Competing risks models for the deterioration of highway pavement subject to hurricane events

Various methods have modeled failures due to hazard events using joint survival functions by assuming independent failure among the events. This paper evaluates the impact of two competing risks events: “natural” crack deterioration, and hurricane failure (Hurricane Categories 1, 2, and 3), on 6702 highway pavement sections using the nonparametric survival probability (Kaplan–Meier estimates) and the cumulative incidence function (CIF). The risks are compared using the Logrank Test (to indicate if the survival probabilities of the risks are significantly different) and the hazard ratio (ratio of hazard rates based on time to failure covariate). From the results, it was observed that the contribution of the Hurricane Category 3 as a competing risk was significantly higher and different from that of crack deterioration. For example, the hazard ratio of the Hurricane Category 3 was twice that of the crack deterioration for the inland urban interstates roadways. Also, the hazard ratio between hurricane category 3 and crack deterioration was about one hundred and sixty percent for rural interstates and slightly above one hundred percent for urban non-interstates and rural non-interstates. The hazard ratios and CIF plots showed that impact of hurricanes on coastal roadways is more significant compared to the inland segments.     

Probabilistic modelling of the bond deterioration of fully-grouted rock bolts subject to spatiotemporally stochastic corrosion

Developing predictive models for quantitative assessment of the deterioration of rock bolts exposed to corrosive environments is essential for rational planning of maintenance activities for anchorage structures. This article presents a probability-based computational model for predicting the time-dependent deterioration of bond capacity of corroding rock bolts due to the attack of chlorides. The inherent stochastic nature involved in the corrosion and degradation process is identified and simulated. A method is developed based on fundamental Mohr–Coulomb theory to evaluate the effect of corrosion on the bond strength due to a failure mode involving splitting of grout cover. Parameters affecting both strength and stress state at the bolt–grout interface are quantitatively related to the degree of corrosion. Integrating the realised corrosion stochastic process and the developed bond loss evaluation method, a computational algorithm based on Monte Carlo simulation is presented for evaluating the bond deterioration in a probabilistic framework. The presented model is used in an illustrative example to show its capability to trace the evolution, throughout the entire design life, of several representative performance indicators of rock bolts as a structure unit or of the interested location within the anchor length.     

An integrated method to optimise the infrastructure costs of bus rapid transit systems

A significant effort has been directed in many countries to develop economically feasible transportation solutions which include, in many cases, buses that run on express lanes or that are used as part of a feeder system; these systems are identified as ‘bus rapid transit systems’ (BRT). The purpose of this paper is to present a reliability cost-based optimisation model of these systems. The model couples the transportation requirements and the mechanical performance of asphalt pavement structures. Also it includes critical transportation parameters such as bus sizes, frequency of the routes and passenger demands. Regarding the pavement, the model takes into account the life-cycle of existing or new pavements, which involves a stochastic model of the pavement's mechanical properties and its overall performance. The model is applied to the actual case of Bogota's rapid transportation system, i.e. Transmilenio, showing the importance of this integrated approach to build efficient BRT systems.     

An analytical approach for quantification of glazing hazard in buildings subject to external explosive blasts

This paper describes a conservative analytical approach for quantification of glazing hazard in terms of number of casualties among building occupiers from flying glass fragments produced by shattered windows due to external explosive blast. Three main stages are discussed in the proposed analytical approach: modelling nonlinear transient–dynamic response of monolithic windows subjected to conventional explosions, conservative estimation of glass fragment trajectories influenced by additional aerodynamic forces due to vented blast pressures and estimation of casualties. Four injury severity levels are considered, ranging from minor cuts and bruises to multiple serious injuries with significant blood loss. The total kinetic energy of fragments at impact on occupiers is estimated and used to predict the severity level of injuries, with calculation based on available injury data from archive events. Comparison studies presented in this paper highlight the lack of robustness of existing methods towards quantification of glazing hazard due to explosive blasts. The proposed analytical method will be of direct importance to both engineers and practitioners involved with planning glazing retrofits for existing buildings and identifying cost-effective combinations of protection measures for new buildings.     

受荷状态下盾构隧道管片锈蚀劣化破坏过程研究

为研究服役期盾构隧道衬砌结构性能衰退演变规律,从隧道结构长期处于水土荷载和周围离子侵蚀环境耦合作用下的特点出发,根据服役盾构管片压弯荷载受荷特征,采用弯矩、轴力导入的方式,等效地模拟盾构隧道管片的实际受力状态,结合围堰式的电化学加速锈蚀方式,研发了可实现压弯受荷状态下进行盾构管片加速锈蚀劣化的试验系统,重点分析不同工况下盾构隧道管片锈蚀劣化发生发展规律。主要结论有：未锈蚀管片裂缝形态主要以受拉横向裂纹为主;未加载锈蚀管片在锈蚀阶段仅产生顺筋锈胀裂纹,裂纹宽度体现出先增大后趋于稳定的特点,加载破坏阶段锈蚀区混凝土在锈胀裂纹和受拉裂纹共同作用下将出现混凝土局部剥离与错动现象;压弯受荷状态下,管片裂缝的扩展是钢筋锈蚀与外加荷载共同作用的效果,管片受拉裂纹与锈蚀裂纹体现出相伴发生发展的规律,管片承载能力存在较大降低。研究成果可为设计基准期内盾构隧道管片衬砌结构长期安全性能评价提供重要参考。     

Characterising the effect of external factors on deterioration rates of bridge components using multivariate proportional hazards regression

Within asset management of infrastructure systems, increases in maintenance needs subject to budgetary constraints have motivated the development of tools to forecast deterioration to optimise maintenance intervention. Current bridge deterioration modelling approaches, including the evolving duration-based methods, routinely rely on a priori categorisation of bridges based on design, functional, and geographic factors to account for their effects on deterioration rates. However, such preclassification is often based on engineering judgement and may not reflect the true influence of these explanatory factors. In the current study, a proportional hazards regression-based methodology was developed to identify the most critical factors affecting deterioration using the entire unsegmented bridge database. The framework designed to perform this duration-based regression on large bridge databases is presented in this paper and results from implementation on a state inventory of over 17,000 bridges are discussed. The results provide insight into the extent that explanatory factors influence deterioration rates of different bridge components. A novel aspect of the developed framework is its ability to analyse the time-dependent effects of explanatory factors on deterioration rates over the lifecycle of the structural components. This analysis can be used to develop multivariate deterioration models and inform decision-making and prioritisation strategies.     

Analysis and design of steel-concrete composite sandwich systems subjected to extreme loads

This paper presents the design guide based on analytical, numerical and experimental investigation of Steel-concrete-steel (SCS) sandwich structural members comprising a lightweight concrete core with density ranged from 1300 to 1445 kg/m³ subjected to static, impact and blast loads. The performance of lightweight sandwich members is also compared with similar members with normal weight concrete core and ultra high strength concrete core (f _c = 180 MPa). Novel J-hook shear connectors were invented to prevent the separation of face plates from the concrete core under extreme loads and their uses are not restricted by the concrete core thickness. Flexural and punching are the primary modes of failure under static point load. Impact test results show that the SCS sandwich panels with the J-hook connectors are capable of resisting impact load with less damage in comparison than equivalent stiffened steel plate panels. Blast tests with 100 kg TNT were performed on SCS sandwich specimens to investigate the key parameters that affect the blast resistance of SCS sandwich structure. Plastic yield line method is proposed to predict the plastic capacity and post peak large deflection of the sandwich plates. Finally, an energy balanced model is developed to analyze the global behavior of SCS sandwich panels subjected to dynamic load.     

生态城市政基础设施的规划设计及实施评述

介绍了生态城南部片区道路路网布局、道路断面形式、市政排水管网布置形式及排水口的特殊处理方式,论述了气力垃圾收集、处理以及气力垃圾系统,研究了城市家具的种类、功能以及实施情况,并对南部片区的市政基础设施的设计以及实施情况进行了系统的总结,为生态城其他片区的开发建设提供参考。     

Unified solution of limit loads of thick wall cylinder subject to external pressure considering strain softening

Based on the unified strength theory [1], a unified strength criterion for strain softening materials, such as concrete or rock, was derived, and the elastic and plastic limit loads of a thick-walled cylinder made of these materials subject to external pressure were also given. In addition, the influence of some factors on the limit loads of such cylinders as the ratio of the external radius to internal radius, r _b/r _a, the coefficient b, which reflects the effect of medium principal stress and the normal stress of the relevant surface on the material destroy degree, the ratio of tensile strength to compressed strength of the material, α, and the damage variable β were discussed in detail. Some examples were given and some meaningful results were obtained. __________ Translated from Journal of Hunan University (Natural Science), 2006, 33(2): 1–5 [译自: 湖南大学学报 (自然科学版)]     

Reducing risks to electric power infrastructure due to extreme weather events by means of spatial planning: Case studies from Slovenia

The paper concerns the potential for spatial planning to improve the reliability of electric power infrastructure. The aim is to reduce risks of electric power outages due to extreme weather events (EWE) by proper siting of installations. A method of evaluating risks due to EWE is applied in two case studies. The first considers ice storms and the damage they cause to power grids; the second considers the damage of heavy rainstorms to hydroelectric power plants (HPPs). The results are presented in the form of a risk assessment method that can be incorporated into spatial planning.     

自然劣化对文物建筑木质构件热性能的影响

为探讨自然劣化对文物建筑木质构件热性能的影响,采用傅立叶变换红外光谱（FTIR）与差式扫描量热分析法（DSC）对4种文物建筑木质构件样品与云南松现代材样品进行官能基团和热稳定性能测定,讨论了自然劣化对其的影响。结果显示,较软木松而言,硬木松即使在自然劣化后仍然有着较好的耐燃性能。同时,木质构件在自然劣化过程中主要发生了木质素与半纤维素的分解。清代劣化材由于木质素含量减少,干燥阶段与固相燃烧阶段所需温度都有大幅度提前,更易热解。另外,虫害情况越严重,老化材纤维素含量越少,放热量随之降低,同时木构件化学结构越不稳定,劣化材干燥阶段所需温度随之降低,热解反应越剧烈。     

The influence of uncertainties on the selection of extreme values of environmental loads and events

Methods customarily applied in situations involving uncertainties, are shown to have important ramifications on the selection of extreme values used in the design of structural elements subjected to environmental load processes. The more practical choice of uncertainty-free environmental, rather than load effect values as basic design parameters, is investigated. It is suggested that the influence of physical uncertainties be anticipated by judiciously increasing the return period of the environmental extreme value; model uncertainty can be taken into account by applying an appropriate safety factor to the corresponding design load effect.     

Optimal design of symmetric angle-ply laminates subject to nonuniform buckling loads and in-plane restraints

Optimal buckling designs of symmetrically laminated rectangular plates under in-plane uniaxial loads which have a nonuniform distribution along the edges are presented. In particular, point loads, partial uniform loads and nonuniform loads are considered in addition to uniformly distributed inplane loads which provide the benchmark solutions. Poisson's effect is taken into account when in-plane restraints are present along the unloaded edges. Restraints give rise to in-plane loads at unloaded edges which lead to biaxial loading, and may cause premature instability. The laminate behaviour with respect to fiber orientation changes significantly, in the presence of Poisson's effect as compared to that of a laminate where this effect is neglected. This change in behaviour has significant implications for design optimisation as the optimal values of design variables with or without restraints differ substantially. In the present study, the design objective is the maximisation of the uniaxial buckling load by optimally, determining the fiber orientations. The finite element method, coupled with an optimisation routine, is employed in analysing and optimising the laminates. Numerical results are given for a number of boundary conditions and for uniformly and non-uniformly distributed buckling loads.     

冷弯薄壁型钢墙柱骨架的轴压性能试验研究和设计建议

由立柱和导轨通过自钻螺钉相连的冷弯薄壁型钢墙柱骨架是轻钢住宅系统中的竖向承重单元。本文对无支撑、钢带支撑、槽钢支撑和十字交叉钢带支撑的C型截面柱的墙柱骨架进行了在轴心压力作用下的足尺试验。试验结果表明:支撑试件比无支撑试件极限承载力最大提高20%,立柱的破坏模式为弯曲屈曲和弯扭屈曲。通过研究现行设计规范与试验结果的误差,提出了在导轨和支撑约束条件下C型截面立柱的计算长度系数可取为0.8。     

钢筋混凝土框架结构抗震与抗连续倒塌的比较

从钢筋混凝土结构受力机制和倒塌破坏准则两方面,对抗震与抗连续倒塌的区别进行了分析与比较,结果表明：抗倒塌不同于抗震,结构抗震设计的有益作用并不能取代抗倒塌设计。     

BLWT tests and design loads on the roof of the new olympic stadium in Piraeus

The paper introduces some peculiar and innovative aspects by the experimental tests carried out in a boundary-layer wind tunnel (BLWT) for the design of the roof of the new Olympic soccer stadium in Piraeus, Greece, using simultaneous pressure measurements and state-of-the-art processing techniques. The wind tunnel data are then used for the numerical simulation of the quasi-static response of the structure in the time domain, so obtaining the time histories of the structural response. The extreme values of the wind effects are evaluated directly from the statistical analysis of the corresponding time histories and are compared with those from dead loads. Finally the uniform pressure distributions are identified which produce the same extreme values of wind effects.     

钢筋混凝土框架抗倒塌与抗震设计的对比分析

以一栋六层框架结构为例,对其抗倒塌设计与抗震设计的结果进行了分析,研究结果表明,抗倒塌设计不同于抗震设计,并提出抗倒塌设计的一些措施,为将来工程抗倒塌设计和相关方面的设计提供了参考依据。     

“递进式”课程设计模式探索与实践——以项目学习法为例

针对目前工程管理专业课程设计各自独立,学生工程整体意识不强的现状,文中从专业培养目标出发,在研究项目学习法的基础上,探索了按照主干课程的开设顺序,依次完成"工程经济与项目评价课程设计—房屋建筑学课程设计—工程估价课程设计—工程招投课程设计(含施工组织设计)—工程项目管理课程设计"各个教学环节,形成了依托于一个工程项目的"递进式"课程设计新模式。新模式的实施,加深了学生对工程整体的认识,实现了建筑设计的三个融合,提高了学生的综合设计能力,并阐述了新模式的组织方式、不足之处及其改进措施。     

新广州火车站雨棚挡雨板结构风荷载优化设计研究

采用数值模拟方法,对新广州火车站雨棚挡雨板结构进行了方案优化设计研究,以减小结构风荷载。数值模拟显示,挡雨板的位置若进行微调,承受的风荷载可显著降低,从而在不增加任何投入的前提下,提高结构的抗风安全性。研究还表明,通过建立适当的数值风洞模型,不仅可获得可信的结果,而且可从流动本身进行机理解释,数值模拟方法是进行此类结构...