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0.30 mm wide were observed in RC beams (B4, B4a, B5,
B5a and B6 in Figure 2) under normal operating
service. This was attributed to the lack of sufficient
transversal reinforcement and the low concrete
strength as evidenced by the as-built document review.
It was proposed to repair the cracked RC elements
using epoxy injections prior to carrying out any
strengthening work. Several strengthening schemes
were proposed including traditional solutions, such as
externally bonded steel plate (EBS), concrete sectional
enlargement and externally bonded fibre reinforced
polymer (EBR) for defected RC beams to resist the
actual, increased design live load. An externally bonded
system using manual lay-up CFRP laminates was
chosen as a repair / strengthening solution to increase Figure 2 Location of defects found in RC beams at the
the shear capacity of the deficient RC elements. The 2nd floor
strengthening design and construction procedure were
in accordance to ACI 440.2R [3] and fib 14 [4]. The
strengthening work was done and completed in 2014.
Currently, the building and the plant are still in
operation with a periodic inspection carried out every
year.
Structural Damage Assessment
Photo B4a
Photo B4
Structural damage assessment of the RC building (crack width = 0.30 mm) (crack width = 0.30 mm)
The condition survey of structural components for the
RC building was implemented to examine and assess
the current level of damage and deterioration of the
structure, and determine the preliminary serviceability
condition of the structural components of the building.
The rating point system was used to evaluate
serviceability, and to compare the current and newly- Photo B5 Photo B5a
built structural condition only, without determining the (crack width = 0.30 mm) (crack width = 0.35 mm)
load capacity of the structural components (see Figures Figure 3 Location of shear cracks found in RC beams at
2 and 3). For damage due to current loading, repair or the 2nd floor
replacement, terms were added to the criteria for the Design verification according to ACI 318
structure in its current condition, i.e. a structural
element that shows small defects, good maintenance During the construction of the building, it was found
and good construction practice was given a condition that the concrete strength (18 MPa) was lower than the
rating of 2 or “Fair condition”. If the same element had design value (30 MPa) therefore the in-situ strength of
some effects/damages from current loading to the level concrete was used to re-assess the actual load capacity.
the replacement of the element will be of more benefit A yield strength of 392MPa was used for the steel
to the whole structure than rehabilitation, then the reinforcement as per inspection. The original design
term “Replacement” was recommended for “Fair floor live loads ranged from 5 to 10 kN/m2 and the
condition” (adopted from RILEM Technical Committee new live load on the 2nd floor is planned to increase by
104 [5]). up to 125% of the original design. The design check
considers the factored load i.e (Mu) and nominal
strength of the section (Mn) multiplied by the strength
reduction factor (Φ) according to ACI 318 [6]. Figure 4
shows a 3D FE model of the Pelletizer building.

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