Active vibration control is an effective way of increasing robustness of the design to meet the stringent accuracy requirements for space structures. This paper presents the results of active damping realized by a pie...Active vibration control is an effective way of increasing robustness of the design to meet the stringent accuracy requirements for space structures. This paper presents the results of active damping realized by a piezoelectric active member to control the vibration of a four-bay four-longern aluminum truss structure with cantilever boundary. The active member, which utilizes a piezoelectric actuating unit and an integrated load cell, is designed for vibration control of the space truss structures. Active damping control is realized using direct velocity feedback around the active member. The placement of the active member as one of the most important factor of affecting the control system performance, is also investigated by modal dissipation energy ratio as indicator. The active damping effectiveness is evaluated by comparing the closed-loop response with the open loop response.展开更多
Adaptive truss structures are a new kind of structures with integrated active members,whose dynamic characteristies can be beneficially modified to meet mission requirements.Active members containing actuating and sen...Adaptive truss structures are a new kind of structures with integrated active members,whose dynamic characteristies can be beneficially modified to meet mission requirements.Active members containing actuating and sensing units are the major components of adaptive truss structures.Modeling of adaptive truss structures is a key step to analyze the structural dynamic characteristics.A new experimental modal analysis approach,in which active members are used as excitatiDn sources for modal test,has been proposed in this paper.The excitation forces generated by the active members, which are different from the excitation forces exerted on structures in the conventional modal test,are internal forces for the truss structures.The relation between internal excitation forces and external forces is revealed such that the traditional identification method can be adopted to obtain modal parameters of adaptive structures.Placement problem of the active member in adaptive truss structures is also discussed in this work. Modal test and analysis are conducted with a planar adaptive truss structure by using piezoelectric active members in order to verify the feasibility and effectiveness of the proposed method.展开更多
The roof system of social housing in Brazil generally consists of components made out of native forest lumber of high market value. Taking into account the increasing number of planted forests and the need to develop ...The roof system of social housing in Brazil generally consists of components made out of native forest lumber of high market value. Taking into account the increasing number of planted forests and the need to develop new products and to add value to this timber, this work deals with the development and structural analysis of a roof system using yellow pine plantation wood （Pinus spp）, a sustainable material which however presents many defects. The NLT （laminated nailed timber） technology was chosen as it allows the use of shorter length and smaller cross section pieces, eliminating major defects. Seven samples of structural trussed rafters in NLT were tested; six made out of graded timber and one ungraded in order to verify the impact of the wood grading in the structural performance of the model. The results showed that the trussed rafter system in NLT meets the necessary structural performance requiring poor conditions of infrastructure for manufacture process, and that the graded wood samples showed better performance than the ungraded one.展开更多
文摘Active vibration control is an effective way of increasing robustness of the design to meet the stringent accuracy requirements for space structures. This paper presents the results of active damping realized by a piezoelectric active member to control the vibration of a four-bay four-longern aluminum truss structure with cantilever boundary. The active member, which utilizes a piezoelectric actuating unit and an integrated load cell, is designed for vibration control of the space truss structures. Active damping control is realized using direct velocity feedback around the active member. The placement of the active member as one of the most important factor of affecting the control system performance, is also investigated by modal dissipation energy ratio as indicator. The active damping effectiveness is evaluated by comparing the closed-loop response with the open loop response.
文摘Adaptive truss structures are a new kind of structures with integrated active members,whose dynamic characteristies can be beneficially modified to meet mission requirements.Active members containing actuating and sensing units are the major components of adaptive truss structures.Modeling of adaptive truss structures is a key step to analyze the structural dynamic characteristics.A new experimental modal analysis approach,in which active members are used as excitatiDn sources for modal test,has been proposed in this paper.The excitation forces generated by the active members, which are different from the excitation forces exerted on structures in the conventional modal test,are internal forces for the truss structures.The relation between internal excitation forces and external forces is revealed such that the traditional identification method can be adopted to obtain modal parameters of adaptive structures.Placement problem of the active member in adaptive truss structures is also discussed in this work. Modal test and analysis are conducted with a planar adaptive truss structure by using piezoelectric active members in order to verify the feasibility and effectiveness of the proposed method.
文摘The roof system of social housing in Brazil generally consists of components made out of native forest lumber of high market value. Taking into account the increasing number of planted forests and the need to develop new products and to add value to this timber, this work deals with the development and structural analysis of a roof system using yellow pine plantation wood （Pinus spp）, a sustainable material which however presents many defects. The NLT （laminated nailed timber） technology was chosen as it allows the use of shorter length and smaller cross section pieces, eliminating major defects. Seven samples of structural trussed rafters in NLT were tested; six made out of graded timber and one ungraded in order to verify the impact of the wood grading in the structural performance of the model. The results showed that the trussed rafter system in NLT meets the necessary structural performance requiring poor conditions of infrastructure for manufacture process, and that the graded wood samples showed better performance than the ungraded one.
