Abstract

In the present study, a refined procedure for the seismic evaluation and retrofitting of reinforced concrete (RC) buildings based on the ‘quadrants assessment method’ and ‘material strain limit approach’ is proposed and numerically analysed. The quadrants assessment method involves the performance point, design base shear and threshold damage limit state. Herein, four existing RC buildings (models 1–4) are considered from the Koyna– Warna region, Maharashtra (zone-IV, India). These four buildings were studied using nonlinear static adaptive pushover analysis employing the SeismoStruct software. Based on the quadrants assessment method, the three-storey RC building (model-1) was retrofitted with RC jacketing, while the other three RC buildings did not need to be retrofitted. Also, significant seismic design parameters like ductility, over strength factor, response reduction factor, etc. were evaluated before and after retrofitting. The results depict that the combination of the ‘quadrants assessment method’ and ‘material strain limit approach’ is a rapid, reliable and refined procedure for seismic evaluation and retrofitting of RC buildings.

Abstract

An effective earthquake (Mw 7.9) struck Alaska on 3 November, 2002. It ruptured 340 km along three faults namely, the Susitna Glacier, Denali and Totschunda faults in central Alaska. The earthquake was recorded at 23 stations in Alaska and the Peak Ground Acceleration (PGA) of 0.32g was recorded at station PS10, which was located 3 km from the fault rupture. In this study, strike-slip Denali fault has been considered for studying the characteristics of ground motions through modified semiempirical approach. The ground motion records of the 2002 Denali earthquake are generated through MATLAB code. The results revealed that modified semi-empirical approach is fairly good in agreement with observed ground motion records at all stations. A perfect match is observed between Fourier amplitude spectra of simulated and observed ground motions at PS09 and CARLO stations. A good match is observed between elastic response spectra of observed and simulated ground motions. Keywords: Denali Earthquake, Fourier Amplitude Spectrum, Ground Motion Prediction Equation, Synthetic Accelerogram.

Abstract

The main objective of the current study is to estimate the seismic vulnerability of buildings in Kathmandu valley through fragility curves. Since the ground motion records are limited for the April 25, 2015, Nepal earthquake, a MATLAB code is written to generate the artificial ground motion records considering each mandal as a site location. Earlier written MATLAB code has been modified with a correction function to obtain synthetic accelerograms at each station. A spatial seismic hazard distribution is plotted through Geographical Information System (GIS) software. Seismic fragility curves are drawn to estimate the damage of buildings.

Abstract

Although the city of Hyderabad in Telangana, India lies in seismic zone II, low to medium intensity tremors that pose a serious concern towards safety of the built envi- ronment are not uncommon. One such series of tremors occurred during 13–20 October 2020, in the financial district of Hyderabad and created a panic situation due to perceivable shaking and jolts with loud sounds associ- ated with hydro-seismicity. To understand the safety of the city’s built environment, a study was conducted on low, medium and tall buildings using ground motions recorded at the International Institute of Information Technology (IIIT), Hyderabad, which is 2.3 km from the epicentre. The amplification of ground motion on the second floor of the Nilgiri Building in IIIT, Hyderabad was 1.2–2.3. The vibrations recorded on the ground floor of the Nilgiri Building were used to develop a site-speci- fic response spectrum. This was further used to obtain the peak responses of the considered buildings through response spectrum analysis. The present study suggests that the low-rise buildings, mid-rise buildings and non- structural elements in high-rise buildings are under threat in the case of high-intensity earthquakes.

Abstract

Although the city of Hyderabad in Telangana, India lies in seismic zone II, low to medium intensity tremors that pose a serious concern towards safety of the built environment are not uncommon. One such series of tremors occurred during 13–20 October 2020, in the financial district of Hyderabad and created a panic situation due to perceivable shaking and jolts with loud sounds associated with hydro-seismicity. To understand the safety of the city’s built environment, a study was conducted on low, medium and tall buildings using ground motions recorded at the International Institute of Information Technology (IIIT), Hyderabad, which is 2.3 km from the epicentre. The amplification of ground motion on the second floor of the Nilgiri Building in IIIT, Hyderabad was 1.2–2.3. The vibrations recorded on the ground floor of the Nilgiri Building were used to develop a site-specific response spectrum. This was further used to obtain the peak responses of the considered buildings through response spectrum analysis. The present study suggests that the low-rise buildings, mid-rise buildings and nonstructural elements in high-rise buildings are under threat in the case of high-intensity earthquakes.

Abstract

Unmanned Aerial Vehicle (UAV) based remote sensing system incorporated with computer vision has demonstrated potential for assisting building construction and in disaster management like damage assessment during earthquakes. The vulnerability of a building to earthquake can be assessed through inspection that takes into account the expected damage progression of the associated component and the component’s contribution to structural system performance. Most of these inspections are done manually, leading to high utilization of manpower, time, and cost. This paper proposes a methodology to automate these inspections through UAV-based image data collection and a software library for post-processing that helps in estimating the seismic structural parameters. The key parameters considered here are the distances between adjacent buildings, building plan-shape, building plan area, objects on the rooftop and rooftop layout. The accuracy of the proposed methodology in estimating the above-mentioned parameters is verified through field measurements taken using a distance measuring sensor and also from the data obtained through Google Earth. Additional details and code can be accessed from h

Abstract

One thousand two hundred and ninety-six different building models were designed and analysed using SAP2000 (ref. 13). Each building model belongs to one of the types mentioned in Table 1 and have been obtained using every permutation of the parameters listed in Table 2. Timehistory (TH) analysis was performed on these models to obtain MISDR, which was then used for training and testing.

Abstract

Experiences from past earthquake disasters clearly shows that the ground motion was responsible for majority of property and life loss. Among the collapsed structures during the 1964 Niigata earthquake, the 1995 Kobe earthquake, the 1999 Kocaeli (Izmit) earthquake, the 2001 Bhuj earthquake and the 2004 Sumatra earthquake, excessive damage had occurred to pile supported bridges, towers, chimneys, high rise structures, etc. In view of this there is a need to study the complex behaviour of soil-pile-structure interaction problems. However, clause 6.1.5 IS 1893-2016, says that soil-structure-interaction (SSI) is not needed for structures founded on rock at shallow depth, but not enough details are given for SSI.

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

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.