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)
• Seismic Load (IS 1893: 2016)

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1. 2. What is One – Way slab?

• The one-way slab is a slab, which is supported by parallel walls or beams, and whose length to breadth ratio is equal to or greater than two.
• It bends in only one direction (spanning direction) while it is transferring the loads to the two supporting walls or beams, because of its geometry. Simply stating it spans and bends in only one direction.

Behavior of One - Way slab:-

• The direction (shorter side of slab) in which load is transferred is known as span. A one-way slab is designed for the spanning direction alone as it bends in only one direction.
• The main tension reinforcing bars therefore run parallel (spaced uniformly) to the shorter span and are usually placed at the bottom of slab.
• In the transverse direction (a longer direction), a minimum amount of reinforcement is provided to take care of the temperature and shrinkage effects in that direction. This steel reinforcement is called the distribution steel or secondary reinforcement.
• This steel also helps in distributing the load. i.e. the point load which has a tendency to punch through the slab. The distribution steel also aids in distributing the load transversely over a larger width, thus offsetting the local effect like plastic shrinkage cracks due to temperature and shrinkage. Even when a slab is supported on all four sides, the behavior of slab is expected to be as one-way slab only as evident from the deflection contour.

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

• Unit weight of Steel = 7850 Kg/m^3
• Unit weight of Soil = 1800 Kg/m^3

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

• Circular section
• Rectangular section
• Trepezodial section
• Tee section
• Genaral section
• Tapered I
• Tapered tube

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1. 5. Define Primary Beams.

• These type of horizontal flexural (beam) structure member which directly connected to supporting compressive structure member that is column.
• Primary beam is also known as main beam which Safely transfer the load to the column acting on it by the slab or by secondary beam if it is present.
• Primary Beams are the beam located at the exterior of the Structural elements.
• Secondary beam are laid on the primary beam.

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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 building has been discussed below. So the design speed can be governed by the below given formula.
• Basic wind speed, Vz = Vb X k1 X k2 X k3 X k4.
• Where,
  1. Vb = Basic wind speed, that is based on the location of the project in India.
  2. k1 = Risk Co-efficient factor.
  3. k2 = Terrain and height factor.
  4. k3 = Topography factor.
  5. k4 = Importance factor.
• And then the, design wind pressure is given by the below formula:
  1. Pz = 0.6 X Vz^2.

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

• The load transfer process of a reinforced concrete building is
  1. Slab
  2. Secondary beam
  3. Primary beam
  4. Column
  5. Foundation
  6. Hard Strata beneath.

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

S.No	One-Way Slab	Two-Way Slab
1	Ly/Lx >= 2; for one-way slab	Ly/Lx<2; For two way slab
2	The one-way slab is suppoted by a beam on two opposite side only.	The two-way slab is supported by the beam on all four sides.
3	In one-way slab, the load carried in one direction perpendicular to the supporting beam.	In two-way slab, the load is carried in both directions.
4	One way slab two opposite side supports beam / walls.	Two way slab four side means all side suppoted beam / wall.
5	One way slab is bend only in one spanning side direction while load transfer.	Two way slab is bend both spanning side direction while load transfer.
6	One way slab economical near about 3.5m.	Two way slab may economical for the panel near about 6m * 6m.
7	Main Reinforcement is in provide short span due to bending	Main Reinforcement is in provide both short and long span due to bending.
8	One way slab near about 100mm to 150mm based on the deflection.	Two way slabs is in the range of 100mm to 200mm based on deflection.
9	Depth required is more	Depth required is less
10	As thickness is more and the amount of steel is also more, it is less economical.	As thickness is less and the amount of steel is also less, it is economical.
11	One way slab deformation profile	One way slab deformation profile

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

• The secondary beams are primarily 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 rests on then slabs.
• So mainly the secondary beams are the beams that are not directly connected to the columns. The secondary beams rest on the other beams that are directly rest on the column and those beams are known as the primary beams.
• So the secondary beams carries a certain amount of total load and help them to distribute the loads in the respective manner.
• As Secondary beams are rested upon the primary beams. They are generally designed as simply supported beams. The torsion at the end is released. They don’t transfer the load to columns. These beams are less critical.
• The ends moment in the secondary beams are negligible as we move away from the column support. What do you mean by pinned and fixed support? The pinned support allow rotations degree of freedom while the fixed support doesn’t allow the rotations. The primary beam is supported by column which provide rigid (fixed) support. But in secondary beam there is no such thing. There is rotation at the ends of them as we can see also. The ends don’t resist the rotation. These moments are countered by causing twisting in the primary beams to which they are supported. Therefore for secondary beam ends act as pinned.

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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

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)
• 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 permanently 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.
• Dead Load factor is 1.

Live Load:

• Live loads are the loads that are 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/sq.m
• Staircase/Corridors : 3 KN/sq.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.

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

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

Assigning Properties:

• The first step in order to assigning the properties to a model using STAAD Pro software.
• Go Properties tab and then there will be a dialogue box and in that dialogue box there is an option called Define menu just click 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, Trapezoidal section etc.
• After choosing the section properties specify the dimensions in that dialogue box.
• And now there will be another option called Add just click on that option and then click OK.
• And 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 opinion 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 dialogue box and in that 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 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 opinion Assign to the selected view and then click on the assign option and then assign the property and done.

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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 Calculate wind pressure for the given building.

PROCEDURE:

Given data:

• Building Location - Darjeeling
• Usage of building - Hospital block
• Building dimensions - 20m X 30m X 20m
• Height of the building - 20m

To Calculate Design Wind Speed:

We know the formula to calculate the design wind speed, that is:

Vz = Vb * K1 * K2 * K3 * K4

Vb = Basic wind speed in m/s = 47 m/s (for the location Darjeeling)

K1 = Risk coefficient; Table1; Cl-5.3.1 (As hospital blocks comes under important buildings, Consider the mean probable design life of structure in years is 100.

Therefore K1 for wind speed 47 m/s is 1.07

K2 = Terrain roughness and height factor (cl-5.3.2), The given height of the building is 20m and mentioned it is in the city center. Therefore, we can say that it comes under terrain category 4.

Therefore K2 is 0.8

K3 = Topography factor (cl-5.3.3), K3 is 1

K4 = Importance factor for cyclic region (cl-5.3.3), K4 is 1

Therefore, Vz = Vb * K1 * K2 * K3 * K4

= 47 * 1.07 * 0.8 * 1 * 1 = 40.23 m/s

To Calculate Design Wind Pressure:

Pz = 0.6 * Vz^2 = 0.6 * (40.23)^2 = 971.071 N/m^2

Similarly, we can calculate the for different heights, the calculation for different height has been done in the excel sheet so the excel sheet has been given below:

Result:

Design wind pressure is calculated.

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

AIM: To Calculate the Dead load and Live load for the above building with reference to IS standards ( assume suitable sections )

PROCEDURE:

Assume the dimensions of the building (L * B * H) is 20m * 30m * 20m

Dead Load due to slabs:

• Assume thickness of the slab of 150 mm
• Dead Load due to the Slabs = Area of slab * thickness of slabX RCC Density.
• Dead Load due to the Slabs = 20 * 30 * 0.15 * 25
• Dead Load due to the Slabs = 2250 KN.

Dead Load due to beams:

• Assume the beams of cross-section 350 * 450mm.
• Dead load due to the beam = Cross sectional area of the beam * Length * RCC Density
• Dead load due to the beam = 0.35 * 0.45 * 20 * 25 = 78.75 KN.

Dead Load due to columns:

• Assume the beams of cross-section 350 * 350mm.
• Dead load due to the beam = Cross sectional area of the beam * Height * RCC Density
• Dead load due to the beam = 0.35 * 0.35 * 20 * 25 = 61.25 KN.

Live Load:

• We can calculate the live load of a given structure by using the IS 875:Part 2,which states different live loads values for different rooms.
• As our building is the Hospital building, the all the proposed live load values for hospital building according to the IS 875:Part 3 has been listed below:

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
Office and OPD Room	2.5 KN/sq.m
Corridor and Passages	4.0 KN/sq.m

RESULT:-

The Dead and Live load of the building is calculated.

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