READ JONES CHRISTOFFERSEN LTD. 500, 144 Front Street West, Toronto, ON M5J 2L7 Phone (416) 977-5335 Fax (416) 977-1427 Web site: www.rjc.ca email: [email protected]HIGH-RISE EARLY DESIGN STUDY STAGE 2 Prepared For: EcoSmart CONCRETE PROJECT 504-999 Canada Place Vancouver, B.C. V6C 3E1 Prepared By: READ JONES CHRISTOFFERSEN LTD. 1285 W. Broadway 3 rd Floor Vancouver, B.C. V6H 3X8 and READ JONES CHRISTOFFERSEN LTD. 500 – 144 Front Street West Toronto, Ontario M5J 2L7 RJC#: 38647.02 February 6, 2004 Vancouver • Victoria • Calgary • Edmonton • Toronto
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READ JONES CHRISTOFFERSEN LTD. 500 – 144 Front Street West
Toronto, Ontario M5J 2L7
RJC#: 38647.02 February 6, 2004
Vancouver • Victoria • Calgary • Edmonton • Toronto
High-Rise Early Design Study – Stage 2 Page i EcoSmart Concrete Project RJC# : 38647.02 February 6, 2004
TABLE OF CONTENTS
Page 1.0 INTRODUCTION 1 2.0 SCOPE OF STUDY 5 3.0 DESCRIPTION OF SYSTEMS 7
3.1 Lift Slab Construction Description 7 3.2 Hybrid Precast Description 9 3.3 Bubble Deck Slab System 10
4.0 CONSTRUCTION COST COMPARISON 11 4.1 Lift Slab Construction 12 4.2 Hybrid Precast Scheme Cost 14 4.3 Cost Impact of Schedule 16 4.4 Cost Impact of Exterior Cladding 17
5.0 CONSTRUCTION SCHEDULE COMPARISON 21 5.1 Lift Slab Construction Schedule 21 5.2 Hybrid Precast System Construction Schedule 24 6.0 ENVIRONMENTAL PERFORMANCE COMPARISON 27 6.1 Lift Slab Construction 28 6.2 Hybrid Precast System 29
7.0 CEMENT USAGE COMPARISON 32 8.0 SUMMARY OF FINDINGS 34 8.1 Construction Cost Comparison 34 8.2 Construction Schedule Comparison 34 8.3 Environmental Performance Comparison 35 8.4 Cement Usage Comparison 35 APPENDIX A Lift Slab Floor Plate and Construction Sequence and Schedule APPENDIX B Hybrid Concrete Slab Floor Plate and Details and Schedule APPENDIX C Bubble Deck System APPENDIX D An Environmental Assessment of Alternative High Rise Structural
Systems Report By Athena Sustained Materials Institute. APPENDIX E Yolles Cast-in-Place Flat Plate Base System
High-Rise Early Design Study – Stage 2 Page 1 EcoSmart Concrete Project RJC# : 38647.02 February 6, 2004 1.0 INTRODUCTION
Read Jones Christoffersen Ltd. was one of two consulting structural engineering
firms retained by the EcoSmartTM Concrete Project to participate in the High Rise
Early Design Study. Stage 1 of the study was completed in October 2003. This
report outlines the findings of Stage 2.
The other firm selected to undertake this review was Yolles Partnership Inc. of
Toronto. Read Jones Christoffersen Ltd. met with Yolles prior to commencing
Stage 1 in order to divide the structural systems to be reviewed to avoid
duplication in this study and, therefore, maximize the number of systems
reviewed on behalf of EcoSmart.
The objective of the EcoSmart Concrete Project is to minimize greenhouse gas
emissions to the atmosphere by replacing Portland Cement in the concrete mix
with Supplementary Cementing Materials (SCM) to the greatest extent possible
while maintaining and improving cost, performance and constructability.
Previous reports prepared by Fast + Epp Structural Engineers,1 and Busby +
Associates Architects,2 had indicated that the increased use of supplementary
cementing materials on the slab portions of high-rise residential construction was
problematic due to the extended cure time required for such concrete. This
extended cure time meant that in normal cast-in-place reinforced concrete
construction the formwork could not be stripped as quickly as with a normal
concrete mix. This delay in the formwork stripping extended the construction
schedule to a point that the use of SCM’s was no longer economically viable in
this form of construction.
1 High volume fly-ash concrete usage for high-rise construction by Fast + Epp Structural Engineers dated November 2000 2 Use of EcoSmart concrete in the Bayview high-rise apartment, Vancouver, B.C., prepared by Busby + Associates Architects, November 2002.
High-Rise Early Design Study – Stage 2 Page 2 EcoSmart Concrete Project RJC# : 38647.02 February 6, 2004
This is particularly frustrating in the use of SCM’s as studies indicate that two-
thirds of all building concrete comprises the horizontal elements and that the
tower slabs comprise of 40% of the total concrete in the project.1 An inability to
utilize SCM’s in these components of a typical high-rise building severely limits
its application to the construction industry.
The objective of this High-Rise Early Design Study is to investigate alternative
structural slab systems for use in a typical high-rise residential building in
Vancouver that could use increased levels of SCM’s to replace normal Portland
Cement in slab construction as outlined in the Terms of Reference of this study, is
to produce the required knowledge for understanding the relationship between the
selection of a high-rise building structural system and its environmental
performance, cost and constructability (i.e. the principles of EcoSmart).
“The goal of this study is not to design new systems for high-rise construction;
instead it is to compare available proven technology based on the principles of
EcoSmart.”
The Terms of Reference of the EcoSmart Project is that it addresses three desired
outcomes:
Early Stage: Develop design methodologies that take EcoSmart concrete
properties into consideration at the time the structure is designed.
De-Materialization: Identify material reduction opportunities by using a smaller
amount of better performance concrete or by using precast elements when
possible.
1 Reference – High Volume Fly Ash Concrete Usage for High Rise construction report by Fast + Epp, November 2000, prepared for the Greater Vancouver Regional District, Air 2000 Program
High-Rise Early Design Study – Stage 2 Page 3 EcoSmart Concrete Project RJC# : 38647.02 February 6, 2004
High-Rise Construction: The fast setting requirements associated with high-rise
construction make it very challenging to apply EcoSmart Concrete to this
important market. The project will search solutions to this issue, both by looking
at traditional cast-in-place methods and by investigating novel approaches such as
hybrid steel/concrete system. The project will invest in the additional research
and design work necessary to produce a real case study using three innovative
building design methods.
Stage 1 Study As part of the Stage 1 Study at least three floor framing systems, one from each of
the following three groups, were to be evaluated:
.1 Traditional cast-in-place concrete.
.2 Conventional precast or hybrid concrete precast.
.3 Steel, or hybrid concrete steel, or other systems as proposed by the
consultant.
A particular building floor plate was created and utilized as the case study. The
floor plate originally proposed was revised to conform more closely to a typical
Vancouver residential tower. This building is to represent a typical high-rise
condominium project located in downtown Vancouver. It is 22-storeys in height
with a floor plate as indicated in the attached Appendices A and B. The building
height is specified in terms of a clear interior room height of 2,400mm. The
exterior envelope is assumed to be a full height double-glazed window wall
cladding system commonly used in this type of building construction in
Vancouver. Alternative comparable building cladding systems can be suggested
as part of the study in order to ensure compatibility with selected structural
systems. There is a requirement that mechanical ducts be incorporated into the
floor system with an average area of 8,000 mm2 in cross section. There is also a
High-Rise Early Design Study – Stage 2 Page 4 EcoSmart Concrete Project RJC# : 38647.02 February 6, 2004
requirement that the acoustical sound transmission rating be a minimum of 52
STC for the floor and the floor to have a minimum 2-hour fire-rating.
The Stage 1 part of the project, as outlined in our previous report dated October
24, 2003, documents a description of the structural system with schematic
drawings of the floor slab for one system of each of the three categories required.
The systems selected by Read Jones Christoffersen Ltd. for the Stage 1 Study
were:
.1 Cast-in-Place Concrete
(a) Lift Slab Construction (b) Post-Tensioned Construction
With Foundation 73,926 1,876,366 Without Foundation 70,537 1,801,824
Cladding Total area Perimeter x Height 219.3 4824.6 Total area 420 92,062 2,025,367 Percentage viewable glazing Percentage 40%Percentage spandral panel Percentage 40%
Percentage opaque glazing Percentage 20%
With insulated backpan (yes/no) Yes
Total 3,901,733
Table 3Precast Hybrid Cost Estimate
High-Rise Design Study – Stage 2 Page 21 EcoSmart Concrete Project RJC# : 38647.02 February 6, 2004 5.0 CONSTRUCTION SCHEDULE COMPARISON
In addition to a cost estimate we have also undertaken an estimated construction
schedule for each of the two schemes reviewed as part of this Stage 2 Study, as
speed of construction has a direct relation to the construction cost of the project.
The base schedule used as a comparative is the normally reinforced cast-in-place
concrete flat plate scheme with 9% SCM as reviewed n the Yolles report. Based
on the review of this system undertaken by Yolles we have taken this base
construction schedule as 22 weeks for the typical floors above the podium deck.
It was agreed between RJC and Yolles that only the construction schedule for the
typical floor tower portion of the project would be compared. It was assumed that
the foundations, below grade portion, and any grade level or podium structure
would have the same construction schedule and cost for all schemes.
The estimated construction schedule for both of the lift slab scheme and the
Hybrid concrete scheme was developed from first principals by RJC personnel
based on specialist input from contractors. These systems are not in common
usage in Canada for this type of structure, so there is not a good track record in
the construction industry on the time requirements for their construction.
Therefore these schedules should be viewed as approximate estimates only with a
possible margin of error.
5.1 Lift Slab Construction Schedule
The construction of the lift slab system comprises of two main phases. Initially,
the floor slab is constructed at ground level with each slab poured on top of the
previous slab, separated by a release agent. The slab edge is formed, the mild and
post-tensioning steel placed, the concrete poured, the surface finished, and once
cured the release agent is applied to the top surface, then the process is repeated
High-Rise Design Study – Stage 2 Page 22 EcoSmart Concrete Project RJC# : 38647.02 February 6, 2004
and each slab poured on top of the one below. Once the concrete reaches
sufficient strength the post-tensioned strands are tightened. We estimate this
phase to take 10 weeks for this project based on a 2 day casting cycle as indicated
in Table 4.
The second phase is the lifting process itself. The lifting process cannot
commence until all 22 floor plates are poured and the post tensioning is
completed. The post tensioning will be done on the lower slabs while the upper
slabs are still being constructed.
The lifting process is shown graphically in Appendix A. Only two levels of steel
columns are initially erected. All the slabs are then sequentially lifted (up to five
at a time) above the second floor and temporarily parked. The second floor slab
(the lowest of the lifted stack of slabs) is then permanently attached by welding
the embedded shear heads to the steel columns at its final location. New column
extensions are then added and the process is repeated.
The placement of the lower level floors take longer than the upper level floors due
to the increased number of floors that need to be handled and parked. Steel cross
bracing, or concrete core walls is added as the floors are lifted to maintain
structural stability. We estimate approximately 11 weeks for this lifting phase for
this building.
Once the 2nd and 3rd floors are locked in place the other trades can now access
these levels to complete their work. However, the slower pace of lifting at the
lower levels may create some delays in completing these levels.
The total estimated construction time for the Lift Slab system is 28 weeks.
High-Rise Design Study – Stage 2 Page 23 EcoSmart Concrete Project RJC# : 38647.02 February 6, 2004
Table 4
Total Days Time Action
3/4 day Placing of 1st set of steel columns 32’ long1/4 day Construction of Jump form around slab edge
Installation of lower level reinforcement of 1st slabInstallation and preparation of shear heads & collars @ 20 column locations (note: shear heads are prefabricated of site)
Installation upper layer reinforcement of 1st slabInstallation of P/T layout in slabInstallation of mechanical and electrical sleevesFinishing any mechanical electrical sleeves and Reinforcement worksPlacing concrete late morning
1/2 day Finish slab after 4-5 hour setting time
Move up form work for 2nd slabSpray seperating compound on previous slabLayout and preperation of shear heads @ column locationsInstallation of lower level reinforcement of 2nd slabInstallation upper layer reinforcement of 2nd slabInstallation of P/T layout in slabInstallation of mechanical and electrical sleevesFinishing any mechanical electrical sleeves and Reinforcement worksPlacing concrete late morning
1/2 day Finish slab after 4-5 hour setting time
Move up form work for next slabSpray seperating compound on previous slabLayout and preperation of shear heads @ column locationsInstallation of lower level reinforcement of next slabInstallation upper layer reinforcement of next slabInstallation of P/T layout in slabInstallation of mechanical and electrical sleevesFinishing any mechanical electrical sleeves and Reinforcement worksPlacing concrete late morning
1/2 day Finish slab after 4-5 hour setting time
45th day 9 weeks Finish 22nd floor slab50th day 10 weeks Finish upper slab Post Tensioning with 7 days delay for strength gain
Lift Slab Construction Schedule for Slab Construction of 22 Floors
1st day
2nd day
1/2 day1 day3rd day
1/2 day
1/2 day
1 day
1 day
6th day 1 day
1/2 day
1/2 day
5th day
1/2 day
1/2 day
1 day
START TYPICAL 2 DAY CYCLE
FIRST FLOOR 3 DAY CYCLE
REPEAT FOR REMAINING 19 SLABS
7th day 1 day1/2 day
CONTINUE 2 DAY CYCLE
4th day
1/2 day1 day
High-Rise Design Study – Stage 2 Page 24 EcoSmart Concrete Project RJC# : 38647.02 February 6, 2004 5.2 Hybrid Precast System Construction Schedule
Our analysis indicates that a 4 day per floor construction cycle, equal to the cast-
in-place concrete flat plate base system, can be achieved for this system (see
Table 5). The schedule of the precast scheme is driven mainly by the cranage time
required to lift the precast planks, beams and column halves into their respective
positions. The column and beam sections require more lifting time due to the
extra time required to plum the elements and tack weld them into position.
Precast Contractors indicated that an average of 30 minutes for these elements
should suffice. For the typical precast planks that only need to be lifted into place
and are supported by the core walls and the perimeter beams the lifting time is
estimated to be an average of 15 minutes per element.
The reinforcement cages can be tied by the rebar crews concurrently with the
precast lifting and then only need to be dropped into the columns and beams. The
rebar at the balconies and the welded wire mesh in the slab do not amount to
significant amount of work with respect to the schedule.
The cast-in-place concrete slab topping also fills the columns and beams to form a
monolithic structure and is placed during the late morning to give the finishers all
afternoon to finish the slab. The next morning lifting of formwork for the core
wall can commence.
The option of slip forming the core in advance was explored but no benefit was
found. It appears that the initial set up of the slip form would delay rather than
accelerate the schedule.
Another approach worth considering would be to replace the precast concrete
perimeter columns with cast-in-place columns. The lifting time would be reduced
as the column forms can be lifted and set plum more quickly by the forming crew.
Placing of the concrete would be at the same time as for the core walls.
Therefore, all horizontal elements would be precast with concrete topping and all
High-Rise Design Study – Stage 2 Page 25 EcoSmart Concrete Project RJC# : 38647.02 February 6, 2004
vertical elements could be cast in place. From an environmental and cost point of
view this would result in no significant change as the perimeter columns only
account for a low amount of greenhouse gases and costs.
Based on our analysis and schedule assumptions as indicated on the Hybrid
Precast Construction schedule in Appendix B, the construction time of this system
is 21 weeks. This is virtually identical to the 22-week schedule of the base
concrete flat plate system. The 1-week difference is due to the initial construction
time required for the fly forms for the flat plate system.
High-Rise Design Study – Stage 2 Page 26 EcoSmart Concrete Project RJC# : 38647.02 February 6, 2004
Table 5
Total Days Time Action
Erect Formwork for core walls (2.5 Hours)Erect Precast 6 Columns =12 pieces at 15min each = 3 hours
1day Parallel Rebar Crews tie reinforcement cages for colums and core walls + Installation1/4 day Pour core walls late afternoon
Strip formwork for core wall (1 hour)Finish Remaining 6 Precast Columns 3 hoursStart Erection of Precast Beams + Planks (56 Pieces x 15min=14 hours) (3.5 Hours)Parallel Rebar Crews tie reinforcement cages for next columns and core wallsParallel Rebar Crews start placing slab reinforcement mesh and bars at cantilever balconiesContinue Erection of Precast Planks 7.5 Hours
Rebar Crews continue layout of rebar in Perimeter beams and on top of erected planks
16 3.Bracing +Stair 45 days Mon 3/22/04 Fri 5/21/04
17 Construction of Curtain Wall 84 days Mon 3/22/04 Thu 7/15/04
18 Drywall 85 days Mon 3/22/04 Fri 7/16/04
12/28 1/4 1/11 1/18 1/25 2/1 2/8 2/15 2/22 2/29 3/7 3/14 3/21 3/28 4/4 4/11 4/18 4/25 5/2 5/9 5/16 5/23 5/30 6/6 6/13 6/20 6/27 7/4 7/11 7/18Dec 2 Jan 4 Jan 1 Jan 1 Jan 2 Feb 1 Feb 8 Feb 1 Feb 2 Feb 2 Mar 7 Mar 1 Mar 2 Mar 2 Apr 4 Apr 11 Apr 1 Apr 25 May 2 May 9 May 1 May 2 May 3 Jun 6 Jun 1 Jun 2 Jun 2 Jul 4 Jul 11 Jul 18
Task
Progress
Milestone
Summary
Rolled Up Task
Rolled Up Milestone
Rolled Up Progress
Split
External Tasks
Project Summary
Group By Summary
LIFTSLAB CONSTRUCTION SCHEDULE
ECOSMART CONCRETE HIGH RISE STUDY
Page 1
Project: LIFT SLAB SCHEDULEDate: Thu 1/15/04
APPENDIX B
HYBRID CONCRETE SLAB FLOOR PLATE AND
DETAILS
ID Task Name Duration Start Finish1
2 Mobilization 0 days Mon 1/5/04 Mon 1/5/04
3 Excavation 0 days Mon 1/5/04 Mon 1/5/04
4 Foundation 0 days Mon 1/5/04 Mon 1/5/04
5 Parking Garage 0 days Mon 1/5/04 Mon 1/5/04
6 Plaza Slab 0 days Mon 1/5/04 Mon 1/5/04
7
8 ERECTION OF BUILDING 88 days Mon 1/5/04 Wed 5/5/04
9 1st Floor to 5th 20 days Mon 1/5/04 Fri 1/30/04
10 6th Floor to 10th 20 days Mon 2/2/04 Fri 2/27/04
11 11th Floor to 15th 20 days Mon 3/1/04 Fri 3/26/04
12 16th Floor to 20th 20 days Mon 3/29/04 Fri 4/23/04
13 21st to Roof 8 days Mon 4/26/04 Wed 5/5/04
14
15 Construction of Curtain Wall 84 days Mon 2/2/04 Thu 5/27/04
16 Construction of Drywall 85 days Mon 2/2/04 Fri 5/28/04
12/28 1/4 1/11 1/18 1/25 2/1 2/8 2/15 2/22 2/29 3/7 3/14 3/21 3/28 4/4 4/11 4/18 4/25 5/2 5/9 5/16 5/23 5/30Dec 28 Jan 4 Jan 11 Jan 18 Jan 25 Feb 1 Feb 8 Feb 15 Feb 22 Feb 29 Mar 7 Mar 14 Mar 21 Mar 28 Apr 4 Apr 11 Apr 18 Apr 25 May 2 May 9 May 16 May 23 May 30
Task
Progress
Milestone
Summary
Rolled Up Task
Rolled Up Milestone
Rolled Up Progress
Split
External Tasks
Project Summary
Group By Summary
HYBRID PRECAST CONCRETE CONSTRUCTION SCHEDULE
ECOSMART CONCRETE HIGH RISE STUDY
Page 1
Project: Hybrid Precast SCHEDULEDate: Thu 1/15/04
APPENDIX E
YOLLES CAST-IN-PLACE FLAT PLATE BASE SYSTEM
Scheme A Flat Plate - Material Construction CostAgreed dimensionsFloor area = 345 m2Floor perimeter = 85mCore wall perimeter = 33mCore wall openings = 11 m2Varied dimensionFloor to Floor = 2.575m
Element Sub-element Material Dimensions Quantities/ Total Unit Cost Cost/ Total costFloor Floor