http://repositorio.lnec.pt:8080/jspui/handle/123456789/1007762 2026-04-04T21:10:30Z 2026-04-04T21:10:30Z Azevedo, N. http://repositorio.lnec.pt:8080/jspui/handle/123456789/1018521 2025-07-21T12:31:33Z 2025-04-01T00:00:00Z

Stability analysis of concrete dam foundations following a hybrid discrete element/finite element approach Azevedo, N. Carlos Pina, Eliane Portela, Laura Caldeira In concrete dam foundations, failure mechanisms are primarily influenced by natural rock discontinuities, the dam-foundation interface, or weaker strata. Instability can manifest beneath the dam, within the abutments, or along adjacent slopes. For arch dam foundations, particular attention is required for failure scenarios involving sliding along weaker surfaces in areas where the arches are supported (along the valley sides and abutments), as well as issues related to seepage at the valley bottom, that may lead to the discontinuities erosion. Sophisticated analyses employ discrete element models, which capture well the discontinuous nature of rock and can incorporate fluid flow through these discontinuities. In stability analyses of concrete dam foundations, interface models whether based on discrete element or finite element techniques typically use planar joint formulations, such as point-to-point, point-to-surface, and edge-to-edge contacts. This paper introduces a new hybrid discrete element/finite element approach. When large displacement may occur, the rock blocks outer surfaces are discretized with spherical particles, allowing interactions to be modelled through particle-to-triangular surface interactions which are known to be computationally robust. Whenever possible, the contact interaction is defined in small displacements using finite element joint elements. A simplified gravity dam equilibrium example is presented to validate the proposed hybrid model. Stability analysis of an idealized arch dam foundation is also performed. The presented results are shown to closely match those obtained with a more complex polyhedral-based discrete element model.

2025-04-01T00:00:00Z Azevedo, N. Cismasiu, I. Pinho, F. Neves, F. http://repositorio.lnec.pt:8080/jspui/handle/123456789/1018511 2025-04-16T13:43:01Z 2025-03-01T00:00:00Z

Numerical modeling of reinforcement solutions in traditional stone masonry using a particle model Azevedo, N.; Cismasiu, I.; Pinho, F.; Neves, F. Traditional stone masonry walls are structural elements in most historic build- ings. To preserve them and improve their ability to withstand extreme events, such as earthquakes, it is necessary to implement effective reinforcement solutions. This paper presents the modeling of traditional Portuguese rubble stone masonry walls, reinforced with external steel mesh, sprayed micro-concrete layers and transverse confinement by steel connectors, which were developed and tested experimentally in uniaxial compression. The modeling is carried out using micro-modeling through a 2D particle model (PM). The process of calibrating the properties of both micro-concrete and concrete is presented, the methodology for generating the numerical models is described and the numerical response is compared with the experimental results. The numerical results show that the PM can adequately reproduce the experimentally observed behavior of this type of reinforcement solution.

2025-03-01T00:00:00Z Oktiovan, Y. Messali, F. Pulatsu, B. Lemos, J. V. Rots, J. http://repositorio.lnec.pt:8080/jspui/handle/123456789/1018216 2025-04-16T13:35:21Z 2024-01-01T00:00:00Z

A contact-based constitutive model for the numerical analysis of masonry structures using the distinct element method Oktiovan, Y.; Messali, F.; Pulatsu, B.; Lemos, J. V.; Rots, J. This study presents a robust contact constitutive model in the distinct element method (DEM) framework for simulating the mechanical behavior of masonry structures. The model is developed within the block-based modeling strategy, where the masonry unit is modeled as deformable blocks with potential crack surfaces in the middle of the bricks, while the mortar joints are defined as zero-thickness interfaces. The modeling strategy implements multi-surface plasticity with damage mechanics, including a tension cut-off, Coulomb failure criterion, and an elliptical compressive cap for the damage in tension, shear, and compression, respectively. Two new features are introduced in this contact model: a piecewise linear softening function for strength degradation in tension and shear and a hardening/softening function to phenomenologically define the compressive damage of masonry composite into the unit-mortar interface. The constitutive model is implemented in commercial DEM software using the small displacement configuration and validated against material and experimental tests on masonry walls subjected to constant pre-compression and monotonically increasing in-plane load. The experimental and numerical results regarding the force-displacement relationship and damage pattern produced by the proposed constitutive model are compared and critically discussed, demonstrating the capability of DEM coupled with the suitable constitutive law in simulating the behavior of masonry structures.

2024-01-01T00:00:00Z Liu, B. Sarhosis, V. Lemos, J. V. http://repositorio.lnec.pt:8080/jspui/handle/123456789/1018215 2025-04-16T13:35:12Z 2024-01-01T00:00:00Z

Quantification of the crack propagation and global failure mechanism of single- and multi-ring masonry arch bridges Liu, B.; Sarhosis, V.; Lemos, J. V. This paper presents the development of a novel crack-based damage quantification method to assess the damage accumulation in masonry arch bridges subjected to externally applied loading. Initially, a damage index was proposed, considering the initiation and extension of tensile and sliding cracks. Then, the proposed damage indexing was adopted into a two-dimensional discrete element code of analysis to evaluate single and multi-ring masonry arch bridges. The numerical model was validated by comparing the computational outputs against the experimental results obtained from the literature. Following the validation, masonry arch bridge models were developed, featuring the four most representative bond configurations in arch barrels. Also, different bond properties were assigned to investigate their impact on the global failure characteristics of single- and multi-ring masonry arch bridges. From the analyses of results of the multi-ring masonry arch bridges investigated in this study, it was shown that the rapid growth of tensile cracks in radial joints and the occurrence of shear slippage in circumferential joints between adjacent rings were observed to be early signs for multi-ring bridges before the ultimate load reached. By analysing the correlation between the normalised damage index with the normalised load, damage accumulation in different masonry arch bridges were identified. This study offers a novel perspective on quantitively evaluating the damage accumulation and failure mechanism of masonry arch bridges and the findings may provide valuable insights into the assessment and management of existing masonry arch bridges.

2024-01-01T00:00:00Z