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。     

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.     

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。     

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 assessment of the current Eurocode 1 design methods for building structure steel columns under vehicle impact

This paper presents a detailed assessment of the static and dynamic force requirements in Eurocode 1 for the design of steel columns under vehicle impact. Numerical simulations of steel columns under vehicle impact were carried out using the finite element package ABAQUS/Explicit. In these numerical simulations, the vehicle was represented by a spring–mass system which had been validated previously by the authors. The assessment results indicate that the equivalent static design force approach in Eurocode 1 is generally conservative for small and moderately sized columns that are typically used in low and medium multi-storey buildings (less than 10 storeys). For bigger columns, it is unsafe to use the Eurocode 1 equivalent static forces. It has also shown that it is acceptable to use a dynamic impulse to represent the dynamic action of vehicle impact on columns, but it is important that both the column and vehicle stiffness values should be included when calculating the equivalent impulse force–time relationship. It is also necessary to consider the two stages of behaviour of the impacting vehicle, before and after the column is in contact with the vehicle engine. This paper presents a method to implement these changes.     

Urban microclimate and energy consumption: A multi-objective parametric urban design approach for dense subtropical cities

Climate change within the urban contexts is a crisis that cities are confronting globally. This issue poses numerous negative consequences such as thermal discomfort and increased energy usage within the building sector. This is especially the case in Western Sydney, Australia, where the average maximum temperature has risen by 7–8 °C within the past 30 years. This increase in temperature is highly concerning, since this region is witnessing rapid urban and infrastructural development and is proposed as the third-largest economy of Australia. Temperature changes in this region will also result in considerably increasing the electricity used for cooling purposes. This paper presents a parametric approach driven multi-objective optimization methodology to discover optimum design solution based on the urban microclimate and cooling energy demand of multi-functional buildings within this urban context. Mitigation measures including a range of design factors at both building (typology and window to wall ratio) and urban scales (aspect ratio and urban grid rotation) are further suggested for developing context sensitive optimum urban layouts. The resultant solutions indicate an improvement in urban thermal comfort, cooling and heating energy use by up to 25.85%, 72.76%, and 93.67%, respectively.     

An integrated ergonomics framework for evaluation and design of construction operations

Labor is one of the most critical resources in the construction industry due to its impact on the productivity, safety, quality, and cost of a construction project. Ergonomic assessment, as a tool and method for analyzing human activities and their interactions with the surrounding environment, is thus crucial for designing operations and workplaces that achieve both high productivity and safety. In construction, however, the constantly changing work environments and laborious tasks cause traditional approaches to ergonomic analysis, such as manual observations and measurements, to require substantial time and effort to yield reliable results. Therefore, to simplify and automate the assessment processes, this study explores the adaptation and integration of various existing methods for data collection, analysis, and output representation potentially available for comprehensive ergonomic analysis. The proposed framework integrates sensing for data collection, action recognition and simulation modeling for productivity and ergonomic analysis, and point cloud model generation and human motion animation for output visualization. The proposed framework is demonstrated through a case study using data from an off-site construction job site. The results indicate that integrating the various techniques can facilitate the assessment of manual operations and thereby enhance the implementation of ergonomic practices during a construction project by reducing the time, effort, and complexity required to apply the techniques.     

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.     

Collision avoidance,virtual guides and advanced supervisory control teleoperation techniques for high-tech construction: framework design

One of the biggest challenges to drill deeper tunnels in the future is to design new maintenance tools. Advanced teleoperation and supervisory control techniques were identified in the Telemach project as potential solutions to carry out this work. Due to limitations of the existing systems, a complete framework merging virtual reality tools and real equipment was designed. A wide range of assistances were developed to reduce the impact of secondary tasks during the maintenance process, offer helpful guiding capability and secure the task execution according to the context. The feasibility of the principle was demonstrated on key operations on a scale one mock-up of a Tunnel Boring Machine section. Attention was paid to develop generic tools, meaning that the whole high-tech construction industry could benefit from these new technologies.     

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.     

Improving interoperability between architectural and structural design models: An industry foundation classes-based approach with web-based tools

Medium and large construction projects typically involve multiple structural consultants who use a wide range of structural analysis applications. These applications and technologies have inadequate interoperability and there is still a dearth of investigations addressing interoperability issues in the structural engineering domain. This paper proposes a novel approach which combines an industry foundation classes (IFC)-based Unified Information Model with a number of algorithms to enhance the interoperability: (a) between architectural and structural models, and (b) among multiple structural analysis models (bidirectional conversion or round tripping). The proposed approach aims to achieve the conversion by overcoming the inconsistencies in data structures, representation logics and syntax used in different software applications.The approach was implemented in both Client Server (C/S) and Browser Server (B/S) environments to enable central and remote collaboration among geographically dispersed users. The platforms were tested in four large real-life projects. The testing involved four key scenarios: (a) the bidirectional conversion among four structural analysis tools; (b) the comparison of the conversion via the proposed approach with the conversion via direct links among the involved tools; (c) the direct export from an IFC-based architectural tool through the Application Program Interface (API), and (d) the conversion and visualization of structural analysis results. All these scenarios were successfully performed and tested in four significant case studies. In particular, the conversion among the four structural analysis applications (ETABS, SAP2000, ANSYS and MIDAS) was successfully tested for all possible conversion routes among the four applications in two of the case studies (i.e., Project A and Project B). The first four steps of natural mode shapes and their natural vibration periods were calculated and compared with the converted models. They were all achieved within a standard deviation of 0.1 s and 0.2 s in Project A and Project B, respectively, indicating an accurate conversion.     

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.     

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.     

The smoothed finite element method (S-FEM): A framework for the design of numerical models for desired solutions

The smoothed finite element method (S-FEM) was originated by G R Liu by combining some meshfree techniques with the well-established standard finite element method (FEM). It has a family of models carefully designed with innovative types of smoothing domains. These models are found having a number of important and theoretically profound properties. This article first provides a concise and easy-to-follow presentation of key formulations used in the S-FEM. A number of important properties and unique features of S-FEM models are discussed in detail, including 1) theoretically proven softening effects; 2) upper-bound solutions; 3) accurate solutions and higher convergence rates; 4) insensitivity to mesh distortion; 5) Jacobian-free; 6) volumetric-locking-free; and most importantly 7) working well with triangular and tetrahedral meshes that can be automatically generated. The S-FEM is thus ideal for automation in computations and adaptive analyses, and hence has profound impact on AI-assisted modeling and simulation. Most importantly, one can now purposely design an S-FEM model to obtain solutions with special properties as wish, meaning that S-FEM offers a framework for design numerical models with desired properties. This novel concept of numerical model on-demand may drastically change the landscape of modeling and simulation. Future directions of research are also provided.     

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...     

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.