scholarly journals Analysis on the Dynamic Wave Attenuation Properties of Metaconcrete Considering a Quasi-Random Arrangement of Inclusions

2021 ◽  
Vol 7 ◽  
Author(s):  
Deborah Briccola ◽  
Anna Pandolfi
Keyword(s):  
Wave Attenuation ◽  
Plain Concrete ◽  
Concrete Specimen ◽  
Longitudinal Direction ◽  
Inclusion Type ◽  
Practical Applications ◽  
Random Arrangement ◽  
Resonant Behavior ◽  
Dynamic Wave ◽  
Positive Quality

The mitigation properties of metaconcrete cast with two types of resonant inclusions are assessed through wave transmission tests. Three cylindric metaconcrete specimens of regular size (20 cm height, 10 cm diameter), containing an equal number of different type of inclusions disposed in a semi-regular lattice, are tested in the longitudinal direction within the sonic range of frequencies. Inclusions, bi-material spheres consisting of a heavy core coated with a soft material, are characterized by a resonant behavior, evaluated numerically with a finite element modal analysis of a unit metaconcrete cell. Each metaconcrete specimen contains six layers consisting of six engineered aggregates of different type. Inclusions are disposed by rotating each layer with respect to the adjacent ones, as so as to create a pseudo-random arrangement. Specimens are excited by a sinusoidal signal of linearly growing frequency, sweeping a range centered at the translational eigenfrequency of the resonant inclusion. A standard plain concrete specimen is used as reference to define a transmissibility coefficient, that facilitates the quantification of the attenuation properties. With respect to plain concrete, all metaconcrete specimens show a marked (up to 80–90%) attenuation of the transmitted signal in proximity of the numerically estimated eigenfrequency of the inclusion. The intensity of the attenuation is weakly dependent on the type of the inclusion, while the frequency where the attenuation is observed depends markedly on the inclusion type. As a very positive quality in the view of practical applications, experimental results confirm that the attenuation effectiveness of metaconcrete is not related to the ordered microstructural arrangement.

scholarly journals A novel experimental method to characterise the shear strength of concrete based on pre-stressed samples. A comparison with existing techniques

2018 ◽  
Vol 183 ◽  
pp. 02049
Author(s):  
Pascal Forquin ◽  
Reem Abdul-Rahman ◽  
Dominique Saletti
Keyword(s):  
Experimental Method ◽  
Shear Fracture ◽  
Plain Concrete ◽  
Concrete Specimen ◽  
Compression Tests ◽  
Second Stage ◽  
Wide Range ◽  
Metallic Ring ◽  
Do So ◽  
Metallic Cell

Mode II shear fracture process can be observed in plain-concrete structures exposed to intensive loadings such as shock, blasting or projectile-impact. It is the reason why the quasi-static and dynamic shear fracturing properties of concrete need to be investigated. In previous works performed by Forquin and coauthors a passive confining cell was applied to PTS (Punch-Through-Shear) specimens in a similar way than in quasi-oedometric compression tests where metallic ring are used as passive confinement. However the change of confining level during the sample loading constitutes a main drawback of this technique. In the present work a novel testing method is proposed based on a pre-stressing of the sample. To do so, the concrete specimen is inserted into pre-stressed metallic cell. During the unloading stage confining stresses are transferred to the ligament of the sample. In a second stage, a differential displacement applied to the central part of the sample toward the side parts produces a shearing of the ligament. The experiments performed in static and dynamic conditions (SHPB testing) allow the shear response of concrete to be determined over a wide range of strain-rates. In the present communication, the testing technique and obtained results are compared to the obtained data with the previous experimental method.

Effect of Specimen Geometry on the Predicted Mechanical Behavior of Polyethylene Pipe Material

2014 ◽  
Author(s):  
Tarek M. A. A. El-Bagory ◽  
Tawfeeq A. R. Alkanhal ◽  
Maher Y. A. Younan
Keyword(s):  
Mechanical Behavior ◽  
Longitudinal Direction ◽  
Primary Objective ◽  
The Other ◽  
Pipe Material ◽  
Ring Specimen ◽  
Design Data ◽  
Practical Applications ◽  
Other Hand ◽  
Gauge Section

The primary objective of the present paper is to depict the mechanical behavior of high density polyethylene, (HDPE), pipes under different loading conditions with different specimen geometries to provide the designer with reliable design data relevant to practical applications. Therefore, it is necessary to study the effect of strain rate, ring configuration, and grip or fixture type on the mechanical behavior of dumb-bell-shaped, (DBS), and ring specimens made from HDPE pipe material. DBS and ring specimens are cut from the pipe in longitudinally, and circumferential (transverse) direction respectively. On the other hand, the ring specimen configuration is classified into two types; full ring, (FR), and notched ring, (NR) (equal double notch from two sides of notched ring specimen) specimens according to ASTM D 2290-12 standard. Tensile tests are conducted on specimens cut out from the pipe with thickness 10 mm at different crosshead speeds (10–1000 mm/min), and ambient temperature, Ta = 20 °C to investigate the mechanical properties of DBS, and ring specimens. In the case of test specimens taken from longitudinal direction from the pipe a necking phenomenon before failure appears at different locations along the gauge section. On the other hand, the fracture of NR specimens occurs at one notched side. The results demonstrated that the NR specimen has higher yield stress than DBS, and FR specimens at all crosshead speeds. The present experimental work reveals that the crosshead speed has a significant effect on the mechanical behavior of both DBS, and ring specimens. The fixture type plays an important role in the mechanical behavior for both FR and NR specimens at all crosshead speeds.

Numerical Simulation of 3-D Failure Process of Reinforced Concrete Specimen under Uniaxial Tension

2007 ◽  
Vol 353-358 ◽  
pp. 949-952 ◽  
Author(s):  
Juan Xia Zhang ◽  
Chun An Tang ◽  
Xiu Yan Zhou ◽  
Xing Jie Hui ◽  
Zheng Zhao Liang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Reinforced Concrete ◽  
Uniaxial Tension ◽  
Process Analysis ◽  
Failure Process ◽  
Plain Concrete ◽  
Concrete Specimen ◽  
Numerical Code ◽  
Concrete Prism

The periodically distributed fracture spacing phenomenon exists in the failure process of the reinforced concrete prism under uniaxial tension. In this paper, A numerical code RFPA3D (3D Realistic Failure Process Analysis) is used to simulate the three-dimensional failure process of plain concrete prism specimen and reinforced concrete prism specimen under uniaxial tension. The reinforced concrete is represented by a set of elements with same size and different mechanical properties. They are uniform cubic elements and their mechanical properties, including elastic modulus and peak strength, are distributed through the specimens according to a certain statistical distribution. The elastic modulus and other mechanical properties are weakened gradually when the stresses in the elements meet the specific failure criterion. The displacement-controlled loading scheme is used to simulate the complete failure process of reinforced concrete. The analyses focus on the failure mechanisms of the concrete and reinforcement. The complete process of the fracture for the plain concrete prism and the fracture initiation, infilling and saturation of the reinforced concrete prism is reproduced. It agrees well with the theoretical analysis. Through 3D numerical tests for the specimen, it can be investigated the interaction between the reinforcement and concrete mechanical properties in meso-level and the numerical code is proved to be an effective way to help thoroughly understand the rule of the reinforcement and concrete and also help the design of the structural concrete components and systems.

Influence of Fiber Type on Concrete Flexural Toughness

2011 ◽  
Vol 287-290 ◽  
pp. 1179-1183
Author(s):  
Jian Guo Han ◽  
Pei Yu Yan
Keyword(s):  
Steel Fiber ◽  
Fiber Type ◽  
Concrete Strength ◽  
Plain Concrete ◽  
Concrete Specimen ◽  
Ratio Method ◽  
Flexural Toughness ◽  
The Common ◽  
Better Than ◽  
Curing Age

Using PCER (post-crack energy ratio) method and plain concrete specimen as reference, the flexural toughness enhancing ability of propylene spinning fiber, propylene monofilament fiber and end-deformed steel fiber was studied. Experiment results show that under the common engineering dosage, the flexural toughness enhancing ability of end-deformed steel fiber is far more outstanding than propylene fibers, and comparing with each other, the flexural toughness enhancing ability of propylene spinning fiber is better than propylene monofilament fiber. As far as one type of fiber is concerned, under the same dosage, along with the enhancement of concrete strength grade, the flexural toughness enhancing ability tends to decrease. Meanwhile, along with enhancement of curing age, the flexural toughness enhancing ability tends to decrease also.

scholarly journals Estimation of the Squirt-Flow Length Based on Crack Properties in Tight Sandstones

Lithosphere ◽  
2022 ◽  
Vol 2022 (Special 3) ◽  
Author(s):  
Chunfang Wu ◽  
Jing Ba ◽  
Lin Zhang ◽  
José M. Carcione
Keyword(s):  
Wave Attenuation ◽  
Direct Method ◽  
Wave Impedance ◽  
Practical Applications ◽  
Detection And Identification ◽  
Flow Length ◽  
Seismic Characterization ◽  
Porosity And Permeability ◽  
The Sichuan Basin ◽  
Fluid Detection

Abstract Tight sandstones have low porosity and permeability and strong heterogeneities with microcracks, resulting in small wave impedance contrasts with the surrounding rock and weak fluid-induced seismic effects, which make the seismic characterization for fluid detection and identification difficult. For this purpose, we propose a reformulated modified frame squirt-flow (MFS) model to describe wave attenuation and velocity dispersion. The squirt-flow length (R) is an important parameter of the model, and, at present, no direct method has been reported to determine it. We obtain the crack properties and R based on the DZ (David-Zimmerman) model and MFS model, and how these properties affect the wave propagation, considering ultrasonic experimental data of the Sichuan Basin. The new model can be useful in practical applications related to exploration areas.

A novel meta-lattice sandwich structure for dynamic load mitigation

2017 ◽  
Vol 21 (6) ◽  
pp. 1880-1905 ◽  
Author(s):  
Bing Li ◽  
Yongquan Liu ◽  
Kwek-Tze Tan
Keyword(s):  
Energy Absorption ◽  
Frequency Band ◽  
Dynamic Load ◽  
Sandwich Structure ◽  
Wave Attenuation ◽  
Band Gaps ◽  
Mass Model ◽  
Resonant Behavior ◽  
The Impact ◽  
Internal Resonators

In this article, a novel meta-lattice sandwich structure is proposed and designed for impulsive wave attenuation and dynamic load mitigation. This original meta-lattice truss core sandwich structure has a similar configuration as a normal lattice sandwich structure, except that its truss bars are composed of meta-lattice truss unit cells. The design philosophy of locally resonant elastic metamaterials is integrated into the meta-lattice truss unit cell whereby a relatively heavier metal core (the resonator) is coated with a soft material layer (rubber coat), which is then connected to an outer shell. Based on this unique construction, several frequency band gaps are created by the locally resonant behavior of the specially designed resonators, in which stress waves within the stopping band gaps are not able to propagate through the material. Analytical spring-mass model is employed to predict the frequency band gaps, whereas numerical finite element simulation is utilized to model the continuum structure under impulsive loadings. The impact response, wave attenuation, and stress distribution contours between normal sandwich structure and meta-lattice sandwich structure are compared and analyzed. The mechanisms of wave mitigation and energy absorption by the internal resonators are thoroughly investigated. Results evidently show that the proposed meta-lattice sandwich structure has a more superior ability for impact mitigation and higher kinetic energy absorption capability due to the locally resonant behavior of the internal resonators.

Flexural Behaviour of Concrete Beams Bonded with Wire Mesh-Epoxy Composite

2014 ◽  
Vol 567 ◽  
pp. 411-416 ◽  
Author(s):  
Ismail M.I. Qeshta ◽  
Payam Shafigh ◽  
Mohd Zamin Jumaat ◽  
Aziz Ibrahim Abdulla ◽  
Ubagaram Johnson Alengaram ◽  
...  
Keyword(s):  
Flexural Strength ◽  
Energy Absorption ◽  
Concrete Beams ◽  
Epoxy Composite ◽  
Plain Concrete ◽  
Concrete Specimen ◽  
Wire Mesh ◽  
Test Results ◽  
Flexural Behaviour ◽  
Flexural Performance

This paper investigates the flexural performance of plain concrete beams bonded with wire mesh-epoxy composite. A total of four beam specimens were prepared and tested. Three specimens were bonded with same amount of wire mesh-epoxy composite with varying composite width and one plain concrete specimen was used as a control. The effect of wire mesh-epoxy composite on enhancing the flexural behaviour of concrete beams as well as the effect of different configurations of composite was studied. Test results showedthat the wire mesh-epoxy composite increased the flexural strength of concrete beams. The increase in energy absorption of bonded beams was remarkable. In addition, specimen with large composite width showed better behaviour with respect to energy absorption capability.

Failure Behavior of RC Slabs Subjected to Medium Velocity Impact

2016 ◽  
Author(s):  
Masuhiro Beppu ◽  
Shinnosuke Kataoka
Keyword(s):  
Shear Failure ◽  
Impact Load ◽  
Concrete Slab ◽  
Reaction Force ◽  
Plain Concrete ◽  
Concrete Specimen ◽  
Failure Behavior ◽  
Velocity Impact ◽  
Reinforced Concrete Slabs ◽  
The Impact

This study is intended to investigate failure mechanism of plain concrete and reinforced concrete slabs subjected to a medium-velocity impact by conducting impact tests. In a series of tests, a steel projectile with a mass of 8.3kg collided a concrete slab with a thickness of 18cm. In order to examine impact response of the concrete specimen, impact load and reaction force were measured. Test results revealed that the impact velocity corresponding to the scabbing limit was about 40m/s and the failure mode of the concrete specimen subjected to the medium-velocity was similar to the punching shear failure.

scholarly journals Experimental Validation of the Attenuation Properties in the Sonic Range of Metaconcrete Containing Two Types of Resonant Inclusions

2020 ◽  
Author(s):  
D. Briccola ◽  
M. Cuni ◽  
A. De Juli ◽  
M. Ortiz ◽  
A. Pandolfi
Keyword(s):  
Natural Rubber ◽  
Experimental Validation ◽  
Wave Attenuation ◽  
Polymeric Coating ◽  
Inclusion Type ◽  
Conventional Concrete ◽  
Resonant Frequencies ◽  
Low Frequencies ◽  
Rubber Coating ◽  
Pdms Coating

Abstract Background Metaconcrete is a new concept of concrete, showing marked attenuation properties under impact and blast loading, where traditional aggregates are partially replaced by resonant bi-material inclusions. In a departure from conventional mechanical metamaterials, the inclusions are dispersed randomly as cast in the material. The behavior of metaconcrete at supersonic frequencies has been investigated theoretically and numerically and confirmed experimentally. Objective The feasibility of metaconcrete to achieve wave attenuation at low frequencies demands further experimental validation. The present study is directed at characterizing dynamically, in the range of the low sonic frequencies, the—possibly synergistic—effect of combinations of different types of inclusions on the attenuation properties of metaconcrete. Methods Dynamic tests are conducted on cylindrical metaconcrete specimens cast with two types of spherical inclusions, made of a steel core and a polymeric coating. The two inclusions differ in terms of size and coating material: type 1 inclusions are 22 mm diameter with 1.35 mm PDMS coating; type 2 inclusions are 24 mm diameter with 2 mm layer natural rubber coating. Linear frequency sweeps in the low sonic range (< 10 kHz), tuned to numerically estimated inclusion eigenfrequencies, are applied to the specimens through a mechanical actuator. The transmitted waves are recorded by transducers and Fast-Fourier transformed (FFT) to bring the attenuation spectrum of the material into full display. Results Amplitude reductions of transmitted signals are markedly visible for any metaconcrete specimens in the range of the inclusion resonant frequencies, namely, 3,400-3,500 Hz for the PDMS coating inclusions and near 3,200 Hz for the natural rubber coating inclusions. Specimens with mixed inclusions provide a rather uniform attenuation in a limited range of frequencies, independently of the inclusion density, while specimens with a single inclusion type are effective over larger frequency ranges. With respect to conventional concrete, metaconcrete reduces up to 90% the amplitude of the transmitted signal within the attenuation bands. Conclusions Relative to conventional concrete, metaconcrete strongly attenuates waves over frequency bands determined by the resonant frequencies of the inclusions. The present dynamical tests conducted in the sonic range of frequencies quantify the attenuation properties of the metaconcrete cast with two types inclusions, providing location, range and intensity of the attenuation bands, which are dependent on the physical-geometric features of the inclusions.

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