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 Microstructure and Mechanical Performance of Resistance Spot Welded Martensitic Advanced High Strength Steel

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 1021
Author(s):  
Yunzhao Li ◽  
Huaping Tang ◽  
Ruilin Lai
Keyword(s):  
Mechanical Properties ◽  
Failure Modes ◽  
Mechanical Performance ◽  
Strong Dependence ◽  
High Strength ◽  
Weld Nugget ◽  
Resistance Spot ◽  
Pull Out ◽  
Cross Tension ◽  
Spot Welded

Resistance spot welded 1.2 mm (t)-thick 1400 MPa martensitic steel (MS1400) samples are fabricated and their microstructure, mechanical properties are investigated thoroughly. The mechanical performance and failure modes exhibit a strong dependence on weld-nugget size. The pull-out failure mode for MS1400 steel resistance spot welds does not follow the conventional weld-nugget size recommendation criteria of 4t0.5. Significant softening was observed due to dual phase microstructure of ferrite and martensite in the inter-critical heat affected zone (HAZ) and tempered martensite (TM) structure in sub-critical HAZ. However, the upper-critical HAZ exhibits obvious higher hardness than the nugget zone (NZ). In addition, the mechanical properties show that the cross-tension strength (CTS) is about one quarter of the tension-shear strength (TSS) of MS1400 weld joints, whilst the absorbed energy of cross-tension and tension-shear are almost identical.

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 Pull-out Behaviour of Extended Hollobolts for Hollow Beam-Column Connections

2018 ◽  
Author(s):  
Mohd Fazaulnizam Bin Shamsudin ◽  
Walid Tizani
Keyword(s):  
Concrete Strength ◽  
Weight Ratio ◽  
High Strength ◽  
Element Model ◽  
Embedment Depth ◽  
Gusset Plates ◽  
Hollow Section ◽  
Hollow Beam ◽  
Pull Out ◽  
Joint Behaviour

The use of structural hollow sections (SHS) as columns in single-storey and multi-storey results in better compression strength, low surface area, architectural attractiveness and high strength to weight ratio. One major constraint when connecting to hollow sections is in accessing and tightening the bolt from the inside of the hollow section. To resolve this issue, full welding is usually applied. But this may suffer from high labour cost, and the potential of low quality welding due to workmanship and varied environmental conditions. Connecting using additional components, such as gusset plates and brackets, helps to ease this problem but lowers aesthetic appeal. To avoid the need to access to the inner face of the column section, new type of fasteners known as blind bolts were introduced. In this paper, experimental and numerical studies were conducted using a new anchored blind bolt known as the Extended HolloBolt (EHB), with the objective of using the component method for predicting joint behaviour within the tensile region. The behaviour of EHB in a group with different connection topologies and configurations was investigated using a total of 36 tests with one row of M16 Grade 8.8 and 10.9 bolts subjected to pull-out loading in tension. The experimental work covers a range of parameters such as bolt gauge, concrete strength, concrete type, bolt embedment depth and bolt class. A finite element model was implemented with good agreement between experimental and simulated load-deflection results, which have a maximum difference of 2.5%, shows that the model is suitable to be used for parametric studies or analytical work in further research on the EHB.

scholarly journals New Hybrid Polyurea-Polyurethane Elastomers with Antistatic Properties and an Influence of Various Additives on Their Physicochemical Properties

Molecules ◽  
2021 ◽  
Vol 26 (19) ◽  
pp. 5778
Author(s):  
Szymon Kosiński ◽  
Marcin Gonsior ◽  
Piotr Krzyżanowski ◽  
Iwona Rykowska
Keyword(s):  
Mechanical Properties ◽  
Surface Defects ◽  
Reference Sample ◽  
High Strength ◽  
Hybrid Coatings ◽  
Polyurethane Elastomers ◽  
Existing Structures ◽  
Ft Ir ◽  
Further Development ◽  
Weathering Effects

Polyurea is a synthetic high-strength elastomeric material that can be sprayed as a coating over existing structures in order to protect against weathering effects. It is ideal for anti-corrosion protection and is characterized by excellent mechanical properties and adhesion to various surfaces. Further development of this technology may allow obtaining new coatings with improved antistatic properties, which would be an excellent alternative compared to used antistatic epoxy paints. This paper will examine the influence of tetraalkylammonium salt (1), potassium hexafluorophosphate solution (2) and imidazolium-based ionic liquid (3) on the improvement of antistatic properties of the polyurea-polyurethane coatings. In addition, the modified samples were also verified in terms of changes in mechanical properties and the appearance of functional groups other than in the reference sample, as well as surface defects that may arise due to incompatibility of the antistatic additive with the polymer matrix. In order to obtain information about the properties mentioned above, the electrical resistance was determined, the tensile strength and elongation were measured, FT-IR spectra were made, and images were taken with the use of scanning electron microscopy. The conducted research showed that the antistatic properties of the tested hybrid coatings could be improved, but their use may be associated with certain limitations that should be taken into account when designing such materials.

scholarly journals The Mechanical Properties of Centrifuged Concrete in Reinforced Concrete Structures

2020 ◽  
Vol 10 (10) ◽  
pp. 3570
Author(s):  
Romualdas Kliukas ◽  
Ona Lukoševičienė ◽  
Arūnas Jaras ◽  
Bronius Jonaitis
Keyword(s):  
Mechanical Properties ◽  
Reinforced Concrete ◽  
Concrete Strength ◽  
Concrete Structures ◽  
High Strength ◽  
Reinforcement Ratio ◽  
Transverse Reinforcement ◽  
Reinforced Concrete Structures ◽  
Test Results ◽  
Moduli Of Elasticity

This article explores the influence of transverse reinforcement (spiral) and high-strength longitudinal reinforcements on the physical-mechanical properties of centrifuged annular cross-section elements of concrete. The test results of almost 200 reinforced, and over 100 control elements are summarizing in this article. The longitudinal reinforcement ratio of samples produced in the laboratory and factory varied from 1.0% to 6.0%; the transverse reinforcement ratio varied from 0.25% to 1.25%; the pitch of spirals varied from 100 mm to 40 mm and the concrete strength varied from 25 MPa to 60 MPa. Experimental relationships of coefficients for concrete strength, moduli of elasticity and limits of the longitudinal strain of centrifuged concrete in reinforced concrete structures in short-term concentrically compression were proposed.

An Ultrasonic Pulse Velocity Test on Fly-Ash Based Geopolymer Concrete in Frequency Domains

2014 ◽  
Vol 700 ◽  
pp. 310-313 ◽  
Author(s):  
Jee Sang Kim ◽  
Tae Hong Kim
Keyword(s):  
Compressive Strength ◽  
Construction Material ◽  
High Strength ◽  
Ultrasonic Pulse Velocity ◽  
Peak Frequency ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
P Wave ◽  
Geopolymer Concrete ◽  
Existing Structures

The Non-Destructive Test techniques on concrete, which can assess the properties of materials without damages, have been developed as the deteriorations of existing structures increase. Among them, the ultrasonic pulse velocity (USPV) method is widely used because it can investigate the states of one material for a long time and repeatedly. However, there have been few researches on the NDT application to geopolymer concrete which is environment friendly construction material without any cement. This paper investigates the variations of ultrasonic pulse velocity and peak frequency of geopolymer concrete under monotonically increasing loads to assess the material conditions with various compressive strength levels by measuring P-wave signals. The pulse velocities and peak frequencies were higher in high strength geopolymer concrete specimens. There are not explicit relations between strength levels and peak frequencies but the peak frequencies are strongly influenced by the applied stress levels. In addition, a predicting equation for compressive strength of geopolymer concrete is derived based on experimental data in similar form for normal concrete.

Mechanical Properties Research on Concrete Block Doped Nano-TiO2 under the Conditions of Common Conservation

2012 ◽  
Vol 238 ◽  
pp. 9-12
Author(s):  
Zhi Yong Deng
Keyword(s):  
Mechanical Properties ◽  
High Performance ◽  
Construction Material ◽  
Concrete Strength ◽  
High Strength ◽  
Concrete Block ◽  
Compressive Properties ◽  
Compressive Test ◽  
High Durability

As a new high performance construction material, concrete doped nano-TiO2 greatly expanded its application in engineering with the advantages of high strength and high durability. By compressive test of concrete block doped nano-TiO2 under the conditions of common conservation, this paper respectively studies the regulation of compressive properties of the concrete block affected by the factors such as concrete strength and nano-TiO2 dioxide.

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.

Mechanical benchmarking of additively manufactured continuous and short carbon fiber reinforced nylon

2021 ◽  
pp. 002199832110200
Author(s):  
Mahdi Mohammadizadeh ◽  
Ankit Gupta ◽  
Ismail Fidan
Keyword(s):  
Mechanical Properties ◽  
Morphological Analysis ◽  
Fiber Composite ◽  
Fiber Reinforced ◽  
Fused Filament Fabrication ◽  
Compression Properties ◽  
Pull Out ◽  
Fiber Size ◽  
3D Printed ◽  
Short Carbon

Mechanical properties of fiber reinforced additive manufacturing (FRAM) parts are affected by the fiber size and orientation. Oriented fiber composite is most likely to produce better properties. The objective of this research is to perform a comparative analysis of the mechanical properties of short and continuous fiber reinforced nylon 6 produced with fused filament fabrication (FFF) technology. In this study, it was observed that tensile, compression and flexural properties are significantly affected by the change in the fiber length and orientation. Scanning electron microscopy (SEM) was performed after mechanical testing to observe the influence of fiber on the final properties. From the testing, it was observed that continuous-FRAM (C-FRAM) parts show better properties in tensile loading and short-FRAM (S-FRAM) in bending. S-FRAM parts show better improvement in flexural and compression properties as compared to CFRAM parts. Morphological analysis of tested 3D-printed parts concluded that the fiber-pull out and fiber breakage are the main failure mechanisms.

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