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

66 2

b eff

effective width of the composite beam compressive resistance of the steel beam flange

C r C r C r

compressive resistance of the concrete above the hollow cores compressive resistance of the concrete below the hollow cores end distance; lever arm between C r and T r end distance; lever arm between C r ’ 1 and T r end distance; lever arm between C r ’ 2 and T r compressive strength of the concrete at 28 days minimum yield strength of the steel section analytical bending moment of the composite beam experimental bending moment of the composite beam

’ ’

1 2

e

e ’ e ’ f ’ f y

1 2

c

M rc M ’

rc

P u

ultimate capacity of the beam radius of hollow cores thickness of the steel section

r t

t 1 t 2

thickness of the concrete above the hollow cores thickness of the concrete below the hollow cores

T r

tensile resistance of the section centroid of the tension block

ȳ

α ratio of average stress in rectangular compression block to specified concrete strength c resistance factor of the concrete section s resistance factor of steel beam 1. Introduction

Conventional composite beams with solid concrete slabs have some disadvantages related to reduced headroom, on-site welding and reinforcement costs, concrete casting, and curing, especially in regions with harsh climate conditions. Precast concrete hollow core (PCHC) slabs have been introduced to the industry to improve these limitations. PCHC slabs feature circular voids within their cross-sections, leading to reduced reinforcing and concrete materials. These slabs are especially preferred in low-seismic areas where timing, ease of construction, and economic and sustainability criteria are a matter of concern. The composite action between the steel beams and PCHC slabs is ensured using headed shear studs that are usually welded to the flange of the steel beam. The shear studs perform a dowel action where they resist the longitudinal shear and uplift forces. The degree of the composite action (DCA) is described as two terms, including the degree of the shear connection and interaction that are directly related (Chiorean and Buru (2017)). The degree of the shear connection is a strength-based property and depends on the equilibrium of the shear forces in a composite beam at the ultimate limit state (ULS) (Sjaarda et al. (2017)). It is defined as the ratio of the ultimate shear strength of the interface to the minimum strength necessary for the section to develop its full flexural capacity. This value is obtained by performing pushout tests (Yanez et al. 2017). The degree of the interaction ( φ ) is a stiffness-based property defined by complex compatibility equations (Oehlers and Seracino (2002)). Oehlers and Seracino (2002) simplified the degree of the composite interaction as the ratio of the neutral axis separation, h, to the maximum neutral axis separation, ℎ ° . The full ( φ=1) , partial ( 0<φ<1 ), and no composite interaction ( φ=0 ) are illustrated in Fig. 1.

Fig. 1. Degree of composite interaction.