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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]

Free‐form reinforced concrete, prestressed concrete and composite components: Calculation of cross‐section values A resource‐efficient use of concrete as a construction material can be achieved by adapting the individual shape of a component under consideration to the stresses that occur and by arranging composite construction materials (e. g. reinforcing steel, prestressing steel or structural steel) in suitable areas of the component. Due to the advancing digitalisation in the construction industry, for example in the context of Building Information Modeling, computer‐aided 3D modelling methods are increasingly being used in the planning of structures. These allow engineers to design components in free form. In reinforced concrete, prestressed concrete and composite construction, the design of such components is currently still associated with great effort. In the context of the development of a practical method for the calculation of free‐form concrete components, this paper presents a CAD‐integrated method for the calculation of cross‐section values. Cross‐section values are required as an essential calculation basis when real, three‐dimensional structural components are treated using simplified calculation theories, such as the beam theory. In this paper, the mathematical and numerical fundamentals of a method for the calculation of cross‐section values of free‐form concrete, reinforced concrete, prestressed concrete and compound components are presented. The calculation method is based on flat geometric regions described by Non‐uniform rational B‐Spline tensor product surfaces, which can be extracted from solid models, for example. [ABSTRACT FROM AUTHOR]

Modelling of the CUBE's TWIST shell This paper gives an overview of the main procedures prepared during the phase of the project development within the field of numerical modelling and design. The roof shell elements represent itself twisted shape that together with complicated structurally demanded inner structure forms quite complicated configuration for the concrete volumes as well as for the used reinforcement. Therefore, custom developed numerical method was required to be prepared. For that, the software solutions Rhinoceros 3D and Grasshopper 3D were used as the main algorithmic environment. The paper additionally gives an insight of important aspects required for production of the formwork components, thermal insulation, biaxially oriented carbon reinforcing grids and other parts of the load‐bearing shells. Finally, the paper gives an idea how was established a collaboration with partners of the CUBE project in particular in the field of structural analysis. [ABSTRACT FROM AUTHOR]

Increase of technical lifetime of infrastructures based on semi‐probabilistic considerations One of the most important measures in the discussion on improved sustainability in construction is to extend the service life of our structures [1]. Therefore, intensive research is conducted with regard to changing environmental conditions as well as external load effects for structures and new materials and their impact on the production and operation of infrastructures. Already now, according to [2], changes in the kinematics of the degradation mechanisms can be observed. In particular, changing environmental conditions (exposures) can accelerate but also slow down the degradation of materials and structures. These understandings of the degradation processes, but also the improved knowledge of the geometry and effective mechanical building material properties, should be effectively transferred into engineering practice for the assessment of structural reliability and remaining service life [3]. This paper presents how the elements of reliability analysis can be combined with the elements of in‐depth testing and monitoring procedures to periodically evaluate the degradation processes due to changing environmental conditions and new building materials. Subsequently, the remaining service life can be continuously updated with the help of semi‐probabilistic partial safety considerations. [ABSTRACT FROM AUTHOR]

Experimental investigation on the effect of static system and load arrangement on the shear resistance of beams with low amounts of shear reinforcement In this paper, an experimental investigation on the shear behaviour of beams with low amounts of shear reinforcement and different static systems is presented. Four simply supported beams under concentrated loads, ten cantilevers and three simulated continuous beams under uniformly distributed loads were tested. The shear reinforcement ratio was varied between 0 (without shear reinforcement) and 2.0 times the minimum shear reinforcement according to EC2. The test results show a significant influence of the static system and the loading type on the crack pattern and ultimate load of the beams tested. While a reinforcement level below the minimum shear reinforcement has almost no influence on the shear resistance of simply supported beams under concentrated loads, a very low shear reinforcement leads to a significant increase in the shear capacity of beams under uniform distributed loads. The crack pattern, however, remains unchanged compared to beams without shear reinforcement where shear failure is characterized by a single critical shear crack. The test results were also compared with design and standard specifications. The comparisons show possible improvement potentials in the currently applied models. [ABSTRACT FROM AUTHOR]

Double‐headed studs as shear and punching reinforcement – Current status and outlook Double‐headed studs have been established for decades as a very effective punching shear reinforcement because these reinforcement elements, which are optimized for shear and punching loads, combine a particularly high anchorage performance with a practicable installation on site. In this paper, an overview of current usability and applicability verifications for double‐headed studs in Germany is given. Afterwards, the currently valid design and construction rules for the use of double‐headed studs as shear reinforcement as well as punching reinforcement are summarized. Finally, the next Eurocode 2 generation 2023+is looked at, with excerpts presenting some significant innovations in the future integration of double‐headed studs into the shear and punching rules. [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]

Influence of the arrangement of the punching shear and composite reinforcement made of L steel plates on the load‐bearing capacity The CLIXS punching shear and composite reinforcement system consists of L steel plates with one or two connected stirrups made of reinforcing steel. It is possible to increase the load‐bearing capacity by more than twice the load‐bearing capacity without punching shear reinforcement. The experimental investigations described in the paper were carried out on square slab cut‐outs with a length of 2.8 m and a thickness of 18 and 25 cm. The load‐bearing capacity as a function of the number of uniform arranged L steel plates was determined based on 17 experiments. For this purpose, test specimen with 6 L steel plates up to 36 L steel plates in the first three perimeters were investigated. In addition, 10 test specimen with different sized areas without L steel plates were tested. The areas without L steel plates were between 25 % and 75 % of the area within the first three perimeters. The use of stirrups with a diameter of 8 mm instead of 6 mm was investigated using two test specimens. [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]

Shape optimisation of eccentrically loaded columns – theory and experimental verification. In shape optimisation, the external shape of the structural component is adapted to the predominant force flow. In this way, large load increases can be achieved with the same material use, or high material savings can be achieved with the same load‐bearing capacity. In this paper, a shape optimisation for eccentrically loaded columns is presented, where the bending stress results from a frame effect of the load‐bearing system. This is the case, for example, in edge columns of typical reinforced concrete skeleton structures, as they are usually used in residential and commercial buildings. The shape optimisation method presented in the article can be applied to columns with an arbitrary ratio of a moment‐normal force loading, provided that a material failure occurs. Results for shape optimisation in the case of a stability failure have already been published separately for centrically pressed columns. The optimisation itself is carried out iteratively on a column segmented over the height under the criterion of achieving a uniform stress state in the component. With the help of an experimental check on 3.3 m high columns, the selected calculation and optimisation method could be verified. In addition to the failure loads, the concrete strains and the deformation behaviour were also analysed and evaluated at selected points of the specimen. [ABSTRACT FROM AUTHOR]

Punching shear in irregular flat slab systems – Recommendations for modeling and design The punching shear verification is often the decisive verification in design due to the concentrated load introduction. Moreover, uneven shear stress distributions often occur in the punching shear area as result of irregular flat slab systems or eccentric loads. In structural design it is often questionable, how a non‐uniform shear stress distribution can be considered with acceptable effort. The direct determination of the shear stress distribution along the control perimeters using FE methods is not explicitly excluded in the current Eurocode 2 but is also not described in more detail. This gives considerable freedom in design for the structural engineer, but also ambiguities for interpreting the results. In this paper, FE approaches for determining the factor β or for directly considering the non‐uniform shear stress distribution are presented and analyzed based on an application example. Finally, recommendations and modelling advice are given for the pragmatic and, as far as possible, realistic determination of factor β for consideration of unbalanced moments. [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]