In the early 21st century, achieving the sustainability of urban environments while coping with increasingly occurring natural disasters is a very ambitious challenge for contemporary communities. In this context, urban resilience is a comprehensive objective that communities can follow to ensure future sustainable cities able to cope with the risks to which they are exposed. Researchers have developed different definitions of resilience as this concept has been applied to diverse topics and issues in recent decades. Essentially, resilience is defined as the capability of a system to withstand major unexpected events and recover in a functional and efficient manner. When dealing with urban environments, the efficiency of the recovery can be related to multiple aspects, many of which are often hard to control. Mainly it is quantified in terms of the restoration of urban economy, population, and built form (Davoudi et al., 2012). In this article, engineering resilience is defined in relation to cities’ capability to be sustainable in the phase of an extreme event occurrence while reconfiguring their physical configuration. In this view, a city is resilient if it is sustainable in the occurrence of a hazardous event. Accordingly, in an urban context, a wide range of nonhomogeneous factors and intrinsic dynamics have to be accounted for, which requires a multi-scale approach, from the single building level to the urban and, ultimately, the global environmental scale. As a consequence, cities can be understood as physical systems assessed through engineering metrics. Hence, the physical dimension represents a starting point from which to approach resilience. When shifting the focus from the single structure to the city scale, human behavior is revealed to be a critical factor because social actors behave and make choices every day in an unpredictable and unorganized manner, which affects city functioning. According to the ecosystem theory, urban complexity can be addressed through the ecosystem theory approach, which accounts for interrelations between physical and human components.
Anna Bozza, Domenico Asprone, and Gaetano Manfredi
In the context of this article, risk governance addresses the ways and means—or institutional framework—to lead and manage the issue of risk related to natural phenomena, events, or hazards, also referred to popularly, although incorrectly, as “natural disasters.” At the present time, risk related to natural phenomena includes a major focus on the issue of climate change with which it is intimately connected, climate change being a major source of risk. To lead involves mainly defining policies and proposing legislation, hence proposing goals, conducting, promoting, orienting, providing a vision—namely, reducing the loss of lives and livelihoods as part of sustainable development—also, raising awareness and educating on the topic and addressing the ethical perspective that motivates and facilitates engagement by citizens. To manage involves, among other things, proposing organizational and technical arrangements, as well as regulations allowing the implementation of policies and legislation. Also, it involves monitoring and supervising such implementation to draw further lessons to periodically enhance the policies, legislation, regulations, and organizational and technical arrangements. UNISDR was established in 2000 to promote and facilitate risk reduction, becoming in a few years one of the main promoters of risk governance in the world and the main global advocate from within the United Nations system. It was an honor to serve as the first director of the UNISDR (2001–2011). A first lesson to be drawn from this experience was the need to identify, understand, and address the obstacles not allowing the implementation of what seems to be obvious to the scientific community but of difficult implementation by governments, private sector, and civil society; and alternatively, the reasons for shortcomings and weaknesses in risk governance. A second lesson identified was that risk related to natural phenomena also provides lessons for governance related to other types of risk in society—environmental, financial, health, security, etc., each a separate and specialized topic, sharing, however, common risk governance approaches. A third lesson was the relevance of understanding leadership and management as essential components in governance. Drawing lessons on one’s own experience is always risky as it involves some subjectivity in the analysis. In the article, the aim has, nonetheless, been at the utmost objectivity on the essential learnings in having conducted the United Nations International Strategy for Disaster Reduction—UNISDR—from 2001 to around 2009 when leading and managing was shared with another manager, as I prepared for retirement in 2011. Additional lessons are identified, including those related to risk governance as it is academically conceived, hence, what risk governance includes and how it has been implemented by different international, regional, national, and local authorities. Secondly, I identify those lessons related to the experience of leading and managing an organization focused on disaster risk at the international level and in the context of the United Nations system.
Amr Elnashai and Hussam Mahmoud
With current rapid growth of cities and the move toward the development of both sustainable and resilient infrastructure systems, it is vital for the structural engineering community to continue to improve their knowledge in earthquake engineering to limit infrastructure damage and the associated social and economic impacts. Historically, the development of such knowledge has been accomplished through the deployment of analytical simulations and experimental testing. Experimental testing is considered the most accurate tool by which local behavior of components or global response of systems can be assessed, assuming the test setup is realistically configured and the experiment is effectively executed. However, issues of scale, equipment capacity, and availability of research funding continue to hinder full-scale testing of complete structures. On the other hand, analytical simulation software is limited to solving specific type of problems and in many cases fail to capture complex behaviors, failure modes, and collapse of structural systems. Hybrid simulation has emerged as a potentially accurate and efficient tool for the evaluation of the response of large and complex structures under earthquake loading. In hybrid (experiment-analysis) simulation, part of a structural system is experimentally represented while the rest of the structure is numerically modeled. Typically, the most critical component is physically represented. By combining a physical specimen and a numerical model, the system-level behavior can be better quantified than modeling the entire system purely analytically or testing only a component. This article discusses the use of hybrid simulation as an effective tool for the seismic evaluation of structures. First, a chronicled development of hybrid simulation is presented with an overview of some of the previously conducted studies. Second, an overview of a hybrid simulation environment is provided. Finally, a hybrid simulation application example on the response of steel frames with semi-rigid connections under earthquake excitations is presented. The simulations included a full-scale physical specimen for the experimental module of a connection, and a 2D finite element model for the analytical module. It is demonstrated that hybrid simulation is a powerful tool for advanced assessment when used with appropriate analytical and experimental realizations of the components and that semi-rigid frames are a viable option in earthquake engineering applications.