大型钢储罐的沉降与结构性能的关系

建造在软土地基上的大型钢储罐易产生各种沉降变形,其中罐周不均匀沉降的影响最为不利。在各类大型储罐沉降变形的大量实测数据基础上,利用傅立叶分解分析罐周不均匀沉降的组成及特点,利用分析得到的谐波沉降对储罐结构进行有限元分析。分析表明,储罐在不均匀沉降下的应力和变形均与其几何参数有关,因此目前基于工程经验且与储罐参数无关的地基变形允许值控制标准,从结构的角度看不尽合理。     

Discontinuity effects at cone-cone axisymmetric shell junctions

In this paper, the problem of a conical shell axisymmetrically intersecting another conical shell, such that the vertices of the cones lie on opposite sides of the plane of intersection, is considered, and associated discontinuity effects quantified for arbitrary loading and geometric parameters of the intersecting cones. The ensuing very practical closed-form results are based on the one-term asymptotic-series solution for the axisymmetric bending of a non-shallow conical shell, and are intended for use in the quick evaluation of stresses and deformations in double-cone pressure vessels, as well as liquid-retaining vessels with intersecting conical portions. As an example of the application of the developed formulation, the stress distribution in a large liquid-filled elevated rhombic tank is evaluated. The stresses obtained on the basis of the closed-form analytical approach developed in the paper are shown to be in good agreement with those obtained from a finite-element analysis, confirming the reliability of the presented formulation.     

立式圆筒形钢制储罐焊接变形在焊接上的控制

根据立式钢制储罐在焊接过程中产生焊接变形的现象,分析了焊接变形的原因,提出了控制焊接中罐板变形的措施,以有效保证工程施工中的焊接质量和罐体制作质量。     

Welding stresses and distortions in multi-cellular box girders

The formation of residual stresses and deformations in weldments is reviewed and an experimental study of eight multi-cellular model steel girders is described. These models represent, to approximately quarter-scale, the construction of double-bottom ships' hulls. Details of the fabrication and welding procedure are given and measured values of residual strains, stresses and deformations are presented. Clear patterns of behaviour are identified and a comparison of experimental and predicted values shows reasonable agreement.     

On the coefficient of temperature expansion of frozen soils

The need for investigation of temperature-induced deformations of frozen soils is demonstrated. Basic concepts associated with temperature-induced stresses and strains are cited. The influence of the “aftereffect” of temperature-induced deformations, which are closely associated with the rheology of frozen soils developed by S. S. Vyalov and his students, is briefly described.     

Ingenieurmodell zum ungewöhnlichen Tragverhalten einzelliger Rechteckkästen mit linear veränderlicher Bauhöhe unter Torsionsbeanspruchung

Simplified calculation model for the exceptional load carrying behaviour of tapered box girders with rectangular cross section under torsion. Prismatic box girders get almost shear stresses due to torsional loading, if diaphragms are situated at the points of loading. Tapered box girders in contrast get high warping normal stresses with different shear stress distributions. The normal stresses can't be ignored, because they are necessary for equilibrium. In this paper firstly the exceptional behaviour is presented, based on some examples. Then an engineering model is shown to calculate the normal and shear stresses with their distributions along the girder and along the cross section. Moreover formulas for the estimation of the deformations – twist and warping deformations – are presented. The accuracy of the engineering model was checked based on comprehensive FE‐calculations.     

裂隙岩体渗流与三维应力耦合的理论与实验研究

围绕裂隙岩体渗流与应力之间的关系问题,从理论出发,经过合理的建模和严密的推演,得出裂隙岩体渗流与三维应力的耦合方程。该方程经过了大量的三轴实验数据的验证,解决了裂隙岩体受到的侧向应力对其渗流是否有影响这一岩石力学学科中争议很大的问题。指出了裂隙侧向应力引起的裂隙侧向变形是影响裂隙岩体渗流的主要因素,其影响符合负指数规律。同时,还分析了裂隙组的渗流问题。     

Wölbkrafttorsion von Durchlaufträgern mit konstantem Querschnitt unter Berücksichtigung sekundärer Schubverformungen

Warping torsion of continuous beam with constant cross‐section considering shear deformation. The analogy between the theory of warping torsion and second order theory of a bending member with tensile force is also valid, if shear‐deformations in both cases are additionally included. On the basis of this analogy the three‐moment equation for continuous beam with constant cross‐section is given. It is demonstrated, that shear‐deformations for open sections can normally be neglected but must be encluded in the case of hollow‐sections. It is also shown, that for these sections warping‐torsion occurs only in ranges of discontinuity, but causes stresses which are in the same order as the stresses of primary torsion.     

大曲率桥梁的安装过程和梁格模型的准确性分析

分析了施工方法对大曲率桥梁应力和变形方面的影响,对利用梁格模型预测施工方法的准确性进行了分析。研究包括施工过程中的应力和变形分析,并将其与梁格模型预测的结果对比。研究结果表明:1)在梁安装过程中会产生翘曲应力;2)在梁安装过程中改进梁格模型的预测数值会比经典梁格模型的预测更为准确;3)当梁由外向内安装时,梁格模型预测的变形要小于梁从内向外安装时的数值。     

考虑岩体变形特性的圆形压力隧洞衬砌应力计算方法

在水工圆形压力隧洞衬砌应力计算中,假定岩体是弹性体,这与岩体变形特性不完全相符。本文根据原位岩体变形试验结果,考虑了岩体弹-塑性变形,按线性强化材料处理,建立了衬砌应力计算方法,给出了岩体产生塑性变形的临界内水压力,并指出了岩体力学参数如何确定。     

Berechnung von gekrümmten Stäben mit Kreishohlprofil unter Berücksichtigung der Querschnittsverformung

Analysis of tube‐bars with initial curvature including deformation of cross‐section. Curved bars under bending show a nonlinear distribution of stresses with peak at internal side of the section. Bernoulli‐hypothesis is still valid but Naviers bending theory can no more be applied. Additionally the effect of deformation of the thin‐walled tube‐section must be taken into account. This effect is unfavourable for stresses and deformations if the bending moment increases the curvature of the bar. This paper gives formulae for calculation of internal forces, stresses and deformations considering both mentioned effects; examples show the application. Finally the principle of virtual work is formulated and demonstrated at a two‐hinged arch.     

Drained and undrained response of deep tunnels subjected to far-field shear loading

An analytical solution for a rectangular opening in an infinite elastic medium subjected to far-field shear stresses has been derived for drained and undrained loading conditions. A number of numerical simulations has been conducted to determine the distortion of a rectangular structure in an infinite elastic medium under far-field shear stresses also for drained and undrained conditions and when there is full slip or no slip at the ground–structure interface. The results show that the shape of the opening has a minor influence on the structure’s deformations and that full-slip conditions result in lower deformations. Undrained conditions tend to reduce distortions when the structure is more flexible than the ground, but tend to increase them for stiffer structures. A comparison between results obtained for a rectangular lined opening and for a circular lined opening are presented, and show that deformations of a rectangular structure with no-slip can be estimated from equations derived for a circular opening with an incompressible liner and also with no-slip. The effects of flexibility, slip condition at the interface, and drained or undrained loading are different for circular tunnels than for rectangular tunnels.     

Effect of the model updating on the earthquake behavior of steel storage tanks

In this paper, effect of the finite element model updating on the earthquake behavior of steel storage tanks considering fluid-structure interaction is investigated. For this purpose, a cylindrical steel storage tank filled some liquid fuel oil located in Trabzon, Turkey is selected as an example. Initial finite element model of the storage tank is developed by ANSYS software and dynamic characteristics (natural frequencies, and mode shapes) are determined analytically. Ambient vibration tests are conducted on the storage tank under natural excitations to obtain dynamic characteristics (natural frequencies, mode shapes and damping ratios), experimentally. Peak Picking technique in the frequency domain is used to extract experimental dynamic characteristics. When the analytically and experimentally identified dynamic characteristics are compared to each other, some differences are found between both results. To minimize these differences, initial finite element model of the storage tank is updated according to experimental results using some uncertainties modeling parameters such as elasticity modulus. To investigate the effect of finite element model updating on the earthquake behavior of the storage tank, earthquake analyses are performed before and after model updating. In the earthquake analyses, YPT330 component of 1999 Kocaeli earthquake is selected and applied to the models in the horizontal directions. It is seen from the analyses that the displacements and the stresses after model updating are more effective than the displacements and the stresses before model updating.     

Repeated loading of soil containing granulated rubber and multiple geocell layers

Sandy soil/aggregate, such as might be required in a pavement foundation over a soft area, was treated by the addition of one or more geocell layers and granulated rubber. It was then subjected to cyclic loading by a 300 mm diameter plate simulative of vehicle passes. After an initial study (that established both the optimum depth of the uppermost geocell layer and of the geocell inter-layer spacing should be 0.2 times plate diameter), repeated loading was applied to installations in which the number of geocell layers and the presence or absence of shredded rubber layers in the backfill was changed. The results of the testing reveal the ability of the composite geocell-rubber-soil systems to ‘shakedown’ to a fully resilient behavior after a period of plastic deformation except when there is little or no reinforcement and the applied repeated stresses are large. When shakedown response is observed, then both the accumulated plastic deformation prior to a steady-state response being obtained and the resilient deformations thereafter are reduced. Efficiency of reinforcement is shown to decrease with number of reinforcement layers for all applied stress levels and number of cycles of applied loading. The use of granulated rubber layers are shown to reduce the plastic deformations and to increase the resilient displacements compared to the comparable non-rubber construction. By optimal use of geocells and granulated rubber, deformations can be reduced by 60–70% compared with the unreinforced case while stresses in the foundation soil are spread much more effectively. On the basis of the study, the concept of combining several geocell layers with shredded rubber reinforcement is recommended for larger scale trials and for economic study.     

大型储油罐抗震性能分析

采用ANSYS有限元软件针对20 000m3储油罐进行了数值分析。计算了罐侧壁环向、竖向应力及基底弯矩随着罐中液面高度变化的地震响应分析,用以验算其抗震性能,并与规范和简化方法比较,验证结果的正确性。结果表明:季节性冻土层的存在明显地影响着场地动力特性,进而影响储罐的抗震安全性。在非冻结场地上该储罐在多遇地震和罕遇地震情况下都是安全的;在冻结场地上该储罐在多遇地震情况下是安全的,而在罕遇地震情况下是不安全的。     

Erection behavior and grillage model accuracy for a large radius curved bridge

The effects of construction procedures on the stresses and deformations in a large radius, horizontally curved, plate girder, bridge were examined along with the accuracy with which grillage models predicted the construction behavior. The examination included a study of the stresses and deformations during construction and a comparison of those quantities to the grillage model predictions. Results from the study indicated that, for the structure that was examined: (1) appreciable warping stresses were generated during girder erection; (2) the classical grillage model predictions were less accurate during girder erection while the “modified” model predictions were more accurate during deck placement; and (3) the predicted grillage model deflections were smaller for an exterior-to-interior girder erection procedure than an interior-to-exterior procedure.     

Interaction of tunnel linings and soft ground

Although soil-lining interaction is highly dependent on the tunnelling technology used, most of the available design methods for tunnel linings fail to take into consideration this important factor. During tunnel excavation, the in-situ stresses are significantly altered, depending on the tunnelling technique as well as the configuration of the tunnel and the characteristics of the soil deposits. The reduced radial stresses are the starting point of the soil-lining interaction at lining activation. This paper presents a method of lining design that considers the details of the excavation procedure and lining installation. Interaction between the tunnel lining and the ground is analysed in two stages—excavation and interaction. The excavation stage is responsible for determining the pre-lining soil deformations and the reduced in-situ stresses. The interaction stage models the soil-lining system together. Soil continuum, tunnel lining, and the interface between them are idealized in the whole system using nonlinear finite-element techniques. The deformations of the soil-lining system, as well as the lining internal forces, and equilibrium soil pressures are determined. Finally, results of the proposed analytical method as well as commonly used procedures are compared with field measurements compiled during the construction of two tunnels in which a precast segmental lining and rib and lagging lining were used.     

Modelling a mine-by test at the Mont Terri rock laboratory, Switzerland

An instrumented mine-by test was conducted at the Mont Terri rock laboratory, Switzerland in 1997–1998 to assess issues associated with tunnel excavation in a middle Jurassic claystone known as the Opalinus Clay. Excavation-induced stresses resulted in unusually large deformations and the development of an excavation disturbed zone (EDZ) around the tunnel where the observed dominant mode of yielding consisted of extensional fracturing. From field and laboratory observations, it has been observed that Opalinus Clay exhibits responses that often are not represented adequately by linear-elastic or elasto-plastic models. In particular, strong non-linear elastic behaviour at low stresses was observed in laboratory tests. This behaviour has been captured by a phenomenological-based model, known as the stress-dependent modulus (SDM) model. The concepts of the SDM model have been extended to a piece-wise pore pressure formulation that captures the hydromechanical rockmass response. These models were implemented into a finite difference method numerical code and used to simulate the short-term deformations and pore pressure response of the ED-B mine-by test. These simply calibrated models provided a reasonable fit to the field data, particularly in regions of unloading where rockmass deformations were not dominated by dilation.     

海洋混凝土储油罐壁的热应力分析

在我国渤海海域 ,冬季海水温度较低 ,而原油进砼罐时温度较高 ,罐体内外温差将会引起较大的温度应力。混凝土罐壁能否承受如此大的温度应力 ,是关系到混凝土平台能否应用于渤海油田的关键性问题。本文通过有限元分析 ,对罐壁在不同变温情况下的应力状态进行了研究 ,并根据罐壁与变温前后的顶底板的组合分析 ,讨论了由变温引起的内在约束对外环壁受力状态的影响 ,并与试验结果进行了对比 ,符合较好     

多年冻土区L型支挡结构的数值分析

  利用数值分析方法模拟施工实况,采用弹塑性本构模型并考虑能够反映土体与墙面相互作用的接触单元,分析墙背填土的变形和受力。从而使L型挡土墙作为在冻土区中使用的一种新支挡结构,其力学性能能得到更加深入细致地研究和检验,以便为工程应用提供参考依据。