bluuebunny/crossref_metadata_2025 huggingface dataset:
10.36: Advanced numerical analysis of steel, concrete and composite structures under fire conditions
Authors: Pires Dalilah , Barros Rafael Cesário , Lemes Ígor José Mendes , Rocha Paulo Anderson Santana , da Mota Silveira Ricardo Azoubel
Published: September 2017

High temperature in common fire causes changes in physical characteristics and mechanical strength of the materials used in the structures. In both steel and concrete, such characteristics deteriorate during the exposure to fire, and the structure load capacity and stiffness are reduced significantly with the increasing temperature. This work is on advanced analysis context of structures under fire, and it aims to develop a computational system for analysis of steel, concrete and composite structures in fire situation, based on the finite element method. The use of advanced analysis as a methodology of analysis/design of structures has various advantages. Among these advantages, there is the capture of strength limit and stability of a structural system and its members directly, without the need for separate verification of each member capacity. This provides a more realistic analysis and determine adequately the performance of a structure in a real fire. To achieve the objective, the CS‐ASA (Computational System for Advanced Structural Analysis) is used and expanded to advanced analysis of structures in fire situation, taking advantage of existing features and adding new ones. Two new modules were created: CS‐ASA/FA (Fire Analysis) and CS‐ASA/FSA (Fire Structural Analysis). The first aims to determine the temperature field in the cross section of the structural elements by FE thermal analysis in permanent and transient regimes. The second was created to perform the inelastic second‐order analysis of structures under fire considering the refined plastic hinge method coupled to strain compatibility method. The adopted numerical methodology is described and, for a more comprehensive validation of the implemented modules, various structural systems under fire are analyzed.
11.01: Shaking table tests on cold‐formed steel building sheathed with gypsum panels
Authors: Macillo Vincenzo , Bucciero Bianca , Terracciano Maria Teresa , Pali Tatiana , Fiorino Luigi , Landolfo Raffaele
Published: September 2017

Shake table tests are particularly indicative to assess dynamic properties and seismic response under earthquakes in the case of a new building structure. In last years the University of Naples was involved in the research project named “Energy Efficient LIghtweight‐Sustainable‐SAfe‐Steel Construction” (Project acronym: ELISSA), which was devoted to the development and demonstration of enhanced prefabricated lightweight CFS skeleton/dry wall constructions with improved antiseismic properties. Within the ELISSA project, in order to evaluate the global building seismic response, shake table tests on a full‐scale two‐storey building, named “ELISSA mockup”, were carried out. The mockup was tested in two different conditions. In the first condition the mockup included mainly structural components of walls, floors and roof, whereas in the second condition it was completed with all nonstructural components. This paper presents the testing program and the obtained results in terms of dynamic identification (fundamental period and damping ratio) and earthquake performance (global lateral response, building drift, acceleration amplification, diaphragm response, and observed damage).
11.04: Examination of the Canadian provisions for the seismic stability of steel structures
Authors: Breton Nicolas , Tremblay Robert
Published: September 2017

This article presents the seismic stability provisions of the CSA S16 design standard for steel structures in Canada. These provisions include notional lateral loads as well as lateral load amplification for P‐delta effects evaluated at maximum lateral displacements including inelastic response. The impact of these provisions is examined through nonlinear response history analyses performed on single‐degree‐of‐freedom models representing steel braced frames for buildings varying from 1 to 15 storeys in height. Buckling restrained braced frames and concentrically braced frames are investigated. The structures are located in eastern and western seismic regions of Canada to account for the difference in anticipated ground motion signature. For each location, firm ground and soft soil conditions are considered. The results show that current code provisions for seismic are sufficient to ensure stable seismic response of structures located in eastern Canada where ground motions are richer in high frequencies. Structural collapse was observed for one third of the structures located in western Canada. Most failures occurred for taller buckling restrained braced frames subjected to long duration subduction interface earthquakes. Collapse also took place for low‐rise concentrically braced frames.
11.06: Application of hybrid simulation for the evaluation of the buckling response of steel braced frame columns
Authors: Imanpour Ali , Leclerc Martin , Siguier Romain , Tremblay Robert
Published: September 2017

Hybrid simulation is an economical structural testing technique in which the critical part of the structure expected to respond in the inelastic range is tested physically whereas the rest of the structure is modelled numerically using a finite element analysis program. This paper describes the application of hybrid simulation for steel I‐shaped columns in Multi‐Tiered Braced Frame (MT‐BFs) structures. A full‐scale W250×101 column part of a two‐tiered concentrically braced frame was physically tested while the rest of the frame was numerically analysed using the OpenSees finite element program. The development and main challenges of the hybrid simulation are first described and the main findings of the hybrid simulation are then presented. The test results show that the testing technique is an effective experimental tool to generate reliable data on column stability limit states. Furthermore, the results from the hybrid simulation confirmed the findings of previous numerical simulations to assess the seismic response of columns in steel braced frames.
11.10: Probabilistic theory of plastic mechanism control
Authors: Castaldo Paolo , Nastri Elide , Piluso Vincenzo , Pisapia Alessandro
Published: September 2017

This work aims at the development of an advanced method for the seismic design of Moment Resisting Frames (MRFs) based on the evaluation of the probability of failure in the attainment of a collapse mechanism of global type in case of stochastic frames. Therefore, the method presented constitutes the probabilistic version of the Theory of Plastic Mechanism Control (TPMC) already successfully developed for frames with deterministic material properties. With reference to MRFs whose members have random values of the yield strength, the failure domain derives from all the possible collapse mechanisms. Under the point of view of structural reliability analysis, the term “failure” means the attainment of a collapse mechanism different from the global one. The design requirements normally needed to prevent undesired collapse mechanisms are probabilistic events within the framework of the kinematic theorem of plastic collapse. At each event corresponds a limit state function representing a hyperplane in the space of the random variables, so that the failure domain is a manifold surface resulting from the intersection of the hyperplanes corresponding to the limit states of the single events. Because of plastic hinges in frame's members are common to many different mechanisms, the single limit state events are correlated. Therefore, by applying the theory of binary systems and taking into account that, from the structural reliability point of view, the limit states are events located in series, the probability of failure is computed by means of Ditlevsen bounds.
11.11: Rocking damage‐free steel column base with friction devices: Development of advanced 3D finite element models in Abaqus
Authors: Dimopoulos Christoforos A. , Freddi Fabio , Karavasilis Theodore
Published: September 2017

Column bases are critical components of a seismic‐resistant steel building as they transfer gravity and lateral forces to the foundations. This paper focuses on the finite element (FE) modelling of a rocking damage‐free steel column base, which uses post‐tensioned high strength steel bars to achieve self‐centering behavior and friction devices to provide energy dissipation capacity. Contrary to conventional steel column bases, the monotonic and cyclic moment‐rotation behavior of the column base can be easily described using simple analytical equations. An advanced three‐dimensional FE model for the column base is developed in ABAQUS. The techniques used to overcome convergence issues in numerical simulations as well as the constitutive laws for the nonlinear behavior of materials and friction interfaces are described in detail. The FE model provides results that are in very good agreement with the results from the analytical moment‐rotation equations. The FE model results are also used to validate a simplified numerical model in OpenSees. Moreover, the FE model provides results that help to assess the level of stress concentration in critical areas of the column base and to evaluate a step‐by‐step design procedure that ensures damage‐free behavior, self‐centering capability, and adequate energy dissipation capacity.
11.12: Derivation of the cyclic behaviour of components in bolted end‐plate beam‐to‐column joints using FEM
Authors: Augusto Hugo , Castro José Miguel , Rebelo Carlos , Simões da Silva Luís
Published: September 2017

In this paper a detailed procedure to isolate the main dissipative components of bolted end‐plate beam‐to‐column steel joints under cyclic loading, and to identify their force‐displacement relationships by analysing the stress and deformation fields in the FE models is proposed. The objective is generalise the component method prescribed in EC3‐1‐8 [1] extending it to reversal loading. It is worth noting that the proposed procedure is quite flexible, and that the assessment of the forces will depend on the idealized mechanical model, although the procedure can be easily adapted to any compatible mechanical model. A detailed numerical model of end‐plate bolted joints is developed using the ABAQUS FE package, capable of representing the various joints components and the several sources of nonlinearity associated to them. The numerical models were previously validated against monotonic and cyclic experimental test data obtained by the research team and with data available in the literature. The proposed procedure is then applied to the developed numerical models, of representative double‐extended end‐plate joints, the force‐displacement relationships are extracted and compared with those obtained from EC3–1–8.
11.13: Hybrid seismic protection system: Buckling restrained brace of nano‐micro composite magneto rheological damper
Authors: Vulcu Cristian , Dubină Dan , Popa Nicolae , Vekas Ladislau , Ghiţă Gheorghe , Sireteanu Tudor , Borbath Istvan , Oprescu Radu
Published: September 2017

The ongoing research project SEMNAL‐MRD (Seismic Protection of Engineering Structures through Dissipative Braces of Nano‐Micro Magneto‐Rheological Fluid Dampers), aims to develop a seismic protection system employing a semi‐active structural control system. The most promising devices appear to be magneto‐rheological (MR) dampers. The current paper presents a case study related to the seismic response of multi‐storey frames equipped with dampers. The paper also describes the typology and working principle of MR dampers. Furthermore, the innovative solution for the current MR damper of composite nano‐micro MR fluid of passive/semi‐active control is presented in terms of technical solution and principle scheme. The experimental and numerical investigation program, developed for the characterization of the MR damper prototype of 10tf capacity, is described. The experimental investigations are to be performed on the MR damper, and respectively on the brace‐damper assembly, for which conventional as well as buckling restrained braces will be considered. Current outcomes of the ongoing experimental and numerical investigations, and the main conclusions are finally presented.
11.14: Seismic performance of high‐strength‐steel frame with buckling hinge beams in energy dissipation bays
Authors: Ke Ke , Chen Yiyi , Yam Michael C.H.
Published: September 2017

Although steel moment resisting frame (MRF) systems had long been recognized as effective seismic resistant structures, recent earthquake events and seismic loss estimations indicated that uniform damages of structural members and significant residual deformations would be expected after even a moderate earthquake event for steel MRF systems designed following the conventional ductility‐based design philosophy, and this incompleteness produced the impetus for overhaul of design methodologies and developing innovative systems. With the goal of enhancing the seismic performance of steel MRF structures in low‐to‐moderate seismic regions, this research explored the seismic behavior of high‐strength‐steel (HSS) frame with energy dissipation bays (EDBs) equipped with buckling hinge beams, denoted as the HSSF‐BHEDB system. In particular, the HSS frame is composed of steel with the nominal yield strength higher than 460 MPa, and the buckling hinge beams in the EDBs are constructed with cross‐sections classified as Class 3 or Class 4 by Eurocode 3. The motive of the novel design concept was to improve the structural nonlinearity of steel MRF systems with encouraging damage evolution mode and controllable residual deformations under earthquakes, and the limited energy dissipation of both the buckling hinge beams composed of slender cross‐sections and HSS members can provide a solution for structures in low‐to‐moderate seismic regions. In this work, the design concept and the rationale of the HSSF‐BHEDB were explored in detail. Then, a large‐scale quasi‐static test of a structure was conducted to provide experimental evidence and assess the feasibility of the design concept, and the behavior of the specimen from inception of yielding to failure was completely investigated. The test results showed that the system was characterized by the damage‐control behavior that diverted inelastic damages in the buckling hinge beams of the energy dissipation bay (EDB) in a wide deformation range. In the stage where the HSS frame initiated inelasticity and the energy dissipation of buckling hinge beams deteriorated, a ductile manner was still achieved. In addition, the controllable residual deformations of the specimen highlighted the satisfactory recentering behavior of the HSSF‐BHEDB structure. Lastly, the applicability of the bilinear hysteretic model of significant post‐yielding stiffness ratio and trilinear hysteretic model for featuring the hysteretic behavior of the HSSF‐BHEDB system in different yielding stages were validated by the test results.
11.27: Elastic buckling load and load resistance of core‐separated assembled BRB confined by two concrete‐infilled tubes
Authors: Zhu Bo‐li , Guo Yan‐Lin
Published: September 2017

This paper presents a novel type of the core‐separated assembled BRB (CSA‐BRB). It consists of two single BRBs confined by concrete‐infilled tubes that are connected longitudinally by two continuous webs. This directly results in a sectional cavity of the CSA‐BRB by spacing two independent BRBs, and significantly enhances its cross‐sectional flexural stiffness and load‐carrying capacity. The two independent steel cores of the CSA‐BRB are strengthened and connected at its end with a core stiffener to form a robust H‐shaped sectional core, as a whole. The core stiffener is inserted into the restraining member by a distance, further remarkably improving the core strength and stiffness at un‐restrained core projections of the CSA‐BRB. The CSA‐BRB is simulated approximately by “an equivalent framed model” and accordingly its elastic buckling load was obtained by using an equilibrium method. A number of numerical examples of CSA‐BRBs were designed and investigated by using a large deflection elastic‐plastic beam element model to predict the influence of the restraining ratios on their load‐carrying capacities. An overall geometric imperfection with the amplitude of l/1000 at mid‐span of the CSA‐BRB is also involved in the analysis. The results obtained reveal that the CSA‐BRBs could achieve required load‐carrying capacity without overall failure, considering the strain hardening (for example 0.02E) of the core after its initial yielding, as well as the ultimate axial compressive strain of 2% applied to the core if the restraining ratio of CSA‐BRBs is greater than around 3.0.
11.28: Seismic response of built‐up steel columns with semi‐continuous base‐plate connections: Experimental results vs. theoretical predictions
Authors: Della Corte Gaetano , Cantisani Gaetano , Landolfo Raffaele
Published: September 2017

The paper describes a comparison of experimental results and theoretical predictions regarding the lateral force‐displacement response of built‐up steel columns with semi‐continuous (semi‐rigid and partial‐strength) base‐plate connections.

Two specimens, representing samples from real columns of an existing industrial building, were fabricated and tested. The columns were both made of two I‐shaped profiles connected by means of battens, but with significant differences in the scheme of battening from one specimen to the other. The base plate connections were also significantly different in the two cases, in terms of local detailing. Preliminary tests were carried out in the elastic range of response, under varying levels of applied axial force. Such elastic tests were used to measure variations of the initial stiffness and corresponding yield displacements with the applied axial force. Subsequently, a cyclic loading test was carried out, per each specimen, to investigate the inelastic response.

Initially, the paper describes and comments on the relative performance of the two tested specimens, in terms of stiffness, resistance and ductility, as resulting from the experimental tests.

Subsequently, the paper provides theoretical predictions along with a comparison to the experimental results. Firstly, results from finite‐element (FE) models – developed using the Abaqus software – are described. Secondly, results from the application of simplified mechanical models are illustrated. The adopted mechanical models essentially followed the component‐method stipulated by Eurocode 3, but with some adaptations and modifications. The paper finally provides a comparison of experimental results with both numerical and analytical models.
11.35: Numerical study on steel braces under reversed cyclic loads
Authors: Faggiano Beatrice , Formisano Antonio , Vaiano Generoso , Landolfo Raffaele , Mazzolani Federico Massimo
Published: September 2017

Diagonals are typically assumed as dissipative elements in seismic‐resistant steel braced structures. However there are still some uncertainties on the behaviour of steel braces subjected to reversed cyclic loadings. The paper deepens such key issue, focusing on the numerical simulation of the experimental tests conducted by Black et al. (1980) on single steel members. FEM analyses are performed by means of the software ABAQUS v6.13‐1 on three struts having either H‐shaped, or circular, or square hollow cross‐sections. A refined model, calibrated by varying boundary conditions, cross sections and slenderness ratios is set up, allowing for a suitable approximation of the hysteretic behaviour in terms of strength, stiffness and ductility. It is a powerful tool for parametric analyses, necessary for acquiring the main aspects of the cyclic behaviour, thus leading to the definition of appropriate design criteria.
11.38: Investigation of innovative steel concentrically braced frame connections using advanced analytical models
Authors: Yang T.Y. , Sargazi Omid , Tobber Lisa
Published: September 2017

This article is not available for publication.
11.44: An integrated experimental and numerical assessment of force‐based design for concentrically braced steel frames
Authors: Ryan Terence , Broderick Brian , Salawdeh Suhaib , Hickey John
Published: September 2017

This study uses an integrated experimental and numerical approach to assess the use of the force‐based design (FBD) methodology presented in Eurocode 8 (EC8) for multi‐storey steel concentrically‐braced frames (CBFs).

In the EC8 approach, the design seismic action is defined by first generating an elastic response spectrum. This spectrum is reduced to create the design spectrum by applying an appropriate behavioural factor (q) to account for energy dissipation. The value of q chosen depends on the form of the lateral‐load resisting structure, the structural material(s) to be used, the ductility class and the degree of irregularity in the structural layout. The design base shear force calculated from the design spectrum is used to estimate the seismic forces on the structure and hence determine the final member cross‐section sizes.

In this study, the FBD approach to the design of structures presented in Eurocode 8 is described and applied to 4‐ and 8‐storey CBF structures. Both dissipative (Ductility Class High – DCH) and non‐dissipative (Ductility Class Low – DCL) design is considered for each structure.

A numerical modelling approach developed using the OpenSees seismic analysis software and validated from a series of full‐scale experimental tests of single‐storey CBFs is outlined. The two‐dimensional reference model assigns appropriate out‐of‐plane rotational stiffnesses to the ends of the bracing members based on the strength and geometry of gusset plates specified.

The experimental work used to validate the model, carried out as part of the BRACED transnational research project funded by the European Commission's Seventh Framework Programme (FP7) is briefly described. The experimental observations support model validation at different levels of earthquake ground motion including elastic, inelastic and ultimate response conditions.

The validated numerical modelling approach is used to perform a series of non‐linear time history analyses (NLTHA) of the designed 4‐ and 8‐storey frames by subjecting them to appropriately scaled simulated ground motion accelerations. The key recorded responses of the NLTHA of the modelled frames (displacements, drift, brace forces and ductility demands) are compared, and the implications of the assumed energy dissipations are discussed.
11.48: An experimental study on welded overlap core: Steel encased buckling‐restrained braces
Authors: Bozkurt Mehmet Bakır , Topkaya Cem
Published: September 2017

Buckling restrained braced frames (BRBFs) can be used as a lateral load resisting system in seismic regions. A typical buckling restrained brace (BRB) is composed of a core segment, debonding material and a buckling restraining mechanism (BRM). The cross‐section of the core segment can be changed along the length to constrain yielding in a limited domain. Most of the BRBs utilize a rectangular core segment which is reduced in width throughout yielding length. The gradual reduction in the width of the core segment produces stress concentrations and employs costly CNC cutting. A novel type of BRB named the welded overlap core steel encased BRB was developed to provide an alternative that does not require CNC cutting of the core plate. This type of a BRB is formed by welding flat bars with different widths to each other. The yielding and non‐yielding segment lengths and areas can be easily tailored to meet the stiffness and strength requirements. An experimental program has been undertaken to study the performance of welded overlap core steel encased BRBs. Pursuant to this goal four BRBs were manufactured and subjected to sub‐assemblage testing. All specimens were tested using the loading protocol recommended in the AISC Seismic Provisions for Structural Steel Buildings (AISC341‐10). Welding detail used to connect the built‐up BRM members was considered as the primary test variable. The experimental results indicated that the proposed core segment concept can be an alternative to more traditional core segment designs. The weld configurations used to connect the buckling restraining mechanisms affected the response significantly. According to the results, properly detailed and inspected welded overlap core BRBs can provide acceptable performance by sustaining cumulative strains in excess of 400 times the yield strain.
11.57: Assessment of the ductile behaviour of CBF structures considering energy dissipation in bolted joints
Authors: Martin Pierre‐Olivier , Rodier Anthony , Couchaux Maël , Kanyilmaz Alper , Degée Hervé
Published: September 2017

In dissipative seismic concept according to Eurocode 8, capacity design leads to additional cost for brace connections. In this concept, connections, either bolted or welded, remain elastic during seismic events whereas the braces dissipate energy by yielding and buckling. However the bolted gusset plate connections of braces are able to dissipate energy by sliding, bearing and block shear when minimal requirements are fulfilled. Within the RFCS project Meakado, both experimental tests and numerical simulations have been performed on bolted connections under cyclic actions to assess this potential dissipative mechanisms. An equivalent non‐linear spring model has been calibrated from these results to represent the ductile behaviour of concentrically braced frames (CBF) bolted joints when the non‐ductile mechanisms are prevented. Taking into account this equivalent spring model, the seismic global behaviour of CBF structures in the context of moderate seismicity have been studied both by time history and by push‐over analyses. Finally this paper proposes a calibration of the behaviour factor q of CBF structures when energy dissipation is considered in the bolted connections of braces together with the braces dissipation. The scope of application of these results is discussed.
11.60: Experimental investigation under cyclic loadings of an innovative passive mitigation device
Authors: Titirla Magdalini D. , Katakalos Konstantinos V. , Papadopoulos Panikos K.
Published: September 2017

The present study focuses on the experimental investigation of an innovative passive mitigation steel device, mentioned as CAR1. It consists of three distinguished parts; the external cylindrical ring, the internal prismatic holder and several superimposed blades that are responsible for the transfer of forces between the aforementioned 2 parts. CAR1 is utilized for strengthening either existing or new steel and R/C structures. The behaviour of the innovative device is changing according to the developed levels of displacement. It is designed so that it can be locked at a preselected level of displacement, thus, offering an extra safety reserve against strong earthquakes. By using CAR1, the beam–column frames can be easily and safely strengthened at many predefined levels according to the desire of the designer. The mechanism of the energy absorption is developed on the superimposed blades through both yielding of steel and friction. The number and dimensions of the superimposed blades, their elastoplastic properties as well as the friction coefficient at their interface, define the equivalent nonlinear constitutive law of CAR1. A full‐scale device was fabricated and experimentally investigated under cyclic loading. The experimental sequences were conducted at the premises of Laboratory for Strength of Materials and Structures of Aristotle University of Thessaloniki. The investigated variables are the geometry of the blades, the rate and number of the cycles of the loading sequence. The obtained results depicted the overall behaviour of CAR1 with respect to the absorbed seismic energy, and whether or not it will break during the cycle loading. Each experimental sequence imposed more than 50 cycles on the investigated specimen, with a different target load and rate each and every time. The results showed that CAR1 is an alternative device for mitigating the energy developed to a structure during an earthquake.
I.11.00: Innovative systems for seismic resistance: The INNOSEIS Project
Authors: Vayas Ioannis , Vamvatsikos Dimitrios , Thanopoulos Pavlos
Published: September 2017

Following the international trends, extensive research on seismic resistant structures has been carried out in Europe during the last decade, with the introduction of several systems with innovative steel‐based elements, as the result of European and national research projects. However, these systems have not claimed a fair share of the steel construction market, as provisions for their design have not been included in the Eurocodes and only a few designers are confident enough to employ them. The INNOSEIS project, which has received funding from the Research Fund for Coal and Steel (RFCS) with the participation of 11 partners, aims to deal with this shortcoming. In this paper, the valorisation actions for 12 such innovative anti‐seismic devices are presented. Information documents for all dissipative systems have been produced and combined in a single volume, translated in several European languages, for the dissemination to all partners of the construction sector such as architects, structural engineers, construction companies, steel producers and all potential decision makers of the construction sector. Criteria are proposed as to determine which of the systems are characterised as devices and are subject to CE marking in accordance with EN 15129, and which may be considered as innovative systems that require a code approval in EN 1998–1. For the latter, pre‐normative design recommendations are drafted that will allow them to receive the status of code‐approved systems. A reliability‐based methodological procedure to define values of behaviour factors (q‐factors) for building structures is proposed, which will be in turn applied to determine q‐factors for structural systems with the anticipated systems. A number of case studies with application examples of realistic steel buildings, in which the systems are employed, are presented. Dissemination of the project includes seminars and workshops in several European and Mediterranean countries, as well as the development of online, printed and electronic material, which is free for all people involved in the construction sector, in order to achieve the wide application of innovative seismic resistance systems in practical design.
I.11.07: Pre‐test numerical simulations for development of prequalified buckling restrained braces
Authors: Zub Ciprian Ionut , Dogariu Adrian , Stratan Aurel , Dubina Dan
Published: September 2017

Buckling Restrained Braces (BRBs) are increasingly used as structural fuse elements due to their stable and quasi‐symmetric cyclic behaviour and capacity to dissipate a large amount of energy. However, a wider adoption of buckling restrained braced frames is often precluded by the proprietary character of most BRBs, need for their experimental qualification and sometimes lack of experience of designers. To overcome these problems, a set of typical BRBs were developed in view of their pre‐qualification. “Conventional” and “dry” devices were considered, with capacities corresponding to typical steel multistorey buildings in Romania. The paper presents the pre‐test numerical simulations program for the “conventional” type of BRBs. The numerical model was developed using the general‐purpose finite element analysis program ABAQUS. The nonlinear cyclic behaviour of the steel core was described by a combined kinematic‐isotropic hardening rule. Calibration of the hardening parameters is also presented. A parametric analysis was performed in order to identify the optimal geometry and mechanical characteristics of brace components. Core aspect ratio, gap size, critical elastic axial load of the buckling‐restraining mechanism were among the investigated geometrical parameters. Also, different values for the friction coefficient were analysed. Outcomes of the finite element investigation were used developing the engineering solution and a design procedure for two conceptually different solutions of “conventional” buckling restrained braces in view of pre‐qualification.
12.01: Global plastic design of stainless steel frames
Authors: Arrayago Itsaso , Real Esther , Mirambell Enrique , Chacón Rolando
Published: September 2017

The use of stainless steel structures has increased during the last decade due to their durability, aesthetics and mechanical properties such as ductility, considerable strain hardening and excellent fire resistance. However, the majority of conducted research works have only focused on single isolated stainless steel members and advances in the analysis of stainless steel frames are limited. EN1993‐1‐4 does not provide global plastic design rules for indeterminate stainless steel structures, such as frames, despite their proved high ductility. On the other hand, the lack of guidance on plastic design is an obstacle for the optimal design of stainless steel structures, leading to uneconomical design. This paper presents a preliminary study on non‐sway stainless steel frames with stocky hollow cross‐sections. The study of the behaviour of stainless steel frames is based on numerical parametric studies, considering the nonlinear material behaviour and different stainless steel types (austenitic and ferritic). The paper deals with the redistribution of internal forces and assesses the existing methods based on global plastic design for frames with stocky cross‐sections, where alternative design approaches accounting for moment redistribution and strain hardening effects are analysed in addition to traditional plastic design method. Preliminary results demonstrate that including bending moment redistribution and strain hardening effects in capacity predictions is essential for an efficient design of stainless steel structures.
12.03: Buckling curves for stainless steel tubular columns
Authors: Afshan Sheida , Zhao Ou , Gardner Leroy
Published: September 2017

Towards the development of more resilient and sustainable structures, interest in the use of high performance construction materials, such as stainless steels, has increased in recent years. Recent studies [1] have highlighted a number of deficiencies in the flexural buckling provisions given in Eurocode 3: Part 1.4 for the design of stainless steel compression members. Therefore, this study aims to investigate the effect of production route (cold‐formed and hot‐finished) and material grade (austenitic, duplex and ferritic) on the behaviour and design of stainless steel square and rectangular hollow section columns. Test data from the literature combined with numerical modelling data generated as part of this study are used to derive a series of buckling curves for the design of stainless steel columns. Reliability analysis in accordance with Annex D of EN 1990 has been carried out to show that the proposed buckling curves comply with the Eurocode reliability requirements.
12.05: Global buckling behaviour of welded Q460GJ steel box columns: Experimental study and numerical simulations
Authors: Zhou Xiong , Kang Shao‐Bo , Yang Bo , Nie Shi‐Dong
Published: September 2017

This article is not available for publication.
12.10: Structural response of high strength steel hollow sections under combined biaxial bending and compression
Authors: Gkantou Michaela , Theofanous Marios , Baniotopoulos Charalampos
Published: September 2017

The benefits of high strength steel (HSS) as a structural material and its potential to lead to smaller sections and thus lighter structures has increased its use in the construction industry. Current design specifications for HSS are widely based on assumed analogies with normal strength steel, since they are based on a limited number of test data on HSS sections that were available when these specifications were published. Hence, their applicability to HSS requires assessment. Even though research towards this direction has grown, literature on the structural response of HSS under combined biaxial bending and compression is scarce. This paper presents a comprehensive numerical study on the cross‐sectional behaviour of S460 and S690 square and rectangular hollow sections under biaxial bending and compression. Finite element models are developed and validated against experimental results on 12 hot‐finished S460 and S690 stub columns under uniaxial eccentric compression. The numerically generated load‐deformation curves, the ultimate loads and the failure modes accurately replicate the experimental ones. Hence, the FE models are deemed able to predict the behaviour of stub columns subjected to combined compression and bending. Upon successful validation, extensive parametric studies aiming to generate additional structural performance data are executed. Two aspect ratios, eight cross‐sections with different thicknesses, and forty‐three combinations of initial loading eccentricities corresponding to different ratios of axial load to bending moments about both axes, are investigated for both steel grades. The results facilitate the determination of interaction failure surfaces and allow the assessment of relevant design specifications. It is concluded that the capacity of Class 1 and Class 2 cross‐sections is adequately predicted by European design provisions, with some conservative predictions occurring for S460 sections in the stocky slenderness range. For HSS semi‐compact cross‐sections under combined loading, the Eurocode provisions appear rather conservative, whilst the capacity of effective cross‐sections is overall well‐predicted.
12.18: Experimental investigation on cold‐formed high strength steel circular hollow sections under combined compression and bending
Authors: Ma Jia‐Lin , Chan Tak‐Ming , Young Ben
Published: September 2017

Cold‐formed high strength steel tubular members are gaining increasing attention from engineers due to their high strength‐to‐weight ratio, strong resistance against torsional buckling and aesthetic appearance. This paper presents a test program on cold‐formed high strength carbon steel tubular sections under combined compression and bending. The nominal 0.2% proof stresses of the test specimens were 900 MPa and 1100 MPa. The specimens were loaded through knife edges at both ends to provide pinned boundary conditions. Different loading eccentricities were applied to the test specimens by shifting the position of knife edges from the centroid of the specimens. As a result, a wide range of bending moment‐to‐axial load ratio was achieved. The beam‐column test set‐up and experimental procedures are detailed in the paper. Furthermore, the ultimate strengths, load‐end rotation histories and the failure modes of the test specimens are also reported. The test results were compared with the design strengths predicted from the American, European and Australian codes. The comparison showed that the existing design rules underestimate the ultimate strengths of the cold‐formed high strength steel tubular beam‐columns.
13.05: Imperfection force of members under longitudinal action having a variable sign
Authors: Biegus Antoni , Czepiżak Dariusz
Published: September 2017

In the calculation model of equivalent stabilizing force qd (shorter – imperfection force) for both bracing system and purlins consistent with EN 1993‐1‐1 it has been conservatively assumed that the member to be restrained is uniformly compressed within its length by an axial force. This is incorrect when the actual distribution of the axial force is considered as non – uniform, having a parabolic shape and sign – variable characteristic (compression and tension). Thus a different imperfection force is generated in comparison with this given in EN 1993‐1‐1.

The actual imperfection loads of the upper flange of the restrained roof rafter being fully fixed to columns have been analyzed. The axial force in the restrained member changes parabolically along its length from tension at the support zone to compression at the central part. Values of tension axial forces Nsup and compression axial forces Nspan depend, among others, on the rigidity of the roof rafter, rigidity of columns and stiffness classification of the rafter to column connection. Parametrical analyzes of the imperfection forces together with evaluation of strains of purlins and bracing system versus axial forces Nsup, Nspan acting in the restrained member have been done. The result of presented analyzes is determination of the safe imperfection force and he strain of purlins and bracing system in different, real design situations and a comparison of obtained results with these based on the conservative model given by EN 1993‐1‐1.
13.15: Seismic design of steel moment resisting frames: Modal strength reduction factors including strength deterioration and panel zone effects
Authors: Loulelis Dimitris G. , Papagiannopoulos George A. , Beskos Dimitri E.
Published: September 2017

Traditional seismic design of framed structures uses a single constant value for the strength reduction factor. In this work, explicit expressions for different values of strength reduction factors for the first significant modes of steel moment resisting frames including strength deterioration and panel zone effects are developed. These factors are functions of modal periods and damage and are designed for four performance levels in a performance – based seismic design framework. The above factors are obtained through extensive parametric studies involving 20 steel frames and 100 far – field ground motions and following a two steps procedure: First an equivalent linear structure with the same mass and elastic stiffness of the original non – linear one is constructed based on equivalent modal damping ratios, which substitute the non‐linearities; then use of these equivalent modal damping ratios in conjunction with modal damping reduction factors leads to modal strength reduction factors. Using these factors, one can obtain the seismic design base shear of a frame through response spectrum analysis. Thus, a more accurate and rational seismic design method is established. Numerical examples are presented to illustrate the method and demonstrate its advantages against conventional seismic design methods.
00.04: Structural fire design – Developments in research and assessment of fire in steel and composite structures
Authors: Knobloch Markus
Published: September 2017

This paper addresses structural fire safety, which is a key consideration in the design of buildings, and a topic attracting worldwide attention. Significant advances in research have increased our knowledge on the behaviour of steel and steel‐concrete composite structures in fire. Some areas are becoming well understood (like the behaviour of isolated elements in conventional building materials), while others areas (such as global behaviour of structures in fire, or constitutive modelling of innovative building materials at elevated temperatures) need further investigation. It is the aim of this paper to review progress in this area and to present latest developments with respect to future European structural fire design.
13.17: A comprehensive assessment of eurocode 3 pt. 1.1 & NBR 8800 steel design codes
Authors: da S. Vellasco Pedro C. G. , de Lima Luciano R. O. , da Silva Luís Simões , Simões Rui , Gervásio Helena
Published: September 2017

This paper compares the axial force and bending moment design procedures of Eurocode 3 part 1.1 and the Brazilian Standard NBR8800. This comparison was performed through a series of practical design examples that were executed according to EC3 pt. 1.1 [1] and NBR 8800 [2]. This strategy led to an assessment of some critical design issues present in these two structural steel codes, focusing on the identification of their main similarities and differences. The main conclusions of the above‐mentioned comparisons will be presented in terms of steel profile axial force and bending moment design capacities. The main reason for this result presentation strategy was due to the fact that the most common steel profile tables are constructed in a discontinuous form, where the same steel profile is able to withstand a non‐negligible range of structural design capacities.
15.07: Second‐order direct analysis of long‐span roof structures
Authors: Liu Yao‐Peng , Chan Siu‐Lai , Du Zuo‐Lei , He Jian‐Wei
Published: September 2017

Long span roofs are widely used in stadium, shopping mall, public hall, warehouse, airport and so on as they can provide large internal spaces. It is a challenging task to design a long span roof for the structural engineers using traditional linear design method due to uncertainty in the assumption of effective length. Second‐order direct analysis (SODA) shows many advantages over the traditional linear design approach in terms of structural safety and cost efficiency. In this paper, the design considerations and procedures of using SODA for design of long span roofs are presented. Both the P‐Δ and P‐δ effects as well as initial imperfections have been taken into account. More importantly, this innovative method is used to trace the structural behaviour of long span structures during offload process so that the structures can be safely and progressively deformed to their designed position with minimize lock‐in stress. A nonlinear spring element is proposed to capture the behaviour of the mechanical jack which is the device for implementation of offload process. Thus, a comprehensive solution is introduced here for offload analysis of long span structures. Finally, a practical long‐span single layer roof structure in Macau is used to demonstrate the validity and accuracy of the proposed method.
00.05: Validation and verification in design of structural steel connections
Authors: Wald František , Gödrich Lukáš , Kurejková Marta , Šabatka Luboš , Kabeláč Jaromír , Kojala Drahoš
Published: September 2017

The only way to prove correctness of simulated results by Finite Element Analyse (FEA) is through a methodical System response quantity process. Without this approval are the results of FEA meaningless and cannot be used in design process for making any decisions. The System response quantity consist of validation, which compares the numerical solution with the experimental data, of verification, which compares computational solutions with highly accurate analytical or numerical solution, and of benchmark cases, the examples for check of the software and its user on approved and simplified input and output.

In the eighties FEA of structural connection was treated by some researchers as a non‐scientific matter. Two decades later it was already a necessarily extension of experimental and analytical work. Today computational analysis, in particular computational mechanics and fluid dynamics, is commonly used as a catalyst of many research fields and an indispensable design tool. The recommendation for design by advanced modelling in structural steel is ready to be used in Chapter 5 and Annex C of EN 1993‐1‐5:2005 [1]. Development of modern general‐purpose software and decreasing cost of computational resources facilitate this trend. The FEA of structural connection is the coming step in structural steel design. As the computational tools become more readily available and easier to use even by relatively inexperienced engineers the proper procedure should be employed when judging the results of computational analysis.

This paper describes the System response quantity for Component Based Finite Element Model (CBFEM) which is a multilevel FEA method to analyse and design connections of steel structures, see [2]. The steel plates in connection are analysed in CBFEM procedure by FEA. The proper behaviour of components is treated by introducing a components representing well its behaviour in term of initial stiffness, ultimate resistance and deformation capacity, of bolts, welds etc. To help with this process is prepared a contribution, which summarises the history of achievements of FEA application in structural connections. Contribution shows the currents trends in advanced modelling of connection components and differences of the research oriented design oriented models. The particular attention is dedicated to design models of generally loaded endplates.