International Journal of Research and Innovation (IJRI)
International Journal of Research and Innovation (IJRI) 1401-1402
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, India 2 Associate Professor, Department Of Civil Engineering, Aurora's Scientific Technological & Research Academy, Hyderabad, India 3 Associate Professor,Department Of Civil Engineering, Aurora's Scientific Technological & Research Academy, Hyderabad, India
Abstract The main objective of the research work presented in this thesis is to provide a systematic procedure to assess 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 displacement 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 documents 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.
*Corresponding Author: P.swetha,
Research Scholar, Department of CIVIL Engineering, Aurora's Scientific Technological & Research Academy, Hyderabad, India Published: october 28, 2014 Review Type: peer reviewed Volume: I, Issue :II
Citation:P.Swetha,(2014)DESIGN AND ANALYSIS OF MULTI STORIED STRUCTURES USING STATIC NON LINEAR ANALYSIS
INTRODUCTION GENERAL Earthquakes in general occur due to intense tectonic 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 location of the earthquake is unpredictable even as on date . structures designed to withstand gravity loads alone cannot be expected to resist the damages caused due to seismic effects . structures designed 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 design structures to remain within elastic limits during earthquakes . the design approach adopted in
the Indian code IS 1893(Part1): 2002 Criteria for Earthquake Resistant Design of Structures is to ensure that structures possess at least a minimum strength to withstand minor earthquakes which occur frequently , without damage ; resist moderate earthquakes without significant structural damage through some non-structural damage may occur ; and aims that structures withstand major earthquakes 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 disasters .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 assessing the vulnerability of existing buildings . Detailed survey of the buildings under the interest is to be undertaken. The basic information collected in the survey should include review of the building configuration , soil profile and the period of construction . This is done with the help of quick checks and evaluation statements . 44
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However , a detailed evaluation is necessary in order 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 respective demands due to the earthquake .the demand in structural members are determined for the seismic 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 establish compliance with prevailing codes. NEED FOR THE INVESTIGATION Low to medium height reinforced concrete frame buildings with masonry infill are common in urban India . All these buildings in general designed to resist gravity loads and hence can’t be expected to resist the latest seismic provisions . Earthquake causes shaking of the ground in unspecified directions . The horizontal shaking along X and Y directions remain a matter of concern . Structures designed 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 ensure 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 effect 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 :
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 bracings may be consider as one method of retrofitting. In the conventional retrofitting technologies adopted to strength the RCC buildings to begin with the pushover analysis is carried out on RCC buildings there after depending on the deficiencies, the retrofitting 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 important 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 intersects the appropriate demand spectrum (capacity equals demand ). To have desired performance , every structure has to be designed for this level of forces
1)To analyze a RC framed building both symmetric and un symmetric using pushover analysis procedure , with ETABS v 9.7 for ascertaining the seismic 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 method of retrofitting . 4)The increasing in base shear .
Representing capacity spectrum , demand spectrum , performance point
5)The reduction in amplitude of maximum displacements. 45
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Building Performance Levels Building performance is a combination of the performance 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 expected to sustain no permanent drift and the structure 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 functional . Non-structural components are expected to sustain negligible damage .
Building Performance Level’s
Immediate Occupancy Level (IO) : Building meeting this performances level are expected to sustain no permanent drift and the structure substantially retains original strengths and stiffness . Minor cracking of facades , partition and ceilings as well as structure elements are seen . Elevators 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):
GENERAL
This level is indicated when some residual strength and stiffness is left in all stories .Gravity load bearing 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 hazards mitigated but many architectural , mechanical and electrical system get damaged
The existing buildings can become seismically deficient since seismic design code requirements are commonly upgraded and advancement in engineering 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 construction practices being adopted around the world , and generated a great demand for seismic evaluation and retrofitting of existing building stocks Thus , it leads to the necessary of non-linear static pushover analysis .
Collapse Prevention Level (CP): Building meeting this performance level are excepted 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 nonstructural component . At this level of performance , the building remains near collapse state
A typical force deformation curve
The static pushover analysis is becoming a popular tool for seismic performance evaluation of existing 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 basic concepts on which the pushover analysis can be based , assess the accuracy of the pushover predictions, 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 concrete 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 without braces
UN symmetrical building plan and section in ETABS V9.7 STRUCTURAL SYSTEMS OF THE BUILDING
storey Slab thickness
G+4 125mm
Beam dimensions Column dimensions Exterior wall Interior wall
230 mm x 450 mm 230mm x 450 mm 230 mm 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. symmetrical building plan and section in ETABS V 9.7
Variable
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 differ is that the Structure is acquainted with braces on the top of the slab connected to beams and columns.
Type of foundation
Description And Plan For Unsymmetrical Building In this present work a G+4 stored rein forced concrete 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
Type of soil
Seismic zone
Type Reference Medium soil IS 1893:2002 Isolated footing ---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 computational scheme and the assumptions involved in modelling nonlinear member behaviour could be different 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 interpret 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.
Frame Hinge Properties Data Geometry of symmetric structure
Reinforcement area in the beams and columns analysed 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 defined at both the column ends and M3 hinges have been defined at both the ends of all the beams.
Define hinges Define the pushover load cases, Fig. 5.10, Fig. 5.11 and Fig. 5.12. In ETABS v9.7 more than one pushover load case can be run in the same analysis. Also a pushover load case can start from the final conditions of another pushover load case that was previously 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. Typically a gravity load pushover is force controlled and lateral 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 giving the displacement to the model to be analysed to a case called PUSH.
• Locate the pushover hinges on the model by selecting all the frame members and assigning them one or more hinge properties and hinge locations as shown in Fig. 5.9
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Pushover curve for the symmetric structure with steel bracings
Static load case
Run analysis windows for the practical building
Pushover curve for the symmetric structure steel bracings
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International Journal of Research and Innovation (IJRI)
Capacity spectrum for symmetrical structure with steel bracings Pushover curve for the un symmetric structure with steel bracings
Capacity spectrum for un symmetrical structure with steel bracings Capacity spectrum for symmetrical structure
• The pushover displaced shape and sequence of hinge information on a step-by-step basis was obtained 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 tabular 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.
Capacity spectrum for un symmetrical structure
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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 information for modeling of the structure, after carrying out the pushover analysis , the pushover curves for both the buildings with and without steel bracings are obtained, based on the performance points obtained the significant contribution by the use of steel bracings is noted and found a great achievement to the field of retrofitting And also illustrates the step by step procedure followed for the static non-linear analysis.
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 remained 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.
DISCUSSION ON RESULTS GENERAL The structures has been modelled and the Pushover analysis of the structures has been carried out accordingly with the ETABS v9.7 DISCUSSION ON RESULTS OF PUSHOVER ANALYSIS 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 monolithically 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 collapse 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 nonlinear 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 Performance Level and further increase in the displacement 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’ Performance Level for the entire Drift. It was observed
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 observed that there were around 280 element hinges in this Performance Level and further increase in the displacement makes the structure enters other Performance Level’s. the structure enter the performance 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 observed 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 having 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 superimposed 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 displacement. At the performance point for the symmetric Structure 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 structure 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 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 0.978 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 Structure with steel bracings the base shear is 1560.99 kN at a displacement of 70.237mm, which was obtained 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 ANALYSIS . FOR THE UN SYMMETRIC STRUCTURE WITHOUT STEEL BRACINGS AND THE UN SYMMETRIC 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 monolithically 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 details 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 represented in the Fig. 5.15. It has been clearly observed from the Table 6.5 that from the Step 7th the building 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 Displacement as 710.770 kN and 19.50mm respectively and further increase in the Displacement at about 44.04mm the building entered in the ‘Residual Strength zone’ with the Base Shear as 1288.160 kN and there are 31 element hinges in this Residual 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 Displacement 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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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).
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 represented 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 building entered in the ‘Residual Strength zone’ with the Base Shear as 1542.697 kN and there are 27 element 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 respectively. 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 Displacement of about 77.919mm. The Building was Totally Elapsed at the Displacement is decreased from 77.919 to 53.316.
Capacity Spectrum Curve table for the un symmetric Structure without steel bracings. At the performance point for the un symmetric Structure with steel bracings the base shear is 2496.045 kN at a displacement of 53.316 mm, which was obtained 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 Damping 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 symmetric Structure with steel bracings
Pushover Curve table for the un symmetrical Structure with steel bracings Observations under Capacity spectrum curve The Fig. 5.19 and Fig. 5.21 shows the capacity spectrum 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 Table 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 performance 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 various steps during the pushover analysis. The effec-
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 essential 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
hingpattern for un symmetrical with steel bracings Performance of zones V
different structures under the
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, effective 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 Zone’s. The Performance point of the Structures was tabulated in the Table 6.9 and Table 6.10 accordingly to the change in the Earthquake Zones Summary This chapter copes with the numerical study and presentation of results of pushover analysis method for the current buildings under study and the results are tabulated and are represented in the form of graphs. The results were studied and based on the study, the conclusions were drawn. The conclusions 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
hing pattern for un symmetrical without steel bracings
• In symmetrical building based an 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 found increased 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 54
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found increased by % and the amplitude and displacement found by reduced % • Based on the above study it is felt that introduction of steel bracings is one proven method of structural 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 accuracy 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 carried 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 studied. 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. REFERENCES 1. A. Kadidand A. Boumrkik, (2008), “Pushover analysis of reinforced concrete frame structures”, at Department of Civil Engineering, University of Banta, Algeria, Asian journal of civil engineering (building and housing) vol. 9, No. 1 pp 75-83. 2. ASCE, (2002), “Standard Methodology for Seismic Evaluation of Buildings”, Standard No. ASCE-31. American Society of Civil Engineers, Reston, Virginia. 3. Ashraf Habibullah and Stephen Pyle, (1998), “Practical three dimensional non-linear static pushover analysis”, Structures Magazine, winter. 4. Ashraf Habibullah S.E., (2008), “Physical object based analysis and design modelling of shear wall systems using etabs”, at Computers & Structures, Inc., Berkeley, California.
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author
P.SWETHA Research Scholar, Department of CIVIL Engineering, Aurora's Scientific Technological & Research Academy, Hyderabad, India
MRS. K. MYTHILI Associate 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
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