Resilient Cities and Structures最新文献

With increasing demand to reduce the carbon emission of buildings, it is crucial to quantify the life cycle environmental impact of new buildings, including the environmental impact due to natural hazards, such as earthquakes. This study presents a novel comprehensive probabilistic framework to quantify the environmental impact of buildings, including uncertainties in the material extraction and production, transportation, construction, seismic exposure and aging (including deterioration), and end-of-life stages. The developed framework is used to quantify the environmental impact of a 3-story residential building located in Vancouver, Canada. The results show that there is a significant variation in the environmental impact of the prototype building in each stage of the life cycle assessment. If the prototype building is hit by the design level earthquake, it is expected that the median environmental impact of the prototype will be further increased by 42%. In addition, by accounting for the probability of occurrence of different earthquakes within a 50-year design life of the prototype building, the earthquake related damage will result in an additional 5% of the initial carbon emission of the building. This shows the importance of including earthquake hazard and deterioration in whole building life cycle assessments.

Enhancing the resilience of critical infrastructure systems requires substantial investment and entails trade-offs between environmental and economic benefits. To this aim, we propose a methodological framework that combines resilience and economic analyses and assesses the economic viability of alternative resilience designs for a Water Distribution System (WDS) and its interdependent power and transportation systems. Flow-based network models simulate the interdependent infrastructure systems and Global Resilience Analysis (GRA) quantifies three resilience metrics under various disruption scenarios. The economic analysis monetizes the three metrics and compares two resilience strategies involving the installation of remotely controlled shutoff valves. Using the Micropolis synthetic interdependent water-transportation network as an example, we demonstrate how our framework can guide infrastructure stakeholders and utility operators in measuring the value of resilience investments. Overall, our approach highlights the importance of economic analysis in designing resilient infrastructure systems.

A framework is presented to quantify the objective-level resilience of reinforced concrete liners of circular tunnels when exposed to enclosed vehicle fire hazards. By assessing the loss of functionality due to fire-induced damage, the framework enables a decision-basis evaluation of the efficiency of various fire mitigation methods for specific tunnel conditions. In this study, the fire-induced damage of concrete tunnel liners due to strength loss and spalling is stochastically simulated and classified based on typical post-fire repair procedures and damage evaluation. The resilience assessment is conducted using Monte Carlo Simulation in combination with a fast-running tool for calculating the thermal impact from vehicle fires on the inside surface of the tunnel liner (developed by the authors in previous work). The proposed approach accounts for uncertainties associated with both the vehicle fire (particularly the combustion energy) and the tunnel conditions (i.e., geometry, dimensions, and the presence of longitudinal ventilation and/or fixed fire-fighting systems (FFFS)). A parametric case study is used to quantitatively demonstrate the effectiveness of FFFS for reducing post-fire losses of tunnel functionality. Other parameters such as tunnel dimensions, traffic restrictions for vehicles with heavy fire hazard risk, and installation or upgrade of the tunnel ventilation system show somewhat less effectiveness for reducing fire-induced damage.

Highly ductile cement-based materials have emerged as alternatives to conventional concrete materials to improve the seismic resistance of reinforced concrete (RC) structures. While experimental and numerical research on the behavior of individual components has provided significant knowledge on element-level response, relatively little is known about how ductile cement-based materials influence system-level behavior in seismic applications. This study uses recently developed lumped-plasticity models to simulate the unique failure characteristics and ductility of reinforced ductile-cement-based materials in beam hinges and applies them in the assessment of archetype frame structures. Numerous story heights (four, eight, and twelve), frame configurations (perimeter vs. space), materials (conventional vs. ductile concrete), and replacement mechanisms within the beam hinges are considered in the seismic analysis of the archetype structures. Results and comparisons are made in terms of the probability of collapse at 2% in 50-year ground motion, mean annual frequency of collapse, and adjusted collapse margin ratio (ACMR) across archetype structures. The results show that engineered HPFRCCs in beam plastic-hinge regions can improve the seismic safety of moment frame buildings with higher collapse margin ratios, lower probability of collapse, and the ability to withstand large deformations. Data is also reported on how ductile concrete materials can reduce concrete volume and longitudinal reinforcement tonnage across frame configurations and story heights while maintaining or improving seismic resistance of the structural system. Results demonstrate future research needs to assess life-cycle costs, predict column hinge behavior, and develop code-based design methods for structural systems using highly ductile concrete materials.

A 9 m high, near full scale three-storey configurable steel frame composite floor building incorporating friction-based connections is to be tested using two linked bi-directional shake tables at the International joint research Laboratory of Earthquake Engineering (ILEE) facilities, Shanghai, China, as part of the RObust BUilding SysTem (ROBUST) project. A total of nine structural configurations are designed and detailed. To have a better understanding of the expected system behaviour, as well as effects of other structural and non-structural elements (NSEs) on the overall system response, experimental testing at component level has been conducted prior to the shake table testing. This paper presents an introduction to the ROBUST project, followed by a numerical study on one of the nine configurations of the structure, having Moment Resisting Steel Frame (MRSF) in the longitudinal direction and Concentrically Braced Frame (CBF) in the transverse direction. Hysteretic properties employed in the numerical models are validated against component test results. The predictions of the building's seismic response under selected base excitations are presented indicating the likely low damage performance of the structure.

This paper proposes the novel concept of retrofitting damaged reinforced concrete frame with self-centering and energy-dissipating rocking wall. Parametric studies were carried out base on pushover and time-history analysis. In both pushover and time-history analysis, the soft-story mechanism was effectively mitigated through the rocking wall retrofit of the damaged structures. The results demonstrated that the stiffness and bearing capacity of the retrofitted system were improved compare to its intact state. Additionally, the seismic response of the damaged frame retrofitted using rocking wall in combination with post-tension and shear-type damper fell within the relevant design limits. Pushover analysis of the rocking wall indicated that there is a linear relationship between the wall thickness and the initial stiffness of the retrofitted system. The addition of post-tension tendon to the rocking wall system enables the wall to self-center and increases lateral stiffness and bearing capacity of the retrofitted system. When the shear-type damper was installed, the energy dissipation of the system was increased, and the stiffness and bearing capacity of the retrofitted system were also improved. In the time-history analysis, it was found that the thickness of the rocking wall is directly related to the maximum inter-story drift and the distribution patterns of inter-story drift of the frame. As the post-tension was added to the system, the maximum inter-story drift under rare earthquake excitation improved significantly. With the addition of shear-type dampers, the overall drift magnitude of the retrofitted system was fundamentally decreased.

Slender RC walls are used commonly in mid- and high-rise buildings to resist lateral loads arising from earthquakes and wind forces. To accommodate architectural constraints, facilitate construction, and maximize structural efficiency, the majority of these walls have complex configurations, comprising planar and non-planar wall elements that often include regular or irregular patterns of openings. To date most laboratory testing of slender RC walls has employed wall specimens with relatively simple configurations and without openings and coupling action which provides only limited understanding of the impact on performance of the variations in configuration and reinforcement detailing observed in real-world construction.

This study presents a 3D continuum modeling approach to improve understanding of the behavior of walls with complex configurations and support recommendations for design of these systems. Planar wall data were used to calibrate the continuum-type modeling approach; experimental data characterizing the response of non-planar walls and walls with openings are used to validate the model.

The resilience index based on the integral of functionality/performance function within a time interval of interest has been widely used in the literature. However, it cannot fully reflect the sensitivity of the resilience of the object (e.g., structure or system) to the variation of functionality. In this paper, a generalized index is proposed to measure the resilience of structures and systems that is sensitive to the instantaneous functionality, as reflected by a generating function involved in the proposed resilience index. The mathematical properties of the proposed resilience model are discussed. It is proven that, the proposed index varies within [0,1], and is a monotone measure. If the generating function is a power function with $\alpha$ being the exponent (called $\alpha$-fairness function), the additivity property (i.e., superadditivity, additivity, and subadditivity) of the resilience index is dependent on the value of $\alpha$. It is also observed that the existing resilience index is a special case of the proposed one. A byproduct is that, with a properly selected generating function, the time-dependent reliability problem of an aging structure can also be described by the proposed resilience index. The applicability of the proposed resilience model is demonstrated through four examples.

Traditional retrofit methods often focus on increasing the structure's strength, stiffness, or both. This may increase seismic demand on the structure and could lead to irreparable damage during a seismic event. This paper presents a retrofit method, integrating concepts of selective weakening and self-centering (rocking) to achieve low seismic damage for non-code compliant reinforced concrete shear walls. The proposed method involves converting traditional cast-in-place concrete shear walls into rocking walls, which helps to lower the shear demand, while allowing re-centering. Two large-scale lateral load tests were performed to validate the retrofit concept on a concrete shear wall designed according to pre-1970s standards. The design parameters investigated were amount of energy dissipating reinforcements and confinement enhancement. Two different methods using Ultra High Performance Concrete (UHPC) were investigated to provide additional confinement to boundary elements of older shear walls. Observations from the tests showed minimized damage and enhanced recentering in the retrofitted wall specimens. Use of UHPC in the boundary elements of the retrofitted walls provided additional confinement and reduced damage in the rocking corners.