Dionysius M. Siringoringo

Estimating Bridge Fundamental Frequency from Vibration Response of Instrumented Passing Vehicle: Analytical and Experimental Study

Driving velocity, natural frequency of vehicle and natural frequency of bridge are the main contributing factors to vibration of a vehicle when passing a bridge. By separating contributions of the first two factors, one can estimate the natural frequency of a bridge indirectly from vehicle acceleration response when it crosses a bridge. In this paper, we apply this concept to estimate the bridge fundamental frequency indirectly using the response of a passing instrumented vehicle. The paper first describes analytical formulation and finite element simulation to demonstrate the feasibility of the method. Afterwards, it describes an experimental verification as a proof-of-concept of the method on a full-scale simply-supported short span bridge by using a light commercial vehicle instrumented with accelerometer. Dynamic responses of the vehicle while passing the bridge are recorded and analyzed. Spectra analysis of the vehicle responses reveal that the first natural frequency of the bridge can be estimated with reasonable accuracy when the vehicle moves with constant velocity. The concept of indirect frequency estimation is useful for assessment of short and medium span bridges where permanent instrumentation and routine visual inspection can be too costly. In this method, one can use inspection vehicle instrumented with vibration sensor to conduct periodic measurements by passing the vehicle over several monitored bridges and estimate their fundamental frequencies. When significant change in frequency is detected, detail inspections can be further conducted to investigate the possible damage on the bridge.

Noncontact operational modal analysis of structural members by laser doppler vibrometer

A system that uses ambient vibration and two laser Doppler vibrometer (LDV) is developed for noncontact operational modal analysis of structural members. The system employs natural excitation tech- nique (NExT) to generate the cross-correlation functions from laser signals, and the eigensystem realization al- gorithm (ERA) to identify modal parameters of struc- tural members. To facilitate simultaneous modal identifi- cation, time-synchronization technique and construction of cross-correlation functions from ambient response of laser signals are proposed. Performance of the proposed system is verified experimentally by evaluating the con- sistency and accuracy of identification results in differ- ent measurement conditions. The work presented here is an extension of the previous study, where a modal-based damage detection method using LDV was formulated. In the present study, application of LDV for structural parameters identification of a combined dynamical sys- tem is proposed. A model that represents the connection properties in terms of additional stiffness and damping is developed, and its importance for structural damage de- tection is discussed. The study shows that the presence of simulated damage in a steel connection can be detected by tracking the modal phase difference and by quantify- ing the additional stiffness and damping.

Bridge monitoring in Japan: the needs and strategies

This paper discusses the development of bridge monitoring in Japan. Firstly, the background of the development of bridge monitoring is described. The need for monitoring was originally influenced by geographical conditions. Due to the fact that Japan is prone to natural disasters and has a severe environment for deterioration; monitoring of the environment and loading conditions with respect to natural hazards has been conducted for several decades. In the last decade, bridge monitoring has extended its function as an instrument for an efficient stock management. Based on the accumulation of bridge stock and concentrated construction in former years, many bridges in Japan are expected to have serious deterioration problems within the next decade. The second part of the paper describes the concept of bridge monitoring as an essential part of risk reduction. To improve bridge safety, monitoring technologies for risk and vulnerability are implemented. In this concept, structural health monitoring serves as a tool for vulnerability monitoring. The third part of the paper outlines strategies implemented for bridge monitoring in Japan. They are categorised into three main groups according to the purpose of monitoring: natural hazard and environment condition, effective stock management, and failure prevention. Examples of bridge monitoring systems that implement these strategies and the lessons learned from monitoring experiences are also presented in this paper.

Vibration Mechanisms and Controls of Long-Span Bridges: A Review

Abstract Dynamic performance is an important consideration in long-span bridge design. Owing to its flexibility and low damping, various types of vibration from different sources of excitation could occur during the lifetime of a long-span bridge. This paper reviews important studies and developments on long-span bridge vibration mechanism and control under wind, seismic, traffic and human-motion excitations. Types of vibration commonly observed on the long-span bridge are discussed from the viewpoint of structure engineering. Discussion for each subject is commenced by describing the vibration mechanism followed by the survey on observed phenomena in many long-span bridges associated with the type of vibration. The paper also describes the engineering solutions adopted as countermeasures for each type of bridge vibration problem.

Seismic response analyses of the Yokohama bay cable-stayed bridge in the 2011 great East Japan earthquake

Yokohama Bay Bridge, with a total span length of 860 m, is the second longest span cable-stayed bridge in East Japan, and one of the most densely instrumented bridges in Japan. On March 11, 2011, the Great East Japan (Tohoku) Earthquake hit northeastern Japan with magnitude of MW 9.0, notably the largest earthquake in Japan’s modern history. Intensity 5+(PGA 1.4–2.5 m/s2) of the maximum scale 7 of Japan Meteorogical Agency’s seismic intensity was recorded on the bridge site. This paper describes seismic response analyses of the bridge, system identification, performance evaluation of link-bearing connections (a seismic isolation system), and postearthquake field observation. Response analyses show that transverse vibration dominated the response of girder and tower, with a maximum girder displacement of 62 cm. The large transverse vibrations induced pounding between tower and girder on the tower–girder connections as shown by the periodic impulses on acceleration records. Meanwhile, longitudinal accelerations indicate that the link-bearing connections functioned properly during the earthquake. System identification reveals nonlinearity of the response as evidenced by variations in natural frequencies and mode shapes during large excitation. Despite these conditions, the bridge did not suffer any structural damages, since the ground motions experienced during the earthquake were less than the design and seismic retrofit ground motions.

Dynamic characteristics of an overpass bridge in a full-scale destructive test

Verification of vibration-based damage detection through a full-scale actual structural testing is an important learning opportunity. From such a test, the evolution of dynamic characteristics can be observed, damage detection methods can be validated, and baseline criteria for typical structural damage can be formulated. This paper describes a case study on a full-scale destructive testing of an overpass reinforced concrete bridge. Damage is introduced by cutting one of the bridge piers at the footing level allowing vertical settlement. This type of damage is expected to simulate the condition in which a bridge suffers from nonuniform pier settlement or hidden damage inside piles of buried foundations. By applying time and frequency domain vibration analysis, as well as a system identification technique, changes in dynamic characteristics caused by the damage are evaluated. The results clearly indicate the changes in frequencies as an indicator of damage presence, while the change in mode shapes can be used to locate the damage. The paper also discusses the application of the damage detection method based on outlier analysis of the autospectra function using the bridge ambient acceleration responses. The results indicate that the presence of damage at an early stage can be detected by observing the outliers in multivariate data, and the detection accuracy improved when damage has significantly changed the dynamic characteristics of the structure.

A Conceptual Review of Pedestrian-Induced Lateral Vibration and Crowd Synchronization Problem on Footbridges

AbstractModern footbridges are often characterized by architectural demands for light, slender, and long structures that may lead to excessive vibration problems. In past decades, occurrences of pedestrian-induced vibration on footbridges have been reported, notably at the Toda Bridge in Japan, the Millennium Bridge in London, and the Solferino in Paris. In 1989, we observed a peculiar type of lateral vibration at the Toda Bridge during the passing of congested crowds. Hundreds of pedestrians walked in a synchronized manner among themselves, which created remarkable lateral vibration in the structure. Approximately 10 years later, public attention on pedestrian-induced lateral vibration increased significantly when the Solferino Bridge in Paris and the Millennium Bridge in London showed a similar phenomenon during the passing of congested crowds. These three most well-known cases have triggered extensive study, and pedestrian-induced vibration has emerged as an important topic in vibration study. A consid...

The Importance of Dense Monitoring of Long-span Bridges for its Performance Re-evaluation

Monitoring of structures offers a wealth of information on structural performance evaluation. While the performance of existing structures may differ from their designs, monitoring of dynamic behaviors potentially provides indications of how close or far the performance is to the designs and unexpected differences that might be important to the safety. This paper presents how two bridges were monitored in Japan as well as dynamic and structural analyses of the monitoring data. Ambient vibration and seismic response records are utilized in performance evaluation of these bridges. The dense sensor instrumentation on the bridges and long-term monitoring provides exceptional opportunities to obtain insight into the behaviors of the bridges and performance of their components.