Week 3 Challenge

QUE.-1.1

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

Ans:- 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?

Ans:-

• In one way slab, the ratio of longer span panel (L) to shorter span panel (B) is equal or greater than 2. Thus, L/B ≥ 2.
• Slab panel is supported on two opposite sides in short direction of one-way slab.
• One way slab bends or deflect in a direction perpendicular to the supporting edges.
• Deflected shape of one way slab is cylindrical.
• one way slab has structural strength in shortest direction
• Main reinforcement is provided in only one direction for one way slabs.

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

Ans:- The value of unit weight of structural steel and soil are given below:

• Unit-weight of Structural Steel: 7850 Kg/m^3
• Unit-weight of Soil: 1800 Kg/m^3

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

Ans:- 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.

5. Define Primary Beams.

Ans:-

• The beams that are connecting columns for transferring loads of a structure directly to the columns are known as primary beams. Usually, primary beams are shear-connected or simply supported and they are provided in a regular building structure.The depth of the primary beams is always greater than the secondary beams. The primary beam acts as a medium between columns and secondary beams.

QUE.-2.1

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

Ans:-

• 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:.
• 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 = Importance factor.
• And then the, design wind pressure is given by the below formula: Pz = 0.6 X Vz^2.

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

Ans:-

• 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.

QUE.-3.1

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

Ans:-

One way slab

• In one way slab, the ratio of longer span panel (L) to shorter span panel (B) is equal or greater than 2. Thus, L/B ≥ 2.
• Slab panel is supported on two opposite sides in short direction of one-way slab.
• One way slab bends or deflect in a direction perpendicular to the supporting edges.
• Deflected shape of one way slab is cylindrical.
• one way slab has structural strength in shortest direction
• Main reinforcement is provided in only one direction for one way slabs.

Two way slab

• In two way slab, the ratio of longer span panel (L) to shorter span panel (B) is less than 2. Thus, L/B < 2.
• Slab panel is supported on four sides of two-way slab.
• Two way slab bend or deflect in both directions.
• Deflected shape of two way slab is dish-shaped.
• Two way slab has structural strength in the shortest direction.
• Main reinforcement is provided in both the direction for two way slabs.

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

Ans:-

• A horizontal beam connecting primary beams (simply supported or shear connected.)
• It will transfer the load to the primary beam and not directly connected to the columns.
• A horizontal beam connecting two rafters in a roof or roof truss.

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

Ans:

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).

Detail the parameters of each load case

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

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/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.

Ans:-

• Go to property section
• Click on Define material.
• Select the section, Rectangular/Circular etc,
• Select the material type concrete, steel , aluminium
• For the rectangular section enter YD & ZD in column below
• click add and close
• Select the material type and assign to the selected view for the support
• click on the support
• click on create
• select type of support do we want to assign the section
• click on add close

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

Ans:-

• First create a simple model by using node in staad Pro.
• Click on Create beam option and create a beam in the direction of x and z axis.
• click on the primary beam in the section.
• right click and add new node in the beam section a node will be added.
• again click on the create 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

Ans-

Wind pressure , according to Is 875 Part 3,

pz = 0.6Vz^2

Where vz = Vb*K1*K2*k3

Vb = Wind speed at certain location = 50

K1 = Risk coefficient = 1.0

K2 = terrain height and structure factor = 1.12

K3 = Topography factor = 0.5

Vz = Vb * K1*K2*K3

= 50 *1.0*1.12*0.5

= 28

pz = 0.6*28^2 = 470.4 = 0.47N/m^2

2. Calculate the Dead load and Live load for the above building with reference to IS standards

(assume suitable sections )

Ans-

The dead load of the section considering the section length 5m and width 0.23m

• Dead load of the section = unit weight * volume of the section
• Unit weight = 25KN/m
• Volume of the section = 0.5*0.23*1 = 0.115m^3
• Dead load = 25 *0.115 = 2.875 KN/m

Live Load = Considering the general building ,

Bath rooms and toilets in all types of the building, kitchens in,

1. Dweeling houses 2 , 1.8
2. Hostel, hotel, hospital 3 , 4.5