|
Des Moines Public Library
Des Moines, Iowa
Buildings Home
> Case Studies: Cultural Buildings>
Des Moines Public Library
 In
the western gateway to downtown Des Moines, Iowa, resides the new
Des Moines Public Library. The David Chipperfield creation replaces
the existing 100 year old facility with more than a shelter for
books. This $32 million, 140,000 square foot project acts as a community
centre with a wide range of educational services and houses a conference
centre, extensive youth and children’s facilities and commercial
space.
The architect envisioned a structure with neat, clean lines. The
vision became reality with concrete. Due to its inherent fire resistance,
additional fireproofing was not required and allowed for the aesthetically
pleasing exposed flat plates and round columns to support the unique
and complex layout. With the public space and quiet environment
of a library, the structural design team favored the thick slabs
as they made it “easier to meet the vibration requirements
because of their increased dampening characteristics over steel
construction.”
With the utilization of exposed concrete slabs came the strict
architectural criterion to keep the soffit flat. This became a great
challenge for the structural engineer. The library live loads were
significant and the raised floor construction, creating an access
space for mechanical and electrical equipment, demanded a thicker
flat slab which adds to the self weight of the structure. To safely
account for the high punching shear at the support locations, the
typical floor framing is comprised of a conventionally reinforced
18” thick flat plate (14 inch thick at roof), supported by
27 inch diameter interior columns and 14 inch diameter exterior
columns. These floor slabs and columns are designed with 6,000 psi
concrete strength to span the general 30-foot x 30-foot bay spacings.
In order to resist the high punching shears, a cruciform-shaped
arrangement of shear stirrups was designed and cast in the slab
at each interior column intersection for all levels.
Constructability was another factor favoring concrete as the material
of choice. The staging area was extremely limited within the congestion
of downtown Des Moines traffic. Concrete’s local availability
allows construction to proceed without stocking significant amounts
of materials on site. To meet the stricter demands of an exposed
concrete structure, pre-pour coordination meetings allowed the construction
manager to make adjustments without delay to the schedule. These
precautions helped ensure all form joints and embed plates were
located correctly, since they have a visual impact on the structure.
Sustainability is featured in this signature structure with the
implementation of green roof construction, the first of its kind
for the City of Des Moines. The function of the Green Roof Infrastructure
provides many benefits to the building and the surrounding community.
In addition to beautifying the built environment, there are intangible
benefits as well. The manufactured microclimates have a noticeable
impact on the heat gain/loss of a building, as well as the air quality,
humidity and reflected heat in the surrounding neighborhood. With
the evaporative cooling effects, air conditioning demands of the
building are reduced, which in turn reduces the “Urban Heat
Island Effect”. The plantings of the microclimate also capture
particulate matter to slow the smog production rates in urban areas.
Another global feature of Green Roofs is the stormwater runoff reduction.
The water is retained by the substrate and taken up in the plants
to return to the atmosphere in transpiration and evaporation, in
lieu of taxing the community’s infrastructure.
To have a durable and low maintenance facility, the design team
incorporated sustainability into the interior of the structure as
well. The building’s cladding is a unique glazing system that
uses a copper screen mesh sandwiched between panes of glass. This
controls light intensity, reduces energy costs, and provides a warm
copper glow in the evenings. Considering all of the project criteria,
the design team felt that “since this is a public facility,
we needed to use durable materials; concrete was an easy choice.”
|
 |
Case Studies:
Cultural Buildings
Educational Institutions
Green Buildings
Healthcare
Hospitality
ICF Buildings
Luxury Residential
Mixed Use
Office Buildings
Religious Structures
Tilt-Up Buildings
| Owner:
Des Moines Library Foundation
Architect:
David Chipperfield,
London, England
HLKB,
Des Moines, Iowa
Structural Engineer:
Jane Wernick,
London, England
Shuck-Britson, Inc.,
Des Moines, Iowa
Construction Manager:
Weitz Company
Des Moines, Iowa
Concrete Contractor:
Miron Construction
Concrete Supplier:
A1 Ready Mix
Rebar Supplier:
Ambassador Steel
|
|
|