Week 3 Challenge
QUESTIONS & ANSWERS
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:
1. Dead load
2. Live load
3. Wind load
4. Snow load
5. Seismic load
2. What is One – Way slab?
- One-way slab is a plane surface of uniformly loaded which deforms into a cyndrical shape and hence the bending
moment develops only one in direction. these type of slab is called one way slab.
3. What is the value of unit weight of structural steel and soil?
The value of unit weight of structural steel and soil are given below
unit weight of structural steel : 7850kg/cu.m
unit weight of soil : 18kg/cu.m
4. Name few sections that can be defined using Properties tab in STAAD Pro.
1. circular sections
2. rectangular sections
3. I sections
4. tapered I sections
5. T sections
6. trapezodial sections
5. Define Primary Beams.
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 directly to the column that they are resting on.
2. 1. State the factors and parameters that influence the design pressure intensity of a high-rise building.
The factors and parameters that influence the design pressure intensity of a high rise buildinh has been disscussed below
So the design speed can be governed by the below given formula :
Vz = Vb X k1 X k2 X k3 X k4.
Where, Vz = basic wind speed, that is based on the location of the project in India
k1 = risk co-efficient factor.
k2 = terrain and height factor.
k3 = topography factor.
k4 = imfortance factor.
And then the design wind pressure formula:
Pz= 0.6 X Vz²
2. Mention the load transfer process of a Reinforced Concrete Building.
Flowchart:
Slabs
Secondary Beams
↓
Primary Beams
↓
Columns
↓
Foundation
↓
Hard strata Beneath
3. 1. Differentiate One-Way and Two way slabs. Elaborate each slab type.
| One-Way Slabs | Two-Way Slabs |
|
|
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b. In one way slab load is carried in one direction perpendicular to the suppoerwd beam. |
b. And in two way slab load is carried in both directions. |
|
c. If L/b ratio is grater than or eqaul to 2, then the slab is considered as the on way slab. |
c. If L/b ratio isless than or eqaul to 2,
then the slab is considered as the on way slab. |
2. Explain the concept of secondary beams with proper sketch.
- The secondary beams are primarly connected to the primary beams mainly simply supported beams.
- The secondary beams are provided for the better distribution of slab load along with the primary beas which rests on slabs.
- In secondary beams, it is important to release the end moments at the supports, because os this all the secondary beams are provided with pnned connection.
3. Mention the Primary load cases.
a. State the Indian Standards for each load case
- Dead load
- Live load
- Wind load
- Snow load
- Earthquake load
b. Detail the parameters of each load case
- Floor loads.
- Concentration loads.
- Plate loads.
- Member loads.
c. Brief each load case
Dead load :
The load is defined as the continous load in a structure i.e the load of machine etc and this load
caused by the weight of the members that are permanently attached to the particular 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
Dead load factor is 1.
Live load:
1. Live loads are the loads that are fully partially vary from time to time on the structure.
2. Live loads are not constant loads throughout of the life span of a structure.
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 .
Mainly we calculated the wind loads fort he roofs of the strcture.
Earthquake load:
- Earthquake loads or seimic loads are also an impotant load case that need to be considered while
designing and analysing of the high-rise strcture of the building.
- And according to the codal provision, the dynamic seismic analysis can be caaried out via any of
the two methods and these two methods are spectum 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 first step in order to assigning the properties to a model in a model using STAAD Pro software, go to the properties tab and then there will be a dialogue box and in that dialogue box there is an option calld define menu just clic on that option.
- After clicking the define option there will be another dialogue box, in that dialogue box there will be a list of existing sectional properties, from that list choose the desired sectional property like circular section, Rectangular section, Trapezaidal section etc.
Assigning Support:
- In order to assign the support to the model using the STAAD Pro software, got to the section tab and then there will be another dialogue box and inthat dialogue box there will be an option called Create New just click on that option.
- After clicking on that option there will be another dialogue box and in that dialogue box there will be another option lie Fixed,Pinned,Fixed but etc.
5. Brief the steps to be followed to create and assign secondary beams in STAAD Pro.
- In order to assign the secondary beam in the model, first we need to right-click on the screen and select the cursor as
the beam cursor.
- After that click the primary beam and right-click on the beam and right-click on the beam, Aftrer that there will be a list
of various options appears on the screen and in that list there will be an option called add node at the mid-point just click
on that option.
- Afterclicking on that option the node at the mid-point of the primary beam added automatically.
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
AIM: To calcualte the wind pressure for the given buiulding.
PROCEDURE:
GIVEN DATA :
Building Dimension : 20m x 30m x 20m height RCC
Building usage : Hospital block in city centre
Location : Darjeeling
Calculate Design wind speed:
Design wind speed formula is:
Vz = Vb X k1 X k2 X k3 X k4.
Where, Vb = basic wind speed (m/sec)
k1 = risk co-efficient .
k2 = terrain Roughness and height factor.
k3 = topography factor.
k4 = imfortance factor
Given data form the IS code:
Vb = 47 m/s.
k1 = 1.07.
k2 = 0.8.
k3 = 1.
k4 = 1.
CALCUALTION:
Vz = Vb x k1 x k2 x k3 x k4.
Vz = 47 x 1.07 x 0.8 x 1 x 1.
Vz = 40.232 m/s
Calculate the wind pressure:
Pz = 0.6 x Vz²
Pz = 0.6 x (40.23)²
Pz = 971.071N
Pz = 0.97117KN
2. Calculate the Dead load and Live load for the above building with reference to IS standards ( assume suitable sections )
- Dead load due to slabs:
Assuming the slab thickness of 150mm.
Dead load due to the slabs = Length x Breadth x Height x Slab thickness.
Dead load due to the slabs = 20 x 30 x 25 x 0.15
Dead load due to the slabs = 225 KN.
In this project we have total of five floor slabs, 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.
Total dead load due to all the slabs = 1125 KN.
- Dead load due to beams:
Assume the beams of cross-section 350x450mm.
Dead load due to beams = Size of the beam x Height.
Dead load due to beams = 0.35 x 0.45 x 25.
Dead load due to beams = 3.94 KN/m.
Dead load due to beams = 4 KN/m
Superimposed loads due to the partition walls:
Assuming 150mm thickness of brickwork.
Height of brickwork = Floor height - depth of the beam.
Height of brickwork = 3.75 - 0.45.
Height of brickwork = 3.3 meters.
Therefore, the dead load due to the brick masondry partition = 3.3 x 0.15 x 18.
The dead load due to the brick masondry partition = 8.91 KN/m.
Live load:
We can calcualte the live load of a given structure by using the IS 875:part2 Which state the defferent live loads values for different rooms.
Hospital building values according to IS 875:part2
OCCUPANCY Live load
For ward rooms, dressing rooms, dormitories and lounges 2.0 KN/sq.m.
Kitchen and laboratory 3.0 KN/sq.m.
Dining room and Cafeteria 3.0 KN/sq.m.
Toilets and Bathrooms 2.0 KN/sq.m.
X-ray rooms and operating rooms 3.0 KN/sq.m.
Officeand OPD rooms 2.5 KN/sq.m.
Corrider and Passages 4.0 KN/sq.m.