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Item type:Publication, Dynamic numerical study of traditional dry-stone walls with YADE(Springer Science and Business Media B.V., 2024-01-01)On the hills of some Andean cities in South America, the population has built their homes on terraces supported by traditional dry-stone retaining walls (“pircas”) without any regulation or code. Because this zone is prone to strong earthquake ground motions, it is necessary a better understanding of the pircas’s out-of-plane behavior and collapse mechanism for risk prevention and mitigation. However, no dynamic studies of this traditional construction exist to date. This work addresses a numerical study of the response of pircas subjected to ground motions in the out-of-plane direction and how different construction techniques (i.e. block arrangements and wall configurations) can affect this response. The dynamic analysis was carried out with the YADE (open-source software for discrete numerical models and focused on the Discrete Element Method, DEM). By varying the vertical separation of Through stones (tie stones) and overlap of stones in the cross-section of the walls, we obtained 5 models which were subjected to a representative seismic signal. Regular and parallelepiped clumps (groups of rigidly joined spheres) were selected for modeling the wall blocks due to their versatility in their geometry and lower computational cost than other types of particles supported by YADE [1]. The effect of the backfill has not been considered yet, since we are focused on the wall configuration effects on the dynamic response. In the absence of dynamic experimental results, the precise calibration of the numerical model has yet to be sought. The results obtained are preliminary. At a later stage, an experimental dynamic test will be carried out, and they can be properly calibrated. The numerical results showed that when the wall presents a cross-section with adequate overlap, the amount of Through Stone (from 2.2 to 3.6 per m2) is not important. On the other hand, when the wall cross-section has no overlap, the wall presents the least resistance to moderate damage levels and collapse. Additionally, it was possible to verify that the pseudo-static out-of-plane response (obtained in a previous study) is more conservative than the dynamic one. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Vulnerabilities and exposure of recent informal urban areas in Lima, Peru(Elsevier Ltd, 2024-10-01)Urban areas are experiencing rapid growth, accompanied by significant disorder in Lima Metropolitan area and many other cities in South America. Due to decades of uncontrolled construction practices, it is imperative to identify and better understand the types of informalities prevalent in these recent urban areas. Addressing this lack of information is crucial for implementing appropriate countermeasures and developing new policies that benefit the communities residing in such areas. It is worth noting that understanding disaster risk aligns with the first priority of the Sendai Framework for Disaster Risk Reduction. In this study, we propose the use of radar satellite imagery recorded by the Sentinel-1 constellation since 2017 to identify clusters of urban growth in Lima Metropolitan area. Then, the informal urban clusters can be depicted by visual inspection of the last recorded high-resolution optical image. With good spatial and temporal resolution, we identified 25 clusters informal areas. Among our findings, we observed that several of these clusters are situated in landfills comprised of construction and other waste, increasing their vulnerability to debris flow, landslides, and earthquakes. Additionally, we noted that some new urban areas mainly consist of temporarily empty houses, highlighting the feasibility of implementing countermeasures, such as relocations, in the early stages of informal occupation. These results underscore the significant contribution of satellite radar imagery in identifying recent informal urban areas. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Numerical and experimental pseudo-static study on block arrangement effects in traditional dry-stone walls for out-of-plane mechanical behavior evaluation(Elsevier Ltd, 2024-12-01)In Lima's slopes, the absence of urban planning has led to housing built on backfills contained by traditional dry-stone retaining walls, called “pircas,” which pose high seismic risk. A previous study [1], which combined numerical and experimental analyses, evaluated pircas through pseudo-static tests that reflected common construction methods in Lima's eastern region. One recommendation from that study was to explore effective stone arrangements to enhance the seismic performance of pircas. Consequently, this study aims to examine how the construction process, particularly the arrangement of stones, impacts the out-of-plane behavior of pircas. The research focuses on identifying construction-feasible configurations that can effectively improve their seismic performance. For this purpose, natural-scale pseudo-static experimental studies and numerical modeling using the Discrete Element Method (DEM) were carried out. The experimental campaign consisted of nine pseudo-static tests on different wall arrangements. The pseudo-static numerical study included seventy wall arrangements. The geometry of the blocks was simplified to eliminate this component from the analysis, which focused on the arrangement of the wall. The numerical and experimental results showed the same trend. The study has demonstrated that the current construction technique can be significantly improved by regularly incorporating through-stones—tie stones that pass through the entire cross-section of the wall—and considering a cross-section with overlap. This approach leads to an increase of up to 50% in lateral strength compared to current practices, verifying the effectiveness of through-stones. The study does not intend to endorse the use of pirca for urban habitation in high seismic sectors. However, these traditional walls can be recommended for slope stability, environmental mitigation, urban agriculture, and protection of natural areas. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Spatial analysis for water supply in seismic emergencies: The Lima–Callao metropolitan area(Frontiers Media SA, 2024-01-01)In urban areas exposed to high-magnitude earthquakes, the drinking water supply would be severely damaged, and domestic services would be disrupted for a large part of the population in the event of an earthquake. The Lima-Callao metropolitan area in Peru, South America, is expected to experience an 8.8 Mw earthquake, and it is estimated that approximately 90% of the population would not have immediate access to emergency water in the case of such an event. The main objective of this paper is to define criteria for a spatial analysis method to guide the design criteria for an Emergency Water Supply System (EWaSS). Methods: This paper combines territorial, urban resilience and participatory approaches and presents the results of an interdisciplinary research with social impact. Thus, it examines the urban territory at macro-, meso- and micro scales; physical-spatial variables indicating risk levels and possible public spaces to implement the system; and socio-spatial variables regarding the population, risk perception and participation in management to strengthen urban resilience. Normative tools and the Geographic Information System are used to spatialize and systematize quantitative and qualitative information. Results and discussion: The EWaSS is an alternative for safe water supply in a post-disaster situation that would provide immediate and autonomous operation during the first 72 h of the emergency. The results show the physical-spatial and social viability of urbanized areas and the system design criteria that guide local actors in making decisions at the three levels of emergency management. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Interactive guide for post-disaster water supply in urban areas(International Association for Earthquake Engineering, 2024-01-01)Water deficit in post-disaster situations due to large past earthquakes has evidenced the difficulty in managing and distributing safe water to the urban population during the first moments after the event and the lack of preparation of the people to cope with this situation. Disorder and panic must be prevented by preparing and educating the people at risk and the local government. This paper aims to develop an interactive, online, GIS-based guide focused on water supply during emergencies caused by seismic events. To accomplish this task, we introduce the Emergency Water Supply System (EWaSS) concept, a network of local autonomous water supply points in public spaces, such as parks and squares. The objective of the EWaSS is to provide safe water in the first moments of the earthquake emergency, articulated with the existing emergency plans at different levels of government. The design of the EWaSS considers a three-scale spatial approach that involves the environmental, social and physical dimensions and the following aspects: quantity and quality of water, security, accessibility; performance in the face of adverse natural phenomena, population density, articulation to the network of public spaces that includes safe areas, evacuation routes and proximity to urban facilities, identification of the level of organization of the community, urban zoning, and social vulnerability. We present the megacity of Lima in South America as a case study in which an 8.8 Mw earthquake is expected. The probability of water supply interruption is high due to out-of-date water and sanitation infrastructure. Although there is a set of wells and tanks aimed to supply water during emergencies, more was needed to cover the whole city population. An interdisciplinary perspective integrates and articulates the knowledge of civil engineering and urban planning disciplines. Emphasis is placed on using collaborative methods with the participation of relevant local actors and stakeholders in disaster risk management to achieve a feasible solution. As a result, the interactive guide is delivered and introduced to the stakeholders, decision-makers, planners and neighborhood organizations. This guide is expected to help strengthen the capacities of the population and state entities in charge of emergency response and increase the population's resilience that could be affected by future earthquake disasters.1 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Out-of-Plane Analysis of Dry-Stone Walls Using a Pseudo-Static Experimental and Numerical Approach in Natural-Scale Specimens(Elsevier Ltd, 2023-08-01)On the slopes of some Andean cities, the population is at high seismic risk due to their informal homes, built without technical advice, based on non-compacted backfill, and supported by dry stone retaining walls (pircas). In this work, we aimed to evaluate the out-of-plane performance of the typical retaining walls of the city of Lima, Peru, located on the slopes of the central Andes. In this first study, the effect of the backfill has not been considered because only the behavior of the wall was studied. Three walls of height 1 m and three of height 1.5 m were built and tested. The construction was carried out by local workers, following their traditional practices, and tests were carried out on a tilting platform to generate out-of-plane gravity loads. Delamination and overturning were the most frequent types of failure. From the experimental tests, we found that the average ultimate resistance to displacement was 31 % and 24 % of the weight for the 1 m and 1.5 m walls, respectively. The discrete element method was used for the numerical models, and the contact parameters of stiffness and friction angle corresponding to the Coulomb model were calibrated using the experimental results. The effects on the mechanical behavior of the use of through stones and overlaps between wall elements were studied. It was concluded that the pircas could be improved to a limited extent with better construction practices, and further studies are therefore required with the aim of improving current construction practices. In a later study, the interaction between the wall and the backfill will be studied numerically and experimentally.