bluuebunny/crossref_metadata_2025 huggingface dataset:
Seismic Vulnerability of Code Compliant RC Frame Building with Unreinforced Masonry Infill Walls
Authors: Gondaliya K.M. , Palsanawala T.N. , Bhaiya V. , Vasanwala S.A. , Desai A.K.
Published: December 2022

Unreinforced masonry (URM) infill walls in Reinforced concrete (RC) buildings are normally designed as non-structural elements. However, in the past, the post-earthquake response of the RC frame building showed that URM infill walls increase the strength and stiffness of the RC frame buildings. Further, it is also observed that URM helped to prevent the disastrous destruction by acting as a structural member in RC frame. In the present study, the performance assessment of a four-storey URM infill RC frame with different infill configurations, namely bare and Open Ground Storey (OGS) is done using fragility analyses. Nonlinear masonry material is modelled as the equitant three strut model in ETABS. Nonlinear static pushover analysis is applied for the analysis of the configured RC frames. The probability of damage states is determined by firstly converting pushover curves into capacity curves and accordingly, performance-point values of Spectral acceleration and Spectral displacement for seismic demand Zone-V (Elastic Response Spectra as per IS 1893:2016) using the capacity-spectrum method (ATC-40) are determined. The fragility function used is an approximation of the continuous to discrete distribution. Fragility curves and mean damage matrix are derived to compare performance with each other. From the vulnerability analyses, it is observed that the OGS framed RC building performs better as compared to the bare frame.
Improving Earthquake Resistant Design and Construction in India
Authors: Kumar S.R.Satish
Published: December 2022

New materials and structural systems are being introduced in construction profession every day either to replace conventional materials whose availability is becoming scarce or to improve the efficiency of construction. New systems are also being introduced to cater to new demands in functionality and aesthetics. While Indian researchers have kept pace with the theoretical aspects of earthquake resistant design, the practical aspects are hardly touched upon since they require testing and implementation in practice. The current codes are prescriptive about the general requirements for strength and detailing and so are inadequate to define and assess the performance objectives of specific structural systems. Consequently, the gap between academics and profession has been widening and has reached extreme proportions and there is an urgent need to revive applied research in earthquake engineering to evaluate seismic performance of practical systems. In this paper, the work carried out by the author and his students at IIT Madras on seismic design and tests carried out on masonry, reinforced concrete, structural steel, steel-concrete composite, cold-formed steel, semi-rigid frames of steel and composite construction and industrial rack systems are reviewed. The importance of understanding the details of the seismic behaviour of these system towards improving the performance is emphasized.
Dynamic Analysis of Block-Type Machine Foundation Using Barkan’s Model for Various Soil Parameters
Authors: Desai K.Y. , Dhut V.R. , Sheth K.N.
Published: December 2022

Machine foundation involves both the static loads and the dynamic loads caused by working of the machine. The machine weighs several tons and is required to restrict amplitudes to only a few microns. Inadequately constructed foundations may result in failures exceeding many times the cost of the capital investment required for properly designed foundations. This necessitated a deeper scientific investigation of dynamic loading and analysis. Method proposed by Barkan (recommended by IS: 2974-1982) for design of machine foundations under harmonic load, still remains the most popular method for vibration analysis of block foundations in Indian industry. Finite Element (FE) is very commonly accepted analysis tool for solution of engineering problems. Effective Pre and Post-processing capabilities make modeling and result interpretation simple. The current paper aims to do the parametric study of dynamic analysis of block foundation using Barkan’s method. For the same, three different machines of 150 rpm, 250 rpm and 450 rpm are taken into account and six different soil types: (a) Medium, Stiff and Hard Clay and (b) Loose, Medium and Dense Sand are considered. Foundation sizes are optimized according to soil cases and each case is analysed using conventional method and FEM model using STAAD Pro. for 0.8, 1 and 1.2 times the soil parameters to cover the confidence range. This study is further extended for the comparison of concrete quantity consumed. The results grossly show that as the clay varies from medium to hard, and sand from loose to dense, the foundation size required, decreases. It was seen that, with the increase in stiffness of soil, natural frequency of machine foundation soil system increases and amplitude of foundation reduces. Also, FEM method of analysis indicates safer amplitude of foundation compared to classical method of analysis, inferring to conventional method being conservative.
Design of Metallic Dampers and Analysis Using MATLAB Program
Authors: Naik MalharP. , Koshti Utsav
Published: December 2022

Earthquakes are one of the major natural hazards to life on the earth and have affected countless areas on almost every continent. The damaged caused by earthquakes are mostly seen in man-made structures which are most of the time responsible for most of the causalities. Therefore, it is necessary that design of structures is done to resist earthquake forces, in order to reduce the loss of life. Passive control devices were developed earlier and have been used extensively in practice. Metallic dampers, one of the passive damping devices, dissipate seismic energy through in-elastic deformation of metals. It utilizes the yielding of metals as the dissipative mechanism. In the present study, characterization of ADAS (Added Damping Added Stiffness) type metallic damper is carried analytically and experimentally to understand cyclic behaviour. It is found that response of metallic damper is a function of its geometry and its mechanical characteristics of the metal. The primary factors affecting ADAS element behaviour are device’s elastic stiffness, yield strength and yield displacement. Attempt has been made to develop design procedure for ADAS type metallic damper in Indian Scenario. Designed damper behaviour is analysed by programming tool MATLAB obtaining solution of equation of motion for different time history data.
Two Stage SEREP Method for Condensation of Space Frame Structure for Dynamic Analysis
Authors: Mohan S.C. , Panwar Nishant , Maniteja AjayC.B.
Published: December 2022

Analysis of frame structure can be done by the computer analysis, but there is requirement of simple and easy model which can give accurate result or with tolerable accuracy. The process of reducing the size of matrix is called condensation. It needs to be converted into system or model having less number of degrees of freedom as huge computational effort is required to analyze big models. Also, the models which requires analysis multiple times, for example, optimization of structural system, condensation is very useful. The single stiffness value can represent the stiffness of the whole story (elastic, rectangular frame with evenly distributed load), which give the responses accurately or tolerable accuracy. With this we can create a single lumped mass system of the frame structure which come very handy in further analysis of structure. For finding the single stiffness value, there are various approach like by using Approximate Story Stiffness Formulas, Static condensation, System Equivalent Reduction Expansion Process (SEREP) etc. Approximate Story Stiffness formulae don’t give very accurate result. To overcome its shortcoming Static Condensation and SEREP methods are used. Static Condensation gives better result but there is significant difference in the responses. Especially for space frame structures it is difficult to directly condense in to single degrees of freedom at each floor level. Hence, the present study proposes two stage SEREP method for condensation of spaceframe structure. Firstly, space frame is reduced to single degrees of freedom at each node, then it is further reduced to single degree of freedom at each floor. The proposed method gives very less (acceptable) error in comparison of natural frequencies.
Structural Fire Analysis of Beams and Slabs Using ANSYS and FEAST Software Program
Authors: Bais Shivansh , Bhatt Govardhan
Published: December 2022

In recent years, building fire has become more frequent event and fire accidents have increased all over the world. Major problem with fire is it provides very less time to handle the situation and due to elevated temperature, reduction in strength of structural member with increase in fire exposure time has been observed. To evaluate this reduced strength of structural members and design for fire load, it is necessary to have the parameters such as fire load, fire exposure time and temperature variation across the structural members. In this paper, evaluation of fire load, equivalent time of exposure and temperature distribution of beams and slabs using finite element analysis software FEAST and ANSYS has been done. For temperature variation, transient heat thermal analysis, in which temperature is increasing continuously over the time, is used. For this analysis, beams and slabs are exposed to surface fire on different surfaces and the temperature distribution of cross section has been evaluated. The results are compared and found to be matching with the European Standard procedure.
Numerical investigation of Reinforced-concrete beam-column joints under contact and close-in blast application
Authors: Debnath Jhuma , Kumar Ajay , Sharma Hrishikesh
Published: December 2022

The behavior of the concrete and the steel material under blast loads are different. They have different mode of failures under blast loads. Also, responses differ according to the blast types concerning the proximity of the charge kept. It causes different failure modes in the structural members. Close-in or contact blast causes the spallation of concrete. In the near-field blasts, it causes bending failure in the structural members. The behavior of the mode of failure of various joint types subjected to contact-blast and close-in blast loads are numerically studied here. Three different joints simulated to carry on blast loads—exterior beam-column joint, interior beam-column joint, and knee joint simulated numerically under the close-in and contact loads. The charge for the contact blasts were applied to the joint is placed in contact with the joint core, and was not put at the beam or the column member of the joint cut section. In the current work, the failure behavior and the response of the RC beam-column joints is concluded.
Flexural Strengthening of Fire Damaged Reinforced Concrete Structural Member
Authors: Gaikwad MaheshD. , Singh Suvir
Published: December 2022

Fire causes extreme damage leading to huge loss of life and property. An extensive damage also occurs to structural members when exposed to fire. Therefore, after fire structural members need to be strengthened to restore their load carrying capacity to withstand the future service loads. The selection of strengthening technique depends on the residual capacity of fire exposed structures and required ultimate load carrying capacity. Further if strengthen structure is exposed to fire in future then strengthening techniques should also have good fire performance and remain intact with the base concrete. In this paper, efforts have been made to study and understand the effectiveness of fire damaged reinforced concrete jacked flexural member. Limited information is available on the flexural performance of fire damaged strengthen members with reinforced concrete jacket and concrete jacket. This work presents a simple and efficient technique to strengthen reinforced concrete beam in flexure using traditional materials. This paper discusses in detail the strengthening strategy program of two-hour fire exposed beam to restore its original load carrying capacity. The reinforced concrete beam is simulated in finite element-based software to compute the thermal profile, which used to calculate residual load capacity. The obtained result of thermal distribution and residual moment capacity are compared with proposed literature models and design code equations. The performance of fire damaged and strengthen beams are studied through moment-curvature relationship load-deflection behaviour. This paper provides a simplified analytical approach to determine the residual capacity of fire damaged beams along with that expected improvements in their capacity after strengthen by reinforced concrete and concrete jacket.
An Experimental Study on Compartment Crib Fires with Open Ventilation
Authors: Narang Aishwarya , Pandey RaviShankar , Kumar Ravi , Dhiman Amit
Published: December 2022

The paper describes an experimental study on the behavior of crib fire with open ventilation conditions. An experimental setup is designed and fabricated in the fire research laboratory, IIT Roorkee to investigate and analyze the crib fire behavior in a compartment. Experiments are carried out in a compartment of the dimension of 4 * 4 * 4 and having a door of 2 * 1(All in meters). The parameters, including the gas temperature, mass loss rate, heat flux, flame temperature, and compartment pressure, were measured during the experiments. Based on experimental results and recognized fire theories, the effect of ventilation conditions on the burning properties of wood cribs was studied.
Effect of Horizontal Curve on the Response of Road Tunnels under Internal Explosion
Authors: Mandal Jagriti , Goel ManmohanDass , Agarwal AjayKumar
Published: December 2022

Internal explosion in a tunnel is a complex loading phenomenon where the tunnel lining is subjected to not only direct impact of explosion but also loading due to multiple reflection of blast waves which could be of magnitude higher than that of incident blast wave. This kind of loading is complex in nature and difficult to predict using simple analysis tools. Further, it poses a serious threat to its structural integrity. Studies have been conducted in the past to understand the behaviour of tunnel under internal explosion. However, they have been focused on straight tunnels ignoring the convex and concave shapes introduced due to horizontal and vertical curves. Shape of the target surface has significant effect on the characteristics of blast wave. This study investigates the effect of horizontal curves on the damage behaviour of tunnel lining due to internal explosion. A series of numerical simulation are performed on box-shaped tunnel with varying curvature radius and the results are compared with that of straight tunnel adopting Multi-Material Arbitrary Lagrangian-Eulerian (MM-ALE) method using LS-DYNA®. Explosive and air are modeled using ALE formulation, whereas, tunnel and soil are modeled using Lagrangian formulation. Further, Jones-Wilkins-Lee equation of state is used to model the explosion. Damage to the tunnel lining is measured in terms of peak particle velocity (PPV) and von-Mises stress. It is observed that walls of curved tunnels undergo more PPV compared with straight tunnel wherein concave wall show the highest PPV. Propagation of blast wave along the tunnel length is significantly affected due to the introduction of curvature resulting in change in reflection patterns. This further leads to variation in stress contours on tunnel lining with higher concentration of stress in curved tunnels than in straight tunnel.
Quality Assessment of Concrete produced with Marble dust as Partial Replacement of Cement using Ultrasonic Pulse Velocity Test
Authors: Singh Gurcharan , Madan S.K.
Published: December 2022

Cement concrete is one of the most frequently used materials in the construction industry. Constant studies are being carried out to find some alternative material to save natural resources and instead make use of industrial byproducts/waste material which is otherwise polluting the environment. Marble dust which is an industrial waste obtained from sawing, shaping, cutting and polishing of different marbles, is a big environmental hazard. Around 6.8 million tonnes of marble dust is currently being dumped annually in Rajasthan, Gujarat and Madhya Pradesh in India. Although past studies have already investigated the use of this material as a substitute for fine aggregates, since its distribution of particle size is nearer to that of cement, it could be more appropriate for partial replacement of cement in concrete. Cement concrete cubes of size 150 mm were cast as control specimens for two different grades of concrete (M25 Grade and M30 Grade). Effect of marble dust on compressive strength of concrete with varying %age of marble dust as partial replacement of cement is investigated in this study. Marble dust is used as 0, 5, 10, 15 and 20 percent partial substitute of cement by weight in concrete mixes. The compressive strength of concrete mixes is studied at age of 28 days and maximum value of compressive strength is observed at 10% partial replacement of marble dust with cement for both grades of concrete. The quality of concrete so produced is also assessed by using Ultrasonic Pulse Velocity (USPV) method. The ultrasonic pulse velocity is 3850, 4100, 4350 and 3710 m/s for M25 grade concrete and 3870, 4120, 4360 and 3700 m/s for M30 grade concrete for 0%, 5% and 15 % partial replacement of marble dust with cement. As per IS :13311(Part 1):1992 these values of pulse velocities represents good quality of concrete and also justified the use of marble dust in concrete up to 15 percent for both grades of concrete (M25 and M30).
Nonlinear Static Analysis of Core Wall RCC Framed Buildings
Authors: Gond AbhishekKumar , Madan S.K.
Published: December 2022

RCC framed buildings mainly consists of shear walls and columns for resisting lateral force due to earthquakes. In most of the framed buildings shear walls are provided in the outer frames. In addition to shear walls provided in the outer frames, RCC lift -well (core wall) is also provided in the inner core of the buildings to accommodate lift. Core wall also acts as shear wall contributing to the lateral resistance to the buildings.
In the present study, nonlinear static analysis is performed to study the behaviour of high rise RCC buildings, the buildings have a centralised lift core wall with a door opening and shear walls in outer frames. The flange of core wall is joined together at regular interval by floor and slabs and connecting beams to provide proper connection in between flange. This Residential G+14 RCC framed building is lying in seismic zone 4 and analysed as per guidelines of is 1893 (part 1) 2016 and ETABS 17.0.1. Responses namely lateral loads, story drift, base shear, story displacement and the formation of plastic hinges compared for two types of buildings, namely with core wall and without core wall to understand the effect of core wall against the lateral loads.
Study of Along and Across Wind Load effects on RCC Chimneys
Authors: Singh Gagandeep , Saxena Kinchit , Shenai Girish
Published: December 2022

Chimney is a hollow, tall and slender structure to discharge smoke or pollutants at a height so that after dilution due to atmospheric turbulence, their concentration and that of their entrained solid particulates is within acceptable limits on reaching the ground under various atmospheric conditions. As large scale industrial developments are taking place all over the world a large number of chimneys would be required to be constructed. As for chimneys the predominant load is mainly wind load. This paper is aimed at deriving standard curves with the help of which one can easily calculate approximate wind load on chimney in shell completed condition. The curves have been plotted for chimneys of various heights, top internal diameter, taper and located in different wind zones. The importance of these curves would be in finalization of initial sizing of chimney and its supporting structure. Wind Analysis is done as per code IS 4998: 2015 and IS 875 (Part 3): 2015. SAP 2000 software is used to determine mode shapes. MS-Excel spreadsheets are used for loading calculations.
Soil-Pile-Structure Interaction (SPSI) in Bridges: A Review
Authors: Sharma A. , Adhikary S.
Published: December 2022

Response of soil influencing motion of pile supported structures or vice-versa is called Soil-Pile-Structure Interaction (SPSI). A part of SPSI is considered beneficial for the structure wherein it increases damping, and period of vibration. This study provides a comprehensive review addressing SPSI in bridge structures. Past research in this field has typically emphasised on Soil-Structure Interaction (SSI), rather than SPSI. An attempt is made here to compile the work done so far in this field. Detailed study, based on discretising the considered models in various articles, and the method for determining the stiffness of the underlying soil was carried out. The articles in this study were carefully chosen such that even if they have not considered SPSI, their models were worth reporting in this study. Response of soil and structure on the application of earthquake ground motion was also studied and discussed here with emphasis given on calculation of stiffness of soil and the interaction between them. It was observed that the material/spring used for modelling of soil is of utmost importance. The theories for the calculation of stiffness of the soil material for different locations of the pile length are also discussed. Few studies have also considered the vertical component of earthquake ground motion in the past. A detailed justification regarding the selection of method of analysis such as linear or non-linear analysis, and adopted approaches for analysis such as discrete or continuous approaches, and their overall influence on the study was observed, and reported here in a concise manner. This article primarily aims to summarize the previously published researches on SSI and SPSI, including their advantages and issues over the structure.
Strength, Durability and Permeability Studies on Cement Concrete with and without Nano-Silica
Authors: Ghosal M. , Chakrabarti A.K.
Published: December 2022

The application of nanomaterials in cement/concrete has resulted in the development of smart materials which are durable, sustainable and high performance oriented apart from being eco-friendly. Several types of nanomaterials are being used by researchers all over the world to improve the properties of cementitious system, amongst them silica nanoparticles (SNPs) have been credited with high pozzolanic reactivity and pore filling effects. It is also very well known that permeability is the major factor for deteriorations of concrete structures in the long term thus affecting its durability. A thorough study was performed on cement mortar composites and standard grade concrete with the additions of colloidal silica nanoparticles(SNPs) in various dosages starting from 0.5%,0.75%,1.0%,1.25% and 1.5% by weight of cement(b.w.c.) to understand the impact from micro-structure improvement to macro-level property enhancement. The results show that in presence of colloidal SNPs (Indian branded) having 35-40% active nano content with 5-40nm particle size the strength increase at 28 days is 32% increasing to 59% at 90 days. An influence on durability is also observed with strength increasing from 4% to 8% with the addition of more SNPs from 0.75% to 1.0% b.w.c. The microstructural investigations reveal that silica nanoparticles refines the pore structure due to accelerated hydrated mechanisms leading to the creation of more hydration products and thus to a more denser microstructure. A M-40 grade standard concrete was prepared as per IS:10262 with the addition of optimized SNPs as found for cement mortar composites strength results at 28 days maximum strength keeping the water-cement(w/c) ratio fixed at 0.4. Tests were conducted on concrete to find out the compressive strength and permeability of concrete. The compressive strength of concrete containing nano materials were found to be 24% more than that of normal cement concrete (NCC) of M-40 grade. The permeability values were found to be decreased by 57% with the addition of nano silica particles to concrete.
Acoustic Analysis of Partially Flexible Cavity with Opening
Authors: Pramanik Subhankar , Das Sreyashi , Niyogi ArupGuha
Published: December 2022

In this study, the SPL at the boundary and within the domain of a rectangular-shaped container with a flexible laminated composite panel with opening have been investigated. Finite Element Analysis (FEM) for the flexible panel has been done and coupled with the acoustic domain using the Boundary Element Method (BEM) through the mobility relation. A MATLAB program has been developed to find flexible panel behavior by FEM and BEM to calculate the sound pressure level for a cavity. Eight-noded isoparametric serendipity elements have been used to model the boundary. A pressure-velocity formulation has been adopted to model the acoustic domain with radiation impedance for window boundary. It has been shown that the presence of a thin flexible plate and opening, drastically changes the SPL pattern inside and at the boundary compared to a rigid cavity due to the relative movement of flexible panel and energy dissipation through the opening by radiation.
Seismic Performance of Superelastic SMA Damper Retrofitted Building
Authors: Kashyap S. , Upadhyaya S. , Gur S.
Published: December 2022

Nonlinear dampers are well known retrofitting system for the building structure, to mitigate seismic hazard. In past, among different type of nonlinear dampers, metallic yield dampers gain significant attention due to its high energy dissipation capacity. However, it has been observed while yield damper reduces floor displacement, but increases floor acceleration and leaves large residual displacement at the end of ground motion. Present study focuses on the application of shape memory alloy (SMA) dampers as an alternative to the yield damper, for retrofitting of building structure under seismic loading. Thus, response analyses are performed for nonlinear building structure without and with yield damper or SMA damper, under a large number of ground motion. Vibration control efficiency of yield and SMA damper are estimated in terms of the absolute maximum values of the floor acceleration, interstory drift ratio, and residual displacement. Response parameters are estimated over wide range of parameters of damper, building structure, and ground motion. Parametric study results revealed that yield damper provides very less acceleration control efficiency and some of cases it become more than uncontrolled structure. In contrast SMA damper slightly improves the acceleration control than yield damper (almost 14 %). In Comparison to the yield damper, SMA damper reduces the interstory drift ratio by 38 % and residual floor displacement by 47 %. Therefore, SMA damper provides major advantage in floor displacement reduction over yield damper, and acts as better re-centring device for seismic retrofitting application.
Retrofitting Solutions for Existing Open Ground Storey RC Buildings
Authors: Bharadwaj K. , Pathak J.
Published: December 2022

In the last few decades with the increase in population and decrease in usable land, there has been an enormous rise in the construction of residential buildings with open ground storey (OGS) to facilitate vehicle parking. Such OGS are created by removing the infill walls in the first storey. However, during the past earthquakes many of such OGS buildings have suffered severe damage and sometimes complete collapse of the structure. This is because OGS buildings, in general, exhibit soft story irregularity. Although the design codes have recommended provisions to enhance the seismic capacity of the OGS buildings, such provisions are barely implemented during construction. In order to avoid casualties and economic losses, it is necessary to retrofit the existing OGS structures. In this work, an attempt is made to strengthen the OGS buildings using masonry infill walls and braces as the retrofitting solutions. The models are developed in Seismostruct and analysed using suitable analytical methods. The behaviour of OGS buildings with masonry and braces at selected locations is evaluated. Retrofitting solutions that provide enhanced seismic performance and maximum parking space are proposed.
Seismic Risk Assessment of Asymmetric Buildings using Fragility Curves
Authors: Rana UpasanaR. , Mevada SnehalV. , Patel VishalB.
Published: December 2022

It is very important and necessary to assess the seismic risk for the buildings subjected to uncertain and highly unpredictable dynamic forces produced from earthquakes. Fragility curves are the best tools for the representation of seismic risk assessment. In the present study, risk assessment of structure subjected to seismic loading is evaluated. Further, the effects of different eccentricities are also studied for seismic risk assessment. The fragility curves are developed for G+5 storied RCC bare frame building as well as G+5 storied RCC building with shear wall. The considered buildings are subjected to ground motions of past recorded earthquakes. Buildings with different eccentricities and various structural configurations are studied for various failure criteria. The responses of the considered buildings subjected to earthquake excitations are evaluated by Incremental Dynamic Analyses. Fragility curves are developed using Monte Carlo method considering various performance levels as per ATC-40. It is observed that for immediate occupancy failure criteria, the probability of failure is increased constantly with increasing the percentage of structural eccentricity. Further, it is observed that very less variation is observed in the probability of failure under life safety and collapse prevention failure stages.
Comparative study on response of jacket platforms under regular waves using Airy’s and Stokes’ fifth-order wave theories
Authors: Sarkar Nilarghya , Ghosh Aparna(Dey)
Published: December 2022

Despite the random nature of ocean waves, to provide engineering solutions, regular wave theories are commonly used to estimate wave forces from the Morison equation in offshore structural analysis. These wave theories can be defined by three basic parameters, namely water depth, wave height and wave period. The applicability of a particular wave theory to a given set of wave characteristics and water depth is governed chiefly by the ratios of water depth and wave height to the wavelength. Airy’s linear wave theory, on account of its simplicity, is a popular choice, especially for preliminary calculations and for providing insight into the basic characteristics of wave-induced water motion. It is, however, applicable to small wave heights and in many conditions the linear theory is incapable of providing a satisfactory assessment of the water particle kinematics. A nonlinear theory is then required, and Stokes’ fifth order wave theory, based on the expansion of the wave solution in series form, provides a more accurate representation of the free-surface and is generally used for high waves in deep water. In this paper, a comparative study is conducted between the wave forces obtained from Morison equation utilising Airy’s wave theory and Stokes’ fifth order wave theory, acting at different levels of a jacket platform. Two sets of water depth, wave height and wave period are selected so that they satisfy the region of applicability of Airy’s wave theory and Stokes’ fifth order wave theory respectively. Two example four-legged jacket platforms are considered. It is found that for design purposes, in most cases the wave forces and structural responses from Airy’s wave theory are more conservative as compared to those from Stokes’ fifth order wave theory, though the converse is obtained in case of deep water conditions near the seabed. Overall, in deep water, high wave conditions, apart from Stokes’ fifth order wave theory, Airy’s wave theory may be used for preliminary estimations of wave forces and deck displacements, but in shallow water conditions, Stokes’ fifth order wave theory is entirely invalid.
Dynamic Analysis of Offshore Wind Turbine Supported by Jacket Substructure under Wind and Wave Loading
Authors: Madhuri Seeram , Bera SiteshSubhra , Prasad Brajkishor
Published: December 2022

Burning of fossil fuel for the production of energy causes severe global warming effects. Renewable energy sources like solar, wind and tidal etc. are the alternative renewable energy sources which contribute in the reduction of adverse global warming effects. Wind turbines are being used for extracting wind energy from several years. Wind blow is continuous with limited disturbance in the offshore region when compared with main land. Offshore wind energy extraction is in research stage at many locations and implemented in European countries. Prediction of response of wind turbine supporting systems is essential in the design to withstand the environmental loads such as wind, wave, current and seismic etc. In the present study, a horizontal axis offshore wind turbine (HAWT) supported on an offshore jacket structure is considered and the response studies are performed. The jacket is considered at a water depth of 51m, thus total height of the jacket is 61m with a free board of 10m.
A wind turbine of 5MW capacity is considered to be on top of jacket structure. The height of the wind tower is assumed as 70m, and a transition structure of 4m height is positioned in between jacket and tower. A free vibration analysis is performed to estimate the natural frequencies and mode shapes of the jacket supported wind turbine. The modal analysis is carried out using ANSYS static structural module.
The response analysis under wind, wave, current and aerodynamic drag loads is performed using SACS 13.2 software. Wind force is estimated based on API 2005 provisions. The aerodynamic forces on the wind turbine blades are evaluated using Betz Theory. Wave loading is calculated using Morison equation and linear Airy’s wave theory. A parametric study is carried out by varying wave period from 6s to 20s. As the structure is symmetric about longitudinal and lateral directions, a wave directional analysis is also carried by considering 0o and 45o wave directions. The structural responses are studied for the combined wind, wave and current loads. Cut-in, rated, cut-out and storm conditions are simulated by modelling wind and aerodynamic loads on the tower, wind interacting area of the jacket and blades. Wave period and direction are varied to simulate different wave conditions. It is observed that the structural response is increasing as the wind velocity is increasing and wave period is decreasing.
Static Stress Analysis of Functionally Graded Cylindrical Stiffened Shells
Authors: Shiyekar S.M. , Awari Akshaya
Published: December 2022

In this paper, a study on bending performance of functionally graded (FGM) cylindrical shells under transverse mechanical load is presented. Computational and analytical tools are used to study the behavior of FGM cylindrical shells under bending. Analytical modeling is based on first order shear deformation theory (FOST) and a finite element computational tool ABAQUS is used to model the FGM cylindrical shell. Material properties are estimated by power law index. Results from computational tools for isotropic and FGM cylindrical shells with various boundary and loading conditions are validated with literature and present FOST. Stiffened FG cylindrical shells with cutouts are analyzed. The FGM circular cylindrical shells subjected to an internal pressure with various arrangements of stiffeners are also analyzed and von – Mises stresses are also studied.
Evaluation of Seismic Performance Factors for Concrete Filled Steel Tube Diagrid Structural System
Authors: Mehtani D.V. , Patel P.V.
Published: December 2022

Seismic performance factors are used in current building codes and standards to estimate strength and deformation demands on seismic force resisting systems that are designed using linear methods of analysis, but are responding in the nonlinear range. Many recently evolved seismic force resisting systems have never been subjected to any signi?cant level of earthquake ground shaking. As a result, the seismic response characteristics of many systems, and their ability to meet seismic design performance objectives, are both untested and unknown. Therefore, it is necessary to determine the seismic performance factors of new seismic force resisting systems proposed for inclusion in building codes that will result in equivalent safety against collapse during an earthquake when properly implemented in the seismic design process. In this study, the response modification factor, overstrength factor and period based ductility for concrete filled steel tube (CFST) diagrid structural system are evaluated. To quantify these factors, the rational procedure introduced in Federal Emergency Management Agency (FEMA) P695, which is based on low probability of structural collapse and encompasses nonlinear static and dynamic analyses, is used. To this end, performance group consisting of 4, 8, 16 and 24 storey diagrid structures with 50° angle of external braces is considered. Nonlinear static analyses are performed to obtain overstrength factor and period?based ductility. Incremental dynamic analyses are then performed to assess collapse margin ratio of the archetypes. For modelling and numerical analysis, Open System for Earthquake Engineering Simulation (OpenSees), an open source software is used.
Meta-analysis of Photometric and Asteroseismic Measurements of Stellar Rotation Periods: The Lomb–Scargle Periodogram, Autocorrelation Function, and Wavelet and Rotational Splitting Analysis for 92 Kepler Asteroseismic Targets
Authors: Lu 卢 Yuting 鈺婷 , Benomar Othman , Kamiaka 上赤 Shoya 翔也 , Suto Yasushi
Published: December 2022

We perform intensity variability analyses (photometric analyses: the Lomb–Scargle periodogram, autocorrelation, and wavelet) and asteroseismic analysis of 92 Kepler solar-like main-sequence stars to understand the reliability of the measured stellar rotation periods. We focus on the 70 stars without reported stellar companions, and classify them into four groups according to the quarter-to-quarter variance of the Lomb–Scargle period and the precision of the asteroseismic period. We present detailed individual comparison among photometric and asteroseismic constraints for these stars. We find that most of our targets exhibit significant quarter-to-quarter variances in the photometric periods, suggesting that the photometrically estimated period should be regarded as a simplified characterization of the true stellar rotation period, especially under the presence of the latitudinal differential rotation. On the other hand, there are a fraction of stars with a relatively small quarter-to-quarter variance in the photometric periods, most of which have consistent values for asteroseismically and photometrically estimated rotation periods. We also identify over 10 stars whose photometric and asteroseismic periods significantly disagree, which would be potentially interesting targets for further individual investigations.
AGN Selection and Demographics in GOODS-S/HUDF from X-Ray to Radio
Authors: Lyu 吕 Jianwei 建伟 , Alberts Stacey , Rieke George H. , Rujopakarn Wiphu
Published: December 2022

We present a comprehensive census of the active galactic nuclei (AGNs) in the GOODS-S/HUDF region from the X-ray to the radio, covering both the obscured and unobscured populations. This work includes a robust analysis of the source optical to mid-IR spectral energy distributions (SEDs) featuring (semi)empirical AGN and galaxy dust emission models and Bayesian fitting techniques, ultra-deep Very Large Array 3 and 6 GHz observations, and an integrated analysis of various AGN selection techniques, including X-ray properties, UV to mid-IR SED analysis, optical spectral features, mid-IR colors, radio-loudness and spectral slope, and AGN variability. In total, we report ∼900 AGNs over the ∼170 arcmin2 3D-HST GOODS-S footprint, which has doubled the AGN number identified in the previous X-ray sample, with ∼26% of our sample undetected in the deepest Chandra image. With a summary of AGN demographics from different selection methods, we find that no one single band or technique comes close to selecting a complete AGN sample despite the great depth of the data in GOODS-S/HUDF. We estimate the yields of various approaches and explore the reasons for incompleteness. We characterize the statistical properties, such as source number density, obscuration fraction, and luminosity function of the AGN sample in this field, and discuss their immediate implications. We also provide some qualitative predictions of the AGN sample that might be discovered by the upcoming JWST surveys.
Inferring Maps of the Sun’s Far-side Unsigned Magnetic Flux from Far-side Helioseismic Images Using Machine Learning Techniques
Authors: Chen Ruizhu , Zhao Junwei , Hess Webber Shea , Liu Yang , Hoeksema J. Todd , DeRosa Marc L.
Published: December 2022

Accurate modeling of the Sun’s coronal magnetic field and solar wind structures requires inputs of the solar global magnetic field, including both the near and far sides, but the Sun’s far-side magnetic field cannot be directly observed. However, the Sun’s far-side active regions are routinely monitored by helioseismic imaging methods, which only require continuous near-side observations. It is therefore both feasible and useful to estimate the far-side magnetic-flux maps using the far-side helioseismic images despite their relatively low spatial resolution and large uncertainties. In this work, we train two machine-learning models to achieve this goal. The first machine-learning training pairs simultaneous Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager-observed magnetic-flux maps and SDO/Atmospheric Imaging Assembly-observed extreme ultraviolet (EUV) 304 Å images, and the resulting model can convert 304 Å images into magnetic-flux maps. This model is then applied to the STEREO-observed far-side 304 Å images, available for about 4.3 yr, for the far-side magnetic-flux maps. These EUV-converted magnetic-flux maps are then paired with simultaneous far-side helioseismic images for a second machine-learning training, and the resulting model can convert far-side helioseismic images into magnetic-flux maps. These helioseismically derived far-side magnetic-flux maps, despite their limitations in spatial resolution and accuracy, can be routinely available on a daily basis, providing useful magnetic information on the Sun’s far side using only the near-side observations.
Early JWST Imaging Reveals Strong Optical and NIR Color Gradients in Galaxies at z ∼ 2 Driven Mostly by Dust
Authors: Miller Tim B. , Whitaker Katherine E. , Nelson Erica J. , van Dokkum Pieter , Bezanson Rachel , Brammer Gabriel , Heintz Kasper E. , Leja Joel , Suess Katherine A. , Weaver John R.
Published: December 2022

Recent studies have shown that galaxies at cosmic noon are redder in the center and bluer in the outskirts, mirroring results in the local universe. These color gradients could be caused by gradients in either the stellar age or dust opacity; however, distinguishing between these two causes is impossible with rest-frame optical photometry alone. Here we investigate the underlying causes of the gradients from spatially resolved rest-frame U − V versus V − J color–color diagrams measured from early observations with the James Webb Space Telescope. We use 1–4 μm NIRCam photometry from the CEERS survey of a sample of 54 galaxies with

log

M

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/

M

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>
10

at redshifts 1.7 < z < 2.3 selected from the 3D-HST catalog. We model the light profiles in the F115W, F200W, and F356W NIRCam bands using imcascade, a Bayesian implementation of the multi-Gaussian expansion technique that flexibly represents galaxy profiles using a series of Gaussians. We construct resolved rest-frame U − V and V − J color profiles. The majority of star-forming galaxies have negative gradients (i.e., redder in the center, bluer in the outskirts) in both U − V and V − J colors consistent with radially decreasing dust attenuation. A smaller population (roughly 15%) of star-forming galaxies have positive U − V but negative V − J gradients implying centrally concentrated star formation. For quiescent galaxies, we find a diversity of UVJ color profiles, with roughly one-third showing star formation in their center. This study showcases the potential of JWST to study the resolved stellar populations of galaxies at cosmic noon.
Association of SCN1A Gene Polymorphism with Phenytoin Response in Patients with Epilepsy: Relevance of Stratification by the History of Febrile Seizure
Authors: Khairani Atitya Fithri , Sutarni Sri , Sholikhah Eti Nurwening , Malueka Rusdy Ghazali , Luthffia Audiza , Vidyanti Amelia Nur
Published: December 2022

AIM: The SCN1A gene encodes the NaV1.1 sodium channel in the central nervous system that serves as the target for phenytoin. Our study aimed to investigate the association of SCN1A polymorphism (SNP rs3812718) with phenytoin response.

MATERIALS AND METHODS: A total of 120 epileptic patients who had received phenytoin for at least 1 year were enrolled in the study and genotyped using the TaqMan assay. They were classified into phenytoin-responsive (n = 62) and phenytoin unresponsive groups (n = 58). Patients were also stratified according to the history of febrile seizure (24 in the febrile seizure subgroup; 96 patients in the no history of febrile seizure subgroup) and epilepsy etiology (47 in idiopathic; 73 in the symptomatic + cryptogenic subgroup).

RESULTS: The frequency of AA (19% vs. 11.3%) and AG genotypes (43.1% vs. 40.3%) was found to be more frequent in phenytoin unresponsive. GG genotypes dominated in the phenytoin responsive group (37.9% vs. 48.4%) but were not statistically significant (p > 0.05). We identified two variables associated with phenytoin response: the etiology of epilepsy (p = 0.012) and history of febrile seizure (0.014). A significant positive association between the rs3812718 genotype and phenytoin response was found when patients were stratified by a history of febrile seizures. In patients without a history of febrile seizures, the AA genotype had a higher risk of phenytoin unresponsiveness than the GG genotype (p = 0.048; OR 3.73, 95% CI: 1.01–13.78).

CONCLUSION: There was no significant association between the rs3812718 polymorphism and phenytoin responsiveness in patients with epilepsy. In the patients without a history of febrile seizure subgroup, AA increased the risk of phenytoin unresponsiveness compared to the GG genotype.