Site measurements have shown that slab loads re-distribute, between the slabs during the concrete curing, while the external Ioadings and structural geometry remain the same. Some have assumed that this is caused by c...Site measurements have shown that slab loads re-distribute, between the slabs during the concrete curing, while the external Ioadings and structural geometry remain the same. Some have assumed that this is caused by concrete shrinkage and creep, but there have been no studies on how these factors exactly influence the load distributions and to what degree these influences exist. This paper analyzes the influences of concrete shrinkage, creep, and temperature on the load re-distributions among slabs. Although these factors may all lead to load re-distribution, the results show that the influence of concrete shrinkage can be neglected. Simulations indicate that shrinkage only reduces slab loads by a maximum of 1.1%. Creep, however, may reduce the maximum slab load by from 3% to 16% for common construction schemes. More importantly, temperature variations between day and night can cause load fluctuation as large as 31.6%. This analysis can, therefore, assist site engineers to more accurately estimate slab loads for construction planning.展开更多
Since 1960s, many research works on the reinforced concrete structure have been published and some concise and practical calculation methods for safety control during construction have been achieved. The reinforced co...Since 1960s, many research works on the reinforced concrete structure have been published and some concise and practical calculation methods for safety control during construction have been achieved. The reinforced concrete structure during construction is a time-dependent structure which consists of a partly completed structure and a formwork-shore system. Experience shows that the most critical condition of the time-dependent structure may happen when the formwork-shore system is partly removed or reset and accidents may occur. In the present paper, effect of ambient temperature variation between day and night is considered, new structural models for reinforced concrete frames, slab-column systems and shear wall structures are proposed, and a new software named Safety Analysis During Construction Considering Temperature(SACT) is also introduced. Compared with on-site measurements, the software SACT is validated for application on construction site.展开更多
In this study,fire tests of four single-section scaled-down utility tunnels were conducted.By analyzing temperature and structural responses of the utility tunnel throughout the fire exposure,the effects on the fire b...In this study,fire tests of four single-section scaled-down utility tunnels were conducted.By analyzing temperature and structural responses of the utility tunnel throughout the fire exposure,the effects on the fire behavior of two different construction methods,cast-in-situ and prefabricated,and of two different materials,ordinary concrete and full lightweight concrete,were explored.The results of the study showed that the shear failure of the cast-in-situ utility tunnel occurred at the end of the top or bottom plate,and the failure of the prefabricated utility tunnel occurred at the junction of the prefabricated member and post-cast concrete.As the temperature increased,the temperature gradient along the thickness direction of the tunnel became apparent.The maximum temperature difference between the inner and outer wall surfaces was 531.7°C.The highest temperature occurred in the cooling stage after stopping the heating,which provided a reference for the fire protection design and rescue of the utility tunnel.The displacement of the top plate of the prefabricated utility tunnel was 16.8 mm,which was 41.8%larger than that of the cast-in-situ utility tunnel.The bearing capacities of the ordinary concrete utility tunnel and full lightweight concrete utility tunnel after the fire loss were 27%and 16.8%,respectively.The full lightweight concrete utility tunnel exhibited good ductility and fire resistance and high collapse resistance.展开更多
基金Supported by the National Nature Science Foundation of China (Nos.50378051,70172005,and 70572007)Excellent Young Teacher Program of Ministry of Education of Chinathe National Science and Technology Planning Project (No.2006BAJ01B04-03)
文摘Site measurements have shown that slab loads re-distribute, between the slabs during the concrete curing, while the external Ioadings and structural geometry remain the same. Some have assumed that this is caused by concrete shrinkage and creep, but there have been no studies on how these factors exactly influence the load distributions and to what degree these influences exist. This paper analyzes the influences of concrete shrinkage, creep, and temperature on the load re-distributions among slabs. Although these factors may all lead to load re-distribution, the results show that the influence of concrete shrinkage can be neglected. Simulations indicate that shrinkage only reduces slab loads by a maximum of 1.1%. Creep, however, may reduce the maximum slab load by from 3% to 16% for common construction schemes. More importantly, temperature variations between day and night can cause load fluctuation as large as 31.6%. This analysis can, therefore, assist site engineers to more accurately estimate slab loads for construction planning.
文摘Since 1960s, many research works on the reinforced concrete structure have been published and some concise and practical calculation methods for safety control during construction have been achieved. The reinforced concrete structure during construction is a time-dependent structure which consists of a partly completed structure and a formwork-shore system. Experience shows that the most critical condition of the time-dependent structure may happen when the formwork-shore system is partly removed or reset and accidents may occur. In the present paper, effect of ambient temperature variation between day and night is considered, new structural models for reinforced concrete frames, slab-column systems and shear wall structures are proposed, and a new software named Safety Analysis During Construction Considering Temperature(SACT) is also introduced. Compared with on-site measurements, the software SACT is validated for application on construction site.
文摘为探究爬模施工进程中索塔空间温度场和应力场分布,掌握塔柱线形特性,提出一种索塔爬模施工仿真分析方法.利用Fortran编程语言开发相应子程序,对结构施加复杂温度边界,实现不同节段混凝土水化放热、收缩徐变.利用Abaqus软件对索塔爬模施工过程进行分析.结果表明:施工过程中索塔空间温度分布不均匀,塔柱表里最大温差达25.9℃,向阳面与背阴面温差最大为9℃;考虑温度效应后,塔柱所受拉应力更大,且空间应力分布具有很强的时变性,索塔线形特征与变化规律也发生改变;施工塔顶累积竖向位移先增大后减小,在爬模第16节段达到最大值20.5 mm;施工过程塔顶累计顺桥向和横桥向位移更大,最大值分别为6.5和22.3 mm.
基金The research was financially supported by the Jilin Provincial Department of Science and Technology Key Research and Development Project(20200403071SF)National Emergency Management Department Safety Accident Prevention Science and Technology Project(Jilin-0001-2018AQ).
文摘In this study,fire tests of four single-section scaled-down utility tunnels were conducted.By analyzing temperature and structural responses of the utility tunnel throughout the fire exposure,the effects on the fire behavior of two different construction methods,cast-in-situ and prefabricated,and of two different materials,ordinary concrete and full lightweight concrete,were explored.The results of the study showed that the shear failure of the cast-in-situ utility tunnel occurred at the end of the top or bottom plate,and the failure of the prefabricated utility tunnel occurred at the junction of the prefabricated member and post-cast concrete.As the temperature increased,the temperature gradient along the thickness direction of the tunnel became apparent.The maximum temperature difference between the inner and outer wall surfaces was 531.7°C.The highest temperature occurred in the cooling stage after stopping the heating,which provided a reference for the fire protection design and rescue of the utility tunnel.The displacement of the top plate of the prefabricated utility tunnel was 16.8 mm,which was 41.8%larger than that of the cast-in-situ utility tunnel.The bearing capacities of the ordinary concrete utility tunnel and full lightweight concrete utility tunnel after the fire loss were 27%and 16.8%,respectively.The full lightweight concrete utility tunnel exhibited good ductility and fire resistance and high collapse resistance.
