Structural Health Monitoring of Concrete Bridges in Rudbar-Manjil Region in Iran

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1 2011 International Conference on Intelligent Building and Management Proc.of CSIT vol.5 (2011) (2011) IACSIT Press, Singapore Structural Health Monitoring of Concrete Bridges in Rudbar-Manjil Region in Iran Mehdi Mohammadpour Lima 1, Sobhan.A Alipour Limaei 2 1 Master of Science in Earthquake Engineering, lecturer in Islamic Azad University of Bandar-e-Anzali 2 Master of Science in Geotechnical Engineering, Road and Transportation Office of Guilan Province Abstract. Iran is located in a seismic prone region and in every year, several earthquakes happen that cause severe damages. Guilan province is located in the north of Iran. High seismic activity of this region, especially Rudbar and Manjil city needed to regular inspection of infrastructure and bridges. Structural health monitoring is an engineering tool that is used for control the changing of condition that gives good information for management, decision and revise codes. In this paper structural health monitoring of 6 mega concrete bridges in Rudbar region are studied and existing condition of main component are assessed then some solutions suggested to solve the problems in these bridges. Keywords: Bridge, Health Monitoring, visual Inspection, Seismic, Rehabilitation 1. Introduction Lifelines and infrastructure have an important role in every country and several thousand dollars have been paid to maintenance and rehabilitation of infrastructures annually. Bridges, as an infrastructure that connect the cities are important from political, economical and social point of view. Guilan is a province on border of Caspian Sea, in the north of Iran, with a high residential density and it has a moderate climate. Rudbar is one of important city that connect the north of Iran, Guilan province to the capital and the other part of Iran. Therefore, there are some important bridges in this region that sustain heavy track loads and passing rate of cars over bridges is significantly increased in recent years. This is because of construction new high way and free way between Guilan province and Qazvin province. Rasht-Qazvin highway that passes through Rudbar is an important free way that facilitates the transmission of goods to industrial towns and capital. In recent years, construction rate of bridges grows up and using new methods are going to be usual in bridges. Construction of long bridges over wide rivers with different geotechnical situation, local condition such as rivers, liquefaction, and landslide has its own challenges. Transportation and goods trade to neighbourhood provinces made Guilan's roads and bridges as vital arteries in economical and political point of view. Management of bridges in the recent years has improved significantly. Using new methods and technology, such as wireless and fiber optic sensor and remote management changed infrastructures management significantly. In this paper, fast assessing of mega bridges in Rudbar has been studied. Using visual inspection as the main source of relevant data to carry out the condition assessment is usual methods for structural health monitoring (SHM). Today's most of decisions are based on visual inspection of projects that give good information and vision to engineer for choosing the best method for maintenance and rehabilitation of mega structures. Using some new methods such as signal processing, image processing, neural network and fuzzy logic etc can help to have a better assessing for bridges. Sometimes a combination of these methods is the best one and engineer chooses the method based on inspection. 1 Corresponding author. Tel.: + ( ); fax: + ( ). address: lima.iust@gmail.com 323

2 The use of non-destructive testing (NDT), monitoring and health monitoring in condition assessment of bridge are increased significantly [1]. 2. Seismic activity of Guilan province The Manjil (a city in Guilan province) earthquake of 20 June 1990 (Ms=7.7 Richter) strongly shocked the northwestern Iranian territory that caused many destructions and human casualties. An estimated people lost their lives and more than were left homeless. The earthquake ground shaking caused enormous destruction of unreinforced Structures (Fig1, 2). The most parts of the imprinted great area were of western high Alborz and Tarom district. The amount of damage in rural areas was very extensive that resulting in the destruction of about 1100 villages [2]. Seismic hazard assessment of Guilan Province including Manjil in Iran has been studied and shown, with respect to historical earthquakes in the region of Guilan province and existing active faults like Manjil-Rudbar, this region has high seismic potential [3] and liquefaction potential [4]. Fig1: Bala Bala bridge, and some evidence about probability of liquifaction around piers Fig2: liquefied sands that have laterally moved toward the Shahroud River in Bala Bala bridge[4] Fig3: Horizontal seismic hazard (PGA over bedrock) map of Guilan province using logic tree for 475 year return period (left), for 2475 year return period (right) [3] 324

3 Table 1: Main faults of Guilan Province [5] No Name Fault Length (km) 1 Manjil-Rudbar Talesh 75 3 Fouman 60 4 North Alborz Khazar(Alborz) Javaher Dasht 74 7 North Qazvin 60 Fig4: Active faults of Guilan province and the city of Rudbar [5] Based on Horizontal seismic hazard (PGA over bedrock) map of Guilan province for 475 and 2475-year return period, Rudbar and Manjil have a high seismic hazard (Fig3). Having 152 km fault in Manjil-Rudbar is show high seismic potential of this region (Fig4 and Table1). Beside high seismic activity and hazard, some cases of liquefaction (Fig5) have been reported during Manjil earthquake 1990[4]. Fig5: Map of Bala-Bala region near Loushan and liquefaction regions in Manjil earthquake 1990[4] 3. SHM of concrete bridges: In this research, six big bridges in Rudbar and Manjil region has studied and health of all-important part of structural members are investigated and based on the existing condition, a SHM score allocated to each of bridge. Six important parameter for SHM are as deck, abutment, river engineering, middle piers, wall for water conduct. The corrosion, water scour, deformed expansion joint rubber, crack existing, etc, that has important role in performance of a bridge are included in this research. The details of selected bridges are as table 2. All of data explored during annually visual inspection that has been done in road and transportation office of Guilan province. Table 2: Name and details of selected concrete bridges in SHM study 325

4 Number Name of Bridge Total Length(Meter) Total Width of Deck(Meter) Number of span 1 Vali Abad old bridge Bala Bala Bridge Totkabon Bridge Shahroud Bridge Vali Asr Bridge Dark Dam Bridge A visual method is used for SHM of these bridges and assumptions are as table 3: Table3: SHM score and determine the condition of bridge's health Total health score Bridge condition 0-25 Bridge is out of service and traffic must be stopped Traffic is limited and an immediately rehabilitation should be done Bridge needs essential repair Bridge needs rehabilitation Bridge is in good condition and just need to maintenance Based on existing condition of bridges the results of SHM are summarized in table 4. Table4: SHM score and determine the condition of bridges Maximum health score based on visual No Inspected Member inspection With conduct wall Without conduct wall Vali Abad old bridge Bala Bala Bridge Totkabon Bridge Shahroud Bridge Vali Asr Bridge Dark Dam Bridge 1 Deck Abutments Middle Piers Water conduct wall Restrain River engineering Fig6: Total SHM score of concrete bridges (out of 100) in Rudbar region (included Manjil city) 326

5 Fig7: Water scour in Totkabon Bridge (lacking of casing) and exposure of rebar Figure 6 shows that Bala Bala and Totkabon Bridge are needed to rehabilitation method and SHM score of middle piers and water scour of them caused some damages. In addition Vali Abad Old Bridge needs more attention to preserve its structural function. Exposures of rebar in middle piers are shown in figure7.some of methods for maintenance of these bridges are: replace short drainage pipe with some longer pipe to conduct the surface water lower than pier cap and deck. Adding some casing protection shield in abutment, embankment and middle piers that exposed to river water current will help to prevention of water scour and landslide in those areas. Retrofitting of damaged area with some new method such as fiber reinforce polymer (FRP), steel jacket and etc can help to structure for sustaining the loads during disasters. 4. Conclusion Lifelines and infrastructure have an important role in every country and several thousand dollars have been paid to maintenance and rehabilitation of infrastructures annually. Iran is located in a seismic prone region and in every year, several earthquakes happen that cause severe damages. Seismic hazard assessment of Guilan Province including Manjil in Iran showed a high seismic potential in this region. In this paper, a SHM study of six concrete bridges based on visual inspection in Rudbar region that included Manjil city has been done and it showed that Bala Bala and Totkabon bridges needed to care and rehabilitate. Some suggestions for rehabilitation of these bridges are replacing short drainage pipe with some longer pipe to conduct the surface water lower than pier cap and deck. Furthermore, adding some casing protection shield in abutment, embankment and middle piers that exposed to river water current will help to prevention of water scour and landslide in those areas. 5. References [1] S.K. Thakkar, Goutam Ghosh and Yogendra Singh,Structural damage identification and health monitoring and damage identification of bridges, Advances in Bridge Engineering, March 24-25, 2006 [2] Mohsen Sartipi,Natural Disasters and Diagnosis of Man-made Factors the Cases of Manjil and Bam, Environmental Sciences, 12,59-66, Summer 2006 [3] G.Ghodrati Amiri, S.A.razavian Ameri, Seismic hazard Assessment of Guilan province including Manjil in Iran,14 th world conference on Earthquake Engineering, October 12-17, Beijing, China, 2008 [4] M. K. Ycgian, V. G. Ghahmman, M. A. A. Nogole-Sadat, and H, Daraie, Liquifaction during the 1990 Maanjil I: case history data, Bulletin of the Seismological of America, Vol,85,1995 [5] IIEES, International Institute of Earthquake Engineering & Seismology, 327