Formwork to reinforced concrete structures

Τίτλος

Formwork to reinforced concrete structures

Θέμα

Reinforced concrete--Design and construction

Δημιουργός

Georgiou, Andreas

Πηγή

Higher Technical Institute

Το πλήρες κείμενο είναι διαθέσιμο από το Υπουργείο Ενέργειας, Εμπορίου Βιομηχανίας και Τουρισμού

Εκδότης

Library of Cyprus University of Technology

Ημερομηνία

2000

Δικαιώματα

Απαγορεύεται η δημοσίευση ή αναπαραγωγή, ηλεκτρονική ή άλλη χωρίς τη γραπτή συγκατάθεση του δημιουργού και κάτοχου των πνευματικών δικαιωμάτων

Μορφή

pdf

Γλώσσα

en

Τύπος

text

Αναγνωριστικό

CED0461

Σύνοψη

The failure of formwork is a major concern of all parties involved in a construction project, the owner, the designer, and the contractor. It's the responsibility of each designer of formwork to ensure that the forms are designed adequately. This requires a careful analysis of the job conditions that exist at each jobsite, a determination of the loads that will be applied to the formwork, and the selection and arrangement of suitable forming materials that have adequate strength to sustain the loads.
It's the responsibility of the workers at the jobsite to fabricate and erect the form work in accordance with the design. A careful check of the design and inspection
of the work during construction are necessary to ensure the safety and reliability of formwork.
Safety is everyone's responsibility and all parties must work together as a team with safety as a major consideration.
1.2 Economy of formwork
Economy should be considered when planning the formwork for a concrete structure. Economy involves many factors, including the cost of materials, the cost of
labor in making, erecting, and removing the forms and the cost of equipment required to handle the forms.
Economy includes also the number of reuses of the form materials, the possible salvage value of the forms or use elsewhere, and the cost of finishing concrete
surfaces after the forms are removed. A high initial cost of materials, such as steel forms, may be good economy because of the greater number of uses that can be
obtained with steel forms.
1.3 Care of forms Forms are made of materials which are subject to considerable damage through
misuse and mishandling. Wood forms should be removed carefully then cleaned, oiled, and stored under conditions that will prevent distortion and damage.
1.4 Allowable Unit Stresses in Material Used for Formwork
In order to attain the maximum possible economy in formwork, it is desirable to use the highest practical unit stresses in designing forms. A knowledge of the
behavior of the pressures and loads that act on forms is necessary in determining the allowable unit stresses.
When concrete is first placed, it exerts its maximum pressure or weight on the restraining or supporting forms. However, within a short time sometimes less than
21 hours, the pressure on wall and column forms will reach a maximum value, then it will decrease to zero. Thus, the forms are subjected to maximum stresses for relatively short periods of time.
As far as beams slabs and girders concerned the concrete begins to set and to bond with reinforcing steel within a few hours after is placed so as to support it self.
Although the forms are usually left in place for several days, the magnitudes of the unit stresses in the forms will gradually decrease as the concrete gain strength. Thus
the maximum unit stresses in the formwork are temporary and of shorter duration than the time the forms are left in place.