2. structure report

8/16/2019 2. Structure Report

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1. INTRODUCTION

The purpose of this report is to summarize design assumption, methodology and follow up of codes and

standards, the design criteria and practices that have been used in structural calculation of the proposed

Official Building of District Technical Office at Doti, Doti. These criteria form the basis of the design for

various structural components of the building.

The basic aim of the structural design is to build a structure safe and fulfilling the intended purpose during

the life span as well as economic in terms of initial and maintenance cost. A building is structurally sound if

the individual elements satisfy the criteria for strength, stability and serviceability and in the seismic area

additional criteria for ductility and energy absorption capacity. The strength criterion is valid for all loads

that will normally be applied to the building during the life time. The concern for overcoming the accidents,

overloading and disasters are needed for a building is necessary though they are not related to the design

directly.

Since Nepal lies in seismically vulnerable zone, and Kathmandu is very much prone to the disaster, the

concept of seismic design is very necessary in building new constructions. According to the philosophy of

seismic design, the structure shall resist minor earthquakes without damage, resist moderate earthquake

with minor structural damages and resist major catastrophic earthquakes without collapse. The structure has

to be ductile and capable of dissipating energy through inelastic actions. Ductility can be achieved by

avoiding brittle modes of failures. Brittle modes of failures include shear and bond failure which concludes

that the structure is designed on Weak Beam Strong Column Philosophy.

The design report includes five sections in which, Section-01 is the introductory section. Section-02 will

summarize the applicable codes and standards followed in structural calculation. Section-03 for soil report

& section-04 deals with the general design criteria and working methodology, the assumptions in load

calculation both for dead load live load and seismic load. Section-05 is the main section which describes the

details of structural calculation of these buildings.

1.1. Building Parameters

Building Description

The Building is three and half storied. The floor to floor height is 10’-6” and the total height from ground

level is 45’-6” whereas the maximum length of the building is 43’-9” and the breadth is 43’-6”.

Location

The building shall be built at Doti, Doti and inspecting the neighborhood, the soil is medium type with no

presence of Black Cotton Soil and the terrain is slight sloppy.

Structural System


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The structure has been designed with Ductile Moment Resisting Reinforced Concrete Frame without

masonry infill wall as per to meet the functional, architectural and economic considerations for aesthetic

building.

Frame System

The structure has three frames in Longitudinal and two frames in transverse direction. To strengthen the

rigidity of the building, the columns have been placed with long side in transverse direction which shall

counteract the lower rigidity at the transverse side of the building. The external walls are 9” and the

partition walls are 4” thick which has been considered as non-load bearing partition walls.

2. DESIGN CODES AND STANDARDS

The structural calculation of this building shall be in accordance with all applicable laws and regulations of

the Government of Nepal, and its referral to any other standards. A summary of the codes and standards

used in structural analysis and design have been listed as below.

Design of Earthquake Resisting Building, Reinforced Concrete Masonry, NBC105

IS:875-1987 (Part 1) , Code of Practice for Design Loads in Building and Structure-Dead loads,

Bureau of Indian Standards, New Delhi,1989

IS:875-1987 (Part 2) , Code of Practice for design loads in Building and Structure-Dead loads,

Bureau of Indian Standards, New Delhi,1989

IS:1893- (Part I)-2002, Criteria for Earthquake Resistant Design structure, Bureau of Indian

standards, New Delhi,1986

IS 456:2000, Plain and Reinforced Concrete- Code of Practice, Bureau of Indian Standards, New

Delhi, 2001

IS 13920:1993, Ductility Detailing of Reinforced Concrete Structures subjected to Seismic Forces-

Code of Practice, Bureau of Indian Standards, New Delhi, 2002

IS 2950 (Part I) -1981, Code of Practice for Design and Construction of Raft Foundations, Bureau of

Indian Standards, New Delhi, 1998

3. SOIL REPORT

As per the Geotechnical investigation at site, the allowable bearing capacity of soil was taken the minimum

value which is 150 KN/m2.


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4. GENERAL DESIGN CRITERIA

4.1. Design Loads

Design loads for all structures have been in accordance to the criteria described below.

4.1.1. Dead Loads:

The structure has been designed considering following dead loads:

4.1.2. Live Loads

The considered live loads on floor at various locations are as followings:

4.1.3. Seismic load:

The site location is on high seismic risk as per seismic hazard map of Nepal. LINEAR STATIC

OR SEISMIC COFFICIENT METHOD has been adopted in earthquake load estimation and

distribution. The seismic forces determined by seismic analysis are directly applied at the special joints

Average load of 9” partition wall on all

frame in floors without openings = 15 KN/m

Average load of 9” partition wall on allframe in floors with openings = 12.5 KN/m

Average load of 4” partition wall on allframe in floors = 7 KN/m

Average load of 4” parapet wall = 3.5 KN/m

(NOTE: Dead load of slabs ,beams, columns all are program calculated as perassignment)

UNIT WEIGHT (MATERIAL)

Reinforced concrete = 25 KN/m3

Steel = 78.5 KN/m3

Brick Masonry = 23.5 KN/m3

Unit weight of soil = 17 KN/m3

Staircase, lobby areas = 4.0 KN/m2

Rooms = 3.0 KN/m2

Imposed load = 3.0 KN/m2

In other areas where uses not identified = 3.0 KN/m2


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created at the center of mass of each floor level. The program calculates the center of stiffness of the

structure and the Torsion is accepted automatically by the program which results in no extra

calculations to carry out the forces due to torsion.

For calculation of the Base Shear, the Building has been classified as Residential Building with

Importance factor of unity as well as the Performance factor of unity as per Clause 8.1.8 of NBC 105.

The zoning factor has been accepted unity as per NBC 105 and the sub soil category is Type II

(Medium Soil).

4.1.4. Load Combinations

The design loads including earthquake for the Limit State Method shall be not less than whichever of

the following load combination gives the greatest effect (NBC105:1994) :

DL + 1.3 LL + 1.25 E

0.9 DL + 1.25 E

DL + 1.25 E (without considering snow load)

1.5 DL + 1.5 LL

Which can been expressed as follows

4.1.5. Allowable Stresses

Each load combination shall not exceed the allowable stress permitted by the appropriate code for that

combination. The IS 1893-(Part-I) 2002 allows a 33% stress increase for seismic and wind design in

which specifies loading combinations to be used for the design of structures and portions thereof when

using the allowable stress design method. These combinations are permitted a one-third increase in

allowable stresses for all combinations including wind or seismic. In foundation design, the allowable bearing capacity could be increased by 33% on the permissible bearing capacity of soil where seismic

or wind load action. In NBC 105:1994, up to 50% increase in the allowable bearing capacity could be

DL+1.3LL+1.25EQx

DL+1.3LL-1.25EQx

Dl+1.3LL+1.25EQy

DL+1.3LL-1.25EQy

0.9DL+1.25EQx

0.9DL-1.25EQx

0.9DL+1.25EQy

0.9DL-1.25Eqy

DL+1.25EQx

DL-1.25EQx

DL+1.25EQy

DL-1.25EQy

1.5 DL + 1.5 LL


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made whenever earthquake load is considered. In foundation design, we have assumed 33% increase

in the allowable bearing capacity of the soil.

4.1.6. MaterialsThe materials described below will be specified and used as a basis for design.

Reinforcing Steel - Reinforcing steel shall meet the requirements of Grade-Fe500.

Cement - Cement used in all concrete mixes will be Portland cement meeting the requirements of IS

standard

Aggregate - Fine aggregates will be clean natural sand. Coarse aggregates will be crushed gravel or

stone. All aggregates shall meet the requirements of IS Code

4.1.7. Design Strengths

The system of concrete and steel reinforcing strength combinations will be used as follows.

Concrete grade, f ck = 25 N/mm2

Reinforcing steel, Fe500 (elongation >14.5%)

Modulus of elastic for steel, Es=200 KN/mm2

Modulus of elastic concrete, E c =5700 (f ck ) KN/mm2

4.1.8. Design Seismic Forces

The computation of horizontal forces and the distribution has been carried out as per clause 8.1.1 and10 of NBC 105:1994.

The horizontal seismic shear force at the base of the structure is given by

V=Cd Wt

Where, Cd is horizontal seismic force coefficient

Cd= CZIK

The horizontal seismic force is distributed at each level I according to the following equation

Fi=V Wi hi /(∑ Wi hi)

For Subsoil Type III, Period of Vibration T=0.06 H3/4

=0.06 x13.893/4

=0.43

From Fig 8.1 from National Building Code, Basic Seismic Coefficient C= 0.08

Seismic Zoning Factor Z= 1.1, for Dipayal

Importance Factor I =1.5 for Essential facilities that should remain functional after an earthquake and

Structural Performance Factor K = 1

Hence, the design horizontal seismic force coefficient Cd = 0.132


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5. STRUCTURAL ANALYSIS & DESIGN

5.1. Structural Analysis by Software:

5.1.1. General :

Structural analysis of this building has been made by SAP2000 Software, produced by CSI,

California Berkeley.

3-Dimensional model has been prepared with the dimension which is shown in the drawings.

No provisional floor for vertical expansion has been considered in the analysis.

The floor diaphragms are assumed to be rigid.

The main beams rest centrally on columns to avoid local eccentricity

For all structural elements, M25 grade concrete will be used. Sizes of all columns in upper floors are

kept the same; however, for columns up to plinth, sizes are increased.

Centre-line dimensions are followed for analysis and design.

Preliminary sizes of structural components are assumed by experience.

For analysis purpose, the beams are assumed to be rectangular so as to distribute slightly larger

moment in columns.

Seismic loads will be considered acting in the horizontal direction (along either of the two principal

directions) and not along the vertical direction, since it is not considered to be significant.

The design seismic force has been applied and automatically distributed by the software at various

floor levels.

The live load has been reduced by 25% for mass source by load.

5.1.2. Modeling

Total weight of Structure: 3543.87 KN

Horizontal Base shear at Plinth level max: 467.79 KN

Fundamental Time period considered: 0.43 sec

Top storey deflection: 37.4 mm

Storey drift: 0.36 mm/m


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5.1.3. Load Combination Definition

Following are the combination definition considered in the structural design of this building

Combo

Name Combo Type Case Type

Case

Name Scale Factor

Steel

Design

Concrete

Design

Alum

Design Cold Design

COMB1 Linear Add Linear Static DL 1.5 No Yes No No

COMB1 Linear Static LL 1.5

COMB2 Linear Add Linear Static LL 1.3 No Yes No No

COMB2 Linear Static DL 1

COMB2 Linear Static EQx 1.25

COMB3 Linear Add Linear Static LL 1.3 No Yes No No

COMB3 Linear Static EQx -1.25

COMB3 Linear Static DL 1

COMB4 Linear Add Linear Static DL 1 No Yes No No


COMB4 Linear Static EQy 1.25

COMB5 Linear Add Linear Static DL 1 No Yes No No


COMB5 Linear Static EQy -1.25

COMB6 Linear Add Linear Static EQx 1.25 No Yes No No

COMB6 Linear Static DL 0.9

COMB7 Linear Add Linear Static EQy -1.25 No Yes No No


COMB8 Linear Add Linear Static DL 0.9 No Yes No No

COMB8 Linear Static EQy 1.25



COMB10 Linear Add Linear Static EQx 1.25 No Yes No No


COMB11 Linear Add Linear Static EQx -1.25 No Yes No No


COMB12 Linear Add Linear Static EQy 1.25 No Yes No No





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5.2. Structural Analysis on SAP

a) 3-D Modeling:

FEM modeling on software has been made considering all slab element as shell.


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b) Base Reactions:

The dead load live load and the calculated seismic force has been provided directly to the

software, which gives the following base reaction:

TABLE: Base Reactions

OutputCase StepType GlobalFX GlobalFY GlobalFZ GlobalMX GlobalMY GlobalMZ

Text Text KN KN KN KN-m KN-m KN-m

1.5 ll+dl 0.00 0.00 13951.74 84023.11 -103483.15 0.00

dl+1.3ll+1.25eqx -1368.59 0.00 9703.83 58628.96 -84164.40 8158.54

dl+1.3ll-1.25eqx 1368.59 0.00 9703.83 58628.96 -59461.57 -8158.54

dl+1.3ll+1.25eqy 0.00 -1368.59 9703.83 70980.38 -71812.99 -10900.08

dl+1.3ll-1.25eqy 0.00 1368.59 9703.83 46277.55 -71812.99 10900.08

0.9dl+1.25eqx -1368.59 0.00 7163.03 42573.20 -65968.64 8158.540.9dl-1.25eqx 1368.59 0.00 7163.03 42573.20 -41265.81 -8158.54

0.9dl-1.25eqy 0.00 1368.59 7163.03 30221.79 -53617.22 10900.08

0.9dl+1.25eqy 0.00 -1368.59 7163.03 54924.62 -53617.22 -10900.08

envelop Max 1368.59 1368.59 13951.74 84023.11 -41265.81 10900.08

envelop Min -1368.59 -1368.59 7163.03 30221.79 -103483.15 -10900.08

dl 0.00 0.00 3543.88 22364.20 -24853.09 0.00

dl+ll 0.00 0.00 9301.16 56015.41 -68988.76 0.00

dl+1.25eqx -1368.59 0.00 7958.92 47303.56 -71926.11 8158.54

dl-1.25eqx 1368.59 0.00 7958.92 47303.56 -47223.28 -8158.54

dl-1.25eqy 0.00 1368.59 7958.92 34952.14 -59574.69 10900.08

dl+1.25eqy 0.00 -1368.59 7958.92 59654.97 -59574.69 -10900.08


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c) Frame Assign diagram.

The frame has been assigned at previous material setup in following pattern.

Frame at Ground Floor Plan


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Frame at Grid 3


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Frame at Grid C


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d) Bending moment diagram.

The bending moment and shear force diagram for the selected most critical frame has been

presented as below.

BMD at Grid C


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SFD at Grid C


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SFD at Grid 3


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BMD at Grid 3


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5.3. Structural Design:

The structural design of all beams and columns has been made as per IS: 456-2000, using SAP 2000

software on LIMIT STATE METHOD of design.

Rebar for Column and Beam at Grid 3


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Rebar for Column and Beam at Grid C


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Rebar for Beam at First Floor Slab


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Rebar for Beam at Second Floor Slab


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Table: Column and Beam Design

The Column Design Details are shown in following table.

TABLE: Concrete Design 1 - Column Summary Data - Indian IS 456-2000

Frame DesignSect DesignType Location PMMCombo PMMArea VMajRebar VMinRebar ErrMsg

Text Text Text mm Text mm2 mm2/mm mm2/mm Text

244 col 15x15 Column 0 dl+1.3ll-1.25eqx 3673.125 0.422 0.422 No Messages

244 col 15x15 Column 1600.2 dl+1.25eqy 1161.288 0.422 0.422 No Messages

244 col 15x15 Column 3200.4 0.9dl+1.25eqx 3135.426 0.422 0.422 No Messages

245 col 15x15 Column 0 dl+1.3ll-1.25eqy 4466.39 0.422 0.422 No Messages


245 col 15x15 Column 3200.4 dl+1.3ll-1.25eqy 3484.22 0.422 0.422 No Messages



246 col 15x15 Column 3200.4 dl+1.3ll-1.25eqy 2872.326 0.422 0.422 No Messages247 col 15x15 Column 0 dl+1.3ll-1.25eqx 3386.196 0.422 0.422 No Messages


247 col 15x15 Column 3200.4 dl+1.3ll-1.25eqx 2532.243 0.422 0.422 No Messages




249 col 15x15 Column 0 dl+1.3ll+1.25eqy 5071.513 0.422 0.422 No Messages

249 col 15x15 Column 1600.2 1.5 ll+dl 1271.162 0.422 0.422 No Messages

249 col 15x15 Column 3200.4 dl+1.3ll+1.25eqy 4119.426 0.422 0.422 No Messages









252 col 15x15 Column 3200.4 dl+1.3ll+1.25eqx 3616.065 0.422 0.422 No Messages













257 col 15x15 Column 0 dl+1.3ll+1.25eqy 4680.153 0.422 0.422 No Messages257 col 15x15 Column 1600.2 dl+1.25eqy 1161.288 0.422 0.422 No Messages




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258 col 15x15 Column 1600.2 dl+1.25eqy 1161.288 0.422 0.422 No Messages258 col 15x15 Column 3200.4 dl+1.3ll+1.25eqy 3583.857 0.422 0.422 No Messages

288 col 15x15 Column 0 0.9dl+1.25eqx 2629.209 0.422 0.422 No Messages
























296 col 15x15 Column 0 dl+1.3ll+1.25eqx 3565.286 0.422 0.422 No Messages





297 col 15x15 Column 3200.4 dl+1.3ll+1.25eqy 4043.422 0.422 0.422 No Messages298 col 15x15 Column 0 dl+1.3ll+1.25eqy 4146.173 0.422 0.422 No Messages














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302 col 15x15 Column 1600.2 dl+1.25eqy 1161.288 0.422 0.422 No Messages302 col 15x15 Column 3200.4 dl+1.3ll-1.25eqy 3083.501 0.422 0.422 No Messages

331 col 15x15 Column 0 0.9dl-1.25eqx 1669.496 0.422 0.422 No Messages



332 col 15x15 Column 0 0.9dl-1.25eqx 1861.885 0.422 0.422 No Messages


332 col 15x15 Column 3200.4 0.9dl-1.25eqx 2080.669 0.422 0.422 No Messages

333 col 15x15 Column 0 0.9dl-1.25eqy 1265.823 0.422 0.422 No Messages























340 col 15x15 Column 3200.4 dl+1.3ll+1.25eqy 2641.062 0.422 0.422 No Messages341 col 15x15 Column 0 dl+1.3ll+1.25eqy 2890.538 0.422 0.422 No Messages













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The Beam Design Details are shown in following table.

TABLE: Concrete Design 2 - Beam Summary Data - Indian IS 456-2000

Frame DesignSect Location FTopCombo FTopArea FBotArea VRebar TTrnRebar ErrMsg

Text Text mm Text mm2 mm2 mm2/mm mm2/mm Text

217 beam 12x18 0 dl+1.3ll-1.25eqy 658.876 348.737 0.7 0.608 No Messages

217 beam 12x18 457.2 dl-1.25eqy 334.451 334.451 0.758 0.552 No Messages




217 beam 12x18 1828.8 dl+1.25eqy 334.451 334.451 0.338 0.321 No Messages


217 beam 12x18 2286 dl+1.25eqy 334.451 334.451 0.338 0.294 No Messages



217 beam 12x18 3200.4 dl+1.3ll+1.25eqy 381.767 362.725 0.741 0.533 No Messages




218 beam 12x18 762 dl-1.25eqy 334.451 334.451 1.008 0.622 No Messages






218 beam 12x18 2286 dl+1.3ll+1.25eqy 371.413 334.451 0.71 0.681 No Messages











219 beam 12x18 3048 0.9dl+1.25eqy 334.451 334.451 0.338 0.304 No Messages






220 beam 12x18 457.2 dl+1.3ll-1.25eqy 373.844 334.451 0.979 0.817 No Messages







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220 beam 12x18 2286 dl+1.25eqy 334.451 334.451 0.407 0.456 No Messages220 beam 12x18 2743.2 dl+1.3ll+1.25eqy 402.015 414.526 0.45 0.528 No Messages






























223 beam 12x18 914.4 dl-1.25eqy 334.451 334.451 0.918 0.744 No Messages223 beam 12x18 914.4 dl+1.3ll-1.25eqy 380.439 334.451 0.566 0.608 No Messages










224 beam 12x18 609.6 0.9dl-1.25eqy 785.128 851.025 1.138 0.768 No Messages




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224 beam 12x18 2438.4 dl+1.3ll+1.25eqy 651.906 584.988 1.241 0.889 No Messages224 beam 12x18 3048 dl+1.3ll+1.25eqy 1421.824 942.629 1.237 1.038 No Messages




225 beam 12x18 1219.2 0.9dl-1.25eqy 397.494 432.794 0.508 0.491 No Messages





















227 beam 12x18 0 dl+1.3ll-1.25eqx 898.127 875.354 0.816 0.866 No Messages

227 beam 12x18 381 0.9dl-1.25eqx 467.029 505.94 0.911 0.841 No Messages


227 beam 12x18 762 0.9dl-1.25eqx 448.281 509.64 0.644 0.775 No Messages


227 beam 12x18 1524 dl+1.25eqy 334.451 334.451 0.747 0.813 No Messages227 beam 12x18 1524 dl-1.25eqy 334.451 334.451 0.783 0.838 No Messages


227 beam 12x18 2286 dl+1.3ll+1.25eqx 507.477 419.028 0.833 0.936 No Messages




228 beam 12x18 0 dl-1.25eqx 863.935 613.014 0.483 0.294 No Messages

228 beam 12x18 609.6 dl-1.25eqx 497.705 465.836 0.523 0.294 No Messages


228 beam 12x18 1828.8 0.9dl-1.25eqx 334.451 334.451 0.433 0.294 No Messages


228 beam 12x18 3048 dl+1.25eqx 334.451 340.807 0.478 0.294 No Messages

228 beam 12x18 3657.6 dl+1.3ll+1.25eqx 435.644 458.31 0.518 0.296 No Messages


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Slab Design:

The design of slab is also illustrated as follows.

Slab Design

Load Calculation

Slab Design material Thickness Density Load kn/m^2

Slab Length 4878 Marble 0.016 26.7 0.4272

Slab width 4878 Screed 0.025 22 0.55

Slab 0.125 25 3.125

Provided depth 125 Plaster 0.012 20 0.24

Cover 20 Partition 1

Effective depth 105 Live load 4

Total 9.3422

Design L 14.0133

Fy 500 Conc_str 25

Ly/Lx 1alpha BM=alpha*W*lx^2 Ast/m

Short Negative 0.037 12.33745937 286

Short Posetive 0.028 9.336455743 628

Long Neg 0.037 12.33745937 286

Long Pos 0.028 9.336455743 213

Effective Depth of slab 60 mm

Provided effective depth 105 mm

Area of Steel at short span 1042.759

0.02000 -100 28361.98 4698.16

301.84Req Reinforcement for Short-

Sagging moment Ast provided Percentage

Moment 12.33746 301.8414021 628.3185 0.598399 0.002875

Basic L/d 23

Prov L/d Slab 140) 46.45714

Thickness mod Factor 2.019876

Fs 139.3147 Mod fact 2.081618

provide 10mm dia @ 6"c/c Ast = 628.3185

10 125 78.53981634

The code requires the minimum area of the steel is 12%

150 mm < 628.32 mm provided

Req Reinforcement for long-Sagging moment Ast provided Percentage

Moment 9.336456 213.0569726 502.6548 0.478719 0.002029

Basic L/d 23

Prov L/d Slab 140) 46.45714

Thickness mod Factor 2.019876

Fs 122.9204 Mod fact 2.359251

provide 10mm dia @ 6"c/c Ast = 502.6548

8 100 50.26548246

Curtail alternate bars at 1/10th oof effective span in each direction . Provide 50 % of max positive steel at to near

supports to resist bending moment due to partial fixity.

Check for shea force at short edges.

Max shear orce intensity in either direction can be taken as 1/2 * w *Lx

Max shear force = 34.17844 kN/m

Nominal shear stress v = 0.326 N/mm2

As for short span 50.265 251.327 mm2


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Percent tension steel

0.24 %

Shear strength of M 25 concrete for 0.24 % steel

c = 0.353 N/mm2

Shear strength in slabs = k* = 0.458 N/mm2 > v OK

Summary

thickness 125 mm

cover 15 mm

Steel short 10 mm φ @ 5 inch c/c

Steel long 8 mm φ @ 4 inch c/c

5.4. Column Design

SNColumn

IDColumn Size

Column

Position

Design RebarValue

mm2

Applied ReinforcementApplied Rebar

Value

mm2

Remarks

1 C3 15"x15" B1 3673 12 no 20 dia 3769.91

2 C2 15"x15"

C1 4466 4 nos 25 dia +8 no 20 dia 4476.77

3 C2 15"x15"

D1 4554 4 nos 25 dia +8 no 20 dia 4476.77

4 C3 15"x15" A2 3386 12 no 20 dia 3769.91

5 C2 15"x15"

B2 4308 4 nos 25 dia +8 no 20 dia 4476.77

6 C1 15"x15" C2 5072 8 nos 25 dia +4 no 20 dia 5183.63

7 C1 15"x15" D2 5264 8 nos 25 dia +4 no 20 dia 5183.63

8 C3 15"x15"

A3 3703 12 no 20 dia 3769.91

9 C2 15"x15" B3 4327 4 nos 25 dia +8 no 20 dia 4476.77

10 C1 15"x15"

C3 4864 8 nos 25 dia +4 no 20 dia 5183.63

11 C1 15"x15" D3 5228 8 nos 25 dia +4 no 20 dia 5183.63

8 C3 15"x15"

A4 3106 12 no 20 dia 3769.91

9 C3 15"x15" B4 3777 12 no 20 dia 3769.91

10 C2 15"x15" C4 4680 4 nos 25 dia +8 no 20 dia 4476.77

11 C1 15"x15"

D4 5008 8 nos 25 dia +4 no 20 dia 5183.63


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5.5. Foundation:

Base Reaction for Footing Design at Ground Floor

The design of isolated foundations is done by manual calculation on the spread sheet.

The isolated footing is designed as per book “Analysis and Design of Substructure” by Swami Sarantaking following data as per spreadsheet.

Checking for two way punching shear for critical perimeter at d/2 away from the face of column isdone and finally, the requirement for shear reinforcement is checked .


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5.6. Design of foundation

Frame-C2 of SAP model Comb-1

Proportioning of Foundation

Column Load(v)= 997.00 Kn

Moment (Mx)= 1.500 Kn.m

Moment (My)= 188.000 Kn.m

Eccentrticity of load (e)= 0.190

Wt. of Foundation is 10% of column load= 98.700 Kn L3 L C

Total load (V) = 1085.7 Kn 1085.700 1240.8 150.00

Allowable Bearing capacity of soil is= 150.00 Kn/m2 7.238 8.272 1

1 -7.238 -8.272

L= 2.92

The Size of foundation is 2.92x2.92 m adopted for design. This may be shown that this size is also adequate form shear failure and settlement considera

Column Size L= 0.380

B= 0.380

Length of Footing = 2.92 m along the longer length of column i.e alonyg X-Di

Bredth of Footing = 2.92 m

along the shorter length of column i.e alonyg Y-

Direction

Depth of Footing

for d= 450

Punching Shear Stress = 0.990963855

Factor Bearing Pressure= 173.637 Kn/m2

0.174 N/mm2

Assume percent of Reinforcement p= 0.15 %

Grade of Concrete f ck = 25 N/mm2

Grade of Steel, f y = 500 N/mm2

for 0.2% steel with M25 concrete from Table 19 of IS 456 gives

Design shear strength of concrete,τc= 0.325 N/mm

2

From the condition that the one-way shear resistance ≥ one-way shear force,we have at a distance d from the face of the column

τc *bd ≥ P

P= 987.000

d= 1.040 ≈ 1.040 m

Column /Pedestal

Unit weight of Soil 19 Kn/m3

Unit weight of Concrete 25 Kn/m3

Foot length (L,dim||Xaxis )= 2.92 m

Foot Breadth (B,dim|| Y axis)= 2.92 m

Thickness of footing (t)= 1.10 m

Clear cover to Reinforcement = 75.00 mm

Main bar dia.of footing = 20.00 mm

Effective depth of footing = 1015.0 mm

Selfweight of footing= 234.476 Kn

Weight of Soil above Footing 64.801 for 1.5 m Depth

Total Weight (V) 1286.277

Area of Footing (A)= 8.526 m2

Sect. Modulus of Foot about X axis(Zx)= 4.150 m3

Sect. Modulus of Foot about Y axis(Zy)= 4.150 m3

Gross Bearing capacity

196.526 Kn.m > 199.5 Kn/m2 Safe

105.190 Kn.m

105.190 Kn.m

196.526

Kn.m

Now for Depth calculation

aq

L

e

A

V

6

1

y Z

y M

x Z

x M

A

V P 2,1

'


31/34

- 31 -

From the condition that the one-way shear resistance ≥ one-way shear force,we have at a distance d from the face of the column

τc *bd ≥ P 1.224 2.9

0.28(2.13*1000)d≥ 1286.277

d= 1.355 ≈ 1.4 m

Assume a thickness D= 1400.0 mm, uptodistance of =2400-75-10,d= 1315 mm

d= 1320 mm

Column Size L= 0.380

B= 0.380

Maximum bending moment

Max. Bearing pressure at distance X-X 156.801 Kn/m2

39.725 Kn/m2

Mxx = 214.14*2.6*1.95*1.95/2+1/2*23.471*2.6*1.95*(2/3)*1.95

431.605 Kn.m

??? (Lx-

cx)/2

431604513.733 N.mm

Max. Bearing pressure at distance Y-Y 156.801 Kn/m2

39.725 Kn/m2

Myy= 182.622*3.5*1.45*1.45*1/2+1/2*54.989*3.5*1.45*(2/3)*1.45

728.528 Kn.m

728528296.012 N.mm

d= 360.29 mm

d= 370 mm

D= 550 mm

Depth is

Ok

Hence this Depth is now corrected to 550 mm

Now,

Foot length (L,dim||Xaxis )= 2.920 m

Foot Breadth (B,dim|| Y axis)= 2.920 m

Thickness of footing (t)= 0.55 m

Clear cover to Reinforcement = 75.0 mm

Main bar dia.of footing = 20.0 mm

Effective depth of footing = 470.0 mm 0.47 m

Selfweight of footing= 117.238 Kn

Weight of Soil above Footing 153.902

Total Weight (V) 1258.140

Area of Footing (A)= 8.526 m2

Sect. Modulus of Foot about X axis(Zx)= 4.150 m3

Sect. Modulus of Foot about Y axis(Zy)= 4.150 m3

Gross Bearing capacity

193.226 Kn/m2

199.5

Kn/m2 Safe

101.890 Kn/m2

101.890 Kn/m2

193.226

Kn/m2

Ast 2345.066 mm2

Provide 16Φ @75 mm center to center mm2

16

75 2680.83 mm3

Ast 4379.544 mm2

Provide 16Φ @75 mm center to center 2680.8 mm2

Provide 1927.2 mm2 along breadth

2133.0 bd

ck f

xx M

y

Z

y M

x

Z

x M

A

V P 2,1

'

'87.0

bck

f

st A

y f

d st

A y

f xx

M

'87.0

bck f

st A

y f

d st

A y

f yy

M


32/34

- 32 -

Top bar of

Provide 16Φ @75 mm center to center 2680.8 mm

pt 0.1953

Providing a uniform thicness of 530 mm for the footing slab is rather uneconomical,such a high thickness is reqired essentially

near the face of the column(due to shear consideration);the effective depth requirement falls of the column (due to shear considerations);the effective depth requirement falls off with increasing distance from the critical section for one-way shear;theoritically,only a minimum thickness

(150 mm,specified by the code) need be provided at the edge of footing.

However,the slope provided at the top of the footing should preferably not exceed about 1:5,as a steeper slope will require the use of additional form

(to prevent the concrete from sliding down)

As the thicness of the footing near the column base is governed by shear (one-way shear)and the effective area aviable at critical section is

is truncated rectancle,the effective depth required is slightly larger han that for a flat footing.

As the thicness of Slab is D= 550 mm, d=470 mm , providing a slope of 1:5 over the remaining distance of over the remaining distance of

along

breadth 800.0 mm

along

length 800.0 mm

Check for one Way shear :

Critical section of is at distance d from edge of columnShear force at Distance of critical sec.from edge of footing = 168.2 Kn/m2

Shear force Vu1=Pemax × 2.92 × 800.0 392.92 Kn

Percentage of Tension Reinforcement 0.195

For M25 Concrete,τc = 0.322 N/mm2

Vuc 441.552

Vu1 < Vuc

Ok

Safe

Critical section of one way shear is at distance 'd' from edge of column

Shear force at Distance of critical sec.from edge of footing = 168.203 Kn/m2

Shear force Vu1=Pemax × 2.92 × 800.0 392.921 Kn

Shear Stress

Percentage of Tension Reinforcement 0.195

For M25 Concrete,τc = 0.332 N/mm

2

(from table 19 IS 456-2000)Vuc 455.055

Vu1 < Vuc

Ok

Safe

Critical section of two way shear is at distance 'd/2' from edge of column

Allowable shear stress τallowable = Ksτc Ks = 0.5βc

(Cl. 31.6.3 IS 456-

2000)

βc = 1.0 βc = the ratio of short side to long side of Column

Ks= 1.0 >1 so

τc= 1.25 N/mm2

τallowable = 1.25 N/mm2

Vuc 1997.50 Kn

Shear Stress at d/2 distance from edge of column= 160.852 Kn/m2 Vu2 = 1025.141 Kn

Vuc> Vu2

Ok

Safe

Transfer of Force at Column Base

Compressive Force, (P) 987.00

Loaded area at the column

base 144400.00 mm2

Supporting area for bearing of footing which one is at slope at rate of

2:01

Spread along the length of upto effective depth 2260.00 mm

Spread along the bredth of upto effective depth 2260.00 mm

Supporting area for bearing A1 5107600.00 mm2

5.95

But as per clause 34.4 0f IS 456 2.0

ck f

c 25.0

2

145.0max, A

A f

br f ck

2

1

A

A

2

1

A

A


33/34

- 33 -

Permissible bearing stress on full area of concrete=

22.50

compressive stress in concrete at base of Column,qu 13.36

Ok

Safe

Check for development lengthColumn bar diameter,ø= 25

Bond

stress τbd 1.75 N/mm2

(Clause 26.2.1.1 IS

456)

For Fully stressed bars in compression (m25,Fe415),

980.00 mm

Development Length available along the length (from the face of Column)

1434.81

Ok

Safe

1384.81

Ok

Safe

bd

y

d

f L

6.14

87.0

distanceend2

wl L

distanceend2

wb B


34/34

5.7. References

Jain, A.K- R.C.C Limit State Design, Nem Chand & Bros, Roorkee, 1990

Shah & Kale- R.C.C Design, Macmillan India Limited

Ashok k. Jain- Advanced Structural Analysis, Nem Chand & Bros, Roorkee, 1990

S.S. Bhavikati-Structural Analysis- II, Vikas Publishing House Pvt. Ltd.

V.N. Vazirani- Analysis of Structures-II, Khanna Publishers

S. Ramamrutham-Theory of Structures, Dhanpat Rai Publishing Company

Swami Saran, Analysis and Design of Substructure

2. structure report

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