João Batista de Paiva

Boundary element formulation of building slabs

Abstract This work presents a boundary element formulation for analysis of building slabs. In order to couple beams and columns with the plate, an alternative formulation of BEM is presented, which considers three nodal values in displacements ( w, ∂w ∂n and ∂w ∂t ) for the nodes at the boundary of the plate. In this formulation three boundary equations are written for all nodes at the boundary and at the domain of the plate. As the nodes of the grid and the column-plate connections are also represented by three nodal values, all these structural elements can be easily coupled. It is supposed that the cross-sections of the columns remain flat after the defection and consequently the assumption of linear variation of the stress in the plate-column contacting surface is also valid. It is also assumed that the plate is connected to the grid at nodes defined along the beams and only vertical forces are transmitted between these structural elements.

A special BEM for elastostatic analysis of building floor slabs on columns

Abstract This work presents a boundary element formulation for the analysis of building floor slabs, without beams, in which columns are coupled with the plate. An alternative formulation of boundary element method is presented, which considers three nodal displacements values (w, ∂w/∂n and ∂w/∂s) for the nodes at the boundary of the plate. In this formulation three boundary equations are written for all nodes at the boundary and in the domain of the plate. As the nodes of the column-plate connections are also represented by three nodal values, all these structural elements can be easily coupled. It is supposed that the cross-sections of the columns remain flat after the deflection and consequently the assumption of linear variation of the stress in the plate–column contact surface is also valid.

Boundary element for plate bending analysis

Abstract This paper is related to the applications of BEM to practical plate bending problems in engineering. Some aspects of the boundary formulations are shown, describing particular characteristics that can be considered to improved numerical solutions. Several different ways of defining the boundary element system of equations are proposed. Comparisons among them are also shown emphasizing some interesting behaviours.

Increase of condylar displacement between centric relation and maximal habitual intercuspation after occlusal splint therapy

The present study assessed condylar displacement between initial maximal habitual intercuspation (MHI) and centric relation (CR), recorded after using a deprogramming occlusal splint for an average period of 7.8 +/- 2.1 months prior to any orthodontic treatment. The sample consisted of 22 subjects, 11 male and 11 female, with an average age of 14.2 +/- 1.4 years, with Class II malocclusion and with no apparent signs or symptoms of temporomandibular dysfunction (TMD). Condylar displacement was measured using a Panadent axis position indicator in decimal fractions of a millimeter. The original mean vertical displacements and the corresponding standard deviations were 4.24 +/- 2.53 mm and 3.86 +/- 2.72 mm, respectively, for the right and left sides. Because a significant negative correlation was observed between original condylar displacements and age factors, the displacement values were statistically adjusted to 2.74 +/- 2.00 mm and 2.44 +/- 1.93 mm. On the horizontal plane, the mean displacements measured were -0.72 +/- 1.53 mm on the right side and -0.51 +/- 1.98 mm on the left. The mean displacement on the transversal plane was 0.03 +/- 0.87 mm. A comparison between these values and those observed in non-deprogrammed groups, as well as those published in the related literature, indicates that use of occlusal splints results in greater mean condylar displacement values, especially vertically, between CR and MHI positions, which contributed to a more accurate orthodontic diagnosis.

Static analysis of soil/pile interaction in layered soil by BEM/BEM coupling

In this article we propose to use the boundary element method (BEM) to analyze soil-foundation interactions. The soil structure is modeled as several dissimilar strata placed one on top of the other, composing a sandwich-like profile. Any of these layers may contain components of the foundations. Each region occupied by a soil layer or by a foundation component is handled as a 3D isotropic, elastic and homogeneous domain, and is analyzed by BEM. As a consequence of the positioning of the various subregions in this model, the technique of successive rigidity can be applied directly, resulting in a considerable reduction in the volume of data being stored and manipulated throughout the analysis.

TMJ response to mandibular advancement surgery: an overview of risk factors

Objective In order to understand the conflicting information on temporomandibular joint (TMJ) pathophysiologic responses after mandibular advancement surgery, an overview of the literature was proposed with a focus on certain risk factors. Methods A literature search was carried out in the Cochrane, PubMed, Scopus and Web of Science databases in the period from January 1980 through March 2013. Various combinations of keywords related to TMJ changes [disc displacement, arthralgia, condylar resorption (CR)] and aspects of surgical intervention (fixation technique, amount of advancement) were used. A hand search of these papers was also carried out to identify additional articles. Results A total of 148 articles were considered for this overview and, although methodological troubles were common, this review identified relevant findings which the practitioner can take into consideration during treatment planning: 1- Surgery was unable to influence TMJ with preexisting displaced disc and crepitus; 2- Clicking and arthralgia were not predictable after surgery, although there was greater likelihood of improvement rather than deterioration; 3- The amount of mandibular advancement and counterclockwise rotation, and the rigidity of the fixation technique seemed to influence TMJ position and health; 4- The risk of CR increased, especially in identified high-risk cases. Conclusions Young adult females with mandibular retrognathism and increased mandibular plane angle are susceptible to painful TMJ, and are subject to less improvement after surgery and prone to CR. Furthermore, thorough evidenced-based studies are required to understand the response of the TMJ after mandibular advancement surgery.

Effects of mandibular advancement surgery combined with minimal maxillary displacement on the volume and most restricted cross-sectional area of the pharyngeal airway

The purpose of this study was to evaluate changes in the volume and most restricted cross-sectional area of the pharyngeal airway as a result of mandibular advancement surgery with minimal maxillary displacement, and to ascertain the change in height of this restricted area and whether gender and age could influence these results. Cone beam computed tomography scans were obtained from 25 patients (seven male and 18 female, average age 35.5 years). The measurements were done using the InVivoDental software (version 5.0). Comparisons were made between measurements taken prior to treatment (T1) and postsurgery (T2, average 6.3 months after surgery). No variation was detected on the scans with regard to head position, which could influence the pharynx airway. Surgery significantly increased the pharynx airway volume at the total (P<0.0001), upper (P=0.0001), and lower (P<0.0001) levels, with respective enlargements of 54.5%, 37.0%, and 91.3%. Gender and age did not influence this increase. A significant enlargement in the minimum area of the pharynx airway was detected (P<0.0001), which changed in shape from a tapering to a rounded shape. Using binomial and multiple logistic regression tests, this constricted site presented an unpredictable change in position as a result of surgery, with no association to gender (P=0.0745) or age (P=0.5879).

Boundary element analysis of capped and uncapped pile groups

Abstract A conventional application of the Boundary Element Method (BEM) to the elastic analysis of sizeable capped pile groups rapidly leads to large computational execution time. This paper develops a BEM formulation for solving such problems more efficiently, and with adequate precision, in which the traction along each pile in a group is represented by a polynomial function. With this approach the tractions need only a few nodes along the shaft to be represented and all the integrals involved can be analytically evaluated. The pile is supposed to be rigid but the formulation can be easily extended to the inclusion of its flexibility. Only vertical displacement compatibility between the soil, the piles and the smooth, rigid cap is enforced. The cap–soil interface is divided into triangular elements, each with three nodes, across which contact pressures vary linearly. Numerical results are presented for single piles and for pile groups, with and without ground-contacting caps. In all these examples the pile loads and group stiffnesses are close to those obtained from other formulations.

Alternative technique for the solution of plate bending problems using the boundary element method

Abstract The objective of this work consists of presenting a boundary element technique for analysis of bending plates where all algebraic representations of rotations for boundary nodes are avoided. The technique requires outside load points whose definition is extensively studied in this article.

Alternative boundary element approach to compute efforts along zoned domain interfaces

Abstract The aim of this work is to present a formulation to compute efforts along interfaces of plates with different stiffnesses. From the integral representation of displacements, written for the entire plate, and avoiding physical separation between subregions, the integral representation of curvatures for interface points is derived. Using this integral equation, bending and twisting moments are then obtained. Examples are presented to illustrate the formulation, comparing the obtained results with the values computed with a finite element code.