Mehedi Ahmed Ansary

HORIZONTAL‐TO‐VERTICAL SPECTRUM RATIO OF EARTHQUAKE GROUND MOTION FOR SITE CHARACTERIZATION

SUMMARY Nakamura’s method, which uses a horizontal-to-vertical Fourier spectrum ratio of microtremor, has become popular to determine the predominant period and amplification of a site. In this study, this method is extended for earthquake ground motion recordings using new strong motion data recorded by JMA-87-type accelerometers. From the analysis of these accelerograms, horizontal-to-vertical Fourier spectrum ratios of a site for di⁄erent earthquakes are also found to be stable irrespective of magnitude, distance and depth. To establish this fact, attenuation relations of velocity response spectra for horizontal and vertical components are derived for three damping ratios (0, 2 and 5 per cent) using the JMA data. Then the horizontal-to-vertical ratios of the velocity response spectra are obtained. The results show that the horizontal and vertical velocity response spectra are dependent on magnitude, distance and depth, but that their ratios are almost independent of magnitude, distance and depth. However, since the current data set consists of mostly intermediate to far field data, this observation should be limited to records of these distance ranges. Introducing station coeƒcients, representing site amplification, to this relation yields the value comparable to the horizontal-to-vertical Fourier spectrum ratio at a specific site. The stability of the spectrum ratio is explained by the transfer function between the ground surface and sti⁄-soil outcrop due to S-wave propagation. These results suggest that site amplification characteristics can be evaluated by one-point two-component surface recordings of earthquake ground motion, in a similar manner as proposed by Nakamura for microtremor. ( 1997 by John Wiley & Sons, Ltd.

District-wise multi-hazard zoning of Bangladesh

Bangladesh is stated as one of the most natural disaster-prone countries in the world. The geographical setting of the country makes it vulnerable to natural hazards. Among different disasters in Bangladesh, tornado, flood, earthquake, and cyclone are major hazards according to the historical occurrences and their potential damages. For proper disaster management, recognition of the existence of the hazards and identification of the vulnerable areas are first important tasks. Thus, the prime objective of this study was to prepare a district-wise multi-hazard zoning map of Bangladesh. For the purpose, firstly a complete district-wise database of four disasters in Bangladesh was prepared. Comparing scenarios of these hazards in Bangladesh and their corresponding scales all over the world, suitable intensity scales and their corresponding damage risk levels were proposed. For calculation of district-wise individual hazard scores, hazard factors and weighting factors for particular hazards were defined based on the organized district-wise historical disaster database of Bangladesh through consultation with experts from relative fields. After that, district-wise individual and multi-hazard scores were calculated. Then, the districts of Bangladesh were subdivided into three zones based on calculated multi-hazard scores. Finally, district-wise multi-hazard zoning map of Bangladesh was prepared. The research findings are crucial and important for policy-makers for decision-making regarding disaster management strategies, i.e. planning for disaster prevention, mitigation, and preparedness actions.

Workplace safety in Bangladesh ready-made garment sector: 3 years after the Rana Plaza collapse

Workplace safety is one of the most important issues in industries worldwide, and is endangered by industrial accidents. Different industrial disasters have resulted in several initiatives worldwide to protect human life and reduce material damage, both nationally and internationally. In Bangladesh, the ready-made garment (RMG) industry is one of the most important export-oriented business sectors, which is facing challenges to ensure workplace safety. The Rana Plaza collapse in Bangladesh is the consequence of such non-compliance. The accident resulted in different local and global initiatives to address the challenges. This article reviews progress and achievement of the initiatives to reduce vulnerability in the Bangladesh RMG industry within 3 years after the deadly accident. In the long run, the challenge is to maintain momentum already created for achieving sustainability in the RMG sector in Bangladesh and maintaining compliance even after the end of support from external partners.

Factors Affecting Vulnerability of Ready-Made Garment Factory Buildings in Bangladesh: An Assessment Under Vertical and Earthquake Loads

The importance of workplace safety in the ready-made garment (RMG) industry in Bangladesh came to the forefront after a series of disastrous events in recent years. In order to reduce the loss of lives and to ensure sustainable development, an in-depth understanding of the determining factors governing structural vulnerability in the RMG industry is needed. This research explores the key factors influencing the vulnerability of factory buildings under both vertical and earthquake loads. For this purpose, an ordered probit model was applied to 3746 RMG factory buildings to determine the key factors that influenced their vertical load vulnerability. A smaller subset of the original sample, 478 buildings, was examined by the same modeling method in greater detail to assess the key factors that influenced their earthquake load vulnerability. This research reveals that column capacity, structural system, and construction materials are the most influential factors for both types of vulnerabilities. Among other factors, soil liquefaction and irregular internal frame affect earthquake load vulnerability significantly. These findings are expected to enable factory owners and designers to better weigh the appropriate vulnerability factors in order to make informed decision that increase workplace safety. The research findings will also help the designated authorities to conduct successful inspections of factory buildings and take actions that reduce vulnerability to both vertical and earthquake loads.