1,051 research outputs found
Design of concrete-filled high strength steel tubular X-joints subjected to compression
[EN] The structural performance and design of concrete-filled high strength steel tubular X-joints subjected to compression are investigated. A numerical investigation on the behaviour of concrete-filled high strength steel tubular chord members under concentrated bearing load has been performed. The high strength steel tubes had nominal yield stresses of 700 and 900 MPa. The infilled concrete had nominal concrete cylinder strengths of 35 and 100 MPa. In order to avoid the failure of brace members and reveal the true capacity of the X-joints, steel bearing plates were used to simulate the brace members. A finite element model was developed and validated against test results. Furthermore, a parametric study comprised 156 finite element analyses was carried out. The strengths of the concrete-filled high strength steel square and rectangular hollow section X-joints obtained from the parametric study together with available data in the literature were compared with the nominal strengths calculated from the CIDECT Design Guide. It is shown that the CIDECT design predictions exhibit significant scatter and could be unconservative for the concrete-filled tubular joints with chord sidewall slenderness ratio beyond 40 in this study. Hence, new design rules are proposed for concrete-filled high strength steel tubular X-joints subjected to compression. It is shown that the proposed design rules are able to provide reasonably good predictions.The research work described in this paper was supported by a grant from the Research Grants Council of the Hong Kong Special Administrative Region, China (Project No. 17209614).Li, H.; Young, B. (2018). Design of concrete-filled high strength steel tubular X-joints subjected to compression. Editorial Universitat Politècnica de València. 483-490. https://doi.org/10.4995/ASCCS2018.2018.7062OCS48349
Cold-Formed Ferritic Stainless Steel Tubular Sections under End-One-Flange Loading Condition
This paper presents experimental and numerical investigations of cold-formed ferritic stainless steel tubular sections under End-One-Flange (EOF) loading condition. A series of web crippling tests was conducted on cold-formed square and rectangular hollow sections of ferritic stainless steel grade EN 1.4003. The web crippling test results were used for the verification of the finite element (FE) model. Upon verification, a parametric study was performed thereafter. The codified web crippling design provisions in American, Australian/New Zealand and European standards for stainless steel structures were assessed. Improved web crippling design rules are proposed for cold-formed ferritic stainless steel tubular sections under EOF loading condition through modifying the design rules of the North American Specification and Direct Strength Method. It is shown that the modified web crippling design rules are able to provide accurate and reliable predictions
Post-fire mechanical properties of high strength steels
[EN] High strength steels are becoming increasingly attractive for structural and architectural applications due to their superior strength-to-weight ratio which could lead to lighter and elegant structures. The stiffness and strength of high strength steels may reduce after exposure to fire. The post-fire mechanical properties of high strength steels have a crucial role in evaluating the residual strengths of these materials. This paper presents an experimental investigation on post-fire mechanical properties of cold-formed high strength steels. A series of tensile coupon tests has been carried out. The coupon specimens were extracted from cold-formed square hollow sections with nominal yield stresses of 700 and 900 MPa at ambient temperature. The specimens were exposed to various elevated temperatures ranged from 200 to 1000 °C and then cooled down to ambient temperature before tested to failure. Stress-strain curves were obtained and the mechanical properties, namely, Young’s modulus, yield stress (0.2% proof stress) and ultimate strength, of the cold-formed high strength steel materials after exposure to elevated temperatures were derived. The post-fire retention factors that obtained from the experimental investigation were compared with existing predictive equations in the literature. New predictive equations are proposed to determine the residual mechanical properties of high strength steels after exposure to fire. It is shown that the proposed predictive equations are suitable for both cold-formed and hot-rolled high strength steel materials with nominal yield stresses ranged from 690 to 960 MPa.Li, H.; Young, B. (2018). Post-fire mechanical properties of high strength steels. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 83-90. https://doi.org/10.4995/ASCCS2018.2018.7222OCS839
Web Crippling of Cold-Formed High Strength Steel Square and Rectangular Hollow Sections under Two-Flange Loading Conditions
The web crippling behavior of cold-formed high strength steel (HSS) square and rectangular hollow sections under End-Two-Flange and Interior-Two-Flange loading conditions is studied. The cold-formed HSS tubular sections had nominal 0.2% proof stresses of 700 and 900 MPa. Finite element (FE) models were developed and validated against test results, showing the capability of replicating the experimental web crippling strengths, failure modes and load-deformation histories. Upon validation of the FE models, an extensive parametric study comprised 112 FE analyses was performed. The web crippling strengths obtained from the experimental and numerical investigations were compared with the nominal strengths calculated from the North American Specification, Australian/New Zealand Standard and European Code for cold-formed steel structures. The comparison results show that the nominal strengths predicted by the existing codified web crippling design provisions are either unconservative or overly conservative. Hence, new design rules are proposed for cold-formed HSS square and rectangular hollow sections by means of Direct Strength Method (DSM). It is shown that the modified DSM is able to provide reasonably good predictions
Multimodal Gen-AI for Fundamental Investment Research
This report outlines a transformative initiative in the financial investment
industry, where the conventional decision-making process, laden with
labor-intensive tasks such as sifting through voluminous documents, is being
reimagined. Leveraging language models, our experiments aim to automate
information summarization and investment idea generation. We seek to evaluate
the effectiveness of fine-tuning methods on a base model (Llama2) to achieve
specific application-level goals, including providing insights into the impact
of events on companies and sectors, understanding market condition
relationships, generating investor-aligned investment ideas, and formatting
results with stock recommendations and detailed explanations. Through
state-of-the-art generative modeling techniques, the ultimate objective is to
develop an AI agent prototype, liberating human investors from repetitive tasks
and allowing a focus on high-level strategic thinking. The project encompasses
a diverse corpus dataset, including research reports, investment memos, market
news, and extensive time-series market data. We conducted three experiments
applying unsupervised and supervised LoRA fine-tuning on the llama2_7b_hf_chat
as the base model, as well as instruction fine-tuning on the GPT3.5 model.
Statistical and human evaluations both show that the fine-tuned versions
perform better in solving text modeling, summarization, reasoning, and finance
domain questions, demonstrating a pivotal step towards enhancing
decision-making processes in the financial domain. Code implementation for the
project can be found on GitHub: https://github.com/Firenze11/finance_lm
Semi-solid slurry of AZ91 magnesium alloy prepared by electromagnetic stirring near liquidus temperature
An electromagnetic stirring process near liquidus temperature was designed and demonstrated experimentally to produce semi-solid slurry of AZ91 magnesium alloy, in order to avoid not only contamination from mechanical stirring but also the inflammation of Mg alloy melt at elevated temperature. AZ91 alloy feedstock was isothermally heat treated at 600-610 for 20 min, and then stirred by electromagnetic field. Globular primary particle characteristic was observed optically in the castings. Mechanical properties were also studied
Tetraaquabis(2-{[5-(pyridin-4-yl)-1,3,4-oxadiazol-2-yl]sulfanyl}acetato)iron(II)
In the title compound, [Fe(C9H6N3O3S)2(H2O)4] or [Fe(POA)2(H2O)4], the FeII atom is located on an inversion center and is ligated by four O atoms of coordinated water molecules in the equatorial plane while two POA ligands acting as monodentate ligands occupy the axial positions through their pyridyl N atoms, completing a slightly distorted octahedral coordination geometry. A three-dimensional supramolecular network is formed by multiple O—H⋯O hydrogen-bonding interactions between the coordinated water donors and the uncoordinated carboxyl acceptors
catena-Poly[[(2,2′-bipyridine-κ2 N,N′)cadmium]-μ3-4-nitrophthalato-κ4 O:O′,O′′:O′′′]
In the title polymeric compound, [Cd(C8H3NO6)(C10H8N2)]n, two O atoms from both carboxylate groups of a nitrophthalate anion coordinate to the CdII cation, forming a seven-membered chelate ring and two carboxylate O atoms from another two nitrophthalate anions and a 2,2′-bipyridine ligand coordinate to the Cd cation to complete the distorted octahedral coordination geometry. The carboxylate groups of the nitrophthalate anion adopt a syn–anti bridging mode, linking adjacent CdII cations and forming a polymeric chain running along the a axis. Weak intra- and intermolecular C—H⋯O hydrogen bonding is present in the crystal structure
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