Circular path and linear momentum method for seismic response analysis of vehicles

We propose a circular path and linear momentum method for the seismic response analysis of vehicles. This method considers the momentum induced by earthquake excitation and applies the concept of centripetal force acting laterally on the vehicle in addition to longitudinal forces. This method is valid for vehicles at rest as well as those moving at a range of speeds. The vertical responses are calculated using a quarter vehicle model. We also calculate the translational motion of the vehicle using a model with six degrees of freedom. Three vehicle types (car, bus, and truck) were used in the analysis. We compared the result with analysis of the response of a shaking vehicle from video footage recorded during the Gorkha earthquake. We used the input ground motion from 10 large earthquakes of moment magnitudes 6.7–9.0. All three components of the ground motion were used in the analysis. Vehicles at rest and moving at various speeds were analyzed. The lateral and longitudinal responses of the vehicles were calculated for different vehicle speeds ranging from 0 to 30.0 m/s, PGA excitations and orientations of the vehicle.</p

Ground motion characteristics of the 2015 gorkha earthquake, survey of damage to stone masonry structures and structural field tests

On April 25, 2015, a M7.8 earthquake rattled central Nepal; ground motion recorded in Kantipath, Kathmandu, 76.86 km east of the epicenter suggested that the low frequency component was dominant. We consider data from eight aftershocks following the Gorkha earthquake and analyze ground motion characteristics; we found that most of the ground motion records are dominated by low frequencies for events with a moment magnitude greater than 6. The Gorkha earthquake devastated hundreds of thousands of structures. In the countryside, and especially in rural mountainous areas, most of the buildings that collapsed were stone masonry constructions. Detailed damage assessments of stone masonry buildings in Harmi Gorkha had done, with an epicentral distance of about 17 km. Structures were categorized as large, medium and small depending on their plinth area size and number of stories. Most of the structures in the area were damaged; interestingly, all ridge-line structures were heavily damaged. Moreover, Schmidt hammer tests were undertaken to determine the compressive strength of stone masonry, brick masonry with mud mortar for normal buildings and historical monuments. The compressive strengths of stone and brick masonry were found to be 12.38 and 18.75 MPa, respectively. Historical structures constructed with special bricks had a compressive strength of 29.50 MPa. Pullout tests were also conducted to determine the stone masonry-mud mortar bond strength. The cohesive strength of mud mortar and the coefficient of friction were determined

GROUND MOTION IN YOGYAKARTA CITY, YOGYAKARTA SPECIAL PROVINCE, INDONESIA ON DENSELY MICROTREMOR OBSERVATIONS AND SHEAR WAVE VELOCITY

Microtremor is currently considered the foremost tool in site effect studies. The ground motion is estimated with microtremor observations, meaning that subsoil mechanical properties and geometry are evaluated and from them an estimate of local amplification is computed. Here, the ground motion is studied by the site effects of seismic hazard zonation of urban areas in Yogyakarta City. The main purpose of this paper is zoning the geological engineering features and assessing seismic of the research urban area. In this regard, the microtremors are measured at 274 sites by single station sampling method and Nakamura technique. The microtremors of all over the city are processed by a model of Mitutoyo-GPL-6A3P. The amplification factor generally ranges between 0.70 and 5.56 and the natural frequency normally varies between 0.40 and 3.30 Hz. The information layers are prepared in GMT used for detecting the zonation of potential seismic hazard. The shear wave velocity is calculated in 12 existing drilling sites based on the geotechnical approach of SPT for soil condition. To study the ground motion, geological engineering condition is investigated using amplification factor, natural frequency, shear wave velocity maps which are analyzed using densely single microtremor observation and SPT from existing drilling sites. Keywords: Ground motion, amplification factors, natural frequency; H/V spectral ratio, microtremor observations, Yogyakarta Urba

ESTIMATION OF SUBSURFACE STRUCTURE BASED ON MICROTREMOR, BORE HOLE OBSERVATIONS AND STOCHASTIC STRONG GROUND MOTION SIMULATIONS IN PALU CITY, CENTRAL SULAWESI, INDONESIA: A VALIDATION AND SENSITIVITY STUDY ON THE 23 JANUARY 2005 (PALU) EARTHQUAKE

In this study, we investigated the subsurface structure and strong ground motion parameters for Palu City. One of the major structures in Central Sulawesi is the Palu-Koro Fault system. Several powerful earthquakes have struck along the Palu-Koro Fault during recent years, one of the largest of which was an M 6.3 event that occurred on January 23, 2005 and caused several casualties. Following the event, we conducted a microtremor survey to estimate the shaking intensity distribution during the earthquake. From this survey we produced a map of the peak ground acceleration, velocity and ground shear strain in Palu City. We performed single observations of microtremors at 151 sites in Palu City. The results enabled us to estimate the site-dependent shaking characteristics of earthquake ground motion. We also conducted 8-site microtremor array investigation to gain a representative determination of the soil condition of subsurface structures in Palu. From the dispersion curve of array observations, the central business district of Palu corresponds to relatively soil condition with Vs ≤ 300 m/s, the predominant periods due to horizontal vertical ratios (HVSRs) are in the range of 0.4 to 1.8 s and the resonant frequency are in the range of 0.7 to 3.3 Hz. Three boreholes were throughout the basin especially in Palu area to evaluate the geotechnical properties of subsurface soil layers. The depths are varying from 1 m to 30 m. Strong ground motions of the Palu area were predicted based on the empirical stochastic green’s function method. Peak ground acceleration and peak ground velocity becomes more than 0.04 g and 30 kine in some areas, which causes severe damage for buildings in high probability. Keywords: Palu-Koro fault, microtremor, bore holes, peak ground acceleration and velocity

SITE RESPONSE CHARACTERISTICS OF H/V SPECTRUM BY MICROTREMOR SINGLE STATION OBSERVATIONS AT PALU CITY, INDONESIA

In this study, we estimated predominant period of an H/V spectrum in Palu City, Indonesia, by using microtremor single station observations. Sulawesi Island, eastern Indonesia, is located at the junction between the converging Pacific-Philippine, Indo- Australian Plates and the Eurasian Plate. One of the major structures in Central Sulawesi is the Palu- Koro Fault system, which extends NNW-SSE direction and cross-cuts Sulawesi along more than 300 km from the North Sulawesi trench passing southward through Palu Bay then turn to the southeast, connecting to the Matano and Lawanopo Faults and further eastward both faults join to Tolo trench. Several earthquakes have been known along Palu-Koro Fault system such as Gimpu earthquake (1905), Kulawi earthquake (1907), Kantewu earthquake (1934), and offshore Donggala earthquake (1968) which caused tsunami that destroyed 800 houses and killed 200 people at Donggala district. Palu City, located at the northern tip of Palu depression, is a capital of the Central Sulawesi Province. It is located in the active seismic zone of the Palu-Koro fault. Spectral ratios for horizontal and vertical motion (H/V) from single-station microtremor records were used to identify the predominant periods of the ground vi- brations. Understanding the parameters of predominant period[s] and seismichazard is important for mitigation and environmental planning of the Palu region. Keywords: H/V spectrum, predominant period[s], microtremor single station observatio

2003年バム地震における組積構造物の倒壊メカニズム

An earthquake of magnitude MW 6.5 occurred at 05: 26 on December 26, 2003 in Bam City, Kerman State, Iran. The epicenter was located at 29.01N and 58.26E. More than 26,000 people were killed, and about 90% of the adobe and masonry structures collapsed. The earthquake was recorded at the center of the city by BHRC. Peak accelerations for longitudinal, transversal, and vertical components were 778.2, 623.4, and 979.9 (gal), respectively. We carried out simple in situ tests to examine bonding strength in the shear and separation directions using a spring balance. From the results of these tests, it was found that bonding strength was very weak and was the cause of collapse of adobe and masonry structures

Seismic Risk Analysis for Critical Infrastructure: The Case Study of a Medical Center and its Supporting Systems in Yangon, Myanmar

Myanmar has a great strike-slip active fault called the “Sagaing Fault Zone” besides the Sumatra-Andaman Subduction Zone. Major cities (Yangon, Naypyitaw, Bago and Mandalay) are at risk along this fault. Recently, in 2012, Thabeikkyin earthquake with Magnitude of 6.8 caused collapse of many residential housings and ground failures near Mandalay. Therefore more attention should be paid for Yangon which has no large earthquakes since 1930 and is the largest not only in population but also in socio-economic activity. One of the most important concerns after an earthquake is to survive under any disastrous conditions. The medical care is requested not only for emergent injured people after an earthquake, but also for various types of patient and aged people from several weeks to longer periods. So medical center must be always functional before and after earthquake. For this purpose, medical buildings should be structurally resilient and also be functional for medical services by sustainable supply of electric power, water and any other delivery service which can be carried out by urban lifeline systems. This research is to investigate the structural vulnerability of hospital buildings and facilities, to assess the performance of urban lifeline systems and to check the operational capability of medical services in which surgical capability and life safety management method should be discussed. The water supply system is adopted as a typical lifeline system in Yangon in this study. One sample medical center in Yangon is adopted to carry out this analysis. Finally, the performance of medical services after the earthquakes can be assessed in a probabilistic manner

Hard and soft measures for earthquake and tsunami disaster mitigation

A destructive earthquake struck the Kobe region on January 17, 1995, and a massive earthquake and tsunami struck eastern Japan on March 11, 2011. We present an overview of the casualty aspects of the 2011 Tohoku earthquake compared with those of the 1995 Kobe earthquake. In the Tohoku disaster, some water gates and seawalls saved some villages from the tsunami effects, though some did not. Based on these examples, we discuss the efficiency of soft and hard measures and consider their respective merits and demerits. The main causes of death in the Kobe and Tohoku EQs were, respectively, collapsing buildings and drowning in the tsunami. Although the time to death was very short in both cases, people often have more time to evacuate in the case of an interplate earthquake leading to a tsunami. Basic countermeasures against tsunamis include such hard measures as water gates, seawalls, and embankments. Soft measures need to be implemented in areas where hard measures are insufficien