The Experts below are selected from a list of 123 Experts worldwide ranked by ideXlab platform
Enrico Spacone - One of the best experts on this subject based on the ideXlab platform.
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reinforced concrete fiber beam element with bond slip
Journal of Structural Engineering-asce, 2000Co-Authors: Giorgio Monti, Enrico SpaconeAbstract:This paper presents a new reinforced concrete beam finite element that explicitly accounts for the slip between the reinforcing bars and the surrounding concrete. The element formulation combines the fiber- section model with the finite-element model of a reinforcing bar with continuous slip. The section model retains the plane-section assumption, but the steel fiber strains are computed as the sum of two contributions, the rebar deformation and the anchorage slip. The model applies to any cross-sectional shape under biaxial bending and both monotonic and cyclic loads. The model theoretical framework is presented first. A sensitivity study on the monotonic and cyclic response of a reinforcing bar shows how the model traces the bar's reduced initial stiffness, bond degradation, and anchorage loss for insufficient anchorage length. Finally, comparison with an experimental test on a Circular Column shows that the prediction with the new model is in good agreement with the test, whereas the original fiber model with perfect bond overestimates the hysteretic energy dissipated during the loading cycles. element to the analysis of RC structures, the introduction of the mechanics of bond-slip of the reinforcing bars appears to be a necessary enhancement toward a realistic description of the cyclic and ultimate behavior of RC structures. Rubiano- Benavides (1998) proposed the use of rotational springs at the element ends to account for the added flexibility due to bond- slip. This approach is more suitable for lumped plasticity mod- els and requires particular care in the selection of the rotational spring's mechanical properties. The framework of the pro- posed model is that of the fiber model, where the rebar re- sponse is modified to account for the effects of bond-slip. The basic idea is to merge the formulation of the reinforcing bar with bond-slip proposed by Monti et al. (1997a,b) into the force-based fiber element proposed by Spacone et al. (1996a). The framework of the fiber-section state determination is re- tained, and a new approach is proposed to compute the rebar stress and stiffness that includes the effects of slip. In the new model, the steel fiber accounts not only for the response of the rebar inside the beam, but also for its anchor- age outside the element, in either a structural joint or a footing. The steel fiber strain is given by the sum of the effects of the rebar deformation and the anchorage slip. The response is still computed in terms of fiber stress and stiffness, which are needed for the fiber-section state determination. An attractive feature of this formulation is the possibility of tracing the response of each bar within a section, which is particularly important when each rebar undergoes a different load history. Therefore, the model is suitable for sections of general shape, including Circular ones, and for sections under biaxial loading. The theoretical framework of the new model is presented first, followed by a series of parametric studies on the perfor- mance of the new model. Finally, the results from an experi- mental test are compared with the prediction obtained with the proposed model.
Giorgio Monti - One of the best experts on this subject based on the ideXlab platform.
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reinforced concrete fiber beam element with bond slip
Journal of Structural Engineering-asce, 2000Co-Authors: Giorgio Monti, Enrico SpaconeAbstract:This paper presents a new reinforced concrete beam finite element that explicitly accounts for the slip between the reinforcing bars and the surrounding concrete. The element formulation combines the fiber- section model with the finite-element model of a reinforcing bar with continuous slip. The section model retains the plane-section assumption, but the steel fiber strains are computed as the sum of two contributions, the rebar deformation and the anchorage slip. The model applies to any cross-sectional shape under biaxial bending and both monotonic and cyclic loads. The model theoretical framework is presented first. A sensitivity study on the monotonic and cyclic response of a reinforcing bar shows how the model traces the bar's reduced initial stiffness, bond degradation, and anchorage loss for insufficient anchorage length. Finally, comparison with an experimental test on a Circular Column shows that the prediction with the new model is in good agreement with the test, whereas the original fiber model with perfect bond overestimates the hysteretic energy dissipated during the loading cycles. element to the analysis of RC structures, the introduction of the mechanics of bond-slip of the reinforcing bars appears to be a necessary enhancement toward a realistic description of the cyclic and ultimate behavior of RC structures. Rubiano- Benavides (1998) proposed the use of rotational springs at the element ends to account for the added flexibility due to bond- slip. This approach is more suitable for lumped plasticity mod- els and requires particular care in the selection of the rotational spring's mechanical properties. The framework of the pro- posed model is that of the fiber model, where the rebar re- sponse is modified to account for the effects of bond-slip. The basic idea is to merge the formulation of the reinforcing bar with bond-slip proposed by Monti et al. (1997a,b) into the force-based fiber element proposed by Spacone et al. (1996a). The framework of the fiber-section state determination is re- tained, and a new approach is proposed to compute the rebar stress and stiffness that includes the effects of slip. In the new model, the steel fiber accounts not only for the response of the rebar inside the beam, but also for its anchor- age outside the element, in either a structural joint or a footing. The steel fiber strain is given by the sum of the effects of the rebar deformation and the anchorage slip. The response is still computed in terms of fiber stress and stiffness, which are needed for the fiber-section state determination. An attractive feature of this formulation is the possibility of tracing the response of each bar within a section, which is particularly important when each rebar undergoes a different load history. Therefore, the model is suitable for sections of general shape, including Circular ones, and for sections under biaxial loading. The theoretical framework of the new model is presented first, followed by a series of parametric studies on the perfor- mance of the new model. Finally, the results from an experi- mental test are compared with the prediction obtained with the proposed model.
Bozidar Stojadinovic - One of the best experts on this subject based on the ideXlab platform.
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Probabilistic seismic demand model for curved reinforced concrete bridges
Bulletin of Earthquake Engineering, 2012Co-Authors: Nicola Tondini, Bozidar StojadinovicAbstract:This article examines the seismic behaviour of curved box-girder concrete highway overpass bridges commonly built in California. In particular, a probabilistic seismic demand model for curved 5-span reinforced concrete box-girder bridges with single Circular Column bents is developed. The principal parameter of the demand model is the bridge curve radius in the horizontal plane, varying from infinity (representing a straight bridge) to a sharp curve radius equal to the length of the bridge. Three bridge prototypes are analyzed: (1) a tall-Column bridge with relatively low lateral stiffness; (2) a bridge commonly designed in California and (3) a short-Column bridge with high lateral stiffness. A probabilistic seismic demand analysis, including a modal analysis and an evaluation of the nonlinear static and dynamic response, are performed for each bridge prototype and each radius value. The magnitude-distance bin approach is used to cover a range of plausible ground motion scenarios. The probabilistic demand models are cast in terms of one engineering demand parameter, the bridge drift ratio, and two intensity measures: the peak ground displacement or velocity, and the spectral displacement at the fundamental period of the bridge, S _ d ( T _1). The demand models show an increase in transverse-direction drift ratio demand for sharply curved bridges.
Zhiliang Tang - One of the best experts on this subject based on the ideXlab platform.
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comparisons of honeycomb sandwich and foam filled cylindrical Columns under axial crushing loads
Thin-walled Structures, 2011Co-Authors: Zonghua Zhang, Shutian Liu, Zhiliang TangAbstract:For the conventional thin-walled energy absorber, the energy dissipation during a collision is concentrated in relatively narrow zones. This means that a great deal of material does not participate in the plastic deformation or enter the large plastic deformation stage. To expand the plastic deformation zones and improve the energy absorption efficiency, the authors presented a new type of honeycomb sandwich Circular Column. This innovative energy absorber is a composite structure composed of two Circular aluminum tubes filled with core shaped as a large-cell honeycomb lattice. In this paper, six different honeycomb sandwich Circular Columns were investigated numerically. Comparisons of the interaction effect between tubes and filler, the deformation modes and the energy absorption abilities of these Columns were conducted. The results were as following. The kagome sandwich Column had the best energy absorption capability, followed by the Columns sandwiched with triangle, hexagon lattices. In addition, foam-filled Columns with different adhesive conditions were also simulated and compared with the honeycomb sandwich Columns. It was found that increasing the adhesive strength improved the energy absorption and changed the deformation mode of the foam-filled Columns. Furthermore, comparison showed that the honeycomb sandwich Columns had higher specific energy absorption capability than the foam-filled tubes except for the strong bonded case. The kagome sandwich Column performed best in crashworthiness, followed by triangle sandwich Column.
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crashworthiness investigation of kagome honeycomb sandwich cylindrical Column under axial crushing loads
Thin-walled Structures, 2010Co-Authors: Zonghua Zhang, Shutian Liu, Zhiliang TangAbstract:For the classic thin-walled energy absorber, the energy dissipation during a collision is concentrated over relatively narrow zones. This means that a great deal of materials of the Columns do not participate in the plastic deformation or not enter into the large plastic deformation stage. To expand the plastic deformation zones and improve the energy absorption efficiency, a new type of kagome honeycomb sandwich bitubal Circular Column is presented in this paper. This innovative impact energy absorber is made of two Circular aluminum tubes filled with core shaped as a large-cell kagome lattice. The interaction effect, deformation mode and energy absorption characteristics of the composite structure are investigated numerically. Observing the collapsing process, it is found that the kagome lattices buckle first, which triggers the outer and inner skin tubes to fold locally. This behavior increases the plastic deformation areas. Moreover, the presence of the outer and inner tubes strengthens the buckling capacity of kagome cell. Furthermore, the folded tube walls intrude into the gap of the honeycomb cell, which further retards the collapse of the honeycomb cell. So the interaction effects between the honeycomb and Column walls greatly improve the energy absorption efficiency. In addition, the effects of geometrical parameters of the kagome honeycomb on the structural crashworthiness are studied. It is found that the cell wall thickness and cell distribution (cell number in the circumferential direction) have distinct effects on the specific energy absorption. Besides, we also studied the foam-filled Column with the same foam density as the kagome honeycomb and compared it with the kagome sandwich structure. It is found that the kagome sandwich Column has higher mean crash force and better energy absorption characteristics.
Liang Sun - One of the best experts on this subject based on the ideXlab platform.
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regular waves onto a truncated Circular Column a comparison of experiments and simulations
Applied Ocean Research, 2016Co-Authors: Liang Sun, Jun Zang, Lifen Chen, Eatock R Taylor, P H TaylorAbstract:Abstract Accurate prediction of hydrodynamic forces on offshore structures is critical for safe and cost effective design of fixed and floating offshore structures exposed to a harsh environment. In the present paper, nonlinear interactions between regular waves and a single surface-piercing truncated Circular Column have been investigated using a frequency domain potential flow solver (DIFFRACT) and a full CFD solver in OpenFOAM for direct comparisons. Both the predicted free surface elevation around the Column and the total force acting on the Column have been analysed and compared with experimental data from MOERI. The degree of non-linearity and the contribution of each harmonic to the free surface run-up and wave forces have been examined, and evaluations of the accuracy and computational efficiency of the potential flow solver and the full CFD solver are provided and compared in the paper. Also of note are the local forms of the scattered waves around the Column in numerical simulations, which are consistent with the Type-1 and Type-2 patterns identified in physical experiments at Imperial College.
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Nonlinear interactions of regular waves with a truncated Circular Column
2013Co-Authors: Liang Sun, Li Chen, Jun Zang, Rodney Eatock Taylor, Paul TaylorAbstract:In this present paper, wave elevations around single truncated Circular Column have been investigated by using a potential-flow solver (DIFFRACT) and a viscous-flow solver in OpenFOAM. Results from time-domain analyses have been compared with measured time series in experiments and results given by WAMIT. Spectral analyses have been carried out for time series to consider the contributions from wave components at different harmonics. RAOs and QTFs of surface elevations have been compared with the results obtained by Kristiansen et al. (2004).