Week 3 Challenge
1
1) The primary load cases to be considered for design :-
* Live load
* Dead load
* Snow load
* Seismic load
* Wind load
2) One – Way slab :-
The ratio of length of longer span to the shorter span is greater or equal to 2.
3) The value of unit weight of structural steel and soil :-
Unit weight of steel = 7850kg/m3
Unit weight of soil = 1800kg/m3
4) Name few sections that can be defined using Properties tab in STAAD Pro :-
* Circle
* Rectangle
* Trapezoidal
* Tapered I
* Tapered tube
* Tee
5) Primary Beams :-
It is a horizontal flexural (beam) structure member which directly connected to supporting compressive structure member that is column.
The load transfer beams to column.
2
1) The factors and parameters that influence the design pressure intensity of a high-rise building :-
Pz = 0.6 Vz^2
Here,
Vz=Vb*k1*k2*k3
Pz = Design wind pressure
Vz = Design Speed
Vz = Vb x K1 x K2 x K3
Vb = Wind Speed
K1 = Probability Factor
K2 = Terrain, Height and Structure size factor
K3 = Tropography Factor
2) The load transfer process of a Reinforced Concrete Building :-
Gravity load (Dead + Live) on the floor and roof slabs is transferred to the columns , down to the foundations, and then to the supporting soil beneath.
3
1) Differentiate One-Way and Two way slabs :-
| One way slab | Two way slab |
| * The ratio of length of longer span to the shorter span is greater or equal to 2 | * The ratio of length of longer span to the shorter span is less than to 2 |
| * The slabs are supported by the beams on the two opposite sides. | * As the loads are carried in both directions (longer and shorter direction). |
| * The loads are carried along one direction. | * Main reinforcement bars are provided in both directions. |
 |
 |
|
 |
2) The concept of secondary beams with proper sketch :-
* A horizontal beam connecting primary beams (simply supported or shear connected).
* It will transfer the load to the primary beam.
3) The Primary load cases :-
a.Indian Standards for each load case :-
* Live load
* Dead load
* Snow load
* Seismic load
* Wind load
b.The parameters of each load case :-
* Dead load (IS 875 part 1):-
Cement
Steel
Sand
Concrete
RCC
Soil
Timber
Factor of safety
* Live load (IS 875 part 2):-
All rooms and kitchen
Bathroom and toilets
Corridors/stair case
Balcony
c. Each load case
* Dead load (IS 875 part 1) :-
Dead loads (DL) are essentially constant during the life of the structure and normally consist of the weight of the structural elements.
Cement = 1440kg/m^3
Steel = 7850kg/m^3
Sand = 1600kg/m^3
Concrete = 2400kg/m^3
RCC = 2500kg/m^3
Soil = 1800kg/m^3
Timber = 700kg/m^3
Factor of safety = 1
* Live load (IS 875 part 2) :-
Live loads (LL) usually vary greatly.
All rooms and kitchen = 2kN/m^3
Bathroom and toilets = 2kN/m^3
Corridors/stair case = 3kN/m^3
Balcony = 3kN/m^3
* Wind load(IS 875 part 3) :-
The force exerted by the horizontal component of wind is to be considered in the design of building. Wind loads depends upon the velocity of wind, shape and size of the building. The method of calculating wind loads on structure is given in IS 875 (Part-3):1987.
* Snow load(IS 875 part 4) :-
The building which are located in the regions where snowfall is very common, are to be designed for snow loads. The code IS 875 (Part-4):1987 deals with snow loads on roofs of the building.
* Earthquake load :-
Earthquake loads depend upon the place where the building is located. As per IS 1893-2016 (Part-I) (General Provisions for Buildings), India is divided into four seismic zones. The code gives recommendations for earthquake resistant design of structures.
4) The steps involved in assigning Properties and Support to a model using STAAD Pro sequentially :-
* Go to Properties Tab
* Click on Define Material
* Choose Section and Material
* Click on Add and Close
* Now Click on Assign to view and assign the Property
* Go to Support Tab
* Click on Create
* Choose Support and click on Add and close
* Now Click on Use Cursor to Assign.
5) The steps to be followed to create and assign secondary beams in STAAD Pro :-
* Now go to the Specification
* Select Beam
* Click on Release
* Click on Start and Tick on Fx and Mz and click Add
* Now Click on End and Tick Fx and Mz and click Add
* Now Assign to the selected Beam
Pratical
a) Calculation the wind pressure for the given building
Given data
Building Dimension : 20m x 30m x 20m height RCC
Building usage : Hospital block in city centre
Location : Darjeeling
For wind load
Pz = 0.6 Vz^2
Here,
Vz=Vb*k1*k2*k3
Pz = Design wind pressure
Vz = Design Speed
Vz = Vb x K1 x K2 x K3
Vb = Wind Speed
K1 = Probability Factor
K2 = Terrain, Height and Structure size factor
K3 = Tropography Factor
The structure in category - 4 and Class B and designed for 100 years.
From IS 875 part 2
Vb = 47m/s
k1 = 1.07(Table 1, clause 5.3.1)
k2 = 0.76(Table 2, clause 5.3.2.2)
k3 = 1(clause 5.3.3.1)
Vz = 47x1.07x0.76x1
= 38.22m/s
Pz = 0.6x38.22^2
= 0.87N/m^2
| Height | k2 | Vz | Pz | Pz in KN |
| 3 | 0.76 | 38.22 | 876.47 | 0.87 |
| 6 | 0.76 | 38.22 | 876.47 | 0.87 |
| 9 | 0.76 | 38.22 | 876.47 | 0.87 |
| 12 | 0.76 | 38.22 | 876.47 | 0.87 |
| 15 | 0.76 | 38.22 | 876.47 | 0.87 |
| 18 | 0.76 | 38.22 | 876.47 | 0.87 |
| 20 | 0.76 | 38.22 | 876.47 | 0.87 |
b) Calculation the Dead load and Live load for the above building with reference to IS standards :-
Self weight of concrete = 25 kN/m^2
Self weight of PCC = 22 kN/m^2
Self weight of brick wall = 18 kN/m^2
Dead load = (Weight of slab x Slab height x building width x building length) + Weight of wall
= (25 x 0.125 x 30 x 20 x 7) + (18 x 20 x3 x 0.250) + (18 x 30 x 3 x 0.250)
= 13800 kN
We take
Live load = 3kN/m^2
Total live load of building = length x width x live load x no. of floors
= 20 x 30 x 3 x 6
= 10800kN