Understanding Beam Support Reactions: Questioning the Sign Convention

In summary, the conversation is about solving a problem from a set of slides which has the person confused about the positive value of 3 kip in the support reactions. They explain their approach and ask for clarification, to which the expert responds by explaining that the +3 kip load is the reaction at point A, while the -9 kips comes from the triangular load between points A and B. They also remind the person that the purpose of the exercise is to find the internal loading of the beam at point B. The person then thanks the expert for the clarification.
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Homework Statement



Hi. Question 1-5 from http://www.slideshare.net/hotman1991/met-302-chapter-01 has me puzzled. In the support reactions in Fy, they state By + 3.00 - 9.00 = 0. I do not understand why the 3 is positive.


Homework Equations





The Attempt at a Solution



When doing it myself, I took point A as the Pivot point. So I have negative 9 kip (from that 0 to 1.5 kip triangle), By, and *negative* 3 kip from the force right beside E. Is there something wrong with my logic?
 
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  • #2
The +3 kip load is the reaction at point A. The load of -9 kips comes from the triangular load between points A and B. Remember, the point of this exercise is to find the internal loading of the beam at point B.
 
  • #3
Wow. Cannot believe I messed that up. Crystal clear now, thanks.
 

1. What is the definition of a beam?

A beam is a structural element that is designed to support loads by resisting bending forces. It typically has a long, narrow shape and is used in construction to span large distances and support weight.

2. How do you calculate the forces acting on a beam?

The forces acting on a beam can be calculated by using the principles of statics. This involves analyzing the external loads, such as weight and forces applied to the beam, and determining the internal forces, such as shear and bending, that are created within the beam.

3. What factors affect the forces on a beam?

The forces on a beam are affected by various factors, including the type of load applied, the length and shape of the beam, the material properties of the beam, and the supports at each end of the beam. These factors can influence the magnitude and direction of the forces acting on the beam.

4. How do you determine the maximum force on a beam?

The maximum force on a beam can be determined by calculating the maximum bending moment, which is the point at which the beam is subject to the greatest stress. This can be done by analyzing the load and support conditions, as well as the properties of the beam, using equations or computer simulations.

5. How can the forces on a beam be reduced?

The forces on a beam can be reduced by using different structural elements, such as trusses or arches, to distribute the load and reduce the bending forces. The material properties of the beam can also be adjusted to increase its strength and ability to withstand external forces.

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