Natural fibers have recently raised attention for presenting adequate mechanical characteristics for reinforcement of structural elements. The use of both natural fibers, in especial Sisal fibers, in wood laminated be...Natural fibers have recently raised attention for presenting adequate mechanical characteristics for reinforcement of structural elements. The use of both natural fibers, in especial Sisal fibers, in wood laminated beams and also wood from reforestation, is in accordance with the current economic interest and ecological appeal. Specifically, the strengthening of wood laminated beams with Sisal fibers is more effective for structures that require an increase in their structural capacity without a significant increase in height of the cross section. Furthermore, it is recommended that this type of reinforcement is used in wood structural elements where the elastic modulus is at least equal to the Sisal fibers. The composition of Sisal fibers is basically of cellulose, lignin and hemicelluloses. In particular, the amount of cellulose and the angle that the micro-fibers with the axis of the fiber characterize the failure strength and the modulus of elasticity. The average mechanical characteristics of the Sisal fiber are： tensile strength 347 to 378 （MPa） and elastic modulus 15.2 （GPa） whereas these properties are lower for strips of Sisal fibers. In this context, this paper deals with the analysis and the viability of the use of Sisal fibers in wood structures as a reinforced material.展开更多
The relation between narratives and agency can be sometimes considered as mutually constitutive. There are cases in which telling a story expresses higher degrees of agency, and respectively, agency is shaped as a nar...The relation between narratives and agency can be sometimes considered as mutually constitutive. There are cases in which telling a story expresses higher degrees of agency, and respectively, agency is shaped as a narrative that expresses the agent＇s reasons. From henceforth, I will contend that a narrative theory, beyond the personal identity problem, can also enlighten how the agent attains giving reasons for the action by making sense of sequences of events. In order to explain how agency is constituted from understanding and control, we must assume a primitive competence for narratives. Agency supposes an ordering that cannot be reduced to temporality, but expresses a certain sense of accomplishment that can be narratively constituted. In this context, I will examine Welleman＇s theory of emotions as an ordering framework of the events in structures of means-ends. A possible objection to his explanation of the agential narratives is that emotions themselves need to be understood as narrative processes. I suggest then that an enactivist approach would be a way of explaining the narrative constitution of agency. One virtue of this approach is that it harmonizes the biological and cultural components of the agency from the most basic layers to the ordinary folk-psychological narratives.展开更多
Plain round bars were commonly used as main bars in the design of RC （reinforced concrete） buildings prior to the 1970s. According to previous research investigating the seismic performance of reinforced concrete me...Plain round bars were commonly used as main bars in the design of RC （reinforced concrete） buildings prior to the 1970s. According to previous research investigating the seismic performance of reinforced concrete members constructed with plain round bars, the strength of those members did not reach the calculated flexural strength due to bond slippage of main bars before yielding. It is important, therefore, to investigate the hysteretic bond mechanisms of plain round bars in concrete. In this research, analytical models were proposed to predict hysteretic bond-slip mechanisms between plain round bar and concrete depending on the results of experiments performed by the authors. In addition, the energy absorption capacity and the equivalent viscous damping factors obtained from the experimental results and analytical models are discussed. As a result of comparisons between the experimental data and the analysis models, good agreements were obtained.展开更多
In topology optimization of structures considering flexibility, degenerated optimal solutions, such as hinges, gray areas and disconnected structures may appear. In this paper, built upon the newly developed morphable...In topology optimization of structures considering flexibility, degenerated optimal solutions, such as hinges, gray areas and disconnected structures may appear. In this paper, built upon the newly developed morphable component based topology optimization approach, a novel representation using connected morphable components(CMC) and a linkage scheme are proposed to prevent degenerating designs and to ensure structure integrity. A lower bound condition of the thickness of each component is also incorporated to completely remove the smallest components in an optimal configuration. Designs of flexible structures, such as compliant mechanism design, maximum compliance structure design, and design of low-frequency resonating micro devices are studied to validate the proposed methodology. Our work demonstrates that the new methodology can successfully prevent degeneration solutions and possesses other advantages, such as minimum member size control in topology optimization of flexible structures.展开更多
文摘Natural fibers have recently raised attention for presenting adequate mechanical characteristics for reinforcement of structural elements. The use of both natural fibers, in especial Sisal fibers, in wood laminated beams and also wood from reforestation, is in accordance with the current economic interest and ecological appeal. Specifically, the strengthening of wood laminated beams with Sisal fibers is more effective for structures that require an increase in their structural capacity without a significant increase in height of the cross section. Furthermore, it is recommended that this type of reinforcement is used in wood structural elements where the elastic modulus is at least equal to the Sisal fibers. The composition of Sisal fibers is basically of cellulose, lignin and hemicelluloses. In particular, the amount of cellulose and the angle that the micro-fibers with the axis of the fiber characterize the failure strength and the modulus of elasticity. The average mechanical characteristics of the Sisal fiber are： tensile strength 347 to 378 （MPa） and elastic modulus 15.2 （GPa） whereas these properties are lower for strips of Sisal fibers. In this context, this paper deals with the analysis and the viability of the use of Sisal fibers in wood structures as a reinforced material.
文摘The relation between narratives and agency can be sometimes considered as mutually constitutive. There are cases in which telling a story expresses higher degrees of agency, and respectively, agency is shaped as a narrative that expresses the agent＇s reasons. From henceforth, I will contend that a narrative theory, beyond the personal identity problem, can also enlighten how the agent attains giving reasons for the action by making sense of sequences of events. In order to explain how agency is constituted from understanding and control, we must assume a primitive competence for narratives. Agency supposes an ordering that cannot be reduced to temporality, but expresses a certain sense of accomplishment that can be narratively constituted. In this context, I will examine Welleman＇s theory of emotions as an ordering framework of the events in structures of means-ends. A possible objection to his explanation of the agential narratives is that emotions themselves need to be understood as narrative processes. I suggest then that an enactivist approach would be a way of explaining the narrative constitution of agency. One virtue of this approach is that it harmonizes the biological and cultural components of the agency from the most basic layers to the ordinary folk-psychological narratives.
文摘Plain round bars were commonly used as main bars in the design of RC （reinforced concrete） buildings prior to the 1970s. According to previous research investigating the seismic performance of reinforced concrete members constructed with plain round bars, the strength of those members did not reach the calculated flexural strength due to bond slippage of main bars before yielding. It is important, therefore, to investigate the hysteretic bond mechanisms of plain round bars in concrete. In this research, analytical models were proposed to predict hysteretic bond-slip mechanisms between plain round bar and concrete depending on the results of experiments performed by the authors. In addition, the energy absorption capacity and the equivalent viscous damping factors obtained from the experimental results and analytical models are discussed. As a result of comparisons between the experimental data and the analysis models, good agreements were obtained.
基金supported by the National Science Foundation (Grant Nos. CMMI-1130948 & CMMI-1334929)
文摘In topology optimization of structures considering flexibility, degenerated optimal solutions, such as hinges, gray areas and disconnected structures may appear. In this paper, built upon the newly developed morphable component based topology optimization approach, a novel representation using connected morphable components(CMC) and a linkage scheme are proposed to prevent degenerating designs and to ensure structure integrity. A lower bound condition of the thickness of each component is also incorporated to completely remove the smallest components in an optimal configuration. Designs of flexible structures, such as compliant mechanism design, maximum compliance structure design, and design of low-frequency resonating micro devices are studied to validate the proposed methodology. Our work demonstrates that the new methodology can successfully prevent degeneration solutions and possesses other advantages, such as minimum member size control in topology optimization of flexible structures.
