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Following the trend of sustainable development and structure reuse, many novel solutions related to demountable shear connectors for application in steel-concrete composite beams have been proposed in recent years. This paper provides a further contribution to the research field by proposing a demountable connection with bolts and welded headed studs. The transfer of shear force between a steel flange and a composite concrete slab cast in an open trough profiled steel sheeting is indirect, passing through a steel plate or angles. The proposed solution enables convenient dismantling and reuse of both the composite slab and the steel profile. The experimental investigation included push-out tests, performed to assess the connection shear behaviour, determine resistance and ductility, and identify failure modes. Various configurations of the demountable connection were analysed, including connections with continuous and discontinuous slabs over the support. The response of the suggested demountable solution was compared to the corresponding non-demountable shear connection with headed studs. According to experimental investigation, finite element models were developed, and their accuracy was validated by comparing numerical predictions with experimental results. Parametric studies were conducted using numerical models to evaluate the effects of key parameters on the connection performance, such as plate and angle thickness, stirrup reinforcement position, and transverse distance between a headed stud and slab edge. Directions for design were proposed taking into account the results obtained.

As members of Project Team SC4.T5, the authors of this paper present the main outcomes from the work that isintended for implementation within the second generation of Eurocode 4. General design and application rules for composite design of precast concrete elements will be presented, with a particular focus on: the effective width of flanges using precast concrete elements for shear lag; design resistance to longitudinal shear; and the design resistance of headed stud connectors in the presence of precast hollow core slabs.

Cartridge fired pins, also known as powder actuated fasteners, have a wide application in different construction industry fields, mostly for joints of cold-formed structural elements and profiled steel sheeting, or for installation of shear connectors in composite steel-concrete structures. Installation of cartridge fired pins is mostly governed by high energy introduction from installation device and mechanical fastener to the steel base material, without initial predrilling of holes. Therefore, large plastic deformations of base material are developed through installation procedure, together with various anchorage mechanisms between fastener and base material. This paper presents experimental investigation of most important influence parameters on behaviour and resistance of cartridge fired pins, such as adjusted installation power level on installation device and steel base material strength. Experimental investigation involved X-ENP-21 HVB cartridge fired pins through double-sided shear tests, tension tests with fasteners installed over X-HVB shear connector with two different steel grades (S275 and S355) and two installation power levels (2 and 3.5), and tension tests with fasteners installed over two thicknesses of pro-filed steel sheeting (0.8 mm and 1.0 mm). Cartridge fired pin resistances together with corresponding failure mechanisms were experimentally quantified and presented in this paper.

Implementation of demountable beams in steel-concrete composite floors enables structure reuse during several life cycles, consequently leading to savings in material consumption and reduction of emissions, providing overall ecological benefits. The behaviour of the innovative demountable beam with a shear connection consisting of headed studs and bolts is analysed in this paper. The proposed beam is formed of a steel profile and a steel-concrete composite slab cast in open trough profiled steel sheeting. Headed studs, welded to the additional steel angles, are placed in sheeting ribs, whereas bolts are installed between ribs, connecting the steel angles and profile flange. A numerical FE model of a full-scale steel-concrete composite beam has been developed to analyse the beam behaviour under service loads. Experimental results of push-out tests have been used to describe the loadslip behaviour of headed studs, whereas bolt response has been simulated according to the experimental investigations of lap joints with preloaded bolts and oversize holes. The parametric study has been conducted by varying the bolt diameter, grade and bolt hole size. The results have validated the applicability of the proposed system, confirming the fulfilment of serviceability limit state requirements.

Push-out tests are commonly used to investigate the shear performance of mechanical connectors applicable in steel-concrete composite beams. These tests can be complemented by numerical finite element simulations to reduce the need for extensive experimental testing. After validation against experimental results, numerical models could be used for additional analysis and parametric studies. The development of finite element models of push-out tests requires special attention to be put on modelling concrete behaviour, especially if concrete failure is the dominant failure mode. The concrete damage plasticity (CDP) models, combining plasticity and damage mechanics to represent the nonlinear behaviour of concrete, are commonly applied. This paper summarises and presents four different CDP models that have been successfully used by researchers in finite element simulations of push-out tests. The applicability of different models has been discussed in the specific case of shear connection with headed studs in profiled steel sheeting with a varied angle between profiled sheeting ribs and the beam. Results of comparative analysis are presented, indicating a significant influence of the applied CDP model on the response of push-out specimen. The best match between experimental and numerical results is accomplished by implementing the material model proposed by Pavlović with calibrated input parameters. Nevertheless, the applicability of each CDP model depends on the specific problem that is being analysed and therefore should be carefully approached.

Headed studs are the most commonly used mechanical shear connectors in composite steel-concrete beams. The behaviour of headed studs differs whether they are applied in solid concrete slabs or composite steel-concrete slabs with profiled steel sheeting. Although design codes provide calculation models for shear resistance of headed studs in profiled steel sheeting, certain weaknesses are attributed to design procedures given in EN 1994-1-1. Alternative design models have been proposed by several researchers. In this paper, novel models are presented and compared through the example of headed studs in different types of profiled steel sheeting., Moždanici sa glavom su najčešće primenjivana mehanička spojna sredstava u spregnutim gredama od čelika i betona. Ponašanje moždanika razlikuje se u zavisnosti od toga da li se primenjuju u punim betonskim pločama ili u spregnutim pločama na profilisanom limu. Iako su proračunski modeli za nosivost moždanika u profilisanom limu dati u standardima za projektovanje, važećim proračunskim procedurama datim u EN 1994-1-1 pripisuju se izvesni nedostaci. Iz tog razloga nekoliko istraživača je predložilo alternativne proračunske modele. U radu su prikazani predloženi modeli proračuna i data je uporedna analiza nosivosti moždanika sa glavom u različitim tipovima profilisanog lima.

Multi-storey car park buildings with steel–concrete composite floor structures are widespread in construction due to the distinct benefits of the implemented structural system. Although there are various possibilities for accomplishing composite action between a steel beam and a concrete slab, some solutions, such as friction-grip bolts commonly applied in the 1970s, did not show good durability. An example is the multi-storey car park building “Obilićev venac” in Belgrade. This case study presents two methods for life extension of the car park building structure. Both approaches focus on applying welded headed studs with the primary intention of providing a durable shear connection. While the first method has been applied during the structure’s reconstruction, the second method is proposed as a novel solution for implementation in steel–concrete composite floors. The application of the proposed connection is discussed and the results of the experimental and numerical research conducted are presented.

For obtaining shear resistance of a welded headed stud in profiled steel sheeting, EN 1994-1-1:2004 defines reduction factors that should be multiplied with the resistance of a headed stud in a solid concrete slab. Two reduction factors are prescribed, for sheeting ribs that are parallel and transverse to the supporting beam. However, the design code does not recognise cases when the angle between ribs and the beam is in the range between 0° and 90°. This research is focused on the specific case in the steel-concrete composite beam design when the angle between profiled sheeting ribs and the beam is 45°. The experimental investigation has been conducted through push-out tests, comparing the response of the connection with a rib-to-beam angle of 45° and the connection with ribs transverse to the supporting beam. In addition, numerical models based on finite element analysis have been made and validated against experimental data. According to the obtained results, similar failure mechanisms manifested through concrete pull-out failure and separation of the concrete cone are observed in shear connections with rib-to-beam angles of 45° and 90°. An increase in the connection resistance is noticed with the decrease of a rib-to-beam angle.

Primena nerđajućeg čelika u savremenom građevinarstvu vezuje se za period inovacija i tehnološkog napretka u industriji čelika tokom poslednjih decenija prošlog i početkom ovog veka. Iako se u osnovi klasifikuje kao legirani čelik, strukturne performanse ovog materijala bitno se razlikuju od onih kod ugljeničnih čelika. Atraktivan površinski izgled koji ne zahteva primenu zaštitnih premaza, visoka otpornost na koroziju, značajan kapacitet plastifikacije, izrazita duktilnost i visoke vrednosti granice razvlačenja i čvrstoće pri zatezanju daju prednost u primeni nerđajućeg čelika u nosećim konstrukcijama ofšor platformi, industrijskih objekata u agresivnim sredinama i mostogradnji. Nerđajući čelik spada u grupu čistih materijala pa se često koristi u nosećim konstrukcijama rezervoara i silosa za skladištenje hrane, tečnosti i medicinskih preparata. Preduslov za širu primenu nerđajućeg čelika u građevinarstvu predstavlja razvoj nove i poboljšanje postojeće tehničke regulative za projektovanje konstrukcija od ove vrste čelika. U tom kontekstu, potreba za stalnim istraživanjima i analizama ponašanja elemenata od nerđajućeg čelika je imperativ. Štapasti čelični proizvodi izrađeni od ugaonika imaju široku primenu u nosećim elementima koji su dominantno opterećeni aksijalnim naprezanjima kao što su: elementi ispune rešetkastih nosača, horizontalnih i vertikalnih spregova objekata u zgradarstvu, pojasni štapovi i štapovi ispune telekomunikacionih stubova i stubova dalekovoda. Važeći međunarodni standardi za projektovanje konstrukcija od nerđajućeg čelika ne daju eksplicitna pravila za dimenzionisanje centrično pritisnutih štapova izrađenih od ugaonika. Razlozi za ovo leže u nedovoljnom broju relevantnih istraživanja koja bi trebalo da pruže činjenice neophodne za dobijanje odgovora na brojne nepoznanice u pogledu graničnih nosivosti i oblika loma ovog tipa konstruktivnog elementa u zavisnosti od niza uticajnih parametara. U kontekstu navedenog, ova doktorska disertacija prik, Application of stainless steel in modern structural engineering is related to innovation period and technological progress in steel industry during the last decades of previous century and at the beginning of this century. Although it is classified as alloy steel, structural behaviour of this material differs significantly from that of carbon steels. Attractive surface appearance that does not require protective coatings, high corrosion resistance, significant plastification capacity, pronounced ductility and high values of yield and tensile strength give advantage to stainless steel application in offshore platforms, industrial facilities in aggressive environments and bridge structures. Since stainless steel belongs to a group of clean materials, it is often used for load-bearing structures of tanks and silos for food, liquids and medical remedies storage. Requirements for a wider application of stainless steel are development of new and improvement of existing technical regulations for the design of stainless steel structures. Therefore, constant research and analysis of stainless steel elements behaviour is of outmost importance. Steel angle bars have a wide application in structural members that are predominantly loaded by axial forces such as: webs of trusses, elements of horizontal or vertical bracings in buildings and as members of telecommunication towers and transmission line poles. Current international standards for the design of stainless steel structures do not provide explicit rules for axially compressed angles. Explanation for this is insufficient number of relevant studies that should provide knowledge necessary for obtaining the answers to numerous unknowns regarding ultimate bearing capacity and fracture modes of this type of structural elements, depending on a number of parameters. In the context of the above, this thesis presents a scientific research on axially compressed pinned angle columns conducted at University of Belgrade, Faculty of Civ

During the assembling of a steel structure with anchors, grout should be used in connections be- tween steel elements and a reinforced concrete support element. In horizontal and vertical joints, grout is used as a good construction practice for solving geometric tolerance problems. Grout can be used with cast-in anchors or post-installed anchors. However, the relation between anchor shear resistance and characteristic grout compressive strength is not described in detail in tech- nical regulations. The behaviour of a connection considering achieved slip tolerances should match the boundary conditions set in the global analysis. In the support joint, grout properties could influence the value of the slip between a steel part and a concrete part of the joint. Slip value could be significant for the relevant design cases featuring the interaction of shear force and ten- sion force. In this paper, results of the push-out test conducted on anchors are presented. Based on the experimental test, the finite element analysis was performed to investigate the shear con- nection behaviour. According to the preliminary results, it can be concluded that a grout strength and a grout thickness influence the connection response when serviceability loads are applied, alt- hough they do not influence the ultimate load bearing capacity of anchors. In some cases, using the contemporary solutions of high strength grout materials, the slip between steel and concrete parts in the connection could be reduced.

Stainless steel sections are used for structures in aggressive environments where the greater material cost can often be justified in return for longer maintenance-free periods, for example in the water treatment, nuclear, petrochemical and food and beverage sectors. This paper presents a comparative imperfection sensitivity study of hot-rolled and laser-welded pin-ended equal angle columns made of austenitic stainless steel grade 1.4301. Although the initial geometric imperfections in these structural elements are similar, there is a difference in the initial stress state due to the different manufacturing processes. The study includes three-dimensional geometric imperfection measurements conducted by a laser scanner, and, in parallel residual stress measurements performed by the sectioning method using water jet cutting. The overall bow, camber, and twist imperfections are determined from the scanned specimens. In addition, the shapes of the residual stress patterns through the thickness of the angle leg are shown. Based on the findings related to imperfection distributions and amplitudes, a FE analysis is performed both on hot-rolled and laser-welded angles to study the influence of the variability of initial imperfections on compression resistance. The separate and combined effects of the measured residual stresses and initial out-of-straightness are considered and the reduction in the buckling resistances of initially straight angle columns is determined. The structural responses of hot-rolled and laser-welded columns are compared and discussed.

Pravila za proračun centrično pritisnutih elemenata ravnokrakog L poprečnog preseka od nerđajućeg čelika nisu eksplicitno definisana u važećem evropskom standardu SRPS EN 1993- 1-4. Ovaj rad ukratko prikazuje rezultate opsežnog istraživanja sprovedenog na ovom tipu konstruktivnih elemenata sa ciljem definisanja preporuka za njihov proračun. Na osnovu sistematičnog eksperimentalnog istraživanja, sprovedena je detaljna numerička analiza i definisana baza podataka graničnih nosivosti stubova. Materijalna i geometrijska nelinerana analiza obuhvatila je tri ključne legure nerđajućeg čelika, austenitnu, feritnu i dupleks leguru. Preporučene su krive izvijanja za kontrolu stabilnosti na fleksiono i fleksiono-torziono izvijanje u skladu sa evropskim proračunskim procedurama., The design rules for centrically compressed stainless steel equal-leg angle members are not explicitly stated in the current European standard SRPS EN 1993-1-4. This paper summarizes the results of extensive research conducted on this type of structural elements aiming to define recommendations for their design. Based on a systematic experimental investigation, a detailed numerical analysis was performed, and a database of columns’ resistances were defined. Material and geometric nonlinear analysis included three key stainless steel alloys, austenitic, ferritic and duplex. The design curves for flexural and flexural–torsional buckling check have been proposed in accordance with European codified procedures.

This paper aims to develop design recommendations for closely spaced built-up stainless steel columns, based on findings gained in performed research at the University of Belgrade. The research focuses on pin-ended built-up columns formed from two press-braked channel chords oriented back-to-back and addresses their flexural buckling capacity about the minor axis. The impact of overall and local chord slenderness, interconnection stiffness, geometric imperfections and material nonlinearity is evaluated. In order to fully exploit their structural performance, two separate approaches for the design of built-up columns with welded or bolted interconnections are defined that include different formulas for shear stiffness.

In keeping with current demands for sustainable development in all segments of the industry, numerous research in the field of steel-concrete composite structures has been focused on developing demountable shear connectors. In the past years, various demountable shear connectors have been suggested, with various mechanisms for transferring shear force between a steel profile and a concrete or composite slab. In this paper, a state of the art on the topic is given, and experimental and numerical research results of push-out and beam tests are summarized., U skladu sa zahtjevima za održivi razvoj u svim segmentima industrije, brojna su istraživanja u području spregnutih čelično-betonskih konstrukcija usmjerena na razvoj demontažnih sredstava za sprezanje. Proteklih godina predlagana su različita demontažna sredstva za sprezanje koja su različitim mehanizmima prenosila posmičnu silu između čeličnog profila i betonske ili spregnute ploče. U ovom radu prikazana su najnovija dostignuća na tu temu dajući sažetke eksperimentalnih i numeričkih rezultata istraživanja vezano uz potisna (push-out) ispitivanja i ispitivanja na nosačima.

In the past decades, many novel shear connectors for implementation in steel-concrete composite beams have been investigated. In this paper, a demountable shear connection between a structural steel beam and a solid concrete deck, consisting of bolts and welded headed studs, is analysed. This system features the indirect shear force transfer through the additional element, a steel plate that is placed between a concrete deck and a top flange. Following the experimental results of previously conducted push-out tests, a numerical model has been developed. The model is used for a detailed analysis of the system behaviour as well as for the parametric study. Influence of a bolt diameter and a bolt hole diameter on shear behaviour of the connection has been discussed., Prethodnih decenija intenzivno su ispitivana nova rešenja spojnih sredstava u smičućim spojevima spregnutih greda od čelika i betona. U ovom radu analiziran je montažno-demontažni podužni smičući spoj konstrukcionog čelika i pune armiranobetonske ploče, ostvaren pomoću zavrtnjeva i elastičnih moždanika s glavom. Ovakav spoj odlikuje se indirektnim prenosom sile smicanja kroz dodatni element, čelični lim, između betonske ploče i gornje nožice grede. Formiran je numerički model testa smicanja prema dostupnim prethodnim eksperimentalnim ispitivanjima. Model je iskorišćen za detaljnu analizu ponašanja podužnog smičućeg spoja, kao i za parametarsku analizu. Ispitivan je uticaj prečnika zavrtnja i prečnika rupe na ponašanje spoja pri smičućem opterećenju.

Prefabricated construction and requirements for reusing the particular structural element, request the application of a support joint realized with anchors. Besides demountability, the connection detail realized with anchors needs to satisfy all support conditions adopted during the structure design. This paper describes the behaviour of anchor shear connection. The connection slip was analysed concerning the grout material properties and the grout thickness. The parametric study was performed using Abaqus software to define the relationship between grout properties and thickness and the slip deformation for load levels corresponding to serviceability limit states.

Human perception of floor vibrations and uncompromised serviceability of equipment are two most important acceptability criteria considering floor vibrations. While verification of deflection is a simple and well-known procedure in structures’ design for serviceability limit state, the fulfilment of floor vibrations acceptability criteria are presented in different standards in the form of various calculation procedures. Results achieved through those calculation procedures are presented in the form of various classification of floor structures. Classification of composite floor structures due to vibrations is inconsistent considering different calculation procedures. Comparison of various calculation procedures for the definition of composite floor vibrations is presented in this paper. In addition, a parametric analysis is performed on the wide range of steel-concrete composite floor structures, through analysis of various composite floor layouts and a wide range of imposed loads values. The analysis of the relation between deflection, vertical vibrations and accelerations of steel-concrete composite floor beams is presented in this paper. The results of the parametric analysis are given through direct relation between deflections of composite beams and achieved floor class for the fulfilment of vibrations acceptability criteria due to the pedestrian walking.

U ovoj doktorskoj disertaciji biće razmatrano elastoplastično ponašanje konstruktivnih mekih čelika pri velikim naprezanjima u plastičnoj oblasti. Biće pokazano da je osnovna karakteristika naponsko deformacijskog dijagrama ove vrste čelika, formiranje horizontalnog platoa tečenja između zone elastičnosti i zone plastičnog ojačanja. Ovaj fenomen, koji se ispoljava u vidu lokalne nestabilnosti atomske rešetke (Lüders band) je samo karakteristika monotong naprezanja, dok kod ponovljenog naprezanja iščezava. Koristeći Preisach-ov histerezisni operator, razvijen je materijalni model, koji sa velikom tačnošću opisuje ponašanje ovih čelika pri monotonom aksijalnom naprezanju. Materijalni model u vidu analitičkog izraza za vezu dilatacija-napon veoma dobro aproksimira oblasti elastičnosti, horizontalnog platoa tečenja i plastičnog ojačanja, karakterističnih za konstruktivne meke čelike izložene ovoj vrsti naprezanja..., In this doctoral dissertation, the elastoplastic behavior of structural mild steel under large deformations is explained. It will be shown that the stress-strain diagram's main characteristic of this steel type is the formation of a horizontal yield plateau between the elastic region and the plastic hardening region. This phenomenon, manifested in the form of local instability of the atomic lattice (Lüders band), is only a characteristic of monotonic loading, whereas in the case of alternating loading it disappears. Using Preisach's hysteresis operator, a material model was developed, describing with excellent accuracy the behavior of this type of steel under monotonic axial loading. The material model in the form of an analytical expression for the strain-stress relationship very well approximates the regions of elasticity, horizontal yield plateau, and plastic hardening characterized for structural mild steel under this type of loading.

У овом раду спроведене су опсежна експериментална и нумеричка испитивања понашања веза са чеоном плочом и четири завртња у реду, као и карактеристичне компоненте ових веза - Т-елемента. Експериментална испитивања укључују тестирања 36 узорака Т-елемената у природној величини, као и четири везе греда-стуб са чеоном плочом и четири завртња у реду, такође у природној величини. Нумеричке анализе, спроведене у софтверском пакету ABAQUS, су обухватале све типове нелинеарности, али и отказ материјала, те се као такве сврставају међу ретке којима су слични проблеми нумерички испитивани. Параметарска студија обухвата 33 различите конфигурације Т-елемената са четири завртња и представља највећу такву студију изведену за ову компоненту. Као основни још увек нерешен проблем, круцијалан за понашање Т-елемената, препознати су положај сила услед ефеката полуге, али и савијање завтњева. Приказан је и предложен нови аналитички модел прорачуна носивости Т-елемената са четири завртња, и квантификована његова предност над до сада постојећим моделима., U ovom radu sprovedene su opsežna eksperimentalna i numerička ispitivanja ponašanja veza sa čeonom pločom i četiri zavrtnja u redu, kao i karakteristične komponente ovih veza - T-elementa. Eksperimentalna ispitivanja uključuju testiranja 36 uzoraka T-elemenata u prirodnoj veličini, kao i četiri veze greda-stub sa čeonom pločom i četiri zavrtnja u redu, takođe u prirodnoj veličini. Numeričke analize, sprovedene u softverskom paketu ABAQUS, su obuhvatale sve tipove nelinearnosti, ali i otkaz materijala, te se kao takve svrstavaju među retke kojima su slični problemi numerički ispitivani. Parametarska studija obuhvata 33 različite konfiguracije T-elemenata sa četiri zavrtnja i predstavlja najveću takvu studiju izvedenu za ovu komponentu. Kao osnovni još uvek nerešen problem, krucijalan za ponašanje T-elemenata, prepoznati su položaj sila usled efekata poluge, ali i savijanje zavtnjeva. Prikazan je i predložen novi analitički model proračuna nosivosti T-elemenata sa četiri zavrtnja, i kvantifikovana njegova prednost nad do sada postojećim modelima., In this research, extensive experimental and numerical investigations of behaviour of end-plate moment connection with four bolts per row are performed, as well as specific component of the connection – T-stub element. Experimental research comprises tests on 36 unscaled specimens of T-stub elements and 4 specimens of beam-to-column joints with end-plate connection and four bolts per row, also in full-size. Numerical analyses, performed with software ABAQUS, included all types of nonlinearities, and material deterioration, hence they can be considered as one of the few most sophisticated analyses used for investigation of the considered problem. The parametric study comprises 33 different configurations of the T-stub element with four bolts per row and it presents the biggest study of this kind for this type of component. Bending of the bolts and position of the prying forces are recognized as the largest, still unsolved problem, crucial for the behavior of the T-stub elements. A new theoretical model for the resistance of the T-stub element with four bolts per row is proposed and its advantage over the existing models is presented and quantified.