厦门港东渡港区18#多用途兼滚半装功能泊位工程

厦门港东渡港区18#泊位工程是一个5万吨级多用途兼滚装功能泊位,位于厦门港东渡港区岸线的北段,南接象屿保税区专用码头16#泊位,北临19#煤码头.     

Efficient estimation of extreme long-term stresses by considering a combination of longitudinal bending stresses

Longitudinal stresses due to combined horizontal and vertical bending moments in ships, corresponding to a return period of 20 years, are estimated by linear response analysis. In principle, the stress should be obtained by combining the stress in all sea states that can occur over a long-term period. A method to determine the desired long-term extreme stress by considering only a few short-term sea states is presented. The sea states have a certain probability of occurrence, and are each identified by a contour line in the (H _s, T _p)-plane. This approach makes it possible to estimate the extreme loads on the vessel in a practical and accurate manner. Moreover, it is shown that the long-term stress can be estimated by combining the individual long-term extreme stresses due to vertical and horizontal bending moments by using the sum-of-squares approach and accounting for the correlation between stresses. It was found that the correlation coefficient can be taken as the largest of the ones calculated along the contour line. It is shown that this correlation coefficient can even be approximated by the normalized phase angle at the wave length where the dominant response has its peak value. A comparison with the results obtained using well-known combination rules is presented. While linear analysis has been used here, it is believed that the approach can be generalized to stresses with nonlinear behavior, and hence represent a significant improvement in calculation efficiency. Received: September 18, 2001 / Accepted: December 18, 2001     

板簧合金清扫器的研制和应用

1 橡胶合金清扫器的结构及存在的问题 目前在用的皮带机专用清扫器品种较多,按刮刀材料可分为橡胶类、陶瓷类、复合材料类、硬质合金类等.从使用的范围和综合效果看,硬质合金类清扫器具有其他材料的清扫器所无法相比的优点,其耐磨性能优越,强度高,能够将板结和冰冻在胶带上的物料清扫下来.这种清扫器以橡胶作为弹性体,可称之为橡胶合金清扫器.     

Prediction method of hydrodynamic forces acting on the hull of a blunt-body ship in the even keel condition

The mathematical modeling group (MMG) model is well known and is widely used in the field of ship maneuverability. However, the MMG model can be applied only after determination of the hydrodynamic coefficients either from comprehensive captive model tests or from general empirical data. Around the cruising speed, when a ship's drift angle is relatively small, several methods have been developed to predict hydrodynamic coefficients from the ship's principal particulars, e.g., Kijima's method. Kijima's method is efficient in predicting the ship's maneuverability at the initial design stage and is even able to assess the effect of changes in stern design. Similarly, for the low speed range when a ship's drift angle is relatively large, several methods for predicting the ship's hydrodynamic coefficients have been proposed, based on captive model tests, such as those by Kose, Kobayashi, and Yumuro. However, most of the methods developed for low speeds cannot be applied to general ship types without additional experiments being performed. In contrast, Karasuno's method uses theoretical and empirical approaches to predict the hydrodynamic forces, even for large drift motions. Although Karasuno's model utilizes the ship's principal particulars and is applicable to a general vessel, it has not been widely used. This is because the form of Karasuno's model is relatively complicated and its accuracy around the cruising speed is less than that for other methods that have been specifically developed for the cruising speed range. A practical method for predicting hydrodynamic forces for the entire operating speed range of blunt-body ships is proposed in this article. It is based on the MMG model and predicts hydrodynamic coefficients based on a ship's principal particulars. A regression model for the proposed method has also been proposed by analyzing 21 different blunt-body ships. Finally, simulations of a very large 4-m crude carrier (VLCC) model using the proposed method were carried out and the results compared with free-running experiments (both at the cruising speed and at low speeds) to validate the efficacy of the model.     

基于空间句法的城市道路网可达性分析

本文论述了分析道路可达性的两种不同方法,深入探讨了空间句法的原理、方法、软件和进一步应用的前景,对空间句法在城市道路网络规划方案评价等方面的应用进行了试验性的探讨。     

给数字万用表增加新功能

一般数字万用表不能直接测量电容、功放、运放等电路。但如果将数字万用表的压电陶瓷片的两端焊下一脚，串联接入一双孔插座A、B，并将A、B固定于表上，双孔外露，则可给数字万用表增加许多新的功能。下面以带有蜂鸣功能的890型数字表为例，介绍使用方法。     

A review of the effect of a／W ratio on fracture toughness （Ⅰ）—experimental investigation in EPFM

Many experimental investigations have previously been performed and recently done on different shipbuilding structural steels where the specimens size and crack depth/specimen width (a/W) were varied. A series of interesting results have been gained. It is worthwhile to have a review on the effect of a/W ratio on fracture toughness, and further theoretical analysis is necessary. In this paper, experimental work in elasticplastic fracture mechanics (EPFM) was discussed. Tests had been carried out on 10 kinds of strength steels. Results showed that J _i and δ₁ values increased with decreasing a/W when a/W<0.3 for three-point bend specimens and that shallow crack specimens which have less constrained flow field give markedly higher values of toughness than deeply notched specimens. However, for a/W>0.3, the toughness was found to be independent of a/W. Slip line field analysis shows that for shallow cracks, the hydrostatic stress is lower than that from standard deeply cracked bend specimen which develops a high level of crack tip constraint, provides a lower bound estimate of toughness, and will ensure an unduly conservative approach when applied to structure defects especially if initiation values of COD/J-integral are used.     

Geometric modelling of bulbous bows with the use of non-uniform rational B-spline surfaces

Nowadays, bulbous bow forms have become a common design feature in most conventional ship designs. The design of a bulbous bow is usually attempted with the use of certain form parameters that are imposed using the designer's experience or regression values that provide the optimum parameters based on experimental tests or computational fluid dynamics (CFD) calculations. In this article, the geometric modelling of a bulbous bow form that complies with a series of parameters is presented. First, a wire model was constructed with cubic B-spline curves that hold certain form parameters that the designer wants to impose. Second, a B-spline surface that fits these splines was mathematically constructed. A review of the influence of the design parameters used on the bulbous bow properties was made. This method could be used prior to numerical optimization of a bulbous bow because different variations of the design can be easily generated. These variations can be tested numerically using CFD software. A practical application example of the method is shown.     

浅谈铁路预应力钢筋混凝土T型简支梁投标报价中应注意的几个问题

近年来,铁路用钢筋混凝土简支梁的评标原则,均是在商务符合性评审的基础上,选择合理低标中标。以渝怀铁路预应力钢筋混凝土简支T梁,赣龙铁路预应力钢筋混凝土简支T梁及浙赣铁路电气化改造工程预应力钢筋混凝土简支T梁3个项目的投标情况为例,进行了详细分析,总结出投标报价应遵循的几个原则:合理分析风险,准确测算成本,巧妙确定利润率,科学确定报价。     

天津开发区会展中心顶管施工技术

天津开发区会展中心排水工程,采用多刀盘土压平衡掘进机顶管技术,2 000 mm和2 200 mm四排管并排顶进,一次连续顶进284.5 m,累计顶进3 650 m。该技术应用,对管路控制满足设计和施工规范,对地表扰动小,同时取得了良好的经济及社会效益。