SSRC 2017 Annual Stability Conference

Session S2: Seismic Stability of Members and Systems
Wednesday, March 22, 2017
9:45 a.m.

Analyses on Seismic Behavior of Corrugated Steel Plate Shear Walls

Corrugated Steel Plate Shear Wall (CoSPSW) is a new type of lateral load resisting system in which corrugated steel wall panels are embedded inside boundary frames, with the corrugation oriented in the horizontal or the vertical direction. Corrugation will form “ribs” on the wall panel, and the axial and out-of-plane bending stiffness is greatly enhanced along the direction parallel to the rib, while the axial stiffness will become minimum along the direction perpendicular to the rib, which is called “According Effects”. As a result, wall panels with vertical ribs or vertical corrugation will be able to resist the gravity loads transferred to them due to enhanced vertical buckling capacity, while wall panels with horizontal ribs or horizontal corrugation will neatly avoid the gravity loads transferred to them. Compared with the unstiffened steel plate shear walls (SPSW), CoSPSWs would have greater elastic buckling capacity, and more resistance to the gravity loads transferred to the wall panel or neatly avoid them depending on direction of the corrugation.

The main focus of this paper is on the seismic behavior of CoSPSWs and comparison with SPSWs. Nonlinear push-over and cyclic analyses were conducted on a group of 3D CoSPSW and SPSW models, and parametric studies were performed with different wall panel and frame configuration, as well as gravity load effects. It turns out that CoSPSWs with deeper corrugation have higher lateral stiffness, lateral strength and energy dissipation capacity than SPSWs; while CoSPSWs with shallower corrugation have higher lateral stiffness and ductility, but lower lateral strength than SPSWs. For all cases investigated, CoSPSWs have stable hysteric curves with almost no pinching. Accordingly, shear walls with weak frame or under gravity loads are studied. When a weaker frame is used, tension field action of the SPSWs cannot fully develop, which causes 18% and 25% reduction in the ultimate lateral strength and energy dissipation. While CoSPSWs is less sensitive to the frame stiffness compared to the SPSWs, especially the vertical CoSPSWs. When gravity loads are applied, the ultimate lateral strength of the wall panels in the SPSWs had a significant reduction of 38%; CoSPSWs is less sensitive to the gravity load effects compared to the SPSWs.

Qiuhong Zhao, Junhao Sun, and Yanan Li, Tianjin University, Tianjin, China

SSRC 2017 Annual Stability Conference

Session S8: Stability of Wall Systems
Thursday, March 23, 2017
3:00 p.m.

Experimental Studies on Corrugated Steel Plate Shear Walls

Corrugated Steel Plate Shear Walls (CoSPSW) are lateral load resisting system in which corrugated steel plates are embedded inside a boundary frame, with the corrugation oriented in the horizontal or vertical direction. This paper presented experimental research on the cyclic behavior of corrugated steel plate shear walls as a new type of steel plate shear wall system. Three 1/3-scale two-story single-bay scaled CoSPSW specimens were designed and tested using quasi-static loading. Two of the corrugated specimens had corrugated panels with the type I geometric property of deeper groove, one horizontal-oriented and one vertical-oriented, while the third corrugated specimen was assembled with corrugated panels with the type II geometric property of shallower groove and also horizontal-oriented. And similar test was conducted on a 1/3-scale single-bay two-story conventional unstiffened SPSW specimen for comparison. Although hysteretic behavior of the unstiffened and corrugated specimens was different, eventually in all the cases, the failure of the specimen was caused by the fractures of the steel infill panels and the yielding and buckling of the bottom of columns. And the specimens all behaved as a desirable sequences of yielding: the infill panels yielded first and dissipated energy, then the boundary beams yielded and formed plastic hinges to dissipate noticeable energy, the boundary columns yielded and formed the plastic hinges at the bottom at the last. All the specimens showed high ductility during the test, and the specimens reached a maximum story drift of at least 0.04 when they failed and dropped to 85% of their shear capacities. The connection between the wall panel, including the flat and corrugated panels, and the boundary frame were capable of developing the full strength of the infill panel. The corrugated steel panel were able to effectively improve the elastic buckling capacity, out-of-plane stiffness and lateral stiffness of the shear wall system, especially the ones with the type I geometric property of deeper groove. Although the ultimate strength of the unstiffened specimen was larger compared to that of the corrugated specimens, the corrugated specimens were able to yield at a relatively larger drift and larger lateral load and dissipate energy through plastic deformation without any pinching in the hysteretic loops. And the ductility ratio of the corrugated specimen was larger than the unstiffened specimen. In a word, the corrugated specimens could solve the major issues that arise in an unstiffened thin SPSW effectively as expected. In addition, the behavior of the corrugated specimens was not greatly affected by changing the corrugation direction, but greatly affected by changing the geometric property of deeper or shallower groove. So further investigation of the better type selection for the corrugated panels was quite necessary in the future study.

Qiuhong Zhao, Jing Qiu, and Nan Li, Tianjin University, Tianjin, China

SSRC 2017 Annual Stability Conference

Session S9: Stability of Shells
Thursday, March 23, 2017
4:15 p.m.

Design Applications of Sandwich Composite Shells with Enhanced Bond

Design, analysis, and construction details of steel-polymer-steel (SPS) and steel-concrete-steel (SCS) sandwich composite caissons for offshore wind farms are described. Simplified analyses are used as a prelude to finite element and other more detailed methods.  Stability issues include local buckling of cylindrical shells with 12 m diameter and 19 mm steel, disbonding of the concrete core from the steel outer layer, and heave flow of sand layers in the case of uplift causing suction at the base.  Further research is called for.

Peter W. Marshall, MHP Systems Engineering, Houston, TX; Vul Thang, University of New Orleans, New Orleans, LA; Jinbo Chen, The University of Texas at Austin, Austin, TX

SSRC 2017 Annual Stability Conference

Session S10: Stability of Plates
Friday, March 24, 2017
8:00 a.m.

Web Crippling Strength of Longitudinally Stiffened Steel Plate Girder Webs Subjected to Concentrated Loading

There are several methodologies for calculation of ultimate load resistance of slender beams subjected to concentrated loads, the two most important are represented in the Code of Standard Practice for Steel Buildings and Bridges (AISC 2010) and Eurocode 3: Design of steel structures Part 1-5 (EC3 Part 1-5). This paper aims at comparing the predictions of four different solutions for ultimate resistance against 45 experimental tests results. This comparison includes the solution of limit state of web local crippling found in the AISC (2010) standard, a reviewed version of the EC3 Part 1-5 rules and a solution based on a modified failure mechanism that considers the longitudinal stiffening influence on slender beams subjected to concentrated loads. The results show that theoretical predictions of ultimate load work well when the influence of a longitudinal stiffener is considered.

Nelson Loaiza and Carlos Graciano, Universidad Nacional de Colombia, Medellín, Colombia; Rolando Chacón, Universitat Politècnica de Catalunya, Barcelona, Spain

SSRC 2017 Annual Stability Conference

Session S7: Stability of Columns
Thursday, March 23, 2017
1:15 p.m.

The Effects of Accurate Boundary Condition Modeling on Column Stability

Idealization of real-world boundary conditions as either “free,” “pinned,” or “fixed” is common in engineering practice. This research explores the effect of modeling more realistic, in-situ support conditions on column stability. Abaqus is used to assess the moment-rotation capacity of a suite of connections representing commonly encountered boundary conditions. Parameters such as variable axial loads, contact or bearing within the connection, and component yielding are incorporated into the FEA model. The results of the FEA are then used in OpenSees to predict column capacity through a large-displacement, inelastic analysis.

Cliff D. Bishop and Patxi Uriz, Exponent Inc., Menlo Park, CA

SSRC 2017 Annual Meeting Presentation

Session SS2A: Technical Presentations: Stability of Thin-Walled Columns
Tuesday, March 21, 2017
3:15 p.m.

Flexural-Torsional Buckling of General Cold-Formed Steel Columns with Unequal Unbraced Lengths

The design of cold-formed steel columns must consider flexural buckling, torsional buckling, and flexural-torsional buckling. The American Iron and Steel Institute incorporated equations for the critical elastic buckling loads corresponding to these failure modes in the North American Specification for the Design of Cold-Formed Steel Members. These equations were originally developed for columns with consistent boundary conditions for all three modes. However it is common in practice to have different unbraced lengths for major axis flexure, minor axis flexure, and torsion. Furthermore, it is common for certain members to be oriented such that intermediate bracing restraint directions do not align with the principal axes. This paper investigates and develops a general formulation of the column buckling equation to incorporate unequal unbraced lengths and non-principal axes.

Robert S. Glauz, RSG Software, Inc., Lee’s Summit, MO

SSRC 2017 Annual Meeting Presentation

Session SS2B: Technical Presentations: Stability at Elevated Temperatures
Tuesday, March 21, 2017
3:15 p.m.

DSM Design of Cold-Formed Steel Columns Failing in Distortional Modes at Elevated Temperatures

This paper extends the scope of previous work by the authors aiming at investigating the structural behavior, strength and Direct Strength Method (DSM) design of cold-formed steel columns failing in distortional modes at elevated temperatures – the temperature-dependent steel constitutive law is based on the EC3-1.2 model. The new results concern pin-ended and fixed-ended columns displaying four cross-section shapes (lipped channels, hats, zeds and racks), with various dimensions, subjected to 7 elevated temperatures (up to 800ºC) and also ambient temperature (for comparison purposes). On the basis of the failure load data obtained in this work, it is first shown that the current DSM distortional design is unable to handle adequately distortional failures at elevated temperatures. Then, a modified DSM design approach is proposed: it consists of incorporating a temperature-dependent reduction factor ratio, based on the EC3-1.2 model, in the existing strength curve – the modified design curves are shown to provide adequate (reliable and mostly safe) failure load predictions for the set of columns under consideration.

Alexandre Landesmann and  Fernanda Cristina Moreira da Silva, Federal University of Rio de Janeiro, Brazil; Dinar Camotim, University of Lisbon, Lisbon, Portugal

2017 Annual Stability Conference Presentation

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

Characterization of Cold-Formed Steel Member Dimensions and Geometric Imperfections Based on 3D Laser Scanning

This paper briefly introduces the full-field laser-based imperfection measurement platform as well as the four-step post-processing toward measurement point clouds from the platform. The first three steps can lead to one application: variation of dimensions and correlation study of cold-formed steel members. The last step of post-processing enables another two applications, i.e., imperfection characterizations and finite shell-element analysis. The imperfections (deviation from perfect) may be characterized in geometric terms: bow, camber, twist, crown of a given flat plate, flare of a given element; or may be characterized in terms of their modal buckling content: fit to flexural modes, torsional mode, local mode, and distortional mode. In addition, the geometric imperfections may be transformed into the frequency domain and power spectrum of the imperfection magnitudes can be obtained. This 1D spectral approach provides a potentially novel means for generating realistic, but random geometric imperfections for use in shell finite element simulations. Shell finite element collapse analyses that compare the sensitivity in response to true, and various simulated imperfections are provided.The simulations indicate how simple modal imperfections are powerful for predicting strength conservatively, but the 1D spectral approach more closely approaches the results from the true (scanned) members. In the future larger Monte Carlo simulations should be performed to assess the reliability of cold-formed steel members using these results.

Xi Zhao and Benjamin W. Schafer, Johns Hopkins University, Baltimore, MD

2017 Annual Stability Conference Presentation

Session SS2A: Technical Presentations: Stability of Thin-Walled Columns
Tuesday, March 21, 2017
3:15 pm

On the Distortional-Global Interaction in Cold-Formed Steel Columns: Relevance, Post-Buckling Behavior, Strength and DSM Design

This work reports results of an ongoing numerical (shell finite element) investigation on the relevance, post-buckling behavior, strength and design of fixed-ended cold-formed steel columns undergoing distortional-global (D-G) interaction. The columns analyzed exhibited three cross-section shapes, in order to study distinct natures of D-G interaction, which may involve distortional and (major-axis) flexural-torsional buckling (plain and web-stiffened lipped channel columns), or distortional and (minor-axis) flexural buckling (Z columns). The occurrence of different types of D-G interaction, namely “true D-G interaction” or “secondary-(distortional or global) bifurcation D-G interaction” are investigated for each of the aforementioned D-G interaction natures. The results presented concern columns with various geometries and yield stresses, ensuring a wide variety of combinations between (i) global-to-distortional critical buckling load ratios and (ii) squash-to-non critical buckling (distortional or global) load ratios. Then, the numerical failure load data obtained are compared with their predictions by (i) the current DSM (Direct Strength Method) column global and distortional design curves, and (when necessary) (ii) proposed DSM-based design approaches, developed to handle D-G interactive failures.

André Dias Martins, Dinar Camotim, and Pedro B. Dinis, University of Lisbon, Lisbon, Portugal

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