Contrary to conventional design methods that assume uniform and slow temperature changes tied to atmospheric conditions,single-layer spherical reticulated shells undergo significant non-uniform and time-variant temper...Contrary to conventional design methods that assume uniform and slow temperature changes tied to atmospheric conditions,single-layer spherical reticulated shells undergo significant non-uniform and time-variant temperature variations due to dynamic environmental coupling.These differences can affect structural performance and pose safety risks.Here,a systematic numerical method was developed and applied to simulate long-term temperature variations in such a structure under real environmental conditions,revealing its non-uniform distribution characteristics and time-variant regularity.A simplified design method for non-uniform thermal loads,accounting for time-variant environmental factors,was theoretically derived and validated through experiments and simulations.The maximum deviation and mean error rate between calculated and tested results were 6.1℃ and 3.7%,respectively.Calculated temperature fields aligned with simulated ones,with deviations under 6.0℃.Using the design method,non-uniform thermal effects of the structure are analyzed.Maximum member stress and nodal displacement under non-uniform thermal loads reached 119.3 MPa and 19.7 mm,representing increases of 167.5%and 169.9%,respectively,compared to uniform thermal loads.The impacts of healing construction time on non-uniform thermal effects were evaluated,resulting in construction recommendations.The methodologies and conclusions presented here can serve as valuable references for the thermal design,construction,and control of single-layer spherical reticulated shells or similar structures.展开更多
本文用40Cr 钢研究了奥氏体晶粒的异常长大过程以及加热前的原始组织对异常长大过程的影响,并利用已有的计算驱动力 P 及阻力 F 的公式进行了定量计算及分析讨论。结果表明,当奥氏体起始晶粒的 P>F 时,晶粒将发生长大。在长大过程中...本文用40Cr 钢研究了奥氏体晶粒的异常长大过程以及加热前的原始组织对异常长大过程的影响,并利用已有的计算驱动力 P 及阻力 F 的公式进行了定量计算及分析讨论。结果表明,当奥氏体起始晶粒的 P>F 时,晶粒将发生长大。在长大过程中,已开始长大的大晶粒不断吞并周围小晶粒,周围小晶粒则基本上不长大。当小晶粒消失,大晶粒彼此相遇时,长大将终止。可以通过预备热处理调整加热前的原始组织,从而改变奥氏体起始晶粒的 D、D_(n,x)、Z_0及r,控制 P 及 F。对 Zener、Gladman,等的公式进行了校验。结果表明,按戚正风公式计算所得 P 与实测结果符合得最好。按 Zener 公式计算所得 P 偏高,按 Gladmom 公式计算所得 P 又偏低。展开更多
In order to perfectly reflect the dynamic corrosion of reinforced concrete (RC) cover in practical engineering,an analytic model of non-uniform corrosion induced cracking was presented based on the elastic-plastic fra...In order to perfectly reflect the dynamic corrosion of reinforced concrete (RC) cover in practical engineering,an analytic model of non-uniform corrosion induced cracking was presented based on the elastic-plastic fracture mechanics theory.Comparisons with the published experimental data show that the predictions given by the present model are in good agreement with the results both for natural exposed experiments and short-time indoor tests (the best difference is about 2.7%).Also it obviously provides much better precision than those models under the assumption of uniform corrosion (the maximal improved precision is about 48%).Therefore,it is pointed out that the so-called uniform corrosion models to describe the cover cracking of RC should be adopted cautiously.Finally,the influences of thickness of local rusty layer around the reinforcing steel bar on the critical corrosion-induced crack indexes were investigated.It is found that the thickness of local rusty layer has great effect on the critical mass loss of reinforcing steel,threshold expansion pressure,and time to cover cracking.For local rusty layer thickness with a size of a=0.5 mm,the time to cover cracking will increase by about one times when a/b (a,semi-minor axis;b,semi-major axis) changes from 0.1 to 1 mm.展开更多
基金This work is supported by the National Natural Science Foundation of China(Nos.51578491 and 52238001).
文摘Contrary to conventional design methods that assume uniform and slow temperature changes tied to atmospheric conditions,single-layer spherical reticulated shells undergo significant non-uniform and time-variant temperature variations due to dynamic environmental coupling.These differences can affect structural performance and pose safety risks.Here,a systematic numerical method was developed and applied to simulate long-term temperature variations in such a structure under real environmental conditions,revealing its non-uniform distribution characteristics and time-variant regularity.A simplified design method for non-uniform thermal loads,accounting for time-variant environmental factors,was theoretically derived and validated through experiments and simulations.The maximum deviation and mean error rate between calculated and tested results were 6.1℃ and 3.7%,respectively.Calculated temperature fields aligned with simulated ones,with deviations under 6.0℃.Using the design method,non-uniform thermal effects of the structure are analyzed.Maximum member stress and nodal displacement under non-uniform thermal loads reached 119.3 MPa and 19.7 mm,representing increases of 167.5%and 169.9%,respectively,compared to uniform thermal loads.The impacts of healing construction time on non-uniform thermal effects were evaluated,resulting in construction recommendations.The methodologies and conclusions presented here can serve as valuable references for the thermal design,construction,and control of single-layer spherical reticulated shells or similar structures.
文摘本文用40Cr 钢研究了奥氏体晶粒的异常长大过程以及加热前的原始组织对异常长大过程的影响,并利用已有的计算驱动力 P 及阻力 F 的公式进行了定量计算及分析讨论。结果表明,当奥氏体起始晶粒的 P>F 时,晶粒将发生长大。在长大过程中,已开始长大的大晶粒不断吞并周围小晶粒,周围小晶粒则基本上不长大。当小晶粒消失,大晶粒彼此相遇时,长大将终止。可以通过预备热处理调整加热前的原始组织,从而改变奥氏体起始晶粒的 D、D_(n,x)、Z_0及r,控制 P 及 F。对 Zener、Gladman,等的公式进行了校验。结果表明,按戚正风公式计算所得 P 与实测结果符合得最好。按 Zener 公式计算所得 P 偏高,按 Gladmom 公式计算所得 P 又偏低。
基金Project(50925829) supported by the National Science Fund for Distinguished Young Scholars of ChinaProject(50908148) supported by the National Natural Science Foundation of ChinaProjects(2009-K4-23,2010-11-33) supported by the Research of Ministry of Housing and Urban Rural Development of China
文摘In order to perfectly reflect the dynamic corrosion of reinforced concrete (RC) cover in practical engineering,an analytic model of non-uniform corrosion induced cracking was presented based on the elastic-plastic fracture mechanics theory.Comparisons with the published experimental data show that the predictions given by the present model are in good agreement with the results both for natural exposed experiments and short-time indoor tests (the best difference is about 2.7%).Also it obviously provides much better precision than those models under the assumption of uniform corrosion (the maximal improved precision is about 48%).Therefore,it is pointed out that the so-called uniform corrosion models to describe the cover cracking of RC should be adopted cautiously.Finally,the influences of thickness of local rusty layer around the reinforcing steel bar on the critical corrosion-induced crack indexes were investigated.It is found that the thickness of local rusty layer has great effect on the critical mass loss of reinforcing steel,threshold expansion pressure,and time to cover cracking.For local rusty layer thickness with a size of a=0.5 mm,the time to cover cracking will increase by about one times when a/b (a,semi-minor axis;b,semi-major axis) changes from 0.1 to 1 mm.
