Search results for "Structural Engineering"
showing 10 items of 1998 documents
Critical and Fracture Planes of 18G2A Steel Under Nonproportional Combined Bending and Torsion
2008
Many multiaxial fatigue failure criteria of materials are based on the critical plane approach [1, 2, 3]. In these criteria, it is assumed that the fatigue failure of material is caused by stresses and/or strains acting in one plane (called critical) within the material. The proper orientation of that plane in fatigue failure criteria based on the critical plane concept must be established for fatigue life calculation. In the paper the damage accumulation method was used to determine the critical plane orientations. In this method, the critical plane is the plane where the maximum damage degree, computed according to the selected fatigue failure criterion, is the highest. The critical plane…
Comparison of impact characteristics of four different ice hockey arena dasher boards
2012
During recent years the incidence of ice hockey related concussions has increased. Therefore, the main aim of this study was to determine how dasher board materials and structures affect impact characteristics and thereby concussion risk. The measurements were divided into two parts; 1. physiological characteristics of body checks were determined in real game measurements, and 2. simulation of body checks in the laboratory. Peak forces and stopping distances were determined from the high-speed camera data, and stiffness values were subsequently calculated. Dasher board materials and structures had a clear effect on impact characteristics. Flexible protective shielding material resulted in 1…
Comparison of frictional forces during the closure of extraction spaces in passive self-ligating brackets and conventionally ligated brackets using t…
2019
Background This study compared the frictional force resulting from the bracket/archwire interface and the stress at the root/periodontal ligament/bone interface, between passive self-ligating brackets and conventionally ligated brackets, during the space closure stage. Material and methods A cone beam tomography was taken to a female patient that required extraction of upper first premolars and passive self-ligating system; three months after its activation, a cone beam tomography was taken again. The designs of the maxillary bone and the entire system were possible through tomography images and stereomicroscopic photographs. Validation of the Finite Element Method (FEM) was achieved compar…
Analysis of static friction and elastic forces in a nanowire bent on a flat surface: A comparative study
2014
ZnO nanowires bent to a complex shape and held in place by static friction force from supporting flat surface are investigated experimentally and theoretically. The complex shapes are obtained by bending the nanowires inside a scanning electron microscope with a sharp tip attached to a nanopositioner. Several methods previously described in the literature are applied along with author's original method to calculate the distributed friction force and stored elastic energy in the nanowires from the bending profile. This comparative study evidences the importance of the usage of appropriate models for accurate analysis of the nanowires profile. It is demonstrated that incomplete models can lea…
Experimental evaluation of the durability of innovative cementitious coatings: photocatalytic activity and colour
2012
Today, in a world context characterized by high pollution levels and increasingly limited natural resources, even in the building sector, focusing on environmental issues, through energy saving and a more rational use of these resources, both during construction and management, is fundamental. An important contribution in this direction is given by the knowledge of the durability of products and building components, especially when innovative products are applied and no information are available on the reliability and service life. The research concerns the evaluation of the durability of cement-based photocatalytic coatings ("rasanti" in the Italian diction), containing different types of …
Overstrength requirements to avoid brittle shear failure in RC slender beams with stirrups
2020
Abstract In this paper, an analytical expression was derived for the prediction of shear strength of slender reinforced concrete (RC) beams with stirrups. Failure occurring in B and D regions of the beam was considered. An expression derived for the shear strength of the B region was based on a modified constant angle truss model. The analytical expression derived consisted of three terms. The first one was related to the concrete contribution expressed through the square root of cylindrical compressive strength, geometrical ratio of longitudinal bars, and depth to width ratio. The second one was relating to the shear force induced by yielding of stirrups to the inclination of the main crac…
Flexural Response of RC Beams Failing in Shear
2020
In this paper, an analytical model to determine the flexural response of simply supported RC beams under four-point bending tests failing in flexure and shear is presented. The model is able to provide load-deflection curves, including also the shear contributions, which are determined assuming a kinematic rigid plastic model able to consider different strength contributions such as the concrete, the dowel action, and transverse reinforcement with progressive yielding. For each contribution, a physical explanation is provided to link the strength evaluation with a specific kinematic evolution for the determination of the overall response of RC beams under combined shear and flexural loads. …
Estimation of the effective diffusivity of blowing agents in closed-cell low-density polyurethane foams based on thermal aging data
2021
Abstract Low-density closed-cell polyurethane (PU) foams are applied as thermal insulation materials due to their low thermal conductivity imparted by that of the physical blowing agent (PBA) used in foam production. However, foam conductivity tends to gradually increase with time, primarily due to changes in the gas composition in foam cells brought about by gas diffusion. To enable predicting the variation of conductivity during the service life of foam insulation, gas diffusivities are usually determined by measuring the gas composition in foams at different aging times. This study considers an alternative approach of estimating the effective diffusivities of gases in PU foams, which is …
Influence of FRP wrapping techniques on the compressive behavior of concrete prisms
2006
Abstract Results of an experimental investigation on the compressive behavior of concrete prisms with square cross-section, externally wrapped with carbon fiber reinforced plastic (CFRP) sheets are presented. The effects of the following parameters were analyzed: local reinforcement at the corners and continuous layers; horizontal and vertical discontinuous strips; number of continuous layers—length of specimens. An analytical model is proposed to determine the maximum bearing capacity of compressed concrete members with square cross-section and externally wrapped with FRP for the different configurations examined, and also able to consider the strength reduction with the length increase of…
ΔJ-integral range estimation for fatigue crack growth rate description
2004
Abstract The paper presents an equation for fatigue crack growth rate description taking into account the ΔJ-integral range, which was verified experimentally for variable bending. Plane, notched specimens were tested under unilaterally restrained bending for different values of stress ratio R. The results of tests and numerical calculations were presented as characteristics of fatigue crack growth rate. It has been shown that in the case of a change of stress ratio from R=−1.0 to R=0.0, the crack rate increases twice for 10HNAP steel and five times for 18G2A steel. The empirical formula presented in the paper describes well the test results of fatigue crack rate in the steels.