Fuzzy approach for optimum replacement time of mixed infrastructures

Investments in infrastructure assets represent a sizable portion in the governments’ public fund. Continuous maintenance, rehabilitation, and replacement are required to maintain the level of service of infrastructure assets. Knowing the replacement needs of infrastructures and the timing of replacement are challenging tasks. This paper presents a decision support tool that aids in deciding the best time to replace several types of infrastructure assets, that is, mixed infrastructure. The paper uses fuzzy logic to model uncertainties in order to identify the useful lifetime of each infrastructure asset. Infrastructure replacement decision is made based on least cost option(s). A fuzzy logic tool is applied in three steps: data fuzzification, fuzzy inference, and data defuzzification. The developments made in the fuzzy logic tool are presented. A numerical example is presented to demonstrate the practical features of the proposed tool.     

Demands and challenges for construction of marine infrastructures in China

The oceans are crucial to human civilization. They provide core support for exploitation and utilization of marine space, resources, and energy. Thus, marine infrastructures are vital to a nation’s economic sustainable development. To this end, this article first describes the main challenges in current ocean utilization, and then reviews the China’s ocean engineering progress. As such, six major sectors are evaluated: 1) global climate change and marine environment, 2) comprehensive utilization of marine space, 3) marine transportation infrastructure interconnection, 4) ocean clean energy development and maricultural facilities, 5) ecological crisis and marine engineering countermeasures, and 6) marine infrastructure operation safety and maintenance. Finally, perspectives on future directions of ocean utilization and marine infrastructure construction in China are provided.     

Self-tuning dynamic models of HVAC system components

A great majority of modern buildings are equipped with Energy Management and Control Systems (EMCS) which monitor and collect operating data from different components of heating ventilating and air conditioning (HVAC) systems. Models derived and tuned by using the collected data can be incorporated into the EMCS for online prediction of the system performance. To that end, HVAC component models with self-tuning parameters were developed and validated in this paper. The model parameters were tuned online by using a genetic algorithm which minimizes the error between measured and estimated performance data. The developed models included: a zone temperature model, return air enthalpy/humidity and CO₂ concentration models, a cooling and heating coil model, and a fan model. The study also includes tools for estimating the thermal and ventilation loads. The models were validated against real data gathered from an existing HVAC system. The validation results show that the component models augmented with an online parameter tuner, significantly improved the accuracy of predicted outputs. The use of such models offers several advantages such as designing better real-time control, optimization of overall system performance, and online fault detection.     

Fitness-oriented multi-objective optimisation for infrastructures rehabilitations

A new multi-objective decision support system (MODSS) is developed for rehabilitation planning of public infrastructures. The method is generic and provides decision-makers a set of optimal rehabilitation tradeoffs over a desired analysis period. Two main objective functions are handled simultaneously, namely cost and performance, in addition to a set of bounding constraints. The method is based on a new fitness-oriented technique where problem knowledge is taken into account. In order to analyse cost and performance together, a normalisation technique of both objectives is achieved through an innovative time-value concept for both cost and condition states. The proposed method is based on life-cycle costing (LCC) methodology using a dynamic Markov chain to represent the deterioration mechanism and genetic algorithm is used to find the optimal rehabilitation profile. A case study is presented with a comparison between the traditional Markov decision process (MDP) and the newly developed method. The MODSS results in a lower LCC and is found practical in providing a complete maintenance and rehabilitation plan over a required study period. It is proven that the developed multi-objective optimisation is an effective tool in analysing real-life situations involving conflicting goals. Also, weighted sum method could be easily implemented and its outcome is sufficient given that many external factors might alter the decision-makers choice irrespectively of the optimisation method that is used. Furthermore, genetic algorithm is proven useful in the optimisation process in overcoming the computational difficulties associated with large combinatorial problems. The new method is beneficial to researchers and practitioners as it provides a major step towards a broad infrastructure management system.     

建筑业的规划和设计模型

就民用建筑工程项目的施工管理进行了论述,从不同角度进行了分析,包括施工和采购项目的分类、建筑物流和服务业务、建筑材料的供应和采购、采购的运输和配送、材料库存位置,以促进建筑施工项目高效运作。     

Evaluation of data driven models for pipe burst prediction in urban water distribution systems

ABSTRACT

The water distribution network is one of the most expensive parts of a water supply system. The fundamental variables of a network, material, diameter, length, age, and the hydraulic pressure of pipes are the factors that affect the pipe burst rate (PBR). Establishing a relationship among the burst rate and these factors is an important step to assess the conditions governing the network and preventing significant water leakage. Implementing the data-driven approach in PBR prediction is an effective method to find the relationship. In the present study, Grasshopper Optimization Algorithm-based Support Vector Regression (GOA-SVR), Gaussian Process Regression (GPR), and Artificial Neural Network (ANN) have been developed to predict PBR in an urban area. The results show that the GPR model outperforms other methods. Furthermore, the sensitivity analysis indicates that the pipe age has a negative effect on PBR modeling while the pipe length is the most relevant variable.     

Impact of new sanitation technologies upon conventional wastewater infrastructures

Abstract

Separation of wastewater split streams and utilization of the resources contained therein are an important prerequisite for a sustainable wastewater treatment. In areas with existing infrastructures, this leads to transition states during which current systems must continue to operate. A simple mass-flow based method was developed to assess the impacts of an incremental transition (co-digestion of blackwater and sewage sludge) upon plant operation. The results proved that blackwater co-digestion could be easily integrated into existing wastewater infrastructures; however, beyond 8% transition thickening was required due to hydraulic limitations in the digester. Additionally, nitrogen recovery was necessary beyond 35% transition to avoid unfavorable C:N ratios. The investigated concept also led to a power gain of 11 kWh/(PE?a) due to enhanced biogas production and aeration savings. The developed Excel-based method was considered suitable for evaluating the benefits and probable tipping points for plant operation during transition to source-separated sanitation systems.     

Real-time performance models for photovoltaic water pumping systems

This purpose of this paper is to develop and validate a model to accurately predict the cell temperature of a photovoltaic (PV) module that adapts to various mounting configurations, mounting locations, and climates while only requiring readily available data from the module manufacturer. Results from this model are also compared with results from published cell temperature models. The models were used to predict real-time performance from a PV water pumping systems in the desert of Medenine, south of Tunisia using 60-min intervals of measured performance data during one complete year. Statistical analysis of the predicted results and measured data highlights possible sources of errors and the limitations and/or adequacy of existing models, to describe the temperature and efficiency of PV-cells and consequently, the accuracy of performance of PV water pumping systems’ prediction models.     

Probabilistic analysis of interdependent infrastructures subjected to weather-related hazards

Simulation of the infrastructure performance using numerical models may significantly assist in developing strategies for improving its resilience to harmful effects of climate change. This paper presents a model for simulating the performance of interdependent infrastructure systems based on an extended network flow approach, i.e. infrastructure systems are considered as a network of nodes connected by directed edges. The model has been specifically developed to simulate the infrastructure performance at a community scale and has higher node resolution compared to typical models of infrastructure systems at the national level. The model is time-dependent so that the infrastructure performance can be assessed at discrete points over a period of time. Parameters describing the performance of infrastructure assets (e.g. production and flow capacities, demands) can be treated as random variables or probabilities can be assigned to failures of the assets. The application of the model is illustrated by the probabilistic assessment of the performance of two interdependent infrastructure systems – electrical power and water, damaged by flooding.     

支撑系统的模拟

对具有不同升降高度、升降机数量和杰克延性的3+3支撑系统的足尺试验进行数值模拟,分析支撑系统性能。介绍了模拟栓接节点、半刚性梁连接及底板偏心的方法。基于Ramberg-Osgood方程,考虑材料非线性,并考虑了轴线不直、表面与轴线不垂直等初始几何缺陷。通过足尺试验得到的破坏荷载和荷载-位移曲线,对非线性分析得到的极限荷载进行修正。数值结果与试验很吻合,表明采用几何非线性和材料非线性分析能很好地研究支撑系统的性能和极限承载力。分析了支撑系统模拟中的一些难题,建立了底板、U型头、栓接节点的力学模型。     

An assessment of models for wastewater sludge characterization

One of the important aspects of the models used for wastewater sludge transport is the determination of energy loss when pumped on long distances. In the literature, two types of non‐Newtonian fluids, the Bingham plastic and the pseudoplastic fluids, have been assumed and received special attention. Based on these two classifications, formulae are derived for the design of pipelines. The purpose of this investigation is to evaluate the existing models for characterising the non Newtonian properties of wastewater sludge and to investigate the effect due to the testing scale of the experimental facilities. As a result, the statistical analysis of the examined data provide useful information for the adequacy of these models.     

The approach to daylighting by scale models and sun and sky simulators: A case study for different shading systems

At the Daylighting Laboratory of the Politecnico di Torino a facility, which consists of a sun simulator and a sky scanning simulator, allows daylighting simulations to be made inside scale models for both research and design purposes. Photometric data and digital images of the luminous environment are the results that are obtained. The “sky” covers one-sixth of the vault, while the “sun” is fixed: therefore the model is rotated to reproduce the entire vault and rotated and tilted to reproduce the relative sun–Earth position.     

重庆主城排水系统突发事故灾难应急体系研究

本文对主城排水系统危害因素分析、主城排水系统突发事故灾难应急体系中部门职责划分、应急响应分级制度与两级预案等方面进行了分析研究,并在实际中应用研究成果,面对2007年的特大暴雨灾害,启动两级应急预案,取得了显著的社会经济效益。     

GPS水准拟合模型的选取与模型误差的补偿

以一次平面和二次曲面拟合模型为例进行了模型优选比较,并运用实例说明了优选模型的合理性,最后用附加模型误差参数的平差方法对不合格模型进行了模型误差补偿。     

Operating in the shadowland: Why water utilities fail to manage decaying infrastructure

Decaying water infrastructure is a growing challenge in high-income countries while at the same time being under pressure from other socioeconomic and environmental issues. This paper analyses why addressing these challenges is so challenging, despite the critical role of water service for society. The paper is based on a study of the Swedish water sector and reveals how the utilities are influenced by several factors that constrain their agency. Most importantly, the utilities operate in a ‘societal shadowland’ where the public and politicians take their services for granted, lowering the sense of urgency and impeding their ability to take action.     

Development of dynamic thermal input models for simulation of photovoltaic generators

ABSTRACT

Development of dynamic thermal input models for simulation of photovoltaic generators (PVG) is the main concern of this work. The dynamic thermal input models consist of insolation and temperature models. The model development involves acquisition of meteorological input data for Kampala at latitude (0.3476^oN) and longitude (32.5825^oE), measurement of physical conditions in which PVG is operating, carrying out thermal balance around PVG and application of solar analytic equations. The emerging models are simple simulated dynamic insolation and temperature models. These models were superimposed with quadruple sinusoidal waves to obtain superimposed simulated dynamic models. Furthermore, the superimposed insolation models were validated with the superimposed sky model and meteorological data while the corresponding temperature model was validated with the experimental data. The developed models become universal by substituting localised input parameters. Moreover, these models are useful for operation, installation, design and dynamic performance analysis of PVG.     

Appropriate boundary conditions for computational wind engineering models revisited

At the first Computational Wind Engineering conference in 1992 “Appropriate boundary conditions for computational wind engineering models using the k-ε turbulence model” were proposed. In this paper it is shown that these conditions can be directly derived by treating the onset flow as a horizontally homogeneous turbulent surface layer, with the flow being driven by a shear stress at the top boundary. This approach is extended to provide the inlet profiles and boundary conditions appropriate for modelling the flow using the standard k-ε, RNG k-ε, Wilcox k-ω and LRR QI turbulence models. Means for their application within the commercial CFD code CFX 12.0 are given. It is shown that within the flow the various turbulence model constants set the effective value of von Kármán's constant, which does vary slightly between models. The discrepancy between the turbulence level set by the standard turbulence model constants and that observed in the atmosphere is discussed. Problems with excessive turbulence generation near the ground and the over-prediction of stagnation pressures are discussed and possible solutions proposed.     

Adaptation of interconnected infrastructures to climate change: A socio-technical systems perspective

Climate change is likely to affect how society will function in this century. Because climate change effects may be severe, a next step is to study not only the effects on natural systems, but also the effects on built infrastructure systems and, in response to anticipated effects, the adaptation of those systems. Studies that discuss interconnected infrastructures, society's backbones, in light of climate change are emerging. We apply a socio-technical systems perspective in order to gain insight into the effects of climate change on our infrastructure systems and possible adaption strategies for the coming decades. We use this perspective to collect and describe the literature on adaptation of infrastructures to climate change. We find that the analysed papers predominantly focus on specific geographic areas and that various types of impacts on and interdependencies of built socio-technical systems are recognized, not only for energy and transport, but also for water infrastructures. A missing step is the modelling of adaptation measures. Recent literature enables an exploration of strategies for adaptation, which should be expected in the coming years.     

论房地产企业传统融资模式

对我国房地产企业的传统融资模式进行了分析,指出传统融资模式存在的问题,提出融资多元化的建议,通过探索和开拓不同的融资模式,从而促进房地产企业的发展。     

Can integrated solutions business models work in construction?

It has recently been suggested that the future of the construction industry lies in adopting a new business model based on the concept of integrated solutions. Integrated solutions are combinations of products and services that address a customer's unique requirements throughout the life cycle, from development and design to systems integration, operations and decommissioning. Research on integrated solutions in other capital goods sectors has shown suppliers have had to create new business models, including developing new approaches to adding value, and building up new capabilities - especially in systems integration. The paper presents some preliminary empirical findings about construction industry perceptions of value, systems integration and integrated solutions that suggest the concept of built environment solutions provision is still at an early stage in its development and that the best opportunity for its introduction is in the context of private finance initiatives in the public sector or large clients who require repeatable solutions in the private sector.