ijri-cce-01-006

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International Journal of Research and Innovation (IJRI)

DESIGN AND ANALYSIS OF MULTI STORIED STRUCTURES USING STATIC NON LINEAR ANALYSIS

P.Swetha1, K. Mythili2, G.Venkat Ratnam3

1 Research Scholar, Department Of Civil Engineering, Aurora's Scientific Technological & Research Academy, Hyderabad, India2 Associate Professor, Department Of Civil Engineering, Aurora's Scientific Technological & Research Academy, Hyderabad, India3 Associate Professor,Department Of Civil Engineering, Aurora's Scientific Technological & Research Academy, Hyderabad, India

*Corresponding Author: P.swetha, Research Scholar, Department of CIVIL Engineering, Aurora's Scientific Technological & Research Academy, Hyderabad, India Published: october 28, 2014Review Type: peer reviewedVolume: I, Issue :IICitation:P.Swetha,(2014)DESIGN AND ANALYSIS OF MULTI STORIED STRUCTURES USING STATIC NON LIN-EAR ANALYSIS

INTRODUCTIONGENERAL

Earthquakes in general occur due to intense tec-tonic activity of earth . In recent times there is a marked increase in the frequency of occurrence of earthquakes all over the world .the intensity and lo-cation of the earthquake is unpredictable even as on date . structures designed to withstand gravity loads alone cannot be expected to resist the dam-ages caused due to seismic effects . structures de-signed for gravity loads are normally well below the elastic limiting stage and lie within the service loads . it is neither practical nor economically viable to de-sign structures to remain within elastic limits dur-ing earthquakes . the design approach adopted in

the Indian code IS 1893(Part1): 2002 Criteria for Earthquake Resistant Design of Structures is to en-sure that structures possess at least a minimum strength to withstand minor earthquakes which oc-cur frequently , without damage ; resist moderate earthquakes without significant structural damage through some non-structural damage may occur ; and aims that structures withstand major earth-quakes without collapse .

India has experienced many large earthquakes in the last two decades resulting in heavy loss of life and property . In fact , more than 50% area in the country is considered vulnerable to earthquake dis-asters .Hence there is an urgent need for seismic evaluation and retrofitting of deficient buildings. The retrofitting is more so desirable as most of the majestic structures are designed to resist gravity loads alone .

A systematic procedure is to be followed while as-sessing the vulnerability of existing buildings . De-tailed survey of the buildings under the interest is to be undertaken. The basic information collected in the survey should include review of the build-ing configuration , soil profile and the period of construction . This is done with the help of quick checks and evaluation statements .

Abstract

The main objective of the research work presented in this thesis is to provide a systematic procedure to as-sess the behavior of a structure symmetrical and unsymmetrical

In plan during the seismic excitation using nonlinear static analysis (pushover) have been performed on the same structure. The literature pertaining to pushover analysis is reviewed. The pushover analysis adopted in the present study is on similar lines with the procedure presented by Ashraf Habibullah and Stephen Pyle using ETABS V 9.7 structural analysis software. The effect of earthquake force in a idealized G+4 story building under maximum earthquake zone, with the help of pushover analysis has been investigated and the results were compared in terms of base shear, displacement, spectral acceleration, spectral displace-ment and effective damping and effective time period .to strengthen the symmetric and un symmetric RCC framed buildings` steel braces are included by using retrofitting method.

The present structure is studied using the evaluation procedures provided in ATC-40 and FEMA-356 docu-ments and IS 1893:2002.

From the above studies it has been observed that nonlinear pushover analysis provides a good estimate of in elastic deformation demands and also reveals weakness that may remain hidden in an elastic analysis.


1401-1402

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However , a detailed evaluation is necessary in or-der to identify the deficiencies associated with the structural components with regard to the expected behavior of the building. The code compliance of the building can be ascertained only when the available member capacities are compared with the respec-tive demands due to the earthquake .the demand in structural members are determined for the seis-mic forces estimated as per IS 1893-2002 through linear static analysis . The member capacities are determined using the procedures prescribed in IS 456-2000 .The deficient members are identified and the Demand to Capacity Ratio(DCR) exceeds unity indicating the need for retrofitting in order to estab-lish compliance with prevailing codes.

NEED FOR THE INVESTIGATION

Low to medium height reinforced concrete frame buildings with masonry infill are common in ur-ban India . All these buildings in general designed to resist gravity loads and hence cant be expected to resist the latest seismic provisions . Earthquake causes shaking of the ground in unspecified direc-tions . The horizontal shaking along X and Y direc-tions remain a matter of concern . Structures de-signed for gravity loads , in general may not be able to safely sustain the effects of horizontal shaking due to earthquakes . Hence it is necessary to en-sure the strength of the structure against horizontal earthquake effects

OBJECTIVES OF THE STUDY

The primary objective of this work is to study the seismic response of RC framed building. The ef-fect of earthquake force on building in a symmetric and un symmetric building under maximum earth quake zone ,with the help of push over analysis has been investigated.

In the present study the main objective is the investigate the impact of steel bracings in improving the seismic capacity of RC buildings.The main objective of undertaking the present study are as follows :

1)To analyze a RC framed building both symmetric and un symmetric using pushover analysis proce-dure , with ETABS v 9.7 for ascertaining the seis-mic load carrying .

2)To compute the seismic response of building in terms of base shear , spectral acceleration, spectral displacement and roof displacements.

3)To study the effect of the steel bracings as a meth-od of retrofitting .

4)The increasing in base shear .

5)The reduction in amplitude of maximum displace-ments.

The study is propose to made with ETABS package on a symmetric and non-symmetric RCC buildings of five story height , the introduction of steel brac-ings may be consider as one method of retrofitting.

In the conventional retrofitting technologies adopt-ed to strength the RCC buildings to begin with the pushover analysis is carried out on RCC buildings there after depending on the deficiencies, the retro-fitting technologies are adopted in the present study the capacity of the building is increased by the use of steel braces provided to connect the columns and beams at the beam columns junction below the roof. a study is made to access the additional shear capacity of the building as well as the additional stiffness for both buildings with both symmetric and un symmetric plans

SUMMARY

In this chapter, the importance of earthquake and the post disaster effects of it and some light has been thrown on the earthquake design philosophy to be adopted in the construction and the various impor-tant seismic codes of India. The scope and objective is also been discussed. Based on the objective of the present study, research papers were collected and studied thoroughly. The review of research papers is discussed in the next chapter named as literature review.

TERMINOLOGY

The following are the definitions which are most commonly used in pushover analysis

Performance Point

It is the point where the capacity spectrum inter-sects the appropriate demand spectrum (capacity equals demand ). To have desired performance , every structure has to be designed for this level of forces

Representing capacity spectrum , demand spec-trum , performance point

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Building Performance Levels

Building performance is a combination of the per-formance of both structures and non-structural components . Different buildings performance level, used to described the performance of building in pushover analysis are described below

Operational Level (OL):

Building meeting this performances level are ex-pected to sustain no permanent drift and the struc-ture substantially retains original strengths and stiffness .major cracking of facades, partition and ceilings as well as structural elements are seen . All the system important to normal operation are func-tional . Non-structural components are expected to sustain negligible damage .

Immediate Occupancy Level (IO) :

Building meeting this performances level are ex-pected to sustain no permanent drift and the struc-ture substantially retains original strengths and stiffness . Minor cracking of facades , partition and ceilings as well as structure elements are seen . El-evators can be restarted . Fire protection is operable . Non- structural components such as equipments and contents stays generally secure , But may not be operative due to mechanical failure or lack of utilities.

Life Safety Level (LS):

This level is indicated when some residual strength and stiffness is left in all stories .Gravity load bear-ing elements function, no out-of-plane failure of walls or tripping of parapets occurs . There may some permanent drift , damage to partitions and the building may be beyond economical repair . Among the non-structural components falling haz-ards mitigated but many architectural , mechanical and electrical system get damaged

Collapse Prevention Level (CP): Building meeting this performance level are ex-cepted to have little residual stiffness and strength ,but load bearing columns and walls function . The building is expected to sustain large permanent drifts , some exit blocked , infill and un-braced parapet failure .Extensive damage to occur to non-structural component . At this level of performance , the building remains near collapse state

Building Performance Levels

A typical force deformation curve

GENERAL

The existing buildings can become seismically de-ficient since seismic design code requirements are commonly upgraded and advancement in engineer-ing knowledge . Future , Indian buildings built over past two decades are seismically deficient because of lack of awareness regarding seismic behavior of structure , The widespread damage especially to RC buildings during earthquakes exposed the con-struction practices being adopted around the world , and generated a great demand for seismic evalu-ation and retrofitting of existing building stocks Thus , it leads to the necessary of non-linear static pushover analysis .

The static pushover analysis is becoming a popu-lar tool for seismic performance evaluation of ex-isting and new structures . The expectation is that the push over analysis will provide adequate system and its components

The purpose of the study is to summarize the ba-sic concepts on which the pushover analysis can be based , assess the accuracy of the pushover predic-tions, identify conditions under which the pushover will provide adequate information and perhaps more importantly , identify causes in which the pushover predictions will be inadequate or even misleading

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PRESENT STUDY

INTRODUCTION

In the present study a rectangular building of G+4 stored symmetrical building and unsymmetrical building with same height are considered, push over analysis of the buildings is taken up with and without steel bracings using the package ETABS.

Description And Plan For Symmetrical Building

In the present work, a G+4 storied reinforced con-crete frame building situated in maximum earth quack Zone V, is taken for the purpose of study. The plan area of building is 1200x900mm with 300mm as height of each typical story. It consists of 4 bays in X-direction and 4 bays in Y-direction. The total height of the building is 1500mm. The building is considered as a Special Moment resisting frame. The plan of building is shown in while the isometric view of the buildings Structure with brace and with-out braces

symmetrical building plan and section in ETABS V 9.7

As the structure is regular and relatively simple the identification of the differences in results can be known in easy and can be discuss in depth.The Structure without braces and Structure with braces are having same frame properties i.e., same beam and column properties the only thing that dif-fer is that the Structure is acquainted with braces on the top of the slab connected to beams and col-umns.

Description And Plan For Unsymmetrical Build-ing

In this present work a G+4 stored rein forced con-crete frame building situated in maximum earth quake Zone V, is taken for the purpose of study . The plan area of building is 1600x1800 mm with 300mm as height of each typical storey. It consists of 5 bays in X-direction and 7 bays in Y-direction. The total height of the building is 1500mm. The building is considered as un symmetrical in plan as a Special Moment resisting frame. The plan of building is shown in while the isometric view of the buildings Structure with brace and with out braces

UN symmetrical building plan and section in ETABS V9.7

STRUCTURAL SYSTEMS OF THE BUILDING

storey G+4Slab thickness 125mmBeam dimensions 230 mm x 450 mmColumn dimensions 230mm x 450 mmExterior wall 230 mmInterior wall 150 mm

Structural dimensions of building

General Data Collection

The building is a G+4 storey building located in zone V. Tables 5.2, Table 5.3, Table 5.4 present a summary of the building parameters .The details of the building are given below.

Variable Type ReferenceType of soil Medium soil IS 1893:2002Type of founda-tion

Isolated footing ----

Seismic zone V IS 1893:2002

Geo technical and Geo logical data

Introduction To Load Patterns

Nonlinear static analysis, or pushover analysis, could be performed directly by a computer program which can model nonlinear behaviour of lateral load resisting members of a structure. However, the com-putational scheme and the assumptions involved in modelling nonlinear member behaviour could be dif-ferent that there may be variations in the pushover results obtained from different software. Therefore, the underlying principles of any software utilized for pushover analysis should be well understood to in-terpret the results of pushover analysis.

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Pushover Analysis Using Etabs V9.7:

The following steps are included in the pushover analysis. Steps 1 to 4 are to create the computer model, step 5 runs the analysis, and steps 6 to 10 review the pushover analysis results.

Geometry of symmetric structure

Reinforcement area in the beams and columns ana-lysed by linear response spectrum

Create the basic computer model (without the pushover data) as shown in fig 5.6 . The graphical interface of ETABS v9.7makes this quick and easy task. Assigned sectional properties & applies all the gravity loads (i.e. Dead load and Live load) on the structure respectively.

In order to know the reinforcement area in the Beam and Columns the Response Spectra linear Analysis was done for the zone II with Soil Type-2 and the Building was designed as per IS 456

Define properties and acceptance criteria for the pushover hinges. The program includes several built-in default hinge properties that are based on average values from ATC-40(3) for concrete members and average values from FEMA-356(2) for concrete members. In this analysis, M3 hinges have been de-fined at both the column ends and M3 hinges have been defined at both the ends of all the beams.

Locate the pushover hinges on the model by se-lecting all the frame members and assigning them one or more hinge properties and hinge locations as shown in Fig. 5.9

Frame Hinge Properties Data

Define hinges

Define the pushover load cases, Fig. 5.10, Fig. 5.11 and Fig. 5.12. In ETABS v9.7 more than one pusho-ver load case can be run in the same analysis. Also a pushover load case can start from the final condi-tions of another pushover load case that was previ-ously run in the same analysis. Typically the first pushover load case was used to apply gravity load and then subsequent lateral pushover load cases were specified to start from the final conditions of the gravity pushover. Pushover load cases can be force controlled, that is, pushed to a certain defined force level, or they can be displacement controlled, that is, pushed to a specified displacement. Typical-ly a gravity load pushover is force controlled and lat-eral pushovers are displacement controlled. In this case a Gravity load combination of 1.5DL+1.5LL has been used. This combination has been defined as GRAV. The lateral loads, have been applied by giv-ing the displacement to the model to be analysed to a case called PUSH.

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Static load case

Run analysis windows for the practical building

Pushover curve for the symmetric structure steel bracings

Pushover curve for the symmetric structure with steel bracings

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Pushover curve for the un symmetric structure with steel bracings

Capacity spectrum for symmetrical structure

Capacity spectrum for un symmetrical structure

Capacity spectrum for symmetrical structure with steel bracings

Capacity spectrum for un symmetrical structure with steel bracings

The pushover displaced shape and sequence of hinge information on a step-by-step basis was ob-tained and is shown in the Fig. 6.1 to 6.4 for the Structure without steel bracings and in the Fig. 6.5 to 6.8 for the Structure with steel bracings. Output for the pushover analysis can be printed in a tabu-lar form for the entire model or for selected elements of the model. The types of output available in this form include joint displacements at each step of the pushover, frame member forces at each step of the pushover, and hinge force, displacement and state at each step of the pushover.

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SUMMARY

This chapter completely takes care of the case study of a Structure under consideration and the various building data surveys done to gather the informa-tion for modeling of the structure, after carrying out the pushover analysis , the pushover curves for both the buildings with and without steel brac-ings are obtained, based on the performance points obtained the significant contribution by the use of steel bracings is noted and found a great achieve-ment to the field of retrofitting And also illustrates the step by step procedure followed for the static non-linear analysis.

DISCUSSION ON RESULTS

GENERAL

The structures has been modelled and the Pushover analysis of the structures has been carried out ac-cordingly with the ETABS v9.7

DISCUSSION ON RESULTS OF PUSHOVER ANAL-YSIS FOR THE SYMMETRICAL STRUCTURE WITHOUT STEEL BRACINGS AND WITH STEEL BRACINGS

Observations under Pushover Curve

The Structures has been given in a Pushover curve for the Structures was graphically generated for both the symmetric and un symmetric Building i.e. Structure without steel bracings and Structure With steel bracings as shown in the Fig. 5.14 and Fig. 5.16 respectively, It has been observe from the Fig. 5.14 and Fig. 5.15 that the base shear was mono-lithically increasing with the Displacement. And for the Drift the Maximum Base Shear was observed to be 796.22 kN and 1560.99 kN respectively. Table 6.1 and Table 6.2 show the step by step details for the change in base shear, and the number of elements falling in different performance levels like immediate occupancy, life safety and col-lapse prevention as the roof Displacement changes.

It has been clearly observed from the Table 6.1 for the symmetric Structure without steel bracings that the hinges were in the elastic region (i.e. A to B) up to a displacement of 19.31mm and further increase in the displacement leads to formation of 56 hinge with this the structure enters into non-linear stage (i.e. B to IO). The structure remains in this Immediate Occupancy performance level till the displacement reached 44.3 mm with the Base shear of 642.7kN at this stage it was observed that there were around 70 element hinges in this Perfor-mance Level and further increase in the displace-ment increases the number of hinge formation in other Performance Levels. the structure enter the performance level of Life Safety With the formation of 10 hinges at the displacement of about 73.66 mm and the building remained in this Life safety Per-formance Level for the entire Drift. It was observed

that the number of element hinges in the life safety Performance Level started with the formation of two Hinges with the Displacement of 106.18 mm and re-mained in the life safety Performance Level for the entire drift with 400 element hinges in it having the Displacement and Base shear as 77.622 mm and 796.22 kN respectively.

pushover table for symmetrical structure without steel bracings

It has been clearly observed from the Table 6.2 that the for the symmetric Structure with Steel bracings it started with the Immediate Occupancy stage (i.e. B to IO) with the formation of 20 element hinges in this Performance Level.The structure remains in this Immediate Occupancy performance level till the displacement reached 26.377 mm with the Base shear of 707.054 kN at this stage it was ob-served that there were around 280 element hinges in this Performance Level and further increase in the displacement makes the structure enters other Performance Levels. the structure enter the per-formance level of Life Safety With the formation of 108 hinges at the displacement of about 80.512 mm and the building remained in this Life safety Performance Level for the entire Drift. It was ob-served that the number of element hinges in the life safety Performance Level started with the formation of 2 Hinges with the Displacement of 111.372 mm and remained in the life safety Performance Level for the entire drift with 40 element hinges in it hav-ing the Displacement and Base shear as 53.316 mm and 2496.04 kN respectively.

Pushover Curve table for the symmetric structure with steel bracings

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Observations under Capacity spectrum curve

The Fig. 5.18 and Fig. 5.20 shows the capacity spectrum curve for a drift, obtained the intersection of pushover curve with response spectrum curve. Firstly both these curves are converted in terms of spectral acceleration and spectral displacement i.e. in the ADRS format, and then they are superim-posed to give the performance point of the structure. The green colour curve seen in the Fig. 5.18 and Fig. 5.20 is the pushover curve for the symmetric Structure without steel bracings and the symmetric Structure with steel bracings respectively and the curve in yellow color is the response spectrum curve in terms of spectral acceleration and spectral dis-placement. At the performance point for the symmetric Struc-ture without steel bracings the base shear is 796.22 KN at a displacement of 77.622 mm, we can observe that the hinges are still in the state of Immediate Occupancy Performance level. Hence, the struc-ture is still safe at this performance point for design based earthquake for the Zone V. Table 6.3 shows the demand, capacity details in terms of single de-mand spectrum ADRS (variable Damping) and ca-pacity spectrum at various steps during the pusho-ver analysis for Drift. The effective time period at the performance point is 0.978 sec and the effective Damping was 0.185 which can be seen between the steps 2nd and 3rd (refer Fig. 5.18 and Table 6.3).

Capacity Spectrum Curve table for the symmetric Structure without steel bracings

At the performance point for the symmetric Struc-ture with steel bracings the base shear is 1560.99 kN at a displacement of 70.237mm, which was ob-tained between steps 1st and 2nd (refer Table 6.4), we can observe that the hinges are still in the state of Immediate Occupancy Performance level. Hence, the structure is still safe at this performance point for design based earthquake for the Zone V. Table 6.4 shows the demand, capacity details in terms of single demand spectrum ADRS (variable Damping) and capacity spectrum at various steps during the pushover analysis for Drift. The effective time period at the performance point is 0.639 and the effective Damping was0.077. which can be seen between the steps 2nd and 3rd (refer Fig. 5.20 and Table 6.4).

DISCUSSION ON RESULTS OF PUSHOVER ANAL-YSIS . FOR THE UN SYMMETRIC STRUCTURE WITHOUT STEEL BRACINGS AND THE UN SYM-METRIC STRUCTURE WITH STEEL BRACINGS

Observations under Pushover curve

The Modelled un symmetrical Structures has been given a initial Drift . The Pushover curve for the un symmetrical Structures was graphically generated for both the Building i.e. un symmetrical Structure without steel bracings and Structure With steel bracings as shown in the Fig. 5.15 and Fig5.17 respectively. It has been observe from the Fig5.15 and Fig. 5.17 that the base shear was monolithi-cally increasing with the Displacement. And for the .Drift the Maximum Base Shear was observed to be 1561.499 kN and2496.045 kN respectively.Table 6.5 and Table 6.6 show the step by step de-tails for the change in base shear, and the number of elements falling in different performance levels like immediate occupancy, life safety and collapse prevention as the roof Displacement changes. When the un symmetrical Structure without steel bracings was given a Drift the further Deformation Performance of the Building was graphically repre-sented in the Fig. 5.15. It has been clearly observed from the Table 6.5 that from the Step 7th the build-ing enter in the Collapse Prevention Performance Level (i.e. from LS to CP) with the formation of 114 element hinges in it with the Base shear and Dis-placement as 710.770 kN and 19.50mm respec-tively and further increase in the Displacement at about 44.04mm the building entered in the Resid-ual Strength zone with the Base Shear as 1288.160 kN and there are 31 element hinges in this Resid-ual strength zone. It has been observed that the Base shear has increased down from 1288.16kN to 1515.75KN in the Total Failure Zone and the no of element hinges in this zone are 13 with Displace-ment of about 99.34mm this was observed. The Building was Totally Elapsed at the Displacement of about 99.34mm so there is no need for assessing the . Drift of the building.

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Pushover curve table for un symmetrical structure without steel bracings

When the un symmetrical Structure with steel bracings was given a Drift the further Deformation Performance of the Building was graphically repre-sented in the Fig. 5.17. It has been clearly observed from the Table 6.6 that the building enter in the Collapse Prevention Performance Level (i.e. from LS to CP) with the formation of 31 element hinges in it with the Base shear and Displacement as 1288.162 kN and 44.04mm respectively and further increase in the Displacement at about 71.77mm the build-ing entered in the Residual Strength zone with the Base Shear as 1542.697 kN and there are 27 ele-ment hinges in this Residual strength zone .At .the building has entered the Total Failure Zone with Base shear, Displacement and number of element hinges as 16207.036kN, 99.34mm and 4 respec-tively. It has been observed that the Base shear has increased from 1561.499kN to 2496.045kN .and no of element hinges in this zone are with Displace-ment of about 77.919mm. The Building was Total-ly Elapsed at the Displacement is decreased from 77.919 to 53.316.

Pushover Curve table for the un symmetrical Struc-ture with steel bracings

Observations under Capacity spectrum curve

The Fig. 5.19 and Fig. 5.21 shows the capacity spec-trum curve, obtained the intersection of pushover curve with response spectrum curve.At the performance point for the un symmetric Structure without steel bracings the base shear is 1245.475 kN at a displacement of 26 mm, which was obtained between steps 1st and 2nd (refer Ta-ble 6.7), we can observe that the hinges are still in the state of Immediate Occupancy Performance level. Hence, the structure is still safe at this per-formance point for design based earthquake for the Zone V Table 6.7 shows the demand, capacity details in terms of single demand spectrum ADRS (variable Damping) and capacity spectrum at vari-ous steps during the pushover analysis. The effec-

tive time period at the performance point is 1.030sec and the effective Damping was 0.201 which can be seen between the steps 1st and 2nd (refer Fig 5.19 and Table 6.7).

Capacity Spectrum Curve table for the un symmet-ric Structure without steel bracings.

At the performance point for the un symmetric Struc-ture with steel bracings the base shear is 2496.045 kN at a displacement of 53.316 mm, which was ob-tained between steps 1st and 2nd (refer Table 6.8), we can observe that the hinges are still in the state of Immediate Occupancy Performance level. Hence, the structure is still safe at this performance point for design based earthquake for the Zone V. Table 6.8 shows the demand, capacity details in terms of single demand spectrum ADRS (variable Damping) and capacity spectrum at various steps during the pushover analysis. The effective time period at the performance point is 0.599 and the effective Damp-ing was 0.077 which can be seen between the steps 2th and 3th (refer Fig. 5.21 Table 6.8).

Capacity Spectrum Curve table for the un symmet-ric Structure with steel bracings

HINGE PATTERNS FOR SYMMETRIC STRUCTURE WITHOUT STEEL BRACINGS AND UN SYMMETRIC STRUCTURE WITH STEEL BRACINGS

Fig. 6.1 to 6.4represent the sequence of formation of hinges from the initial stage i.e. from the elastic stage to the total collapse stage for the symmetric Structure without Steel bracings and the symmetric Structure with steel bracings respectively. These are color coded and are represented by respective color at different pushover steps. These hinges are essen-tial to closely study the behavior of the structure.

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hing pattern for symmetrical without steel bracings

hing pattern for symmetrical with steel bracings

hing pattern for un symmetrical without steel brac-ings

hingpattern for un symmetrical with steel bracings

Performance of different structures under the zones V

The Capacity Spectrum Curves for The symmetric Structure without Steel bracings under maximum Earthquake Zones V. The performance point of the building in terms of Base shear, Roof Displacement, Spectral Acceleration, Spectral Displacement, ef-fective Time Period, and Effective Damping of the structure.The symmetric Structure without Steel bracings and The Structure With Steel bracings were first analysis by the Non Linear Static analysis and were Designed accordingly to the Indian IS 456-2000. Pushover Analysis on these building was performed accordingly under the different Zones. The Perfor-mance point of the Structures was tabulated in the Table 6.9 and Table 6.10 accordingly to the change in the Earthquake Zones

SummaryThis chapter copes with the numerical study and presentation of results of pushover analysis method for the current buildings under study and the re-sults are tabulated and are represented in the form of graphs. The results were studied and based on the study, the conclusions were drawn. The con-clusions for the present study are given in the next chapter.

CONCLUSIONS

After having perform the pushover analysis on two different buildings with and without steel bracings following conclusions are drawn

In symmetrical building based an the per-formance point obtained from pushover curve (fig no page no )and the same building with steel bracings (fig no page no) the value of base share is found in-creased by % and the amplitude and displacement found by reduced % In un symmetrical building based on the performance point obtained from pushover curve (fig no page no )and the same building with steel bracings (fig no page no) the value of base share is

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found increased by % and the amplitude and dis-placement found by reduced %

Based on the above study it is felt that introduc-tion of steel bracings is one proven method of struc-tural retro fitting

SCOPE FOR FURTHER STUDY

In the present study, the pushover analysis has been carried out for the G+4 storey buildings. This study can further be extended for tall buildings.

In the present study, the conceptual design i.e., the sizes of beams and columns are kept common. Work can be done to optimize the sizes of various frame elements using pushover analysis.

Further studies can be done to compare the accu-racy of non-linear pushover analysis and non-linear time history analysis taking the displacement as a common parameter.

Laboratory tests on the structures should be car-ried out to backup the numerical results so that these results can be more informative and valuable.

More studies are required to carried out before generalized conclusions can be drawn

A retrofitting of frames with weak storey and un symmetrical elevations are also needed to be stud-ied.

SUMMARY

This chapter, details the discussions drawn based on the present work and the scope for the further study and Investigation based on the present study was discussed.

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AUTHOR

P.SWETHAResearch Scholar, Department of CIVIL Engineering, Aurora's Scientific Technological & Research Academy, Hyderabad, India

MRS. K. MYTHILIAssociate Professor, Department of CIVIL Engineering, Aurora's Scientific Technological & Research Academy, Hyderabad, India

MR. G.VENKAT RATNAM

Associate Professor, Department of CIVIL Engineering, Aurora's Scientific Technological & Research Academy, Hyderabad, India

Abstract

ijri-cce-01-006

Documents

majestic structures

research work

design structures

structures designed

pushover analysis

gravity loads

moderate earthquakes

minor earthquakes