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河南广播电视发射塔属于超高结构,施工时高空作业面狭小,危险性大。针对工程实际情况,分别从钢柱吊装、外塔柱安装、桉叶糖钢柱吊装以及桉叶糖柱内法兰施工几方面分别制定相应的安全防护措施。实践表明,这些措施满足了现场施工、吊装的需要,为工人操作提供了安全平台,解决了高空作业工作面狭小、安全防护困难的特点。到目前为止,施工过程中未出现任何安全问题,取得了良好的防护效果。 相似文献
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以武汉天河国际机场T3航站楼为研究背景,根据设计需要将钢柱设计为圆锥式变截面钢柱,采用MIDAS/GEN有限元软件对圆锥式变截面钢柱分节吊装进行模拟计算。由于倾斜钢柱的吊装稳定尤为重要,因此对钢柱拼接、吊装施工步、模拟受力分析、吊装就位等关键施工点与安全点提出了更高要求。只有倾斜钢柱精确安装才能保证结构的安全、立面的造型。 相似文献
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河南省广播电视发射塔设计总高度为388.0m,作为超高结构,其难点在于塔身外围桉叶糖形钢柱的吊装,方案设计分别从超高塔结构施工时垂直运输机械的选择、布置方式、塔式起重机基础、塔式起重机安装和拆除几个方面进行分析,最终采用一台ZSC 50180平臂式塔式起重机作为桉叶糖形钢柱主要吊装工具,布置方式为井道内附着式,同时塔楼顶部安设一台SCM-D300动臂塔式起重机,作为桅杆天线的吊装以及ZSC50180的拆除,满足了吊装需要,为工程顺利进行起到了关键作用。 相似文献
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大体量屋面网架安装,采用分段整体吊装,多台吊车同步作业,精心组织,严密指挥,合理选择吊装机具,简化了施工操作,施工更安全、可靠、经济。 相似文献
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基于三维弹性理论,先对位移表示的地基动力方程进行Laplace变换,再进行双重傅里叶变换,获得直角坐标系下弹性半空间地基受任意竖向动荷载作用下的Laplace变换域中的位移解析表达式;然后对地基上有限大矩形薄板的边值问题进行Laplace变换,并求得地基板的Laplace变换域中的含有未知地基反力的挠度解析解;最后结合板与地基的变形协调方程,完全求得弹性半空间地基板在移动荷载作用下的Laplace变换域中的解析解。在此基础上,利用Laplace数值逆变换得到地基板时间域内的动力响应。算例结果表明本文的研究方法是切实可行的。用该文方法可精确分析地基板在任意移动载荷作用下的动力特性。 相似文献
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Muñoz-Leoz B Antigüedad I Garbisu C Ruiz-Romera E 《The Science of the total environment》2011,409(4):763-770
Riparian wetlands bordering intensively managed agricultural fields can act as biological filters that retain and transform agrochemicals such as nitrate and pesticides. Nitrate removal in wetlands has usually been attributed to denitrification processes which in turn imply the production of greenhouse gases (CO2 and N2O). Denitrification processes were studied in the Salburua wetland (northern Spain) by using undisturbed soil columns which were subsequently divided into three sections corresponding to A-, Bg- and B2g-soil horizons. Soil horizons were subjected to leaching with a 200 mg NO3− L− 1 solution (rate: 90 mL day− 1) for 125 days at two different temperatures (10 and 20 °C), using a new experimental design for leaching assays which enabled not only to evaluate leachate composition but also to measure gas emissions during the leaching process. Column leachate samples were analyzed for NO3− concentration, NH4+ concentration, and dissolved organic carbon. Emissions of greenhouse gases (CO2 and N2O) were determined in the undisturbed soil columns. The A horizon at 20 °C showed the highest rates of NO3− removal (1.56 mg N-NO3− kg−1 DW soil day− 1) and CO2 and N2O production (5.89 mg CO2 kg−1 DW soil day− 1 and 55.71 μg N-N2O kg−1 DW soil day− 1). For the Salburua wetland riparian soil, we estimated a potential nitrate removal capacity of 1012 kg N-NO3− ha− 1 year− 1, and potential greenhouse gas emissions of 5620 kg CO2 ha− 1 year− 1 and 240 kg N-N2O ha− 1 year− 1. 相似文献
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A. Sakaguchi K. Kawai T. Imanaka S. Endo M. Yamamoto 《The Science of the total environment》2010,408(22):5392-5398
The first results on the feasibility of using 236U to reconstruct the level and spatial distribution of close-in fallout deposition from the Hiroshima A-bomb are reported, coupled with the use of global fallout 137Cs and 239 + 240Pu. The results for global fallout 236U in soil samples (0-30 cm) from Ishikawa prefecture showed that the deposition density of 236U from the global fallout can be accurately evaluated using AMS. All deposited 236U, 137Cs and 239 + 240Pu appeared to have been recovered using 30-cm cores. It was also noted from the depth profiles for 236U/239 + 240Pu and 236U/137Cs ratios that the downward behavior of 236U in the soil was apparently similar to that of 239 + 240Pu, while the 137Cs was liable to be retained in upper layers compared with 236U and 239 + 240Pu. The accumulated levels were 1.78 × 1013 atoms m− 2 for 236U, 4340 Bq m− 2 for 137Cs and 141 Bq m− 2 for 239 + 240Pu. The ratios of 236U/137Cs and 236U/239 + 240Pu were (4.10 ± 0.12) × 109 and (1.26 ± 0.04) × 1011 atoms Bq− 1, respectively. Results of 236U, 137Cs and 239 + 240Pu measurements for the seven soil cores (0-30 cm) from Hiroshima were discussed on the basis of ratios of 236U/137Cs and 236U/239 + 240Pu by comparing with those from the background area in Ishikawa, indicating that the global fallout dominates the current level of 236U accumulation in soil in the Black-rain area around Hiroshima after the Hiroshima bomb, and the contribution of the close-in fallout 236U produced by the Hiroshima A-bomb seems difficult to observe. 相似文献
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