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Machine learning for design and analysis of steel frame halls The use of digital tools in design and construction processes increases efficiency, especially for recurring tasks and processes, such as the dimensioning of components or structures, which follow similar patterns. This paper develops an artificial intelligence (AI)‐based assistant for use in the pre‐design and design of steel frame halls as a prototypical co‐pilot. For this purpose, the necessary database of steel frame halls is first compiled from project archives of TRAGRAUM Partnerschaft Beratender Ingenieure mbB. This will be examined in the context of data analyses according to the decisive description parameters and similarities, so that finally suitable AI surrogate models for the prediction of the hall parameters are trained by means of regression analyses. Furthermore, an interface to the finite element program SOFiSTiK is implemented, which passes the predictions of the AI regarding the parameters of the steel frame halls to a parameterized input file and triggers the calculation and design. In the course of the calibration of the AI substitute models, in addition to the approximation qualities, possible safety margins to be provided are also discussed in the context of this article. This article shows that the prototypical co‐pilot for the preliminary design of steel frame halls could be successfully implemented. Furthermore the AI newly generated hall frames can be classified as stable with respect to the validation considerations. An outlook on future further developments of this approach as well as the transfer to other applications complete this paper. [ABSTRACT FROM AUTHOR]

Lateral torsional buckling of girders with rotational restraints – influence and application of the new rules in prEN1993‐1‐1:2020 This paper presents the results of a study that investigated the effects of the innovations introduced in the draft standard for the 2nd generation of EN 1993‐1‐1 for the lateral‐torsional buckling (LTB) verification of beams with I and H cross‐sections on the regulations for the calculation of the minimum stiffness of a rotational restraint to avoid LTB. In the first part of the paper, the background of the existing and new regulations is discussed together with previous proposals for adapting the definition of the minimum rotation bedding. Then, based on theoretical considerations and numerical calculations of the realistic load‐bearing capacity of rotationally restrained beams, it is shown that the new regulations for LTB in prEN1993‐1‐1 lead to very precise predictions of the load‐bearing capacity of rotationally restrained girders and beams, provided that rotational stiffness is also taken into account in the determination of the corresponding slenderness for LTB. In addition, it is shown that the currently valid specifications for the minimum rotational stiffness contained in the National Annex of DIN EN 1993‐1‐1 are also sufficiently accurate for practical use and do not contradict the newly introduced regulations for torsional buckling. The planned tightening of the regulations on the minimum rotational stiffness in prEN 1993‐1‐1, Annex D are thus shown to be unnecessary. [ABSTRACT FROM AUTHOR]

Investigation of an engineering model for the assessment of the seismic behaviour of large mobile equipment For large mobile equipment in seismically active regions, seismic stability is an essential and often decisive design criterion. The seismic behaviour of such large equipment is usually characterised by complex nonlinear types of behaviour (uplift, tilting and rocking), which are difficult to compute and analyse in practice. In this paper, a highly simplified engineering model is presented or developed step by step, which should be able to represent basic features of the typical behaviour of large mobile equipment transverse to the rail under seismic excitation. The typical rocking motion of the equipment, as determined in previous analyses, is to be reflected in the simplified model. The engineering model will be designed in such a way that it is able to reproduce qualitative statements about uplift and rocking or tilting as a function of incisive model parameters and seismic excitation. The dissipation mechanisms of the model are presented and seismic tilting spectra are generated using different approaches. The suitability and applicability of these approaches for assessing uplift and rocking tendencies for large mobile equipment is reviewed using representative series of bucket wheel machines and stackers as examples. In addition, parameters are determined for quantitative application to further large mobile equipment and the delimitation criteria of qualitative and quantitative applicability are compiled. [ABSTRACT FROM AUTHOR]

Damage equivalence factors for deck slabs of steel railway bridges According to EN 1993‐2, the fatigue verification of railway bridges can be based on internal forces due to the standard load model 71. These internal forces are to be multiplied by a dynamic coefficient Φ2 and a damage equivalence factor λ. In this paper, factors λ1 allowing for the damage effect of traffic on quadrilaterally supported plates with torsionally flexible supports at the longitudinal edges as encountered in single‐track railway‐brides in a span range between 10.0 and 27.5 m are derived for three standard traffic situations. The required damage equivalence factors λ are obtained from the factors λ1, considering the annual traffic volume and the requested service life. [ABSTRACT FROM AUTHOR]

Unexpected fatigue cracks at main girders of a railway bridge – strain measurements under service and analyses based on fracture mechanics At a steel railway bridge, erected and taken into service in 1960, fatigue cracks were detected at some transverse stiffener to web connections at the lower flange of the main girder. These findings were surprising, because this specific connection detail was suggested in previous national design standards for fatigue. The paper presents the comprehensive strain measurements under service to show the local stress field at the critical detail within the web plate of the main girder, indicating the well‐known phenomenon of distortion‐induced fatigue, but with unexpectedly high resonance‐like bending stresses in the web. Based on fracture mechanics analyses, with implementation of the measured strain/stress data due to local and global effects at the transverse stiffener connection, as well as the measured material properties (fracture toughness and crack growth parameters) the remaining fatigue life was analysed. The positive results allow an unrestricted train operation in the future. It also turned out, that the mixed‐mode effects must be taken into account and considering only mode I at the crack tip may lead to unsafe results. [ABSTRACT FROM AUTHOR]

Design model for headed studs as shear connectors under additional tensile loading Headed studs are primarily subjected to shear when used as shear connectors in usual steel‐concrete composite structures. Consequently, initial design rules for shear connectors in composite structures did not address tensile forces directly. In case of horizontally lying headed studs embedded in a thin concrete slab such as in composite bridges, the headed studs may be subjected to tensile forces. For horizontally lying studs, current design rules consider a possible failure caused by a tensile load due to pull‐out by specifying geometric boundary conditions. As a consequence, relatively long shear connectors are required, which lead to uneconomical or impractical embedment lengths of the shear connectors. As meanwhile European code rules for fasteners under shear and tension (EN 1992‐4) have been developed, the upcoming Eurocode 4 refers to them for the design of shear connectors under combined tension and shear in composite structures. The fastening technology allows a direct design for tensile loading for different failure mechanisms, considering the influence of the reinforcement and concrete strength. Following this idea, this paper presents a design model for shear connectors in steel‐concrete composite structures under additional tensile loading based on experimental and numerical investigations considering recent developments in fastening technology. [ABSTRACT FROM AUTHOR]

Transversal load introduction into unstiffened girder webs – interaction with shear force and bending moment and implementation in new Eurocode version Transversal load introductions into unstiffened girder webs are often used economic solutions in building structures, not directly covered in the current Eurocode. Within this paper an engineering design model, developed at TU Graz, is evaluated for cases with additional high shear forces and bending moments acting at the girder. The resulting load carrying behaviour, in cases of interaction between Fz & Vz & My, is presented, based on comprehensive numerical studies, also for girders which are susceptible to web buckling. Finally, the modified design model is presented, which will be part of the new Eurocode version prEN 1993‐1‐1. In addition, a more general solution is shown, which could also be implemented in the Eurocode in form of a national Annex. [ABSTRACT FROM AUTHOR]

Penstocks with multiple thrust rings – accurate forces at thrust rings due to constraining effects and comparison with a simple design model Thrust rings are a component of penstocks and have to transfer the longitudinal forces of the steel pipe to the surrounding rock mass. Longitudinal forces occur primarily due the pressure loads at valves or at pipe covers. Within this paper, the realistic load bearing behaviour of different penstocks geometries with multiple thrust rings is presented, including constraining effects due to internal pressure and temperature. Results are shown with and without friction effects between steel pipe and surrounding concrete and are based on numerical FE analyses. In addition, a simple 1D beam model (design model), developed by the authors, is presented. The forces at the thrust rings are compared between both models. It is shown that also for different load combinations the simple 1D beam model gives accurate results for practical application. The FE study also shows, that always the load combinations with the constraining effects due to internal pressure and temperature must be analysed – a superposition of the results of the individual load cases leads to misleading results. [ABSTRACT FROM AUTHOR]

Design and execution of membrane structures according to prCEN/TS 19102 This paper reflects the progressive development of the first European design standard for membrane structures. It will be published in future as CEN/TS 19102 "Design of tensioned membrane structures". In addition to design rules, it will also contain interim execution rules based on the design concept. The current status of the planned regulations in these two areas is presented in this article. [ABSTRACT FROM AUTHOR]

During an earthquake, steel frame buildings with bracings are prone to high absolute floor acceleration demands, thereby causing damage to acceleration‐sensitive non‐structural elements and building content. Inelastic deformations in steel bracings and/or their end connections often necessitate the use of capacity design rules to meet the life safety requirements established by seismic design standards. This paper presents an alternative steel frame building configuration where energy dissipation is mostly achieved through friction dampers acting as dissipative connectors between the floor diaphragms and the steel frame(s) with bracings. The dampers consist of friction pads made from composite materials which are not susceptible to galvanic corrosion. Physical experiments suggest that the friction pads are effective in dissipating the seismic energy through friction. Nonlinear response history analyses of a prototype 6‐storey steel frame building featuring friction dampers as dissipative floor connectors demonstrate that a) higher mode effects are mitigated; b) capacity‐design in the steel frame(s) with bracings is not imperative to ensure a uniform lateral drift distribution; and c) the seismic response variability in storey‐based engineering demand parameters is reduced remarkably compared with that of the conventional counterpart with rigid diaphragms. All‐in‐all, the alternative building configuration has high potential to minimize earthquake‐induced repairs over a building's service life. [ABSTRACT FROM AUTHOR]

Monitoring of the Theodor Heuss bridge in Düsseldorf – part 2: modelling and model improvements for a measurement‐based fatigue analysis Due to calculated deficits in the fatigue bearing capacity of the orthotropic deck, a monitoring system was installed at the Theodor Heuss bridge to measure strains at significant locations for one year. Part 1 of this paper describes the monitoring system and findings on the load‐bearing behavior resulting from the measured data. This second part follows with data‐based fatigue evaluations and the lifetime prediction. The basis of the evaluations is a structural model, which is calibrated based on two load tests in summer and winter. From this, transfer factors are derived, taking into account different load positions, which compensate the distance of the measuring points to the decisive design points. In this way, the measured stress range histograms are transformed into representative load spectra, which are finally used for the lifetime prediction. The evaluations show that further load reserves are available for most components and that a significant improvement is achieved compared to the recalculation. Only the corners of the floor beam cut‐out (cross girder tooth) still show significant deficits, which are also confirmed by the existing cracks. A decision on the future of the Theodor Heuss bridge, which depends on further factors, is currently pending. [ABSTRACT FROM AUTHOR]

When the water content is small, the strength and stiffness of loess is considerably high. But with the increasing of water content, the shear strength of loess decreases since the matric suction of unsaturated loess decrease. If loess is soaked in water for long time after reaching the saturated state and the linking intensity weakened, the loess would be prone to softening deformation, so as to the stress of the tunnel supporting structure, which will cause the decreasing of the stability and durability of the tunnel. Therefore, the in-situ monitoring of surrounding rock deformation and stress characteristics of supporting structure is very important and was carried out in the deep-buried tunnel in naturally water-rich loess in this paper. The time–space effect of tunnel surrounding rock deformation, mechanical response of primary support, and secondary lining were monitored and analyzed. The results indicated that the deformation of surrounding rock was quite large, and the reserved settlement was insufficient. The analysis and calculation of the surrounding rock pressure and the stress of the steel arch indicated that the primary supporting structure of the upper bench was unsafe, the arch-foot had a trend of bending deformation to the side of the tunnel′s inner contour, and the inverted arch had a trend of uplift. Through the analysis of the contact pressure and the stress of the secondary lining reinforced concrete, the sidewall had a trend to deform to a side of the tunnel′s inner contour due to squeezing of the surrounding rock. The inverted arch had a trend to uplift, indicating the significant change and redistribution of the groundwater and surrounding rock stress field. The stress and deformation of supporting structure were highly complex both in space distribution and time development. The research results could provide specific reference and guidance for the design and construction of deep-buried tunnels in naturally water-rich loess. [ABSTRACT FROM AUTHOR]

Simplified design of cast steel components under fatigue loads Theoretically, cast steel is ideally suited for use in structures subject to fatigue loads due to its high mechanical strength and virtually free shaping possibilities. However, the component resistance is determined by manufacturing‐related imperfections. Due to a lack of knowledge and the absence of easily applicable design approaches, the use of cast steel components is usually rejected or countered by the highest demands on manufacturing quality. This blanket choice is usually uneconomical and not necessary from a technical point of view, since even major casting defects do not necessarily reduce the performance of a component. In this paper, an easy‐to‐use design approach is presented, which allows the determination of manufacturing quality based on local stresses. The link between fatigue strength and allowable defect sizes is established by newly defined resistance categories. The component design is carried out by limiting maximum stress ranges, is based on established verification concepts, and is thus directly adapted to practical construction applications. Influences such as medium‐voltage dependence, shape tolerances, brittle fractures, stress gradients and interaction of neighbouring flaws are considered by reduction factors or additional conditions. [ABSTRACT FROM AUTHOR]

Appropriate local stress fields in crane runway girders due to wheel load This paper summarises the basis of design and further development of local stresses in crane runway girders. Moreover, three test series on crane runway girders in the laboratory are presented which lately have been conducted at Graz University of Technology. The following girders have been investigated: a hot‐rolled section with welded flat rail for light crane service, a welded box section for medium crane service and a welded I‐section with A 120 rail for heavy crane service. For all cases, the essential results are summarised and compared to additional finite element calculations and corresponding code regulations. Thus, the reader is able to assess the accuracy of the formulae for local stresses in crane runway girders. The presented latest findings will also be included in the second generation of EN 1993‐6, which is under development at the moment. [ABSTRACT FROM AUTHOR]

• A PQ control strategy and fault equivalent model of the IIDG. • An analysis and calculation model for multiple faults with IIDGs. • A novel systematic fault analysis and calculation method with IIDGs. • An iterative correction algorithm. The short-circuit characteristics of low-resistance grounded systems (LRGSs) under multiple faults have fundamentally changed because of the high penetration level of inverter-interfaced distributed generators (IIDGs). However, an analysis and calculation method for multiple faults (ACMMF) with IIDGs that is a standard basis for fault features, relay protection, safe evaluation and design of LRGSs is currently lacking. A novel systematic ACMMF is analytically proposed in this paper based on ideal transformer and multiport network theory. Based on the proposed ACMMF, composite networks under various fault conditions are established, which provides a straightforward presentation of fault current paths and equivalent impedance and simplifies the modelling procedure for fault analysis and calculation. Furthermore, to overcome the strong nonlinear inter-IIDG couplings, an iterative correction algorithm is proposed for accurate IIDG fault current calculations. Finally, the accuracy of the proposed method is verified by PSCAD/EMTDC simulation. The results show that the proposed methods have good adaptivity to different system structures, operation modes, fault types and flexible access of IIDGs. [ABSTRACT FROM AUTHOR]