Interactive analysis and design of cold-formed steel cladding system

An interactive graphical analysis-design environment for determining the ultimate capacity and reduction factors for cold-formed purlin-sheeting systems is presented herein. The technique employs an elastoplastic nonlinear finite element approach, and the predicted results are in good agreement with those obtained from full-scale vacuum tests. This approach is used to derive reduction R-factors according to the recommended design approach in the current design standards. This approach can be very useful in exploring practical design scenarios that are beyond the scope of the current standards. The approach can be used for checking both strength and serviceability limit states, and can predict failure mode and location

Web-based knowledge-based system on liquid retaining structure design as instructional tool

2002-2003 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

Infant brain subjected to oscillatory loading

Past research into brain injury biomechanics has focussed on short duration impulsive events as opposed to the oscillatory loadings associated with Shaken Baby Syndrome (SBS). A series of 2D finite element models of an axial slice of the infant head were created to provide qualitative information on the behaviour of the brain during shaking. The test series explored variations in subarachnoid cerebrospinal fluid (CSF) thickness and geometry. A new method of CSF modeling based on Reynolds lubrication theory was included to provide a more realistic brain-CSF interaction. The results indicate that the volume of subarachnoid CSF, and inclusion of thickness variations due to gyri, are important to the resultant behaviour. Stress concentrations in the deep brain are reduced by fluid redistribution and gyral contact. These results provide direction for future 3D modeling of SBS

Dynamic Response of a SDOF System Subjected to Simulated Downburst Wind

This study provides an investigation of the dynamic response of a Single Degree Of Freedom (SDOF) structure subjected to simulated downburst winds. Wind speed time histories were simulated using an analytical model of a downburst wind field and an Autoregressive Moving Average (ARMA) turbulence simulation (Chay et al 2005). A variety of turbulence and damping conditions were investigated. The structure is a simple spring-mass-damper system. The investigation was conducted in the time domain using a direct numerical integration of the equations of motion (Paz 1997). The response of the system under the action of the downburst winds is compared to that of the same system subjected to simulated boundary layer winds. The paper also presents an investigation of the affect that various downburst traits, such as the radius to maximum velocity and storm direction, have on the dynamic response. Finally, a case study is presented which examines the dynamic response of the SDOF system when subjected to a simulation of the 1983 Andrews Air Force Base downburst (Fujita 1990)

Knowledge-based system on optimum design of liquid retaining structures with genetic algorithms

Author name used in this publication: K. W. Chau2003-2004 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

Evaluation of Displacement-Based Analysis and Design Methods for Steel Frames with Passive Energy Dissipators

This report investigates the use of displacement-based, or pushover methods of analysis in the design of frames incorporating passive dissipative devices. An extensive analysis and design study of 3-, 6- and 10-storey frames, both undamped moment-resisting frames (MRFs) and retrofitted with hysteretic and frictional dissipators has been performed. Frames were modelled using the finite element program Sap2000 and were analysed using both non-linear static pushover analysis and non-linear time history analysis. The principal aims were to assess the degree of improvement in performance achieved through use of the devices, and the suitability of various displacement-based analysis methods for estimating the seismic response of frames fitted with dissipative devices. It was found that both dissipative systems led to substantial improvements in frame performance, in terms of plastic hinge formation (reduced to virtually zero) and deformation (reduced by a factor of more than 2). Base shears remained similar to those for the undamped MRFs. Pushover analyses were found to be a useful design tool for the unretrofitted frames, giving good estimates of the overall displacement demands, base shears and plastic hinge formation. However, the various pushover approaches proved less successful at estimating the performance of the dissipative frames, where they appeared to underestimate the beneficial effects of energy dissipation. Of the various pushover methods assessed, the FEMA 356 approach appears to offer the most accurate and realistic estimate of seismic performance, with the exception of the inter-storey drift distribution. For the 6- and 10-storey frames (both ductile MRFs and dissipative frames), pushover methods using fixed, single load patterns gave rather poor estimates of the distribution of inter-storey drift with height. Far better drift estimates were obtained using the modal pushover method, in which pushover results obtained using force distributions based on the first three modes are combined by the SRSS method

Monotonic and Cyclic Tests on Shear Diaphragm Dissipators for Steel Frames

This report describes a series of cyclic tests on a yielding shear panel device of the form proposed by U. Dorka (unpublished) at the University of Kassel, Germany. The device consists of a short length of square hollow section (SHS) with a diaphragm plate welded inside it. It is positioned between the braces and the main members of a braced frame, with the diaphragm lying in the plane of the frame, so that it is loaded in pure shear as the frame undergoes lateral deformation. An extensive series of tests on 100 mm square dissipative devices mounted in a single-storey, planar, K-braced frame was successfully performed, under both monotonic and cyclic loads. The devices proved easy and cheap to manufacture, fit, remove and replace. All the devices tested yielded at quite low deformations and sustained very large ductilities without failure. The load carried by the device continued to increase after yield, with a ratio of maximum force carried to yield force of around 1.7 in most tests. While a device with a 2 mm diaphragm appeared to offer the maximum energy dissipation capacity, thinner devices were prone to buckling and to fracture under repeated large- amplitude cycling. A thickness of 3 mm (i.e. thickness to breadth ratio of 0.03) is recommended as offering the best combination of dissipative capacity and robustness. A 3 mm device dissipated approximately 1.3 kJ of energy when the frame in which it was fitted underwent a single displacement cycle of amplitude 30 mm. It is concluded that these devices offer a simple, cheap and robust way of dissipating significant amounts of energy in seismically loaded frames. Some improvements to the rig design and suggestions for further work are offered in section 4.6

Genetic algorithms for design of liquid retaining structure

Series: Lecture notes in computer scienceAuthor name used in this publication: K. W. Chau2001-2002 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

Hybrid knowledge representation in a blackboard KBS for liquid retaining structure design

Author name used in this publication: K. W. Chau2003-2004 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

Buckle interaction in deep subsea pipelines

The paper investigates the interaction between propagation buckling and lateral buckling in deep subsea pipelines. Lateral buckling is a possible global buckling mode in long pipelines while the propagation buckling is a local mode that can quickly propagate and damage a long segment of a pipeline in deep water. A numerical study is conducted to simulate buckle interaction in deep subsea pipelines. The interaction produces a significant reduction in the buckle design capacity of the pipeline. This is further exasperated due to the inherent imperfection sensitivity of the problem