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general neural network based methodology that has the potential to replace the computationally-intensive site-specific seismic analysis of structures is proposed in this paper. The basic framework of the methodology consists of a feed forward back propagation neural network algorithm with one hidden layer to represent the seismic potential of a region and soil amplification effects. The methodology is implemented and verified with parameters corresponding to Delhi city in India. For this purpose, strong ground motions are generated at bedrock level for a chosen site in Delhi due to earthquakes considered to originate from the central seismic gap of the Himalayan belt using necessary geological as well as geotechnical data. Surface level ground motions and corresponding site-specific response spectra are obtained by using a one-dimensional equivalent linear wave propagation model. Spectral acceleration values are considered as a target parameter to verify the performance of the methodology. Numerical studies carried out to validate the proposed methodology show that the errors in predicted spectral acceleration values are within acceptable limits for design purposes. The methodology is general in the sense that it can be applied to other seismically vulnerable regions and also can be updated by including more parameters depending on the state-of-the-art in the subject. [ABSTRACT FROM AUTHOR]

A mathematical model based on the three-dimensional (3-D) boundary element method (BEM), including porous and non-porous breakwaters, is developed to determine the wave trapping characteristics of porous breakwater over the partially reflecting walls with variable bathymetry. In this formulation, a special form of Green's function is utilized to solve the Laplace equation in the 3-D domain to enhance the numerical accuracy. The order of convergence of the present numerical scheme shows a better convergence rate than simple Green's function. The numerical scheme with and without the porous breakwater is compared with the analytical studies of Yu et al. (1994) and Lee (1969), respectively. In addition, the numerical simulation for sloping bathymetry is conducted and compared with the analytical results of Wang et al. (2011). The numerical validation exhibits good agreement with and without porous breakwaters. Based on validation, the current numerical scheme is implemented on the realistic Visakhapatnam Port, Andhra Pradesh, India, at four different synthetic key locations S1 to S4 to analyze the hydrodynamic performance of porous and non-porous breakwaters. Wave amplification is determined for different porosity parameters, including variable linear resistance and inertial coefficient, and different reflecting coefficients of the port wall. Moreover, the wave amplitude within the Visakhapatnam Port is also estimated through a contour plot with and without porous breakwaters to identify the safe location for the moored ship. Overall, the porosity of the breakwaters and partial reflection coefficient on the port wall plays a significant role in inducing or reducing the resonance inside the port. [ABSTRACT FROM AUTHOR]

In this study, soil response was carried out for the Greater Delhi region. A folded Proterozoic formation was identified as Delhi ridge, passes through its central part along SSW-NNE direction, and appears to be a main geomorphic feature for the study area. The Delhi ridge is an exposed quartzite rock of about 10-100 m wide and ~25 km long with gentler dipping both toward east and west. We have considered the exposed part as an outcrop side near the ridge axis and the dipping area as rigid base away from the ridge axis for ground motion study during the occurrence of the 25 November 2007 earthquake with magnitude M 4.3 (Richter scale) that occurred at Delhi-Haryana State boundary. The degree of shaking was very strong and reported major cracks in the buildings near the epicenter area. We have studied the soil response parameters at the surface level, considering horizontally stratified soil layers above rigid base. The equivalent linear method was used for soil response analysis at 25 sites in Greater Delhi area. The peak amplification factors vary from 3.2 to 5.9 and peak resonance frequency varies from 1.2 to 5.3 Hz. The correlation among the peak amplification factor ( A) and frequency ( f) was empirically established as A = 0.36 f + 3.60. Increasing peak amplification factor was found at sites with increasingly thicker alluvium deposit with lower frequency contains ground motion and vice versa. Seismic zoning map was also reconstructed for peak amplification factors and predominant periods for the study area for the mitigation purposes of earthquake damage. The average shear wave velocity up to 30 m soil depth is also obtained for site classification. The average velocity to 30 m [ $$ \overline{{V_{\text{s}} }} (30) $$] is a widely used parameter for classifying sites for predicting their potentiality to amplify seismic shaking. A lower value [ $$ \overline{{V_{\text{s}} }} (30) $$] thus yields a more conservative estimate of ground motion, which generally increases as $$ \overline{{V_{\text{s}} }} (30) $$decreases. Present estimate of $$ \overline{{V_{\text{s}} }} (30) $$varies from 315 to 419 m/s. In this study, we have identified two site classes C and D, as per National Earthquake Hazard Reduction Program. The city planner or engineers can directly use these data for site-specific assessment during retrofitting of the existing structure, demolition of the old buildings and design a new structure to avoid major destruction of the buildings due to future earthquake. [ABSTRACT FROM AUTHOR]