Travanca and André
180
deviations from the idealised perfect state of the structure is often considered in a simplified manner using equivalent initial geometric imperfections whose values were
calibrated to obtain conservative results [43].
The following equivalent initial geometric imperfections are typically introduced in
the analysis:
● global imperfections expressed as initial sway imperfections of the system; and
● local imperfections, such as element out of straightness, joint looseness and load
eccentricities.
8.3.4 Steel Design Verifications
8.3.4.1 Ultimate Limit States
Regarding the verifications of the ultimate limit states (ULS), code rules usually divide
them into five different parts [16]:
1) resistance of the steel cross‐section against tensile, compressive, shear and torsion
forces, individually or combined;
2) resistance of the steel element: flexural buckling, torsional buckling, flexural‐
t orsional buckling, coupled local and global buckling, shear buckling, flange‐induced
buckling and web resistance to high local transverse forces (web buckling, crippling
and crushing);
3) resistance of the connections against tensile, compressive, shear and torsion forces,
individually or combined;
4) resistance to fatigue and brittle failure; and
5) loss of equilibrium of the structure or any part of it, considered as a rigid body.
The design procedures to verify the safety of steel elements to these ULS are given in
the various parts of Eurocode 3, namely BS EN 1993‐1‐1 [44,45], BS EN 1993‐1‐6 [46],
BS EN 1993‐1‐8 [47,48], BS EN 1993‐1‐9 [49,50] and BS EN 1993‐3‐1 [21,33].
Of particular relevance to the safety of monopoles is the resistance of the bolted joints
connecting adjoining tubular sections and also connecting the base of the tower to the
foundation element. However, guidance is not provided in the Eurocodes. A suitable
method is proposed in the Steel Design & Construction Bulletins 65, 66, 67 and 78 [51]
published by the New Zealand Heavy Engineering Research Association (HERA); reformulated in [52] to suit the requirements of the Eurocodes.
For the design of anchoring elements to concrete, reference is made to the rules
given in design documents such as [53–57] or to the design guidelines included in the
technical manuals developed by the manufacturers of proprietary fastening solutions,
as long as they comply with the principles and requirements for structural design set
in the applicable design codes. Safety against relevant anchor failure modes should be
evaluated, namely [16]:
● tension resistance of the steel anchor;
● shear resistance of the steel anchor;
● tension resistance of the concrete;
● shear resistance of the concrete;
● bond resistance in the interface between the anchor and the surrounding concrete; and
● concrete splitting resistance.
180
deviations from the idealised perfect state of the structure is often considered in a simplified manner using equivalent initial geometric imperfections whose values were
calibrated to obtain conservative results [43].
The following equivalent initial geometric imperfections are typically introduced in
the analysis:
● global imperfections expressed as initial sway imperfections of the system; and
● local imperfections, such as element out of straightness, joint looseness and load
eccentricities.
8.3.4 Steel Design Verifications
8.3.4.1 Ultimate Limit States
Regarding the verifications of the ultimate limit states (ULS), code rules usually divide
them into five different parts [16]:
1) resistance of the steel cross‐section against tensile, compressive, shear and torsion
forces, individually or combined;
2) resistance of the steel element: flexural buckling, torsional buckling, flexural‐
t orsional buckling, coupled local and global buckling, shear buckling, flange‐induced
buckling and web resistance to high local transverse forces (web buckling, crippling
and crushing);
3) resistance of the connections against tensile, compressive, shear and torsion forces,
individually or combined;
4) resistance to fatigue and brittle failure; and
5) loss of equilibrium of the structure or any part of it, considered as a rigid body.
The design procedures to verify the safety of steel elements to these ULS are given in
the various parts of Eurocode 3, namely BS EN 1993‐1‐1 [44,45], BS EN 1993‐1‐6 [46],
BS EN 1993‐1‐8 [47,48], BS EN 1993‐1‐9 [49,50] and BS EN 1993‐3‐1 [21,33].
Of particular relevance to the safety of monopoles is the resistance of the bolted joints
connecting adjoining tubular sections and also connecting the base of the tower to the
foundation element. However, guidance is not provided in the Eurocodes. A suitable
method is proposed in the Steel Design & Construction Bulletins 65, 66, 67 and 78 [51]
published by the New Zealand Heavy Engineering Research Association (HERA); reformulated in [52] to suit the requirements of the Eurocodes.
For the design of anchoring elements to concrete, reference is made to the rules
given in design documents such as [53–57] or to the design guidelines included in the
technical manuals developed by the manufacturers of proprietary fastening solutions,
as long as they comply with the principles and requirements for structural design set
in the applicable design codes. Safety against relevant anchor failure modes should be
evaluated, namely [16]:
● tension resistance of the steel anchor;
● shear resistance of the steel anchor;
● tension resistance of the concrete;
● shear resistance of the concrete;
● bond resistance in the interface between the anchor and the surrounding concrete; and
● concrete splitting resistance.