Isn't rehabilitation and repair possible? Yes, it is possible but it is also an obstinate thing to do. You definitely can change but all the temporary works, false works, form works and etc will be extremely high for preliminaries and generals section. Now, the other problem would be, where can the staging or platform for this rehabilitation work be secured to? None of the structure is sound for a safe working platform connection, shoring or other works.

Now, clamps for typical tubular scaffolding system need at least 2 to 3 up to 6kN. With such delamination or dilapidation or worst, loss of surface; where can staging components secured to?

Talking about galvanization, oxidation, rusting, corrosion or what so ever you want to call it, it is no longer feasible to do jacketing or retrofitting.

1. Jacketing increases weight and change the polarization of the ion movement in a rust or galvanization circuit. Introduction of steel jacket will change the existing point from anode to cathode which will aggravate areas which was not corroded earlier. This will affect all since most of the connection plates shall be replaced and this is the major contributor to induced or reverse polarization of the oxidation circuit.

2. The introduction of CFRP is great since it is lightweight but is not holistic since this polymer will deteriorate over time after exposed elements and vibration. CFRP usually can last or effective for only 5 years. This mean routine checks and periodical checks are required after reinstatement. That is another cost which people failed to see. There is difference when talking about physical construction cost and economics of such works.

3. Change of material and fittings. Changes of material may not be deemed as feasible since all material including paint have its own property especially their moduli value. I don't subscribe to the simpleton argument. It can be feasible when under static condition or at rest. Nevertheless, under active condition or dynamic, that is another issue. Changes in barometric pressure does change the wind load and movement which will induce the structure to moments. Propagation of force and moment due to mentioned action will give different outcome for old retrofitted structure and newly replaced structure. Lost of mass for any steel structure will create deficit in their capacity and ability.

In short, structural rehabilitation or repair only suffice intended performance when the structure does not lapse its ultimate state limit. In this case, people surrounding the building can be considered as blessed since this structure haven't disintegrated, fall and impale some of you. Count your blessing and Godspeed!