Anat Ruangrassamee

Control of nonlinear bridge response with pounding effect by variable dampers

Under strong ground excitations, highway bridges experience severe nonlinearity induced by inelastic deformation at plastic hinges of piers and pounding between two adjacent decks. To mitigate the nonlinear response of bridges, semi-active control was implemented using variable dampers. This research was conducted to investigate the effectiveness of variable dampers in improving the seismic response including pounding effect. It is found that the friction-type damping force scheme gives the largest reduction of deck displacement, relative displacement between two decks, and the flexural hysteretic curvature at the plastic hinge of a pier. Pulse-like acceleration response resulted from pounding between two decks is reduced extensively.

Investigation of Tsunami-Induced Damage and Fragility of Buildings in Thailand after the December 2004 Indian Ocean Tsunami

The December 2004 Indian Ocean tsunami caused human loss and devastating damage to civil engineering structures along the west coast of southern Thailand. This damage was investigated to evaluate the vulnerability of structures. Criteria for post-tsunami investigation were developed, and a database system was established to manage and present the data. The database of reinforced concrete (RC) buildings was then analyzed to find the relationship between the damage level and (a) the distance from the shoreline or (b) the inundation height. A representative RC columns capacity to resist lateral forces was measured by a full-scale loading test to gain insight into the relationship between the observed damage and the actual structural performance.

Building damage in Thailand in the 2004 Indian Ocean tsunami and clues for tsunami-resistant design

The unprecedented devastating Indian Ocean tsunami, which struck the western coast of southern Thailand on 26 December 2004, caused more than 5300 deaths, and heavy damage to buildings in the affected areas. This paper presents field observations of damage to buildings and infrastructure hit by the tsunami in southern Thailand. The clues obtained from the performance of these structures, which have not been designed for seismic or tsunami loadings, are valuable for improvements in safe and economical design of buildings against future tsunamis. Two important features beneficial for disaster reduction on coasts are low seawalls and openings in walls in buildings. The former helps partially dissipate the energy of the incoming waves while the latter serves to reduce the unbalanced pressure on the walls of buildings. The survival of a large number of buildings suggests that it is possible to design tsunami-resistant structures with reparability performance level, with a consequence of fast recovery and minimum economic loss. This is of practical significance for the design of evacuation shelters to save human lives. Consideration of a suitable tsunami design velocity is also addressed.

Analysis of Tsunami Flow Velocities during the March 2011 Tohoku, Japan, Tsunami

The March 2011 Tohoku, Japan, tsunami caused severe damage to many buildings, bridges, and lifelines along the Pacific coast of Japan. To analyze its effects on structures, the tsunami flow velocity and the tsunami flow depth are needed to estimate the force acting on structures. Videos recording tsunami flows are available on many websites. Ten cases of tsunami flow velocities and flow directions are analyzed from videos by estimating the movement distances of observed objects. The analyzed tsunami flow velocities are 3–5 m/s in Kamaishi City, 2 m/s in Ofunato City, 3–6 m/s in Kesennuma City and 1.5 m/s in Iwaki City. The analyzed velocities fall in the range of 1.0 g h to 1.5 g h . A case study of tsunami simulation is performed to estimate the velocity in Kesennuma City. At the same locations as the recorded videos, the tsunami flow velocities from the simulation agree the velocities from recorded videos.

PROBABILISTIC SEISMIC HAZARD MAPS OF THAILAND

In this study, the probabilistic seismic hazard map of Thailand and neighboring areas is developed. Thailand is located close to the Andaman thrust in the west and the Sunda arc in the south which are the boundaries between the Eurasian plate and Indo-Australian plate. Several active faults in this region have caused earthquakes which affects Thailand. Earthquakes recorded from 1912 to 2006 by the Thai Meteorological Department and the US Geological Survey are used in the analysis. Two attenuation models for active tectonic regions which give good correlations with actual measured accelerations are used in predicting peak horizontal accelerations in Thailand. Maps of peak horizontal accelerations at rock sites with 2% and 10% probabilities of exceedance in 50 years are developed. For the peak horizontal acceleration with 10% probability of exceedance in 50 years, the maximum accelerations are about 0.25 g in the northern part of Thailand and 0.02 g in Bangkok. For the peak horizontal acceleration with 2% probability of exceedance in 50 years, the maximum accelerations are about 0.4 g in the northern part of Thailand and 0.04 g in Bangkok.

Performance of Structures in the Mw 6.1 Mae Lao Earthquake in Thailand on May 5, 2014 and Implications for Future Construction

An Mw 6.1 earthquake struck northern Thailand on the 5th of May 2014. The epicenter was located near Mae Lao district in Chiang Rai province. The earthquake caused unprecedented damage to structures, the most damaging earthquake ever in recorded Thai history. Five hundred and ninety-four buildings out of 10,863 were damaged to the extent that they were unsafe for occupancy. This article presents a reconnaissance investigation of damage to buildings and bridges in the two districts—Phan and Mae Lao—which suffered the most damage. Attention is paid to the performance of buildings with similar configurations and structural design, but with different layout of unreinforced masonry infills as non-structural components.

PERFORMANCE OF BRIDGES WITH SOLID AND PERFORATED PARAPETS IN RESISTING TSUNAMI ATTACKS

Tsunamis have damaged bridges with various configurations to different extents. This paper reports an experimental investigation of the tsunami loads on two types of bridge configurations, namely bridges with solid and perforated parapets. The results reveal that the maximum forces acting on the bridge deck with 60% perforated parapets are about 17% lower than the one with solid parapets. However, the percentage of force reduction is found to be smaller than the percentage of perforation area in the parapets. It is also noted that the perforated parapets in the bridge deck can substantially reduce the tsunami forces acting on it throughout the force time-history. Hence, as far as the horizontal forces are concerned, the experimental results indicate that the bridge with perforation in parapets would suffer less damage as compared to the one with solid parapets because of the smaller energy input into the structure.

CALIBRATION OF TSUNAMI LOADING ON A DAMAGED BUILDING

The survival of a large number of buildings in southern Thailand with minor structural damage under 2–6 m inundation heights above the ground in the 2004 Indian Ocean tsunami tragedy suggests that it is necessary to calibrate the formulas stipulated by FEMA-55 [2000] for computing tsunami loadings. In this study, the weather monitoring building of the Meteorological station at Takua Pa, Phang Nga is used as the case study. The building suffered only minor structural damage to the columns and girders. However, most of the nonstructural members such as infill brick panels were damaged, except a few which contributed to significant reserve strength against the tsunami attack. The FEMA-55 loading is calibrated with the actual building performance from a field load test. The maximum velocity that occurred at the site in that event is assessed, and a velocity suitable for computation of tsunami load for southern Thailand is recommended.

Correlation analysis of a reinforced-concrete building under tsunami load pattern and effect of masonry infill walls on tsunami load resistance

The 26 December 2004 Indian Ocean tsunami caused damage to many buildings and killed a lot of people in several Indian Ocean countries, including Thailand. Several reinforced-concrete (RC) buildings in Southern Thailand that were gravity-load-designed buildings suffered damage due to the tsunami. To understand the behaviour of RC buildings under tsunami loads, the one-story building, which was the former office of the Thai Meteorological Department located in Phang-Nga province, was tested under tsunami load patterns. In this research, the RC building is modelled for three-dimensional non-linear static pushover analysis. In the building model, masonry infill walls are idealised as diagonal struts by using uniaxial non-linear springs, and plastic hinges are modelled by non-linear fibre elements. The results of the building model agree well with test results. The effect of masonry infill walls is investigated by considering various wall arrangement patterns. The building with masonry infill walls can resist the lateral load two times higher than the resistance of the building without masonry infill wall. The masonry infill walls with the appropriate arrangement can significantly improve the load-resisting capacity of the building under tsunami loads.

SEISMIC RESPONSE CONTROL OF A CABLE-STAYED BRIDGE BY VARIABLE DAMPERS

Cable-stayed bridges exhibit unique responses under a strong motion. It is partly due to the complexity in their damping mechanism. Recently, the benchmark problem of a cable-stayed bridge was developed to clarify the effectiveness of various seismic control strategies. Due to the new development of magnetorheological dampers, the application of variable dampers in bridges becomes possible. In this study, the effectiveness of the nonlinear viscous damping force scheme and the two-step friction damping force scheme are investigated. It is found that the nonlinear viscous damping force scheme is effective to control the response of the cable-stayed bridge with less demand for the damping force capacity of a damper. In addition, the two-step friction damping force scheme shows the improvement over conventional friction damping because the energy dissipation of a damper can be increased.