bluuebunny/crossref_metadata_2025 huggingface dataset:
10.38: Effects of heat‐treatment methods on mechanical performance of high‐tensile strength steel subject to elevated temperatures
Authors: Du Yong , Liew J. Y. Richard , Xiong Ming‐Xiang
Published: September 2017

This study is motivated by increasingly prevalent use of high tensile‐strength steel (HTS) in constructions, where fire is one of the extreme conditions that need to be taken into account in design phase. Previous studies showed lack of awareness regarding the effects of heat‐treatment methods on temperature dependent mechanical properties of the HTS. With this research gap being identified, standard tensile tests for Grade S690 steels made from Quench‐Temper (QT) Process and Thermo‐Mechanically Controlled Process (TMCP) were conducted. Transient‐state were adopted. The mechanical properties were compared and their differences were discussed. In General, the elastic moduli were similar for HTSs from different heat‐treatment methods, but the effective yield strength of TMCP‐S690 deteriorated more than that of QT‐S690 at elevated temperatures.
11.02: In‐plane quasi‐static cyclic tests on lightweight steel drywall non‐structural partition walls
Authors: Pali Tatiana , Bucciero Bianca , Terracciano Maria Teresa , Macillo Vincenzo , Fiorino Luigi , Landolfo Raffaele
Published: September 2017

The seismic damage of non‐structural components could involve functionality interruption of the most affected buildings and substantial economic losses. Among non‐structural components, the lightweight steel ceiling‐partition wall systems can represent a significant investment in the construction sector. Nevertheless, the proper seismic design of these systems plays a secondary role within the current structural design, by leading to a lack of specific design provisions. Since the behaviour of these systems cannot be easily simulated with traditional analysis methods, the experimental characterization is an effective procedure. For these reasons, a specific research activity was started over last few years at the University of Naples Federico. The main objective of the research is to investigate the seismic performance of lightweight steel drywall non‐structural building components, i.e. partition walls and suspended continuous ceilings made of lightweight steel profiles sheathed with gypsum‐based panels. The presented paper describes and discusses particularly the in‐plane quasi‐static reversed cyclic tests carried out on lightweight steel drywall partition walls. The obtained results could be considered a starting point for developing the in‐plane seismic design assisted by testing of lightweight steel drywall partition walls according to European prescriptions.
11.08: Reliable calibration of cyclic models for steel members
Authors: Chisari Corrado , Francavilla Antonella B. , Latour Massimo , Piluso Vincenzo , Rizzano Gianvittorio , Amadio Claudio
Published: September 2017

Accurate response predictions of steel structures subjected to earthquake loading involve the use of models able to simulate properly the cyclic behaviour of the regions where nonlinear phenomena take place. These include hardening, softening, strength and stiffness degradation, pinching and gap closure. In case of full‐strength joints, all nonlinear effects appear in the members connected, and particular relevance is assumed by softening and strength degradation. Even though a number of phenomenological models have been developed in the last decades, their calibration seems to have received less attention. Usually, calibration is based on matching the experimental and numerical cyclic responses under loading protocols proposed by standards. These protocols have been developed to give a reliable estimate of the cyclic deformation demand of the considered structural system, since demand strongly depends on the loading history and the hysteretic behaviour when dealing with structural elements characterised by nonlinear behaviour. In general, the accuracy of a numerical model calibrated minimising the discrepancy between experimental and computed response is controlled by the sensitivity of the considered response on the parameters, and since the original aim of loading protocols is not the calibration of numerical models, investigation is needed to assess the predictive capability of so calibrated models.

In this work, a calibration procedure based on the minimisation of response discrepancy is presented and critically discussed, with reference to an experimental programme carried out at the University of Salerno. In particular, cyclic, monotonic and pseudo‐dynamic tests were carried out on a hollow square member, with the aim of calibrating an advanced phenomenological model. It is shown that a calibration based on cyclic response under ordinary loading protocols only is not robust, since its accuracy under different loading conditions may deteriorate. In particular, loading histories characterised by sudden strong impulses after small‐amplitude cycles may involve parameters which are not well represented by ordinary cyclic loading protocols. The introduction of the monotonic test in a multi‐objective framework may be effective, and its accuracy is confirmed by the results of pseudo‐dynamic tests.
11.09: Validation of probabilistic theory of plastic mechanism control by means of Monte Carlo simulations
Authors: Castaldo Paolo , Nastri Elide , Piluso Vincenzo , Pisapia Alessandro
Published: September 2017

This work aims at the validation of the Probabilistic Theory of Plastic Mechanism Control (P‐TPMC), reported in a companion paper, by means of Monte Carlo simulations. P‐TPMC is devoted to stochastic frames with the aim to assure a collapse mechanism of global type despite of the influence of random material variability. A mechanism of global type develops when all the beams are yielded at their ends while the columns remain in elastic range with the only exception of the base sections of the first storey columns.

A parametric analysis is performed considering steel moment resisting frames having different number of bays and different number of storeys. Moreover, in order to achieve a predefined level of reliability in the attainment of the design goal, the parametric analysis is also repeated for increasing values of an overstrength factor of the dissipative zones aiming to its calibration. Finally, a quadratic regression has been derived to provide a simple relationship to compute the value of the overstrength factor needed to include the influence of random material variability in the application of deterministic Theory of Plastic Mechanism Control.
11.15: Seismic behaviour of single layer cylindrical lattice steel shells
Authors: Cedrón Francisco , Elghazouli Ahmed Y.
Published: September 2017

Cylindrical lattice shell structures are commonly used in many applications such as in train stations, gymnasia, and sports halls. In comparison with their behaviour and design under gravity loading, their behaviour under seismic loading has received less attention, particularly in terms of the development of practical design procedures. Current European codes of practice lack specific guidance on the seismic design of these shells. In this paper, the salient considerations influencing the seismic response of single layer cylindrical lattice shells are examined. The effect of key geometric parameters such as the rise to span ratio, length to span ratio, inter‐element angles, as well as the structural mass, on the characteristic natural periods and corresponding vibration modes are investigated using the finite element program OpenSees for two typical situations of boundary conditions. The influence of these parameters on the axial forces and bending moments in the members when subjected to the horizontal and vertical components of an earthquake is also assessed. The response is evaluated in the linear and nonlinear ranges, including representative time history analyses, with due consideration of both material and geometric nonlinearities. The results provide an insight into the main factors that govern the seismic behaviour of single layer cylindrical lattice shells, with a view to supporting the development of practical design and assessment procedures for this structural form.
11.17: Seismic retrofitting of concentrically braced frames by rocking walls and viscous dampers
Authors: Barbagallo Francesca , Bosco Melina , Marino Edoardo M. , Rossi Pier Paolo
Published: September 2017

In this paper, a design procedure for seismic retrofitting of concentrically braced frames is proposed and validated. The reasons leading to the need of an enhancement of the seismic performance of these frames may be multiple. As an example, the expected response of concentrically braced buildings may not match the desired performance objectives because (1) the initial design of the structures was deficient or (2) the design performance objectives have changed in time due to an update of the seismic hazard map or to more demanding requirements of the owners of the building. In this paper, rocking walls are proposed to ensure an almost uniform distribution of the storey drifts along the height of the building. To achieve a direct and efficient control of the ultimate peak ground acceleration, the design procedure is founded on the displacement‐based approach. The equivalent viscous damping ratio capacity of the concentrically braced structure with rocking walls is calculated based on semi‐empirical relationships specifically calibrated for concentrically braced frames. Viscous dampers are added and arranged between the existing structure and the rocking walls. The design internal forces of the rocking walls are evaluated considering also the contributions of the higher modes of vibration. The proposed design procedure is applied to an eight‐storey chevron braced frame and its effectiveness verified by incremental dynamic analysis.
11.18: Seismic analysis of innovative hybrid steel concrete coupled walls
Authors: Zona Alessandro , Leoni Graziano , Dall'Asta Andrea
Published: September 2017

An innovative hybrid steel concrete coupled wall made by a single reinforced concrete wall connected to two steel side columns by means of dissipative steel links is considered in this study. Such a hybrid system is conceived to take advantage of the stiffness of the reinforced concrete wall and of the dissipation capacity of the steel links acting as dissipative fuses that can be replaced if damaged. The performance of the studied structural system under seismic conditions is assessed by means of multi‐record nonlinear incremental dynamic analysis. To this end a set of buildings is designed following a recently proposed ductile design approach and varying two parameters: the building height and the degree of coupling between the steel columns and the reinforced concrete wall. A material and geometric nonlinear finite element model developed within an open source software is introduced and the main results of the numerical analyses are presented to provide insight into the expected seismic response. Overall, the outcomes of the numerically simulated response results indicate that the proposed hybrid steel concrete coupled wall has interesting potentialities as seismic resisting system being able to effectively exploit the lateral stiffness of the RC wall as well as the dissipation capacity of the steel links.
11.19: Seismic fragility assessment of steel frames: Application of advanced reliability analysis
Authors: Hazay Máté , Vigh László Gergely
Published: September 2017

During the application of advanced design procedures (e.g. performance based design) engineers may need to compute the actual risk of the structures. The fragility of structures exposed to seismic effects is often characterized by the fragility curves that show the failure (or collapse) probability under an earthquake characterized by a given intensity measure. Since the accurate calculation of such curves can be computationally demanding and extremely complicated due to the high nonlinearity of the problem and the difficulties in describing the seismic effect, common methodologies often invoke significant simplifications: neglecting certain types of uncertainties, assuming certain distribution model, using simplified analysis procedures to calculate the mechanical response of the structure, etc. It is emphasized that uncertainties in the resistance are often handled in a vague manner in the calculations, since their relevance is thought to be secondary in comparison to the uncertainties in the seismic effect.

Current paper illustrates a comprehensive methodology bridging over the above gaps. In order to accomplish this goal, fragility curves are determined on the basis of the full probabilistic approach. The stochastic model properly incorporates all the relevant random variables with proper distribution types and parameters. The mechanical response of the structure is computed by nonlinear dynamic (time‐history) analysis in OpenSees finite element software. Reliability analysis is completed using First Order Reliability Method in FERUM. In order to perform the iterative calculations, the coupling of the stochastic and the mechanical model had to be performed, which required the synchronization of the above mentioned software.

The main steps and results of the current framework are illustrated through an example of a) low‐rise and b) three‐storey steel portal frames. According to the results, the uncertainties in the resistance may have a significant effect on the probability of failure. Considering, that the results of the approximate methods found in the literature may significantly differ from the results obtained by reliability analysis, there is an understandable need for the more frequent usage of the full probabilistic approach as a background for practical applications, hence all types of uncertainties can be handled elaborately.
11.21: Experimental evaluation and explicit fracture simulations of stainless steel seismic dampers
Authors: Baiguera Marco , Vasdravellis George , Karavasilis Theodore L.
Published: September 2017

Seismic dampers with high post‐yield stiffness were recently proposed by the authors as the main energy dissipative system in a seismic‐resistant steel frame. The dampers are hourglass‐shaped pins made of duplex stainless steel and their high post‐yield stiffness significantly reduced the residual drifts of the frame after the design earthquake. This work evaluates the cyclic behaviour of the proposed dampers both experimentally and numerically. Two different geometries of full‐scale prototype dampers were tested under various standard and random cyclic loading protocols in a configuration that reproduced the damper‐brace connection in the actual steel frame. The results of fourteen tests showed that the proposed dampers possess excellent hysteresis and fracture capacity. Following the tests, explicit numerical simulations were carried out using the Abaqus software. Geometry‐independent fracture criteria were calibrated using the results of monotonic and cyclic tests on coupon specimens made of duplex stainless steel, and explicitly included in the numerical simulations of the dampers. The finite element models are able to accurately capture the initiation and evolution of fracture in the prototype dampers subjected to both standard and random cyclic loading histories. The results can be used to calibrate reliable macro‐models for seismic collapse simulations of the proposed frame.
11.24: Impact of column flexural stiffness on behaviour of steel plate shear walls
Authors: Curkovic Ivan , Skejic Davor , Dzeba Ivica
Published: September 2017

In the past 40 years steel plate shear walls (SPSW) have seen increased application as vertical stabilization systems of structures. Steel plate shear walls (SPSW) may be considered as vertically installed cantilever composed of boundary frame elements (beams and columns) and very slender steel infill panel. In the past, the loss of stability of the infill plate was prevented by adding vertical and horizontal stiffeners, while the present application relies on post‐critical tension field action of the infill panel. For cost‐effective implementation of steel plate shear wall (SPSW) systems the infill steel panel needs to be completely utilized through ability of tension field formation over the entire steel plate. Due to such load bearing mechanism additional transverse forces are exerted on boundary frame members. Hence, in order to ensure expansion of the tension field throughout the entire infill panel the required minimal flexural stiffness of boundary frame element cross‐section shall be met. This requirement is based on assumptions valid for plate girders, where previous studies, indicate that for steel plate shear walls (SPSW) this requirement could be conservative or even completely unnecessary.

This paper presents the results of experimental and numerical research. Laboratory testing included two different specimen groups. In order to determine the influence of the infill panel on the behaviour of moment resisting frame (MRF) three steel moment resisting frame (MRF) specimens were tested in the first group, while experiments of the second group included three steel plate shear wall (SPSW) specimens. In each specimen group flexural stiffness of the boundary columns was varied. Experimental results show that steel plate shear wall (SPSW) specimens whose boundary columns do not meet the required minimal flexural stiffness exhibited small “pull‐in” of their columns. Furthermore, the experimental data was used to calibrate numerical models that have been used for additional parametric numerical analyses. Specifically, the influences of three column flexural stiffness values as well as two steel grades of the infill panel were investigated for five different aspect ratio (L/H) values. Impact of the above parameters was assessed through comparison of residual relative horizontal displacement profiles.
11.30: Experimental behaviour of base plate joints equipped with self‐centering system and friction dampers
Authors: Santiago A. , da Silva L. Simoes , da Silva L.C. Fernandes , Cavallaro G. Ferrante , Francavilla A. , Latour M. , Piluso V. , Rizzano G.
Published: September 2017

A FREE from DAMage friction connection is a connection where friction dampers are introduced by adding friction pads, sliding on slotted steel plates, pre‐stressed with high strength bolts. Even though such a technology provides great advantages in terms of removal of damage to the structural elements, it has the main drawback to provide a limited re‐centering capability. In fact, during a seismic loading history, FREEDAM joints rotate concentrating the dissipation in the friction interface but, due to their high stiffness, after the end of the ground motion, they remain in a deformed position, leaving also the structure with residual drifts resulting in out‐of‐plumbs.

The goal of the work is to propose an approach to provide FREEDAM structures with a self‐centering capacity by studying particular devices, to be installed in beam‐to‐column joints or column base joints. In this paper, the attention is focused on the problem of re‐centering of base plate joints studying a detail consisting in a connection located at the base of the columns of the first storey equipped with friction dampers and threaded bars. The threaded bars work as elastic springs thanks to sets of Belleville washers used to increase the deformability and to allow the opening of a gap in the connection. The main breakthrough of the proposed technology with respect to the existing literature, aside from the methodology employed for the design of the friction connection, is that the self‐centering capability is obtained with re‐centering elements (threaded bars and Belleville springs) which are not conceived to be extended up to the end of the column at the top storey of the building, but they have a size similar to the column splice's cover plates. The work reports the results of a preliminary experimental investigation on this joint detail which has regarded cyclic and pseudo‐dynamic tests. The experimental results presented seems very encouraging towards the possible development of base plate joints with self‐centering capacity combined with friction dampers.
11.32: Linked columns with friction dampers as a technique for seismic retrofit of steel moment resisting frames
Authors: Bonchev Georgi , Belev Borislav , Mualla Imad
Published: September 2017

The existing steel moment‐resisting frames (MRFs) designed to seismic codes of older generation typically have limited local ductility capacity and may not perform to the desired “strong‐column‐weak‐beam” concept due to the lack of capacity design provisions. All these deficiencies require modifications for reducing their seismic vulnerability.

The paper proposes a seismic retrofit technique for steel moment frames based on the linked column concept. The linked columns are dual piers connected throughout their height with short horizontal replaceable ductile link elements. Developed in the last decade for new seismic‐resistant steel structures, the linked column frame structural system combines two sub‐systems – a primary lateral force resisting system composed of linked columns and secondary moment resisting frames mainly involved in resisting gravity loads.

During a seismic event, the relative deformations of the closely spaced piers activate the links which are designed to yield in shear or bending for seismic energy dissipation, but they also help in controlling interstorey drifts and limiting the forces transferred to the surrounding structural members.

The authors present a new innovative design of the linked columns. Instead of short steel beams, rotational friction dampers (RFDs) are used as seismic links in order to avoid the damage expected in conventional link elements. The RFDs are supplied by a Danish company and have been used for seismic protection in many projects for the last decade. They have proven energy‐dissipation capacity and can be delivered in different shapes and slip capacities at relatively low cost.

In this study three‐, six‐ and nine‐storey four‐bay steel MRFs have been analyzed using the capacity spectrum method. The added linked columns are arranged symmetrically on both sides of the first interior columns of the MRFs.

The results obtained for three different arrangements of the seismic links are presented and summarized. They indicate that the seismic retrofit using linked columns with rotational friction dampers is a promising technique for seismic upgrade of existing steel moment frames.
11.34: Cross‐aisle seismic behaviour of drive‐in rack systems
Authors: Shaheen Mahmoud S.A. , Rasmussen Kim J.R.
Published: September 2017

This paper presents the results obtained from a comprehensive series of earthquake tests carried out on fully loaded drive‐in steel storage racks. The earthquake waveforms used are actual ground motion records obtained from various locations around the world. The ground motions were applied in the cross‐aisle direction, in which the frames are made of a series of couples of uprights interconnected by diagonal braces to form upright frames. The upright frames were fully braced from top to bottom, and presented the most commonly used system configuration in the industry. In the tests, the 3D structural response was recorded to understand the global behaviour of drive‐in rack systems. The paper also presents the sequence of failures of different components that occurred during the tests, and the impact of these on the system behaviour.
11.36: Influence of type of loading protocols and restraining parameters on cyclic response of steel BRB
Authors: Ghowsi Ahmad Fayeq , Sahoo Dipti Ranjan
Published: September 2017

Buckling‐restrained braces (BRBs) are the special type of braces capable of yielding in both tension and compression under axial loading. These BRBs provide the nearly symmetrical hysteretic response and the higher energy dissipation potential as compared to the conventional steel braces. However, the use of relatively slender core plates in BRBs results in the smaller elastic and post‐elastic axial stiffness and the possibility of end plate rotation at the transition zone resulting in the unexpected premature damages. One of the possible way to change the stiffness of BRBs is to change the yielding core slenderness ratio to an acceptable limit. The range of reduction of yielding core ratio of BRBs depends on the required magnitude of hysteric energy dissipation as well as maximum and cumulative displacement ductility levels. This research is focused on the influence of core cross‐sections, friction between the core and restrainers, gap between core and restrainers, loading protocols, and core slenderness ratio on the cyclic performance of steel BRBs. A numerical study has been conducted for a series of BRB elements using the finite element software ABAQUS. Numerical models are validated by comparing the predicted results with the findings of a past experimental study on six numbers of steel BRBs subjected to different types of loading protocols. The energy dissipation potential of BRBs did not change significantly with the nature of loading protocols. However, the cyclic response of BRBs was significantly influenced by magnitude of friction and gap between the core and restraining elements. Moreover, the strength adjustment factors are unaffected by the different types of loading and as core cross‐sections.
11.41: Numerical investigation of influence of plate yield point on performance of steel plate shear wall
Authors: Moammer Omid , Deylami Ardeshir. , Jafari Khashayar , Raisszadeh Amir Hossein
Published: September 2017

Steel plate shear walls (SPSW) consist of thin infill steel plates attached to beams and columns in steel frames. SPSW are efficient lateral load resisting systems and can act as an alternative to traditional systems. In this study, the nonlinear response of single‐story single‐bay SPSW models having different yield points of infill plates (100, 180, 250 MPa.), were numerically investigated under lateral loading. The other variables in the analysis were the aspect ratio of panels (2 and 2.5), and thickness of the steel plates (3, 5 and 7 mm.). The models were designed according to the “AISC Steel Design Guide 20” and the “AISC 341–10 Provisions”. Finite element models of SPSWs were developed and analysed using ABAQUS nonlinear program. The results show that, using low yield point steel leads to more ductility and with some consideration influence the stiffness of models.
11.42: Cyclic behaviour of European carbon steels
Authors: Both Ioan , Zub Ciprian , Stratan Aurel , Dubina Dan
Published: September 2017

The deformation capacity of steel structures subjected to seismic or other repetitive loadings depends on structural configuration, member and connection characteristics, as well as on the cyclic response of material. While monotonic response of steel is generally available from standard tensile tests, information on response of steel under low cycle and extremely low cycle loading is limited. For numerical analysis, a basic option to determine the steel structures response is to use the tensile properties affected by a calibrated damage of the material. The literature offers several models for more rigorous analysis but these models are more reliable if their calibration is based on experimental results. Experimental results are found in the literature but mostly for low strain cycles. In the case of higher strains, the testing procedure, including the testing machine, requires supplementary support to avoid lateral displacement of the machine cross‐head which makes these tests more difficult to be performed. A dedicated device for the cyclic loading was designed against lateral displacement of the machine cross‐head. In comparison to the tensile test specimen, the cyclic test specimens have a shorter calibrated length. The paper presents the results of an experimental research on four European steel grades (S275, S355, S460 and S690) subjected to cyclic loading with constant and variable amplitudes. The specimens were tested with a universal testing machine of 250 kN under quasi‐static strain rate. The results emphasize the stress‐strain curve, number of maximum cycles for constant amplitude, maximum strain for variable amplitude and hardening or softening for the steel response to cyclic loading. Based on experimental data, parameters for modelling cyclic response of steel in Abaqus were determined.
11.49: Lifetime seismic performance assessment of steel frame structures
Authors: Hickey John , Broderick Brian
Published: September 2017

Steel Concentrically Braced Frames (CBFs) are stiff, lightweight, potentially low‐cost structures that efficiently resist lateral load through diagonal bracing members. Under dissipative seismic design principles, these bracing members are allowed to behave inelastically during infrequent high‐intensity earthquakes. In Eurocode 8 based design the extent of this inelasticity is effectively controlled by the behaviour factor, q. Increasing the behaviour factor results in a greater degree of nonlinear behaviour, however doing so allows for reduced member sizes and consequently reduced initial costs.

The conventional aim of seismic resistant CBF design has been solely to ensure life safety given the occurrence of an appropriate maximum earthquake event. However, like most structures, when designed in accordance with modern codes, CBFs are unlikely to suffer collapse. Yet, significant losses can still be incurred as a consequence of seismic action, primarily due to non‐structural damage caused by smaller, more frequent events. Hence, the overall suitability of a particular CBF design, compared to either other structural forms such as moment resisting frames or alternative CBF solutions, cannot be adequately assessed by examining life safety requirements alone. This paper therefore considers damage to both structural and non‐structural elements caused by seismic events across the entire hazard range. The expected damage, and the resulting losses, over the expected lifetime of the facility are calculated probabilistically, by applying a lifetime seismic performance assessment procedure. Thus, comprehensive comparisons are made between alternate frame designs.

Using the OpenSees computational platform to perform non‐linear time‐history analysis and the PACT performance assessment tool to estimate expected losses, this work investigates the impact of the behaviour factor on the lifetime seismic performance of low rise CBFs designed to Eurocode 8. Alternative Moment Resisting Frame (MRF) designs are also examined. On a general level, the study demonstrates how performance assessment can be employed to improve and optimise design. More specifically to CBFs, it is demonstrated that the ideal behaviour factor is not necessarily the largest value recommended by the code. The work also highlights the significance of losses suffered by acceleration‐sensitive non‐structural components and the consequent importance of limiting floor accelerations as well as storey drifts in order to fully exploit the damage limiting potential of CBFs.
11.50: Modelling hysteretic behaviour of U‐shaped steel dampers
Authors: Atasever Kurtulus , Celik Oguz C. , Yuksel Ercan
Published: September 2017

Conventional approach to earthquake resistant building design relies upon strength, stiffness, and inelastic deformation capacity, which are great enough to withstand a given level of design earthquake effects. However, modern approach in today's designs aims to mitigate seismic energy before the input energy reaches the structural elements. Dissipating seismic energy through the inelastic deformation of metallic dampers is one of the cost effective solutions. After appearing concept of dissipating energy through the inelastic deformation (mainly yielding and post yielding) of metallic dampers, numerous types of metallic dampers, such as X‐shaped, J‐shaped, U‐shaped, shear panel, triangular plate dampers have been developed and their effectivenesses have been proved both theoretically and experimentally. Inelastic hysteretic behaviour of U‐shaped devices is somewhat complex and varies with geometry of the damper. To address this issue and possibly attain some practical results, this present paper focuses on modelling hysteretic behaviour of U‐shaped dampers. ABAQUS has been used as the computational tool in which a finite element model made of the C3DR8 solid element is adopted. Nonlinear kinematic and isotropic hardening material assumptions are considered to determine cyclic behaviour at 0º, 45º and 90º loading directions. For each analysis, effective stiffness, effective damping ratio, and maximum reaction forces (i.e. horizontal strengths) of the damper are calculated to evaluate performance. As an additional parameter, two different loading protocols are taken into consideration. Hysteretic curves and deformed shapes of a selected damper type taken from an existing experimental work and this numerical study show very good agreement proving that the modelling assumptions made during the analyses are appropriate and sufficient for a better prediction of behaviour. Additional numerical analyses on several dampers under various loading protocols reveal that effective damping ratio of the damper is more than ξeff =40% at the maximum displacement level due to significant energy dissipation through plastic deformation of the damper. A numerical example of mixed use of U‐shaped steel dampers and rubber isolation bearings on a selected two story steel framed building is also discussed.
11.52: Local buckling behavior and plastic deformation capacity of H‐shaped beams under reversed axial forces
Authors: Suzuki Atsushi , Kimura Yoshihiro , Kasai Kazuhiko
Published: September 2017

In general, beams with concrete slabs in the moment resisting steel frames are assumed to be rigid axially when pushover or dynamic analyses are conducted. Consequently, axial forces acting on the beams are not considered in a design procedure. However, steel beams are subject to axial forces when a frame has buckling restrained braces during the earthquake. Ultimate strength, plastic deformation capacity, and cumulative plastic deformation capacity of beams with axial forces decrease and severe damage may occur to compare with beams with no axial force.

The purpose of this research is to elucidate the characteristics of H‐shaped beams under alternating axial force, which models the reversed axial forces from the dampers. Firstly, this paper conducts monotonic and cyclic loading tests on beams to understand local buckling behaviors under different loading protocols of axial force (no axial force, constant compressive axial force, and alternating axial force). Secondly, influences of the loading protocol of axial force on the ultimate strength, plastic deformation capacity, and cumulative plastic deformation capacity are investigated. Thirdly, the differences of capacity due to the magnitude of axial force and the number of cycles are examined. Finally, the effects of the width‐thickness ratio of beams on the buckling behaviors and performances under the alternating axial force are summarized.

As a result, beams under the alternating axial force show local buckling under the compressive axial force and the pinching effect under the tensile axial force. Although the performances of beam under alternating axial force degrade to compare with those under no axial force, larger ultimate strength, plastic deformation capacity, and cumulative plastic deformation capacity than those under the constant compressive axial force are obtained. This enhancement of performances under alternating axial force is originated by the stretch of residual deformation due to local buckling under the compressive axial force when tensile axial force is applied to the beam.
11.53: Reduced cross‐sections in seismic resistant steel structures
Authors: Köber Helmuth , Stoian Marina
Published: September 2017

In case of flexural dissipative members in eccentrically braced frames, a detail with reduced beam flanges sections at the link ends leads to a better control of the inelastic deformations along the dissipative member, together with a reduction of the plastic hinge rotation demand and with significant lateral stiffness of the braced frame.

Configurations resembling the “dog‐bone” near the ends of the upper stories diagonals in concentrically braced frames ensure on one hand, the abidance of the slenderness demand for the braces and on the other hand, small values of the amplification ratio Ωi(N)=NplRd,i/NEd,i. The reduced cross‐section of the diagonal in the “dog‐bone” detail zones ensures an adequate tensile capacity of the braces and small Ωi(N) values. At the same time the buckling behaviour and slenderness of the braces is not significantly affected by the reduced cross‐sections near the member ends and the slenderness demand of the braces will be fulfilled.

A favourable global plastic hinge mechanism can be sized by design for concentrically braced frames by providing configurations with reduced cross‐sections for potentially plastic zones located in the frame girders in the neighbourhood of the beam/column connections. So plastic deformations can develop in the braces, at the bottom of first‐story columns and in potentially plastic zones located near the ends of frame girders, and a favourable global plastic failure mechanism can be achieved. The same design concept can be used for sizing a favourable global plastic mechanism for frames with rigid beam/columns connections equipped with buckling restrained braces.

Configurations with “dog‐bone” details near the base of bottom‐story columns appear to be safer from the point of view of assuring the general stability of the first‐story column in the situation when plastic deformations occur in the potentially plastic zone at the bottom of the column. Further, a better control of the plastic deformations along the first story columns is ensured.
11.56: Test rig for seismic experiments of drive‐in racks
Authors: Shaheen Mahmoud S.A. , Rasmussen Kim J.R.
Published: September 2017

This paper describes the construction and commissioning of an experimental facility for testing heavily loaded full‐scale steel storage racks under seismic excitation. A one‐degree‐of‐freedom rig was built to test drive‐in racks with pay load up to 60tons. The rig was supported on rollers moving along girders attached to the ground. Different sets of non‐destructive tests took place during the commissioning process. The first set of tests was for commissioning the hydraulic actuator. The test results showed that the test rig setup was able to reproduce feedback signals that are very close to earthquake demand waveforms based on actual recordings of seismic events at various locations around the world. The second set of non‐destructive tests was for determining the dynamic friction coefficient in the rig. Force versus displacement test results under different loading conditions showed that the average friction coefficient was not sensitive to the speed of the jack or the weight, and was found to be in the order of 1% which is negligible. Hence, the test rig was found to operate as intended and met the design objectives.
11.59: Study on highly elastic seismic structural system based on very‐high strength steel and damage‐control fuses
Authors: Lin Xuchuan , Hu Yangyang , Okazaki Taichiro
Published: September 2017

A highly elastic seismic structural system that enables continuous use after major earthquakes is proposed, by making full use of the benefits of high‐strength steel, damage‐control fuses and energy dissipators. The high‐strength steel has a minimum specified yield stress of over 690 MPa. An experiment study is carried out to examine the performance of welds between high‐strength steel components and the effects of fuses on protecting the welded beam‐to‐column connections. Full penetration weld applied to the high‐strength steel worked well, and the beam using high‐strength steel achieved an elastic deformation rotation of about 0.018 rad and a maximum bending moment larger than its estimated plastic bending moment. The damage‐control fuses are effective to prevent the high‐strength steel components from yielding. The replacement of fuses is confirmed to be feasible, and the visible buckling deformation can be used as an indicator of replacement.
11.62: A numerical study on the seismic performance of experimentally‐tested steel single‐storey concentrically braced frames
Authors: Penelov Chavdar , Hadzhiyaneva Irena , Belev Borislav
Published: September 2017

The paper presents an overview on nonlinear modeling and numerical evaluation of the seismic response of two steel single‐storey concentrically braced frames with X‐brace configuration previously tested by other researchers.

The numerical simulations included series of nonlinear time history analyses using OpenSees computational framework. The brace members were modeled with fiber frame finite elements with distributed plasticity taking into account their initial imperfections. The material model accounted for the low‐cycle fatigue effects based on the approach proposed by several other research works on the topic.

The maximum response displacements of the investigated specimens were also evaluated following the procedure given in Annex B of EN 1998–1 (Eurocode 8). However, the previously conducted shake table testing and the herein presented numerical results indicated that this procedure may significantly underestimate the displacements of single‐storey dissipative short‐period CBFs designed with high values of the behaviour factor.

It was also found that the numerical estimation of the maximum and residual lateral response displacements of the analyzed CBFs based on nonlinear time history analysis is very sensitive to small variations of the material properties and assumed damping model (damping matrix definition). Therefore the experimentally‐obtained response displacements can be realistically predicted only if the parameter variations are taken into account in the numerical analyses.

The authors believe that the use of high values for the behaviour factor in the design of low‐rise CBFs may result in excessive residual displacements and low‐cycle failure of the brace members. It is suggested the further revisions of Eurocode 8 impose lower reference values of the behaviour factor for the short‐period steel CBFs with slender braces in order to reduce their ductility demand and related damage in strong earthquakes.
11.63: Seismic protection of gas tanks
Authors: Henriques Jose , Morelli Francesco , Salvatore Walter , Degée Hervé
Published: September 2017

Recent earthquakes demonstrated the susceptibility of industrial plants to such events. In extreme situations, as the earthquake in Fukoshima (Japan), the impact of the seismic action on these infrastructures leads to catastrophic results with consequences for the environment, neighbour population and economy. The impact of an earthquake on an industrial plant may result in a local failure, leading to an interruption on the operation, or a total collapse. In any of these cases, it is imperative the improvement of such facilities with high importance class. It is to this end that the European project PROINDUSTRY is ongoing. The objective is the development of innovative seismic protection systems for industrial buildings or infrastructures made of steel. In the present paper the numerical study of a gas tank is presented. For this type of infrastructures, amongst the different devices under development, the base isolation system was selected as it is seen as the most suitable. The proposed device is the Curved Surface Slider (CSS). In order to evaluate the performance of such device, numerical studies, namely Incremental Dynamic Analysis, were conducted. The results of these analyses lead to a calibration of the main properties of this device, static friction and vibration period, and allowed to verify the effective protection of the gas tank upon an earthquake event.
I.11.03: Influence of splitting beam and column stiffness on CBFS ductile behaviour
Authors: Georgiev Tzvetan , Raycheva Lora
Published: September 2017

Concentrically braced frames with X‐bracing configuration (X‐CBFs) are one of the most popular systems for seismic resistant design. Their ductile behaviour is provided primarily by yielding of braces in tension and to a small extent by plastic rotation in buckled braces. An improved CBF configuration by introducing bracings with modified sections was developed in research program. In order to facilitate joint detailing, it is efficient that braces intersect into a horizontal member named ”splitting beam”. Experimental study has shown that braces, being above and below the splitting beam, often do not buckle simultaneously. This leads to concentration of inelastic deformations within one of the brace and causes unbalanced horizontal and vertical force. Finally, it might result in reduced storey ductility and premature brace fracture.

It was assessed through extensive parametric non‐linear analysis that splitting beams in cooperation with columns have crucial impact on the brace buckling sequence and on the type of the global plastic mechanism. An analytical model and design procedure for determining the stiffness and strength demand of splitting beams and braced frame columns are proposed. The procedure ensures achievement of buckling of both halves of compression braces and formation of anticipated plastic mechanism. Some case studies based on static nonlinear analysis are presented.
I.11.05: Parametric finite element analyses of detachable short links
Authors: Zimbru Mariana , D'Aniello Mario , Stratan Aurel , Landolfo Raffaele , Dubina Dan
Published: September 2017

Detachable short links are an effective system to guarantee both large dissipative capacity and the possibility to repair easily the structure by replacing the damaged links after an earthquake. Therefore, the detailing of links and the design of their connections are of paramount importance given their role in the overall structural performance of eccentrically braced frames (EBFs). Recent analytical and experimental studies highlighted that shear links under large deformations and with axial restraints may develop shear overstrength larger than EC8 recommended value (i.e. 1.5) and significant tensile axial forces, which are not accounted for in EC8. This feature is crucial for detachable links, because the link end connections should be designed to resist also these forces in order to prevent undesirable and premature failure. In light of these considerations, this paper presents the results of a comprehensive parametric finite element study devoted to investigate the behaviour of end‐connections of replaceable links. The finite element models are validated against the results of full‐scale experimental tests carried out on a three‐storey EBF. The obtained results allows evaluating both the level of axial force in the link, varying the boundary conditions, the link length and the shape of the profile.