الفهرس 
LITERATURE REVIEWOnly 14 pages are availabe for public view
 |  | from | 342 |  |  |
| | | from | 342 | | |
Abstract
Four full-scale specimens were tested under eccentric shear loading to study the behavior, failure modes, and load-carrying capacity of branch plate-to-CHS column connections. The specimens were designed to investigate the impact of varying load eccentricity and branch plate depth on the connection’s performance. The capacity of the connection was assessed based on different failure modes and compared to current design guidelines. The comparison revealed discrepancies between the tested specimens and the existing design guidelines, primarily attributed to the influence of changing load eccentricity.
Finite element verification using ANSYS workbench 18.20 were employed with the experimental testing done before by (Voth & Packer, 2012), additionally, verification with the tested specimens in this study, the verification done with the respect to failure modes, position of failure and the load-displacement behavior for all specimens, after getting a good agreement between FEM and the specimens used in verification, an exten-sive parametric study performed in two phases.
In the first phase, a total of 48 specimens were utilized to examine the impact of varying parameters: chord diameter (D0), chord side wall thickness (t0), and branch plate depth-to-the-chord diameter ratio (η). Throughout this phase, a constant load eccentricity of 35.0 mm from the chord face was maintained. The outcomes of this study led to the proposal of a modification to the current design guidelines (DGL). The proposed modification takes into account the average results obtained from all specimens. It identifies that specimens with small chord slenderness (less than 30) are deemed unsafe based on the DGL perspective. The proposed modification exhibits an average value of 0.97 and a standard deviation of 0.11 across all studied specimens. This small parametric study reveals that load eccentricity has a significant effect on the load carrying capacity of the connection.
To examine load eccentricity, an extensive parametric study considered 295 specimens. Four parameters were analyzed: chord diameter (D0), chord side wall thickness (t0), branch plate depth-to-chord diameter ratio (η), and load eccentricity-to-branch plate depth ratio (φ). The study proposed a modification to the current design guidelines (DGL), reducing the standard deviation from 0.43 to 0.09. The modification specifically addressed specimens with fixed small eccentricity and load eccentricity up to 12 times the chord diameter.
7.2 Conclusions
The main conclusions from this study are summarized as follows:
• Specimen length and end conditions greatly affect the connection behavior and chord surface deformations. Short specimens (L<10 times the chord diameter) exhibit stiff chord surfaces and may alter failure modes.
• Excessive chord surface deformations, not exceeding 3% of the chord diameter (3%d0), are the dominant failure mode for connections with small eccentricity (<0.25 times the branch plate depth, h1).
• Geometrical parameters, specifically 2γ and η, significantly influence connection behavior and load-carrying capacity. Increasing 2γ decreases load capacity, while increasing η enhances carrying capacity.
• Specimens with small eccentricity and thin chord thickness (t0 < 15.0 mm) experience chord punching at the tension side of the branch plate after reaching the 3%d0 deformation limit. Specimens with t0 > 15.0 mm encounter premature weld failure despite adequate weld size.
• Load capacity decreases as load eccentricity increases, with a more pronounced decrease for small eccentricities compared to larger ones. Small eccentricities exhibit a higher rate of load degradation.
• Load capacity increases with increasing the value of η up to a value of 1.0, beyond which it remains constant.
• Moment capacity decreases with increasing load eccentricity until it reaches 1.50h1, after which load eccentricity has no significant effect on moment carrying capacity.
• Specimens with the same product of (η * t0) exhibit similar moment carrying capacity.
• The current design guidelines (DGL) are found conservative in many cases due to ignoring the effect of changing the load eccentricity.
• The proposed modification to the DGL agrees well with the results of the studied specimens. The average and standard deviations for specimens with small eccentricity are 0.97 and 0.11, respectively. Similarly, for specimens with variable eccentricities, they are 0.88 and 0.09, respectively.
• The modified design equations may be conservative for specimens with large branch plate depth (η > 1.0). For smaller values of η, the equations may overestimate the load capacity, particularly for specimens with small eccentricity (φ < 0.50).
7.3 Future work
The conducted study clearly indicates that load eccentricity has a significant impact on the load carrying capacity, as demonstrated by the figures from the parametric study. However, there are certain points that need to be addressed in future research, such as:
- The effect of shear lag should be studied as it is evident that the load carrying capacity and moment carrying capacity are effective for the small eccentricities.
- To extend the scope of this study, an analytical model should be developed to establish an equation that can be used in design guidelines.
- More research attention should explore potential strengthening techniques for branch plate-to-CHS column connections to enhance their load carrying capacity.
- Studying the effect of chord stress level on the carrying capacity of the connection. This would involve analyzing how different stress levels in the chord affect the overall performance and load-carrying capacity of the connection.
- Explore the influence of axial load in combination with eccentric shear loading. By considering the simultaneous presence of axial load and eccentric shear loading, the study can provide insights into the behavior and capacity of the connection under more realistic loading conditions.
- Studying the behavior of the branch plate-to-CHS column connection under effect of cyclic loading.