Diolkos - Concrete projects

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Concrete projects

Is evidence of reduced construction cost the smallest cost per cubic meter of the readymade concrete? (or the equivalent of the lesser included per cubic meter reinforcing steel weight?).
Note: This is a common way to estimate the construction cost of privet buildings in Greece.

Certainly not, after missing the factor that multiplies the cost per cubic meter, which is the total cubic meters of the project (i.e. for the total cost is not enough the unit price only, but quantity too). All structural designs, for a specific project, will not produce (apart from quality) the same amount of materials and construction workability.
Worth the extra cost in a design, of a reinforced concrete project, to produce cutting / shaping lists for reinforcement steel? Are drawings, required by the city planning authorities, enough to proceed in construction?

Not only worthwhile but it is not possible to realize a structural design without them. Cutting and shaping lists of reinforcing steel is an engineering work because it requires access to the calculations of the design, knoledge of relevant standards and special (additional) calculations. It is extremely rare in private projects to have this list prepared in the structural design. In these projects (i.e. almost all the private projects) the lists are produced by those performing the work in the yards having any knowledge of how to do it, nor the necessary data for it. Drawings required by the city planning authorities (so to issue the building permission) does not include, among other things, such lists.
Besides the forgoing technical issue, is there another significant benefit from the develop-ment of these lists?

The blacksmiths are paid by the kilo so they have interest to "sell" more steel. This list identifies, among others, the weight of steel expected to be delivered at each stage of construction of the building, so there is always a reference.
Is it good to put more reinforcing steel in the project than the anticipated by the design?

It is rather bad. The modern design logic (in force since 1991 when first applied the Greek Seismic Regulation) puts hierarchy in the strength of members. Over reinforcing destroys this basic assumption and so may reduce the overall strength of the building in a possible earthquake. Another reason is that large quantities of rebars restrict the proper connection of the reinforcement to concrete or reduce the concrete cover. Poor connection to the concrete means that the steel, although it is more in quantity, cannot take the necessary forces, poor cover means in part the forgoing and in part corrosion of reinforcement in time (and probably spelling of concrete). So over reinforcing is not only financially bad.
What, concerning the technical supervision of a reinforced concrete project, a structural engineer does?

He (she) inspects if the foundation soil is the one expected, he gives instructions for excavation of foundation, defines the position of the project on site.
He examines if the formwork is consistent with the architectural and structural design, checks if there is a stability issue, checks whether the timber is appropriate for the type of concrete finish, watches if oil, needed for the formwork, will not pollute reinforcement rebars, ...
Monitors the construction of steel reinforcement, depending on the complexity, in more than one on site visit (because fitted rebars are difficult to amend after others are placed on top), checks whether the shape, diameter, position in the formwork, the quantity and the anticipated concrete cover is the expected. Captures the final positions of rebars and updates the structural drawing for changes to the site (as build drawings).
Checks if there are proper test sample moulds on site, attends the construction team if they are suitable for concrete pouring, gives instructions to the foreman (for work process, spare parts etc) or attends the procedure remaining on site specially if there is provision of reinforcement rebars placing, during pouring process, or if there is an issue that may require his presence. Gives instructions for maintenance and removal of formwork.
As many times there is the need for a solution provision on site or to assess changes, the structural supervisor of the construction should only be a structural engineer and who should be well aware of the design beforehand.