Case Study: Buckling Load

Case Study: Buckling Load

Buckling is critical in building a structure because it tells the stress load that the column could hold before it buckles, or bends. People often use Euler's formula to calculate the critical buckling load of the long columns with central loading.

E is the Young's modulus of the column material, or the elasticity of the column material. I is the area moment of inertia of the cross-section, and L is the length of the columns. The equation above is just a general equation. The calculation usually depending on the end conditions of the columns. Some of the common end conditions is in the figure 1.

Figure 1. End Conditions

Figure 2. Effective Lengths of the End Conditions

The table in figure 2 above shows an effective lengths of the column based on the end conditions in which L represents the actual length of the column.  

http://www.amesweb.info/CompressionMemberDesign/CompressionMemberDesign.aspx

The link above is one of the sites that was built to calculate the buckling load of the columns.

Links:

http://www.efunda.com/formulae/solid_mechanics/columns/columns.cfm

http://www.amesweb.info/CompressionMemberDesign/CompressionMemberDesign.aspx

Group Meeting: 05/04/2016

Week 6: 05/04/2016

During this meeting, the group put together the sketches of the horse stable for the final sketch. The sketch contained the dimensions of the stable, such as the sizes of the stalls, doors, and the thickness of the walls. While making a rough sketch, the group came to a problem with the roof dimensions. The group did decide to have a sky light for the stable. However, the group did not go into depth about the roof. It was found that knowledge of Bernouli's principle is required in order to calculate the slope of the roof due to the pressure. The group will bring this problem up to Professor Mitchell during the team meeting on Friday. Besides the sketch, the group decided to include the cistern, and the compost into the horse stable design as a final deliverable. Below is a rough sketch of the horse stable.

Sketch 1

Sketch 2

The group decided to have both the 2D and 3D sketches of AutoCAD and SketchUp done by Wednesday night.

Case Study: Wind Loads

Case Study: Wind Loads

In order to prevent the horse stable from collapsing, loads are needed to be considered. There are three categories of loads, horizontal, vertical, and longitudinal loads. Wind loads are being looked at for this specific case study. Wind load is a type of horizontal load. It is caused by the movement of the air in which the wind pressure could have caused a damage to the building. Wind loads depend on the wind speed, the surface shape, and exposed area.

The wind pressure can be calculated through the following equation:

P = C_D X Q

P is the wind pressure (per square foot, psf) on the surface. C_D is the drag coefficient that could range from 0.6 to 2.4 (for most rectangular buildings, the value of C_D is 1.0). Q is the dynamic pressure of a moving air. Q can also be defined as (½ V²D), where V is the wind velocity and D is the air density.

In general, people use 20 to 30 pounds psf as a value of the dynamic pressure of a moving air (Q) for the wind loads. However, during the storm, the Q value can be as high as 60 pounds psf which is corresponding to the wind velocity of 150 mph or higher.

For the Pennsylvania region, if the height zone is less than 30 ft, the wind pressure would be 15 psf. If the height zone is between 30 to 49, the wind pressure would be 20 psf. If the height zone is between 50 and 99, the wind pressure would be 25 psf, and if the height zone is over 1200 ft, the wind pressure would be 40 psf.

In general, a suction of at least 10 psf should be considered. If the wind pressure is from 30 to 50 psf, a suction of one-half of that wind pressure should be considered.

According to the American Society of Civil Engineers (ASCE), for a building that is 300 ft height, the wind load should be 20 psf, and for every 100 ft increase in height, the wind load should be increase by 2.5 psf.

Source: Lin, T. Y., and Sidney D. Stotesbury. Structural Concepts and Systems for Architects and Engineers. New York: Van Nostrand Reinhold, 1988. Print.