Introduction to building

The Bechtler Museum, located in downtown Charlotte, North

Carolina, was designed by Swiss architect Mario Botta. Established on the 2nd

of January 2010, Bechtler museum exhibits modern artworks from the mid 20th

century. This 3390 square meter four-story structure has a soaring glass atrium

that extends throughout the museum’s core and diffuses natural light into the

building. The dominant feature of this solid structure is its fourth floor which

extends from the core of the building, cantilevered and supported by the

signature column rising from the open atrium below.

A rigorous, yet elegant simplicity selection has been made by Botta

in the palette of materials used which includes the combination of glass, steel,

black granite, terracotta, polished concrete and wood. Botta had designed

intending for a strong, contemporary structures that layer the colours, texture

and materials for a solid architectural and sculptural power that connects to

the dynamic art inside it.

1

Orthographic drawings

Second Floor Plan

Third Floor Plan Fourth Floor Plan

A A

First Floor Plan

B

B

2

Front elevation Section A-A

3

1

2

4

5

Section B-B

3

4

1. Skylight

2. Terracotta Cladding

3. Wall

4. Composite Concrete Slab

5. Column with Terracotta

Tile

Load Distributions

The cantilever of the building is

supported by W40 x 362 wide flange

steel beams installed in the roof

structure and fourth floor. Above and

below each walls at the cantilever

there will be a cross beam.

The loads from the top are

transferred downward through the

load transferring walls to the

foundation footings.

The column is an important part of

the structure to support the fourth

floor. It is placed in the middle of the

cantilever and directly under the steel

beams

To transfer the load more effectively.

The longer the span of the cantilever and the further it is from the supporting structure, the larger the load.

The cross bracing tension cables are used to strengthen the structure of the glass atrium especially when

large loads are transferred from the top.

5

Detailing

1. Skylight

The load from the top is distributed to the

wide flange steel girders that spans across

the roof and is transferred to the wall

system.

The coffered design of the skylight is used

to lighten the roof weight while concealing

the large steel beams and mechanical

structures.

Front section of skylight

Side section of skylight

Air conditioning duct

Wide flange steel girder

Water resistant roof membrane

Wall

Terracotta tile cladding

Metal decking

Parapet

Wall

6

Detailing

2. Terracotta cladding

The custom engineered TerraClad™ used is

composed of fire clays, colored aggregate,

and fluxes that were fired to a specific firing

curve allowing the terracotta to be frost

resistant and high freeze thaw.

Sectional view of the

cladding system

1

2

3

1

Clip with isolator

Installation of cladding system 7

Ship lapped design

The incorporation of ship lapped open joint design of the

panel had shield the structure from moisture that enter the

ventilated cavity. Gaskets and isolators of the rain screen

provide a snug fit between panels and the framing system

to prevent wind induced rattle and allow for movement of

the aluminum framing due to thermal expansion.

2

3

8

Detailing

3. Wall

Gypsum Board

Insulation

Plaster

Plywood

The drywalls of the Bechtler Museum allow

for equal load transfers as the walls are more

stable. The insulation also maintains the

temperature in the interior due to the four

seasons experienced in North Carolina. The

gypsum board on the drywall is also fire-

proof and acoustically beneficial causing it to

be a preferable building material.

9

Construction detail of

Drywall

Terracotta

Cladding

Waterproof

Membrane

Metal Stud

Granite Flooring

Concrete

Wide flange steel

girder

C-Channel

4. Composite Concrete Slab

Metal Decking

The composite concrete wall slab acts as a support

for Bechtler museum. It works by increasing the load

capacity of flooring system. The concrete slab

together with in-situ infill in conjunction with welded

shear studs onto I-beam to enable the slabs and the

steel beams to act compositely.

Construction detail of

composite floor system

10

Detailing

Wide flange steel girders are set up to

form the structure of the cantilever. Then

metal decking are fixed to the steel beams

using shear studs. The edge of the metal

decking was folded up to prevent the

poured concrete from flowing out. A layer

of black granite and insulation is used as

the floor finishes.

For the exterior wall, steel studs used as

terracotta tile tracks system are fixed onto

the c-channel.

Detailing

5. Column with terracotta tile cladding

(Pic) The column was first assembled for

visual inspection prior to its disassembly

and transportation to site.

The sculptural column rising up 3 story

(47 feet tall) was constructed with the use

of hot dipped galvanized attachments in

place of stainless steel fasteners onto the

concrete column.

The column is made of concrete with

specified 28-days compressive strength

of 12,000 psi. The reason concrete is

used because it could support larger load

with a slender frame compared to other

materials.

Corrugated Decking

Crossbeam

Flange Girder

Flange Steel

Terra-cotta Pavers

Concrete Floor Slab Aluminum Cladding

Convex Steel Frame

Aluminum Cladding

Column connects with

Steel Anchor Bolts

Terra-cotta Ceiling

Cladding

11

Before applying the cement to the decking, concrete

ratio experiments had been done to find out the most

suitable ratio for the concrete flooring. First trials of

concrete mixing used no sands as the binding agent,

the ratio of cement to water is 2: 1.

After mixing it, the mixture

was left for several hours

under the sun to let it dry.

The final product of the cement

was smooth and powdery. It was

easily crack as it did not has

aggregates such as sand to hold

the concrete mixture.

Corrugated paper was used as metal decking as it

has corrugated surface similar to the metal

decking. Smooth sand was added into the

concrete mixture. The ratio of cement to sand to

water is 2: 1.5: 1.

As the result, the mixture did not go under the wire mesh as the sand

particles are not small enough to pass through the wire mesh. The

corrugated paper was not suitable as metal decking as it absorbs the

water of the concrete mixture.

Modelling process Composite concrete flooring

12

Corrugated paper had been replaced with

plastic board. Plastic board is more suitable

than corrugated paper as it is light and

waterproof. It had been cut into metal

decking shape and sprayed for metallic

surface purpose.

The sand mixture was filtered by using

wire mesh to enable smoother surface

for the final product compared to

previous batches of concrete mixtures.

The ratio of cement to sand to water is

2: 1: 0.5.

During the process of drying,

many bubbles appeared on the

surface of concrete as the

narrow gap between the metal

decking was not completely

filled in with concrete. As the

result, the concrete cracked on

the next day.

The ratio of cement to sand to

water is adjusted to 5: 1.5.

Wood shreds were added into

the concrete mixture to reduce

the possibility of cracking of

concrete.

Composite concrete flooring

13

Metal Decking Process

Balsa wood is used as the material for I-beam

under the metal decking. This is because balsa

wood is available in different type of thickness. It

is also a light material hence the floor system will

not be too heavy as the cantilever section is only

supported by one column.

After aligning, both structural system is ready to be glued. Each

connections of the structural systems was connected using hot

glue gun to increase the durability and strength of the structures.

Plastic model pipes are

used as c-channels as it

is light and available in

different sizes. Cutting

mat was used to make

sure all the c-channels

are aligned.

The floor system with materials representing

the black granite, concrete with metal

decking, steel girders, c-channels and metal

studs.

Composite concrete flooring

14

Column making

A white modelling board I-beam was

added in the center of the column

acting as the load structural system

and to also hold the concrete

together.

First trial of the concrete column

without an I-beam in the middle. The

column was made by filling up the

straw mold. It broke off into pieces.

First trial of the frame for the

terracotta tiles of the column.

Soldering tool and alloy were used to

combine the alloy rings. The alloy

could not combine properly and it

took too much time.

Hot glue gun was used instead for

the joint of the frames. A protractor

was used to determine the position of

the vertical frames on the rings.

Load bearing column

After completion of the internal

framing, excess glue stains were

removed with nail polish remover. It

was then sprayed with gray paint.

The column was then inserted into

the alloy frame and column specific

terracotta cladding were attached

onto frame. 15

Grey board was used as a

substitute for the Terracotta

cladding. This is due to the texture

and thickness. Different colours

and paint to water ratio were

tested on the board.

The grey board was cut upon the

surface, the measurements were

scaled from the length and width

to simulate the gaps between

alternating cladding.

A separate set of grey board was cut

into individual pieces to be used as the

ship-lapped design of the panels.

The grey boards was then

painted with brown with a slight

addition of peach in order to

match the colour of the original

cladding.

An issue faced during the cutting of

the cladding is that the pieces tend

to come loose, or break completely

mainly because each cladding were

cut individually and the minute scale

of the cladding.

Due to the cutting of the coloured grey board

into individual strips of cladding, the grey board

was repainted . This caused excess water

from the paint to be absorbed by the board

making the strips flimsy during the assembly

and completion of the cladding.

Terracotta cladding

16

Dry wall composed of several

layers; the first exterior layer was

made of a 0.2mm thick balsa wood

to represent ply wood, 0.1mm balsa

wood as gypsum board and wool in

between the two as insulation.

Long plastic sticks matching the

height of the wall are placed in

intervals along the wall as steel

studs

Putty filler was applied onto the 0.1mm

balsa as the internal plastering and was

smoothened out.

The tile cladding tracks system

made with plastic sticks was

glued onto the external wall.

The terracotta cladding was then

attached to the exterior surface of the

wall.

Dry wall

17

White model making board was

used for the flat surface whereas

the curved surface of the skylight

uses white card as it is more

flexible.

Plastic sheets were curved and

attached onto the gaps of the

upper surface of the skylight.

A difficulty faced during

construction of the curved surface

was the accurate gradient of the

curve causing numerous attempts

of different measurements in

order to achieve the proper

curvature.

The plastic sheets were then

engraved with vertical lines to

allow bending of the sheets.

Due to the fact that the skylight spans horizontally over the whole model with

minimal support from the wall, the weight distribution of the roof and skylight

were an initial problem. It was then solved with the addition of I-beams made

from mounting boards inserted in between the skylight to act as support.

Skylight

18

After this project, we realized appropriate construction method is important to avoid uneven load distribution and

cause structural failure of the building. The materials used should be considerate and tested first before applying

it in final model. In this case, concrete is hard to handle as it may crack easily due to the improper mixture.

During the modelling phase, parts that are made separately required thorough planning to ensure premade parts

are able to connect to one another accurately. This applies to real life construction too as precast parts must be

precise to avoid problems.

In addition, the progress of the model and report should be simultaneous. The materials and model should be

kept properly to avoid loss or damage as this is also a common issue on actual construction sites. As such, our

group should work systematically and on time to meet the deadline requirements.

19

Conclusion & Final Model

Architecture Week, (2010). Bechtler Museum. [image] Available at: http://www.architectureweek.com/2010/0407/design_4-3.html [Accessed

14 Jun. 2014].

Architecture Week, (2010). Bechtler Museum by Botta. [image] Available at: http://www.architectureweek.com/2010/0217/design_1-2.html

[Accessed 13 Jun. 2014].

ArchwebDWG, (2014). Bechtler Museum of Modern Art. [image] Available at:

http://www.archweb.it/dwg/arch_arredi_famosi/mario_botta/Bechtler_Museum/Bechtler_museum_dwg.htm [Accessed 10 Jun. 2014].

Bechtler Museum of Modern Art. (n.d.). 1st ed. [ebook] Available at: http://www.kingguinn.com/libraries/portfolio/publications/317.pdf

[Accessed 13 Jun. 2014].

Boston Valley Terra Cotta. (2014). 1st ed. [ebook] Institute. Available at:

http://www.swrionline.org/UserFiles/File/Fall09/Project%20Showcase%20Presentations/Architectural%20Terra%20Cotta%20Ventilated%20

Ceramic%20Screen%20Wall%20Systems%20by%20Sheri%20Carter.pdf [Accessed 14 Jun. 2014].

Innovative Manufacturing in Architectural Ceramics. (n.d.). 1st ed. [ebook] New York: Boston Valley. Available at: http://www.triton-

ca.com/pdf_files/BV_TerraClad%20Design%20Guide.pdf [Accessed 13 Jun. 2014].

Steelconstruction.info, (2014). Acoustic performance of floors. [online] Available at:

http://www.steelconstruction.info/Acoustic_performance_of_floors [Accessed 15 Jun. 2014].

Worldarchitecturemap.org, (2014). WAM | Bechtler Museum of Modern Art | Charlotte. [online] Available at:

http://www.worldarchitecturemap.org/buildings/bechtler-museum-of-modern-art [Accessed 15 Jun. 2014].

Reference

20