Understanding Beam Support Reactions: Questioning the Sign Convention

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The discussion revolves around a homework problem regarding beam support reactions, specifically questioning the sign convention used in the calculations. The user is confused about why a force of 3 kips is considered positive in the equation for vertical reactions at point B. After analyzing the problem, it becomes clear that the +3 kip load represents a reaction at point A, while the -9 kip load arises from a triangular distributed load. The user realizes their earlier misunderstanding and acknowledges the clarity gained from the discussion. The focus remains on accurately applying sign conventions in structural analysis.
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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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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.
 
Wow. Cannot believe I messed that up. Crystal clear now, thanks.
 
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