SEISMIC VULNERABILITY OF REINFORCED CONCRETE BRIDGES IN PAKISTAN

Different researchers have performed seismic hazard assessment studies for Pakistan using faults sources which differ from Building Code of Pakistan (BCP 2007) with diverse standard deviations. The results of seismic hazard studies indicate that BCP requires gross revision considering micro and macro level investigations. The recent earthquakes in Pakistan also damaged bridge structures and some studies have been conducted by different researchers to investigate capacity of existing bridges. The most of bridge stock in Pakistan has been designed assuming seismic loads as 2%, 4% and 6% of dead loads following West Pakistan Code of Practice for Highway Bridges. The capacity of eight selected real bridges, two from each seismic zone 2A, 2B, 3 & 4 is checked against BCP demands. Static and dynamic analyses were performed and the piers were checked for elastic limits. It is established that piers are on lower side in capacity and the bridges in zone 2A are generally less vulnerable. Whereas the bridges in zone 2B, 3 and 4 are vulnerable from medium to very high level. Hence, an in-depth analytical vulnerability study of bridge stock particularly in high-risk zone needs to be conducted on priority and appropriate seismic retrofitting schemes need to be proposed.

Stochastic Generator of Earthquakes for Mainland France

Mainland France is characterized by low-to-moderate seismic activity, yet it is known that major earthquakes could strike this territory (e.g., Liguria in 1887 or Basel in 1356). Assessing this French seismic hazard is thus necessary in order to support building codes and to lead prevention actions towards the population. The Probabilistic Seismic Hazard Assessment (PSHA) is the classical approach used to estimate the seismic hazard. One way to apply PSHA is to generate synthetic earthquakes by propagating information from past seismicity and building various seismic scenarios. In this paper, we present an implementation of a stochastic generator of earthquakes and discuss its relevance to mimic the seismicity of low-to-moderate seismic areas. The proposed stochastic generator produces independent events (main shocks) and their correlated seismicity (only aftershocks). Main shocks are simulated first in time and magnitude considering all available data in the area, and then localized in space with the use of a probability map and regionalization. Aftershocks are simulated around main shocks by considering both the seismic moment ratio and distribution of the aftershock’s proportion. The generator is tested with mainland France data.

Mapping Earthquake Risk Sensitivity of Land Use Plan at Local Level for Sustainable Risk Sensitive Land Use Planning (RSLUP)

Risk-Sensitive Land Use Planning (RSLUP) is the process of mainstreaming disaster risk management parameters in land use planning. To ensure the effectiveness and sustainability of RSLUP, it is necessary to identify and understand the existing risk sensitivity of the land use plan. This research aims to develop a GIS-based multi-criteria zoning approach for mapping earthquake risk sensitivity of the land use plan of a local level area. For this purpose, Uttara Residential Model Town (URMT) (third phase), Dhaka, Bangladesh has been selected as the study area considering its earthquake risk for exposure to a potential earthquake. The methodology applied in this research is comprised of two steps. Firstly, assessment of the spatial earthquake risk sensitivity of the proposed land use plan of the study area based on the risk themes and corresponding risk attributes including both natural characteristics as well as built environment factors. They are macro-form risks (seismic hazard assessment), risks in urban texture (proximity from primary roads), special risk areas (geomorphic suitability and proximity from waterbody), open space scarcity risk, and risks in critical facilities (potential temporary disaster shelter and health facilities). Secondly, preparation of earthquake risk sensitivity zoning map by overlaying the spatial risk attribute maps based on weights determined through Analytical Hierarchical Process (AHP). This research brings out the importance and a methodology to assess risk sensitivity of the land use of an area at the local level, which can further foster sustainable RSLUP reflecting the risk sensitivity accordingly and effectively.

Seismic Permanent Deformation Analysis for Gravel Dams in High Altitude Meizoseismal Areas

It is commonly believed that the permanent deformation is introduced by the meizoseismal impacts of embankment dams, which is impossible to be reinstated and will further endanger the safety and normal use thereof. In this study, a three-dimensional finite element model of the dam have been established with the equivalent nodal force approach to calculate the permanent deformation of the dams under seismic protection. It was indicated by the results that the acceleration response of dams was not intense in the meizoseismal areas and the vertical seismic permanent deformation mainly occurred at the top of the dams, of which the collapse rate is less than 1% with small lateral and horizontal seismic permanent deformation. Moreover, the dam profile has been indicated with inward shrinkage upon the seismic permanent deformation, which is beneficial to the stability of the dam slopes. However, seismic measures are required to improve the seismic performance of the dam area because of the large acceleration and permanent seismic deformation at the dam tops. The research results provide a decision basis for seismic hazard assessment and reinforcement solutions of similar dams.