考虑围岩蠕变特性的TBM隧道管片衬砌受力特性研究

为研究深部高地应力岩层中修建TBM隧道时管片衬砌结构的力学行为,以某深埋TBM工法隧道为研究对象,建立基于围岩蠕变和管片分块效应的衬砌-围岩复合模型,研究考虑时间效应下管片衬砌的受力特性。结果表明:考虑围岩蠕变效应下管片衬砌受力表现出明显的时间效应。随着围岩蠕变时间的延长,管片衬砌的形变、内力和接缝张开量均呈现两阶段增长,具体表现为前期呈线性增长,后期增加趋缓。洞周围岩应力经历三阶段变化,即先减小后增大直至稳定。围岩蠕变时间为100年时,管片衬砌的内力和形变量均接近极限值。研究结果可为深部高地应力且考虑围岩蠕变效应下的TBM隧道衬砌结构设计提供参考。     

对一个计算船体失效概率公式的讨论

本文讨论了文献[1]给出的计算船体失效概率公式在原理及数值结果方面存在的问题，进而导得了相应的正确表达式。该式可用于分析各个海况对船体安全性的影响，为船体可靠性长期分析，提供了一个有效途径。     

Evaluation of expected maximum values of forces acting on containers and lashing rods on a container ship

The appearance of a number of large container ships in the 8000 TEU range raises the importance of a plan for container lashing arrangements on deck in relation to the design of the ship. Therefore, it is expected that a new method for evaluating the lashing arrangements on deck will be introduced which is applicable regardless of the ship's size and the lashing pattern, instead of using the standards of several different societies, as happens at present. To evaluate the lashing arrangements on deck, the expected maximum values of the forces acting on the containers and lashing rods should be evaluated. This paper presents a new method of evaluating the container lashing arrangements on a container ship using an "acceleration ellipsoid." The applicability of the acceleration ellipsoid to an evaluation of the expected maximum values of the forces was examined by comparing the expected maximum values of the forces calculated by the long-term distribution calculation known as the "Fukuda method," to those calculated using the acceleration ellipsoid. By comparing these results, it was confirmed that the expected maximum values of the forces calculated using the acceleration ellipsoid were not less than those calculated through by the long-term distribution calculation. It is concluded that the acceleration ellipsoid can be used to evaluate the expected maximum values of the forces acting on containers and lashing rods. Received: December 14, 2000 / Accepted: March 22, 2001     

从短期试验结果预测新建预应力混凝土梁收缩和徐变的长期效应

基于计及钢筋配筋率、预应力钢筋松弛等影响的桥梁收缩、徐变长期效应计算式,提出了从梁体混凝土短期试验值推算相应素混凝土在该桥梁工作环境下收缩应变及徐变系数的方法;结合CEB FIPMC90收缩模型与徐变模型思想,得出计算桥梁素混凝土收缩应变及徐变系数的CEB FIPMC90修正公式。理论分析与试验结果比较表明,预测理论值给出了较好的精度。该预测方法,不需做材料的收缩、徐变试验,亦避免从标准环境下试验值推算桥梁工作环境下收缩、徐变可能产生的误差。     

波浪弯矩设计值与长期预报理论计算值的比较

本文分析了国际船级社协会（ＩＡＣＳ）纵向强度标准Ｓ１中，波浪弯矩值成采用ＩＡＣＳＷＰ／Ｓ委员会推荐的海浪谱和海况统计资料条件下的长期预报理论计算值的关系，大量计算实践表明后者总体上要比前者大１．５倍。文中建议为了把长期技术应用于船体波浪弯的直接设计计算，对上述预报过程可取１０概率水平时地长期预报值作为船体波浪湾矩设计值。     

大跨径预应力混凝土梁桥长期挠度控制分析

目前国内大跨径预应力混凝土梁桥存在的主要病害是跨中下挠过大和箱梁梁体裂缝。本文对跨中下挠过大的主要原因进行了分析,介绍了施工控制中线形控制的方法,然后用恒载零弯矩理论给一座已建的95 160 95m连续刚构桥重新配置预应力束,并对原设计和恒载零弯矩配束从内力、位移、预应力筋用量三方面作一比较, 最后提出了控制跨中下挠过大的一些措施。     

Cost effective future derailment mitigation techniques for rail freight traffic management in Europe

Safe and reliable traffic management is vital for uninterrupted and successful operation of the European rail network, where mixed traffic (i.e. freight and passenger) services are run. Although rail freight derailment is infrequent, its consequences can be severe and may result in different forms of costs, including infrastructure; rolling stock; traffic disruptions; injuries and fatalities. The objective of this research paper is to conduct a cost benefit analysis (CBA) to identify cost effective mitigation techniques for efficient rail freight traffic management in Europe, by 2050. Reviewing previous derailments and studies, eight sets of derailment causes are analysed and, for each of them, sets of mitigation techniques are aimed at for their alleviation. The study finds that the highest cumulative costs of derailment are associated with ‘wheel failure’, while the lowest cumulative cost is identified for ‘excessive track width’. Regarding mitigation techniques, the lowest cumulative benefits are demonstrated for ‘track height’ interventions, whereas ‘wheel failure’ alleviation demonstrates the highest benefits, in value terms (all by 2050). In most cases, the benefit to cost ratio did not exceed 2.6; in two cases (‘track height’ and ‘rail failures’) the ratio remained below 1 – a negative outcome where cost is higher than benefit. The study suggests that the most cost-efficient interventions are those applied to ‘hot axle box and axle rupture’ and ‘spring and suspension failure’.     

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     

考虑结构长期性能多梁式预应力混凝土斜梁桥合理施工方法研究

采用梁格法建立多梁式预应力混凝土斜梁桥空间有限元分析模型,通过模拟不同施工过程进行计算分析,发现采用不同施工方法实现的结构成桥后的内力和变形差异很大;支座反力的分布也有较大的差别.成桥后钢束二次效应对结构的内力和反力的影响也较大,因此在设计选择斜粱桥施工方法时应引起注意.     

Estimation of nonlinear long-term extremes of hull girder loads in ships

This paper deals with a estimation of long-term extreme value for a given return period, say D=100 yr. In principle, this response is obtained by combining the response in all the sea states. The long-term response for a linear system can be effectively obtained by determining the response for each sea state, specified by the significant wave height, H_s, and the peak period, T_p, in the frequency domain. However, if the response is nonlinear, time domain simulation and a long time series would be required, to limit statistical uncertainty. Therefore, the long-term analysis becomes rather complicated and time consuming. For the long-term analysis, it is crucial to introduce ways to improve the efficiency in the calculation. In this work, it is shown that, the long-term extremes can be estimated by considering only a few short-term sea states. A long-term analysis based on identifying the most important sea state, defined by the coefficient of contribution, using linear analysis is applied. An iteration procedure is thereafter used to find the nonlinear long-term extreme values. It is concluded that only a limited number of sea states is necessary to get an acceptable estimate of the nonlinear D-year response as long as the most important sea states are included, i.e., the sea state with the maximum coefficient of contribution.