Analysis and Design of a Multi-storey Reinforced Concrete Building

Transcription

1 United Arab Emirates University College of Engineering Civil and Environmental Engineering Department Graduation Project II 1 Analysis and Design of a Multi-storey Reinforced Concrete Building Prepared Sultan Saif Saeed Alneyadi Sultan Khamis AL-shamsi Hasher Khamis AL-azizi Rashed Hamad AL-Neyadi Abdulrahman Abdulla Jarrah Adviser Dr. Usama Ebead Second Semester 2007/2008

2 Outline Objectives Summary General Approach Building Types Concrete Structural Elements Slabs Flat Slab Design of Flat Slab Columns Rectangular Columns Design of Rectangular Columns Shear walls Design of Shear Walls Foundations Pile Group Design of Pile Group Economic Impact Enviromental Impact Conclusion 2

3 Objectives The Objectives of the Project are:- 3 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

4 Summary Our graduation project is a residential building in Abu- Dhabi. This building consists of 12 repeated floors. 4

5 General Approach Obtaining an architectural design of a regular residential multistorey building. Al-Suwaidy residential building in Abu Dhabi. 5 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.

6 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 6 The primary purpose of an office building is to provide a workplace and working environment for administrative workers.

7 Residential buildings 7

8 Office buildings 8

9 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. 9

10 Structural Elements 10 Any reinforced concrete structure consists of : Slabs Columns Shear walls Foundations

11 Flat Slab Structural System 11 Flat slab is a concrete slab which is reinforced in two directions Advantages Disadvantages

12 Types of Flat slab 12

13 Defining properties Slab thickness = 23 cm Concrete compressive strength = 30 MPa Modules of elasticity of concrete = 200 GPa Yielding strength of steel = 420 MPa Combination of loads (1.4Dead Load Live Load) 13

14 ACI ACI contains the current code requirements for concrete building design and construction. 14 The design load combinations are the various combinations of the prescribed load cases for which the structure needs to be checked. 1.2 DL LL

15 Flat Slab Analysis and Design Analyzing of flat slab mainly is done to find 1. Shear forces. 2. Bending moment. 3. Deflected shape. 4. Reactions at supports. 15

16 Deflection Results and Discussion 16

17 Results and Discussion Reactions at supports must be checked by a simple method. 17

18 Flat Slab Reinforcement 18

19 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. 19

20 Types of column Tied Columns Over 95% of all columns in building in non-seismic regions are tied columns Spiral Columns Spiral columns are generally circular. It makes the column more ductile. Spiral column Rectangular column 20

21 Steel Reinforcement in Columns The limiting steel ratio ranges between 1 % to 8 %. 21 The concrete strength is between 25 MPa to 45 Mpa. Reinforcing steel strength is between 400 MPa to 500 Mpa.

22 1. Calculate factored axial load Pu Design procedure 2. Select reinforcement ratio 3. Concrete strength = 30 MPa, steel yield strength = 420 MPa 4. Calculate gross area 5. Calculate area of column reinforcement, As, and select rebar number and size. 22

23 Columns to be designed 23

24 Guidelines for Column Reinforcement Long Reinforcement Min. bar diameter Ø12 Min. concrete covers 40 mm 24 Min. 4 bars in case of tied rectangular or circular Maximum distance between bars = 250 mm Short Reinforcement ( Stirrups) Least of: (16) diameter of long bars least dimension of column (48) diameter of ties A sp S d c

25 Column Design 25 A = 8- # of bars = s A c

26 Reinforcement of Columns 26

27 Shear walls 27 A shear wall is a wall that resists lateral wind loads which acts parallel to the plane of the wall.

28 Shear walls 28 Wind results in a pressure on the surface of the building Pressure increases with height Positive Pressure, acts towards the surface of the building Negative Pressure, acts away from the surface of the building (suction)

29 Wind pressure 29 q = Velocity pressure (Wind speed, height and exposure condition) G = Gust factor that depends on the building stiffness Cp = External pressure coefficient

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

31 Velocity Pressure 31 V = 160 km/h Kz = To be determined from the equations Kzt = 1 (level terrain adjacent to the building not on hill) Kd = 0.85 (rectangular building) I = 1 (use group II)

32 Important factor 32

33 Velocity Exposure Coefficient ( Kz) 33

34 North south direction Design of the wind force 34

35 Shear wall axial reactions 35

36 Calculating Velocity Pressure 36 V 145 (km/hr) α 9.5 Zg Kzt 1 Kd 0.85 I 1 G 0.85 Cp (windward) 0.8 Cp (leeward) -0.5 B (m) km/h 1 Level Tributary Height Height (z) (ht) Kz qz (kn/m2)

37 Design of the wind pressure 37 G 0.85 qb = qz (at the top of the building) Cp (windward) 0.8 Cp (leeward) -0.5 B (m) Level Height (z) m Tributary Height (ht ) m Kz qz (kn/m2) Design Wind Pressure(KN/m^2) Design Wind Force (KN) lee ward wind ward lee ward wind ward Total (qb G (qz G CP) (qb G CP) (qz G CP)(B)(ht ) (floor level) CP)(B)(ht ) Moment (KN.m) sum

38 Computing total moment acting toward N-S Direction 38 M = total floor level *height (z)

39 W-E Direction Computation 39 B= L= Level Height (z) m Tributary Height (ht ) m Kz qz (kn/m2) Design Wind Pressure(KN/m^2) wind ward (qz G CP) lee ward (qb G CP) wind ward (qz G CP)(B)(ht ) Design Wind Force (KN) lee ward (qb G CP)(B)(ht ) Total (floor level) Moment (KN.m) sum

40 East west direction Design of Shear Wall 40 North south direction

41 Interaction Diagram 41

42 Shear Wall Reinforcement 42

43 Foundations Foundations are structural components used to support columns and transfer loads to the underlying Soil. 43 Foundations Shallow Deep Isolated Combined Strap wall Raft footing footing footing footing footing Caissons Piles

44 Pile foundation 44 Our building is rested on a weak soil formation which can t resist the loads coming from our proposed building, so we have to choose pile foundation. Pile cap Weak soil Piles Bearing stratum

45 Pile foundation Piles are structural members that are made of steel, concrete or timber. 45

46 Function of piles As with other types of foundation, the purpose of a pile foundation is: To transmit a foundation load to a solid ground 46 To resist vertical, lateral and uplift load Piles can be Timber Concrete Steel Composite

47 General facts Usual length: 10m-20m Usual load: 300kN-3000kN Advantages Concrete piles Corrosion resistance Can be easily combined with a concrete superstructure Disadvantages 47 Difficult to achieve proper cutoff Difficult to transport

48 Pile foundation Piles can be divided in to two major categories: 1. End Bearing Piles If the soil-boring records presence 48 of bedrock at the site within a reasonable depth, piles can be extended to the rock surface 2. Friction Piles When 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.

49 Pile Cap Reinforcement Pile caps carrying very heavy point loads tend to produce high tensile stresses at the pile cap. 49 Reinforcement is thus designed to provide: Resistance to tensile bending forces in the bottom of the cap Resistance to vertical shear

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

51 First type This section shows how pile caps are designed to carry only vertical load, and the equation used to determine the resistance of cap is 51 P i = Q n i Where P Q n is the strength of the pile cap per one pile is the total force acting on the pile cap is the number of piles used to support the pile cap

52 Columns layout & Reactions ( Vertical Load ) 52 Column Reaction Total Reaction kn kn

53 Design of pile cap (Vertical Load only) 53 Pile Cap 2 Reaction = kn Pile diameter = 0.9 m Capacity for one pile = 0.8 * 50 * 18 * π * 0.9 = KN Need 3 piles Length between piles = (2*0.3) + (3*0.9) + (2*0.9)*2 =6.9 m Width = 1.5 meters Actual forces on each pile = P = = kn i Q i n

54 Second type Second type This 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 54 P i Q M r i i = ± 2 n r

55 Shear walls layout & reactions 55 wall M (KN.m) N (KN) W W W W W W W W W W W W W W

56 Design of pile cap (Vertical Load & moment) Shear wall # (1): M = Q = Assume 8 piles 56 P= Q n ± M r r *(1.909) P= ± So, P *(4.26) P= ± So, P Capacityof Pile Capacityof Pile = KN = KN

57 Economical impact Reinforced 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. 57

58 Environmental impact Although the cement production is environmentally challenging, the final product of a reinforced concrete building is environmentally friendly. 58

59 Gantt Chart 59

60 Conclusion We have applied our gained knowledge during our graduation project We are able to use structural software ( SAFE ) We have practiced real life engineering practices This GP enables us to go into the market with an excellent background regarding design of RC At this point, we would like to thank all instructors, engineers, and Al Ain Consultant Office for their grateful effort. 60

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