HI. I'M DAVID LINARES FROM VENEZUELA. I'M A CIVIL ENGINEER. I'VE BEEN USING STAAD PRO FOR ALMOST 1 YEAR. I HAVE DOUBTS WHEN IT COMES ON SEISMICS LOADS.
I'M GOING TO ADD A SIMPLE EXERCISE HERE OF WHAT I DO WHEN I DESIGN ANY STRUCTURE. I WILL ADD SOME PICS SO YOU CAN SEE HOW I WORK AND SEE WHERE MY DOUBTS ARE. HOPE YOU CAN ANSWER MY QUESTIONS.
AS YOU CAN SEE AT THE EXAMPLE PIC 1, I HAVE A STRUCTURE THAT HAVE APPLIED SELF WEIGHT AND DISTRIBUTED FORCES ON 2 BEANS FOR DEAD LOAD.
EXAMPLE PIC 1
NOW AS YOU CAN SEE AT EXAMPLE PIC 2 I ADDED MY SEISMIC LOAD CASES AT X, Y AND Z DIRECTIONS
EXAMPLE PIC 2
THEN I STARTED TO ADD THE SEISMIC LOADS AT EVERY LOAD CASES AS YOU CAN SEE AT EXAMPLE PIC 3
EXAMPLE PIC 3
SO IF YOU NOTICED, AT EXAMPLE PIC 3, YOU CAN SEE THAT ON MY SEISM (X DIRECTION) LOAD CASE I ADDED SELF WEIGHT POSITIVE AT X, Y AND Z DIRECTION. I ADDED TOO MY DISTRIBUTED FORCE AT EVERY DIRECTION TOO (X, Y, Z) AND POSITIVE. AND FOR LAST I ADDED MY RESPONSE SPECTRUM.
THEN AT SEISM (Y DIRECTION) LOAD CASE AND SEISM (Z DIRECTION) LOAD CASE I ONLY ADDED THE RESPONSE SPECTRUM.
I DO THIS WAY BECAUSE AT THE PLACES I'VE WORKED PEOPLE DO THIS WAY. ALSO I'VE SEEN VIDEOS ON YOUTUBE AND PEOPLE DOES THE SAME. BUT I REALLY DON'T KNOW WHY. I HAVEN'T BEEN EXPLAINED WHY PEOPLE DO IT THIS WAY.
SO MY QUESTIONS ARE:
1.- WHY DO I HAVE TO ADD POSITIVE SELF WEIGHT AT X, Y AND Z DIRECTION?
2.- WHY DO I HAVE TO ADD ANY LOAD (IN THIS CASE MI DISTRIBUTED LOAD ON BEANS) AT EVERY DIRECTION AND POSITIVE?
3.- WHY DO I HAVE TO ADD ALL THE SELF WEIGHTS AT EVERY DIRECTION AND LOADS AT EVERY DIRECTION FIRST AND FOR LAST MY RESPONSE SPECTRUM?
4.- WHY DO I HAVE TO DO ALL OF THIS ONLY AT X (DIRECTION) AND AT Y AND Z DIRECTIONS ONLY ADD MY RESPONSE SPECTRUM?
PLEASE I WOULD REALLY LIKE TO KNOW WHY IS DONE THIS WAY.
I REALLY APRECIATE YOUR ANSWER AND EXPLANATION ABOUT THIS TOPIC, BECAUSE MEANWHILE I'M DOING THIS I FEEL LIKE A ROBOT DIS KNOWING WHAT I'M A DOING.
DAVID LINARES.
ligonza.david@gmail.com