Iris Publishers- Open access Journal of Civil & Structural Engineering | Wide Flange Beams: Trends Towards Higher Steel
Performance
Authored by Riccardo Zanon
Rolled structural shapes (L, I, H, U) were developed already in
the 19th century, answering the need to simplify shapes built up
from plates assembled together by rivets. The advantages in terms
of weight savings, fabrication simplification, manpower time and
cost reduction were integral to the acceptance of rolled shapes in
every field of structural steelwork. When it comes to H-structural
shape, the flagship plant of Differdange, Luxembourg (Europe)
developed the parallel wide-flange beams based on the patent
by Engineer Henry Grey (1898). With the first beam rolled out in
1901 and achieving the iconic step of 1m tall beam in 1911, the
widespread of parallel flange beam was rapid and nowadays has
become the standard product of steelwork. Today, the geometric
range of available H structural shapes is extensive (beam height
from 80mm up to 1150mm, flange width from 50mm up to 476mm,
flange thickness from 4mm up to 140mm) with a well-established
presence of producers around the world allowing for market
competition, product availability and reliable supply chain. Beside the expansion of geometric properties, the development
of optimized rolling procedures occurred over several decades. In
particular the combination of thick material in high-strength steel
(by maintaining ductility, toughness and compacity compliant to
design requirements) is a technical challenge taken up by producer
to follow the continuous strieve towards bolder structures [1].
Since the 1990, thermo-mechanical rolling has become a standard
for the most advanced plants in Europe. In order to enhance the
benefits of thermomechanical rolling, the quenching and selftempering
process (QST) was developed specifically for sections
with thick flanges [2] (Figure 1). Implementing this innovative
procedure made it possible to economically obtain fine-grain high
steel strengths (460MPa – Grade 65) for heavy sections (thinkness
up to 140mm) without the costly addition of alloying elements. More recently higher grades (485MPa – Grade 70) have been
successfully implemented in high-rise projects since 2015 and the
strieve to develop higher strength (550MPa – Grade 80) has been
already announced by steel producer.
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