Analysis and Design of a Multi-storey Reinforced Concrete Building

United Arab Emirates University College of Engineering Civil and Environmental Engineering Department Graduation Project IISecond Semester 2007/2008 PreparedSultan Saif Saeed Alneyadi 200203903Sultan Khamis AL-shamsi200101595 Hasher Khamis AL-azizi200106031 Rashed Hamad AL-Neyadi200204018 Abdulrahman Abdulla Jarrah 200210915

Adviser Dr. Usama Ebead

OutlineObjectivesSummaryGeneral ApproachBuilding TypesConcreteStructural ElementsSlabsFlat SlabDesign of Flat SlabColumnsRectangular ColumnsDesign of Rectangular ColumnsShear wallsDesign of Shear WallsFoundationsPile GroupDesign of Pile GroupEconomic ImpactEnviromental ImpactConclusion

ObjectivesThe Objectives of the Project are:-

Carrying out a complete analysis and design of the main structural elements of a multi-storey building including slabs, columns, shear walls and foundations

Getting familiar with structural softwares ( SAFE ,AutoCAD)

Getting real life experience with engineering practices

SummaryOur graduation project is a residential building in Abu- Dhabi. This building consists of 12 repeated floors.

General ApproachObtaining an architectural design of a regular residential multi-storey building.Al-Suwaidy residential building in Abu Dhabi.

Establishing the structural system for the ground, and repeated floors of the building.

The design of column, wind resisting system, and type of foundations will be determined taking into consideration the architectural drawings.

Types of building

Buildings are be divided into: Apartment building Apartment buildings are multi-story buildings where three or more residences are contained within one structure. Office building The primary purpose of an office building is to provide a workplace and working environment for administrative workers.

Residential buildings

Office buildings

Concrete Mixtures Concrete is a durable material which is ideal for many jobs.The concrete mix should be workable.It is important that the desired qualities of the hardened concrete are met.Economy is also an important factor.

Structural Elements

Any reinforced concrete structure consists of :SlabsColumnsShear wallsFoundations

Flat Slab Structural System Flat slab is a concrete slab which is reinforced in two directions

Advantages

Disadvantages

Types of Flat slab

Defining propertiesSlab thickness = 23 cmConcrete compressive strength = 30 MPaModules of elasticity of concrete = 200 GPaYielding strength of steel = 420 MPaCombination of loads (1.4Dead Load + 1.6 Live Load)

ACI 318-02ACI 318-02 contains the current code requirements for concrete building design and construction.

The design load combinations are the various combinations of the prescribed load cases for which the structure needs to be checked. 1.2 DL + 1.6 LL

*Flat Slab Analysis and DesignAnalyzing of flat slab mainly is done to find Shear forces.Bending moment. Deflected shape. Reactions at supports.

*Results and DiscussionDeflection

Results and DiscussionReactions at supports must be checked by a simple method.

Flat Slab Reinforcement

Columns

It is a vertical structural member supporting axial compressive loads, with or with-out moments.Support vertical loads from the floors and roof and transmit these loads to the foundation.

Types of columnSpiral columnRectangular column Tied ColumnsOver 95% of all columns in building in non-seismic regions are tied columns Spiral ColumnsSpiral columns are generally circular. It makes the column more ductile.

Steel Reinforcement in ColumnsThe limiting steel ratio ranges between 1 % to 8 %.

The concrete strength is between 25 MPa to 45 Mpa.

Reinforcing steel strength is between 400 MPa to 500 Mpa.

Design procedure1. Calculate factored axial load Pu2. Select reinforcement ratio3. Concrete strength = 30 MPa, steel yield strength = 420 MPa 4. Calculate gross area5. Calculate area of column reinforcement, As, and select rebar number and size.

Columns to be designed

Guidelines for Column ReinforcementLong ReinforcementMin. bar diameter 12Min. concrete covers 40 mmMin. 4 bars in case of tied rectangular or circularMaximum distance between bars = 250 mmShort Reinforcement ( Stirrups)Least of:(16)diameter of long barsleast dimension of column (48)diameter of ties

dcSAsp

Column Design

8- # of bars =

Reinforcement of Columns

Shear walls

A shear wall is a wall that resists lateral wind loads which acts parallel to the plane of the wall.

Shear wallsWind results in a pressure on the surface of the buildingPressure increases with heightPositive Pressure, acts towards the surface of the buildingNegative Pressure, acts away from the surface of the building (suction)

Wind pressure

q = Velocity pressure(Wind speed, height and exposure condition)G = Gust factor that depends on the building stiffnessCp = External pressure coefficient

Gust G Factor & External pressure Cp coefficientfor Stiff Structures take G =0.85 Windward Wall, Cp = +0.8Leeward Wall, Cp = varies between -0.2 & -0.5Depending on the L/B RatioL/B = 18.84 m /26.18 m = 0.719 < 1 then , Cp = -0.5

Velocity Pressure

V = 160 km/hKz = To be determined from the equationsKzt = 1 (level terrain adjacent to the building not on hill)Kd = 0.85 (rectangular building)I = 1 (use group II)

Important factor*

*Velocity Exposure Coefficient ( Kz)

*Design of the wind forceNorth south direction

*Shear wall axial reactions

*Calculating Velocity Pressure145 km/h 0.85 11

V (km/hr)1459.5Zg274.32Kzt1Kd0.85I1

G0.85Cp (windward)0.8Cp (leeward)-0.5B (m)26.18

LevelHeight (z)Tributary Height (ht )Kzqz (kn/m2)12431.751.361.1502251139.53.51.341.12984910363.51.311.107994932.53.51.281.0843918293.51.251.058688725.53.51.221.0304066223.51.180.998873518.53.51.140.9630924153.51.090.921495311.53.51.030.871364283.50.950.80727014.540.850.715176

*Design of the wind pressureqb = qz (at the top of the building)

G0.85Cp (windward)0.8Cp (leeward)-0.5B (m)26.18

LevelHeight (z) mTributary Height (ht ) mKzqz (kn/m2)Design Wind Pressure(KN/m^2)Design Wind Force (KN)wind ward (qz G CP)lee ward (qb G CP)wind ward (qz G CP)(B)(ht )lee ward (qb G CP)(B)(ht )Total (floor level) Moment(KN.m)12431.751.361.1502250.782153-0.48884635.834345-22.39646558.2308102503.9248261139.53.51.341.1298490.768297-0.48884670.399094-44.792931115.1920254550.08497210363.51.311.1079940.753436-0.48884669.037332-44.792931113.8302624097.889443932.53.51.281.0843910.737386-0.48884667.566683-44.792931112.3596143651.6874458293.51.251.0586880.719908-0.48884665.965161-44.792931110.7580923211.984664725.53.51.221.0304060.700676-0.48884664.202965-44.792931108.9958962779.3953496223.51.180.9988730.679233-0.48884662.238149-44.792931107.0310792354.683748518.53.51.140.9630920.654903-0.48884660.008720-44.792931104.8016501938.8305314153.51.090.9214950.626617-0.48884657.416871-44.792931102.2098021533.147032311.53.51.030.8713640.592527-0.48884654.293292-44.79293199.0862221139.491559283.50.950.8072700.548944-0.48884650.299721-44.79293195.092651760.741210614.540.850.7151760.486320-0.48884650.927427-51.191921102.119348459.5370657sum1229.70745228981.39785

*Computing total moment acting toward N-S DirectionM = total floor level *height (z)

*W-E Direction Computation

LevelHeight (z) mTributary Height (ht ) mKzqz (kn/m2)Design Wind Pressure(KN/m^2)Design Wind Force (KN)wind ward (qz G CP)lee ward (qb G CP)wind ward (qz G CP)(B)(ht )lee ward (qb G CP)(B)(ht )Total (floor level)Moment(KN.m)12431.751.361.1502250.7821531-0.4888525.7875879-16.117242441.90483041801.9077051139.53.51.341.1298490.7682974-0.4888550.6615328-32.234484982.89601773274.39269910363.51.311.1079940.7534359-0.4888549.6815633-32.234484981.91604822948.977735932.53.51.281.0843910.7373860-0.4888548.6232356-32.234484980.85772052627.8759168293.51.251.0586880.7199079-0.4888547.4707271-32.234484979.70521202311.451149725.53.51.221.0304060.7006763-0.4888546.2025923-32.234484978.43707722000.1454696223.51.180.9988730.6792333-0.4888544.7886449-32.234484977.02312981694.508855518.53.51.140.9630920.6549025-0.4888543.1842734-32.234484975.41875831395.2470284153.51.090.9214950.6266165-0.4888541.3190931-32.234484973.55357801103.30367311.53.51.030.8713640.5925275-0.4888539.0712612-32.234484971.3057461820.0160796283.50.950.8072700.5489438-0.4888536.1973543-32.234484968.4318392547.454713814.540.850.7151760.4863200-0.4888536.6490728-36.839411373.4884841330.6981787sum884.938441520855.9791983

*Design of Shear WallEast west direction

North south direction

*Interaction Diagram

*Shear Wall Reinforcement

FoundationsFoundations are structural components used to support columns and transfer loads to the underlying Soil.

FoundationsIsolated Combined Strap wall Raft Shallowfooting footing footing footing footing CaissonsPiles Deep

Pile foundationOur building is rested on a weak soil formation which cant resist the loads coming from our proposed building, so we have to choose pile foundation.

Pile foundationPiles are structural members that are made of steel, concrete or timber.

Function of pilesAs with other types of foundation, the purpose of a pile foundation is:To transmit a foundation load to a solid groundTo resist vertical, lateral and uplift load

Piles can beTimberConcreteSteelComposite

Concrete pilesGeneral facts Usual length: 10m-20mUsual load: 300kN-3000kNAdvantages Corrosion resistanceCan be easily combined with a concrete superstructureDisadvantagesDifficult to achieve proper cutoffDifficult to transport

Pile foundationPiles can be divided in to two major categories:End Bearing PilesIf the soil-boring records presenceof bedrock at the site within a reasonable depth,piles can be extended to therock surfaceFriction PilesWhen no layer of rock is present depth at a site, point bearing piles become very long and uneconomical. In this type of subsoil, piles are driven through the softer material to specified depths.

Pile Cap ReinforcementPile caps carrying very heavy point loads tend to produce high tensile stresses at the pile cap.Reinforcement is thus designed to provide: Resistance to tensile bending forces in the bottom of the cap Resistance to vertical shear

Design of the pile capbearing capacity of one pile:Rs = Cu As .LLength of pile penetration L = 18 meters Adhesion factor of soil (clay) = 0.8Untrained shear strength Cu =50 Diameter = 0.9 m For piles with diameter 0.9 mRs = 2035.75 KN

First typeThis section shows how pile caps are designed to carry only vertical load, and the equation used to determine the resistance of cap is

Where P is the strength of the pile cap per one pileQ is the total force acting on the pile capn is the number of piles used to support the pile cap

Columns layout & Reactions ( Vertical Load )

ColumnReactionTotal ReactionkNkN1129.631555.562246.852962.28382.664591.9210393.384720.5621458.355500.223400.854810.224627.747532.8825384.144609.6830158.31899.632355.264263.12

Design of pile cap (Vertical Load only)Pile Cap 2Reaction = 4610.4 kNPile diameter = 0.9 mCapacity for one pile = 0.8 * 50 * 18 * * 0.9 = 2035.75 KNNeed 3 piles Length between piles = (2*0.3) + (3*0.9) + (2*0.9)*2 =6.9 mWidth = 1.5 metersActual forces on each pile = = 1536.8 kN

Second typeSecond typeThis section shows how pile caps are designed to carry vertical load and lateral loads ( Bending Moment), and the equation used to determine the resistance of cap is

Shear walls layout & reactions

Design of pile cap (Vertical Load & moment)Shear wall # (1):M = 14072.11561Q = 12285.6Assume 8 piles

Economical impactReinforced concrete is proven to be a very economical solution in the UAE. the most affordable solution for multistory building such as the one we are making the analysis and design for.

Environmental impactAlthough the cement production is environmentally challenging, the final product of a reinforced concrete building is environmentally friendly.

Gantt Chart

ConclusionWe have applied our gained knowledge during our graduation projectWe are able to use structural software ( SAFE )We have practiced real life engineering practicesThis GP enables us to go into the market with an excellent background regarding design of RCAt this point, we would like to thank all instructors, engineers, and Al Ain Consultant Office for their grateful effort.

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