A CONSIDERATION ON THE CREEP STRAIN OF CONCRETE : The effect of the delayed elasticity and the creep recovery upon the creep stress anarisys of the static prestressed concrete member

1989 ◽  
Vol 402 (0) ◽  
pp. 71-78
Author(s):  
SEIICHI WATANABE ◽  
HIROSHI MUGURUMA
Keyword(s):  
Creep Strain ◽  
Prestressed Concrete ◽  
Creep Recovery ◽  
Concrete Member ◽  
Creep Stress

Off-Axis Creep Recovery of Unidirectional Carbon/Epoxy Composites at High Temperature

2007 ◽  
Vol 334-335 ◽  
pp. 65-68 ◽  
Author(s):  
Masamichi Kawai ◽  
H. Kamioka ◽  
Jian Qi Zhang ◽  
Tetsuya Matsuda
Keyword(s):  
High Temperature ◽  
Creep Strain ◽  
Composite System ◽  
Kinematic Hardening ◽  
High Stress ◽  
Unidirectional Composite ◽  
Constant Stress ◽  
Creep Recovery ◽  
Creep Stress ◽  
Proposed Model

Off-axis creep recovery behavior after complete unloading during creep at a constant stress is examined for a unidirectional T800H/3631 carbon/epoxy composite laminate at high temperature. Creep and creep recovery tests are performed on plain coupon specimens with four kinds of fiber orientations: 10, 30, 45 and 90°. It is observed that the creep strain appeared at a high stress does not completely recover after full removal of the creep stress, indicating that an irrecoverable creep strain has developed under the prior constant stress loading. Variable stress creep simulations are attempted using the modified kinematic hardening model for homogenized anisotropic inelastic composites in which an accelerated change in kinematic hardening over a certain range of viscoplastic strain is considered. Comparison with experimental results demonstrates that the proposed model can adequately describe the off-axis creep and creep recovery behaviors of the unidirectional composite system under constant and variable stress conditions.

Visco-elastoplastic Characterization of a Flax-fiber Reinforced Biocomposite

2021 ◽  
Vol 58 (1) ◽  
pp. 78-84
Author(s):  
Constantin Stochioiu ◽  
Horia-Miron Gheorghiu ◽  
Flavia-Petruta-georgiana Artimon
Keyword(s):  
Viscoelastic Behavior ◽  
Flax Fiber ◽  
Creep Recovery ◽  
Fiber Direction ◽  
Fiber Reinforced ◽  
Glass Fiber Composites ◽  
Creep Stress ◽  
Static Mechanical ◽  
Long Term Behavior ◽  
Sample Damage

In the presented study, the load induced long-term behavior of a biocomposite material is analyzed. The studied material is a unidirectional flax fiber reinforced epoxy resin, material, whose quasi-static mechanical properties can compare with those of glass fiber composites. Samples with a fiber direction of 0� were subjected to two types of multi-level creep-recovery tests, one with a varying creep duration, and the other with a varying creep stress, with the purpose of discriminating the viscoplastic and viscoelastic behavior of the composite. Results show a significant viscous response in time, dependent on both creep duration and creep stress, up to 20% of the elastic one. Sample damage is absent, leading to the conclusion that the viscoplastic response is caused by the permanent reorganization of the fiber�s internal structure.

scholarly journals BEHAVIOR OF CHEMICALLY PRESTRESSED CONCRETE MEMBER

1974 ◽  
Vol 1974 (225) ◽  
pp. 101-108 ◽  
Author(s):  
Hajime Okamura ◽  
Yukikazu Tsuji
Keyword(s):  
Prestressed Concrete ◽  
Concrete Member

scholarly journals Analysis of Test System Misalignment in the Creep Test

1982 ◽  
Vol 104 (4) ◽  
pp. 280-284
Author(s):  
Han C. Wu ◽  
T. P. Wang
Keyword(s):  
Creep Strain ◽  
Creep Test ◽  
Test System ◽  
Neutral Axis ◽  
Strain Level ◽  
Initial Strain ◽  
Creep Tests ◽  
Test Sheet ◽  
Creep Stress ◽  
Creep Time

An analysis of test system misalignment is presented for the creep test. Sheet type rectangular 1100-0 aluminum specimens are used for discussion. It is found that the creep strain at the geometric centerline of the specimen is different than that at the neutral axis. However, this difference in the creep strain decreases with time. Generally, the effect of misalignment decreases with creep time. Creep tests conducted with long pullrods and large initial strain level (high creep stress) will tend to minimize the effect of misalignment.

Experimental investigation of the hygrothermal creep strain of wood–plastic composite lumber made from thermally modified wood

2019 ◽  
Vol 33 (9) ◽  
pp. 1248-1268 ◽  
Author(s):  
Murtada Abass A Alrubaie ◽  
Roberto A Lopez-Anido ◽  
Douglas J Gardner ◽  
Mehdi Tajvidi ◽  
Yousoo Han
Keyword(s):  
Creep Strain ◽  
Water Immersion ◽  
Creep Recovery ◽  
Short Term ◽  
Creep Response ◽  
Plastic Composites ◽  
Thermally Modified Wood ◽  
Term Creep ◽  
Modified Wood ◽  
Short Term Creep

The hygrothermal effect on the short-term creep behavior of extruded thermally modified wood fiber–high-strength styrenic copolymer plastic composites (wood–plastic composites (WPCs)) was investigated on specimens preconditioned for 1 month under water immersion (distilled water (DW) and saltwater (SW)). These specimens were then tested in the same conditions for short-term creep and creep-recovery response using a submersible clamp. The short-term creep tests of WPC specimens (that are immersed in water as a function of different temperatures) have not yet been reported in previous studies. The objective of this study was to determine whether the hygrothermal creep response of WPC material evaluated through water immersion differs from the creep response published in the literature for other environmental exposure conditions. The experiments included measuring 30 min of creep and 30 min of creep recovery on the specimens immersed in SW and DW at two different levels of flexural stresses (9% and 14% of the flexural strength) and three temperature values (25, 35, and 45°C). The average creep strain recovery (%) of the specimens was higher for the specimens immersed in SW during testing than the control specimens. The WPC material is considered to have a potential use in structural applications in environments where the temperature is below 45°C because of the following factors: the low deformation under the short-term sustained loading, the decrease in the deformation rate with respect to the increase in load duration, maintaining the modulus of elasticity over a range of temperatures from 25°C to 45°C under sustained load, and the ability to recover more than 69% of the average creep strain under water immersion when the loading source is removed. The creep strain fractional increment (CSFI) of the WPC in this study under all conditions was 13% which is 86% lower than the CSFI of the WPCs reported in previous studies.

scholarly journals An Improved Equation for Predicting Compressive Stress in Posttensioned Anchorage Zone

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Young-Ha Park ◽  
Moon-Young Kim ◽  
Jong-Myen Park ◽  
Se-Jin Jeon
Keyword(s):  
Finite Element Method ◽  
Compressive Stress ◽  
Prestressed Concrete ◽  
Approximate Equation ◽  
The Finite Element Method ◽  
Concrete Member ◽  
Design Specifications ◽  
Compressive Stresses ◽  
Aashto Lrfd ◽  
Accurate Stress

Validity of the approximate equation for predicting compressive stress in the posttensioned anchorage zone presented in the AASHTO LRFD Bridge Design Specifications was investigated in this study. Numerical analysis based on the finite element method (FEM) and theoretical analysis showed that the AASHTO formula gives relatively accurate stress values when the effect of duct holes is neglected. However, it was found that the formula can significantly overestimate the stresses in the actual prestressed concrete member with spaces occupied by ducts. Therefore, an improved equation was proposed for the existing AASHTO equation to consider the effect of the duct holes on the stress distribution. This resulted in relatively accurate prediction of the distribution and magnitude of the compressive stresses even with the presence of the duct holes. The proposed equation was also validated by comparing with the stresses measured in the test of a posttensioned full-scale specimen. This study is expected to contribute to the design of the anchorage zone in prestressed concrete structures by suggesting a more reasonable way to assess the appropriateness of anchorage devices.

Research and Analysis about Partical Compression for Individual Anchored Prestressed End Strength

2013 ◽  
Vol 395-396 ◽  
pp. 841-844
Author(s):  
Ping Pang
Keyword(s):  
Reinforced Concrete ◽  
Theoretical Calculation ◽  
Bearing Capacity ◽  
Prestressed Concrete ◽  
Calculation Formula ◽  
Concrete Member ◽  
Concrete Members ◽  
Standard Formula ◽  
Reinforced Concrete Member ◽  
Measured Load

According to the specification given, the theoretical calculation formula of the theoretical value is higher than the measured load values. Specifications given by the bureau of compressive bearing capacity formula is suitable for ordinary reinforced concrete member. For prestressed concrete members, especially scattered end anchorage of prestressed concrete member, the standard formula is not applicable.

scholarly journals Microstructural Characterization of Alloy 617 Crept Into the Tertiary Regime

2015 ◽  
Author(s):  
Thomas M. Lillo ◽  
Richard N. Wright
Keyword(s):  
Image Analysis ◽  
Creep Strain ◽  
Void Formation ◽  
Microstructural Characterization ◽  
Low Energy ◽  
Creep Tests ◽  
Alloy 617 ◽  
Creep Stress ◽  
Creep Strains

The dislocation structure and area fraction of creep voids in Alloy 617 were characterized following creep tests interrupted at total creep strains ranging from 2–20%. A range of creep temperatures (750–1000°C) and initial creep stresses (10–145 MPa) produced creep test durations ranging from 1 to 5800 hours. Image analysis of optical photomicrographs on longitudinal sections of the gage length was used to document the fraction of creep porosity as a function of creep parameters. In interrupted creep tests performed at 750°C, minimal levels of creep porosity were found even in samples crept to ∼20% total creep strain. At 1000°C, creep porosity was negligible below total creep strains of 10% and increased thereafter with increasing total creep strain. Also, creep porosity increased with decreasing creep stress for a given total creep strain. TEM performed on the gage sections did not reveal significant creep void formation on grain boundaries or in the grains at the sub-micron level. However, dislocation boundaries exhibited extensive dislocation rearrangement and dislocation-dislocation reactions. It was concluded that the onset of tertiary creep did not result from creep void formation and more likely arose due to the formation of low energy dislocation substructures.

Sign in / Sign up

Export Citation Format

Share Document