Functionality analysis of an urban water supply network after strong earthquakes

An urban water supply network(WSN)is a crucial lifeline system that helps to maintain the normal functioning of modern society.However,the hydraulic analysis of a significantly damaged WSN that suffers from pipe breaks or leaks remains challenging.In this paper,a probability-based framework is proposed to assess the functionality of WSNs in the aftermath of powerful earthquakes.The serviceability of the WSN is quantified by using a comprehensive index that considers nodal water flow and nodal pressure.This index includes a coefficient that reflects the relative importance of these two parameters.The demand reduction(DR)method,which reduces the water flow of nodes while preventing the negative pressure of nodes,is proposed.The difference between the negative pressure elimination(NPE)method and the DR method is discussed by using the example of a WSN in a medium-sized city in China.The functionality values of the WSN are 0.76 and 0.99 when nodal pressure and nodal demands are used respectively as the index of system serviceability at an intensity level that would pertain to an earthquake considered to occur at a maximum level.When the intensity of ground motion is as high as 0.4 g,the DR method requires fewer samples than the NPE method to obtain accurate results.The NPE method eliminates most of the pipes,which may be unrealistic.     

Seismic reliability analysis of urban water distribution network

An approach to analyze the seismic reliability of water distribution networks by combining a hydraulic analysis with a first-order reliability method （FORM）, is proposed in this paper. The hydraulic analysis method for normal conditions is modified to accommodate the special conditions necessary to perform a seismic hydraulic analysis. In order to calculate the leakage area and leaking flow of the pipelines in the hydraulic analysis method, a new leakage model established from the seismic response analysis of buried pipelines is presented. To validate the proposed approach, a network with 17 nodes and 24 pipelines is investigated in detail. The approach is also applied to an actual project consisting of 463 nodes and 767 pipelines. The results show that the proposed approach achieves satisfactory results in analyzing the seismic reliability of large-scale water distribution networks.     

城市交通系统抗震可靠性研究

本文通过对城市交通系统各组成单元可靠性的研究,从系统网络全局出发,以单元可靠度作为控制参数,对交通系统网络的可靠性进行研究。文中指出了震后救护队的最佳选址以及需要改建、加固的路段等,从而为震前交通系统的防灾规划提供理论依据。     

大型城市管网抗震可靠性分析与优化

本文提出了地震作用下供水系统的渗漏模型,发展了地震后带渗漏管网的流分析技术,结合一次二阶矩方法获得了地震后供水管网的功能可靠度。针对供燃气管网系统则提出了一类高效精确的大型网络抗震连通可靠度分析的概率解析算法———递推分解算法。以上述管网抗震可靠性分析理论为基础,分别发展了基于模拟退火算法的供水系统网络拓扑优化分析理论和基于遗传算法的供燃气网络系统拓扑优化理论。     

城市供水管网地震时的水力分析研究

震后,供水管网处于低压供水状态,使得管网中部分用户的水压和水量不能得到全部满足,导致管网部分节点的实际配水量小于需水量,为此,在传统的管网水力分析基础上考虑节点流量随水压的动态变化,进而求解管网节点实际流量和水压。为了比较传统的水力分析和考虑不同节点流量与节点压力的关系对水力分析结果的影响差异,对一实际管网进行了震后水力分析。结果表明,考虑节点流量随水压动态变化的水力分析能得到合理的节点压力和节点流量计算值。     

城市电网的整体可靠度分析及局部评估

在从整体上分析城市电网系统可靠性的基础上，进一步讨论了电网系统的确定关键单元的分析方法，及最终供给点的最大可靠度、最大供电量的供电线路的确定方法。即从整体和局部两方面进行了电网系统的可靠性分析。     

基于GIS的地下管网抗震分析系统

本文提供了一个地下管道震害快速预测方法,给出了供水管网和供气管网地震影响范围判定分析方法以及关键环节判定方法,完成了一个基于Arc View GIS的多功能的地下管网抗震分析系统的研制。     

供电网络系统的可靠性分析

研究了生命线工程系统中供电网络系统的可靠性分析方法。在元件可靠性分析的基础上,进行供电网络系统工程地震可靠性分析,提出了供电网络系统功能失效分级及失效等级的判定方法,并建立了功能失效系数的概念,给出了供电网络系统功能失效系数的计算方法,从而实现了供电网络系统功能失效分析的定量化。     

Seismic response of an urban bridge-support system in soft clay

The numerical simulation of an instrumented urban bridge support and its foundation system was conducted. The bridge works as a deck in a surface subway station and was built 12 yr ago in the so-called Lake Zone in Mexico City, where very soft clays, exhibiting low shear strength and high compressibility prevail. Since the beginning of its construction, pile loads, soil–raft contact pressures and the overall response of the foundation system have been monitored. Within this period, several earthquakes have occurred. Thus, an extensive database of accelerations, pore pressures and load histories have been recorded. In particular, this paper focuses on the bridge response observed during two moderated intensity events, the 2004, 6.3 M_w, Guerrero Coast and the 1999, 7.0 M_w, Tehuacan earthquakes. Finite element models were developed to reproduce the measured responses and to assess the soil–foundation-support performance for long-term conditions, including the effects of potential changes in the dynamic soil properties due to regional subsidence. The computed dynamic responses obtained with the simulation for the free field and structure compares fairly well with the recordings.     

Hazard analysis system of urban post-earthquake fire based on GIS

IntroductionPost-earthquake fire is described as the fire caused by earthquake directly or indirectly. Among the post-earthquake disasters or seismically secondary disasters, post-earthquake fire is usually the most dangerous. Experiences from historic earthquakes indicate that seismically secondary disasters may cause more severe damages and threaten our society seriously than the earthquake itself. To relieve the post-earthquake fire and minimize the economic loss, it is necessary to set up …     

Fractal and chaotic phenomena of seismic dissipated energy in an energy system of engineering structures

Fractal and chaotic phenomena in engineering structure are discussed in this paper, it means that the characters of fractal and chaos on dynamic system of seismic dissipated energy activity intensity E _d and activity intensity of seismic dissipated energy moment I _e are analyzed carefully. Based on the conceptions of the energy system of engineering structures Θ, seismic dissipated energy activity intensity E _d and activity intensity of seismic dissipated energy moment I _e, the chaotic phenomena of dynamic systems E _d and I _e are discovered by theoretic derivation, then the fractal characters of them are also discovered from theoretical inferring and numerical computation. Attractor of relative dimension d ₂, Renyi entropy of the second order k ₂, mean predictable time scale 1/k ₂ and other parameters of the dynamic system which were constructed in light of a large number of actual measuring seismic data have been achieved in the end. These parameters are exactly what the fractal and chaotic phenomena have represented in practical dynamic system, which may be valuable for earthquake-resistant theory and analytical method in practical engineering structures.     

Assessing urban low-carbon performance from a metabolic perspective

How to mitigate anthropogenic carbon emissions in cities determines to a large degree whether global temperature targets in this century are to be met. Using 12 cities in or outside China as case studies, we quantified the critical processes of carbon metabolism based on the urban carbon metabolism assessment framework(CMAF) proposed. The differences of sector contribution, and per capita and intensity among carbon throughflows, carbon inflows and carbon emissions were evaluated.Furthermore, we established an indicator system for CMAF consisting of flow-based and structural indicators to compare the low-carbon performances of cities. The results showed that the total carbon throughflow(TCT) and total carbon inflow(TCI) in Chinese cities were 7–12% higher than in European and American cities regarding the manufacturing and services sector on average, but 6–9% lower in the household consumption sector. Beijing, Tianjin, Nanjing and Guangzhou had lower per capita TCT and TCI than in European and American cities such as Paris and Los Angeles, while their carbon intensities were about three times as much. The per capita TCT in a city was found significantly correlated with per capita energy consumption and had a certain correlation with per capita building or housing area. This study found that TCT, TCI and carbon dioxide emission each provided unique information to measure the potential climatic impact of cities. The difference in the ranking of low-carbon performance between the investigated cities was significant both in terms of flow-based and structural indicators. We suggest these assessment indicators of carbon metabolism be integrated into urban resources management to reflect both the decarbonization status and future emission reduction potential more accurately and to provide systemic decision support for achieving the goal of carbon neutrality in cities.     

Fractal and chaotic laws on seismic dissipated energy in an energy system of engineering structures

ＩｎｔｒｏｄｕｃｔｉｏｎＯｗｉｎｇｔｏｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｎｏｎｌｉｎｅａｒｓｃｉｅｎｃｅｓｓｕｃｈａｓｆｒａｃｔａｌｄｙｎａｍｉｃｓ,ｃｈａｏｔｉｃｄｙｎａｍｉｃｓ,ｓｙｎｅｒｇｅｔｉｃｓｓｃｉｅｎｃｅａｎｄｏｔｈｅｒｓｃｉｅｎｃｅｉｎ...     

Effects of bottleneck blockage on the resilience of an urban stormwater drainage system

ABSTRACT

Severe urban floods have frequently caused social and financial infrastructure problems due to a lack of hydraulic capacity of urban drainage systems or the structural failure of network elements. Conventional, reliability-based design methods of drainage networks only provide acceptable performance under expected conditions of loading. In this study, a new approach based on resilience is proposed for the rehabilitation of urban drainage systems; this approach is able to maintain a predefined service level under both external and unexpected internal loads, including different scenarios of blockage and a severe rainfall event. The performance of different design methods: resilient, non-resilient, deterministic and uncertain models, is comprehensively compared and the most appropriate approaches are introduced. The results show that the new resilient approach outperforms conventional design/rehabilitation methods in terms of flood volume reduction. Additionally, the single blockage scheme and the Poisson distribution-based model show the best performance to enhance the resilience of the network.     

具有中介状态的生命线网络系统抗震可靠性分析

现有的生命线抗震可靠性分析多采用两元易损性假设，即假设单元和系统的工作状态仅有“连通”与“断开”两种，并以连通可靠度近似代替系统抗震可靠性。事实上，系统或单元的工作状态从“连通”与“断开”是渐变的，或者说从连通到不连通之间具有中介状态，通过建立生命线工程的震后工作状态判别准则，定义了“连通-中介-断开”三维可靠性向量。并在传统“连通—断开”模式下的网络系统可靠性评估方法的基础上，提出具有中介状态的生命线网络工程系统抗震可靠性评估方法。     

Linking urban water balance and energy balance models to analyse urban design options

Using a water balance modelling framework, this paper analyses the effects of urban design on the water balance, with a focus on evapotranspiration and storm water. First, two quite different urban water balance models are compared: Aquacycle which has been calibrated for a suburban catchment in Canberra, Australia, and the single‐source urban evapotranspiration‐interception scheme (SUES), an energy‐based approach with a biophysically advanced representation of interception and evapotranspiration. A fair agreement between the two modelled estimates of evapotranspiration was significantly improved by allowing the vegetation cover (leaf area index, LAI) to vary seasonally, demonstrating the potential of SUES to quantify the links between water sensitive urban design and microclimates and the advantage of comparing the two modelling approaches. The comparison also revealed where improvements to SUES are needed, chiefly through improved estimates of vegetation cover dynamics as input to SUES, and more rigorous parameterization of the surface resistance equations using local‐scale suburban flux measurements. Second, Aquacycle is used to identify the impact of an array of water sensitive urban design features on the water balance terms. This analysis confirms the potential to passively control urban microclimate by suburban design features that maximize evapotranspiration, such as vegetated roofs. The subsequent effects on daily maximum air temperatures are estimated using an atmospheric boundary layer budget. Potential energy savings of about 2% in summer cooling are estimated from this analysis. This is a clear ‘return on investment’ of using water to maintain urban greenspace, whether as parks distributed throughout an urban area or individual gardens or vegetated roofs. Copyright © 2007 John Wiley & Sons, Ltd.     

Assessment of reference evapotranspiration across an arid urban environment having poor data monitoring system

Estimation of reference evapotranspiration (ET₀) in urban areas is challenging but essential in arid urban climates. To evaluate ET₀ in an urban environment and non-urban areas, air temperature and relative humidity were measured at five different sites across the arid city of Isfahan, Iran, over 4 years. Wind speed and sunshine hours were obtained from an urban surrounding weather station over the same period and used to estimate ET₀. Calculated ET₀ was compared with satellite-based ET₀ retrieved from the MOD16A2 PET product. Although MODIS PET was strongly correlated with the Valiantzas equation, it overestimated ET₀ and showed average accuracy (r = 0.93–0.94, RMSE = 1.18–1.28 mm/day, MBE = 0.73–0.84 mm/day). The highest ET₀ differences between an urban green space and a non-urban area were 1.1 and 0.87 mm/day, which were estimated by ground measurements and MODIS PET, respectively. The sensitivity of ET₀ to wind speed and sunshine hours indicated a significant effect on cumulative ET₀ at urban sites compared to the non-urban site, which has a considerable impact on the amount of irrigation required in those areas. Although MODIS PET requires improvement to accurately reflect field level microclimate conditions affecting ET₀, it is beneficial to hydrological applications and water resource managers especially in areas where data is limited. In addition, our results indicated that using limited data methods or meteorological data from regional weather stations, leads to incorrect estimation of ET₀ in urban areas. Therefore, decision-makers and urban planners should consider the importance of precisely estimating ET₀ to optimize management of urban green space irrigation, especially in arid and semi-arid climates such as the city of Isfahan.     

Dynamic analysis method of a combined energy dissipation system and its experimental verification

A combined energy dissipation system is developed in this paper. In this system lead rubber dampers and their parallel connection with oil dampers are used in the braces of a structural frame. A dynamic analysis method of the system, including the modelling of the lead rubber damper and the oil damper, is proposed. In the analysis method, the restoring force characterestics of the lead rubber damper is simulated by the Bouc–Wen hysteretic model, and the behaviour of the oil damper is simulated by a velocity and displacement‐related model in which the contributions of the oil damper to the damping force and stiffness of the system are considered. A series of shaking table tests of a three‐storey steel frame with the combined energy dissipation system are carried out to evaluate the performance of the system and to verify the analysis method. The test and analysis show that the performance of the combined energy dissipation system is quite satisfactory and there is a good agreement between the analysis and test results, which indicates that the analysis method proposed in this paper is valid and suitable for the dynamic analysis of the combined energy dissipation system. Copyright © 2002 John Wiley & Sons, Ltd.     

Correlation failure analysis of an uncertain hysteretic vibration system

In this paper, a numerical method for correlation sensitivity analysis of a nonlinear random vibration system is presented. Based on the first passage failure model, the probability perturbation method is employed to determine the statistical characteristics of failure modes and the correlation between them. The sensitivity of correlation between failure modes with respect to random parameters characterizing the uncertainty of the hysteretic loop is discussed. In a numerical example, a two-DOF shear structure with uncertain hysteretic restoring force is considered. The statistical characteristics of response, failure modes and the sensitivity of random hysteretic loop parameters are provided, and also compared with a Monte Carlo simulation.