2017 Annual Stability Conference Presentation

Session S5 – Stability of Members and Connections
Thursday, March 23, 2017
8:00 am

Stability of Extended Beam-to-Girder Shear Tab Connections Under Gravity Induced Shear Force

A coordinated experimental and numerical investigation of the behaviour and stability requirements of full-depth extended shear tabs is described in the paper. Based on the FE analyses, the load transfer mechanism and the buckling capacity of the stiffened portion of the full-depth shear tab were determined. The parameters, which influenced the buckling of the stiffener, were studied; including the depth and thickness of the shear plate, the depth of the girder, the width of the girder flanges, and the flexibility of the girder web. Further FE analyses were completed to determine the buckling capacity of the shear tab with reduced depth of the stiffener. In addition, the load-transfer mechanism and buckling capacity of these shear plates were modeled when they are used in double-sided configurations, i.e. when a beam is placed on both sides of the girder.

Mohammad Motallebi and Colin A. Rogers, McGill University, Montreal, QC; Dimitrios G. Lignos, Swiss Federal Institute of Technology, Lausanne (EPFL), Lausanne, Switzerland

2017 Annual Stability Conference Presentation

Session SS2B – Technical Presentations: Stability at Elevated Temperatures
Tuesday, March 21, 2017
3:15 pm

Effect of Boundary Conditions on the Creep Buckling of Steel Columns in Fire

A computational study using Abaqus was performed to investigate the influence of boundary
conditions on the creep buckling behavior of steel columns at elevated temperatures of fire. W12×120
wide flange columns with the unsupported length of 240 inches are used in the simulations. Thermal
creep of steel is modeled following equations proposed by Fields and Fields for the creep of ASTM A36
steel. Four different classical support conditions and seven imperfection amplitudes are considered to
quantify the effect of boundary conditions on the time-dependent strength of steel columns in fire.
Thermal restraints, both axial and rotational, were ignored in the analyses. Representative results from
creep buckling tests simulated at 500 °C are presented and discussed. Results from creep buckling
simulations presented in this paper indicate that the rotational and translational restraint at the column
ends along with the initial crookedness of the column have a significant impact on the predictions of the
time-dependent strength of steel columns subjected to fire.

Mohammed A. Morovat, Michael D. Engelhardt and Todd A. Helwig, University of Texas at Austin, Austin, TX

2017 Annual Stability Conference Presentation

Session SS1A – Technical Presentations: Stability of Thin-Walled Components and Assemblages
Tuesday, March 21, 2017
1:40 pm

Numerical Study on the Behavior and Design of Screw Connected Built-up CFS Chord Studs

This study presents the development and validation of a finite element modeling protocol in ABAQUS for screw connected, back-to-back built-up cold-formed steel (CFS) columns using results from experiments conducted at Johns Hopkins University. The goal is to examine the buckling, peak, and post-peak behavior (with an example shown in the figure) of built-up CFS columns of different cross section sizes and sheathing conditions, and under monotonic loading to improve existing built-up CFS column design guidelines so that all relevant failure modes are considered. Ongoing working includes cyclic collapse analyses, the characterization of chord stud buckling limit states, and a framework to implement these limit states in seismic simulations of CFS-framed shear walls.

Smail Kechidi and Nouredine Bourahla, University of Blida 1, Blida, Algeria; David C. Fratamico and Benjamin W. Schafer, Johns Hopkins University, Baltimore, MD; José Miguel Castro, University of Porto, Porto, Portugal


2017 Annual Stability Conference Presentation

Session S12 – Advances in Stability Analysis
Friday, March 24, 2017
1:00 pm

Non-Uniform Modal Decomposition of Thin-Walled Members by the Constrained Finite Element Method

In the paper a new method, the constrained finite element method is applied for the modal decomposition of thin-walled members. With the help of this method the thin-walled member can be enforced to deform in accordance with some predefined criteria. In stability analysis, thus, it becomes straightforward to directly study various buckling types, for example flexural buckling, flexural-torsional buckling, distortional buckling, etc., as desired by the user. The main focus of the paper is on the special feature of the method that modal decomposition can be performed for non-uniform members, too, more specifically, for any members built of from prismatic segments. The connecting segments can have different cross-sections: this makes it possible, among others, to build a single realistic shell model with e.g., directly modeling gusset plates or strengthening plates, while still to utilize modal decomposition advantages. Moreover, the segments can be constrained into different deformation modes, that is the enforced deformations may vary from segment to segment: this allows calculating the critical load value directly to a certain type of buckling in a certain part of the member. Thus, unlike in a regular shell finite element buckling analysis, it is not necessary to check hundreds of mostly interacted buckling modes to find a desired mode, but this desired mode can be found in a way which is more direct, more objective, and more efficient.

Sándor Ádány, Budapest University of Technology and Economics, Budapest, Hungary