In an unpredictable world where human intervention or unexpected environmental conditions can prevail, damage can occur to manmade structures. Whilst structural design allows for redundancy, or a structural capability beyond the general working load of the structure, it is necessary to be able to analyse and understand the residual capability of a damaged structure to ensure the safety of personnel in the vicinity of the structure and assess the potential to facilitate repair.Idealised Structural Unit Method (ISUM) can allow rapid assessment of large structural arrangements by simplification into smaller constituent parts, which are assessed against pre-calculated failure data for each part. The method has potential benefits for allowing rapid assessment of damaged steelplated structure that would otherwise require the use of high fidelity modelling of the entire structures, such as through the use of finite element analysis. This paper presents a study on the use of ISUM to assess damaged steel-plated structures and its limitations through the collapse analysis of stiffened steel panels. A new ISUM is proposed for strength assessment of damaged structural arrangements. Analysis is undertaken to assess the effects of geometrical and material property variations that can occur in a structure as well as the effects of damage aperture size and shape on the collapse strength of stiffened steel panels. The study shows 2 that while ISUM can be applied in the assessment of damaged steel-plated structures, implementing the proposed new ISUM allows greater accuracy in the calculation of the collapse strength of damaged stiffened steel panels. The paper also concludes that the assessment of larger structural units for application in the ISUM assessment, will allow the effects of the damage on surrounding structure to be captured, which can influence the deflection shapes that will lead to collapse of the structure.

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A new route to Anatoxin-a 1 is reported which involves a tandem methyllithium mediated ring opening/intramolecular cyclisation as a key step to provide the required 2-acetyl-9-azabicyclo 14.2.1 I nonane ring structure in one synthetic operation.Certain strains of Anabaena flos aqua, a freshwater blue-green algae, produce an alkaloidal neurotoxin that has proved fatal to livestock, waterfowl and fish.' This toxin was identified by Xray crystallography2 and spectroscopy3 as a secondary amine containing the 9-azabicyclo[4.2. llnonane ring structure and was named anatoxin-a 1 or 'Very Fast Death Factor' (VFDF).4 The LD50 intraperitoneal (IP) mouse for purified toxin is 200 pg kg-1 body mass, with a survival time of 4-7 min.5 Anatoxina mimics the neurotransmitter acetylcholine and acts as a potent agonist for the nicotinic acetylcholine receptor (nAChR).6 Such powerful biological activity coupled with its unique ring structure has led to numerous racemic7 and chiralg syntheses of this molecule over the last twenty years. Construction of the aforementioned ring system and introduction of the methyl ketone at the correct oxidation level have proved to be the major challenges in this regard. We wish to report a short and efficient route to anatoxin-a which allows access to a variety of analogues.The key step in our approach involves a tandem methyllithium induced 13-lactam ring opening-intramolecular cyclisation, to afford the desired ring structure, complete with methyl ketone in one synthetic operation. Transformation of the resultant alcohol 5 to Boc-dihydroanatoxin-a 7 was easily achieved and the synthesis was completed using methods developed by Rapoport and coworkers.sh,d The advantage of our route stems from the accessibility of multigram quantities of the relatively simple precursors and an early entry into the 2-acetyl-9-azabicyclo [4.2.1] nonane ring system. The 13-lactam 2 was prepared by careful addition of chlorosulfonyl isocyanate to 1,5-~yclooctadiene in dichloromethane (DCM) containing anhydrous sodium carbonate at 0 "C and hydrolysis of the chlorosulfonyl P-lactam intermediate. Removal of the polymeric side products by work up and flash silica chromatography afforded the (3-lactam 2 as a white solid in 48% yield. Alkylation to provide the benzyl protected (3-lactam 3 could be achieved in 60% yield by treatment of 2 with sodium hydride (1,l equiv.) in THF followed by addition of benzyl bromide in the presence of a catalytic amount of 18-crown-6 ether. In our hands the alkylation of 2 under phase transfer conditions proved to be the most efficient method, affording 3 as a white solid in excellent yield (95%). Treatment of the benzyl protected P-lactam 3 with MCPBA in DCM provided the racemic epoxide 4 in 84% yield, as a white solid. X-ray crystallography9 confirmed the relative anti-relationship of the (3-lactam to the epoxide, and was attributed to the reaction of the peroxyacid with the least hindered face of the double bond. This relationship provides the correct geometry necessary for the key nitrogen...

Across many industries damage events leading to a breach in structural integrity continue to occur.An area where this can lead to particularly unsafe conditions is in the maritime environment, where it may be difficult to rescue crew and cargo. In order to improve structural safety through design for the survivability or to assess the residual strength of a damaged vessel in an emergency response or salvage scenario, it is critical to understand the influence of the damage. This paper investigates the use of FEA on ultimate collapse strength of damaged steel grillages and the influence of the damage aperture on the developing failure modes within the structure. The study finds that the presence of damage, in the form of a hole, can lead to the failure mode changing as damage aperture size is increased leading to significant changes to the ultimate collapse strength of the structure. It concludes that to assess the damaged strength of steel plated structures, it is critical that modelling methods are able to capture and account for such mode changes in order to accurately assess the true residual strength of the structure.

A n e w method for the construction of 1,5-dioxadecalins and spiroketals which utilises acid o r base catalysed intramolecular additions of alcohols t o allene sulphoxides is described.