Structural Design And Analysis For Concrete Building - Building complex

 

Structural Design Criteria 

1. Codes and Standards

Unless otherwise specified herein, the following tables list the codes and manuals that shall be followed in design.

LOADS
BS 6399 - 1: 1996	Loading for buildings - Part 1. Code of Practice for Dead and Imposed Loads
BS 6399 - 2: 1997	Loading for buildings - Part 2: Code of practice for wind loads
BS 6399 - 3: 1988	Loading for buildings - Part 3: Code of Practice for Imposed Roof Loads

 

 

reinforced concrete
QCS 2010	Qatar Construction Specifications
BS 8110 - 1: 1997	Structural use of concrete Part 1: Code of Practice for Design and Construction
BS 8110 - 2: 1985	Structural use of concrete Part 2: Code of Practice for Special Circumstances
BS 8110 - 3: 1985	Structural use of concrete Part 3: Design Charts for Singly Reinforced Beams, Doubly Reinforced Beams and Rectangular Columns
BS 8004: 1986	Code of Practice for Foundations

2. Material Requirements

2.1 Concrete Grades

The characteristic concrete cube compressive strength after 28 days in N/mm² shall be as follows:

Cast-in-situ reinforced concrete                                                                            35  MPa

Cast-in-situ reinforced concrete for slab-on-grade                                                                   30  MPa

Blinding concrete                                                                                                       20  MPa

 

2.2  Reinforcing Rebar

Uncoated mild steel plain bars according to BS 4449 denoted “R"

Minimum yield Stress                                                                                    250  N/mm2

High tensile steel deformed bars according to BS 4449 denoted “T"

Minimum yield Stress                                                                                    460  N/mm2

Steel wire fabric mesh according to BS 4483

Minimum yield Stress                                                                                                   460  N/mm

2.3 Concrete Cover 

The cover shall not be less than as given below, according to the type of structural member and the placing and exposure conditions as follows:

·   Condition 1: Concrete placed in forms and not to be exposed later to the weather, groundwater, freshwater, or to any combination of these.               

·   Condition 2: Concrete placed in forms but later to be exposed to the weather, groundwater, freshwater, or to any combination of these.

·   Condition 3: Concrete placed directly in contact with the ground.

·   Condition 4: Concrete to be exposed to corrosive vapors, corrosive groundwater, seawater or sea spray. Sufficient protection to the reinforcement shall be provided by: adopting the minimum cover for exposure condition 3 and applying a protective coating or membrane on the concrete surface. The method of protection shall be in accordance with the provisions of the specification and to the approval of the Engineer.

 

Structural Member	Minimum Cover (mm) for Placing of Reinforcement for Exposure Condition
	Condition 1	Condition 2	Condition 3
Pad footings and Pile Caps	-	65	75
Strip footings	-	50	65
Bored or Cast Piles	-	50	75
Columns of all types	30	40	75
Walls, including retaining walls	25	30	75
Beams	30	40	65
Slabs, including concrete joist and hollow block construction	25	30	65
Cover to embedded pipes	25	30	65
Reinforcement adjacent to blocks in hollow block slab construction which are integral with the structure	10	-	-

 

3. Loading

3.1      Dead Loads

3.1.1   Unit Weight of Materials

Unit weight of reinforced concrete                                                                 24.0 kN/m³

Unit weight of plain concrete                                                                          22.0 kN/m³

Unit weight of block walls 20 cm*20cm*40cm (including plaster)               3.30 kN/m²

Unit weight of block walls 15 cm*20cm*40cm (including plaster)               2.80 kN/m²

Unit weight of block walls 10 cm*20cm*40cm (including plaster)               2.20 kN/m²

Unit weight of structural steel                                                                         78.5 kN/m³

 

3.1.2 Minimum Super Imposed Dead Loads 

         

Stairs flooring                                                                                                 2.00 kN/m²

Horizontal concrete roof flooring                                                                   3.00 kN/m²

Offices and other areas flooring (100 mm floor finish)                                  2.00 kN/m²

Lightweight partitions per floor area                                                              1.00 kN/m²

False ceiling and services                                                                                0.50 kN/m²

 

3.2 Live Loads

3.2.1 Minimum Live Loads

Load Description	Uniformly distributed load kN/m2
- Domestic & residential areas	2.00
- Offices, meeting rooms, classrooms, laboratories dining rooms, cafes and restaurants.	3.00
- Stairs, Corridors, lounges & balconies	4.00
- Assembly areas with fixed seating	4.00
- Shopping and exhibition areas	4.00
- Mosques and Prayer Areas	5.00
- Car parking areas (not exceeding 2500 kg gross mass), aisle ways and ramps	2.50
-Roofs not accessible except for normal maintenance and repair.	0.60
- Mechanical (HVAC) Rooms	7.50
-Storage Areas	2.4 for each meter of storage height

 

3.3 Wind Loads

The buildings shall be designed for wind loads calculated in accordance with BS 6399, Part 2, using the standard method.

Basic wind speed (mean hourly wind speed)                                                    24 m/sec

Altitude factor                                                                                                    Sa = 1.0

Direction factor                                                                                                  Sd = 1.0

Seasonal factor                                                                                                   Ss = 1.0

Probability factor                                                                                               Sp = 1.0

 

3.4 Load Combinations

The structure shall be designed for load combination in accordance with BS 8110-1:1997 as follows:

 

3.4.1 Ultimate Limit State Load Combinations

1.4D

1.4D+1.6L

1.4D+1.4Wx

1.4D-1.4Wx

1.4D+1.4Wy

1.4D-1.4Wy

D+1.4Wx

D-1.4Wx

D+1.4Wy

D-1.4Wy

1.2D+1.2L+1.2Wx

1.2D+1.2L-1.2Wx

1.2D+1.2L+1.2Wy

1.2D+1.2L-1.2Wy

3.4.2 Serviceability Limit State Load Combinations

D

D+L

D+Wx

D-Wx

D+Wy

D-Wy

D+L+Wx

D+L-Wx

D+L+Wy

D+L-Wy

 

Where

D                        (SELF + WALLS + FLOOR COVER+CEILING)

L                         (Live)

SELF                      (Indicating self-weight of the structural elements)

WALLS                  (Indicating Internal Partitions Load)

COVER                 (Indicating Flooring Cover Load)

LIVE                      (Indicating Live Loads)

Wx                       (Indicating Wind Loads in X-Direction)

Wy                       (Indicating Wind Loads in Y-Direction)

 

4. Serviceability Limits States 

 

4.1 Deflection of Concrete

To avoid excessive deflections and damage to non-structural elements, the residual deflection after the initial camber shall be limited to the following values:

 

L/250         Total deflection.

L/500      Or 20 mm (whichever is lesser) for the part of deflection after the construction of brittle materials.

L/350      Or 20 mm (whichever is lesser) for the part of deflection after construction of non-brittle partitions or finishes.

 

For beams (L<= 10 m), it will generally be satisfactory to use the span/effective depth ratios given in BS8110-Part 1 table 3.9, clause 3.4.6.3 for reinforced concrete.

Where L is the span of the beam or slab or in the case of a cantilever its length.