Conventional Strain Measurement Research Articles

Deep learning enables accurate soft tissue tendon deformation estimation in vivo via ultrasound imaging

Image-based deformation estimation is an important tool used in a variety of engineering problems, including crack propagation, fracture, and fatigue failure. These tools have been important in biomechanics research where measuring in vitro and in vivo tissue deformations are important for evaluating tissue health and disease progression. However, accurately measuring tissue deformation in vivo is particularly challenging due to limited image signal-to-noise ratio. Therefore, we created a novel deep-learning approach for measuring deformation from a sequence of images collected in vivo called StrainNet. Utilizing a training dataset that incorporates image artifacts, StrainNet was designed to maximize performance in challenging, in vivo settings. Artificially generated image sequences of human flexor tendons undergoing known deformations were used to compare benchmark StrainNet against two conventional image-based strain measurement techniques. StrainNet outperformed the traditional techniques by nearly 90%. High-frequency ultrasound imaging was then used to acquire images of the flexor tendons engaged during contraction. Only StrainNet was able to track tissue deformations under the in vivo test conditions. Findings revealed strong correlations between tendon deformation and applied forces, highlighting the potential for StrainNet to be a valuable tool for assessing rehabilitation strategies or disease progression. Additionally, by using real-world data to train our model, StrainNet was able to generalize and reveal important relationships between the effort exerted by the participant and tendon mechanics. Overall, StrainNet demonstrated the effectiveness of using deep learning for image-based strain analysis in vivo.

Estimate of the hydraulic force in the aging heart: a cardiovascular magnetic resonance imaging study

BackgroundCoupling between left ventricle (LV) and left atrium (LA) plays a central role in the process of cardiac remodeling during aging and development of cardiac disease. The hydraulic force (HyF) is related to variation in size between LV and LA. The objectives of this study were to: (1) derive an estimate of left atrioventricular HyF using cine- Magnetic Resonance Imaging (MRI) in healthy subjects with a wide age range, and (2) study its relationship with age and conventional diastolic function parameters, as estimated by reference echocardiography.MethodsWe studied 119 healthy volunteers (mean age 44 ± 17 years, 58 women) who underwent Doppler echocardiography and MRI on the same day. Conventional transmitral flow early (E) and late (A) LV filling peak velocities as well as mitral annulus diastolic longitudinal peak velocity (E’) were derived from echocardiography. MRI cine SSFP images in longitudinal two and four chamber views were acquired, and analyzed using feature tracking (FT) software. In addition to conventional LV and LA strain measurements, FT-derived LV and LA contours were further used to calculate chamber cross-sectional areas. HyF was approximated as the difference between the LV and LA maximal cross-sectional areas in the diastasis phase corresponding to the lowest LV-LA pressure gradient. Univariate and multivariate analyses while adjusting for appropriate variables were used to study the associations between HyF and age as well as diastolic function and strain indices.ResultsHyF decreased significantly with age (R²=0.34, p < 0.0001). In addition, HyF was significantly associated with conventional indices of diastolic function and LA strain: E/A: R²=0.24, p < 0.0001; E’: R²=0.24, p < 0.0001; E/E’: R²=0.12, p = 0.0004; LA conduit longitudinal strain: R²=0.27, p < 0.0001. In multivariate analysis, associations with E/A (R2 = 0.39, p = 0.03) and LA conduit strain (R2 = 0.37, p = 0.02) remained significant after adjustment for age, sex, and body mass index.ConclusionsHyF, estimated using FT contours, which are primarily used to quantify LV/LA strain on standard cardiac cine MRI, varied significantly with age in association with subclinical changes in ventricular filling. Its usefulness in cohorts of patients with left heart disease to detect LV-LA uncoupling remains to be evaluated.

Determination of Whole Field Strain in Composite Reflector Using Photogrammetry

Conventional strain measurement techniques cannot be used to obtain the strains in composite reflectors under thermal environment. Though photogrammetry can be used to measure the deformations it cannot provide information on strains. In this work a methodology is developed to determine the strains from the displacements obtained from photogrammetry coordinate measurement. The strains are determined by applying equilibrium conditions and not from the gradient of the displacements. The results are verified using simulated data as well as experiment. It is demonstrated for a composite reflector of a typical spacecraft when subjected to thermal load. The methodology developed in this work helps in obtaining the strain distribution without using expensive digital image correlation equipment. This methodology can be used on wide variety of applications like inflatable structures, flexible structures etc., where strain gauge measurements are not possible to be carried out.

DEVELOPMENT OF A STRETCHABLE CONDUCTIVE SENSOR FOR FLEXIBLE DEFORMATION: A PRELIMINARY STUDY

This research presents preliminary characterization studies for a stretchable conductive sensor. It was developed specifically to detect strain changes that occur including flex changes. Some issues in conventional strain measurement are found to be less suitable due to the inaccuracy to measure the strain for an elongation using a flexible curve ruler, especially strain related to angle changes. Therefore, a study on the development of a stretchable conductive sensor is required. This initial study will focus on characterizing the suitability of fabric materials and thread patterns to develop a sensor that will be used to measure stretch more accurately. In this study, conductive yarns were constructed with two types of stretchable fabrics having different percentages of spandex elements. The thread will be sewn to the side of the fabric in two of the fabric states, namely course (horizontal) and wales (vertical). For both conditions, five (5) similar samples were sewn for 8% and 15% spandex fabric. Preliminary results found that the best sensor performance was a fabric containing 15% spandex material with conductive threads sewn along the horizontal orientation of the fabric. In a study on resistance varying with the tension applied to the sensor, model D showed the best performance when stretched up to a force of 4 N. The resistance shown by the sensor varies from 47MΩ to 66MΩ relative to the applied force from 0 N to 4 N. The results of this preliminary study are expected to be used in widespread measurement applications.

Experimental investigation of aeroelastic instabilities in an aeroengine fan: Using acoustic measurements

Aeroelastic instabilities will occur to the aero-engine fans inevitably during transient operations, causing excessive blade vibration and threatening the structural integrity. However, the complicated fluid-solid coupling interactions in aero-engine are difficult to be described precisely using current numerical or analytical models. Instead, experimental investigations on the flow induced blade vibration can reveal the aeroelastic performance of aero-engines, which is regarded as an effective approach to provide instructive guidance in the design of aero-engine. In this paper, experiments on a realistic aero-engine fan with 3.5 stages is conducted to study the typical aeroelastic instabilities, including the blade forced response, flutter, and acoustic resonance. In addition to the conventional blade strain measurements, the duct acoustic array measurements are also implemented to characterize the distinguishing acoustic features of the aeroelastic instabilities. Particularly, the acoustic mode decomposition technique is employed to provide insight into the unsteady flow as the aeroelastic instabilities occur, by which the blade vibration and aerodynamic excitation are bridged. The run-up test is conducted firstly to investigate the blade forced response and flutter; thereafter, a transient test is designed to encounter the acoustic resonance. The results illustrate the acoustic features of aeroelastic instabilities properly, validating the feasibility of acoustic measurement for instability identification. When the blade forced response occurs in the run-up test, the amplitude of Tyler-Sofrin mode increases significantly. The flutter also occurs in the run-up test and is believed to be excited by the rotating instability, where a sloping strip in the acoustic mode spectrum can be observed. In terms of the acoustic resonance, a nonsynchronous tonal component is observed below the blade passing frequency, where the dominant acoustic mode order matches the nodal diameter number. This paper presents an alternative way to study vibrations using acoustic measurements and the acoustic mode decomposition, which is validated by experiments on a realistic aero-engine fan.

Study of Bond-Slip Behavior and Constitutive Model of a New M-Section Steel-Skeleton Concrete.

In this study, the bond–slip behavior between a new type of M-section steel skeleton (i.e., M-section steel) applied in assembled shear wall structures and concrete was investigated. First, push-out tests were conducted on 21 M-section steel–concrete (MSSC) specimens, wherein the effects of the concrete cover, concrete strength, and anchorage length on the bond strength between the M-section steel and concrete were considered. Further, the crack patterns, strain distribution of M-section steel, and bond–slip curves of the MSSC specimens were investigated using conventional strain measurement and a non-contact optical three-dimensional deformation measurement system, Digital Image Correlation-3D (DIC-3D). The experimental results demonstrated that the bond–slip curves of the MSSC specimens were divided into four stages: the linear ascending, non-linear ascending, non-linear descending, and residual stages. The initial average bond strength was mainly affected by the concrete strength and anchorage length, whereas the concrete cover and anchorage length influenced the residual average bond strength , and the ultimate average bond strength was affected by the concrete strength, concrete cover, and anchorage length. Consequently, a bond–slip constitutive model of M-section steel and concrete was proposed based on the experimental results, and consistency was observed in comparison with the test results, which verified the applicability of the proposed model. Furthermore, to verify the rationality of the bond–slip constitutive model, a numerical simulation was performed, wherein the bond–slip curves, stress clouds, and interfacial bond damage process of the MSSC specimens were investigated. The numerical simulation results indicated that the bond–slip constitutive model could accurately predict the entire failure process of the MSSC specimens.

Ultrasound deep learning for monitoring of flow–vessel dynamics in murine carotid artery

Several arterial diseases are closely related with mechanical properties of the blood vessel and interactions of flow–vessel dynamics such as mean flow velocity, wall shear stress (WSS) and vascular strain. However, there is an opportunity to improve the measurement accuracy of vascular properties and hemodynamics by adopting deep learning-based ultrasound imaging for flow–vessel dynamics (DL-UFV). In this study, the DL-UFV is proposed by devising an integrated neural network for super-resolved localization and vessel wall segmentation, and it is also combined with tissue motion estimation and flow measurement techniques such as speckle image velocimetry and speckle tracking velocimetry for measuring velocity field information of blood flow. Performance of the DL-UFV is verified by comparing with other conventional techniques in tissue-mimicking phantoms. After the performance verification, in vivo feasibility is demonstrated in the murine carotid artery with different pathologies: aging and diabetes mellitus (DM). The mutual comparison of flow–vessel dynamics and histological analyses shows correlations between the immunoreactive region and abnormal flow–vessel dynamics interactions. The DL-UFV improves biases in measurements of velocity, WSS, and strain with up to 4.6-fold, 15.1-fold, and 22.2-fold in the tissue-mimicking phantom, respectively. Mean flow velocities and WSS values of the DM group decrease by 30% and 20% of those of the control group, respectively. Mean flow velocities and WSS values of the aging group (34.11 cm/s and 13.17 dyne/cm2) are slightly smaller than those of the control group (36.22 cm/s and 14.25 dyne/cm2). However, the strain values of the aging and DM groups are much smaller than those of the control group (p < 0.05). This study shows that the DL-UFV performs better than the conventional ultrasound-based flow and strain measurement techniques for measuring vascular stiffness and complicated flow–vessel dynamics. Furthermore, the DL-UFV demonstrates its excellent performance in the analysis of the hemodynamic and hemorheological effects of DM and aging on the flow and vascular characteristics. This work provides useful hemodynamic information, including mean flow velocity, WSS and strain with high-resolution for diagnosing the pathogenesis of arterial diseases. This information can be used for monitoring progression and regression of atherosclerotic diseases in clinical practice.

Brillouin scattering spectrum-based crack measurement using distributed fiber optic sensing

Brillouin scattering-based distributed fiber optic sensing (Brillouin-DFOS) technology is widely used in health monitoring of large-scale structures with the aim to provide early warning of structural degradation and timely maintenance and renewal. Material cracking is one of the key mechanisms that contribute to structural failure. However, the conventional strain measurement using the Brillouin-DFOS system has a decimeter-order spatial resolution, and therefore it is difficult to measure the highly localized strain generated by a sub-millimeter crack. In this study, a new crack analysis method based on Brillouin scattering spectrum (BSS) data is proposed to overcome this spatial resolution-induced measurement limitation. By taking the derivative of the BSS data and tracking their local minimums, the method can extract the maximum strain within the spatial resolution around the measurement points. By comparing the variation of the maximum strain within the spatial resolution around different measurement points along the fiber, cracks can be located. The performance of the method is demonstrated and verified by locating and quantifying a small gap created between two wood boards when one of the wood boards is pushed away from the other. The test result verifies the accuracy of the crack strain quantification of the method and proves its capability to measure a sub-millimeter crack. The method is also applied to a thin bonded concrete overlay of asphalt pavement field experiment, in which the growth of a transverse joint penetrating through the concrete–asphalt interface was monitored. The method successfully locates the position, traces the strain variation, and estimates the width of a crack less than wide using a Brillouin-DFOS system with spatial resolution.

Magnetomechanical response of a steel monopile during impact pile driving

This paper reports on a measurement campaign in which the magnetomechanical response of a steel monopile is recorded during installation with a hydraulic impact hammer. By comparing impact-induced changes in the magnetic stray field of the structure to the measured strain, this effect is analysed for the first time under dynamic loading conditions on such a large scale. It is shown that the measured stray field displays an excellent correspondence with the strain in terms of frequency content and amplitude ratio for hammer blows that induce compressive strain pulses of different magnitude. Using the data, a non-contact method is developed and validated to infer the hammer-induced strains using the dynamic magnetic stray field. The proposed method can be applied during pile installations when the use of conventional strain measurement devices is challenging, e.g. in the offshore environment.

Distributed Strain Sensing to Study a Composite Liner for Cast Iron Water Pipe Rehabilitation

Abstract The use of cured-in-place pipe lining systems for the rehabilitation of cast iron water pressure pipe has grown significantly in the past 20 years. With limited information on the performance of these lining systems in service, strain measurements are needed to evaluate theoretical findings about three-dimensional strength limits. The application of distributed optical fiber sensing to study the properties of a polymer composite liner was investigated in this research. Polyimide optical fibers were installed into flat liner coupons fabricated in the laboratory, and the specimens were subsequently tested in uniaxial tension and four-point bending. Using optical frequency domain reflectometry, Rayleigh backscatter was monitored from preinstalled optical fiber sensors and strains of up to 4,000 με were obtained. Comparisons between experimental optical fiber measurements and results obtained from conventional strain measurement techniques (i.e., extensometer and crosshead displacement) showed a strong correlation with an average difference of 3 % in four-point bending and 6 % in tension. However, the orientation and diameter of the composite fiber reinforcements were observed to affect distributed sensing performance.

Forming Limit Diagrams of Low-Carbon Steels Obtained Using Digital Image Correlation Technique and Enhanced Formability Predictions Incorporating Microstructural Developments

In the present work, drawing quality (DQ) and interstitial-free (IF) steel sheets were subjected to limiting dome height tests for determining strain-based forming limit diagrams (FLDs) experimentally and effect of dynamic (variable) material properties, such as work hardening ‘n’ and plastic anisotropy ( $$\bar{r}$$ ), on FLDs has been studied and simulated by PAMSTAMP™ finite element software. Dot prints on the steel specimens and an efficient optical strain measurement system GOM™ which works on the digital image correlation technique principle were used to measure limiting strains accurately instead of conventional circle grid analysis technique and strain measurement by traveling microscope. The dynamic (variable) material properties (n) and ( $$\bar{r}$$ ) were estimated by studying the microstructural developments in terms of changes in grain average misorientation and crystallographic texture, respectively, at different strains and strain paths, during deformation. In our proposed work, a novel technique of incorporating dynamic (variable) material properties (n and $$\bar{r}$$ ) in FE simulations was carried out during FLDs predictions. Though marginal but improved predictions in FLDs were observed in both IF and DQ steels. In addition to strain-based FLDs, stress-based FLDs were also determined for both grades. Interestingly, in both cases it was noticed that IF steel had higher formability than DQ steel.

Dynamic Visible Monitoring of Heterogeneous Local Strain Response through an Organic Mechanoresponsive AIE Luminogen.

Local strain concentration is critically important for damage formation of structural components. Therefore, it is of particular interest in developing the structural health monitoring (SHM) method for large-scale, full-field, and on-site monitoring of local strain response in complicated structural components in service. The present work investigated a SHM method based on a pure organic mechanoresponsive luminogen (MRL), 1,1,2,2-tetrakis(4-nitrophenyl)ethane, for heterogeneous local strain concentration. Invisible heterogeneous local strain response in complicated weld joints is transformed into visible fluorescence under monotonic tension and cyclic stress loading. The local strain (<15%) calculated by fluorescence intensity has a good agreement with the results obtained by the conventional digital image correlation method, indicating good measurement accuracy of the calibrated organic MRL method. The heterogeneity of local strain in complicated weld joints increases along with elongation and number of stress cycles. Moreover, the higher mean stress and stress amplitude can induce significantly higher accumulated local strain in the relatively soft fusion zone region. Compared with conventional strain measurement methods, the present organic MRL method opens up new possibilities for large-scale, full-field, and on-site monitoring of local strain concentration and damage in complicated structural components.

Non-destructive testing derived parameters for microstructure-based residual service life assessment of aging metallic materials in nuclear engineering

Abstract Metallic components in nuclear engineering are exposed to extensive loads such as pressurization and temperature changes which can affect the properties of the material significantly depending on the load spectrum applied. In view of developing a procedure to evaluate the residual service life of metallic components in nuclear power plants aged during service, metastable austenitic steel AISI 347 (German designation: X6CrNiNb18−10) has been considered as an example. To this purpose, total strain-controlled fatigue tests were carried out under different environmental conditions and monitored by continuously measuring thermometric, resistometric, electromagnetic and electrochemical parameters. These parameters provide an information gain in terms of material characterization when compared to conventional strain measurements. Based on these parameters, the short time evaluation procedure StrainLife has been developed, which allows the determination of local S-N curves with a significantly reduced effort as compared with traditional procedures. This method has been implemented into the structural simulation program PROST for the integrity assessment of the components while considering local fatigue properties. This very effective method allows for the determination of local fatigue properties including the strain-specific local scatter of the metallic microstructure properties of the material which has not been possible by traditional means.

Damage diagnosis in bridge structures using rotation influence line: Validation on a cable-stayed bridge

This study proposes a new damage identification technique for condition assessment of bridge structures. The method is based on the concept of rotation influence line (RIL) at the bridge bearing locations, and solely relies on measurements obtained from two points at either end of the bridge e.g., RILR and RILL. The sensitivity of the rotation measurement to damage is first investigated using a 1-D simply supported beam model and it is demonstrated that unlike conventional strain measurements, the rotation measurement is capable of providing useful information about damage even though it is far from the measurement point. Further, an existing cable-stayed bridge is considered to validate the capability of RIL in damage identification. A comprehensive three-dimensional finite element model (FEM) of the bridge is established and calibrated using the measured static and dynamic responses. Numerous field tests are conducted on this large-scale structure to extract static and dynamic characteristics, including natural frequencies, mode shapes and influence lines (ILs). Sixteen hypothetical damage scenarios are induced in the numerical model, including symmetric and asymmetric cases of cable loss. A damage index based on the normalised discrepancy of RIL between the benchmark state and an unknown state is introduced and through extensive investigations it is demonstrated that regardless of damage location, either RILR or RILL (or both) can successfully identify the induced damage in all of the sixteen damage scenarios. In contrast, the success of strain-based measurement is highly dependent on the closeness of damage to the sensor location, thus a much higher number of strain gauge sensors is required not to misidentify damage. The contribution of this work is four-fold. First, a novel and robust damage identification technique based on RIL is proposed which has not been reported in the literature. Second, the method solely relies on two measurement points e.g., two tilt meters at either end of the bridge and it is capable of identifying damage, even far from the sensor location. Third, the validation of the technique is demonstrated through extensive numerical and field test investigations on a statically indeterminate cable-stayed bridge structure. Finally, it is demonstrated that the conventional strain-based measurement is very likely to misidentify cable damage even with extreme case of cable loss.

Damage evolution and deformation behaviour of dry and saturated sandstones: Insights gleaned from optical measurements

Microscopic properties have a marked influence on the macroscopic mechanical response of sandstones. Improved understanding of the mechanical behaviour of these rocks caused by their microscopic properties is imperative for the successful design of rock structures. Here we experimentally investigate the damage evolution and deformation behaviour of three types of sandstones from Australia with contrasting petrographic properties under dry and saturated conditions with the aid of an optical strain and deformation measurement system (ARAMIS camera). More accurate and representative strain measurements are obtained using ARAMIS camera images compared to conventional strain measurement techniques. The results revealed that the quartz content of sandstone alone is not indicative of its strength, as the sandstone with the highest quartz content showed the lowest strength and this was attributed to the superior influence of other microscopic properties, such as grain size and porosity. However, the quartz content displayed a significant influence on the water-weakening behaviour of the sandstones, where the sandstone with the greatest quartz content was least affected by saturation and the sandstones with considerable clay mineral content showed greater weakening due to water. It was also found that some clay minerals are susceptible to swelling in the presence of water, and this can increase the initial crack volume and affect deformation characteristics. ARAMIS camera images clearly illustrated a more brittle behaviour by the sandstone with the greatest quartz content and notable early deformation by the sandstones with greater clay mineral content. Moreover, it was found that the overall deformation of sandstones was influenced by the swelling capacity of the constituent clay minerals, in addition to their composition by percentage.

Measuring strain fields in FRP strengthened RC shear walls using a distributed fiber optic sensor

This paper presents results on the applications of a truly distributed fiber-optic sensor (DFOS) in the cyclic testing of a reinforced concrete (RC) shear wall. To improve the performance of the wall, the RC shear wall is strengthened using externally bonded fiber-reinforced polymer (FRP) sheets. The DFOS is used as a replacement for conventional strain gauges to measure the strain distribution in the FRP sheet. Conventional electrical strain measurement techniques require a priori knowledge of measurement location and do not provide spatial information over a large area of a structural component, such as a wall. In recent years, the development of fiber-optic sensing technologies offers clear advantages compared to the conventional strain measurement approach. In particular, the DFOS has the unique capability of capturing strain at any location along the length of a fiber, without pre-determining the measurement locations before the test. The DFOS provides high precision strain measurement by optical frequency domain reflectometry. This allows full two-dimensional spatial strain measurement over the entire area of the shear wall. The DFOS can capture detailed response and failure mechanisms of the concrete and FRP as well as their contributions to the resistance of the shear wall. Experimental results are used to develop a better understanding of the behavior of RC shear walls retrofitted with FRP sheets, and assist in improving design guidelines for the application of FRP in RC structures.

Specimen aspect ratio and progressive field strain development of sandstone under uniaxial compression by three-dimensional digital image correlation

The complete stress–strain characteristics of sandstone specimens were investigated in a series of quasi-static monotonic uniaxial compression tests. Strain patterns development during pre- and post-peak behaviours in specimens with different aspect ratios was also examined. Peak stress, post-peak portion of stress–strain, brittleness, characteristics of progressive localisation and field strain patterns development were affected at different extents by specimen aspect ratio. Strain patterns of the rocks were obtained by applying three-dimensional (3D) digital image correlation (DIC) technique. Unlike conventional strain measurement using strain gauges attached to specimen, 3D DIC allowed not only measuring large strains, but more importantly, mapping the development of field strain throughout the compression test, i.e. in pre- and post-peak regimes. Field strain development in the surface of rock specimen suggests that strain starts localising progressively and develops at a lower rate in pre-peak regime. However, in post-peak regime, strains increase at different rates as local deformations take place at different extents in the vicinity and outside the localised zone. The extent of localised strains together with the rate of strain localisation is associated with the increase in rate of strength degradation. Strain localisation and local inelastic unloading outside the localised zone both feature post-peak regime.

Monitoring Poisson’s Ratio Degradation of FRP Composites under Fatigue Loading Using Biaxially Embedded FBG Sensors

The significance of strain measurement is obvious for the analysis of Fiber-Reinforced Polymer (FRP) composites. Conventional strain measurement methods are sufficient for static testing in general. Nevertheless, if the requirements exceed the capabilities of these conventional methods, more sophisticated techniques are necessary to obtain strain data. Fiber Bragg Grating (FBG) sensors have many advantages for strain measurement over conventional ones. Thus, the present paper suggests a novel method for biaxial strain measurement using embedded FBG sensors during the fatigue testing of FRP composites. Poisson’s ratio and its reduction were monitored for each cyclic loading by using embedded FBG sensors for a given specimen and correlated with the fatigue stages determined based on the variations of the applied fatigue loading and temperature due to the autogenous heating to predict an oncoming failure of the continuous fiber-reinforced epoxy matrix composite specimens under fatigue loading. The results show that FBG sensor technology has a remarkable potential for monitoring the evolution of Poisson’s ratio on a cycle-by-cycle basis, which can reliably be used towards tracking the fatigue stages of composite for structural health monitoring purposes.

DEFORMATION MONITORING OF RETROFITTED SHORT CONCRETE COLUMNS WITH LASER SENSOR

Abstract. This paper presents one of the applications of monitoring mechanical tests carried out in Construction Materials Laboratory of Istanbul Technical University. In Turkey, as in many countries, large amount of existing buildings exposed to seismic hazard, therefore various analytical and experimental studies are being conducted to contribute to the solution of the problem. One of the new generation retrofitting techniques is to strength the structural members by using Fiber Reinforcing Polymer (FRP). This study summarize the results of monitoring of deformations short concrete column samples under the incremental compression load. In this study, result of two rectangular short columns are given. One of them was tested as a reference sample, the other sample were tested after strengthening by PET reinforced polymer composite materials. Besides conventional displacement and strain measurement systems, laser scanning method was used to get three dimensional deformed shape of sample at each selected steps.

DEFORMATION MONITORING OF RETROFITTED SHORT CONCRETE COLUMNS WITH LASER SENSOR

This paper presents one of the applications of monitoring mechanical tests carried out in Construction Materials Laboratory of Istanbul Technical University. In Turkey, as in many countries, large amount of existing buildings exposed to seismic hazard, therefore various analytical and experimental studies are being conducted to contribute to the solution of the problem. One of the new generation retrofitting techniques is to strength the structural members by using Fiber Reinforcing Polymer (FRP). This study summarize the results of monitoring of deformations short concrete column samples under the incremental compression load. In this study, result of two rectangular short columns are given. One of them was tested as a reference sample, the other sample were tested after strengthening by PET reinforced polymer composite materials. Besides conventional displacement and strain measurement systems, laser scanning method was used to get three dimensional deformed shape of sample at each selected steps.