Influence of variability of material mechanical properties on seismic performance of steel and steel-concrete composite structures

Modern standards for constructions in seismic zones allow the construction of buildings able to dissipate the energy of the seismic input through an appropriate location of cyclic plastic deformations involving the largest possible number of structural elements, forming thus a global collapse mechanisms without failure and instability phenomena both at local and global level. The key instrument for this purpose is the capacity design approach, which requires an appropriate selection of the design forces and an accurate definition of structural details within the plastic hinges zones, prescribing at the same time the oversizing of non-dissipative elements that shall remain in the elastic field during the earthquake. However, the localization of plastic hinges and the development of the global collapse mechanism is strongly influenced by the mechanical properties of materials, which are characterized by an inherent randomness. This variability can alter the final structural behaviour not matching the expected performance. In the present paper, the influence of the variability of material mechanical properties on the structural behaviour of steel and steel/concrete composite buildings is analyzed, evaluating the efficiency of the capacity design approach as proposed by Eurocode 8 and the possibility of introducing an upper limitation to the nominal yielding strength adopted in the design

Steel-based applications in earthquake-prone areas

Steel-Earth project aims at distributing among technicians, engineers, design companies and standardization bodies the results of three past RFCS projects (Steel-Retro [3], Opus [2] and PrecaSteel [1]), providing useful tools for the design and for the retrofit of existing buildings. Technical documents and practical applications to case studies, regarding design of steel and composite steel/concrete buildings and innovative steel-based techniques for the retrofit of existing r.c. and masonry constructions, have been elaborated and collected into a volume distributed during the final workshop of the dissemination project. Pre-normative and background documents concerning the design of steel and composite structures and the rehabilitation of existing constructions have been prepared. A lot of attention has been paid to the analysis of the influence of overstrength factors on the seismic design of steel and composite structures. The prepared documents have been distributed to the attending people and to the members of WG 2 (CEN/TC 250/SC 8/WG 2 “Steel and Composite Structures”) during the final workshop of the project. Technical sheets, working examples and background documents have been translated into several languages (German, French, Italian, Romanian and Greek) and are free available on the website of the project (https://www.steelconstruct.com/site/), where information regarding Steel-Earth are also presented.11 Workshops in Italy, Greece, Germany, Belgium, Portugal, Spain and Romania and 5 conferences in Emilia-Romagna have been organized, as well as 2 practical courses for engineers and academic people in Pavia (Italy). Flash-drives with the technical documents and applications elaborated in Steel-Earth have been distributed to the attending people

Combined analysis of HPV DNA, p16, p21 and p53 to predict prognosis in patients with stage IV hypopharyngeal carcinoma

We examined p16, p21 and p53 expression in combination with the presence of human papillomavirus (HPV) DNA as molecular markers to predict survival in patients with stage IV hypopharyngeal squamous cell carcinoma (HSCC).Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Towards screening Barrett’s Oesophagus: current guidelines, imaging modalities and future developments

Barrett’s oesophagus is the only known precursor to oesophageal adenocarcinoma (OAC). Although guidelines on the screening and surveillance exist in Barrett’s oesophagus, the current strategies are inadequate. Oesophagogastroduodenoscopy (OGD) is the gold standard method in screening for Barrett’s oesophagus. This invasive method is expensive with associated risks negating its use as a current screening tool for Barrett’s oesophagus. This review explores current definitions, epidemiology, biomarkers, surveillance, and screening in Barrett’s oesophagus. Imaging modalities applicable to this condition are discussed, in addition to future developments. There is an urgent need for an alternative non-invasive method of screening and/or surveillance which could be highly beneficial towards reducing waiting times, alleviating patient fears and reducing future costs in current healthcare services. Vibrational spectroscopy has been shown to be promising in categorising Barrett’s oesophagus through to high-grade dysplasia (HGD) and OAC. These techniques need further validation through multicentre trials

Strut-and-tie model for the support of steel beams crossing concrete beams

International audienceSteel and concrete construction can still be regarded as two distinct industrial sectors leading to separated design procedures. Even steel-concrete composite buildings remain designed as steel structures, with a limited benefit of the presence of concrete slabs. For some years however, a more integrated design between both materials is investigated. It tries to combine them in order to take advantage from their respective qualities : the high resistance of the steel on one hand and the low cost and good fire resistance of the concrete on the other hand, for example. One of the advantages of the concrete is also the easiness in the fabrication of joints, thanks to the monolithic nature of the concrete cast in place, whereas the metallic joints by bolting or welding ask for more technical work, and represent a non-negligible part of the cost of a structure. It is therefore rather natural, in a hybrid concrete-steel conception, to try to use this advantage of the concrete. In this context, this article presents a work that was made in the RFCS SMARTCOCO project. It focuses on the design of the support of a steel secondary beam crossing a primary beam in concrete, by simple direct contact. On the basis of an experimental campaign comprising five full-scale tests, the angle of diffusion of the forces and the distribution of the stresses in the stirrups are studied and a specific strut-and-tie model is developed. Specimens of this campaign consist of a simply supported concrete beam crossed in its middle by a steel profile, with or without stiffeners, loaded by two jacks, one at each end of the steel profile. First the experimental campaign is described. Then, internal stresses are compared with the predictions of a strut and tie model deduced from elastic stress trajectories. Finally, simplified design guidance is deduced

Exact solutions for the coupled warping beam problem

International audienceExact solutions for coupled warping beam problem are developed in the present paper. The torsion and shear warping problems are considered together, and three beam formulations are considered, regarding the influence of the bi-moment and bi-shear terms. In the first case, where the bi-moment and bi-shear terms are neglected, the exact solutions have a simple polynomial form. In the second and third cases, the exact solution have a more elaborate form, consisting of hyperbolic terms. The coupling between the modes results from the lack of symmetry of the cross-section and is captured in the exact solution for all modes. © 2023 Elsevier Lt

A new strategy for analysis of erection stages including an efficient method for creep analysis

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Behavior of a new shear connector for U-shaped steel-concrete hybrid beams

International audienceThis paper presents an investigation of the behavior of a new type of shear connectors used in U-shaped steel-concrete hybrid beams. Besides the role in transferring the force between concrete and steel material, this new type of shear connectors, welded on the upper flange of the U-shaped steel beam, serves to maintain the shape of the steel cross-section during concrete encasement. Several forms of shear connectors can be used such as L-shaped or square cross-section. The experimental investigation of the behavior of these shear connectors using asymmetrical push-out tests is presented in this paper. A finite element model has been developed in order to identify the stress behavior of the connectors and the surrounding concrete. The FE model is validated by comparing its results against experimental data and then used to perform a parametric study. Based on the parametric study results, an analytical formula for calculating the force transfer capacity of the shear connector is proposed

Effect of climatic actions on buildings with internal insulation and thermal breaks: Multi-scale approach and thermo-hydro-mechanical modeling

International audienceFor buildings designed with internal insulation, thermal bridges at the junction between slabs and walls are a common issue, since they create heat loss from inside of the building. Thermal break systems (TBS), which are composed of structural elements (rebars and steel profiles) and insulation material, are used to reduce this heat loss and to transfer shear forces from the slab to the walls. Insulation system of TBS generates a temperature gap from wall to slab. As a consequence, while the wall is exposed to climatic actions and is repeatedly dilated and contracted, whereas the slab pertains a constant temperature and does not present any volumetric variation, thus the TBSs are submitted to large displacement constrains. The paper illustrates the effect of the thermal dilatation and contraction of the walls, which create a supplemental force in the TBSs, and consequently cracking of the walls. A numerical model of a quarter of a building’s storey is submitted to the climatic actions computed at the location of Embrun city, in France. One side of the L-shape wall is supposed to face to the south, and the other one to the west. The thermal and mechanical analysis are performed with the software CASTEM. In thermal analysis, air temperature and flux of solar radiation signal are defined from databases of METEO FRANCE, and are applied on the exterior surface of the walls. The results of the first calculation, by thermo-hydro-mechanical analysis (THM) with elasticity behavior, confirm that a significant stress level in tension occurs in the concrete at the corner of the walls and the nearby interface elements of the TBS. Furthermore, the TBSs that are close to the corner of the walls pertain the highest horizontal and axial forces, and are at risk to exceed the limit strength. Based on those results, a second calculation, which includes the coupling of damage with shrinkage and creep model from the THM analysis, is made for determining more realistic forces in the TBSs, and analyzing the cracking pattern of the walls. © 2021, Scipedia S.L.. All rights reserved

Recent advances in steel-concrete composite and hybrid structures: Concrete elements reinforced by steel profiles

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