PSI - Issue 64

Parinaz Panjehbashi Aghdam et al. / Procedia Structural Integrity 64 (2024) 65–73 Panjehbashi et al. (2024)/ Structural Integrity Procedia 00 (2019) 000 – 000

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2.5. Degree of the composite action (DCA)

As aforementioned, the degree of the composite action (DCA) is a stiffness-based characteristic defined by compatibility equations at the ultimate state (US). In this section, the DCA is calculated for the composite beam featuring a 254 mm PCHC slab, as presented in Figure 8. The performance of the concrete in the hollow core section was neglected in these calculations.

Fig. 8. Analytical model of the flexural specimen with 254 mm PCHC slab at the US. The predicted bending moment at the US (M rc ) is determined by computing the moment of forces about the neutral axis location, as below:

(1)

'

'

'

'

1 1 r r M C e C e C e = + + 2 2 . . . rc r

While, the C r , C ’

r1, and C ’

r2 represent the compressive strengths of the steel beam flange, concrete above, and

below the hollow cores, respectively. The lever arm between the C r , C ’ r2 and tensile resistance (T r ) is defined as e, e’ 1 , and e’ 2, respectively. he C’ r represents the total compressive strength of the concrete given by Eq.2. The value of the C r can then be calculated as Eq.3. r1, and C ’

(2)

'

'

'

'

1 r c eff C C C f b t t = + = + 2 1 2 . ( ) r r

'

2 (3) As the calculated bending moment will be compared to the corresponding experimental value, the capacity reduction factors ( and ) are considered equal to 1. The b eff corresponds to the effective width of the composite beam. The f’ c and f y define the compressive strength of the concrete and the minimum yield strength of the steel beam, respectively. Also, t 1 and t 2 are the thickness of the concrete above and below the hollow cores, respectively. In addition, A s represents the cross-section area of the steel beam. Finally, the DCA of the composite specimen is calculated as the ratio of the analytical ( M rc ) and experimental ( M ’ rc ) bending moments as below: (4) The degree of the composite action was calculated as 64% and 68% for the specimens with 254- and 203 mm PCHC slabs, respectively. The composite action between the steel beam and PCHC slabs is currently neglected in the design process. Considering the realistic composite action between the steel beams and PCHC slabs will result in a smaller steel beam section and a reduction in concrete material and sustainable structures. s y A f C − r r C = ' (%) rc rc M M DCA =