Example Project

The Tabor Center is a 1.3 million ft2 (120,000 m2) [20,000 ft2 (1860 m2) per floor] multi-use facility in the center of downtown Denver. It consists of twin office towers of 32 and 40 stories. The tower structure is composed of three elements: the exterior wall, the cen-

^^v^Formwork systems Influence factor

Conventional column/ wall form

Ganged forms ■ load gathering system

Літр form

Slip form

Self-raising form

Building design

n

&

Cl

2

e

HD

3

Lateral support system

Most suited for frames and retaining walls

Shear walls Bearing waits Retaining wails

Shear walls Frames and framed sheer wall

Shear walls

Shear Walls Tube systems Tube in tube

Building height

Up to 120 fl

Up lo 350 ft

Up lo 350 It

Average 400 ft Min recorded = 60 ft Max recorded – 600 ft

At [east 300 ft No max.

4>

a.

tc

JL

to

ГТ

c

■6

2

Column / wall size and

location

System can handle variation ol column/ wall size and location

System can handle moderate variation of columns/walls size and localion

Walls should be of the same location Walls size variation can be accommodated

System can handle resonably modular design

Openings/

inserts

System can handle openings/inserls ol different size and location

Variation in opening’s size and location can be accommodated at additional cost

Openings/inserts should be regualily occuring from floor to floor

Should be minimum Too many openings/ inserts make this system impractical

Syslem can handle moderate variation in openings size and location

Job specification

c

о

13

Й

‘tr.

S

О

о

s

ф

а.

to

Concrete finish

*As-cast‘ concrete finish

Produces smooth exposed concrete finish Tie pattern and number should be designed Form liners can be used to produce

architectural concrete

System produces rough concrete finish No ties

Smooth concrete finish

Form flners can be used

Construction

sequence

Slabs and walls are placed concurrently

Slabs end walls are placed concurrently Walls can be paced ahead of the floor slab

System

is used when no floor Slab is available

Typically, walls are pfaced entirety or at least several stories ahead ol the floor

Walls are ahead of the floor.

Other method is used for the first 2-3 stories

cycle Tima

1 Floor/week

1 floor every 3-4 days

і floor every 2-3 days

1 floor every day Rate of placing = 8-20 InJhr

1 Floor every 2-3 days

^^■^Formwok system Influence faclor

Conventional column/wall loan

Ganged forms ■ load gathering system

Jump form

Slip form

Self* raising form

Local conditions

Area practice

More ellicient in areas of high quality, fow-cost labor force

Work best in high – cost, low-quality labor force

System is easy to learn and adapi Learning curve is quite short

System can be teamed in 2—3 weeks

System requires high – quality supervision

Weather

Generally no! a major factor

A major faclor, waifs should have sufficient strength before stripping which is largely influenced by weather condition High winds limit the crane movement

Hor or cold weather affects the concrete rate of selling which slow the rale of rise

In cold weather, forms should be protected and concrete should be healed

u

ГЇ

о

S

(4

У

OJ

Й

Access to site

Generally not a factor for foose forms

Can be a major faclor it (he syslerti is pr$- assembled in a local yard facility

Site must be accessible, forms can be up to 16 fl high and 44 fl wide

System must have a limited access for material delivery

Min. site access is required lor concrete placing and rebar delivery

Site $гге

Not a factor

Can be a major factor if the forms have to be built in Site

Nol a major factor, forms are preass ambled and unloaded directly

Not a major factor, system can be used in restrict?-.; small sites

systems

Influence factor ‘ч’чЧч^

Conventional column/wall form

Ganged forms • load gathering system

Jump form

Slip form

Self-raising form

Supporting organization

Cost

Stripping

Hand strip High stripping cost

Crane is used to strip the system High stripping cost

Forms are equiped with mechanism for stripping Min stripping cost

Forms are stripped at the end of the project Min. stripping cost

Forms are equiped with mechanism lor stripping

Min stripping cost

Reuse

Lass than 10

Between 40 and SO Reuses could be horizontally or vertically

Between 15 and 30

Between 50 and 100 {i. e., between 200 and 400 ft high)

At least 30 reuses should be available vertically

c

G

E

Э

O’

о

о»

_c

H

о

X

Location of adjacent building and obstruction

Generally not a factor

A major factor, system must have a Iree space to be moved from floor to floor

Minimum free space should be available for crane movement

Not a major factor, system can be used in downtown restricted areas

Crane time

Not a factor, system car be hand-set

Crane-dependent system, sufficient ciane lime is a must

System substantially reduces crane time Average crane time pick = 20 min.

Crane is used only for materials delivery and concrete placing

C rane • і nd e pe ndent system

Operating

system

Hand-set system, crane increases system efficiency and reduces cost

Crane-set system Crane serves two functions: lifting and supporting the forms

Crane is used only to lift the forms Crane is not used lor forms dismantling

Locomotion is provided by electric, pneumatic. or hydraulic Jacks climbing on smooth steel rods

System is lifted by hydraulic, electric, or pneumatic lifters.

>. – м r; ot * c n r?

іл E

Safety

No special safety features is required

Special care for handling the large ganged units by crane

Safety features Safe guarded platform No one needs to be on the form during crane handling

For hydraulic systems, special safety precautions must be taken to prevent fire several hundred feet above the ground

> – о =

II

Supporting yard facility, supplier or make-up area

Not a major factor, but system is more alficient, it a local yard facility is available

A major factor, system must have an adequate make-up area or close by supplier

System is rented or purchased

Continuous materials delivery is a must. Un­interrupted concrete placement must be assured.

System is pre­assembled, make-up area is not a factor. Local supplier must be available

tral core, and the interior deck area that ties the two together (tube in tube). The core is structural steel with a concrete diaphragm or infill walls up to floor 12 to resist part of the lateral loading. The deck area is also structural steel with a metal deck and concrete fill. The exterior wall consists of closely spaced columns (tube sys­tem). A study showed that the crane time is not adequate for hoisting formwork and it will only be used for material handling and concrete placing. Architectural concrete is required for the exterior walls.