An approach to the optimum thermal design of office buildings

The paper describes a method for determining a thermal design for an office building which minimizes the sum of initial costs and running costs discounted over the life of the building whilst satisfying constraints deriving from technological and comfort requirements.A thermal model of an office building is described in terms of heat supply and heat losses and some ingenious features of the modelling are presented. Costing techniques for heating and insulating the building are also described. An optimization algorithm based on geometric programming is then applied to the thermal model and typical results are presented. The importance of sensitivity analyses of the results is stressed.     

中国建筑抗震设计规范与欧洲规范Eurocode 8关于抗震设计反应谱的比较

通过比较GB50011-2001《建筑抗震设计规范》、GB50011-2010《建筑抗震设计规范》和欧洲Eurocode8规范,说明GB50011-2010《建筑抗震设计规范》地震影响系数曲线更符合理论意义和统计规律。并按三种规范的规定绘制了不同条件下地震影响系数曲线,利用图形直观地分析了新规范的一些新特点及不足之处。     

短肢剪力墙力学分析模型对比及其选择研究

详细论述了短肢剪力墙这一新型结构体系目前常见的几种结构计算分析模型及其适用性,然后选用不同的分析模型和分析方法对同一个结构进行计算,通过算例分析和比较不同模型计算结果存在差异的原因,最后提出了一些合理选取短肢剪力墙力学分析模型的适用性建议。     

An equivalent stiffness approach for modelling the behaviour of compression members according to Eurocode 3

The development of design procedures based on inelastic advanced analysis is a key consideration for future steel design codes. In advanced analysis the effect of imperfections has to be modelled in such a way that the incremental analysis fully captures this effect in the process of moment redistribution. In modelling the influence of imperfections on the behaviour of individual members of real structures, different approaches have been used to globally represent this effect in the overall analysis of structural systems. They are referred to as the initial bow imperfection approach or as the equivalent transverse load approach. When using the abovementioned approaches in analysis of multiple member structural systems, the designer is required to arrange the directions of bow imperfections or equivalent transverse loads in such a way that the imperfection arrangement leads to the least constrained solution, i.e. the lowest ultimate load predicted from all possible sets of member initial imperfection arrangements. Since there is still ongoing research on the development of simple application rules ensuring that the designer obtains a unique solution when choosing a certain set of member initial imperfections, there is at the same time interest in the development of alternative approaches to modelling the influence of member imperfections on the behaviour of structural systems. This paper provides the necessary background information as well as describes the formulation and modelling techniques used in the development of a new approach to modelling the influence of imperfections on the stability behaviour of structural components and systems. This new approach, called hereafter an equivalent stiffness approach, has an advantage over the previously described approaches since an imperfect member is treated as a hypothetically straight element, flexural and axial stiffnesses of which at each load level are predicted in a continuous fashion dependent upon the actual force and deformation states. This type of modelling does not require any explicit modelling of equivalent geometric imperfections or equivalent forces and their directions in advanced analysis; therefore also it does not require any buckling mode assessment. Moreover, the effects of strain hardening and section class may conveniently be included in modelling. Finally, European buckling curves are used to estimate the values of parameters of the developed model that can be immediately used in advanced analysis conducted according to Eurocode 3.     

A parametric approach for performance optimization of residential building design in Beijing

During the early design stage of green residential buildings, there are tremendous potential of using parametric optimization to achieve preferable green performance, such as building energy consumption efficiency, daylighting, ventilation and thermal comfort. Taking residential design features into consideration, this paper presents an optimization workflow and effects based on a case study of a residential building project in Beijing. Firstly, 27 design parameters related to residential spatial form and building envelope were selected for the optimization. The simulation results of the cooling and heating load were taken as the optimization objects. Secondly, optimized schemes were obtained from 6246 simulation results, with 1925 verified simulation results proving that the optimized result is reliable. Finally, analysis was performed to establish the correlations between design parameters and performance in order to create the easy access for architects to determine design parameters depending on the performance sensitivity of each parameter. Analysis results showed that parametric optimization of spatial form and building envelope at the design stage is a feasible approach to reducing energy consumption in residential building design.

     

表冷器热力计算方法的分析与比较

从理论基础、计算方法及计算精度等几方面对干球温度效率法、湿球温度效率法、干湿工况等价法等表冷器热力计算方法进行了比较.结果表明,干湿工况等价法物理意义明确、计算方法简单、计算精度较高.     

Comparison and further development of parametric tropical cyclone models for storm surge modelling

Cyclone forced storm surges cause severe damage to coastal structures and loss of human lives and properties. In cyclone protection and warning it is important to be able to calculate the cyclone air pressure and wind field on the basis of rather limited information, such as cyclone position, pressure drop, maximum wind speed and radius to maximum wind speed. In the present work, parametric cyclone models based on such limited information are investigated and compared. Analytical expressions of the tangential and radial velocity distributions are derived from the governing momentum equations. It is found that the analytical models provide very similar air pressure and tangential wind speed distributions. Instead of using a simple formulation of the deflection angle, the derived analytical expression of the radial velocity distribution is used and compared to earlier numerical solutions. A procedure is formulated for estimation of the shape of the cyclone on the basis of maximum wind speed versus pressure drop relations. Finally, examples of comparisons of measured and calculated air pressures and wind speeds and directions are presented.     

An alternative approach for the energy and environmental rating of advanced glazing: An electrochromic window case study

The combined methodology for the rating of advanced glazing proposed in this work, aims to add the economical and the environmental aspect to the existing evaluation systems. Taking into account the special characteristics of the advanced glazing, a life cycle assessment (LCA) study and an eco-efficiency analysis have been combined to provide an alternative rating scheme, which has been applied to an electrochromic window as a case study. The proper graphical representation of the selected indicators leads to figures clearly depicting a rating result for the selected product. Such rating schemes can be useful for the consumers and also for the product manufacturers, requesting for additional necessary input apart from its typical technical characteristics only the product expected lifetime, its purchase cost and the energy required for its production.     

A simplified model of fires in road tunnels. Comparison with three-dimensional models and full-scale measurements

A new simplified model (UPMTUNNEL) for the simulation of accidental fires in road tunnels with longitudinal ventilation is presented. The model follows a mixed approach, and has characteristics typical of both field and zone models. Like field models, the proposed model calculates the main properties at every point in the whole domain. The tunnel is divided in two zones: the plume, located upstream from the point at which the smoke hits the ceiling, and a diffusion zone extending downstream. Each of these two regions is analyzed assuming steady-state conditions. The plume is described by one-dimensional conservation equations for turbulent flows. To deduce the 1D equations, the 3D problem is considered to be parabolic along the center-line of the flame, and self-similar profiles in planes normal to this line are assumed. The diffusion region is studied as an incompressible unidirectional problem, described by the energy conservation equation. 3D models and full-scale experiments have been used in order to validate the results of the UPMTUNNEL model. Two different general-purpose codes are employed: FLUENT and PHOENICS, in which the eddy break-up and k–ε–g turbulent combustion models have been, respectively, implemented.     

Comparison and evaluation of analytical models for the design of geosynthetic-reinforced and pile-supported embankments

Geosynthetic-reinforced and pile-supported (GRPS) embankments are becoming more and more popular as this technique showed good performances in practice. Various design methods were introduced to analyze GRPS embankments. However, the applicability of these design methods was not always fully validated. This paper focuses on the review of projects containing field observations of GRPS embankments. The comparison results showed that the assumptions related to the subsoil support, geosynthetic, arching shape, and its evolution are not consistent in the analytical methods. Comparison results with twenty-five full-scale cases and six series of experiments emphasize that these available design methods produce significantly different results in predicting loads transfer mechanism. The analytical models predict arching for cohesionless fill better that for cohesive fill soils. Besides, the analytical methods which consider subsoil support such as the CUR226 and EBGEO methods give results that are in a better agreement with experimental data as compared to other methods which do not consider the subsoil support. The CUR226 (2016) analytical model seems to be able to give the best performance with measured data when compared to other design methods. Finally, the results pointed out that the limit equilibrium model is adequate and has good performance.     

Protecting fire fighters exposed in room fires: Comparison of results of bench scale test for thermal protection and conditions during room flashover

Heat flux conditions measured in seven room fires are discussed. The conditions varied from just below flashover in a sparsely furnished bedroom to flashover and severe postflashover fire in a typically furnished recreation room. These heat flux conditions are compared with the protection level provided by fire fighter turnout coats conforming to NFPA 1971,Protective Clothing for Structural Fire Fighting. This standard requires that the turnout coat or pants assembly must protect the wearer against second degree burns when a heat flux of 84 kW/m² (2 cal/cm².s) is applied to its outside surface for a minimum of 17.5 seconds [thermal protective performance (TPP) of 35]. The results imply that fire fighters have only ten seconds or less to escape under most flashover conditions. However, the turnout coats provide good protection in many other fire situations. Practical definitions for flashover are given, and possible means for making the TPP test more relevant for research and development work are discussed.     

An effective stress-based parametric study on the seismic stability of unsaturated slopes with implications for preliminary microzonation

Bulletin of Engineering Geology and the Environment - The stability of unsaturated slopes under seismic loading has become an important issue over the past few years which is the indication of its...     

中英混凝土规范受剪承载力计算对比

分别介绍了我国和英国混凝土结构设计规范中两种不同思路的斜截面受剪承载力计算方法,并通过算例对其进行对比,在此基础上总结分析了各自的优缺点,对我国混凝土结构的设计具有一定的参考价值。     

An updated and expanded set of thermal property data for green roof growing media

Vegetated (green) roofs alter the roof surface energy balance and hence affect both building energy consumption and the transport of heat into the environment. Quantitative evaluation of the energetics of green roof systems requires accurate knowledge of the moisture-dependent thermal properties of the growing media. To support this need for data and to supplement previously published data we conducted a laboratory study to measure thermal conductivity, volumetric heat capacity, and thermal diffusivity of 12 green roof soil samples of varying composition. The results indicate that thermal properties vary significantly as a function of growing media design. Growing media incorporating expanded slate as their aggregate had thermal conductivities that were two to three times those of media that used a porous silica-based aggregate. Media incorporating expanded clay as the aggregate had thermal conductivities roughly in the middle of these extremes. In general the thermal conductivity nearly tripled as the growing media moisture levels were increased from relatively dry to saturated. Also, it was found that compaction typical of green roof systems that have been installed for multiple seasons can increase thermal conductivity of moist soils by 30-40% over their uncompressed values.     

中、美、日三国建筑门窗保温性能检测标准的比较

随着国内门窗市场的日趋饱和,越来越多的门窗企业将产品打入国际市场。门窗的保温性能是门窗各项性能中非常重要的一项,保温性能的好坏直接影响建筑物的能耗高低。本文通过对中、美、日三国建筑门窗保温性能检测标准的比较,分析了他们的共同点和差别,为国内门窗企业严把质量关,争取更大的国外市场提供一些帮助。     

复合保温石膏板外墙内保温系统热桥部位温度计算和结露情况的设计判定方法

根据<民用建筑热工设计规范>、<夏热冬冷地区居住建筑节能设计标准>等相关建筑节能设计规范,对采用复合保温石膏板外墙内保温系统的建筑围护墙体热桥部位的内表面温度计算方法、热桥结露设计判定进行探讨,并针对全国部分大中型城市的气候条件结合典型建筑围护构造推导热桥部位温度和结露情况.     

An effective approach to prediction of the collapse mode in automotive seat structure

Safety is an important issue in automobile design, in which the seat structure plays a crucial part. Engineering of the seat structure has a wide range of benefits for the manufacturer in the areas of cost savings and better design techniques. The seat in an automobile must not only be comfortable for the passenger, but must also be designed to protect the occupant from a wide range of impact situations. The seat structure in our advancing automotive world must also have a simple, lightweight design to keep down material and manufacturing costs. Despite the importance of seat structure design, many manufacturers do not have the time or money to perform an in-depth analysis of multiple different designs. The nonlinear behaviour of the seat structure forces engineers to use virtual prototyping and numerical analysis in its design. Use of a complex model and the long computation time of a numerical model drive up the cost and limit the turn around time in the production and design of an automobile seat structure.This paper proposes a cost-effective analysis of a seat system to ensure the safety of the occupants in the case of a frontal impact. In order to predict the major collapse mode of a seat structure in this scenario, the strength effectiveness of each component in the seat system is examined using a self-developed experimental procedure. To be sure of shear deformation of the inner track section of the seat structure, a detailed FE simulation is carried out, leading to an effective 2-D finite element method with plastic hinge to represent the major collapse mode. The simulation results are then compared with corresponding tests in order to verify their validity.     

Econometric models of power prices: An approach to market monitoring in the Western US

Given the limitations of data and resources available for market monitoring in electricity markets where regional transmission organizations (RTO) do not exist, we argue that econometric models of power prices could provide a useful screening tool for market monitoring. To explore its feasibility, we developed several econometric models of power prices at two major trading hubs in the West: Palo Verde and Mid-Columbia. We show that our models explain a large portion of the variation in power prices in Palo Verde and can establish a benchmark that can be used to identify outlier prices that are potentially the result of anti-competitive behavior.