Energy In/Out of Place

This book, and the online workshop that preceded it, are attempts to intensify the sense of place within our scholarship and in our scholarly practices. They are formed from the efforts of five research teams examining energy cultures in five different locations around the world. Team members weren’t necessarily experts on their given places, but many were bound to these sites through time, kith, and kin

Numerical simulation of soft brick unreinforced masonry walls subjected to lateral loads

Unreinforced soft-brick masonry structures comprise a large portion of buildings in earthquake prone regions of India. Recent earthquakes have extensively damaged such structures. Experimental and numerical studies on soft brick unreinforced masonry structures are scarce in literature. In this paper, numerical simulation of soft brick unreinforced masonry panels subjected to lateral loads is performed. At the panel level, the masonry structure is modelled using the micro modelling approach within a finite element framework. Monotonic load envelope curve is generated through a pushover analysis of the finite element model. The in-plane failure modes are identified, and the effect of aspect ratio and axial stress on failure is examined. Cyclic load analyses are performed on the finite element model to understand the complex hysteretic behaviour of unreinforced soft-brick masonry walls

Seismic fragility assessment of load‐bearing soft‐brick unreinforced masonry piers

Unreinforced masonry (URM) made with soft bricks comprises a large percentage of the building stock in developing countries. However, the poor performance of URM piers during earthquakes has led to renewed interest in understanding their behavior under lateral loads. Little experimental data is available on the seismic response, analysis, and design of URMs made of soft bricks. In this study, the micro-modeling technique is used to simulate the in-plane behavior of load-bearing, soft-brick URM piers. The parameters required in the constitutive models are obtained from material tests and used to develop a calibrated numerical model of the URM piers. Piers with various aspect ratios subjected to various axial stresses are numerically modeled to obtain monotonic and cyclic responses, and their critical displacement limit states are identified. Changes in the failure modes of masonry piers with variations in the aspect ratio and axial stress are established. Load-bearing piers exhibit three distinct failure modes: bed sliding, diagonal shear cracking, and flexure, depending on the aspect ratio and axial stress. The seismic fragility of each pier failure type is examined using nonlinear time history analyses. The results show that bed-sliding piers collapse at extremely low PGA levels. Piers failing through diagonal shear cracking also fail at low PGA levels. Flexural piers can resist seismic forces up to a slightly higher PGA level and thus are the last to collapse. The results also indicate that the effect of uncertainty in ground motions is more significant than the effect of variability in the masonry pier capacities. © 202

Evaluation of seismic displacement demand for unreinforced masonry shear walls

Unreinforced, non-engineered low-strength brick masonry structures comprise a large percentage of buildings in the Himalayan region and have been extensively damaged in recent earthquakes. Due to the high seismic hazard of the region and the inherent vulnerability of non-engineered masonry structures, a seismic assessment of masonry construction in this region is imperative. In this study, a suite of strong ground motions is developed using data from major Himalayan earthquakes. Using a mechanistic-based procedure for predicting the monotonic load envelope which identifies limit states of cracking, strength, and collapse using stress-based criteria, a hysteretic model was calibrated to experimental data of unreinforced masonry shear walls. Nonlinear time history analyses are performed on the validated single degree of freedom models of two unreinforced masonry walls. The analytical results correlate well with observed damage to masonry structures in Himalayan earthquakes. Peak ground acceleration of ground motion is observed to be the key parameter influencing displacement of walls. A linearly increasing trend is observed between the PGA and the observed displacement up to a PGA value of 0.1g. A weak correlation is observed between displacement and ground motion frequency parameters

A state-of-the-art review of the electrocoagulation technology for wastewater treatment

The continued increase in urbanisation and industrialisation across the world has dramatically increased the amount and variety of waste, and, in particular, wastewater, being generated. Wastewaters contain a large variety of both organic and inorganic contaminants. Various wastewater treatment technologies have been developed over the last few decades to address the increasing concern around effective contaminant removal from wastewater. Electrocoagulation (EC) is one such technology that is broad-based, highly reliable, and cost-effective. It also has a high pollutant removal efficiency and generates less sludge when compared with other techniques. However, despite being effectively used to treat a wide range of wastewater, a thorough examination of its efficiency under various process variables has not been critically examined. Various operating factors, such as pH, current density, the conductivity of the solution, electrode material, and mixing conditions, impact the electrocoagulation system. This paper aims to provide a comprehensive overview of the electrocoagulation technique and examine the current challenges to the efficiency of the technique due to the various operating conditions. Some recent advances in the EC technology that present opportunities to improve treatment efficiency and increase the scope to treat newer varieties of wastewater are addressed

Time-Frequency Analysis of Strong Ground Motions from the Mw 6.8 1991 Uttarkashi Earthquake

The stress build-up along the plate boundary of the Indian and Asian plates is a source of major destructive earthquakes in the state of Uttarakhand. The high seismic hazard in the region has led the Indian Standard Code 1893:2016 to place the entire state of Uttarakhand in seismic zone IV and V, corresponding to seismic intensity levels of severe and very severe, respectively. On 20th October 1991, a strong earthquake having a moment magnitude Mw 6.8, occurred along the Main Central Thrust in the Uttarkashi and Garhwal regions. Field observations indicated that the maximum damage intensity corresponded to a level of IX as per the modified Mercalli Intensity scale. Reconnaissance studies performed in the aftermath of the earthquake indicate that the high lateral forces generated by the horizontal shaking associated with the strong ground motions caused severe destruction of stone masonry and concrete block structures prevalent in the region. Strong ground motions from the 1991 Uttarkashi earthquake are obtained from 13 stations with hypo-central distances varying from 22 to 155 km. The 26 horizontal waveforms are analyzed and their key characteristics, such as Peak Ground Acceleration (PGA), Peak Ground Velocity (PGV), Arias Intensity (AI), and Predominant Period (Tp) and significant duration are tabulated. The frequency content is analyzed using fast Fourier transforms and the time-frequency analyses are performed using continuous wavelet transforms. The results indicate that the arrival of high-amplitude waves with high frequencies corresponding to the resonant frequency range of low-rise structures at several sites corresponds to observed enormous damage to the structures. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd

Time–Frequency Analysis of Strong Ground Motions from the 2011 Sikkim Earthquake

In 2011, a Mw 6.9 intraplate earthquake struck the state of Sikkim in India.The earthquake caused substantial damage to the built environment in Sikkim.The ground motions from the damaging earthquake were recorded at six stations in Sikkim.A detailed analysis of the key characteristics of these strong ground motions can enable a better understanding of the enormous structural damage.While it is recognized that the amplitude and frequency content of seismic waves are the two key characteristics that can be correlated with observed structural damage, it is often the sequence of arrival of frequency and amplitude, which affects the response of the structure.This sequencing is understood from continuous wavelet transforms (CWTs) which can, at any given instant of time, convey information on both the time and frequency characteristics of the seismic wave.In this paper, published reconnaissance studies are examined to tabulate significant details of the observed structural damage from six towns affected by the 2011 Sikkim earthquake.These damage observations are then correlated with the CWT representations of the seismic waves corresponding to these towns. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd

Wavelet Analysis of Near-Field Ground Motions from the Mw 7.8 2015 Gorkha Earthquake

The 2015 Nepal earthquake was one of the strongest quakes to strike the landlocked Himalayan country. The earthquake resulted in strong ground motions that severely affected various structures in the region. The unreinforced masonry structures were destroyed. Recorded ground motions from only five stations are available in the public domain. However, characterizing these ground motions in the time domain does not provide any information about the sequence of frequencies and amplitudes arriving at the station, which are key to understanding structural damage. The continuous wavelet transforms (CWT) are useful for such improved characterization of ground motions, as they provide a 3D view of time, frequency, and amplitude, thus enabling a comprehensive understanding of the damage potential of the ground motions. In this paper, recorded near-field ground motions from the earthquake are analyzed in the time and frequency domains. It is observed that the response spectra show a very wide acceleration sensitive region and some ground motions contain significant velocity pulses, both of which strongly influence structural damage. Further, it is observed that CWTs properly represent the critical characteristics of ground motions which can be correlated with the observed non-uniform damage to the built environment. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd