The subject vessel repair slipway is located within the Shahid Rajaee Port Complex. This marine slipway, with a capacity for hauling vessels of up to 1,500 tonnes, was constructed in 1988 (1367 SH) adjacent to the port’s eastern breakwater.
The total length of the slipway structure is 286 m, with a longitudinal slope of 13.7%.
The slipway structure consists of a series of longitudinal and transverse reinforced concrete beams, which are supported on 80 concrete piles.
The structural elevation varies from +8.6 m at the highest point to −7.8 m relative to Chart Datum (C.D.) at the end of the slipway. Rails are installed on the longitudinal beams to allow the cradle structure to travel along the slipway.
Over time, exposure to adverse environmental and weather conditions caused serious deterioration of the main structural elements. Considering the operational importance of the slipway, the port authorities therefore identified the need for its major rehabilitation.
In order to develop an appropriate and optimized rehabilitation design, a detailed understanding of the existing deterioration and damage was first required. Accordingly, following inspections of the various structural elements within the atmospheric, tidal, and submerged zones, the following items were subject to specialized investigation:
Evaluation of the compressive strength test results of concrete cores extracted from the concrete beams;
Measurement of chloride ion and sulfate ion concentrations at different depths within the concrete;
Determination of carbonation depth;
Schmidt hammer testing.
Following identification of the structural deficiencies and deterioration mechanisms, various rehabilitation solutions were developed. After carrying out the required analyses, calculations, and structural modelling, the preferred rehabilitation option was selected.
Under the selected rehabilitation scheme, the deteriorated areas of concrete within the longitudinal and transverse beams, as well as the slab surrounding the control room area, were identified. Detailed procedures for concrete removal, surface preparation, and recasting, together with the specifications for the repair concrete and construction requirements in accordance with recognized codes and technical guidelines, were provided.
For the steel structures, including the cradle and rails, the required methods for surface preparation, protective coating and painting, as well as the strengthening or replacement of corroded elements, were also described in full detail.
