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The present work reviews the laser cladding process as a repairing technique and the conventional repairing techniques and different heat source models. In this review work, the authors have tried to address the various traditional methods studied for repairing and surface modification. The dominantly used heat source model for numerical modelling of the repairing techniques and the mechanism of the laser cladding process, along with its advantages over the conventional repairing techniques, is also reviewed. This paper also focuses on the predominantly used laser of high power for the cladding process and the effect of process parameters on the quality of the clad layer. The different materials used as clad materials for repairing purposes during the laser cladding process have also been discussed briefly. In this paper, the authors have surveyed literature from different regions of the globe and considered the literature since 1969. This review discusses the various conventional repairing techniques used for repairing, heat source model, process parameters, and different materials used in the laser cladding process. The authors have also briefed the advantages, disadvantages, and application in each of the sections. The use of laser cladding for in-situ repairing process, development of a precise model, use of low-power laser, and application of laser cladding for actual engineering components was also considered in future research work.

This study investigates satellite-based information driven snow accounting routines to simulate snow processes in mountainous regimes that are inherently associated with data scarcity. Simple, independent and parsimonious snow accounting routines that are fully driven by remote sensing (RS) information such as the land surface temperatures and snow-cover information along with distributed temperature index-based snow-melt models, are presented. RS based snow-cover distribution does not only provide the crucial information on areal extent of snow, but can also be a highly imperative proxy for the precipitation accumulations in these data scarce regions, as the availability and resolution of the data doesn’t depend on the mountainous terrain. These models are calibrated independently on the snow-cover distribution, can be coupled with any rainfall-runoff models to simulate “snow-processes informed” discharge and are flexible enough to be extended to a wide geographical extent. These models, in addition to simulating the snow accumulation and melt processes, also use the timing of snow appearance and disappearance. This accounting of snow can be inverted to obtain seasonal precipitation estimates in data scarce snow dominated regions, which can be a very crucial information for water resources planning. Specific results pertaining to the validation of the models in Switzerland and southern Germany (ungauged scenario) are shown.

Given the importance of snow on different land and atmospheric processes, accurate representation of seasonal snow evolution, including distribution and melt volume, is highly imperative to any water resources development trajectories. The limitation of reliable snowmelt estimation in mountainous regions is, however, further exacerbated by data scarcity. This study attempts to develop relatively simple extended degree-day snow models driven by freely available snow-cover images. This approach offers relative simplicity and a plausible alternative to data-intensive models, as well as in situ measurements, and has a wide range of applicability, allowing for immediate verification with point measurements. The methodology employs readily available MODIS composite images to calibrate the snowmelt models on spatial snow distribution in contrast to the traditional snow-water-equivalent-based calibration. The spatial distribution of snow-cover is simulated using different extended degree-day models with parameters calibrated against individual MODIS snow-cover images for cloud-free days or a set of images representing a period within the snow season. The study was carried out in Baden-Württemberg (Germany) and in Switzerland. The simulated snow-cover data show very good agreement with MODIS snow-cover distribution, and the calibrated parameters exhibit relative stability across the time domain. Furthermore, different thresholds that demarcate snow and no-snow pixels for both observed and simulated snow cover were analyzed to evaluate these thresholds' influence on the model performance and identified for the study regions. The melt data from these calibrated snow models were used as standalone inputs to a modified Hydrologiska Byråns Vattenbalansavdelning (HBV) without the snow component in all the study catchments to assess the performance of the melt outputs in comparison to a calibrated standard HBV model. The results show an overall increase in Nash–Sutcliffe efficiency (NSE) performance and a reduction in uncertainty in terms of model performance. This can be attributed to the reduction in the number of parameters available for calibration in the modified HBV and an added reliability of the snow accumulation and melt processes inherent in the MODIS calibrated snow model output. This paper highlights that the calibration using readily available images used in this method allows for a flexible regional calibration of snow-cover distribution in mountainous areas with reasonably accurate precipitation and temperature data and globally available inputs. Likewise, the study concludes that simpler specific alterations to processes contributing to snowmelt can contribute to reliably identify the snow distribution and bring about improvements in hydrological simulations, owing to better representation of the snow processes in snow-dominated regimes.

Vibrations in four buildings located at different positions along the Delhi Metro Rail Corporation (DMRC) network have been measured and reported. Vibrations developed due to the passage of metro trains through tunnels located at a depth up to 30 m from the ground level were measured on the considered buildings at different floor levels. To interpret the effect of vibrations on buildings, different vibration parameters, viz. Peak Ground Acceleration (PGA), Peak Ground Velocity (PGV) and frequency content are obtained from the recorded vibrations. These parameters change with the location, depending on the dynamic characteristics of the soil profile at the site of measurement and the building. It is observed that the maximum amplitude of vibrations measured during this study is more than the threshold provided by standards of different countries and can cause vibration of rigid building components, annoying physical sensations in the human body, interference with activities such as sleep and conversation, rattling of window panes and loose objects and fear of damage to the building and its contents.

Laser Beam Micromachining has revolutionized the industrial world by providing a better solution for machining the materials at micro level. LBMM has a wide application in these days because of its precise machining capability. In this paper, an overview of LBMM of metals is given so that an idea can be obtained about the process. The use of various type of laser and previous researches have been studied in this paper. The effect of various parameters like fluence energy, wavelength, pulse rate, threshold fluence and pulse frequency have been studied. In previous researches, it was observed that these parameters effect the geometries, morphology, machining speed, scanning speed and machining efficiency and many other characteristics of the material to a great extent which have been studied in this paper.

Considering the snow effect on land and atmospheric processes, accurate representation of seasonal snow evolution including the distribution and melt volume, is highly imperative to strengthen water resources development trajectories in mountainous regions. However, along with the high sensitivity to climate change, the limitation of reliable snow-melt estimation in these regions is further exacerbated with data scarcity. This study thus attempts to develop relatively simpler degree-day snow-models driven by freely available gridded datasets for data scarce snow-fed regions. The methodology uses readily available MODIS imageries to calibrate the snow-melt models on snow-distribution instead of snow-amount. In addition, freely available cloud masks from geostationary satellites are also used to complement the snow-melt models. The major advantage of this approach is the possibility of regional calibration using freely available reasonably accurate climate data, without the need of direct snow depth measurements. These models offer relative simplicity and plausible alternatives to data intensive physically based model as well as in-situ measurements and have a wide scale applicability allowing immediate verification with point measurements.Bavaria region in Germany is selected for this study. E-OBS (European Observations) gridded precipitation and temperature datasets (0.25 degrees) are considered here instead of the ground measured data to replicate “a data scarce scenario” as in most of the mountainous regions around the globe. The coarser meteorological inputs are downscaled applying the delta method using WorldClim monthly climate surfaces to 0.0833 degrees (~1km) grids. MODIS images are also resampled and upscaled to 1km resolution for uniformity. The qualitative pixel-to-pixel comparison suggest a very good agreement with MODIS data and the calibrated parameter sets depict plausible temporal stability.The snow-melt volume will be further used in HBV hydrological model as standalone input to simulate the streamflow in one of the snow-fed catchments in Bavaria and to evaluate the performance of this approach in streamflow. The abstract will the updated as soon as the results are available.

In general practice, the shallow foundations serve as economic and reliable solution to support high-rise buildings, bridges, and other heavy structures constructed on rock-mass. The aim of the present study is to simulate fractured homogenous rock-mass in finite element framework and to obtain bearing capacity of a strip footing. For this purpose, both displacement-based finite element (FE) analysis and finite element limit analysis (FELA) are carried out and results are compared. Finite element models of the flat rock-mass with supported foundations are developed in finite element package ABAQUS. The foundation is modeled using two-node cubic beam (B23) and rock-mass using plane-strain quadratic (CPE8R) element with reduced integration, having “Equivalent Mohr–Coulomb parameters.” Models with the same rock and foundation properties are modeled in OptumG2 based on FELA to obtain the upper-bound (UB) and lower-bound (LB) solutions with a constitutive model based on the Hoek–Brown failure criterion. The comparative study illustrates the critical issues that arise while implementing the failure criterion using the equivalent Mohr–Coulomb parameters, particularly in bearing capacity estimation, where the overburden pressure is low.

Alteration in ground motion characteristics due to topography can trigger earthquake-induced localized damage and other earthquake-related devastation. Existing literature cites many incidents in which topographic amplification has been noticed during the same seismic event. However, it is often difficult to separate the effects of geometry and near-surface geology in absence of refined topographic amplification models. Based on hill geometry, a few standards/codes (Eurocode 8, NTC-08 and AFPS) suggest the amplification factors or aggravation factors to address this issue. However, topographic amplification of hills subjected to recorded ground motion is mostly lacking in literature. This paper presents a parametric study of 2D symmetrical bell-shaped hills having different shape ratios (ratio of height to half of the base width of the hill) using finite element code ABAQUS. Wave propagation problem is simulated using 2D linear plane strain elements. Numerical models are subjected to the recorded earthquake ground motion suite (22 far-field record) from FEMA P695 along viscous boundaries at base. Parasitic boundaries are used at vertical sides to ensure shear failure mode. The largest size of the element is limited to 1/15th times the desired wavelength (10 Hz) of selected ground motion suite. Topographic amplification values are quantified at different spatial points along the hill profile to study the variation in amplification of peak ground acceleration (PGA) values. It is observed that topography is mostly amplifying the PGA values at the peak of the hill and de-amplifying the PGA values at the foot of the hill.

Conical excavations without support are often made in some field projects, such as foundations for piers, oil and water tanks. The seismic stability of these excavations has been given least importance in the research field. The instability of these unsupported excavations might increase during a seismic event. Hence, a realistic estimation of the seismic stability of unsupported excavations is a prominent issue, especially for the perpetual purpose. In the present study, seismic stability number for unsupported excavations has been proposed using the finite element (FE) analyses. Due to symmetry in the geometry about the vertical axis, axisymmetric FE models have been developed using OptumG2 software based on the finite element limit analysis approach. The soil (clay, with isotropic and constant undrained shear strength property) has been modelled as a perfectly plastic Tresca material following an associated flow rule. Boundary conditions were considered as per the field conditions, and seismic loads were considered as pseudo-static force applied in terms of horizontal seismic coefficient, αh. Adaptive meshing technique was adopted to predict the results reasonably closer to exact solutions. The seismic stability of these conical excavations is reported in terms of stability number. Moreover, the effects of depth of excavation, inclination angle, intensity of seismic loading, etc. on the seismic stability number are explored in detail. For deeper insights and influence of various affecting parameters, non-dimensional design charts are presented. Further, it has been observed that the considered parameters have significant effects on the seismic stability of conical excavations.

The process of laser cladding offers superior metallurgical and mechanical properties of the product. This is possible through the additive nature of the process but brings challenges in controlling the surface requirements and defects. The generation of thermal stresses in the cladding material as well as the substrate materials results in delamination and formation of a substantial crack in the remelted zone. One of the strategies followed to control the defect formation and also to manage the microstructure in the cladding material, preheating is often applied. Moreover, preheating also facilitates the localized melting of the cladding material over the substrate for better melting and remelting. In the current investigation, a laser source is simulated in COMSOL and two paths for preheating a cavity on stainless steel materials are used. The power of the laser source is kept fixed at 70 W and the other parameter like laser traverse speed and beam spot diameter has been fixed at 1.5 mm/s and 1 mm respectively. The numerical solution of the system of equations resulted in time–temperature information. Later, the heat transfer gradient is computed for the paths from the time–temperature information acquired through numerical simulation and the best one is selected to obtain a uniform heat distribution. The study revealed that the path which followed a circular pattern results in a better heat transfer gradient for effective preheating of the substrate material.

Determination of soil pressure under seismic condition has always been an issue in designing of earth retaining structures such as abutments and retaining walls. Estimation of lateral earth pressure is often carried out using limit equilibrium approach. This approach was first proposed by Coulomb and further enriched by various researchers, like Rankine, Mononobe-Okabe, Caquot, and Sokolovski, for seismic earth pressure using pseudo-static, pseudo-dynamic, and modified pseudo-dynamic method. Despite the abundance of research, there is lack of a consensus approach as the previous studies are based on assumptions like linear soil wedge failure surface which limits them to a subset of real earth pressure problems. The aim of present study is to provide seismic earth pressure coefficients considering the classic system of vertical wall retaining horizontal backfill. The finite element models are developed using ABAQUS, with rigid wall and purely frictional soil properties. Soil mass is modeled using plane-strain quadratic quadrilateral (CPE8R) elements with Mohr–Coulomb yield criterion. The seismic inertial force is incorporated using pseudo-static approach in terms of horizontal seismic coefficient, αh. Sufficiently large lateral boundary is provided to include failure surface and avoid boundary effects. Effect of various governing parameters, such as backfill soil friction angle, ϕ, with different backfill–wall interface friction angle, δ, and horizontal seismic coefficient, αh, on seismic earth pressure coefficient is explored in detail. The distribution and magnitude of the active and passive earth pressure are compared with those obtained from the classical methods and given in design codes.

Generally, one-dimensional (1D) wave propagation or ground response analysis (GRA) is preferred to evaluate the effect of local site conditions subjected to an earthquake ground motion [1]. For a site with complex and irregular stratigraphy, two-dimensional (2D) and three-dimensional (3D) ground response is preferred over 1D wave propagation for more realistic evaluation of ground response under seismic load. In present study, 1D, 2D (plane strain) and 3D (solid) finite element (FE) models are developed using Abaqus [2] considering two different soil profiles (with multilayer linear viscoelastic materials) of different dynamic characteristics. The kinematic constraints are used along the lateral boundaries of FE models, whereas the base is considered to be fixed in vertical direction. The maximum size of used elements is selected according to the recommendation of ASCE/SEI 4-98 [3] and ASCE/SEI 4–16 [4], for wavelength corresponding to 10 Hz. A recorded ground motion is applied at base of FE models (1D/ 2D/ 3D) and 1D wave propagation model developed in SHAKE2000. The simulated ground motions are compared in terms of transfer functions. On the other hand, a recorded ground motion is de-convoluted through the considered soil profiles using SHAKE2000 [5] separately and then de-convoluted ground motion is applied at the base of FE models. Again, the simulated ground motions (in terms of response spectra and acceleration time history) of different FE models are compared with the recorded one. The results are found to be in excellent agreement for all the considered cases.

Reliable representations of spatial distribution of snow and subsequent snow-melt are critical challenges for hydrological estimations, given their crucial relevance in mountainous regimes especially because of the high sensitivity to climate change. Relatively accurate physically based models are data intensive while in-situ measurements of snow-depth are prone to be non-representative due to local influences. Likewise, lack of snow-depth information and to some extent, cloud cover in the mountains limit the usage of Remote-sensing images in snow estimation. Against this backdrop, this work presents a methodology incorporating available remotely-sensed images (MODIS Snow-cover products) and simple distributed snow-melt models to estimate a time-continuous spatial snow extent in snow dominated regimes. The methodology employs relatively cloud-free MODIS composite images to calibrate the spatial distribution of snow simulated by different distributed degree-day models. These variants of models are run in a domain of 500m x 500m grids, and incorporate daily precipitation, daily min-, max- and mean temperatures, and daily radiation data interpolated onto the aforementioned grids. Variations in the models include a simple degree model followed by incorporation of different aspects governing snow hydrology such as precipitation induced melt, radiation, topography, and land use. The modeled snow depths in each grid are reclassified to ‘1’ (snow depths above a threshold) and ‘0’ (no snow), and calibrated against MODIS snow-cover for cloud-free days with snow. Snow-melt parameters are then estimated for the region of interest. The result is a spatial snow-cover distribution time-series. This approach is replicated in different regions viz. Baden-Württemberg and Bavaria in Germany, and in Switzerland. Results suggest good agreement with MODIS data and the parameters show relative stability across the time domain at the same sites and are transferrable to other regions. Calibration using readily available images used in this method offers adequate flexibility, albeit the simplicity, to calibrate snow distribution in mountainous areas across a wide geographical extent with reasonably accurate precipitation and temperature data. The final validated spatial snow-distribution data can be, as a stand-alone input, coupled with distributed hydrological models to reliably estimate streamflow in data-scarce mountainous catchments.

This paper presents a numerical study on capacity envelopes of strip foundations placed on the top and the face of two typical soil slopes at different offset distances and subjected to earthquake effects using the pseudostatic method. The capacity is estimated using nonlinear two-dimensional (2D) finite-element limit analysis (FELA). Modified swipe and probe analyses are performed to develop vertical forcemoment (V-M) and vertical force-shear force (V-H) capacity envelopes. Characteristic features of these capacity envelopes and critical failure modes of foundations on slopes are identified and compared with the foundations on flat ground. Relative influence of the soil and structure inertia on the capacity envelope of the foundation is also explored. The critical failure mode of a foundation on slope, subjected to gravity and seismic action, depends on the effective column height of the structure. A comparison of the capacity envelopes of typical foundations with the corresponding RC columns indicates that the foundation design methods of the current building codes cannot avoid premature failure of foundations on slopes, prior to columns Behavior and Critical Failure Modes of Strip Foundations on Slopes under Seismic and Structural Loading

The columns and the supporting foundations are invariably subjected to the interacting axial force, V, shear force, H and moment, M. It is quite common to consider the interaction of these forces in design of structural components, but the available standards and literature usually ignore the effect of interaction in case of foundations on slopes. Further, very little information is available about seismic capacity of foundations located on slopes. This article presents a numerical study on evaluation of the V–H–M capacity envelopes of strip foundations placed on top and face of slopes and subjected to earthquake action, with an objective of enabling a direct comparison with the capacity of the supported columns. Nonlinear 2D finite element limit analyses are performed for this purpose. Modified ‘Probe’ analyses are carried out for two representative c-ϕ soil slopes to develop the V–H– M capacity envelopes. The computed capacity envelopes are compared with their counterparts on flat ground. The characteristic features of the capacity envelopes are identified and explained considering the failure patterns under different combinations of V, H and M. A comparison of the capacity envelopes of counterpart foundations on flat ground and of columns is presented to highlight the relative hierarchy of strength of columns and foundations of a typical building on slope. V–H–M seismic capacity envelopes of strip foundations on slopes for capacity design of structure-foundation system