Structural Assessment and Rehabilitation of a Coastal Reinforced Concrete Platform: A Case Study of a Public Multipurpose Plaza in Pattaya City, Chonburi

Abstract

This study presents an approach to the condition assessment, repair, and strengthening of a reinforced concrete multipurpose platform located along the coast of Pattaya City, Chonburi Province, which has been in service for more than 17 years. The structure was assessed through visual inspection together with field tests, including compressive strength testing of concrete cores, carbonation depth measurement, half-cell potential testing, and pull-off testing of the concrete surface. Severe damage was identified at several locations, particularly at the column caps, of which 32.5% were severely damaged, and beams within the tidal zone, primarily due to insufficient concrete cover. Field observations and structural model analyses further indicated that some columns experienced unusually severe damage associated with short-column behavior, in which sand accumulation around the column bases increased the internal stresses and produced flexural moments approximately four times those under the normal condition. The concrete compressive strength remained higher than the original design value. Structural rehabilitation included repair of deteriorated concrete cover, replacement of corroded reinforcement, and strengthening of the pier columns by wrapping them with carbon fiber reinforced polymer (CFRP) to enhance axial compressive and flexural capacities through confinement. For the beams, the bottom reinforcement was replaced and supplemented with CFRP laminates to increase flexural capacity. Severely damaged column caps were demolished and recast with increased concrete cover. Damaged precast hollow-core slabs were replaced with a cast-in-place slab system incorporating additional secondary beams to provide one-way load transfer. Finally, the concrete surfaces were treated with silane to reduce water absorption and chloride penetration into the concrete.