Liquid-containment shells of revolution: A review of recent studies on strength,stability and dynamics

In civil engineering, shell structures are widely used as liquid-containment vessels. Understanding how the shell responds to relevant loading conditions is important for the design of safe and economical liquid-containment shell structures. This paper reviews recent research on the strength, stability and vibration behaviour of liquid-containment shell structures, and traces the developments pertaining to the design of these facilities to withstand various loading and environmental effects such as liquid pressure, wind pressure, ground movement and thermal effects. Results of recent feasibility studies of non-conventional shell forms for liquid containment are also reported, and areas of focus for future research are suggested.     

地埋式污水处理池与传统化粪池使用效果分析

对传统化粪池与地埋式污水处理池进行了分析对比,阐述了地埋式污水处理池的设计优点,指出经过各级部门的有力推广,地埋式污水处理池会创造化粪池的革命新时代。     

某大型储罐基础沉降分析及处理措施

对某大型储罐的沉降原因进行了分析,并提出了控制沉降的方法。实践证明:在进行大型储罐的设计施工工作时,重点是控制罐基础的整体倾斜沉降和不均匀沉降,以保证储罐的正常运行。     

Wind loading and its effects on single-layer reticulated cylindrical shells

In this paper, the wind load distribution as well as its effects on single-layer reticulated cylindrical shells, which are widely used in practice, is investigated. At first, wind pressure distributions on three rigid cylindrical shell models considering different shape ratios are measured simultaneously in a wind tunnel. Some special characteristics of the measured wind pressure, especially its fluctuating component, are discussed. Then, considering the special structural mechanical behaviors, the effects of wind load, especially the fluctuating component, on the limit load-carrying capacity and the stability of the shells are investigated by both equivalent static analysis and dynamic analysis. Suitable methods to get a reasonable estimation of wind load effects in estimating the equivalent static wind load distribution for such shells are investigated. Finally, with comparison analyses using different methods mentioned in this paper, the efficiency of the method in estimating the effective wind load distribution presented by the authors previously for single-layer reticulated spherical shells is demonstrated, and some advices for estimating the wind load distribution on single-layer reticulated cylindrical shells is given for wind-resistant design in practice.     

谈化粪池的应用与发展

简述了化粪池的使用现状,分析了化粪池使用中存在的问题,介绍了化粪池的布置和设计,展望了化粪池的发展趋势,指出化粪池的设置应与城市污水处理统筹考虑。     

LNG储罐穹顶裂缝控制及防治措施

结合LNG储罐穹顶裂缝形式,分析了LNG储罐穹顶裂缝产生的原因,从结构设计和施工两方面提出了裂缝控制和处理的具体措施,从而解决了储罐穹顶的裂缝问题,保证了LNG储罐穹顶的质量。     

楔形与等截面静压桩沉桩贯入阻力对比研究

基于Vesic圆孔扩张理论,考虑贯入深度对扩孔压力的影响,得到了一种扩孔压力的迭代算法;在此基础上,分析了楔形与等截面静压桩沉桩贯入阻力的差异性,并考虑极限滑动摩阻力的影响,建立了两种桩型的静压沉桩贯入阻力计算公式。为了验证该方法的可行性,对楔形与等截面桩进行模型对比试验,并利用该方法对模型试验进行计算分析,试验及理论结果均表明,等截面桩沉桩贯入阻力在贯入初期上升较快,后期上升缓慢,而楔形桩整个沉桩过程贯入阻力始终保持稳步增长。同时,等截面桩最终沉桩贯入阻力要比平均截面半径相等的楔形桩贯入阻力小得多,说明在相同贯入阻力前提下,采用楔形桩将能大幅度减少桩身材料,降低成本。     

Experimental study on settlement and scour characteristics of artificial reef with different reinforcement type and soil type

An artificial reef has been actively installed to restore marine ecosystems and increase fish catching. The artificial reef which installed on soft ground loses its function due to the settlement and scour of seabed. This study performed a series of laboratory tests to investigate settlement and scour characteristics of seabed according to different reinforcement type, reinforced area and soil type. Two reinforcement types with different reinforced area were applied to reduce settlement and scour of ground: geogrid and geogrid-bamboo mat. Soil types of ground are clay, silt and sand deposits. A series of laboratory tests includes California bearing ratio test, large size settlement test, and two-dimensional wave channel test. The test results indicated that the reinforced artificial reef had less settlement and scour depth than the unreinforced artificial reef. Especially, the artificial reef reinforced with geogrid-bamboo mat had more improved stability than that with geogrid due to high bending stiffness of bamboo mat.     

喷射火与水喷淋系统联合作用下LPG储罐热响应研究

为研究喷射火灾和水喷淋系统联合作用下卧式LPG储罐热响应行为规律,利用FLUENT建立LPG储罐热响应模型进行数值计算。通过调节喷淋水量的大小,探讨了水膜在储罐壁面的分布规律;设无喷淋冷却模拟试验为对照组,对比研究了不同喷淋质量流率对喷射火灾环境下LPG储罐的保护效果。结果表明:罐壁表面上水膜厚度变化与水喷淋质量流率成正比关系;壁面外部温度越高对应的表面水膜厚度越小。储罐壁和罐内介质达到相同温度和压力所需的时间明显变长,其上升速率不断降低,得出了安全阀第一次开启所需时间与喷淋质量流率两者之间的经验公式。     

Centrifuge study into the effect of liquefaction extent on permanent settlement and seismic response of shallow foundations

Centrifuge experiments were conducted to investigate how the liquefaction extent affects the seismic and post-seismic settlement of shallow foundations resting on saturated sand. Two rigid foundations with different bearing pressures were placed on the ground surface in a model container. Multiple input motions were applied to achieve different extents of soil liquefaction. The results indicate that foundation settlement can be divided into three distinct phases: (I) during shaking, (II) during the time period after shaking has ceased and before soil reconsolidation in the shallowest layers has taken place, and (III) during soil reconsolidation. Contrary to the free-field ground, most of the total settlement of the foundations occurred before soil reconsolidation, i.e., during Phases I and II. The volumetric strain during these phases was not significant as opposed to the shear strain produced by the foundation surcharge. It was demonstrated that foundation settlement is not necessarily proportional to the liquefied depth of the sand. The extent of the liquefaction in the sand medium mostly affected the post-seismic settlement of the foundations, while the co-seismic settlement was relatively the same for both foundations. The response of the foundations was significantly influenced by the liquefaction extent, whereas the foundations did not experience large accelerations when the soil profile was entirely liquefied. However, the foundations tolerated large settlement under severe liquefaction conditions. The results of this study highlight the role of the liquefaction extent on co-seismic and post-seismic settlement as well as the seismic response of shallow foundations.     

变截面与等截面桩复合地基沉降对比分析

通过对某地区红粘土的桩基工程及软基处理工程的研究,提出了一种新型混凝土预制单桩复合地基,分别进行2组等截面桩和3组变截面桩的单桩复合地基对比模型试验,并研究了5组单桩复合地基在一定条件下的荷载—沉降变化的规律,得到了一些科学的结论。     

Mass balance and isotope effects during nitrogen transport through septic tank systems with packed-bed (sand) filters

Septic tank systems are an important source of NO3(-) to many aquifers, yet characterization of N mass balance and isotope systematics following septic tank effluent discharge into unsaturated sediments has received limited attention. In this study, samples of septic tank effluent before and after transport through single-pass packed-bed filters (sand filters) were evaluated to elucidate mass balance and isotope effects associated with septic tank effluent discharge to unsaturated sediments. Chemical and isotopic data from five newly installed pairs and ten established pairs of septic tanks and packed-bed filters serving single homes in Oregon indicate that aqueous solute concentrations are affected by variations in recharge (precipitation, evapotranspiration), NH4+ sorption (primarily in immature systems), nitrification, and gaseous N loss via NH3 volatilization and(or) N2 or N2O release during nitrification/denitrification. Substantial NH4+ sorption capacity was also observed in laboratory columns with synthetic effluent. Septic tank effluent delta15N-NH4+ values were almost constant and averaged +4.9 per thousand+/-0.4 per thousand (1 sigma). In contrast, delta15N values of NO3(-) leaving mature packed-bed filters were variable (+0.8 to +14.4 per thousand) and averaged +7.2 per thousand+/-2.6 per thousand. Net N loss in the two networks of packed-bed filters was indicated by average 10-30% decreases in Cl(-)-normalized N concentrations and 2-3 per thousand increases in delta15N, consistent with fractionation accompanying gaseous N losses and corroborating established links between septic tank effluent and NO3(-) in a local, shallow aquifer. Values of delta18O-NO3(-) leaving mature packed-bed filters ranged from -10.2 to -2.3 per thousand (mean -6.4 per thousand+/-1.8 per thousand), and were intermediate between a 2/3 H2O-O+1/3 O2-O conceptualization and a 100% H2O-O conceptualization of delta18O-NO3(-) generation during nitrification.     

Effect of vacuum removal on consolidation settlement under a combined vacuum and surcharge preloading

The combined vacuum and surcharge preloading technique is extensively used to accelerate the consolidation process of subsoils. The effect of vacuum pressure is often considered as a loading/unloading cycle of mean effective stress, such that elastic rebound occurs after vacuum removal, which cannot explain the observed postconstruction settlement in the field. In this study, the stress state of subsoils subject to vacuum and surcharge preloading is analyzed and decomposed into two components: (a) geostatic consolidation at a different depth, and (b) loading/unloading in the minor principal stress direction. A series of consolidated drained triaxial tests is conducted to simulate the soil behaviour after vacuum removal. Results show that the contribution of unloading in the minor principal stress direction outweighs the magnitude of elastic rebound after vacuum removal, and hence continued settlement dominates. A field case for highways is provided to further demonstrate the proposed mechanism.     

LNG储罐外壳自振特性及地震响应分析

主要研究LNG储罐外壳的自振特性和地震响应分析,应用ANSYS建立LNG储罐外壳有限元模型,得到有限元模型的频率、振型、最大相对位移等,选取三种地震波进行了LNG储罐外壳的地震响应分析,得到LNG储罐特殊位置点的位移、加速度、等效应力时程曲线。     

Numerical evaluation on shell buckling of empty thin-walled steel tanks under wind load according to current American and European design codes

Liquid storage steel tanks are vertical above-ground cylindrical shells and as typical thin-walled structures, they are very sensitive to buckling under wind loads, especially when they are empty or at low liquid level. Previous studies revealed discrepancies in buckling resistance of empty tanks between the design method proposed by the American Standard API 650 and the analytical formulas recommended by the European Standard EN1993-1-6 and EN1993-4-2. This study presents a comparison between the provisions of current design codes by performing all types of numerical buckling analyses recommended by Eurocodes (i.e. LBA-linear elastic bifurcation analysis, GNA-geometrically nonlinear elastic analysis of the perfect tank and GNIA-geometrically nonlinear elastic analysis of the imperfect tank). Such analyses are performed in order to evaluate the buckling resistance of two existing thin-walled steel tanks, with large diameters and variable wall thickness. In addition, a discussion is unfolded about the differences between computational and analytical methods and the conservatism that the latter method imposes. An influence study on the geometric imperfections and the boundary conditions is also conducted. Investigation on the boundary conditions at the foot of the tank highlights the sensitivity to the fixation of the vertical translational degree of freedom. Further, it is indicated that the imperfection magnitude recommended by the EN1993-1-6 is extremely unfavorable when applied to large diameter tanks. Comments and conclusions achieved could be helpful in order to evaluate the safety of the current design codes and shed more light towards the most accurate one.     

基于内框架支撑体系的大型敞口贮液池设计与分析

通过对一个大型敞口贮液池的工程设计实例的介绍,对大型敞口贮液池计算力学模式进行比较和优化,引入基于内框架支撑体系敞口贮液池的设计计算模式。通过对内框架支撑体系敞口贮液池计算模式受力特点的分析计算,得出了内框架支撑体系敞口贮液池简明设计计算方法,并采用SAP2000软件进行了计算比较分析,分析结果表明这一计算方法是可靠的,工程实例也证明了这一计算方法的合理可行性,从而也为这一结构体系的广泛应用提供了借鉴。     

福建液化天然气超低温储罐工程高性能砼的应用研究

福建液化天然气储罐工程由于特殊使用条件对砼的耐久性提出了严格的要求,本文通过对砼配合比以及耐久、热工等各项性能的试验研究,并对试验结果分析讨论,得出的数据和结论在福建液化天然气超低温储罐工程中实践应用。     

油罐腐蚀泄漏液体影响范围建模及应用

分析总结储罐内部介质三相区域（含油污水区域、油相区域、气相区域）腐蚀原因,确定易腐蚀减薄区域。建立腐蚀泄漏后液体影响范围数学模型。以某油库汽油罐含油污水区域泄漏为例,计算储罐泄漏液体影响范围,为确定储油罐泄漏安全防护距离及应急救援提供依据。相对于油相区域、气相区域,含油污水区域对储罐内壁腐蚀比较严重;相对于油相区域—气相区域交界面,含油污水—油相区域交界面腐蚀较为严重。     

加油加气站地下储罐泄漏事故模拟及影响因素分析

利用多相混合数值模拟模型对加油加气站常用石油燃料(汽油、液化石油气)地下储罐不同位置发生泄漏事故在罐池中渗流扩散过程进行模拟,得到汽油、液化石油气(LPG)气相和液相饱和度、危险浓度区域、流速等空间分布规律以及流动趋势变化,并对影响汽油、LPG流动的主要因素进行分析,对比讨论其泄漏渗流扩散的特点。模拟结果表明:在泄漏口周围地下环境条件相同情况下,地下储罐泄漏时汽油渗流扩散比液化石油气渗流扩散缓慢;汽油地下储罐泄漏主要对地下环境造成污染,液化石油气对地下环境造成污染而且给外界环境带来火灾爆炸危险;汽油渗流速度低,整个流场只存在层流,渗流扩散方向主要受重力影响。LPG液相泄漏受重力影响尤为明显;LPG气体渗流扩散方向受出口位置、泄漏速度方向、重力、储罐罐壁形状影响;出口位置是控制气体渗流方向关键因素。