Strength Capacity and Failure Mode of Shear Connectors Suitable for Composite Cold Formed Steel Beams: Numerical Study
Abstract
:1. Introduction
2. The Proposed Shear Connectors and Push Test Setup
3. Description of the FE Model
- Three-dimensional solid elements (C3D8) were used to model the key structural members to obtain detailed structural behavior (CFS beam, bolts, concrete slab, and shear connector components).
- Mechanical properties of the steel beams and shear connectors [20,21] were obtained in compliance with BS EN ISO 6892-1:2009. These properties were used to develop the stress-strain constitutive relationships used in the FE models. Table 1 shows the yield strength, ultimate strength, and elastic modulus.
- For reinforced concrete elements, the ABAQUS program’s concrete damaged plasticity model for reinforced concrete elements was used, which can reflect the complete inelastic behavior of concrete in stress and compression, including damage characteristics. The concrete damaged plasticity model, which takes into account isotropic elastic damage and plastic behavior of materials, can simulate tensile cracking and compressive crushing of concrete materials [26,27].
- For bolts and nuts, the mechanical properties were assumed to be elastic-perfectly plastic. For Grade 8.8 bolts, the yield strength was 640 MPa and the elastic modulus was 210,000 MPa.
- The welding between headed stud shear connectors and CFS flange were modeled using the ‘‘tie’’ type constraint in ABAQUS.
- The ABAQUS contact function was used to model the interaction between components, including the interface between the two channels, between the concrete slab and the metal deck, between the metal deck and the beam, between the shear connectors and concrete slab, between the bolt shanks and the web of the beam, between the bolt heads and the web of the beam, and between the web of the channel and the shear connectors.
- A contact was simulated as a surface-to-surface contact with a small sliding choice. To avoid mutual penetration of the steel and concrete in the normal direction, a “hard contact” was assumed for the normal contact behavior, while a friction contact with a coefficient of m = 0.3 was applied tangentially to the surface of the contact pairs.
- The loads were applied to the beam at one-point loads (as shown in Figure 3 and Figure 4) and were increased gradually until failure. In addition, normal forces were sustained for both concrete slabs using a yoke assembly operated by a hand hydraulic pump to replicate the actual situation of the composite beam in structures and prevent the rotation of the last studded rib at the top of the push test specimen. The magnitude of the normal force is kept at about 0.1 of the vertical applied loads.
- The values of the damage parameters used in the model are as follows: dilation angle = 30, eccentricity e = 0.1, the ratio of initial equibiaxial compressive yield stress to initial uniaxial compressive yield stress was fb0/fc0 = 1.16, the ratio of the second stress invariant on the tensile meridian to that on the compressive meridian Kc = 0.6667, viscosity parameter = 0.0001.
4. Results and Discussion
4.1. Bracket Shear Connectors
4.2. Standard Headed Stud Shear Connector (HSSC)
5. Validation of the Proposed FE Model
6. Conclusions
- The developed finite element models are in good agreement with the experimental results of the push tests and observations. The deformed shapes and the relevant failure modes were accurately captured by the model for all types of shear connectors. For example, the concrete crushing and shear connector rotation in SBSC, DBSC, and HPSC push test specimens were clearly captured by the FE model.
- The concrete damaged plasticity model in ABAQUS can accurately capture crushing and the longitudinal crack of a concrete slab, which is the common failure mode for SBSC, DBSC, and HPSC.
- The developed finite element models accurately model the interaction between the metal decking and concrete slab. For DSBC, the separation between the concrete slab and metal deck occurred is clearly captured by the proposed finite element models. This weak connection is due to the DBSC shear connector’s wide flange surface (double of the SBSC) that leads to such separation.
- The bearing around the bolt of shear connector that is near to the concrete slab (which was the only bolt resisting the rotation after concrete slab crushing) in the test results of SBSC, DBSC, and HPSC specimens is accurately predicted by the model by observed stress concentration around the bolt hole connecting the shear studs to the web of the cold formed beam.
- The proposed finite element models have clearly captured the failure modes of HSSC specimens being the deformation of the shank and the pulling-out of the stud from the thinner flange of steel beam for HSSC specimens, while no crack was observed in the concrete slab.
- The finite element results of ultimate loads were found to be in very acceptable agreement with experimental data, ranging between 0.94 and 1.04. However, the results of the section analysis are generally conservative compared to experiments.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
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Specimen | Fy (MPa) | Fu (MPa) | Fu/Fy | E (GPa) | Elongation (%) |
---|---|---|---|---|---|
SC250-23 | 518.67 | 558.45 | 1.07 | 187.42 | 9.20 |
SC250-20 | 542.65 | 575.74 | 1.06 | 191.05 | 9.10 |
Hot rolled plate | 321.79 | 464.82 | 1.44 | 185.6 | 23.70 |
Reinforcement mesh | 640.82 | 676.91 | 1.05 | 191.67 | - |
SDP51-10 | 678.37 | 687.00 | 1.01 | 201.25 | - |
Specimen | Avg. Pu,per connector (kN) | Predicted Value by Finite Element Results | |
---|---|---|---|
Ppre. Per connector (kN) | Averg. Exp./pre. Ratio | ||
SBSC250-20 | 43.03 | 43.63 | 0.99 |
DBSC250-20 | 52.15 | 55.34 | 0.94 |
HPSC250-20 | 55.45 | 55.27 | 1.00 |
HSSC250-20 | 54.93 | 53.80 | 1.02 |
SBSC250-23 | 44.58 | 43.00 | 1.04 |
DBSC250-23 | 53.60 | 55.79 | 0.96 |
HPSC250-23 | 55.15 | 55.45 | 0.99 |
HSSC250-23 | 53.97 | 53.80 | 0.94 |
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Elsawaf, S.A.; Bamaga, S.O. Strength Capacity and Failure Mode of Shear Connectors Suitable for Composite Cold Formed Steel Beams: Numerical Study. Materials 2021, 14, 3627. https://doi.org/10.3390/ma14133627
Elsawaf SA, Bamaga SO. Strength Capacity and Failure Mode of Shear Connectors Suitable for Composite Cold Formed Steel Beams: Numerical Study. Materials. 2021; 14(13):3627. https://doi.org/10.3390/ma14133627
Chicago/Turabian StyleElsawaf, Sherif A., and Saleh O. Bamaga. 2021. "Strength Capacity and Failure Mode of Shear Connectors Suitable for Composite Cold Formed Steel Beams: Numerical Study" Materials 14, no. 13: 3627. https://doi.org/10.3390/ma14133627