基于超固结黏性土CU指标求解函数的“m”法修正

 由于基坑开挖卸载,墙前被动区土体由正常固结状态转化为超固结状态,其固结不排水剪(CU)指标将发生变化,因此弹性地基梁计算理论应予以修正。根据超固结比(OCR)与不排水强度、上覆土压力间关系,引入不排水强度与固结不排水剪(CU)指标间关系,逐步推导出多土层条件下超固结土CU指标的求解函数,将其应用于弹性地基梁“m”法计算理论,提出一种新的考虑分步开挖卸载后被动区黏性土超固结作用影响的m值修正计算法。武汉长江隧道工程有限元算例结果显示,随着超固结比增大,开挖面一定深度下各黏性土层CU指标、m值均有不同程度提高,其中粉土提高幅度尤为大,按该修正法计算出的支护体位移较未修正前更接近实测结果。     

Alkalinity measurements within natural waters: towards a standardised approach

A discussion on the measurement of alkalinity in bicarbonate bearing and acidic waters is presented as a move towards developing a standardised approach within the aquatic sciences. The discussion is based on theoretical and practical considerations. Practical illustrations are provided from measurements of calcium bicarbonate bearing waters (River Thames) and acidic to near neutral waters from acidic soil systems with calcium bearing groundwater sources (the mid-Wales region and the Scottish Dee basin). A comparison of single endpoint and Gran procedures is made and the various error terms assessed. It is concluded that single endpoint and Gran methodologies are applicable in the standard pH titration used in aquatic research (pH 4.5-4.0). However, analytical errors increase, particularly for the single endpoint titration, the lower the endpoint/endpoint-range in pH. For the Thames, the value of a single endpoint over a Gran procedure is illustrated. The Thames results show that some buffering components may still be titrated out within the Gran titration range used: this leads to an underestimate in the alkalinity. Indeed, by making a comparison between single endpoint and Gran alkalinity measurements, the Thames results indicated the presence of unexpected buffering components: the interrogative nature of this type of analysis is highlighted. A standardised approach is outlined.     

采用半主动摩擦阻尼器进行建筑结构综合振动控制和健康监测：第二部分——数值分析

在第一部分中提出的模型修正及采用半主动摩擦阻尼器进行建筑结构振动控制和损伤监测的综合程序的基础上，对所提程序的可行性和应用问题进行数值研究。首次在建筑案例中采用模型修正计划确定结构参数。对影响模型修正的噪声测量、不完全测量信息和阻尼器刚度进行评估。通过与具有相同局部反馈控制策略但没有Kalman过滤器以及具有全部反馈控制策略情况的对比，评估了带有Kalman过滤器，由局部反馈策略控制的半主动摩擦阻尼器建筑物地震响应的控制性能。确定适宜修正和振动控制模型的最优阻尼器刚度。最后，对不同损坏程度和有无噪声污染区域提出了两种破坏情形，以确保损伤监测方案的精确性。另外，对所提出的损伤监测方案与传统的敏感性方法进行对比，数值结果证明了综合程序的可行性。     

Multi-point vibration measurement and mode magnification of civil structures using video-based motion processing

Image-based vibration measurement has gained increased attentions in civil and construction communities. A recent video-based motion magnification method was developed to measure and visualize small structure motions. This new approach presents a potential for low-cost vibration measurement and mode shape identification. Pilot studies using this approach on simple rigid body structures were reported. Its validity on complex outdoor structures has not been investigated. In this study, a non-contact video-based approach for multi-point vibration measurement and mode magnification is introduced. The proposed approach can output a full-field vibration map that increases the efficiency of the current structural health monitoring (SHM) practice. The multi-point approach is developed based on the local phases which also fill the gap of the existing intensity-based multi-point vibration measurement. As an extension of the phase-based motion magnification, the multi-point measurement result is then integrated with the maximum likelihood estimation (MLE) to estimate the magnified frequency bands at each identified structure mode for operational deflection shape (ODS) visualization. This proposed method was tested in both indoor and outdoor environments for validation. The results show that using the developed method, mode frequencies and mode shapes of multiple points in complex structures can be simultaneously measured. And vibrations in each mode can be visualized separately after magnification.     

Multi‐objective Optimization of Sensor and Excitation Layouts for Frequency Response Function‐Based Structural Damage Identification

Abstract: The accuracy of many damage identification methods depends significantly on the quality of measurements collected by sensors, such as accelerometers, concerning the response characteristics of a structure. Often the number of sensors used to collect measurements is limited due to available funds, equipment, and access. In addition, the excitation location can significantly affect a sensor's ability to collect quality measurement information. Therefore, both the location and number of sensors and the location of the excitation must be optimized to maximize the quality of information collected. A multi‐objective optimization approach is presented that minimizes the number of sensors specified while maximizing the sensitivity of the frequency response functions (FRFs) collected at each specified sensor location with respect to all possible damaged structural elements. The multiple Pareto‐optimal sensor/excitation layouts obtained aid in determining the number of sensors required to obtain an effective level of measurement information. The benefit of using Pareto‐optimal sensor/excitation layouts is investigated by using the optimized layouts to collect measurement information for a FRF‐based structural damage identification method. Trial results confirm that an increase in damage identification accuracy and efficiency is achieved when Pareto‐optimal sensor/excitation layouts are used instead of nonoptimal layouts. In addition, the Pareto‐optimal layouts improved damage identification accuracy in noisy measurement environments due to increasing the quality of measurements collected.     

多区域变风量空调系统优化控制研究

变风量系统由于其可观的节能效果在大型商务建筑中得到日益广泛的应用。应用日见广泛的直接数字控制器及集成楼宇控制系统(BMS)大大地提高了空调系统的检测及监控,这也为空调系统在系统层次上的优化控制奠定了基础。本文提出了变风量系统的送风静压和送风温度优化控制方法以及多区域新风量优化控制方法。这些控制方案及控制程序在VAV空调系统的动态仿真平台上进行测试以评估它们的动态控制性能、节能及空气品质特性。     

基于工程量清单的计量支付集成化管理

对当前计量支付中存在的问题进行了分析,以计量支付流程为核心,利用信息技术集成业主、监理和承包商三方,提出基于工程量清单的计量支付集成化管理模型,从而提高工程项目计量支付效率和工程管理效率。     

An integrated approach of form finding and construction simulation for glass fiber‐reinforced polymer elastic gridshells

Glass fiber‐reinforced polymer (GFRP) elastic gridshell is composed of long continuous GFRP tubes and achieves its shape through the elastic deformations during the lifting construction process. However, the complicated mechanical behaviors during the practical forming process are rarely examined in the previous researches. In this research, an innovative approach consolidating the form‐finding analysis and the construction simulation is proposed for the GFRP elastic gridshells. The integrated approach, which is developed with the ABAQUS and Python, is based on finite element analysis and iterative optimization; therefore, the mechanical deformations of gridshell can be accurately taken into account. The procedure of the integrated analysis is comprehensively presented by taking a typical double‐hump gridshell as an example. The form‐finding results (i.e., the flat lattices) derived from the iteration are found to be insensitive to the initial input. The structural behavior indexes (e.g., deflections, support reactions, and sectional stresses) during the lifting construction process are also available in the analysis. Based on the indexes, some general structural features of such gridshells are concluded. The achievements provide novel perspectives for the form‐finding analysis of GFRP elastic gridshells where lifting construction is involved, which is beneficial for the design and analysis of such structures.     

3D Object Classification Using Geometric Features and Pairwise Relationships

Object classification is a key differentiator of building information modeling (BIM) from three‐dimensional (3D) computer‐aided design (CAD). Incorrect object classification impedes the full exploitation of BIM models. Models prepared using domain‐specific software cannot ensure correct object classification when transferred to other domains, and research on reconstruction of BIM models using spatial survey has not proved a full capability to classify objects. This research proposed an integrated approach to object classification that applied domain experts’ knowledge of shape features and pairwise relationships of 3D objects to effectively classify objects using a tailored matching algorithm. Among its contributions: the algorithms implemented for shape and spatial feature identification could process various complex 3D geometry; the method devised for compilation of the knowledge base considered both rigor and confidence of the inference; the algorithm for matching provides mathematical measurement of the object classification results. The integrated approach has been applied to classify 3D bridge objects in two models: a model prepared using incorrect object types and a model manually reconstructed using point cloud data. All these objects were successfully classified.     

Comprehensive evaluation for construction performance in concurrent engineering environment

As a reformation of work pattern, concurrent engineering (CE) is commonly regarded as a systematic approach to integrated, concurrent design of products and its related processes, including manufacture and support processes. In the past several decades, the application of CE in many industries including construction industry has brought about a great enhancement of productivity. On the other hand, the application of CE has also resulted in a series of problems due to the simultaneous execution of different work phases. Among these problems, performance evaluation in a CE environment is a serious one for decision-makers to determine whether CE should be adopted in their blueprint of innovation. In this paper, a new evaluation method for construction performance in a CE environment based on evidence theory is presented. Compared with existing evaluation methods, it can perfectly deal with some negative influences of CE, such as the diversification of evaluation objectives, incomplete information of evaluation objectives, variance of evaluation indexes. In order to illustrate the viability and adaptability of this method, an example of application is given by this paper.     

Postbuckling analysis and imperfection sensitivity of viscoplastic plates and cylindrical panels

The postbuckling behaviour of elastic-viscoplastic rectangular plates and cylindrical panels is analysed. The rate-dependent inelastic material behaviour is modelled by a unified theory of viscoplasticity. Initial geometrical imperfections of the inelastic structure are included and their effect on the postbuckling behaviour is investigated. The analysis relies on an incremental approach in which at each loading increment the Galerkin method is employed. Results are presented for a plate made of an elastic-viscoplastic material and subjected to a uniaxial compression, applied at a constant strain rate on both edges. The results display the applied loading against the out-of-plane displacement, and the effects of loading rate and imperfection sensitivity. It turns out that there is a significant difference between the postbuckling behaviour of a plate in the two cases: (1) when the bifurcation buckling of a geometrically perfect plate occurs in the elastic region, and (2) when it occurs after a plastic flow takes place.     

基于三重底线理论的PPP 项目可持续评价

为解决当前我国PPP模式面临的以经济效益为主要目的,忽视社会与环境影响的问题,针对PPP项目进行系统、全面的可持续性评价迫在眉睫。基于“三重底线”理论,结合PPP项目特征从经济、社会、环境、合作及项目特征5个维度建立了可持续评价指标体系,包括14个可持续标准指标和45个关键属性指标。引入模糊逻辑思维构建评价模型,通过三重模糊数学计算得出PPP项目整体可持续性指数,采用欧几里得距离法确定PPP项目可持续水平,并识别出阻碍项目可持续水平的因素,并以说明性案例分析验证模型的可行性和合理性。     

Profile evaluation of rail joint in a 3-m wavelength based on unsupervised learning

Previously, electronic straightedges with a length of 1 m were widely used to measure the longitudinal profiles of rail joints. However, owing to the lack of an efficient measurement device, rail joints with 3-m wavelengths are seldom studied. In this study, a rail measurement trolley based on the chord-reference method was developed with a measurement wavelength of up to 3 m. A field measurement was performed on a 53-km metro line, and the waveforms of 4340 rail joints were obtained. First, to visualize the distribution of the dataset and to find out the common features, t-distributed stochastic neighbor embedding dimensionality reduction was applied to the rail joint dataset, and each rail joint waveform was mapped to a point in a two-dimensional space. Second, K-means was applied to the rail joint dataset, and six categories of rail joints were obtained. The results indicated that there are two types of rail joints: M-type and W-type, accounting for 18.41% and 76.08% of the total number of joints, respectively, and the remainder are bolted rail joints. Third, to better evaluate rail joint status, the concept of rail joint triangle (RJT) is proposed, and five shape-based features of a rail joint in 3-m wavelength are defined. Finally, using RJT distribution analysis, we observed that the shape-based features provide more essential information about a rail joint, such as symmetry, asymmetry, M-type, or W-type, compared with conventional indexes such as the quality index. Notably, compared with the waveform of a rail joint at 1 m, a 3-m waveform provides significantly more essential information, which can be meaningful for future research on the dynamic impact of rail joints, as well as profile grinding around rail joints. To help other researchers follow our research, our dataset is available on Mendeley Data (RWJ-3 m dataset).     

建成环境可步行性研究及测度发展综述

提高城市步行环境质量是改善城市空间品质的重要一环。可步行性（Walkablity）是评价城市步行环境质量的一种测度,明确其研究发展脉络和影响因素及相应指标有助于指导城市实践。在此背景下,利用WOS（Web Of Science）数据库获得原始文献三千余篇,借助文献信息可视化软件CiteSpace生成文献共被引网络图谱,形成五个话题聚类。通过精读各聚类重点高被引文献,将五个聚类分为了“发展阶段”和“分支话题”两个维度进行具体讨论,剖析其研究要点。梳理了可步行性研究发展脉络,并对可步行性测度指标及方法进行了总结,能为当下城市更新策略提供借鉴,对我国城市可步行性测度方面具有实际意义。     

A Two‐Dimension Dynamic Bayesian Network for Large‐Scale Degradation Modeling with an Application to a Bridges Network

Modeling the stochastic evolution of a large‐scale fleet or network generally proves to be challenging. This difficulty may be compounded through complex relationships between various assets in the network. Although a great number of probabilistic graph‐based models (e.g., Bayesian networks) have been developed recently to describe the behavior of single assets, one can find significantly fewer approaches addressing a fully integrated network. It is proposed an extension to the standard dynamic Bayesian network (DBN) by introducing an additional dimension for multiple elements. These elements are then linked through a set of covariates that translate the probabilistic dependencies. A Markov chain is utilized to model the elements and develop a distribution‐free mathematical framework to parameterize the transition probabilities without previous data. This is achieved by borrowing from Cooke's method for structured expert judgment and also applied to the quantification of the covariate relationships. Some metrics are also presented for evaluating the sensitivity of information inserted into the covariate DBN where the focus is given on two specific types of configurations. The model is applied to a real‐world example of steel bridge network in the Netherlands. Numerical examples highlight the inference mechanism and show the sensitivity of information inserted in various ways. It is shown that information is most valuable very early and decreases substantially over time. Resulting observations entail the reduction of inference combinations and by extension a computational gain to select the most sensitive pieces of information.     

Evaluation of calculation methods of mean skin temperature for use in thermal comfort study

A method was established to evaluate calculation methods of mean skin temperature, in order to find appropriate ones for use in human thermal comfort study. In this method three indexes, including reliability, sensitivity and number of measurement sites, were proposed. Under air temperatures of 21 °C, 24 °C, 26 °C, and 29 °C, 22 subjects’ local skin temperatures (21 sites) and electrocardiograms were measured, and their thermal sensation and thermal comfort were inquired. Human heart rate variability indicated the physiological relation between mean skin temperature and ambient temperature for the sensitivity evaluation. Adopting the evaluation method, 26 types of mean skin temperature calculation methods were evaluated based on the experimental data. The results indicate that a calculation method of mean skin temperature with 10 sites is the most appropriate one, due to its high reliability, excellent sensitivity and fewer measuring sites. When it was applied to reflect thermal comfort, the performance was good.     

Assessment of the integrated urban water quality model complexity through identifiability analysis

Urban sources of water pollution have often been cited as the primary cause of poor water quality in receiving water bodies (RWB), and recently many studies have been conducted to investigate both continuous sources, such as wastewater-treatment plant (WWTP) effluents, and intermittent sources, such as combined sewer overflows (CSOs). An urban drainage system must be considered jointly, i.e., by means of an integrated approach. However, although the benefits of an integrated approach have been widely demonstrated, several aspects have prevented its wide application, such as the scarcity of field data for not only the input and output variables but also parameters that govern intermediate stages of the system, which are useful for robust calibration. These factors, along with the high complexity level of the currently adopted approaches, introduce uncertainties in the modelling process that are not always identifiable. In this study, the identifiability analysis was applied to a complex integrated catchment: the Nocella basin (Italy). This system is characterised by two main urban areas served by two WWTPs and has a small river as the RWB. The system was simulated by employing an integrated model developed in previous studies. The main goal of the study was to assess the right number of parameters that can be estimated on the basis of data-source availability. A preliminary sensitivity analysis was undertaken to reduce the model parameters to the most sensitive ones. Subsequently, the identifiability analysis was carried out by progressively considering new data sources and assessing the added value provided by each of them. In the process, several identifiability methods were compared and some new techniques were proposed for reducing subjectivity of the analysis. The study showed the potential of the identifiability analysis for selecting the most relevant parameters in the model, thus allowing for model simplification, and in assessing the impact of data sources for model reliability, thus guiding the analyst in the design of future monitoring campaigns. Further, the analysis showed some critical points in integrated urban drainage modelling, such as the interaction between water quality processes on the catchment and in the sewer, that can prevent the identifiability of some of the related parameters.     

The systematic use of geotechnical data for characterization of transportation routes

An integrated system approach is presented describing the acquisition, organization and development of route geotechnical data/information for use in planning, analysis and design of complex transportation facilities in geo-technically variable terrain. A unified landform-based approach to geotechnical route characterization is conceptually delineated and formalized. Geotechnical functions required to process data are identified, defined, and integrated into a system within the overall facility design process. Probabilistic techniques used within the characterization approach can objectively consider geotechnical variability and uncertainty including limitations in available geotechnical data/ information. Procedures presented here provide geotechnical tools for project planning, analysis and design of transportation routes.     

Uncertainty in urban stormwater quality modelling: The influence of likelihood measure formulation in the GLUE methodology

In the last years, the attention on integrated analysis of sewer networks, wastewater treatment plants and receiving waters has been growing. However, the common lack of data in the urban water-quality field and the incomplete knowledge regarding the interpretation of the main phenomena taking part in integrated urban water systems draw attention to the necessity of evaluating the reliability of model results. Uncertainty analysis can provide useful hints and information regarding the best model approach to be used by assessing its degrees of significance and reliability. Few studies deal with uncertainty assessment in the integrated urban-drainage field. In order to fill this gap, there has been a general trend towards transferring the knowledge and the methodologies from other fields. In this respect, the Generalised Likelihood Uncertainty Evaluation (GLUE) methodology, which is widely applied in the field of hydrology, can be a possible candidate for providing a solution to the above problem. However, the methodology relies on several user-defined hypotheses in the selection of a specific formulation of the likelihood measure. This paper presents a survey aimed at evaluating the influence of the likelihood measure formulation in the assessment of uncertainty in integrated urban-drainage modelling. To accomplish this objective, a home-made integrated urban-drainage model was applied to the Savena case study (Bologna, IT). In particular, the integrated urban-drainage model uncertainty was evaluated employing different likelihood measures. The results demonstrate that the subjective selection of the likelihood measure greatly affects the GLUE uncertainty analysis.     

Effect of geometrical factors on stability characteristics of portal frames

This paper is concerned with the effect of slanting the columns and changing the ratio of the member lengths on the buckling and post-buckling behaviour of portal frames. Two types of structures are considered: hinged- and rigid-base frames, each type subjected to two loading patterns. In the first pattern (perfect loading), equal vertical loads are applied to the nodes. The second pattern (imperfect loading) consists of the same vertical loads and, additionally, of a horizontal nodal force. Numerical results are presented that show the beneficial effect of slanting the columns by negative angles (i.e. clockwise for the left-hand column and anticlockwise for the right-hand one), and the degrading effect of slanting the columns by positive angles. The effect has been observed both in perfect frames and in the frames subjected to imperfect loading. The paper considers also the effect of the frame geometry on the structure's sensitivity to imperfections. The imperfection sensitivity analysis of the frames is carried out according to a definition of sensitivity which differs somewhat from that commonly used.