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Item type:Publication, Photogrammetry-aided numerical seismic assessment of historical structures composed of adobe, stone and brick masonry: Application to the San Juan Bautista Church built on the Inca temple of Huaytará, Peru(Elsevier Ltd, 2024-04-01)This research presents a cost-effective surveying methodology to assist the seismic assessment of complex heritage buildings, based on terrestrial structure-from-motion (SfM) photogrammetry. The method was applied to the study of the seismic performance of the church of San Juan Bautista – Inca temple of Huaytará, Peru, an emblematic case study due to its complex architecture and coexistence of different construction materials. The geometrical model for the seismic assessment was developed with an error of less than 2 % using SfM photogrammetry. Non-linear static pushover analyses were performed on 3D FEM models of the nave and the towers to evaluate their individual response under seismic loading. Mechanical properties of different structural materials of the church were evaluated based on laboratory experimental tests on mortar and adobe, contemporary and ancient fired brick, Inca stone, colonial stone and rubble stone units. Non-linear pushover analyses were conducted in four directions perpendicular to the perimeter walls, and the response of the structure was compared with the seismic demand specified in Peruvian Standards. The simulations show that damage-prone areas are the western and eastern facades, with cracking at the connections between orthogonal walls, as well as at the interface of adobe masonry with Inca stone masonry. The towers exhibit similar seismic response, with lower strength capacities compared to the main nave. In this case, flexural overturning mechanisms and cracking at the interface between stone and adobe masonry were observed. The displacement-based seismic assessment using the N2 method shows that a peak ground acceleration of 0.21 g could lead to the collapse of the north and south facades of the main nave. The towers showed a much smaller capacity with PGA leading to collapse of approximately 0.09 g. Overall, this study contributes to the understanding of the seismic performance of the Huaytará-Huancavelica church, highlighting vulnerabilities and providing valuable information for its preservation and future interventions. Future investigations should focus on on-site tests that will allow the estimation of the effect of existing damage on the structural response and their incorporation in the numerical model. - Some of the metrics are blocked by yourconsent settings
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, Seismic numerical analysis of an Inca stone wall in Sacsayhuaman using rigid body dynamics within a finite element framework(Elsevier Ltd, 2024-07-01)The study and conservation of the stone heritage is a global concern, mainly when the buildings are in seismic zones. Stone structures can be very simple or considerably complex, depending on their style and form of construction. A clear example is the Inca architecture in Peru, which has different and complex typologies due to its cultural diversity. Inca structures of remarkable heritage value are in Cusco, an area of active cortical faults that might produce a seismic event at any time. The main objective of this research is to contribute to the knowledge of the seismic vulnerability analysis of Inca's stone walls by using the dynamics of rigid bodies (within the finite element method) to evaluate the possible out-of-plane failure mechanisms. This methodology allows for reducing the high number of degrees of freedom usually considered when modelling an entire irregular large stone wall by other approaches, such as continuum models. A wall section from the archaeological site of Sacsayhuaman (Cusco, Peru) is analysed as a case study. Each stone is discretised and modelled as a rigid body, and the interaction among blocks is evaluated within a finite element numerical framework. The structure's predominant frequencies are evaluated using updated methods such as white noise and sinusoidal signals. Then, a non-linear dynamic analysis of the studied wall is performed considering three Peruvian seismic records. The analyses show that the structure could suffer significant damage and endanger its structural stability for cortical earthquakes with a Peak Ground Acceleration (PGA) greater than 0.2 g. Considering the historical significance of these structures, the analysis of Inca stone walls' seismic safety accounts for potential residual movements between individual stones. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Efficient beam-based model for reinforced concrete walls considering shear-flexure interaction(Elsevier Ltd, 2024-09-15)This paper presents an efficient beam-based modelling scheme for the seismic analysis of reinforced concrete structural walls. The model combines a force-based beam element with a fibre section for flexural response and a zero-length element for shear response. The fibre-based element simulates the nonlinear flexural behaviour through uniaxial material laws that account for concrete cracking, concrete crushing, and yielding and rupture of reinforcing bars. The zero-length element represents the shear behaviour with a trilinear lateral force-displacement curve representing, in a phenomenological way, nonlinear deformations caused by diagonal cracking. The reduction of shear resistance caused by inelastic flexural deformations is accounted for in the model to reproduce failures due to shear-flexure interaction. The model has been validated using data from 52 tests on wall specimens exhibiting flexure, shear and mixed shear-flexure modes from experimental campaigns reported in the literature, showing good accuracy in predicting the effective stiffness, maximum strength and displacement capacities obtained in the tests. Model results for ultimate displacement capacity correlate better with experimental results than simplified code-oriented expressions in performance-based evaluation standards and recommendations. Considering its balanced accuracy and computational efficiency, it is concluded that the proposed modelling scheme can effectively be used for performance-based seismic design and assessment of RC wall buildings. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Numerical simulation of Peruvian RC wall buildings using an efficient beam-based model(International Association for Earthquake Engineering, 2024-01-01)In countries of high seismicity, such as Peru and Chile, the typical medium-to high-story buildings use reinforced concrete (RC) walls as their lateral load-resisting system owing to an overall satisfactory behaviour in previous seismic events. The advent of performance-based methods for seismic design of buildings demands nonlinear structural models that are efficient, reliable, and easy to calibrate. In the case of RC wall structures, such models have to consider the prominent flexure-shear interaction of wall members. This study employs an efficient beam-based computational model considering flexure-shear interaction to simulate the seismic response of three prototype RC wall structures representative of modern Peruvian buildings. These structures' geometrical, reinforcement and loading conditions were determined by analyzing a database of 20 buildings constructed in Peru between 2010 and 2022. The wall computational model, developed in OpenSees, uses fibre-based beam-column elements to simulate the flexural response and a zero-length element connected in series for the shear response. Uniaxial concrete and steel laws are combined with appropriate regularization and fatigue criteria to reproduce flexural failures due to concrete crushing and bar fracture. Shear deformations and failure are modelled using a phenomenological trilinear shear force-deformation model in the zero-length element, which is affected by the flexure demands to consider flexure-shear interaction effects. Nonlinear analyses of the wall structures were conducted with the proposed modelling approach. The research aims to study the typical failure of RC wall buildings, their displacement capacity, and the displacement and shear force demands. The nonlinear evaluation shows that displacement capacity averages 11.2‰ total drift. A primary failure mode corresponds to concrete crushing of walls by flexural deformation because of their highest axial load and lower confinement zones. The rare earthquake demands an average of 8.4‰ total drift in the flexible direction of the buildings, and the average amplification over the shear design force is 3.1 in both directions. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Evaluation of the seismic behaviour of an Inca stone wall using rigid body dynamic methods(Springer Science and Business Media B.V., 2024-01-01)Peru has around 7 360 prehispanic archaeological monuments [1] according to the Ministry of Culture of Peru. These structures, built with irregular shapes and variable configurations, are very complex to evaluate. Unfortunately, some of these constructions are in poor conservation state due to external factors such as earthquakes, soil settlements or human activity [2]. For example, some Inca culture stone walls from archaeological sites such as Puka Pukara, Sacsayhuaman, Huchuy Qosqo and Chinchero present visible damage directly associated with previous earthquakes [3]. In this research, the dynamic response of an Inca stone wall from Sacsayhuaman is evaluated using rigid body dynamics in Abaqus [4]. Sacsayhuaman archaeological site is made up of enormous retaining walls with large carved stones and dry joints. The stones were modelled with their irregular shapes as rigid bodies and their interactions by means of interfaces with normal and shear stiffness. All mechanical properties were adequately calibrated based on experimental tests and literature review. The results confirm that the use of rigid body dynamic methods can help to evaluate the seismic performance of stone structures and to identify the most probable collapse mechanisms during a seismic event. - 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.