Slender steel structures such as masts and towers consisting of or supporting cylindrical elements or chimneys can be susceptible to vortex shedding. Vortex-induced vibrations (VIV) can occur in slender structures because a fluctuating cross-wind force is generated from vortices shed alternately from opposite sides of the structure. Significant VIV occur when the frequency of the vortex shedding is the same as the natural frequency of the structure. If the critical wind speed for VIV often occurs for a structure and the vibration amplitudes caused by the VIV are critical with respect to fatigue, the result can be failure of the structure. An effective method of damping the vibrations can be to install a tuned liquid sloshing damper (TLSD). This paper focuses on the design of a TLSD and compares this with the tuned mass damper (TMD) solution.
Compared with the fabrication and installation of a TMD, it is much simpler to make a container and fill it with liquid. The container is often made as a square box or a cylinder that is easily mounted at the top of a mast, tower or chimney, thus providing the most efficient damping of the critical vibration mode. A TLSD is also preferred when it comes to maintenance as only the liquid level has to be checked, whereas a TMD needs maintenance and possibly repair or even replacement of damper parts.
A TLSD is designed by calculating the dimensions that will result in a mode shape of the sloshing liquid with a frequency close to the natural frequency of the structure that is to be damped. As the liquid moves in the container, so the sloshing energy of the water reduces the dynamic response of the structure subjected to VIV. Experiments have shown that the TLSD has a rather broadband efficiency and also that it is effective with sloshing liquid mass values down to < 1 % of the effective mass of the mode it is designed to damp.
Ramboll has experience with the design of both types of dampers, TMD and TLSD, for broadcast masts and towers and for chimneys. In particular, at a broadcast tower in Norway where a TMD has been replaced by a TLSD, Ramboll has tested the efficiency of the TLSD for comparison with the TMD replaced. This paper will present these results and give an introduction to TSLD design.

Bolt-and-nut assemblies under tension loading can either fail by bolt fracture or thread failure. The latter failure mode is arguably undesirable because it leads to failure at a comparatively low deformation level. Moreover, incipient thread failure is challenging to detect in the case of over-tightening since the bolt remains in the bolt hole after this type of failure occurs. The failure mode of bolt-and-nut assemblies is determined by several well-known factors such as the thread engagement length and the relative strength of bolt and nut. However, one factor that has received limited attention in the literature is the placement of the nut along the threaded portion of the bolt. We have performed a series of direct tension tests on various single M16 bolt-and-nut assemblies where the placement of the nut was varied. Some of the assemblies experienced that placing the nut close to the thread run-out, i.e. near the unthreaded portion of the bolt (the shank), led to thread failure, whereas placing the nut sufficiently far from the thread run-out led to bolt fracture. We carried out finite element simulations of the tests in order to investigate further the mechanisms occurring during failure. In the case where the nut was located close to the thread run-out, the simulations revealed that necking of the bolt affected the effective overlap of the internal and external threads. This effect seemed to contribute to thread failure in both tests and simulations.

The resistance of a typical shear connection with headed shear studs in a composite beam is analysed for the normal case in accordance with EN 1994-1-1. The reducing effect of a trapezoidal metal decking to the ultimate loadbearing capacity is considered with empirically derived reduction factors and equations that were developed between the late 1970s and early 1980s. The RFCS research project “DISCCO” [1] investigated the shear stud resistance with novel types of steel decking. In many cases, the shear resistance predicted by EN 1994-1-1 [2] was not reached in tests.
In the respective experiments with composite beams and deep decking, a concrete cone failure mode was identified and not a pure shear failure of the stud. This failure mode acted in combination with the loadbearing capacity of the shear stud, which formed one or two plastic hinges in the shaft depending on the actual geometry.
Based on these observations, new equations have been developed to predict the shear connection's resistance with more accuracy. The yield hinge mechanism of the shear stud, which was developed by Lungershausen [3], was extended by the aforementioned loadbearing component “concrete cone”. The formulae consider the geometry of the stud and the steel decking and the material strength of the stud and the concrete. The statistical evaluation of the equations developed demonstrates good agreement with test results.

This article provides an overview of the outcomes of a European-funded project called BarrierPlus. A new type of water-based barrier coating was developed for structural steel applications. The advantages of this coating include enhanced moisture resistance, low volatile organic compounds (VOCs) and one-component self-crosslinking free of isocyanates. To enable this performance, a latex polymer binder was uniquely designed without using soap-like molecules, known as surfactants, to form the dispersion. By minimizing surfactants in the coating, the barrier properties were significantly enhanced. The latex was successfully scaled up to 15 kg quantities by an SME, coating formulations were scaled to pilot quantities and a variety of characterization and coating performance tests were completed. A life cycle assessment found that the BarrierPlus coating has a better environmental profile than an industry benchmark solvent-borne coating and showed promising results relative to commercial waterborne benchmarks.

The objective of this article is to facilitate the use of semi-continuous joints by providing ready-to-use tables and charts for design, which also permit the benefits accruing from the use of semi-continuous composite beams to be directly identified. The relevant features for the design of composite beams, such as bending moment distribution, maximum deflection and natural frequency, are derived analytically. The influence of semi-continuous steel joints on the performance of single-span composite beams is analysed. The article concludes with an example of the use of a new slim-floor beam type - the composite slim-floor beam (CoSFB). The tables and charts derived are applied in this example with the intention of demonstrating the advantages of using semi-continuous joints in combination with composite beams. The present article extends the design of semi-continuous steel beams presented in the previous article on this subject [1].

In industry and plant engineering especially, high flexibility is required at joints between steel and concrete. According to current standards, the maximum number of fasteners is limited to an arrangement of 3 × 3 anchors on an anchor plate. The load-carrying behaviour of large anchor plates under tension, shear and restraining forces was investigated within the scope of the research project “Large Anchor Plates with Headed Studs for Highly Stressed Constructions in Industry and Plant Engineering”. This paper describes the research results obtained at the University of Stuttgart for large anchor plates under shear loading. Findings for large anchor plates under tension and restraining forces are given in [20], which were mainly investigated at the University of Kaiserslautern.
The shear behaviour and distribution of forces within the anchor plate are crucial issues in the development of a design concept for steel-to-concrete joints with large anchor plates. The influence of different parameters, such as the dimensions of the anchor plate, the embedment depth of the headed studs or the eccentricity of the shear force, have been studied in several test series. Supplementary reinforcement was placed close to the headed studs in tension to strengthen the load-carrying capacity of the joint. The distribution of the shear forces has been assessed by means of numerical investigations together with the influence of further parameters such as concrete strength and reinforcement ratio. With regard to the load distribution within the anchor plate, elastic and plastic design approaches have been taken into account.
Based on these studies, a suitable design model has been developed for steel-to-concrete joints with large anchor plates and a higher number of fasteners than originally permitted. Owing to the consideration of supplementary reinforcement, in addition to the plastic design approach, an alternative economical solution is given which links the component method according to EN 1993-1-8 to the fastener technique according to EN 1992-4.

This paper presents the experimental and numerical investigations of an innovative composite floor system with deconstructability. In this system, a composite slab formed with metal profiled decking is connected to a steel beam using demountable shear connectors. A series of push tests was conducted to investigate the behaviour of this form of shear connector. In addition to the push tests, a full-scale composite beam was tested to failure in the laboratory under a number of cycles of monotonic loading. For direct comparison, a similar composite beam test was conducted using the same section size and concrete strength, but using conventional welded headed stud connectors. Test results showed that the behaviour of the composite beam with demountable shear connectors is comparable with that of the specimen with welded shear connectors. After the test was terminated, the demountable shear connectors were unfastened and the composite floor could be easily lifted off from the steel beam. Test results showed that these demountable shear connectors possess high ductility in comparison to the equivalent welded shear connectors. Simple design rules currently use in Eurocode 4 for welded shear connections and Eurocode 3 for bolts are proposed to predict the shear resistance of this form of demountable shear connector.

The prefabrication of concrete slabs reduces construction time and the total life cycle cost of composite steel-concrete buildings and bridge decks. Using bolts as shear connectors embedded in prefabricated concrete slabs enables reuse and easy replacement of slabs as structural members suitable for a circular economy construction concept. The results of static push-out experiments on M16 and M24 bolts, grade 8.8, are shown here. The focus is on the validation of advanced finite element (FE) modelling by experiments. Damage material models for bolt and concrete slab were used and the most realistic preloading of the bolts modelled with threads was achieved by turning the nut in the FE model. An explicit dynamic solver with mass scaling function was used for quasi-static analysis including fracture. Two failure modes obtained in experiments - bolt shear and concrete crushing - were realistically modelled by the FEA, which shows that the model is suitable for a parametric study leading to theoretical models of failure modes and slip capacity of the shear connection. Results indicate that the bolts with nuts on both sides of the steel flange can be successfully used as demountable shear connectors.

Grouped headed studs may be successfully utilized to achieve the longitudinal shear connection between prefabricated slabs and steel beams. The behaviour of the studs and the ultimate resistance of the group were analysed using the results of experimental push tests and by employing advanced FE analyses. Different arrangements of studs in the group were investigated, focusing on minimal distance between the studs. It is demonstrated that the full shear resistance of a group of headed studs is achieved even when the distances between the studs are less than the minimum requirement according to EN 1994-1-1. Concrete class C30/37 is the minimum that should be used. Furthermore, the paper presents a new model for calculating the shear resistance of grouped headed studs. The proposed design model is based on an equivalent stud diameter and can be used for various arrangements of headed studs in a group. The shear resistance formula and the requirements for ductility are consistent with the existing Eurocodes. Fatigue loading is not considered in this paper, so the proposed recommendations are valid for buildings including multi-storey car parks.

A new form of shear connection, so-called composite dowels, first appeared in Europe in last decade. It enabled economic construction of steel-concrete composite bridges without an upper steel flange, using a direct connection between steel web and concrete slab. It finally resulted in new economic structural forms and composite sections that had not been used in bridge engineering before. In 2010 the European Commission launched an international project to build three different innovative bridges in three different European countries (Germany, Poland, Romania). Each bridge project was supported by a national consortium consisting of design office, general contractor and university. This economic technology has developed fast: by the end of 2016, at least 34 bridges using composite dowels had been constructed in Europe (13 in Germany, 11 in Poland, 4 in Czech Republic, 4 in Austria, 2 in Romania). These structures use different kinds of composite section that in many cases are not covered by standard design procedures for composite structures. The need for a consistent design method was evident. This leads to a clear design concept that covers the contribution of concrete slabs in transmitting part of the vertical force in composite sections and finally breaks with the concept of a “steel skeleton” constituting the fundamental part of the composite beam. The approach proposed here needs to be as simple and clear as possible, so it assumes some simplifications at this stage. It is intended to cover many types of composite section, externally reinforced section and conventional composite section.

This paper presents the basis for the design of steel and composite beams with large web openings. The main design requirements are the transfer of shear by Vierendeel bending and the control of web buckling next to and between the openings. Cellular beams with regular circular openings are a common example of highly perforated beams and their flange areas are often highly asymmetric. For these beams, web-post moments may be generated to develop the full shear resistance of the cross-section.
Tests on beams with circular, elongated circular and rectangular openings are presented which are used to verify the design methodology. In addition, the openings cause local displacements due to shear and bending, which add to the overall deflection of perforated beams. Simplified formulae are presented to determine the additional deflection relative to the equivalent solid-web beams.

The direct tension indicator (DTI) method is specified in EN 1090-2 as one of the tightening procedures for preloading bolting assemblies to a specified level of preload. As Germany so far has no experience of using the DTI method, recent experimental and theoretical investigations were carried at the Institute for Metal and Lightweight Structures, University of Duisburg-Essen, Germany, with the main focus being the loadbearing behaviour of preloaded bolting assemblies with DTIs under external axial tensile loading. Whereas tension connections employing preloaded bolting assemblies are quite common in Germany, in the UK, for example, bolted connections are preferably designed as shear connections, as far as is known. As a result of the investigations presented below, it can be summarized that, under tensile loading especially, preloaded bolting assemblies with DTIs might suffer from a severe loss of preload - something that should be considered in preloaded bolted connections in which the preload is taken into account in the design of the connections, e.g. in slip-resistant connections, to activate the slip resistance, and in tension connections subjected to fatigue. Based on these investigations, recommendations have been formulated for preloaded bolting assemblies with DTIs under external axial tensile loading.

Kienlesberg Bridge is the new link for trams, pedestrians and cyclists between the inner city and the science centre in the north-west of Ulm. The bridge crosses a railway junction near the main station and a new high-speed rail link. The geometric boundary conditions lead to unequal spans and complex alignments. Therefore, the scheme that won the design competition, which is now under construction, proposed a bridge made of steel. The superstructure was designed as a semi-integral continuous beam with main girders of varying depth. Owing to the pedestrian and cyclists' path on one side, the orthotropic plate cross-section is asymmetric and the main girders have varying depths. Special calculations and details were necessary for dynamic and noise control reasons. The bridge is being built using incremental launching.

Dedicated to Prof. Dr. Eng. Akimitsu Kurita on his 70th birthday, in honour of his scientific achievements, guidance and the education of his students.
Fire safety in bridge design is not as developed as fire safety in building design, even though a bridge failure can cause significant economic damage impacting on an area. This paper addresses an unanswered question with regard to fire safety, i.e. the capability to identify the governing failure mode of a bridge subjected to severe fire loading and ranking the regions of greatest fire exposure risk. Hence, this proposed methodology is also expected to support forensic work identifying the failure mode where a bridge has failed due to a severe fire, as will be shown using the 9-Mile Road Overpass collapse as an example. In an effort to mitigate fire damage, the fire protection panel (FFP) is introduced, which is part of a sacrificial structure shielding the bridge superstructure from exposure to fire from underneath.

Dedicated to Prof. Dr. Akimitsu Kurita on his 70th birthday
The use of composite columns with special types of sections e.g. concrete filled tubes with massive inner cores became very popular in the last years. These sections are not in the scope of the simplified design method of Eurocode 4. The paper deals with a design proposal for columns with those sections based on the general design method and it shows how this method can also be used extending the scope of the simplified design method in Eurocode 4.

Preliminary structural design is used for estimating and comparing design alternatives. It is mainly a manual procedure based on experience and documented in the form of design tables or charts. In an effort to automate this procedure for steel composite office buildings, the Sustainable Office Designer (SOD) has been developed as a SketchUp plug-in. It can generate optimized preliminary structural designs for given rectangular boundary shapes and employs a rapid approximate calculation instead of an expensive structural analysis. Steel columns are used and verified according to DIN EN 1993-1-1, while beams are designed as composite members and verified to DIN EN 1994-1-1. Pre-calculated design tables are used for slab systems. Optimization results are obtained and compared for different objectives, e.g. life cycle assessments (LCA) and costs.

Dedicated to Prof. Dr. Akimitsu Kurita on his 70th birthday
Bridges are of vital importance to Europe's infrastructure and composite bridges have already become a popular solution in many countries, representing a well-established alternative to concrete bridges. Their competitiveness depends on several factors such as site conditions, local costs of materials and labour and the contractor's experience. One outstanding advantage of composite bridges compared with concrete bridges is that the steel girders can carry the weight of the formwork and the fresh concrete during casting. Another major advantage is savings in construction time, which reduces disturbance to traffic and, consequently, saves money for the contractor, but even more so for road users - a fact that has been neglected for a long time. Recently, this factor has increasingly attracted attention as the latest studies show the need to take into account not only simple production costs, but also construction time and maintenance costs when deciding on a specific bridge type. All these needs are met by integral abutment bridges as well. In addition, this bridge type has the potential to outclass traditional bridges with transition joints as it not only reduces production and maintenance costs, but saves on economic and socio-economic costs as well.

Dedicated to Prof. Dr. Eng. Akimitsu Kurita on his 70th birthday, in honour of his scientific achievements, guidance and the education of his students.
This paper explores a new interdisciplinary method for internal damage detection and tracking in composite materials using thermo-chemical sensing. A micro-sized network of strings is interwoven into the composites. Each string consists of a pair of tubes containing one of two different non-polar reactants. A local defect within the composites causes straining and cracking of the tube shell, resulting in direct contact between the two non-polar reactants. The latter undergo a chemical reaction resulting in a polar product. When exposed to a microwave energy source, a polar product heats up dramatically within seconds in comparison to the surrounding composite material or the non-polar reactants. This localized thermal signature can be rendered visible by an infrared camera.
This study summarizes the findings of an in-depth computational and experimental study of this sensing technology which is expected to be applicable across industries using composites, among them aerospace, automotive, offshore and bridge engineering. Potential applications in steel offshore or steel bridge engineering involve using composite sensing patches to cover fatigue fracture-critical components. Defects initiating on the steel substrate surface are expected to be sensed on demand with this proposed sensing technology.

Dedicated to Prof. Dr. Akimitsu Kurita on his 70th birthday
In current bridge design codes or specifications, the dynamic effects of vehicles are considered by using a dynamic amplification factor (DAF) or dynamic load allowance (IM). However, a DAF is defined based on the ratio of the maximum dynamic load responses to the static load responses, and it is more appropriate for maximum value-based strength design. For fatigue design, stress cycles other than the maximum stress ranges could contribute to fatigue damage accumulations. Meanwhile, on the capacity side, a reduction in fatigue strength due to structural deterioration, which is related to local environmental conditions, including temperature, humidity, etc., could introduce more uncertainties into structural safety and reliability evaluation. However, such multiple stress range effects and structural deterioration are not included in current bridge fatigue design. To evaluate the vehicular dynamic effects for the life cycle fatigue design of short-span bridges, the present study proposes a new dynamic amplification factor for life cycle bridge fatigue design (DALC), which is defined as the ratio of the life cycle nominal live load stress range to the maximum static stress range. In contrast to other traditionally defined dynamic factors, the newly defined DALC includes information about both the structural loading and the structural capacity. Therefore, the multiple stress cycles from vehicle-induced vibrations and the structural deteriorations from road surface conditions and corrosion of structural members are included. Parametric studies of DALC were carried out for multiple parameters and variables in the bridge's design life cycle, for instance, possible faulting days in each year, fatigue strength exponent, corrosion parameters and corrosion level. The stochastic properties and uncertainties from these variables are also considered in the DALC calculation.

Dedicated to Prof. Dr. Akimitsu Kurita on his 70th birthday
The shrinkage of concrete is a material phenomenon that occurs due to the reduction in the concrete's volume over time. In composite beam-like structures, the shrinkage of concrete elements affects strains and stresses in the overall composite section. The ability to identify and estimate early-age shrinkage in beam-like structures allows the creation of a baseline for strain-based structural health monitoring, and enables a more thorough understanding of structural performance and condition. In this project, the early-age shrinkage behaviour of steel-concrete composite beam structures was studied with an integrated approach using monitoring data from a reduced-scale test structure and simulation results from finite element analysis. A simplified analytical expression was developed to study further the range of magnitude of shrinkage in the concrete slab and the resultant strain distribution in steel girders. The goal of this paper is to create an innovative, comprehensive and widely applicable procedure that identifies and quantifies early-age shrinkage in steel-concrete composite beam-like structures and its effects on the overall composite cross-section.

Dedicated to Prof. Dr. Akimitsu Kurita on his 70th birthday
To assess fatigue behaviour, experimental tests were conducted on material specimens furnished with hammer peening tracks, with two different types of treatment being employed. The results of fatigue tests on treated specimens were compared with those of untreated specimens and assessed. Non-linear analyses with the FE program ADINA, taking into account the stress-distortion behaviour of a material subjected to fatigue, were conducted as part of the test concept, specimen analysis, evaluation of the test results and probing the mode of action of both techniques.

This paper deals with the evaluation of fatigue cracks in a box type radial crane runway girder with full penetration welds between the web and flange. After 20 years of service fatigue cracks were observed which were initiated in the flange at the toe of the full penetration weld with the web. The observed cracks in the crane runway girder vary in length from a few mm to 330 mm with a summation of the lengths of all observed cracks being 750 mm, on a total length of 56000 mm, thus being only 1.3 %.
The investigation consists of the fatigue analysis described in this paper and additional experimental investigations with scale tests of approximately 1:2 on equivalent I sections with a concentrated load and with a line load to investigate whether cracks stop when they have grown through the residual tensile stress field. For this analyzed crane runway girder with multi-layered full penetration welds and with small cracks at the weld toes in the flange, based on EN 1993-6 the damage would be 1.0 for a design class 98 which is not far from the “class” 92 found by Kuhlmann et al, [1] for tests with rolling wheels, however, related to weld failures from the root of not fully penetrated fillet welds in combination with crack initiations at the weld toe.

Steel circular tubular elements are among the most commonly used types of structural element in offshore structures. The objective of this paper is to perform a comparative analysis of design standards for offshore structures with a focus on the structural design of these elements. The intention is to reach a conclusion about the level of safety that offshore and construction standards provide regarding the design of tubular circular elements. To this end, the bearing capacity obtained with ISO 19902 and Eurocode 3 (which does not contain specific provisions for offshore structures) parts 1-1 and 1-6 will be compared in a broad parametric study. Subsequently, the accuracy and level of safety that ISO and EC3 assume are assessed through numerical analysis using the ABAQUS software. The performance of a set of steel circular tubular elements is evaluated under axial compression and hydrostatic pressure. Finally, the interaction between axial compression and hydrostatic pressure is also analysed.

This paper summarizes the work carried out in the context of an ongoing investigation that aims to understand and characterize the structural behaviour of thin-walled single-cell regular convex polygonal section (RCPS) tubes, such as those widely employed in the steel construction industry. In particular, the first-order and buckling (bifurcation) behaviours are addressed and it is shown that they
i. exhibit several peculiarities, stemming essentially from the cross-section rotational symmetry, and
ii. can be significantly influenced by distortion-type deformation.
iii. The analytical and numerical results reported in this paper are obtained using generalized beam theory (GBT) and its computationally efficient specialization for RCPS recently developed by the authors [1]. In particular, the unique modal decomposition features of GBT make it possible to
i) identify the most relevant cross-section deformation modes,
ii) draw valuable conclusions concerning the mechanics of the problem under consideration from the analysis of the (modal) solution, and
iii) develop analytical and semi-analytical formulae for problems of significant practical interest.

Development of efficient design guidance for stainless steel structures (considering non-linear behaviour, strain hardening and allowing for moment redistribution in indeterminate structures) is crucial for the widespread use of this corrosion-resistant material. This paper presents an experimental programme involving ferritic stainless steel simply supported and continuous beams (RHS and SHS) and the assessment of existing cross-sectional classifications and different plastic design methods available in the literature for indeterminate stainless steel structures, not currently allowed in stainless steel standards. The analysis indicated that some cross-sectional classification limits seem to be too optimistic for ferritic stainless steels and further research is needed in order to extend plastic design to these grades.