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THE INFLUENCE OF VARIOUS ERRORS ON THE DURABILITY OF STEEL STRUCTURES FOR INDUSTRIAL BUILDINGS
1 INTRODUCTION
The industrial buildings with steel framing systems require large financial resources and, therefore it is essential that their service condition are permanently checked and kept under control.
The reliability of an industrial steel building is significantly influenced by the quality of design, quality of erection and also by the working environment.
Therefore the identification of any possible errors and the assessment of their influence on the loadbearing capacity of the structural steel members and on their durability are needed in order to set up the retrofitting solutions. Figure 1 presents a general picture of defects, errors, their influence on the structural performance and the principal means of intervention to remediate the damaging effects.
A survey carried out on steel industrial buildings in service has lead to the following
percentages of error sources:
9% - design errors;
6% - workshop fabrication errors;
40% - assembling errors on construction site;
45% - service errors.
2 DESIGN ERRORS
After a careful examination of the contract documents and especially the structural drawings and specifications, the following design errors have been identified:
unproper layout of industrial buildings with respect to neighbouring terrain features causing severe pollutant concentrations;
the use of carbon steels with low corrosion resistance instead of weathering steels;
ignoring certain phenomena such as natural ageing, corrosive fatigue and corrosive cracking that may favour the steel brittleness and premature failures;
selection of steel members with small cross-sectional areas vulnerable to corrosive
wearing and excessive number of change in size connections sensitive to corrosion;
the use of steel members with large perimeter/cross-sectional area ratios;
difficult access to the members surface for periodic painting and current maintenance;
inappropriate supporting conditions (purlins on trusses, trusses on columns) and also beam-column connections or column-footing connections causing accumulation of dust and/or water;
unsuitable bolt spacing leading to pieces tear out or to debonding of the adjacent components and to corrosive spots between them;
the use of intermittent fillet welds when steel structures are exploited in a corrosive atmosphere;
inappropriate design and construction of the roof cladding structure causing condensation and speeding up the corrosion process;
insufficient roof slope and insufficient overlap of the steel cladding panels causing water seepage;
inappropriate selection of the protective systems.
3 CONSTRUCTION ERRORS
The survey carried out on six steel framed industrial buildings has enabled the identification of the following construction errors:
lack of the mill test certificate;
disregarding the thicknesses of the steel members specified in the design drawings;
unproper welding procedures, causing residual stresses, stress concentrations and large distortions of the welded member;
insufficient tightening of the bolted connections;
incorrect surface preparation of the steel members before the application of the paint coatings;
deterioration of the preliminary corrosion protection systems during transport, handling, temporary storing and assemblage;
application of fewer paint coatings than specified in the project;
inadequate quality control of the protective system in workshop and for/or at the construction sites;
negligence in filling up the reception certificates both in workshops and/or construction sites.