Overview of health monitoring and inspection for highway bridges in vietnam

Hội nghị Khoa học công nghệ lần thứ XXII Trường Đại học Giao thông vận tải 
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OVERVIEW OF HEALTH MONITORING AND INSPECTION FOR 
HIGHWAY BRIDGES IN VIETNAM 
Trần Việt Hùng1* 
1 Trường Đại học Giao thông vận tải, Số 3 Cầu Giấy, Hà Nội 
* E-mail: tranviethung@utc.edu.vn; Tel: 0912338980 
Abstract. Many highway bridges have been constructed in Vietnam recent years. 
Some of the technical problems occurred while construction process and service of the 
bridge. An issue of great concern with bridge health monitoring system is how to use 
the monitoring data for health and condition assessment of the bridge structure. 
Current Vietnamese engineers only evaluate bearing capacity of the bridge before 
open to traffic or data analysis needs to replace or limit the loading bridge. In this 
paper, we will present methodologies for bridge health monitoring, inspection and 
maintenance of bridges in Vietnam. 
Keywords: Bridge health monitoring, load testing, highway bridge. 
1. INTRODUCTION 
Bridges are key components in the transportation infrastructure. Bridge structures 
can be damaged and downgraded by a result of aging, environmental factors, increased 
traffic load, inadequate design, no regular repair, and maintenance of the bridge. The 
failure includes structural collapse and loss of serviceability and functionality, which 
include excessive deformation, cracking of concrete, steel corrosion, or other limited 
safety values. The loss of serviceability and functionality, although not catastrophic or 
life-threatening, is the most frequent and involves significant cumulative costs in terms 
of maintenance and rehabilitation, traffic disruption, and environmental impacts. 
Bridge health monitoring is becoming increasingly important to transportation both for 
management and for maintenance and repair planning. Development of bridge health 
monitoring technology for surveillance and assessment of existing or new bridge has 
decreased risks in the construction and service process of the bridge. 
In great problems, we need to predict the failure and structure assessment, and 
distribute bridge health monitoring systems for existing bridges and new bridges. 
However, these systems are very expensive and high experiment; it is very difficult to 
apply for all bridges in Vietnam right now. Previous research was also attempted to 
develop an advanced maintenance management system, named Bridge Management 
System of Vietnam (V-BMS), concurrently with a computerized database for highway 
bridges in Vietnam (Hai, 2008). Thus, the need of bridge management is very 
important to predict, reduce risks, and take a measure to promptly handle. 
Vietnamese engineers also attached special importance to the ongoing 
management activities in terms of inspection, maintenance, repair, upgrade and 
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replacement, and the environment factors. Current road traffic system has many old 
and weak bridges. These bridges are near or past their intended service life and are 
carrying unanticipated traffic loads. They were designed by different standards, 
diagrams of vertical load. Our engineers would like to avoid risks and technical 
problems while the service process. It is necessary must inspect, evaluate and 
maintenance works regularly or periodically. Thence we will promptly prevent the 
possibility of potential risks and incidents. Besides, some problems have occurred in 
Vietnam while the bridge was under construction also defining issues of technical risk 
management. Risk assessment and management are critical for ensuring public safety 
and establishing a rational prioritization of bridge projects for maintenance and 
rehabilitation. However, only few assessment reports summarizing technical problems 
occurred, which is explained why this field is very new in Vietnam. 
In this paper, we focus to consider bridge health monitoring, bridge inspection, 
and discuss the importance of technical risk management in bridge construction 
projects in Vietnam. 
2. LOADING TEST FOR BRIDGE IN VIETNAM 
Currently, there are several hundreds of old bridges need to repair and rebuild 
immediately. However, no funds may have to simultaneously build a series of new 
bridges. 
Load testing of the highway bridge is becoming an increasingly common 
procedure for determining bridge load capacity in Vietnam. During the process of 
structural inspection and evaluation, the collected data might not be able to clarify 
numbers of unknown parameters due to material deterioration or loss of sectional 
strength, which is potentially caused by the lack of routine structural inspection and 
maintenance as per the code requirements, overloading, and poor quality of 
construction. Consequently, by observing structural responses and behaviors under the 
application of pre-identified loads which present the loads that are likely to carry in 
reality, actual load testing is proven to be beneficial not only to evaluate the load-
carrying capacity of existing structures, but also to validate the design of new 
constructions before fully-loaded occupancy. Load testing can also be utilized to 
monitor the condition of structures, which have been deteriorated or have undergone 
extensively major structural repairs or strengthening. Load testing need to do both in 
static and dynamic method depending on engineers’ interested parameters. The flow 
chart of bridge inspection can be shown in Fig. 1. 
In Vietnam, almost concrete bridges were constructed in last time and now. In an 
inspection, a process or object is viewed closely with a critical appraisal. Inspections 
are usually carried out by an inspector or a professional engineer. The items are 
important when making these inspections as reasons for conducting the inspections, 
preliminary inspections, and detailed inspections. 
Hội nghị Khoa học công nghệ lần thứ XXII Trường Đại học Giao thông vận tải 
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Preparation
Preliminary 
inspection
Detail 
inspection
Data collection
Field 
measurement & 
condition survey
Load testing
Analysis of the 
measured results
Visual survey
Reporting with 
documentation, 
conclusion and 
recommendation
RepairRebuild
No
Yes
Good
Fig. 1. General flow chart of bridge inspection 
The measurement items of bridge inspection include: 
+ For girder bridge: Stress measure for girder, deck slabs, deflection of span, 
corrosion, loss prestress force, vibration of span without moving load and with moving 
load. Vietnamese engineer measures deformation of structure with using tenxomet and 
strain gauge devices. 
The relationship between deformation, ε and young modulus, E is expressed as: 
Measurement following to 1 direction: 
E =  1 2
0
( ( ) ( ))
( )
x
S x x
d x dx
D
 −
=  (1) 
where σ, ε, and E denote stress, deformation of structure, and young modulus, 
respectively. In Vietnam, the young modulus of steel structure is using E = 2.100.000 
kg/cm2 but young modulus of concrete structure is very difficult to determine exactly. 
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Measurement following to 2 directions: 
1 1 22
2 2 12
( )
1
( )
1
E
E
  

  


= + −

 = +
 −
 (2) 
where ϑ is poison factor; σ1, σ2 and ε1, ε2 is denote stress and deformation 
following to 1 and 2 directions. 
+ For cable stayed bridge: except for above contents of the girder bridge, more 
measurement of cable force, vibration of cable, stress and displacement of pylon. The 
relationship between frequencies and cable tension may be determined to the 
consideration of the sag-extensibility and bending stiffness of a cable. On condition 
that both cable ends be considered as hinges, the relationship between cable force and 
vibration frequency can be approximately expressed as: 
2
24 n
f
T mL
n
 
=  
 
 (3) 
where T, m, L, and 
nf denote cable tension, mass density, length of cable, and 
the nth natural frequency, respectively. In Vietnam, the natural frequency usually used 
the first mode of vibration, determined by forced oscillation (H. Ha et al., 2005). 
Vietnamese engineers usually also evaluate the bearing capacity of the bridge 
before open to traffic, replacement or limit the loading bridge. Especially after a few 
bridges collapsed in Vietnam during both under construction or servicing necessary to 
the regular inspection and maintenance. Thus, the large span bridges were built 
recently in Vietnam such as Bai Chay bridge, My Thuan bridge, Can Tho bridge and 
so on were inspected before open to traffic (show in Fig. 2). Goal of work of 
inspection and structural health monitoring include determining real load bearing 
capacity of the bridge as the base for checking and taking over work and stipulate to 
exploit regulation of a project; evaluating the effect of technical-technological solution 
in design and construction of a project. However, all the results of checking are 
measured in normal weather; it needs a structure health monitoring system to measure 
in change able weather such as earthquake, strong whirlwind and strong storm to find 
the unusual sign. Example of Binh bridge was permanent designed according to the 
special design specifications based on Finnish standard, AASHTO LRFD, and 
Japanese standard. Load testing and bridge structural health monitoring demands with 
checking of technical-technological solution in design and construction, loading test to 
determine real load bearing capacity of bridge in 2005, structure health monitoring in 
2007, 2008 (show in Figs. 3 and 4) and up to now. 
Testing loads are 24 HUYNDAI trucks loading with sand or bliding stone to 
ensure the weight of each truck is about 24 to 25 tons (80% of designed load). It is a 
common practice to load testing new bridges with a static load (DL + LL) equivalent 
to 80 of the maximum design life bending moments. The results include stress of 
Hội nghị Khoa học công nghệ lần thứ XXII Trường Đại học Giao thông vận tải 
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girder, deflection of girder, displacement of pier and pylon, vibration frequency and 
stress of cable stayed. Example of stress measurement of cables shows in Table 1. 
This bridge has the advantages of using material steel-concrete composite in long span 
cable stayed. 
Fig. 2 Load testing (truck) of bridge in Vietnam 
Fig. 3 Loading test of Binh bridge 
Table 1. Stress measurement of cable ((CCCRE-UTC (2005, 2007 and 2008) and 
H.Ha et al., (2005)) 
Cable 
No. 
7/2005 10/2007 8/2008 
Allowable stress 
(kg/cm2) Frequency 
(Hz) 
Stress 
(kg/cm2) 
Stress 
(kg/cm2) 
Stress 
(kg/cm2) 
S1 1.07 5157.63 5314.03 5192.79 7182 
S2 1.07 4775.18 - - 7182 
S19 1.12 5688.56 - - 7182 
S20 0.98 5146.55 5076.16 5082.41 7182 
Fig. 4 Profile, arrangement of stay cables and ties down cables of Binh bridge 
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4. LONG – TERM BRIDGE HEALTH MONITORING 
4.1. Current situation of bridge health monitoring in Vietnam 
Bridge health monitoring system (BHMS) is one of the innovative and reliable 
systems for diagnostic monitoring and evaluating the bridge actual conditions. The 
BHMS will enable monitoring of an overall bridge integral behavior, as well as 
degradation of critical structural components during a bridge normal operation for 
immediate decision making or the bridge long-term performance assessment. With the 
application of BHMS, bridge structural responses, deformation or vibration can be 
readily detected and quickly analyzed and evaluated (Dao Duy Lam 2015, 2016). 
Under unexpected or serious situations, traffic overloading, excessive impact loading, 
unpredictable wind or earthquake loading, etc., the system will wirelessly transmit 
signals in real time and display bridge locations found critical to the remotely-located 
workstation for immediate measures, such as bridge closing, weigh or speed limit 
posting, as well as for long-term strategic planning, such as bridge rehabilitation or 
strengthening, to protect against progressive damages. A few the sensors, strain gauges 
and accelerometers will be attached to the structure on pre-defined locations and wired 
to signal amplifier, data acquision and computer module. The structures will have been 
continually monitored for days, weeks or months depending upon the reliability and 
accuracy of structural health determination. For the safety of these giants, some long-
term bridge monitoring systems were developed and installed. With advanced system, 
a large amount of infrastructure can be managed more effectively, and potential losses 
or failures can be minimized. 
In Vietnam, Bai Chay bridge is the first bridge applied BHMS. Bai Chay bridge 
was constructed out of pre-stressed concrete; the main span has a length of 435 m, and 
the bridge spans an international strait. In order to prevent environmental impact and 
maintain a navigation clearance that was sufficiently wide (200 m) and high (50 m) for 
ships to pass under the bridge, the bridge was constructed on land by using the 
balanced cantilever system based “climbing formwork” (for the towers) and 
“formwork traveler” (for the girders). A distributed optical fiber sensing system was 
installed on a bridge under construction for monitoring the deformation in the towers 
and girders of the bridge as construction progressed. This is one of the most typical 
modern monitoring systems recently (shown in Fig. 5). Following to Iwaki (2006a), 
optical fiber sensing system has the potential to achieve a more precise management of 
the construction quality with the advantage of performance. The system can easily 
acquire a large amount of distributed strain data. The deformations in the towers and 
girders can be calculated from the strain distribution values. The towers and girders act 
as rigidly supported cantilevers. 
Their relative displacements are given as follows: 
1 2
0
( ( ) ( ))
( )
x
S x x
d x dx
D
 −
=  (4) 
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where: d(x) is the relative displacement of a tower or girder; ε1(x) and ε2(x), the 
strain values of two sensors; D, the interval of each sensor; and S, the spatial 
resolution of the distributed strain sensor. 
4.2. Monitoring for environmental and natural disasters 
The scope of monitoring includes two major types of parameters, load effects and 
responses. The load effects refer to those due to wind, earthquake, temperature, and 
live loads (movements, highways, or railways). The responses refer to displacements, 
accelerations, stresses, strains, and forces of the members of bridge structure, and 
displacements and stresses of main cables. A natural hazard occurs frequently in 
Vietnam such as typhoon, flood and nowadays is greatly influenced by climate 
changes. Monitoring of the peak displacements and actual stresses of the main cables 
and their anchorages are the important subjects to be considered. Currently, almost 
long span bridges have not been arranged monitoring system except the monitoring 
system was arranged in Bai Chay bridge, Phu My bridge, Can Tho bridge (the longest 
cable-stayed bridge in Southearth of Asia) and Thuan Phuoc bridge (the longest 
suspension bridge in Vietnam). 
Fig. 5 Sensors for structural monitoring in Bai Chay bridge (Iwaki, 2006b) 
5. CONCLUSIONS 
This paper introduces current situation of management and service of highway 
bridges in Vietnam. With the current bridge system, the regular inspection and load 
testing of bridges need to contribute to early detection of defects, errors, which can 
quickly remedy, repair, and reduce the possible risk to the bridges in Vietnam. But to 
do this, the bridge’s managers must have management systems for synchronization, 
automatically updated. It is bridge health monitoring systems and the management 
agency risk responsibility. 
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Vietnamese engineers and managers need to research, analysis of specific 
incidents that happened is a valuable archive for the engineers complete their work 
projects, the actual document is important to consider risk management technique 
effectively and the analysis, prevention and timely treatment of risk are completely 
realizable. 
REFERENCES 
[1]. Center of civil consulting, research and experiment belong to University of 
Transport and Communications (CCCRE-UTC, 2005), Report of load testing 
result of Binh bridge-HaiPhong City. 
[2]. Center of civil consulting, research and experiment belong to University of 
Transport and Communications (CCCRE-UTC, 2007), Report of structural 
health monitoring result of Binh bridge. 
[3]. Center of civil consulting, research and experiment belong to University of 
Transport and Communications (CCCRE-UTC, 2008), Report of structural 
health monitoring result of Binh bridge. 
[4]. D.T. Hai (2008), Computerized Database for Maintenance and Management of 
Highway Bridges in Vietnam, Journal of Bridge Engineering, Vol. 13, Issue 3, 
pp. 245-257. 
[5]. H. Ha, N. H. Hung, V. V. Toan and B. T. Long (2005), Test for stayed-cable 
force by the force oscillation method, Transport and communications science 
journal, Vol. 12, pp. 66-76 (Vietnamese). 
[6]. H. Iwaki (2006a), Long Span Cable Stayed Bridge Monitoring Using Distributed 
Optical Fiber Sensing System, in Optical Fiber Sensors, OSA Technical Digest 
(CD) (Optical Society of America), paper MF5. 
[7]. I. Hideaki (2006b), Integrated Bridge Monitoring System, Presentation files for 
technical transfer and training – Bai Chay bridge, Vietnam. 
[8]. Đào Duy Lâm (2015): “Nghiên cứu đánh giá các hệ thống quan trắc hiện hành 
cho cầu dây văng và dây võng tại Việt Nam”, Mã số DT154001. Chủ nhiệm đề 
tài: Đào Duy Lâm. Đề tài KHCN cấp Bộ GTVT, 2015. 
[9]. Dao Duy Lam, Nguyen Viet Trung, Hoang Nam (2016), BHMS for cable-stayed 
bridges in Vietnam: Current status and Future researches, EASEC 14: East Asia-
Pacific Conference on Structural Engineering & Construction, 2016.