Structural Design Homework: Landing Support Analysis

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Homework Statement

For the first picture , i was told that the landing is supported by the beam . So ,when we are doing the load analysis , the load analysis of the staircase and landing are combined . however , for the second example , the landing is said to be the support . so , when we are doing the load analysis , the load analysis of the landing has to be done separately .

Homework Equations

The Attempt at a Solution

Why ? I think the author is wrong . I agree that for case 2 , the landing is said to be the support of 2 staircase ( up and down) . For the first case , why can't i say the landing is the support ?

 

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The first figure shows the loading condition of the first case ( first part is staircase , second part shows the landing ) , while the second and third figure shows the loading condition of the second case ( separated analysis for staircase and landing.)