The causes affecting the Degree of Earthquake damages to buildings
High rising buildings generally fall when the earthquake hits them and cause utmost destruction or damage with a loss of lives and the fall depends on several reasons.
Earthquake is really a destructive natural destroyer that is destroying some towns and cities continuously over the centuries and damaging them. This destruction for earthquakes can happen upon some conditions of ground or construction based mostly on sediments in flood plains, converted land or former landfill grows the effect of the vibrations though the harder rocks prevent the shaking amount. The result of the effect can be seen in a huge devastated way like damaging of lives and buildings and animals etc. in some cases the land may even dissolve like quicksand and make buildings sink.
Poor construction can make buildings more vulnerable for the earthquake damage and where the bricks have been held in place with the right mortar will survive long. Besides the construction, there are various other factors that are responsible for the damage of building for earthquake and they are breakable columns, stiffness elements, expandable ground floor, short columns, shapes, sizes, numbers of storeys, kind of foundation, location of the buildings, structural layouts etc.
Here all the above cause of damages is being discussed to give a clear overview of the problems and damages and the factors are also stated those can improve the degree of earthquake that damages the buildings. The factors are:
- Difference between design and actual response range
- Breakable columns
- Irregular arrangement of hardness element in plan
- Adjustable ground floor
- Short columns
- Shape of the floor plan
- Shape of the building in height
- Slabs support columns without beams
- Damages happen by previous earthquake
- Strong concrete building with a frame structural system
- Number of storyes
- Foundation types
- Place of the connected buildings in the block
- Slab levels of near structure
- Bad structural layout
Wrong measurement of excepted earthquake characteristics are used in the earthquake design of the form is both popular and difficult reason for the damage of the buildings.
Most of the structures have been failed in earthquake as per the failure of column and the column may fail for decline of concrete that made cyclic loading and less number of ties fixed in the column at the important locations.
Cores in structures are the main stiffness element and its location as building would influence the behavior of the structures when earthquake affects and make damage.
If the stiffness is decreased heavily of a structure then the stress falls on the structural elements of increased story may increase and fail.
This reason is not very much familiar in comparison of ordinary column failure yet short column may fail in cutting in heavy manner and also make the structure fall.
It is said that the square shaped floor plan is the best insecure behavior than other shapes so the extent of building insecure damage is made by the floor shape plan.
The normal upper storey have most insecure response capered with buildings which have upper storyes in the form.
Flat slab system is the weakest structural system which does not have any good resistance against seismic effects and those system is very flexible and has low flexibility
There are many buildings that have faced earthquakes previously and can face earthquakes again and will fail if the repairing had not done well. It is also seen that repairing a long ago can cause same damage though the methods have improved and the effects are also.
this system is actually a base of weakness in buildings as it goes through many inter-storey drift by seismic excitation which needed more cost to repair.
When the storeys number increases the chance of affected by earthquake gets high, high rises buildings’ storeys don’t have the strength to bear the capacity of the building.
The types of foundation raises the degree of earthquake damages in two forms – direct and indirect; for direct effect of foundation form it clear itself in number of characteristics and the failure of foundation member is rarely happening but leaves effect. On the other hand, the indirect one has out of plane movements of individual columns based in the case of isolated foundations.
The location of the connected buildings on block affects on the structure and increases the fail of the buildings.
The impulse loading from adjacent buildings have a significant influence on the increment of the damages ; the increase of damages in structures with various floor level slabs are significantly greater than buildings with the same floor slab level.
The poor adjustment between architectural engineer and structural engineer at conceptual design phase can make bad structural layout.