重型钢柱支撑架吊装安装方法

北京大兴国际机场旅客航站楼及综合换乘中心中南指廊钢柱吊装施工中,针对钢柱单重大又无法使用大型机械的困难,应用了移运小车水平运输、支撑架吊装的施工方法。实践证明,该法操作简单、劳动强度低、生产效率高,且可保证施工安全。     

超高层地下室超长倾斜钢柱整体吊装施工技术

依托厦门英蓝国际金融中心项目地下室倾斜钢柱的施工,对20. 4 m超长倾斜钢柱的吊装技术进行综合分析、研究。总结了倾斜钢柱地面拼装、整体吊装以及倾斜钢柱防止倾覆等技术措施,采用“两层一节分段、地面拼装、整体吊装”的施工方案,提高了施工效率,保证了施工质量和安全。     

型钢混凝土柱施工工艺研究

根据型钢混凝土的施工工艺流程,从型钢柱制作、尺寸复核、钢柱吊装、绑扎钢筋等方面,阐述了型钢混凝土柱的施工操作要点,并提出了其施工质量控制方法,为以后类似工程项目施工积累了经验。     

建筑钢结构吊装施工工艺及稳定性验算研究

钢结构工程吊装过程中安全尤为重要。以某文教钢结构工程为例,以GKL17钢梁和QD3GZ-4钢柱的吊装为研究对象,针对钢梁和钢柱吊装施工工艺进行了分析;并通过有限元分析软件Midas实现了钢柱和钢梁的吊装模拟,对吊装作业钢丝绳、卸扣选用以及钢柱和钢梁吊耳板承载力进行了验算。验算结果表明钢柱和钢梁及焊缝受力均满足规范要求,确保了钢梁和钢柱吊装施工过程中的安全性。     

河南广电发射塔安全施工技术分析

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。     

武汉天河国际机场T3航站楼圆锥式变截面钢柱分节吊装施工技术

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。     

屋面塔式起重机基座设计施工综合技术

国家会议中心二期主体结构施工中,在屋面设4座塔式起重机,起重机支座生根于主体结构钢柱顶部.为满足塔式起重机的垂直度要求,基座采用刚度很大的立体桁架,对桁架进行合理分段,运至工地后采用地面拼装、整体吊装方案,实现了零误差安装,保证了屋面起重机安全运行.     

超高塔垂直运输机械的选择分析

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。     

预应力悬拉索钢结构旋转安装技术

西安海洋公园二期极地馆及海洋风情商业街工程北极熊馆采用片式钢管桁架结构,其上为索膜结构形式,中间钢柱通过预应力拉索固定,GZ1倾斜于屋面,GZ2悬于空中,塔式起重机无法将其直接吊装到位。针对工程施工难点,经方案比选,采用预应力悬拉索旋转安装方案。介绍了钢柱下端固定、上端旋转的核心原理及施工阶段的关键技术点,保证了施工质量。     

屋面网架结构分段整体吊装施工技术探讨

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。     

移动荷载下弹性半空间地基上矩形薄板的动力响应解析研究

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。     

Nitrogen transformations and greenhouse gas emissions from a riparian wetland soil: an undisturbed soil column study

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.     

Feasibility of using U to reconstruct close-in fallout deposition from the Hiroshima atomic bomb

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.     

Phosphate removal in agro-industry: Pilot- and full-scale operational considerations of struvite crystallization

Pilot-scale struvite crystallization tests using anaerobic effluent from potato processing industries were performed at three different plants. Two plants (P1 & P2) showed high phosphate removal efficiencies, 89 ± 3% and 75 ± 8%, resulting in final effluent levels of 12 ± 3 mg PO₄³⁻-P L⁻¹ and 11 ± 3 mg PO₄³⁻-P L⁻¹, respectively. In contrast, poor phosphate removal (19 ± 8%) was obtained at the third location (P3). Further investigations at P3 showed the negative effect of high Ca²⁺/PO₄³⁻-P molar ratio (ca. 1.25 ± 0.11) on struvite formation. A full-scale struvite plant treating anaerobic effluent from a dairy industry showed the same Ca²⁺ interference. A shift in the influent Ca²⁺/PO₄³⁻-P molar ratio from 2.69 to 1.36 resulted in average total phosphorus removal of 78 ± 7%, corresponding with effluent levels of 14 ± 4 mg P_total L⁻¹ (9 ± 3 mg PO₄³⁻-P L⁻¹). Under these conditions high quality spherical struvite crystals of 2-6 mm were produced.     

Photolytic reaction mechanism and impacts of coexisting substances on photodegradation of bisphenol A by Bi2WO6 in water

Bi₂WO₆ displayed great photolytic degradation efficiency to bisphenol A (BPA) under simulated solar light irradiation but its reaction mechanism and the impacts of coexisting substances on the degradation remain unclear. In present study, the reaction mechanism was investigated using DMPO spin-trapping ESR spectra and experiments with scavengers of hydroxyl radicals (OH) and holes. The results supported that hole oxidation mainly governed the photodegradation process. As a common humic substance in natural water, humic acid accelerated the degradation of BPA when its concentration was 1 mg/L, while the photodegradation was impeded with the increase of humic acid concentration in the range of 5-20 mg/L. Almost all anions, including NO₃⁻, HCO₃⁻, Cl⁻, SO₄²⁻ inhibited the degradation of BPA by Bi₂WO₆ and their inhibition effects followed the order of SO₄²⁻ > Cl⁻ > HCO₃⁻ > NO₃⁻. Cations of Na⁺, K⁺, Ca²⁺ and Mg²⁺ displayed slight suppressing effect on BPA degradation mainly due to the impact of Cl⁻ coexisting in the solution. However, Cu²⁺ hindered the BPA photodegradation heavily. Fe³⁺ and H₂O₂ affected the photodegradation in a complicated way: they suppressed or promoted the photodegradation depending on their concentrations. This could be the result of competition between photolyitc hole generated by Bi₂WO₆ and OH produced by Fe³⁺ or H₂O_2.