Documents disponibles écrits par cet auteur

Micromechanical evaluation of the damping behavior of modified silica fume admixed concrete / Tongyan Pan in Journal of engineering mechanics, Vol. 138 N° 12 (Décembre 2012) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 138 N° 12 (Décembre 2012) . - pp.1411–1419. Titre : Micromechanical evaluation of the damping behavior of modified silica fume admixed concrete Type de document : texte imprimé Auteurs : Tongyan Pan, Auteur ; Kaiming Xia, Auteur Année de publication : 2013 Article en page(s) : pp.1411–1419. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Damping  capability  Modified  silica  fume  Loss  modulus  Loss  tangent  Storage  modulus  Micromechanical  modeling Résumé : Vibration reduction or damping capability is highly desired for structural stability when hazardous impact loads are applied to a concrete structure. Damping capability of concrete structures depends primarily on the viscoelastic response of concrete material to the magnitudes and frequencies of impact loads, which in turn requires a minimum level of stiffness and damping capacity of concrete. A common industrial byproduct material—silica fume that showed certain antishock potential when mixed with concretes—was modified with silane in this study toward improved capabilities in both stiffness and damping. To evaluate the effectiveness of the modified silica fume (MSF), a series of dynamic flexural tests and numerical analyses were conducted, of which the results are presented. A three-dimensional micromechanical model was developed based on the discrete element method (DEM), which was then employed to study the stiffness and damping behavior of the admixed concrete. A 10% usage of MSF (by weight of cement) was found to significantly enhance the storage and loss moduli and the loss tangent of concrete. The DEM model developed can be used for evaluating and designing energy-absorbing concretes for general military and civil uses. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000446 [article] Micromechanical evaluation of the damping behavior of modified silica fume admixed concrete [texte imprimé] / Tongyan Pan, Auteur ; Kaiming Xia, Auteur . - 2013 . - pp.1411–1419. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 138 N° 12 (Décembre 2012) . - pp.1411–1419. Mots-clés : Damping  capability  Modified  silica  fume  Loss  modulus  Loss  tangent  Storage  modulus  Micromechanical  modeling Résumé : Vibration reduction or damping capability is highly desired for structural stability when hazardous impact loads are applied to a concrete structure. Damping capability of concrete structures depends primarily on the viscoelastic response of concrete material to the magnitudes and frequencies of impact loads, which in turn requires a minimum level of stiffness and damping capacity of concrete. A common industrial byproduct material—silica fume that showed certain antishock potential when mixed with concretes—was modified with silane in this study toward improved capabilities in both stiffness and damping. To evaluate the effectiveness of the modified silica fume (MSF), a series of dynamic flexural tests and numerical analyses were conducted, of which the results are presented. A three-dimensional micromechanical model was developed based on the discrete element method (DEM), which was then employed to study the stiffness and damping behavior of the admixed concrete. A 10% usage of MSF (by weight of cement) was found to significantly enhance the storage and loss moduli and the loss tangent of concrete. The DEM model developed can be used for evaluating and designing energy-absorbing concretes for general military and civil uses. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000446

Microstructural mechanisms of early age cracking behavior of concrete / Tongyan Pan in Journal of engineering mechanics, Vol. 137 N° 6 (Juin 2011) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 137 N° 6 (Juin 2011) . - pp.439-446 Titre : Microstructural mechanisms of early age cracking behavior of concrete : fracture energy approach Type de document : texte imprimé Auteurs : Tongyan Pan, Auteur ; Yajun Liu, Auteur ; Erol Tutumluer, Auteur Année de publication : 2011 Article en page(s) : pp.439-446 Note générale : Mécannique appliquée Langues : Anglais (eng) Mots-clés : Portland  cement  concrete  Early  cracking  Fracture  energy  Multiscale  analysis  Interfacial  transition  zone Résumé : This paper presents findings from a study directed at identifying key properties of ingredient materials that are influential on the early age cracking behavior of concrete, with an emphasis on the effects of aggregate size, aggregate morphologies, and water-cement ratio (w/c). Fracture energy (GF) was determined using a wedge-split test configuration for concrete samples at the age of 12 h. Based on image analysis, three signature morphologies of aggregate particles, i.e., the angularity, surface texture, and surface area, were quantitatively determined in terms of developed angularity index (AI), surface texture (ST) index, and surface area (SA) measurement, respectively. The high consistency between GF and aggregate SA of the concrete samples suggests that the interfacial transition zone (ITZ) at the cement paste-aggregate interface is the critical location that primarily accommodates the 12 h cracking of concrete. The critical role of ITZ in the early age cracking of concrete was further confirmed by its microstructural and chemical features under scanning electron microscopy/energy dispersive X-ray spectroscopy. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i6/p439_s1?isAuthorized=no [article] Microstructural mechanisms of early age cracking behavior of concrete : fracture energy approach [texte imprimé] / Tongyan Pan, Auteur ; Yajun Liu, Auteur ; Erol Tutumluer, Auteur . - 2011 . - pp.439-446. Mécannique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 137 N° 6 (Juin 2011) . - pp.439-446 Mots-clés : Portland  cement  concrete  Early  cracking  Fracture  energy  Multiscale  analysis  Interfacial  transition  zone Résumé : This paper presents findings from a study directed at identifying key properties of ingredient materials that are influential on the early age cracking behavior of concrete, with an emphasis on the effects of aggregate size, aggregate morphologies, and water-cement ratio (w/c). Fracture energy (GF) was determined using a wedge-split test configuration for concrete samples at the age of 12 h. Based on image analysis, three signature morphologies of aggregate particles, i.e., the angularity, surface texture, and surface area, were quantitatively determined in terms of developed angularity index (AI), surface texture (ST) index, and surface area (SA) measurement, respectively. The high consistency between GF and aggregate SA of the concrete samples suggests that the interfacial transition zone (ITZ) at the cement paste-aggregate interface is the critical location that primarily accommodates the 12 h cracking of concrete. The critical role of ITZ in the early age cracking of concrete was further confirmed by its microstructural and chemical features under scanning electron microscopy/energy dispersive X-ray spectroscopy. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i6/p439_s1?isAuthorized=no

Quantum - chemistry study of asphalt oxidative aging / Tongyan Pan in Industrial & engineering chemistry research, Vol. 51 N° 23 (Juin 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 23 (Juin 2012) . - pp. 7957-7966 Titre : Quantum - chemistry study of asphalt oxidative aging : An XPS - aided analysis Type de document : texte imprimé Auteurs : Tongyan Pan, Auteur ; Yang Lu, Auteur ; Stephen Lloyd, Auteur Année de publication : 2012 Article en page(s) : pp. 7957-7966 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Oxidation Résumé : Asphalt derived from crude oil (or petroleum) is an important base organic material for many industrial purposes. Oxidative hardening occurs throughout the service life of asphalt materials, which could significantly change the desired physicochemical properties. The study of asphalt oxidative hardening has thus far been focused on the changes in the physical properties, mainly the viscosity and ductility of bulk asphalt. Such phenomenological approaches meet the direct engineering needs, however do not help understand the fundamental physicochemical mechanisms of asphalt hardening. From this standpoint, this paper aims at exploring the chemical basis of asphalt oxidative hardening by establishing an ab initio quantum chemistry (QC) based physicochemical environment, in which the possible chemical reactions between asphalt ingredients and oxygen, as well as the incurred changes in their physical behavior, can be readily studied. X-ray photoelectron spectroscopy (XPS) was used to validate the bulk asphalt model, of which the results showed high agreement to the model predictions, and thereby prove the validity of the QC-based models developed for studying the oxidative behavior of general asphalt materials. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=25990310 [article] Quantum - chemistry study of asphalt oxidative aging : An XPS - aided analysis [texte imprimé] / Tongyan Pan, Auteur ; Yang Lu, Auteur ; Stephen Lloyd, Auteur . - 2012 . - pp. 7957-7966. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 23 (Juin 2012) . - pp. 7957-7966 Mots-clés : Oxidation Résumé : Asphalt derived from crude oil (or petroleum) is an important base organic material for many industrial purposes. Oxidative hardening occurs throughout the service life of asphalt materials, which could significantly change the desired physicochemical properties. The study of asphalt oxidative hardening has thus far been focused on the changes in the physical properties, mainly the viscosity and ductility of bulk asphalt. Such phenomenological approaches meet the direct engineering needs, however do not help understand the fundamental physicochemical mechanisms of asphalt hardening. From this standpoint, this paper aims at exploring the chemical basis of asphalt oxidative hardening by establishing an ab initio quantum chemistry (QC) based physicochemical environment, in which the possible chemical reactions between asphalt ingredients and oxygen, as well as the incurred changes in their physical behavior, can be readily studied. X-ray photoelectron spectroscopy (XPS) was used to validate the bulk asphalt model, of which the results showed high agreement to the model predictions, and thereby prove the validity of the QC-based models developed for studying the oxidative behavior of general asphalt materials. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=25990310