The common profiled steel cladding systems used in Australia and its neighboring countries are made of very thin (0.42 mm) high strength steel (G550 with a minimum yield stress of 550 MPa) and are crest-fixed. However, these claddings often suffer from local pull-through failures at their screw connections during high wind events such as storms and cyclones. Past experience and researches have shown that the loss of steel roofs has often occurred due to local pull-through failures of their screw connections under uplift or suction loading. Loss of claddings always led to a progressive collapse of the entire building. This situation is continuing because of the lower priority given to the design of roof and wall cladding systems. At present, steel design codes do not provide guidelines for the design of crest-fixed steel roof or wall claddings. Past research has shown that European and American recommendations for steel claddings cannot be used for Australian crest-fixed cladding systems as they were developed mainly for valley-fixed claddings subjected to gravity loading instead of crest-fixed claddings subjected to wind uplift/suction loading. Therefore at present the design of thin steel cladding systems is based on laboratory tests and is expensive. These situations inhibit the innovative design and advances in the steel cladding industry. Since the local pull-through failures in the less ductile G550 steel claddings are initiated by transverse splitting at the fastener hole, analytical studies have not been able to determine the pull-through failure loads accurately. Therefore in the first stage of this research an appropriate fracture/splitting criterion was developed using a series of large scale and small scale experiments of crest-fixed steel claddings. A shell finite element model of crest-fixed steel cladding was then developed that included the new fracture/splitting criterion and advanced features such as hyperelastic material modelling, contact simulations, residual stresses and geometric imperfections. The improved finite element analyses were able to model the pull-through failures associated with splitting as evident from the comparison of their results with the corresponding full-scale experimental results. An extensive series of parametric studies considering the effects of material properties and geometric parameters of the two commonly used trapezoidal cladding profiles was undertaken using finite element analysis. Appropriate design formulae for the pull-through and dimpling failure load of trapezoidal profiles were then derived for optimization purposes and to simplify the current design method. This will then lead to modification and optimisation of cladding profiles to satisfy the requirements of both strength (safety during cyclones and storms) and economy. This thesis presents the details of large scale experimental studies undertaken and the results including the criterion for the splitting/fracture failure of high strength steel cladding systems. It describes the many advances made in the finite element modelling of crest-fixed steel cladding systems including the effects of localised pull-through and dimpling failures. Finally, it presents a simple design method for trapezoidal steel cladding systems under wind uplift or suction loading.
| Identifer | oai:union.ndltd.org:ADTP/264870 |
| Date | January 2003 |
| Creators | Mahaarachchi, Dhammika |
| Publisher | Queensland University of Technology |
| Source Sets | Australiasian Digital Theses Program |
| Detected Language | English |
| Rights | Copyright Dhammika Mahaarachchi |
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