Question

buildings colllapse due to earthquakes






plzz answer 10 points​

Answer 1

$\huge\mathfrak\purple{hello!!}$

The energy resulting by the earthquake causes buildings to collapse.

Answer 2

plsssssss mark me brainliest

i dint copy from google

this is my school project

Reason #1: The Soil Fails

Earthquakes move the ground side to side and up and down—simultaneously. The force behind

this movement is powerful enough to turn soft soil instantly into quicksand, eliminating its ability to

bear weight. It’s enough to quickly transform sloped sites into landslides or mudslides.

Buildings constructed on either soft soil or on steeply sloped sites in a seismic zone, therefore,

are at special risk. When an earthquake hits, it’s as if they are being shaken back and forth in a

pool of Jell-O. When the shaking finally stops, these buildings are sometimes found slumping into

the soil. Taller buildings or those built of rigid concrete may stay intact but topple over in the

unstable soil. Both problems can be directly attributed to soil failure. Such failures were behind

much of the $4 billion in damage resulting from the Mexico City earthquake of 1985.

The design lesson here is a simple one: Avoid building on sites with precarious slopes in

earthquake zones. Sand boils, bogs, or bad soils are to be avoided, as well.

If soft soils are unavoidable, a building’s piers should be set as deeply as possible—all the way to

the bedrock where feasible—and the building’s foundation should be designed to be as rigid as

possible, without being brittle. Since deep, dense soils and bedrock will move less than the less

dense soils above, anchoring a building deep in the ground will make it better able to withstand  

the shock waves.

Reason #2: The Foundation Fails

One of several factors that determine a foundation’s ability to withstand the forces of an

earthquake is the building’s mass. All buildings can carry their own weight; even poorly

constructed ones can resist some additional lateral loads, such as those from a normal wind. But

buildings are not necessarily designed or constructed to resist the irregular, multidirectional, and

intense side-to-side loads that occur during an earthquake, particularly when earthquakes hit in a

series of waves.

Such is the case during a foundation connection failure, when a building literally slides off its

foundation. This kind of failure is an indication that as the foundation was moved by shock waves,

it was not strong enough to pull the structure above along with it.

A building’s height also impacts its ability to withstand the forces of an earthquake. The higher the

building, the greater its potential to break apart—especially near the foundation—as it shifts back

and forth, often out of sync with the foundations below.

If an earthquake is powerful enough, no building is immune from foundation failure. In less

powerful quakes, however, these problems can now be avoided. The use of anchor bolts to tie

the building to its foundation helps prevent the two from separating. Reinforcements to the

foundation wall also help to protect against the concentration of shear forces at grade.

Another key to minimizing the risk of foundation failure is redundancy in a building’s structural

elements. A foundation’s load-bearing capacity must be great enough to accommodate the

additional loads caused by inertia as the building’s mass shifts during an earthquake. While the

goal is to design a system that prevents collapse, it’s equally important that a system is designed

to allow some members to fail without triggering a “domino effect” failure of the entire system.

Reason #3: A “Soft Floor” Fails

You’ve visited them hundreds of times: medical office buildings, hospitals, or other structures

constructed atop a parking garage or an expansive ground-floor lobby. These lower-level floors

are known as “soft floors,” i.e., floors with minimal interior shear walls, additional floor-to-floor

height, or large open spaces with concentrations of building mass above.  

Study photographs of older failed buildings and you’ll find that the upper levels of a building often

remain intact while the lower floors crumble. This is because the concentration of forces is at the

ground floor, where most soft floors are located. Wherever they are, however, soft floors

represent a break in a building’s structural continuity. With fewer walls and little infill, soft floors

are typically less rigid than the building constructed on top of them, making soft floors and the

columns that support them susceptible to failure in an earthquake.

One solution, of course, is to avoid soft floors altogether. A more practical alternative, however, is

to “harden” these spaces with additional engineered shear support. The spans between columns

should be as small as possible, and column connections at ground level should be designed to

resist and distribute lateral forces. To avoid concentrating lateral loads into members that are not

intended to resist them, it’s also important to provide sufficient clearance between rigid infill and

adjacent structural members.