Causes and analysis of steel structural failures - Assessment and Refurbishment of Steel Structures - page 25

2.2 Errors in the design of structures
These errors can be divided into:
• Errors in the conceptional design and arrangement of the structure (e.g. insufficient
security of dimensional stability and robustness of the structure)
• Errors in the documentation for the design and the calculations (imperfections in
geological documentation, false values and positions of loading effects, ignoring
important influences that can have an effect on the structures, etc.)
• Imperfections in calculating and dimensioning the structural elements, selection of a
calculation model that does not accord with the real behaviour and functions of the
system,
• Wrong selection of constructional materials
• Errors in solution of constructional details, discrepancies between the structural solution
and static scheme
• Ignoring the requirements for maintenance and anticorrosive protection.
2.2.1 Errors in the project
The causes of about one third of failures can be found in errors originating in the process
of designing. The method of design and requirements for static calculations in most cases
guarantee the reliability of the structure and only in exceptional cases do they cause
failure. When some influences are neglected, such as off-centre stress, off-joint loading
of member systems, temperature effects, this can result in a failure. There are also some
imperfections in determining the correct loading values (e.g. loading of working
platforms in the load-bearing structures of heating plants). Many errors originate from
designing incorrect constructional details when processing manufacturing drawings as a
background for the fabrication in the bridge building shop. Also insufficient
communication between designers' offices and bridge building shops can lead to errors.
When solving problems with structure for complex structures, errors occur most
frequently if the chosen calculation schema does not reflect the interaction among
individual parts of the structure with sufficient accuracy. The failure of the steel structure
of a conveyer bridge in the area of support No.4 is such an example (Figure 2.1). It deals
with a bridge for transporting coal with direct chord lattice main
Figure 2.1 Schema for a conveyor
bridge