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Steel, an indispensable enduring metal used in all facets of life, contributes significantly to the global economy. Atmospheric corrosion is the inexorable natural degradation of alloys to ores in the presence of the atmosphere. The rate of deterioration is a decisive life factor of environmentally exposed steel, and it is necessary to trace its dynamics in different atmospheres at different exposure times. Spatial hazard corrosion maps for rural and urban conditions have been developed for over five decades to apprehend metal loss or corrosion rate dynamics in diverse conditions (PS11, PS21 and PS31) across the Indian subcontinent. The impact of cumulative hazards on Indian standard structural steels is interpreted to perceive sectional losses of beams in various environments for different zones. Sectional losses are greater in zone 5 of the PS31 environment and are significant in junior and lightweight beams, while heavy beams are relatively unaffected.

Reinforced concrete (RC) bridges deteriorate due to strength loss induced by aging of the structure, extreme weathering conditions and unplanned increased service loads. These load variations and aging factors can compromise structural reliability and reduce the service life for continuous satisfactory operation of service bridges in the future. Accurate prediction of bridge functionality relies on reasonable models of bridge strength and applied loads, and time-dependent reliability assessments can be used to gain a reliable understanding of bridge conditions so that appropriate solutions can be found. In this work, the reliability of bridges under harsh conditions was studied using time-variant and time-invariant reliability models in which both load and resistance are considered as time-dependent parameters. Combinations of the condition rating and time-dependent load were used to gain accurate insights into the degradation of the structural resistance of existing bridges. The results of this study showed the significant impact of aging and the influence of traffic loads on the service life of both national highway bridges and rural road service bridges. These observations could be used to devise appropriate planning strategies and plan rational decisions to ensure bridge safety in the future.

The ability to assess and evaluate the condition of existing bridges adequately and accurately is a critical aspect of bridge maintenance and management, which involves condition assessments. Multiple hazards can affect existing bridges, making them vulnerable or risky, and any decision support concerning their management requires special attention. A rational and systematic framework for making practical decisions about the hazards present in a region and the appropriate level of risk is presented in this paper. An analytical hierarchy process (AHP) framework is proposed to rank hazards in hierarchical order based on a region's characteristics and a suitable analysis range, which provides the degree of risk that could jeopardise bridges. The proposed method can assist decision makers in selecting appropriate strategies for improving existing bridges. As a result, bridge inspection costs can be significantly reduced, maintenance and repair funds can be more effectively allocated and the safety, mobility, longevity and reliability of highway transportation assets can be improved. The approach was used in a case study of existing reinforced concrete (RC) bridges in the Barak Valley region in Assam, India. Such an approach is novel to the Indian subcontinent.

In this study, a methodology is being proposed for performing seismic fragility analysis of corrosion affected bridges located in the coastal region of India. The study performed adopting this advanced corrosion rate model capturing nonlinearity that necessitates pitting corrosion as a realistic corrosion degradation mechanism rather than conventional uniform corrosion. With the application of advanced corrosion model, a distinct improvement over seismic fragility assessment achieved due to its capability to capture nonlinearity in the overall process of corrosion transport. The proposed model exhibits the corrosion rate accelerates after initial cracking of the concrete cover until at a phase, when severe cracking occurs leading to spalling of concrete. Based on the current degradation mechanism, the study estimates the capacity limit states of deteriorating reinforced concrete (RC) T-girder bridges as well as the impact of bridge degradation on the seismic response assessed using nonlinear time history analysis (NLTHA). However, the NLTHA of the finite element bridge models performed considering erraticism about material properties, geometries, ground motions and corrosion degradation parameters such that the uncertainties associated with the bridge population could be realistically taken into account as per the basic corrosion mechanism. Comparisons are drawn with respect to general and pitting corrosion as well as the adverse effect of pitting corrosion on the bridge service life has been identified. Thus, the output of the seismic fragility analysis would indicate some useful information in understanding the nonlinear crack growth of bridge vulnerability in marine environment, such that proper maintenance strategies could be framed for adequate safety of the highway infrastructure system for its enhanced design life.

Site-specific assessment of wind speed is essential in analysing the susceptibility of any slender structure. With the increasing number of occurrences of extreme wind events in the Indian subcontinent, a quantitative measure of wind hazard based on recent developments has become the need of the hour for India. The Indian standard (IS 875: Part 3) is a national code for reference to the basic wind speed in India, essentially for infrastructural planning and design of mid-rise to tall structures, and the specified basic wind speeds in the code are computed based on a 50-year return period by using the Gumbel probability distribution. However, recently reported cyclones were extreme wind events that already exceeded the specified value in the code. The Gumbel distribution (type I) is applied in the present study by using the method of moments on the long-term wind data (yearly maxima) considering the past few decades (40 years) available for forecasting the wind speed at different return periods. The Anderson–Darling test results are also accommodated to establish the accuracy of the tail behaviour of the statistical distribution used, where the p-value is found to be less than 0.05. Further, in the present study, a site-specific basic wind speed map is also proposed considering latest event data. Indeed, based on the present study, a 100-year return period for basic wind speed is recommended instead of 50 years to ensure enhanced structural safety and serviceability during the design life.

Steel is an imperative engineering material due to its endurance; it accounts for a significant part of the world economy. It has enormous demand all over the world for its extensive use in construction and other industries. These industries are experiencing inevitable atmospheric exposure, and exposed steel structures are rapidly deteriorating due to induced atmospheric corrosion. This study assessed and interpreted trends in atmospheric corrosion rates in India for the last 39 y, and spatially mapped seasonal decade-by-decade trends. Northeast India has been identified as the most corrosive region in the country, with the rainy season being the most corrosive season. Corrosion maps for India are prepared on the basis of 39 y of atmospheric data. A corrosion zone map is prepared to classify the country into five different zones based on the rate of atmospheric corrosion. Long-term atmospheric corrosion rates are projected for the next 50 y in all major cities across the country. Long-term corrosion is estimated to reduce the rate of atmospheric corrosion by 81% after 10 y of exposure and 91% after 50 y of exposure.

Determination of structural damage index (DI) is tedious and time consuming process using the available conventional methods. Traditional multivariable regression (MVR) model had been fitted by res...

Structural damage index (SDI) is determined to implement damage-based design (DBD) which is a useful design philosophy in terms of safety and reliability nowadays. Literature is available to determ...

The probabilistic approach for estimating deterioration of existing RC bridges due to multiple hazards becomes an important subject for the bridge management system. In the present study, a multi-h...

This paper investigated multi-objective seismic damage assessment procedure. Primarily, it estimates damage index (DI) of reinforced concrete-framed residential buildings situated in seismic zone V as per IS-1893-2016 (0.36 g) in India. Three-dimensional DI has been estimated for a four-storey building by Park–Ang method. With the increase in the storey number, calculation of Park–Ang DI becomes tedious and more time-consuming procedure; therefore, this method is not suitable for large-scale damage investigation. To avoid the complexity, a simplified method has been proposed to estimate global damage index (GDI) of buildings easily. For this purpose, a four-storey residential building having plan aspect ratio 0.5, 0.75 and 1 has been analysed. In this study, the most influential parameters such as inter-storey drift, joint rotation and peak roof displacement have been combined to estimate GDI of structures directly. Based on this study, it has been observed that 0.893 times ground-storey DI (i.e. local DI) estimates similar Park–Ang GDI for a four-storey building. In this study, it has been observed that ground floor experiences maximum damage and top floor experiences least damage for all cases. The proposed approach effectively estimates reliable GDI that is useful for small- to large-scale damage assessment of buildings.

Stochastic tools have been developed to estimate the potential for tsunami generation in a particular region under consideration. This paper identifies 13 probable zones on the earth where there is a high likelihood for tsunami generation in the future. The conditional probabilities for future tsunami and earthquake occurrences are estimated for all the identified zones. Also, total probabilities for future tsunami events are computed. Forecasting is done on the basis of conditional probability obtained using the best fit model among Lognormal, Gamma, Log-Logistic and Weibull distributions. The obtained probabilities of tsunami are validated by calculating the region-specific threshold probabilities. Also, a country wise expectation of anticipated tsunami is developed for each zone. Zones 5 (Northwest U.S.A and Bering Sea Islands), 6 (Kuril & Kamchatka Islands) and 7 (Japan, Northeast China and Korea) have the highest ratio of tsunamigenic earthquakes to the total number of earthquakes. The zone 7 has the highest probability of tsunami occurrence in the near future as calculated from the total probability theorem. However, zones 1 (Southwest coast of South American continent), 7 and 11 (Papua New Guinea and Solomon Islands) are expected to experience a tsunami in the near future (before 2022) as per the current forecasting study.

Deterioration of RC bridges due to chloride induced corrosion is a grave concern worldwide. It occurs essentially, when the reinforcement embedded in concrete is exposed to marine or aggressive environments. Over the past few decades, many studies aimed at determining the parameters influencing the service life of structures affected by reinforcement corrosion. The aim of the present work is to put forward a reliable and simple service life model for predicting the useful life or period of RC bridges affected by chloride ingress and to validate the output of the model with the deterioration of an existing RC bridge structure. The application of the service life model has been done in an Indian bridge in the context of coastal environment. Parametric studies have been conducted in the model for examining the effect of various parameters such as water-cement ratio, reinforcement diameter, cover thickness, type of binder and corrosion rate on the variation of service life of the RC bridge structure. The results of the parametric study explained in a detailed manner so as to get an actual insight of the structural degradation mechanism for structures exposed to chemically aggressive environments.

This paper investigated multi-objective seismic damage assessment procedure. Primarily, it estimates damage index (DI) of reinforcement concrete (RC) framed low-rise residential buildings under the...

The present study discusses the amalgamation of the deterioration (aging) hazard along with earthquake hazards directly affecting in the bridges of Barak valley (Assam). In the proposed approach, the Weibull parameter employed for determining hazard function ha(t) of the bridges due to aging, however, active faults with their PGA values extracted, and responsible for generating higher magnitude of earthquake in the region identified as well as the mean annual rate of exceedance for different magnitude (λm) calculated. The combination of deterioration due to aging and earthquake hazard rate provides how bridges are affected by maturity and sudden violent shock of the ground in a seismically active prone region. The combined hazard function shows a significant reduction in service life having an increase in hazard rate for different magnitudes (>5, >6, >7, and >8). Further, the Northeast region of India is prone to earthquakes of higher magnitudes, and the area is tectonically active. Numerous researches demonstrated in the past to estimate the multi-hazards effects on the structures. Indeed, such assessment has not been attempted in the NEI region; hence, this proposed approach and the selected objectives would provide significant ideas and facts about the condition of bridges to make rational decisions for the bridge management authorities in terms of safety, rehabilitation, repair, and inspection of the bridges available in the Barak valley region.

A damage index study is necessary for evaluating the post-earthquake health of structures, and it is also required in performance based seismic design (PBSD), where engineers can design a s...

Concrete structure may be affected due to antagonistic environment, hence responsible for reducing in their strength, stiffness and reliability. However, in general, this unreliability may damage the safety and design life of the concrete structure, therefore, in order to evaluate the current condition of such structures, time dependent reliability assessment of concrete ageing structure essentially must be considered. In this work, the influence on safety and serviceability of structures alongwith various uncertainties such as time variant loading state [i.e. considering dead, live, seismic and wind loads alongwith their effects in combination] of the structure and the effect of ageing on strength-deterioration phenomenon due to various-environmental aggressive parameters need to be extended and examining that the reliability is vulnerable to the selection of initial component strength, however, strength-deterioration models exhibits less sensitivity to the corresponding component strength within the structural system. The critical component need to be identified before performing, conversely, the system reliability helps to reduce the size of analysis. To keep sustaining of reliability, the effect of periodic inspection and maintenance presented in this study throughout the design life/service period of a structure (in order to examine/show the time variant effects in various selected inspection time intervals that yields valuable results) presented in this study.

This study presents the spatial variation of seismicity parameters and artificial neural network (ANN) model for earthquake magnitude prediction in the northeast region of India considering updated earthquake catalogue of magnitude Mw ≥ 4.0 that occurred from year 1731 to 2015 in the study area. The study area has been divided into 17 seismic source zones keeping in view the spatial variation in earthquake occurrences, distribution pattern of events and orientation of seismic sources. Seismicity parameters were estimated for each source zone as well as for the whole study area. The estimated ‘b’ value in this study varies from 0.50 to 0.84 in different seismic source zones and for the whole study area it is found as 0.77. The proposed ANN technique to predict the possible magnitude of earthquakes in the identified seismic source zones is based on feedforward backpropagation neural network model with single hidden layer. Total five input parameters namely, longitude, latitude, elapsed time between two events, cumulative magnitude probability and seismic energy and one output parameter namely, magnitude of earthquakes were used in ANN. The ‘b’ value estimated in this study was used as an input unit in ANN in calculating the cumulative magnitude probability for different zones. The performance of ANN was evaluated by estimating the mean absolute error (MAE), sum of squared error (SSE) and Mean squared error (MSE). And the results obtained in this study show that the ANN model yields good prediction accuracy for earthquake magnitude in NE India.

This paper deals with the description of the probabilistic methodology to evaluate the failure probability of the bridges in the Cachar district (Assam, India) based on the present condition data. Condition assessment of the bridge decks is done by the help of visual inspection following as per National Bridge Inventory (NBI) Survey procedure adopting the condition rating of bridges is evaluated and categorized. The aging and maturity of the bridge are the important factor, the work thinking adopted is from initial age of construction to till date and estimation of the adequate probabilistic distribution with respect to the data available of the study area selected, and then the parameters of probability distribution and its contents come to act in finding of the probability failure percentage. The paper also establishes the facts about the bridge deck failure percentage in 20 years (in time) and the condition of the bridge deck in 10% probability failure state; with respect to years and the outcome it shows that the condition of the rural bridges (being in higher condition rating) are in unsatisfactory state than the highway bridges and also shows the difference in condition of the concrete and pre-stressed bridges in the district. The concept of the study would provide a rational decision-making idea about the condition of the in-service bridges and probability of failure of the deck component available, which however will ensure the maintenance service and its proper cost utilization.

The utilization of fibers and waste materials from industry in concrete is making a remarkable change in properties of concrete. For the present study a comparison of effectiveness in strength properties when rubber, GGBS and silica fumes are used as a substitute for fine aggregate and cement respectively and alkali-resistant glass fibers are added in concrete. The effect of addition or replacement of fibers and materials on strength parameters are studied. Fine aggregate is replaced with crumb rubber and cement is also replaced with GGBS in addition to Silica fumes, as required target strength is not attained when fine aggregate is replaced with rubber. A maximum of 30% of replacement of rubber is done, depending upon the results, it is known that replacement of rubber should be restricted and low w/c ratios should be adopted. Simultaneously, in another mix glass fibers are added to plain concrete in varying percentages, maximum of 1.5%. It is observed that the use of glass fibers in concrete mixes increases tensile strength without affecting its compressive strength, thus making it beneficial to use glass fibers as there is significant increase in strength. Depending upon the percentage of replacement and addition six trial, mixes are adopted. The strength comparison is done between the six trial mixes with nominal mix of grade M25 and are presented here.

In this study, an effort has been made to perform seismic hazard analysis (SHA) for the state of Assam, considering earthquake catalog collected since 1761–2015 using PSHA and DSHA methods at bed r...

This study presents the forecasting of time and magnitude size of the next earthquake in the northeast India, using four probability distribution models (Gamma, Lognormal, Weibull and Log-logistic) considering updated earthquake catalog of magnitude Mw ≥ 6.0 that occurred from year 1737–2015 in the study area. On the basis of past seismicity of the region, two types of conditional probabilities have been estimated using their best fit model and respective model parameters. The first conditional probability is the probability of seismic energy (e × 10 20 ergs), which is expected to release in the future earthquake, exceeding a certain level of seismic energy (E × 10 20 ergs). And the second conditional probability is the probability of seismic energy (a × 10 20 ergs/year), which is expected to release per year, exceeding a certain level of seismic energy per year (A × 10 20 ergs/year). The logarithm likelihood functions (ln L) were also estimated for all four probability distribution models. A higher value of ln L suggests a better model and a lower value shows a worse model. The time of the future earthquake is forecasted by dividing the total seismic energy expected to release in the future earthquake with the total seismic energy expected to release per year. The epicentre of recently occurred 4 January 2016 Manipur earthquake (M 6.7), 13 April 2016 Myanmar earthquake (M 6.9) and the 24 August 2016 Myanmar earthquake (M 6.8) are located in zone Z.12, zone Z.16 and zone Z.15, respectively and that are the identified seismic source zones in the study area which show that the proposed techniques and models yield good forecasting accuracy.

The lateral displacement of Reinforced Concrete (RC) frame building during an earthquake has an important impact on the structural stability and integrity. However, seismic analysis and design of RC building needs more concern due to its complex behavior as the performance of the structure links to the features of the system having many influencing parameters and other inherent uncertainties. The reliability approach takes into account the factors and uncertainty in design influencing the performance or response of the structure in which the safety level or the probability of failure could be ascertained. This present study, aims to assess the reliability of seismic performance of a four storey residential RC building seismically located in Zone-V as per the code provisions given in the Indian Standards IS: 1893-2002. The reliability assessment performed by deriving an explicit expression for maximum roof-lateral displacement as a failure function by regression method. A total of 319, four storey RC buildings were analyzed by linear static method using SAP2000. However, the change in the lateral-roof displacement with the variation of the parameters (column dimension, beam dimension, grade of concrete, floor height and total weight of the structure) was observed. A generalized relation established by regression method which could be used to estimate the expected lateral displacement owing to those selected parameters. A comparison made between the displacements obtained from analysis with that of the equation so formed. However, it shows that the proposed relation could be used directly to determine the expected maximum lateral displacement. The data obtained from the statistical computations was then used to obtain the probability of failure and the reliability.

Structural damage can be controlled in performance based seismic design (PBSD) according to the requirement under a certain hazard level. During strong ground motion (GM) such buildings suffer minor to major damages depending on the shaking level of GM. The available damage assessment methods are complex, tedious and time-consuming procedure. In the present study, a simplified empirical model has been proposed that computes the GDI in a single step using the engineering demand parameters (EDPs) namely joint rotation, Inter storey drift (IDR), peak roof displacement. It has been found that the proposed method gives results of GDI near to Park-Ang model. It has been observed that the ground storey suffers maximum damage for all cases. Further, a relationship has been established between ground story DI and global DI. The proposed model effectively berlongferestimates reliable DI and could be used as a powerful tool for estimating seismic damage in buildings, especially for massive structures.

The detonation of an explosive charge extremely near or above the ground could be devastating causing deformation to the structural frame of the building, cracking of walls, exploding huge areas of windows and shattering all kinds of life saving systems. Depending upon the type and size of explosive used, the possible structural collapse happens when the blast waves produced during explosion, impacting the structure over time. This paper presents to study the characteristics of blast waves and understanding the relationships between various parameters considered in blast loading such as incident overpressure, reflected overpressure, phase duration and scaled distance. Analysis and quantification of uncertainties of the TNT equivalency of different explosives with respect to pressure and impulse observed. Focus was given to formulate an empirical equation from the extracted experimental data considering the influential parameters affecting the blast resistant design that governs the modeling of blast loads. This equation could help in predicting the safe distances beyond which the blasting of different types of explosives would cause minimum impact on the structure. Thus for designing a structure to be resisting blast weight, the foremost important task is to have a realistic overview about the prediction of pressures impacting on a structure and this paper gives essential outline of the detonating effects due to various types of explosives on structures.

There is saying that earthquakes do not kill people however, the structures do, therefore, the earthquake mitigation becomes vital for the structure located in the earthquake-prone region. One such tool for the risk investigation is fragility analysis. It shows the probability of exceedance (POE) of certain damage level at particular intensity measures (IM). The method at first used for the nuclear power plants in 1984 and from 1990 its utilization was connected in building too. In the present work, the four story reinforced concrete (RC) framed residential building with different bay ratios such as 0.25, 0.50, 0.75 and 1.00 considered. The Non-Linear Time History Analysis (NLTHA) carried out and the inelastic behavior of the building is captured in the form of damage measures such as maximum inter-story drift ratio (MIDR), roof displacement (Δ), and the joint rotation (Ѳ). The two types of fragility curves has been obtained such as (1) considering the effects of only MIDR, and (2) considering the combined effects of MIDR, Δ, and Ѳ. However, past work by researchers is mostly dealing with the former type of fragility assessment. While for later type of fragility curve, limited work has been done. This paper presents the effects of the bay ratio (plan aspect ratio) in the fragility curve. It concluded that, combining the effects of response parameters has tremendous effect on the shape of the fragility curve and its effect must be considered in the study of fragility analysis.

The performance and reliability of highway bridges deteriorate with respect to time due to aggressive environmental conditions such as corrosion, freeze–thaw, alkali–silica reaction and increasing road freight volumes, resulting in effective influences in service life of the structure as well as potential loss of the economy. Thus, it becomes necessary to consider life-cycle cost with these aggressive environmental conditions during the survival period of degrading highway bridges for better planning and management. In this study, an implementation of time-dependent reliability approaches in the serviceability and safety evaluation of highway girder bridges under aggressive environmental conditions has been investigated for both time-dependent non-stationarities in the loads and strength. The influence of several parameters such as live-load variations, rate of occurrence of live load, degradation of initiation time, strength degradation rate, correlation of strength and number of bridge girders affected on the time-dependent structural reliability of bridges are examined. Parametric analysis is carried out to show the responsiveness of time-dependent structural reliability with the initial strength of component and strength deterioration models. Thus, the analysis of results indicates helpful information that could be employed for superior forecasting of the effective service life of degrading RC bridges as well as in predicting the optimum time for periodic inspection and creating maintenance strategies for continued service life of the bridges.

This paper presents the results of the nonlinear time history analysis of six different reinforced concrete moment frames. The frames were designed using two major seismic design methods as Force Based Design (FBD) and Direct Displacement Based Design (DDBD) in which former is a conventional method while later one is a performance based approach of design. However, in this study, 4, 8 and 12 stories RC framed building with two × three bays were designed according to Indian standard and the Federal Emergency Management Agency (FEMA) considering two design approaches (FBD and DDBD) studied. Analysis and design for this study performed using SAP2000 v15.1 tool. Both design approaches performed using nonlinear time history analysis for five different real recorded ground motions of north-eastern region, India. The parameters such as inter-storey drift, displacement, material strain, and ductility demand obtained from the analyses of the frames designed using both design methods are noted and compared. This study examined, discussed and shown about the applicability of existing methods adopted considering the FBD and DDBD in a cost-effective manner to achieve desired level of performance.

Fly ash (FA) is a byproduct obtained after burning of coal in power plant as waste, however considered as one of the building materials having reasonable binding properties. Indeed, in this study, FA is being used as a surrogate material of cement essentially to study the cyclic loading characteristics applying in a beam-column joint (BCJ) to examine the seismic performance during high magnitude earthquake (Mw>6) having larger duration sustaining of corner frequency of an event responsible for damages. Nevertheless, in a BCJ, beam is primarily designed considering under-reinforced condition or allowed the section to fail through plastic hinge formation (i.e. ductility) so that dissipation of energy could be controlled by forming capacity of column-beam ratio 1.4 as per IS-1893-2016 and IS-456. Conversely, in this study, five types of exterior BCJs prepared and investigated experimentally for a curing of 28 days. Further, flexural strength ratio of the sample maintained as 2.0. It has been observed that, 20FAS28 sample provides as well as performed well in the higher displacement level than control concrete. Indeed, stiffness degradation exhibits slightly higher than the control concrete. On the other hand, there is 11 % higher ductility as well as 7 % higher dissipation energy observed for 20FAS28 sample than other samples. Further, it has been found that brittleness index (BI) is similar for 20FAS28 sample with control concrete. This study explores identifying the suitability of FA ranges and helps to understand the effects of admixtures for it’s effective utilization in the field application as an alternative material and thereby expecting minimizing the construction cost.