Strain monitoring in a reinforced concrete slab sustaining service loads by distributed Brillouin fibre optic sensors

2010 ◽  
Vol 37 (10) ◽  
pp. 1341-1349 ◽  
Author(s):  
Beatriz Martín-Pérez ◽  
Amre Deif ◽  
Bruno Cousin ◽  
Chunshu Zhang ◽  
Xiaoyi Bao ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Concrete Slab ◽  
Fibre Length ◽  
Experimental Program ◽  
Small Scale ◽  
Fibre Optic ◽  
Reinforced Concrete Slab ◽  
Rc Structures ◽  
Strain Monitoring ◽  
Rc Slab

Reinforced concrete (RC) structures deteriorate and as a result crack due to extreme loading and (or) environmental conditions. Damage accumulation as such adversely affects the structure’s durability properties, impairing its service life. The intensity of cracking in an RC structure is usually regarded as the key criterion toward damage assessment and repair intervention. This paper presents the results of an experimental program in which the concrete strains of a small-scale RC slab sustaining in-service loads were monitored by traditional electrical strain gauges and distributed Brillouin fibre optic sensors in an attempt to detect damage due to crack formation. A comparison of these measurements with classical bending theory is also presented. The results show that distributed Brillouin fibre optic sensors can capture both tensile and compressive strains in concrete; however, the accuracy of their measurements is dependent on the proper installation of the sensors and the fibre length over which the strains are to be measured.

Pre-Test and Analysis of a Reinforced Concrete Slab Subjected to Blast From a Non-Confined Explosive

2018 ◽  
pp. 272-287
Author(s):  
Fausto B. Mendonça ◽  
Girum S. Urgessa
Keyword(s):  
Dynamic Analysis ◽  
Large Scale ◽  
Concrete Slab ◽  
Wave Parameter ◽  
Experimental Program ◽  
Small Scale ◽  
Maximum Displacement ◽  
Reinforced Concrete Slab ◽  
Test Experiment ◽  
Rc Slabs

A large scale experimental program consisting of testing 10 RC slabs with different variations of concrete compressive strength, reinforcement ratio and retrofit was conducted in Brazil. As part of that test program, a small-scale blast pre-test setup and associated dynamic analysis were conducted in order to confirm the proper functioning of the blast test sensors (pressure gages, displacement meter and accelerometers). The results of the pre-test were compared with theoretical blast wave parameter predictions using established equations and maximum displacement predictions using simplified dynamic analysis. The pre-test experiment provided useful insights and was shown to be critical for the success of the subsequent large scale blast tests.

scholarly journals Comparison of Predicted and Experimental Behaviour of RC Slabs Subjected to Blast using SDOF Analysis

2018 ◽  
Vol 68 (2) ◽  
pp. 138 ◽  
Author(s):  
F. B. Mendonca ◽  
G. Urgessa ◽  
K. Iha ◽  
R. J. Rocha ◽  
J.A.F.F. Rocco
Keyword(s):  
Reinforced Concrete ◽  
Concrete Slab ◽  
Experimental Program ◽  
Reinforced Concrete Slab ◽  
Peak Displacement ◽  
Blast Damage ◽  
Reinforced Concrete Slabs ◽  
Military Facilities ◽  
Rc Slabs ◽  
Sdof Analysis

<p>Explosions emanating from terrorist attacks or military weapons cause damage to civilian and military facilities. Understanding the mechanical behaviour of reinforced concrete structures subjected to blast is of paramount importance for minimizing the possible blast damage. A full-scale experimental program consisting of six reinforced concrete slabs with compressive strengths of 60 MPa, 50 MPa and 40 MPa, measuring 1.0 m × 1.0 m × 0.08 m, and subjected to 2.7 kg of non-confined plastic bonded explosive, was conducted in blast test area of Science and Technology Aerospace Department (Brazilian Air Force). This paper compares experimentally measured peak displacement values with theoretical values. Theoretical analysis was carried out using single degree of freedom (SDOF) models. The comparison showed that SDOF analysis worked very well in predicting the reinforced concrete slab peak displacement against blast effects. Qualitative analysis after the experiments showed that the blast wave shape generated by the cylindrical explosive was not uniformly distributed on the slabs for the standoff distance of 0.927 m∕kg1/3.<br /><br /></p>

scholarly journals Ultrasonic pitch and catch technique for non-destructive testing of reinforced concrete slabs

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Wael A. Zatar ◽  
Hai D. Nguyen ◽  
Hien M. Nghiem
Keyword(s):  
Reinforced Concrete ◽  
Concrete Slab ◽  
Point Contact ◽  
Test Method ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
Reinforced Concrete Slab ◽  
Reinforced Concrete Slabs ◽  
Rc Slab ◽  
Non Destructive

Abstract This study aims at evaluating reinforced concrete (RC) bridge elements using ultrasonic pitch and catch (UPC) non-destructive testing (NDT) technique. A validation reinforced concrete slab with two embedded layers of rebars and artificial defects (voids, honeycombs, and debondings) was designed and tested. A commercial UPC NDT device (hereafter called “UPC device”), which is based on the ultrasonic shear-wave test method using dry-point-contact transmitting and receiving transducers in a “pitch-catch” configuration, was used to map internal defects of the validation RC slab. The recorded data from the UPC device was analyzed using a modified synthetic aperture focusing technique (SAFT). A software was developed to reconstruct 2-D images of the RC slab cross-sections using novel signal filtering and processing techniques. The results revealed that the 2-D image reconstructed from the developed software accurately exhibited locations and horizontal dimensions of the steel rebars, voids, and debondings. In addition, the developed software was capable to provide much higher resolution and sharper images of the anomalies inside the RC slab compared to the UPC device’s proprietary imaging software.

Behavior of Two-way RC Slabs Combination Strengthened with CFRP Strips and Steel Sheets

2014 ◽  
Vol 501-504 ◽  
pp. 1048-1052 ◽  
Author(s):  
Xiao Jin Li ◽  
Yi Yan Lu ◽  
Na Li
Keyword(s):  
Reinforced Concrete ◽  
Concrete Slab ◽  
Concrete Slabs ◽  
Test Results ◽  
Reinforced Concrete Slab ◽  
Steel Sheets ◽  
Reinforced Concrete Slabs ◽  
Rc Slab ◽  
Rc Slabs ◽  
Strengthening Technique

A total of four two-way reinforced concrete slabs strengthened with three methods were tested. The four test specimens were one unstrengthened reinforced concrete slab (control), one slab strengthened with CFRP strips, one slab strengthened with steel sheets, and one slab strengthened with an innovative method of applying CFRP strips and steel sheets combination bonding to the tension face of the slab. The test results show the CFRP-Steel combination strengthened technique is a rapid and effective strengthening technique for two-way RC slab. The increase in ultimate capacities of CFRP-Steel combination strengthened slab is 221.1% over the control slab, 84.4% over the CFRP-strengthened slab, and 45.2% over the steel-strengthened slab. In addition, the CFRP-Steel combination strengthened slab exhibited superior ductility than the CFRP-strengthened slab.

scholarly journals Behavior of Self Compacting Reinforced Concrete One Way Bubble Deck Slab

2020 ◽  
Vol 23 (1) ◽  
pp. 1-11
Author(s):  
Ali H. Yaagoob ◽  
Ibrahem S. Harba
Keyword(s):  
Reinforced Concrete ◽  
Experimental Work ◽  
Ultimate Load ◽  
Concrete Slab ◽  
Experimental Program ◽  
Shear Reinforcement ◽  
Reinforced Concrete Slab ◽  
Ball Diameter ◽  
New Type ◽  
Deck Slab

Reinforced concrete slab with plastic voids (Bubbled Deck system) is a new type of slabs which has two-dimensional arrangement of voids within the slab that is developed to decrease the slab self-weight while maintaining approximately the same load carrying capacity as compared with the solid slabs. Plastic voided slabs have the ability to reduce concrete amount by about 30 percent and this reduction is so important in terms of cost saving and enhancement the structural performance. In this research paper investigation is carried out to study the shear strength behavior of one-way bubble deck slab using self-compacting reinforced concrete. The experimental program consists of testing thirteen one-way slabs with dimensions of (1700 length, 700 width and 150 thick) mm. One of the tested slabs is a solid slab (without balls) is used as a reference, the remaining twelve bubbled slabs with ball diameter (73, 60) mm are divided into five groups according to the parameters of the experimental work, the parameters of the experimental work include: type of slab (bubble and solid slabs), ball diameter (73, 60) mm, shear reinforcement and spacing between balls. The experimental results showed that the bubbled slabs without shear reinforcement have a decrease in the ultimate load as compared to solid slab by about 3.7% to 14.3% and an increase in the deflection at ultimate load by about 10% to 22%, at the same time the first crack load decreases by about 15.3% to 42.4% as compared to solid slab due to decreases of moment of inertia of bubble slab compared to solid slab. Also, the results showed that the bubbled slabs withe shear reinforcement (multi-leg) have an increase in the ultimate load as compared to solid slab by about 35.4% to 57.3% and an increase in the deflection at ultimate load by about 1% to 15%, at the same time the first crack load decreases by about 2.8% to 27.4% as compared to solid slab.

scholarly journals Natural Frequencies Reduction of RC Slab Subjected to Incremental Concentrated Loads

2019 ◽  
Vol 8 (3) ◽  
pp. 17
Author(s):  
Mezgeen S. Ahmed ◽  
Abdulhameed A. Yaseen ◽  
Fouad A. Mohammad
Keyword(s):  
Reinforced Concrete ◽  
Modal Analysis ◽  
Natural Frequencies ◽  
Concrete Slab ◽  
Experimental Modal Analysis ◽  
Experimental Program ◽  
Concentrated Loads ◽  
Reinforced Concrete Slab ◽  
Reinforced Concrete Slabs ◽  
Set Up

Reinforced concrete slabs are frequently used in many engineering structures such as buildings and bridges. Damages in an engineering structure including reinforced concrete slab are classified as light, moderate, and severe cracks. A special treatment is required for every typical crack-damage to strengthen its structure. The reinforced concrete slab experiencing cracks reduce stiffness as well as its strength. An experimental program was set up to establish a relation between cracks and changes of a dynamic system characteristics of the slab through natural frequencies. The aim is to perform experimental modal analysis (EMA) as a non-destructive vibration testing method for diagnosing the structural integrity of the slab. For this purpose, two RC square slabs specimens of dimensions 1200mm x 1200mm x 40mm were used. As a first part of the project, a reinforced concrete slab was subjected to an increasing partially concentrated loads at the slab’s center to introduce cracks. After each incremental load steps (5, 10, 12kN) the slab was unloaded. Then, a free-free set-up for the slab was established by using the flexible elastic ropes (bungee cords). After the dynamic test of 5, 10 and 12kN loads, the slab was strengthened using external CFRP sheets (type TR30S). Next, experimental modal analysis was performed to establish a relation between cracks and changes in natural frequencies of the slab. The overall trend of frequency decrease after occurring damage that would be expected for all modes. However, it is not guaranteed all modes have same sensitivity to the applied load that inflicts severe cracks.

Experimental and numerical assessment of the flexural behaviour of semi-precast-reinforced concrete slabs

2020 ◽  
Vol 23 (9) ◽  
pp. 1865-1879
Author(s):  
MI Sifan Mohamed ◽  
Julian Ajith Thamboo ◽  
Thuraisingam Jeyakaran
Keyword(s):  
Reinforced Concrete ◽  
Bond Strength ◽  
Surface Treatment ◽  
Concrete Slab ◽  
Precast Concrete ◽  
Small Scale ◽  
Flexural Behaviour ◽  
Interface Shear ◽  
Reinforced Concrete Slab ◽  
Reinforced Concrete Slabs

Semi-precast-reinforced concrete slab system offers more economic method of construction as it minimises the need of formwork at site. The assembly of semi-precast slab system involves two steps: (1) casting of semi-precast slab at the yard and (2) overtopping of concrete at the site. One of the main factors that influence the performance of such slab system is the interface bonding between precast and overtopping concrete. Therefore, in order to better understand the performance of this slab system, a research was carried out to investigate the influence of surface treatment methodologies to the overall flexural behaviour through experimental and numerical studies. In total, five representative semi-precast slabs were constructed and tested to assess the flexural performance with different surface preparation methods and concrete overtopping. Further small-scale precast with overtopped concrete couplets and triplets were casted and tested as the representative semi-precast concrete slab types to examine the interface shear and tensile bond strength characteristics with those different surface treatments. The experimental results revealed that the surface treatment methods have influenced the flexural behaviour of the slabs, where the interface shear bond strength exceeds more than 1.0 MPa and the slab system behaves monolithically under flexural action. Moreover, numerical modelling technique for this slab system was developed based on the finite element framework to further analyse the overall flexural behaviour. Subsequently, good agreements between experimental and developed numerical model results were found. Finally, parametric analyses were performed to further assess the influences of concrete strengths, spans and reinforcement ratios on the safe imposed pressure applicable for this slab system.

Numerical Study of Damage Model for Reinforced Concrete Slab under Complex Boundary Condition Subjected to Air Blast Load

2014 ◽  
Vol 578-579 ◽  
pp. 762-766
Author(s):  
Dan Li ◽  
Shuang Bin Yang ◽  
Jun Lin Tao
Keyword(s):  
Reinforced Concrete ◽  
Shear Failure ◽  
Concrete Slab ◽  
Damage Model ◽  
Reinforced Concrete Slab ◽  
Air Blast ◽  
Complex Boundary Condition ◽  
Rc Slab ◽  
Complex Boundary ◽  
Punching Failure

This study applies the nonlinear finite element analysis software LS-DYNA to conduct a numerical simulation of damage mode of reinforced concrete slab under complex boundary condition subjected to air blast load. The factors affecting damage model of reinforced concrete slab, standoff distance and explosives location, were analyzed. The results show that: With the increase of the standoff distance, the failure mode of RC slab gradually changes from localized punching failure to shear failure at the support. With the location for explosive changing from the center of RC slab to the beam plate combination, the failure mode of RC slabs gradually changes from localized punching failure to bending-shear failure under close-in blast loading.

Discrimination of Acoustic Emission Signals for Damage Assessment in a Reinforced Concrete Slab Subjected to Seismic Simulations

2013 ◽  
Vol 38 (3) ◽  
pp. 303-310 ◽  
Author(s):  
Francisco A. Sagasta ◽  
Juan L. Torné ◽  
Antonio Sánchez-Parejo ◽  
Antolino Gallego
Keyword(s):  
Acoustic Emission ◽  
Reinforced Concrete ◽  
Concrete Slab ◽  
Mechanical Energy ◽  
Low Frequency ◽  
Shaking Table ◽  
Reinforced Concrete Slab ◽  
Rc Structures ◽  
Steel Columns ◽  
Ae Signals

Abstract The purpose of this work is to distinguish between Acoustic Emission (AE) signals coming from mechanical friction and AE signals coming from concrete cracking, recorded during fourteen seismic simulations conducted with the shaking table of the University of Granada on a reinforced concrete slab supported on four steel columns. To this end, a particular criterion is established based on the Root Mean Square of the AE waveforms calculated in two different temporal windows. This criterion includes a parameter calculated by optimizing the correlation between the mechanical energy dissipated by the specimen (calculated by means of measurements with accelerometers and displacement transducers) and the energy obtained from the AE signals recorded by low-frequency piezoelectric sensors located on the specimen. The final goal of this project, initiated four years ago, is to provide a reliable evaluation of the level of damage of Reinforced Concrete specimens by means of AE signals to be used in future Structural Health Monitoring strategies involving RC structures.

Evaluation and comparison of concrete constitutive models in numerical simulation of reinforced concrete slabs under blast load

2021 ◽  
pp. 204141962110489
Author(s):  
Hani Mahdavi Talaromi ◽  
Farhad Sakhaee
Keyword(s):  
Reinforced Concrete ◽  
Numerical Models ◽  
Concrete Slab ◽  
Constitutive Models ◽  
Computation Time ◽  
Material Model ◽  
Reinforced Concrete Slab ◽  
Rc Structures ◽  
Reinforced Concrete Slabs ◽  
Concrete Damage

Numerical models have been used recently to analyze concrete structures subjected to high-impulsive loads. A material model that can well capture the mechanical behaviors is crucial to obtain reliable results. Present study, focused on reinforced concrete slab as a major load carrying element of the RC structures under blast loading. By performing several simulations in popular and powerful concrete constitutive models, including concrete damage R3, HJC, CSCM, and Winfrith the accuracy of these models was investigated. Maximum deflections have been compared with each other and expanded further to compare with experiments. Result showed all models have an acceptable accuracy in estimating maximum slab deflection. Concrete Damage R3 presented the highest accuracy. HJC has the second rank and CSCM and Winfrith have the third and the fourth places, respectively. HJC needed the minimum computation time. CSCM had minimum input parameters but includes maximum calculation time. Winfrith had the lowest accuracy, however this model presented very conservative results. Uniaxial compressive and tensile stress-strain curves showed that the models which presented higher values of strength, evaluated lower maximum values of deflection.

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