Optimal intervention strategies for multiple objects affected by manifest and latent deterioration processes

In the existing infrastructure management systems, optimal interventions strategies (OISs) are determined for objects that deteriorate gradually (manifest deterioration process, MDPs), under the assumption that with appropriate inspection and intervention strategies the probability of failure of object can be neglected. Objects that deteriorate suddenly (latent deterioration process, LDPs), for example, due to scouring during a flood or earth movements during an earthquake are not considered. The determination of OISs for an object that deteriorates due to both MDPs and LDPs requires the consideration of both. The latter, however, means that the probability of failure of the object must be considered. In this article, a Markov model is presented that can be used to determine OISs for multiple objects of multiple types affected by uncorrelated MDPs and LDPs. The model is an extension of the model proposed by Mayet and Madanat (Incorporation of seismic considerations in bridge management systems. Computer-Aided Civil and Infrastructure Engineering, 17:185–193, 2002). In the model, a set of condition states (CSs) is used to describe the condition of objects of each type, where each set is composed of non-failure CSs and failure CSs. The probabilities of going from each non-failure CS to each failure CS are estimated using normalised fragility curves, and the probabilities of going from each non-failure CS to each non-failure CS are initially estimated using the Markov deterioration prediction model of Kobayashi, Kaito, and Lethanh (A Bayesian estimation method to improve deterioration prediction for infrastructure system with Markov chain model. International Journal of Architecture, Engineering and Construction, 1:1–13, 2012a) and later adjusted taking into consideration the probabilities of entering the failure CSs. The use of the model is demonstrated using a road link comprising one road section and one bridge.     

The impact of property price on construction output

The interaction between the construction market and the overall economy has attracted much attention, but few studies have investigated the influence of the property market on the construction market in terms of property price. The disaggregated data of Hong Kong’s housing and retail construction sectors are collected to investigate the impact of property price on construction output. The newly developed autoregressive distributed lag (ARDL) bounds testing approach and the error correction (EC)-based Granger causality test are employed. The bounds testing results suggest that there exist stable long-run relationships between construction output and property price for both housing and retail construction sectors. Specifically, a 1.00% increase in the housing price and retail price lead to a 0.55% and 0.42% increase in construction outputs for the two sectors respectively. In addition, the Granger causality tests confirm a distinct long-run causal flow from property price to construction output. Furthermore, the proposed ARDL approach provides an effective method for forecasting construction output.     

深部基岩地面预注浆模型试验及数值计算分析

依托深部基岩地面预注浆工程,研究了注浆质量控制方法,通过模型试验,对影响注浆的因子进行了试验分析,得出浆液扩散半径和注浆后的结石体抗压强度的影响规律及应用有限元软件分析试验规律的适用条件。     

基于纤维模型的火后钢筋混凝土框架构件性能模拟

对钢筋混凝土框架整体结构中梁、柱、板构件截面进行离散,并对高温损伤后构件(梁、板)截面中的纤维赋予相应温度的材性,对板采用分层壳单元模型,并赋予每层单元相应温度的材性,使受损构件和非受损构件结合组成整体框架结构。利用SAP2000方便快速的建模功能,然后导入ABAQUS中,利用其强大的非线性分析功能进行高温后框架整体力学性能的分析。通过对比发现:荷载—位移曲线、应变等与试验结果吻合较好,表明该方法可靠。借助这种方法,进一步进行了悬臂梁、框架梁火后的应变比较和荷载位移曲线比较并探究其规律,结果表明:翼缘对悬臂梁的承载力和刚度的提高幅度较大,翼缘对框架梁的影响较小。     

高强钢焊接箱形柱受力性能研究(Ⅰ)：残余应力统一分布模型

现有高强钢焊接箱形截面残余应力分布模型仅适用于特定强度等级的高强钢,尚缺乏适用于不同强度等级高强钢的残余应力分布模型。为此,基于不同强度等级高强钢焊接箱形截面残余应力的已有试验,研究钢材的强度等级、板件厚度及宽厚比对残余应力分布和峰值的影响,提出不同强度等级高强钢焊接箱形截面的残余应力统一分布模型。该模型采用多重阶梯函数形状,适用于屈服强度460~960MPa的焊接箱形截面,且满足每个板件自平衡条件和对称性。将残余应力统一分布模型的形状、数值和已有试验结果进行对比,证明该模型的准确性。在基于纤维模型的极限承载力数值分析中,分别采用残余应力统一分布模型和已有分布模型计算高强钢焊接箱形柱的受压承载力,并将各自得到的极限承载力与已有试验结果进行对比。研究结果表明,采用残余应力统一分布模型后,不同等级高强钢焊接箱形柱的纤维模型计算能更准确地预测其极限承载力。残余应力统一分布模型可为不同等级高强钢焊接箱形柱的二阶非弹性分析提供参考。     

CROSS - a Program for Determination of Coefficients of Subgrade Reaction

Soil Mechanics and Foundation Engineering -     

Optimal controller synthesis for second order time delay systems with at least one RHP pole

An optimal H₂ minimization framework is proposed in this paper for devising a controller of PID in nature, based on a refined IMC filter configuration. The tuning strategy is for controlling time delay system with at least one pole which falls on the right half of the s-plane. An underdamped model based filter is used in place of the unity damping ratio (critically damped) filter available in the literature to improve the reset action. The method has a single adjustable closed loop tuning parameter. Guidelines have been provided for choosing the pertinent tuning parameter based on the sensitivity function. Simulation work has been executed on diverse unstable models to support the advantages of the proposed scheme. The proposed controller yields improved performances over other recently reported tuning techniques in the literature. Experimental implementation is carried out on an inverted pendulum for demonstrating the practical applicability of the present method. The efficacy of the intended controller design is quantitatively analyzed using the time integral performance index.     

COUPLING MODEL OF TWO PHASE FLOW IN A FRACTURE-ROCK MATRIX SYSTEM AND ITS STOCHASTIC FEATURE ANALYSIS

This study is concerned with developing a two-dimensional two-phase model thatsimulate the movement of non-aqueous phase liquid (NAPL) in a fracture-rock matrix system. Theintrinsic permeability and the fracture aperture are represented in the model via its Karhunen-Loeve expansion. Other parameters and the nodal unknowns, water saturations and waterpressures, are represented by their stochastic spectral expanions. The errors resulting fromtruncation of Karhunen - Loeve and polynomial chaos expansions to a finite number of terms areanalyzed. The eigenvalues of stochastic process is found out for any point in the special domain ofthe problem at any instant in time.     

基于统计方法的高速钢凸包型仿生表面磨损量建模

采用激光技术在W6Mo5Cr4V2高速钢试件表面加工出凸包型仿生单元。选取凸包的直径、间距和高度作为仿生单元参数,应用Box-Behnken中心组合试验设计方法,设计并进行高速钢仿生表面的摩擦磨损试验,通过回归分析,建立高速钢仿生表面磨损量与仿生单元参数之间的二阶数学模型。分别应用F检验法和相关系数检验法,验证磨损量数学模型显著。磨损量模型的预测精度分析和磨损试验表明,建立的数学模型能够描述磨损量与仿生单元参数之间的关系。通过方差分析,得到高速钢凸包型仿生单元参数对仿生表面磨损量的影响程度依次为间距、高度和直径。     

IFC架构及模型构成分析

针对IFC（建设和设备管理行业工业基础类）标准表达建筑信息模型（BIM）的复杂性问题,分析了IFC标准体系构成的主要思想和BIM模型表达过程的核心环节。在研究IFC标准体系的基础上,梳理了各层之间的资源组织情况。利用一个矩形梁实例,从建筑实体对象、材料属性、关系组织和几何表达等方面,对IFC标准表达BIM模型的过程进行了深入分析,通过分析得到了IFC标准描述建筑信息模型的4个关键要素。