Ivan Lukačević

University of Zagreb Faculty of Civil Engineering

The use of composite structures in construction is increasing. The optimized combination of the two materials concrete and steel produces particularly cost-efficient structures. This book presents a large number of numerical examples with detailed explanations of the provisions of Eurocode 4. It deals with the most common structural components in b...

Fatigue of welded steel details is a very complex phenomenon influenced by many factors. To improve its fatigue strength by extending the crack initiation period in total fatigue life, high-frequency mechanical impact (HFMI) method can be employed. The previously developed two-stage model (TSM), which considers the crack initiation and propagation...

According to the commercial production greenhouses classification, corresponding design working lives are shorter than 50 years, implying the reduction of characteristic snow load in the design process. To adjust the snow load to a shorter return period, the standard EN 13031–1 provides the procedure for calculating the snow adjustment factors, whi...

In the last few decades, the application of lightweight cold-formed composite steel–concrete structural systems has constantly been increasing within the field of structural engineering. This can be explained by efficient material usage, particularly noticeable when using cold-formed built-up sections and the innovative types of shear connections....

Welded steel details are critical components from the aspect of fatigue. Additional fatigue resistance can be achieved by the High-Frequency Mechanical Impact (HFMI) treatment. This treatment increases the crack initiation period by improving the weld geometry, introducing compressive residual stresses, and increasing the weld toe’s hardness. The s...

The complex nature of the fatigue strength of welded steel details, which is influenced by a multitude of factors, can be improved by extending the crack initiation phase of the total fatigue life. This enhancement can be achieved through the use of the High-Frequency Mechanical Impact (HFMI) method. This study discusses the fabrication and laborat...

Industrial photogrammetry is a reliable method to achieve submillimeter accuracy when mapping 2D or 3D objects. In the field of fatigue testing of steel welded details, it can be used to find a new method of crack initiation assessment. Fatigue testing is an important method for determining and predicting the durability of structural details in ser...

The LWT-FLOOR project addresses the growing need for innovative solutions in the construction industry, focusing on enhancing structural elements value and usability over their life cycle. Therefore, the LWT-FLOOR project introduces an innovative solution for composite floor systems by investigating the performance of demountable shear connections...

Cold-formed steel composite floors are lightweight systems whose application increased in the last few decades. According to the design guidelines, the frequency of floor systems should be more than 4 Hz while in the case of light steel floors, the natural frequency of the system should be in the high frequency range above 8 Hz. The main focus of t...

Steel and composite shear wall systems are used for vertical stabilisation of buildings and have been widely investigated in recent decades. Such systems provide excellent shear strength and ductility while allowing material savings due to optimal material usage and an increase in construction speed. A double-skin cold-formed steel shear wall fille...

It is known that steel-concrete composite systems are very efficient. However, such steel-concrete composite systems can be optimised using cold-formed steel elements and innovative shear connections. In other words, by considering demountability and reusability, the negative impact of the built environment on the whole ecosystem can ultimately be...

The combination of steel and concrete in structural engineering has gained widespread use due to the numerous benefits of leveraging both materials' favourable mechanical properties. In recent years, researchers have explored alternative solutions utilising cold-formed steel elements and lightweight concrete, seeking improved performance compared t...

The vast majority of existing structures in Croatia, as well as in other European countries, are made of unreinforced masonry. The seemingly ideal building material presents a great challenge for engineers in earthquake-prone zones. Given that structural failure can have significant consequences in terms of loss of human lives as well as financial...

In recent decades, the use of built-up cold-formed steel sections in composite steel-concrete structures has become increasingly popular due to their advantages. These systems are easy to manipulate, transport and erect because of their reduced weight. These advantages are even more significant when the system is designed to be demountable, reflect...

Steel-concrete composite structures are very attractive because of their characteristics, which can be emphasised by using cold-formed steel instead of hot-rolled ones. This paper presents possible analytical approaches and a parametric finite element study of cold-formed steel-concrete composite beams in bending. Analysed beams are formed of back-...

This study explores the utilisation of built-up cold-formed steel elements combined with concrete to create efficient and lightweight composite floor systems suitable for both new constructions and reconstructions, thanks to their reduced self-weight. The main focus of this paper is to investigate different analytical approaches for determining the...

Spot welding is a fast and productive technology widely used in industry to join various cold‐formed steel (CFS) elements. Depending on the type of analysis and model complexity, various definitions of spot welds in finite element (FE) models can be applied. In structures with a large number of spot welds, simple models that use a reduced number of...

There is a surging demand for innovations that would increase the value of construction elements and materials in their life cycle. Therefore, the subject of this research is the shear connection in the floor composite system of cold‐formed steel and concrete slab. Composite systems can be further improved by a demountable type of shear connection,...

This paper investigates the bending resistance of an innovative lightweight composite floor system, LWT-FLOOR. The system consists of built-up cold-formed steel elements that are spot-welded and connected to the concrete slab using demountable shear connectors. As the system under investigation is new, the existing standards do not provide guidelin...

In the last decades, the post-earthquake assessment and strengthening of existing structures are becoming one of the most critical fields of civil engineering. Most parts of Europe, as well as many existing buildings in Croatia, are built in masonry. For that reason, the main objective of this paper is to show the role of updating knowledge in the...

Nowadays, composite steel-concrete systems are among the most cost-effective construction systems for application in multi-storey buildings as they combine structural efficiency and allow accelerated construction speed. Additional optimisation of these systems is possible through the application of cold-formed steel elements and innovative solution...

Except for the main advantage of the composite systems, which is the efficient utilisation of used materials, these structural systems are known for reusability, high degree of prefabrication and long-span capability. Because of these advantages, the range of applications of composite structures is continuously expanded. Since cold-formed steel sec...

Cold-formed steel profiles are increasingly in demand in the construction market because of their speed of assembly and low material consumption. Thus, it is necessary to investigate their behavior in depth, since in recent years they have been used as the main structural components of buildings. The paper presents an experimental program where sev...

Cold-formed steel elements are commonly used in construction due to their advantages, such as material savings and reduced self-weight. Such advantages can be significantly enlarged by using built-up solutions. Such solutions have been presented in the literature over the past few decades. The most common way to assemble such elements are using scr...

Osim povoljnog iskorištenja upotrijebljenih materijala u spregnutim sustavima, spregnuti sustavi čelik-beton poznati su po montažnoj ugradnji i sposobnosti svladavanja velikih raspona. S obzirom na navedene prednosti, mogućnost uporabe ovog tipa sustava je raznolika. Ovaj rad predstavlja numeričku analizu spregnutog nosača izvedenog od hladno oblik...

Researches show that composite systems made by combining cold‐formed steel (CFS) elements and concrete can produce excellent properties compared to traditional solutions. One of the solution which employs CFS elements and concrete is the subject of research within the LWT‐FLOOR project. The LWT‐FLOOR system consists of built‐up CFS beams with corru...

Composite structural systems have many benefits, such as a high degree of prefabrication, reusability and long span capability. The main advantage of such systems is manifested through the optimal utilisation of structural steel and concrete. Additionally, allowing for demountability and reusability, the system can also result in a much smaller car...

Primjena spregnutih konstrukcija čelik-beton ima velike prednosti kao što su upotreba mon-tažnih elemenata i svladavanje velikih raspona, te optimalna iskoristivost čelika i betona što se posebno očituje uporabom hladno oblikovanih čeličnih profila. Rad predstavlja numeričku parametarsku analizu inovativne spregnute međukatne konstrukcije sastavlje...

To provide the foundations for economic and social prosperity, countries worldwide need to be making a term investment in their building assets. However, there is a lack of a systematic approach, such as manufacturing innovations, to maximize the values of building components and materials in its entire lifecycle. Steel-concrete composite floor sys...

The material saving obtained by using thin‐walled cold‐formed steel elements is well‐known for small structures as well as for common industrial structures. Additional to the truss type structures, another solution for obtaining light‐weight elements consist of connecting cold‐formed steel profiles as the flange to the corrugated steel sheets as th...

Cold-formed steel back-to-back built-up beams are efficient and very attractive structural elements which can also offer excellent efficiency in production, both in capacity and material savings. The connection between such built-up steel components can be easily obtained by screws or bolts, but the developments in the welding processes also lead t...

Steel plate shear walls (SPSW) have been increasingly applied in structures as a lateral load resisting system. SPSW systems utilize thin unstiffened plates as the infill between boundary members. Infill panels are very slender elements and buckle under low lateral loads due to which SPSW relies on the post‐critical tension field action of the infi...

Rekonstrukcija postojećih zgrada je aktualna tema posljednjih godina. Nedavni potres u Zagrebu senzibilizirao je i javnost na problematiku osjetljivosti starih zgrada na seizmička djelovanja. Čelik ima značajnu ulogu u svim aspektima rekonstrukcije jer pruža pouzdana rješenja za sanacije i ojačanja. U radu je dan pregled metoda rekonstrukcije s nag...

Application of steel in refurbishment of earthquake-prone buildings Refurbishment of existing buildings has become an increasingly topical issue in recent years. The recent Zagreb earthquake has also increased public awareness about the issue of sensitivity of old buildings to seismic loads. Steel plays a significant role in all aspects of refurbis...

In welded structures, fatigue damage often occurs in welds, which are the points of geometrical and material discontinuity. Accordingly, post-weld treatment methods have been developed. One of the relatively new methods is the high-frequency mechanical impact treatment. The method is characterised by the change in weld geometry, local increase in h...

Knjiga uz definiranje i objašnjenje osnovnih pojmova iz teorije pouzdanosti obrađuje praktičnu primjenu norme EN 1990 kroz brojene numeričke primjere. Između ostalog, u knjizi su istaknute i neke od smjernica budućeg razvoja ove norme. Temeljna i vodeća norma EN 1990 korektno prepoznaje da dostizanje zahtjevnijih ciljeva ponašanja konstrukcije ne m...

Cold-formed back-to-back built-up steel beams are efficient and very attractive structural elements which with the material savings and low self-weight can also offer excellent efficiency in production, especially with the application of CNC technologies. The connection between the cold-formed back-to-back built-up steel components can be easily ob...

Built-up corrugated web beams (CWB) represent an assembly of multiple cold-formed steel components of various thicknesses connected by means of screws or welding. Recently, tests on such built-up beams have been performed within the CEMSIG Research Center of the Politehnica University of Timisoara, in which the connections between the components we...

Built-up cold-formed steel elements are efficient structural elements, very attractive due to material savings, but also for ease of construction. The connection between the built-up beam components can be easily obtained by screws, but the developments in the welding process also led to other solutions like spot welding. The WELLFORMED research pr...

Dual structures obtained by combining moment resisting frames with innovative bracing systems such as replaceable shear panels or seismic links have significant advantages among conventional solutions. The major advantages of such systems are energy dissipation in the specific locations and re-centring capability which significantly reduces repair...

Numerical studies on built-up beams made of cold-formed thin-walled spot-welded steel

Due to high stress concentrations, welded joints represent the most common locations of fatigue crack initiation in steel structures that are prone to fatigue. Welding affects material properties by the process of heating, cooling, and combining basic and additional material. Since welding is the primary process of joining elements in steel structu...

This paper presents the fatigue life assessment of a welded detail in an existing steel railway bridge. The fatigue life is assessed based on strain measurements due to the passage of characteristic trains. Characteristic trains are an integral part of the load model formed by „Croatian railways„ data. Strain gauges that measure deformations are se...

In this paper, a brief overview of the scientific projects and possibilities of the numerical calculations is given. Four doctoral thesis from the Faculty of Civil Engineering, University of Zagreb are presented. Numerical calculations were made in the Simulia Abaqus program package, which is one of the widely used general purpose software for nume...

In this study, linear and non-linear dynamic analyses of a cable-stayed steel frame subjected to seismic actions are performed. The analyzed cable-stayed frame is the main supporting structure of a wide-span sports hall. Since the complex dynamic behavior of cable-stayed structures results in significant geometric nonlinearity, a nonlinear time his...

A review of current surveys related to composite columns made of concrete filled tubes with embedded steel cores, known as Geilinger columns, is presented in the paper. Advantages and scope of application of this innovative composite column type are presented. Calculation of such columns according to the general method given in EN 1994-1-1, which i...

A lattice girder frame was compared with a combined lattice and Vierendeel girder frame on a singlestory building with a frame span of 62.0 m, column height of 15.0 m, and ridge height of 17.3 m. The lattice girder frame has the advantage of being a cheaper solution when considering steel usage. In contrast, the combined girder frame is a less comp...

The values of creep and shrinkage of the concrete deck slab of a composite highway bridge are calculated at different time periods in the age of the concrete. For the corresponding values of creep and shrinkage and types of loading, the corresponding values of modular ratio, nL and the shrinkage strains are determined. The modular ratio nL is deter...

This chapter shows the calculation of the value of time-dependent strains of concrete due to creep and shrinkage. These values influence the determination of the effects of actions. In the chapter, the effect of action is related to the calculation of the design bending moment at the internal support of the continuous composite beam. This moment is...

This chapter deals with a simply supported secondary composite beam under uniformly distributed loads. Analysis of the composite beam is performed for the construction stage and for the composite stage. The design checks are conducted for both ultimate limit state and serviceability limit state. Verifications for the ultimate limit state and servic...

This chapter demonstrates the design of a composite column subject to axial compressive load and bending moment. The concrete-filled column consists of the circular hollow section filled with concrete. Second-order effects are included in two ways, by using a first-order analysis modified with appropriate amplification according to clause 6.7.3.4(5...

This chapter demonstrates the design of continuous composite slab over three spans. One need to consider the construction stage, where the profiled steel sheeting acts as shuttering, and the composite stage, where the concrete and the steel sheeting form a composite unit. The design resistance of the composite slab against longitudinal shear is car...

The concrete-filled column consists of the rectangular hollow section filled with concrete in combined compression and uniaxial bending. The application of the method for buckling resistance based on second-order analysis taking into account the imperfections means that about the z-z axis there is bending due to the imperfections of the member. For...

The calculation and structural detailing of a Hoesch Additive Floor (HAF) in a carpark building is considered. The floor resistance is obtained by summing resistances of profiled steel sheet and ribbed reinforced concrete slab without composite action. Referring to EN 1994, the system is a combination of two materials, steel and concrete, with the...

This chapter demonstrates the design of the continuous composite beam which is the structural member of floor of a warehouse. It deals with important aspects of the design of the considered beam for the persistent design situations for ultimate limit state. The serviceability verifications are performed taking into account secondary effects of shri...

This chapter demonstrates the design of a continuous composite slab over two spans. The composite slab consists of a cold-formed profiled steel sheeting covered with a concrete slab containing reinforcement. The composite slab is supported by steel beams, which act compositely with the concrete slab. The design resistance of the composite slab agai...

This chapter illustrates the use of lightweight aggregate concrete in a composite slab. The obvious advantage of lightweight aggregate concrete is weight saving. However, this advantage must be balanced against the effect of the reduced modulus of elasticity, which results in larger deflections of the slab. The design resistance against longitudina...

The purpose of this chapter is to design the simply supported composite beam according to the elastic-elastic procedure. One of the essential features of the chapter is to illustrate the determination of the effective flexural stiffness EIL by two procedures that are used in practice. The first procedure is the direct determination of the effective...

The concrete-filled column is calculated using the simplified method of design in two ways. The first method is based on the application of European buckling curves, and the second is based on second-order analysis, taking into account the imperfections. The purpose of this chapter is to compare the two methods, which are based on a simplified proc...

This chapter designs a two-span composite beam according to the plastic–plastic procedure. In this case, action effects are calculated by rigid plastic global analysis, and the resistance to bending is based on a plastic model. For this procedure, all cross-sections of the composite beam should be in class 1. The continuous beam has changed the sta...

This chapter illustrates the method of calculation of the effective width of the concrete flange due to shear lag. The method is recommended in clause 5.4.1.2, EN 1994-1-1. It is considered that a continuous composite beam consists of two spans and a cantilever. We need to calculate the value of the effective width of the concrete flange beff for t...

The purpose of this chapter is to show the calculation and the arrangement of the headed stud connectors in the case of the simple supported composite beam. The essence of the chapter is the calculation and the arrangement of the headed stud connectors in the solid slab. Therefore, the design of the beam is conducted more simply without considering...

This chapter shows the design of a two-span composite beam using the elastic– plastic procedure. Action effects are calculated by elastic global analysis and the resistance to bending is based on a plastic model. Analyses for ultimate limit state and serviceability limit state are also conducted by elastic global analysis. This example illustrates...

This chapter deals with the fatigue assessment of a composite highway bridge. Analysis and dimensioning of the bridge were conducted in accordance with appropriate European standards. The bridge was verified for the following design situations: transient, permanent and accidental. The required criteria for static loading are met. The chapter focuse...

This chapter demonstrates the design of a composite column subject to axial compression. The concrete-filled column consists of a circular hollow section filled with concrete. In concrete-filled hollow sections no longitudinal reinforcement is normally necessary. However, if the design for fire resistance is required, the longitudinal reinforcement...

This chapter demonstrates the design of a composite column with fully concrete-encased H-section subject to axial compressive load and biaxial bending. The composite column consists of an H-column section with square concrete section encasement.The verification of the considered composite column is carried out in accordance with clause 6.7.3, EN 19...

This chapter shows the design of the composite floor slab that is supported by the composite beam at 3,6 m centres. It illustrates the design of the resistance of composite slab taking into account the end anchorage and the additional reinforcement provided in troughs of profiled sheeting. The profiled steel sheeting acts as shuttering and carries...

This chapter illustrates four types of secondary beam to primary beam pinned joints. In cases where speed of erection is an important consideration, the secondary to primary beam pinned joint can be used. In this case, the secondary beam is connected to the primary beam by means of the single extended end plate which is welded onto the cleat. The c...

Pinned joints of composite beams to steel or composite columns are often used in multi-storey buildings. Pinned joints are normally assumed to give vertical support and to be able to rotate without damage. This chapter illustrates a pinned joint of a composite beam to a steel column with angle cleats. It also illustrates the type of shear plate con...

Fatigue verification is mainly needed for bridges, but this chapter demonstrates the application for buildings with composite floors on which a forklift is travelling. Generally, fatigue problems are treated in EN 1993-1-9 in great detail. In EN 1993-1-9, the unified European rules for fatigue verifications are given. Fatigue in reinforcement and c...

This chapter demonstrates the design of a composite column with partially concrete-encased H-section subject to axial compressive load and bending moment. In order to ensure adequate force transfer between the steel and the concrete, stud connectors and reinforcement are provided. The resistance of the cross-section to combined compression and bend...

This chapter shows the design of a simply supported composite beam according to the elastic–plastic procedure. Action effects are calculated by elastic global analysis and the resistance to bending is based on a plastic model. For the elastic– plastic procedure, the cross-section should be at least in class 2. An important feature of the chapter is...

This chapter explains the determination of the values of creep and shrinkage of concrete in a composite beam with cross-section. The effects of creep and shrinkage of concrete produce internal forces and moments in cross-sections, and curvatures and longitudinal strains in members. The effects that occur in statically determinate systems are classi...

Throughout the bridge life a traffic loading will produce large numbers of repetitive loading cycles in bridge elements which could lead to fatigue damage. Fatigue reliability assessment of steel railway bridges using deterministic procedures is often conservative. More realistic verification of performance of existing bridge structures can be achi...

Fatigue life evaluation of existing bridges is an important task especially for bridges reaching design life or subjected to increasing traffic volume. This paper presents probabilistic fatigue life assessment of welded railway bridge based on field measurement and numerical methods which can be applied to any fatigue sensitive structure. Due to th...

Numerički primjeri namijenjeni su svim učesnicima izgradnje čiji su predmet interesa konstrukcijski elementi sastavljeni od čelika i betona. Osnovne ideje koncipiranja takvih elemenata bitno se razlikuju u odnosu na one kod kojih je započeo njihov razvoj. Korištenje komercijalnih kompjuterskih programa, kod proračuna elemenata od čelika i betona, g...

The paper deals with a parametric study of composite beams made of the high performance steel (HPS) to verify their reliability level according to EN 1990. Parametric studies on composite beams can provide only relative representations of certain advantages of using HPS. However, these advantages can be accepted only in case of confirmation of the...

The modelling of beam to column joints is analyzed taking into account real behaviour of such joints as described by the Mj-φ curve. General considerations relating to the new joint design philosophy, as based on Eurocode 3, are given in the initial part of the paper. The method of components, an analytical method for characterization of joints, is...

Knjiga" Projektiranje spregnutih konstrukcija prema Eurocode 4" predstavlja nezaobilaznu literaturu inženjera-projektanata spregnutih konstrukcija u praksi. Prije svega knjiga se temelji na konačnoj verziji koncepta pouzdanosti europske norme za spregnute konstrukcije EN 1994-1-1 i kao takva je jedinstvena na hrvatskom jeziku. Teoretske postavke ko...

One of the aims in preparation of the new generation of Eurocodes is the development of technical bases for the extension of existing procedures. The current procedure for the fatigue limit state verification is based on the deterministic S-N concept which should be given a probabilistic alternative. In the latter, the values of statistical paramet...

Orthotropic steel decks are widely used in bridge decks structure of highway bridges. The results of inspection of orthotropic steel decks show that their fatigue life can be shorter than the one of other elements. According to some research as early as after 25 to 30 years, damage in the form of cracks can be seen in some of the details categories...

Unjustifiably neglected especially in European practice, semi-rigid bolted beam-to-column joints with flange cleats allow great savings in the design, fabrication and erection. With simple stiffening of angle flange cleats and some small additional cost of execution better mechanical behaviour of this type of joint can be obtained. There are severa...