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     

沥青加热技术中的热负荷计算

介绍了常见的沥青拌和厂（站）和沥表储库中供热系统设计和热源设备造型的关键－系统的热负荷计算方法。     

辽宁交通数据交换平台建设

数据交换是系统之间、部门之间进行数据共享的重要手段之一。本文针对辽宁交通数据交换平台建设，介绍了数据交换的原理，数据中心架构和具体功能，以及建设过程中应该注意的事项。     

无砟轨道桩板结构路基设计计算

鉴于无砟轨道桩板结构路基没有相应的设计规范,在分析其结构特点和使用要求的基础上,借鉴相关行业标准和研究成果,将荷载分为永久荷载、可变荷载和偶然荷载,提出按承载能力极限状态和正常使用极限状态分别进行荷载效应组合,取各自的最不利组合以分项系数形式的表达式进行桩板结构路基设计计算。对荷载分项系数、组合值系数、准永久值系数以及结构抗力设计值和正常使用规定限值提出建议值。建议:承载板长度宜取20~50 m、厚度宜取0.5~0.8 m,并按一定原则设置;桩间距纵向宜取5~10 m,横向宜与线间距相对应;设置过渡段以满足过渡衔接处差异沉降和竖向转角要求。     

关于"载重线公约-附则I修正案"生效

国际载重线公约-附则I的修正案,是"国际载重线公约"自1966年4月5日(在伦敦1966年国际载重线公约缔约)以来较大的一次修订,"修正案"的生效和施行将对船舶、海上财产以及船上人命安全等方面产生重大影响.该文基于作者对规范的理解并结合了一定的案例分析,以期裨益读者.     

全电力船舶的电力推进系统建模与仿真

本文介绍了全电力船舶的典型推进系统并给出了仿真结果。由于模型的复杂性,仿真计算的工程量非常巨大。因此设计了一个可供替代的简化仿真系统。从船舶网络的角度来看,简化系统的仿真结果和实际模型的结果十分接近。     

低路堤荷载作用下钢波纹管涵切向应变现场测试

为研究钢波纹管涵在低路堤荷载作用下的力学性能,依托泗许高速安徽淮北段一处试验涵,对荷载分别作用于超车道、行车道、应急车道情况下管涵的切向应变进行现场测试。试验数据表明：当荷载作用于不同车道时,钢波纹管切向应变不同,随着荷载的移动,波纹管不同断面同一角度的切向应变值不同但变化规律相似。试验结果可以为今后的钢波纹管涵洞设计和施工提供理论依据。     

桩自平衡测试技术及其在桥梁工程中的应用

结合杭州湾跨海大桥的工程实例对桩自平衡测试技术的原理、应用以及测试过程中的施工注意事项作了综合的介绍.     

High speed tensile test of steel sheets for the stress-strain curve at the intermediate strain rate

This paper presents stress-strain curves of steel sheets for an auto-body obtained at intermediate strain rates with a servo-hydraulic type high speed tensile testing machine. The apparatus has the maximum stroke velocity of 7.8 m/sec to obtain the tensile material properties at a strain rate of up to 500/sec. A special jig fixture is specially designed for accurate acquisition of tensile loads with reduction of the load-ringing phenomenon induced by unstable stress wave propagation at high strain rates. Tensile testing of steel sheets for an auto-body was carried out to obtain stress-strain curves of mild steel and advanced high strength steels at strain rates ranged from 1/sec to 200/sec. The test results provide interesting information regarding the stress-strain curves at intermediate strain rates ranged from 1/sec to 200/sec and demonstrate that strain rate hardening is strongly coupled with strain hardening.     

强化处理工艺影响膜片弹簧载荷变形关系的分析

研究了强化处理工艺对膜片(碟形)弹簧载荷变形特性的影响机理,并进行了载荷变形特性试验,通过试验数据分析载荷变形与喷丸、强压等强化处理工艺的关系,发现残余应力是强化处理效果的主要表现形式.采用X射线应力仪对样件进行了残余应力测试,分析了残余应力的分布规律,发现残余应力和局部材料特性改变是影响载荷变形的主要因素,由此给出了初步解决方案.