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Fire resistance of cold-formed steel columnsSteel Construction3/2016190Completed Phd theses

Kurzfassung

Keine Kurzfassung verfügbar.

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Simon, Pavel; Hrdlicka, Libor; Dráb, Ales; Zverina, VojtechA composite dowel bridge in the Czech Republic - Development, optimization and implementation of a railway bridgeSteel Construction3/2016191-199Articles

Kurzfassung

The floods in the Czech Republic in the last few decades have resulted in a significant number of bridges having to be rebuilt. Unfortunately, the work meant long-term traffic closures for railway bridges, coupled with significant costs for renovation and for providing alternative transport services. As a result, the minimum clear headroom above the design flood level required for new bridges and for reconstructing existing bridges has been increased. This initiated a search for new approaches to designing individual parts of bridge crossings, aiming to comply with the stricter conditions. The research aims to decrease costs in comparison with the costs of raising the finished grade level of the railway, especially at places where adjacent sections such as railway stations etc. are connected.

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Berthellemy, Jacques; Schavits, David; Erre, CharlotteCrossing motorways under traffic without intermediate piersSteel Construction3/2016200-206Articles

Kurzfassung

The European research programme SBRI attempted to reveal the costs caused during the service life of a bridge - direct costs for the bridge owner as well as indirect costs for users. The principal results of SBRI should make it possible to take better account of the true costs of a central pier by considering the risks in the construction phase and those that may threaten the highway overpass during its service life.
CEREMA has developed two economic solutions to reach the objective of avoiding the central pier:
1) The solution implemented at Ko Wé Kara in New Caledonia is a steel-concrete composite tied arch bridge with innovative and economic details:
- innovative radial hangers made of welded plates, and
- innovative reinforcement against accidental impact of over-height vehicles.
2) One other possible solution is the composite steel-concrete gantry bridge. The European research programme PRECOBEAM allowed the use of tests and experimental projects to finalize a new system of connection to lower the cost of this type of structure: a strip along which the cutting line of the steel dowels is made in a clothoid shape (CL), which improves the fatigue resistance. CEREMA introduced this innovation in its research programme.
A composite structure can take various forms. It can associate, for instance, the steel web of a beam directly with a concrete flange. It can also constitute a composite deck with a bottom plate stiffened by connecting CL-shape indented strips. An outstanding project of this type in New Caledonia is described in detail. Of course, this type of bridge is an integral bridge and the article includes some recommendations for the design and construction of integral bridges.

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HISTWIN_PLUSSteel Construction3/2016206News

Kurzfassung

Keine Kurzfassung verfügbar.

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Dias, Vincent; Odenbreit, ChristophInvestigation of hybrid steel-glass beams with adhesive silicone shear connectionSteel Construction3/2016207-221Articles

Kurzfassung

Glass is used in current construction applications mostly as a façade element, its structural role being only rarely exploited, despite its significant resistance to in-plane compression. A steel-glass composite beam was built to investigate a hybrid steel-glass assembly and its loadbearing behaviour. To fulfil this objective, the existing types of steel-glass connection were evaluated, which allowed the possibilities offered by adhesive jointing to be highlighted. The selection of the adhesive, detailed in the present article, constituted a crucial aspect. An excessively soft connection does not transfer the shear loads between the glass and steel adherends, whereas an excessively stiff connection leads to failure of the glass. A two-component structural silicone was chosen and its properties were assessed with the help of an intensive test programme. As a result of this programme, a new quasi-incompressible hyperelastic material law was developed in order to represent the silicone elastomer behaviour. Numerical simulations were conducted in parallel to large-scale four-point bending tests on the adhesively bonded steel-glass composite beams. The aims were, on the one hand, to assess the bending stiffness of the steel-glass composite beam and, on the other, to validate the numerical simulations to conduct parametric studies.

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Steau, Edward; Keerthan, Poologanathan; Mahendran, MahenWeb crippling capacities of rivet fastened rectangular hollow flange channel beams under one flange load casesSteel Construction3/2016222-239Articles

Kurzfassung

A new rivet fastened rectangular hollow flange channel beam (RHFCB) was proposed using an intermittently rivet fastening process as an alternative to welded beams. The rivet fastened RHFCB allows greater section optimisation and flexibility in designing suitable combinations of web and flange widths and thicknesses for many industrial applications. In the industrial applications of rivet fastened RHFCBs as flooring, roofing or modular building systems, their flanges will be fastened to supports, which will provide increased capacities. However no research has been conducted to investigate the web crippling capacities of RHFCBs with flanges unfastened and fastened to supports under one-flange load cases. Similarly the applicability of current design rules for cold-formed steel sections are not suitable for rivet fastened RHFCBs. Hence to address these issues, an experimental study was conducted to investigate the web crippling behaviour and capacities of RHFCBs based on the new AISI S909 standard test method. This study included rivet fastened RHFCBs with flanges unfastened and fastened to supports under End One Flange (EOF) and Interior One Flange (IOF) load cases. Tests with flanges fastened to supports showed that web crippling capacities increased by 39 and 5 % for EOF and IOF load cases. Comparisons of experimental web crippling capacity results with predictions using the current AS/NZS 4600 and AISI S100 design standards showed that web crippling design equations are conservative for rivet fastened RHFCBs with flanges unfastened and fastened to supports under EOF and IOF load cases. Hence new equations are proposed to determine the web crippling capacities of rivet fastened RHFCBs. This paper presents the details of this web crippling experimental study of rivet fastened RHFCB sections and the results.

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Mirambell, Enrique; Bordallo, Jordi; Real, EstherTorsion and its interaction with other internal forces in EN 1993-1-1 - a new approachSteel Construction3/2016240-248Articles

Kurzfassung

This paper presents and clarifies the treatments included in EN 1993-1-1 [1] relating to checking the resistance of steel cross-sections under torsion and its interaction with other internal forces. Specifically, the origin of the formulations for shear-torsion interaction, which has not been found in the literature, is presented. Furthermore, a very simple formulation based on the expressions used for shear-torsion interaction is developed in order to take into account bending-warping torsion interaction for symmetrical I-sections (IP and HE steel profiles). Such a formulation overcomes the overly conservative approach given in EN 1993-1-1 [1] for class 1 and class 2 cross-sections (plastic and compact cross-sections). Finally, a rigorous method for determining the bending resistance of cross-sections is proposed considering the interaction with shear and torsion. The proposal is well suited to the concept of cross-section class and is perfectly consistent with the approaches set out to consider bending-shear and bending-warping torsion interactions.

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Helbig, Thorsten; Riederer, Jochen; Kamp, Florian; Oppe, MatthiasFree-form on every scale - "Tornado" roof structure for Bory Mall, Bratislava, SlovakiaSteel Construction3/2016249-354Reports

Kurzfassung

The Bory Mall Shopping Centre, designed by the Italian architect Massimiliano Fuksas, is a mixed use development located on the outskirts of Bratislava, Slovakia.
The roof to the shopping mall's central plaza is a free-form steel gridshell. The concept for its shape is consistent from the footprint to the shape of the grid nodes. The gridshell is assembled from standard rolled steel hollow sections but uses the freedom created by individually shaped CNC-milled grid nodes to achieve a smooth transition between high slenderness at the bottom and the necessary stiffness at the top.
Working in close collaboration with Massimiliano Fuksas Architects, Knippers Helbig provided support for the development of the roof structure right from the start of the project and rounded off their services by providing detailed design of the free-form central “Tornado” façade grid nodes, which were fabricated and built by Metal Yapi.

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World Steel in Figures 2016 is availableSteel Construction3/2016254News

Kurzfassung

Keine Kurzfassung verfügbar.

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Schueremans, Luc; Furtado, Ana ClaudiaFRISOMAT - steel innovator in cold-rolled buildingsSteel Construction3/2016255-258Reports

Kurzfassung

Keine Kurzfassung verfügbar.

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Euro Space Center at Libin-TransinneSteel Construction3/2016258News

Kurzfassung

Keine Kurzfassung verfügbar.

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ECCS news: Steel Construction 3/2016Steel Construction3/2016259-263ECCS news

Kurzfassung


Events:
The Pacific Structural Steel Conference 2016 / WINERCOST'17 /P Eurosteel 2017

Announcements: In Memoriam / Numerous reaction and testimonies have been received / Steel Construction Day 2016 in Belgium / Steel Construction Day 2016 in Norway
Technical Committees (TC) activities

TC news: Activities of ECCS TC6 „Fatigue and Fracture” / News from ECCS-TC 11 „Composite Structures” / Annex A - Membership / News from ECCS TC16 „Wind Energy Support Structures”

Other ECCS news: ECCS Meeting 2016 / EUROPEAN STEEL BRIDGES AWARDS CEREMONY

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Announcements: Steel Construction 3/2016Steel Construction3/2016264Announcements

Kurzfassung

Keine Kurzfassung verfügbar.

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Contents: Structural Concrete 3/2016Structural Concrete3/2016Contents

Kurzfassung

Keine Kurzfassung verfügbar.

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Hordijk, DickOld and new meet at the 2017 Maastricht fib Symposium!Structural Concrete3/2016307-308Editorials

Kurzfassung

Keine Kurzfassung verfügbar.

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von Greve-Dierfeld, Stefanie; Gehlen, ChristophPerformance based durability design, carbonation part 1 - Benchmarking of European present design rulesStructural Concrete3/2016309-328Technical Papers

Kurzfassung

The paper reports on a benchmark of European deemed-to-satisfy rules for exposure class XC (carbonation exposed structural members). The benchmark of the descriptive rules was carried out following the probabilistic design approach for carbonation-induced corrosion developed in [1] and adopted in fib bulletin 34: Model Code for Service Life Design (2006) [2] and fib Model Code for Concrete Structures 2010 [3], respectively. To perform a representative study, three groups of European countries were selected, representing different parts of Europe, south (Spain, Portugal), middle (Netherlands, Great Britain and Germany) and northern Europe (Denmark, Norway). Reliability ranges for carbonation-induced depassivation of rebar were calculated for “favourable” and “unfavourable” design situations in exposure classes XC2, XC3 and XC4 [4]. In each design situation the deemed-to-satisfy rules of selected countries were followed. The probabilistic calculations were mainly based on short-term carbonation data. However, some calculations were also based on long-term observation. The latter was implemented for independent validation purposes. The calculated reliability ranges are very broad and in some “unfavourable” situations, the deemed-to satisfy requirements do not guarantee the required limit state (LS) arget reliabilities for the particular exposure. In “favourable” situations less stringent demands would have been sufficient.

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Gehlen, Christoph; Osterminski, Kai; Weirich, TimHigh-cycle fatigue behaviour of reinforcing steel under the effect of ongoing corrosionStructural Concrete3/2016329-337Technical Papers

Kurzfassung

This paper presents the results of the corrosion fatigue behaviour of profiled reinforcing steel bars. Cyclically loaded rebar was simultaneously exposed to different corrosive environments - moderate to severe corrosive environments simulating XC or XD/XS exposure. Corrosion was configured naturally without any external polarization. Rebar was exposed to the corrosive solutions either directly or, when embedded in concrete, indirectly. In this latter case, corrosive agents penetrated towards the steel surface through an open crack. Low frequency was applied to enable extended corrosion periods. The potential drop method was utilized to detect and quantify the crack initiation and crack growth of the rebar. Using this method it was possible to determine the ratios between the number of cycles to crack initiation and the cycles to failure. Based on this method, the Nini/NF ratios were almost always between 0.8 and 0.9 - values that are similar to ratios determined for rebar tested in air (reference). This indicates that the fatigue life of rebar in carbonated concrete or concrete containing chloride is strongly dependent on crack initiation and less on crack growth. The S-N curves derived from the corrosion fatigue tests deviate significantly from the curve that was measured during the reference fatigue tests (tests in air). The S-N curves of rebar tested under corrosion fatigue load were linear, with a slope that was much steeper than the slope of the reference rebar tested in air.

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Prudente dos Santos, João Pedro de Oliveira Dias; Crémona, Christian; Campos da Silveira, António Paulo; de Oliveira Martins, Luís CaladoReal-time damage detection based on pattern recognitionStructural Concrete3/2016338-354Technical Papers

Kurzfassung

Structural health monitoring (SHM) can be defined as the process of developing and implementing structural damage detection strategies. Ideally, this detection should be carried out in real-time before damage reaches a critical state and impairs structural performance and safety. Hence, it must be based on sensorial systems permanently installed on the target structures and on fully automatic detection methodologies.
The ability to detect damage in real-time is vital for controlling the safety of old structures or for post-retrofitting/post-accident situations, where it might even be mandatory for ensuring a safe service. Under these constraints, SHM systems and strategies must be capable of conducting baseline-free damage identification, i.e. they must not rely on comparing newly acquired data with baseline references in which structures must be assumed as undamaged.
The present paper describes an original strategy for baseline-free damage detection based on the application of artificial neural networks and clustering methods in a moving windows process. The proposed strategy was tested on and validated with numerical and experimental data obtained from a concrete cable-stayed bridge and proved effective for the automatic detection of small stiffness reductions in single stay cables as well as the detachment of neoprene pads in anchoring devices, requiring only a small number of inexpensive sensors.

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Zhao, Yuxi; Zhang, Dawei; Shen, Shijun; Ueda, TamonAxial loading capacity of concrete-jacketed RC columns with pre- and post-corrosion damageStructural Concrete3/2016355-364Technical Papers

Kurzfassung

The main objective of this study is to investigate the effect of pre- and post-jacketing corrosion and loading damage on concrete-jacketed reinforced concrete (RC) columns under uniaxial loading and to develop a methodology for predicting the corresponding compressive strength. The pre- and post-damage involved preloading up to 50 % of the peak load of the core column, an electrochemical process to accelerate the migration of chlorides from an external electrolyte into the test columns and a wetting-drying cycle process with a controlled current to speed up the corrosion of the steel reinforcing bars in the test columns. Uniaxial loading tests were performed to determine the structural performance of the concrete-jacketed columns with and without corrosion damage. The failure mode and load-displacement and load-strain responses of the test columns were recorded, and the related mechanisms are discussed. A model capable of evaluating the compressive strength of unjacketed or jacketed RC columns with and without corrosion damage was then developed. The analytical approach considered the effect of reinforcement corrosion on the effective loadbearing area of the concrete and the confinement effect of the stirrups. The analytical results agree well with the experimental results, indicating the reliability and effectiveness of the models developed.

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Debernardi, Pier Giorgio; Taliano, MaurizioAn improvement to Eurocode 2 and fib Model Code 2010 methods for calculating crack width in RC structuresStructural Concrete3/2016365-376Technical Papers

Kurzfassung

The analysis of the mechanical behaviour of a reinforced concrete tie subjected to a monotonic loading in the stabilized cracking stage is performed here by way of a theoretical general model that considers the effect of the so-called Goto cracks (secondary cracks). It is shown, in particular, that the average bond stress along the transmission length depends not only on the concrete strength as assumed by the fib Model Code for Concrete Structures 2010, but also on reinforcement ratio and bar diameter. In this regard, tabulated theoretical values of the average bond stress are proposed as a function of the aforementioned parameters. Moreover, the secondary cracks reduce the effect of tension stiffening on the relative mean strain. On the basis of the main results obtained with the general model, some improvements are suggested for the calculation methods proposed by fib Model Code 2010 and Eurocode 2 concerning the average value of the bond stress and taking into account the influence of the secondary cracks on the mean deformation. An improved calculation method is therefore performed. Finally, the theoretical results of crack spacing and crack width obtained with the general and improved methods are compared with experimental data obtained from extensive research on RC ties.

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Visintin, Phillip; Oehlers, Deric J.Mechanics-based closed-form solutions for moment redistribution in RC beamsStructural Concrete3/2016377-389Technical Papers

Kurzfassung

When it comes to the efficient design of reinforced concrete beams and frames, moment redistribution is used to: reduce the absolute maximum magnitude of the moment in the critical region, equalize the critical moments on either side of interior columns and fully utilize the capacity of the non-critical regions of a member. Although important, historically, moment redistribution has proved to be difficult to quantify due to the complexity of quantifying hinge rotations. Although numerous empirical expressions exist for plastic hinge lengths, i.e. the length over which the ultimate curvature can be integrated in order to give hinge rotations, a comparison with a global dataset yields poor results. Using a recently developed mechanics-based moment-rotation approach, it is possible to quantify the moment-rotation characteristics of reinforced concrete hinges. In the tension region, the approach applies partial interaction theory directly to simulate the mechanisms associated with slip of the reinforcement relative to the surrounding concrete as cracks widen, whereas in the compression region, partial interaction shear-friction theory is used to describe the formation and failure of concrete softening wedges. It is shown how the moment-rotation approach explicitly allows for the size dependency. Furthermore, mechanics-based solutions for moment redistribution are then derived and it is shown how these can be simplified at the ultimate limit state for use in the design office.

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di Prisco, Marco; Martinelli, Paolo; Dozio, DanieleThe structural redistribution coefficient KRd: a numerical approach to its evaluationStructural Concrete3/2016390-407Technical Papers

Kurzfassung

Structures made of a material with a very high standard deviation, such as fibre-reinforced concrete, exhibit an exceptionally safe prediction of the maximum bearing capacity when this is derived from characteristic values identified by means of small specimens. This is emphasized when the structures are characterized by high redundancy. In this regard, two reference tests representing two extreme situations are considered: a) simply supported unnotched full-scale beams characterized by a statically determinate loading scheme and b) full-scale slabs on the ground characterized by a statically indeterminate loading scheme. The Italian standard and, more recently, the fib Model Code for Concrete Structures 2010 have introduced a coefficient (structural redistribution factor) that is able to take into account the reduced variability of mechanical bearing capacity when associated with a large volume involved in the failure process and/or when the structure is able to redistribute stresses significantly, thus favouring the average rather than the minimum strength. A numerical procedure taking into account the expected heterogeneity of the mechanical characteristics in the structure is introduced for the first time to evaluate the redistribution factor.

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Atta, Ahmad; Zaher, Fahmy; Etman, EmadStructural performance of continuous RC slabs strengthened in negative moment regions with a mineral-based compositeStructural Concrete3/2016408-424Technical Papers

Kurzfassung

An experimental programme was proposed and carried out to assess the effectiveness of the mineral-based composite (MBC) technique for the flexural strengthening of negative moment regions in continuous reinforced concrete slabs. In addition to the testing of the two reference specimens, the experimental programme included the testing of nine continuous RC slab specimens with different strengthening techniques, namely, using ordinary steel bars and MBC material. This experimental programme was conducted to study the failure modes, the load-deflection behaviour and the failure loads.
Furthermore, we present and describe a comparative study between the two strengthening techniques, namely, steel reinforcing bars with MBC or steel bars with epoxy mortar. Based on the experimental results presented, both strengthening techniques for continuous slabs are evidently efficient. In this study the measured results for the average crack spacing were compared with the limits stipulated in CEB-FIP code 1990 and the failure load calculations were extended with an analytical approach based on the ultimate theory for the failure load calculation. In conclusion, the results obtained from the analytical model are in agreement with the experimental results.

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D'Antino, Tommaso; Triantafillou, Thanasis C.Accuracy of design-oriented formulations for evaluating the flexural and shear capacities of FRP-strengthened RC beamsStructural Concrete3/2016425-442Technical Papers

Kurzfassung

Fibre-reinforced polymer (FRP) composites have been employed in the last few decades largely for the strengthening and seismic retrofitting of existing reinforced concrete (RC) structures. Several studies are available in the literature and different analytical models have been proposed for evaluating the FRP contribution in strengthened RC elements. This paper analyses the accuracy of analytical models widely used for evaluating the flexural and shear contributions provided by the FRP. Some of those models are included in design guidelines. In particular, the analytical models for evaluating the FRP strain at intermediate crack-induced debonding failure are analysed. The accuracy of each formulation is assessed comparing the analytical provisions with the experimental results collected from two databases, one for bending and one for shear. The results obtained show that most of the analytical flexural models achieve a good level of accuracy and only a few models provide inadequate results. A new formulation proposed for evaluating the FRP shear contribution is shown to be generally conservative, which comes at the expense of accuracy.

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Lee, Deuck Hang; Han, Sun-Jin; Kim, Kang SuDual potential capacity model for reinforced concrete beams subjected to shearStructural Concrete3/2016443-456Technical Papers

Kurzfassung

The shear resistance mechanisms of a reinforced concrete (RC) member with shear reinforcement can be divided into the contributions of the concrete and the shear reinforcement. The shear resistance mechanisms of concrete can be further divided into the shear resistance of the intact concrete in the compression zone, the aggregate interlock in the cracked tension zone and the dowel action of the longitudinal tension reinforcement. The shear demand curves and potential shear capacity curves for both tension and compression zones have been derived in this study, with the assumption that the shear failures of RC members are dominated by the flexural-shear strength. The shear capacity model was also proposed on this basis. In the proposed model, the crack width and the local stress increase in reinforcement were calculated based on the bond behaviour between the reinforcement and its surrounding concrete. Further, the crack concentration factor was introduced to consider the formation and propagation of the critical shear crack that developed from the flexural cracks. The results of a total of 1, 018 shear tests were collected and compared with the analysis results provided by the proposed model. It was demonstrated that the proposed model provides a good estimate of the shear strengths of RC beams.

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