Finite element analysis of concrete cracking at early age

Mauren Aurich,Américo Campos Filho,Túlio Nogueira Bittencourt,Surendra P. Shah 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.37 No.5

The study of the early age concrete properties is becoming more important, as the thermal effects and the shrinkage, even in the first hours, could generate cracks, increasing the permeability of the structure and being able to induce problems of durability and functionality in the same ones. The detailed study of the stresses development during the construction process can be decisive to keep low the cracking levels. In this work a computational model, based on the finite element method, was implemented to simulate the early age concrete behavior and, specially, the evaluation of the cracking risk. The finite element analysis encloses the computational modeling of the following phenomena: chemical, thermal, moisture diffusion and mechanical which occur at the first days after the concrete cast. The developed software results were compared with experimental values found in the literature, demonstrating an excellent approach for all the implemented analysis.

Structural analysis of a prestressed segmented girder using contact elements in ANSYS

Paula M. Lazzari,Américo Campos Filho,Bruna M. Lazzari,Alexandre R. Pacheco 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.20 No.3

Studying the structural behavior of prestressed segmented girders is quite important due to the large use this type of solution in viaducts and bridges. Thus, this work presents a nonlinear three-dimensional structural analysis of an externally prestressed segmented concrete girder through the Finite Element Method (FEM), using a customized ANSYS platform, version 14.5. Aiming the minimization of the computational effort by using the lowest number of finite elements, a new viscoelastoplastic material model has been implemented for the structural concrete with the UPF customization tool of ANSYS, adding new subroutines, written in FORTRAN programming language, to the main program. This model takes into consideration the cracking of concrete in its formulation, being based on fib Model Code 2010, which uses Ottosen rupture surface as the rupture criterion. By implementing this new material model, it was possible to use the three-dimensional 20-node quadratic element SOLID186 to model the concrete. Upon validation of the model, an externally prestressed segmented box concrete girder that was originally lab tested by Aparicio et al. (2002) has been computationally simulated. In the discretization of the structure, in addition to element SOLID186 for the concrete, unidimensional element LINK180 has been used to model the prestressing tendons, as well as contact elements CONTA174 and TARGE170 to simulate the dry joints along the segmented girder. Stresses in the concrete and in the prestressing tendons are assessed, as well as joint openings and load versus deflection diagrams. A comparison between numerical and experimental data is also presented, showing a good agreement.

Numerical simulation of the constructive steps of a cable-stayed bridge using ANSYS

Paula M. Lazzari,Américo Campos Filho,Bruna M. Lazzari,Alexandre R. Pacheco,Renan R. S. Gomes 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.69 No.3

This work addresses a three-dimensional nonlinear structural analysis of the constructive phases of a cable-stayed segmental concrete bridge using The Finite Element Method through ANSYS, version 14.5. New subroutines have been added to ANSYS via its UPF customization tool to implement viscoelastoplastic constitutive equations with cracking capability to model concrete’s structural behavior. This numerical implementation allowed the use of three-dimensional twenty-node quadratic elements (SOLID186) with the Element-Embedded Rebar model option (REINF264), conducting to a fast and efficient solution. These advantages are of fundamental importance when large structures, such as bridges, are modeled, since an increasing number of finite elements is demanded. After validating the subroutines, the bridge located in Rio de Janeiro, Brazil, and known as “Ponte do Saber” (Bridge of Knowledge, in Portuguese), has been numerically modeled, simulating each of the constructive phases of the bridge. Additionally, the data obtained numerically is compared with the field data collected from monitoring conducted during the construction of the bridge, showing good agreement.

Numerical simulation by the finite element method of the constructive steps of a precast prestressed segmental bridge

Gabriela G. Machado,Américo Campos Filho,Paula M. Lazzari,Bruna M. Lazzari,Alexandre R. Pacheco 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.85 No.2

The design of segmental bridges, a structure that typically employs precast prestressed concrete elements and the balanced cantilever construction method for the deck, may demand a highly complex structural analysis for increased precision of the results. This work presents a comprehensive numerical analysis of a 3D finite element model using the software ANSYS, version 21.2, to simulate the constructive deck stages of the New Guaiba Bridge, a structure located in Porto Alegre city, southern Brazil. The materials concrete and steel were considered viscoelastic. The concrete used a Generalized Kelvin model, with subroutines written in FORTRAN and added to the main model through the customization tool UPF (User Programmable Features). The steel prestressing tendons used a Generalized Maxwell model available in ANSYS. The balanced cantilever constructive steps of a span of the New Guaiba Bridge were then numerically simulated to follow the actual constructive sequence of the bridge. A comparison between the results obtained with the numerical model and the actual vertical displacement data monitored during the bridge's construction was carried out, showing a good correlation.

Clinical comparison of marginal fit of ceramic inlays between digital and conventional impressions

Franklin Guillermo Vargas-Corral,Américo Ernesto Vargas-Corral,Miguel Angel Rodríguez Valverde,Manuel Bravo,Juan Ignacio Rosales Leal 대한치과보철학회 2024 The Journal of Advanced Prosthodontics Vol.16 No.1

Purpose. To evaluate the metameric disparities among monolithic zirconia materials with differing yttrium compositions across various lighting conditions. Materials and Methods. Thirty-six square-shaped zirconia samples measuring 10 × 10 × 0.5 mm were prepared from monolithic zirconia materials with three different yttrium contents. A 0.2 mm thick layer of polymerized dual-polymerizable self-adhesive resin cement was created using a silicone mold with the same dimensions as the prepared zirconia specimens. To evaluate metamerism, color measurements were conducted using a spectrophotometer device on a neutral gray background in a color measurement cabinet that offers four different illumination environments. All samples underwent aging by subjecting them to 10000 thermal cycles using a thermal cycle tester. Following thermal aging, color measurements were taken once more, and the data were recorded using the CIE L*, a*, b* color system. Two-way ANOVA and Post-hoc Bonferroni tests were employed to analyze the data. Results. It was observed that there was no statistical difference among the color measurements made in different illumination environments of the monolithic zirconia ceramics used to evaluate metamerism (P > .05). This observation remained consistent both before and after thermal aging. After thermal aging, the color of monolithic zirconia materials exhibited a tendency towards red and yellow hues, accompanied by a decrease in brightness levels. Conclusion. It can be stated that different illumination conditions did not affect the metamerism of monolithic zirconia materials, but there was a color change in monolithic zirconia materials after a thermal aging period equivalent to one year.

Using element-embedded rebar model in ANSYS for the study of reinforced and prestressed concrete structures

Bruna M. Lazzari,Américo Campos Filho,Paula M. Lazzari,Alexandre R. Pacheco 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.19 No.4

ANSYS is a software well accepted by professionals and academics, since it provides a variety of finite elements, material constitutive models, and linear and nonlinear analysis of structures in general. For the concrete material, for instance, the software uses an elastoplastic model with the Willam-Warnke surface of rupture (1975). However, this model is only available for finite elements that do not offer the possibility of use of the element-embedded model for rebars, demanding a much larger amount of elements to discretize structures, making numerical solutions less efficient. This study is, therefore, about the development of a computational model using the Finite Element Method via ANSYS platform for nonlinear analysis of reinforced and prestressed concrete beams under plane stress states. The most significant advantage of this implementation is the possibility of using the element-embedded rebar model in ANSYS with its 2D eight-node quadratic element PLANE183 for discretization of the concrete together with element REINF263 for discretization of rebars, stirrups, and cables, making the solutions faster and more efficient. For representation of the constitutive equations of the steel and the concrete, a proposed model was implemented with the help of the UPF customization tool (User Programmable Features) of ANSYS, where new subroutines written in FORTRAN were attached to the main program. The numerical results are compared with experimental values available in the technical literature to validate the proposed model, with satisfactory results being found.

Synaptophysin and caspase-3 expression on lumbar segments of spinal cord after sensorimotor restriction during early postnatal period and treadmill training

Felipe Stigger,Silvia Barbosa,Marília Rossato Marques,Ethiane Segabinazi,Otávio Américo Augustin,Matilde Achaval,Simone Marcuzzo 한국운동재활학회 2018 JER Vol.14 No.3

Acute and Repeated 28-Day Oral Dose Toxicity Studies of Thymus vulgaris L. Essential Oil in Rats

Juan Rojas Armas,Jorge Arroyo-Acevedo,Manuel Ortiz-Sánchez,Miriam Palomino-Pacheco,Américo Castro-Luna,Norma Ramos-Cevallos,Hugo Justil-Guerrero,Julio Hilario-Vargas,Oscar Herrera-Calderón 한국독성학회 2019 Toxicological Research Vol.35 No.3

Thymus vulgaris L. is widely used as an ingredient in cooking and in herbal medicine. However, there is little information about its toxicity. The present study was performed to evaluate the acute and repeated 28-day oral dose toxicity of thyme essential oil in rats. For the acute toxicity test, two groups of three rats were used. The rats received a single dose of essential oil: 300 or 2,000 mg/kg of body weight (bw). The rats were observed individually during the first four hours, and then daily until day 14. For the toxicity test with repeated doses, four groups of 10 rats were used. Doses of 100, 250, and 500 mg/kg/day were tested for 28 days. At the end of the experiment, blood was collected and the animals were sacrificed. Histopathological examination showed that in the lungs of rats given the 2,000 mg/kg bw dose, polymorph nuclear infiltrates, hemosiderin macrophages, and interstitial space thickening were present. In the repeated dose study, all rats survived the 28-day treatment period and apparently showed no signs of toxicity. The hematological and biochemical parameters were not altered. The histopathological study of the organs showed severe changes in the lung, with the dose of 500 mg/kg/day; in the other organs, no alterations were observed or the changes were slight. The body weight was only altered in male rats given the 500 mg/kg dose. The relative weight of the organs did not show any significant changes. Our studies revealed that the essential oil of Thymus vulgaris has moderate oral toxicity according to the results of the acute test, whereas the results of the 28-day oral toxicity test suggest that the no-observed-adverse effect level (NOAEL) is greater than 250 mg/kg/day.

Diagnosis of Bowel Endometriosis Using Endoscopic Ultrasound-guided Fine Needle Aspiration

Ana Catarina Carvalho,Ricardo Cardoso,Francisco Pires,Sofia Ventura,Francisco Portela,Paula Ministro,Américo Silva 대한소화기학회 2023 대한소화기학회지 Vol.81 No.1

Endometriosis is a relatively common gynecological condition in women of reproductive age. The rectosigmoid region is the most commonly affected segment when the gastrointestinal tract is involved. A differential diagnosis of colorectal neoplasia is difficult because of the similar clinical, endoscopic, and radiology findings. A 42-year-old female presented with abdominal distention and was subsequently diagnosed with a large bowel obstruction in the rectum. A temporary colostomy was performed, and endoscopy revealed a rectal mass obstructing the rectum. The biopsy showed normal mucosa, and it was difficult to exclude rectal malignancies even after the imaging workup. Endoscopic ultrasound demonstrated a hypoechoic lesion below the rectal mucosa, and fine needle aspiration confirmed the diagnosis of bowel endometriosis. Bowel endometriosis is a challenging diagnosis. Endoscopic ultrasound- guided fine-needle aspiration is useful for acquiring adequate samples for histological confirmation and a definitive diagnosis of bowel endometriosis.