3,979 research outputs found
Nonlocal damage propagation in the dynamics of masonry elements
No full textIn this work, a nonlocal damage-plasticity model for dynamic finite element analyses of cohesive structural elements is presented. The proposed cohesive model is able to reproduce the main relevant behaviors of quasi-brittle materials despite being quite simple, i.e. governed by only a few parameters which can be determined by standard laboratory tests. In particular, the model is able to reproduce the mechanisms of cohesive materials under static or dynamic loads: degradation of the mechanical properties (damage) and accumulation of irreversible strains (plasticity). Moreover, the model also simulates the cyclic macroscopic behavior of quasi-brittle materials, taking into account the loss and recovery of stiffness due to crack closure and reopening. The latter effect represents a particularly important characteristic in the case of dynamic loads. The proposed formulation is implemented as a constitutive model for two-dimensional plane stress four-node quadrilateral elements. The second order equations of motion are solved adopting the implicit Newmark time integration scheme. The proposed model is validated and its dynamic performance is numerically demonstrated through the analysis of a large-scale structural element
A coupled interface-body nonlocal damage model for the analysis of FRP strengthening detachment from cohesive material
No full text"In the present work, a new model of the FRP-concrete or masonry interface, which accounts for. the coupling occurring between the degradation of the cohesive material and the FRP detachment, is presented;. in particular, a coupled interface-body nonlocal damage model is proposed. A nonlocal damage and plasticity. model is developed for the quasi-brittle material. For the interface, a model which accounts for the mode I,. mode II and mixed mode of damage and for the unilateral contact and friction effects is developed. Two. different ways of performing the coupling between the body damage and the interface damage are proposed. and compared. Some numerical applications are carried out in order to assess the performances of the proposed. model in reproducing the mechanical behavior of the masonry elements strengthened with external FRP. reinforcements.
A Conversation with Jessica B. Harris
No full textA conversation with culinary historian and award-winning author Jessica B. Harris, moderated by Gabrielle Fulton Ponder
Modeling of smart concrete beams with shape memory alloy actuators
Get PDFIn the present work, a computational strategy for the modeling of reinforced concrete beams with SMA actuators for cracks repair is developed. In particular, for the concrete, an original transition damage-fracture technique is proposed in order to simulate the microcrack arising, their coalescence and, finally, the macrocrack development. Microcracks are modeled adopting a nonlocal damage and plasticity approach, which is able to consider the tensile and compressive damaging, accumulation of irreversible strains and the unilateral phenomenon. Macrocracks are modeled using a cohesive zone interface which accounts for the mode I, mode II and mixed mode of damage, the unilateral contact and the friction effects. The interface models the transition from the continuum damage (simulating the presence of microcracks) to fracture. A uniaxial SMA model able to reproduce both the pseudo-elastic behavior and the shape memory effect is adopted for the reinforcing SMA bars.Finite element simulations are developed in order to reproduce the behavior of smart concrete beams subjected to three-point bending experimental tests available in literature (Kuang and Ou, 2008, Daghia et al., 2011). The construction phases of the beam are simulated and the loading history, consisting in three-point bending tests, are reproduced; in particular, the repairing phase due to pseudo-elastic behavior and shape memory effect is reproduced. Numerical results are compared with experimental data to validate the computational strategy
Coupled body-interface nonlocal damage model for FRP detachment
No full textThe present paper deals with the modeling of the detachment mechanism of Fiber Reinforced Polymers
(FRP) reinforcements from cohesive, i.e. quasi-brittle, materials. A new plastic-damage model able to
describe the main features characterizing the macroscopic behavior of cohesive materials is presented.
To overcome the analytical and computational problems induced by the softening constitutive law, an
integral-type regularization technique is adopted. The evolution of the plastic strain is governed by introducing
a suitable yield function. For the FRP-quasi brittle support interface, a cohesive zone model, which
accounts for damage, unilateral contact and friction effects, is developed. The provided interface formulation
is also able to consider the influence of the degradation state of the support on the interface collapse
mechanism, i.e. the coupling of the interface and body damage, evaluated on the bond surface. A
numerical procedure is presented and implemented in a finite element code. Some numerical applications
are carried out in order to assess the performances of the proposed model, presenting a comparison
with experimental data
Jessica Stremer: Cook Prize 2024, Silver Medal Acceptance Speech
No full textAuthor Jessica Stremer gives an acceptance speech for Great Carrier Reef (Holiday House)https://educate.bankstreet.edu/cook/1013/thumbnail.jp
Effective seismic strengthening and monitoring of a masonry vault by using Glass Fiber Reinforced Cementitious Matrix with embedded Fiber Bragg Grating sensors
No full textThe research proposes the combined use of a Glass Fiber Reinforced Cement Matrix (GFRCM) composite with an integrated fiber optic sensing system for innovative seismic retrofitting of masonry vaults. The need of eco-compatibility of bonding material with masonry support implies the use of Hydraulic Lime Mortar (HLM) as bonding matrix that, in contrast, is characterized by lower adhesion capacity respect to polymeric resins and not well-known carrying-load properties. Hence, monitoring of the operating features of the GFRCM reinforcement has been pursued with an advanced fiber optic sensing system realized through Fiber Bragg Grating (FBG) sensors. The use of FBG sensors is justified by a large number of advantages such as small sensor dimensions, low weight as well as high static and dynamic resolution of measured values, distributed sensing feature allowing to detect anomalies in load transfer between reinforcement and substrate. Specifically, the proposed retrofitting and monitoring technique is designed and applied to an old masonry pavilion vault. A nonlinear finite element model of the reinforced structure is developed in order to quantify the effectiveness of the GFRCM strengthening layer and to derive the convenient position of the optic fibers for a correct monitoring of the reinforced vault. An experimental campaign is carried out in order to verify the proper behavior of the proposed strengthening and sensing strategy
Jessica Pierce: The Last Walk: Caring for Our Animal Companions
Get PDFBioethicist and author Jessica Pierce will discuss end-of-life care, dying, and euthanasia in the lives of our companion animals.https://thekeep.eiu.edu/humanitiescenter_authenticity1314/1003/thumbnail.jp
Modeling approaches for masonry structures
No full textDifferent scale approaches, micromechanical, multiscale and macromechanical or phenomenological, are presented to study the structural response of masonry elements. First, a micromechanical model is introduced and the masonry is considered to be a heterogeneous material, made of mortar and bricks joined by interfaces, where the mortarbrick decohesion mechanisms occur. To this end, a special interface model combining damage and friction is proposed. Then, two multiscale procedures are presented, that consider regular arrangements of bricks and mortar, modeled by nonlinear constitutive laws which account for damage and friction effects. A homogenization technique is developed to derive two different equivalent continuum models at the macro-level, a micropolar Cosserat continuum and a nonlocal Cauchy model. Finally, a macromechanical model, based on the adoption of a classical No-Tension Material (NTM) model, and on the presence of irreversible crushing strains, is proposed. A zero tensile strength is assumed, thus fracture strains arise when the stress is zero. Moreover, an elastoplastic model is considered for the material response in compression. Numerical applications are performed on a masonry arch and two masonry panels, by adopting the three approaches presented. Comparisons with experimental outcomes, published elsewhere, are performed
- …
