July/August 2023 - 100

Underpinning was also required.
The underpinning was needed to
provide vertical support for this facade,
as well as temporary lateral support for
the 20 ft (6 m) deep excavation required
for the new below grade parking deck to
be constructed.
Challenges: Shoring the existing
facade presented unique challenges. The
total height of this facade was 29 ft (9 m)
and was in very poor condition. Similar
to building 2108/2110, the facade at
ground level had a large storefront
opening approximately 12 ft (3.6 m) in
height. This opening used a wooden
lintel to transfer the vertical load of the
facade above it into two narrow and very
deteriorated brick piers, both less than 2
ft (0.6 m) in width, at each side of the
opening. Therefore, these piers needed
to be unloaded prior to demolition taking
place.
Initially, the shoring facade was
going to be similar to the one provided
at building 2114/2116, which consisted
of a combination of:
* Steel frames with vertical drilled
piles and lateral braces on both
sides of the facade.
* Alternating underpinning piers that
would provide vertical support for
the facade' s foundat ion and
temporary earth retention to allow
for the 20 ft (6 m) excavation
required for the new underground
garage.
However, once the new facade shoring
design was complete, the contractor
encountered a new challenge: the
building was now deemed unsafe for
crews to access the interior of the
building - not allowing for the newly
designed facade shoring frame to be
installed. As a result, the contractor
switched gears and came up with a new
design that allowed for the existing
deteriorated facade to be vertically and
laterally supported from outside the
building only.
Another challenge came up when
installing one of the three alternating
underpinning piers. Very soft and wet
soils were encountered while digging
for the center pier. This made the
excavation of the two end piers not
practical.
Solutions: To overcome the challenges
that the precarious conditions of
the existing building brought up, the
contractor designed a cantilevered
shoring frame that would allow for this
to be installed outside of the building.
The frame essentially reached out and
" grabbed " the existing facade, holding
this 30 ft (9 m) in the air while the
proposed building was constructed.
The frame consisted of three sets of
vertical posts bearing on a single
concrete pad that was used to counterbalance
the overturning moments. On
top of these posts, main girders sat and
extended below the facade's wood lintel
at the opening providing a bearing
surface for the facade. Then, a series of
smaller vertical and horizontal braces
were used to stabilize and laterally
support the facade.
The challenges that the very soft
and wet ground conditions created on
the underpinning operations were
overcome by replacing the two endunderpinning
piers with bracket piles.
Bracket piles were designed to provide
vertical support for the facade and
temporary lateral earth retention for
the excavation.
Alan Quiroga is an engineer at Steele
Foundation. He holds a master's in civil
engineering from George Mason University.
Before joining Steele in 2019, he was an
operations manager for a civil engineering
unit in the U.S. Air Force.
As president of Steele Foundation, Andy
Steele drives the leadership and direction of
the company with professionalism, integrity,
commitment to quality and more than 35
years in the engineering and construction
field. Since joining the firm in 1991, he has
worked on the engineering and construction
of nearly 1,000 sheeting, shoring and
underpinning projects.
Conclusion
The revitalization of the historic block
between 14th, V and W streets
Northwest in Washington, D.C., through
the Collection 14 project showcases the
successful transformation of aging
structures into a vibrant multi-use
development. By preserving the
character and culture of the neighborhood,
particularly the period streetfacing
building facades of 2108/2110,
2114/2116 and 2124, the project
seamlessly blends the rich history of
the area with modern construction
elements. The complex nature of the
undertaking, including the challenging
subsurface conditions, necessitated
specialized sheeting, shoring and
underpinning work. As a result, this
block now stands as a testament to the
dedication and ingenuity required to
preserve the heritage of the past while
creating a dynamic and thriving space
for the present and future.
100 * DEEP FOUNDATIONS * JULY/AUG 2023

July/August 2023

Table of Contents for the Digital Edition of July/August 2023

TOC
July/August 2023 - Intro
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July/August 2023 - TOC
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