bluuebunny/crossref_metadata_2025 huggingface dataset:
08.13: Structural performance assessment of steel frames with reinforced concrete walls
Authors: Vogiatzis Tzanetis , Avdelas Aris
Published: September 2017

In recent years, there has been a growing interest towards the use of a composite structural system consisting of steel frames with reinforced concrete walls (SRCWs) as an economical alternative within earthquake resistant wall systems. The SRCW system is classified as Composite Structural Systems Type 1 in EN 1998‐1:2004. It has been shown that the SRCW system has the potential to be applicable as a lateral‐resistance system for low‐to‐moderate rise buildings located in earthquake‐prone regions as it has the potential to offer strength appropriate for resisting the lateral forces from earthquakes and stiffness adequate for controlling drift. Within the frame of this paper, analytical studies are conducted in order to obtain a better understanding of the SRCW system structural performance. Numerous three dimensional (3D) nonlinear Finite Element (FE) models have been developed using ANSYS software package. The detailed developed 3D FE models include the horizontal and vertical boundary steel elements, the discrete reinforcing bars, discrete stirrups as longitudinal and transverse confinement reinforcement, the shear connectors, the top and seat angles and the web angles including the bolts. Results and findings of this study are indicative of effectiveness of the headed studs geometry and material properties.
08.15: Axial behaviour of concrete filled lean duplex stainless steel square hollow sections
Authors: Lam Dennis , Yang Jie , Mohammed Asif
Published: September 2017

Stainless steel hollow sections have been used in building constructions for a number of years due to their durability and superior mechanical properties. However, they are less favourable than the carbon steel counterpart owing to their relatively high cost. A new, low nickel content stainless steel (EN 1.4162) or commonly referred as ‘lean duplex’ has been developed; which has over two times the strength of the more familiar austenitic stainless steel but at approximately half the cost. This more economical alternative would definitely be an attractive option to the construction industry. This paper presents the behaviour of axially loaded concrete filled composite stub columns with lean duplex stainless square hollow sections. A series of tests was performed to consider the behaviour of short composite stainless steel columns under axial compressive loading, covering lean duplex stainless steel square hollow sections filled with normal to high strength concrete. Based on the experimental studies, a modified equation based on the current Eurocode 4 on steel concrete composite structures is proposed.
08.16: Static shear capacity of small‐scaled pin shear connectors
Authors: Wolters Kevin , Kopp Maik , Feldmann Markus , Claßen Martin , Schäfer Johannes
Published: September 2017

Through the use of high‐strength steel as well as high‐strength (HSC) and ultra‐high‐performance concrete (UHPC) in composite constructions slender, wide spanning and highly sustainable composite surface elements can be implemented for the use in architecturally sophisticated structures. Due to their favourable ratio of strength to weight, the high‐strength concrete and steel allow a significant reduction of the dimensions of load‐bearing elements compared to normal‐strength materials. Thus, for certain fields of application the theoretical thicknesses of concrete chords can be reduced to less than 30 mm. However, for such slender composite structures and concrete chords the applicability of conventional shear connectors like headed studs is no longer given. The systematic connection of the composite cross sections requires novel, small‐scale shear connectors transmitting anchorage and shear forces through the composite joint.

Therefore, the focus of the paper is on the local static load‐bearing and slip capacity of the pin‐structures due to shear forces. The paper presents the experimental and numerical results as well as the engineering models with the resulting design equations.
08.21: Shear strength of headed stud push‐out tests: Comprehensive literature review focusing on slab type, failure mode, and large‐diameter headed stud
Authors: Hirama Chihiro , Ishikawa Takashige , Hisagi Akie
Published: September 2017

In the revised 2011 Japanese Industrial Standards, headed studs of 10 mm and 25 mm diameters were addressed. However, consideration of their mechanical properties remains insufficient; the shear strength characteristics of headed studs with diameters of more than 25 mm should be considered. To verify the shear strength of headed studs with other diameters, studies have been conducted using various methods. However, few studies have examined their overall shear strength tendencies. In this literature review, therefore, the shear strength tendency is comprehensively evaluated using experimental data from existing push‐out test results.

The push‐out test results were obtained from published studies. Of the 1,002 results, the shear strength characteristics of headed studs were analyzed in terms of the headed stud diameter, slab type, and failure mode. The shear strength of the headed studs in solid slabs was approximately equal to the product of the headed stud tensile strength and total cross‐sectional area of the headed stud shaft component. The shear strength value was approximated because the push‐out test results were influenced by both the pure shear strength and concrete strength. This tendency was especially prominent in the case of headed stud failure. A similar tendency, although with variations, was observed in the case of concrete failure.

The shear strength of headed studs in slabs with a steel deck cut on the flange also showed a trend similar to that in solid slabs. On the other hand, the shear strength of headed studs in slabs with a steel deck across the flange showed a different tendency and was less than that in solid slabs. The specimens having slabs with steel decks across the flange could be classified as those having headed studs welded through a steel deck and those having headed studs directly welded to the flange. However, their shear strength tendency was almost equal. The shear strength of headed studs with a diameter of more than 25 mm in solid slabs gradually decreased with the increasing diameter in both failure modes. Through comprehensive studies, three kinds of shear strength evaluation formulas were derived. Furthermore, the shear strength of the headed studs with a diameter of more than 25 mm were studied by slab type and failure mode.
08.25: The influence of the concrete slab on the behaviour of steel‐concrete composite joints for braced frames
Authors: Fasan Marco , Bedon Chiara , Amadio Claudio
Published: September 2017

In current practice, the design of seismic resistant steel‐concrete composite braced frames generally aims to ensure a structural behaviour for beam‐to‐column joints as close as possible to perfect hinges, hence preventing any kind of interaction with the bracing system. The global performance of steel‐concrete composite joints, on the other hand, is markedly affected by the structural interaction between the concrete slab and all the steel components at the beam‐to‐column intersection. This is especially true during seismic events, when compression forces can typically arise in the concrete slab in the vicinity of the column, leading to the occurrence of struts in contact with the column itself. As such, for appropriate design assumptions, it is thus necessary to fully understand the influence of the joint components interactions.

To this aim, in this paper a refined Finite Element (FE) model representative of a hinged beam‐to‐column joint in a braced frame is implemented in the ABAQUS computer software and validated with experimental results. A full 3D solid modelling approach is first taken into account, with careful consideration for the geometrical and mechanical properties of each joint component, as well as for the corresponding contact interactions, including properly calibrated damage material models. After a preliminary validation of the FE modelling approach carried out towards earlier full‐scale experimental tests, a parametric FE study is proposed. By taking into account four different geometrical configurations for a reference steel‐concrete composite joint, in particular, being characterized by (i) absence of slab, (ii) presence of slab with partial interaction with the column (i.e. isolated slab), (iii) presence of slab with interaction (even with small gap on one side) and (iv) fully interacting slab, major FE outcomes are critically discussed. It is shown, in this regard, that the isolation of the slab is typically associated to important effects on the structural performance of the joint itself, compared to a fully interacting concrete slab.
08.34: Influence of profiled steel sheet on the load‐carrying capacity of concrete composite slabs with rebar truss
Authors: Wan Haiying , Feng Ran , Li Tangying
Published: September 2017

This article is not available for publication.
08.35: Compressive behavior of concrete filled double skin sections consisting of corrugated plates and ultra‐high strength steel corner tubes
Authors: Farahi Mojtaba , Heidarpour Amin , Zhao Xiao‐Ling , Al‐Mahaidi Riadh
Published: September 2017

Concrete filled tubular (CFT) sections and the most recent configuration of these sections, concrete filled double skin tubular (CFDST) sections, are being increasingly utilized in structural constructions due to their high strength and great performance under fire. CFDST sections generally consist of two steel hollow sections where the gap between the steel skins is filled with concrete. In this study, the mechanical performance of a new type of CFDSTs consisting of corrugated steel skins and ultra‐high strength steel (UHSS) or mild‐steel (MS) corner tubes is investigated. The efficiency of corrugated skins and UHSS or MS corner tubes is experimentally examined through conducting monotonic compressive tests. It is shown that employing steel skins with corrugated geometry may significantly increase the post‐peak compressive strength of CFDST sections. In addition, the experimental results are revealed that the non‐ductile compressive behaviour of ordinary CFDST sections can be effectively improved by employing UHSS corner tubes in fabrication of these sections. A finite element modelling framework is also developed to simulate the behaviour of the proposed high strength corrugated CFDST columns. The numerical modelling is first validated against the experimental results. The outcome of the paper indicates the potential of corrugated CFDSTs with UHSS or MS corner tubes to be used in various civil engineering construction.
08.37: Experimental analysis of concrete‐filled double skin tubular columns subjected to eccentric loads
Authors: Ibañez Carmen , Piquer Ana , Hernández‐Figueirido David , Martínez‐Ramos Óscar
Published: September 2017

The results obtained from an experimental campaign on concrete‐filled double‐skin steel columns subjected to eccentric loads are presented in this paper. The program includes columns with equivalent cross‐sectional area but with different shape combinations of the inner and outer steel tubes: circular‐circular, circular‐rectangular and square‐circular tubes. The experiments have been designed considering columns with steel tubes of different dimensions and concrete infill with different strength: normal (NSC) and high strength concrete (HSC). Besides, all the tubes employed for the configuration of the columns are thin‐walled steel tubes.

The effects of materials and geometry are studied in order to find the best configuration attending to ultimate capacity, strength index and concrete contribution ratio. Results show that as expected, the use of HSC results in an increment in the load bearing capacity and in the concrete contribution ratio of the columns, which decreases with eccentricity. Regarding the shape effect, the configuration with circular‐circular tubes proved to be the most efficient, contrarily to the rectangular‐circular double skin section.
08.48: Double‐steel plate composite shear walls: In‐plane seismic behaviour
Authors: Elmatzoglou Michaela , Avdelas Aris
Published: September 2017

Double‐steel plate concrete (SC) composite shear walls are a structural system intensively used in nuclear facilities due to its exceptional performance. It consists of a concrete core with exterior steel faceplates serving as reinforcement. These steel faceplates are anchored to the concrete infill using headed steel studs which guarantee the composite action between the two different materials. The focus of this research is the investigation of the seismic performance of rectangular SC composite shear walls for application to buildings. A simple and cost‐efficient form of the SC wall is proposed based on the research conducted by Vazouras and Avdelas [1]. Its efficiency has been proved through extensive numerical analysis using a simplified finite element model developed in ANSYS [2] to simulate the nonlinear cyclic response of SC walls. The accuracy of the developed numerical model was validated using experimental data reported in the literature [3, 4]. The numerical predictions included global force‐displacement responses, strain and stress distributions on each material and damage to the steel plates and concrete. A typical damage pattern of the SC walls included yielding, local buckling and tearing of the steel plates in conjunction with cracking and crushing of the infill concrete. The impact of various parameters on the in‐plane response of SC walls has been investigated including wall aspect ratio, reinforcement ratio, slenderness ratio, wall thickness, yield strength of the steel plates and uniaxial compressive strength of concrete.
08.50: A study on the bond stress‐slip behavior between engineered cementitious composites and structural steel sections
Authors: Rana Mohammad M. , Lee Chi King , Al‐Deen Safat
Published: September 2017

The performance of traditional steel‐concrete composite beams, which are commonly used in many building floor systems, could be further enhanced by introducing Engineered Cementitious Composites (ECC) as an additional composite component. The performance of such ECC‐concrete‐steel composite beams under high shear loading conditions will be significantly affected by the bond‐slip behavior between ECC and structural steel section. When studying the bond slip behavior between ECC and structural steel, simple push test is an inexpensive and convenient method to investigate the complex interaction between ECC and steel. Such push test study is an important step toward understanding the bond behavior and evaluating the performance of these types of beams. In this context, this paper presents results from twelve specially designed push tests that aim to determine the bond characteristics between ECC and structural steel strips. The results of this study present the bond stress‐slip behavior and failure modes under different cover thickness of ECC and the bond length specimens.
08.52: Numerical modeling of circular CFT columns with experimental verification
Authors: Hwang Ju‐young , Kwak Hyo‐Gyoung
Published: September 2017

CFT column has a lot of structural advantages due to the composite behavior between in‐filled concrete and steel tube. This paper deals with the resistance capacity of CFT columns by numerical method with developed bond‐slip model between in‐filled concrete and steel tube which can simulate the behavior of CFT without changing mechanical properties of in‐filled concrete. Since the applied axial load to in‐filled concrete is delivered to steel tube by the confinement effect and the friction, the governing equation related to the slip behavior can be constructed on the basis of the force equilibrium and the compatibility conditions. Developed model is described behavior of CFT to take into account this effect of bond‐slip to calculate confinement effect of in‐filled concrete by steel tube. Moreover, experimental verification of suggested numerical model is conducted with double curvature bending test.
09.11: Acoustic emission signal characteristics of damage accumulation in non‐buckling steel plate shear wall
Authors: Sun Feifei , Xiao Ben , Zhang Yunfeng
Published: September 2017

This paper deals with acoustic emission (AE) monitoring of non‐buckling steel plate shear walls, in order to estimate damage accumulation of steel plate walls under cyclic loading. When material or any internal element in steel members develops plasticity or crack begins to form and grow rapidly, a large amount of energy will be released quickly within a short period. This would produce a series of transient stress waves, which is called AE signals. AE signals of the overall process contain useful information of irreversible accumulated damage in structural fatigue fracture progression. Continuous monitoring of low cycle fatigue plastic damage accumulation in steel plate walls is demonstrated in a corrugated‐shape steel plate wall under cyclic loading. Using the laboratory test data, the relationship between AE signals and fatigue damage accumulation in steel plate walls have been studied. It is revealed that the AE hit counts and energy can be used as one of the reference standards for judging the degree of plastic damage accumulation of material. AE damage accumulation evaluation based on AE hit and AE energy is a promising method for damage evaluation of steel hysteretic damping member. Compared with other conventional damage evaluation methods, it provides a new nondestructive testing approach to quantify the plastic damage of material, and it can be used to evaluate the member condition that are difficult to access.
09.13: The right choice of steel: Towards an optimized choice of the steel grade for toughness assessment
Authors: Tibolt Mike , Kühn Bertram , May Marc
Published: September 2017

The choice of steel is generally ruled in EN 1993‐1‐1: 2005. The standard specifies several requirements for the choice: the material properties, the ductility, the toughness properties and the through‐thickness properties.

The simplified design rules in the different parts of EN 1993 are based on the principle of limit state design. It assumes that the resistance of cross‐sections and members are determined in tests which comply with product standards (e.g. EN 10025‐4) and execution standards (e.g. EN 1090‐2: 2008) and which are evaluated according to EN 1990. Since the tests are conducted at room temperature, the design rules and the safety concept apply to the upper shelf region of the toughness‐temperature curve where the steel behaves ductile with sufficient toughness. Hence, the design rules only cover ductile failure modes and are only related to the material properties. For brittle failure in the lower shelf region, the assumptions for the design rules and safety concepts are no longer met. Therefore, brittle failure is accounted for with the right choice of the steel with sufficient toughness (Table 2.1 in EN 1993‐1‐10: 2005). This two‐way safety assessment ensures appropriate safety of steel structures in the full temperature application range.

Table 2.1 has been mainly derived for welded construction details in bridges subject to fatigue. In consequence, the rules in EN 1993‐1‐10: 2005 could be extremely conservative if applied to elements subject to quasi‐static loading. According to EN 1993‐1‐10: 2005, an alternative approach to Table 2.1 consists in the application of fracture mechanic theory. However, the procedure in the standard is only generally described. Therefore the approach is rarely used and Table 2.1 is applied, so to speak, for elements in buildings and bridges. Finally, this often leads in general structural applications to an uneconomic choice of steel for toughness assessment.

This paper gives guidance on the right choice of the steel grade according to the Eurocode and highlights the advantages of thermomechanical steels for each criterion. In addition, a new table for the choice of the steel grade for elements under compression and subject to quasi‐static loads will be proposed in this paper. The table is based on the same fracture mechanic approaches and standard detail than Table 2.1, but with the difference that crack growing is adapted to quasi‐static loading.
09.18: Innovative composite deck slab for railway bridges: Analysis of the fatigue behaviour of the shear connectors using the strain‐life method
Authors: Takacs Patrik , Fink Josef
Published: September 2017

At Vienna University of Technology, Institute of Structural Engineering, a new, extremely slender steel‐concrete‐steel composite (SCSC) plate is under investigation to meet the requirements of today's standards related to the geometric conditions and noise emission in the substitution of old railway bridges. The layered construction consists of two steel cover plates with an unreinforced concrete core. Perforated shear connectors, welded alternately to the outer steel plates, work together to ensure the transmission of the shear flow between the outer plates. In addition to the distribution of the traffic load in cross direction, the SCSC deck slab also acts as main girder bottom flanges in longitudinal direction of the bridge construction. After the examination of the static load bearing capacity in former research programs [1, 2], the current investigations are focussed on the fatigue behaviour of the shear connector of the SCSC plate.

In the course of research a nonlinear, three‐dimensional finite element model served as the basis for a lifetime calculation using the local strain‐life method. The aim was to investigate the relation between the range of traffic load and the bearable number of load cycles of the SCSC plate till crack initiation in the shear connectors. This paper provides an overview of the approaches used to calculate fatigue life and gives a brief summary of the results.
10.02: Numerical simulation of fire‐resistance test of steel beam
Authors: Cábová Kamila , Lišková Nikola , Benýšek Martin , Zeman Filip , Wald František
Published: September 2017

The paper describes a virtual furnace for fire‐resistance tests following standard fire conditions. The model takes advantage of great possibilities of computational fluid dynamics code Fire Dynamics Simulator. The model is based on an accurate representation of a real fire furnace of fire laboratory PAVUS a.s. located in the Czech Republic. It includes geometry of the real furnace, material properties of the furnace linings, burners, ventilation conditions and also a tested specimen with measurement devices. The model allows controlling of gas temperature and the static over pressure in the volume of the furnace as it is specified in requirements of European standard for fire resistance tests. The accuracy of the model is validated to a fire test of empty horizontal furnace executed in the fire laboratory, which was except other carried out to harmonize initial settings of burners in the model. Then, the virtual furnace is used to investigate thermal behaviour for fire‐resistance test of a steel beam. The results of the virtual furnace illustrate the great potential for investigating the thermal behaviour of fire‐resistance tests.
10.03: Numerical investigation on the fire behaviour of steel beams with local fire protection damages
Authors: Bihina Gisèle , Zhao Bin
Published: September 2017

The mains results from a numerical investigation on protected steel beams with localized fire protection damages in the Auditorium of Maison de la Radio in Paris are presented. These damages were caused by the implementation of a suspended ceiling fixed to the beams by means of rails, and observed near and at fixation points. In order to check the fire behaviour of these beams, a numerical study coupling a heat transfer analysis and a structural bearing capacity calculation was conducted under Ansys computer code. The partial lack of fire protection was accounted for by considering square holes through the whole sprayed protection thickness in the heat transfer analysis. Critical sizes beyond which the required R90 fire resistance rate is not met were defined, which enables to avoid any costly refurbishment of the sprayed fire protection.
10.04: Behaviour of plane frames of high strength steel in fire
Authors: Shakil Saani , Lu Wei , Puttonen Jari
Published: September 2017

Mechanical properties given in the design code EN 1993‐1‐2, are obtained from researches on low strength mild steel. The applicability of these material properties to high strength steel (HSS) grade is thus, an area of interest. In this study, the behaviour of a planar frame made of high strength steel (HSS) in fire is studied by applying the finite element method. A material model was created using stress‐strain formulation from EN 1993‐1‐2 with reduction factors being from elevated temperature tests of HSS in literature as well as from EN 1993‐1‐2. FE analysis is carried out by Abaqus software using dynamic explicit solver so that non‐linear deformations can be simulated. Continuum elements are used to create FE model because of their capabilities to catch temperature distribution and local failure across cross‐sections of frame members. The FE model is validated by simulating experimental tests on mild steel frame from literature. With this validated model, the behaviour of the frames made of mild steel or HSS were compared based on deformation, critical temperatures, duration for collapse, and failure modes. Further, the behaviour of HSS frames using material data from different references were also compared. It is observed that deviations of mechanical properties at elevated temperatures from those in EN 1993‐1‐2 affect the behaviour of the frame.
10.07: Numerical analysis of the fire resistance of high‐strength steel circular columns
Authors: Tondini Nicola , Demonceau Jean‐François
Published: September 2017

High strength steels (HSS) have specific chemical compositions, which primarily depend on rolling tempering techniques, element thickness and the producer. Nonetheless, EN1993‐1‐12 related to HSS up to S700 grade does not provide any additional note on the design of steel structures subjected to fire and the designer is referred to EN1993‐1‐2 valid up to S460 grade. This paper presents the results of a numerical analysis on the behaviour at elevated temperature of Circular Hollow Sections (CHS) columns made of HSS. In details, three full‐scale HSS CHS columns with average measured yield strength of 822 MPa and 3.15 m long were tested under the standard ISO fire with constant eccentric compression load. Two members were made of a cross section 323.9 mm × 10 mm and one of a cross section 355.6 mm × 12 mm. The constant applied loads during the tests were respectively equal to 10%, 14% and 19% of the axial capacity of the columns at ambient temperature. Then, a nonlinear thermomechanical finite element model made of solid elements was developed by means of ABAQUS. A fully‐coupled analysis using Geometrically and Materially Nonlinear Imperfect Analysis (GMNIA) was employed meaning that the temperature field was determined together with the stress‐displacement fields. The calibration of the numerical model was carried out against experimental data by exploiting the thermal and the mechanical properties of steel provided in EN1993‐1‐2. A sensitivity analysis was performed to highlight the main parameters that affect the simulation results, i.e. mesh size, residual stresses, geometrical imperfections etc. The calibration process showed a good agreement between the numerical results and the experimental outcomes both in terms of failure temperature and of failure mode. With the calibrated model, it was finally possible to perform a preliminary parametric analysis by varying the applied load and the column relative slenderness to assess the appropriateness of the buckling curve included in EN1993‐1‐2 to predict the fire resistance of HSS CHS columns.
10.11: Fire design of rectangular hollow section joints
Authors: Bączkiewicz Jolanta , Malaska Mikko , Pajunen Sami , Heinisuo Markku
Published: September 2017

The component method is a design approach for the characterization of the mechanical properties of structural joints and it is referred to in Eurocode 3 Part 1‐8. Eurocode design rules for open sections are already based on the component method. The design rules for joints between tubular hollow sections are still based on simple theoretical mechanical models validated against experimental test results. However, there are research activities in progress to extend the application of the component method also to hollow section joints in the next revision of Eurocode. The fire design of steel joints is carried out in accordance with Eurocode 3 Part 2. Eurocode gives only a guidance on how the temperature of the joint components can be assessed based on the local values of thermal resistance of the joint's fire protection. The method is not sufficient for the component method and Tampere University of Technology is currently carrying out experimental fire research to better understand the temperature distributions in the vicinity of the joint. The aim of the research is to develop experimental methods to determine steel temperatures at the actual joint component, spring, locations and to transfer this information into the joint design approach based on the component method. This paper introduces an experimental research demonstrating the actual temperature distributions within the joint area and highlights the differences between the failure modes and the design criteria at normal temperature design and fire design of a joint.
10.13: Bending resistance evaluation of shallow floor beams exposed to fire
Authors: Leskela Matti V.
Published: September 2017

For the moment, the Eurocode 4 standards give detailed analysis rules merely for the standard or ordinary composite beams where the concrete section rests on the top flange of a steel beam. In contrast to shallow floor beams (abbreviated as SF‐beams), where only the bottom flange is directly exposed to fire, the ordinary composite beams do not have any inborn fire protection. Although the SF‐beams are not excluded from the scope, no special design rules are given for them, and they only appear in one schematic figure in EN 1994‐1‐2. The basic method for evaluating the bending resistance of fire exposed composite beams is based on the employment of rigid‐plastic stress blocks in steel and concrete. However, it is also possible to utilize elasto‐plastic analysis, where the flexural strain distribution and the corresponding stresses are taken into account, and the maximum compressive strain of the concrete could be set to control the straining. The analysis results between the rigid‐plastic and elasto‐plastic sagging bending resistances of fire exposed SF‐ beams are compared and the additional useful information obtained from the latter analysis is illustrated. For any strain distribution that fulfils the equilibrium of internal stress resultants of the composite section, there is a well‐defined bending moment, curvature and bending stiffness. The data following from the elasto‐plastic stress analysis can further be utilized for evaluating nominal deflections that cannot be associated with the rigid‐plastic resistance analysis.
10.16: Behaviour of high‐strength bolts at elevated temperatures under double‐shear loading
Authors: Seif Mina , Weigand Jonathan , Peixoto Rafaela , Vieira Luiz
Published: September 2017

During fire events, connections in steel structures may be subjected to large unanticipated deformations and loads. These fire effects can produce failures of connections, including local buckling of the connection zone, rupture of connection plates, shear rupture of bolts, and bolt tear‐out rupture of beam webs. Thus, a key issue in evaluating the response of structural systems to fire effects is the proper representation of material behaviour, including fracture, at elevated temperatures. Temperature‐dependent material behaviour of structural steel plates has been studied by many researchers, both experimentally and numerically. However, the behaviour of structural steel bolts at elevated temperatures, especially under shear loading, is not well established in the literature.

This paper presents results from recently conducted tests of high‐strength structural bolts subject to double shear loading at elevated temperatures. The parameters varied between tests included the bolt grade, bolt diameter, and temperature. Bolt grades A325 and A490 were tested. For each bolt grade, three different diameters were tested (19 mm, 22 mm, 25 mm) at five different temperatures (20 °C, 200 °C, 400 °C, 500 °C, and 600 °C). Three tests were conducted for each combination of parameters. Degradation in the mechanical and material properties were characterized. In addition, a new component‐based model for high‐strength bolts was developed based on the experimental data. The component‐based model is shown to accurately account for the temperature‐dependent degradation of bolt shear strength and stiffness, while also providing the capability to model load reversal.
10.17: Mechanical properties of high strength Q690 steel at elevated temperatures
Authors: Wang Weiyong , Zhang Linbo
Published: September 2017

High strength steels have been used extensively as primary load bearing structural members in many applications in the building industry. Therefore, fire safety design of structures using such steels has become more important. Deterioration of mechanical properties and creep deformation are considered the most important factors affecting the behaviour of steel structures in fires. A research project based on experimental studies was, therefore, undertaken to investigate the deterioration of mechanical properties and creep of high strength Q690 steel with nominal yield strength of 690MPa. Tensile coupon tests were undertaken to determine the mechanical properties of this steel at temperatures ranging from 20 to 900°C. Test results showed that the currently available reduction factors are not applicable to fire safety design of high strength Q690 steels. Therefore, new predictive equations for the mechanical properties of yield strength and elasticity modulus were developed at elevated temperatures. Creep test were also carried out to quantity the creep deformation of Q690 steel at temperatures ranging from 450 to 900°C. Results from creep tests are utilized to develop relations for expressing creep as a function of temperature and stress. These relations, which are based on Fields & Fields model, can be utilized to account for creep effect in modelling the response of Q690 steel structures exposed to fire.
10.19: The steel and fibre‐reinforced concrete circular hollow section composite column exposed to fire
Authors: Illia Tkalenko , Alexey Tretyakov , František Wald , Josef Novak , Radek Stefan , Alena Kohoutková
Published: September 2017

The recent development in technology of production and transport of the steel fibre‐reinforced concrete enables its utilization in composite steel‐concrete structures. This work is focused on development of mechanical behaviour and design model of circular hollow section (CHS) composite steel and fibre‐concrete (SFRC) column at elevated temperature. Research includes two levels accuracy/complexity, allowing simplified or advanced approach to design following the coming changes in European standard for composite member design in fire (EN1994‐1‐2:2005) [1]. Experimental studies of the project include mechanical tests of heated fibre‐concrete samples in tension and compression, thermal behaviour under uniform and non‐uniform loading of stubs of CHS and tests of full scale SFRC CHS columns in steady‐state and transient‐state regimes. Developing advanced finite element method (FEM) simulation of global mechanical behaviour of SFRC CHS columns is a multi‐levelled composite mechanical and thermo‐model and provide numerous numerical experiments. Together with standard steel material model in fire, FEM model of mechanical behaviour of fibre‐reinforce concrete at elevated temperature is prepared. Validated simplified and advanced thermal model of SFRC CHS at elevated temperature gives temperature fields and moisture distribution inside section which depends on direction, heat flux, sizes and gives possibility to model different fire cases of full‐scale columns in bending and buckling at elevated temperature.

Prepared analytical and simplified FEM mechanical model of column is taking in account degradation of mechanical properties, analytical models of transfer of heat inside column section and provides simplified solutions for designers.
10.22: Comparing the fire behaviour of composite columns made with concrete filled double‐skin and double‐tube steel sections
Authors: Camargo Aline L. , Rodrigues João Paulo C. , Fakury Ricardo H. , Lopes Ruben
Published: September 2017

The use of composite concrete filled hollow columns has increased in the last decades. This type of column has several advantages, such as the exemption of using formworks, a higher load bearing capacity and the prospect use of smaller cross sections. Although it has a good behaviour in fire situation, the use of slender columns, mainly in tall buildings, makes necessary to find solutions for increasing the fire resistance. In this sense, this paper presents a comparative experimental study on the fire resistance of composite columns made with concrete filled double‐skin and double‐tube steel sections and with restrained thermal elongation. A set of fire resistance tests, on a special set‐up, were carried out. The double‐tube columns had two steel tubes, one external and one internal, with approximately half the diameter of the outer tube, both tubes were concrete filled. The double‐skin columns had also two steel tubes, but the inner tube was void. Several parameters were investigated, such as the load level, stiffness of the surrounding structure and type of concrete infill. The paper presents results for fire resistance, restraining forces, axial deformation and deformed shapes of the tested columns.
10.26: Parametric numerical analysis of cold‐formed steel Σ‐shaped beams under fire
Authors: Laím Luís , Rodrigues João Paulo C.
Published: September 2017

A numerical investigation into the structural behaviour of cold formed steel beams commonly used in warehouses and industrial buildings subjected to fire is presented in this paper. The structural performance of cold‐formed steel beams under fire conditions has been studied over the last years. However, the great majority of them have been performed on single and lipped channel beams and assumed that the internal forces and moments at supports of the members remain unchanged throughout the fire exposure. Hence, a detailed parametric numerical investigation into the response of axially and rotationally restrained compound cold‐formed steel beams in fire has been addressed in this paper. Therefore, in the first phase of this research, a suitable finite element model was developed and calibrated with results of experimental fire tests previously carried out by the authors. And then, a parametric analysis was undertaken using the calibrated finite element model with the purpouse of investigating numerically the effect of some parameters such as section geometry, initial applied load on the beam, slenderness and the influence of those two kinds of elastic restraint on the critical temperature of the beams.

Finally, the results of this research showed mainly that the critical temperature of this type of beams with elastically restrained thermal elongation may drop significantly and, beyond a certain value of axial or rotational stiffness of the surrounding structure it may be no longer possible to change the fire response of them.
10.29: The thermal response of corrugated web beams subjected to fire
Authors: Both Ioan , Kyzlik Petr , Vacha Jaroslav , Wald Frantisek , Zaharia Raul
Published: September 2017

The corrugated web beams represent an alternative for material saving by decreasing the web thickness. By reducing the web thickness to values of 1.5 mm to 3 mm, the thermal massivity of the web is reduced, leading to faster temperature increase in fire situation. Moreover, since the flange thickness is unchanged compared to a common flat web beam, the temperature gradient between the two parts is higher in case of corrugated web beams.

In a previous study of the authors, an ISO fire test was performed on five typologies of individual elements in a furnace, in which the temperature development in the corrugated web beams were monitored. Starting from the simple relations provided in EN 1991‐1‐2, an analytical model was proposed to consider the heat transfer by conduction from the web to the flange. Two of the individual elements tested were also studied numerically, using the general purpose computer code Abaqus. The temperatures obtained numerically follow closely the temperatures recorded during the three considered specimens.

The present paper further validates the numerical model against the experimental results obtained for the other three specimens and presents a numerical study on the recently added typology of corrugated web beams with the web thickness of 6 mm.
10.30: Mechanical response of steel structures in fire: Influence of different material and creep models
Authors: Dolinar Urška , Ogrin Anita , Planinc Igor , Hozjan Tomaž
Published: September 2017

The paper deals with the influence of viscous creep of steel on the behaviour of steel structures during fire. Two stress‐strain relationships for structural steel, combined with Harmathy's explicit model of viscous creep at elevated temperatures, are presented in the paper: (i) bilinear stress‐strain relationship and (ii) modified Poh's stress‐strain relationship. The presented models have been implemented in self‐developed software Pozar for numerical analysis of mechanical response of planar steel frames in fire. Further on results are validated against experimental ones published by Rubert and Schaumann, 1985. The numerical results, obtained with stress‐strain relationship according to the Eurocode 3, are added for comparison. It is shown that all tested models give satisfactory results for small load ratios. Poh's stress‐strain relationship in combination with Harmathy's model of viscous creep and newly proposed coefficients give the best results among the tested models with explicitly considered viscous creep. However, none of the considered models give good agreement with the experiment at high values of load ratio. Furthermore, the comparison between the different material and creep models is conducted for three heating regimes, namely linear heating regime and fast and slow natural fire development. A prominent influence of the employed material model on the final midspan displacements is observed.
10.33: Flexural buckling behaviour of high strength steel columns under fire conditions
Authors: Winful Dorothy A. , Afshan Sheida , Cashell Katherine A. , Barnes Adrienne M. , Pargeter Richard J.
Published: September 2017

In this paper, a numerical modelling study using the finite element (FE) analysis package ABAQUS [1] has been carried out to study the flexural behaviour of square and rectangular hollow section columns made from high strength steel (HSS) grades S690QL and S700MC at temperatures up to 800°C. The FE model was validated using existing experimental data and then parametric studies were performed on columns with varying length and cross‐sectional properties. The results have been compared with recommendations given in Eurocode 3 Part 1–2 [2]. The analyses showed that the Eurocode is generally conservative with respect to the buckling coefficients derived and safely predicts the buckling behaviour resistance of columns made from S700MC and suggest a lower buckling curve may be needed for S690QL. It was also shown that the 0.2% proof stress rather than the stress at 2% total strain is a better parameter for deriving buckling curves in fire.
10.34: Creep properties of grade S275JR steel at high temperature
Authors: Torić Neno , Brnić Josip , Boko Ivica , Čanađija Marko , Turkalj Goran , Lanc Domagoj , Brčić Marino , Burgess Ian W. , Harapin Alen , Divić Vladimir , Uzelac Ivana
Published: September 2017

The paper describes an ongoing research project which aims to determine the creep properties of European steel Grade 275JR. The purpose of the research is to develop a reliable temperature‐, stress‐ and time‐dependent creep model for this alloy, since there is very little information available in the scientific community regarding its creep properties. The research within the project is focused on a series of stationary creep tests, which will be used to obtain time‐dependent creep strains in the temperature range 400–600°C. The stress range for which the creep evolution is studied in this project is between 25% and 90% of the value of the stress at 0.2% strain at any particular temperature level. Comparisons between the creep output for the alloy analysed and existing creep data are presented in the paper.
10.35: Influence of joint stiffness on the behaviour of steel bearing frame under fire conditions
Authors: Maslak Mariusz , Pazdanowski Michal , Wozniczka Piotr
Published: September 2017

The reaction of the bearing steel frame to the direct fire exposure associated with the influence of monotonically increasing temperature of the constituent components is considered in this paper. For the comparative purposes, the frames with beam‐to‐column joints differing in rigidity are analysed in detail. Depending on whether there are stiffening ribs present, and the location of these ribs if present, the fire resistance of the considered structural component is determined by its failure mode. This may occur as the local instability in the column web or as the destruction of the column flange or beam flange. The internal arrangement of the joint is also one of the factors determining the redistribution of internal forces generated in the frame components when subjected to fire conditions. To show this, the dependencies specifying the relationships between temperature of the frame components and the bending moments and axial forces induced in these components during fire are presented, discussed and mutually compared. These relationships are arrived at after the detailed analysis of a numerical example, in which fire behaviour of three similar steel frames differing in the beam‐to‐column joint rigidity is considered. In the first analysed case the joint without ribbing is examined, while in the second case a joint with horizontal ribs and in the third case a joint with horizontal and diagonal ribs are analysed. The relationships listed above are accompanied by corresponding relationships specifying the dependencies between the steel temperature and the frame beam deflection. Additionally, the rigidity of the flexible supports, modelling the resistance of the columns to the horizontal displacement of the joints, is differentiated in the analysis. In conclusion, it has been shown that the analysed types of the considered frame exhibit substantial differences in the predicted structural response if the joints applied in them and subjected to fire differ in rigidity. Specification of these differences and their qualitative and quantitative description constitute the main objective of this work.