Displacement Of Slab Research Articles

Safety of Air Transport in Relation to Pavement Condition of Runways

Even though the satisfactory condition of the airfield pavement in terms of serviceability, there are some situations, when air traffic safety is affected. There are extreme phenomena in global warming scenarios. In particular, the increase in air temperature during the summer months, due to which decreases the quality of the pavement. At the aerodrome, there are defects in the pavement structures on the runway of large and significant characters, which can cause emergency conditions. Aerodrome pavements must meet the required operational functions, which are characterized mainly by reliability, safety, and serviceability throughout their lifetime. This problem needs to be diagnosed and solved (ICAO 2018). Since most of the aerodrome movement areas are built of cement concrete, control measurements of temperatures and horizontal displacements of cement-concrete slabs started to be carried out since 2011. The article describes the results of measurements and evaluation of non-standard situations occurring at the monitored aerodrome in terms of runways serviceability and air traffic safety.

Damage destruction evolution law of high-speed railway CRTS II slab ballastless track interface under train braking and temperature load

The train braking and temperature load are simplified as shear loads and based on the cohesive stress constitutive model and test parameters, an interfacial nonlinear finite element model for the cohesion-displacement relationship of high-speed railway CRTS II slab ballastless track interface was established and verified by theoretical analysis. Damage destruction evolution law of the interface under shear loads, and the influence of shear steels on the interfacial longitudinal maximum cohesion and ultimate yield displacement are studied. Results indicates that the error between axial force difference of track slab and the interfacial constraint reaction is no more than 2%, which verified the correctness of the interfacial nonlinear finite element model; the longitudinal displacement of track slab increases with the increase of shear loads, and it decreases as the distance from the loading end increases; the interfacial longitudinal cohesion can fluctuate up and down at a certain value with the increase of longitudinal displacement, and then the interface gradually loses cohesion until it is completely destroyed and enters the sliding state. The three shear steels layout forms are all made the interfacial longitudinal maximum cohesion and ultimate yield displacement increase, the contributions of interfacial longitudinal maximum cohesion are 21.46%, 23.54% and 53.03%, respectively, and the contributions of ultimate yield displacement are 9.72%, 15.61% and 44.92%, respectively. Shear steel plays an important role in satisfying deformation demand of track structure.

Low-velocity impact behaviour of two way RC slab strengthening with CFRP strips

There are a lot of studies focused on behaviour of reinforced concrete (RC) slabs under static and dynamic loadings in the literature. However, investigations related to Carbon Fibre Reinforced Polymer (CFRP) strengthened RC slabs subjected to impact load are still relatively rare. Consequently, an experimental study was performed in order to determine impact behaviour of two way simply supported RC slabs strengthened with CFRP strips. The arrangement and width of CFRP strips were varied in an experimental study. The impact load was applied to slabs using moveable drop-weight test machine designed by the authors. A total of nine RC slabs that were 1000 × 1000 × 80 mm dimensions were manufactured. RC slabs were strengthened using CFRP strips with a width of 50 and 100 mm as orthogonally and diagonally in both one and two directions. One of the specimens was un-strengthened and manufactured as reference specimens. The time-history of the impact force, the accelerations of two points, the center displacement of slabs and the strains of four points on CFRP strips were measured. The crack patterns of slabs are also observed. In the light of experimental results, the effects of applied strengthening method on low-velocity impact behaviour of RC slabs were determined and interpreted. Besides, the finite element models of RC slabs strengthened with CFRP strips are generated using ABAQUS software. It is found out that the proposed finite element model could be used for evaluation of dynamic responses of RC slabs strengthened with CFRP strips subjected to low-velocity impact load.

Effect of gap on vertical deformation and deterioration stress of CRTS-I ballastless track

To explore the influence of gap on deformation and deterioration stress of track structure, a finite element model of CRTS-I slab ballastless track with gap is established by ABAQUS on the basis of plastic damage constitutive relation of concrete. The effects of different sizes and different positions of gap on displacement and stress of the track structure are calculated and analysed. The influence law of gap on deformation and deterioration stress is drawn by comparison with the calculation of normal track structure. The results show that increasing gap size sharply increases vertical displacement of both rails and slab and also seriously deteriorates transversal and longitudinal stress on the track slab to a great extent. Moreover, the effect of gap at slab centre on deteriorated stress and deformation is less than that of gap at slab end. The study can obviously provide theoretical reference for the maintenance standard.

Experimental Investigation on Flexural Behavior of Granite Stone Slabs with Near Surface Mounted CFRP Bars and Screw‐Thread Steels

An experimental study that investigates the behavior of stone slabs strengthened in fixure with near surface mounted (NSM) technique using screw‐thread steels and carbon fiber‐reinforced polymer (CFRP) bars is presented. A total of ten full‐scale stone slabs were tested under a four‐point bending loading to investigate the effect of groove dimension, reinforcement ratios, and reinforcement materials on the flexural performance of stone slabs. The test results included failure characteristics, yield and ultimate capacities, deflection of midspan, and cracking behavior of stone slabs. The test results indicate that with the increase of groove height and groove width, cracking load and middeflection decrease by 6.4%–14.18%; however, failure load and middeflection increase by 4.7%–41.2%. Cracking load, failure load, and failure displacement of stone slabs adopting NSM screw‐thread steels increased by 10.9%, 167%, and 617%, respectively, under the maximum reinforcement ratios of 0.629% over the control slab without NSM bars. Meanwhile, with the increase of reinforcement ratios, the failure mode transforms from brittle failure to ductile failure. The calculation results of strength are in agreement with the experimental results. Finally, it can be concluded that NSM CFRP bars are more effective than NSM screw‐thread steels to improve flexural capacity with the same reinforcement ratios.

Effect of gap on vertical deformation and deterioration stress of CRTS-I ballastless track

To explore the influence of gap on deformation and deterioration stress of track structure, a finite element model of CRTS-I slab ballastless track with gap is established by ABAQUS on the basis of plastic damage constitutive relation of concrete. The effects of different sizes and different positions of gap on displacement and stress of the track structure are calculated and analysed. The influence law of gap on deformation and deterioration stress is drawn by comparison with the calculation of normal track structure. The results show that increasing gap size sharply increases vertical displacement of both rails and slab and also seriously deteriorates transversal and longitudinal stress on the track slab to a great extent. Moreover, the effect of gap at slab centre on deteriorated stress and deformation is less than that of gap at slab end. The study can obviously provide theoretical reference for the maintenance standard.

Structure Design of Photonic Crystal Based MOEMS Accelerometer Sensor for Supplemental Restraint System in Automobile Passenger Safety

Leading cause of human death in most of country is roadway crashes. Supplemental restraint system playing vital role in preventing and protecting the passengers and drivers in case of accidents thereby providing chance of last line of defence against serious injuries. So there is need of sensor which sense the signals precisely with high sensitivity, low energy consumption and EMI insensitivity in harsh conditions which modifies the technology involved in present sensors used in automobile crash sensing. Work which is carried out here is designing structure of PhC stationed optical approach accelerometer sensor for supplemental restraint system or Airbag for vehicle passenger safety. Functionality of MOEMS device achieved through four free ends of slab is fixed and horizontal displacement of main slab using MEEP software for rods in air configuration. As the main slab displaces there will be change in spacing which alters the electromagnetic waves and which shift the transmission spectrum wavelength. Shift in wavelength of 0.001 for each micro displacement from 0 to 0.6 micrometre, prove the design methodologies and its validation. Interrelation between optical and mechanical system discussed here will measure the acceleration of vehicle. Q factor of 6000 observed for each submicron displacement representing accuracy level of proposed design for fabrication of device in future.

Estimation of Vertical Floor Displacement Using a Wavelet De-Noising Method

The horizontal response of structural and nonstructural systems during seismic events has been studied for a long time. However, the effect of the vertical response of floors on building contents and nonstructural systems has still remained a topic of concern. A wavelet de-noising method along with the experimental data obtained from a full-scale test at E-Defense is used to estimate the vertical floor displacement of a five-story steel moment frame building in base-isolated and fixed-base configurations. Vertical displacements of slabs and beams are calculated from the experimental data and formulated based on their out-of-plane dominant frequencies. A curve fitting approach is then carried out to estimate vertical displacements at floors and stories. In these tests, partition wall damage such as buckling of studs occurred at slab displacements of about 1 in.

Geological setting, emplacement mechanism and igneous evolution of the Atchiza mafic-ultramafic layered suite in north-west Mozambique

The Atchiza mafic and ultramafic-layered suite (hereafter, “Atchiza Suite) crops out in an area 330 km2 west of the Mozambican Tete province. In an early account of the geology of this intrusion, it was considered the continuation of the Great Dyke of Zimbabwe, an idea that was aborted after detailed studies. Nevertheless, the Ni concentrations in the Atchiza outcrop rocks are considerable. Our investigation used field evidence, hand specimens and petrography descriptions, mineral chemistry studies using electron microprobe analysis and tectonic analysis to arrive at a plausible mineralogical composition and understanding of the tectonic setting for the igneous evolution. The mineral composition from the Atchiza Suite indicates that these are cumulates. The magmatic segregation from the petrographic and mineral composition reasoning indicates that dunite-lherzolitic peridotite-olivine gabbro-gabbronorite-gabbro-pegmatitic gabbro is the rock formation sequence. Olivine and chromite were the first phases formed, followed by pyroxene and plagioclase. In addition, it is shown that these minerals are near-liquidus crystallization products of basaltic magma with olivine Fo: 87.06 in dunite, mean values of clinopyroxene are (Wo: 36.4, En: 48.0, Fs: 15.2), orthopyroxene (Wo: 2.95, En: 73.0, Fs: 24.2) and plagioclase An: 71.3, respectively. Opaque minerals comprise Fe–Ti oxides and (Fe, Cr) spinel up to 4.8 vol.%, but chromitite layers are not present. Most of the opaque minerals are interstitial to pyroxene. Sulphides are common in gabbros, with pyrrhotite, pentlandite, chalcopyrite, pyrite and covellite together comprising 0.4–2.0 vol.%. The whole rock Rare Earth Element (REE) concentrations are mainly a result of differentiation, but slight crustal contamination/assimilation contributed to the REE contents. In addition, they also show Eu enrichment, suggesting that plagioclase fractionation was important in the rock. The Atchiza Suite preserves a deep-seated plumbing system of the continental rift environment. The intrusion resulted from the emplacement of mafic magma in space created by extensional forces. Space was created through a connecting fault generated as a result of overall extensional, torsion and slab displacement in a rift system. The geometry of the body is tectonically controlled, and it agrees with the tectonic framework of the Zambezi Belt during the Rodinia breakup in the early Neoproterozoic.

Fire Test on Two-Way Slab with Two Edges Clamped and Two Edges Simply Supported

This paper describes the results of a fire test conducted on two-way slab with two edges clamped and two edges simply supported. The details of support condition, arrangement of reinforcement, position of displacement transducers and thermocouple trees are described. The experimental results such as the temperature distributions within the slab, vertical deflections and horizontal displacements are presented. The experimental results show that the temperature distribution along the slab depth was nonlinear and the temperature gradients in the slab were large. Main cracks near the clamped edges occurred on the top surface of the slab. It is shown that two-way slab with two edges clamped and two edges simply supported has good fire resistance.

Review of Push-Off Tests for Base Friction of Cement Concrete Pavement

Concrete pavement slabs experience volume change due to the variation of temperature and moisture level. The frictional drag acting on the bottom of slab due to the base friction is in the opposite direction of horizontal slab displacement, and resist against the horizontal slab movements. The magnitude of frictional force and horizontal slab displacement has interdependent relationship. In the present study, the interface friction of typical concrete pavements was evaluated by performing a number of push-off tests. In this paper, reviews of classical friction theory and friction characteristics at the interface of concrete slabs and the underlying subbases are presented.

Fire Test on Two-way Simply Supported Concrete Slab

This paper describes the results of a fire test conducted on two-way simply supported concrete slab. The details of support condition, arrangement of reinforcement, position of displacement transducers and thermocouple trees are described. The experimental results such as the temperature distributions within the slab, vertical deflections and horizontal displacements are presented. The experimental results show that the temperature distribution along the slab depth was nonlinear and the temperature gradients in the slab were large. Three main cracks parallel to the short span direction occurred on the top surface of the slab. It is shown that two-way simply supported concrete slab has good fire resistance.

Measurements of snow slab displacement in Extended Column Tests and comparison with Propagation Saw Tests

The Extended Column Test (ECT) has become increasingly popular for assessing snowpack stability. What happens to the snow slab and the underlying weak layer during the test remains largely unknown. Such work has been done for the Propagation Saw Test (PST), but not for the ECT. We therefore analyzed high-speed videos of ECTs and adjacent PSTs using particle tracking to better understand the mechanics of the ECT. Our results show that in an ECT, tapping on one end of the column had no observable effect on the opposite end, and that fracture initiates in an area of the weak layer directly under the shovel at the free edge of the column. We observed no signs of progressive damage accumulation in the weak layer during tapping, but rather a single rapid collapse when fracture initiated. In contrast, in PSTs, we observed slab bending prior to weak layer fracture. During fracture, weak layers in ECTs compact on the order of several mm, similar to measurements obtained from PSTs. Measured propagation speeds, on the order of 20 to 30ms−1, were also similar to those from PSTs. The similarities between ECT results and those with PSTs give us confidence that the fracture mechanics are similar regardless of the triggering mechanism. From a practical perspective, our results suggest that the ECT is indeed measuring the propensity of a crack to propagate at the small scale of the ECT block, thus providing information on a critically important property of snow stability in our tests.

Wireless Sensing Based on RFID and Capacitive Technologies for Safety in Marble Industry Process Control

This paper presents wireless sensing systems to increase safety and robustness in industrial process control, particularly in industrial machines for marble slab working. The process is performed by abrasive or cutting heads activated independently by the machine controller when the slab, transported on a conveyer belt, is under them. Current slab detection systems are based on electromechanical or optical devices at the machine entrance stage, suffering from deterioration and from the harsh environment. Slab displacement or break inside the machine due to the working stress may result in safety issues and damages to the conveyer belt due to incorrect driving of the working tools. The experimented contactless sensing techniques are based on four RFID and two capacitive sensing technologies and on customized hardware/software. The proposed solutions aim at overcoming some limitations of current state-of-the-art detection systems, allowing for reliable slab detection, outside and/or inside the machine, while maintaining low complexity and at the same time robustness to industrial harsh conditions. The proposed sensing devices may implement a wireless or wired sensor network feeding detection data to the machine controller. Data integrity check and process control algorithms have to be implemented for the safety and reliability of the overall industrial process.

Fatigue-Life Prediction of Full-Scale Concrete Pavement Overlay over Flexible Pavement: Super-Accelerated Pavement Testing Application

Thin concrete pavement overlay placed on the top of flexible pavements is referred to as a thin whitetopping (TWT) pavement, which is one of the rehabilitation treatments for deteriorated flexible pavements. The primary goal of this study is to evaluate the fatigue performance of full-scale TWT pavement due to repeated traffic loading. Super-accelerated pavement (SAP) tests on full-scale TWT concrete slabs were performed under static and constant cyclic loading. The stationary dynamic deflectometer (SDD) (a truck-mounted SAP testing device) was used to statically and dynamically load the TWT slabs. In order to monitor the response of the TWT slabs, accelerometers and linear variable differential transformers (LVDTs) were installed and the dynamic displacements of slabs were recorded during the entire testing period. The test results show that the tested slabs have dynamic displacement peaks around the number of load repetitions corresponding to the first visible cracks. The dynamic displacement increased at a higher rate after the occurrences of the first visible crack. In addition, the tested slabs showed a stress redistribution phenomenon during the crack propagation. The concepts of the stress level and equivalent fatigue life were used to eliminate, in part, influences of other factors (that is, the water-cement ratio [w/c] and aggregate type and gradation) and correct the effect of different stress ratios, respectively. The S-N curve developed from this study was very close to Thompson and Barenburg’s S-N curve after the application of the equivalent fatigue-life concept.

Experimental Study on the Behavior of Two-Way Concrete Slab under Furnace Loading

This paper describes the results of a furnace test conducted on two-way concrete slab with clamped edges. The details of clamped support condition, arrangement of reinforcement, position of displacement transducers and thermocouple trees are described. Detailed experimental data in the form of describing slab cracking, the temperature distributions within the slab, vertical deflections and horizontal displacements are presented. The experimental results show that the temperature distribution along the slab depth was nonlinear and the temperature gradients in the slab were large. Extensive cracks occurred on the top surface of the slab and formed in an elliptical pattern. It is shown that two-way concrete slab with clamped edges has good fire resistance.

Post-punching behaviour of flat slabs strengthened with a new technique using post-tensioning

This work presents an experimental study concerning the post-punching behaviour of flat slabs strengthened with a new technique based on post-tensioning with anchorages by bonding using an epoxy adhesive. This strengthening technique proved efficient with respect to ultimate and serviceability states. Five slab specimens were tested in the post-punching range and it was found that the post-punching resistance was on average 78% of the punching resistance. This paper reports the development of strand forces and slab displacements from the beginning of the tests, including the bond stresses developed at several stages of the loading process. It was observed that top reinforcement bars were capable of transmitting post-punching loads to the prestressing strands. Taking this into account and based on the load bath envisaged from the column to the slab, expressions for the vertical load capacities corresponding to the parts of the load path are presented and compared with the experimental results, showing their ability to predict both ultimate loads and modes of failure. Compared with other strengthening techniques, the one proposed here not only upgrades ultimate and serviceability behaviour but also adds post-punching resistance, which is a great advantage in the event of progressive collapse, since it may avoid the collapse of an entire structure, thus reducing the risk of material and human losses.

Influences of CA Mortar Elastic Modulus on Stress and Deformation of Slab Track in High Speed Railway

CA mortar is a key component of slab track. It is used as the material for leveling damping structure layer between the rigid track slab and concrete trackbed of slab track in high speed rail. In order to determine functions of CA mortar with low elastic modulus (EM), the beam/plate theory on elastic foundation was applied to the calculation of slab track’s stress. Under the bonding or no-bonding condition, the influence of CA mortar’s EM on the warping stress and displacement of track slab were calculated. Stress distribution of CA mortar under the common effects of train load and temperature gradient was explored, and the intensity requirement of CA mortar with different EM was put forward. Calculation results show that longitudinal and lateral bending moments of base plate both increase with the increasing of CA mortar’s EM; when the CA mortar’s EM is in the range of 50～10000MPa, there is gap between track slab and the mortar and the deformation of CA mortar (50mm thick) is not enough to compensate the warpage of the track slab; with the increasing of CA mortar’s EM, the tensile and compressive stresses of CA mortar both increase under the common effects of train load and temperature gradient, thus higher requirements on tensile and compressive strength are demanded when CA with high elastic modulus is used.

Study of the wavefield generated by a gas exploder used for artificial avalanche release

Abstract A study of the entire wavefield (3D) generated by the detonation of a Gazex® device performed on the Gamsleiten slope, at Obertauern, Austria is presented. The main aim of the study was to determine whether the detonation can trigger snow avalanches in remote locations. A linear array of sensors in the vicinity of the blasting point combining six 1D and two 3D seismic sensors was deployed. Three independent Gazex® detonations were subsequently triggered in intervals of approx. 15 min. The signals obtained were similar. Waves propagating through the ground (P waves) and sound waves were clearly detected. The corresponding ground velocities and accelerations were determined. The frequency content of the whole signals was band-limited to 10–40 Hz, although the frequency content of P waves was lower than that of sound waves in the three components. A different behaviour in the frequency content evolution of the two wave groups was observed. P waves suffered distortion and attenuation with distance. This was not observed in the sound waves which showed local amplifications. The maximum values of the velocity and acceleration measured correspond to the sound waves observed in the horizontal components. The values of the ground accelerations obtained for the whole signals were 6 times lower than the value of the critical acceleration, which is the value that is required for the inclined snow slab to be stable. Cumulative snow slab displacements caused by long vibrations were also considered. The results suggest that in this case the likelihood of a snow avalanche release due the Gazex® device detonations is low. However, this result cannot be generalized to other snow and terrain conditions and to other conventional explosives. Specific studies should be carried out at the target sites/situations. Another important finding was the significant contribution of the horizontal components to the ground movement. This indicates that it is necessary to consider the whole wave field (3D) in this type of study.

Transmission electron microscopy characterization of TiN/SiN x multilayered coatings plastically deformed by nanoindentation

Plastic deformation of TiN 5 nm /SiN 0.5 nm multilayers by nanoindentation was investigated by transmission electron microscopy in order to identify deformation mechanisms involved in film failure resulting from severe plastic deformation. The TiN layers exhibited a crystalline fcc structure with a [002] preferential orientation; further crystal growth was interrupted by the amorphous SiN x layers. After severe plastic deformation collective vertical displacement of slabs of several TiN/SiN x -bilayers, which resulted from shear sliding at TiN/TiN grain boundaries, was observed. They are, together with horizontal fractures along the SiN x layers, vertical cracks under the indenter tip following the TiN grain boundaries and delamination from the substrate, the predominant failure mechanisms of these coatings. The deformation behaviour of these films provides an experimental support for the absence of dislocation activity in grains of 5 nm size.