Documents disponibles écrits par cet auteur

Composite wood-concrete beams using utility poles / Richard M. Gutkowski in Journal of structural engineering, Vol. 137 N° 6 (Juin 2011) 

Public ISBD [article]  in Journal of structural engineering > Vol. 137 N° 6 (Juin 2011) . - pp. 625-634 Titre : Composite wood-concrete beams using utility poles : time-dependent behavior Type de document : texte imprimé Auteurs : Richard M. Gutkowski, Auteur ; Nathan J. Miller, Auteur ; Massimo Fragiacomo, Auteur Année de publication : 2011 Article en page(s) : pp. 625-634 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Composite  beams  Concrete  Connectors  Creep  Laboratory  tests  Notches  Poles  Wood  Time  dependence  Timber  construction Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper describes the behavior of wood-concrete composite beams in which the wood layer is composed of recycled utility poles. Two full-scale laboratory specimens of 7,500-mm (295-in.) span were constructed, with the concrete slab cast on the timber poles left unshored. The connection was obtained by cutting six notches in the timber poles. A threaded steel dowel is placed in each notch extending through both layers with a nut on the bottom of the beam that can be tightened once the concrete has cured. Since the material in each layer exhibits a time-dependent response, it is necessary to examine the effects of sustained loading. After 28 days of initial curing of the concrete layer during which the midspan deflection was monitored, both beams were subjected to the service load to estimate the composite efficiency. The beams were very stiff and values of 96% and 98% were obtained, respectively, demonstrating the high efficiency of the notched connection system used. A comparison was made with results obtained in the literature for ramp load tests of two similar specimens, which had exhibited composite efficiencies of about 94% and 96%, respectively. A sustained load of approximately 11% of the estimated static ultimate load capacity was then applied to one of the specimens, which was monitored over time. The applied load resulted in a midspan moment of 24  kN·m (212  kip·in.) while the calculated ultimate capacity corresponded to a midspan moment of 226.5  kN·m (2,005  kip·in.). The final deflection was found to increase to 44.4 mm (1.75 in.) after 256 days, which was more than twice the initial elastic deflection owing to the application of the dead and live loads. The deflection attributable to the dead load was 19.1 mm (0.75 in.), and the deflection attributable to the live load was 2.54 mm (0.10 in.). An existing one-dimensional (1D) finite-element program was utilized to predict the time-dependent deflection at the end of a 50-year service life. The comparison with experimental results showed good approximation, particularly for the midspan deflection. The software predicted a 54-mm (2.14-in.) midspan deflection at the end of a 50-year service life, corresponding to 1/139 of the span. This was sufficiently high to suggest that either larger cross-section and/or precambering of the wood layer could be needed when the serviceability limit state of maximum deflection in the long-term is a required performance criterion. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i6/p625_s1?isAuthorized=no [article] Composite wood-concrete beams using utility poles : time-dependent behavior [texte imprimé] / Richard M. Gutkowski, Auteur ; Nathan J. Miller, Auteur ; Massimo Fragiacomo, Auteur . - 2011 . - pp. 625-634. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 137 N° 6 (Juin 2011) . - pp. 625-634 Mots-clés : Composite  beams  Concrete  Connectors  Creep  Laboratory  tests  Notches  Poles  Wood  Time  dependence  Timber  construction Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper describes the behavior of wood-concrete composite beams in which the wood layer is composed of recycled utility poles. Two full-scale laboratory specimens of 7,500-mm (295-in.) span were constructed, with the concrete slab cast on the timber poles left unshored. The connection was obtained by cutting six notches in the timber poles. A threaded steel dowel is placed in each notch extending through both layers with a nut on the bottom of the beam that can be tightened once the concrete has cured. Since the material in each layer exhibits a time-dependent response, it is necessary to examine the effects of sustained loading. After 28 days of initial curing of the concrete layer during which the midspan deflection was monitored, both beams were subjected to the service load to estimate the composite efficiency. The beams were very stiff and values of 96% and 98% were obtained, respectively, demonstrating the high efficiency of the notched connection system used. A comparison was made with results obtained in the literature for ramp load tests of two similar specimens, which had exhibited composite efficiencies of about 94% and 96%, respectively. A sustained load of approximately 11% of the estimated static ultimate load capacity was then applied to one of the specimens, which was monitored over time. The applied load resulted in a midspan moment of 24  kN·m (212  kip·in.) while the calculated ultimate capacity corresponded to a midspan moment of 226.5  kN·m (2,005  kip·in.). The final deflection was found to increase to 44.4 mm (1.75 in.) after 256 days, which was more than twice the initial elastic deflection owing to the application of the dead and live loads. The deflection attributable to the dead load was 19.1 mm (0.75 in.), and the deflection attributable to the live load was 2.54 mm (0.10 in.). An existing one-dimensional (1D) finite-element program was utilized to predict the time-dependent deflection at the end of a 50-year service life. The comparison with experimental results showed good approximation, particularly for the midspan deflection. The software predicted a 54-mm (2.14-in.) midspan deflection at the end of a 50-year service life, corresponding to 1/139 of the span. This was sufficiently high to suggest that either larger cross-section and/or precambering of the wood layer could be needed when the serviceability limit state of maximum deflection in the long-term is a required performance criterion. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i6/p625_s1?isAuthorized=no

Experimental tests of notched and plate connectors for LVL-concrete composite beams / David Yeoh in Journal of structural engineering, Vol. 137 N° 2 (Fevrier 2011) 

Public ISBD [article]  in Journal of structural engineering > Vol. 137 N° 2 (Fevrier 2011) . - pp. 261-269 Titre : Experimental tests of notched and plate connectors for LVL-concrete composite beams Type de document : texte imprimé Auteurs : David Yeoh, Auteur ; Massimo Fragiacomo, Auteur ; Mary de Franceschi, Auteur Année de publication : 2011 Article en page(s) : pp. 261-269 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Composite  structures  Timber  Concrete  Connections  Tests Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper reports the experimental results of symmetrical push-out tests performed on notched and toothed metal plate connectors for laminated veneer lumber (LVL)-concrete composite floor systems. The characteristic shear strength and slip moduli were evaluated for three types of connectors: (1) a 300-mm-long rectangular notch cut in the LVL joist and reinforced with a 16-mm-diameter lag screw; (2) a triangular notch reinforced with the same lag screw; and (3) two 333-mm-long toothed metal plates pressed in the lateral surface of two adjacent LVL joists. The shear force versus relative slip relationships are presented together with analytical prepeak and postpeak approximations which can be used to carry out nonlinear finite-element analyses of LVL-concrete composite beams. The failure mechanisms of the notched connections are also discussed. Analytical design formulas for shear-strength evaluation of notched connections derived in accordance with New Zealand Standards and Eurocodes are proposed based on four possible failure mechanisms. Good approximation was found if a slight modification of the Eurocodes formulas is introduced. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i2/p261_s1?isAuthorized=no [article] Experimental tests of notched and plate connectors for LVL-concrete composite beams [texte imprimé] / David Yeoh, Auteur ; Massimo Fragiacomo, Auteur ; Mary de Franceschi, Auteur . - 2011 . - pp. 261-269. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 137 N° 2 (Fevrier 2011) . - pp. 261-269 Mots-clés : Composite  structures  Timber  Concrete  Connections  Tests Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper reports the experimental results of symmetrical push-out tests performed on notched and toothed metal plate connectors for laminated veneer lumber (LVL)-concrete composite floor systems. The characteristic shear strength and slip moduli were evaluated for three types of connectors: (1) a 300-mm-long rectangular notch cut in the LVL joist and reinforced with a 16-mm-diameter lag screw; (2) a triangular notch reinforced with the same lag screw; and (3) two 333-mm-long toothed metal plates pressed in the lateral surface of two adjacent LVL joists. The shear force versus relative slip relationships are presented together with analytical prepeak and postpeak approximations which can be used to carry out nonlinear finite-element analyses of LVL-concrete composite beams. The failure mechanisms of the notched connections are also discussed. Analytical design formulas for shear-strength evaluation of notched connections derived in accordance with New Zealand Standards and Eurocodes are proposed based on four possible failure mechanisms. Good approximation was found if a slight modification of the Eurocodes formulas is introduced. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i2/p261_s1?isAuthorized=no

Finite-element model updating and probabilistic analysis of timber-concrete composite beams / Zona, Alessandro in Journal of structural engineering, Vol. 138 N° 7 (Juillet 2012) 

Public ISBD [article]  in Journal of structural engineering > Vol. 138 N° 7 (Juillet 2012) . - pp. 899–910 Titre : Finite-element model updating and probabilistic analysis of timber-concrete composite beams Type de document : texte imprimé Auteurs : Zona, Alessandro, Auteur ; Michele Barbato, Auteur ; Massimo Fragiacomo, Auteur Année de publication : 2012 Article en page(s) : pp. 899–910 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Timber  construction  Composite  beams  Finite  element  method  Nonlinear  analysis  Probability  distribution Résumé : Timber-concrete composite beams are an increasingly common design solution for medium-to-long span floors in new buildings. Thus, there is a significant need for accurate models and analysis tools to predict the response and performance of timber-concrete composite beams. In this paper, a nonlinear finite-element (FE) frame model with deformable shear connection is adopted to estimate the short-term structural response of timber-concrete composite beams for which experimental results are available. The FE model is used in conjunction with a probabilistic analysis methodology, which explicitly accounts for the uncertainties in the parameters that describe the constitutive models for timber, concrete, and shear connectors. The objectives of this study are (1) the evaluation of the variability of global and local structural response quantities owing to the uncertainties in the constitutive parameters of timber, concrete, and shear connectors; and (2) the analysis of the correlation between experimental measurements and numerical results based on FE models in which the values of the constitutive parameters are set equal to their experimentally identified mean values and in which the values of the constitutive parameters are optimized through FE model updating, respectively. The results presented in this study show that uncertainties in the constitutive parameters of timber, concrete, and shear connectors have a significant influence on the correlation between the experimental and numerical results. In addition, the optimal values of material parameters obtained using the FE model updating procedure may show substantial variations with respect to the parameters’ mean values as identified in the experimental testing. Prospective developments directed toward design applications and based on the obtained results are also discussed. ISSN : 0733-9445 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29ST.1943-541X.0000509 [article] Finite-element model updating and probabilistic analysis of timber-concrete composite beams [texte imprimé] / Zona, Alessandro, Auteur ; Michele Barbato, Auteur ; Massimo Fragiacomo, Auteur . - 2012 . - pp. 899–910. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 138 N° 7 (Juillet 2012) . - pp. 899–910 Mots-clés : Timber  construction  Composite  beams  Finite  element  method  Nonlinear  analysis  Probability  distribution Résumé : Timber-concrete composite beams are an increasingly common design solution for medium-to-long span floors in new buildings. Thus, there is a significant need for accurate models and analysis tools to predict the response and performance of timber-concrete composite beams. In this paper, a nonlinear finite-element (FE) frame model with deformable shear connection is adopted to estimate the short-term structural response of timber-concrete composite beams for which experimental results are available. The FE model is used in conjunction with a probabilistic analysis methodology, which explicitly accounts for the uncertainties in the parameters that describe the constitutive models for timber, concrete, and shear connectors. The objectives of this study are (1) the evaluation of the variability of global and local structural response quantities owing to the uncertainties in the constitutive parameters of timber, concrete, and shear connectors; and (2) the analysis of the correlation between experimental measurements and numerical results based on FE models in which the values of the constitutive parameters are set equal to their experimentally identified mean values and in which the values of the constitutive parameters are optimized through FE model updating, respectively. The results presented in this study show that uncertainties in the constitutive parameters of timber, concrete, and shear connectors have a significant influence on the correlation between the experimental and numerical results. In addition, the optimal values of material parameters obtained using the FE model updating procedure may show substantial variations with respect to the parameters’ mean values as identified in the experimental testing. Prospective developments directed toward design applications and based on the obtained results are also discussed. ISSN : 0733-9445 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29ST.1943-541X.0000509

Long-term behavior of prestressed LVL members / Matthew Davies in Journal of structural engineering, Vol. 137 N° 12 (Décembre 2011) 

Public ISBD [article]  in Journal of structural engineering > Vol. 137 N° 12 (Décembre 2011) . - pp. 1553-1561 Titre : Long-term behavior of prestressed LVL members : I: Experimental tests Type de document : texte imprimé Auteurs : Matthew Davies, Auteur ; Massimo Fragiacomo, Auteur Année de publication : 2012 Article en page(s) : pp. 1553-1561 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Creep  Frames  Prestressing  Stress  relaxation  Timber  construction  Time  dependence  Laminated  wood Résumé : This paper presents the results of experimental tests undertaken to resolve questions regarding the viability of multistory prestressed timber structures, specifically the reduction in the prestress load over time. Reduced- and large-scale specimens were tested for 1 year in controlled and uncontrolled heated indoor conditions. Specimens included beams and two-bay frames made from radiata pine laminated veneer lumber (LVL) with a box-shaped cross section. The prestress load was applied through the center of the section by using an unbonded tendon. All relevant quantities such as load in the prestress tendon, deflection, timber moisture content, environmental temperature, and relative humidity were monitored throughout the test. Functions were fitted to the one-year experimental curves and then used to indicate more clearly the trends of the prestress losses during the testing. For a beam in which all timber is loaded parallel to the grain, a reduction in prestress of 1.4% was found after 1 year, whereas for a frame in which 11% of its length is loaded perpendicular to the grain, the loss increased to 7% because of the presence of columns. Furthermore, an attempt was made to separate the contributions made to prestress losses by key factors, namely creep and mechano-sorption of the LVL that is parallel and perpendicular to the grain; relaxation of the prestressing strand; and shrinkage/swelling on account of environmental variations. The most important factor is the proportion of timber that is loaded perpendicular to grain compared with the timber loaded parallel to grain. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i12/p1553_s1?isAuthorized=no [article] Long-term behavior of prestressed LVL members : I: Experimental tests [texte imprimé] / Matthew Davies, Auteur ; Massimo Fragiacomo, Auteur . - 2012 . - pp. 1553-1561. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 137 N° 12 (Décembre 2011) . - pp. 1553-1561 Mots-clés : Creep  Frames  Prestressing  Stress  relaxation  Timber  construction  Time  dependence  Laminated  wood Résumé : This paper presents the results of experimental tests undertaken to resolve questions regarding the viability of multistory prestressed timber structures, specifically the reduction in the prestress load over time. Reduced- and large-scale specimens were tested for 1 year in controlled and uncontrolled heated indoor conditions. Specimens included beams and two-bay frames made from radiata pine laminated veneer lumber (LVL) with a box-shaped cross section. The prestress load was applied through the center of the section by using an unbonded tendon. All relevant quantities such as load in the prestress tendon, deflection, timber moisture content, environmental temperature, and relative humidity were monitored throughout the test. Functions were fitted to the one-year experimental curves and then used to indicate more clearly the trends of the prestress losses during the testing. For a beam in which all timber is loaded parallel to the grain, a reduction in prestress of 1.4% was found after 1 year, whereas for a frame in which 11% of its length is loaded perpendicular to the grain, the loss increased to 7% because of the presence of columns. Furthermore, an attempt was made to separate the contributions made to prestress losses by key factors, namely creep and mechano-sorption of the LVL that is parallel and perpendicular to the grain; relaxation of the prestressing strand; and shrinkage/swelling on account of environmental variations. The most important factor is the proportion of timber that is loaded perpendicular to grain compared with the timber loaded parallel to grain. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i12/p1553_s1?isAuthorized=no

Long-term behavior of prestressed LVL members / Massimo Fragiacomo in Journal of structural engineering, Vol. 137 N° 12 (Décembre 2011) 

Public ISBD [article]  in Journal of structural engineering > Vol. 137 N° 12 (Décembre 2011) . - pp. 1562-1572 Titre : Long-term behavior of prestressed LVL members : II: Analytical approach Type de document : texte imprimé Auteurs : Massimo Fragiacomo, Auteur ; Matthew Davies, Auteur Année de publication : 2012 Article en page(s) : pp. 1562-1572 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Creep  Frames  Losses  Prestressing  Stress  relaxation  Timber  construction  Time  dependence  Laminated  wood Résumé : This paper investigates the long-term behavior of beams and frames made from laminated veneer lumber (LVL) prestressed with unbonded tendons. A formula for the evaluation of the prestress losses during the service life was derived from the integral equations of wood and tendons using the age-adjusted effective modulus method. All phenomena affecting the time-dependent behavior of the system, such as creep, mechano-sorption, thermal and moisture strains of the wood, and relaxation and thermal strains of the steel tendon, were considered. The formula was validated on experimental results showing the possibility to adequately predict the losses, although with some approximation. The formula was simplified further by removing some parameters that have little or almost no effect, and rewritten in a nondimensional format, leading to an easy-to-use closed-form solution suitable for implementation in codes of practice. The most important parameters governing the prestress losses were the proportion of the timber member’s length loaded perpendicular to the grain, and the ratio between the axial stiffnesses of the tendon and timber frame. An increase in these parameters significantly raises the amount of prestress loss. Possible methods for the mitigation of losses in a frame are finally presented and briefly discussed. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i12/p1562_s1?isAuthorized=no [article] Long-term behavior of prestressed LVL members : II: Analytical approach [texte imprimé] / Massimo Fragiacomo, Auteur ; Matthew Davies, Auteur . - 2012 . - pp. 1562-1572. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 137 N° 12 (Décembre 2011) . - pp. 1562-1572 Mots-clés : Creep  Frames  Losses  Prestressing  Stress  relaxation  Timber  construction  Time  dependence  Laminated  wood Résumé : This paper investigates the long-term behavior of beams and frames made from laminated veneer lumber (LVL) prestressed with unbonded tendons. A formula for the evaluation of the prestress losses during the service life was derived from the integral equations of wood and tendons using the age-adjusted effective modulus method. All phenomena affecting the time-dependent behavior of the system, such as creep, mechano-sorption, thermal and moisture strains of the wood, and relaxation and thermal strains of the steel tendon, were considered. The formula was validated on experimental results showing the possibility to adequately predict the losses, although with some approximation. The formula was simplified further by removing some parameters that have little or almost no effect, and rewritten in a nondimensional format, leading to an easy-to-use closed-form solution suitable for implementation in codes of practice. The most important parameters governing the prestress losses were the proportion of the timber member’s length loaded perpendicular to the grain, and the ratio between the axial stiffnesses of the tendon and timber frame. An increase in these parameters significantly raises the amount of prestress loss. Possible methods for the mitigation of losses in a frame are finally presented and briefly discussed. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i12/p1562_s1?isAuthorized=no

Moment Redistribution in continuous steel-concrete composite beams with compact cross section / Natalino Gattesco in Journal of structural engineering, Vol. 136 N° 2 (Fevrier 2010) 

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Proposal to account for concrete shrinkage and environmental strains in design of timber-concrete composite beams / Massimo Fragiacomo in Journal of structural engineering, Vol. 139 N° 1 (Janvier 2013) 

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State of the art on timber-concrete composite structures / David Yeoh in Journal of structural engineering, Vol. 137 N° 10 (Octobre 2011) 

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Timber frame moment joints with glued-In steel rods. I / Massimo Fragiacomo in Journal of structural engineering, Vol. 138 N° 6 (Juin 2012) 

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Timber frame moment joints with glued-in steel rods. II / Massimo Fragiacomo in Journal of structural engineering, Vol. 138 N° 6 (Juin 2012) 

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