Prefab City A compendium of strategies for prefabricated building techniques in urban environments
Site Access There are several logical reasons for using cranes in prefab construction. Sites completely surrounded are rendered inaccessible to bulky construction equiptment.Other existing site conditions like single access to site, corner site, or narrow site greatly limit the access points to bring in construction equiptment and modules. Buildings can be constructed on these accessible (but difficult) sites and open sites using stick frame methods, but in some cases the speed of prefabricated construction methods can expedite the process.
courtyard
crane necessary for construction
surrounded site
single access to site
INTRODUCTION DETERMINANTS
corner site
narrow site
full access to site
Site Access + Assembly • 28
PRECEDENTS
CONTEXT
crane necessary for speed
DEPLOYMENT
alley
Crane Operation + Extents Special crane components There are some extra equiptment items that make craning a module more efficient and precise. Rigging keeps the forces of tension perpindicular to the module, reducing the bending forces on the unit. An antirotation device helps control a crane’s motion and the way the module shifts from pickup Winch up
Winch left
to placement.
Winch right Winch down
Emergency stop Start
Stop
Jog
Reset
Wood frame modules are best moved with strapping and rigging. Steel frame modules use
Crane school
hooks and holes intentionally in the design of
Heavy equiptment training school is essential for
modular structures to pick up the unit (as in
crane training and operation. It involves written
shipping containers).
tests based on state laws and practical examinations employing students’ skilled
Outriggers extending from the crane vehicle are
manipulation of the crane operations.
necessary to temporarily ground the module to the site. The jib is very useful to hold the modular unit in an almost upright position. It has the potential to resolve design issues thanks to its ability to
Crane cab controls
suspend the module in a way different from the way a crane typically does.
Rigging for wood frame module
INTRODUCTION
Small And Large Crane Extents All Terrain Crane Tadano ATF 110G-5 130 Ton capacity
jib
20°
20°
DETERMINANTS
143' 80° jib 122' 44°
95' 20°
80° 42'
170'
CONTEXT
101' 130'
PRECEDENTS
360° work area
outrigger
72'
24'-7"
340'-0"
outrigger
20'-0"
190'-0"
56'
DEPLOYMENT
Telescopic Boom Crane National Crane 1395 20 Ton capacity
360° work area
Site Access + Assembly • 30
Crane + Obstacles Hand signals
Permitting obstacles
between the crane operator and the individual on
Inspectational Services Department include: long
site guiding the placement of the crane. These
form permit, amendment, use of premise permit
simple gestures are necessary for several
(for using open space), electrical & fire alarm
reasons. Construction sites are often loud. There
permits, plumbing, gas, and sprinkler installation
is a lot of space between the crane operator and
permits.
Hand signals are necessary for communication
Permits in Boston one must obtain through the
the individual conducting the crane’s motions. The dual perspectives of crane operator and
Call Boston Public Works Department 24 hours
conductor are critical in ensuring safety and
prior to work to get a permit. Coordinate with
precision.
recycling, santiation, and street sweeping. Signs must be posted near the sitewith the construction schedule. In addition to this, it may be required to hire an officer to direct traffic.
Hoist
Swing
Lower
Raise Boom + Lower Load
Raise Boom
Lower Boom + Raise Load
Lower Boom
Stop
Hand signals
INTRODUCTION
Obstacles on a construction site There are a variety of existing physical barriers
that must be worked around. These can lead to interesting, even fruitful design moves. They includew but are not limited to:
DETERMINANTS
Utility poles Power lines Lamp posts Trees Fire hyrdants
PRECEDENTS
CONTEXT
DEPLOYMENT
Subterranian utilities
Site Access + Assembly • 32
Off Frame Assembly Site Dimensions Determined by Truck Turn Truck turn dimensions can influence the decision to use a site or not. Sometimes scale and cost can dictate the use of an off frame assembly system. Often obstacles, like powerlines, can make modular construction on a site unfeasible without the use of an off frame solution. Still other obstacles, like sidewalks and buildings surrounding the site (both immediately and across
20' 6' 52' 6'
the street), can impact the delivery of an off frame modular unit. Knowing the limits and minimum site dimensions can transform a once unusable site into a valuable piece of real estate.
Standard Semi Truck
Efficiency
minimum site dimensions 20’ wide x 53’ deep module dimensions 8’-6” wide x 53’ deep
Efficiency percentage is calculated by dividing the area of the module by the area of the smallest possible rectangular site. It is clear that the most dense and efficient module-site relationship happens when the module is shorter and wider, as in the case of the oversized load (width) example.
Module
Site
43 %
INTRODUCTION 25'
6'
6'
6'
53'
53'
53'
6'
6'
6'
Stretch Semi Truck
Oversized Load (Width)
Oversized Load (Length)
minimum site dimensions 25’ wide x 48’ deep module dimensions 16’ wide x 48’ deep
minimum site dimensions 17’ wide x 63’ deep module dimensions 16’ wide x 48’ deep
21 %
64 %
50 %
Site Access + Assembly • 34
PRECEDENTS
CONTEXT
minimum site dimensions 41’ wide x 80’ deep module dimensions 8’-6” wide x 80’ deep
DETERMINANTS
17'
DEPLOYMENT
41'
Off Frame Assembly From Truck to Site
Off-Frame Modular Delivery Module delivery is possible without a crane. The truck begins its delivery by backing into the site. Next jacks are placed underneath the module, taking the load off of the transportation chassis. The chassis is then removed by pulling it out into the street. In some cases, like the illustrated scenario, a chassis must be cut into pieces because the distance between the in place module and existing structure across from the site does not allow its removal.
Backing up
Entering site
INTRODUCTION DETERMINANTS DEPLOYMENT CONTEXT
Removing chassis from site
Breaking up chassis
Site Access + Assembly • 36
PRECEDENTS
Placing jacks under module