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International Symposium of the International Federation for Structural Concrete, fib Symposium 2023

作者： Sierra, Pablo L. Poliotti, Mauro Yang, Yuguang García, Xavier Martinez Chacón, Rolando International Centre for Numerical Methods in Engineering Barcelona Spain Delft University of Technology Delft Netherlands Polytechnic University of Catalonia Barcelona Spain

ISBN: (纸本)9783031325106

In this work, dynamic characterization of a simply supported beam is carried out during different steps in a failure load test. The main goal of this work is to evaluate the evolution of the structural dynamic parameters of the beam with different status of damage. Real-scale prestressed concrete beams are tested to investigate its shear behaviour as a part of a large research program at TU Delft. Four dynamic tests are performed at different damage status of the beam: firstly in the initial or undamaged condition;secondly after the first flexural cracks;then, after shear cracking;and finally in the full damaged condition. The dynamic excitation is performed with an impact load at fixed location on the top of the beam and the vibration data is recorded by three different systems. The first one is a cost-effective and open source monitoring equipment, consisting of seven low-cost accelerometers. The second system is based on five trusted high performance accelerometers. The last one is a commercial alternative consisting of four high accuracy piezoelectric accelerometers. Acceleration data is analysed afterwards using Operational Modal Analysis techniques to obtain modal frequencies, modal shapes and damping of the structure in the different states. The obtained dynamic behaviour of the structure and its results are discussed and compared. It is concluded that a change in the frequency of the first flexural mode is only observed when the damage in the beam is very significant, while no changes are observed with the occurrence of flexural and shear cracks. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Prestressed concrete

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A pulse-echo measurement setup to determine viscoelastic material parameters

A pulse-echo measurement setup to determine viscoelastic mat...

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2023 International Congress on Ultrasonics, ICU Beijing 2023

作者： Dreiling, Dmitrij Itner, Dominik Hetkämper, Tim Birk, Carolin Gravenkamp, Hauke Henning, Bernd Measurement Engineering Group Paderborn University Paderborn33098 Germany Institute of Structural Analysis University of Duisburg-Essen Essen45141 Germany International Centre for Numerical Methods in Engineering Barcelona08034 Spain

Due to their versatility, the application of polymers in research and industry continues to *** the majority of design processes are simulation-aided, precise material parameters are required to obtain realistic *** quasi-statically and destructively measured material parameters provided by manufacturers for this purpose are usually *** acoustic method is generally capable of measuring the frequency-dependent viscoelastic material parameters in a non-destructive *** particular, an ultrasonic transmission measurement setup for determining these parameters has already been presented in previous ***, this approach has several drawbacks, including a low sensitivity to shear *** increase the sensitivity to shear parameters, a measurement setup using a pulse-echo method with a corresponding inverse approach is presented to obtain viscoelastic material parameters of polymers.A brief comparison is made between the transmission and pulse-echo methods. © 2024 Institute of Physics Publishing. All rights reserved.

关键词： Ultrasonic transmission

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Structural performance of chloride-corroded hybrid fibre-reinforced concrete under sustained loads 15th

Structural performance of chloride-corroded hybrid fibre-rei...

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15th fib International PhD Symposium in Civil engineering, 2024

作者： Bajić, Petar Leporace-Guimil, Bruno Andrade, Carmen Tošić, Nikola de la Fuente, Albert Jordi Girona 1–3 Barcelona08034 Spain International Centre for Numerical Methods in Engineering CIMNE Spain Paseo General Martínez Campos 41 9° Madrid28010 Spain

ISBN: (纸本)9782940643240

Cracks in concrete act as preferential pathways for agents from the exterior, which may trigger detrimental corrosion processes. The addition of fibres to concrete is reported to alter cracking formation and to improve its post-cracking behaviour. This paper an experimental campaign with the objective of comparing the structural performance of two types of reinforced concrete elements subjected to chloride ingress: conventionally reinforced and reinforced using a hybrid approach, where in addition to steel bars, fibres are also used. Specimens were exposed to 3% NaCl under varying cracking conditions. Non-destructive tests (corrosion potential, corrosion current and resistivity of the concrete matrix) were used to monitor corrosion. After the exposure, specimens were subjected to bending until failure in a three-point bending test. In all specimens, corrosion initiation during the first month was detected based on the value of corrosion potential below –200 mV. In the third month of exposure, one specimen showed signs of a high corrosion rate (1.48 μA/cm2), whereas others showed signs of moderate corrosion (0.13–0.78 μA/cm2). Based on visual inspection, corrosion products were observed to concentrate in cracked regions of all specimens. © Fédération Internationale du Béton–International Federation for Structural Concrete.

关键词： Cracks

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Relationship between Radon and Oxygen Diffusion Coefficients in Opc Concretes in Terms of Porosity

SSRN

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SSRN 2023年

作者： Linares-Alemparte, Pilar Souto-Allaoui, Marina Andrade-Perdrix, Carmen Spain International Centre for Numerical Methods in Engineering Spain

Exposure to radon in indoor settings is presently the second cause of lung cancer. One of the solutions proposed to prevent its penetration and accumulation in buildings is to install radon barriers such as concrete flooring with suitable characteristics, a low radon diffusion coefficient in particular. That raises the need to determine the radon diffusion coefficient in ordinary Portland cement (OPC) concrete, the type normally deployed in such *** diffusion coefficient for radon gas in concrete is difficult to establish experimentally for a number of reasons. The first and foremost is the need for a standardised source of radon, which is normally costly. Another is trial duration, which lasts several days given the need to ventilate the diffusion cell once the radon concentration in the receiver container reaches the steady state. Hence the pursuit of alternative, less complex methods for finding the radon diffusion coefficient, based on more readily determined parameters. The oxygen diffusion coefficient, for instance, can be found experimentally at lower cost and complexity for it obviously calls for no source of radon. Rather, oxygen is drawn from the laboratory air itself and the test takes much less time for it involves no need to ventilate the *** article describes a preliminary study conducted to establish the relationship between the oxygen and radon diffusion coefficients in OPC concrete. It focuses on the equations to calculate the radon coefficient from empirical measurements of the value for oxygen, which can be measured more readily or even derived from other parameters such as air permeability or electrical resistivity. Inasmuch as gas diffusion in concrete is closely related to material porosity (in turn primarily dependent on concrete batching, curing and moisture content), the results for several types of concrete with different porosities are discussed. © 2023, The Authors. All rights reserved.

关键词： Porosity

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In-situ measurements of corrosion rate: methods and observed values 2nd

In-situ measurements of corrosion rate: Methods and observed...

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2nd Workshop on Capacity Assessment of Corroded Reinforced Concrete Structures, CACRCS DAYS 2020

作者： Andrade, C. CIMNE: International Center for Numerical Methods in Engineering-UPC Spain

ISBN: (纸本)9782940643103

Measurement of the corrosion on site has been approached mainly by visual inspection complemented by the determination of the chloride content or the carbonation depth in the concrete. The measurement of the loss in diameter of the bar, which is the crucial parameter for structural assessment has very seldom aroused interest, and even less the question of which are the possible variations in the same structure. in the present communication will first be commented the methods for on-site determination of the corrosion penetration and the corrosion rate as indicated in Rilem Recommendation on the Measurement of the Polarization Resistance. Typical levels of corrosion in function of the type of concrete and its level of contamination will be presented. The effect of climatic conditions will be underlined as in this is another critical aspect when site assessment is made. Details on how many samples to take and how to interpret the results will be commented together with recommendations on how to generalize measurements on a single visit. © 2021, Fédération Internationale du Béton – International Federation for Structural Concrete.

关键词： Corrosion rate

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On the Seismic Design of Ductile RC Buildings Considering Soil-Structure Interaction Effects 1

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2nd Eurasian Conference on OpenSees Days, EOSD 2022

作者： Baquero, Juan-Sebastián Bairan, Jesús-Miguel Ledesma, Alberto Pontificia Universidad Católica del Ecuador Quito Ecuador Universitat Politècnica de Catalunya Barcelona Spain International Centre for Numerical Methods in Engineering CIMNE Barcelona Spain

ISBN: (数字)9783031301254

ISBN: (纸本)9783031301247

Soil-structure interaction (SSI) may condition the seismic performance of buildings in different ways. Previous studies show that SSI effects on structural response parameters may be either beneficial or detrimental, depending on specific characteristics of the structure, the soil, and the demand. Despite the great efforts put over the last decades into developing performance-based seismic design (PBSD) practices, engineers still rely on prescriptive code requirements for design purposes. Considering SSI effects, ASCE-7, for example, allows determining a reduced design-shear demand (V~ ) that obeys the interacting soil-structure system behavior. It is calculated by reducing the conventional shear demand, V, by a variation Δ V, according to V~ = V- Δ V≥ αV;where α controls the magnitude of the reduced demand. α depends on the response modification factor (R ), resulting in a more significant reduction for structures presenting limited inelastic responses than for more ductile ones. This study investigates the behavior of α in ductile RC buildings while exposing the need to reflect not only the beneficial effects of SSI but the detrimental ones in determining the design-shear demand. To this end, 729 3D soil-structure systems (SSS) with different plan aspect ratios, slenderness ratios, and soil shear wave velocities were designed and analyzed using OpenSeesPy. Linear and nonlinear analysis procedures (APs) recommended at ASCE-41 are used to evaluate the response of the designed buildings. Based on these responses, a machine-learning (ML) technique is used to generate an estimation model for α, showing that the slenderness ratio, λstr, the fixed-base period, T, and the wave parameter, σSSI are key parameters to explain up to 90% of its variation. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Soil structure interactions

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A continuation framework for quasi-periodic solution branches based on different torus discretization strategies 30

A continuation framework for quasi-periodic solution branche...

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30th International Conference on Noise and Vibration engineering, ISMA 2022 and 9th International Conference on Uncertainty in Structural Dynamics, USD 2022

作者： Bäuerle, S. Seifert, A. Kappauf, J. Hetzler, H. University of Kassel Institute for Mechanics Engineering Dynamics: Numerical Methods Group Mönchebergstraße 7 Kassel34121 Germany

ISBN: (纸本)9789082893151

In dynamical systems, the study of stationary solutions - such as equilibrium points or periodic orbits - is of fundamental interest. Quasi-periodic oscillations are another stationary solution type, which receives increasing attention from practitioners: as a kind of higher dimensional periodic solution, they contain at least two base frequencies that have no rational ratio. This leads to an infinite "period length". Such a quasi-periodic trajectory evolves in state space on a torus surface and fills it densely. Due to the density, it is permissible to study this finite torus surface instead of the infinite trajectory. In this contribution, we present two approximation methods - a FOURIER-GALERKIN and a quasi-periodic shooting method - for computing such finite surfaces. These methods are implemented in the software framework COSTAR in MATLAB® for continuing equilibria, periodic and quasi-periodic solution curves. We discuss results of curve continuation using the example of a quasi-periodically forced DUFFING oscillator. © 2022 Proceedings of ISMA 2022 - International Conference on Noise and Vibration engineering and USD 2022 - International Conference on Uncertainty in Structural Dynamics. All rights reserved.

关键词： MATLAB

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Globularization Mechanism and Near Isotropic Properties in Subcritical Heat‑Treated Ti6Al4V Fabricated by Directed Energy Deposition

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Acta Metallurgica Sinica(English Letters) 2023年第6期36卷 937-948页

作者： Guohao Zhang Zhiwei Hao Meng Wang Xufei Lu Zhuang Zhao Qian Wang Xin Lin Jing Chen Weidong Huang State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China MIIT Key Laboratory of Metal High Performance Additive Manufacturing and Innovative Design Northwestern Polytechnical UniversityXi’an 710072China International Center for Numerical Methods in Engineering Universidad Politecnica de Cataluna08034 BarcelonaSpain Institute of Machinery Manufacturing Technology China Academy of Engineering PhysicsMianyang 621054China

Microstructure with globularαphase is desirable as it contributes to preferable comprehensive mechanical properties for titanium ***,titanium alloys fabricated by directed energy deposition(DED)are mainly characterized by the lamellarαphase within the basket-weave microstructure,which often leads to severe anisotropy and inferior low cycle fatigue(LCF)*** address this,the subcritical annealing and the cyclic annealing were applied to DED Ti–6Al–4V in order to achieve the transformation from the lamellarαphase to the globularα*** microstructural characteristics and the globularization behavior ofαphase during heat treatment were *** results show that the aspect ratio ofαis significantly decreased with the subcritical annealing due to the coarsening of lamellarα.Furthermore,the globularαis obtained with the cyclic annealing as a combination result of the termination dissolution and the side surface growth of the lamellarα.These contribute to a pronounced reduction of 85.4%in the ductility anisotropy,compared with the as-built specimens,and superior comprehensive mechanical properties including LCF are achieved with the formation of globularα.

关键词： Directed energy deposition Ti-6Al-4V Subcritical heat treatment Coarsening Globularization

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RMSD Calculations for Comparing Protein Three-Dimensional Structures 10th

RMSD Calculations for Comparing Protein Three-Dimensional S...

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10th International Conference on numerical methods and Applications, NMA 2022

作者： Sapundzhi, Fatima Popstoilov, Metodi Lazarova, Meglena Department of Communication and Computer Engineering Faculty of Engineering South-West University "Neofit Rilski" Blagoevgrad2700 Bulgaria Department of Mathematical Modelling and Numerical Methods Faculty of Applied Mathematics and Informatics Technical University of Sofia Sofia1000 Bulgaria

ISBN: (纸本)9783031324116

The root Mean Square Deviation (RMSD) is a popular measure of structural similarity between protein structures in the field of bioinformatics. The RMSD calculations involve alignment and optimal superposition between matched pairs of atoms, searching for the lowest RMSD result for both structures. Among the popular methods for calculating the optimal rotation matrix that minimizes the RMSD are the Kabsch algorithm and the Quaternion algorithm. The aim of this research is to present a simple tool for calculation of the RMSD between pairs of aligned three dimensional structures by applying the methods mentioned above. As an implementation language the object-oriented C# programming language has been chosen. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Proteins

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A coarse-grained bonded particle model for large-scale rock simulation

Rock Mechanics Bulletin

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Rock Mechanics Bulletin 2024年第4期3卷 58-69页

作者： Chengshun Shang Liping Li Kaiwei Chu Zongqing Zhou Guillermo Casas Wenfeng Tu Yuxue Chen Shangqu Sun School of Qilu Transportation Shandong University250061JinanChina International Center for Numerical Methods in Engineering(CIMNE) 08034BarcelonaSpain Universitat Politecnica de Catalunya(UPC) 08034BarcelonaSpain Geotechnical and Structural Engineering Research Center Shandong University250061JinanChina College of Civil Engineering and Architecture Shandong University of Science And Technology266590QingdaoChina

For solving the computationally intensive problem encountered by the discrete element method(DEM)in simulating large-scale engineering problems,it is essential to establish a numerical model that can effectively simulate large-scale *** this study,the coarse-graining effect of a linear-Mindlin with bonding model was studied in the unconfined compression strength(UCS)and Brazilian tensile strength(BTS)*** found that the main reason for the coarse-graining effect of the BTS tests is that the type I fracture toughness is positively correlated with the size of the *** on the results analysis and fracture mechanics,the coarse-grained(CG)modeling theory was combined with a bonded particle model(BPM)for the first time and a coarse-grained bonded particle model(CG-BPM)was developed,which can be effectively used to model the tensile strength of large-scale rocks with different particle *** excavation damage zone(EDZ)in an underground research laboratory(URL)was selected as an application case,which shows that the coarse-grained bonding model presented in this paper is more accurate and reliable than the traditional one in large-scale rock simulation,at least in the scenario where tensile failure is dominant.

关键词： numerical simulation Discrete element method(DEM) Coarse-grained bonded particle model(CGBPM) Large-scale rock

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