Resilient Cities and Structures最新文献

Use of indices that quantify the seismic residual capacity of buildings damaged in earthquakes is one way to draw judgements on the building's safety and possibility of future use. In Japanese damage assessment guidelines, several approximate calculation methods exist to evaluate the residual capacity of buildings based on visually observed damage and simplifying assumptions on the nature of the building's response mechanism and member capacities. While these methods provide a useful residual capacity ratio that enables a ‘relative’ comparison between buildings, the exact relationship to a physically meaningful residual capacity is unclear. The aim of this study is to benchmark the ‘approximations’ of residual capacity. To do so, a shake-table test was conducted on a ¼ scale 4-storey RC structure and a residual capacity evaluation was undertaken based on observed damage states. With the help of a numerical model, a benchmark residual capacity at each of the damage states is determined and compared to the approximate residual capacity calculation results via guidelines. It was found that approximate methods are generally accurate prior to yield but can become overly conservative post-yield. Simplifying assumptions of equal member deformation capacity used in the residual capacity ratio calculation was found to be suitable given constraints of rapid field evaluations.

This paper studies the behavior of a reinforced concrete (RC) structural frame employing a tessellated structural-architectural (TeSA) shear wall as the lateral-load resisting element. TeSA walls are made of interlocking modules (tiles) that provide easier repairability and replaceability. A nonlinear finite element model of a TeSA wall with tiles interlocking in one direction (1-D interlocking) is validated using test data. An RC frame from a building is modeled with a 1-D interlocking TeSA shear wall. The effects of varying rigidity of the wall-frame connections (rigid, hinged, slotted) on the lateral strength of the system and the axial load demands of the gravity-load resisting systems are evaluated. Finally, the effect of connection details on the damage of the TeSA wall is also studied. The study shows that the lateral strength of the system is the highest with a rigid connection between the wall and the system, followed by the system with hinged connections. Slotted connections, which provided no vertical coupling between the wall and the frame result in the lowest lateral strength. TeSA wall experienced “slight damage” up to a drift ratio of 2%. The system with rigid connections between the wall and the frame experienced the most damage, followed by system with hinged and slotted connections.

This paper presents a simple and practical structural connection able to develop predetermined discrete variable friction forces at target design displacement levels. The innovative connection is termed Modified Friction Device (Modified FD). Modified FDs are used to transfer the seismic induced horizontal forces from the floors to the core wall seismic force-resisting system of a building. The schematics of the physical embodiment of the Modified FD are presented. The components and the assembly of the Modified FD are discussed. The mechanics of the Modified FD are explained. Results from static structural analyses of two types of finite element models of the Modified FD are presented. The first model is developed using solid finite elements and it is used to assess the expected kinematics and the expected force-displacement response of the Modified FD. The second model is developed using a truss finite element and it can be used to efficiently simulate the force-displacement response of the Modified FD in numerical earthquake simulations of structural systems. The force-displacement response of the Modified FD computed using a numerical earthquake simulation of an eighteen-story reinforced concrete core wall building model is presented. The seismic response of the building model with Modified FDs is compared with the seismic response of the building model with monolithic connections and the seismic response of the building model with friction devices with constant friction forces. The results presented in this paper show that it is possible to develop a simple and practical structural connection with predetermined discrete variable force-displacement response to limit the seismic induced horizontal forces transferred between the floors of the flexible gravity load resisting system and the core wall piers in high-performance earthquake resilient buildings.

Diaphragms are essential structural elements of the earthquake-resisting system in a building. Diaphragms are the building slabs subjected to in-plane forces which are transferred to the vertical elements of the earthquake-resisting system. In-plane forces can arise from inertial loads and from self-equilibrating forces caused by the interaction between elements of the vertical earthquake-resisting system of different stiffness. The analysis and design of diaphragms is one of the most challenging tasks in design of buildings nowadays.

This paper describes a stringer-panel model used as a macro-element for the modeling of building diaphragms in linear and nonlinear time-history analyses. The element was coded in the open-source finite element software OpenSees. The linear version of the element is first used to support the design of diaphragms in a building. Then, the nonlinear response of the diaphragms is assessed with the nonlinear version of the element.

Key response parameters of diaphragms modeled with the dynamic stringer-panel method in a high-rise building of complex geometry are presented. Results show significant redistribution of internal forces occurs through the diaphragm after cracking, leading to a general reduction of the tensile forces and an increase in the compressive forces. The clear load path, computational stability, efficiency, and highly design-oriented representation of the results of this method make it an attractive alternative for its use in the modeling and design of diaphragms in performance-based seismic design.

As a novel coupling beam for coupled shear wall structures, the bending-type frictional steel truss coupling beam (BFTCB) concentrates the deformation and energy dissipation in friction dampers at the bottom chord, allowing the main body to remain elastic during earthquakes. As the preparatory work for resilient structure design based on the BFTCB, this work concentrates on developing the hysteretic model for BFTCB. Firstly, the BFTCB stiffness-strength decoupling mechanism was introduced, i.e., the shear strength is provided by friction dampers while webs control its initial stiffness. Secondly, a hysteretic model that reflects the BFTCB two-stage sliding characteristic was proposed. The model consists of a trilinear backbone curve and the unloading and reverse loading rules. The model has eight control parameters, of which two core parameters (initial stiffness and limiting shear strength) are derived from the BFTCB stiffness-strength decoupling mechanism, whereas the remaining parameters are obtained by theoretical analysis and empirical calibration. The hysteretic model was then compared with the test curves and demonstrated good accuracy. Finally, a series of FE prototypes of BFTCB with different design stiffnesses and strengths was adopted to verify the hysteretic model. The results showed that the proposed model fitted well with the FE prototypes, indicating its applicability to BFTCB with varying core design parameters. Therefore, the hysteretic model can be adopted for BFTCB to support the resilient shear wall structure design.

With urban residents’ increasing reliance on metro systems for commuting and other daily activities, extreme weather events such as heavy rainfall and flooding impacting the metro system services are becoming increasingly of concern. Plans for such emergency interruptions require a thorough understanding of the potential outcomes on both the system and individual component scales. However, due to the complex dynamics, constraints, and interactions of the elements involved (e.g., disaster, infrastructure, service operation, and travel behavior), there is still no framework that comprehensively evaluates the system performance across different spatiotemporal scales and is flexible enough to handle increasingly detailed travel behavior, transit service, and disaster information data. Built on an agent-based model (ABM) framework, this study adopts a data-driven ABM simulation approach informed by actual metro operation and travel demand data to investigate the impact of flood-induced station closures on travelers as well as the overall system response. A before-after comparison is conducted where the traveler behaviors in disaster scenarios are obtained from a discrete choice model of alternative stations and routes. A case study of the Shanghai Metro is used to demonstrate the ability of the proposed approach in evaluating the impacts of flood-induced station closures on individual traveler behavior under normal operation and a series of water level rise scenarios of up to 5m. It was found that, when the flood-induced station closures only affect a few river-side stations in the city center, the travelers experience only minor disruptions to their trips due to the availability of unaffected stations nearby as a backup. However, as the water level increases and more stations (mainly in the suburban area) are affected, up to 25% of trips are no longer being fulfilled due to the loss of entrances, exits, or transfer links. The system experiences overall less crowdedness in terms of passenger volume and platform waiting time with a few exceptions of increased passenger load due to concentrations of passenger flows to alternative stations under flooding-induced station closures. The proposed approach can be adapted to other disaster scenarios to reveal the disaster impacts on both aggregated and disaggregated levels and guide the design of more spatio- and temporally-targeted emergency plans for metro systems.

Tunnels are critical infrastructure for the sustainable development of urban areas worldwide, especially for modern metropolises. This study investigates the effects of salient parameters, such as the soil conditions, tunnel burial depth, tunnel construction quality, and aging phenomena of the lining, on the direct seismic losses of circular tunnels in alluvial deposits when exposed to ground seismic shaking. For this purpose, a practical approach is employed to probabilistically assess the direct losses of single tunnel segment with unit length, as well as of tunnel elements representative of the Shanghai Metro Lines 1 and 10, assuming various levels of seismic intensity. The findings of this study can serve as the basis for decision-making, seismic loss, and risk management based on the principles of infrastructure resilience.

Engineering structures are often subjected to the influences of performance deterioration and multiple hazards during their service lives, and consequently may suffer from damage/failure as a result of external loads. Structural reliability and resilience assessment is a powerful tool for quantifying the structural ability to withstand these environmental or operational attacks. This paper proposes new formulas for structural time-dependent reliability and resilience analyses in the presence of multiple hazards, which are functions of the duration of the reference period of interest. The joint impacts of nonstationarities in multiple hazards due to a changing environment, as well as the deterioration of structural performance, are explicitly incorporated. The correlation between the structural resistances/capacities associated with different hazard types is modeled by employing a copula function. It is observed that, under the context of multiple hazards and aging effects, the time-dependent resilience takes a generalized form of time-dependent reliability. The proposed formulas can be used to guide the adaptive design of structures, where adaptive strategies are identified across a range of possible future service conditions. An example is presented to demonstrate the applicability of the proposed method for structural reliability and resilience analyses.

In October and November of 2018, the upper reach of the Yangtze River was blocked twice by landslide dams. A large landslide dam on a major river can impound a huge amount of water and trigger catastrophic flooding once it fails, imposing great risk to the downstream communities. Considering the chain of large dams and densely populated cities along the river, there is an urgent need to improve the system resilience of the Yangtze River to the landslide dam break hazard. This study presents a basin-scale emergency risk management framework based on an overtopping-erosion based dam failure model and a 1-D flood routing analysis model. Basin-wide inundation and detailed flood risk analyses are carried out considering engineering risk mitigation measures, which will facilitate the decision-making on future emergency risk mitigation plans. The proposed framework is applied to the landslide dam on the Yangtze River in November 2018. Results show that excavating a 15 m-depth diversion channel could effectively mitigate the flood risk of downstream areas. Further mitigation measures, including evacuation, removal of obstacles in the river, and preparation of certain intercept capacity in downstream reservoirs, are suggested based on the hazard chain risk analysis. The mitigation results in the case prove the effectiveness of the proposed framework. The incorporation of open-access global databases enables the application of the framework to any large river basin worldwide.

The global petroleum distribution network already faces a significant threat of disruption due to annual coastal flooding of major refining centers, which is expected to further increase with the effects of climate change. This study considers the impacts that sea level rise projections might have on the annual flood risk to coastal refineries, and how regional disruptions propagate across the network. Both the annual regional risk in terms of expected production disruption under a range of climate scenarios, as well as the expected production disruption due to a major flood event impacting refining hubs of high importance are assessed throughout the 21^st century. These risks are propagated across the network to model the global impact of coastal flood-induced refining disruptions. This analysis provides insights on the relative risks that different climate scenarios and flood events pose globally, informing potential mitigation and adaptation needs of critical facilities. Due to the highly interconnected nature of the global petroleum product distribution network, these results highlight the need for mitigation considerations for even regions with low domestic production disruption risk due to coastal flood hazards, as disruptions in remote regions can have cascading consequences resulting in significant disruption to petroleum product supply around the world. Furthermore, such results can inform decisions regarding technology transitions or energy diversification in light of the new understanding of climate risks to coastal refineries and the global petroleum distribution network.