Height limitations are not uncommon in multi-storey buildings due to economic requirements and esthetical considerations. Substantial spaces are normally required to enable the passage of large pipes and ducts beneath...Height limitations are not uncommon in multi-storey buildings due to economic requirements and esthetical considerations. Substantial spaces are normally required to enable the passage of large pipes and ducts beneath steel beams leading to uneconomic floor heights. The most adopted solution for this issue is the use of steel beam web openings to provide the required space for services. These openings could lead to a significant decrease of the beam load carrying capacity depending on the adopted openings shape, size and location. These aspects motivated the present study based on FE simulations calibrated against numerical and test results. The results accuracy enabled a comprehensive parametric analysis of beams with web openings to be made focused on the profile size, web opening location, among others. The study also investigated the efficiency of longitudinal stiffeners welded at the opening region and benefits of using an adequate edge concordance radius in beams with rectangular and square openings. The obtained results showed the need of using welded longitudinal stiffeners in order to increase the beams ultimate load carrying capacity. This adoption can double or even triple the ultimate load of beams with rectangular and square opening heights equal to 0.75 H, respectively.展开更多
contributes for decisions at several production levels.However,taking length measurements is a cumbersome task that,when applied to living individuals,can induce considerable stress,increasing the risk of damage or hi...contributes for decisions at several production levels.However,taking length measurements is a cumbersome task that,when applied to living individuals,can induce considerable stress,increasing the risk of damage or hindering their growth.Computer vision is one of the most used non-contact tools to overcome this issue,being fast,consistent and repeatable.However,its use in aquatic environments is limited by the high cost,the difficulty of calibrating the system in underwater conditions and the complexity of implementation.This paper proposes a low-cost easy-to-use vision system that can take measurements on live fish in aquatic conditions,without the need for a special calibration or a demanding in-water calibration service.The present work implemented a compact stereo vision system and developed a method that estimates the correct length of fish,based on the variation of the angle of incidence of the light rays in the water.Given some structural conditions such as a short baseline,the system is able to measure fish with an error of less than 1%.The short baseline allows to have a compact system and reduces the effect of water refraction on the 3D reconstruction.A set of experiments were performed with real fish,working robustly for a set of orientations of the fish(even when the caudal fin and snout are on different distances to the cameras).展开更多
文摘Height limitations are not uncommon in multi-storey buildings due to economic requirements and esthetical considerations. Substantial spaces are normally required to enable the passage of large pipes and ducts beneath steel beams leading to uneconomic floor heights. The most adopted solution for this issue is the use of steel beam web openings to provide the required space for services. These openings could lead to a significant decrease of the beam load carrying capacity depending on the adopted openings shape, size and location. These aspects motivated the present study based on FE simulations calibrated against numerical and test results. The results accuracy enabled a comprehensive parametric analysis of beams with web openings to be made focused on the profile size, web opening location, among others. The study also investigated the efficiency of longitudinal stiffeners welded at the opening region and benefits of using an adequate edge concordance radius in beams with rectangular and square openings. The obtained results showed the need of using welded longitudinal stiffeners in order to increase the beams ultimate load carrying capacity. This adoption can double or even triple the ultimate load of beams with rectangular and square opening heights equal to 0.75 H, respectively.
基金partially funded by the Research Program ACORES2020,with the participation of Azorean Funds,Portuguese Funds,and European Funds.
文摘contributes for decisions at several production levels.However,taking length measurements is a cumbersome task that,when applied to living individuals,can induce considerable stress,increasing the risk of damage or hindering their growth.Computer vision is one of the most used non-contact tools to overcome this issue,being fast,consistent and repeatable.However,its use in aquatic environments is limited by the high cost,the difficulty of calibrating the system in underwater conditions and the complexity of implementation.This paper proposes a low-cost easy-to-use vision system that can take measurements on live fish in aquatic conditions,without the need for a special calibration or a demanding in-water calibration service.The present work implemented a compact stereo vision system and developed a method that estimates the correct length of fish,based on the variation of the angle of incidence of the light rays in the water.Given some structural conditions such as a short baseline,the system is able to measure fish with an error of less than 1%.The short baseline allows to have a compact system and reduces the effect of water refraction on the 3D reconstruction.A set of experiments were performed with real fish,working robustly for a set of orientations of the fish(even when the caudal fin and snout are on different distances to the cameras).
