NBC105: 2019 Seismic design of buildings in Nepal: New provisions in the code

The NBC 105: 2019 Seismic Design of Buildings in Nepal is the revised version of the original code for seismic design first published in 1994. The code has never been reviewed and updated since then till the moment. Recognizing the development in research and technology and new knowledge learnt from various large earthquakes in last 25 years, the Government of Nepal decided to initiate the first revision of the seismic design code. The objective of this revised standard is to provide designers with general procedures and criteria for the structural design of buildings prevalent in Nepal. This paper presents the basic features of the revision and the principles adopted in the standard. A new seismic hazard map of Nepal was proposed at the outset based on probabilistic format. Accordingly the PGA values for various locations of Nepal were revised. The performance requirements have been introduced precisely in terms of collapse prevention and damage limitation; there is a further recommendation to verify the performance requirements checking the ultimate limit state and serviceability limit state. It is proposed to check life safety and damage limitation performance requirements. Two different spectra are proposed for seismic coefficient method and modal response spectrum method. Four types of sub soil category are proposed. Very soft soil category is added in addition to previous three categories. This new soil category represents a very deep soft soil found in Kathmandu valley. Research has indicated that hard soil should have greater acceleration demand at smaller periods. This issue is rarely addressed in design codes internationally and the revised version of the NBC 105 is one of the first codes to accommodate this in practice. The revised code, retaining the linear analysis, introduces the non-linear methods of analysis. The empirical formulae for determination of fundamental translation period have been revised. Other principal changes include the importance classes and importance factors, load combinations and load factors. The Performance factor (K), which was used in the earlier version to obtain seismic coefficient, does not reflect the modern seismic design philosophy of reducing the elastic seismic forces. The response reduction factors (Ductility factor, R and Overstrength factor, ) are introduced. The horizontal base shear coefficient will be determined separately for ultimate limit state and serviceability limit state. The horizontal design spectrum for the modal response spectrum method has been given different for ultimate limit state and for serviceability limit state. A separate section on structural irregularity has been added. The revised code now requires checking the inter-story drift for both serviceability limit state and ultimate limit state. The standard has been developed in a new format considering the recent development in the research and technology as well as the lessons from the recent earthquakes. The whole document has been spread over 10 sections with 2 annexes separately for ductile detailing of structural concrete and structural steel

Probabilistic seismic hazard assessment of Nepal for revision of national building code NBC105

Being located in seismically active Himalayan mountain belt, Nepal has been the locus of many devastating earthquakes. The Mw 8.4 Bihar-Nepal earthquake of 1934 AD was the biggest earthquake disaster in Nepal that had highlighted the need of a building seismic design code for safer construction. Though the necessity was realised earlier, Nepal developed its first National Building Code (NBC-105) only in 1994 after the 1988 Mw 6.9Udayapur earthquake in eastern Nepal. In April 2015, central Nepal witnessed the Mw 7.8 Gorkha earthquake, which had epicentre at Barpak village of Gorkha district, about 75 km west of Kathmandu. The ground mtions recorded at soft soil sites in Kathmandu Valley clearly show strong site effect resulting in high energy in long period, i.e. at 3s to 5s. A comparative study has revealed that, at least in Kathmandu Valley, the observed ground motions exceeded the seismic design demand proposed by NBC-105 for some period ranges. Unsurprisingly, the earthquake caused extensive damage to buildings and infrastructures in 14 districts(mostly towards east of the epicentre due to further ruptured directivity effect) and killed 8,970 people. This earthquake also triggered revision of the existing national building code (known as NBC- 105)by the Government of Nepal.A key feature of the revision of NBC-105 has been re-assessment of national seismic hazard by adopting a probabilistic approach. Since the development of NBC-105 in 1994, a large number of studies have been carried on seismo-tectonics, active fault, paleoseismology, seismicity, geodesy etc, which have significantly increased the level of knowledge on seismic sources in the central Himalayas. In addition, after the 2015 Gorkha earthquake, much knowledge is gained on the geometry of the main seismogenic fault, the Main Himalayan Thrust (MHT) also called the Main Frontal Thrust (MFT) at the surface of the Himalayan front. Based on recent researches, in contrast to seismic sources adopted in 1994, a fault source (MHT) and area sources, i.e. northern garbens in Tibet, strike-slip event dominant sources in eastern and western Nepal and a source south of MHT are considered for seismic hazard analysis. As there is no specific Ground Motion Prediction Equation (GMPE) for the Himalayas, based on seismo-tectonics, GMPEs are adopted including Next Generation Attenuation laws. More than two GMPES are used for each source using the logic tree approach. Seismic hazard is computed for 2%, and 10% probability of exceedence in 50 year. In contrast to hazard map of 1994, the zones of relatively higher Peak Ground Acceleration (PGA) i.e. 0.36g to 0.46g are, for 10% probability of exceedence in 50 year, concentrated just above the locked portion of MHT throughout the country. The PGA values gradually decrease towards the north and south of MFT. This pattern of PGA distribution is consistent with the coupling nature of the MHT in the Himalayas

Intentional pesticide poisoning and pesticide suicides in Nepal

Introduction Intentional pesticide poisoning is a major clinical and public health problem in agricultural communities in low and middle income countries like Nepal. Bans of highly hazardous pesticides (HHP) reduce the number of suicides. We aimed to identify these pesticides by reviewing data from major hospitals across the country and from forensic toxicology laboratories. Methods We retrospectively reviewed medical records of 10 hospitals for pesticide poisoned patients and two forensic laboratories of Nepal from April 2017 to February 2020. The poison was identified from the history, referral note, and clinical toxidrome in the hospitals and from gas chromatography analysis in the laboratories. Data on demographics, poison, and patient outcome were recorded on a data collection sheet. Simple descriptive analysis was performed. Results Among hospital cases (n = 4148), the commonest form of poisoning was self-poisoning (95.8%) while occupation poisoning was rare (0.03%). Case fatality was 5.3% (n = 62). Aluminum phosphide (n = 38/62, 61.3%) was the most commonly identified lethal pesticide for deaths. Forensic toxicology laboratories reported 2535 deaths positive for pesticides, with the compounds most commonly identified being organophosphorus (OP) insecticides (n = 1463/2535; 57.7%), phosphine gas (n = 653/2535; 25.7%; both aluminum [11.8%] and zinc [0.4%] phosphide) and organochlorine insecticides (n = 241/2535; 9.5%). The OP insecticide most commonly identified was dichlorvos (n = 273/450, 60.6%). Conclusion The data held in the routine hospital medical records were incomplete but suggested that case fatality in hospitals was relatively low. The pesticides identified as causing most deaths were dichlorvos and aluminum phosphide. Since this study was completed, dichlorvos has been banned and the most toxic formulation of aluminum phosphide removed from sale. Improving the medical record system and working with forensic toxicology laboratories will allow problematic HHPs to be identified and the effects of the bans in reducing deaths monitored

Public's willingness to pay towards a medical device for detecting foot ulceration in people with diabetes

Diabetic foot ulceration (DFU) is a common and serious complication among diabetic patients. A medical device has been developed to prevent the occurrence of DFU. The aim of this study was to investigate the willingness to pay (WTP) for this device among the general public in the UK.A contingent valuation survey was administered to 1051 participants through an online survey including questions on socio-demographic characteristics, self-reported health, knowledge of diabetes and medical devices, and WTP. A two-part model was used to analyse determinants of WTP, including a logistic model in the first part and a generalised linear model with a log-transformed WTP in the second part.More than half (55.9%) of the participants expressed a positive WTP. The annual mean (standard deviation) and median (interquartile range) WTP values were £76.9 (69.1) and £50 (80), respectively. Older age, middle-level education, good/excellent self-reported health, visiting doctors once/2-5 times, diabetes experience, medical device experience and more than average self-perceived likelihood of using similar devices were associated with a higher likelihood of willingness to pay. Younger age, male gender and higher household income were associated with higher WTP values.This study demonstrated that people are willing to pay for this device and they tend to contribute when they have experience of diabetes or similar devices and perceive self-benefit