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While damping devices can provide supplemental damping to mitigate building vibration due to wind or earthquake effects, integrating them into the design is more complex. For example, the Canadian code does not provide building designs with inline friction dampers. The objective of this present article was to study the overstrength, ductility, and response modification factors of concrete frame buildings with inline friction dampers in the Canadian context. For that purpose, a set of four-, eight-, and fourteen-story ductile concrete frames with inline seismic friction dampers, designed based on the 2015 National Building Code of Canada (NBCC), was considered. The analyses included pushover analysis in determining seismic characteristics and dynamic response history analysis using twenty-five ground motion records to assess the seismic performance of the buildings equipped with inline seismic friction dampers. The methodology considered diagonal braces, including different 6 m and 8 m span lengths. The discussion covers the prescribed design values for overstrength, ductility, and response modification factors, as well as the performance assessment of the buildings. The results revealed that increasing the height of the structure and reducing the span length increases the response modification factors. [ABSTRACT FROM AUTHOR]

Various risks significantly influence pricing of bids and a wide range of factors impact bid pricing risks. Of these, client's reputation and the record of projects owned by a client have vital contribution on the issue. Current practices however fail to capture the impacts of client-related factors. There is a need for developing a practical quantitative approach, which enables estimators to process bid risk allocation easily. Through reliability analysis, the developed method proposed in this study enables practitioners to make informed bid/no-bid decisions based on estimating the probabilities of schedule and cost overruns. Estimating the probability of project failure enables estimators to quantify the risk element of bid price. In addition, schedule and cost overrun cumulative probability distributions can be used to estimate the expected value of these variables. The practicability of this proposed method is tested by empirical data obtained from 40 university construction projects of one client, for estimating the bid price of a low-rise building. For researchers, findings provide illuminating insight into the potential of using reliability analysis as a valuable tool for bid decision-making practices. So too, the proposed method offers a blueprint for estimating and calculating time and contingency - and managing associated risks - in planning construction projects. The contribution of this study for the world of practice lies in providing a simple, rapid and cost-effective method for bid decision-making processes. [ABSTRACT FROM AUTHOR]

The non-structural elements (NSE) of a building could be hazardous in the event of an earthquake. Hence, a seismic risk assessment is critical for identifying hazardous elements. This paper proposes a method for visualizing a building's NSEs to assess their seismic risks using Building Information Modeling (BIM) to visualize and automatically mapping risk factors. The relevant Canadian and American standards were used to calculate the level of risk associated with each NSE for a typical six-story residential building. [ABSTRACT FROM AUTHOR]

This study presents a workable procedure for developing and updating deterioration prediction models based on the results of a Non-Destructive Evaluation (NDE) technique, Ground Penetrating Radar (GPR). To this end, a system reliability based deterioration model was developed for a simply-supported reinforced concrete bridge deck, designed according to the Canadian Highway Bridge Design Code (CHBDC-S6). The superstructure element-level deteriorated conditions for different time intervals were applied in the non-linear finite element model developed for the entire bridge deck, and the system level reliability indices were estimated accordingly. The salt contamination was assumed to affect the top surface, soffits of the deck, and beams due to infusion of de-icing salt material. The resulting primary deterioration model was updated based on a GPR test localized defect map that was obtained for an existing bridge with similar plan dimensions. The results indicate that the assumed conservative uniformly defected superstructure is reliable in this case, that is, the estimated reliability indices for the uniform and localized defect plans do not differ considerably. [ABSTRACT FROM AUTHOR]

The effect of process parameters viz., welding speed, pulse energy and frequency on the aspect ratio and the peak temperature in the numerical simulation of Nd: YAG laser welding of Hastelloy C-276 is presented. The experimental conditions are designed based on Taguchi L9 orthogonal array and the simulation is performed in SYSWELD 16, a 3 D software package. The optimized parameters for attaining a maximum aspect ratio and a minimum peak temperature (responses) were determined by computing the Signal-to-Noise Ratio (SNR). Mathematical model based on regression analysis was developed for predicting the responses using statistical software Minitab-16. Further, the simulation results are correlated with the regression and artificial neural network models. The deviation is estimated to be less than 10% indicating their effectiveness in predicting the responses. The experimental macrograph for the optimized condition is concurrent with the numerical simulation. [ABSTRACT FROM AUTHOR]

Transportation of prefabricated modules is a critical process in modular construction and can cause additional stresses which may damage individual modules, leading to additional costs and time during the installation and operational phase if damaged parts are not timely restored or replaced. Therefore, utilizing a tracking and condition monitoring system is useful for modular building manufacturers to detect damaged modules upon arrival to the project job site. The tracking system, developed in this study, consists of a acceleration-sensor-based data acquisition (DAQ) module and a storage module, along with automated data analysis module to assess the structural condition of prefabricated building modules during transportation. The system uses the acceleration Root Mean Square (RMS) parameter and unsupervised clustering algorithms for damage detection. After detailed analysis, using performance measurement techniques: confusion matrix and accuracy score , it was found that the DBSCAN clustering algorithm yielded full accuracy score in the case of more than one level of damage compared to k-means , mean shift, and agglomerative clustering algorithms, which yielded accuracy scores of 0.81, 0.79, and 0.78 respectively. The developed system addresses existing challenges of cost and complexities associated with commercially available hardware systems and can provide evidence to support manufacturers' insurance claims on repair and/or replacement costs. However, the developed system should be tested further on more prefabricated building modules instrumented with a larger number of sensors. • This study introduced an automated data driven-based monitoring system. • A sensor-based data acquisition and storage module was developed. • A workflow was developed to detect and classify transportation-induced structural damages. • A visualization-based method was developed to identify the failed sensors. • The developed system can be used as a quick and effective solution to ensure all prefabricated building modules are transported safely. [ABSTRACT FROM AUTHOR]

The objective of this research is to evaluate the reliability of bridge decks that use nonconventional materials or structural forms such as externally restrained deck systems where the available deterioration models developed for conventional systems are not applicable. The method developed here adopts the reliability theory and establishes a deterioration model for such bridge decks based on their failure mechanisms. The externally restrained deck is an innovative structural system introduced about a decade ago to the construction industry and provides corrosion-free replacement for conventional reinforced concrete decks. Because there is no established deterioration model available for these innovative systems, it is difficult to predict the reliability of such bridge decks at different instances of time. The developed method has been applied to an innovative structure with an externally restrained deck system, namely the Crowchild Trail Bridge, in Calgary, Canada, as a case study. A finite-element model of the bridge has been developed and calibrated with experimental results giving static deflection, vibration characteristics, load distribution, and crack patterns. The system reliability has been determined at different times using the proposed method. The results show that the design is quite conservative and there is a very low probability of failure for such a system during its design life. [ABSTRACT FROM AUTHOR]

While the authors of current bridge management systems (BMSs) have noted the need for expanding the systems to include more functional aspects of bridge performance, to date no method has been proposed for the incorporation of bridge rating against climate change impacts. This paper presents a new procedure for extending the asset management scope for highway bridges to incorporate the bridges' resilience or vulnerability against climate change impacts. The proposed procedure draws from the projected demands of climate change--a worldwide phenomenon that is expected to produce its most dramatic impacts in cold regions. The following bridge resilience indicators are proposed: abutment washout, pier scour, abutment erosion, deck flooding, and abutment permafrost stability. The formulations for the proposed indicators require weights to be assigned to each indicator. The other requirement comprises capacity measures that indicate how well a bridge is equipped to withstand the projected climatic effects. The new procedure has been applied to 14 highway bridges in the Canadian Arctic to demonstrate how public investments in transportation infrastructure could be better managed and protected. The method comes with an Inspection Form that transportation agencies and their bridge inspectors can use for rating bridges on climate change resilience. [ABSTRACT FROM AUTHOR]

Two-way concrete flat slabs provide a number of benefits for office buildings, parking garages and apartments - for example, reduced formwork, prompt erection, minimal increase in story heights, and flexibility of partitions. Concrete flat slabs could be vulnerable to punching shear failure in the event of a fire. There are a limited number of studies available on concrete flat slabs for punching shear failure in fire. In the present study, a set of six reinforced concrete slabs are tested in ambient and elevated temperature to investigate their strength characteristics in punching shear failure. A model to estimate the punching shear capacity is developed and correlated with the available experimental data. Using the above model, a detailed parametric study is carried out to study the effects of various factors affecting the punching shear behavior. It is also shown that the existing code provisions for punching shear cannot predict slab behavior under fire exposure in some cases. [ABSTRACT FROM AUTHOR]

The concrete gravity dams are designed to perform satisfactorily during an earthquake since the consequence of failure is catastrophic to the downstream communities. The foundation in a dam is usually modeled by a substructuring approach for the purpose of seismic response analysis. However, the substructuring cannot be used for solving nonlinear dynamic problems that may be encountered in dam-reservoir-foundation systems. For that reason, the time domain approach is preferred for such systems. The deconvolved earthquake input model is preferred as it can remove the seismic scattering effects due to artificial boundaries of the semi-infinite foundation domain. Deconvolution is a mathematical process that allows the adjustment of the amplitude and frequency contents of a seismic ground motion applied at the base of the foundation in order to get the desired output at the dam-foundation interface. It is observed that the existing procedures of deconvolution are not effective for all types of earthquake records. A modified procedure has been proposed here for efficient deconvolution of all types of earthquake records including high-frequency and low-frequency ground motions. [ABSTRACT FROM AUTHOR]

In structural health monitoring (SHM), various sensors are installed at critical locations of a structure. The signals from sensors are either continuously or periodically analyzed to determine the state and performance of the structure. An objective comparison of the sensor data at different time ranges is essential for assessing the structural condition or excessive load experienced by the structure which leads to potential damage in the structure. The objectives of the current study are to establish a relationship between the data from various sensors to estimate the reliability of the data and potential damage using the statistical pattern matching techniques. In order to achieve these goals, new methodologies based on statistical pattern recognition techniques have been developed. The proposed methodologies have been developed and validated using sensor data obtained from an instrumented bridge and road test data from heavy vehicles. The application of statistical pattern matching techniques are relatively new in SHM data interpretation and current research demonstrates that it has high potential in assessing structural conditions, especially when the data are noisy and susceptible to environmental disturbances. [ABSTRACT FROM AUTHOR]

Damage often causes changes in the dynamic characteristics of a structure such as frequencies and mode shapes. Vibration-based damage identification techniques utilize the changes in the dynamic characteristics of a structure to determine the location and extent of damage in the structure. Such techniques are applied in this study to the Crowchild Bridge, a steel-free deck continuous bridge located in western Canada. While the numerical models of the bridge are correlated with the measured dynamic characteristics, computer simulation is used to study the identification of a number of different damage patterns, and the effects of measurement errors and incomplete mode shapes on the quality of results are evaluated. The effectiveness of some selected damage identification techniques is examined; the potential difficulties in identifying the damage are outlined; and areas of further research are suggested. A three-dimensional finite-element model and a simple two-dimensional girder model of the bridge have been constructed to study the usefulness of the selected damage identification methods. Another promising damage detection method proposed here is based on the application of neural networks that combines a vibration-based method. [ABSTRACT FROM AUTHOR]

The seismic design provisions in the current edition of the National building code of Canada significantly differ from those in the earlier version of the code . Although the code has moved from the earlier prescriptive provisions towards a more performance-based design, such design principles have not yet been fully implemented. In the present work, four ductile steel moment-resisting frame buildings with heights of 5, 10, 15, and 20 storeys, were designed for Vancouver using the newer code, and their performances were studied to determine the level of seismic protection implied in the code. Synthesized and scaled real ground motion records were used to evaluate the nonlinear dynamic response of these structures. Although the buildings achieved the collapse prevention performance objective of the code, variations in evaluated performance parameters for the different buildings were observed. Also, building performance was found to be affected by the presence of infill walls, as well as by the nature of selected ground motion records and the methods used to scale them to Vancouver uniform hazard spectra. [ABSTRACT FROM AUTHOR]

Fire following an earthquake is an important factor causing damage to buildings and life-line structures. Therefore, besides satisfying structural design requirements for normal loads, such as dead and live loads including the seismic hazard, buildings should also be designed to withstand the fire following earthquakes for a certain minimum duration as required for a desired level of performance. This period of time will allow occupants to evacuate the building safely and the emergency crews to cope with the fire. Also, it is essential to reduce the post-earthquake fire (PEF) ignitions and minimize the damage to active fire protection systems as much as possible to prevent the spread of fire. This paper presents a state-of-the-art review on the PEF hazard and discusses the causes, mitigation measures, and performance of building structures under this hazard. Mitigation measures that could be developed based on the experience from the structural engineering field are identified. Both local and global approaches that should be taken to mitigate the PEF hazard, including structural and nonstructural design, various urban planning aspects, and their interactive combinations, are discussed. Based on the review, it is concluded that that there is a strong need for the development of guidelines for structural fire safety design for PEF scenarios. In addition, appropriate analysis and numerical simulation techniques for the evaluation of the structural performance under earthquake-induced fire conditions need to be developed. It is also necessary to conduct experimental studies to validate such numerical models and refine them. Les incendies suivant un séisme sont une importante cause de dommages aux bâtiments et aux structures vitales. Ainsi, en plus d’être conçus pour répondre aux exigences de conception structurale pour les charges normales telles que les charges permanentes et en mouvement, incluant le risque sismique, les bâtiments devraient être conçus pour résister aux incendies suivant les séismes pour une durée minimale requise par le niveau de rendement désiré. La durée permettra aux occupants d’évacuer le bâtiment en toute sécurité et aux équipes d’urgence de combattre l’incendie. De plus, il est essentiel de réduire l’allumage d’incendies suivant les séismes et, dans la mesure du possible, de minimiser les dommages causés aux systèmes actifs de protection contre les incendies afin de prévenir la propagation de l’incendie. Cet article présente une revue de la technologie récente sur les dangers d’incendies suivant les séismes et analyse les causes, les mesures d’atténuation et le comportement des structures de bâtiments lors de tels dangers. Les mesures d’atténuation qui peuvent être établies en se basant sur l’expérience de l’ingénierie des structures sont identifiées. Les approches locales et globales qui devraient être prises pour atténuer le danger d’incendie suivant un séisme, incluant la conception structurale et non structurale, divers aspects de la planification urbaine ainsi que leurs combinaisons interactives sont abordées. Cette revue conclut qu’il est fortement nécessaire de développer des lignes directrices de conception structurale de sécurité incendie pour les cas d’incendies suivant un séisme. De plus, il faut développer une analyse appropriée ainsi que des techniques de simulation numériques pour l’évaluation du comportement structural lors d’incendies causés par un séisme. Il est également nécessaire de réaliser des études expérimentales pour valider et raffiner de tels modèles numériques. [ABSTRACT FROM AUTHOR]

Located in Victoria, British Columbia (BC), Canada, the Portage Creek Bridge is a 124 m long, three-span structure with a reinforced concrete deck supported on two reinforced concrete piers, and abutments on H piles. The bridge was designed prior to the introduction of current bridge seismic design codes and construction practices. Therefore, it was not designed to resist the earthquake forces as required by today's standards. The bridge is on a route classified as a Municipal Disaster Route scheduled to be retrofitted to prevent collapse during a design seismic event, with a return period of 475 years (i.e., an event with 10% probability of exceedance in 50 years). Conventional materials and methods were used to retrofit most of the bridge. The dynamic analysis of the bridge predicted the two tall columns of Pier No. 1 will form plastic hinges under an earthquake resulting in additional shear to the short columns of Pier No. 2. A non-linear static pushover analysis indicated that the short columns will not be able to form plastic hinges prior to failure in shear. The innovative solution of Fiber Reinforced Polymer wraps (FRPs) was chosen to strengthen the short columns for shear without increasing the moment capacity. The FRP wraps and the bridge were instrumented as one of 36 demonstration projects across Canada sponsored by ISIS (Intelligent Sensing for Innovative Structures) Canada, a federally funded Network of Centres of Excellence, to assess the performance of FRP and the use of FOS (Fiber Optic Sensors) for Structural Health Monitoring (SHM). The two columns of the bridge pier were strengthened with GFRP (Glass Fiber Reinforced Polymer) wraps with eight bi-directional rosette type strain gauges and four long gauge fiber optic sensors attached to the outer layer of the wraps. In addition, two 3-D Crossbow accelerometers are installed on the pier cap above the columns and a traffic web-cam mounted above the deck at the pier location. The data is collected through high speed internet line to an interactive web page at ISIS Canada's web site. The bridge can now be monitored from anywhere. The data collected so far has proved the reliability of the instrumentation system. [ABSTRACT FROM AUTHOR]

Model updating is an important step for correlating the mathematical model of a structure to the real one. There are a variety of techniques available for model updating using dynamic and static measurements of the structure's behavior. This paper concentrates on the model updating techniques using the natural frequencies or frequencies and mode shapes of a structure. An iterative technique is developed based on the matrix update method. The method has been applied to the finite element models of a three span continuous steel free deck bridge located in western Canada. The finite element models of the bridge have been constructed using three-dimensional beam and facet shell elements and the models have been updated using the measured frequencies. From the study it is clear that the initial model needs to be built such that it represents the actual structure as closely as possible. The results demonstrate that the difference between the modal parameters from the model and field tests affect the quality of the model updating process. [ABSTRACT FROM AUTHOR]

Thin shells are prone to fail by buckling. In most of the practical situations, shell structures have membrane stresses as well as bending stresses and the response of these shells becomes nonlinear. Linearization of the nonlinear equilibrium equations gives rise to an algebraic eigenvalue problem, solving which, buckling load is obtained. Eigenvalue buckling analysis is computationally much cheaper than nonlinear analysis involving tracing the load-deflection path and finding the corresponding collapse load. But buckling loads obtained by eigenvalue buckling analysis are always overestimated, and for systems with large prebuckling rotations this approach may give highly unconservative results. For better prediction of the actual buckling load of a structure, a new methodology involving the proper combination of eigenvalue buckling analysis and geometric nonlinear analysis is used here. This method is computationally cheaper than nonlinear buckling analysis but more reliable than linear buckling analysis. The methodology is used to calculate the buckling load of shells of revolution. The conical frustum shell element with two nodal circles is used in the present study. Also discussed is how to include the effect of initial geometric imperfection in buckling analysis. [ABSTRACT FROM AUTHOR]

Criteria weights formulation is the most essential component of a multi-criteria prioritization scheme. The research reported in this paper sought to critically compare a recently developed multi-criteria optimization criteria weights method to the well-known analytic hierarchy process (AHP) as well as the method employed by the bridge management software BrM (formerly Pontis), which is licensed to all 50 State Departments of Transportation in the United States. Using four criteria for demonstration (bridge performance, utility, vulnerability to climate-triggered extreme events, and vulnerability to climate-triggered extreme loads), the new method clearly separates the concept of prioritization from the concept of optimization. The study demonstrates that there is an important and practical difference between a suitable criteria weight formulation for asset management optimization, on one hand, and the type of formulation required for a general selection problem, on the other hand. More importantly, the new method performs better than both the AHP and the BrM on all the important measures. [ABSTRACT FROM AUTHOR]

Ground-Penetrating Radar (GPR) is a popular non-destructive technique for evaluating RC bridge elements as it can identify major subsurface defects within a short span of time. The data interpretation of the GPR profiles based on existing amplitude-based approaches is not completely reliable when compared to the actual condition of concrete with destructive measures. An alternative image-based analysis considers GPR as an imaging tool wherein an experienced analyst marks attenuated areas and generates deterioration maps with greater accuracy. However, this approach is prone to human errors and is highly subjective. The proposed model aims to improve it through automated detection of hyperbolas in GPR profiles and classification based on mathematical modeling. Firstly, GPR profiles are pre-processed, and hyperbolic reflections were detected in them based on a trained classifier using the Viola–Jones Algorithm. The false positives are eliminated, and missing regions are identified automatically across the top/bottom layer of reinforcement based on user-interactive regional comparison and statistical analysis. Subsequently, entropy, a textural factor, is evaluated to differentiate the detected regions closely equivalent to the human visual system. These detected regions are finally clustered based on entropy values using the K-means algorithm and a deterioration map is generated which is robust, reliable, and corresponds to the in situ state of concrete. A case study of a parking lot demonstrated good correspondence of deterioration maps generated by the developed model when compared with both amplitude- and image-based analysis. These maps can facilitate structural inspectors to locally identify deteriorated zones within structural elements that require immediate attention for repair and rehabilitation. [ABSTRACT FROM AUTHOR]

The primary objective of structural health monitoring (SHM) is to determine whether a structure is performing as expected or if there is any anomaly in its behavior compared with the normal condition. It is also useful in detecting the existence, location, and severity of damage. Vibration-based damage detection methods are very frequently used in SHM. However, because of complicated features of real-life structures, there are uncertainties involved in the key input parameters (e.g., measured frequencies and mode shape data), which affect the performance of these methods. If vibration-based methods are incorporated with semianalytical methods, such as statistical pattern recognition techniques, better accuracy can result in structural health assessment. This paper explores the statistical pattern recognition techniques for damage detection and/or degradation in structures. A case study, the Portage Creek Bridge in Victoria, British Columbia, Canada, has been used. The following two approaches of the statistical pattern recognition techniques have been used: statistical pattern comparison and statistical model development. After filtering and normalizing the data obtained from the SHM system installed in the bridge, damage sensitive features have been extracted by autoregressive modeling of the time series data. Both idle and excited states of the bridge are considered in this case. From the statistical analysis of the strain and acceleration data, although the bridge is in a good condition, there is a small but steady deterioration in its performance. The study also demonstrates the feasibility of the statistical pattern recognition techniques in assessing the structural condition of a practical structure. [ABSTRACT FROM AUTHOR]

Reliable construction project cost estimation relies on accurate quantity takeoffs (QTOs), traditionally done with error-prone 2-D drawings, but the emergence of Building Information Modeling (BIM) has improved QTO speed, accuracy, and reliability. However, the quality of BIM models can influence quantity accuracy, an aspect often overlooked in research on automating QTO with BIM. This paper develops an integrated framework to automatically extract and visualize construction quantities from BIM models. The system includes a Quantity Precision Check (QPC) module for automating more accurate QTO outputs. These outputs are then automatically transferred to an external database and visualized through a user-friendly dashboard on the Microsoft Power BI platform. This dashboard allows for comparisons between 2-D and BIM quantities and helps track changes in quantities over time due to design changes. The system was successfully validated in an infrastructure construction project in Canada, where it identified a 39% inconsistency in wall elements' material quantities and reduced steel quantity by 10% due to design changes. Overall, the system offers a speedy, reliable, and efficient tool for construction estimators, site managers, and cost control teams to provide accurate quantities to the procurement team and make swift decisions in response to design change impacts on construction costs. • This study introduces an automated QPC/QTO system for architectural and structural BIM models. • A QPC/QTO system workflow was developed to automatically calculate their quantities and check their accuracy in the BIM model. • The Data Extraction and Analysis Module was developed to automatically calculate, and check the accuracy of the quantities of each category. • The Data Visualization Module was developed to visualize the final QTO results and inconsistencies in BIM parameters after each update. • The system can be used as a fast and reliable tool for construction estimators to provide accurate quantities to the procurement team. [ABSTRACT FROM AUTHOR]

According to the Canada infrastructure report 2016, 62.6% of roads in Canada are in a good condition, nevertheless, with current investment rates, significant road networks will suffer a decline in their condition and will be vulnerable to sudden failure. Accordingly, this paper tackles the pavement resilience from an asset management perspective and aims at developing a resilience-based asset management framework for pavement networks. This was carried out through the development of five components: (i) a central database of asset inventory, (ii) a pavement condition and level of service assessment models, (iii) a regression of the effect of freeze–thaw on pavement network, (iv) a financial and temporal models, and (v) an optimization model to formulate the mathematical denotation for the proposed resilience assessment approach and integrate the above components. The model results were promising in terms of maintaining pavement resiliency by selecting a near optimal intervention plan that meets the municipality limitations. [ABSTRACT FROM AUTHOR]

Vibration based method for Structural Health Monitoring (SHM) utilizes the dynamic response of a structure measured using a set of sensors to identify the modal properties and potential damage in the structure. Signal processing tools are widely used for analyzing these response signals. Change in the dynamic characteristics of a structure can provide an indication of damage. However, a direct comparison of the vibration signals at different periods of time may not be sufficient to identify the modal properties and the damages. Therefore, it is important to analyze the vibration signals to extract the modal properties and the morphologies of the changes in these response-signals and correlate them with the types, location and magnitude of structural damage. This present article presents a set of novel techniques for system identification and damage detection in structures based on their vibration signals. The modal parameters are estimated using Frequency Domain Decomposition (FDD) and the response signals are decomposed into intrinsic mode functions (IMF) using empirical mode decomposition (EMD) technique. Those IMFs are then processed with Hilbert-Huang transform (HHT) to obtain their corresponding Hilbert spectra, which allows the estimation of the time-varying instantaneous properties of those response signals. Then a marginal Hilbert spectrum (MHS)-based technique has been applied on the Hilbert spectrum coefficients to calculate associated Damage Indices (DI). The proposed method was tested using experimental tests conducted on a cantilever steel beam prototype at the CBRI laboratory, Roorkee, India, and a three-storey steel frame at Concordia University, Canada. Modal parameters were identified from system identification and the damage locations were determined by comparing the DIs of the damaged steel beam and frame with that of the corresponding baseline (undamaged) structures. [ABSTRACT FROM AUTHOR]

Due to the excessive use of disposable face masks during the COVID-19 pandemic, their accumulation has posed a great threat to the environment. In this study, we explored the fate of masks after being disposed in landfill. We simulated the possible process that masks would experience, including the exposure to sunlight before being covered and the contact with landfill leachate. After exposure to UV radiation, all three mask layers exhibited abrasions and fractures on the surface and became unstable with the increased UV radiation duration showed aging process. The alterations in chemical groups of masks as well as the lower mechanical strength of masks after UV weathering were detected to prove the happened aging process. Then it was found that the aging of masks in landfill leachate was further accelerated compared to these processes occurring in deionized water. Furthermore, the carbonyl index and isotacticity of the mask samples after aging for 30 days in leachate were higher than those of pristine materials, especially for those endured longer UV radiation. Similarly, the weight and tensile strength of the aged masks were also found lower than the original samples. Masks were likely to release more microparticles and high concentration of metal elements into leachate than deionized water after UV radiation and aging. After being exposed to UV radiation for 48 h, the concentration of released particles in leachate was 39.45 μL/L after 1 day and then grew to 309.45 μL/L after 30 days of aging. Seven elements (Al, Cr, Cu, Zn, Cd, Sb and Pb) were detected in leachate and the concentration of this metal elements increased with the longer aging time. The findings of this study can advance our understanding of the fate of disposable masks in the landfill and develop the strategy to address this challenge in waste management. [Display omitted] • Overloading landfills with disposable face mask wastes raises environmental concerns. • The aging and degradation of disposable masks were accelerated in landfill. • The physicochemical properties of masks changed after aging in landfill leachate. • Microparticles and metal elements were released from aged masks in leachate. [ABSTRACT FROM AUTHOR]