Stochastic collocation-based nonlinear analysis of concrete bridges with uncertain parameters

This paper focuses on the stochastic response of concrete bridges considering uncertainty in bearing and abutment stiffness. A multi-span simply supported bridge with concrete girders is selected. A 3D-dimensional model is prepared, and nonlinear response history analyses are performed. For the numerical dynamic simulation, the non-sampling stochastic method based on generalized polynomial chaos (gPC) expansion is utilised. The uncertain parameters include the vertical and shear stiffness of bearings and the lateral stiffness of abutments are presented by the truncated gPC expansions. Furthermore, the system response such as base shear, acceleration, velocity and displacement in different columns is presented by gPC expansion with unknown deterministic coefficients. The stochastic Galerkin projection is employed to calculate a set of deterministic equations. A non-intrusive solution, as a set of collocation points, determines the unknown gPC coefficients of the system response and the results are compared with Monte Carlo simulations. The key advantage of spectral discretization is the combination of the mentioned method with the spatial discretization, e.g. finite element model. This study also emphasises the accuracy in results and time efficiency of the proposed non-sampling method for uncertainty quantification of stochastic systems comparing to sampling procedure (e.g. Monte Carlo simulation).     

航空发动机进气总温传感器测温误差研究

航空发动机进口总温测量的准确性是优化发动机控制率、保障发动机飞行安全的关键因素之一。针对影响传感器测量准确性的响应时间、恢复系数，通过空气动力学和热力学理论，分析出具体的影响因素，设计了多种结构模型，并通过热风洞试验、FloEFD软件建模和热流体仿真，从材料及结构上系统地提出了优化途径和改善办法并进行了验证，尤其是分析了双余度传感器的响应一致性误差并提出改善方法。研究结果为同类传感器的设计提供了参考和借鉴。     

Probabilistic seismic damage assessment of reinforced concrete buildings considering directionality effects

Most of buildings and structures are usually projected according to two main axes. However, the geographical position of these buildings varies randomly. Such random distributions of the azimuthal positions of structures, in most of the cities, generally, are not accounted for when assessing their seismic risk; certainly, the direction of the seismic loads is another highly random variable. Moreover, an additional important source of uncertainty is related to the structural response, mainly due to the random character of the mechanical properties. There is a consensus that uncertainties must be considered for adequately assessing the seismic risk of structures, but these directionality effects have not been deeply explored so far. In this article, the influence of the high uncertainty involved in these input variables on the expected seismic damage is analysed. Thus, an actual earthquake, which affected the southern part of Spain, is studied. Notably, damages on a group of affected buildings, located close to the epicentre, are analysed and discussed in detail. The results show that the influence of the random azimuthal position of structures is an important source of uncertainty and that it should be taken into account when estimating the expected seismic risk in urban areas.     

高温气冷堆舱室抗商用飞机撞击的耦合数值分析

本文建立了大型商用飞机撞击典型高温气冷堆核电站反应堆舱室的非线性有限元模型，计算中混凝土舱室直接采用工程用钢筋混凝土的损伤塑性本构模型，飞机结构采用Johnson-Cook本构模型。对飞机高速撞击高温气冷堆核电站反应堆舱室非线性撞击过程进行模拟计算，得出正面和侧面撞击条件下的撞击载荷曲线、撞击位移云图、反应堆舱室混凝土破坏情况等结果。评估表明，反应堆舱室结构在撞击条件下的整体损伤微小，可为保护内部关键设备提供重要的屏障功能。     

两池火耦合作用下柴油拱顶罐热响应的数值模拟

化工园区多池火事故是典型的高后果低概率事件。鉴于目前两池火辐射模型存在一定局限性，本文采用数值模拟方法，以3个直线排布的5000m³柴油拱顶罐为研究场景，从热释放速率、火焰形态、热辐射强度三方面分析两池火燃烧特性，并与单池火场景对比，考虑储罐间距这一影响因素，进一步研究目标储罐热响应。结果表明：采用GB 50160—2008（2018年版）规定的防火间距，两燃烧罐产生的池火会发生耦合作用，并得出目标储罐受到的热辐射强度分布，最高热辐射达17.04kW/m²；两池火作用下目标储罐的温度、Mises应力与失效时间分别为644℃、356MPa、936s，单池火为488℃、280MPa、2880s，目标储罐在两池火作用下的变形也比单池火更为严重；随着储罐间距增加，目标储罐的温度与Mises应力逐渐减小，失效时间逐渐增加，当储罐间距为标准防火间距的2.5倍（20m）时，失效时间为2800s，与单池火作用产生的失效时间2880s较为接近。本研究可为优化储罐防火间距及区域韧性提升提供理论指导。     

[成形过程仿真优化与集成计算材料工程]限定加热管布局的快速热循环注塑成形模具电加热系统优化

针对管道布局、最大允许能耗给定条件下快速热循环注塑成形（RHCM）注塑模具型腔表面快速均匀加热的问题，提出以单根加热棒热流密度为设计变量，以模具型腔表面升温效率和温度分布均匀性为目标，结合有限元模拟、响应面设计以及多目标粒子群优化技术来优化RHCM模具电加热系统。与优化前相比，加热系统优化后，模具型腔表面最大温差降低63.4%，加热系统总能耗降低9%。对比了不同注塑成形工艺条件下成形的平板塑件表面质量，结果表明，相对传统注塑成形（CIM）工艺，RHCM工艺将制品表面粗糙度Ra从320 nm降低到118 nm，并有效抑制了制品表面熔接痕、缩痕等缺陷；发现制品表面粗糙度与型腔表面对应点温度成负相关，说明优化后的型腔表面温度分布更有利于提升制品表面质量。     

Economic Evaluation of Power System Flexibility by Commercial Air Conditioner Control with Large Penetration of Photovoltaic Generation

High penetration of intermittent renewable energy such as photovoltaic (PV) and wind power could cause shortage of power system flexibility. Demand response is expected to help supply ancillary service instead of the conventional power plant. Commercial air conditioners are a promising responsive load for demand response because they account for a large proportion of power consumption in the power system. We calculate a system operation cost and hourly operation pattern of each power plant by using the optimal power generation model considering flexibility supply from controlling commercial air conditioner. We obtained the following results as an effect of commercial air conditioner control. (1) The power generation of oil fired power plants decreases at peak time and annual fuel cost of oil fired plant is reduced by approximately 30% at most in Kanto area. (2) The percentage of rated operation mode of LNG combined cycle plants increases. (3) Curtailed energy rate of PV decreases because a power storage amount by pumped hydropower generation increases. (4) Required battery capacity to reduce PV curtailed amount decreased by combining battery energy storage system in case of high penetration of PV.     

Optimal supplementary frequency controller design using the wind farm frequency model and controller parameters stability region

In most of the existing studies, the frequency response in the variable speed wind turbines (VSWTs) is simply realized by changing the torque set-point via appropriate inputs such as frequency deviations signal. However, effective dynamics and systematic process design have not been comprehensively discussed yet. Accordingly, this paper proposes a proportional-derivative frequency controller and investigates its performance in a wind farm consisting of several VSWTs. A band-pass filter is deployed before the proposed controller to avoid responding to either steady state frequency deviations or high rate of change of frequency. To design the controller, the frequency model of the wind farm is first characterized. The proposed controller is then designed based on the obtained open loop system. The stability region associated with the controller parameters is analytically determined by decomposing the closed-loop system's characteristic polynomial into the odd and even parts. The performance of the proposed controller is evaluated through extensive simulations in MATLAB/Simulink environment in a power system comprising a high penetration of VSWTs equipped with the proposed controller. Finally, based on the obtained feasible area and appropriate objective function, the optimal values associated with the controller parameters are determined using the genetic algorithm (GA).     

A finite line source simulation model for geothermal systems with series- and parallel-connected boreholes and independent fluid loops

A model for the simulation of geothermal systems with parallel- and series-connected boreholes is presented. Mass and heat balance problems are formulated for each component in the system and are assembled into system-level problems. A third problem is formulated to account for heat transfer in the bore field, using the finite line source solution. This third problem is coupled to the system-level heat balance problem by an analytical solution of the heat transfer inside boreholes with multiple U-tubes. The simulation model allows for any number of independent fluid loops within the bore field or within individual boreholes and allows for combinations of specified inlet fluid temperatures and heat extraction rates in independent fluid loops. The model accounts for the axial variation of the fluid and borehole wall temperatures and heat extraction rates. The capabilities of the model are demonstrated through three example simulations.     

Domestic demand-side response with heat pumps: controls and tariffs

ABSTRACT

Electric heat pumps feature prominently in projected energy transitions in the UK and elsewhere. Owing to their high electricity consumption, heat pumps are viewed as important targets for demand-side response (DSR). Findings are presented from a field trial of a new control system that aims to optimize heat pump performance, including under time-varying tariff conditions. The trial involved monitoring 76 properties with heat pumps, but without dedicated heat storage; 31 of these received the control system. Interviews were conducted with a subsample of 12 participants. The controller successfully evened out electricity demand over the day (reducing the evening peak), but this was associated with increased late night and daytime temperatures. Interview participants reported some disturbance owing to overnight heating and noise, as well as usability issues with the controller interface and hardware. These issues present risks to the future acceptability of such systems. While the system delivered short-term demand reductions successfully, longer-term demand shifting risked causing unacceptable disturbance to occupants. Future control systems could overcome some of the issues identified in this pioneering trial through more effective zoning, using temperature caps or installing dedicated heat storage, but these may either limit the available flexibility or be challenging to achieve.