without a concrete slab, with other web heights and thicknesses than in WTA 500/300x15.

Bearing Capacity and Deformability of Three-Component Steel Reinforced Concrete Constructions Made of Lightweight Concrete

The article contains the study of strength and deformability of three-component steel-reinforced concrete structures made of a thin-walled steel shell, light concrete and rigid reinforcement in the form of a light steel thin-walled profile. The results of calculation, simulation and experimental researches of more than 40 steel-concrete elements are presented. The diagrams of the work of these constructions are compared with the comparison of experimental data and numerical modeling, which confirm the correctness of the introduction of the calculation model into the software complex, where special attention was paid to the boundary conditions of the work of the structure. The model with the indication of the concentration of internal stresses and the nature of the deformation of the structure in general, which fully corresponded to the experimental research, was analyzed. An adapted calculation algorithm for three-component steel-concrete constructions is presented, where the coefficients of working conditions for each of the constituent constructions are indicated. The relationship between relative flexibility and the lowering coefficient of operation of a thin-walled cylindrical steel shell is shown. Appropriate conclusions are formulated.  Â

An interface element for numerical analysis of flat plate/shell elements with deformable connection

Abstract The use of numerical methods such as the finite elements method for solving structural analysis problems is becoming ever more efficient. An interface element capable of associating flat plate/shell element in three different combinations has been developed. In a structural analysis, when only the flat plate/shell’s finite elements are used in the discretization, some problems concerning dimensional variation of the transversal section, as well as overlapping of areas can occur. . The aforementioned problems can be solved by the developed interface elements that can also simulate a possible deformable connection that is existent in the association of materials with different characteristics, such as the composite steel-concrete elements. One of the applications of the finite elements developed is for the numerical simulation of composite steel-concrete elements, such as the composite beam formed by a reinforced concrete slab attached to a steel beam using a deformable connection. In this case, the concrete slab and the steel beam are discretized by the flat plate/shell element, and the deformable connection done by the interface elements. In the validation of the implemented elements, we used numerical and experimental results found in the literature, and analytical solutions considering the classical plate theory.

CALCULATION AND DESIGNING THE SHORT STEEL-CONCRETE COLUMN

Design new construction of steel-concrete element, taken a basic formula for calculation steel-concrete column by short duration static stress. Described the possible variants of connection of the profiled sheet in a single holder.

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

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”).

Method of Dimensioning Stress-Strain State of Steel Concrete Plate

The steel-concrete constructions experience an increased development this last time. The main advantages are that they ensure the economy of materials, energy and labour. The steel-concrete elements allow a rational use of the concrete in the tensile zone, ensure a reduction of the weight of the building, its cost and also reduce the formwork. The calculations carried out by the authors make it possible to establish the dependence between the constraints and the deformations in the principal directions under a biaxial state of stresses, to obtain the expressions of the principal moments, determine the parameters of the deformations of the concrete Eb, Ebi, νb, νbi, obtained through the reduction of the tensile and compressive stresses of the concrete in an isotropic conventional homogeneous state. The expressions of the constraints in the plate are gotten and compared between the theoretical values and the experimental convergence of the results with a variation of less than 8%.

Advanced coating of interior of tanks for rising environmental safety - novel applications of polyurethanes

Advanced coating of interior of tanks for rising environmental safety - novel applications of polyurethanesThe aim of this study was to develop urethane elastomers of predefined properties to be used as elastic coating in the cargo tanks of tankers. A method for coating the liquid polyurethane system onto steel and steel-concrete elements, and a way to join polyurethane coating with the aforementioned elements, were elaborated. The technique of injection the reactive liquid polyurethane system onto cold steel elements was used. The method for utilization and recovery of urethane oligomerols from the waste polyurethane coating in chemical recycling by using low molecular weight glycols as glycolysis agents was proposed.

The unloading of building materials submitted to fire

The unloading of building materials is considered in uniaxially oriented structures. It is shown how the uncertainty encountered in numerical simulations between loading or unloading can be resolved when using the principle of Duhamel and assuming that the plastic strain is not affected by a temperature variation. A solution is also proposed to consider the inelastic behaviour of a material with a non-linear stress-strain relationship like the linear-elliptic one that is often used for steel. The analysis of three composite steel-concrete elements tends to prove that the consideration of inelastic behaviour is not critical in simply supported beams. It seems to be of more importance in an hyperstatic beam and even more in a centrically loaded composite column.

A three-dimensional rupture analysis of steel liners anchored to concrete pressure and containment vessels

Steel liners or plates are anchored to concrete pressure and containment vessels for nuclear and offshore facilities. Due to extreme loading conditions a liner may buckle due to the pull-out or shearing of anchors from the base metal and concrete. Under certain conditions attributed to loadings, liner metal deterioration and cracking of concrete behind the liner, the liner may fail by rupture. This paper presents a three-dimensional analysis of steel-concrete elements, using finite element in which a provision is made for liner instability, anchor strength and stiffness, concrete cracking and finally liner rupture. The analysis is tested first on an octagonal slab with and without an anchored steel liner. It is then extended to concrete pressure and containment vessels. The analytical results obtained are compared well with those available from the experimental tests and other sources.