100% Positive Material Identification

Poster Session Scholars at TITANIUM EUROPE 2016 (continued)
day installation time, this repair can be
completed using standard contracting
tools, equipment, and labor. The speed
of the repair also reduces costs beyond
labor by decreasing costs associated with
the economic impact of long-term lane
closures and bridge ratings.
This poster will discuss the
advantages and disadvantages of
the NSM and external unbonded
reinforcement techniques for flexural
strengthening; describe the titanium
alloy bars, bridge girders, and
construction practices; and detail the
laboratory findings on the structural
performance of the specimens. It will
further demonstrate that titanium alloy
bars offer a structurally effective and
cost competitive alternative to current
materials for maintaining and preserving
aging and deteriorated highway
infrastructure assets world-wide.
MacKenzie Lostra, Oregon State
University, Corvallis, Oregon USA
Lostra received her bachelor’s degree
in civil engineering from the University
of Arizona in 2014 and is now pursuing a
master’s degree in Structural Engineering
at Oregon State University. Her
background in research has been focused
on seismic resiliency of reinforced
concrete structures and innovative
retrofitting methods. Her advisors
include Christopher Higgins and Andre
Barbosa.
Abstract:
Titanium retrofitting of seismically
vulnerable columns is an opportunity
to expand the amount of viable
structural materials and methods for
improving stability and safety in older
concrete structures that do not meet
modern seismic code requirements. The
enhancement of reinforced concrete (RC)
columns with unsatisfactory ductility
properties using external titanium bars
and spirals poses room for increased
understanding of the behavior of
rectangular retrofitted RC columns
under seismic demands, simulated by
monotonic-cyclic loading sequences.
The research utilizes four physical
models at full scale, which are modeled
after the McKenzie River Bridge
in Oregon, to measure changes in
ductility and strength. These columns,
similar to many others on RC bridges
constructed during the 1950-60’s, have
poor internal detailing, with insufficient
bending and shear reinforcement,
making them susceptible to seismic
forces. Specifically, poor detailing of the
internal foundation bar lap splice creates
a bond-slip failure mode, in which the
longitudinal reinforcement between
the foundation and column no longer
acts as a continuous development when
high stress level is reached; this reduces
the stiffness of the joint between the
foundation and the column.
The bending stresses imposed on a
free-standing column are concentrated
in this zone, therefore strengthening of
the base of the column is necessary to
resist seismic loads. Titanium is both
economic and efficient for this purpose
and possesses many desirable qualities
such as its resistance to corrosion, low
stiffness, and high strength. Four cases
will be tested in this research: a control
specimen (conventionally reinforced)
and three retrofitted specimens with the
retrofit extended above the lap splice,
below the lap splice, and the lap splice
removed entirely.
The results are expected to
demonstrate improved ductility in
the retrofitted columns by increasing
passive confinement in the columns
and providing additional, more flexible
reinforcement. The confinement provided
by the titanium coil and the leverage
from the vertical ligaments should
allow for proactive strengthening and
resiliency of the columns, extending
the displacement and load capacity.
In turn, this can lead to more resilient
bridges that are able to withstand larger
deformations without losing axial
strength. If the testing results in notably
improved performance of the retrofitted
columns to that of the un-retrofitted
column, titanium can continue to be
researched as a structural material in
civil engineering and become more
widely available and practical for use in
retrofitting structures that require it.
The research will provide preliminary
data for an ongoing study of rectangular
RC columns and seismic retrofitting at
Oregon State University. Testing for this
project is expected to conclude over the
course of the next two months and future
testing under an additional graduate
student over the next several years.
Alfonso Garcia, Rolls Royce UTC
Nottingham, Faculty of Engineering
The University of Nottingham
University Park, United Kingdom.
Garcia started a career in design
several years ago in Mexico, working
for companies in fields such as near
net-shape manufacturing, sheet metal
forming, advanced manufacturing
processes, product and tooling design. He
is currently working in a Ph.D. project
funded by Rolls Royce at the University
of Nottingham.
Abstract:
The joining of massive titanium sections
cut from plate is an attractive alternative
to manufacturing large components by
forging, as it offers a simple route to near
net shaping, reducing the overall cost of
components made in this way. A novel
approach to this problem, using a process
based on diffusion bonding (DB) and
hot isostatic pressing (HIP), has been
developed as a research PhD project at
the Rolls Royce University Technology
Centre (RR-UTC) in the University of
Nottingham and is currently patented in
the United Kingdom.
In this method, gaps between
adjoining Titanium plates from
dissimilar alloys (Ti-6Al-4V and Ti-6Al-
2Sn-4Zr-6Mo) are “sealed” by a shallow
laser weld around the majority of the
join line. The final part of this interface is
sealed in a vacuum by electron beam (EB)
welding, thus creating a leak-tight gap
containing a vacuum. These structures
can then be “HIPed” without needing to
be encapsulated, offering considerable
cost advantages.
TITANIUMTODAY 35