The structural response of Insulating Glass Units (IGUs), formed of glass plates sealed by perimeter metal spacers entrapping a gas, is strongly influenced by the complex interaction between the ...glass plates and the gas, as well as by the structural coupling of the plates through the spacers. The former effect, called “load sharing”, depends on the flexural stiffness of the plates and the pressure variation of the compressible gas due to applied actions. The more accurate and direct model to evaluate the load sharing is the recently proposed Betti’s Analytical Method (BAM) (soon included in the new Eurocode on structural glass), which allows to evaluate the IGUs response under the most various support conditions and external loads. In this paper, the BAM model is revisited, and the result obtained by means of conjugate BAM-numerical analyses are carefully validated by means of comparison with the results of experimental tests. In particular, the results of an extensive experimental campaign, performed on Double GUs (DGUs) subjected to line-distributed and concentrated loads, both at the environmental and at high temperature, are presented. To properly account for the influence of geometric parameters on the DGU response, elements with various aspect ratio, glass thickness and cavity thickness have been considered.
•The validation of BAM model for DGUs was made.•Complete analytical/numerical/experimental analyses for DGUs were carried out.•Structural effects of variations of gas temperature were considered.•“Load sharing” mechanism under linear/concentrated loads was studied.•Results were presented in terms of temperature/load–deflection responses.
Abstract
Der Arbeitskreis „Baugruben“ der Deutschen Gesellschaft für Geotechnik (DGGT) veröffentlicht seit 1968 regelmäßig Empfehlungen für die Berechnung, Bemessung und Konstruktion von ...Baugrubenumschließungen. Der vorliegende Beitrag gibt einen Überblick über die aktuellen Diskussionen im Arbeitskreis. Im vergangenen Jahr erfolgte in der Hauptsache die Mitwirkung bei der Kommentierung der Entwürfe des neuen Eurocode 7. Ein weiterer Schwerpunkt war die Überarbeitung der EB 52 „Tragfähigkeit von Steifen“.
Translation abstract
Report of the working group for recommendations on excavations: current and future works
The working group for excavations of the German Geotechnical Society (DGGT) has since 1968 regularly published recommendations for analysis, design and construction of excavations. The present report provides an overview of current works of the working group. In the reporting period, the focus is on the participation in commenting on the drafts of the new Eurocode 7 and the design of struts.
It has been recognized that the shear capacity of old bridges can play a crucial/key role in evaluating their structural safety. Determination of the shear capacity of critical cross‐sections ...presents a much greater challenge than the assessment of their bending capacity.
Due to abovementioned problems, the shear capacity of shorter reinforced concrete bridges with T‐beams has been evaluated with various models. Four different models were examined, the currently valid Eurocode 2, draft of the new version of Eurocode 2, the currently valid Eurocode 8‐3 and the model corresponding to modified compression field theory (MCFT). According to all the models, the capacity of deck of existing reinforced concrete bridge was calculated. This bridge was previously inspected and the actual amount and shape of the shear and bending reinforcement was determined.
The results obtained with different models were compared and the typical parameters which influence the shear capacity were analyzed. The results in terms of shear capacity show that different models can give quite different results for the same bridge.
•Tests of eccentrically loaded column bases allow an analysis of the influence of moment-shear interaction on the punching shear capacity.•A more brittle failure is observed for column bases with ...larger shear slenderness whereby increasing load eccentricities positively affect the ductility.•Innovative measurements allow the continuous measurement of inner concrete strains close to the column revealing new insights on the punching failure of column bases.•The slab deformations are significantly affected by load eccentricities due to a skewing rotation.•Current design approaches reveal further potential for optimizing coefficient β to allow for more progressive design approaches in the future.
In the past, the punching shear behavior of centrically loaded column bases has been predominantly investigated even though eccentric loads frequently occur in engineering practice. To consider this corresponding uneven shear stress distributions around the column, many design approaches define coefficients to increase the acting load. Due to the limited test data for eccentric punching tests, an assessment of the design approaches is not reliably possible. To fill this gap of experimental test results, four centrically loaded and fourteen eccentrically loaded punching tests were conducted to analyze the effects of systematically graded load eccentricities.
The tests reveal a significant influence of load eccentricity on the punching shear capacity and the load-bearing behavior. With increasing eccentricity, the crack formation shifts to the higher loaded side going along with an incompletely developed punching cone. Innovative measurements of the strains in the slab allow to analyze the circumferential multi-axial stress state inside the concrete. In contrast to centrically loaded column bases, this compression ring does not fully develop under eccentric loads. Based on these measured tangential strains, an experimental approach for describing the influence of the load eccentricity on the punching shear strength is derived and compared with the design approaches of Eurocode 2, Model Code 2010 and the stable version of the next generation of Eurocode 2. Overall, the results indicate optimization potential for more advanced design provisions of column bases with eccentric loads.
This paper focuses on the assessment of the behaviour of Concrete Filled Steel Tube (CFST) columns with square/rectangular cross-section, made with Rubberized Concrete (RuC), under flexural loading. ...The study aims to evaluate the differences between this type of composite members and typical CFST members made with standard concrete (StdC), namely in terms of the influence of the rubber aggregate replacement ratio on member strength, ductility, and energy dissipation capacity. The experimental campaign comprised the testing of 16 square members, 12 RuCFST and 4 StdCFST, and 4 rectangular RuCFSTs. A number of parameters were investigated, namely the cross-section slenderness (i.e., the width-to-thickness ratio of the steel tube), the aggregate replacement ratio (i.e., the percentage of sand aggregate of the concrete mixture that is substituted by rubber particles), axial load level and lateral loading type. The test results are compared with the member capacities obtained with the application of Eurocode 4. The results show a minimal influence of the type of concrete infill on the monotonic and cyclic behaviour of the members and also allow concluding that the European code is conservative in predicting the capacity of the specimens. Furthermore, the results obtained demonstrate that the cross-section slenderness has an important role on the behaviour of these members. Nonetheless, the requirements pertaining this parameter that are currently defined in Eurocodes 4 and 8 can be relaxed.
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•Experimental assessment of the flexural behaviour of square/rectangular rubberized CFSTs is presented•Influence of concrete typology, cross-section slenderness and lateral loading regime on the flexural response of CFSTs is presented•Square/rectangular CFST and RuCFST test specimens exhibited a ductile behaviour, both under monotonic and cyclic loading•Test results point to a possible relaxation of the cross-section slenderness limits defined in Eurocode 4 and 8.
EUROPEAN CODE DEVELOPMENTS Hicks, Stephen J.; Schäfer, Markus; Couchman, Graham
ce/papers,
February 2023, 2023-02-00, Letnik:
6, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The second generation of Eurocode 4 has been developed through several project teams that report to CEN TC250 Subcommittee 4 (CEN/TC250/SC4) ‘Design of composite steel and concrete structures’, which ...is chaired by Dr Graham Couchman. Given that work on the revised version of Eurocode 4 is nearing completion, this paper presents a selection of the changes that will be included, together with some of the technical challenges that needed to be overcome. Finally, further enhancements that might be considered worthy for inclusion within future editions of this standard are presented.
An offshore aluminum floor structure made from inverted T-shaped beams and a transversely stiffened deck was investigated experimentally and numerically. The deck assembly contained weld-connected ...extruded profiles with a closed trapezoidal stiffener and flat plating, which constituted the beams' top flange. A bending test was designed to produce a state of pure axial compression perpendicular to the stiffeners in the deck without the influence of transverse loading on the deck. The compressed floor deck developed buckling deformations where the deck profiles/stiffeners deflected elastically with alternating upward/downward buckling bows between the floor beams, occurring at an average membrane compression stress of 30 N/mm2 in the deck plate. Ultimately, the average membrane stress was 54 N/mm2, and the deck stiffener deflections were >10 mm. The compressive deck plate stresses gradually redistributed to the regions near the webs of the floor beams, where failure occurred by inelastic buckling of the deck plate. FE simulations accurately reproduced the bending resistance of the floor structure, the observed buckling forms and displacements in the deck, and the strain and stress distributions in the deck plate. The existing design provisions for compressed transversely stiffened plates are insufficient and provide capacities less than half of that from the experiment.
•An experiment for a stiffened floor deck in transverse compression was presented.•Stiffener deflections and deck plate buckling occurred in the specimen.•Stress redistribution and post-buckling capacity were observed.•Modeling options for the stiffened deck and various capacity models were studied.•Capacity predictions by various methods were found conservative.
Research on stainless steel structures has primarily focused on the structural response of individual members, whilst the response of joints has received far less attention to date. This paper ...reports for the first time full-scale tests on stainless steel beam-to-column joints, subjected to static monotonic loads, whilst the companion paper reports numerical studies on similar connection typologies to the ones studied herein. The joint configurations tested include one flush and one extended end plate connection, two top and seated cleat connections, and two top, seated and web cleat connections of single-sided beam-to-column joints. All connected members and connecting parts including bolts, angle cleats and end plates are in Grade EN 1.4301 stainless steel. The full moment-rotation characteristics were recorded for each test and the experimentally derived stiffness and moment resistance for each joint was compared to the codified provisions of EN1993-1-8. It was verified that the connections displayed excellent ductility and attained loads much higher than the ones predicted by design standards for carbon steel joints.
•The papers report for the first time experimental results on full-scale stainless steel beam-to-column joints.•Stainless steel joints are shown to possess excellent ductility and high strength.•Current design standards are assessed and found overly conservative in the strength prediction of stainless steel joints.•Current design standards do not accurately predict the observed failure mode.
•Axial performance of ultra-high strength CFST columns is presented.•Measures to improve ductility are provided.•Confinement effect should be ignored for calculating axial resistance.•Modified ...Eurocode 4 method is applicable to ultra-high strength CFST columns.
The use of high strength concrete and steel have significant advantages for composite members subject to significant compression as in the cases of high-rise buildings. Current design codes place limits on the strengths of steel and concrete due to limited test data and experience on the behaviour of composite members with the high strength materials. To extend their applications, a comprehensive experimental program has been carried out to investigate the behaviour of concrete filled steel tubes (CFSTs) with high- and ultra-high- strength materials at ambient temperature. This article presented some new findings on the axial performance of 56 short CFSTs. High tensile steel with yield strength up to 780MPa and ultra-high strength concrete with compressive cylinder strength up to 190MPa were used to prepare the CFST test specimens. The key issue is to clarify if the plastic cross-sectional resistance could be used at ultimate limit state as for CFSTs with the normal strength materials. To address this, experimental and analytical methods were adopted where the test results were compared with the predictions by various design codes world widely, and design recommendations were therefore proposed so that the prediction methods could be safely extended to the short CFSTs with the high- and ultra-high- strength materials.
The main objective of the research presented in this paper is to investigate the flexural behaviour of concrete filled steel tube (CFST) columns of circular cross-section, made with rubberized ...concrete (RuC). A second objective is to identify behavioural differences between this type of composite members and typical CFST members made with standard concrete (StdC), namely in terms of the influence of the rubber aggregate replacement ratio on member strength, ductility, and energy dissipation capacity. The paper describes the preparation and development of an experimental campaign, involving the testing of 16 circular specimens, 12 RuCFST and 4 StdCFST. The definition of the test campaign considered a number of parameters, namely cross-section slenderness, aggregate replacement ratio, axial load level and loading type. A special device was developed as part of an innovative testing setup, aimed at reducing both the cost and preparation time of the specimens. This paper also describes the comparison of the test results with design provisions from Eurocode 4. The test results show a marginal influence of the type of concrete infill on the monotonic and cyclic behaviour of the members and also allow concluding that Eurocode 4 is conservative in predicting the capacity of the tested specimens. Moreover, it is found that the cross-section slenderness does not have a significant influence on the monotonic and cyclic behaviour of the specimens, pointing out for the possible relaxation of the cross-section slenderness limits currently specified in Eurocodes 4 and 8.
•The flexural behaviour of Concrete Filled Steel Tube is investigated.•A comparison is made between the test results with the design provisions from Eurocode 4.•Marginal influence of the type of concrete infill on the monotonic and cyclic behaviour•Eurocode 4 is conservative in predicting the flexural capacity of circular CFST.•Cross-section slenderness does not have a significant influence on the monotonic and cyclic behaviour.
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