Optimisation of a combined Stirling cycle–organic Rankine cycle using a genetic algorithm

In a Stirling cycle a huge amount of energy is wasted due to the losses. This wasted energy may be utilised as a heat source for the boiler of an organic Rankine cycle (ORC). Combination of these two cycles leads to an increased cycle efficiency compared to a single Stirling cycle and the analysis and optimisation of the integrated system is carried out. Optimisation is performed using the genetic algorithm and considering three decision variables: the temperature of the cold tank of the Stirling cycle, the pressure ratio and the temperature of the ORC condenser. In optimisation, the efficiency is considered as the objective function and the highest value is achieved by adjusting the decision variables. Using this method, the efficiency of the overall combined cycle was improved in which the highest efficiency was obtained to be 41.5%.     

A comparative study of time-based maintenance and condition-based maintenance for optimal choice of maintenance policy

Cost-effective maintenance of infrastructure systems within an acceptable level of safety and performance is the major concern of managing agencies. Recent maintenance approaches have offered two distinct maintenance policies: time-based maintenance (TBM) and condition-based maintenance (CBM). This paper compares the two policies under different cost environments for stochastically deteriorating infrastructures. The performance of TBM and CBM is evaluated from the viewpoint of condition transition and life cycle cost. We found the optimal maintenance solutions for TBM and CBM using dynamic programming and performed a simulation study. The simulation study showed that TBM causes some unexpected deterioration that leads to high cost, while CBM maintains a certain level of condition steadily under consistent inspection, which enables steady spending at the management level. The life cycle cost under CBM is relatively symmetric and has a more concentrated distribution than TBM, which has a large number of outliers from unexpected deteriorations. Finally, we evaluated the life cycle cost with a change in the inspection–repair cost ratio to find the most appropriate cost environment for each maintenance policy. While CBM needs periodic inspections, it still has more advantages than TBM when the inspection cost is relatively low.     

应用LCC概念进行供热系统优化规划

应用寿命周期费用（ｌｉｆｅｃｙｃｌｅｃｏｓｔ）的概念和系统工程的方法,将热源,热网,热用户作为一个整体进行规划,使其技术和经济指标最佳,建立了以寿命周期费用最小为目标的供热系统优化规划数学模型,该模型用于大庆市供热工程中,效果很好。     

费用效率法在工程项目全寿命周期成本评价中的应用

工程项目全寿命周期成本分析秉承可持续发展思想,从项目全寿命周期来考虑成本问题,涉及项目的初始投资、运行维护和报废回收以及社会环境效益等多方面的因素。本文介绍了当前我国工程项目全寿命周期成本研究的基本情况,并结合实例应用费用效率法对某工程项目方案进行评选,结合其结果说明全寿命周期成本分析方法可以对工程项目全寿命周期成本进行有效控制,从而实现工程项目的经济性与合理性,为投资者决策提供参考意见。     

Extension of dynamic programming models for management optimisation from single structure to multi-structures level

The aim of this article is the management optimisation (inspection, maintenance and rehabilitation (IM&R)) of a group of structures. It is supposed that the optimisation is constrained by limited available budget at the beginning of each time period during the entire time horizon thus creating an economical dependence between the decisions related to each of the structures. A Lagrangian relaxation technique is used for the extension of existing dynamic programming methods from single structure to multi-structures level. The methodology is illustrated by using a Generalised Partially Observable Markov Decision Process having a decision tree composed of a sequence of two decisions at the beginning of each time period, namely an inspection decision followed by a maintenance action decision. A numerical example concerning the optimisation of IM&R of 16 different bridges is presented.     

面向全寿命周期的节能建筑设计方法研究

本文从建筑设计方法的角度出发,结合全寿命周期的节能建筑设计实际,对面向全寿命周期的节能建筑设计方法进行了简要的分析。     

Multi-strategy budget allocation decision support system for seismic rehabilitation of road infrastructure

Economic efficiency is an important factor in seismic rehabilitation of road infrastructures. An inventory of structures is screened to identify seismically deficient parts and prioritise them in the order of need for rehabilitation purposes. In most cases, the financial resources for road infrastructure rehabilitation projects are limited. Therefore, there is a need to efficiently allocate resources to various projects. This article presents a multi-strategy decision support system (DSS) for seismic rehabilitation budget allocation across existing road infrastructures. This DSS employs a multi-criteria assessment module that takes into account different criteria to estimate the financial needs for rehabilitation and to establish an allocation methodology based on the available budget in a fiscal year. To select the optimal package of projects, a genetic algorithm (GA) optimisation module is developed. Multi-objective decision-making is conducted under a specific decision strategy (DS) by solving a (0–1) Knapsack problem. To demonstrate the applicability of the GA-based approach, a hypothetical decision-making problem is presented. The results reveal that the optimal package is more sensitive to the available budget and DS than to the weights of criteria and project scores. Using this system, managers can compare their decisions for different strategies and significantly improve management efficiency.     

Maintenance strategies optimisation of metro tunnels in soft soil

This paper proposes a quantitative approach for selecting effective maintenance strategies for metro tunnels in order to reduce maintenance cost and ensure tunnel safety in the presence of structural degradation during the service life. A non-stationary gamma process is used to simulate the tunnel gradual degradation and to investigate the effects of different maintenance measures on the life cycle maintenance cost of metro tunnels in soft soil. Two commonly applied reinforcement methods, Aramid Fibre Reinforced Polymer and bonded steel plate reinforcement, are investigated in this study. The feasibility of the proposed methodology is demonstrated with maintenance strategies based on periodic and aperiodic inspection policies. Numerical results show that the optimisation of maintenance strategy can reduce the life cycle maintenance cost of metro tunnels in soft soil while ensuring sufficient level of structural safety, and the maintenance strategy with aperiodic inspection policy produces lower maintenance cost.     

Life cycle utility-informed maintenance planning based on lifetime functions: optimum balancing of cost,failure consequences and performance benefit

Decision-making regarding the optimum maintenance of civil infrastructure systems under uncertainty is a topic of paramount importance. This topic is experiencing growing interest within the field of life cycle structural engineering. Embedded within the decision-making process and optimum management of engineering systems is the structural performance evaluation, which is facilitated through a comprehensive life cycle risk assessment. Lifetime functions including survivor, availability, and hazard at component and system levels are utilised herein to model, using closed-form analytical expressions, the time-variant effect of intervention actions on the performance of civil infrastructure systems. The presented decision support framework based on lifetime functions has the ability to quantify maintenance cost, failure consequences and performance benefit in terms of utility by considering correlation effects. This framework effectively employs tri-objective optimisation procedures in order to determine optimum maintenance strategies under uncertainty. It provides optimum lifetime intervention plans allowing for utility-informed decision-making regarding maintenance of civil infrastructure systems. The effects of the risk attitude, correlation among components and the number of maintenance interventions on the optimum maintenance strategies are investigated. The capabilities of the proposed decision support framework are illustrated on five configurations of a four-component system and an existing highway bridge.     

LNG常压储罐预冷热力分析

对LNG常压储罐预冷进行热力分析,得到定压下LNG储罐液氮质量流量与储罐温度的关系、预冷时间与储罐温度的关系,探讨了LNG储罐实际预冷过程控制。     

基于建筑产品寿命周期的建筑节能评价体系研究

节约能源、减少污染的建筑节能已成为全球普遍关注的焦点,同时也成为实现社会、经济和生态可持续发展的根本途径.我国在建筑节能方面虽然已颁布了一系列的指标,但是缺乏科学的评价体系.正是在这样的背景下,提出全寿命周期评价(LCA)方法并将其运用到建筑节能评价体系中,提供理论依据和实例论证,以推动中国建筑节能战略的实施,加快建筑节能工作的步伐,促进建筑节能目标的早日实现.     

介于深、浅仓间的圆筒仓侧压力计算方法探讨

《钢筋混凝土筒仓设计规范》(GB50077-2003)(本文简称《筒规》)对深仓和浅仓侧压力计算采取了两种不同的方法——杨森(Janssen)和兰金(Ranki ne)公式,介于深仓和浅仓之间的筒仓在此处侧压力值出现间断,文章通过几种方法对介于其间的深仓和浅仓筒仓不同高度的仓壁水平侧压力进行分析比较,提出了一些计算建议。     

两种土压力计算方法对比分析

介绍了郎肯土压力理论和延伸的郎肯土压力理论两种土压力计算方法,在实测数据的基础上,通过具体实例计算,对比分析了两种计算方法的差异,结果表明,工程上常用的郎肯土压力理论虽具有计算简便、参数容易获得等优点,但无法对土体基质吸力状态的变化进行考虑,采取延伸的郎肯土压力理论对其计算值进行对比、校核,对于深入理解、合理选用常用计算方法得出的土压力值具有有益的参考。     

Multiobjective optimisation algorithm for sewer network rehabilitation

Understanding of deterioration mechanisms in sewers helps asset managers in developing prediction models for estimating whether or not sewer collapse is likely. Effective utilisation of deterioration prediction models along with the development and use of life cycle maintenance cost analysis contribute to reducing operation and maintenance costs in sewer systems. This article presents a model for life-cycle maintenance planning of deteriorating sewer network as a multi-objective optimisation problem that treats the sewer network condition and service life as well as life-cycle maintenance cost (LCMC) as separate objective functions. The developed model utilises Markov chain model for the prediction of the deterioration of the network. A multi-objective genetic algorithm is used to automatically locate an appropriate maintenance scenario that exhibits an optimised tradeoff among conflicting objectives. Monte Carlo simulation is used to account for LCMC uncertainties. The optimisation algorithm provides an improved opportunity for asset managers to actively select near-optimum maintenance scenario that balances life-cycle maintenance cost, condition and service life of deteriorating sewer network. A case study is used to demonstrate the practical features of developed methodology.     

全寿命周期理论在建设项目决策设计阶段中的应用

依据对国内外建设项目前期决策和设计阶段的比较研究,本文提出了适用于建设项目前期决策和设计阶段的全寿命周期决策理论的基本框架,并针对我国建设项目前期决策和设计阶段管理的现行制度中存在的不足和问题,提出了改进建议和具体措施。