Authors: Naan Babu Chouhan, Puskar Guha Biswas, Dr. Subash Chandra Bose, Shiva Shankar K M
Certificate: View Certificate
The assignment manages with the Design and Analysis of Corporate Office structure with post-tensioned Slabs. The development has been arranged and taken apart for the customary floor. The drawings and various subtleties are inspected with Structural Consultant concerning National Building Corporation (NBC). Fundamental format is the fundamental piece of primary planning. In aggregates, etc on extra making we used the admixtures and plasticizers, etc. Along these lines, the advancement materials are changing from regular daily existence. In past times, the designs are worked with just ground floor in a manner of speaking. i.e., free house. In this undertaking we have arranged and analyzed constructed Stilt+12 floors and OHT. In different seismic zones to really investigate the changed limits because for deficiency of land and budget of land is profound and other most item is the urbanization, etc. For the improvement of the multi-story structures Offices, as of now a days we are moving to Pre-Tension and Post Tension systems, and variety in cost for regular piece and tensioned techniques chunks.
In the current compositionally world, the "standard shape" essential of precast pretensioned concrete is consistently unreasonable. To meet these compositionally troublesome applications while at this point giving a strong significant development, makers show cast set up improvement.
In current times multi-story high elevations structures are widely built. post tensioned are one of the parts in the construction of buildings. the use post tension slab provides more advantages than the 2-way slab. in this way, the present study aims to comparing numerous features like depth, material quantities, cost for 2-way and post tensioned slabs. a slab of size 24m x 36 m slab is taken from existing building and from that slab, a post-tension panels of size 15.150m x 12.5m is designed different seismic zones to track down the distinction in the base shear and sidelong powers. The Quantities of The Materials Are evaluated and budget of Construction for center and shell are Determined and Related. From The Study It Is Considered That Post Tension Methods are More Reasonable Than traditional technique.
Organogram of the structural materials
A. Principle Of Post-Tensioning
In Post strain, the ligaments are tensioned after the substantial has solidified. Normally metal or plastic channels are set inside the substantial prior to projecting. After the substantial solidified and had sufficient strength, the ligament was set inside the pipe, focused and moored against the substantial. Grout might be infused into the pipe later. This should be possible either as pre-cast or cast set up
B. Post Tensioning Systems
Numerous exclusive post-tensioning frameworks are accessible. A few providers produce frameworks for ligaments made of wires, strands or bars. The most well-known frameworks found in piece and extension development are multi-strand frameworks for extremely durable post-tensioning ligaments and bar frameworks for both brief and long-lasting circumstances.
II. POST-TENSIONING SYSTEM MATERIALS AND COMPONENTS
4. Ducts for Tendons
5. Grouting for Tendons
A. Types Of Slabs Considered For Post-Tensioning
SOLID FLAT SLAB
B. Benefits Of Flat Slab
C. Inconveniences Of Flat Slab
D. Flat Slab With Drop Panels
A. Code books
The analysis will be carried out by using ETABS software to find the steel %, consumption of concrete, displacement, maximum shear, maximum bending moment, Flexural strength.
C. Load calculation
IV. ARCHITECTURAL DRAWINGS
Check for the limits for the Direct Design Method
There are one range toward every path The boards are square with length proportion: 15.150/12.5 = 1.21 < 2.0
There is no counterbalanced section.
There is no distinction in progressive range lengths.
Slabs thickness = 300mm
Dead Load=12kN/m2 WuLL =5.5 x 1.5 = 8.5 kN/m2
Wu LL/Wu DL = 8.5/22 =0.386< 3
Thus O.K Hence all constraints are fulfilled and
Material Properties: M35, M40, Fe550
Unit weight of cement concerning Indian Standard code- 875 (Part1)
Live Load for place of business with reference of Indian Standard code-875 (Part II)
Live Load= 5.5kN/m2 Floor Finish thickness = 100 mm
Unit weight of P.C.C = 24 kN/m2 Reference IS 875 (Part-01)
Complete burden, w = 22 kN/m2 Factored load, wu = 33kN/m2
Post-tensioning strands details:
Extreme Tensile Stresses = 1884 N/mm2
Nominal area of strands = 98.7 mm2
Jacking_force = 75% of the Ultimate_tensile Forces
Extreme_tensile Forces = 186 kN
Planning of inward commonplace segment
Size of Column = 900 x 400 mm
Grade of Concrete, M40 Steel grade, Fe550
A. Load Calculation
Load because of self-weight and Live burden on section of stilt floor to terrace.
Section thickness from piece Ground floor and Terrace=300mm
Pillar size 1200 mm x 600 mm
Pillar thickness in floor Ground floor to Terrace = 0.6 mtr
Live burden for ground to terrace 5kN/m2 Dead burden s + 12 = 0.3 x 25 = 7.5 kN/m2
bar s + 12 =9 kN/m2 Total burden s + 12 = 22 kN/m2
Self-weight of Single section:
1 to 13 = 378 kN
G to 1 = 117 kN
Total =495 Kn
Nos of floors = 12 + stilt
Length along the section =15.15m
Width of the section =12.5m
Stacking to the floors =22kN/m2
Impact region of the section =12.5 x 15.150m Therefore complete burden on the segment is
=12.5 x15.150x13x22 =54161.25kn
By adjusting the structure zone essential breeze speed and force at various level is taken from Indian Standard code-875-1987 (Part-3)
Fundamental Wind Speed 44 m/s
Territory Category 2
Class of Structure A
Width of the structure 24 m
length of the structure 36 m
height of the structure 47m
Zone III SEISMIC ANALYSIS FOR ZONE III
DATAS; Number of Stories = STILT+ 12 Each stories height = 3 m,DL/ unit area of floor = 04 KN/m2 ,Weight of partition on floor = 02 KN/m2, Live load = 03 KN/m2, Roof = 1.51 KN/m2, Building Size = 24 x 36m,column size = 900 x 400 mm, beam size = 600 x 300 mm, solution
Design parameters omrf ( R ) = 3 ,Zone 3 = 0.16
Importance Factor ( I ) = 1 Type of soil = Hard Soil 2.
2. Seismic weight: Floor Area = 24 x 36 =864 m2
Eff weight @ very floor except roof = ( 4 + 2) + (0.25 X 3) = 6.75 KN/m2 ,Weight of beams @ every floor and roof = ( 0.4 x 1.2 x 300 x 25 ) = 3600 KN, Weight of column at each floor = ( 0.9 x 0.4 x 3.0 x 25 x 25.0 ) = 675.0 KN, Weight of the column at roof = 0.5 x 270 = 135.0 KN, Equivalent load at roof level = ( 4 x 864 ) +3600 + 135 = 3519.5 KN ,Equal load at each floor = ( 6.75 x 864 ) +3600 +270 = 9702 KN, Seismic weight of building W = 3519.5 + ( 9702 X 13 ) = 129645 KN.3.
3. Natural period & base shear: Fundamental natural period of vibration of Moment Resisting Frame without infill is;
Ta = 0.075h0.75 h = 13 x 3+8 = 47 m, Ta = 0.075h0.75 Ta = 0.075 x 13 0.75 = 0.513 (Sa / g ) = ( 1/ Ta ) (Sa / g ) = ( 1/ 0.51347 ) = 1.948, FOR ZONE 3 Zone 3 = 0.16 FOR ZONE 1 0.1 Ah = (Z /2) X (I / R) X (Sa / g ) REPLACE VALUE FROM 0.16 TO 0.1, Ah = (0.16 / 2) x (1/3) x 1.9475 = 0.0519 BASE SHEAR AND LATERAL FORCES CHANGES Base Shear Vb = W X Ah Base Shear Vb = 129645 X 0.0519 = 6728.5755 KN.
4. Plan Of A Section
Mx =1751Kn-m,My=850 KN-M
eccentricity=20 mm, Mu (e)=29541 x 0.02 =591.8 kn-m Finally MX =1751KN-M ,MY=850 KN-M Section is 900 x 400 Calculation of pu/fckbd= 29540/40*400*900 1.3 evaluation of p/fck= 1.31/40 = 0.03255
Computation of uni hub second limit of the segment because of accepted rate in x course d/D = (40+16/2)/400 0.12
From Code book SP-16 diagram no 36 pg no 144,
Mux1 = Mu/fckbd2 0.38, Moment conveying limit in y heading is given by the accompanying condition Muy1 = Mu/fckbd2=0.38x40x650x650=5779.8kn-m MX/Mux1 =1750/4924.8 0.355344379 My/Muy1 =850/5779.8 0.147063912 Load conveying limit of the column=? Pux z/ag is determined. ( Pg-no 105 and 71 code is 456) Pu = 20x900x400 = 7200 kn Examination condition: (from code is456 cla39.6 pgno71 ) (MX/Mux1 ) αn + (My/Muy1 )αn αn esteem relies upon the pu/pz values Pu/pz =29540/7200 =4.102, in the event that the worth of αn is under 0.2, αn=1 αn is more prominent than 0.2 then αn=2 Therefore 0.2182 + 0.147 2 = 0.0691<1
5. Plan Of The Normal Balance: Hub load Pu= 29541 kn, Column size 900mm x 400mm ,Safe-bearing limit of the soil= 750 kn/m2, Area of the footing=(load/safe bearing limit of the soil)= 19693.333/750 =26.25771
SI NO :Wi ( KN ) Height greetings ( m ) Wi x hello 2 (Wi x hey 2 )/( εWi x howdy 2 ) Q ( KN ) Vi ( KN ) Mu =0.38x40x900x900x400=4924.8 kn-m = 5.12 m x 5.12 m,Depth of the balance D= 6feet = 1830 mm, d=1830-50-(20/2) =1770 mm.
Nominalshearstress:Tv=vu/bd=14847.19*10^3x1.5/((2(2670+2420)x750.01)) = 1.23,
Admissible pressure: Tc = 0.25 x (square base of fc) = 0.25x ( square foundation of 40) =1.58.Tv < Tc , Hence protected.
6. Plan of post-tensioned section: Area of pre-stressing steel Ap = 1974.5 mm2, effective profundity of segment as for first Layer ligament = 240 mm, Effective profundity of segment as for second Layer ligament = 0,Effective profundity of segment as for third Layer ligament = 0, Effective profundity of segment as for fourth Layer ligament = 0, Effective profundity (d) = 240.0 mm Effective support proportion (Ap x fp/(b x d x fck) = 0.1431
From table ?11 of code Stress in Tendon as an extent of the plan strength ƒpu/(0.87 x fp) = 1.00 fpu = 1618.21 ratio of the profundity of neutral axis to that of the centroid of the ligament in the strain zone xu/d = 0.3031 xu = 161.621 Moment opposing limit of segment by Tendons = 1489.5 kN?m India - USSI default Indian Material*SAVED* Concrete - Spanning Members Top Reinforcement Cover Bottom Reinforcement Cover Reinforcement Provided = 6Y_16+5Y_32 Ast = 5226.5 mm2 Cover to Main Reinforcement = 40 mm Effective profundity to support = 560.5 mm = 1149.5 kn?m Design Moment at basic segment = 1850.5 kn?m Total Flexural limit of segment = 2638.54 kn?m Calculation of stress @ Service:? Area of web = 480000 Y1 = 100 Y2 = 400 Depth of neutral hub from top fiber Yt = 229.54 Depth of Neutral hub from base fiber Yb =370.5 Moment of Inertia of T segment Ixx = Section modulas, Zt = 1E+08 Section modulas, Zb = 9E+07 Eccentricity e = 163.5 mm Available ligament force at administration (first Layer) = 108 kn Available ligament force at administration (second Layer) = 0 kn Available ligament force at administration (third Layer) = 0 kn Available ligament force at administration (fourth Layer) = 0 kN Effective power for every strand = 108.5 kN Total compelling power @ Service P = 2160 kN Moment because of self weight = 705.5 kN?m, Moment because of very forced dead burden = 220 kN?m, Moment because of Live burden = 549.5 kN?m, Secondary Moment = ?358.5 kN?m Moment because of Earthquake load = 0 kN?m, Combination for Limit condition of usefulness = Service Moment = 1116.5 kN?m 1.0 (DL + LL + PT)=33059186651,
Stress due to coordinate prestress = P/A=1.945 and for drop slab=2.3
Stress because of ligament erraticism @ Top fiber = Pe/Zt =2.45 and for drop slab= 2.65
Stress because of ligament flightiness @ Bottom fiber = Pe/Zb =3.96 and for drop slab= 4.15
Stress because of Applied_loads @ Top fiber = M/Zt=7.75 and for drop slab= 7.9
Stress because of Applied_loads @ Bottom fiber = M/Zb =12.51 and for drop piece =12.9
Stress @ outrageous top fiber Ft = ?3.35 N/mm2 and for drop section = - 3.65n/mm2.
Stress @ outrageous base fiber Fb = 10.49 N/mm2 &for drop section = 11.15 n/mm2.
Negative sign indicates Tensile stress
Losses occurred in post tensioning for flat slab and drop slab:
a. Losses happened because of erosion of the ligament in its conduit
b. Losses happened because of immediate distortion of the substantial; coming about out of non-synchronous tensioning of a few ligaments (versatile misfortune).
c. Losses happened because of Anchorage pull-in.
d. Losses happened because of conceded substantial shrinkage.
e. Losses happened because of creep disappointment of cement.
f. Losses happened because of unwinding of Prestressing steel.
V. RATE ANALYSIS
A. Purpose of Rate Analysis
VI. FINAL RESULTS
A. Direct Stress- Flat Slab-1.93, Drop Slab-2.3
Report of direct prestress, tendon eccentricity, applied loads & extreme stresses
Note: For huge corporate and commercial complex, Capitals slabs are much more economical and practically safe with good key factors when compared to all the methods.
VII. FINAL OUTCOME
1) The conventional method is much higher when compared to other methods 2) The Flat slab without drop is much economical when compared to different methods, whereas it shows 10% reduction is cost estimation and expenditure on the project and possess good strength when against conventional method. 3) The Flat slab with drop shows 5% reduction in cost estimation as compared to conventional method. Whereas it can still be more economical by reduction in depth of the slab and providing more spacing between drops c/c. Note: For huge corporate and commercial complex, Capitals slabs are much more economical and practically safe with good key factors when compared to all the methods. VII. FINAL OUTCOME 1) The base shear and lateral forces of PT building with drop is greater than the PT flat slab building, which is safer in the seismic Zones 3,4 & 5. 2) The drop slab building has smaller deflections when compared to all the slabs. 3) The steel consumption in the drop is more when compared to conventional and PT flat slab. 4) The life span of the drop panel slab in greater when compared to PT flat slab and conventional slab. 5) According the graph achieved, the Direct stresses, Tendon eccentricity, applied load and Extreme stresses in more in PT slab with drop as compared to PT Flat slab. 6) The Losses achieved in the graph is less in the PT slab with drop against the PT flat slab. 7) “Economic variation”. 8) By achieving the result, The Flat slab is more economical than the conventional slab and capital slab 9) The consumption of the formwork is less in the flat slab when compared to the capital slab and conventional slab. 10) The consumption of the concrete and steel can be still reduced by decreasing the depth of the slab in the capital PT slab. 11) The more clearance height in between the floor to floor gives the good position, for interior works. 12) Due to post-tensioning of level plate chunk, there is no much impact on hub force except for shear and second on segment increments. 13) The diversion at focus of level plate chunk is controlled more successfully by illustrative and Trapezoidal ligament than three-sided ligament. 14) Post-tensioned plan of level chunk permits almost 30% decrease in steel and 19 % decrease in concrete when contrasted with Reinforced concrete substantial level piece. 15) Result achieved against the PT flat slab allows nearly 17% reduction in formwork when compared to the conventional slab. 16) Result achieved that the consumption of concrete, formwork and reinforcement is merely same when compared both PT Flat slab and PT flat slab with drop panel.
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Copyright © 2022 Naan Babu Chouhan, Puskar Guha Biswas, Dr. Subash Chandra Bose, Shiva Shankar K M . This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.