Due to excessive displacements of tall buildings occasioned by lateral loads, lateral load resisting systems are usually provided to curtail the load effect. The resistance may be offered by Frame Action, Shear Walls,...Due to excessive displacements of tall buildings occasioned by lateral loads, lateral load resisting systems are usually provided to curtail the load effect. The resistance may be offered by Frame Action, Shear Walls, or combined Walls and Frames (also known as Dual System). In this study, finite element based software, ETABS, was used to generate and analyse three-dimensional building models for the assessment of the relative effectiveness of the various lateral load resisting systems. Three models were used, one each for the three resisting systems. Each model consisted of three samples representing three different building heights of 45 m, 75 m, and 99 m. Wind Design Spreadsheet complying with the appropriate British Standards was used to compute preliminary wind load coefficients using the wind speed values from the relevant wind isopleth map of Nigeria as primary data. Lateral wind load was then applied at floor levels of each of the building samples. Each building sample was subjected to three-dimensional analysis for the determination of both the lateral displacements of storey tops and interstorey drifts. The results of the work showed that the dual system was the most efficient lateral-load resisting system based on deflection criterion, as they yielded the least values for lateral displacements and inter-storey drifts. The moment frame was the least stiff of the resisting systems, yielding the highest values of both the lateral displacement and the inter-storey drift.展开更多
A novel multi-laser beams measuring system （MLBM） for high precision detection on displacement of flow fields based on laser backscatter was designed and studied. MLBM has many advantages, such as simple structure, ...A novel multi-laser beams measuring system （MLBM） for high precision detection on displacement of flow fields based on laser backscatter was designed and studied. MLBM has many advantages, such as simple structure, high stability, and no limitation of the monochromaticity of laser. By circumventing the strong influence of atmospheric backscattering on the high sensitivity of target echo detection, high precision detection on backscatter density of laser by signal processing was achieved. Furthermore, the signal densities of various distances were extracted by time sampling and precise frequency control of digital circuit. Finally, the MLBM system including devices integrated of emitting and reviving equipments and program was obtained. Detection experiments showed that our system has high precision and the measurement error could be controlled within 5% to 10%.展开更多
Understanding the drifting motion of a small semi-submersible drifter is of vital importance regarding monitoring surface currents and the floating pollutants in coastal regions. This work addresses this issue by esta...Understanding the drifting motion of a small semi-submersible drifter is of vital importance regarding monitoring surface currents and the floating pollutants in coastal regions. This work addresses this issue by establishing a mechanistic drifting forecast model based on kinetic analysis. Taking tide–wind–wave into consideration, the forecast model is validated against in situ drifting experiment in the Radial Sand Ridges. Model results show good performance with respect to the measured drifting features, characterized by migrating back and forth twice a day with daily downwind displacements. Trajectory models are used to evaluate the influence of the individual hydrodynamic forcing. The tidal current is the fundamental dynamic condition in the Radial Sand Ridges and has the greatest impact on the drifting distance. However, it loses its leading position in the field of the daily displacement of the used drifter. The simulations reveal that different hydrodynamic forces dominate the daily displacement of the used drifter at different wind scales. The wave-induced mass transport has the greatest influence on the daily displacement at Beaufort wind scale 5–6; while wind drag contributes mostly at wind scale 2–4.展开更多
In order to enable a wind tunnel support to have a high enough natural frequency to prevent experiencing mechanical resonance and excessive vibration displacement, five kinds of wind tunnel support structures have bee...In order to enable a wind tunnel support to have a high enough natural frequency to prevent experiencing mechanical resonance and excessive vibration displacement, five kinds of wind tunnel support structures have been simulated and analyzed individually under five different load conditions by means of a nonlinear finite element numerical method. With natural frequency and three directions vibration displacement given, simulation and analyses indicated that additional supports is more beneficial than heightening the rigidity of steel reinforced concrete in support pillars and adopting steel wrappers on the pillars to increase natural frequency of support structure. Increasing the rigidity of steel reinforced concrete, adopting steel wrappers and providing additional supports are all helpful in reducing three directions vibration Max displacement. and additional supports are comparatively more effective. Therefore, a structure scheme with steel reinforced concrete support pillars, steel wrappers and additional supports should be adopted in practical wind tunnel support construction.展开更多
双烟囱结构在自然风作用下存在气动干扰效应,从而诱发较大风致振动,威胁结构安全.合理计算和预测风振响应是双烟囱抗风设计的关键.以某中心距为8倍平均直径的双烟囱结构为研究对象,开展刚性模型测力和气弹模型测振风洞试验,将试验结果...双烟囱结构在自然风作用下存在气动干扰效应,从而诱发较大风致振动,威胁结构安全.合理计算和预测风振响应是双烟囱抗风设计的关键.以某中心距为8倍平均直径的双烟囱结构为研究对象,开展刚性模型测力和气弹模型测振风洞试验,将试验结果与中国规范、欧洲规范和CICIND(International Committee on Industrial Construction)规范计算值进行比较,详细研究双烟囱在不同风向角下的风致响应特性.研究结果表明:在烟囱串列布置下,迎风侧烟囱具有遮挡和干扰效应,一方面使得背风侧烟囱底部弯矩减小,另一方面使其横风向位移大于在其他风向角下的值;由于厂房的干扰效应,风振系数中国规范计算值与试验值接近;当烟囱高度超过厂房高度后,计算值较试验值偏大;对于横向响应,中国规范计算值较试验值大37.1%,欧洲规范计算值与试验值接近,仅偏小6.9%,CICIND规范计算值比试验值小17.1%.展开更多
文摘Due to excessive displacements of tall buildings occasioned by lateral loads, lateral load resisting systems are usually provided to curtail the load effect. The resistance may be offered by Frame Action, Shear Walls, or combined Walls and Frames (also known as Dual System). In this study, finite element based software, ETABS, was used to generate and analyse three-dimensional building models for the assessment of the relative effectiveness of the various lateral load resisting systems. Three models were used, one each for the three resisting systems. Each model consisted of three samples representing three different building heights of 45 m, 75 m, and 99 m. Wind Design Spreadsheet complying with the appropriate British Standards was used to compute preliminary wind load coefficients using the wind speed values from the relevant wind isopleth map of Nigeria as primary data. Lateral wind load was then applied at floor levels of each of the building samples. Each building sample was subjected to three-dimensional analysis for the determination of both the lateral displacements of storey tops and interstorey drifts. The results of the work showed that the dual system was the most efficient lateral-load resisting system based on deflection criterion, as they yielded the least values for lateral displacements and inter-storey drifts. The moment frame was the least stiff of the resisting systems, yielding the highest values of both the lateral displacement and the inter-storey drift.
基金supported by National Natural Science Foundation of China under Grant No.60425101-1Fund for Innovative Research Groups of NSFC under Grant No.60721001
文摘A novel multi-laser beams measuring system （MLBM） for high precision detection on displacement of flow fields based on laser backscatter was designed and studied. MLBM has many advantages, such as simple structure, high stability, and no limitation of the monochromaticity of laser. By circumventing the strong influence of atmospheric backscattering on the high sensitivity of target echo detection, high precision detection on backscatter density of laser by signal processing was achieved. Furthermore, the signal densities of various distances were extracted by time sampling and precise frequency control of digital circuit. Finally, the MLBM system including devices integrated of emitting and reviving equipments and program was obtained. Detection experiments showed that our system has high precision and the measurement error could be controlled within 5% to 10%.
基金supported by the National Key Research and Development Program of China(Grant No.2017YFC0405401)the National Science&Technology Pillar Program(Grant No.2012BAB03B01)+1 种基金the Fundamental Research Funds for the Central Universities,Hohai University(Grant No.2014B30914)the Natural Science Foundation of Jiangsu Province(Grant No.BK2012411)
文摘Understanding the drifting motion of a small semi-submersible drifter is of vital importance regarding monitoring surface currents and the floating pollutants in coastal regions. This work addresses this issue by establishing a mechanistic drifting forecast model based on kinetic analysis. Taking tide–wind–wave into consideration, the forecast model is validated against in situ drifting experiment in the Radial Sand Ridges. Model results show good performance with respect to the measured drifting features, characterized by migrating back and forth twice a day with daily downwind displacements. Trajectory models are used to evaluate the influence of the individual hydrodynamic forcing. The tidal current is the fundamental dynamic condition in the Radial Sand Ridges and has the greatest impact on the drifting distance. However, it loses its leading position in the field of the daily displacement of the used drifter. The simulations reveal that different hydrodynamic forces dominate the daily displacement of the used drifter at different wind scales. The wave-induced mass transport has the greatest influence on the daily displacement at Beaufort wind scale 5–6; while wind drag contributes mostly at wind scale 2–4.
文摘In order to enable a wind tunnel support to have a high enough natural frequency to prevent experiencing mechanical resonance and excessive vibration displacement, five kinds of wind tunnel support structures have been simulated and analyzed individually under five different load conditions by means of a nonlinear finite element numerical method. With natural frequency and three directions vibration displacement given, simulation and analyses indicated that additional supports is more beneficial than heightening the rigidity of steel reinforced concrete in support pillars and adopting steel wrappers on the pillars to increase natural frequency of support structure. Increasing the rigidity of steel reinforced concrete, adopting steel wrappers and providing additional supports are all helpful in reducing three directions vibration Max displacement. and additional supports are comparatively more effective. Therefore, a structure scheme with steel reinforced concrete support pillars, steel wrappers and additional supports should be adopted in practical wind tunnel support construction.
文摘双烟囱结构在自然风作用下存在气动干扰效应,从而诱发较大风致振动,威胁结构安全.合理计算和预测风振响应是双烟囱抗风设计的关键.以某中心距为8倍平均直径的双烟囱结构为研究对象,开展刚性模型测力和气弹模型测振风洞试验,将试验结果与中国规范、欧洲规范和CICIND(International Committee on Industrial Construction)规范计算值进行比较,详细研究双烟囱在不同风向角下的风致响应特性.研究结果表明:在烟囱串列布置下,迎风侧烟囱具有遮挡和干扰效应,一方面使得背风侧烟囱底部弯矩减小,另一方面使其横风向位移大于在其他风向角下的值;由于厂房的干扰效应,风振系数中国规范计算值与试验值接近;当烟囱高度超过厂房高度后,计算值较试验值偏大;对于横向响应,中国规范计算值较试验值大37.1%,欧洲规范计算值与试验值接近,仅偏小6.9%,CICIND规范计算值比试验值小17.1%.
