Plastic Collapse of Frame Essay Example
PLASTIC COLLAPSE OF A PORTAL FRAME
AIM
The purpose of this experiment is to find out how a portal frame deflects when horizontal and vertical external loads are applied to it. This experiment will then help in the comparison between what is theoretically expected to happen to the portal frame and what is actually recorded to happen during the experiment. The portal frame in this experiment is part of a statically indeterminate structure.
BACKGROUND INFORMATION
For any material, there is initially a positive linear increase between stress and strain as a linear varying load is applied to it (this happens as the material stretches initially). This relationship is linear until the magnitude of the stress reaches the yield value of the material.
At this value, elongation increases rapidly with the external load rapidly decreasing to zero.
If the deformed material is taken and external load is applied to it increasing from zero magnitude, the same effect happens.
Bending
There is also the concept of bending which is inevitable in the portal frame, (due to a downward load acting against upward reactions.) For any section in the structure, there will be compression at the 'head' of the bending moment arrow and tension at the tail of the arrow. The top horizontal part of the portal frame will be sagging due to the downward applied load. There will be compression at the top and tension at the bottom of the top
(middle) horizontal part of the portal frame.
Apparatus
The apparatus involved a mild steel portal frame, which had been clamped into a loading rig such that it was vertical from the side view. The loading rig connected to the portal frame such that there was vertical load at the centre of the beam and horizontal load at the top of a column. There were two gauges, one to measure the vertical deflection and the other, the horizontal deflection. A set square was also used in the experiment.
PROCEDURE
The loading rig was inspected for
AIM
The purpose of this experiment is to find out how a portal frame deflects when horizontal and vertical external loads are applied to it. This experiment will then help in the comparison between what is theoretically expected to happen to the portal frame and what is actually recorded to happen during the experiment. The portal frame in this experiment is part of a statically indeterminate structure.
BACKGROUND INFORMATION
For any material, there is initially a positive linear increase between stress and strain as a linear varying load is applied to it (this happens as the material stretches initially). This relationship is linear until the magnitude of the stress reaches the yield value of the material.
At this value, elongation increases rapidly with the external load rapidly decreasing to zero.
If the deformed material is taken and external load is applied to it increasing from zero magnitude, the same effect happens.
Bending
There is also the concept of bending which is inevitable in the portal frame, (due to a downward load acting against upward reactions.) For any section in the structure, there will be compression at the 'head' of the bending moment arrow and tension at the tail of the arrow. The top horizontal part of the portal frame will be sagging due to the downward applied load. There will be compression at the top and tension at the bottom of the top
(middle) horizontal part of the portal frame.
Apparatus
The apparatus involved a mild steel portal frame, which had been clamped into a loading rig such that it was vertical from the side view. The loading rig connected to the portal frame such that there was vertical load at the centre of the beam and horizontal load at the top of a column. There were two gauges, one to measure the vertical deflection and the other, the horizontal deflection. A set square was also used in the experiment.
PROCEDURE
The loading rig was inspected for