scholarly journals High-Performance Steel Bars and Fibers as Concrete Reinforcement for Seismic-Resistant Frames

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Andres Lepage ◽  
Hooman Tavallali ◽  
Santiago Pujol ◽  
Jeffrey M. Rautenberg
Keyword(s):  
High Performance ◽  
Volume Fraction ◽  
Lateral Displacement ◽  
High Strength ◽  
Longitudinal Reinforcement ◽  
Concrete Compressive Strength ◽  
Viable Option ◽  
Earthquake Resistant ◽  
Steel Bars ◽  
Displacement Reversals

Experimental data are presented for six concrete specimens subjected to displacement reversals. Two specimens were reinforced longitudinally with steel bars Grade 410 (60 ksi), two with Grade 670 (97 ksi), and two with Grade 830 (120 ksi). Other experimental variables included axial load (0 or 0.2fc′  Ag) and volume fraction of hooked steel fibers (0 or 1.5%). All transverse reinforcement was Grade 410, and the nominal concrete compressive strength was 41 MPa (6 ksi). The loading protocol consisted of repeated cycles of increasing lateral displacement reversals (up to 5% drift) followed by a monotonic lateral push to failure. The test data indicate that replacing conventional Grade-410 longitudinal reinforcement with reduced amounts of Grade-670 or Grade-830 steel bars did not cause a decrease in usable deformation capacity nor a decrease in flexural strength. The evidence presented shows that the use of advanced high-strength steel as longitudinal reinforcement in frame members is a viable option for earthquake-resistant construction.

Dynamic Attenuation and Compressive Characterization of Syntactic Foams

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Bhaskar Ale ◽  
Carl-Ernst Rousseau
Keyword(s):  
High Performance ◽  
Volume Fraction ◽  
Ultrasonic Attenuation ◽  
Dynamic Properties ◽  
High Strength ◽  
Particulate Composites ◽  
Syntactic Foams ◽  
Core Elements ◽  
Marine Applications ◽  
Damping Materials

Hollow particulate composites are lightweight, have high compressive strength, are low moisture absorbent, have high damping materials, and are used extensively in aerospace, marine applications, and in the manufacture of sandwich composites core elements. The high performance of these materials is achieved by adding high strength hollow glass particulates (microballoons) to an epoxy matrix, forming epoxy-syntactic foams. The present study focuses on the effect of volume fraction and microballoon size on the ultrasonic and dynamic properties of Epoxy Syntactic Foams. Ultrasonic attenuation coefficient from an experiment is compared with a previously developed theoretical model for low volume fractions that takes into account attenuation loss due to scattering and absorption. The guidelines of ASTM Standard E 664-93 are used to compute the apparent attenuation. Quasi-static compressive tests were also conducted to fully characterize the material. Both quasi-static and dynamic properties, as well as coefficients of attenuation and ultrasonic velocities are found to be strongly dependent upon the volume fraction and size of the microballoons.

Improving UV Resistance of Fibers: Idealized Computational Model Predicting the Distribution of UV Blocking Cylindrical Nanoparticles in Protective Polymeric Layer

2015 ◽  
Vol 10 (1) ◽  
pp. 155892501501000
Author(s):  
Abdelfattah Mohamed Seyam ◽  
Rahul Vallabh ◽  
Ahmed H. Hassanin
Keyword(s):  
Aspect Ratio ◽  
Computational Model ◽  
High Performance ◽  
Volume Fraction ◽  
Three Dimensional ◽  
High Strength ◽  
Uv Protection ◽  
Uv Resistance ◽  
Premature Failure ◽  
Areal Coverage

High strength fibers such as PBO and Kevlar are used to produce composites, bulletproof vests, tendons of giant scientific balloons, and other high performance products. These fibers, however, are known to degrade upon exposure to Ultraviolet (UV) radiation which causes premature failure of the end-products. Improving UV resistance of high strength fibers like PBO through methods such as adding UV inhibiting particles during filament spinning or dyeing/coating process is not only extremely difficult, but often fails to provide the adequate UV protection. As an alternative to conventional approaches, UV protection of high performance yarns/braids can be effectively achieved by covering them with a polymeric sheath containing dispersed UV inhibiting nanoparticles. In this work, a computational model was developed to optimize critical factors such as thickness (weight) of the protective sheath and the amount of UV blockers for a given particle size, which influence the UV protective efficiency of the sheath. In order to simulate three-dimensional dispersion of nanoparticles in a polymer matrix, the model considers a random distribution of cylindrical nanoparticles of different size, aspect ratio, and volume fraction in a three-dimensional volume of protective sheath of a given length, width, and thickness. 2D visualization and image analysis techniques were utilized to determine the area projected by the particles on the x-y plane (areal coverage provided by nanoparticles). The areal coverage values obtained from the model were found to be higher than the experimental results due to the agglomeration of nanoparticles in the sheath caused during the polymer compounding process. However, the purpose of the model is to serve as a benchmarking tool to aid in the design and development of UV protective sheaths and films, and not to estimate absolute UV protection values. Analysis of the relationship between areal coverage and various input parameters in the model show that areal coverage increases with an increase in particle volume fraction and film thickness, and a decrease in particle diameter and length. It was also found that areal coverage was more significantly influenced by particle aspect ratio than by particle length.

Study on the Compressive Strength and Mixing of Ultra-High Performance Concrete

2013 ◽  
Vol 357-360 ◽  
pp. 825-828
Author(s):  
Su Li Feng ◽  
Peng Zhao
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
High Performance Concrete ◽  
High Strength ◽  
Strength Properties ◽  
Test Method ◽  
Test Results ◽  
Concrete Compressive Strength ◽  
Ultra High Performance Concrete ◽  
Mixture Ratio

The test in order to obtain liquidity, higher intensity ultra-high performance concrete(UHPC), in the course of preparation, high intensity quartz sand to replace the ordinary sand,reasonable mixture ratio control low water-cement ratio,the incorporation of part of the test piece ofsteel fibers, produced eight specimens . In the ordinary molding and the standard conservation 28d thecase, the ultra-high-performance concrete compressive strength of more than 170MPa.Thepreparation of the test method and test results will provide the basis for further study of the law of themechanical properties of ultra high strength properties of concrete.

A Methodology for Synthesizing High-Performance Robots Fabricated With Optimally Tailored Composite Laminates

1987 ◽  
Vol 109 (1) ◽  
pp. 74-86 ◽  
Author(s):  
C. K. Sung ◽  
B. S. Thompson
Keyword(s):  
Composite Laminates ◽  
High Performance ◽  
Volume Fraction ◽  
Three Dimensional ◽  
High Strength ◽  
Fiber Volume ◽  
Cross Sectional ◽  
Fiber Properties ◽  
Robot Arms ◽  
The Matrix

An essential ingredient of the next generation of robotic manipulators will be high-strength lightweight arms which promise high-performance characteristics. Currently, a design methodology for optimally synthesizing these essential robotic components does not exist. Herein, an approach is developed for addressing this void in the technology-base by integrating state-of-the-art techniques in both the science of composite materials and also the science of flexible robotic systems. This approach is based on the proposition that optimal performance can be achieved by fabricating robot arms with optimal cross-sectional geometries fabricated with optimally tailored composite laminates. A methodology is developed herein which synthesizes the manufacturing specification for laminates which are specifically tailored for robotic applications in which both high-strength, high-stiffness robot arms are required which also possess high material damping. The parameters in the manufacturing specification include the fiber-volume fraction, the matrix properties, the fiber properties, the ply layups, the stacking sequence and the ply thicknesses. This capability is then integrated within a finite-element methodology for analyzing the dynamic response of flexible robots. An illustrative example demonstrates the approach by simulating the three-dimensional elastodynamic response of a robot subjected to a prescribed spatial maneuver.

scholarly journals OPTIMIZATION OF UHPFRC BEAMS SUBJECTED TO BENDING USING GENETIC ALGORITHMS

2014 ◽  
Vol 20 (4) ◽  
pp. 527-536 ◽  
Author(s):  
Goran Ćirović ◽  
Vlastimir Radonjanin ◽  
Milan Trivunić ◽  
Milan Trivunić ◽  
Dragan Nikolić
Keyword(s):  
Mechanical Properties ◽  
Genetic Algorithms ◽  
High Performance ◽  
Experimental Studies ◽  
High Strength ◽  
Steel Fibres ◽  
Four Point Bending ◽  
Steel Bar ◽  
Steel Bars ◽  
Prestressed Reinforcement

Ultra high performance fibre reinforced concrete (UHPFRC) is cementitious composite with very high strength, and when compared with ordinary concrete it is a more superior material both in terms of its mechanical properties and its durability. In order to predict the behaviour of UHPFRC beams, first of all, experiments were carried out to investigate the mechanical properties of composites containing 2% and 4% of steel fibres. Following this, four beams of 2 m in length were tested by subjecting to four point bending. Two beams contained only micro steel fibres, while the remaining two contained conventional steel bar reinforcement. On the basis of experimental studies and recommendations by the AFGC for UHPC, the behaviour of the beams was modelled and optimization was carried out using genetic algorithms (GA) according to the criterion of minimum price. In this paper, the prices of individual UHPFRC beams are also shown in comparison with beams, which contain steel bars or prestressed reinforcement.

An Optimal Design of Composite Robot Arms

1989 ◽  
Author(s):  
C. K. Sung ◽  
S. S. Shyl
Keyword(s):  
Composite Laminates ◽  
High Performance ◽  
Design Methodology ◽  
Volume Fraction ◽  
Robot Manipulator ◽  
High Strength ◽  
Fiber Volume ◽  
Low Mass ◽  
Design Requirements ◽  
Fast Settling

Abstract A design methodology considering the issue of manufacturability, in particular, is presented for synthesizing high-performance articulating robotic systems fabricated with optimally-tailored composite laminates. By optimally specifying the types of fiber, matrix, stacking sequence, fiber volume fraction, fiber layups, etc., the synthesized composite material may possess significantly superior characteristics such as high damping, high stiffness, high strength and low mass. In accordance with the design requirements, the minimum deflection during articulating motion or the fast settling time after the power stopped, the design objectives and constraint conditions were specified. As an illustrative example, a two-link robot manipulator fabricated with aforementioned composite laminates is employed for demonstrating the proposed design methodology.

Ductility of Ultra-High Performance Concrete and its Correlation with Tensile Strength Increase

2015 ◽  
Vol 665 ◽  
pp. 21-24
Author(s):  
B.I. Bae ◽  
Hyun Ki Choi ◽  
Chang Sik Choi
Keyword(s):  
Tensile Strength ◽  
High Performance ◽  
High Performance Concrete ◽  
Volume Fraction ◽  
High Strength ◽  
Reinforcement Ratio ◽  
Fiber Reinforced Concrete ◽  
Strength Increase ◽  
Ultra High Performance Concrete ◽  
Fiber Volume

In this study, ductility of members with ultra-high performance concrete was investigated using moment-curvature analysis for the verification of safety under large deformation of ultra-high performance concrete structural members. For the analysis of members with ultra-high performance concrete, mathematical stress-strain model was selected among the results conducted by other researchers on the compressive and tensile behavior of high strength concrete and fiber reinforced concrete. According to the investigation on ductility of members with ultra-high performance concrete, decrease of ductility was observed with increase of tensile strength of concrete under the same reinforcement ratio. Members with 2~3% of reinforcement ratio, which usually be used in the field engineering, show the decrease of ductility with increase of fiber volume fraction. As a results of parametric study, limitation of maximum reinforcement ratio ( or limitation of net tensile strain ) suggested by current design code is not safe when using ultra-high performance concrete.

scholarly journals Seismic Behavior of RC Beam Column Joints with 600 MPa High Strength Steel Bars

2020 ◽  
Vol 10 (13) ◽  
pp. 4684
Author(s):  
Jian Feng ◽  
Shuo Wang ◽  
Marco Meloni ◽  
Qian Zhang ◽  
Jingwen Yang ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Axial Compression ◽  
High Strength Steel ◽  
Seismic Behavior ◽  
Failure Modes ◽  
High Strength ◽  
Longitudinal Reinforcement ◽  
Seismic Properties ◽  
Steel Bars ◽  
Energy Dissipation Capacity

This paper presents an experimental investigation of the seismic performance of interior beam–column joints with beams reinforced with Grade 600MPa longitudinal steel bars. Six full-scale reinforcement concrete (RC) interior joints are designed with different axial compression ratios and longitudinal reinforcement ratios, which are tested under reversed cyclic loading. Failure modes, hysteretic curves, skeleton curves, energy dissipation capacity, and the ductility of joints are investigated systematically. Moreover, the effect of the different axial compression ratios and longitudinal reinforcement ratios on the seismic behavior of the joints are deeply studied. Comparisons performed between specimens demonstrate that among the beam–column joints with 600 MPa high strength steel bars, specimens with high reinforcement ratios have better energy dissipation capacity, slower stiffness degradation, and lower ductility. Moreover, with the increase of the axial compression ratios, the energy dissipation capacity and ductility become weaker. The test results show the favorable seismic properties of beam–column joints equipped with 600 MPa high strength steel bars, which can be regarded as the research basis of the popularization and application of 600 MPa high strength steel bars in reinforcement concrete frame structures.

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