bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen‐Doped Carbon Composites with Ordered Macropores and Hollow Walls
Authors: Yao Wen , Chen Jianmin , Wang Yajing , Fang Ruiqi , Qin Ze , Yang Xianfeng , Chen Liyu , Li Yingwei
Published: September 2021

Metal‐organic frameworks provide versatile templates for the fabrication of various metal/carbon materials, but most of the derived composites possess only microspores, limiting the accessibility of embedded active sites. Herein, we report the construction of cobalt/nitrogen‐doped carbon composites with a three‐dimensional (3D) ordered macroporous and hollow‐wall structure (H‐3DOM‐Co/NC) using a single‐crystal ordered macropore (SOM)‐ZIF‐8@ZIF‐67 as precursor. During the pyrolysis, the interconnected macroporous structure of SOM‐ZIF‐8@ZIF‐67 is mostly preserved, whereas the pore wall achieves a solid‐to‐hollow transformation with Co nanoparticles formed in the hollow walls. The 3D‐ordered macroporous carbon skeleton may effectively promote long‐range mass transfer and the hollow wall can facilitate local accessibility of active sites. This unique structure can greatly boost its catalytic activity in the selective hydrogenation of biomass‐derived furfural to cyclopentanol, much superior to its counterparts without this well‐designed hierarchically porous structure.
Photocatalytic Decarboxylative Coupling of Aliphatic N‐hydroxyphthalimide Esters with Polyfluoroaryl Nucleophiles
Authors: Yi Xiangli , Mao Runze , Lavrencic Lara , Hu Xile
Published: September 2021

Polyfluoroarenes are an important class of compounds in medical and material chemistry. The synthesis of alkylated polyfluoroarenes remains challenging. Here we describe a decarboxylative coupling reaction of N‐hydroxyphthalimide esters of aliphatic carboxylic acids with polyfluoroaryl zinc reagents (Zn‐ArF) via synergetic photoredox and copper catalysis. This method readily converts primary and secondary alkyl carboxylic acids into the corresponding polyfluoroaryl compounds, which could have a wide range of F‐content (2F‐5F) and variable F‐substitution patterns on the aryl groups. Broad scope and good functional group compatibility were achieved, including on substrates derived from natural products and pharmaceuticals. Mechanistic study revealed that a [Cu‐(ArF)2] species could be responsible for the transfer of polyfluoroaryl groups to the alkyl radicals.
Fused Bithiophene Imide Dimer‐Based n‐Type Polymers for High‐Performance Organic Electrochemical Transistors
Authors: Feng Kui , Shan Wentao , Ma Suxiang , Wu Ziang , Chen Jianhua , Guo Han , Liu Bin , Wang Junwei , Li Bangbang , Woo Han Young , Fabiano Simone , Huang Wei , Guo Xugang
Published: September 2021

The development of n‐type organic electrochemical transistors (OECTs) lags far behind their p‐type counterparts. In order to address this dilemma, we report here two new fused bithiophene imide dimer (f‐BTI2)‐based n‐type polymers with a branched methyl end‐capped glycol side chain, which exhibit good solubility, low‐lying LUMO energy levels, favorable polymer chain orientation, and efficient ion transport property, thus yielding a remarkable OECT electron mobility (μe) of up to ≈10−2 cm2 V−1 s−1 and volumetric capacitance (C*) as high as 443 F cm−3, simultaneously. As a result, the f‐BTI2TEG‐FT‐based OECTs deliver a record‐high maximum geometry‐normalized transconductance of 4.60 S cm−1 and a maximum μC* product of 15.2 F cm−1 V−1 s−1. The μC* figure of merit is more than one order of magnitude higher than that of the state‐of‐the‐art n‐type OECTs. The emergence of f‐BTI2TEG‐FT brings a new paradigm for developing high‐performance n‐type polymers for low‐power OECT applications.
Application of Relaxation Dispersion of Hyperpolarized 13C Spins to Protein–Ligand Binding
Authors: Qi Chang , Wang Yunyi , Hilty Christian
Published: September 2021

Nuclear spin relaxation dispersion parameters are proposed as indicators of the binding mode of a ligand to a protein. Hyperpolarization by dissolution dynamic nuclear polarization (D‐DNP) provided a 13C signal enhancement between 3000–6000 for the ligand 4‐(trifluoromethyl) benzene‐1‐carboximidamide binding to trypsin. The measurement of 13C R2 relaxation dispersion was enabled without isotope enrichment, using a series of single‐scan Carr–Purcell–Meiboom–Gill experiments with variable refocusing delays. The magnitude in dispersion for the spins of the ligand is correlated to the position with respect to the salt bridge between protein and the amidine group of the ligand, indicating the ligand binding orientation. Hyperpolarized relaxation dispersion is an alternative to chemical shift or NOE measurements for determining ligand binding modes.
The Anionic Pathway in the Nickel‐Catalysed Cross‐Coupling of Aryl Ethers
Authors: Borys Andryj M. , Hevia Eva
Published: September 2021

The Ni‐catalysed cross‐coupling of aryl ethers is a powerful method to forge new C−C and C−heteroatom bonds. However, the inert C(sp2)−O bond means that a canonical mechanism that relies on the oxidative addition of the aryl ether to a Ni0 centre is thermodynamically and kinetically unfavourable, which suggests that alternative mechanisms may be involved. Here, we provide spectroscopic and structural insights into the anionic pathway, which relies on the formation of electron‐rich hetero‐bimetallic nickelates by adding organometallic nucleophiles to a Ni0 centre. Assessing the rich co‐complexation chemistry between Ni(COD)2 and PhLi has led to the structures and solution‐state chemistry of a diverse family of catalytically competent lithium nickelates being unveiled. In addition, we demonstrate dramatic solvent and donor effects, which suggest that the cooperative activation of the aryl ether substrate by Ni0‐ate complexes plays a key role in the catalytic cycle.
Double‐network polyvinyl alcohol composite hydrogel with self‐healing and low friction
Authors: Zhang Zhouqiang , Ye Zishuo , Hu Feng , Wang Wenbo , Zhang Shoujing , Gao Li , Lu Hailin
Published: September 2021

Polyvinyl alcohol (PVA) hydrogel is considered the most promising candidate for artificial cartilage because of its good lubricity and low permeability. However, the efficacy of single‐network PVA hydrogels under variable loads has not yet been determined. In this study, a one‐step physical‐cross‐linking method was used to compose PVA/PEG double‐network composite hydrogels. We changed the polyethylene glycol (PEG) content of the composite gel and tested the frictional‐wear performance under different loads and speeds. With the mass fraction of PEG at 30 wt.%, the hardness of the PVA/PEG composite gel increased to 167.7% that of pure PVA. Under dry‐friction conditions, the average coefficient of friction was approximately 0.14 and the wear rate on the surface of the hydrogel was insignificant. The cross‐linking between PVA and PEG greatly enhanced the stability of the composite hydrogel polymer network. The structure of the composite gel was analyzed by a variety of standard methods. The hydrogel has excellent biocompatibility and self‐healing ability and is a self‐lubricating, self‐healing candidate material for articular‐cartilage repair.
Preparation and characterization of polyaniline microcapsule loaded with 2,2′‐azobis(2‐methylpropionitrile) initiator and its controlled release
Authors: Zhang Qifan , Zuo Mingming , Wang Yu , Liu Weiwei , Zuo Xiaobing
Published: September 2021

The thermal curing of acrylate adhesive consisting of acrylate monomer or prepolymer and 2,2′‐azobis(2‐methylpropionitrile) (AIBN) initiator is quite common. However, the two‐component adhesive is not suitable for large areas, large gap bonding, or potting because of its fast‐curing speed and intense heat release. To solve these problems, microencapsulating the initiator AIBN in the adhesive and controlling its release is proposed. Here, a new series of polyaniline microcapsules loaded with AIBN for the preparation of delayed‐release initiator were synthesized via an emulsification‐polymerization method. The coumarone indene resins were doped in polyaniline to control the release of the encapsulated AIBN. The characterization results indicate that the coumarone indene resin had been successfully mixed into the microcapsule polyaniline shell, and the interior of the microcapsules doped with resin had a rich pore structure. When a Span 80 and Tween 80 composite emulsifying system was used and its concentration was controlled at 0.1%–1.0%, the resulting microcapsules were homogeneous with good dispersibility. The release of the microcapsule was slow, and the release rate and release time could be precisely controlled by adjusting the type and doping amount of coumarone indene resin in the microcapsule shell material as well as the external temperature. For example, when the doping amount of coumarone indene resins in the PANI shell material increased from 0.2 to 1.0 g or when the temperature ranges from 75to 85°C, the release time of AIBN from the microcapsule decreased from 9 to 2 h and 12 to 3 h, respectively. With increasing demands for high performance delayed‐release initiators, the prepared polyaniline microcapsules loaded with AIBN show great potential for practical applications in adhesive, self‐healing coating, and petroleum exploitation.
Design, synthesis, and α‐glucosidase‐inhibitory activity of phenoxy‐biscoumarin–N‐phenylacetamide hybrids
Authors: Ansari Samira , Azizian Homa , Pedrood Keyvan , Yavari Ali , Mojtabavi Somayeh , Faramarzi Mohammad A. , Golshani Shiva , Hosseini Samanesadat , Biglar Mahmood , Larijani Bagher , Rastegar Hossein , Hamedifar Haleh , Mohammadi‐Khanaposhtani Maryam , Mahdavi Mohammad
Published: September 2021

Thirteen new phenoxy‐biscoumarin–N‐phenylacetamide derivatives (7a–m) were designed based on a molecular hybridization approach as new α‐glucosidase inhibitors. These compounds were synthesized with high yields and evaluated in vitro for their inhibitory activity against yeast α‐glucosidase. The obtained results revealed that a significant proportion of the synthesized compounds showed considerable α‐glucosidase‐inhibitory activity in comparison to acarbose as a positive control. Representatively, 2‐(4‐(bis(4‐hydroxy‐2‐oxo‐2H‐chromen‐3‐yl)methyl)phenoxy)‐N‐(4‐bromophenyl)acetamide (7f), with IC50 = 41.73 ± 0.38 µM against α‐glucosidase, was around 18 times more potent than acarbose (IC50 = 750.0 ± 10.0 µM). This compound was a competitive α‐glucosidase inhibitor. Molecular modeling and dynamic simulation of these compounds confirmed the obtained results through in vitro experiments. Prediction of the druglikeness/ADME/toxicity of the compound7fand comparison with the standard drug acarbose showed that the new compound7fwas probably better than the standard drug in terms of toxicity.
Kundige inlanders – Indigenous Contributions to Jacob Breyne's (1637–1697) Work
Authors: Gehrke Louisa‐Dorothea
Published: September 2021

During the seventeenth century, the Dutch East India Company employees often made it their task to collect rare exotic plants in the colonies that reachlied the botanical gardens in their native country and from there, the rest of the world. One of them was Willem ten Rhijne, a doctor and botanist, who acquired plants not only for the garden in Amsterdam but also for the scientist Jacob Breyne, a citizen of Gdańsk. A fracture of their correspondence is kept in the Gotha research library, encompassing five letters from Ten Rhijne, written between 1680 and 1686. Those documents draw attention to the titular kundige inlanders, indigenous experts on botany. Analyzing these documents, this article argues that indigenous scientific systems influenced the works of Breyne to a retraceable extent but also emphasizes that their impact was heavily mediated by his and Ten Rhijne's understanding of themselves as European scientists and the latter's association with the company.
Organizational use of ecosystem service approaches: A critique from a systems theory perspective
Authors: Small Angela , Owen Alice , Paavola Jouni
Published: September 2021

Although corporate sustainability theory is well established, there is limited research on the use and understanding of the ecosystem service (ES) approaches based on an advanced conceptualization of the environment in organizational practice. This article analyzes the use of ES approaches in organizations using a system theory lens, conducting empirical research on the contribution of ES approaches to corporate environmental management. Drawing from 30 semistructured interviews with ES practitioners from private, policy, and third sector organizations, we find that ES approaches provide practitioners with an advanced understanding of the environment as a system, the interconnections between the organization and the environment, and a better awareness of temporal and physical attributes of the environment. Overemphasis on ecological systems, limited acknowledgment of the nesting of the social system within the ecological system, and limited detailed practitioner knowledge are barriers for advancing the use of the ES approaches in corporate sustainability practice.
Mushroom Species Stereum hirsutum as Natural Source of Phenolics and Fatty Acids as Antioxidants and Acetylcholinesterase Inhibitors
Authors: Mišković Jovana , Rašeta Milena , Čapelja Eleonora , Krsmanović Nenad , Novaković Aleksandra , Janjusevic Ljiljana , Karaman Maja
Published: September 2021

Many lignicolous mushroom species are used as a food supplement and may represent an alternative treatment of Alzheimer's disease (AD). This study aimed to evaluate acetylcholinesterase inhibition (AChEI) of Stereum hirsutum together with antioxidant activity (AO) and cytotoxic activity against HepG2 cells. Different extracts (water, ethanol, methanol, polysaccharide) were analyzed, with respect to their mineral composition and chemical content.

Ethanol extract was the most potent in AChEI (98.44 %) and demonstrated cytotoxic activity (91.96 % at 900.00 μg/mL), while the highest AO was demonstrated for polar extracts (methanol and water) as well. These activities may be attributed to determined phenolics (hydroxybenzoic and quinic acid) and fatty acids (FA), while biflavonoid amentoflavone may be responsible for cytotoxic activity. The most prevalent FA was linoleic (40.00 %) and the domination of unsaturated FA (UFA) (71.91 %) over saturated (26.96 %) was observed.

This is the first report of AChEI of S. hirsutum extracts and first detection of amentoflavone. Due to high amount of UFA and well‐expressed AChEI, this species can be considered as a potent food supplement in the palliative therapy of AD.
Solution Structure and Acid‐Base Properties of Reduced α‐Conotoxin MI
Authors: Faragó Zoltán , Mirzahosseini Arash , Horváth Dániel , Pálla Tamás , Horváth Péter , Perczel András , Noszál Béla
Published: September 2021

The reduced derivative of α‐conotoxin MI, a 14 amino acid peptide is characterized by NMR‐pH titrations and molecular dynamics simulations to determine the protonation constants of the nine basic moieties, including four cysteine thiolates, and the charge‐dependent structural properties. The peptide conformation at various protonation states was determined. The results show that the disulfide motifs in the native globular α‐conotoxin MI occur between those cysteine moieties that exhibit the most similar thiolate basicities. Since the basicity of thiolates correlates to its redox potential, this phenomenon can be explained by the higher reactivity of the two thiolates with higher basicities. The folding of the oxidized peptide is further facilitated by the loop‐like structure of the reduced form, which brings the thiolate groups into sufficient proximity. The 9 group‐specific protonation constants and the related, charge‐dependent, species‐specific peptide structures are presented.
Direct Conversion of Hydrazones to Amines using Transaminases
Authors: Carter Eve M. , Subrizi Fabiana , Ward John M. , Sheppard Tom D. , Hailes Helen C.
Published: September 2021

Transaminase enzymes (TAms) have been widely used for the amination of aldehydes and ketones, often resulting in optically pure products. In this work, transaminases were directly reacted with hydrazones in a novel approach to form amine products. Several substrates were investigated, including those with furan and phenyl moieties. It was determined that the amine yields increased when an additional electrophile was added to the reaction mixture, suggesting that they can sequester the hydrazine released in the reaction. Pyridoxal 5’‐phosphate (PLP), a cofactor for transaminases, and polyethylene glycol (PEG)‐aldehydes were both found to increase the yield of amine formed. Notably, the amination of (S)‐(−)‐1‐amino‐2‐(methoxymethyl)pyrrolidine (SAMP) hydrazones gave promising results as a method to form chiral β‐substituted amines in good yield.
Promoting Wellness in Counselors‐in‐Training: Impact of a Wellness Experiential Group
Authors: Mumbauer‐Pisano Jayna , Kim Nayoung
Published: September 2021

We investigated the effectiveness of a 5‐week wellness group curriculum for counselors‐in‐training (N = 60). A repeated measures multivariate analysis of variance was conducted to evaluate whether the curriculum positively affected perceived wellness among participants. The results showed statistically significant differences in scores, indicating a higher level of wellness after the intervention.
Numerical analysis of steel double side joints with flush and extended end plate under accidental situation
Authors: Damian Kukla , Aleksander Kozłowski , Tomasz Siwowski
Published: September 2021

Column loss is one of the accidental situations used to simulate extreme event during robustness analysis. Joints in steel framed structures play the main role in load transfer not only in persistent design situation but also in accidental design situation. According to EN 1991‐1‐7 joints should demonstrate sufficient ductility for absorbing significant strain energy without rupture, to allow developing transfer of actions by alternative load paths following an accidental event. To study the behavior of semi‐rigid steel joints numerical analysis of double side bolted end‐plate joints were conducted. End plate joints with flush and extended plate were analyzed. 3D numerical models based on finite element method using Abaqus software were created. Monotonic vertical loading at the top of column was applied. Geometrical and material non‐linearity were included in the model. Models of specimens were validated with previously made own experimental tests. The main aim of the study was to check ability of investigated joints to create catenary action, estimation of tying forcers in the joints and determine available rotation capacity of the connections. In the future, numerical models will be used for further parametric analysis.
Assembling bolted joints under water: influence of a surrounding medium on bolt preload and slip factor
Authors: Ripsch Benjamin , Henkel Knuth‐Michael
Published: September 2021

Due to recent failures of high‐strength steel bolts that were assembled in the splash zone and the submerged zone of offshore structures, the applicability of European steel construction standards regarding subsea use was investigated. It was found, that Eurocode 3 and EN 1090‐2 do not cover specific requirements for the installation of bolts under water. The influence of water on tightening, bolt preload and slip factor of faying surfaces were examined using special testing equipment. Different tightening me‐thods and alternative washer systems were applied. Lubrication of bolts used according to the standards mentioned does not seem suitable for underwater application. Self‐loosening and bolt overload are potential risks that come with under water installation of corresponding bolt assemblies. Design surface class of faying surfaces could be verified under water, but failure behavior was different when tested under water compared to regular testing conditions.
Advanced fatigue verification method for record breaking bridges
Authors: Bjærre Simon , S⊘rensen Jesper W. , Polk Henrik
Published: September 2021

Designing and reviewing suspension bridges with world record breaking main spans in countries like Turkey, China and Norway requires a new and advanced method for fatigue verification. COWI's in‐house software IBDAS (Integrated Bridge Design and Analysis System) is used to perform the full fatigue verification including load modelling, finite element modelling, stress history analysis and damage evaluation based on the damage accumulation method. Discussions of boundary conditions are avoided by utilizing a global IBDAS beam model for the overall static system. A few segments of the girder in the global model are replaced by a semi‐local shell model in which a fine local shell model with all local geometry is placed at the location of interest. Fatigue data points used for verification are defined in the local model, typically based on hot‐spot extrapolation methods. In IBDAS, the extrapolation can be defined whereby the fatigue data point stress histories can be used directly for fatigue evaluation with the reservoir cycle counting method. Hereby, time‐consuming bookkeeping of FE node output is avoided. This paper presents technical aspects of the fatigue verification method used for the latest suspension bridge designs including the advantages of utilizing a fully integrated system.
Torsional behaviour of thin‐walled members with regular perforation systems
Authors: Bernuzzi Claudio , Montanino Andrea , Simoncelli Marco
Published: September 2021

Thin‐walled cold‐formed (TWCF) steel members that are frequently used in steel storage rack systems generally present a monosymmetric cross‐section. The adopted design approaches derive strictly from those developed for the more traditional bisymmetric solid web members, despite i) the presence in rack components of the eccentricity between the shear center and the cross‐section centroid and ii) the regular perforation systems.

The paper is addressed to the torsional response of TWCF members used for the vertical elements (uprights) in storage racks, which present regular perforation systems currently neglected in routine design. Attention is focused on the evaluation of the warping constant, which reflects directly in the distribution of the normal stresses associated with the bimoment. The approach considered by the future rack design code is discussed and a refined model based on the theory of elasticity is proposed to account for the sequence of solid and perforated cross‐sections along the longitudinal axis of the member. The proposed numerical applications are related to two different cross‐sections and the discussed research outcomes allow for an appraisal of the errors associated with a warping constant defined by neglecting the presence of regular perforation systems.
Investigations of initial imperfections of steel scaffold structures
Authors: Mercier Charlotte , Khelil Abdelouahab , Mahmoud Firas Al , Blin‐Lacroix Jean‐Luc , Pamies Alain
Published: September 2021

Analysis and design of structures sensitive to second order effects require to take into account initial imperfections. Scaffold structures, due to their low rigidity, are very sensitive to second order effects. The accuracy of the design of such structures is based in part on the estimation of initial imperfections affecting the structure. In the 60s, the C.E.C.M., the European Convention of Steel Construction, has launched a test campaign to determine the degree of initial imperfections of each type of cross‐section. Five buckling curves have been established. The European design code for steel structures, Eurocode 3 Part 1‐1, classifies cold‐formed hollow tubular sections among sections with many imperfections, i.e. curve ‘c'. A test campaign has launched to analyse the experimental buckling curve behaviour of cold‐formed hollow sections of scaffold structures. Nineteen buckling tests on simply supported members and nine buckling tests on scaffolding ladders, from various European suppliers, have been carried out. Statistical studies of the experimental results highlight that the estimation of the initial imperfection currently defined for the cold‐formed tubular sections is far too penalizing for the sections used in the field of scaffolds.
Investigations on the influence of cold‐forming and associated residual stresses on the fatigue strength of thin‐walled details
Authors: Geers Thorben , Hoffmeister Benno , Heinemeyer Christoph
Published: September 2021

A code for the design of cold‐formed thin‐walled structures in accordance with fatigue requirements currently does not exist in Europe. Part 1993‐1‐3 of the Eurocode [1] only standardizes the static design. In part 1993‐1‐9 [2] for design and construction under fatigue loads cold‐formed thin‐walled profiles are explicitly excluded. Corresponding elements have, however, become established in the construction of racking systems, as they represent an efficient and economical way of creating storage capacities. In contrast to the former use of storage systems, manual retrieval and storage (S/R), increasing automation through S/R‐machines leads to cyclical loads in uprights and struts. In addition to purely static loads, this results in a dynamic component that cannot be neglected.

Experimental investigations, such as monotonic and cyclic tensile tests, are used to determine changes in material properties after cold‐forming by bending. Special focus is put on the influence of bending radii in combination with the thickness on the plastic deformation and associated internal residual stresses. These parameters can have a significant impact on the fatigue behavior. The aim of the tests with a new invented testing device is to provide a basis for the development of adequate fatigue design rules for storage systems.
Structural performance of composite steel rubberised concrete members under combined loading conditions
Authors: Mujdeci Ayse , Bompa Dan , Elghazouli Ahmed
Published: September 2021

This paper investigates the structural behaviour of rubberised concrete‐filled steel tubular (RuCFST) members under a wide range of axial‐bending loading conditions. The results of an experimental programme on circular concrete‐filled steel tubes (CFST), incorporating conventional and rubberised concrete (RuC) materials with various rubber content ratios, are presented. After describing the specimen details and testing arrangements, the influence of the RuC infill on the behaviour of test members in terms of moment‐axial interaction and ductility, is examined. The test results show that whilst the cross‐sectional capacity of RuCFST members is reduced with the increase in rubber content, significantly higher ductility is obtained compared with conventional counterparts. An enhancement of about 85% in ductility is obtained for members with 60% rubber content compared to those with conventional concrete. Finally, the test results are compared with current design guidelines, indicating that the latter tend to overestimate the capacity, particularly for relatively high rubber contents.
Behaviour of Composite Plate Shear Walls with Variable Column Stiffness
Authors: Curkovic Ivan , Skejic Davor , Dzeba Ivica , Lukacevic Ivan
Published: September 2021

Steel plate shear walls (SPSW) have been increasingly applied in structures as a lateral load resisting system. SPSW systems utilize thin unstiffened plates as the infill between boundary members. Infill panels are very slender elements and buckle under low lateral loads due to which SPSW relies on the post‐critical tension field action of the infill panel. Such load transfer mechanism has two downsides: a) significant transverse forces are exerted on the boundary elements, particularly columns; b) load bearing capacity of the tension infill panel after yielding is lower than yielding of the panel in shear. In order to preclude these shortcomings relatively new vertical stabilization systems, termed composite plate shear walls (CPSW), were developed where stiffening of the infill panel using reinforced concrete plate was introduced. However, lack of research on CPSW systems led to creation of structural building codes which adopted requirements prescribed for SPSW. Experimental and numerical research has been conducted on CPSW. Three specimens, with varying column flexural stiffness, were tested. The obtained results show less prominent column “pull‐in” when compared to SPSW. The results were assessed comparing stiffness, resistance and ductility between the above‐mentioned systems. Finally, the experimental results were used to calibrate numerical models. Afterwards, the obtained numerical results served for more detailed comparison of behaviour between SPSW and CPSW.
Flexural Behaviour of Prefabricated Ultra‐Shallow Steel‐Concrete Composite Slabs
Authors: Alali Ahmed Abdulla , Tsavdaridis Konstantinos Daniel
Published: September 2021

This paper presents the results of a parametric finite element (FE) study that investigates the flexural behaviour and bending capacity of a recently developed steel‐concrete composite flooring system subjected to static bending tests. The flooring system is composed from prefabricated ultra‐shallow slab units (aka PUSS) that consist of T‐ribbed concrete floors encased within and connected to two C‐channel steel edge beams with horizontally oriented shear connections. The study considers three unique types of shear connection systems, that compose of only horizontally oriented web‐welded shear studs (WWSS), only horizontal steel dowels or a combination of horizontal steel dowels with WWSS. The failure mechanism, the shear resisting capacity of the shear connection systems and their behaviour under flexural loads are examined. The present work explores the influence of variable parameters on the performance of the PUSS flooring system. In particular, the parameters under critical investigation are the type, arrangement, and size of the shear connectors (WWSS and steel dowels) as well as the location of the main pressure caused by the applied load. Based on the results, the location of the applied loads contributed greatly to the behaviour of the shear connectors, moment resistance capacity and failure mechanism of the slabs. In addition, horizontal dowels provided greater bond between concrete and steel in comparison to WWSS.
3D‐Printing with steel of a bolted connection
Authors: Erven Maren , Lange Jörg , Feucht Thilo
Published: September 2021

Additive Manufacturing seems promising for the steel construction industry, especially for small components with complex shapes. With Wire‐and‐Arc‐Additive‐Manufacturing (WAAM) a process was found which is fast and cheap compared to other Additive Manufacturing processes for metals. Furthermore, arc‐welding is well known in steel construction industry.

Bolted head plates are a common connection. Although they are relatively easy to produce, they are uneconomical in load transfer due to straining of the plates which are subject to bending. This type of connection is predestined for Additive Manufacturing. Rethinking the structure by taking into account the potentials of Additive Manufacturing brings a clear advantage compared to the conventional production. Thus, with a material saving of 60 % the same load capacity of the original flat head plate can be achieved.

The paper shows how the new production process WAAM can significantly change the shape of structures on the example of a bolted head plate. Therefore, all steps from the original design to the manufactured structure are demonstrated, including the structure finding by using topology optimization, the manufacturing with different parameters and a first testing of the manufactured structures.
Meshless numerical simulation of steel connections: application to the T‐stub component
Authors: de Cisneros Juan José Jiménez , Berrospi Giovani , Cook Víctor
Published: September 2021

Finite element analysis is a widely used simulation technique in steel design to analyze the structural behavior of structural components, such as beams, columns or connections. The major steps involved in finite element simulations are the definition of the basic parameters and the discretization in elements of the component, also known as preprocessing; the analysis of the model and the post‐processing by the representation and the interpretation of the obtained results. On the particular case of bolted connections, the most time‐consuming of these three phases is that of preprocessing, because on traditional finite element technology is required that the real geometry of the CAD model is simplified to be meshed and analyzed; this task is specifically severe and requires paying close attention on the case of components affected to concentration stresses. Nowadays, different techniques have been proposed and developed with this objective: reduce costs in terms of time and specialized human resources because the workflow is easier and simpler. One of these methods are the known as the meshfree methods, that do not require connection between nodes and are based on the interaction of the points of the geometry with the neighbors, so the processor analyzes taken as base the real CAD geometry and no simplifications are needed.

On this paper is exposed the meshless method based on the theory of external approximations as an alternative to the classic finite element method. This method is based on the theory where all parts of the assembly are considered as different elements, and the approximation of displacements inside is arbitrary and not only by polynomials. The convergence of the simulation model is based on the external equilibrium of the assembly. The method is applied to a practical case: the simulation of the T‐stub connection. The T‐stub component corresponds to one T‐shaped steel profile bolted through their flanges and loaded through their web until collapse, and its behavior is similar to the tension zone of beam to column bolted end plate connections. The analysis of strength, stiffness and ductility have been widely investigated experimentally, by simulation and theoretically, and they are obtained from the force‐displacement characteristic curve. Information presented by Bursi and Jaspart on the paper “Benchmarks for finite element modelling of bolted steel connections” are considered to elaborate the models and to compare the results.
New Eurocode 4 design rules for shallow floor construction
Authors: Hicks Stephen J. , Braun Matthias , Markovic Zlatko , Way James
Published: September 2021

As members of Project Team SC4.T5, the authors of this paper present the main outcomes from the work that are intended for implementation within EN 1994‐1‐1 (Eurocode 4). General design and application rules for shallow floor beams will be presented, with a particular focus on: the classification of the composite cross‐section; non‐linear bending resistance; and the introduction of transverse bars as shear connectors.
A numerical study on the structural performance of a ductile connection under fire conditions
Authors: Liu Yu , Huang Shan‐Shan , Burgess Ian
Published: September 2021

The component‐based model of a novel ductile connection has been incorporated into the software Vulcan in order to facilitate global frame analysis within a performance‐based structural fire engineering design process. This paper reports on the validation and verification of the model, as well as the applications of the model in order to investigate the effects of the ductile connections on the structural responses of long‐span frames at high temperature. Firstly, three single‐beam models with the novel connections at both ends, connected to rigid supports, are used to verify that the component‐based connection model has been correctly incorporated into Vulcan, via comparisons against detailed finite element modelling with Abaqus. The structural performance in fire of long‐span frames with the novel ductile connections has been compared with the performance of the same frames with idealized rigid, idealized pinned and conventional end‐plate connections, initially using a limited sub‐frame model. Results show that, compared with the above mentioned three connection types, the ductile connection provides much higher axial and rotational ductilities to accommodate the deformations generated by the connected beams as their temperatures rise. As part of this process, these connections are instrumental in greatly reducing the axial forces to which the surrounding structure is subjected. Finally, parametric studies varying several key parameters have been carried out, in order to optimize the design of the ductile connection to enhance its performance subject to catenary action at very high temperature to prevent potential connection fracture and progressive collapse.
A Retrofit Method to Mitigate Progressive Collapse in Steel Structures
Authors: Ciman Luca , Freddi Fabio , Tondini Nicola
Published: September 2021

Accidental events, such as impact loading or explosions, are rare events characterized by a very low probability of occurrence. However, their effects often lead to very high human losses and economic consequences as are likely to trigger the progressive collapse of the buildings. The progressive collapse of structures attracted the attention of many researchers and the topic has been widely investigated in recent years. In addition, increasing interest has been shown also on the definition of retrofit strategies able to increase the robustness of existing structures. The present work investigates the performance and the design of a retrofit solution to increase the robustness of steel moment resisting frames. A case study structure is selected and modelled in OpenSees, including both mechanical and geometrical non‐linearities. Non‐linear static analyses have been carried out on the frame, simulating a column loss scenario to investigate the subsequent load redistribution. The simulations showed that the case study was unable to redistribute the load and hence retrofitting was required. Among others, a truss system was added at the rooftop level of the building allowing the definition of an alternative load path. The analyses outcomes showed how the proposed retrofit method allows to increase the robustness of the case study structure and allowed for critical remarks on the checks required when this retrofit system is employed.
Hot‐dip galvanizing of steel structural members: an alternative to passive fire insulation?
Authors: Bihina Gisèle , Zhao Bin
Published: September 2021

Observations from several experimental campaigns in the past years in Europe on unloaded steel members have highlighted the positive impact of hot‐dip galvanizing on the heating of steel profiles. Indeed, the temperature rises more slowly on a hot‐dip galvanized steel profile than on a bare one.

This work led to a proposal for an amendment to Part 1‐2 of Eurocodes 3 and 4 regarding the fire design of steel (Eurocode 3) and composite steel and concrete (Eurocode 4) structural members. This amendment recommends a 50% reduction of the surface emissivity of a carbon steel profile as long as the applied zinc coating is present, followed by a “return to normal” of the fire behaviour of steel once the zinc layer has melted.

Therefore, an experimental campaign was conducted in order to verify the recommendations of the proposed amendment on the one hand, and to calibrate an advanced calculation model on the other hand. This investigation, presented in this paper, has put into evidence the conservativeness of the proposed amendment. The latter can have a significant impact on the fire design of steel structures for low fire resistance requirements, especially in case of welded structural members which are often made of slender walls prone to heat up very quickly when exposed to a fire.
Advanced Numerical Study of Composite Steel‐Concrete Structures at High Temperature
Authors: Barros Rafael C. , Silveira Ricardo A.M. , Pires Dalilah , Lemes Ígor J.M.
Published: September 2021

The composite steel‐concrete structures use has several advantages, such as the reduction of cross‐sectional dimensions and weight of the structure, which is one of the main reasons for it is use today. However, under fire situation, the material and mechanical properties changes, causing significant strength and stiffness loss as a result of temperature rise. In this work, the temperature influence on the behavior of composite steel‐concrete structures is studied through an inelastic second order (ISO) numerical investigation. For this, two computational modules, CS‐ASA/FA and CS‐ASA/FSA are developed and adapted for the study of composite structures in fire. The first module calculates the temperature field in any cross‐section. The second module performs the ISO analysis through the coupling between the Refined Plastic Hinge Method (RPHM) and the Strain Compatibility Method (MCD). In this way, the evolution of the temperature in cross‐sections, the interaction diagrams between axial force and bending moment and the structures equilibrium path as a function of the time in fire are presented for composite steel‐concrete beams, columns and frames. The proposed numerical methodology success is proved by comparison with experimental and numerical responses available in the literature.
Behaviour and design of duplex stainless steel CHS stub columns at elevated temperature
Authors: Mohammed Asif , Cashell Katherine A.
Published: September 2021

This paper investigates the behaviour and design of duplex stainless steel stub columns with a circular hollow cross‐section (CHS) at elevated temperature. A numerical model is developed to supplement the limited number of test results available in the literature. Following validation, the numerical approach is employed to gain an understanding of the critical behavioural characteristics which have not previously been studied. In addition, the paper considers and extends the continuous strength method (CSM) to include duplex stainless steel for CHS stub columns in fire. This approach employs a base curve linking the cross‐sectional resistance to the deformation capacity and is implemented herein using an elastic, linear hardening material model. The cross‐sectional resistances obtained from the CSM are compared with those from the numerical analysis, as well as with the standardised procedures in the European, American and Australia/New Zealand design standards. It is demonstrated that the proposed design method can lead to more accurate and less scattered strength predictions compared with current design codes.
Industry 4.0 for Steel Construction: an Outlook
Authors: Tankova Trayana , Pires J. Norberto , da Silva Luís Simões
Published: September 2021

In the era of internet and robots, sophisticated devices and real‐time simulation, the construction sector remains highly dependent on manual labor which is also the main source of delays, lack of quality, and human injuries. The rapid development in technological areas such as mechatronics, computers, sensors, programming, human interfaces and artificial intelligence (AI) – offers huge potential for modern applications.

Nowadays, additive manufacturing is rapidly growing, and it could offer efficient solutions for steel construction since it can be executed in any shape and scale. There are a few solutions in additive manufacturing technologies, which can process materials and produce components. However, there is a gap in the market for capacity to link the processed material conditions and characteristics to the production parameters in real‐time. Real‐time and cognitive re‐planning of the process parameters becomes significantly important when components with large‐scale and complex shapes are considered.

This paper presents a summary of existing technologies for automatic construction process, it identifies the critical issues which hamper the adoption of new technologies in construction and describes an additive manufacturing solution currently being implemented.
Comparison Between Two Types of Seismic Tests of Racking Systems
Authors: Bové Oriol , Ferrer Miquel , Almansa Francesc López , Roure Francesc
Published: September 2021

This paper is the result of both experimental and numeric analyses on pallet rack components. Two cyclic testing protocols for beam‐end connectors of adjustable racking systems are compared; such experiments are named as “code type” and “Castiglioni”. Both protocols share the same test mock‐up: an assembly of a doubly‐pinned upright segment with a cantilever beam specimen. These tests consist in an up‐to‐failure increasing push‐pull process at the free beam end. In the “code type” test, the imposed displacement loops are centered around zero; conversely, in the “Castiglioni” tests, both upward and downward displacement segment runs are centered around a vertical static equilibrium situation (to take the gravitational load into account). The “code type” test is expected to result in a higher number of cycles than the “Castiglioni” one because of the two following features of the latter: (i) the gravitational load is always present, thus resulting in a higher demanding test, and (ii) the failure point is precisely predefined and usually produced before the total breakdown. This paper describes and compares experiments using both protocols. Additionally, these tests are numerically simulated.
Investigation of the buckling behaviour of ring‐stiffened cylindrical shells under axial pressure
Authors: Pasternak Hartmut , Li Zheng , Jäger‐Cañás Andreas
Published: September 2021

Tanks and silos are often designed as ring‐stiffened cylindrical shells. Nowadays, the load‐increasing effect of tight ring stiffeners under axial compression has received just little attention in research and practice. Considering the structural safety, the ring‐stiffened shell needs to be estimated on the conservative side in practice. This is not desirable in terms of modern lightweight steel structures. Recently research results based on the numerical studies show that the axial buckling behavior of cylindrical shells can be enhanced by using ring stiffeners. In addition, the analysis of ring‐stiffened structures with numerical calculations demonstrate that cylindrical shells with ring stiffeners under axial pressure are uneconomic according to the current design standard in practice. Therefore, the results guaranteed by experiments are required, before the extensive parametric studies are putted into practice. In this paper, small specimen series are carried out to calibrate numerical models, which are subsequently used in parameter studies, because the large‐scale experiments, in the scale range of e.g. 1: 1 are cost‐intensive and therefore difficult to carry out in the laboratory. Consequently, relative small specimens with the selected radius of 796 mm and thickness 1 mm are tested. The small cylindrical shells are manufactured by welding of two half‐cylindrical shells and the ring stiffeners are spot‐welded to the cylindrical shell. The geometrical imperfection of shells is measured by a 3D scanning technologies. Finally, the experiments by means of geometrically and materially nonlinear analysis with imperfections included are recalculated on the basis of the measured data. The results illustrate that the numerical simulation agrees well with the experimental results.