Abstract

Hazard plays a vital role in assessing the risk of any area. For earthquake hazard estimation, it is essential to obtain ground motion records from various seismic stations. However, it is not always easy to get ground motion data. The present study is an attempt to generate ground motions of the recent September 24, 2013, Pakistan earthquake using modified semi-empirical approach, which is based on w2 model. The first part of the method considers a time series having the basic spectral shape of acceleration. The deterministic model of rupture source has been used in the second part ofthe method to simulate the envelope of accelerogram. For the study, a MATLABcode is written to generate synthetic accelerograms atstations Awaran, Panjgur, Tagas, Korak, and Gajar. The results are compared with Ground Motion Prediction Equation (GMPE) proposed byRamkrishnan et al., in 2019 [1]. The PGAvalues obtained from modified semi-empirical method gives satisfactorily good results in comparison with the PGAvaluesfromGMPE. However, slight variation is observed between synthetic accelerogram PGAvalues and GMPE values at Gajar, Korak, Tagas, Panjgur stations.

Abstract

An effective earthquake (Mw 7.9) struck Alaska on 3 November 2002. This earthquake ruptured 340 km along Susitna Glacier, Denali, and Totschunda faults in Central Alaska. The peak ground acceleration (PGA) was recorded about 0.32 g at station PS10, which was located 3 km from the fault rupture. The PGA would have recorded a high value if more instruments had been installed in the region. A numerical study has been conducted to find out the possible ground motion record that could occur at maximum horizontal slip during the Denali earthquake. The current study overcomes the limitation of number of elementsto model the Denali fault. These numerical results are compared with observed ground motions. It is observed that the ground motions obtained through numerical analysis are in good agreement with observed ground motions. From numerical results, it is observed that the possible expected PGA is 0.62 g at maximum horizontal slip of Denali fault.

Abstract

The advent of the cracked moment of inertia (MoI) in Indian code provisions has sparked many discussions and confusions regarding what MoI is to be used in the design of structures in service load case and ultimate load case. The intent of this study is to understand the uncracked and cracked moment of inertia, what code provisions recommend, their applicability and the possible reasoning behind the recommendations. Solved examples are presented along with this review study to clear the usage of cracked MoI and u n d e r s t a n d t h e s i g n i  c a n c e o f s u c h recommendations.

Abstract

Earthquake safety of buildings is one of the primary concerns of structural engineers throughout the world. The performance of buildings during past earthquakes has brought out the lacunas in design, analysis and execution of these structures. The constant endeavour for uniqueness has led to the distribution of irregularities along the plan and height of buildings. One of such attempts is the development of Open Ground Storey (OGS) buildings. It is the dominant parameter having vertical irregularity, if not rectified, may often lead to the collapse of structure. Reinforced concrete building with OGS; absence of infill wall in a ground storey, is prevailing construction practice in most places in India. It causes a sudden decrease in lateral stiffness (K) and strength (V), from adjacent upper to ground storey, results in accumulation of stresses due to large lateral displacement in ground storey columns to cause soft storey effect. The problem can be solved by increasing K and V of the ground storey relative to the adjacent upper storey. Seismic codes specify the design process for buildings with OGS by relative K and V of ground and adjacent upper storey. Quantifying design criteria for such structural configurations based on Design Amplification Factor (DAF) for ground storey columns is preferable. K and V of storey depends on masonry strength, central opening (OP) in infills and interaction between wall infill and frame. In the current study, DAF is proposed to overcome OGS effect considering the above parameters. Additional parameters like Stiffness factor (KF) and strength factor (VF), ratios of elastic lateral stiffness (KE) and maximum

Abstract

In this study, a three-dimensional, four-storied, reinforced concrete (RC) building is designed for seismic zone-IV and seismically evaluated for different infill configurations along with consideration of openings in infills to develop a realistic model. Four models are considered, i.e. model I (full RC-infilled frame without lintel beam), model II (bare frame without lintel beam), model III (full RC-infilled frame with lintel beam) and model IV (bare frame with lintel beam). In this study, we have evaluated the effect of lintel beams on response reduction factor of the frame structure. The nonlinear static adaptive pushover analysis has been done using Seismostruct program. In seismic design, the response reduction factor (R-factor) reduces from the elastic to inelastic strength. The R-factor is one of the design tools to show the level of inelasticity in a structure and so it has significant importance in the earthquake engineering field. The response reduction factor mainly consists of ‘ductility reduction factor’ and ‘over strength factor’, which are evaluated from static adaptive pushover analysis. Ultimately the response reduction factor is obtained for the building and compared with the value recommended by IS 1893 Part-1 (2016). The results depict that the R-factor values of full RC-infilled frames and bare frames with incorporation of lintel beams are higher than other frames without lintel beam. However, R-factor values of bare frames are lower than the corresponding values recommended in the BIS code.

Abstract

Construction of buildings without keeping enough setback from plot boundary is very common practise in India. This lead to very closely spaced buildings with practically zero or few mm gap between them. The intension behind this is to utilize the maximum plot area, without knowing the consequences of damage due to pounding during moderateto-severe earthquake shaking. In this study, an attempt is made to check the adequacy of separation distance clause of IS 1893:2016 and also a comparison is made with similar clauses in international codes of practise. For this purpose, four low to mid-rise RC buildings located in seismic zone IV were designed as per IS 456:2000 and IS 1893:2016. These buildings are assumed to be closely spaced with each other, in pair of two, for four different cases. Further, the linear and non-linear time history analysis (NLTHA) were carried out by considering ground motion time histories of three moderate earthquakes recorded in India. From the study, it was found that the separation distance clauses prescribed in IS 1893-2016 are on conservative side

Abstract

Estimating the time, location and the size of an earthquake event using neural networks is an emerging technology. Present study aims to predict the near future earthquake events in each of the regions partitioned as clusters of epi-central locations of earthquakes related to Indian subcontinent. K-means clustering algorithm is applied to develop a catalogue of earthquake epicenters. Two approaches are considered for the purpose of forecasting. In the first approach regions obtained as clusters are considered as the area sources. The distribution of time series of (temporal distribution) events are divided into five time periods viz., 15 days, 30 days, 60 days, 90 days and 180 days. The accuracy of forecasting a magnitude for the next time period is studied using application of Recurrent Neural Network In the second approach the seismic data of each cluster is further grouped into three categories of magnitude viz., minor (≤ 4 Mw), moderate (between 4 Mw and 6 Mw) and strong (> 6 Mw). Accuracy of forecasting for each of the group belonging to the clusters is computed considering the same five time periods. The epicentral locations represented as latitude and longitude is the inputs for recurrent neural network. The results show that accuracy of second approach is significantly more than first approach. Finally, an attempt has been made to compare the accuracy level of Recurrent Neural Network method with the accuracy level of Gutenberg Richter law in predicting the earthquakes for future 60 days. It has been observed that Gutenberg-Richter law poorly forecasts near future earthquake.

Abstract

Buildings damaged in past earthquakes have exemplified the poor performance of reinforced concrete moment resisting frame (RC MRF) buildings due to inadequate design and wrong construction practices. The only way to avoid damage to existing buildings is to retrofit them. There is a large stock of RC MRF buildings constructed as per old Indian standards. With the latest revisions in codal provisions, these buildings are considered to be inadequately designed. Therefore, a large stock of existing buildings needs to be retrofitted. However, retrofitting of houses is not a common practice among the general public in India. To encourage retrofitting among the general public, the efficacy of retrofitting needs to be proven with the well-laid process. In this paper, a case study is done to understand the performance of G+5 storey RC MRF precode building after partial and full column retrofitting. Pushover Analysis (POA) is performed to obtain the capacity of the precode building. The capacity is compared with the seismic demand of that area to decide whether retrofitting is required or not. Initially, ground storey columns are retrofitted and POA is performed to study the damage distribution and obtain the updated capacity curve. It is observed that damage shifted to the first storey. Further, the first storey columns are retrofitted and POA is performed again. From the hinge mechanism, it is observed that the damage propagated to the second storey. Further, the second storey columns are retrofitted and POA is performed again to obtain updated capacity and

Abstract

In building construction, reinforced concrete (RC) Frame structures are frequently used due to ease of construction and rapid progress of work. In this study, two types of infill’s are used ie, unreinforced masonry infill and semi-interlocked masonry infill. For the analysis purpose of infill, a double strut nonlinear cyclic model is used. The main objective of the study is to investigate the importance of interlocked brick infill in the RC frame structure. For understanding the same, nonlinear static pushover analysis is carried out on analytical models using finite element based software, SeismoStruct. The response reduction factor components such as ductility reduction factor and overstrength factors were computed from nonlinear static pushover analysis and finally, the response reduction factor is calculated for all models. The primary focus is given to numerical modeling, nonlinear behavior of brick masonry RC buildings subjected to lateral loads and calculation of the response reduction factor of'RC'infilled frames with different aspect ratios.

Abstract

A ground-structure vibration response study was carried out at the Ramappa Temple near Warangal, Telangana, India, shaken by underground blasting undertaken at the neighbouring Devadula Lift Irrigation Project to build water tunnels. The intensities of vibrations were examined–subsurface and ground vibrations were measured using velocity meters, and shaking at the temple using accelerometers. The study concluded that high-frequency vibrations of the ground were filtered by the soft natural clay bed underneath, and vibrations at the temple structure were small and well below the levels that can cause damage to it. Here we present the scientific findings of the vibrations recorded during the blasts and their implications.