Selection of Roof Casting Formwork Systems for the Bird

Island Project: Case Study

Presentors:

Muhammad Umar nazir (cn-015)

Imran naeem (cn-012)

Selection of Roof Casting Formwork Systems for the Bird

Island Project: Case Study

• Authors:

Tariq Abdelhamid, Ph.D

Mohamed El-Gafy, Ph.D, P.E

Panagiotis Mitropoulos, Ph.D

• JOURNAL:

PRACTICE PERIODICAL ON STRUCTURAL DESIGN AND CONSTRUCTION © ASCE / NOVEMBER 2009

Contents

• Abstract

• Scope

• Summary

• Objective

• Methodology

• Literature Review

• Data Analysis

• Conclusions

ABSTRACT

• Formwork is a major contributor to profitability—or the lack of it—on most large and complex concrete jobs.

• Formwork has major consequences for the project schedule, as well as all related trades, such as ironworkers and cement finishers.

• Consequently, selecting a formwork system and planning its field operations must consider the effects of the system on the overall project.

• This may result in significant difficulties in meeting the project requirements.

• The paper illustrates the complexities involved in the selection and deployment of a formwork

SCOPE

• This paper reports on an in-depth study of the formwork system selection

problem on the Bird Island Flats Tunnel project.

• The project is a part of the Central Artery/Tunnel project in Boston,

Massachusetts.

SUMMARY

• The challenge on this $290 million project was the budget and schedule requirements for thetunnel roofs.

• The width and thickness of the roofs were on average 18.29 m 60 ft and 2.44 m 8 ft,respectively.

• The conventional shoring methods were not able to keep the project on time for criticalinterim milestones as well as on budget.

• The alternative forming systems available did not provide a solution because of the timeand effort required for setup and takedown operations.

• The management team solicited proposals from formwork manufacturers, and chose thesystem from CONESCO Industries.

OBJECTIVE

• This study has two objectives:

• First to identify the issues involved in the selection and

sequencing of a custom-made formwork system

• Second to formulate a detailed analysis method to

improve decision-making.

METHODOLOGY

• The paper consists of two parts.

• The first part describes the project and presents the issues involved in the selection of the formwork system. It identifies the complexities of the decisions that faced the construction team, and describes how the selection was made and how the final decision came about.

• The second part presents analytical methods and techniques to support the decision-making process. A detailed analysis and comparison of formwork systems is performed that accounts for all the key formwork parameters. Such analysis is necessary in order to select the best system for the project.

LITERATURE REVIEW

• Conventional System

The conventional system available consisted of a number of aluminum joiststhat are supported by standard I beams. The concrete is poured against 2.3 cm3/4 in. plywood that is placed on the aluminum joist. The concrete, plywood,aluminum joists, and standard I beams are supported on steel shoring legs. Thesystem is very similar to scaffolds used for work done at high elevations. Thesystems available were categorized by the capacity of the shoring legs. 10, 25,and 100 kip/leg shoring systems were available. The cross section and layout ofsuch a system is shown in Fig.

CONVENTIONAL FORMWORK

LITERATURE REVIEW

• CONESCO Roof Casting Machines

• The winning proposal for a formwork system called the “Roof Casting Machines”was submitted by the CONESCO Corporation. Each Roof Casting Machineconsisted of two major components, a self-propelled traveler and the form set. Thetraveler is a three-dimensional rectangular frame equipped with a gasoline enginewhich makes it able to transport the custom form set to its desired location.Hydraulic cylinders on the traveler are used for initial horizontal and verticaladjustments of the form sets. The form set is also equipped with hydraulic cylindersfor further adjustment. A detailed illustration of the traveler and form set is shownin Fig.

CONESCO ROOF CASTING MACHINE

Machine Types with Height and Width Changes

MACHINE

TYPE

HEIGHT

(meters)

WIDTH

(meters)

TRAVELLER

MIN MAX MIN MAX

I A 7.43 9.54 11.43 15.70 I A

I B 5.53 7.56 11.43 15.70 I B or II B

II A 7.41 7.60 12.95 22.71 II A or II B

II B 5.18 9.34 12.80 22.56 II B

III 6.28 9.05 17.53 28.50 III

CONESCO ROOF CASTING MACHINE

ANALYSIS

• M/O started the system evaluation process by comparing the available

conventional shoring systems and the CONESCO casting machines.

• This comparison was based on operating cost, acquisition cost, technical

performance of the systems, and ability to adjust formwork to tunnel

dimensions.

• The records we have state $4,772,300 in net savings, and 36 weeks saved in

schedule time, when comparing the conventional system to the CONESCO

casting machines

ANALYSIS

CONVENTIONAL CONESCO DIFFERENCE

COST ($) 1,500,000 3,500,000 -2,000,000

PRODUCTION

(m2/MH)

.42 1.62 1.2

MAN HOURS (MH)

REQUIRED

164,900 28,473 136427

TIME (WEEKS) 86 50 36 (8 months)

MH COST (50$/MH) 8,245,000 1,423,650 6,821,350

TOTAL COST ($) 9,745,000 4,923,650 4,821,350

CONCLUSIONS

• The case study has focused on time and cost related to the use of three different formwork systems.

• A time-cost trade–off analysis was also followed when investigating alternative sequencing schemes for the one system that was selected using computer simulation.

• Contractors in projects involving nonconventional formwork must carefully consider the implications of formwork systems selection and sequencing of concrete casting operations.

• The use of simulation in this study reveals its utility to a long-term and comprehensive approach to planning and management.