Project 1_Comparative study of different storey buildings for Seismic forces
Aim - Comparative study of different storey buildings for Seismic forces.
Introduction - studying the Factors influencing the dynamic characteristics of a building, Factors influencing the Natural Period of a building, Factors influencing the Mode shape of oscillations
Procedure -
we need to create 10 different models for the comparison. so for that we will start with creating model - A which is 2 storey building to create that procedure is -
1. Open new file
2.then add the Indian code and SI units
3.create the grids as given in the question 5 column 4 rows at a 4m distance
4 . Create the 2 story at 3m distance plinth at 1.5 m and assign 1st storey as master storey and other stories similar to the 1st storey.
5.then click ok we will see the plan and 3d view of the grids provided
6.then go to define - add new materials concrete and steel concrete of M30 grade and rebar of Fe 415
7.then go to define - section property - frame section then add new beam and column section select the proper material and the rebar
Beam - 300 x 400
Column - 400 X 400
8.then go for the define - slab section - add new property give the thickness of slab 150mm and modelling type membrane and materials.
9. Go for define load patterns add the load patterns live , dead, wall, EQX and EQY
And for EQX and EQY modify the lateral load
Direction and eccentricity for EQX - X for EQY - Y
Seismic zone - 3
Site type - 2
10. Then define the mass source
100 % of dead load
25% of live load
10. Then check the load cases of all the loads are present
11. Then go to define and create load combination
12. After this start modelling beam and column and slab
13.start with modelling column go to quick draw and select the column property we created C400x400 and place on the intersection of grids
14.for beam go to quick draw beam select the property we created B300x400 and model the beam on the grids
15.then place the slab by using quick slab and keep the similar story option
16.then go to select and object type then select all the beam and then go to assign - frame load - distributed - load pattern - wall . Load - 10kn/m
17.than select the floors assign 3kn/m of live load
18.then select all the slabs and assign diagrams
19. everything is done then check the model from analyze tab
20.once model is checked then run analysis
21.the for period sec go to tables - analysis results - structure output - model information - modal periods and frequencies
for next 9 models we will save as the previous model and make the needed changes in the new model.
The step by step procedure with sceenshots is given below -
Result -
1. Effect of verrying column size on building -
E - mode 1 - 1.731 s
F - mode 1 - 1.73 s
There is no significant difference in the time period of both the models
G - mode 1 - 4.17 s
H - mode 1 - 4.416 s
Time period of varying column size is less than the uniform column size
2. Effects of mass pn time period
H - 4.416 s
J - 4.425 s
K - 4.435 s
The live load is uniform in all the stories even if it is different there is no significant difference in the time period.
But mass is directly proportional to the lateral displacement.
3. effect of building height on time period -
A - 0.5 s
B - 1.036 s
F - 1.73 s
H - 4.416
As the height increases the time period is definitely increasing.
4. Effect of column orientation on time period
B - 1.036 s
C - 1.145 s
D - 1.12 s
The deflection will be more in building D than the building C in lateral load case because building column size of building C 550 is X direction
5. Effect of flexural stiffness of structural elements on mode shapes
B - 1.036 s
Close to zero - 2.62 s
6. Effects of axial stiffness of vertical members on mode shapes -
H - 4.416 s
Zero axial area - 5.99 s
7. Effects of degree of fixity at column base on mode shape -
B - pinned support - 1.03 s
Fixed support - 0.941 s