Mitsuo Kawatani

Pseudo-static approach for damage identification of bridges based on coupling vibration with a moving vehicle

This paper presents a methodology for damage identification based on a time domain approach, considering the coupling vibration between a bridge and a moving vehicle, including the effect of roadway surface roughness. The fundamental idea of the proposed method is to identify damage directly from changes in the element stiffness using a pseudo-static formulation derived from the equations of motion for coupling vibration. The element stiffness index (ESI), which indicates the ratio of a damaged flexural rigidity of the finite element of bridges to an undamaged one, is adopted as the indicator of bridge damage. A numerical example reveals that the concept and procedure suggested in this paper can provide a method for extending engineering choices in damage identification of bridge structures.

Modal parameter identification of short span bridges under a moving vehicle by means of multivariate AR model

This study is intended to investigate the feasibility of health monitoring of short span bridges based on modal parameter identification using the vibration data of the bridge induced by a moving vehicle. The idea of this study using the traffic-induced vibration of short span bridges which is a kind of non-stationary process is that the modal parameters identified repeatedly under a given moving vehicle provide a pattern which may provide useful information to decide current health condition of bridges. The autoregressive (AR) model is adopted for identifying modal parameters such as frequency and damping characteristics of the bridges. Mode shapes of bridges are obtained using multivariate AR model. Feasibility of the modal parameter identification for health monitoring of short span bridges is observed through a moving vehicle laboratory experiment. Pattern changes of identified parameters are observable by comparing the identification results between intact and damaged girders, which encourages the use of the method for long term health monitoring even for short span bridges.

Feasibility investigation for a bridge damage identification method through moving vehicle laboratory experiment

This paper investigated the feasibility of the pseudo-static damage identification method derived from a bridge–vehicle interaction system through a moving vehicle laboratory experiment. The element stiffness index, defined as the ratio of flexural rigidity of a damaged member to that of an intact member, serves as the damage indicator. Three vehicle models and two travelling speeds were considered in the experiment to examine the effect of vehicles dynamic characteristic and travelling speed on identified results. It is demonstrated that locations and severities of damages are detectable using the proposed method in spite of the probable changes of roadway roughness and environmental conditions. In addition, adopting higher vehicle speed as well as the vehicle with frequency close to that of the bridge increased the probability of detecting damages.

Seismic responses of a highway viaduct considering vehicles of design live load as dynamic system during moderate earthquakes

This study is intended to investigate the seismic response of a highway viaduct under vehicle loadings during moderate earthquakes of high probability occurrence. The highway bridge design code of the Japan Road Association (JRA code) does not consider the live load in the seismic design of highway bridges because of the low possibility that both heavy traffic and an earthquake occur at the same time. However, frequent traffic jams in urban areas involve a high possibility of encountering an earthquake during a traffic jam. To clarify the effect of traffic to seismic responses of highway viaducts, heavy vehicles are considered as dynamic system in a three-dimensional dynamic response analysis. The design live load of the JRA code is assumed to be a critical traffic condition for the highway bridges, even during earthquakes. Observations through numerical analyses demonstrate that considering heavy vehicles as a dynamic system reduces seismic responses of the highway viaduct compared with those responses disregarding vehicular loadings and considering vehicles as additional mass.

An Analytical Approach to Train-induced Site Vibration Around Shinkansen Viaducts

This study is intended to establish an analytical approach to evaluate the site vibration caused by the passage of bullet trains over Shinkansen viaducts. In this approach, to simplify the problem the entire train–bridge–ground interaction system is divided into two subsystems: train–bridge interaction and foundation–ground interaction. In the train–bridge interaction problem, the analytical programme to simulate the traffic-induced bridge vibration is developed. Then, the dynamic responses of the viaducts are calculated to obtain the dynamic reaction forces at the bottoms of the piers. Applying these reaction forces as input excitation forces in the foundation–ground interaction problem, the site vibration around the viaducts is simulated and evaluated using a general-purpose programme.

SEISMIC BEHAVIOR OF STEEL MONORAIL BRIDGES UNDER TRAIN LOAD DURING STRONG EARTHQUAKES

This paper investigated dynamic responses of steel monorail bridges incorporating train-bridge interaction under strong earthquakes. Two types of steel monorail bridges were considered in the study: a conventional type with steel track-girder; an advanced type with composite track-girder and simplified lateral bracing system. During strong earthquakes, monorail train was assumed standing on the track-girder of monorail bridges. Observations through the analytical study showed that considering the monorail train as additional mass rather than a dynamic system in numerical modeling overestimated effect of the train load on seismic performance of monorail bridges. Earlier plastic deformations at the end bracing of the girder system absorbed seismic energy and reduced the stress at the pier base.

Wireless Sensor Node Development for Bridge Condition Assessment

This paper presents an on-going research project on development of a wireless sensor node equipped a MEMS accelerometer, which is aiming to design a wireless sensor node to meet specific requirements of the drive-by bridge monitoring for short span bridges. The performance of a trial piece of the sensor node is investigated through vibration tests on a model bridge in laboratory and a real pedestrian bridge. This paper also covers brief statements about the sensor node. The results indicate that acceleration responses taken from the wireless sensor node are comparable with those from the conventional sensing device with wired acceleration transducers.

Probabilistic Investigation on Dynamic Response of Deck Slabs of Highway Bridges

Probabilistic assessment on the code-specified impact factors of RC decks is investigated by means of a three-dimensional traffic-induced dynamic response analysis of bridges combined with the Monte Carlo simulation technique. The random variables considered in the simulation are the roadway roughness, bump height, traveling position of vehicles, vehicle running speed and axle load of three-axle vehicles. Statistical parameters of the random variables are taken from surveying data on Hanshin and Meishin Expressways in Japan. A simple span steel-girder bridge with RC decks that is experimentally verified is considered as a numerical example. This study demonstrates that the impact factor of the deck near expansion joints dominates the design impact factor due to the bump at the expansion joint of bridges.