Introducing heterogeneities into the structure is an effective way to enhance the plasticity in metallic glasses (MGs). As natural heterogeneity, the original randomly distributed free volume in MGs has been found to ...Introducing heterogeneities into the structure is an effective way to enhance the plasticity in metallic glasses (MGs). As natural heterogeneity, the original randomly distributed free volume in MGs has been found to be in favor of plasticity. However, the exact correlation between the free volume distribution and mechanical response is still unclear. In this paper, we investigate the shear banding in MGs with different structural disorders, characterized by both the free volume concentration (FVC) and the free volume dispersion (FVD). It is found that, either high FVC or wide FVD leads to low activation stress of shear band; wide FVD promotes the multiplication of shear bands but high FVC restricts it. It reveals that the yield strength in MGs is dependent on the amount of free volume while the plasticity mainly relies on the distribution. An optimum combination of the two aspects probably helps to design a MG of both good plasticity and high strength.展开更多
Performance analysis of the Pangu Plaza under earthquake and wind loads is described in this paper. The plaza is a 39-story steel high-rise building, 191 m high, located in Beijing close to the 2008 Olympic main stadi...Performance analysis of the Pangu Plaza under earthquake and wind loads is described in this paper. The plaza is a 39-story steel high-rise building, 191 m high, located in Beijing close to the 2008 Olympic main stadium. It has both fluid viscous dampers （FVDs） and buckling restrained braces or unbonded brace （BRB or UBB） installed. A repeated iteration procedure in its design and analysis was adopted for optimization. Results from the seismic response analysis in the horizontal and vertical directions show that the FVDs are highly effective in reducing the response of both the main structure and the secondary system. A comparative analysis of structural seismic performance and economic impact was conducted using traditional methods, i.e., increased size of steel columns and beams and/or use of an increased number of seismic braces versus using FVD. Both the structural response and economic analysis show that using FVD to absorb seismic energy not only satisfies the Chinese seismic design code for a ＂rare＂ earthquake, but is also the most economical way to improve seismic performance both for one-time direct investment and long term maintenance.展开更多
超大跨度钢箱梁悬索桥的结构阻尼和刚度较小,其竖向模态频率低且密集,随风速变化加劲梁可能先后发生多次涡激振动。首先针对某超大跨度悬索桥,进行有限元建模和动力分析。为研究悬索桥多模态涡激振动响应机理和有效抑振措施,在忽略气动...超大跨度钢箱梁悬索桥的结构阻尼和刚度较小,其竖向模态频率低且密集,随风速变化加劲梁可能先后发生多次涡激振动。首先针对某超大跨度悬索桥,进行有限元建模和动力分析。为研究悬索桥多模态涡激振动响应机理和有效抑振措施,在忽略气动刚度和气动阻尼影响时,通过简化Scanlan经验非线性涡激力数学模型得到简谐涡激力数学模型。然后以各竖向模态涡振最大位移响应为优化目标,基于液体黏滞阻尼器参数敏感性分析和调谐质量阻尼器(tuned mass damper,TMD)参数优化设计方法,分别确定阻尼器参数和TMD参数。最后探讨了黏滞阻尼器耗能系统控制悬索桥多阶竖向模态涡振的可行性,详细分析了TMD系统控制涡激振动的效果。结果表明:在塔梁间设置黏滞阻尼器对各竖向模态主要起振区域的涡振位移控制效果不理想;TMD系统能有效抑制常遇风速范围内加劲梁的多阶竖向模态涡振响应,将最大振幅严格控制在容许值以内,提高了加劲梁抵抗涡振变形的能力。展开更多
基金supported by the National Natural Science Foundation of China (Grants Nos. 10725211, 11002144, 11021262)the National Natural Science Foundation of China-NSAF (Grant No. 10976100)+1 种基金the National Key Basic Research Program of China (Grant No. 2009CB724401)the Key Project of Chinese Academy of Sciences (Grant No. KJCX2-YW-M04)
文摘Introducing heterogeneities into the structure is an effective way to enhance the plasticity in metallic glasses (MGs). As natural heterogeneity, the original randomly distributed free volume in MGs has been found to be in favor of plasticity. However, the exact correlation between the free volume distribution and mechanical response is still unclear. In this paper, we investigate the shear banding in MGs with different structural disorders, characterized by both the free volume concentration (FVC) and the free volume dispersion (FVD). It is found that, either high FVC or wide FVD leads to low activation stress of shear band; wide FVD promotes the multiplication of shear bands but high FVC restricts it. It reveals that the yield strength in MGs is dependent on the amount of free volume while the plasticity mainly relies on the distribution. An optimum combination of the two aspects probably helps to design a MG of both good plasticity and high strength.
文摘Performance analysis of the Pangu Plaza under earthquake and wind loads is described in this paper. The plaza is a 39-story steel high-rise building, 191 m high, located in Beijing close to the 2008 Olympic main stadium. It has both fluid viscous dampers （FVDs） and buckling restrained braces or unbonded brace （BRB or UBB） installed. A repeated iteration procedure in its design and analysis was adopted for optimization. Results from the seismic response analysis in the horizontal and vertical directions show that the FVDs are highly effective in reducing the response of both the main structure and the secondary system. A comparative analysis of structural seismic performance and economic impact was conducted using traditional methods, i.e., increased size of steel columns and beams and/or use of an increased number of seismic braces versus using FVD. Both the structural response and economic analysis show that using FVD to absorb seismic energy not only satisfies the Chinese seismic design code for a ＂rare＂ earthquake, but is also the most economical way to improve seismic performance both for one-time direct investment and long term maintenance.
文摘超大跨度钢箱梁悬索桥的结构阻尼和刚度较小,其竖向模态频率低且密集,随风速变化加劲梁可能先后发生多次涡激振动。首先针对某超大跨度悬索桥,进行有限元建模和动力分析。为研究悬索桥多模态涡激振动响应机理和有效抑振措施,在忽略气动刚度和气动阻尼影响时,通过简化Scanlan经验非线性涡激力数学模型得到简谐涡激力数学模型。然后以各竖向模态涡振最大位移响应为优化目标,基于液体黏滞阻尼器参数敏感性分析和调谐质量阻尼器(tuned mass damper,TMD)参数优化设计方法,分别确定阻尼器参数和TMD参数。最后探讨了黏滞阻尼器耗能系统控制悬索桥多阶竖向模态涡振的可行性,详细分析了TMD系统控制涡激振动的效果。结果表明:在塔梁间设置黏滞阻尼器对各竖向模态主要起振区域的涡振位移控制效果不理想;TMD系统能有效抑制常遇风速范围内加劲梁的多阶竖向模态涡振响应,将最大振幅严格控制在容许值以内,提高了加劲梁抵抗涡振变形的能力。
