Wind And Seismic Analysis And Design Of Multistoried Building (G+30) By Using Staad Pro

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1 Wind And Seismic Analysis And Design Of Multistoried Building (G+30) By Using Staad Pro V.Rajesh 1, K Jaya Prakash 2 1 PG Scholar, Pydah College of Engineering, Kakinada, AP, India. 2 Assistant Professor, Pydah College of Engineering, Kakinada, AP, India. ABSTRACT In These Modern Days The Buildings Are Made To Fulfill Our Basic Aspects And Better Serviceability. It Is Not An Issue To Construct A Building Any How Its, Important To Construct An Efficient Building Which Will Serve For Many Years Without Showing Any Failure. The Project Titled WIND AND SEISMIC ANALYSIS AND DESIGN OF MULTISTORIED BUILDING (G+30) BY USING STAAD PRO, Aims In Finding Better Technique For Creating Geometry, Defining The Cross Sections For Column And Beam Etc, Creating Specification And Supports (To Define A Support Weather It Is Fixed Or Pinned),Then The Loads Are Defined. After That The Model Is Analyzed By Run Analysis. Then Reviewing (Whether Beam Column Passed In Loads Or Failed) Results. Then The Design Is Performed. INTRODUCTION 1.1 INTRODUCTION: In 21 st century due to huge population the no.of areas in units are decreasing day by day. Few years back the populations were not so vast so they used to stay in Horizontal system(due to large area available per person).but now a day s people preferring Vertical System(high rise building due to shortage of area).in high rise buildings we should concern about all the forces that act on a building,its own weight as well as the soil bearing capacity.for external forces that act on the building the beam, column and reinforcement should be good enough to counteract these forces successfully. And the soil should be good enough to pass the load successfully to the foundation. For loose soil we preferred deep foundation (pile).if we will do so much calculation for a high rise building manually then it will take more time as well as human errors can be occurred. So the use of STAAD-PRO will make it easy. STAAD-PRO can solve typical problem like Static analysis, Seismic analysis and Natural frequency. This type of problem can be solved by STAAD-PRO along with IS-CODE. Moreover STAAD-PRO has a greater advantage than the manual technique as it gives more accurate and precise result than the manual technique. 1.2 STAAD-PRO STAAD-PRO was born giant. It is the most popular software used now days. Basically it is performing design works. There are four steps using STAAD- PRO to reach the goal Prepare the input file Analyze the input file Watch the results and verify them Send the analysis result to steel design or concrete design engines for designing purpose. Prepare the input file First of all we described the structure. In description part we include geometry, the materials, cross sections, the support conditions. Analyze the input file. We should sure that we are using STAAD-PRO syntax. Else it wills error. We should sure that all that we are inputting that will generate a stable structure.else it will show error. At last we should verify our output data to make sure that the input data was given correctly. 2.Watch the results and verify them. Reading the result take place in POST PROCESSING Mode. First we choose the output file that we want to analyze (like various loads or load combination).then it will show the results. 2.1 Send the analysis result to steel design or concrete design engines for designing purpose. If someone wants to do design after analysis then he can ask STAAD-PRO to take the analysis results to be designed as design.the data like Fy mainfc will assign to the view Then adding design beam and design column.running the analysis it will show the full design structure. FORMULATION OF PROBLEM 3.1TYPES OF LOAD USED DEAD LOAD (DL):- All permanent constructions of the structure form the dead loads. The dead load comprises of the weights of walls, partitions floor finishes, false ceilings, false floors and the other permanent constructions in the buildings. The dead load loads may be calculated from the dimensions of various members and their unit weights. the unit weights of plain concrete and reinforced concrete made with sand and gravel or crushed natural stone aggregate may be taken as 24 kn/m and 25 kn/m respectively Page 116

2 3.1.2 LIVE LOAD (LL):- Imposed load is produced by the intended use or occupancy of a building including the weight of movable partitions, distributed and concentrated loads, load due to impact and vibration and dust loads. Imposed loads do not include loads due to wind, seismic activity, snow, and loads imposed due to temperature changes to which the structure will be subjected to, creep and shrinkage of the structure, the3.2.3 WIND LOAD CALCULATION: differential settlements to which the structure may undergo WIND LOAD (WL):- Wind is air in motion relative to the surface of the earth. The primary cause of wind is traced to earth s rotation and differences in terrestrial radiation. The radiation effects are primarily responsible for convection either upwards or downwards. The wind generally blows horizontal to the ground at high wind speeds. Since vertical components of atmospheric motion are relatively small, the term wind denotes almost exclusively the horizontal wind, vertical winds are always identified as such. The wind speeds are assessed with the aid of anemometers or anemographs which are installed at meteorological observatories at heights generally varying from 10 to 30 metres above ground. Risk level SEISMIC LOAD (SL):- SEISMIC LOAD can be calculated taking the view of acceleration response of the ground to the super structure. According to the severity of earthquake intensity they are divided into 4 zones. 1. Zone I and II are combined as zone II. 2. Zone III. 3. Zone IV. 4. Zone V. 3.2 CALCULATION OF LOADS DEAD LOAD CALCULATION: MAIN WALL LOAD (From Above Plinth Area To Below The Roof) Should Be The Cross Sectional Area Of The Wall Multiplied By Unit Weight Of The Brick. (UnitWeight Of Brick Is Taken As 19.2 KN/m 3 ). According To The Is-Code PLINTH LOAD Should Be Half Of The Main Wall Load. Internal Plinth Load Should Be Half Of The Plinth Load. Parapate Load Should Be the Cross Sectional Is Multiplied By Unit Weight. SLAB LOAD Should Be Combination Of Slab Load Plus Floor Finishes. Slab Load Can Be Calculated as the Thickness of Slab Multiplied by Unit Weight of Concrete(According To Is-Code Unit Weight of Concrete Is Taken as25 KN/m 3 ).And Floor Finishes Taken As KN/m LIVE LOAD CALCULATION: o Live Load Is Applied All Over The Super Structure Except The Plinth. Generally Live Load Varies According To The Types Of Building. For Residential Building Live Load Is Taken As 2KN/m 2 on Each Floor And 1.5KN/m 2 on Roof. Negative Sign Indicates Its Acting On Downward Direction. The basic wind speed (V,) for any site shall be obtained from and shall be modified to include the following effects to get design wind velocity at any height (V,) for the chosen structure: Terrain roughness, height and size of structure. Local topography. Risk Coefficient (ki Factor) gives basic wind speeds for terrain Category 2 as applicable at10 m above ground level based on 50 years mean return period. In the design of all buildings and structures, a regional basic wind speed having a mean return period of 50 years shall be used.terrain, Height and Structure Size Factor (k, Factor) Terrain - Selection of terrain categories shall be made with due regard to the effect of obstructions which constitute the ground surface roughness. The terrain category used in the design of a structure may vary depending on the direction of wind under consideration. Wherever sufficient meteorological information is available about the nature of wind direction, the orientation of any building or structure may be suitably planned. Topography (ks Factor) - The basic wind speed Vb takes account of the general level of siteabove sea level. This does not allow for local topographic features such as hills, valleys, cliffs, escarpments, or ridges which can significantly affect wind speed in their vicinity. The effect of topography is to accelerate wind near the summits of hills or crests of cliffs, escarpments or ridges and decelerate the wind in valleys or near the foot of cliff, steep escarpments, or ridges. WIND PRESSURES AND FORCES ON BUILDINGS/STRUCTURES: The wind load on a building shall be calculated for: The building as a whole, Individual structural elements as roofs and walls, and Individual cladding units including glazing and their fixings. Pressure Coefficients - The pressure coefficients are always given for a particular surface orpart of the surface of a building. The wind load acting normal to a surface is obtained by multiplying the area of that surface or its appropriate portion by the pressure coefficient (C,) and the design wind Page 117

3 pressure at the height of the surface from the ground. The average values of these pressure coefficients for some building shapes Average values of pressure coefficients are given for critical wind directions in one or more quadrants. In order to determine the maximum wind load on the building, the total load should be calculated for each of the critical directions shown from all quadrants. Where considerable variation of pressure occurs over a surface, it has been subdivided and mean pressure coefficients given for each of its several parts. Then the wind load, F, acting in a direction normal to the individual structural element or Cladding unit is: F= (Cpe Cpi) A P d Cpe = external pressure coefficient, Cpi = internal pressure- coefficient, A = surface area of structural or cladding unit, and Z=Zone factor given in Table 2, is for the Maximum Considered Earthquake (MCE) and service life of structure in a zone. The factor 2 in the denominator of Z is used so as to reduce the Maximum Considered Earthquake (MCE) zone factor to the factor for Design Basis Earthquake(DBE). For Zone II (Z=0.10 Low Seismic Intensity) For Zone III (Z=0.16 Moderate Seismic Intensity) For Zone IV (Z=0.24Severe Seismic Intensity) For Zone V (Z=.36Very Severe Seismic Intensity) I=Importance factor Important service and community buildings, such as hospitals; schools; monumental structures; emergency buildings like telephone exchange, television stations, radio stations, railway stations, fire station buildings; large community halls like cinemas, assembly halls and subway stations, power stations. (Importance Factors -1.5) All other buildings(importance Factors-1.0) Sa/g=Average Response Acceleration coefficient. R=Response reduction factor. However it should be notice that the ratio of I and R should not be greater than 1. P d = design wind pressure element Fundamental Natural Period SEISMIC LOAD CALCULATION: Design Lateral Force The design lateral force shall first be computed for the building as a whole. This design lateral force shall then be distributed to the various floor levels. The overall design seismic force thus obtained at each floor level shall then be distributed to individual lateral load resisting elements depending on the floor diaphragm action Design Seismic Base Shear The total design lateral force or design seismic base shear (Vb) along any principal direction shall be determined by the following expression: V B = A h W Ah = horizontal acceleration spectrum. W = seismic weight of all the floors The design horizontal seismic coefficient Ah for a structure shall be determined by the following expression: A h = The approximate fundamental natural period of vibration (T,), in seconds, of a moment -resisting frame building without brick in the panels may be estimated by the empirical expression: Ta=0.075 h 0.75 for RC frame building Ta=0.085 h 0.75 for steel frame building h = Height of building, in m. This excludes the basement storeys, where basement walls are connected with the ground floor deck or fitted between the building columns. But it includes the basement storeys, when they are not so connected. The approximate fundamental natural period of vibration (T,), in seconds, of all other buildings, including moment-resisting frame buildings with brick lintel panels, may be estimated by the empirical Expression: T=. Where, h= Height of building d= Base dimension of the building at the plinth level, in m, along the considered direction of the lateral force Distribution of Design Force Page 118

4 Vertical Distribution of Base Shear to Different Floor Level 1.5(DL ± EL) 0.9 DL ± 1.5 EL For wind load analysis of a building the code refers The design base shear (V) shall be following load combination. distributed along the height of the building as per the following expression: Qi=Design lateral force at floor i, Wi=Seismic weight of floor i, hi=height of floor i measured from base, n=number of storeys in the building is the number of levels at which the masses are located.distribution of Horizontal Design Lateral Force to Different Lateral Force Resisting Elements In case of buildings whose floors are 3.4 DL +LL DL+WL DL+0.8LL+0.8WL Both WL and EL are applied in X and Z direction. These loads are also applied further in negative X and Z direction. So for Seismic analysis there are 18 load combinations and for Wind load analysis there are 11 load combinations. REINFORCED CEMENT CONCRETE: capable of providing rigid horizontal diaphragm Generally concretes are strong in action, the total shear in any horizontal plane shall be compression and very negligible respond (almost distributed to the various vertical elements of lateral zero) to the tension. So reinforced (steel bars) are force resisting system, assuming the floors to be provided to resist the tension and to counteract the infinitely rigid in the horizontal plane. moment which can t resist by the concrete. The partial In case of building whose floor diaphragms safety factor for concrete generally taken as 1.5 due to cannot be treated as infinitely rigid in their own plane, non-uniform compaction and inadequate curing and the lateral shear at each floor shall be distributed to the partial safety factor for steel is taken as 1.15.The vertical elements resisting the lateral forces, compressive strength of concrete is always taken as considering the in-plane flexibility of the diagram. because it is always lesser than the cube strength. So Dynamic Analysis for the design work the maximum strength of the concrete is taken as 0.67f ck /1.5=.45f ck and for steel is Dynamic analysis shall be performed to obtain the f y /1.15=.87 f y design seismic Force, and its distribution to different levels along the height of the building and to the various lateral load resisting elements, for the followingbuildings: Regular buildings -Those greater than 40 m in height in ZonesIV and V and those Greaterthan 90 m in height in Zones II and Zones 111. Irregular buildings All framed buildings higher than 12m inzones IV and V and thosegreater than 40m in height in Zones11 and III. The analytical model for dynamic analysis of buildings with unusual configuration should be such that it adequately models the types of irregularities present in the building configuration. Buildings with plan irregularities cannot be modelled for dynamic analysis. For irregular buildings, lesser than 40 m in height in Zones 11and III, dynamic analysis, even though not mandatory, is recommended. Dynamic analysis may be performed either by the Time History Method or by the Response Spectrum Method. However, in either method, the design base shear (VB) shall be compared with a base shear (VB) 3.3 LOAD COMBINTION For seismic load analysis of a building the code refers following load combination. 1.5(DL + IL) 1.2(DL + IL ± EL) BEAM:- Effective depth of a beam is the distance between centroid of area the tension member to the maximum compression member. Generally the span Page 119

5 length to effective depth ratio is taken as followings for different beams. CANTILEVER-7 SIMPLY SUPPORTED-20 CONTINUOUS-26 The Reinforced should be given both transversally and longitudionally.transverse reinforcement is provided to hold the longitudinal bar in its position. Maximum reinforcement for beam shouldn t be more than 6percent. building was made with the combination of seismic load, live load and dead load. And 2 nd 30storey building was made with the combination of wind load, live load and dead load.the Beam and column size of both buildings are same. Internal column size are (0.8m 0.8m).External column size was taken as (.75m.75m).The beam size was taken as (.45m.3m).More internal size was taken because it always taken more load than the external. If greater size will not provide then it will fail in compression FOLLOWINGS ARE THE INPUT DATA, CONCRETEDESIGN, ANDDEFLECTION ANDSHEARBENDING OF A 30STOREYBUILDIGUSING DEAD LOAD, SEISMIC LOAD AND WIND LOAD COMBINATION COLUMN:- The minimum shear reinforcement for a beam should be.75d or 300mm which is lesser. The member who takes compression load is known as column or struct.basically column can be define as Long or Short according to the L and D ratio. If lex /B or l ey /D more than or equal to 12 then that is called long column else short column. Where l ex is the effective length in X-axis. l ey is the effective length in Y-axis. B is the breadth of member. D is the effective depth of member. Generally code permits reinforcement up to 6% in column But in site maximum 2.5% reinforcement are taken. Generally in middle portion of the column more sizes are taken because it took more load than others. 4.Comparison of Two 30-Storey Building 4.1 COMPARISION OF TWO 30-STOREY BUILDING Afterthe basic work is done. Then it was made with two different load combination.1 st 30-storey (A 30 storey building under seismic, live and dead load combination) DATA REQUIRED FOR THE ANALYSIS OF THEFRAME.. Type of structure --> multi-storey fixed jointed plane frame. Seismic zone II (IS 1893 (part 1):2002) Number of stories 30, (G+29) Floor height 3.5 m No of bays and bay length 4nos,5 m each. Imposed load 2 KN/m 2 on each floor and 1.5 KN/m 2 on roof. Materials Concrete (M 35) and Reinforcement (Fe500). Size of column.8m.8m internal column size. Page 120

6 Size of column 75m.75m external column size. Size of beam.45m.45m Depth of slab 125 mm thick. Specific weight of RCC 25KN/m 2. Specific weight of infill 19.2 KN/m 2. Type of soil Medium soil. Response spectra As per IS LOAD DISTRIBUTION BY TRAPEZOIDAL METHOD Seismic Load Effect On Structure In (X+Ve) Seismic Load Effect On Structure In (X-Ve) The Structure Under Dl From Slab The Structure Under Live Load Page 121

7 Seismic Load Effect On Structure In (Z+Ve) Seismic Load Effect On Structure In (Z-Ve) DATA REQUIRED FOR THE ANALYSIS OF THE FRAME.. 1. Type of structure --> multi-storey fixed jointed plane frame. 2. Number of storeys 30, (G+29) No of bays and bay length 4nos, 5 m each. 3. Floor height 3.5 m 4. No of bays and bay length 4nos, 5 m each. 5. Basic wind speed As per IS 875 (PART 3), 50 m/s for CTC. Imposed load 2 KN/m 2 on each floor and 1.5 KN/m 2 on roof. Materials Concrete (M 35) and Reinforcement (Fe500). Size of column.8m.8m internal column size 75m.75m external column size. Size of beam.45m.45m Depth of slab 125 mm thick 45 Specific weight of RCC 25KN/m 3. Specific weight of infill 19.2 KN/m 3 Wind intensity and height As per IS 875 (PART 3), 1.5 KN/m 2 at a height 105 m in CTC STAAD.Pro INPUT COMMAND FILE 1. STAAD SPACE INPUT FILE: WL.STD 2. START JOB INFORMATION 3. ENGINEER DATE 28-NOV END JOB INFORMATION 5. INPUT WIDTH UNIT METER KN 7. JOINT COORDINATES ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; Page 122

8 ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; STAAD SPACE -- PAGE NO. 2 CONCLUSION From the above comparison between two 30- storey building taking same beam and column size using different load combination it was clearly visible that the top beams of a building in wind load combination required more reinforcement than the building under seismic load combination (for example beam no 1951 required 5 no of 20 mmø and 6 no of 20 mmø bars whereas for Seismic load combination it required 13 nos of 10 mmø and 21 nos of 10 mmø).but the deflection and shear bending is more in wind load combination compare to seismic. But in lower beams more reinforcement is required for wind load combination. For column the area of steel and percentage of steel always greater required for wind load combination than the seismic load combination.(example column no 129 A st required for WL combination is 8371 mm 2 and percentage of steel is 1.56 where as for the SL combination A st required is 1911 mm 2 and percentage of steel is 3.43). The deflection value is more in WL combination than the SL combination. REFERENCES 1. IS 875 (Part III for wind load design). 2. IS IS 1893 (for seismic analysis). 4. STAAD-Pro user guide. 5. Earthquake Resistant Design Of Structures By Pankaj Agarwal. Page 123