Panitan Lukkunaprasit

Seismic effectiveness of tuned mass dampers for damage reduction of structures

The effectiveness of tuned mass dampers (TMD) for control of structures under seismic ground motion is investigated. Since describing the effectiveness of TMD using displacement reduction of the structure is found to be insufficient after yielding of the structure, damage reduction of the structure is proposed instead. Numerical simulations of a 20-storey reinforced concrete building modeled as an equivalent inelastic single-degree-of-freedom (SDOF) system subjected to both harmonic and the 1985 Mexico City (SCT) ground motions are considered. It is demonstrated that although TMD cannot reduce the peak displacement of the controlled structure after yielding, it can significantly reduce damage to the structure. In addition, certain degrees of damage protection and collapse prevention can also be gained from the application of TMD. This is of particular significance in view of the current trend toward performance-based design in which TMD may be installed to achieve the target performance of buildings designed for seismic loads.

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.

Experimental and Numerical Modeling of Tsunami Force on Bridge Decks

Tsunamis are destructive waves which contain a series of long period waves. These waves propagate at very high speed and travel transoceanic distance with very litter energy losses. When tsunamis approach a shore, their tremendous energy remains nearly unchanged and the high inundation level and the fast moving water of tsunami flow cause loss of human lives and catastrophe to coastal structures including bridges (Figure 1). The extensive bridge damage caused by recent tsunamis in particularly in the unprecedented 2004 Indian Ocean tsunami event demonstrates an urgent need for an effective method to estimate tsunami forces on bridges. Due to the complexity of wave propagation on shore and wave-structure interaction, physical and numerical approaches have been adopted to investigate tsunami-induced forces on bridges. Even though tsunami force acting on vertical wall-type coastal structures has been studied by many researchers since last five decades, but the assessment of tsunami force on bridge is still in its early stage. There has still no conclusive argument on how big tsunamis are. The occurrence of the 2004 Indian Ocean tsunami shows the enormous force exerted by the tsunami which had floated a 10-MW barge-mounted diesel station 3 km inland in Banda Acheh, shifted a heavy dredger onto the wharves in Sri Lanka and drifted a police patrol boat 1.2 km inland in Thailand. This disastrous wave force is once again shown in the most recent tsunami triggered by the 2011 Tohoku Region Pacific Ocean Offshore Earthquake. The post-tsunami survey have evidently demonstrated the damage of bridges in Sumatra, Sri Lanka, India and Thailand during the 2004 tsunami event as reported by Kusakabe et al. (2005), Unjoh (2005), Iemura et al. (2005), Yim (2005), Saatcioglu et al., (2005), Tobita et al., (2006), Ballantyne (2006), Maheshwari et al. (2006), Scawthorn et al. (2006), Sheth et al. (2006), EEFIT (2006) and IIT (2011). These bridges suffered failure through a total or partial washaway of bridge deck from their abutments and excessive settlement of foundation. The failure of bridges disrupts the accessibility of the community; nevertheless, the great concern is hamper the emergency relief efforts that are needed immediately after this disastrous event.

DUCTILITY ENHANCEMENT OF MODERATELY CONFINED CONCRETE TIED COLUMNS WITH HOOK-CLIPS

This paper describes an experimental investigation of the effectiveness of hook-clips in improving performance of conventional 90-deg. hook-ties and cross-ties in moderately confined reinforced concrete tied columns. The tie configurations provided in the 5 large-scale specimens tested included 90-deg. hook-ties and cross-ties, with and without hook-clips, and 135-deg. hook-ties. The columns were subjected to moderate levels of compression and cyclic lateral loads. The hook-clips were found to be effective in improving performance of concrete columns confined with 90-deg. hook-ties and cross-ties, resulting in the displacement ductility factor and energy dissipation capacity to be increased by roughly 85% and 400%, respectively.

Dynamic plastic analysis using stress resultant finite element formulation

Abstract A stress resultant finite element formulation is developed for the dynamic plastic analysis of plates and shells of revolution undergoing moderate deformation. A nonlinear elastic-viscoplastic constitutive relation simulates the behavior of rate-sensitive and -insensitive materials. A local time step subdivision procedure is developed to stabilize the direct numerical integration of the system of nonlinear dynamic equations; satisfactory accuracy is obtained with large time steps. The simple nonlinear viscoplastic constitutive model approximates the nonlinear dynamic behavior of metals over a wide range of strain rates and has the advantage that the need to identify the state of the material during deformation is eliminated and the numerical algorithm thereby simplified. Direct step-by-step integration techniques are used to solve the system of equations governing the motion of a structure under dynamic loading. An implicit Runge-Kutta scheme in conjunction with a Newton-Raphson iteration technique is used in solving systems of first order ordinary differential equations.

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.

Influence of bridge deck on tsunami loading on inland bridge piers

The customary method of computing the hydrodynamic force on a pier of a bridge is based on the model tests of stand-alone piers. This implicitly ignores the influence of the deck on the flow pattern around the piers. The hydrodynamic force exerted on the piers by a solitary-like wave generated in a hydraulic wave flume is investigated using a complete pier-deck model, which includes both the pier and deck in the actual proportion. The experimental results reveal that the hydrodynamic force on the piers is influenced by the presence of the deck. For the complete bridge configuration studied, the actual force component which results from the hydrodynamic pressure acting on the piers only could be increased by as much as 50% over that for the case of stand-alone piers. This is due to the influence of the deck in obstructing the free splashing and topping over of the wave upon striking the piers, resulting in accumulation of fluid in front of the piers, and hence increasing the pressure on them. Thus, the hydrodynamic force computed based on experiments on stand-alone piers could be non-conservative for design of piers.

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.