scholarly journals Long-term Test Arrangement for Externally Strengthened Reinforced Concrete Elements

10.14311/452 ◽  
2003 ◽  
Vol 43 (4) ◽  
Author(s):  
T. Vaňura ◽  
P. Štěpánek ◽  
I. Švaříčková ◽  
J. Adámek
Keyword(s):  
Epoxy Resin ◽  
Epoxy Resins ◽  
Glass Fibers ◽  
High Strength ◽  
Space Saving ◽  
External Strengthening ◽  
Long Term Behavior ◽  
Concrete Elements ◽  
Special Space

Methods for external strengthening of concrete use elements of very high tensional strength glued on to its tensioned surface. These elements may be of metal, carbon fibers (CFRP), glass fibers or others, usually having very good mechanical properties. However, these high-strength elements are normally attached to concrete by epoxy resins. Epoxy resins have a low Young`s modulus and therefore a higher rate of creep may have an influence on the long-term behavior of such external strengthening. In order to verify this idea experimentally a special space-saving arrangement of tests is described in this paper. Panels act as loaded beams but simultaneously as a load for the other panels in a stand. The different load magnitude acting on a different layer of panels should make it possible to study the long-term influence of the degree of shear force on the glue creep. Certainly, the glue creep may be dependent on the type of epoxy resin; therefore several epoxy resin types are included in the tests.

Numerical analysis and investigation of short- and long-term behavior of unidirectional composites

2017 ◽  
Vol 52 (5) ◽  
pp. 659-678
Author(s):  
Elias Dib ◽  
Jean François Caron ◽  
Wassim Raphael ◽  
Ioannis Stefanou ◽  
Fouad Kaddah
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Fiber Strength ◽  
Fiber Type ◽  
Glass Fibers ◽  
Shear Lag ◽  
Unidirectional Composites ◽  
Long Term Behavior ◽  
Shear Lag Theory

This study gives a detailed analysis on estimating the ultimate tensile strength of unidirectional fiber reinforced composites and its creep behavior under sustained tension load. We develop two different micromechanical models that allow us to estimate the longitudinal tensile strength and the evolution with time of fiber and matrix stresses around arbitrary array of fiber breaks. The first model is based on the shear-lag theory while the second one is developed using the software Abaqus. The comparison of the above models allowed to validate the fundamental assumptions of the shear-lag theory (first model) as well as several numerical issues related to time integration and spatial discretization. The Monte–Carlo method was used in order to account for the stochastic fiber strength and its impact on the ultimate tensile strength (short-term) and creep (long-term behavior) of unidirectional composites. Finally, a parametric investigation on the fiber type and the load level on the long-term behavior of unidirectional composites was performed showing an accelerating creep effect for fibers of inferior quality such as glass fibers compared to carbon fibers.

Mechanical and Structural Stability of Perovskites Membranes in Reducing Environments

2002 ◽  
Vol 752 ◽  
Author(s):  
Nagendra Nagabhushana ◽  
William F. Haslebacher ◽  
Venkat K. Venkataraman ◽  
Sukumar Bandopadhyay
Keyword(s):  
Mechanical Stability ◽  
High Strength ◽  
Air Separation ◽  
Membrane Reactors ◽  
Structure Property ◽  
A Site ◽  
Long Term Behavior ◽  
Catalytic Membrane Reactors ◽  
Perovskite Type

ABSTRACTMixed ionic electronic conducting perovskite type oxides are promising materials for potential use in various applications such as in fuel cells and membranes for air separation. An important issue in the development of the perovskites is the structural, chemical and mechanical stability of these materials at high temperatures and reducing environments (oxygen partial pressure from 0.21 to 10−17 atm) encountered in membrane reactors. SrFeO3 oxides doped with La on the A-site and Cr on the B-site showed high strength at room temperature in air. The strength degrades rapidly with an increase in temperature in air as compared to in N2 and CO2/CO environment. Fracture in the material is characterized by non-equilibrium segregation of elements within the grains. The observations provide valuable structure-property correlation as applicable to the long-term behavior of the material in advanced catalytic membrane reactors.

scholarly journals Theoretical Investigation of Nonlinear Time-Dependent Behavior of Two-Way High-Strength Concrete Walls

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Yue Huang ◽  
Rui Rao ◽  
Yonghui Huang ◽  
Zilin Zhong
Keyword(s):  
Geometric Nonlinearity ◽  
High Strength Concrete ◽  
High Strength ◽  
Time Dependent ◽  
Fourier Series Expansion ◽  
Time Step ◽  
Strength Concrete ◽  
Dependent Behavior ◽  
Long Term Behavior

High-strength concrete (HSC) walls have been increasingly used in the past decades. However, the time-dependent behavior of HSC wall panels in two-way action was not investigated, and the time effect of creep is not included in the design codes in most countries. For this purpose, the nonlinear long-term behavior of two-way HSC wall is investigated in this paper. A theoretical model is developed using time-stepping analysis considering geometric nonlinearity and creep of concrete. A rheological material model that is based on the generalized Maxwell chain is adopted to model the concrete creep. Von Karman plate theory is used to derive the incremental governing equations. The equations are solved numerically at each time step based on a Fourier series expansion of the deformations and loads and numerical multiple shooting method. It shows that the model can effectively predict the time-dependent behavior of two-way HSC panels, where the out-of-plane deflection and internal bending moments increase with time due to the combined effects of creep and geometric nonlinearity, which may ultimately lead to creep buckling failures. A parametric study shows that the long-term behavior of the panel is very sensitive to the in-plane load level and eccentricity, slenderness ratio, aspect ratio, and edge support conditions.

LONG TERM BEHAVIOR OF CONCRETE MEMBER STRENGTHENED WITH INTERNAL PRESTRESSING SYSTEM

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
Isamu Yoshitake ◽  
Tatsuhiko Mimoto ◽  
Takuya Sakaki ◽  
Jun Mizushima
Keyword(s):  
High Strength ◽  
Concrete Member ◽  
Loading Test ◽  
Concrete Members ◽  
Prestressing Force ◽  
Pull Out ◽  
Long Term Behavior ◽  
Strengthening Method ◽  
Prestressing Tendon

To maintain and retrofit appropriately concrete structures, various strengthening materials and methods have been developed and applied. One of the effective and reliable strengthening method for concrete is an application of the prestressing system. The present study focuses on a strengthening system using an internal anchorage and a prestressing tendon. The strengthening system is acceptable even in relatively narrow workspaces, and also applicable for joints between existing and additional concrete members. In our previous investigations, a static push-out and pull-out tests were performed to examine the load-bearing capacity of the prestressing tendon embedded in the wedge anchor. The test confirmed that the prestressing tendon can be anchored firmly in an internal wedge hole filled with high-strength mortar. Long-term behavior of the strengthened member should be examined to confirm the applicability of the system. The load and deformation of a concrete member subjected to sustained force by the prestressing bar were measured for 1 year. This paper reports the long-term loading test, and discusses the time-dependent properties of the strengthened concrete member. The test result confirms that the loss of prestressing force is negligible for actual applications.

scholarly journals Bonded Orthodontic Retainer and Fixed Partial Denture Made with Fiber Reinforced Composite Resin

2011 ◽  
Vol 05 (02) ◽  
pp. 237-240 ◽  
Author(s):  
Ovul Kumbuloglu ◽  
Ahmet Saracoglu ◽  
Cenk Cura ◽  
Atilla User
Keyword(s):  
Tooth Movement ◽  
Glass Fibers ◽  
Orthodontic Tooth Movement ◽  
Fiber Reinforced ◽  
Partial Denture ◽  
Fiber Reinforced Composite ◽  
Fixed Partial Denture ◽  
Reinforced Composite ◽  
Long Term Behavior

ABSTRACTRetention is the phase of orthodontic treatment which maintains teeth in their orthodontically corrected positions, following the cessation of active orthodontic tooth movement. Development of resin-impregnated, fiber-reinforced composite materials has provided the potential to develop new approaches for stabilizing teeth and replacing teeth conservatively. This case report describes the rehabilitation of a patient with orthodontic and prosthetic problems. The long-term behavior of glass fibers splint must be evaluated in clinical studies. (Eur J Dent 2011;5:237-240)

Epoxy Resin Embedment

1968 ◽  
Vol 26 ◽  
pp. 100-101
Author(s):  
J. G. Adams ◽  
M. M. Campbell ◽  
H. Thomas ◽  
J. J. Ghldonl
Keyword(s):  
Electron Microscopy ◽  
Electron Beam ◽  
Epoxy Resin ◽  
Light Microscope ◽  
Epoxy Resins ◽  
Image Contrast ◽  
Tissue Preservation ◽  
Resin System ◽  
Excellent Quality

Since the introduction of epoxy resins as embedding material for electron microscopy, the list of new formulations and variations of widely accepted mixtures has grown rapidly. Described here is a resin system utilizing Maraglas 655, Dow D.E.R. 732, DDSA, and BDMA, which is a variation of the mixtures of Lockwood and Erlandson. In the development of the mixture, the Maraglas and the Dow resins were tested in 3 different volumetric proportions, 6:4, 7:3, and 8:2. Cutting qualities and characteristics of stability in the electron beam and image contrast were evaluated for these epoxy mixtures with anhydride (DDSA) to epoxy ratios of 0.4, 0.55, and 0.7. Each mixture was polymerized overnight at 60°C with 2% and 3% BDMA.Although the differences among the test resins were slight in terms of cutting ease, general tissue preservation, and stability in the beam, the 7:3 Maraglas to D.E.R. 732 ratio at an anhydride to epoxy ratio of 0.55 polymerized with 3% BDMA proved to be most consistent. The resulting plastic is relatively hard and somewhat brittle which necessitates trimming and facing the block slowly and cautiously to avoid chipping. Sections up to about 2 microns in thickness can be cut and stained with any of several light microscope stains and excellent quality light photomicrographs can be taken of such sections (Fig. 1).

Subcritical Crack Growth and Long-Term Strength in Rock and High-Strength and Ultra Low-Permeability Concrete

2009 ◽  
Vol 58 (6) ◽  
pp. 525-532 ◽  
Author(s):  
Yoshitaka NARA ◽  
Masafumi TAKADA ◽  
Daisuke MORI ◽  
Hitoshi OWADA ◽  
Tetsuro YONEDA ◽  
...  
Keyword(s):  
Crack Growth ◽  
Subcritical Crack Growth ◽  
High Strength ◽  
Low Permeability ◽  
Term Strength

KUBOTA KNC-03

Alloy Digest ◽  
2010 ◽  
Vol 59 (1) ◽  
Keyword(s):  
Compressive Strength ◽  
High Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
High Strength ◽  
Temperature Performance ◽  
Resistance To Oxidation

Abstract Kubota KNC-03 is a grade with a combination of high strength and excellent resistance to oxidation. These properties make this alloy suitable for long-term service at temperature up to 1250 deg C (2282 deg F). This datasheet provides information on physical properties, hardness, elasticity, tensile properties, and compressive strength as well as creep. It also includes information on high temperature performance as well as casting and joining. Filing Code: Ni-676. Producer or source: Kubota Metal Corporation, Fahramet Division. See also Alloy Digest Ni-662, April 2008.

ATI 6-2-4-2

Alloy Digest ◽  
2020 ◽  
Vol 69 (8) ◽  
Keyword(s):  
Tensile Strength ◽  
Titanium Alloy ◽  
High Temperature ◽  
Creep Strength ◽  
High Strength ◽  
Heat Treating ◽  
Good Combination ◽  
Long Term Stability ◽  
Temperature Performance

Abstract ATI 6-2-4-2 is a near-alpha, high strength, titanium alloy that exhibits a good combination of tensile strength, creep strength, toughness, and long-term stability at temperatures up to 425 °C (800 °F). Silicon up to 0.1% frequently is added to improve the creep resistance of the alloy. This datasheet provides information on composition, physical properties, hardness, and tensile properties as well as creep. It also includes information on high temperature performance as well as forming, heat treating, machining, and joining. Filing Code: Ti-169. Producer or Source: ATI.

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