Issue 74

E. Sharaf et alii, Fracture and Structural Integrity, 74 (2025) 262-293; DOI: 10.3221/IGF-ESIS.74.17

2 3 n

2 2 n

2

2

4

3

2

4

2 



2 

3 3            4 6    8 4 4 ) n n n n n n n

(

3

2

2

2

2

2

2



f

(26)

0

3

2

2  ( (4 4 2 n n

n  

  

))

2

2

The equivalent mass in an SDOF system can be calculated using the following formula:

 

m

( 1) m m f 

(27)

[n,(n 1)] 

0[n,(n 1)] 

eq

where n represents the number of the floor whose mass is to be shifted, and f 0 is the mass-shifting coefficient to the lower floor, which was derived in its original form from Eqn. (22). Meanwhile, m eq is defined as the total equivalent mass of the frame. A multi-degree-of-freedom (MDOF) frame structure may have many modes of vibration. Usually, we use the first mode of vibration in orthogonal directions to estimate seismic demand. The fundamental period of the equivalent SDOF system is given by:

m K

eq

2  

(28)

T

eq

A step-by-step flowchart of the proposed method for the computation of the fundamental time period of the RC MRFs is provided in Fig. 6.

Figure 6: Proposed procedure flowchart.

N UMERICAL MODELING FRAMEWORK

Assumptions and scope he assumption of this study mainly examines bare frame buildings, excluding the stiffness contribution of infill walls. The building models examined range from 3 to 30 stories in height. For each number of stories studied, different storey heights were chosen, which vary from 2.5m to 4m. The suggested formula has mainly been derived through estimating the fundamental time period of RC moment-resisting frames under elastic conditions. Modeling approach The frame structure shown was modeled using frame elements in the ETABS environment. The beams and columns were idealized as linear elastic elements. Each member (beams and columns) was discretized into a single frame element between T

272