The Pull-Out Method For On-Site Estimation of the Elastic Modulus of Concrete

2005 ◽  
Vol 40 (6) ◽  
pp. 505-511 ◽  
Author(s):  
P Antonaci ◽  
P Bocca
Keyword(s):  
Elastic Modulus ◽  
Concrete Strength ◽  
Displacement Curve ◽  
Concrete Mass ◽  
Existing Structures ◽  
Pull Out ◽  
Site Evaluation ◽  
Displacement Transducers ◽  
Force Displacement

The paper describes a new experimental mechanical method for the on-site evaluation of the elastic modulus of concrete. It is based on a modification of the well-known pull-out test, which is currently used for the estimation of concrete strength. The method consists in pulling out a metal insert embedded in the concrete mass and measuring the force-displacement curve consequent to the extraction. Three displacement transducers were used in order to correctly detect the displacement of the insert. Moreover, an adequate number of loading-unloading cycles was performed in order to stabilize the system and eliminate possible phenomena of mutual sliding between the mechanical parts of the apparatus and between the insert and the concrete mass. By performing a certain number of pull-out tests the stiffness value of the system is obtained. The material deformability is then estimated through an appropriate correlation curve between pull-out stiffness and elastic modulus, which has been worked out on the basis of finite element simulations and experimental results. The proposed method offers interesting possibilities of application for the characterization of existing structures at affordable costs.

Bond behavior of high strength concrete under reversed pull-out cyclic loading

2002 ◽  
Vol 29 (2) ◽  
pp. 191-200 ◽  
Author(s):  
M Alavi-Fard ◽  
H Marzouk
Keyword(s):  
Cyclic Loading ◽  
Bond Strength ◽  
High Strength Concrete ◽  
Concrete Strength ◽  
High Strength ◽  
Displacement Curve ◽  
Bond Slip ◽  
Strength Concrete ◽  
Pull Out ◽  
Normal Strength

Structures located in seismic zones require significant ductility. It is necessary to examine the bond slip characteristics of high strength concrete under cyclic loading. The cyclic bond of high strength concrete is investigated under different parameters, including load history, confining reinforcement, bar diameter, concrete strength, and the rate of pull out. The bond strength, cracking, and deformation are highly dependent on the bond slip behavior between the rebar and the concrete under cyclic loading. The results of cyclic testing indicate that an increase in cyclic displacement will lead to more severe bond damage. The slope of the bond stress – displacement curve can describe the influence of the rate of loading on the bond strength in a cyclic test. Specimens with steel confinement sustained a greater number of cycles than the specimens without steel confinement. It has been found that the maximum bond strength increases with an increase in concrete strength. Cyclic loading does not affect the bond strength of high strength concrete as long as the cyclic slip is less than the maximum slip for monotonic loading. The behavior of high strength concrete under a cyclic load is slightly different from that of normal strength concrete.Key words: bond, high strength, cyclic loading, bar spacing, loading rate, failure mechanism.

scholarly journals The Structural Diagnosis of Existing RC Buildings: The Role of Nondestructive Tests in the Case of Low Concrete Strength

2020 ◽  
Vol 5 (11) ◽  
pp. 100
Author(s):  
Silvia Santini ◽  
Angelo Forte ◽  
Lorena Sguerri
Keyword(s):  
Mechanical Properties ◽  
Concrete Strength ◽  
High Strength ◽  
Ultrasonic Pulse ◽  
Assessment Process ◽  
Structural Safety ◽  
Existing Structures ◽  
Nondestructive Tests ◽  
Compression Properties ◽  
Pull Out

In the structural safety assessment process of existing structures, knowledge of the mechanical properties of the materials is key. Different experimental activities carried out on materials extracted from existing reinforced concrete buildings show a high strength variability, especially concrete. In the past, the lack of standardized quality control for materials and workmanship caused nonuniform and homogeneous properties within the same structure. The most accurate and reliable experimental technique consists of performing direct tests on the materials, but these are considerably expensive and invasive. In this paper, alternative indirect methods that estimate material properties by correlating different physical measures were proved to reduce invasive inspections on existing buildings and infrastructures, especially in built heritage. A complete experimental activity concerning destructive and nondestructive tests was conducted on elements (four portions of a column and a beam portion) removed from an Italian school building built in 1940. Destructive and nondestructive methods were compared and appropriate correlation laws developed to predict the main mechanical properties of the studied material. Reliable correlations were identified considering the pull-out test, Sonic–Rebound (SonReb) combined method and ultrasonic pulse velocities (UPVs). The latter were mapped by tomography, which highlighted the compression properties of concrete in the different structural sections.

scholarly journals Why Should the “Alternative” Method of Estimating Local Interfacial Shear Strength in a Pull-Out Test Be Preferred to Other Methods?

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2406
Author(s):  
Serge Zhandarov ◽  
Edith Mäder ◽  
Uwe Gohs
Keyword(s):  
Shear Strength ◽  
Interfacial Shear Strength ◽  
Traditional Approach ◽  
Interfacial Shear ◽  
Frictional Stress ◽  
Displacement Curve ◽  
Pull Out ◽  
Alternative Method ◽  
Fiber Reinforced Materials ◽  
Force Displacement

One of the most popular micromechanical techniques of determining the local interfacial shear strength (local IFSS, τd) between a fiber and a matrix is the single fiber pull-out test. The τd values are calculated from the characteristic forces determined from the experimental force–displacement curves using a model which relates their values to local interfacial strength parameters. Traditionally, the local IFSS is estimated from the debond force, Fd, which corresponds to the crack initiation and manifests itself by a “kink” in the force–displacement curve. However, for some specimens the kink point is hardly discernible, and the “alternative” method based on the post-debonding force, Fb, and the maximum force reached in the test, Fmax, has been proposed. Since the experimental force–displacement curve includes three characteristic points in which the relationship between the current values of the applied load and the crack length is reliably established, and, at the same time, it is fully determined by only two interfacial parameters, τd and the interfacial frictional stress, τf, several methods for the determination of τd and τf can be proposed. In this paper, we analyzed several theoretical and experimental force–displacement curves for different fiber-reinforced materials (thermoset, thermoplastic and concrete) and compared all seven possible methods of τd and τf calculation. It was shown that the “alternative” method was the most accurate and reliable one, while the traditional approach often yielded the worst results. Therefore, we proposed that the “alternative” method should be preferred for the experimental force–displacement curves analysis.

scholarly journals Evaluation of the EC8-3 confidence factors for the characterization of concrete strength in existing structures

2012 ◽  
Vol 45 (11) ◽  
pp. 1737-1758 ◽  
Author(s):  
Xavier Romão ◽  
Rui Gonçalves ◽  
Aníbal Costa ◽  
Raimundo Delgado
Keyword(s):  
Concrete Strength ◽  
Existing Structures

scholarly journals Numerical simulation of fiber-matrix debonding in single fiber pull-out tests

2020 ◽  
Vol 2 (1) ◽  
pp. 21-35
Author(s):  
Lukas Hoppe
Keyword(s):  
Crack Initiation ◽  
Cohesive Zone ◽  
Single Fiber ◽  
Displacement Curve ◽  
Fe Model ◽  
Pull Out ◽  
Peridynamic Model ◽  
Reference Experiment ◽  
Fiber Matrix ◽  
Force Displacement

The present work deals with the numerical crack simulation of fiber-matrix debonding in single fiber pull-out tests. For this purpose, two models are used: a finite element model (FE model) with the cohesive zone approach and a peridynamic model. For calibration a reference experiment is applied. In addition analytical equations are used for reference values. The influence of the model parameters and the material parameters of the cohesive zone model on the force-displacement curve is investigated. Besides the free fiber length, the critical interface strength, the critical energy release rate as well as the initial interface stiffness have a great influence on the force-displacement curve of the pull-out test. From the crack simulation it can be seen that Mode I has an influence on the crack initiation, but further crack growth after initiation is dominated by Mode II. The FE model can be calibrated in a way that the crack initiation point and the maximum force correspond to the reference experiment. The peridynamic model depicts a comparable crack formation process.

scholarly journals Erratum to: Evaluation of the EC8-3 confidence factors for the characterization of concrete strength in existing structures

2012 ◽  
Vol 45 (11) ◽  
pp. 1759-1759
Author(s):  
Xavier Romão ◽  
Rui Gonçalves ◽  
Aníbal Costa ◽  
Raimundo Delgado
Keyword(s):  
Concrete Strength ◽  
Existing Structures

Effect of Undercut on the Characterization of the Mechanical Properties of Silicon Nanocantilevers with Dynamic and Static Test

2015 ◽  
Vol 645-646 ◽  
pp. 1072-1077
Author(s):  
Jia Hong Zhang ◽  
Fang Gu ◽  
Xian Ling Zhang ◽  
Min Li ◽  
Yi Xian Ge ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Effective Length ◽  
Displacement Curve ◽  
Resonant Frequencies ◽  
Static Test ◽  
Critical Point Drying ◽  
Force Displacement

The elastic mechanical properties of silicon nanocantilevers are of prime importance in biotechnology and nanoelectromechanical system (NEMS) applications. In order to make these applications reliable, the exact evaluation of the effect of the undercut on the mechanical properties of silicon nanocantilevers is essential and critical. In this paper, a numerical-experimental method for determining the effect of the undercut on resonant frequencies and Young’s modulus of silicon nanocantilevers is proposed by combining finite element (FE) analysis and dynamic frequency response tests by using laser Doppler vibrometer (LDV) as well as static force-displacement curve test by using an atomic force microscope (AFM). Silicon nanocantilevers test structures are fabricated from silicon-on-insulator (SOI) wafers by using the standard complementary metal-oxide-semiconductor (CMOS) lithography process and anisotropic wet-etch release process based on the critical point drying, which inevitably generating the undercut of the nanocantilever clamping. Combining with three-dimensional FE numerical simulations incorporating the geometric undercut, the dynamic resonance tests demonstrate that the undercut obviously reduces resonant frequencies of nanocantilevers due to the fact that the undercut effectively increases the nanocantilever length by a correct value ΔL. According to a least-square fit expression including ΔL, we extract Young’s modulus from the measured resonance frequency versus the effective length dependency and find that Young’s modulus of a silicon nanocantilever with 200-nm thickness is close to that of bulk silicon. However, when we do not consider the undercut ΔL, the obtained Young's modulus is decreased 39.3%. Based on the linear force-displacement response of 12μm long and 200nm thick silicon nanocantilever obtained by using AFM, our extracted Young’s modulus of the [110] nanocantilever with and without undercut is 169.1GPa and 133.0GPa, respectively. This error reaches 21.3%. Our work reveals that the effect of the undercut on the characterization of the mechanical properties of nanocantilevers with dynamic and static test must be carefully considered.

Towards Automated Mechanical Characterization of Biological Samples Using Atomic Force Microscopy (AFM)

2011 ◽  
Author(s):  
Rajarshi Roy ◽  
Wenjin Chen ◽  
Lei Cong ◽  
Lauri A. Goodell ◽  
David J. Foran ◽  
...  
Keyword(s):  
Mechanical Characterization ◽  
Electrical Circuit ◽  
Displacement Curve ◽  
Biologically Relevant ◽  
Force Microscopy ◽  
Afm Indentation ◽  
Atomic Force ◽  
Force Displacement ◽  
Large Sections

The mechanical properties of biomaterials have long been a subject of interest for researchers due to their potential in predicting biologically relevant questions, like proliferation of cancer in tissue. A popular technique of estimating material properties of biomaterials is the AFM, which consists of a probe that indents the material of interest. However, region localization for AFM indentation is challenging, especially when probing large sections of the tissue. Furthermore, identifying the point of contact between AFM tip and the specimen on the force-displacement curve involves uncertainties that are difficult to predict. In this work, we try to address these two issues. We use a vision-guided positioning system to achieve region localization, and we use a resistance based-electrical circuit to identify the point of contact between AFM tip and the specimen.

scholarly journals Deformation and Mechanical Properties of a Constant-Friction-Force Energy-Absorbing Bolt

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Tao Song ◽  
Tianbin Li ◽  
Lubo Meng ◽  
Chunchi Ma ◽  
Chaofei Li ◽  
...  
Keyword(s):  
Energy Absorption ◽  
Friction Force ◽  
Displacement Curve ◽  
Pull Out ◽  
Constant Friction ◽  
Combined Action ◽  
Face Plate ◽  
Energy Absorbing ◽  
Rock Tunnels ◽  
Force Displacement

The conventional bolts used in surrounding rock tunnels with large deformation often fail. As a solution to this problem, we developed an extensible bolt with energy-absorbing and constant-friction-force (EACF) characteristics. The EACF bolt mainly comprises a damping device, a hollow threaded bolt, a tightening nut, and a face plate. To reveal its working mechanism, the bolt was tested in terms of its friction, displacement, and energy absorption through a modified tensile test device in a laboratory. The static pull-out test results showed that the axial force-displacement curve of the bolt can be mainly divided into three stages: a conical extrusion stage, an elongation stage, and an elastic failure stage. The EACF bolts exhibited stable energy absorption behaviors when subjected to static loading. The maximum constant friction force could be adjusted by increasing the size and diameter of the straight section of the damping block, and the maximum elongation could be adjusted by increasing the length of the damping cylinder. When the properties of the bolt materials are kept constant, increasing the diameter of the damping block can help achieve a high constant resistance. The proposed EACF bolt has reliable deformation and energy-absorption properties, which ensure its stability when employed in tunnels under the combined action of support and surrounding rocks.

Characterization of interfaces in CVD-coated nicalon fiber-reinforced SiC

1989 ◽  
Vol 47 ◽  
pp. 556-557
Author(s):  
K.L. More ◽  
R.A. Lowden
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Chemical Vapor ◽  
Chemical Vapor Infiltration ◽  
Frictional Stress ◽  
Fiber Reinforced ◽  
Pull Out ◽  
Carbon Coated ◽  
Fiber Matrix

The mechanical properties of fiber-reinforced composites are directly related to the nature of the fiber-matrix bond. Fracture toughness is improved when debonding, crack deflection, and fiber pull-out occur which in turn depend on a weak interfacial bond. The interfacial characteristics of fiber-reinforced ceramics can be altered by applying thin coatings to the fibers prior to composite fabrication. In a previous study, Lowden and co-workers coated Nicalon fibers (Nippon Carbon Company) with silicon and carbon prior to chemical vapor infiltration with SiC and determined the influence of interfacial frictional stress on fracture phenomena. They found that the silicon-coated Nicalon fiber-reinforced SiC had low flexure strengths and brittle fracture whereas the composites containing carbon coated fibers exhibited improved strength and fracture toughness. In this study, coatings of boron or BN were applied to Nicalon fibers via chemical vapor deposition (CVD) and the fibers were subsequently incorporated in a SiC matrix. The fiber-matrix interfaces were characterized using transmission and scanning electron microscopy (TEM and SEM). Mechanical properties were determined and compared to those obtained for uncoated Nicalon fiber-reinforced SiC.

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