bluuebunny/crossref_metadata_2025 huggingface dataset:
Timber encasement of steel structures as an alternative fire insulation
Authors: Bihina Gisèle , Durif Sébastien , Bouchaïr Abdelhamid , Saulnier Véronique , Zhao Bin
Published: September 2021

This paper presents the results of an investigation on the thermal behaviour of fire‐exposed steel profiles embedded in timber elements.

Several tests were performed on small unloaded specimens in a small furnace. The different specimens were made of bare steel profiles, timber elements or steel‐timber hybrid members. Different welded I or T steel sections and wood species were used. The specimens were set horizontally (3‐side exposure) or vertically (4‐side exposure) in the furnace and heated using a couple of burners. The temperatures of the steel profiles were measured by welded K thermocouples.

The results from this experimental campaign, in terms of temperature of the furnace and of the specimens, density and moisture content of timber, were then used to calibrate a heat transfer model under Ansys finite element code. This 2D numerical model is mainly based on the behaviour laws of structural steel and timber from Eurocodes 3 and 5 respectively. Regarding the specific heat of timber, several relationships were applied. A comparative analysis of experimental and numerical results confirms the fire insulation brought to steel by timber. It also highlights the ability of the model to simulate the thermal behaviour of both steel and timber, in terms of heating and charring rates.
Multi‐scale bolt connection model for thermomechanical simulations
Authors: Xu Qingfeng , Hofmeyer Hèrm , Maljaars Johan
Published: September 2021

A multi‐scale simulation approach is proposed to predict the fire resistance of structures comprising connections by bolts, as a supplement to an existing two‐way coupled CFD‐FEM method. In the existing model, fire is modelled by CFD, and its effects on the overall structure are found via thermodynamic and thermomechanical models. In this paper, detailed thermomechanical models are presented to predict the behaviour of a bolt connection, in order to find the equivalent linear elastic stiffness for the bolt connection that is modelled as a spring in the overall structure. Each load step, the stiffness of the spring is determined by the detailed model, which for a certain temperature, boundary conditions, and load type, predicts the connection behaviour, including geometric and material non‐linearity and failure. It will be shown that the detailed model simulates existing experiments for elevated temperatures well, and is able to predict all possible failure modes as listed in the Eurocode for ambient temperatures. It is then demonstrated that the model can also be used for all these failure modes for elevated temperatures. In the near future, a strategy will be developed to include the detailed models in the overall structure, within the two‐way coupled CFD‐FEM method.
Shallow composite floor beams – Proposal of a simplified analytical method for standard fire rating
Authors: Zanon Riccardo , Yildiz Sevilay , Obiala Renata , Braun Matthias
Published: September 2021

Shallow composite floor beams are a widely accepted solution for office, residential and other types of buildings. In most of their applications a standard fire resistance between R30 to R120 is required. Several fire tests were carried out in different laboratories over the last decades with various structural configurations, showing that this structural solution exhibits an integrated fire resistance without additional fire protection. In the frame of various programs, extensive research has been done on the fire behavior, completed by numerical simulations. Several scientists have proposed analytical methods to assess the resistance. Nevertheless, the Eurocode does not contain a method for assessing the standard fire resistance of composite shallow floor beams. This paper presents a simplified analytical method to determine the sagging moment resistance of Slim Floor Beams (SFB – being composed by a rolled section (or equivalent) with a wider plate welded below the bottom flange) under standard fire exposure. First, an FE model has been developed and validated on experimental tests. Afterwards, a parametric study covering various geometrical configurations and material choices has been performed. An analytical model for determining the sagging moment resistance is proposed and validated by comparison with results obtained by numerical simulation.
Behavior of Composite Floor Assemblies Subject to Fire: Influence of Slab Reinforcement
Authors: Choe Lisa , Ramesh Selvarajah , Zhang Chao , Clifton Charles
Published: September 2021

A series of fire experiments are being conducted on the 2‐story steel framed building with composite floors in the National Fire Research Laboratory. This paper presents a brief overview of experimental design and discusses some results of the first test conducted on 6.1 m by 9.1 m composite floor assembly exposed to a standard fire. The test floor slab was constructed with lightweight concrete cast on 7.7 cm deep formed steel deck units and welded wire fabric (60 mm/m2) as the minimum shrinkage reinforcement required in the U.S. practice. The structural steel beams and girders were sprayed with a cementitious fire resistive material for a 2‐hour restrained fire resistance rating. While the test floor assembly resisted mechanical loads (2.7 kN/m2) applied using hydraulic actuators, its underside was exposed to a natural gas‐fueled compartment fire that was equivalent to the standard gas temperature‐time relationship. The study revealed that the test floor assembly could withstand an imposed load at a large vertical deflection on the order of span / 16, but the concrete slab failed due to limited ductility and strength prior to 2 hours in a standard fire. Simple post‐test predictions were performed incorporating tensile membrane action in the floor slab to compare with the measured behavior. Limited comparisons discuss the contribution of steel decking and slab reinforcement to the load‐carrying capacity of a floor assembly in fire.
Mechanical Properties of Steel–Concrete Composite Girder Subjected to Thermal History due to Fire
Authors: Takahashi Yusuke , Imagawa Yusuke , Ohyama Osamu
Published: September 2021

Fire damage to bridges occurs frequently in Japan and in other countries. Previous bridge fire accidents suggest that it is important to understand the structural performance of bridges after their exposure to fire. The Japan Society of Civil Engineering has proposed guidelines for the diagnosis and repair of steel bridges that have been exposed to fire. This guideline shows that the judgement temperature of steel members is 400°C. This temperature was established based on previous bridge fire accident reports and material testing after fire. It is unclear if the basis for evaluation has been the structural members. Therefore, it is necessary to clarify the effect of the rigidity reduction on the structural performance and judgement temperature of steel girder bridges after fire. The authors have studied the mechanical properties of steel–concrete composite girders as a medium span bridge before and after fire. A fire test was carried out to clarify the temperature distribution of the steel–concrete composite girder and static loading tests before and after fire were conducted to confirm the effect of the rigidity reduction from the fire. This study considers the validity of the judgment temperature from the test results.
Experimental and Numerical Investigations on Steel Columns Compartment Subjected to Travelling Fires
Authors: Nadjai Ali , Alam Naveed , Charlier Marion , McGillighan James , Vassart Olivier
Published: September 2021

In the frame of the European RFCS TRAFIR project, three large compartment fire tests involving steel structure were conducted by Ulster University, aiming at understanding in which conditions a travelling fire develops, as well as how it behaves and impacts the surrounding structure. During the experimental programme, the path and geometry of the travelling fire was studied and temperatures, heat fluxes and spread rates were measured. Influence of the travelling fire on the structural elements was also monitored during the travelling fire tests. This paper provides details related to the influence of travelling fires on structural steel columns. The experimental data is presented in terms of the gas temperatures recorded in the test compartment near the column, as well as the temperatures recorded in the steel column at different levels. The scope of the experimental work is extended using CFD simulations with FDS software, which demonstrate with good agreement with measurements in the steel column exposed to travelling fires.
Numerical Simulation and Design of Stainless Steel Columns under Elevated Temperatures
Authors: Martins André Dias , Camotim Dinar , Gonçalves Rodrigo , Dinis Pedro Borges
Published: September 2021

This paper presents and discusses the first results of an ongoing Abaqus numerical (shell finite element) investigation on stainless steel columns under elevated temperatures and prone to local or global buckling, performed in the context of the project “StaSteFi ‐ Fire Design of Stainless Steel Members”. In particular, geometrically and materially non‐linear shell finite element models are employed to obtain the failure loads of columns (i) with several cross‐section shapes (SHS, RHS, CHS, EHS and I‐section), (ii) prone to local or global buckling, (iii) made from three stainless steel grades (ferritic 1.4003, austenitic 1.4301 and duplex 1.4462), (iv) subjected to various elevated temperatures (θ=100, 200, 300, 400, 500, 600, 700 and 800°C) and (v) containing both initial geometrical imperfections and residual stresses. The failure loads gathered are then used to assess the prediction quality of the Eurocode 3 stainless steel design rules and explore the development and calibration of novel design approaches.
The Continuous Strength Method for the design of stainless steel members under combined loading
Authors: Arrayago Itsaso , Real Esther , Gardner Leroy , Mirambell Enrique
Published: September 2021

The Continuous Strength Method (CSM) provides accurate cross‐section resistance predictions since allowance is made for the partial spread of plasticity and the beneficial effects of strain hardening. Although CSM design provisions for different loading conditions are available, the method was limited to the determination of cross‐sectional resistance until recent research by Arrayago et al. (2020) proposed a consistent new approach to the design of stainless steel hollow section members subjected to compression. Extension of the CSM to the design of stainless steel members subjected to combined compression and bending moment is presented in this paper. The analysis is based on numerical results generated in the current study and existing results collected from the literature on stainless steel hollow section members. The results demonstrate that the adoption of the CSM design equations to predict column strength considerably improves the accuracy of the calculated beam‐column capacities. The reliability of the proposed approach is demonstrated through statistical analyses performed in accordance with EN 1990.
Modelling of Stainless Steel AISI 316L in Finite Element Simulations
Authors: S⊘nstab⊘ Johan Kolst⊘ , Faksvåg Kristian Ullern , Jakobsen Lars Omland , Clausen Arild Holm
Published: September 2021

This paper addresses numerical modelling of a rolled, austenitic stainless steel of grade AISI 316L, corresponding to EN 1.4404. The study comprises uniaxial tension tests at a range of temperatures (from –20°C to 200°C) and at two different strain rates (10–3 s–1 and 10–1 s–1). It appears that the material is very ductile and hardens significantly. The strength and hardening depend on temperature, while the strain‐rate effect is minor. The results from the tension tests are used to calibrate two different material models. The first one is a fully parametrized elasto‐viscoplastic model of Johnson‐Cook type, incorporating temperature and strain rate as variables, and including the one‐parameter Cockcroft‐Latham failure criterion. The other model is defined through direct input of the true stress‐strain curve at a given temperature and rate. This model does not incorporate failure. In the validation part of the study, the models are employed in numerical simulations of plane‐strain tension tests on notched specimens. It appears that both models capture the main features of the tests.
Effects of galvanization on the mechanical properties of high and ultra‐high strength steel tubes
Authors: Najafabadi Esmaeil Pournamazian , Heidarpour Amin , Raina Sudhir , Arashpour Mehrdad , Zhao Xiao‐Ling
Published: September 2021

A widely used corrosion protection technique for steel structures is hot‐dip galvanizing. This method increases the life of steel structures and reduces maintenance costs. In this technique, steel elements are cleansed through caustic cleaning, rinsing, pickling, and dipping in flux solutions. After cleaning, components are dipped in molten zinc until a protective layer is formed. The galvanizing procedure and its effects on structural mild steel materials have been studied. However, the effects of galvanizing on mechanical properties of high and ultra‐high‐strength steels (HSS and UHSS) have received limited attention. This mechanical investigation is vital since UHSS, and HSS steels are sensitive to heating and cooling cycles, and their mechanical behavior may change when exposed to high‐temperature during hot‐dip galvanizing. To this end, an experimental program was designed and carried out to find out the mechanical behavior of standard coupons taken from UHSS and HSS tubes after galvanizing. HSS and UHSS tubes were cleansed and dipped in a molten zinc bath (460 °C) for 3.0 and 10.0 minutes. For comparison, a mild steel tube with the same dimensions was also galvanized by dipping in zinc for 10.0 minutes. After galvanizing, dog‐bones and short tubes were cut out from the tubes for standard tensile and compressive tests, respectively. The tests revealed that the ultimate tensile strength of HSS and UHSS tubes decreased noticeably while the changes in their yield strengths were not significant. These changes were more significant for longer molten zinc bath dipping times. For HSS and mild steel specimens, the heat exposure had a similar effect as normalizing or annealing done after casting steel. For mild steel, normalizing or annealing increases yield, and ultimate strength and the same thing happened here. It was shown how the observed behaviors and changes were related to the grade of steel materials and their manufacturing process. Finally, optical microscopy was conducted to inspect the micro‐scale properties of the zinc layer. Microscopic results show that under the same zinc dipping time the zinc layer thickness on UHSS and HSS is almost double of that on mild steel which can increase the lifespan of the galvanized parts while decreasing the adhesion of the zinc layer to the steel base.
Application of Continuous Strength Method in high strength steel sections
Authors: Lin Hui , Hu Ying , Qian Song‐Ting , Sulaiman Maher
Published: September 2021

High strength steel has been employed in modern steel‐framed building structures. It should be highlighted that these steel structures may be built‐up through fabrication of hot‐rolled steel sections or welded high strength steel plates. This study performed an extensive series of compression tests on high strength stub columns. These columns were made of Q620E steel plates through welded steel plates. The ultimate loads and displacements were extracted from the load‐displacement curves observed from the tests. The continuous strength method (CSM) was employed for analysis of the local buckling behavior of stub columns. In addition, a series of tensile strength tests were performed for standard steel coupons. A modified stress‐strain constitutive model was then proposed for design purpose for high strength steels. The predicted ultimate loads were compared with the recorded ultimate loads. It can be found that a reliable predication may be achieved in application of CSM in high strength steel sections.
Bending response of three‐layers sandwich panels with steel skins and aluminium foam core
Authors: Capone Paolo , Latour Massimo , D'Aniello Mario , Babcsan Norbert , Landolfo Raffaele , Rizzano Gianvittorio
Published: September 2021

The introduction in the market of metal foams represents a significant opportunity to increase the use of metal in the construction market. In fact, the development of new products made of metal foams and steel could allow improving the performances of conventional buildings in terms of stiffness and resistance. The first structural applications of these materials have already shown the potentialities of composites made of foam and steel, verifying the possibility to realize mono‐dimensional and bi‐dimensional elements with high resistance‐weight ratio. The reduction of the structural weight can represent a significant advantage in many cases, such as for buildings in seismic zone or infrastructures. Within this framework, the objective of the preliminary work presented in this paper is to analyze the response of composite sandwich panels made of steel and aluminium foam with a set of tests which will serve as the basis of development for a new system of dry assembled composite floors. The tests have been carried out at the laboratory StrEngTH of the University of Salerno, verifying the mechanical properties of only‐foam panels and of double skin glued sandwich panels. The tests have allowed to obtain the basic mechanical properties of both foams and sandwich panels.
Seismic response of a steel resilient frame equipped with self‐centering column bases with friction devices
Authors: Elettore Elena , Freddi Fabio , Latour Massimo , Rizzano Gianvittorio
Published: September 2021

In the last two decades many researchers focused on the development of innovative building structures with the aim of achieving seismic resilience. Among others, steel Moment Resisting Frames (MRFs) equipped with friction devices in beam‐to‐column joints have emerged as an effective solution able to dissipate the seismic input energy while also ensuring the damage‐free behaviour of the system. However, to date, little attention has been paid to their column bases, which represent fundamental components in order to achieve resilience. In fact, column bases designed by current conventional approaches lead to significant seismic damage and residual drifts leading to difficult‐to‐repair structures. The present paper evaluates the seismic performance of steel MRFs equipped with an innovative damage‐free, self‐centring, rocking column base joints. The proposed column base consists of a rocking splice joint where the seismic behaviour is controlled by a combination of friction devices, providing energy dissipation capacity, and pre‐loaded threaded bars with disk springs, introducing restoring forces in the joint. The design procedure of the column base is presented, a numerical OpenSees model is developed to simulate the seismic response of a perimeter seismic‐resistant frame, including the hysteretic behaviour of the connection. Non‐linear dynamic analyses have been carried out on a set of ground motions records to investigate the effectiveness of the column base in protecting the first storey columns from yielding and in reducing the residual storey drifts. Incremental Dynamic Analyses are used to investigate the influence of the record‐to‐record variability and to derive fragility curves for the whole structure and for several local engineering demand parameters of the frame and of the column base connection. The results show that the damage‐free behaviour of the column bases is a key requirement when self‐centering of MRFs is a design objective.
Response Behaviour of High‐Rise Modular Building under Wind and Seismic Loads
Authors: Yee Shiou Shen , Kong Kian Hau , Liew J Y Richard , Dai Ziquan
Published: September 2021

Singapore has adopted modular construction method known as Prefabricated Prefinished Volumetric Construction (PPVC), where this method requires modules to be prefabricated in a factory environment and subsequently transported to site for installation. A 40‐storey steel‐concrete composite PPVC building consisting of a modular structural frame and a central reinforced concrete (RC) core wall subjected to wind and seismic loading combinations are studied on the global response behavior building drift behavior. The case study is used to investigate the structural response behavior throughout the working life of the building under the service limit state. The adjacent modules are connected horizontally using a tie steel plate idealized by a pin‐pin connection while upper and lower modules are connected vertically using a vertical steel thread rod secured with locking nut idealized by a pin‐ended connection. The modules are braced to a central RC core wall. Continuous semi‐rigid floor diaphragm action is also considered in each floor. The study reveals the importance of inter‐module connection and the floor diaphragm action for the structural interaction between modules and central RC core wall.
New Design Proposal for Stiffened Curved Plates under Compression
Authors: Piculin Sara , Može Primož
Published: September 2021

In this paper, the stability behaviour of longitudinally stiffened, transversally curved steel plates under uniform compressive stresses is investigated and new design guidelines are proposed to extend the scope of the current European standards for flat plated structures to stiffened curved plates. For this purpose, a numerical model is built in Abaqus, which is verified with own test results and numerical results from the literature. It incorporates geometric imperfections based on the modification of node coordinates using sinusoidal functions, and is further used in a comprehensive parametric study based on nonlinear numerical analysis (GMNIA). The parametric study investigates the effects of curvature, slenderness of the plate, size of stiffeners and shape of initial imperfections on the ultimate resistance of the stiffened curved plates. From the results, some important conclusions are drawn regarding the structural behaviour and the positive effects of curvature on the cross‐sectional resistance. In particular, it is found that stiffened curved plates are less sensitive to the shape of the initial imperfections compared to flat stiffened plates, and the introduction of curvature generally adds a reserve of resistance to the stiffened panel under compressive stresses. Based on numerical results, design rules are proposed for longitudinally stiffened curved plates subjected to compressive stresses. The rules are in accordance with the formalism of EN 1993‐1‐5 for flat plated structures and follow the effective width concept. The maximum loads obtained from numerical analysis are compared with the new design rules and a good correlation is obtained.
Assessment of the Imperfections for Plate Buckling of Unstiffened Plates
Authors: Schönfeld Larissa , Naujoks Bernd , Ludwig Christian
Published: September 2021

In this study different approaches and combinations of imperfections using GMNIA of unstiffened plates are examined. The imperfections have a crucial influence for the determination of the load bearing capacity of thin plates. According to EN 1993‐1‐5 Annex C, when using GMNIA, the user can choose between equivalent geometric imperfections and a combination of the geometrical and the structural imperfections. The exact influence of the individual imperfections and their combination on the load bearing behavior has not been conclusive clarified. Furthermore, EN 1993‐1‐5 Annex C does not recommend a suitable residual stress model. This study aims to compare the ultimate loads due to compression loading using different imperfection approaches. Ten different combinations are investigated by using GMNIA. The results show that for larger plate slenderness, many of the ultimate loads are above the Winter‐Curve. The influence of the structural imperfections on the ultimate load is higher than the influence of the geometrical imperfections. An appropriate residual stress model is recommended. The geometrical imperfections should be given as a function of the plate slenderness.
Optimisation and compressive testing of additively manufactured stainless steel corrugated shells
Authors: Zhang Ruizhi , Gardner Leroy , Meng Xin , Buchanan Craig , Matilainen Ville‐Pekka , Piili Heidi , Salminen Antti
Published: September 2021

Axially compressed circular cylindrical shells with large diameter‐to‐thickness ratios are known to be highly sensitive to initial geometric imperfections, which can drastically reduce their load‐carrying capacity. Their design typically involves the application of severe knock‐down factors on their theoretical buckling loads, which greatly impair their structural efficiency. In this paper, with the aim of reducing sensitivity to imperfections and enhancing load‐bearing resistance, optimised corrugated cylindrical shells are designed, additively manufactured, tested and analysed. Two corrugated shells with different equivalent diameter‐to‐thickness ratios, along with a reference circular cylindrical shell, were produced by powder bed fusion (PBF) additive manufacturing from martensitic precipitation hardening stainless steel powder. The structural performance of the PBF corrugated and circular shells was experimentally investigated, including tensile coupon tests, initial geometric measurements and compression tests. Numerical analyses were also carried out in parallel with the testing. The experimental and numerical results demonstrate that the optimised corrugated cross‐sections have lower imperfection sensitivity and higher axial resistances compared with their reference circular sections.
Evaluation of the Seismic Response of an Innovative Hybrid Steel‐Timber Structure
Authors: Mowafy Ahmed , Imanpour Ali , Chui Ying Hei
Published: September 2021

This study evaluates the seismic response of an advanced hybrid steel‐timber structure using a nonlinear static and dynamic analyses. A three‐story prototype building located in Vancouver, BC, Canada was designed first. The gravity load resisting system (GLRS) consists of cross‐laminated timber (CLT) floor slabs, glulam beams, and glulam columns. The lateral load resisting system (LLRS) includes a chevron‐type steel Concentrically Braced Frame. The numerical model of the structure was then developed in the OpenSees program. Nonlinear hysteresis response of steel braces and timber joints were explicitly simulated. The results of the analysis revealed that the hybrid structure possess an acceptable lateral stiffness while providing sufficient ductility to dissipate seismic energy. No unsatisfactory response was observed in the timber system.
Experimental Validation of Detachable Links for Eccentrically Braced Frames
Authors: Bozkurt Mehmet Bakır , Topkaya Cem
Published: September 2021

Eccentrically braced frames (EBFs) subjected to seismic actions dissipate energy through yielding of link members. Other members of the framing are on the other hand designed to remain mainly elastic during a seismic event. The framing can be reused after an earthquake if the link members can be replaced. In line with this, the last decade has witnessed development of replaceable links. However, most of the proposed details are not well suited for replacement under residual drift conditions. Consequently, this paper presents details of an experimental validation of a detachable link concept where a splice connection is introduced at the mid‐length of the link to facilitate replacement under residual frame drift. The concept was studied by conducting six nearly full scale EBF tests under quasi‐static cyclic loading. Different splice details employing bolted connections with vertical slotted or site drilled holes and welded connections were developed. The link length ratio, type of mid‐splice connection and the amount of residual drift were considered as the variables of the testing program. The specimens were subjected to the loading protocol recommended in AISC Seismic Provisions for Structural Steel Buildings (AISC‐341). The experimental results suggested that the detachable links with the proposed connection details can satisfy the link rotation capacity limits of AISC‐341. The detachable links performed similar to conventional links while their replaceability under residual drift was demonstrated.
Human Induced Vibration of Long Rectangular Steel and Composite Floors
Authors: Pap Zsuzsa B. , Kollár László P.
Published: September 2021

Recently several light‐weight, long span floors are built (e.g. steel‐framed structural systems), where the design is governed by vibration control. In these cases the acceleration due to human‐ or machine‐induced vibration can be very high, which may cause human discomfort. Long rectangular plates subjected to concentrated loads are often investigated by a replacement beam with a so called “effective width”, and the amplification factor is calculated according to a SDOF system, which in the case of resonance is equal to 1/2ξ, where ξ is the damping ratio. Since damping in lightweight, steel‐framed structural systems is very low (1–3%), dynamic amplification (calculated according to an SDOF system) can be rather high. However, the steady‐state dynamic response of beams and long plates subjected to periodic loads are significantly different. The steel‐framed floors are mechanically long even in that case when the ratio of the sides of the floor is around one due to the high orthotropy. For long plates, the response and the amplification factor are substantially different from those of beams. Hence, design based on effective width may lead to 2‐4 times higher acceleration than the real values. As an example the roof of a gymnasium under construction is examined, where different sport activities (walking, running, aerobic) will take place. The natural frequency of the floor supported by steel joists is small, close to the frequency of walking, therefore a detailed vibration analysis was performed.
Investigation of the Seismic Performance of a Special Truss Moment Frame with SMAs Incorporated
Authors: Ntina Maria , Sophianopoulos Dimitrios
Published: September 2021

The present work deals with the improvement of the seismic performance of Special Truss Moment Frames (STMFs) by incorporating Shape Memory Alloys (SMAs) as dissipation devices in the special segment, which have the ability to recover their initial geometry after mechanical distortion by unloading through the phase transformation (martensitic‐austenitic phase). STMFs were initially designed with a special segment located in the middle of the truss to dissipate the input energy through the formation of plastic hinges at the four corners of the chord members. This mechanism is replaced with the input energy dissipation through the SMA deformation in a pin‐ended special segment. In what follows, a single‐story single‐bay frame is examined incorporating 1, 12 and 25 SMAs per diagonal, simulated via a 4‐DOF mechanical model consisting of two lumped masses, under selected ground motions. To further evaluate the performance of the frame with SMAs incorporated and at the same time verify the 4‐DOF model, a non‐linear dynamic time‐history analysis was conducted using SeismoStruct 2018 finite element software. The response of the proposed system is compared with the response of the conventional one. Results showed that the proposed system leads to decrease of the maximum displacement and would potentially allow a much lighter construction.
Shake Table Testing of Self‐Centring Concentrically Braced Frames
Authors: Goggins Jamie , Jiang Yadong , Broderick Brian M. , Salawdeh Suhaib , O'Reilly Gerard J. , Elghazouli Ahmed Y. , Alwahsh Hatim , Bogdanovic Aleksandra , Rakicevic Zoran , Gjorgjiev Igor , Poposka Angela , Petreski Borjan , Markovski Igor
Published: September 2021

The self‐centring system presented in this paper is a novel damage control technique designed to improve the resilience of concentrically braced frames (CBF) under seismic action. Namely, traditional CBFs can undergo large residual drifts following an earthquake event which can limit the opportunity for cost‐effective repair of the structure. Additionally, the gusset plates connecting the brace members to beams and/or columns can experience substantial rotations as a result of the compression buckling of the bracing members. Through the utilisation of post‐tensioning strands placed between flanges of beams, the novel self‐centring concentrically braced frame (SC‐CBF) system can return the frame to its original position after significant inelastic deformations experienced during large earthquakes, resulting in minimum residual drifts.

In this paper, shake table testing of the aforementioned SC‐CBF system subjected to realistic earthquake loading is presented. The research is carried out as part of the H2020 “Seismology and earthquake engineering research infrastructure alliance for Europe” SERA project. Four sets of bracing configurations, incorporating varying square hollow section (SHS) braces and gusset plates were utilised in the shake table testing. Uniaxial loading with varying shake table accelerations was executed and the structural response evaluated using data from strain gauges (SG), load cells (LC), displacement transducers and accelerometers. The measured results provide information on the important parameters such as the tensile and compressive strength of the braces, post‐buckling capacity, gusset plate strains and post‐tensioning force. These findings are then presented and the crucial local and global response performance emphasised.
Cyclic loading in vertical stainless steel links
Authors: Chacón Rolando , Martínez Jean
Published: September 2021

Vertical links are dissipative devices in form of beam‐column segments that are included in eccentrically braced frames (EBF). Studies related to different configurations of links have been presented for carbon steel elements. Moreover, stainless steel is a nonlinear metallic material with particular appeal for its structural use due to a considerable amount of capabilities such as corrosion, circular life‐cycle, strength, ductility and aesthetics. Despite the increase on the use of stainless steel for structural elements in construction, the behavior of this material for structural purposes is not described as carbon steel in all applications. The elastic stiffness, maximum load, shear deformation capacity as well as the energy dissipation in long links are generally affected by the defined geometrical parameters. Due to the material nonlinearity, this influence may be affected considerably. In this paper, a numerical model aimed at depicting the cyclic behavior of vertical short and long links subjected to seismic lateral loads is presented. The model accounts for the material nonlinearity, the geometrical nonlinearity and the detailed definition of boundary conditions from the link connection to the EBF.
Seismic Design and Performance Assessment of Steel Frames Considering Joints' Behaviour
Authors: Lemma Melaku , Rebelo Carlos , Silva Luís
Published: September 2021

Steel joints play an important role in the overall seismic behavior of steel frames. In the case of beam‐to‐column joints, the joints are composed of two regions: the connection where the beam and column are fastened together by mechanical means, and the panel zone, which is the region in the column web where deformation occurs. The deformations in the panel zone of the beam‐to‐column joint could significantly affect the seismic behavior of steel joints. In addition, the stiffness of the connection also plays a role. This paper aims to assess the effect of joint modelling on design and the seismic performance of steel moment resisting frames (MRFs) through nonlinear analyses using different modelling strategies. A parametric study is conducted on three steel moment resisting frames of 3, 6 and 9 storeys. These frames are designed for both gravity and seismic load cases according to the current Eurocodes. Beam‐to‐Column joints are designed and characterized based on the pre‐normative design recommendations obtained in the scope of the Equaljoints project. Consequently, simplified modelling methods that disregard the joints, and refined modelling techniques that account for the joints' dimension and behavior are adopted for three different joint types classified based on stiffness and strength of the joints. A systematic assessment of the performance of each frame is assessed through nonlinear analyses. An integrated design and performance assessment tool is developed in Python and implemented using OpenSees.
Experimental assessment of bolted T‐stubs under cyclic loading
Authors: Oliveira Sara , Costa Ricardo , Rebelo Carlos , da Silva Luís Simões
Published: September 2021

A rational and efficient seismic design requires a detailed characterization of the members and joints behaviour. The prediction of moment‐rotation response of steel beam‐to‐column joints under cyclic loading is not fully addressed in EN 1993‐1‐8 nor EN 1998‐1. Additionally, EN 1998‐1, requires experimental evidence for the use of dissipative steel beam‐to‐column joints. Therefore, new design tools are required to predict the cyclic behaviour of beam‐to‐column joints. In the scope of the European projects “EQUALJOINTS – European preQUALified steel JOINTS” and “EQUALJOINTS+ ‐ Valorisation of knowledge for European prequalified steel joints” a software that provides analytical predictions of cyclic and monotonic response of prequalified steel beam‐to‐column joints was developed. This software embodies the cyclic component method (CCM), which is an extension for cyclic loading of the component method, coded in EN 1993‐1‐8. The cyclic behaviour of the components, required to feed the CCM, can be gathered from experimental tests using specimens similar to the component to be characterized, e.g. T‐stubs. With this objective an experimental campaign on 14 T‐stubs was conducted at University of Coimbra. Results from tests and assessment of available models are presented in this paper.
Cyclic Behavior of Tubular Steel Columns with High Yield‐to‐Tensile Strength Ratio under Asymmetric Loading Protocols
Authors: Hamauzu Shingo , Skalomenos Konstantinos A.
Published: September 2021

This paper investigates the cyclic behavior of steel columns subjected to single‐sided cyclic loading protocols driven by residual deformations. First, nonlinear time‐history analyses are performed to steel framed structures using a set of repeated earthquakes. Then, based on the dynamic analysis results, a set of single‐sided loading protocols is developed to envelop the asymmetric seismic behavior of the examined frames. The developed protocols are used to identify the new single‐sided capacity margins of steel columns in terms of strength and ductility as well as evaluate the potential of using novel high‐strength materials. In this paper: (a) the new asymmetric loading protocols are proposed based on the seismic behavior of three medium‐rise frame buildings with different beam‐to‐column strength ratios (i.e. Mpc/Mpb) which are analyzed with the aid of the finite element analysis (FEA) software ABAQUS; (b) a computational databank of the inelastic responses of square tubular steel columns with high yield‐to‐tensile (YT) strength ratio is developed by subjecting column FEA models with various width‐to‐thickness ratio and axial loads to both conventional and asymmetric cyclic loading protocols. Due to the asymmetrical nature of the cyclic protocols, a lower post‐peak strength deterioration was observed in columns that enables the definition of new, extended, ductility capacity margins. The ductility capacity ratios under the asymmetric loading protocols were found to be 1.15 to 1.71 higher than those obtained under the conventional protocols enabling the use of high‐strength steels in steel columns of smaller width‐to‐thickness ratio.
Lateral‐torsional buckling of a stiffened beam with semi‐rigid joints
Authors: Vild Martin , Bajer Miroslav , Barnat Jan , Šabatka Lubomír , Wald František
Published: September 2021

The paper presents an experiment and a numerical analysis of a steel beam subjected to three‐point bending. The beam was connected to short column stubs by bolted end plates. The joints were designed as semi‐rigid and their influence on the lateral‐torsional buckling resistance of the beam was evaluated. The cross‐sections of the beams and the columns were IPE 180 and HEB 140, respectively. The columns were 1 m long and were rigidly connected to the loading frame at their ends. The beams were 3.3 m long and were loaded at midspan. 9 beams were tested in total, from which 3 beams were without any stiffeners, 3 beams had two inclined stiffeners welded prior to the test, and 3 beams upon which the stiffeners of the same geometry were welded under load equal to 50 % of the bending resistance of the unstiffened beam. The stiffeners were at one third and two thirds of the beam span. The experiment was modelled in software using Component‐based Finite Element Method. Shell elements were used for plates and special nonlinear springs and interpolation links for simulation of bolts and welds. Geometrically and materially nonlinear analysis with imperfections was used. The experimental results were compared to the model. A sensitivity study with various levels and kinds of initial imperfections was performed.
Buckling resistance of compression members with back‐to‐back connected angle sections
Authors: Beyer André , Bureau Alain , Jaspart Jean‐Pierre
Published: September 2021

This paper focusses on the buckling resistance of compression members made of back‐to‐back connected angle sections. The studied built‐up members are connected through bolted packing plates. Due to the flexibility of this connection, these members generally do not fully work as a single member but the connection stiffness has to be accounted for. In Eurocode 3 Part 1‐1 it is currently admitted to neglect the effect of the connection stiffness if the packing plates possess a maximum distance of 15 imin (imin is the minimum radius of gyration of one individual angle section, also called “chord”). Elsewise the influence of the packing plates on the member resistance should be accounted for. The limit distance of 15imin appears to be much lower than the past practice, consequently leading to a more conservative design and a complexification of the fabrication. This paper therefore presents a sensitivity analysis focusing on the influence of several parameters as: the distance of packing plates, the presence of clearance in bolt holes and the influence of preloaded bolts. These parameters are studied with a numerical model based on solid finite elements. Owing to the use of solid elements, it is possible to model explicitly the bolts, the packing plates and all contact regions.
Interaction of geometric and material nonlinearities in stainless steel frames
Authors: González‐de‐León Isabel , Arrayago Itsaso , Real Esther
Published: September 2021

Adequate mechanical properties make stainless steel an excellent construction material for structures. The current stainless steel European structural code EN1993‐1‐4 (2015) is largely based on provisions given for carbon steel EN1993‐1‐1 (2005) and does not establish specific design rules for the global analysis of stainless steel structures. Thus, the same classification criterion applies in both codes for sway and non‐sway structures, as well as providing the same predicting expressions for the amplification of bending moments in basic structures, despite the considerable differences between the mechanical behaviour of these two materials. However, recent numerical research on stainless steel frames with H cross‐sections by Walport et al. (2019) showed that the degradation of stiffness due to material nonlinearities considerably affects the response of stainless steel frames, causing greater deformations and increasing second order effects.

In order to contribute to the optimal design of stainless steel structures, this paper investigates the influence of the nonlinear material response of stainless steel alloys on frame‐type structures with Rectangular Hollow Sections based on the experimental results conducted by Arrayago et al. (2019), and the interaction of material and geometric nonlinearities.
Lateral torsional buckling of an I‐shaped hoisting spreader beam
Authors: Snijder Hubertus H. , Ploegmakers Dirk , Dekker Rianne , Maljaars Johan
Published: September 2021

I‐shaped hoisting spreader beams are widely used in practice when lifting heavy objects by crane. In general, I‐shaped beams that are subjected to a bending moment may be sensitive to lateral torsional buckling. Eurocode 3 (1993‐1‐1 [1]) provides a calculation method to determine the lateral torsional buckling resistance using buckling curves. The method requires the elastic critical moment to calculate the relative slenderness. Different solutions for elastic critical moments are available which usually require fork end conditions. However, hoisting spreader beams do not have fork end conditions nor do they have lateral supports. Thus, the available calculation methods cannot be used and a new method is developed. A numerical model is validated against an experiment and subsequently used to investigate different types of spreader beam configurations. First a method to determine the elastic critical moment of a hoisting spreader beam is developed. Then the lateral torsional buckling resistance is evaluated using the buckling curves. The applicable buckling curve is determined by choosing the least conservative curve that can be used with a partial factor of 1.0. This results in buckling curve d to evaluate the lateral torsional buckling resistance of hoisting spreader beams.
Simplified design method for stiffened cellular beams against web‐post buckling
Authors: Glorieux Antoine , Cajot Louis‐Guy , Hanus François
Published: September 2021

Web‐post buckling next to Vierendeel effect, is one of the main failure modes for cellular beams. Several solutions are available to avoid web‐post buckling, such as ring stiffener or infill opening. A new cost‐effective solution is to weld a vertical plate stiffener on the web‐post. This plate stiffener should bring enough inertia to prevent buckling. It is not necessary that the plate stiffener is welded to the flanges, so it does not require as accurate cutting as a ring stiffener or an infill opening. An analytical method is proposed to calculate the bearing capacity of such a stiffened cellular beam. This consists in an adaptation of the existing design method presented in prEN 1993‐1‐13 for steel beams and in EN 1994‐1‐1: Eurocode 4 Annex Composite beams with Web Openings for composite beams. The analytical method has been compared to a numerical parametrical study using Finite Element software SAFIR®. Influence of various parameters has been studied. Results show that depending on the geometry, vertical stiffeners can increase the bearing capacity of the beam up to 35%. In all modelled cases, the stiffener avoids the web‐post buckling. Two main webpost failure modes were identified, buckling of the first unstiffened web‐post (generally when only one web‐post is stiffened) and bending of the first stiffened web‐post. For the latter, a verification has been added in the analytical method. Additionally, a cost analysis has been performed to compare different solution to increase the bearing capacity of the beam.