In this paper the authors present numerical and analytical approaches for establishing rules for dimensioning MCL steel connectors for serviceability and fatigue limit states. Two unit models were adopted for the stress calculations by means of FEM: the first one for taking into account the notch effect of the longitudinal cutting line on the stress pattern in a uniformly tensioned steel plate, the second one for determining the stress pattern in a steel connector due to longitudinal shearing between the steel and concrete parts of the beam. A mathematical approach for establishing an envelope of the connector's resistance is presented. A detailed study of the fatigue behaviour of steel connectors is presented in the second part of the paper. Possible crack patterns and their development mechanisms are described, justified by appropriate FEA and test results.

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Composite dowels are powerful shear connectors in steel-concrete composite structures, especially for prefabricated composite bridges. The advantages of composite dowels over other shear connectors are their increased strength and sufficient slip capacity even in high-strength concrete. The National Technical Approval for Germany [1], [2] from 2013 allows the design of composite structures with composite dowels for hogging and sagging moments under static and cyclic loading. However, the design of structures with cyclic loading in combination with centric tension perpendicular to the composite dowels (transverse tension) is neglected. Therefore, one part of national project P967 “External reinforcement for composite bridges”, funded by FOSTA, the Research Association for Steel Application, was to determine how transverse tension affects the static capacity and fatigue resistance of composite dowels. To investigate this effect, two test series, each with six push-out tests, were carried out. The test setup and the results of the static and cyclic shear tests in combination with transverse tension are presented in this paper.

In the case of frame bridges with external reinforcement, the reinforcing elements have to be anchored in the abutment wall. Owing to the interaction of negative bending moment and longitudinal shear force in the abutment area, the force transfer between concrete, external steel reinforcement and normal steel reinforcement is complex. Two frame structure tests were carried out to investigate the loadbearing behaviour and rational anchorage length of external reinforcement in abutments. Two different anchorage lengths were tested, and the structural behaviour and failure modes of the two specimens were compared and analysed. The results indicate that the anchorage length has a great influence on the loadbearing capacity, and the pull-out effect at the end of the external reinforcement should be paid special attention. The detail stress distribution and the M-V interaction in the anchored external reinforcement were obtained from the tests and the results fit well with the theoretical calculation. Mechanical models are proposed to evaluate the pull-out effect and optimize the anchorage length of the external reinforcement.

Composite dowels with different shapes have been developed and used in composite members during the last two decades. At the Chair of Concrete and Masonry Structures at Technical University of Munich (TUM), composite dowels with a clothoid shape are used for filigree composite beams and columns. In both types of application the composite dowels are used as external reinforcement and Ultra-High Performance Concrete (UHPC) is chosen instead of normal-strength concrete. This article describes mainly the results of the preliminary push-out tests that were carried out in order to determine the structural behaviour of composite dowels in thin UHPC elements and verify the influence of the UHPC web thickness, the steel thickness of the shear connector, the concrete compressive strength and the influence of reinforcement on the loadbearing capacity and failure modes. The paper also includes an overview of and the outlook for the experiments with composite beams and composite columns.

In steel-concrete composite beams, lifting effects between the steel section and the concrete slab usually occur incidentally and have comparatively small load ordinates compared with the shear forces transferred. For this reason, lifting forces are generally irrelevant for the dimensioning of the composite joint. Nevertheless, this statement does not apply if shear connectors are used for the systematic anchorage of pull-out forces. Although the anchorage behaviour of conventional shear connectors, e.g. headed studs, has already been studied extensively, appropriate investigations into the anchorage behaviour of concrete composite dowels are lacking, especially for composite dowels in slender or cracked concrete slabs. In this paper, the anchorage behaviour of a puzzle-shaped concrete composite dowel is investigated in cracked and uncracked concrete. To this end, particular test setups were developed. All tests were simulated using a three-dimensional, non-linear finite element model. Finally, an engineering model for calculating the anchoring capacity of single composite dowels and composite dowel groups in reinforced and unreinforced concrete is presented.

Cuauhtémoc Stadium, a first division football stadium in Puebla, México, with more than 51 000 seats, has recently been completely renovated. The brand-new façade has become an icon for the club and for the city. The façade is designed as a skin of single-layer ETFE foil in a combination of three different shades of blue and translucent white. The design and construction of the façade is the result of an international collaboration between local contractor DÜNN Lightweight Architecture, from Zapopan, Mexico, and LEICHT Structural engineering and specialists consulting GmbH, based in Munich, Germany. This paper will elaborate on the boundary conditions of the project and the technical decisions made for the construction of the façade.

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This article explains a method for determining how semi-continuous joints influence the deflection, natural frequency and bending moment distribution of single-span beams with constant inertia under uniformly distributed load. The method is adequate for simple hand calculations, allowing the structural engineer to assess potential savings already in the pre-design phase. Further, the economical potential of semi-continuous joints according to EN 1993-1-8 [1] is demonstrated by an application example.

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This article reviews prior research on connections between through-plates and circular hollow sections (CHS) and presents a finite element (FE) study validated against laboratory experiments. The FE analysis indicates that, for a given geometric configuration, the behaviour of through-plate-to-CHS connections closely matches the sum of branch-plate-to-CHS connection behaviour in plate tension and compression. A connection design strength, which is shown to be valid for a wide range of connection geometries and which is the sum of existing design recommendations for branch plate-to-CHS connections loaded in axial tension and compression, is hence proposed for through-plate-to-CHS T-connections. This therefore enables maximum advantage to be taken of the capacity of this type of “reinforced” tubular connection.

In many practical applications, columns are often fixed to a practically rigid concrete structure at the column base. This additional restraint should increase the real load-carrying capacity if the section is susceptible to lateral-torsional buckling. However, this effect is rarely taken into account in design, as most current design rules do not provide sufficient guidance on how to account for this additional rigidity, and so the column base fixity is often ignored. The background to the verification formulae for lateral-torsional buckling (LTB) of I-section beam-columns in Eurocode EN 1993-1-1 consists of comprehensive parametric numerical studies for members with “end fork” conditions only, i.e. for members with free rotational and warping deformations at both ends. However, these specific boundary conditions are not clearly mentioned in the code.
In the study presented in this paper, a comprehensive series of numerical FEM analyses for the realistic lateral-torsional buckling behaviour of beam-columns with one-sided rotation and warping restraints was carried out and compared with the results based on the LTB resistance of the Eurocode, calculated with increased idealized buckling loads (Ncr, Mcr) that account for the end restraints. The most important results of this study are presented in this paper and the ultimate capacity is compared for two different beam-column design methods in Eurocode 3: the interaction concept (EN 1993-1-1, 6.3.3) and the general method (EN 1993-1-1, 6.3.4).
In addition, a simplified formula is given for the additional bi-moment at the end restraint, which is to be used for designing the welded joint. Finally, an improved LTB design curve (buckling reduction factor &khgr;LT) is presented, developed at the authors' institution, which may be used for the cases studied.

Underpressure in a tank with a fixed roof may arise in the final stage of its construction as well as during its usage. After completing the construction, when the tank is empty and all manholes and valves, through which air could get into the tank, are tightly closed, underpressure may arise in the case of a sudden change in the weather (air pressure and temperature), which is particularly dangerous in spring or summer. When the tank is in use, underpressure may arise if breather valves are obstructed, e.g. covered by snow during pumping out a product stored in the tank. Underpressure may cause extensive deformations of the shell or the roof of the tank. However, the shell undergoes deformation more frequently, since the roof has a stiff supporting structure.
This article presents stages of deformations of the tank shell and their development from the occurrence of the first deformation to either removal of the causes of underpressure or cracking of the steel shell and thus automatic equalization of pressure inside the tank with atmospheric pressure.

During high wind or earthquake action, high-rise multi-storey buildings respond with relatively large storey drifts. The building envelope, in this case a curtain wall, exposed to this in-plane shear resists the action with its drift capacity. This paper describes tests on two different configurations of a newly developed unitized curtain wall, “Qbiss Air” (QAir), using three different cyclic protocols. The protocols were derived on the basis of the serviceability limit state for regions with moderate to high wind and seismicity. The details and configuration influence the response of the system significantly, so the design of the structure can provide accurate information for the design of such systems.

The applicability of extended stiffened end plate (ESEP) connections used as link-to-column connections in eccentrically braced frames (EBFs) with long (flexural yielding) links is examined in this paper. A finite element method (FEM) is used for this purpose, based on a validated parametric FE benchmark. Analysing the numerical model of an ESEP connection designed to the recent seismic design rules for special moment frames reveals that the link-to-column connections of EBFs sustain more severe conditions than the moment connections of moment-resisting systems. The design approach implemented is examined and the results are discussed. The results demonstrate that ESEP connections can be used as a successful alternative for the link-to-column connections of EBFs and the system with this type of connection can achieve the required rotations for long or flexural links.

This paper looks at the problem of connection flexibility in steel-concrete bridge girders under moving loads. The static action of the load changing location on the structure is considered. An analytical model of the girder is used assuming strain discontinuity at the steel-concrete interface as a result of beam-plate partial interaction. The effects of a flexible connection are characterized by the proposed index defined on the basis of the internal forces in the girder. This index can be calculated during loading tests on the basis of the neutral axis position at the section of the girder considered. Numerical analyses show that values of the index characterizing beam-plate interaction depend on the position of the load on the structure and the function describing connection stiffness.

Many famous footbridges show have a spectacular, eye-catching design or functionality. They feature extravagant structures, large spans or outstanding locations and they are globally published and widely discussed amongst professionals and laymen.
However, there are smaller and simpler bridges, whose good and appropriate design, structural behaviour and sustainability can only be seen at the second look. While not having showy features they are beautiful, reasonable, efficient, sometimes trendsetting but always interesting enough to justify careful attention.
This paper presents five bridges - designed by schlaich bergermann partner, completed within the past few years - that are characterized especially by their apparent simplicity: a simple beam bridge in Backnang, three arch bridges in Dortmund, a prestressed concrete beam bridge in Hamburg, a two-span stress ribbon bridge in Schwäbisch Gmünd and a fixed-end beam bridge in Esslingen.

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