Engineering Commons^™

Gsi Modeling Overview: Requirements For Macroscopic Gas/Surface Interaction Coupling To Cfd Codes, Matthew Maclean, Jochen Marschall

Ablation Workshop

An overview is presented of a generalized finite-rate surface chemistry model that has been developed for gas/surface interaction coupling to the Data-Parallel Line-Relaxation (DPLR) code. Species from the gaseous environment are allowed to interact with species adsorbed onto one or more phase of a surface and with one or more phases of a bulk thermal protection system through an arbitrary number of finite-rate reactions. The reactions may include types such as adsorption, desorption, Eley-Rideal recombination, Langmuir-Hinschelwood recombination, partial or total dissociative adsorption, oxidation, reduction, sublimation, or condensation where forward and reverse rates are constrained by thermodynamics. A simple pyrolysis model …

High Enthalpy Ablation Testing At Dlr Cologne, Bunkard Esser, A. Gülhan, U. Koch

Ablation Workshop

Testing thermal protection capabilities of ablative materials is one of the main working areas of DLR’s arc heated facilities LBK in Cologne. Work on this particular topic has been intensified about five years ago with the following major focus points:

• Significant improvement of the facilities testing capabilities with respect to cold wall heat flux rates and stagnation pressure.
• Ablation testing in Martian atmosphere.
• Influence of dust particle erosion on ablation.

Nitric Oxide Plif Measurements In The Hypersonic Materials Environmental Test System (Hymets), Paul M. Danehy

Ablation Workshop

A nonintrusive laser-based measurement system has been applied for the first time in the HYMETS (Hypersonic Materials Environmental Test System) 400 kW arc-heated wind tunnel at NASA Langley Research Center. Planar laser-induced fluorescence of naturally occurring nitric oxide (NO) has been used to obtain instantaneous flow visualization images, and to make both radial and axial velocity measurements. Results are presented at selected facility run conditions, including some in simulated Earth atmosphere (75% nitrogen, 20% oxygen, 5% argon) and others in simulated Martian atmosphere (71% carbon dioxide, 24% nitrogen, 5% argon), for bulk enthalpies ranging from 6.5 MJ/kg to 18.4 MJ/kg. …

Experimental Data Need For High-Fidelity Material-Response Models, Jean R. Lachaud, Ioana Cozmuta, Nagi N. Mansour

Ablation Workshop

Several high-fidelity material-response models are being developed by the hypersonic community. These models require, in addition to the input parameters traditionally used in the state-of-the-art material-response codes, data not currently available - at least in the open literature. The presentations in the session will describe both state-of-the-art experimental techniques and innovative methods in support of model development and data acquisition for high-fidelity models.

A Life-Cycle Assessment Of Cold-Formed Steel Enclosures Verses Alternative Enclosures In Commerical Buildings, K. J. Van, L. Xu

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

In North America, the operation of buildings accounts for approximately one third of the total energy use and greenhouse gas emissions each year. Over the life of a building, the total energy use is a combination of the embodied energy in the building materials and the operating energy of the building. Building enclosures (walls and roofs) have a huge impact on both the embodied energy and the operating energy of buildings. Historically, steel has been blacklisted as a material with a high embodied energy. This has led to a misconception that steel enclosures use significantly more energy than other enclosure …

Behavior And Design Of Axially Compressed Sheathed Wall Studs, L. C. M. Vieira Jr., B. W. Schafer

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

The objective of this paper is to summarize efforts in a multi year project dedicated to developing a reliable design method for cold - formed steel wall studs that rely on sheathing for bracing. Testing on single columns with sheathing, and full - scale walls with sheathin g, are summarized. Particular emphasis is placed on the observed limit states given the different sheathing conditions. The sheathing supplies beneficial restraint to the wall studs and the stiffness of this sheathing - based restraint is characterized exper imentally and analytically. A unique application of the Direct Strength Method of design is explored …

Lateral Torsional Instability Of Single Channels Restrained By Angle Cleats, G. M. Bukasa, M. Dundu Masce

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

A series of experiments on the lateral tors ional instability of single channels is presented. The channels are restrained by a purlin – angle cleat connection and subjected to a two point loading system in order to simulate a distributed load. Failure of the channels occurred by local buckling of the compression zone of the flange and web and lateral torsional buckling of the channels between points of lateral support. Tests have shown the purlin–angle cleat connection to be capable of restraining the frames from failing due to lateral-torsional buckling. This eliminates the idea of having fly-bracings, which is normally …

Extending Direct Strength Design To Cold-Formed Steel Beams With Holes, Christopher D. Moen, Benjamin W. Schafer

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

The extension of the American Iron and Steel Institute’s Direct Strength Method (DSM) to cold-formed steel beams with holes is nearly in place. DSM was first introduced to th e AISI specification in 2004 as an alternative to the effective width met hod, and is widely considered a major advancement in cold-formed steel component design. In DSM, the beam elastic buckling properties for a general cross-section are obtained with a computer analysis utilizing the finite strip method. A disadvantage of the finite strip method and DSM has been that discrete holes along the member length could not be easily accounted …

Load-Carrying Capacity Estimation On Cold-Formed Thin-Walled Steel Columns With Built-Up Box Section, Yuangqi Li, Xingyou Yao, Zuyan Shen, Rongkui Ma

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

The use of cold-formed thin-walled steel structural members has increased in recent years, and most of their sections are open section with only one symmetrical axis, which would likely fail by twisting and interaction with the others buckling mode, such as local buckling and distortional buckling. To improve the ultimate strength of columns, built-up box section can be used. In this paper, a series of loading capacity tests on high-strength cold- formed steel columns with built-up bo x section are presented, including 21 axially-compressed columns and 19 eccentrically-compressed columns sub- jected to bending moments about weak axis as well as …

Flexural And Cyclic Behaviour Of Hollow And Concrete-Filled Steel Tubes, S. Arivalagan, S. Kandasamy

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

This paper presents a study on the flexural and cyclic behaviour of concrete filled steel hollow beam sections. The specimens in-filled with normal mix concrete, fly ash concrete, quarry waste concrete and low strength concrete (Brick-bat-lime concrete) and hollow steel sections were tested. Measurements of strains and deflections were made under two-point loading. A theoretical model was also developed to predict the moment carrying capacity. The capacities of the beams were compared with the ultimate capacity obtained using the international standards EC4-1994, ACI-2002 and AISC-LRFD-1999. The result of the experimental investigation showed that the moment carrying capacity increases based on …

Overview Of Recent Changes And Additions To Aisi Standards, Helen Chen, Roger Brockenbrough, Richard Haws

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

Since the publication of the 2007 edit ions of AISI standards, changes and additions have been made to some of the standards. This paper will provide an overview of the majo r revisions to those standards.

Steel Roof Deck Diaphragms On Cold-Formed Steel Framing, Thomas Sputo

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

No abstract provided.

Experimental Investigation On 6 Feet Wide Cold-Formed Steel Framed Shear Walls With Steel Sheet Sheathing, Cheng Yu, Yujie Chen

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

An AISI sponsored research project on the performance of 6 feet wide cold- formed steel (CFS) framed shear walls with single sided steel sheet sheathing is recently completed at the Un iversity of North Texas. This research project is aimed at determining the required seismic detailing for 6 feet wide 8 feet high CFS shear walls using two steel sheets, one is 4 feet wide, and the other is 2 feet wide. Both monotonic and cyclic tests are conducted and various parameters in the framing and sheathing details are considered in the test program. Those parameters include framing member thickne …

Angle Cleat Base Connections, M. Dundu, S. Maphosa

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

Tests, performed on base connections fabricated from cold-formed channels and hot-rolled angle cleats, are presented in this paper. This research is part of an on- going research to develop portal frames made out of cold-formed steel. The base connections are subjected to an axial load and moment. Hot-rolled angle cleats are used to prevent premature failing of the base connections. Several loading configurations are considered and these are dependent on the eccentricity of the load. In all the tests the cold-formed channels failed by local buckling. A significant amount of bearing distortion was observed in the heavily loaded flange. The …

Study On The Behavior Of Cold-Formed Steel Angle Tension Members, R. Padmapriya, S. Kandasamy

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

Cold-formed steel tension members with bolted end connections are frequently used in a variety of structures such as trusses, transmission towers etc. Among all the shapes, angles are widely used. When angle sections are connected with gusset plates and eccentrically loaded, their ultimate load- carrying capacity is influenced by the effect of shear lag. This paper presents the details of an experimental and numerical investigation with a primary objective of studying the effect of shear lag on cold-formed steel single and double angles subjected to tension. Seventy-two single plain and lipped angles made from thicknesses 2,3 and 4 mm connected …

Cold Formed Steel Tension Members With Two And Three Staggered Bolts, D. M. Fox, R. M. Schuster

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

The second edition of the North American Specification for the Design of Cold Formed Steel Structural Members was published in October of 2007 for use in Canada, Mexico, and the United States. This Specification contains two country specific a ppe ndices, namely Appendix A (ANSI/AISI S100- 07) for use in the US and Mexico and Appendix B (CSA S136- 07) for use in Canada. Both Appendix A and B require that a bolt stagger reduction factor of 0.90 be used when calculating the tearing failure strength [resistance] of a cold formed steel member in tension with staggered bolts. This 10% …

Shear Behavior Of Screw Connections For Cold-Formed Thin-Walled Steel Structures, Yuangqi Li, Xingyou Yao

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

Self-drilling screws are the primary mean s to fasten cold-formed thin-walled steel members in construction. There are several failure modes for shear connections with self-drilling screws, including screw tilting, hole bearing, edge tearing, tensile fracture in net s ection of connected elements and shear fracture of screws. Meanwhile, the “g roup effect” will exist when a large number of screws are used in a shear connection. A series of tests (75 specimens) on single lap shear connections with self-drilling screws has been carried out and the results report ed in this paper. The end distance, screw spacing, pattern of screws …

Single Shear Bolted Connection Tests Of G500 1.20mm Thin Sheet Steel At Elevated Temperatures, Shu Yan, Ben Young

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

The current design rules on bolted connections of thin sheet steels for cold-formed steel structures are applicable for ambient temperature condition only. Research on such kind of connections at high temperatures is limited. In this study, 47 single shear bolted connection specimens fabricated from G500 1.20mm thin sheet steel and 9 coupon specimens were conducted by using steady state test method in the temperature range from 22ºC to 900ºC. Two failure modes were observed in the single shear bolted connection tests, namely the net section tension, and bearing . The test results were compared with the predicted values calculated from …

Some Aspects On Seismic Design On Frames Designed With Cold Formed Steel Shapes, Gabriel Valencia

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

The response of cold-formed steel structures to seismic excitations is not the same as that of structures designed with rolled shapes, in fact, the seismic design codes require that the shapes, meet minimum width/thickness ratios, which virtually no commercial cold formed steel shapes meet, so the design of structures with these elements is excluded from those codes. Different types of beam- to -column connections, made using cold-formed steel shapes have been tested, in order to establish their response to cyclic loads of increasing magnitude. The analysis of these connections using theoretical models with Finite Element Analysis (FEA), and through monotonic …

Strength Prediction Model For Power Acutated Fasteners Connecting Steel Members In Tension And Shear-North American Applications, J. R. Ubejd Mujagic, Perry S. Green, William G. Gould

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

Power-actuated fasteners (PAFs), also referred to as pins, are small nail-like or threaded stud t ype connectors. They can be used in conjunction with several materials and in a number of different applications. Typical applications in steel include attachments of deck sh eeting or diaphragms, architectural or mechanical components, or miscellaneous support brackets or connections to supporting steel members. Traditionally, the design strength of the connections featuring power-actuated fasteners has been determined through standardized testing protocols. In the United States, this protocol is embodied in the American Society for Testing and Materials (ASTM) Standard E 1190. The purpose of this …

Evaluating The Lrfd Factor For Cold-Formed Steel Compression Members, Karthik Ganesan, Christopher D. Moen

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

This paper summarizes recent work to determine if the LRFD resistance factor for cold-formed steel compression member s can be increased above its current value of φ c =0.85. An experimental database of 675 concentrically loaded columns with plain and lipped C-sections, plain and lipped Z-sections, hat sections and angle sections, including members with holes was compiled. The predicted strength of each specimen was calculated with the AISI-S100-07 Main Specification and Direct Strength Method (DSM). Test-to-predicted strength statistics were employed with the first order second moment reliability approach in AISI-S100-07 Chapter F to calculate the resistance factors. The observed trends …

Feasibility Study For A Repetitive Member Factor For Cold-Formed Steel Framing Systems, S. Clayton, S. F. Stephens

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

Cold-formed steel has become a preferred building material for structural framing in many different types of structures, commonly used as repetitive members such as floor joists, roof rafters, roof trusses and wall studs. For wood framed structures with repetitive members, a repetitive member factor increases the allowable bending stress from 1.00 to 1.50 times the reference design value, depending on both the type of material and the type of load. Currently, however, the bending strength of cold-formed steel repetitive members is not permitted to be increased, even though the method of framing is quite similar to that of wood except …

Improvements To The Fire Performance Of Light Gauge Steel Floor Systems, B. Baleshan, M. Mahendran

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

Light gauge steel frame (LSF) struct ures are increasingly used in commercial and residential build ings because of their non- combustibility, dimensional stability and ease of installation. A common application is in floor-ceiling systems. The LSF floor-ceiling systems must be designed to serv e as fire compartment boundaries and provide adequate fire resistance. Fire-rated floor-ceiling assemblies have been increasingly used in buildings. However, limited research has been undertaken in the past and hence a thorough understanding of their fire resistance behaviour is not available. Recently a new composite floor-ceilin g system has been developed to provide higher fire rating. But …

Review Of Aisi Design Guide For Cold-Formed Steel Purlin Roof Framing Systems-Component Stiffness Method, Michael W. Seek

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

This paper reviews the Component Stiffness Method for determining anchorage forces in roof systems as presen ted in Chapter 5 of the new AISI Design Guide for Cold-Formed Steel Purlin Roof Framing Systems . The four steps in the general methodology of the component stiffness method are presented. First, the development of forces requiring an chorage in purlin roof systems is discussed. Next, calculation of the stif fness of each of the components of the roof system and the procedure for distributing these forces through the system is presented. The final step, evaluation of the effectiveness of the anchors in …

The 2008 Aisi Cold-Formed Steel Design Manual, Richard C. Kaehler, Helen Chen

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

The 2008 edition of the AISI Cold-Formed Steel Design Manual has been published. The new edition includes updated examples and design aids as well as newly developed example problems and design aids covering new material in the 2007 edition of the North American Specification for the Design of Cold-Formed Steel Structural Members . Also included are all current AI SI structural Test Standards.

Performance Of Knee-Braced Cold-Formed Steel Shear Walls Subjected To Lateral Cyclic Loading, Mehran Zeynalian Dastjerdi, Hamid Reza Ronagh

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

Light weight Steel Framed structures currently in use in Australia, are normally braced using face mounted thin straps, cross braces that are of the same shape as studs, or compressed cement boards screwed to the face of the walls. While these are found adequate in low seismic regions of Australia, an investigation into the earthquake resistance properties of LSF have led authors to investigate alternative bracing types that may present a more favourable ductility. Knee braces that are specially designed for this purpose are introduced in the paper and studied in a specially designed testing rig. The tests are on …

20th International Specialty Conference: Recent Research And Developments In Cold-Formed Steel Structures, Wei-Wen Yu Center For Cold-Formed Steel Structures

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

No abstract provided.

Impact Of Corner Radius On Cold-Formed Steel Member Strength, V. Zeinoddini, B. W. Schafer

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

The objectives of this paper are to expl ore (a) how corners of cold-formed steel members are included or ignored in current design methods, and (b) the effectiveness of recent proposals for modifying the strength prediction for local buckling to account for corners. The imp act of round corners is examined on the behavior and strength of isolated elements and on full members using material and geometric nonlinear collapse analysis with shell finite elements in ABAQUS. Comparisons between the available methods and the nonlinear finite element analysis are completed to explore the regimes in which the methods are accurate, as …

Buckling Analysis Of Cold-Formed Steel Members With General Boundary Conditions Using Cufsm Conventional And Constrained Finite Strip Methods, Z. Li, B. W. Schafer

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

The objective of this paper is to provide the theoretical background and illustrative examples for elastic buckling analysis of cold-formed steel members with general boundary conditions as implemented in the forthcoming update to CUFSM. CUFSM is an open source finite strip elastic stability analysis program freely distributed by the senior author. Although the finite strip method presents a general methodology, the conventional implementation (e.g. CUFSM v 3.13 or earlier) employs only simply-supported boundary conditions. In this paper, utilizing specially selected longitudinal shape functions, the conventional finite strip method is extended to general boundary conditions, including the conventional case: simply-simply supported, …

Arc-Spot Welds For Multi-Overlap Roof Deck Panels, N. Guenfoud, R. Tremblay, C. A. Rogers

CCFSS Proceedings of International Specialty Conference on Cold-Formed Steel Structures (1971 - 2018)

Roof deck construction often incorporates cold-formed steel panels that are connected to the underlying framing with the use of arc-spot welds. The welds are commonly located in areas where multiple layers of roof deck exist, such as at sidelaps or endlaps. CSA S136 restricts the use of multi-layer connections to being less than 2.5 mm thick; as well, the thickness of the supporting steel must exceed 2.5 times the aggregate thickness of the deck. In effect, the standard does not allow for the use of arc-spot welds for 18 ga (1.21 mm) and 16 ga (1.52 mm) roof deck panels. …