Sustainable Development of Critical Infrastructure

The existing reliability-based codes for structural design must rely on "calibration" in specifying the required level of safety. This means that the safety level underlying a reliability-based design will be the same as that of the current traditional code-based design. In other words, reliability does not contribute to the decision on the required safety level for the design of structures or infrastructure systems. It relies on what is in existing codes of structural design. Proposed is an alternative for the development of reliability-based design in which the decision on the required safety level does not depend on "calibration"; instead, it is based on acceptable risk or risk-averseness. For this purpose, uncertainties are divided into two broad types - namely, aleatory and epistemic. The aleatory type is associated with the variability in the observed information (or data-based), whereas the epistemic type is associated with one's inability to accurately estimate or predict reality (i.e., knowledge-based). The two types of uncertainties can and should be treated separately. In either case, the same probability principles are required and adopted. The effects of the aleatory type are represented in terms of a failure probability; whereas, due to the effects of the epistemic type, the relevant failure probability (or safety index) becomes a random variable. Values within this random variable correspond to different confidence levels. To ensure an adequate safety level of structures, a high confidence level would be appropriate (e.g., the 90% or 95% confidence). Observe that the mean value of the safety index (obtained with the existing total uncertainty approach) is associated with a 50% confidence level which is obviously too low for ensuring safety of structures; thus, the need for calibration. The proposed approach is illustrated with examples of the design of simple structural elements. Also, the safety levels of major infrastructure systems are examined for the purpose of identifying the confidence levels underlying current engineering practice.

Infrastructure systems are subjected to progressive and/or sudden performance deterioration throughout their service life. This deterioration may start from the day the structure enters into service and, if not effectively managed, can cause a significant reduction in the structural functionality and safety. Over the last decades, research efforts have shown that life-cycle management techniques can be successfully used to manage such deteriorating systems. In these techniques, various modules are integrated to form a comprehensive framework responsible for the assessment of the life-cycle performance, analysis of system and component performance interaction, management activities (e.g., inspections, monitoring, and maintenance) optimization, and updating the life-cycle performance based on information obtained from structural health monitoring and/or controlled testing. Nowadays, aspects regarding the evaluation of the time-variant performance are gaining increasing attention in the design, assessment, and management of infrastructure. A special consideration is given to performance measures which cover sustainability aspects. Accordingly, there exists a need for well-established methods which can quantify the metrics of sustainability and allow their integration into the life-cycle management process. The aim of this paper is to highlight the role of life-cycle management concepts and methodologies in the sustainable development of infrastructure systems. The goals and benefits of such management concepts are discussed and their recent applications to bridge structures are presented.

Multi-hazard risk assessment enables one to estimate the benefit of expenditures for risk mitigation - a reduction in potential future losses. This leads to improved decision-making in design, inspection and repair of all types of structures, new and existing. It is especially relevant and useful for complex, spatially distributed systems - such as levees, pipelines and railroads - when seeking to allocate limited resources to different `segments' comprising a long linear `lifeline' (or a network of such lifelines). To demonstrate an approach based on random field concepts (to characterize how loads and resistances vary in space and time), we assess the risk of sliding (limit-equilibrium failure) of long earth slopes, dams or levees. In this instance, the stochastic model indicates fitting observations: (1) that slope failure events involving very long or very short distances along the slope axis are highly improbable; and (2) predicts the "most likely width of the failure zone" for long earth slopes and embankments. It can also evaluate the mean rate of increase in the `system failure' risk-per-unit length, a key controllable parameter in risk management of a system of long linear structures such as levees.

Likely global climate trends and the consequent global sea level rise, combined with potentially increased rates of extreme storms, necessitate the reconsideration of current planning, engineering and management practices of infrastructure. Recent storms, such as the 2012 hurricane Sandy, resulted in inundation of coastal areas, flooding of tunnels and subway stations, power loss, and shutdown of nuclear power plants. Risks from such storms entail significant uncertainties. Increasing resilience to disasters requires bold decisions and actions that may pit short-term interests against longer-term goals. Quantitatively assessing these risks requires the development of spatial risk profiles based on:(1) hazard likelihood assessment; (2) scenario identification; (3) consequence and criticality assessment using inventories of assets along coastal areas, particularly of population centers; (4) vulnerability and inundation assessment; and (5) benefit-cost analysis to manage risks and enhance infrastructure and community resilience. The paper focuses on the Washington, DC area. However, the methodology can be used to examine other regions.

With the turn of the last two decades, sustainability has become a watch word, taking on global dimensions and significance. The concept of sustainability - which calls for a paradigm shift in the status quo of development - has grown to influence core human values encompassing significant attributes such as the physical, economic, and social survival of the human race. Civil infrastructure systems are not left out in this evolution, and stakeholders have drawn attention to the need to design, construct, and manage infrastructure efficiently so as to obtain maximum return on investment in light of increasing demand, dwindling resources, and continued infrastructure deterioration. As a result, different stakeholders have instituted their own ideas about sustainability and how it can be realized for civil infrastructure. Inasmuch as this has helped to broaden the concept of sustainability, it has also created a very fragmented field. This article examines the progression of various sustainable actions and initiatives in the field of highway infrastructure and how these individual entities could be synchronized to standardize developments in the provision of sustainable highway infrastructure.

The United Nations Office for Disaster Risk Reduction reported that the 2011 natural disasters - including the earthquake and tsunami that struck Japan - resulted in $366 billion in direct damages and 29,782 fatalities worldwide. Storms and floods accounted for up to 70 percent of the 302 natural disasters worldwide in 2011, with earthquakes producing the greatest number of fatalities. Average annual losses in the US amount to about $55 billion. Enhancing community and system resilience could lead to massive savings through risk reduction and expeditious recovery. The rational management of such reduction and recovery is facilitated by an appropriate definition of resilience and associated metrics. In this paper, a resilience definition is provided that meets a set of requirements with clear relationships to the metrics of the relevant abstract notions of reliability and risk. Those metrics also meet logically consistent requirements drawn from measure theory and provide a sound basis for the development of effective decision-making tools for multi-hazard environments. Improving the resiliency of a system to meet target levels requires the examination of system enhancement alternatives in economic terms within a decision-making framework. Relevant decision analysis methods would typically require the examination of resilience based on its valuation by society at large. Methods for valuation and benefit-cost analysis - based on concepts from risk analysis and management - are introduced.

This is the first in a succession of papers on the risk analysis of pipelines due to multi-hazards in mountain areas. The present paper is focused on the risk of rain-caused landslide which would induce damage to the pipeline. Considering the spatial variations of soil hydraulic properties - such as permeability and pore size distributions - the random field model for unsaturated seepage is presented by the application of the stochastic finite element method. A 3D probability-based slope stability analysis model due to the rainfall by the application of limit equilibrium method is applied. The spatial variation of soil hydraulic properties is analyzed.

In mountain areas, the pipeline system is friable to multi-hazards such as: (1) the rainfall-induced flood and landslide; (2) the deterioration of the pipe materials due to the erosive effects of soil, gas, and wastewater inside or outside the pipe, and; (3) improper municipal construction. In the second of a series of papers on the risk analysis of a pipeline in a mountain area, the risk analysis models of rain-caused landslide and rain-induced flood are applied to evaluate the safety grade of the pipeline system. The extreme value distribution functions of the rain-induced flooding in different rainfall recurrence intervals are modeled by taking into account the terrain features and surface runoff of a specific gully, and also the statistics of the rainfall records in the recent 30 years in Chongqing. Taking into account the multi-damage modes of the pipe under multi-hazards, a comprehensive hierarchical model for the risk assessment of the pipeline is proposed. In the end, the application of the present model in Chongqing is given approval of its practicability.

When carbonation reaches the depth of the rebar embedded into the concrete, the high alkalinity of the concrete pore solution is neutralised and hydration products are dissolved. As carbonation progresses, the corrosion could extend enough to deteriorate the structural performance. In this paper, a time-dependent structural reliability analysis method, taking the carbonation into consideration, is proposed. To predict the corrosion process of reinforced concrete (RC) structures, spatial variability of corrosion has to be considered. A computational procedure to integrate the spatial variability of corrosion due to carbonation into life-cycle reliability assessment of existing RC structures is established. An illustrative example of a RC structure subjected to carbonation is presented. The emphasis is placed on investigating the effects of the spatial variation of inspected carbonation depths on the reliability estimates of RC structures.

This paper poses the minimization of sustainability impacts from structural upgrades and repairs as a shortest path problem solved by Dijkstra's algorithm. A case study is presented that evaluates the impact of retrofit and repair options in terms of sustainability metrics and "full-cost price". Alternative bridge seismic retrofits and repairs minimizing negative impacts to the environment, economy, and society are found using the proposed algorithm. The sustainability metrics considered are: carbon dioxide emissions, embodied energy, downtime, and monetary costs. In addition to seeking the minimum expected value, the associated variance - as well as the shortest path for the uncertainty of each of these measures - is found. Results highlight impacts of traditional engineering decisions on the environment and society and display uncertainty variations associated with sustainability metrics. This framework is anticipated to help guide the selection of sustainable structural upgrades and, in the future, facilitate accommodation of stakeholder preferences regarding target sustainability measures.

Traffic load effects of multi-span, cable-supported bridges are significantly different from those of small- and medium-span bridges. However, the current traffic load codes are generally specified for small- and medium-span bridges, which are extremely conservative for the design of multi-span, cable-supported bridges. A profound and comprehensive review on existing research of traffic load models for large span bridges is presented, providing theoretical foundation for the concepts of performance-based traffic load models. Different structure performance levels, design states and parameters are discussed under varied traffic load service levels. Novel techniques in related traffic load research fields are introduced to explore the possible performance-based design methodology and process. Application of the traffic load effect analysis is stated by two practical examples. According to the results, it is indicated that concepts of performance-based design are more accurate and efficient for the traffic load effect and provide the structure optimization with favorable conditions.

Key components of life cycle analysis of concrete structures are models for the assessment of the actual condition and for the prediction of its further development. Durability models have to consider the different influencing effects and degradation processes throughout the entire life cycle of a structure taking into account mutual dependencies, interactions, scattering and uncertainties. If reinforced concrete structures have been repaired during their lifetime, aging and deterioration of maintenance measures -like surface coating or concrete cover replacement - also must be taken into account. Degradation mechanisms of repair measures are different and they are going to be crucial for the durability of the repair measure. Taking into account the important parameters - like bond properties between concrete and repair mortar under thermal gradients, or of the adhesion influencing parameters of surface coatings - prediction models are needed. In this contribution, first ideas are presented on how the complex dependencies of the functionality and durability of repair measures may be recorded.

The frost resistance and compressive strength degradation of concrete under the simultaneous action of compressive load and freeze-thaw cycles are experimentally investigated in this paper. In order to track the strength degradation process, the nondestructive tests are carried out after each freeze-thaw cycle to get the residual strength for each specimen. Based on the experimental data, a variable, Kss, is proposed to describe the damage velocity and a prediction model of compressive strength degradation of concrete under freeze-thaw cycles and external load is established. By comparing with other researchers' indoor experiment data and outdoor inspection data, the model is proved to be reliable to predict the compressive strength degradation of concrete in a cold region.

An important issue in structural engineering is improving performance and safety by retrofitting/strengthening or repairing of existing reinforced concrete structures. Attaching a steel bracing system is one of the common solutions for retrofitting or repairing of damaged structures. An efficient load transfer between existing structural members and an attached retrofit system is significant to such repairs. For steel bracing systems, the load transfer between the steel system and existing concrete structures are achieved through proper anchorage between them. A typical steel-to-concrete connection includes a steel attachment - consisting of a baseplate welded to the attached member - and the anchors that actually connect the steel to concrete as bolting system. In the present paper, the reliability method is used to assess the safety of the steel bolting system that is used to connect steel frame systems to existing reinforced concrete columns. Herein, the steel frame systems are used to retrofit/strengthen existing reinforced concrete corbel beams as a structural support system. The effect of applied loadings, bolts geometry, bolts spacing variation and concrete quality on the concrete breakout strength are examined for the current problem. Reliability is assessed by estimating the failure probability of the single bolt failure and system bolt failure. The results are used to determine the parameters affecting safety of the connection system and to improve the performance and the technique of strengthening/repairing of the steel supporting frame systems.

Chinese contractors operating overseas have experienced difficulties in adjusting to the international environment. This, in fact, mirrors earlier international experiences of western firms entering new markets. So, as with much in life, the main lessons have already been learned by our predecessors and the challenge is to pass them on to the next generation. One of the key differences in moving from a relatively mature and well-regulated construction environment, as China is, to a range of different and largely immature markets is the need to become much more aware of risks that in the home market, to a large degree, are covered by an established legal, regulatory and operating environment. To understand the differences, it is first necessary to understand the characteristics of the home market. In China, there are many features of the system that effectively provide a safety net to contractors who fail to perform. This paper describes how the operating environment in China, in many respects, provides a poor grounding for Chinese contractors moving overseas and, hence, how important it is for such firms to adopt a rigorous approach to risk management as will be covered by other papers.

In this paper, project risk management is studied through the fuzzy quantitative evaluation of risks and the counter-measures of its mitigation. Based on knowledge engineering, we established the so-called "Risk-Knowledge Framework" model as the basis of building knowledge base, which serves as the skeleton of system procedure for the problem solving. The fuzzy mathematical model is established for quantitative analysis of different risks through fuzzy reasoning. Correspondingly, a prototype software recognized as Knowledge-Based Fuzzy Decision Supporting System (KB-FDSS), is developed for verifying the solution. Testify of the risks by KB-FDSS through practical project were carried out and favorable results were achieved.

The reinforced concrete structure during construction is a time-dependent structure consisting of a partly-completed structure and a formwork shore system. During construction, the time-dependent structure may be under the most vulnerable stress state and accidents may occur. For safety control, new structural models and analysis methods are proposed to simulate load transfer and demonstrate the influence of daily temperature variation. A new software - Safety Analysis during Construction Considering Temperature (SACT) - is developed. SACT is suitable for analyzing reinforced concrete frames, slab-column systems, and shear wall structures. SACT is developed using modular techniques and object-oriented techniques. Since each module is object-oriented and designed in C++ language, the system development is much less complicated. After comparing with field test data, a good agreement has been observed. The proposed software, SACT, can provide accurate simulation of reinforced structures during construction under various circumstance. It is also a convenient software for construction safety control in practice.

The Norwegian pavilion is a complex membrane structure in the 2010 Shanghai World Expo. A study was made on the key technical problems of the structure design. As it is the first application of the TENARA membrane and a polyester belt is used instead of edge cables of membrane structures for the first time, the tensile test studies the tension performance of the TENARA membrane and polyester belt. The reasonable compensation value of TENARA membranes is put forward to provide reliable data for design on the membrane structure. The study on form-finding analysis of membrane structure and node design is made to ensure the safety of the structure. Further, the global stability of cable-membrane is analyzed by the scale model test. Based on the above study, the mechanical properties of the material are determined and the key technical problems are solved, so the safety and stability of the structure is ensured.

This research aims to propose an effective method which simulates the evacuation process and evaluates the human casualty during the building collapse of a structure. The explicit nonlinear dynamic time-history method is used to analyze the collapse process of a three-story steel frame structure during earthquakes. Combining the cellular automata (CA)-based evacuation simulation with the results of the nonlinear dynamic time-history analysis shows that the occupant flows in the building are mainly distributed in stairs and corridors. When collapse occurs, the main casualties are in the first story corridor. The method quantitatively assesses: (1) seismic casualties, which has a positive effect on the structural design to resist building collapse; (2) the building layout design to speed up evacuation; and (3) the determination of guidelines for post-disaster rescue.

Reinforced concrete elements with a rectangular section are commonly used in frame structural buildings and bridges. Such reinforced concrete structures failed often with the force combination of axial load, bending, shear and torsion caused by wind and earthquake. However, there is little research on four loading combinations: (1) tension/compression; (2) bending; (3) shear; and (4) torsion, especially for the axial force effects on the failure mechanism and bearing capacity of reinforced concrete members. In this paper, a theoretical study and deduction of the unified failure model on the reinforced concrete members with rectangular section under combined axial force, bending, shear and torsion were carried out with the ultimate equilibrium theory. The results of a theoretical analysis were compared with the experimental results of RC members under combined loading actions. Both the theoretical results and test results showed good correlation.

A simple and unified failure model is proposed for rectangular reinforced concrete (RC) members subjected to axial loads, bending, shear force and torsion. As observed in experiments, there are two distinct types of failure mechanisms, ductile failure and brittle failure. They are analyzed separately and different analyses are proposed, respectively, only using failure criteria and equilibrium conditions. In the present paper, a lower-bound limit analysis of ductile failure is proposed. First, the warped 3-dimensional failure surface is demonstrated; then, stress distributions on the failure surface can be described; and, finally, equilibrium conditions would lead to the interaction relationship among external loads.

A simple and unified failure model is proposed for rectangular reinforced concrete (RC) members subjected to axial loads, bending, shear force and torsion. There are two distinct types of failure mechanisms, ductile failure and brittle failure. In the present paper, a lower-bound limit analysis of brittle failure is proposed. The normal-section at failure is considered intact and stress distributions at failure can be presumed. Then, the interaction relationship can be deducted when stress distributions reach the failure criterion of concrete and RC members fails at the same time. Combined with the ductile failure analysis proposed in part I, a unified failure model is obtained and it is in good agreement with experimental results. Not only can this unified failure model explicitly explain failure mechanisms, but ultimate bearing capacities also can be easily calculated and the failure mechanism can be quickly determined. Overall, this model is significant for the analyses of reinforced concrete structures in engineering.

In this study, a new damage assessment procedure is proposed to make assessment of structural damage for masonry-infilled, reinforced concrete (R/C) structures subject to earthquakes. The structural damage index is defined as a weighted combination of damage indices of each component in the structure. The weight factor for each component is determined by considering the effects of the component failure on the structural failure. Then, the state of the structure is classified according to the structural damage index. In the, end a 3-story building is analyzed to demonstrate the feasibility of the presented procedure in practice.

To evaluate seismic performance of superimposed reinforced concrete (RC) walls, six full-scale cantilever units, four representing the superimposed RC walls and two representing the cast-in-place RC walls, were tested under quasi-static reversed cyclic loading. The hysteresis property, deformation capacity and failure patterns of the superimposed walls were studied. Based on the test, micro model finite element analysis (FEA) of the six units was conducted using ANSYS, and the numerical results were compared with the test ones to validate the finite element model. The results indicate that the failure modes, hysteretic loops and envelope curves obtained by the numerical analysis agree well with the test results. The finite element model - considering the concrete interface by using "contact element" - can be used to simulate the behavior of horizontal joints of the superimposed RC walls. The model and parameters adopted are reasonable in analyzing the seismic behavior of superimposed RC walls.

To discuss the robustness of a structure in terms of the rationality of its geometric topology, the relative importance for components is considered as the key. Firstly in this paper, the sphere of influence caused by the local damage on one component is analyzed. As well, the influence distribution map of the local damage is plotted. Then, the quantity of the sphere of influence is proposed and defined as the relative importance for the component. Based on the obtained influence distribution map and the quantitated relative importance, the optimization of the geometric topology of a cable dome to improve its robustness can be further considered. Finally, as an example, the analysis of a Geiger cable dorm is implemented to prove the effectiveness of the presented method. Meanwhile, the roles of the influence distribution map and the quantitated relative importance in optimizing the system are shown.

Robustness has been recognized as the ability of a structure to maintain stable functioning in the face of local damages. The purpose of the robustness analysis is to quantify such an overall performance and to identify the defect of the structural topology. This paper presents a methodology to quantitatively analyze the structural robustness from the topological point of view. In the proposed method, the structural failure is viewed as a transformation and feedback process between the damage input and the failure output. By using the uncertain disturbance and the topological change of the structure to respectively measure two such quantities, the transfer matrix is established not only to describe the structural topology, but also to determine the operation of the closed-loop system. By studying the related properties of the transfer matrix, the importance of each loading path, the robustness of the entire structure, as well as the most vulnerable part of the system can be found concisely.

Local damages to a structure will cause disproportionate collapse if the system is lacking robustness. The engineering significance of robust design is to provide a relatively rational structural form in the conceptual design in order to meet the function of the building and to reduce the impact of the incidents. From the topological point of view, this paper presents a robust design methodology of structures. It includes a detailed discussion on how to describe the structural quality and how to account for the design uncertainty. In the design process, the section parameter of each member in the ground structure is chosen as the design variable. Minimizing structural vulnerability - which is subject to the constraint conditions like construction measures and capacity requirements - is treated as the objective function. The results of the examples show not only the difference between the traditional optimization and the robust design, but also the conformity with the qualitative experiences.

Structural vulnerability has been a main focus in structural community for decades since the collapse of Ronan Point Tower in 1968. Its quantitative evaluation, however, is still a problem today. In this paper, a new concept of flow potential in structures is brought forward, based on which a procedure to evaluate structural vulnerability is presented. Two structure examples are given to demonstrate the calculation of flow potential in structures and the feasibility of the proposed index of structural vulnerability.

A new method is proposed to determine key elements in framed structures, where the relative condition number of the global stiffness matrix is chosen as the quantitative indicator of structural robustness. By comparing the mathematical meaning of the relative condition number with the physical meaning of the structural robustness, the structural robustness can be evaluated from the relative condition number between the modified system and the original structure. A simple statically determinate truss was used to verify the applicability of the proposed approach. A more complex Kiewitt single-layer shell was further adopted to show the effectiveness of the proposed method. The numerical results indicate that the proposed structural robustness indicator can not only clearly reflect the characteristics of framed structures, but also effectively predict the influence of individual structural members on the behaviour of the structural system.

High-speed railway is one of the most important critical infrastructure projects in China and has developed rapidly in recent years. Its operational safety and comfort level draw great attention from the society. The random track irregularities may cause unacceptable dynamic responses of high speed trains and degrade the operational safety and passengers'comfort. In current Chinese safety control practices, comprehensive track inspection cars are used to record track irregularity data and corresponding vibration data of inspection cars at a regular frequency. In this paper, the track irregularities data recorded from Beijing-Guangzhou High-Speed Railway are studied following an advanced stochastic modeling approach. A simplified train-track interaction model is created using SIMPACK, which allows for the numerical analysis of the dynamic responses of high speed trains to randomly track irregularities. On the basis of the simulation results of this simplified model, dynamic response for the train under different traveling velocities is analyzed.

Approaches considered to improve safety at rural high speed signalized intersections most likely will adversely affect the operational aspect of the intersection, and vice-versa. Vehicle Detection Systems and Advanced Warning Systems (AWS) have been used to end the green phase for the major road approaches in a safe manner and to warn drivers of an upcoming change of phase, respectively. If phase termination is by max-out, it will eliminate the expected safety benefit by ending the green phase without considering vehicles that may be traveling the dilemma zone. In order to address this concern, an intelligent detection control system (D-CS) was developed by Texas A&M University. The main feature of this system is to identify if trucks are located in the dilemma zone in order to extend the green beyond the maximum limit to allow them to safely cross the intersection. This research evaluates the D-CS and traditional vehicle detection systems in a Canadian environment. For this evaluation, operational and safety performance of both systems were determined and compared at high speed signalized intersections. This paper only presents results for the operational evaluation. Parameters considered for this evaluation include: control delay, percent of vehicles stopping on red, and percent of vehicles in the dilemma zone. For field data collection, video cameras were used to record actual data (traffic volume, signal timing, others) at two signalized intersections. Results indicated that the D-CS has a better operational performance than the traditional vehicle detection system.

Given the limitations of built-in emission estimation modules within current traffic simulations and signal optimization tools, this study aims to explore how the environmental impacts of transport are related to mobility measurements at signalized intersections based on high-fidelity simulation. The metamodeling-based method - involving experimental design, high-fidelity simulations, and multivariate regression analysis - is developed in this paper. The high-fidelity simulations - from microscopic traffic modeling and emerging emission estimator - provide the flexibility of utilizing various intersection types, vehicle types, and other characteristics such as drivers' behaviors, fuel types and meteorological factors. The multivariate multiple regression analysis provides large gains in expected prediction accuracy by taking the correlations between the response variables into account. The case studies demonstrate the operability of the proposed methodology and also set up the base for extensive application of simulation optimization to sustainable traffic operations and management.

In the area with subway engineering, maintenance optimization is an important issue for engineers and subway administrations because these actions allow maintenance costs to be reduced with acquired reliability. Aiming to optimize the maintenance strategy of subway vehicles, this paper presents a multi-objective maintenance model of cost effectiveness. Moreover, there is no doubt that subway vehicles have more than two statuses, rather than simple linear 0-1 statuses (working or failure). This paper develops a multi-status subway vehicle model to reflect the reality. A multi-population genetic algorithm is employed to solve the non-linear model. Additionally, to subsidize the optimized maintenance strategy, this paper studies a case of driven locking mechanism subsystem in subway vehicle. The result shows the advantages of optimized selective maintenance. The maintenance strategy proposed in this paper reveals a new method of subway maintenance.

This paper generates a failure criterion model to analyze the ultimate strength of a steel-concrete sandwich composite (SC) wall subject to biaxial membrane forces, which are tension and compression on each side of the wall and in-plane shear. The failure criterion is demonstrated in principal stress space and σ_x - σ_y - τ_xy space, respectively. Test data in literature for a steel concrete composite wall is summarized and 7 shear wall tests are conducted to verify the model.

The Pakistan Chashma (PC) nuclear project was constructed on soft soil site. Research was done to find the effect of wave incoherence on PC Nuclear Island. To find out the inner margin in original design response spectra and as a technical support for further seismic margin evaluation, two kinds of incoherence effects were studied: random spatial variation and wave passage. Compared to the results from the coherent analysis, the wave passage effect led to a larger margin than the random spatial variation. Considering the wave incoherence effect will reduce the unnecessary conservative in the seismic analysis of nuclear project.

CAP1400 is a new type nuclear plant designed by SNERDI. As a 3rd generation nuclear plant, it should survive after a large commercial plane crash on its shield building. A large wide-body commercial plane is chosen as the impact aircraft and these phenomena will be modeled by LS-DYNA. This paper will demonstrate the results of these impact simulations and how to check the rationality of these analyses.

Enclosed circular coal yards have been widely utilized for environmental protection and land conservation purposes. On the basis of in-situ testing, experimental modeling, and numerical evaluation, this study presents a comprehensive methodology for the determination of the key design parameters and the experimental and analytical modeling of coal stockpile structural systems. Multiple engineering applications show that the proposed approach is reliable and economical.

Some advances on tower destruction mechanics of overhead transmission lines and prevention technologies in ice disasters are introduced. First, based on the numerical and experimental study on the tower-line system with ice-shedding and broken conductors, dynamic responses of the tower-line system were obtained and the unbalanced tensions, as well as the uplift loads, were proposed. Secondly, study on the bearing capacity of K-type joints with an included angle less than 30 degrees was completed. The first ultra-high voltage (UHV) steel tubular cup type tower in the world was designed for transmission lines in heavy icing areas, and the prototype test was carried out in the UHV tower test station. Thirdly, the bearing capacity and the destruction modes of transmission towers with galloping conductors were studied. A practical calculation method of the galloping loads was obtained. A constructional measure realized by the bolt strengthening technology was proposed for the transmission towers in the galloping area with high intensity. Lastly, the structural reinforcement technologies of the transmission towers after ice disaster were developed, especially for the enhancement of design standards and reinforcement technology for main members of transmission towers.

This paper reviews and analyzes history and the present situation of turbine generator foundation in China for the last ten years. It states dynamic analysis, static deflection analysis and model test technology. By analyzing project examples, this paper introduces the development and application of this technology. In order to advance China's technology of turbine-generator foundation designing, this paper provides reference for designing foundations of turbine generators.

This paper presents an overview of the Shanghai Expo ultra-deep underground substation project and introduces several critical engineering issues encountered in the design and construction. This paper will provide a better understanding of the construction of an underground substation and relevant techniques for underground substation construction.

A power plant is a kind of critical infrastructure. The single-span, concrete, frame-bent structure - called a "single frame structure" - is often used in the main building because of the equipment layout optimized design. The Kobe, Chi-Chi, and Wenchuan earthquakes show that the single-span frames are easily damaged. So, the "Code for Seismic Design of Buildings" (GB50011) and the electric industry codes make strict rules for the use of single-frame structures. In order to distinguish the similarities and differences between a "single frame structure" in the main power plant and a conventional single-frame structure, a dynamic elastic-plastic time-history analysis is carried out based on the characteristics of the main building structure in power plant. The scope of application is given for this kind of structure and the design guide specifically complies with the engineering design.

With a lack of design code for a braced frame steel structure, one research project - Research and Application for Seismic Design of Steel Structure of Main Building in Thermal Power Plant - has been carried out. Systemic experiments and theoretic research for a braced frame steel structure have been completed, and some theories about steel structure arrangement, connection and seismic design have been gained. Construction design for main power buildings of some thermal power plants have been completed according to the achievement, and some experience in design and application has been accumulated. The achievement is conducive in promoting the application of braced frame steel structures.

The pump house of a coastal power plant, adopting a direct current water intake system, is located near the sea, with features of bulky volume, large embedded depth, complex design loads and difficult construction. Pump houses of the Shenzhen Eastern power plant were constructed by floating the caisson. Each caisson weighs 5000 tons and is 30.1 meters long, 19.2 meters wide, and 10.6 meters high. After caissons were prefabricated at a specialized dock, one of them was towed to a semi-submerged barge using airbags. It was then transported to a designated place for diving and fitted into position after floating. Shipping such a large-scale caisson from a dock to a semi-submersible barge is rare in China. Moreover, it may broaden design thought and provide a new construction method for other large pump houses of coastal power plants.

A proper foundation design is crucial for the structural stability of offshore wind turbines (OWT) in the severe ocean environments. As one of the typical foundation types for OWT, the high-rise pile cap foundation has been utilized in wind farms of China. In this study, a 3-dimensional finite element model for simulating the pile-soil interaction subjected to multi-axis complex loads is proposed and verified with existing experimental data. The bearing capacity of the high-rise pile cap foundation under various ultimate limit state (ULS) conditions is investigated. Local scour usually occurs around the pile and significantly reduces the bearing capacity of the foundation. Numerical simulation shows that scour could amplify the lateral displacement and tilt of the foundation.

The operational and environmental variability (OEV) will mask subtle changes caused by damage for in-situ civil infrastructures. Thus, it is one of the obstacles that significantly hinder the application of structure health monitoring. An approach based on cointegration and control chart technique is proposed for identifying damage from continuous, long-term, static response with the presence of varying OEV. Cointegration theory is used as a data normalization technique to remove the stochastic common trend, which is induced by OEV, in the measured static response observed from several locations on the structure. The multivariate, exponentially weighted, moving average control chart is employed as a statistic metric to detect the presence of damage and then the drop-one-out strategy is implemented to localize damage. The proposed method is validated by a numerical simulation and monitoring response from a large-span bridge. Results demonstrate that this method can successfully identify damage despite the operational and environmental variations.

This paper presents the displacement monitoring of expansion joints of long-span steel bridges, with emphasis laid on the effect of viscous dampers. Monitored data from the Sutong Bridge and the Jiangyin Bridge were analyzed and compared with those of the Runyang Suspension Bridge. Decomposition of displacement signals in various frequency bands shows that the temperature-induced movements are only a very small portion of the total cumulative displacements, while - due to the small but fast movements caused by vehicle/wind loads - the cumulative displacements of long-span steel bridges may be very considerable. The viscous dampers can reduce the vehicle/wind-induced displacements but have no significant influence on the temperature-induced movements. In addition, the measured temperature-displacement relationships of the Sutong Bridge are not linear ones (as reported previously), but are hysteretic due to the time delay between temperature and displacement signals.

Random uncertainty is recognized as one of the main barriers against the application of existing damage detection techniques on actual structures. This paper investigates the damage localization of simply supported beams with original random uncertainty. A new index, DIILMSD, which is based on the idea of "Second Order Difference of Displacement Influence Line", has been presented. The damage localization method based on DIILMSD has been theoretically discussed and its application to the random uncertain case is studied as a highlight. Numerical examples have been conducted to examine the suitability of the method. It is proved that this method can work in the presence of random uncertainty in geometric and material properties, which means that it is suitable for real-world beams. Another significant attraction of this method is that only mid-span displacement measurements are required during the application process of this method.

Damage localization of real-world continuous bridges with original random uncertainty is studied in this paper. By employing influence line analysis, an index termed as "Difference Index of Influence Line for Vertical Support Reaction (DIILSR)" has been presented. A damage localization method based on DIILSR has been established. A significant attraction of this method is that a comparatively small quantity of measurements is required because the number of bridge bearings is usually small. Damage position can be detected by comparing two DIILSR graphs before and after damage. If the slopes of two attachment lines between one point (x₂=x' + m) and its two adjacent points change, it can be known that damage occurs within the region [x', x' + m] or [l - x' - m, l - x']. The effectiveness of the proposed method is demonstrated by a numerical simulation performed on a bridge with multiple damages.

An active sensing diagnostic system using PZT for Structural Health Monitor of reinforced concrete has currently been under investigation. As an embedded system, it is good for structural health monitoring of the locations that can't be easily accessed, such as bridge footing areas or piles. To fundamentally understand the damage algorithm, an accurate Finite Element Analysis (FEA) for the system has been performed. In the simulation model, the rebar with PZT and epoxy layers is built using 2D axisymmetric type. The analysis uses the direct coupled-field module. Material properties, such as the Raleigh damping coefficients, are discussed. The numerical model has been validated with the experimental testing. The good consistency between simulation and testing shows that the model is reasonably accurate, which provides a base for further system optimization. A potential signal improvement method is explored. By changing the PZT layout into a different configuration, the output signal is increased to four times larger than the original one. Further simulation analysis is made for concrete structure with debonding damage. The results from simulation are consistent with test ones. It shows that the output sensor's amplitude increases potentially with the debonding size.

For decades, monitoring concepts for structural systems have been subjected to a rapid development process. They have become more and more important in the intervention planning (e.g., maintenance, repair) on new and existing structures. Nevertheless, there is still a strong need for the efficient use of structural monitoring data in the reliability assessment. In an extended sense, structural monitoring can be considered similar to quality assurance and acceptance sampling, since it is not practically possible to continuously monitor all performance indicators in all critical sections of an entire structural system. The aim of this paper is two-fold: (a) the probability density of strain of sensor locations based on the monitoring data was researched; and (b) to shift the reliability index to the differentiation value. An illustration of the proposed approach is provided on Hongdao Bay Bridge located in Qingdao, China. The monitoring system has been working since 2011.

OpenSees is an open-source, object-oriented software framework developed at UC Berekeley. The OpenSees framework has been recently extended to deal with structural behaviour under fire conditions. This paper summarizes the key work done for this extension and focuses on the application of the developed OpenSees to study the influence of fire scenarios and bracing system on the resistance of steel frames against fire-induced progressive collapse. Single- and multi-compartment fire scenarios are applied. Additional horizontal and vertical restraints are applied to the frame to simulate the braced steel frame. A parametric study is carried out to find the fire-induced progressive collapse mechanisms of steel frames under various fire scenarios and restraining conditions. The collapse mode of frames is in the form of lateral drift and downward collapse of frames. It is proved that these two collapse nodes can be resisted by applying lateral and vertical restraint on the frame, respectively. The combination of two restraints has a better resistance effect.

An overview of the performance spectra method is first provided. Using this method, a 3-story, special moment-resisting frame is then retrofitted with four different types of supplemental dampers to meet two different performance targets. The results of the nonlinear time-history analyses show that the trial damping designs obtained by the method were close to the initial performance targets without any design iterations. The performance spectra can underestimate the reduction in base shear due to higher mode effects. However, this can be corrected using the supplemental damping properties computed from the method. This design example demonstrates the effectiveness of the performance spectra procedure for producing trial performance-based designs using different types of supplemental damping devices.

The self-centering, energy-dissipative (SCED) brace is an innovative cross-bracing system that eliminates residual building deformations after an earthquake while simultaneously dissipating energy to reduce drifts. Several recent studies are summarized which have confirmed and extended the capabilities of SCED braces. These include a multi-storey SCED frame shake table test, a high axial-capacity SCED brace prototype, and a telescoping configuration called the T-SCED brace which greatly increases axial elongation capacity. These recent advancements have improved the desirability of SCED braces for use in high-rise structures because the braces can now better accommodate the larger forces and elongations prevalent in tall buildings. SCED braces may also provide an increased level of performance compared to other damping systems for tall buildings because they are designed to return a structure to its original, undeformed position after an earthquake. This paper reviews several potential configurations for the use of SCED braces in tall buildings, including the use of SCED braces in tall braced frames, coupled with shear walls and with vertical outriggers.

Sustainable development requires attention not only to initial costs, but also to long-term performance. Although common structural systems can be designed economically to protect the lives of users during an earthquake, most cannot easily be designed to be usable after an earthquake. As an alternative, controlled rocking systems are being developed to economically provide not only life safety, but also seismic resilience. This paper gives an overview of the research that has demonstrated the seismic performance of controlled rocking systems in concrete, steel, timber, and masonry. Although most practical implementations have been in low- to mid-rise buildings, recent research has shown that multiple mechanisms could make controlled rocking systems competitive for taller structures.

New damping systems - the Viscoelastic Coupling Damper (VCD) and Viscoelastic-Plastic Coupling Damper (VPCD) - have been developed to improve the performance of tall, reinforced concrete (RC) buildings subject to both wind and earthquake loads. VCDs are introduced in lieu of RC coupling beams to take advantage of differential shear deformations between adjacent walls during lateral loading of the structure. The VCDs utilize multiple viscoelastic (VE) material layers that are bonded to alternating steel plates with each consecutive steel layer extending out to the opposite side and anchored into the walls using a number of alternate connection details. When the building is subject to frequent or design level wind storms or low level earthquakes, the damper exhibits both a displacement-dependent elastic restoring force providing coupling to the walls and a velocity-dependent viscous force, providing supplemental damping to the building. In regions of severe seismicity, a ductile "fuse" element can also be included in the damper to enhance its performance. The "fuse" is capacity designed such that if predefined load levels are reached in the damper during extreme seismic loading, connection elements act as force-limiting members and prevent damage from occurring in adjacent structural elements. The response during severe earthquakes is viscoelastic at small amplitudes and becomes plastic once the connections start yielding, resulting in what is termed a Viscoelastic-Plastic (VEP) hysteresis. Replaceable connections are utilized to allow for repair or replacement after an earthquake. This paper describes the Viscoelastic and Viscoelastic-Plastic response of this new damping system and provides some examples of the design concept and applications of this technology.