bluuebunny/crossref_metadata_2025 huggingface dataset:
05.21: Bolted steel angles in compression: Influence of realistic end supports
Authors: Kettler Markus , Unterweger Harald
Published: September 2017

For compression members with primarily axial forces, steel angles with bolted connections are often used. Due to the eccentric connection on only one leg additional bending moments are acting on the member, leading to a complex load carrying behaviour with flexural and/or lateral torsional buckling phenomena. The paper mainly focuses on the presentation of the influence of realistic end support conditions at the gusset plates on the member capacity in compression.

The compression capacity of steel angles with bolted connections according to various test results from literature, a large series of sophisticated numerical analyses and common code regulations are presented in a unified form, using the normalized slenderness about the weak axis as basis. Thus, a direct comparison of about 300 laboratory tests with numerical results for bolted angle members is possible, whereby limit cases for the stiffness of the end support of the gusset plate (rigid or hinged) are considered. The systematic conducted numerical calculations show (beside the well‐known influence of one‐bolt or two‐bolt connections) a very high influence of the end support of the gusset plate. The significant difference in the compression member capacity between clamped and hinged support of the gusset plate is even more pronounced than the difference between one‐bolt and two‐bolt connections – a state of affairs that is either not, or only insufficiently, reflected in current design code regulations.

Even if the boundary conditions of the compression member are considered by using the corresponding ideal buckling capacity (based on a LBA calculation) for the calculation of, no single buckling curve seems to be appropriate to represent the load carrying capacity of the compressed member.
06.03: Dynamic increase factor for nonlinear static alternate path analysis of steel moment‐resisting frames against progressive collapse
Authors: Ferraioli Massimiliano , Lavino Angelo , Mandara Alberto
Published: September 2017

The paper investigates the dynamic increase factor to be assumed in the nonlinear pushdown analysis of seismically designed steel moment‐resisting frames as a consequence of sudden column removal. The influence of the fundamental parameters, as well as the effect of various design variables, such as the number of stories, the number of bays, the location of the removed column and the level of seismic design load were investigated. The dynamic increase factor was estimated by direct comparison of static analysis with full nonlinear dynamic analysis. Eventually, the values obtained were expressed as a function of the vertical displacement at the location of the removed column and then compared with the GSA formulation based on the ductility factor.
07.16: On the distortional buckling capacity of pallet rack uprights
Authors: Crisan Andrei , Kraus Matthias , Handabut Andreea
Published: September 2017

In nowadays commercial environment, the storage of goods on standardized pallets represent the standard for many companies. As a direct consequence, pallet rack storage systems have become an essential part in their intralogistics. Usual load bearing structures of storage systems consist of longitudinal and transversal frames. In longitudinal direction, along the aisle, the vertical distance between beams is varied function requirements. In transversal direction, usually the frame is a truss structure composed of uprights as chords, diagonals and struts.

For the load bearing structure of pallet rack systems, the uprights represent the main elements. Following a long optimization process to increase the load bearing capacity of cold formed elements, the critical load associated with local buckling was increased by introducing folds acting as longitudinal stiffeners. This approach solved local buckling problems but created the premises for another sectional instability, i.e. distortional buckling. The stability issue is further accentuated by arrays of holes along the length of the uprights. These holes enable the user to customize the shelf height, depending on storage requirements

Based on an extensive experimental program developed within the ACTEX laboratory (https://erris.gov.ro/ACTEX), the present paper presents the findings of a numerical study conducted for a heavy load pallet rack upright profile. The aim is the identification of stabilizing stiffness needed to prevent the development of distortional buckling. Based on the numerical results, a series of preliminary solutions are proposed to restrain distortional buckling and improve the cross sectional stability of pallet rack uprights.
07.18: Cold‐formed C‐sections encased in ultra‐lightweight concrete: Development of a Eurocode‐based design method
Authors: Hegyi Péter , Dunai László
Published: September 2017

A new direction of development in the field of light‐gauge building systems is when the load bearing elements made of cold‐formed steel (CFS) sections are encased in an ultra‐lightweight material. This material, apart from heat insulation and fire protection effects, can provide bracing effect to the CFS elements, too, therefore can increase the resistance against stability failures. Such lightweight material is the polystyrene aggregate concrete (PAC). Based on previous experimental results this paper develops design method for calculating local, distortional and global resistance of PAC‐encased CFS C‐sections. The proposed design method is based on the specifications of Eurocode, therefore applies the effective width method for calculating local buckling. The proposed procedure considers the effect of continuous bracing of PAC by replacing it with an elastic half‐space, similar to sandwich beam theory. Close form equations are derived to be able to calculate the effective width of plate elements by hand calculation. Distortional buckling is treated as buckling of an equivalent beam resting on elastic foundation, considering the additional stiffness provided by the infill material. The global flexural buckling failure modes of columns are dealt with separately using different mechanical models. Each calculation procedure was compared to existing experimental results in order to evaluate them.
07.19: Geometric imperfection measurements on cold‐formed steel channels: An approach using 3D non‐contact laser scanner
Authors: Selvaraj Sivaganesh , Madhavan Mahendrakumar
Published: September 2017

A 3D non‐contact laser scanning method to quantify the deviations in cold‐formed steel (CFS) channel sections (plain and lipped) is presented. The methodologies to segregate the different categories of imperfections from the deviations in the geometry of CFS member are also presented. A total of 13 different C‐sections with varying cross‐sectional parameters totaling to 78 specimens were studied. The nature of imperfections in the CFS members was found to correlate with the geometric properties such as slenderness ratios, torsional constant and plate slenderness. The bow and camber imperfection (global out‐of‐straightness) in the members is presented with respect to the minor and major axis slenderness ratios. A new combined global and cross‐sectional parameter (J/L) was introduced against the deviation due to twist of the CFS member. To predict the imperfection magnitudes based on their geometrical properties, a new set of expressions were suggested.
07.20: Application of the compound strip method in buckling analysis of cold‐formed steel built‐up sections
Authors: Khezri Mani , Abbasi Mandana , Rasmussen Kim J. R.
Published: September 2017

In this paper, the compound strip method is utilised and extended for the stability analysis of cold‐formed steel built‐up sections. The discrete fasteners are incorporated in the analysis such that they can be placed anywhere within the length of the member. A beam element with geometrical and material properties of the fastener is adopted to model the connection between the individual sections. The stiffness matrix terms for the connection element are derived and added directly to the global stiffness matrix of the considered built‐up sections. The proposed numerical technique is verified through various examples and the results are compared with the finite element solutions. The results obtained demonstrate that the developed technique can accurately and efficiently model the behaviour of cold‐formed steel built‐up sections. Furthermore, the influence of the fasteners properties, their longitudinal spacing and also the boundary conditions on the overall buckling behaviour of built‐up sections is examined through numerical examples. The simplicity of the proposed technique facilitates an extensive parametric study of cold‐formed built‐up sections including the search for optimal placement of fasteners and combinations of component sections in built‐up profiles.
08.02: Experimental research of multiple perfobond connectors for composite girders
Authors: Neto C. , Costa‐Neves L. F. , da S. Vellasco P. C. G. , Jordão S. , Ihaddoudene A. N. T.
Published: September 2017

Extensive research has been carried out in recent years focusing on the behaviour of innovative connectors for steel and concrete composite girders. Those elements exhibit large resistance and adequate behaviour under different load types, and at the same time are easy to fabricate and to erect on site. Among these types, the Perfobond connector or Perfobond rib, consisting of a perforated steel plate welded to the steel beam flange, has been extensively studied by numerous authors, due to its particularly convenient efficiency, behaviour and ductility characteristics.

Although many connector types have been studied in the past, few studies focused on the behaviour of groups of special connectors, a typical arrangement used in conventional headed stud connectors.

This paper focuses on the behaviour of multiple Perfobond connectors placed side‐by‐side on a steel girder and immersed in the reinforced concrete slab. This quite innovative arrangement enhances the resistance from a single connector classic layout, but the proximity to other connectors may significantly change the behaviour of individual connectors that interact with each other.

Fourteen push‐out tests on groups of Perfobond connectors were carried out at the Civil Engineering Department of the University of Coimbra, Portugal, while this paper reports and discuss the results.

The investigated variables were: the number of connectors, ranging from one (the basic arrangement) to three; the spacing between connectors; the transverse reinforcement within the connector's holes; and the concrete strength. The results are presented and discussed concentrating on the connector's structural response for shear transfer capacity, ductility and collapse modes. A comparative assessment of these properties focusing on the number of connectors and its spacing is presented and discussed, aiming at establishing preliminary conclusions about the behaviour of Perfobond groups. In addition, a brief comparison of the experimental results with existing analytical models for Perfobond connectors is also presented to establish the most convenient model for this particular geometry. Finally, some adapted models referred in the literature to cope with Perfobond groups are applied to the tested geometries and the analytical and experimental tests are compared and discussed.
08.09: Design of cold‐formed steel composite flooring systems with partial shear connection
Authors: Kyvelou Pinelopi , Gardner Leroy , Nethercot David A.
Published: September 2017

Recently conducted research has shown that the development of composite action within systems comprising cold‐formed steel beams and wood‐based floorboards is feasible, leading to substantial improvements in structural performance. Based on the findings from a numerical investigation into the degree of interaction that may be achieved and the resulting benefits that may be obtained by treating the floor as a composite system, proposals for the design of such systems have been devised. At the core of the proposals is the calculation of the attained degree of shear connection and the shear bond coefficient of the system − as a function of the properties of its components and connectors – leading to accurate predictions of moment capacity and flexural stiffness. The method, which has been developed based on the fundamental concepts of current design methods employed in Eurocode 3, Eurocode 4 and Eurocode 5, provides practical and accurate design rules for cold‐formed steel composite floors, which are suitable for incorporation into future revisions of the Eurocodes.
08.31: Analysis of the load transfer between materials in composite concrete encased steel columns loaded axially
Authors: Grzeszykowski Bartosz , Szmigiera Elżbieta Danuta
Published: September 2017

The analysis of the load distribution between steel and concrete parts of the composite concrete encased I‐shaped steel columns subjected to short‐term axial load is presented. The variable parameters were: two loading conditions − load scheme I (specimens loaded through the entire cross‐section simultaneously), load scheme II (specimens loaded only through the steel profiles protruded from the top end) and concrete class (C25/30 and C40/50). Obtained in the experiment longitudinal strains of both steel and concrete were used to compute the force transferred through the steel and concrete parts of the columns. To provide a reference level for the discussion on the results the analytical solution assuming the perfect bond between steel and concrete, Hooke's law for steel and the Rüsch formula for unconfined concrete were used. The force for which the stress in steel and concrete computed using the strain readings obtained from the experiment starts to deviate from the full bond analytical model predictions can be interpreted as the force for which the loss of adhesive bond occurs. Furthermore on the basis of the equilibrium of the infinitesimal cross section of a column, method for estimating the shear stress at which the debonding occurs is shown. The analysis showed that for columns under the load scheme I composite action of steel and concrete is in effect for the entire load range regardless of the concrete class. For elements under the load scheme II the composite action of both materials is in effect only up to a specific value of the force that changes along the height of the column. Presented method can be applied to composite steel‐concrete columns under any configuration of boundary conditions subjected to axial compression. Moreover it can be used to specify the area for which the shear connectors should be provided, to validate constitutive models of shear stress – slip behaviour that can be used is FEM analysis and to analyse adhesive bond properties also in columns made of another materials, for example reinforced concrete members strengthened with FRP sheets.
08.43: Composite effect of binding frames installed inside composite mega column (more than 1m in width)
Authors: Kang Ji‐Su , Ju Jeong‐Su , Hwang Seul‐Ki , Park Yong‐Pil , Yom Kyong‐Soo , Choi Sung‐Mo
Published: September 2017

Composite columns are increasingly used due to the construction of super‐tall buildings and large‐scale buildings. Studies on the shapes of and construction technologies for structural members using steel tubes are being conducted actively. Welded built‐up CFT columns previously developed and commercialized by the authors of this study (ACT‐1 columns) are structurally stable and economically efficient. However, the 1m limit in the width of the columns and their small interior spaces impose a difficulty in installing reinforcing materials and thus deteriorate the ease and efficiency with which they are constructed. This study suggests placing thick plates at the centers of the surfaces of the existing ACT‐1 column and installing a binding frame (binding frames) at the central thick plates to enhance the integrity and resist lateral pressure caused by concrete casting. Finite element analysis was conducted with the variables of the number and cross‐sectional size of the binding frame and the cross‐sectional size of the steel tube to estimate the structural behavior of the steel tubes. Hydraulic tests were conducted to analyze load‐displacement relations and identify the influence of the binding frames on the relations. The variables in the tests were the number and cross‐sectional size of the binding frame, welding details, column joint and the cross‐sectional size of the steel tube.
08.47: Experimental study of cross‐section shape and infill influence on CFST stub columns subjected to axial load
Authors: Hernández‐Figueirido David , Ibañez Carmen , Piquer Ana , Martínez‐Ramos Óscar
Published: September 2017

In this paper, the results of an experimental campaign on 12 concrete‐filled steel tubular (CFST) stub columns subjected to concentric load are presented. Different cross‐section shapes are considered in this campaign, i.e. oval, circular, square and rectangular as well as different types of concrete infill, i.e. normal, high strength or ultra‐high strength concrete, in order to study their effect on the ultimate capacity of the columns. Besides, the influence of the steel tube wall thickness is also analysed by including in the tests specimens with thin‐wall tubes, whose behaviour needs to be studied in depth.

The experimental program is designed so as all the tested specimens have equivalent cross‐sectional area in order to extract consistent conclusions. The ultimate capacity of each specimen is registered during the tests and a comparison of the shape effect based on this parameter is accomplished. Finally, the dependency of the failure modes on the cross‐sectional shape and type of infill of the specimens is carried out.
09.03: Size effect of as‐welded and post‐weld treated construction details under fatigue loading
Authors: Dürr André , Bucak Ömer , Roth Jakob
Published: September 2017

For the typical construction detail of the transverse stiffener is only given a geometric influence for the length of the welded stiffeners for fatigue design in the as‐welded state in the current version of Eurocode 3 part 1–9. A size effect for the plate thickness is not considered, although numerical calculations with the notch stress concept have shown that an influence of wall thickness is given. For the post‐weld treatment method “High Frequency Mechanical Impact Treatment” (HFMI) the known design recommendations are based only on experimental research programs with maximum plate thicknesses of 30mm. Hence, due to missing fatigue tests it is unknown if in addition a size effect for thick‐walled profiles should be considered for this typical construction detail in the fatigue design.

Therefore an extensive research program analyzing the size effect of thick‐walled profiles subjected to fatigue loadings for typical welded construction details was performed at the University of Applied Sciences Munich [1]. In the framework of the experimental research program fatigue tests on specimens with plate thicknesses up to 100mm on the construction detail of the transverse stiffener especially for high strength steel grades (HSS) were conducted. Besides investigations on specimens in the as‐welded state, the effect of the post‐weld treatment method HFMI was examined. Within this paper the results of this research program on the construction detail transverse stiffener is summarized and a conclusion regarding the size effect for thick‐walled profiles in the fatigue design for this detail is given.
09.04: Fatigue behaviour of the closed rib to deck and crossbeam joint in a newly designed orthotropic bridge deck
Authors: Wu Weijian , Kolstein Henk , Veljković Milan , Pijpers Richard , Vorstenbosch‐Krabbe Jos
Published: September 2017

Orthotropic decks are widely used in large span and movable steel bridges and the design is dominated by fatigue resistance. Closed rib to deck welded joints in the orthotropic decks are sensitive to fatigue loads and a number of fatigue cracks are reported in bridge inspections. For the design of new bridge decks, thicker deck plates are proposed for reducing stresses in fatigue sensitive locations like the conjunction of the deck plate, rib and crossbeam. Compared to the joints in span, the variation of stress at the crossbeam is larger due to the high stress concentration near the weld root. In this study, fatigue tests are carried out on a full‐scale orthotropic deck segment to study the initiation and propagation of fatigue cracks in the deck plate. Trapezoidal stiffeners are welded to a 20 mm thick deck plate and different welding methods are used in manufacturing the specimen. Various load levels are applied on the deck plate by hydraulic jacks. The strain gauges are attached both at the top and bottom of the deck plate in the vicinity of the expected crack paths. The strain history and distribution of strain ranges at the characteristic sections are analysed. An ultrasonic method, time‐of‐flight diffraction, is used to inspect the sizes of the cracks after testing. Comparison of the number of cycles that corresponds to a crack propagation is given in the hot spot S‐N curve figure. With a failure criterion of 10% strain range deviation, the fatigue strength scatter of the 20 mm thick deck plate is similar to that of the 12 mm deck.
09.05: Remaining fatigue life of steel railway bridges: Improved models for considering realistic behaviour
Authors: Kugler Paul , Unterweger Harald
Published: September 2017

Many steel railway bridges will reach the end of their scheduled design service life within the next years. One can also observe some bridges, considerably younger than their scheduled design service life, with insufficient remaining fatigue life and rarely cracks in structural elements. Mostly because of the early applications of the welding technology and sometimes insufficient consideration of fatigue effects, e.g. neglecting of high local secondary stresses. It is a great challenge and very expensive, if a couple of bridges have to be replaced in a short period. Therefore, it is important to have models for realistic fatigue verification to extend the service life.

The focus of this paper is to show different approaches – both on the load and the resistance side – to verify an extended service life of steel railway bridges. For example, the big potential of the use of real, measured stress spectra is presented, instead of the common approach according to the Eurocode. In addition, the application of the consequent Miner's rule results in another significant reduction of equivalent stress ranges for application of the fatigue strength curves of the Eurocode.

Furthermore, the simplified and conservative assumptions regarding the fatigue resistance in conventional assessment procedures according to the Eurocode (nominal stress approach) are compared with alternative concepts for typical welded joints. For example, the geometric (hot spot) stress concept, the effective notch stress concept and fracture mechanics. The Eurocode already allows the use of the geometric stress concept, but gives little guidance. The practical implementation of these concepts is shown for a representative detail of a steel bridge, considering a variety of geometries.

Fracture mechanics approaches are state of the art in mechanical engineering, but still relatively uncommon in civil engineering. These concepts allow for the explicit consideration of real or assumed “non‐detected” flaws or cracks in the component, thereby eliminating the need of an exact knowledge of the past load history, up to the considered defect size. It is shown that the fracture mechanics concept is suitable for steel bridges to determine the remaining fatigue life of critical details.

Finally, a multilevel framework is presented to give guidance for engineers to evaluate the service life of a specific steel railway bridge.
09.10: Shear damage evaluation of bolted steel joints
Authors: Ribeiro João , Santiago Aldina , Rigueiro Constança
Published: September 2017

The purpose of this study is to address a way of predicting the ductility capacity of steel joints. Recent research studies show that a joints’ ability to perform under elevated deformations, without fracturing, is a key factor in enabling mechanisms preventing collapse to be developed, and thus, improve the overall robustness of steel framed structures. This theme is becoming rather timely as building owners and insurers try to assess the collapse risk of their buildings, and the probability of a wide spread collapse if subjected to extreme events, either due to natural or terrorist causes. However, regarding this matter, current design code guidelines are limited to a prescriptive approach, by recommending a nominal tying force to be met, or quantifying a force that reproduces accidental scenarios, such as an impact of a vehicle, ships or helicopters, which do not address the overall behavior and performance of the structure.

This paper presents an evaluation of the shear damage state of a bolted steel joint. For that, it is necessary to establish the shear damage parameters that are required to numerically obtain the rupture of steel elements, allowing the prediction of the ductility of steel joints. Previous authors’ research has showed that a ductile damage model may be insufficient to capture its end‐plate fracture and to establish a joints’ rupture. Hence, this study looks forward to improve the damage threshold for smaller triaxial stress states, within the shear and compression zones.

In order to achieve this objective, a finite element model is developed and compared with real scale test results of a bolted steel joint under bending. The numerical model takes into account the strain softening of the material by means of a continuum damage mechanics approach and making use of the “element deletion” technique to approximate the fracture pattern of the studied joint. The analyses are carried out using the finite element software ABAQUS.
09.12: Assessment of old mild steel structures related to brittle fracture
Authors: Sieber Lars , Stroetmann Richard
Published: September 2017

In the safety assessment of old mild steel structures the verification of sufficient material toughness is important for the decision on necessary repair and reinforcement measures. Based on extensive fracture mechanics investigations the assessment methods in DIN EN 1993‐1‐10 [1] were developed. The determination of permissible element thickness for certain steel grades was derived and tabulated for welded structures made of steels according to DIN EN 10025 with predominantly high toughness's. This simplified method is not suitable for mild steel structures with holes for riveted or bolted joints. In this article, experimental and analytical studies of the brittle fracture behaviour of structures with holes made of old mild steel are presented. The results were carried out through various research projects at the Institute of Steel and Timber Construction of the Technische Universität Dresden and its cooperation partners (see, e.g. [2]).

The main topics are extensive material analyses to determine the fracture toughness in the brittle‐ductile transition region according to the Master Curve concept. The evaluations confirm that different grades of steel can be defined depending on the manufacturing process. Additionally, the newly obtained results will be compared to those from previous studies and existing correlations of impact and fracture toughness are checked for their suitability for old mild steels. Furthermore, the analysis of mechanical properties and metallography on components with punched holes to analyse the crack initiation of quasi‐static stressed components made of old mild steel are described.
09.16: Edge clamping effect on the fatigue resistance of an orthotropic steel bridge deck
Authors: Van Bogaert Philippe
Published: September 2017

Orthotropic steel decks are an excellent solution for long span bridges, except if the spreading of wheel loads through the pavement is poor. In the latter case they are heavily sensitive to fatigue cracking. The most critical locations of fatigue cracks are the connection of longitudinal stiffeners to the deck plate and the cutouts and cope‐holes in the webs of the transverse stiffeners. OSD with variable depth are seldom used, since the idea contradicts with one of the main assets to limit the bridge deck depth. However, in few cases variable depth may be meaningful as in the case of a railway bridge across river Dyle, recently built in Mechelen (Belgium). This 50 m span bridge consists of 2 lateral stubs of 1.55 m diameter connected by the OSD. The tubes are slightly bent to foster arch thrust action and rotated towards the bridge axis. In addition, the arch springs are encased in the concrete abutment. Due to this arrangement, the crossbeams are partially clamped in the lateral tubes of high torsion stiffness. The effect of the end clamping of crossbeams reduces the tension in the lower part of the crossbeam web, also near the outer cope holes, where the largest stress concentrations occur and fatigue resistance is the lowest. The reduction of the magnitude of these stress concentrations is significant and depends on the crossbeam span. However, the effect disappears if the crossbeam web is higher, thus confirming it is due to bending tension of the crossbeams. In addition, the influence length of crossbeams has been verified in the case of river Dyle bridge and complies well with Eurocode.
10.05: Experimental investigation on ferritic stainless steel post‐fire mechanical properties
Authors: Ho Wing Kei , Huang Yuner
Published: September 2017

Stainless steel has been increasingly applied in construction applications due to its mechanical, aesthetic and environmental advantages. Strength and stiffness reduce significantly when steel members are exposed to fire. However, previous researches have shown that part of strength and stiffness can be recovered after steel material is cooled down to room temperature. Understanding the post‐fire behaviour of stainless steel is necessary before its application to construction. Ferritic stainless steel, embedded with the advantages of high strength, good corrosion resistance and relatively low cost, has a great potential to be widely utilized as a construction material. Hence, an experimental investigation has been conducted to investigate the post‐fire mechanical properties and effects of cooling rates for ferritic stainless steel of type EN 1.4003. The experimental program consists of 34 coupon specimens, including 4 non‐fire‐exposed coupons and 30 heat‐treated coupons. The designed temperature of heat treatment is ranged from 24°C to 1000°C with the chosen cooling methods as cool‐in‐air, cool‐in‐air‐with‐fan and cool‐in‐water. A heat soak time of 20 minutes is selected for every round of heating. The influence of elevated temperatures and cooling methods on the post‐fire mechanical properties is presented in this paper. Mechanical properties of Young's modulus, yield strength, ultimate strength, strain at ultimate strength and Ramberg‐Osgood parameter obtained from test program are reported.
10.14: Fire design method for eccentrically loaded concrete‐filled steel tubular columns based on interaction diagrams
Authors: Espinós Ana , Albero Vicente , Ibáñez Carmen , Romero Manuel L. , Hospitaler Antonio
Published: September 2017

In this paper, a simplified design method for evaluating the fire resistance of eccentrically loaded concrete filled steel tubular (CFST) columns is presented. The developed method is based on the results of an extensive parametric analysis conducted in the framework of the RFCS European Project FRISCC (Fire resistance of innovative and slender concrete filled tubular composite columns) and is currently being evaluated by the Working Group SC4.T4 for its approval as the method to replace the current Annex H in EN1994‐1‐2, which was proved in previous investigations to be unsafe for slender columns.

The method presented in this paper is based on the provisions of Clause 6.7.3.6 of EN 1994‐1‐1 for room temperature design, using bending moment – axial force interaction curves specially built up for the fire situation. These interaction curves are obtained by considering several possible positions of the plastic neutral axis within the cross‐section, and determining the internal forces and moments from the plastic stress blocks, which results particularly challenging for CFST sections subjected to elevated temperatures, given the thermal gradient that occurs within the cross‐section. For simplifying this process, equivalent temperatures are proposed, which allow using a single uniform temperature for representing each part of the composite section. Appropriate coefficients are also proposed for evaluating the effective flexural stiffness for second‐order analysis at elevated temperatures. The influence of the cross‐section shape, load eccentricity and percentage of reinforcement is accounted for in the proposal.
10.28: Fire performance of concrete filled steel tubular columns with built‐in stirrups
Authors: WU Bo , ZANG Jian‐bo , Zhang Qiang
Published: September 2017

Two concrete filled steel tubular columns with built‐in stirrups (i.e., Specimens 1 and 2) and one control column (i.e., concrete filled steel tubular column without built‐in stirrups, Specimen 3) were exposed to the ISO834 standard fire, and fire behaviors of the three columns were investigated and compared with each other. The steel usage of Specimen 1 (2) (i.e., total weight of the steel tube and stirrups) was the same as that of Specimen 3 (i.e., weight of the steel tube). The distance between the stirrup's centerline and inner surface of the steel tube was 20mm for Specimen 1, and 50mm for Specimen 2. The height and outer diameter of all the three columns were, respectively, 3800mm and 320mm. The axial load applied to Specimens 1 and 2 was identical with that applied to Specimen 3. Test results show that when the steel usage keeps unchanged, the fire endurance of the concrete filled steel tubular column with built‐in stirrups is much longer than that of the column without built‐in stirrups. Finally, a finite element analysis (FEA) model was developed and verified against the experimental results, and a parametric study has been preliminarily performed to reveal the fire performance of the concrete filled steel tubular columns with built‐in stirrups.
10.31: Simplified analytical determination of the temperature distribution and the load bearing resistance of slim‐floor beams
Authors: Braun Matthias , Zaganelli Dario , Hanus Francois , Obiala Renata , Cajot Louis‐Guy , Peirce Anthony
Published: September 2017

This contribution presents an analytical method to determine the distribution of temperature within a steel section integrated into a concrete slab, which is subjected to a time‐dependent heat flux. The method developed is based on an analytical solution of the general heat equation for transient conduction simplified to be usable for the calculation of the load bearing resistance of the slim‐floor beam. This simplified analytical solution is validated by comparison against results obtained from numerical simulations. A possible extension of the developed method to fire protected sections is given.
11.16: Seismic performance evaluation of MRFS with dissipative continuous columns
Authors: Yan‐wen Li , Guo‐qiang Li , Fei‐fei Sun
Published: September 2017

The Dissipative Continuous Column (DCC) concept is proposed as a gravity load and seismic energy dissipating dual‐functional structural component. The proposed DCC is made up of two closely spaced continuous columns which are interconnected with replaceable steel strip dampers (RSSDs) over the height. It works in a way similar to pin supported coupled shear walls, but minimizes the construction invasive and ensure rapid return to occupancy after severe earthquakes. The innovative moment resisting frame (MRF) system with DCCs can also mitigate the inter‐storey drift concentration and reduce the soft storey failure risk significantly due to the contribution of large flexure stiffness of the DCCs. Based on the experimental test results, a simplified analysis model of the DCCs is developed for the design and seismic performance evaluation of the MRFs system with DCCs. The simplified analysis model consists of dual column and multiple zerolength equivalent elasto‐plastic springs with rigid end. Numerical models of a 4‐story conventional steel MRF and a 4‐story steel MRF with DCCs were set up using the proposed simplified model. Nonlinear Dynamic Time History Analysis were undertaken, and the results showed that the MRFs with DCCs can reduce the economic loss by limiting the structural damage in the replaceable steel strip dampers and mitigating both the maximum inter‐story drift ratio and drift concentrations.
11.23: Influence of the uniaxial material model of steel on the seismic response of steel structures
Authors: Bosco Melina , Ghersi Aurelio , Marino Edoardo M. , Rossi Pier Paolo
Published: September 2017

The model proposed by Menegotto and Pinto [1] is widely used to simulate the dynamic response of steel structures and steel bars of reinforced concrete structures. In 1983, Filippou et al. [2] highlighted a flaw in the original formulation of this material model. They observed that, if partial unloading takes place at strains lower than the maximum recorded value, the reloading path provides forces that are higher than those expected. Filippou et al. deemed that such errors were not particularly significant for reinforced concrete members and did not propose any modification to the analytical formulation of the model.

More recently, some authors have independently investigated this issue and highlighted that the above‐mentioned flaw may affect the prediction of the seismic response of steel structures. Thus, some modifications have been proposed [3–5] and implemented in OpenSees computer program.

In this study, the seismic response of a steel moment resisting frame and that of a braced frame are analysed by nonlinear dynamic analysis by means of the OpenSees program. For each structure, the stress–strain relationship of steel is separately modelled by means of the original formulation of the model by Menegotto and Pinto and by the modified versions proposed by Zsarnóczay and Budaházy [3], Kolozvari et al. [4] and Bosco et al. [5]. The seismic response predicted by the considered models is compared. Attention is focused on the moment–curvature time‐history at the ends of the members of the framed structure and on the axial force‐axial deformation time‐history of braces. Global response parameters are also considered in terms of the maximum storey drifts.
11.33: Performance evaluation of an innovative HCW system with Shear Dissipative Links
Authors: Das Rajarshi , Zona Alessandro , Vandoren Bram , Degée Hervé
Published: September 2017

This paper presents an improved approach to a newly suggested design procedure of an innovative Hybrid Coupled Wall (HCW) system. This system consists of a reinforced concrete (RC) shear wall with dissipative steel links and steel side columns, where the RC wall carries almost all the horizontal shear force while the overturning moments are partially resisted by an axial compression‐tension couple developed by the two side steel columns rather than by the individual flexural action of the wall alone. The design objective is to reduce or possibly avoid the damage in the RC wall while concentrating the seismic damage to the replaceable steel links which are shear critical, i.e. intended to fail in shear rather than flexure. This increases the energy dissipation ability of the whole system and thus improves its resistance towards seismic ground motion. This present piece of investigation also aims to bring clarity to some important points such as: definition of an efficient coupling ratio with or without uniform link distribution, lower and upper limits of the coupling ratio compatible with the assumed link distributions, relationship between the coupling ratio and the total building height. The proposed design procedure is applied to case studies considering various assumptions for the design parameters. The designed solutions are analysed through several nonlinear finite element models in order to evaluate the results of the design methodology and provide useful information on the ductility capacity of the proposed innovative HCW system for different coupling ratios and efficient energy dissipation characteristics of the shear links.
11.37: Hybrid tests of a full‐scale two‐story buckling‐restrained braced RC frame
Authors: Wu An‐Chien , Tsai Keh‐Chyuan
Published: September 2017

A novel implementation of buckling‐restrained braces (BRB) in new reinforced concrete (RC) frame construction is investigated. Seismic design and analysis methods for the use of the proposed steel cast‐in anchor bracket (CAB) as the connection for the BRB and RC members are investigated. The steel CAB is designed to resist the normal and shear forces transferred from the BRB in order to secure the seismic performance of RC buildings. In this study, a full‐scale two‐story RC frame with BRBs (BRB‐RCF) is tested using hybrid and cyclic loading test procedures. The BRBs are arranged in a zigzag configuration and designed to resist 70% of the story shear. The gusset design incorporates the BRB axial and RC frame actions, while the beam and column members comply with ACI 318‐14 seismic design provisions. When the inter‐story drift ratio for both stories reached 3.5%, the overall lateral force versus deformation response was still very stable. The hysteresis energy dissipation ratios in the four hybrid tests range from 60% to 94% in the two stories, indicating that BRBs can effectively dissipate seismic input energy. Test results confirm that BRBs enhanced the RC frame stiffness, strength and ductility, complied with performance‐based seismic design. No failure of the proposed steel CABs and RC discontinuity regions was observed in the tests. This study demonstrates that the proposed design and construction methods for the CABs are effective and practical for real applications.
11.43: Seismic performance of staggered steel plate shear wall systems in high rise buildings
Authors: Verma Abhishek , Sahoo Dipti Ranjan
Published: September 2017

Unstiffened Steel Plate Shear Walls (SPSWs) are used as the lateral load‐resisting systems in building structures. The energy dissipation mechanism of SPSWs is consisted of the tension yielding of web plates and the formation of plastic hinges at the ends of horizontal boundary elements (HBEs). High‐rise buildings experience the high overturning moments leading to the high axial demands in the vertical boundary elements (VBEs) of SPSWs. The presence of high axial forces in VBEs can cause a reduction in their flexural capacity resulting in the drift concentration or even soft‐story mechanisms in the lower storey levels during an earthquake event. Past studies have shown that a staggered arrangement of steel plates may help in reducing the force demand in VBEs. Two simple methods are investigated in this study to r b educe the VBE forces are (i) by increasing the width of the web plates and (ii) by staggering the web plates over the frame height. A 20‐story steel frame building has been considered as the study frame. Three types of systems are designed to study the effect of aspect ratio and staggering on the seismic behaviour of SPSW. Force‐displacement characteristic of SPSW used in the numerical model is validated with the test results. Both nonlinear static and dynamic analyses are carried out in this study. Axial and shear force demands in the VBEs are reduced for the study frame, while achieving the desired hinge mechanisms. Nonlinear dynamic analyses under twenty spectrum‐compatible design‐level ground motions exhibited that staggered steel plate shear wall systems reduced the inter‐story drift by about 50% with respect to their conventional counterpart.
I.11.68: Seismic behaviour of concentrically braced frames in the moderate seismicity context
Authors: Kanyilmaz A. , Castiglioni C.A. , Degée H.
Published: September 2017

There has been a large amount of research investigating the performance of concentrically braced frame (CBF) structures in the high‐seismicity regions. Indeed, most building codes are appropriately advanced for the design of these structures in the high seismicity context. However, although CBFs represent a very common structural solution in the low‐to‐moderate seismic regions, there is not enough experience and experimental evidence showing their performance in such context. Within the European research project MEAKADO (RFSR‐CT‐2013‐00022), this subject has been investigated deeply by means of experimental and numerical activities. The objective of the MEAKADO was to study an intermediate way of design to reach a sufficient safety by means of a reduced but controlled amount of ductility in the structural system. This article summarized the results of the full‐scale tests conducted within MEAKADO, which investigated the behavior of CBFs in the low‐to‐moderate seismicity context. Tests focused on the secondary frame action, contribution of the compression diagonal in X‐braced frames and ductility provided by standard bolted bracing connections.
12.11: Experimental and numerical studies on Q690D welded Box‐section columns under cyclic loading
Authors: Suwen CHEN , Xing CHEN , Yan‐Bo WANG , Zhili LU , Guo‐qiang LI
Published: September 2017

To evaluate hysteretic performance of Q690D high‐strength steel (HHS) welded box‐section columns, cyclic tests and numerical studies have been carried out. Firstly, cyclic loading tests were performed on two box‐section Q690D HSS welded columns with nominal axial compression ratio of 0.35. Failure modes were observed as elastic‐plastic local buckling of plate. The hysteretic curves and skeleton curves of the test specimens were produced and show that the tested columns have good energy dissipation capacity. It also shows that second order effect cannot be neglected for HHS welded columns. Then a finite element model has been built to simulate the cyclic loading tests. Comparison of numerical and test results verified the effectiveness of the built numerical model, which can then be used for further parametric analysis.
12.16: Numerical investigation of the local buckling behaviour of high strength steel circular hollow sections
Authors: Toffolon Andrea , Taras Andreas
Published: September 2017

The introduction of high‐strength steel (HSS) hollow sections with yield strengths of fy=690 MPa and beyond in the construction sector is currently made more difficult by a lack of knowledge on the specific local and local+global buckling behaviour of slender HSS cylindrical hollow‐sections. With rising yield strength, buckling phenomena become more relevant. Eurocode 3 design provisions classify CHS as “slender \ class 4” at a diameter to thickness ratio of D\t=90·∊2, with ∊2=235\fy. For HSS with fy=690 MPa and beyond, the majority of cold‐formed and many hot‐finished CHS will be class 4 and should be designed accordingly. However, no straightforward rules for the design of class 4 HSS CHS are found in EC3. This paper discusses initial numerical studies on the specific local buckling behavior of HSS CHS sections. The study represents the initial steps in the recently initiated RFCS research project “HOLLOSSTAB”, during which new design rules for HSS hollow sections are developed on the basis of an “Overall Interaction Concept” (OIC). This concept – similarly to the Direct Strength Method (DSM) used in North America for the design of cold‐formed steel open cross‐sections – makes use of the results of (numerical) linear buckling analyses (LBA) for the whole member to determine the slenderness and consequently an “overall” buckling reduction factor. The paper discusses how this approach fits into the general framework of buckling design checks for cylindrical structures, discusses existing rules and their implications for HSS CHS, shows numerical results and introduces initial design proposals based on the OIC approach.