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00:00hi kids today we will learn some basics required to be studied before learning
00:07the concept of bridges so let's start what is a load it is the weight
00:14experienced by a structure and the load is of three types the first one is
00:22dead load it is the weight of the structure itself it remains constant
00:30dead load does not change or remains constant for example it is the weight of
00:38materials used to make the bridge so dead load of the bridge is the weight of
00:46the bridge itself next is the live load it is the additional weight experienced
00:54by the structure like weight of travelers and vehicles experienced by
01:02the bridges this type of weight changes over time
01:11you
01:13number of travelers and vehicles never remain the same over time so this way is
01:20never constant there is also one more type of weight that does not remain
01:28constant and it is environmental weight examples of environmental weight are
01:36snowfall rain
01:42and wind any structure or any bridge experiences this type of weight it can
01:53be weight of the rainfall it can be weight of the snowfall it can be weight
01:59of the blowing wind but it does not remain constant what is force force is
02:08action of push or pull and results from the interaction of two objects in the
02:17case of a bridge the live load that is the load of travelers and vehicles that
02:23pass by the bridge acts as a push force on the bridge environmental forces rain
02:33snow and wind acts as a push force on the bridge and the weight of the bridge
02:41itself acts as a dead load on the bridge bridge deck bridge deck is a passage
02:50which is used by people or their vehicles to cross the bridge the deck of
02:56the bridge may be made up of concrete steel or wood span of the bridge in case
03:07of a bridge it is the distance between two supports like here in this bridge
03:15span is a distance between two supports and it's a single span bridge that is
03:22there is single continuous slab with two supports at each end now here is an
03:30example of double span bridge there are two such portions in bridge where there
03:40is no support in between this is one span and this is second span there is
03:48support at each end of a span now here we have a multiple span bridge there are
03:56numerous bands joined together and there is support at each end of the span
04:05in the case of bridges span can be simple continuous and cantilever any of
04:16these spans may be constructed using beams girders or trusses now let's see
04:26span of an arch bridge in case of arch bridges this is simple or single span of
04:35an arch bridge now let's see the spans in case of suspension bridges and cable
04:44stayed bridges remember suspension bridges and cable stayed bridges are the
04:53longest bridges in the world this is a single span suspension bridge and this
05:04is a multiple span suspension bridge material a bridge can be made up of any
05:14material like concrete steel stones and even combination of any of these this is
05:25a bridge made up of concrete this is a bridge made up of steel and this is a
05:34bridge where steel and concrete both are used form of the bridge the form of the
05:43bridge can be a beam arch or a truss suspension or a cable stayed bridge we
05:53will learn about different types of bridges in our next assignment different
05:59types of bridges are made up of different materials and every type of
06:05material has certain elasticity that is it has ability to change shape while a
06:13force is acting on it and then move back into its original shape and this is
06:22because of this elasticity that bridges experience stress without breaking many
06:31types of stress that a bridge faces are compression tension bending torsion and
06:41even shearing so kids today we learned some basics about the bridges now you
06:50may go ahead and take a quiz to learn more bye-bye