Resilient Cities and Structures最新文献

Resilience of a community after an extreme event depends on the resilience of different infrastructure including buildings. There is no well-established approach to characterize and integrate building resilience for community-level applications. This paper investigates how different potential functionality measures can be used to quantify building resilience indexes, and how the results could be aggregated for a set of buildings to provide an indicator for the resilience of an entire community. The quantification of building resilience is based on different functionality measures including repair cost, occupancy level, and asset value. An archetype city block with four different buildings is defined. The individual results for each building are combined using a weight-based approach to quantify the resilience index for the city block. The study then considers small-scale communities with different number of buildings to investigate the influence of contractor availability and collapse probability on the resilience indexes for the set of buildings. Both parameters are shown to be important when quantifying the resilience index. It is also demonstrated that the overall resilience of a community is directly influenced by the resilience of individual buildings. The findings presented here are useful both from the perspective of quantifying the resilience of a community on the basis of its building inventory, as well as for possible inclusion into a holistic framework that aims to quantify community resilience.

Rapid urbanization has resulted in increased demand for tall buildings in many large and medium-sized cities around the world. Current code-based standards for seismic design are primarily aimed at minimizing life-safety risks under major earthquakes. While reinforced concrete (RC) high-rise buildings designed following current code requirements are expected to achieve collapse-prevention, the contribution of higher modes of vibrations to the dynamic response of these structures can produce seismic demands significantly larger than those obtained from prescriptive code-based procedures, causing unexpectedly higher structural and non-structural damage to these buildings. These imply considerable costs associated with the loss of residences and business operations as well as the post-earthquake recovery of cities. This paper presents a concise review of the current state-of-the-art and state of research pertaining to the understanding, estimation and mitigation of higher-mode effects on the seismic response of tall and slender RC structures. The paper is organized into four main foci: (1) analytical studies on understanding and quantifying higher-mode effects, (2) available experimental work on this topic, (3) advances in code practices in accounting for higher-mode effects in seismic design of RC tall buildings, and (4) recent developments in innovative systems intended to mitigate higher-mode effects in RC tall buildings. The paper concludes by briefly summarizing future challenges facing the construction of earthquake-resilient RC tall buildings that are essential in building resilient cities of the future.

Climate change can accelerate infrastructure deterioration in coastal areas because increased temperature and humidity can promote steel corrosion. This study (1) projects corrosion rate changes for reinforced concrete and steel structures in 223 coastal counties, (2) assesses the impact of corrosion rate changes on the useful life of structures, and (3) evaluates direct economic losses due to shortened useful life of highway bridges over the period 2000-2100. The results show that the useful life of concrete structures may decrease by 1.7-2.7% under the representative concentration pathway (RCP) 8.5 and decrease by 0.7-1.1% under RCP 4.5 by the end of the 21st century. The useful life of steel structures may decrease by 7.9-15.9% under RCP 8.5 and 3.3-6.7% under RCP 4.5. Concrete bridges may suffer an average loss of $6.5-11.7/m² under RCP 8.5 and $3.3-16.5/m² under RCP 4.5 due to shortened useful life. Steel bridges may suffer an average loss of $73.4-111.3/m² under RCP 8.5 and $46.9-81.2/m² under RCP 4.5. In both climate scenarios, 10% of counties may have negative losses and 10% of counties may have losses greater than $20 million due to corrosion rate changes for concrete and steel bridges. The results reveal the spatial difference of climate change impacts on infrastructural deterioration and suggest the importance of developing regional specific adaptation strategies.

Tornadoes can destroy or severely damage physical infrastructure including buildings in a community. This can result in direct losses but also indirect losses such as the closure of key social institutions reverberating further through the community (e.g., schools). Despite significant losses in past events, building codes and standards have not previously included tornado hazards because of the relatively low probability of a direct strike. The recent release of the ASCE 7–22 standard considers tornadoes for Risk Category 3 and 4 buildings, i.e. ranging from schools to critical facilities. This study proposes a series of design combinations of a reinforced masonry school building with different performance targets intended to enable schools to reopen sooner. Tornado fragilities were developed for a school building having improved designs using tornado loads determined based on the new tornado chapter in ASCE 7–22, and then integrated into a community level model with school attendance zones to examine the effect. The ultimate goal in this study is to investigate the effect of improving school building designs would have on maintaining school continuity (and more rapid return) for school children.

This paper proposes kriging metamodels for the dynamic response of high-rise buildings with outrigger systems subject to seismic and wind loads. Three types of outrigger systems are considered. Three-dimensional (3D) finite element models of high-rise buildings with outrigger systems are developed using ANSYS. Data generated from the finite element models are used to develop the proposed kriging metamodels. A sensitivity analysis is then carried out to determine the most sensitive input parameters in kriging metamodels to gain insights and suggest possible future developments. The proposed kriging metamodels are used to develop fragility estimates for high-rise buildings with three types of outrigger systems under seismic and wind loads.

Tools that quantify community disaster resilience are essential for informed decision-making on community disaster resilience improvement measures. One of the major research gaps in quantifying community disaster resilience are community disaster recovery simulations. Such simulations enable an insight into factors that enable a rapid and efficient community disaster recovery and vice versa. The iRe-CoDeS framework presented in this paper, simulates community disaster recovery as a time-stepping loop, where at each time step the interplay of demand and supply of community components for various resources and services dictates components’ ability to operate and recover. Disaster resilience of a community is then quantified using a multi-dimensional metric, where each dimension represents the unmet demand of a community regarding a certain resource or a service, labelled Lack of Resilience (LoR). This paper presents how such a demand/supply approach can be applied to account for resource and service constraints, impeding factors, that prolong component recovery and thus decrease community disaster resilience. Housing resilience of North–East San Francisco exposed to a Mw7.2 earthquake on the San Andreas Fault is quantified to illustrate the proposed approach. rWhale application framework recently developed at the NHERI SimCenter is used for this purpose, presenting how such a regional simulation on the effect of natural disasters on communities can be extended using the iRe-CoDeS framework to simulate community disaster recovery and quantify community disaster resilience. It is shown that housing resilience quantification results obtained in the case study focused on a part of San Francisco are in accordance with the existing estimates of housing resilience. The evolution of the post-disaster community-level supply and demand for recovery resources and services is obtained, identifying how and when the unmet demand for these resources and services impedes community recovery. Lastly, the effect of community’s ability to mobilize resources and services needed for its recovery on its disaster resilience is investigated.

Balloon type cross laminated timber (CLT) rocking shear walls are a novel seismic force resisting system. In this paper, the seismic performance of four 12-story balloon type CLT rocking shear walls, designed by a structural engineering firm located in Vancouver (Canada) using the performance-based design procedure outlined in the technical guideline published by the Canadian Construction Materials center (CCMC)/National Research Council Canada (NRC), is assessed. The seismic performance of the prototype CLT rocking shear walls was investigated using nonlinear time history analyses. Robust nonlinear finite element models were developed using OpenSees and the nonlinear behavior of the displacement-controlled components was calibrated using available experimental data. A detailed site-specific hazard analysis was conducted and sets of ground motions suitable for the prototype buildings were selected. The ground motions were used in a series of incremental dynamic analyses (IDAs) to quantify the adjustable collapse margin ratio (ACMR) of the prototype balloon type CLT rocking shear walls. The results show that the prototype balloon type CLT rocking shear walls designed using the performance-based design procedure outlined in the CCMC/NRC technical guideline have sufficient ACMR when compared to the acceptable limits recommended by FEMA P695.

This paper presents the development and testing of a novel internal dissipation connection for the use of post-tensioned rocking columns. The solution is one of the many referring to the dissipative controlled rocking (DCR) bridge design philosophy. The internal dissipaters are carefully designed to be cost-effective and reduce the overall construction cost. The dissipaters are fully threaded, Grade 300 bars connected to the permanent column and foundation longitudinal reinforcement with threaded couplers. In this research, a DCR column is subjected to subsequent earthquake events, and the dissipaters' strain design limits are chosen such that there is no need for replacing after a significant seismic event. The result is a recommended design strain limit of 1.5% for the dissipaters that guarantees the structural integrity of the DCR column after a seismic event. Additionally, a cumulated strain of 5% is recommended for the dissipaters before replacement is suggested. The proposed connection detailing with replaceable internal dissipaters, combined with post-tensioned high strength bars and well-confined concrete, provided self-centring capabilities (no residual displacement), dissipation capacity and significantly less damage in the bridge column than a traditional reinforced concrete solution.