Cold-Formed Steel Behavior and Design



560.761 Cold-Formed Steel Structures

Overview

Cold-formed steel structures see broad use in civil engineering. The primary characteristic of such cold-formed steel structures; whether they be rack structures, buildings, or secondary systems in larger buildings, is that due to the use of thin sheet steel, stability must be addressed with great care. This course will provide the tools practicing engineers use to design these structures, including codes and specifications, software tools, and experimental methods. In addition, the course will go far beyond the typical practicing engineering implementations and delve into the origins of the design methods in current use, the theories which underpin modern analytical and computational tools used in exploring cold-formed steel behavior, and provide a thorough introduction to the research currently underway in cold-formed steel structures.

Course organization

Part 1: Primarily focused on design, some homework, followed by a take home exam

Part 2: Focus on origins of design methods, underlying mechanics and theory, current research topics, etc. some homework and/or mini-projects, followed by a final project.

A word about background

The course is open to all comers, completion of an undergraduate steel design course is nearly mandatory. Courses in advanced (matrix) analysis of structures, advanced steel design, structural stability, finite elements will all be helpful – but are not required. The instructor is aware that the student’s enrolled in the course have a wide variety of backgrounds – this may mean that some explanations offered in class will not be targeted to all students; however, sufficient material will be provided in the course that student’s will be able to readily complete homework, succeed on the mid-term, and complete a useful project. Specifically, expectations for undergraduate and graduate students in this course are different.

Other Details

Course website: ce.jhu.edu/cfs

Instructor: Ben Schafer, schafer@jhu.edu, 203 Latrobe Hall

Office Hours: Open door policy, or by appointment

560.761 Cold-Formed Steel Structures

Topics list

Introduction to CFS

Sections, Applications, Materials, Specifications, History, Industry,

Related Organizations, Current research

Introduction to stability of CFS members (practical introduction to CUFSM)

Pcr, Mcr, local, distortional, global buckling, half-wavelength

Practical CFS Member Design by AISI-S100-07 Main Specification – Effective Width

Column

Local buckling and effective width

Local-global interaction

Distortional buckling

Beam (same breakdown)

Practical CFS Member Design by AISI-S100-07 Appendix 1 – Direct Strength Method

Column

Beam

Practical CFS Member Design by AISI-S100-07 Main Specification, complete

General, Elements, Members, Assemblies, Connections, Fatigue, DSM, 2nd Order

(we will be on this one for a little while, as we breakdown the spec. in its entirety)

(including identification of topics for further examination as desired)

Stability of cold-formed steel members background and analytical methods

plate stability – thin plate theory

plate assemblages

member stability – flexural-torsional buckling

Effective Width

Origins

Extensions to webs, unstiffened elements, unified method

Complications with optimized sections

Computational stability of cold-formed steel members background

semi-analytical finite strip method (CUFSM)

plate ( shell elements for FE implementations

comparing semi-analytical FSM results to FE sheel results

Distortional buckling

Origins

Development of design provisions

Role of restraining systems

Recent debates

Direct Strength Method

Origins

Current Work

Complications

Future Work

International cold-formed steel specifications

Eurocode (additional checks they have, other methods they use..)

Australia (Lite Steel beam provisions, earlier DB provisions)

Others? Brazilian? Hong Kong - China? India?

CFS Rack Structures

Members

Connection systems

Frame stability

Earthquake engineering of

CFS Framing

Basic framing system: walls, floors, roofs

Lateral load bearing systems

AISI-COFS Standards

Sheathed wall systems

Metal buildings and the role of CFS

Purlins, Girts, Sheeting

Standing Seam roofs

Diaphragms

Bracing cold-formed steel so that it works

Basic understanding of bracing (flexural bracing, torsional bracing…)

Cold-formed steel systems and bracing (discrete, ‘continuous’)

Where do we go from here

Imperfections and their role in CFS member stability and strength

Global imperfections, measured, impact,

Local imperfections

Distortional imperfections

General imperfection fields

Experiments with cold-formed steel

standardized testing

tension test for sheet steels

stub column tests

rotational restraint tests

fastener tests

beam tests

wall testing

Nonlinear FE modeling of cold-formed steel to collapse

inputs (imperfections, residual stress-strain, material)

element

solution controls

reliability

needs - limitations

Optimization of cold-formed steel members

parametric optimization

general shape optimization (classifiers?)

general topologic optimization

Advanced Computational Stability of cold-formed steel members

FSM for other boundary conditions

GBT

cFSM

Residual stresses in cold-formed steel members

mechanical origins

predictive model for stress-strain

connections to cold work of forming in the Spec

recommendations

Inelastic bending of cold-formed steel members

inelastic reserve in general

inelastic local, distortional, and LTB…

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