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Finite Element: Bending of Prismatic Beams
Friday, November 6, 2009
What is a Beam?
A beam is a structural element that primarily carries bending (flexure or
transverse) loading.
Beams generally carry vertical forces but they can also sustain horizontal
loads (e.g. due to an earthquake).
Beams are characterized by: a) shape of cross-section, b) length, c)
material, and d) type of supports
Beams are used in the construction sectors are typically made of steel,
reinforced concrete, or wood
Types of Beam
The most common types of steel beam is the
I-beam or wide-flange beam or a universal
beam. They are commonly used in steelframed
buildings and bridges
Other common beam profiles are the C-channel, the hollow structural
beam, and the angled-beams
For Further reading please
A beam is a structural element that primarily carries bending (flexure or
transverse) loading.
Beams generally carry vertical forces but they can also sustain horizontal
loads (e.g. due to an earthquake).
Beams are characterized by: a) shape of cross-section, b) length, c)
material, and d) type of supports
Beams are used in the construction sectors are typically made of steel,
reinforced concrete, or wood
Types of Beam
The most common types of steel beam is the
I-beam or wide-flange beam or a universal
beam. They are commonly used in steelframed
buildings and bridges
Other common beam profiles are the C-channel, the hollow structural
beam, and the angled-beams
For Further reading please
Fluid Mechanic: Water Hammer
Friday, October 23, 2009
Water hammer (or, more generally, fluid hammer) is a pressure surge or wave resulting when a
fluid in motion is forced to stop or change direction suddenly (momentum change). Water
hammer commonly occurs when a valve is closed suddenly at an end of a pipeline system, and a
pressure wave propagates in the pipe. Valve closure can result in pressures well over the steady
state values, while valve opening can cause seriously low pressures, possibly so low that the
flowing liquid vaporizes inside the pipe.
The excessive pressure may fracture the pipe walls or cause other damages to the pipeline
system. The possible occurrence of water hammer, its magnitude and the propagation of the
pressure wave must be carefully investigated in connection with the pipeline design.
(J.Houghtalen:2009)
The simple example where it is happen when you turn OFF a water flow suddenly (like a
dishwasher, a clothes washer, a toilet or even closing a hand faucet suddenly. Shutting off the
flow suddenly sends a pressure or shock wave down the water line through the water shocking
the pipes and creating the 'hammer' noise. These shock waves travel faster than the speed of
sound and can exert very great instantaneous pressures. Over time, water hammer can damage
pipes, valves and eventually weaken pipe joints. (R. Hancock: 2002)
The Hazard causes by water hammer are various. Firstly danger of high pressure: the
excess pressure resulting from water hammer is added to the initial pressure. If the total pressure
is greater than a maximum permissible pressure there is a risk of the pipe rupture or joint failure.
Secondly is a danger of negative pressure: negative relative pressure may result from water
hammer, if these pressure are below -10m of water column, a pocket cavitation or water vapor is
created, with possible collapse of the conduit wall or sucking in the joint seals. The pipe lining
material may also be damaged. Finally risk of the pipe fatigue resulting from rapidly alternating
positive and negative pressures with singly may not lead to actual failure of the conduit.
(Y.Labye: 1988)
fluid in motion is forced to stop or change direction suddenly (momentum change). Water
hammer commonly occurs when a valve is closed suddenly at an end of a pipeline system, and a
pressure wave propagates in the pipe. Valve closure can result in pressures well over the steady
state values, while valve opening can cause seriously low pressures, possibly so low that the
flowing liquid vaporizes inside the pipe.
The excessive pressure may fracture the pipe walls or cause other damages to the pipeline
system. The possible occurrence of water hammer, its magnitude and the propagation of the
pressure wave must be carefully investigated in connection with the pipeline design.
(J.Houghtalen:2009)
The simple example where it is happen when you turn OFF a water flow suddenly (like a
dishwasher, a clothes washer, a toilet or even closing a hand faucet suddenly. Shutting off the
flow suddenly sends a pressure or shock wave down the water line through the water shocking
the pipes and creating the 'hammer' noise. These shock waves travel faster than the speed of
sound and can exert very great instantaneous pressures. Over time, water hammer can damage
pipes, valves and eventually weaken pipe joints. (R. Hancock: 2002)
The Hazard causes by water hammer are various. Firstly danger of high pressure: the
excess pressure resulting from water hammer is added to the initial pressure. If the total pressure
is greater than a maximum permissible pressure there is a risk of the pipe rupture or joint failure.
Secondly is a danger of negative pressure: negative relative pressure may result from water
hammer, if these pressure are below -10m of water column, a pocket cavitation or water vapor is
created, with possible collapse of the conduit wall or sucking in the joint seals. The pipe lining
material may also be damaged. Finally risk of the pipe fatigue resulting from rapidly alternating
positive and negative pressures with singly may not lead to actual failure of the conduit.
(Y.Labye: 1988)
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