In recent years, rapid advances have taken place in earth-quake engineering as applied to steel structures with major
emphasis given to (1) development of advanced procedures
for seismic performance assessment, (2) development of
advanced design procedures for plastic mechanism control,
(3) improvements in structural design detailing, (4) better
modeling of members and connections for dynamic non-linear analyses, (5) development of new damping devices for
supplementary energy dissipation, (6) development of self-centering structural systems, (7) development and testing of
new design strategies for reducing structural damage under
severe ground motions. Even though such advances have
reached in some cases a refinement level justifying their in-troduction in seismic codes, the updating of Eurocode 8 with
design criteria and new design strategies reflecting newly
developed knowledge is still in delay. In the actual version
of Eurocode 8, some advances, such as new structural ty-pologies like braced frames equipped with buckling re-strained braces and dissipative truss moment frames, are still
not codified even if they have already gained space in
American codes.
Because of these rapid advances, weaknesses of Euro-code 8 and new structural typologies to be codified have
been recognized and a document focusing on such weak-nesses and new research needs has been published [1]. In
particular, the sharing of knowledge obtained has been rec-ognized to be critical to improve the seismic design of steel
structures. Therefore, a Thematic Issue on “New Advances
in Seismic Design and Assessment of Steel Structures” can
be considered timely.
Many researchers, all joined by the common interest in
design, testing, analysis and assessment of steel structures in
seismic areas, have accepted to contribute to this special is-sue. As a result, this thematic issue is composed by eleven
contribution covering important design topics for seismic
resistant steel structures.
Two works [2, 3] are devoted to the seismic design of
Concentrically Braced Frames (CBFs), pointing out the
drawbacks of the design provisions suggested by Eurocode 8 and also reported in the Italian Technical Code for Construc-tions. In particular, the need to revise the design procedure
suggested for columns of CBFs is discussed showing that
both the stability and resistance indexes of columns are often
exceeded. The results obtained are in agreement with those
presented by other researchers [4-8] who recommended de-sign procedures based on a rigorous application of capacity
design principles. Also the third manuscript of the thematic
issue is devoted to CBFs, but aiming to the development of a
new buckling restrained system which can be easily dis-mounted [9]. As it is well known, buckling restrained braces
(BRBs) are basically constituted by two parts: an internal
slender steel member, known as the “core” and a restraining
member, known as the “casing”. The core component has the
key role of dissipating energy, while the casing component
restrains the brace core from overall buckling in compres-sion. The buckling restraining mechanism can be obtained
by enclosing the core (rectangular or cruciform plates, circu-lar rods, etc.) either in a continuous concrete/mortar filled
tube or within a “all-steel” casing. Despite of the use of such
braces allows to obtain wide and stable hysteresis loops, thus
overcoming the main drawbacks of traditional braces due to
the poor cyclic response resulting from overall buckling, and
their design is already codified in ANSI/AISC 341-10 [10],
their use is still not codified in Europe testifying an impor-tant weakness of Eurocode 8.
Two papers of the present thematic issue are devoted to
beam-to-column connections [11, 12]. The first one [11]
presents the results of a wide experimental program recently
carried out at Salerno University dealing with extended end
plate connections, with and without Reduced Beam Section
(RBS), connections with bolted T-stubs and, finally, innova-tive connections equipped with friction dampers. The second
work [12] is mainly devoted to the theoretical development
of the analysis of the influence of gravity loads on the seis-mic design of RBS connections. In particular, it deserves to
be underlined that such influence is commonly neglected in
codified rules, such as ANSI/AISC 358-10 [13], because
experimental tests constituting the base of the recommended
design procedures are typically based on cantilever schemes
where gravity loads are not applied.
Methods for conceptual and preliminary seismic design of buildings with steel structure