Week 3 Challenge

1.

1. State the primary load cases to be considered for design.

The primary load cases that are to be considered for design are listed below:

• Dead Load (IS 875: Part I).
• Live Load (IS 875: Part II).
• Wind Load (IS 875: Part III).
• Snow Load (IS 875: Part IV).
• Seismic Load (IS 1893: 2016).

2. What is One – Way slab?

ONE-WAY SLAB:-

• One-way slab is a plane surface of uniformly loaded which deforms into a cylindrical shape and hence the bending moment develops only in one direction. These type of slab is called one-way slab.
• one-way slab is a slab in which the ratio of the longer span to its shorter span is more than or equal to 2.
• one-way slab load distribution takes place along its shorter span.
• In one way slab bending happens at the shorter span of the slab.

3. What is the value of unit weight of structural steel and soil?

• The value of unit weight of structural steel is:- 78KN/m
• The value of unit weight of soil is:- 18KN/m

4. Name few sections that can be defined using Properties tab in STAAD Pro.

Few sections that can be defined using Properties tab in STAAD Pro are listed below:

• Circular sections
• Rectangular sections
• I-Sections
• T-Sections
• Tapered-I sections
• Trapezoidal sections
• Custom Geometric Sections.

5. Define Primary Beams.

• The primary beams are the beams that are directly connected with the column on both the ends.
• The function of the primary beams are to transfer the load of the slab or seconday beam directly to the column.

2.

1. State the factors and parameters that influence the design pressure intensity of a high-rise building.

ANSWER

Pz = 0.6 Vz^2

Where;

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. Mention the load transfer process of a Reinforced Concrete Building.

The load transfer process of a reinforced concrete building is listed bellow in a sequential form

1. SLAB
2. SECONDARY BEAM
3. PRIMARY BEAM
4. COLUMN
5. FOUNDATION
6. SOIL

3.

1. Differentiate One-Way and Two way slabs. Elaborate each slab type.

ONE WAY SLAB

• One-way slab is supported by a beam on two opposite sides only.
• In one-way slab load is carried in one direction perpendicular to the supported beam.
• In one way slab the ratio of the longer span to the shorter span is greater or equal to 2
• The deflected shape of the one-way slab is cylindrical.
• In one-way slab the bending takes place only in one direction that is along the shorter span

TWO WAY SLAB

• Two-way slab is supported by beam on all the four sides.
• And in two-way slab load is carried in both directions.
• In two way slab the ratio of the longer span to the shorter span is smaller then 2
• The deflected shape of the two-way slab is saucer-like shape
• In two-way slab,bending takes place along the both span.

2. Explain the concept of secondary beams with proper sketch.

SECONDARY BEAM :-

The secondary beams are the beams connected to the primary beams mainly simply supported beams.

• The secondary beams are provided for the better distribution of slab loads along with the primary beams which rest on the slabs.
• The secondary beams are not directly connected to the columns.
• So the secondary beams carries a certain amount of total load and help them to distribute the loads in the respective manner.
• In secondary beams,it is important to release the end moments at the supports,because of this all the secondary beams are provided with the pinned connection.

3. Mention the Primary load cases.
a. State the Indian Standards for each load case
b. Detail the parameters of each load case
c. Brief each load case

ANSWER:-

a. State the Indian Standards for each load case:

• Dead Load (IS 875:Part 1).
• Live Load (IS 875:Part 2).
• Wind Load (IS 875:Part 3).
• Snow Load (IS 875:Part 4).
• Earthquake Load (IS1893:2016).

b. Detail the parameters of each load case:

• Member Loads
• Concentration Loads
• Floor Loads
• Plate Loads

c. Brief each load case:

Dead Load:-

• The dead load is defined as the continuous load in a structure i.e the load of machine etc and this load caused by the weight of the members that are pemanently attached to the particular structure.
• The dead load of the structure comprised of the load of the column, load of the beam , loads of the floor slab, roofing,walls, the load of the windows or may be the load of the electrical fixture. All the loads which is permanent on the structure is called as the dead load of the structure.

Some of the Dead Load(Unit Weight) of the following materials:

• Cement : 1440 Kg/cu.m.
• Steel : 7850 Kg/cu.m.
• Sand : 1600 Kg/cu.m.
• Concrete : 2400 Kg/cu.m.
• RCC : 2500 Kg/cu.m.
• Soil : 1800 Kg/cu.m.

Live Load:-

• Live loads are the loads that fully or partially vary from time to time on the structure.
• Live loads are not constant loads throughout of the life span of a structure.
• Live loads may vary time to time according to its usage or the occupancy.
• Live load may vary depend on the type of the structure such as the residential building,commercial building,industrial building etc.
• For residential building we use 3KN/sq.m Live Load.
• Live loads on floors and the roofs consist of all loads which are temporarily placed on the structure. Some of the live loads (Unit Weight) are:

• All rooms and kitchen : 2 KN/sq.m.
• Bathrooms and Toilets : 2 KN/sq.m.
• Balcony : 3 KN/cu.m.
• Staircase/Corridors : 3 KN/cu.m.

Wind Load:-

• Wind Load is a force on a structure that is arising from the impact of the wind. Wind load is an important load case for the structure. We considered this type of load where the structure are situated or located in the hilly areas of the mountain areas where we can expect high speed of the winds that can affect the structure. In those areas we need to consider the wind loads.
• Mainly we calculated the wind loads for the roofs of the structure.

Earthquake Load:-

• Earthquake loads or seismic loads are also an important load case that needs to be considered while designing and analysing of the high-rise structure of the building.
• Mainly we considered this type of loads where there are high chances of earthquakes or we can say we have to consider this load in the earthquake prone areas,where there is a high risk of earthquake.
• And according to the codal provision,the dynamic seismic analysis can be carried out via any of the two methods and these two methods are spectrum analysis and the time history analysis.

4. Detail the steps involved in assigning Properties and Support to a model using STAAD Pro sequentially.

Assigning Properties:-

The steps that are involved in assigning the properties and support to a model using the STAAD Pro software have been discussed below:

• Go to the Properties tab and then there will be a dialoige box and in that dialouge box there is an option called Define menu just click on that option.
• After clicking the define option there will be another dialouge box,in that dialouge box there will be a list of existing sectional properties,from that list choose the desired sectional property like Circular section,Rectangular section,Trapezoidal section etc.
• After choosing the section properties provide the dimensions in that dialouge box.
• And now there will be another option called Add just click on that option and then click OK.
• Now assign the property to the model or structure and to assign the property,select the section that we have just created from the created section,and click on the opion Assign to the selected view and then click on the assign option and then assign the property and done.

Assigning Support:-

• In order to assign the Support to the model using the STAAD Pro software,go to the Section tab and then there will be another dialouge box and in that dialouge box there will be an option called Create New just click on that option.
• After clicking on that option there will be another dialouge box and in that dialouge box there will be another options like Fixed,Pinned,Fixed But etc.
• Click on the desired end conditions,then there will be an option called Add just click on that option.
• And now assign the Support to the model or structure,and to assign the support select the support that we have just created from the created section,and click on the opion Assign to the selected view and then click on the assign option and then assign the property and done.

5. Brief the steps to be followed to create and assign secondary beams in STAAD Pro

The steps that are involved in creating and assigning the secondary beams in STAAD Pro are discussed below:

• Firstly create the nodes in the x-axis.
• Then use the translition command to copy the nodes in other direction
• After providing the nodes create the secondary beam.

• Now select the primary beam and provide the node at the mid point.
• From there we can create the secondary beam in between the primary beam.

Practical
1. Calculate the wind pressure for the given building
a. Building Dimension : 20m x 30m x 20m height RCC
b. Building usage : Hospital block in city centre
c. Location : Darjeeling

ANSWER

GIVEN:-

• Building Dimension : 20m x 30m x 20m height RCC
• Building usage : Hospital block in city centre
• Location : Darjeeling

CALCULATION OF THE WIND SPEED

Formulae for the calculation of the wind speed is:-

Vz=Vb.K1.K2.K3.K4

where,

Vb= Basic Wind Speed (m/sec).

K1=Risk Co-efficient.

K2=Terrain Roughness and Height Factor.

K3=Topography Factor.

K4=Importance factor.

As per IS code:-

Vb= 47m/s

K1=1.07

K2=0.8

K3=1

K4=1

Calculation for wind speed

Vz=Vb.K1.K2.K3.K4

Vz=47x1.07x0.8x1x1

Vz=40.23m/s

Calculation for the wind pressure

Pz=0.6Vz2

Pz=0.6x40.23(2)m/s

Pz=971.071N

Pz=0.971KN

calculations done in Exel sheet

2. Calculate the Dead load and Live load for the above building with reference to IS standards ( assume suitable sections )

DEAD LOAD due to Slab

Assuming the slab thickness of 150mm.

Dead Load due to the Slabs =Area of slab x thickness of the slab x density of RCC

Dead Load due to the Slabs = 20 X 30 X 0.15 X 25

Dead Load due to the Slabs = 225 KN.

Here we are assuming the total number of floor are 5

therefore,

Total dead load due to all the slabs = 5 X Dead Load due to the Slabs.

Total dead load due to all the slabs = 5 X 225=1125KN

Dead Load Due To Beams

Assume the beams of cross-section is 350X450mm.

Dead load due to the beams = Size of the beam X Density of RCC

Dead load due to the beams = 0.35 X 0.45 X 25.

Dead load due to the beams = 3.94 KN/m.=4KN/m

Superimposed Loads due to the Partition walls:

Assuming 150mm thickness of brickwork.

Height of brickwork = Floor height - depth of the beam.

Height of the brickwork=3.75-0.45

Height of brickwork =3.3

Therefore,the dead load due to the brick masonary partition=3.3x0.15x18=8.91KN/m

LIVE LOAD

The live load for a building is taken as per IS code 875 part 3, that has bee listed bellow:-

• For bedrooms:-2KN/m2
• For Kitchen:-3KN/m2
• Toilets:- 2KN/m2
• Staircase:- 3KN/m2
• Lift passage:- 7.5KN/m2