mention the investigations made by: Albermani and Kitipornchai
1993 and 2003; Albermani et al 2004; Carril Júnior 2000; El-
Ghazaly and Al-Khaiat 1995; Kahla 1994 and 2000, Kitipornchai
and Albermani 1992; Madugula and Wahba 1998; Menin 2002, Rao
and Kalyanaraman 2001; Saxena et al 1989; Wahba et al 1996 and
Wahba et al 1998.
Kahla 1994, numerically modelled the dynamical effects present
in guyed steel towers including the cable galloping effects. Later the
same author, Kahla 2000, dynamically modelled the rupture of a
cable present in guyed steel towers. The analysis indicated that the
guyed steel towers cable rupture, disregarding the wind actions, was
one of the most severe critical load hypotheses for the investigated
structures.
Wahba et al 1996, considered the dynamical nature of the load
acting in guyed steel towers like wind, earthquakes and cable gallop.
The finite element method was used to model the tower bars as 3D
truss and 3D beam elements obtaining the structural models
dynamical characteristics. In a subsequent phase these results were
compared to experiments. This paper also described the results of
experiments made to identify the main parameters that influence the
guyed steel towers natural frequencies, as well as, their and
associated vibration modes.
Ghazalyt and Khaiatz 1995, evaluated telecommunication guyed
steel tower designs based on discussions of the various non-linear
aspects involved on their numerical modelling. This paper also
contemplated the development and comparisons of the results of a
3D model for a 600 meter height guyed steel tower.
Wahba et al 1998, performed an investigation of the numerical
models used in telecommunication guyed steel towers. The authors
stressed the relevance of considering the non-linear effects present
even at service load levels. In a subsequent paper, Madugula and
Wahba 1998, described two different finite element models for the
dynamical simulation of guyed steel towers. This paper also
contemplated an experimental modal analysis of reduced-scale
guyed steel towers models that produced results in consonance with
the developed numerical models.
Menin 2002, evaluated telecommunication guyed steel towers
from their static and dynamical structural responses. The static
analysis compared linear and non-linear mathematical models. The
dynamical analysis employed the Monte Carlo simulation method
including the wind load floating parcel producing interesting results.
Albermani and Kitipornchai 2003, used the finite element
method by means of a geometrical and physical non-linear analysis
to simulate the structural response of telecommunication and
transmission steel towers. This was followed by a later work of
Albermani et al 2004, that investigated the possibility of
strengthening steel truss towers from a restructure and
rearrangement of their bracing systems. The adopted solution
consisted on the addition of axially rigid systems to intermediate
transverse planes of the tower panels.
The main purpose of the adopted modelling strategies was to
investigate the structural behaviour of the guyed steel towers,
preventing the occurrence of spurious structural mechanisms that
could lead to uneconomic or unsafe structure. The towers
investigated in the present paper (50m, 70m and 90m), have a truss
type geometry with a square cross section. Hot rolled angle sections
connected by bolts compose the main structure as well as the
bracing system. Prestressed cables support the main structure, which
must be always in tension. Some of these cables are linked to a
specific set of bars arranged to improve the system torsional
stiffness. The geometry configuration of the three guyed towers are
depicted in Fig. 1.
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