|back to menu|
|CONSTRUCTION PHASES - PART 01||
6.1 Construction phases main warnings
Construction phases drawings are a sequence of schemes which are aimed at focusing important details concerning the proceeding of the works. Being the drawings represented as schemes they can not be taken as detailed drawings but as sketches of the most relevant aspect that is underlined.
It is extremely important therefore to point out the following:
Flow chart of global construction phases should be considered as a proposal for work organisation which will be co-ordinated by the PCU-TA and responsibility of it is not up to General Engineering.
6.2 Construction phases technical warnings
Most of the difficulties related to the current work may be found in the methods and in the procedure to be followed, therefore construction phases and assembling techniques should be carefully evaluated. Nowadays not many companies in the World have the expertise in stone bridge constructions and moreover this peculiar work has got requisites that are somehow unique.
Technical warnings are given in the following paragraphs.
6.2.1 Dismantling works
6.2.2 Season times
6.2.3 Construction materials maturing times
During the construction works, special care should be taken about the different times of all the works, in order that no structure is loaded before the proper maturing time. To gather the right prescriptions for this peculiar aspect it has to be referred either to structural design final report, either to LGA’s report concerning the characteristics of all the types of mortars.
Also the right time of maturing of the works for the foundations has to be carefully known trough the specifications, warnings and recommendations given for that group of strengthening works in order that no unforeseen settlements take place. A schematic reference list may be here next reported, and reconstruction works should be planned to suit all the time requirements:
proper time for loading of the arch with the bridge elements, (to be evaluated depending also on calculations of the structure during the working phases).
6.2.4 Load bearing arch assembling times
The load bearing arch should be assembled following a strict timetable in order that no delays take place and the execution of the works doesn’t exceed the foreseen season time. Assembling times of the voussoirs should be preliminary evaluated, with on site tests, by the Company that is in charge of the reconstruction works with the approval of the Supervisor and with a verify of the correct organisation of the yard. The yard organisation should be improved and optimised whether times are not matching the requirements.
Anyhow, during the assembling phase of the arch, until the centering has been dismantled, works may be performed also in the night-hours with 2 or 3 group of workers, (of course the yard in this case needs more facilities for the mentioned purpose). The full-time performing of the works is a procedure that has been followed also during other stone bridge construction works and shouldn’t be considered as an anomalous proposal.
Being the times so much important, while the centering is on site, it is desirable that all the construction materials for the works were already prepared off-site, ready for final assembling, including: stones, mortar, cramps, dowels and lead with a secure quantity margin to avoid delays in supplying of additional construction materials.
6.2.5 Symmetrical proceeding of the construction works
The construction of the load bearing arch, as well as all the other portions of the bridge, should be mounted at the same time, proceeding from both sides of the arch springers and from lower to upper portions.
If the works are not symmetrically performed, from both the springers (east and west), the load bearing centering may be subjected to unforeseen movements that may lead to very dangerous loading configurations, to a different geometrical shape of the arch and to collapse of the structure.
Same symmetrical approach should be followed for what concern the transversal section loading of the bridge: spandrels and other bridge elements should be mounted at the same time on both south and north elevations in order that no torsion stress is caused.
CREDITS:Intellectual property of this report and of the design drawings is owned by General Engineering s.r.l.
author of the text: arch. Manfredo Romeo – other contributes have been mentioned in related paragraphs
© - General Engineering Workgroup -
Final Design Report
|back to menu|
|GENERAL ENGINEERING - P.zzale Donatello 4 - 50132 Firenze - Italy - ph. +39 055 2345256 - fax. +39 055 2476074|