Depth Sections Research Articles

New strength–strain model and stress–strain relationship for square and rectangular concrete columns confined with CFRP wraps

The aim of this paper is to develop new models for the prediction of the ultimate strength, the ultimate strain, as well as the axial stress–strain relationship of square and rectangular concrete columns confined with carbon fiber reinforced polymer (CFRP) wraps. An experimental database covering 360 specimens with an unconfined compressive strength ranging from 11 to 94 MPa was collected from previous studies. In addition, the performance of eight existing strength and strain models was evaluated using the collected data. In this study, new strength–strain model considering the cross-sectional aspect ratio and the shape coefficient as a function of the depth of the rectangular cross-section was proposed using linear regression analysis. The proposed model provides a better correlation and a good fit with the experimental data compared to the other existing models. On the other hand, a new stress–strain relationship describing the axial behavior of square and rectangular columns confined with CFRP wraps was proposed, in which the parameters of confinement, such as the corner radius and the depth of the rectangular section were considered. The proposed relationship was validated with a set of experimental stress–strain curves and compared with four other existing models. The results showed that the proposed relationship provides good accuracy and better predictions over the existing models.

Velocity Analysis Using N-Th Root Stack

The estimation of seicmic wave velocity in the subsurface is one of the most important process in seismic data processing. The result is very crucial for the conversion af seismic data fromtime section into depth section. The N-th Root Stack which has not been widely used in the industry in fact a powerful method for estimating seismic wave velocity from seicmic record. The method attenuates the background/random noise effectiviely which facilitates tre fitting of the velocity spectrum can be done anccurately. In addition, the noise is also effectivdy suppressed during the CDP stackins, yielding the clear inrim i doking amplitude Synthetic records have been used to demonstrate the effectiveness of the N-th Root Stack Comparison with the Delay and Sum method also demonstrate the superiority of the N-th Root Stack.

VELOCITY ANALYSIS USING N-TH ROOT STACK

The estimation of seicmic wave velocity in the subsurface is one of the most important process in seismic data processing. The result is very crucial for the conversion af seismic data fromtime section into depth section. The N-th Root Stack which has not been widely used in the industry in fact a powerful method for estimating seismic wave velocity from seicmic record. The method attenuates the background/random noise effectiviely which facilitates tre fitting of the velocity spectrum can be done anccurately. In addition, the noise is also effectivdy suppressed during the CDP stackins, yielding the clear inrim i doking amplitude Synthetic records have been used to demonstrate the effectiveness of the N-th Root Stack Comparison with the Delay and Sum method also demonstrate the superiority of the N-th Root Stack.

Grinding performance and theoretical analysis for a high volume fraction SiCp/Al composite

SiCp/Al composite is widely used in space shuttle slides, automotive and machine tools. In this paper, ground surfaces of SiCp/Al composite, obtained with different grinding process parameters, are characterized in terms of friction and wear performances under dry and lubricated conditions. The wear mechanism of SiCp/Al composite is firstly found the combination of cohesive and abrasive wear, then a method to calculate the wear volume of SiCp/Al composite is proposed, and a comprehensive wear evaluation system of SiCp/Al composite is established, in which the three indicators of friction coefficient, wear depth, and equivalent wear section area are adopted to evaluate usability performance. The prediction models of the wear indicators were established and the errors between the experimental and predicted results are within 7%. Finally, the NSGA-II multi-objective algorithm is used to optimize surface performance of the SiCp/Al composite, and the optimized grinding process parameters are obtained as the wheel speed of 33 m/s, the table speed of 0.4 m/min and the grinding depth of 9 μm.

Long span post-tensioned box girder bridge in Bratislava

The paper describes an analysis and detailed design of the 470 m long D4 motorway bridge in the Slovak capital Bratislava. This bridge is a part of 2 932.50 m long D4 motorway crossing of the Danube River and its surrounding areas. The 210 m long main span of the post-tensioned three span box girder bridge is the longest span which has ever been built in Slovakia. The Ministry of Transportation and Construction of the Slovak Republic requirement was to cross all future rowing tracks by a single span. The depth of the cross section varies from 4.39 m at span to 13.09 m at piers. 35 m wide cross section carries 4-lane carriageway, median, sidewalk and cycling path. The central part of carriageway is built by the balanced cantilever method. The overhangs carrying outer lanes are built by wing traveller machine and supported by the precast struts. The bridge is currently under construction as a part of PPP project of Bratislava ring road (the motorway D4 Bratislava, Jarovce - Bratislava, Ivanka north section).

Forensic assessments of the influence of reinforcement detailing in reinforced concrete half-joints: A nonlinear finite element study

This paper presents the results of forensic assessments on reinforced concrete half-joint beams tested within the literature through the application of nonlinear finite element analyses. The software package ATENA Science was utilised, in which critical evaluations were conducted into the accuracy of the software in predicting the response of reinforced concrete half-joints with inadequate reinforcement detailing. It was shown that the load capacity of the half-joints could be predicted accurately, with an average experimental-over-predicted ratio of 1.04 and a coefficient of variation of 7.3%. The predicted crack patterns and modes of failure consistently coincided with those obtained experimentally, exhibiting localised failures at the re-entrant corner of the nib, along with failures located within the full depth of section due to an inadequate amount of shear reinforcement. Moreover, the combination of bar reductions to replicate severely corroded reinforcement at critical zones highlighted the influence deterioration mechanisms have on the structural capacity, with reductions of more than 50% observed in comparison to newly constructed half-joints with no deterioration.

Investigation of the Structural Behaviour of RC Beam-Column Sub-frame Subjected to Progressive Collapse

The aim of this study is to investigate the effects of varying design variables on the structural behaviour of reinforced concrete (RC) sub-frames under progressive collapse. A finite element modelling approach is presented and validated against the experimental results concerning a 2D frame (3 columns and 2 beams) and a 3D frame (4 columns and 3 beams). The performance of the RC sub-frame is discussed by choosing the scenarios of the exterior, interior, and multiple column loss, respectively, and by increasing the number of stories and bays. Further studies are conducted based on the numerical method to reveal the effect of beam longitudinal reinforcement ratio (BLRR), beam section depth (BSD), and concrete compression strength (CCS). The results show that both BLRR, CCS and BSD have a significant influence on the compressive arch action (CAA) capacity of the structure under progressive collapse, and the load-carrying capacity of the RC sub-frame increases with an increasing number of stories.

High-throughput volumetric adaptive optical imaging using compressed time-reversal matrix

Deep-tissue optical imaging suffers from the reduction of resolving power due to tissue-induced optical aberrations and multiple scattering noise. Reflection matrix approaches recording the maps of backscattered waves for all the possible orthogonal input channels have provided formidable solutions for removing severe aberrations and recovering the ideal diffraction-limited spatial resolution without relying on fluorescence labeling and guide stars. However, measuring the full input–output response of the tissue specimen is time-consuming, making the real-time image acquisition difficult. Here, we present the use of a time-reversal matrix, instead of the reflection matrix, for fast high-resolution volumetric imaging of a mouse brain. The time-reversal matrix reduces two-way problem to one-way problem, which effectively relieves the requirement for the coverage of input channels. Using a newly developed aberration correction algorithm designed for the time-reversal matrix, we demonstrated the correction of complex aberrations using as small as 2% of the complete basis while maintaining the image reconstruction fidelity comparable to the fully sampled reflection matrix. Due to nearly 100-fold reduction in the matrix recording time, we could achieve real-time aberration-correction imaging for a field of view of 40 × 40 µm2 (176 × 176 pixels) at a frame rate of 80 Hz. Furthermore, we demonstrated high-throughput volumetric adaptive optical imaging of a mouse brain by recording a volume of 128 × 128 × 125 µm3 (568 × 568 × 125 voxels) in 3.58 s, correcting tissue aberrations at each and every 1 µm depth section, and visualizing myelinated axons with a lateral resolution of 0.45 µm and an axial resolution of 2 µm.

A comparison of machine learning- and regression-based models for predicting ductility ratio of RC beam-column joints

Seismic response of Reinforced Concrete (RC) beam-column joints has always been evaluated by researchers due to their undeniable influence on the overall behavior of RC building frames under seismic loads. In the present study, an attempt has been made to predict displacement ductility ratio of RC joints using machine learning- (Artificial Neural Network and Random Forest) and regression-based (linear, nonlinear and ridge) methods. Therefore, a dataset including the results of over 170 experimental studies conducted on RC joints was collected from the international peer-reviewed publications. Parameters reflecting beam and column dimensions (length, cross section width and depth), reinforcement detailing (longitudinal and transverse reinforcement of beams and columns), material properties (concrete compressive strength, yield strength of longitudinal and transverse reinforcement) and retrofitting techniques were considered as input variables for predicting the only output parameter, displacement ductility ratio. The predicted and actual values were compared together and the efficiency of the models was assessed by Taylor diagram and performance metrics including RSME, MAE, MAPE and R2. The evaluation results proved the high reliability of proposed models for predicting ductility of RC joints.

Scan-less machine-learning-enabled incoherent microscopy for minimally-invasive deep-brain imaging.

Deep-brain microscopy is strongly limited by the size of the imaging probe, both in terms of achievable resolution and potential trauma due to surgery. Here, we show that a segment of an ultra-thin multi-mode fiber (cannula) can replace the bulky microscope objective inside the brain. By creating a self-consistent deep neural network that is trained to reconstruct anthropocentric images from the raw signal transported by the cannula, we demonstrate a single-cell resolution (< 10μm), depth sectioning resolution of 40 μm, and field of view of 200 μm, all with green-fluorescent-protein labelled neurons imaged at depths as large as 1.4 mm from the brain surface. Since ground-truth images at these depths are challenging to obtain in vivo, we propose a novel ensemble method that averages the reconstructed images from disparate deep-neural-network architectures. Finally, we demonstrate dynamic imaging of moving GCaMp-labelled C. elegans worms. Our approach dramatically simplifies deep-brain microscopy.

Global Buckling Behavior of CFST Columns with Assembling Errors

Concrete-filled steel tubular (CFST) column has been widely used in engineering practice. In the process of assembling two columns to form a slender member, assembling errors (AE) are inevitably produced at the section of connection. When the AE are too large, the global buckling resistance of slender column would be significantly affected. Therefore, it is necessary to investigate the influence of AE on the stability performance of slender CFST columns. In this study, an axial compressive test involving three CFST columns with AE (AE-CFST columns) was conducted. A refined finite element (FE) model is established for further parametric analysis. Based on a simplified analytical model by analyzing the isolated steel connecting plate, a theoretical formula is proposed for predicting the critical thickness [Formula: see text] of the connecting plate. When the thickness [Formula: see text] of the connecting plate meets its requirement, the failure at the section of connection caused by AE could be effectively prevented. Stability design curves considering the influence of AE ratio (the ratio between assembling error and sectional depth of column) are proposed based on numerous FE examples. It is found that the proposed design curves are reliable for the design of AE-CFST columns with different AE ratios.

Reliability Assessment of a Fully Laterally Restrained Steel Floor Beam to Eurocode 3

Parametric uncertainties should always be considered when setting design criteria in order to ensure safe and cost effective design of engineered structures. This paper presents the results of the reliability assessment of a fully laterally restrained steel floor I-beam to Eurocode 3 design rules. The failure modes considered are bending, shear and deflection. These were solved to obtain reliability indices using first order reliability method coded in MATLAB environment. Parametric sensitivity analyses were carried out at varying values of the design parameters to show their relative contributions to the safety of the beam. It was seen that reliability indices generally decreased with an increase in load ratio, imposed load, beam span in bending, shear stress and deflection respectively. In addition, increasing the beam span beyond 10 m, load ratio above 1.4 and imposed load beyond 30 kN/m made the beam fail as these parameters gave negative reliability indices. For failure in deflection, reliability index rose with an increase in the radius of gyration and overall depth of the beam section accordingly. Furthermore, the reliability index surged as the thickness of the web increased when taking into account, shear failure. The results of the analysis showed that the steel beam is very safe in shear and at some load ratios and imposed loads for failure in bending and deflection respectively. The average values of reliability indices obtained for load ratios ranging from 1.0 to 1.4 fell from 3.017 to 3.457 for all failure mode studied. These values are within the recommended reliability indices by the Joint Committee on Structural Safety for structure with moderate failure consequences and beams in flexure.

A Nonlinear Prediction Model of Antislide Pile Top Displacement Based on MIC‐SVR for Jurassic Landslides

In this study, a nonlinear prediction model of antislide pile top displacement is proposed. Based on the quantitative analysis of the rock mass structure characteristics of the soft and hard interbedded sliding bed in the Jurassic strata, the post‐thrust force and geometric characteristics of the top of antislide pile displacement, and bending moment, the main controlling factors affecting the displacement of the top of antislide pile were determined by maximal information coefficient (MIC). Through orthogonal experiment design and 3DEC numerical experiment, a database of main controlling factors (sliding bedrock inclination, thrust size, embedded depth, and pile section size) of pile top displacement was established and a nonlinear prediction model of the displacement of the top of antislide pile based on the main controlling factors was proposed. Finally, two engineering examples were used to validate the performance of this model, with the comparisons of four prediction methods (SVR, MIC‐SVR, LSTM, and ELMAN). The results show that the MIC‐SVR model has a practical reference value for the prediction of the displacement of the top of an antislide pile in the Jurassic landslide in the Three Gorges Reservoir Area.

ПРИНЦИП НАИМЕНЬШЕГО ДЕЙСТВИЯ В РАСЧЕТЕ ГЛУБИНЫ ВЫХОДНОГО СЕЧЕНИЯ ВОДОСЛИВА С ШИРОКИМ ПОРОГОМ

Purpose: development and experimental verification of a method for determining the flow depth in the outlet section of a broad-crested weir, based on the use of the variational principle of least action. Materials and methods. To develop a calculation method, the previously obtained dependences to determine the flow depth in the outlet section of a horizontal canal with a flow moving in a subcritical mode, and a method for determining the flow depth at the crest of a broad-crested weir were used. The theory was tested using a laboratory experiment and computer simulation in the ANSYS 17.0 software package. Results. The comparison of the results of experiments and computer simulation showed the conformance of the calculation results by the method based on the least action principle. The verification was carried out using the Fisher criterion, the criterion value according to the experimental data is 14.35, the criterion tabular value is 19.45, which indicates the adequacy of the proposed method to the experimental data. Conclusions. Based on the direct variational principle of least action, taking into account the influence of centrifugal forces in the flow, a calculation method that makes it possible to determine the outlet section depth of the broad-crested weir has been obtained. The resulting depth also corresponds to the transitional regime, in which the flooded regime changes to the non-flooded one, and in which the type of pool junction changes from surface to bottom one. The comparison showed a discrepancy of 0.4 % with data from outside authors. Experiments with the formation of a stuck jet in the outlet section of the weir showed that the depth in this case does not correspond to the proposed calculation method, this principle is also not implemented when the weir is flooded.

Lithospheric transdimensional ambient-noise tomography of W-Europe: implications for crustal-scale geometry of the W-Alps

SUMMARYA full understanding of the dynamics of mountain ranges such as the Alps requires the integration of available geological and geophysical knowledge into a lithospheric-scale 3-D geological model. As a first stage in the construction of this geo-model, we derive a new 3-D shear wave velocity model of the Alpine region, with a spatial resolution of a few tens of kilometres, making it possible to compare with geological maps. We use four years of continuous vertical-component seismic noise records to compute noise correlations between more than 950 permanent broad-band stations complemented by ∼600 temporary stations from the AlpArray sea-land seismic network and the Cifalps and EASI linear arrays. A specific pre-processing is applied to records of ocean–bottom seismometers in the Liguro-Provençal basin to clean them from instrumental and oceanic noises. We first perform a 2-D transdimensional inversion of the traveltimes of Rayleigh waves to compute group-velocity maps from 4 to $150\, \mathrm{ s}$. The data noise level treated as an unknown parameter is determined with a Hierarchical Bayes method. A Fast Marching Eikonal solver is used to update ray path geometries during the inversion. We use next the group-velocity maps and their uncertainties to derive a 3-D probabilistic Vs model. The probability distributions of Vs at depth and the probability of presence of an interface are estimated at each location by exploring a set of 130 million synthetic four-layer 1-D Vs models. The obtained probabilistic model is refined using a linearized inversion. Throughout the inversion for Vs, we include the water column where necessary. Our Vs model highlights strong along-strike changes of the lithospheric structure, particularly in the subduction complex between the European and Adriatic plates. In the South-Western Alps, our model confirms the existence of a low-velocity structure at $50-80\, \mathrm{ km}$ depth in the continuation of the European continental crust beneath the subduction wedge. This deep low-velocity anomaly progressively disappears towards the North-Western and Central Alps. The European crust includes lower crustal low-velocity zones and a Moho jump of $\sim \, 8-12$ km beneath the western boundary of the External Crystalline Massifs of the North-Western Alps. The striking fit between our Vs model and the receiver function migrated depth section along the Cifalps profile documents the reliability of the Vs model. In light of this reliability and with the aim to building a 3-D geological model, we re-examine the geological structures highlighted along the Cifalps profile.

The role of groundwater in the spatio-temporal variations of vegetation water use efficiency in the Ordos Plateau, China

Groundwater influences the water and carbon cycle by supplying moisture to plants in the semi-arid and arid zones. However, little is known about the response of ecosystem water use efficiency (WUE) to climate change in different groundwater depth (GD) sections. Recent research has shown that plant photosynthesis and growth are closely related to GD via field experiments but the wider recognition of GD effect on regional-scale ecosystems has not been yet established. In this study, we test whether the GD has an impact on ecosystem WUE and its variability to climate change at the regional scale. Based on the observed data of nearly 3000 wells, meteorological data (precipitation and pan evaporation), and the 0.01°-resolution remote sensing datasets including gross primary production (GPP), evapotranspiration (ET), and normalized difference vegetation index (NDVI), we explored the spatio-temporal variations of WUE and its composites (i.e., GPP and ET), and their characteristics depending on GD under different aridity conditions and biomes across the Ordos Plateau, a semi-arid to arid area in northern China. Results show that WUE increases with decreasing GD due to water availability in the semi-arid lands where WUE variability is mainly regulated by biological processes (i.e., GPP), while WUE is insensitive to the changes in GD across the arid zone where the physical processes (i.e., ET) control WUE change. However, when drought happens the groundwater-independent vegetation in the arid zone can also utilize groundwater, characterized by lower reductions of GPP with the decrease in GD. A dense vegetation condition (i.e., large NDVI) is more vulnerable to climatic disturbance over the semi-arid zone because it tends to decrease GPP and WUE, especially in the large GD regions. These findings have important implications for reasonable land use and groundwater management over the semi-arid and arid regions.

Main Controlling Factors and Models of Organic Matter Accumulation in Lower Carboniferous Dawuba Formation Shale in Southern Guizhou, China.

A set of high-quality marine facies organic-rich shales developed in the Lower Carboniferous Dawuba Formation, which is considered to be the main target of shale gas exploration and development in Guizhou Province. In this paper, 53 samples from Well ZY1 are selected, and the core observation data, field-emission scanning electron microscopy (FE-SEM) images, and geochemical data of these samples are analyzed. On the basis of these data, the main influencing factors of organic matter enrichment in the Dawuba Formation shale were identified and an organic matter accumulation model was established. The results show that total organic carbon (TOC) values of the Dawuba Formation in the ZY1 well vary between 1.97 and 4.11%, with high values appearing at the depths of 2796–2814 m (3.00–4.11) and 2877–2894 m (1.97–3.49). The redox-sensitive element enrichments are generally low, indicating that these samples were deposited under oxic–suboxic conditions. The micronutrients (Zn, Cu, and Ni), biological Ba (BaXS), and P/Al also show low values, indicating low primary productivity. The chemical index of alteration (CIA) and terrigenous clastic input index (Ti/Al) showed two obvious high-value zones, indicating that shale in the study area was affected by terrigenous inputs. Similarly, the calculation results show that Fe/Mn and Rb/K values have two abnormal data segments at the same depth. The anomaly of these data at the same depth section further suggests that the shale was affected by terrigenous input during deposition. Moreover, the terrigenous input reaches the maximum in the above TOC high-value region, and it is inferred by combining with the core observation results that the gravity flow occurs in this depth. The carbon isotope of kerogen (δ13Corg) ranges from −26.84 to −24.36%, indicating that the source of organic matter is likely to be terrestrial plants. This is further supported by the widespread presence of filamentous organic matter using FE-SEM, despite the low productivity and poor preservation conditions during deposition of the Dawuba Formation; the enhanced terrigenous input may have provided additional sources of organic matter for the Dawuba shale.

Lineaments analysis of Bafoussam (West-Cameroon) using remote sensing and vertical electrical sounding: Hydrogeological implication

The study proposes to map the tectonic accidents existing in Bafoussam locality using the remote sensing and vertical electrical sounding methods. The principal component analysis and directional filtering applied respectively to Landsat8 and SRTM images allowed to extract remote sensing lineament map. The interpretative rose diagram shows a distribution of lineaments following four directions: NE-SW, NW-SE, N-S and E-W. The main directions are from N30°E to N80°E; these are those of large strike-slip of the Central Pan-African Fold Belt (CAFB) in Cameroon and from the extension of the Central Cameroonian Shear Zone (CCSZ) in the studied area. The superimposition of these lineaments on the hydrographic network map enabled establishing genetic links because rivers flow following the main N30°E and the secondary N120°E lineament directions. The superimposition of the iso-resistivity maps resulting allowed to extract the geophysical lineament map which has been confirmed by achieving resistivity sections in depth. These lineaments are N40°E to N60°E directed comparable to the network fracture and foliation direction on orthogneiss flagstones within the area. These lineaments superimposed on those automatically extracted by remote sensing show a good correlation following the two methods used. The both mapping methods therefore allowed to extract the fracturing map zone. As groundwater is generally stored in the fracture network of hard rocks, the results of this study will thus provide progress in the course of wells and boreholes implantation. The second generation of fractures with a N140°E striking direction is the most appropriate for the hydrogeological studies in Bafoussam.

Results of studying the azimuthal anisotropy of the paleozoic basement with vsp technique at the Bystrovka vibroseismic test site

At the Bystrovka vibroseismic test site (Novosibirsk region) 3-component refracted waves profiling was performed at three intersecting lines. Shear waves analysis made possible to detect anisotropy of the Paleozoic basement occurring at depth of about 10 m and to suggest symmetry elements of this medium along with their orientation. Compressional waves data were used to construct depth sections estimating head waves velocities. These velocities demonstrate significant variation in lines of different orientation. The results obtained agree with previously performed VSP.

Integrated geological interpretation of remote sensing data (Boysun structural-tectonic zone)

In recent years, remote sensing data are increasingly used in the practice of oil and gas prospecting. This article discusses the main methodological aspects of identifying oil and gas promising structures by using materials for interpreting remote sensing data and a complex of geological and geophysical data. Remotely sensed data exhibit a regional review of the various geological formations and tectonic fracture zone and faults that are otherwise not possible detection by human eyes on the ground. The method of structural interpretation space image allows you to: detail the internal structure of oil and gas regions; to reveal the position and features of the tectonic blocks, structures of the second and third (anticlines, synclines, monoclines, etc.) orders; identify major disruptive violations; identify chains of local structures; fix the transverse structural elements that determine tectonic fragmentation. By deciphering the remote sensing data, the distribution and nature of the lineament network marking disjunctive dislocations and zones of increased fracturing are revealed and analyzed, as well as ring structures are detected, which in most cases indicate local structures of the sedimentary cover at different depth sections. The lithology and lineament interpreted from these multi-level data were integrated with data collected from the ground.