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H. Asaue et al.
27.1 Introduction
Nowadays, as road infrastructures have been constructed intensively since 1960s,
almost those are reaching their life-span 50 years recently in Japan. Accordingly
ageing rate of more than 50 years old shifted to 43% in coming 10 years from
18% of 2013 [1]. Replacement of those aging infrastructures with new ones would
be the most ideal measure; however, due to decrease of construction budget, lifeprolonging tactics are appeared to be the most adaptable for those existing aging
infrastructures. Among the infrastructures, concrete bridge decks hold many difficult
problems, resulting in taking a lot of cost to maintain. Specifically, it is planned by
three major expressway companies that more than 90% of the renewal budget for
15 years will be used for bridge slabs. The RC bridge slabs are so principal members of
road infrastructures to maintain that many organizations have studied intensively for
their deterioration mechanisms, countermeasures against deterioration, and so forth.
In order to simulate the peculiar failure process of the bridge decks experimentally,
test slabs have been subjected to wheel loading tests with NDT approaches [2]. A
three-dimensional approach using AE tomography [3] have been applied recently,
and fatigue failure mechanisms could be explained by a velocity distribution of
elastic waves [4]. In addition, acceleration of deterioration due to water infiltration
is a problem in actual RC slabs. In this study, 3D AE and elastic wave tomography
was applied to the wheel load running test on the RC slabs with submerged upper
surface. As a result, clarified the relationship between deterioration progress and
velocity distribution of RC slabs with water effect.
Final form of deterioration specified in RC decks namely ‘aggregation’ is
discussed by the findings. Note ‘aggregation’ is the final form of deterioration of
RC decks, remaining only aggregate from concrete where cement hydrated matrix
is washed out by excessive water pressures filled in the cracks due to mobile loads.
27.2 AE and Elastic Wave Tomography
AE and Elastic wave tomography can estimate internal velocity distribution of the
structure, analysis procedure is shown as follows, some sensors can record arrival
time of elastic wave when the wave is generated by an AE activity or a hammering.
After each arrival time is determined, the propagation velocity of through the path
of elastic wave is calculated by both of the distance from the excitation point to the
receive point and T obs (observed propagation time) which is obtained by Formula
(27.1):
T obs = T o − T s
(1)
where T s is the excitation time and T o is the arrival time. On the other hand, in the
algorithm of the tomography, the inverse of velocity which is specifically referred
H. Asaue et al.
27.1 Introduction
Nowadays, as road infrastructures have been constructed intensively since 1960s,
almost those are reaching their life-span 50 years recently in Japan. Accordingly
ageing rate of more than 50 years old shifted to 43% in coming 10 years from
18% of 2013 [1]. Replacement of those aging infrastructures with new ones would
be the most ideal measure; however, due to decrease of construction budget, lifeprolonging tactics are appeared to be the most adaptable for those existing aging
infrastructures. Among the infrastructures, concrete bridge decks hold many difficult
problems, resulting in taking a lot of cost to maintain. Specifically, it is planned by
three major expressway companies that more than 90% of the renewal budget for
15 years will be used for bridge slabs. The RC bridge slabs are so principal members of
road infrastructures to maintain that many organizations have studied intensively for
their deterioration mechanisms, countermeasures against deterioration, and so forth.
In order to simulate the peculiar failure process of the bridge decks experimentally,
test slabs have been subjected to wheel loading tests with NDT approaches [2]. A
three-dimensional approach using AE tomography [3] have been applied recently,
and fatigue failure mechanisms could be explained by a velocity distribution of
elastic waves [4]. In addition, acceleration of deterioration due to water infiltration
is a problem in actual RC slabs. In this study, 3D AE and elastic wave tomography
was applied to the wheel load running test on the RC slabs with submerged upper
surface. As a result, clarified the relationship between deterioration progress and
velocity distribution of RC slabs with water effect.
Final form of deterioration specified in RC decks namely ‘aggregation’ is
discussed by the findings. Note ‘aggregation’ is the final form of deterioration of
RC decks, remaining only aggregate from concrete where cement hydrated matrix
is washed out by excessive water pressures filled in the cracks due to mobile loads.
27.2 AE and Elastic Wave Tomography
AE and Elastic wave tomography can estimate internal velocity distribution of the
structure, analysis procedure is shown as follows, some sensors can record arrival
time of elastic wave when the wave is generated by an AE activity or a hammering.
After each arrival time is determined, the propagation velocity of through the path
of elastic wave is calculated by both of the distance from the excitation point to the
receive point and T obs (observed propagation time) which is obtained by Formula
(27.1):
T obs = T o − T s
(1)
where T s is the excitation time and T o is the arrival time. On the other hand, in the
algorithm of the tomography, the inverse of velocity which is specifically referred