Indian Code Research Articles

Effects of Beam Members on Performance of Buildings under Seismic Forces

The main aim of the paper is to present an analysis to study on non-linear seismic analysis of reinforced concrete (RC) framed buildings as per the provisions of Indian code IS1893-2016 to evaluate the response of the building configurations depending upon the section sizes of the horizontal members; beams and as per variation in its cross-sectional area. The response of buildings has been noted in terms of quantities as the time period of buildings.Indian seismic code IS 1893 has been employed for the design provisions of the seismic analysis and the structures have been evaluated for seismic zone II. The design software STAAD.Pro has been used for the dynamic analysis.The response of the structure under lateral force system, induced due to seismic activities is must be analysed to understand the behaviour of structure under dynamic forces. The paper evaluates the most common but important response factors of the structure which are most important in the design of building. The paper also shows the detailed results of the time period of buildings for various building configuration. The evaluated results have been tabulated and analysed with the help of a comparative study of the obtained data. The work is useful for better understanding of the performance of the reinforced concrete buildings as per the different sizes and sections and stiffness of the beam elements.

Numerical study on the uplift capacity of under-reamed piles in clay with linearly increasing cohesion

ABSTRACT The present study deals with the determination of the uplift capacity for an under-reamed pile in clay, whose cohesion increases linearly with depth, by following the finite element analysis methodology. The analysis was performed for: i) pile without under-ream, ii) single under-reamed pile and iii) double under-reamed pile. The geometry of the pile was selected following the relevant Indian standard code, and the analysis was performed for the different values of linearly increasing cohesion and for the various shaft adhesion. The safe and collapse load determined from the load-deformation curve indicated that its magnitude was highest for the double under-reamed pile followed by the single under-reamed pile. For the selected range of the embedment depth and the linearly increasing cohesion, the safe load for the single and the double under-reamed pile was found about 396% and 547% respectively higher than the pile without any under-ream.

Performance Behavior of Eccentrically Braced Steel Frame under Seismic Loading

Recent past growth of multi-story buildings structures with emphasis on steel has been found satisfactory. For solving the better-quality accommodation in the region where the chances of earthquakes are likely, role of bracing system enhances the performance of building under lateral load effect of earthquakes. Various methods of bracing systems are available in practices however, eccentrically braced frames (EBFs) are fairly new lateral force resisting system established to resist seismic event in a probable manner. Properly designed and detailed EBFs perform in a ductile manner through shear or flexural yielding of link element. The ductile yielding indicates wide hysteresis loop, which is excellent energy dissipation essential for high seismic event. The seismic performance of multi-story steel frame is designed according to the Indian code (IS800:2007). A simple computer-based pushover analysis is a procedure for performance-based design of buildings subjected to earthquake loading. Pushover analysis gets much importance in the past due to its ease and efficiency of the results. In this study eight frames were taken,among these, six frames which were braced as V, Inverted V, and Diagonal and remaining two are frames without bracing in two alternate heights (4 and 8 story). Seismic response of frames is studied using non-linear static analysis (pushover analysis) in terms of base shear, roof displacement, spectral displacement, spectral acceleration and story drift.

Effect of Admixtures on the Thermo-Physical Properties of Non Autoclaved Light Weight Block Using Marble Dust

In the present study, use of marble dust an inert filler produced by the marble cutting industries in the development of light weight block (LWB) of density 800 kg/m3 by non-auto clave method has been studied. Various mechanical and thermo-physical properties have been evaluated. It has been possible to replace cement by up to 20% when no additive is used. With the use of activator and super plasticizer at 50% replacement of cement by marble dust, compressive strength and water absorption are well within the Indian standard code 2185. With the use of accelerator and super plasticizer it is possible to reduce the de moulding time from 48 hrs to 6 hrs. Thermal conductivity of blocks varies from 1.16 to 2.30 [W/mK]. The variation in thermal conductivity depends upon its density which varies from 800 kg/m3 to 2400 kg/m3.

Comparative Study of Seismic Analysis of Building with Light Weight and Conventional Material

In recent decades, the lightweight materials are used in construction instead of conventional material. Lightweight construction is considered to be favourable due to the saving in construction cost and materials. AAC block is a lightweight structural material with excellent acoustic and thermal insulation properties. Due to the use of lightweight material in construction in seismic zone reduce the percentage of damages. In this paper the attempt has been made to carry out the project comparative study of seismic analysis of building with lightweight and conventional material. Structural model of multi storey building (G+3) and analysis is carried out in STAAD-Pro by RSM (Response Spectrum Method). Building using infill AAC (Autoclaved aerated concrete) block and conventional clay brick masonry are designed for the same seismic hazard in accordance with the applicable provisions given in Indian codes. The analytical results of the buildings will be compared. The project is also aimed at getting familiarity with STAAD-Pro.2008.

Displacement-Based Design of RC Frames Using Design Spectra of Indian Code and Its Seismic Performance Evaluation

A set of 4-, 8-, 12-, and 15-storied reinforced concrete moment resisting frames were analysed and designed by direct displacement-based design method and performance-based plastic design method. The design spectra of Indian Standard IS 1893:2016 have been used for the calculation of base shear after its proper synchronization with respect to both the methods. The seismic performance evaluation was done by nonlinear static pushover analysis, and the parameters of comparison were (a) pushover curves, (b) storey drifts and (c) response reduction factor. Results show satisfactory performance of both the methods in terms of capacity and deformation. The response reduction factor values obtained for both approaches are greater than the IS 1893:2016-specified value which indicate the enhanced ductility for both methods.

Wind Response of Tall Buildings using Indian and Australian Standards

India is one of the country having approx. 1.3 billion population. Continuous population increase and lack of availability of open spaces makes use of Tall Buildings essential. Increased demand of tall buildings makes wind analysis of the tall buildings considerable. The codal provisions available to carry out dynamic analysis of building subjected to wind. This paper discusses the Indian and Australian codal provisions available to carry out wind analysis of Tall Buildings. IS 875 (Part-3):1987, Indian code of practice gives procedure to calculate along wind response of tall structures. IS 875 (Part-3):2015 gives a simplified procedure to calculate along as well as across wind response of tall structures. An Australian code AS/NZS 1170.2-2002, Structural design actions - Wind actions is used carry out wind response study of tall buildings. AS 1288—2006 gives selection and installation of Glass in buildings subjected to wind.

Empirical Period-Height Relationship for reinforced Concrete Moment Resisting Buildings in India

The fundamental period of vibration of buildings is the unique parameter that has a major influence on the earthquake induced lateral forces. Many design codes provide simple empirical period -height relationships for the determination of the fundamental period of vibration but using these equations time period and the resulted base shear are conservatively estimated. In most design cases the results obtained using conservative estimates formulae are largely deviating from the required engineering accuracy. Therefore a relationship is sought that will give accurate prediction of period of vibration for structural assessment of Indian reinforced concrete moment resisting frame buildings. On the basis of fundamental period of vibration of an Indian reinforced concrete moment resisting frame (RC MRF) building, obtained by finite element analysis, new equation has been proposed. In this study 21 existing reinforced concrete moment resisting frame buildings in India, with varying length, width and height are considered. The fundamental time periods of all the selected buildings were calculated using finite element method and IS 1893(Part 1) : 2002 based empirical formula. The comparison of proposed equation with Indian code shows that finite element analysis yielded 100 % higher periods as compared to the code approach.

Performance of Buildings Using Site Specific Ground Motion of Kolkata, India

Kolkata, capital of West Bengal, India, is presently congested with moderate to high rise buildings, and may undergo damage during future earthquakes due to the amplification of seismic waves by the soft alluvial soil. Further, most of the buildings are open ground storey (OGS), which is very vulnerable to earthquakes. Therefore, in the present study, the performance of some typical G+1, G+4 and G+9 storied buildings are analyzed using the available site-specific time history of the city by non-linear time history analysis (NLTHA). The analysis has been carried out for maximum considerable earthquake (MCE) and design basis earthquake (DBE) by both considering the stiffness of the infill wall (WI) and without considering stiffness of infill wall (WOI). The result signifies that, in almost all locations, the percentage of roof displacements obtained by site specific time history are more than the Indian codal compatible time history for both WI and WOI. Thus, performance will not be satisfactory for the buildings which are designed according to the Indian seismic code. The present study also corroborates that for almost all the buildings, the ground storey drift remains below immediate occupancy (IO) level during DBE and it varies IO to life safety (LS) level during MCE. However, all the storey drift are below Collapse Prevention (CP) limit. It is to be mentioned that for all the buildings the inter storey drift is higher than the Indian codal (IS-1893 (Part 1):2016) permissible limit (0.4%) during both DBE and MCE. However, the storey drifts result for WI buildings are comparatively lower than WOI buildings which are due to addition of stiffness of infill in each floor and fundamental modal spectral acceleration is lower.

Supervisory control using fuzzy logic for fault ride-through capability of a hybrid system in grid supporting mode

This paper demonstrates a novel fuzzy-supervisory control algorithm for power extraction and management in a grid-tied low concentration photovoltaic (LCPV) system with battery energy storage system (BESS). The novelty of this paper lies in avoiding dump load (DL) at the dc link, to regulate dc link voltage (Vdc) under all conditions, with an increase in power dispatch. This increases system efficiency and lessen power extraction from BESS. The supervisory controller directs all converters and maintains power balance at the dc link. Enhanced reactive power (Q) support of the grid inverter during a grid fault is controlled by using the magnitude of grid voltage sag. This control prevents islanding of the dc micro-grid as per the Indian grid code. Variation in duty cycle of the converter for optimum power extraction from LCPV generator is done by using fuzzy logic. Power references of converters depend on different operational modes and grid condition.

A numerical study on the validation of thermal formulations towards the behaviour of RC beams

Abstract Thermal analysis of building components is done to predict thermal loads and deformations that affect the overall design criteria of any building subjected to thermal loading. However due to complexity of the problem specially in case of composite structures, this is mostly done using numerical software packages and no clear guidelines are available in structure design codes which are being constantly updated. For example, the British and Indian codes for design do not provide a clear guideline for designing structural components at elevated temperatures having non-constant profile distribution. The paper gives an insight towards a rational design of beams subjected to temperature changes through describing a detailed numerical validation of the mathematical equations for thermal stresses in a beam subjected to a temperature change T(y). The beams are subjected to different constant, linear, and non-linearly varying temperature profiles along their depth and the behavior is checked for the different beam conditions. The boundary conditions in this study include perfectly clamped ends, simply supported and a range of intermediate cases providing various levels of axial and flexural restraints. The theoretical formulations have been accordingly manipulated. For each case, thermal stress curves are extracted from the analysis against the validation of the mathematically derived equations. It is found that the choice of support conditions of the flexural elements have a considerable influence over their behaviour in thermal analysis in terms of thermal stress/strain due to axial strain, bending and curvature.

A Novel Approach for Accurate Assessment of Design Wind Speed for Variable Wind Climate

For a widely varied wind climate in India, a single type of Extreme Value Distribution (EVD) is not suitable to fit wind speed data for all geographical locations and climatic conditions. This may lead to the inappropriate estimation of the design wind speed (Vd). In this study, a new approach, combining the merits of both the block maxima and the peaks over threshold approaches, has been used to determine the Vd. The hourly mean wind speed data of three stations, viz., Trivandrum, Bombay and Calcutta have been classified into block of months of the years 1973−2005, 1969−2007, and 1969−1994 respectively. The extreme peaks over the appropriate threshold value have been fitted into the generalized EVD (type-I, II and II). The results indicate that Fréchet distribution is the most suitable distribution for all three stations. March has the highest Vd for Trivandrum, whereas, for both Bombay and Calcutta it is September. Bombay shows highest overestimation of the Vd as given in Indian code of standard, whereas, for Trivandrum, and Calcutta these deviations have been found to be comparatively less. The five plotting position formulae have also been compared based on two goodness of fit tests, viz., R2, and RMSE.

Simplified Design Equation for Web Tapered - I Sections Using Finite Element Modeling

AbstractThe web - tapered I-columns have the capacity to resist the flexural buckling and lateral torsional buckling at a particular location where as in the rest of the member the capacity is lower. There needs a focusing on the nonprismatic members, to find the buckling capacity and standard procedures are to be framed in Indian Code IS 800:2007. This exploratory research explores simulated finite element models covering a total of 60 web tapered column sections having taper ratios (h2/h1) from 1.0 to 3.0 using FEA software ANSYS17.2. With an elaborate Eigenvalue buckling analysis, this research has come up with newer design equation for calculating the buckling load of web tapered I columns. This novel equation could predict the buckling stress for any taper ratio of web tapered I column of any length.

Effect of soil condition on seismic response of isolated base buildings

In the present paper, nonlinear time history and response spectrum analyses were carried out using Etabs-2015 software to study the influence of soil condition beneath the isolated base. The effects of soil flexibility are considered in the current study to examine the differences in spectral acceleration, base shear, story displacements, story drifts and story shear obtained following the seismic provisions of Indian standard code. Various soils are systematically compared and discussed for a seismic performance of multistory buildings. Parametric analysis of the buildings fitted with isolation devices is carried out to choose the appropriate type of soil. The study shows that the value of base shear increases with an increase of soil flexibility and superstructure stiffness. It also observed that the spectral acceleration (SA) and spectral displacement (SD) are higher in soft soil condition, which gives us evidence that the response spectral of a structure is associated with soil condition. The paper concluded that the hard soil and medium soil are suitable for base isolation building. In addition, analysis and design considerations for base isolated and conventional structures are suggested to enable the designer to get a better understanding at the preliminary design stage.

Incorporation of Dynamic SSI Effects in the Design Response Spectra

Many studies in the past on dynamic soil–structure interactions have revealed the detrimental and advantageous effects of soil flexibility. Based on such studies, the design response spectra of international seismic codes are being improved worldwide. The improvements required for the short period range of the design response spectra in the Indian seismic code (IS 1893:2002) are presented in this paper. As the recent code revisions has not incorporated the short period amplifications, proposals given in this paper are equally applicable for the latest code also (IS 1893:2016). Analyses of single degree of freedom systems are performed to predict the required improvements. The proposed modifications to the constant acceleration portion of the spectra are evaluated with respect to the current design spectra in Eurocode 8.

Seismic hazard assessment at micro level in Gandhinagar (the capital of Gujarat, India) considering soil effects

Gandhinagar City (the Capital of Gujarat, India) falls under Zone III on the seismic zoning map of India where an earthquake of magnitude 6 can be expected. It is a well established fact that the site amplification/ shaking and damage is large in soil covered areas. To estimate the effect of soil on ground motion and to estimate the strong ground motion parameters at surface, soil modeling and the ground response analysis have been conducted along uniformly distributed 14 boreholes drilled upto a depth of 50 m. The methodology is divided into three parts (i) Estimation of depth of Engineering Bed layer (EBL) (a layer with a shear wave velocity 400 m/s ≤ Vs ≤ 750 m/s, N value >80 and minimum soil variation below it) through soil modeling, (ii) Estimation of Ground Motion at EBL due to scenario earthquake at nearby active fault and (iii) Estimation of surface strong ground motion using 1D ground response analysis through SHAKE 2000 program. The EBL is found at a depth of 21–33 m (shallower in central part and deeper in northern and southern parts). The Near-Field scenario earthquake (Eq.) of magnitude Mw 6.0 has been considered along East Cambay Fault (normal fault, 60° dip) located at about ~ 20 km east and Far Field scenario Eq. of Mw 7.6 is considered along Kachchh Mainland Fault located ~270 km west. The Peak Ground acceleration (PGA) of 0.172–0.237 g have been estimated at surface due to near field earthquake scenario. The mean spectral acceleration maps for 0.1–0.4 s, 0.4–0.7 s, 0.7–1.0 s and 1.0–1.5 s have also been computed. The mean spectral acceleration for the period of 0.1–0.4 s has been varying from 0.330 g to 0.508 g, for period of 0.4–0.7 Sec, it has been varying from 0.151 g to 0.161 g and for period between 1.0 and 1.5 Sec, it has been found from 0.83 g to 0.09 g. The PGA is found increased by 5–38% in the first subsurface soil layer in Gandhinagar city. The PGA of the order of 0.059–0.072 g and peak Spectral acceleration of the order of 0.187–0.259 g have been computed (with predominant periods of ~0.1 s and 0.31 s) due to Far-Field Eq. scenario and are found less than Indian code. The PGA and Spectral acceleration (Sa) values are found higher than the Indian code in the period range of 0.1–0.4 s (one to four storey buildings) for Near Field Eq. Scenario.

Probabilistic verses deterministic method of seismic performance evaluation

Seismic performance evaluation of existing buildings by probabilistic approach and by deterministic approach has been compared and benefits of probabilistic approach are highlighted. An old building constructed in the 80s and situated in Indian seismic zone V has been taken for the study. Different retrofitting strategies have been implemented to improve global seismic performance. Effectiveness of any retrofitting scheme is assessed by both approaches. Static pushover analysis has been implemented for deterministic approach. For stochastic approach, a probabilistic-based methodology based on Pacific Earthquake Engineering methodology has been developed. The methodology accounts well the associated uncertainties in the process of seismic evaluation. Incremental dynamic analysis-based fragility curves have been developed. It is concluded that probabilistic approach provides comparatively a broad insight into evaluation process and it accounts capacity, demand and modeling uncertainties and is able to predict the seismic performance of retrofitted buildings to futuristic earthquakes. The study also recommends the implementation of performance-based design philosophy based on probabilistic approach in Indian seismic code to match with developing countries’ current design philosophy.

Seismic performance of reinforce concrete buildings designed according to codes in Bangladesh, India and U.S.

This paper focuses on the comparison of seismic design provisions in Bangladesh (BNBC-1993), India (IS-1893), and the U.S. (ASCE 7-10) in relation to analysis, design, and seismic performance of reinforced concrete buildings on the basis of the type of allowable analysis procedures, zoning system, site classification, fundamental vibration period of the structure, response reduction factor, importance factor, minimum design lateral force, allowable story drifts, and design response spectra.Three geometrically similar commercial reinforced concrete buildings in high seismic regions of Bangladesh, India, and U.S. were designed and detailed per the respective codes. Three-dimensional nonlinear dynamic analyses of the designed structures were conducted. Each structure was subjected to a pair of orthogonally applied artificial ground motions compatible with the design response spectrum for each building code. The structural performance of each building was compared in terms of roof displacements, inter-story drifts, load-carrying capacity of beams and columns, and overall energy dissipation characteristics. The comparisons allowed an in-depth evaluation of the differences in the seismic performance of buildings designed according to ASCE 7-10, BNBC-1993, and IS-1893 codes. The Indian code performed better when subjected to the ground motion that is intended to represent the Indian design response spectrum.

Optimal Design of RC Frames using a Modified Hybrid PSOGSA Algorithm

AbstractThe present study has been taken up to emphasize the role of the hybridization process for optimizing a given reinforced concrete (RC) frame. Although various primary techniques have been hybrid in the past with varying degree of success, the effect of hybridization of enhanced versions of standard optimization techniques has found little attention. The focus of the current study is to see if it is possible to maintain and carry the positive effects of enhanced versions of two different techniques while using their hybrid algorithms. For this purpose, enhanced versions of standard particle swarm optimization (PSO) and a standard gravitational search algorithm (GSA), were considered for optimizing an RC frame. The enhanced version of PSO involves its democratization by considering all good and bad experiences of the particles, whereas the enhanced version of the GSA is made self-adaptive by considering a specific range for certain parameters, like the gravitational constant and a set of agents with the best fitness values. The optimization process, being iterative in nature, has been coded in C++. The analysis and design procedure is based on the specifications of Indian codes. Two distinct advantages of enhanced versions of standard PSO and GSA, namely, better capability to escape from local optima and a faster convergence rate, have been tested for the hybrid algorithm. The entire formulation for optimal cost design of a frame includes the cost of beams and columns. The variables of each element of structural frame have been considered as continuous and rounded off appropriately to consider practical limitations. An example has also been considered to emphasize the validity of this optimum design procedure.

Comparative Study of Along-Wind Response of Major International Codes with Indian Code

Comparative Study of Along-Wind Response of Major International Codes with Indian Code