Function
- This is an exclusive function for analyzing the structure system with effective beam installed, and it specifies the treatment method of the effective beam stiffness installed in the analysis model.
(If effective beam is installed, this option must be checked.)
Call
From the Main Menu select [Analysis] tab > [Analysis Control] group > [Design Analysis Control]
Input
Design Analysis Control
1. EBWM (Effective Beam Width Method)
: When analyzing lateral loads, the installed slab stiffness is ignored and the effective beam is considered to resist. (Load Case: Wind, Seismic, RS)
When analyzing the gravity load, it ignores the stiffness of the effective beam and analyzes it as the stiffness of the slab.
(Load Case: Remaining load conditions excluding lateral load)
2. FEM (Finite Elements Method)
: Ignoring the installed effective beam, analyze the lateral load and the gravity load. (Load Case : All Load Case)
Note
Stiffness reduction factor for flat plate slab analysis:.
1. The analysis of flat plate slab systems subjected to lateral load generally uses the finite element analysis method, the effective beam width method, and the equivalent frame method.
2. ACI 318-05 requires that the effect of cracks be taken into account when calculating the stiffness of the slab when performing analysis using these methods.
If cracks in the slab are not taken into account, the actual stiffness of the slab may be overestimated, and the moment distributed to the slab may increase from the actual value, and the lateral displacement of the entire frame may be underestimated.
3. Several researchers have been conducting research to reflect the phenomenon of the decrease in the flexural stiffness of the slab due to cracks in the analysis model.
4. Vanderbilt, Corley, and Moehle et al suggested that the stiffness reduction factor of the slab be 1/3 or 1/4.
5. ACI318-05 (R13.5.1.2) suggested that it is appropriate to reduce the slab stiffness by 1/2 to 1/4.
However, these coefficients are too simplistic to explicitly take into account the effect on the geometry of the column and slab, the magnitude of the gravity load, and the magnitude of the lateral load.