Week 3 Challenge

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

The primary load cases taht are to be considered for design are

• Dead load (IS 875:part I)
• Live load (IS 872: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 salb is a plane surface of unifromly 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 shorte span. Hence, bending also happens at the shorter span of the slab.

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

• The unit weight of structural steel is 7850 Kg/cu.m.
• The soil has dry unit weight of 15.5 kN/sq.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

• Circular sections
• Rectangular sections
• I-sections
• T-sections
• Tapered I-sections
• Trapezoidal sections
• Custom geometric sections

5. Define Primary Beams.

The primary beams are beams taht are directly connected with column on both the ends. The fuction of primarybeams is to tranfer the load of slab to the columns on which they are resting.

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

Factors affecting growth, height and structural form of a high rise building

• Loading
• Sequential Loading
• Strength and stability
• Stiffness
• Drift limits
• Human comfort
• Creep, shrinkage and temperature
• Fire

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

The load transfer procedure of a reinforced concrete building has been illustrated below

Slabs>Secondary beams>Promary beams>Columns>Foundation>Sub soil.

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

• One way slab is supported by a beam on two oppositesides only, where as a two way slab is supported by beam on all four sides
• In one way slab load is carried in one direction perpedicular to the supported beam, where as in two way slab, load is carried in both directions
• If L/b ratio is greater than or equal to 2, then it is conidered as one way slab, If the L/b ratio is less than 2, then it is considered as two way slab.
• Deflected shape of one way slab is cylindrical, where as the two way slab deflection shape is saucer like structura.
• Quantity of stell is less in one way slab when compared to two way slab.
• In one way slab bending take splace only in one direction where as in two way slab bending takes place along bothe spans.

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

• Secondary beams are primarily connected to the primary beams, mainly simply supported beams
• Secondary beams are provided for better distribution of slab loads along with the primary beams which rest on the slab
• So, in brief secondary beams are beams that are not directly connected to columns
• They rest on primary beams and transfer the slab's load on to primary beams ie., secondary beams carry a certain amount of roof loads and help in distributiong the roof load in respective way.
• In secondary beams it is important to release the end moments at the supports, because of this all the secondary beams are provided with pinned connections.

3. Mention the Primary load cases.
a. State the Indian Standards for each load case

• Dead load (IS 875:part I)
• Live load (IS 872:part II)
• Wind load (IS 875:Part III)
• Snow load (IS 875:part IV)
• Seismic load (IS 1893:2016)

b. Detail the parameters of each load case

• Member loads
• Concentrated loads
• Floor loads
• Plate load

c. Brief each load case

1. Dead load :

• The dead load is defibned as continuous load in a structure i.e the load of machine etc and this load caused by the weight of the mebers that are permanently attached to that structure
• The dead load of the structure is self weight of columns, beams, slabs, roofs, walls, window load or may be the load of electrical equipments, all loads that are permanent on the structure are referred as dead load.
• Dead load factor is 1
• Dead load (Unit weight) of some of the materilal

1. cement : 1140 Kg/cu.m
2. steel : 7850 Kg/cu.m.
3. sand : 1600 Kg/cu.m
4. concrete : 2400 Kg/cu.m
5. RCC : 2500 Kg/cu.m
6. Soil : 1800 Kg/cu.m

2. Wind load :

• Wind laod 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 consider this type of load where the structures are situated in the hilly regions where a high spedd of wind is expected
• Wind loads are primarily calculsted for the roofs of tje structures.

3.Earthquake laod :

• Earthquake loas or seismic loads are also an important load case that needs to be considered while desigining and analysis of the high rise structure of the building.
• Mainly we consider these loads in earthquake prone zones, where there is high risk of earthquakes
• and according to the codal provision, the dynamic seismic analysis can be carried out via any of the two methods namely, spectrum analysis and the time history analysis.

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

Steps involved in assigining properties :

• Initially noedes and beams are assigned using geometry tab and the properties come into picture after these two steps.
• To assign properties to any model, initially go to properties tab and select on define option to define the required properties.
• After defining all the required properties, assiging process is to be done
• Assigning properties to a model can be aone in four ways namely, assign to view, assign using cursor, assign to selected elements and assign to edited list.
• Select the properties and selct a way to assign these properties to gthe model as per the requirement.
• For example, assign to view option is used to assign the same property to all the elements in the current view

Steps involved in assiging the supports :

• after defining and assigning the properties to all the elements in the model, the supports are create dfrom the supports tab and there are many supports availble in STAAD pro like fixef support pinned support etc
• Initiallhy the required supports are to be defined using define option in supports tab and these supports are to be assigned to the nodes as per the requirement
• There are four options available to assign supports to the model namely, assign to view, assign using cursor, assign to selected elements and assign to edited list.
• For example, assign ussing the cursor is used to manually assign the selected support to the specific node using cursor
  
  

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

Steps involved in creating and assigining the secondary beams

1. first create a simple model by using the nodes in STAAD pro
2. Click on the create beam option and create a beam in the direction of X and Z axis
3. Right click on the primary beam in the section
4. Right click and add node at the mid of the beam
5. Click on the create beam to draw the beam along the mid bay
6. Finally make the moments zero at the newly created nodes (ie., release Fx and Mz).

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

Procedure :

Given ;

Building dimentions : 20m*30m*20m

Building usage : Hospital block

Location of building : Darjeeling

Step 1 : calculation of design wind speed

we know the formula to calculate the design wind speed, that is

Vz = Vb*k1*k2*k3*k4

where

• Vb = Basic wind speed (m/s)
• k1 = risk co-efficient
• k2 = Terrain roughness and height factor
• k3 = topography factor
• k4 = importance factor

Given data from IS code:

Vb = 47 m/s

k1 = 1.07

k2 = 0.8

k3 = 1

k4 = 1

Calculation :

Vz = Vb*k1*k2*k3*k4

Vz = 47*1.07*0.8*1*1

Vz = 40.23 m/s

Step 2 : calculation of wind pressure

Pz = 0.6Vz2

Pz = 0.6*40.3*40.3

Pz = 971.071N

Pz = 0.9711 KN

Similarly, we can calculate this for different heights, the calculation for different height has been done in the excel sheet as shown below

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 laod due to the slabs = length*breadth*height*slab thickness

Dead load due to slabs = 20*30*25*0.15

dead load due to slabs = 225KN

In this project we have total five floor slabs,

Total dead load due to all five slabs = 5*dead load due to slab

Total dead load = 5*225

Total dead load due to all the slabs = 1125KN

Dead load due to beams :

Assuming beam of cross section 350*450mm

Dead load due to beam = size of beam* height

= 0.35*0.45*25

= 3.94KN/m

Dead load due to beam = 4KN/m

Super imposed loads due to the partition walls :

Assuming 150mm thick of brickwork

heighe of brick work = Floor height - depth of beam

height of brick work = 3.75 - 0.45

= 3.3m

Therefore, the dead load due tothe brick masonry partition = 3.3*0.15*18

Dead load due to the brick masonry partition = 8.91KN/m

Live Load :
We can calculate the live load of a given structure by using the IS 875:part2, which states different live load values for different rooms

as our building is the hospital building, the all proposed live load values for hospitalbuilding according to the IS 875:part3 has been listyed below

• For ward rooms, dressing rooms, dormitories and lounges = 2.0KN/sq.m
• Kitchen and laboratory = 3.0KN/sq.m
• Dinning room and cafeteria = 3.0KN/sq.m
• Toilets and bath rooms = 2.0KN/sq.m
• X-ray rooms and operationg rooms = 3.0KN/sq.m
• office and OPD room = 2.5KN/sq.m
• Corridor and passages = 4.0KN/sq.m