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There is a significant number of old metallic bridges with high levels of structural degradation due to their long service period. Fatigue problems are especially important in these structures since the majority of them were not designed taking into account this phenomenon. Several investigations showed that riveted joints are critical details since several fatigue cracks were found in these joints. In this sense, strengthening methodologies need to be studied. The strategy that has been considered a good solution is the implementation of injection bolts to replace faulty rivets. The structural performance of injection bolts has been demonstrated essentially under quasi-static conditions presenting good results. This paper intends to contribute to the scientific knowledge regarding the fatigue behavior of connections with preloaded injection bolts in the context of a bridge strengthening scenario. An experimental investigation was conducted to compare the fatigue performance of connections with preloaded injection bolts and preloaded standard bolts. Single and double shear connections were tested. New S–N design curves were proposed based on a statistical analysis of the results and compared with the S–N curves proposed in EC3-1–9. The obtained results showed that the use of injection bolts lead to lower scatter and improvement of fatigue life. It was verified that the Eurocode 3 is not able to represent the fatigue strength of connections whose performance is influenced by old metallic materials. Additionally, the fatigue behavior of these connections was assessed by numerical analysis. The relevance of the fatigue crack initiation was evident., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Steel & Composite Structures

All over the world, the number of civil engineering structures, particularly bridges with long service periods, has been increasing. The most common evidences of damages are the presence of corroded metallic elements and cracks in structural details due to the fatigue phenomenon. A large number of cases were found in which fatigue cracks were detected in structural details, such as riveted connections. Different strategies can be implemented for repairing and strengthening operations of old metallic riveted bridges. However, the use of injection bolts has been considered as an alternative with important advantages. In this regard, it is essential to study their performance under fatigue loading. In this investigation, an experimental campaign has been performed to assess the fatigue strength of injection bolts by means of comparison with standard bolts. These fatigue tests are defined to be representative of a structural strengthening scenario of an old metallic bridge. Experimental results show that injection bolts contribute to significantly reduce the scatter in the data related to fatigue resistance. For double shear specimens, the characteristic curve proposed for connections with injection bolts presents a detail category with 15% higher value when compared to non-injected specimens. The beneficial effect is also verified in terms of slip deformation. For single shear specimens, the overall effect of the adhesive is not clear., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Steel & Composite Structures

In North America and Europe, there is a significant number of centenary metallic bridges that require maintenance and strengthening operations. These structures need to be adapted to increasing traffic intensities, and their structural integrity should be constantly evaluated. Fatigue damages were not considered in the original design of old metallic bridges, and riveted connections are one of the most frequent sources of fatigue damages on these structures. This paper intends to be a contribution for the reliable assessment of the fatigue behavior of riveted connections by proposing S-N curves for these structural details. Experimental fatigue data is analyzed from multiple bridges across Europe, and different statistical methods were implemented. A normal distribution function was implemented following the ISO 12107 standard, and the results were compared with the implementation of the two-parameter Weibull distribution function. Different estimation methodologies were implemented to determine the parameters of the Weibull distribution. S-N curves obtained by the statistical analysis were then compared with design recommendations from North American and European standards., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public. Erratum DOI: 10.1061/AJRUA6.0001081 The following correction should be made to the original paper: in all places where it is written “probability of failure,” the text should read “probability of survival,” including in Tables 2 and 3., Steel & Composite Structures

Purpose: In the last decades, the demand and use of renewable energies have been increasing. The increase in renewable energies, particularly wind energy, leads to the development and innovation of powerful wind energy converters as well as increased production requirements. Hence, a higher supporting structure is required to achieve higher wind speed with less turbulence. To date, the onshore wind towers with tubular connections are the most used. The maximum diameter of this type of tower is limited by transportation logistics. The purpose of this paper is to propose an alternative wind turbine lattice structure based on half-pipe steel connections. Design/methodology/approach: In this study, a new concept of steel hybrid tower has been proposed. The focus of this work is the development of a lattice structure. Therefore, the geometry of the lattice part of the tower is assessed to decrease the number of joints and bolts. The sections used in the lattice structure are constructed in a polygonal shape. The elements are obtained by cold forming and bolted along the length. The members are connected by gusset plates and preloaded bolts. A numerical investigation of joints is carried out using the finite element (FE) software ABAQUS. Findings: Based on the proposed study, the six “legs” solution with K braces under 45° angle and height/spread ratio of 4/1 and 5/1 provides the most suitable balance between the weight of the supporting structure, number of bolts in joints and reaction forces in the foundations, when compared with four “legs” solution. Originality/value: In this investigation, the failure modes of elements and joints of an alternative wind turbine lattice structures, as well as the rotation stiffness of the joints, are determined. The FE results show good agreement with the analytical calculation proposed by EC3-1-8 standard., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Steel & Composite Structures

This paper describes a study of the S650 high strength steel material properties including the effect of cold-formed angle. Coupon specimens with different cold-formed angles (90°, 100°, 120°, 140°, 160°and 180°) and different thicknesses (4 mm and 6 mm) were examined. Relationships between cold-formed angle and yield stress as well as tensile stress of the material were determined, based on the tensile coupon test results. Yield and tensile stresses assessed by consid ering the influence of the cold-formed angles were compared with those without considering this influence. Analyses revealed that both yield and tensile stresses decreased with increasing cold-formed angle. Ductile-damage material models available in the finite element analysis software ABAQUS were used to simulate tensile coupon tests. The experimental and numerical results showed good agreements., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Steel & Composite Structures

This paper describes a study of the behaviour of cold-formed high strength steel angles. Thirty-six specimens with different cold-formed angles (90°, 100°, 120°, 140°, 160°, and 170°) and different thicknesses (4 mm and 6 mm) were considered. The initial geometric imperfections of the specimens were determined using the 3D laser scanning method. The magnitudes of these geometric imperfections for torsional and torsional-flexural buckling and flexural buckling analyses were proposed. The commercial finite element analysis (FEA) programme ABAQUS with shell elements S4R was used for finite element analyses. Different material strengths in corner and flat parts along with different proof stresses (0.2%, 0.01%, and 0.006%) were considered in the numerical models. The experimental and FEA results showed good agreement. Influence of cold-formed angle on non-dimensional slenderness and reduction factor curves of the 4 mm thick columns with 90° and 120° cold-formed angles was analysed., Steel & Composite Structures

The maintenance and safety of ancient bridges is a major concern of governmental authorities. In particular, the safety of old riveted bridges fabricated and placed into service at the end of the 19th century deserves particular attention. These structures are susceptible to exhibit high fatigue damage levels due to their long operational period with increasing traffic intensity associated to an original design not covering the fatigue phenomenon. This paper reviews recent fatigue behaviour investigations on single and double shear riveted joints performed by Universities of Porto (Portugal), Trás-os-Montes e Alto Douro (Portugal), and Wrocław (Poland), in particular concerning the fatigue characterization of riveted joints extracted from representative Portuguese riveted bridges, namely the Eiffel, Luiz I, Fão, Pinhão and Trezói bridges. In order to overcome the influence of scatter and establish a reliable assessment for the obtained experimental data, two statistical approaches were used: implement linearized boundaries following the recommendation in ASTM E739 standard and defining probabilistic S–N fields using the Castillo & Fernández-Canteli model. This statistical analysis allows to propose design S–N curves for single and double riveted joints and evaluate the applicability (safety) of using the design curves suggested in Eurocode 3 as well as design curves proposed by Taras and Greiner., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Steel & Composite Structures

Currently, onshore wind turbines are economical for 2.5 mega-watt inland installation [1]. One of the alternatives to achieve the higher power capacity in onshore wind turbines is to go to higher altitude, which increases the wind speed and has more uniform wind pressure, leading to higher possible annual energy production and relatively lower maintenance costs due to wind shear induced vibrations. This paper deals with a predesign of a new type of tower that should overcome known disadvantages of steel tubular towers for heights over 150 meters. This first part of the paper addresses the viability of a hybrid support structure in respect of ultimate limit states and structural dynamics as part of the requirements in exploring the feasibility of the hybrid tower concept. The hybrid wind turbine tower concept consists of a lattice (lower) structure and a tubular tower for the higher tower segment. The study cases found in literature were designed with maximum height of 160m and the 2.5MW wind turbine. Moreover, they used commercial "L" sections which leads to high number of connections and bolts. The project that supports the present paper aims at using optimally design hollow cross sections, to reduce the number of connections, and low maintenance type bolts. The developed study case is made for 220m tower height and using 5MW wind turbine., Steel & Composite Structures

Friction connections with long open slotted holes have been proven to be a competitive alternative to the conventional flange connections in steel tubular towers for wind energy converters. As full-scale tests are not available, results of Finite Element Analysis (FEA) of the real-scale tower geometry are used in this paper to investigate the influence of tower cross section shape, execution tolerance (gap between the shells) and length of the connection on the bending resistance. Buckling behaviour of the shell in the vicinity of the friction connection in circular and polygonal towers is compared. The friction connection is thoroughly examined and recommendations for execution tolerances are given. The influence of two types of the execution tolerances on the connection strength is considered: inward bended “fingers”, leading to inclined gaps, and a parallel gap created by different tower diameters., Steel & Composite Structures