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Solomon Tesfamariam
School of Engineering, The University of British Columbia, Kelowna, BC, Canada

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Journal article
Published: 27 July 2021 in International Journal of Disaster Risk Reduction
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Critical infrastructures are an integral part of our society and economy. Services like gas supply or water networks are expected to be available at all times since a service failure may incur catastrophic consequences to the public health, safety, and financial capacity of the society. Several resilience strategies have been examined to reduce disaster risk and evaluate the downtime of infrastructures following destructive events. This paper introduces an indicator-based downtime estimation model for buried infrastructures (i.e., water and gas networks). The model distinguishes the important aspects that contribute to determining the downtime of buried infrastructure following a hazardous event. The proposed downtime model relies on two inference methods for its computation, Fuzzy Logic (FL) and Bayesian Network (BN), which are adapted for the current application. Finally, through a case scenario, a comparison of the two inference methods, in terms of results and limitations, is presented. Results show that both methods incorporate intuitive knowledge and/or historical data for defining fuzzy rules (in FL) and estimating conditional probabilities (in BN). The difference stands in the interpretation of the outcome. The output of the FL is a membership that defines how well the downtime fits the fuzzy levels while the BN output is a probability distribution that represents how likely the downtime is in a certain state. Nevertheless, both approaches can be utilized by decision-makers to easily estimate the time to restore the functionality of buried infrastructures and plan preventive safety measures accordingly.

ACS Style

Melissa De Iuliis; Omar Kammouh; Gian Paolo Cimellaro; Solomon Tesfamariam. Quantifying restoration time of pipelines after earthquakes: Comparison of Bayesian belief networks and fuzzy models. International Journal of Disaster Risk Reduction 2021, 64, 102491 .

AMA Style

Melissa De Iuliis, Omar Kammouh, Gian Paolo Cimellaro, Solomon Tesfamariam. Quantifying restoration time of pipelines after earthquakes: Comparison of Bayesian belief networks and fuzzy models. International Journal of Disaster Risk Reduction. 2021; 64 ():102491.

Chicago/Turabian Style

Melissa De Iuliis; Omar Kammouh; Gian Paolo Cimellaro; Solomon Tesfamariam. 2021. "Quantifying restoration time of pipelines after earthquakes: Comparison of Bayesian belief networks and fuzzy models." International Journal of Disaster Risk Reduction 64, no. : 102491.

Journal article
Published: 15 May 2021 in Probabilistic Engineering Mechanics
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Generally, in designing nonlinear energy sink (NES), only uncertainties in the ground motion parameters are considered and the unconditional expected mean of the performance metric is minimized. However, such an approach has two major limitations. First, ignoring the uncertainties in the system parameters can result in an inefficient design of the NES. Second, only minimizing the unconditional mean of the performance metric may result in large variance of the response because of the uncertainties in the system parameters. To address these issues, we focus on robust design optimization (RDO) of NES under uncertain system and hazard parameters. The RDO is solved as a bi-objective optimization problem where the mean and the standard deviation of the performance metric are simultaneously minimized. This bi-objective optimization problem has been converted into a single objective problem by using the weighted sum method. However, solving an RDO problem can be computationally expensive. We thus used a novel machine learning technique, referred to as the hybrid polynomial correlated function expansion (H-PCFE), for solving the RDO problem in an efficient manner. Moreover, we adopt an adaptive framework where H-PCFE models trained at previous iterations are reused and hence, the computational cost is less. We illustrate that H-PCFE is computationally efficient and accurate as compared to other similar methods available in the literature. A numerical study showcasing the importance of incorporating the uncertain system parameters into the optimization procedure is shown. Using the same example, we also illustrate the importance of solving an RDO problem for NES design. Overall, considering the uncertainties in the parameters have resulted in a more efficient design. Determining NES parameters by solving an RDO problem results in a less sensitive design.

ACS Style

Souvik Chakraborty; Sourav Das; Solomon Tesfamariam. Robust design optimization of nonlinear energy sink under random system parameters. Probabilistic Engineering Mechanics 2021, 65, 103139 .

AMA Style

Souvik Chakraborty, Sourav Das, Solomon Tesfamariam. Robust design optimization of nonlinear energy sink under random system parameters. Probabilistic Engineering Mechanics. 2021; 65 ():103139.

Chicago/Turabian Style

Souvik Chakraborty; Sourav Das; Solomon Tesfamariam. 2021. "Robust design optimization of nonlinear energy sink under random system parameters." Probabilistic Engineering Mechanics 65, no. : 103139.

Journal article
Published: 10 May 2021 in Computers and Geotechnics
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A new efficient approach for uncertainty quantification of pipeline structural response undergoing reverse-slip fault rupture displacements in sand is presented using multi-fidelity Gaussian processes. Uncertainty quantification problems generally take large numbers of scenarios to be analysed considering variations in the influencing parameters. Analysing large numbers of computationally expensive detailed geo-technical numerical models is practically not feasible. Hence, a multi-fidelity approach employing Gaussian process is proposed to tackle this problem which combines the accuracy of a relatively few number of detailed geo-technical numerical models and the efficiency of large numbers of simplified numerical models to track the uncertainty response. The detailed model utilizes a previously validated pipe-soil finite element (FE) model including a non-linear sand constitutive model implemented in finite element software ABAQUS. The simplified model utilizes beam element pipe and bi-linear soil springs. The multi-fidelity model is first trained using data from high-fidelity and low-fidelity model analyses, thereafter cross-validated and subsequently used to quantify uncertainty in the peak compressive strains generated and to identify the most sensitive input variables. Finally, fragility curves are derived for a site specific pipe-soil fault rupture problem.

ACS Style

Sandip Dey; Souvik Chakraborty; Solomon Tesfamariam. Multi-fidelity approach for uncertainty quantification of buried pipeline response undergoing fault rupture displacements in sand. Computers and Geotechnics 2021, 136, 104197 .

AMA Style

Sandip Dey, Souvik Chakraborty, Solomon Tesfamariam. Multi-fidelity approach for uncertainty quantification of buried pipeline response undergoing fault rupture displacements in sand. Computers and Geotechnics. 2021; 136 ():104197.

Chicago/Turabian Style

Sandip Dey; Souvik Chakraborty; Solomon Tesfamariam. 2021. "Multi-fidelity approach for uncertainty quantification of buried pipeline response undergoing fault rupture displacements in sand." Computers and Geotechnics 136, no. : 104197.

Journal article
Published: 06 May 2021 in Engineering Structures
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This paper presents the results of shake table tests and periodical friction tests to evaluate the dynamic and long-term performance of a novel connector using a wood friction (friction-based connectors). The friction-based connectors are a quite simple system in which the wood is bolted transversely to generate friction force. The shake table tests showed that the type of hysteresis loop of the wall with the friction-based connectors exhibited a bilinear, and significantly reduced the maximum response displacement even when the conventional walls were combined. In addition, more than 60% of the total energy was absorbed by the wall with friction-based connectors, even the load bearing ratio of the wall was about 30%. The periodical friction tests of the connectors and the wall with the friction-based connectors indicated that the friction forces were mostly linked to the relaxation behavior of wood, and although the friction forces were significantly affected by humidity fluctuations, long-term friction forces were expected to be maintained.

ACS Style

Yoshiaki Wakashima; Koichiro Ishikawa; Hidemaru Shimizu; Akihisa Kitamori; Doppo Matsubara; Solomon Tesfamariam. Dynamic and long-term performance of wood friction connectors for timber shear walls. Engineering Structures 2021, 241, 112351 .

AMA Style

Yoshiaki Wakashima, Koichiro Ishikawa, Hidemaru Shimizu, Akihisa Kitamori, Doppo Matsubara, Solomon Tesfamariam. Dynamic and long-term performance of wood friction connectors for timber shear walls. Engineering Structures. 2021; 241 ():112351.

Chicago/Turabian Style

Yoshiaki Wakashima; Koichiro Ishikawa; Hidemaru Shimizu; Akihisa Kitamori; Doppo Matsubara; Solomon Tesfamariam. 2021. "Dynamic and long-term performance of wood friction connectors for timber shear walls." Engineering Structures 241, no. : 112351.

Journal article
Published: 20 January 2021 in Structural Safety
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This paper proposes a subset simulation (SS) based approach for space and time-dependent reliability analysis of corroding pipelines. It is assumed that the pipeline can fail either due to leakage and/or burst. We propose two distinct approaches for tackling the problem. In the first approach, we treat the problem as a time-variant system reliability problem. The problem is formulated as a series system where failure at one of the defect locations will result in failure of the pipeline. This approach is particularly suitable when there are only a limited number of corrosion defects. In the second approach, the reliability analysis problem is treated as a ‘space-time variant’ reliability analysis problem. This approach is particularly suitable when exact knowledge about the number of defects is not available. In both the approaches, the time-dependent probability of failure is represented in an auto-regressive form such that the probability of failure at a given time can be computed based on the probability of failure at the previous time and an incremental failure probability. A simple composite limit-state function is proposed for computing the incremental failure probability. SS is used for computing the initial and incremental failure probabilities. To illustrate performance of the proposed approach, four pipeline problems representing different scenarios are considered. For all cases, the proposed approach is found to yield highly accurate results.

ACS Style

Souvik Chakraborty; Solomon Tesfamariam. Subset simulation based approach for space-time-dependent system reliability analysis of corroding pipelines. Structural Safety 2021, 90, 102073 .

AMA Style

Souvik Chakraborty, Solomon Tesfamariam. Subset simulation based approach for space-time-dependent system reliability analysis of corroding pipelines. Structural Safety. 2021; 90 ():102073.

Chicago/Turabian Style

Souvik Chakraborty; Solomon Tesfamariam. 2021. "Subset simulation based approach for space-time-dependent system reliability analysis of corroding pipelines." Structural Safety 90, no. : 102073.

Journal article
Published: 13 January 2021 in Theoretical and Applied Fracture Mechanics
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We present a novel stochastic extended finite element (S-XFEM) method for solving fracture mechanics problems under uncertainty. The proposed S-XFEM couples XFEM and a novel multi-output Gaussian process based machine learning algorithm, referred to as the hybrid polynomial correlated function expansion (H-PCFE). With this approach, the underlying stochastic fracture mechanics problem is decoupled into multiple classical fracture mechanics problems. Since solution of a classical fracture mechanics problem is computationally expensive, we utilize the H-PCFE model as a surrogate to emulate the behavior of the system. Training samples required for training the H-PCFE model are generated by using the XFEM. Because of the intrinsic capability of XFEM in providing a mesh insensitive solution, the proposed approach can provide reasonable result from a coarse mesh. On the other hand, H-PCFE is capable of providing highly accurate solution from very few training samples. Overall, the proposed S-XFEM is highly efficient in solving stochastic fracture mechanics problems. The proposed approach is used for solving three stochastic fracture mechanics problems. Different case studies involving reliability analysis and stochastic fracture propagation have been reported. The procedure yields highly accurate results for all problems, indicating its possible applications to other large scale systems.

ACS Style

Edel R. Martínez; Souvik Chakraborty; Solomon Tesfamariam. Machine learning assisted stochastic-XFEM for stochastic crack propagation and reliability analysis. Theoretical and Applied Fracture Mechanics 2021, 112, 102882 .

AMA Style

Edel R. Martínez, Souvik Chakraborty, Solomon Tesfamariam. Machine learning assisted stochastic-XFEM for stochastic crack propagation and reliability analysis. Theoretical and Applied Fracture Mechanics. 2021; 112 ():102882.

Chicago/Turabian Style

Edel R. Martínez; Souvik Chakraborty; Solomon Tesfamariam. 2021. "Machine learning assisted stochastic-XFEM for stochastic crack propagation and reliability analysis." Theoretical and Applied Fracture Mechanics 112, no. : 102882.

Journal article
Published: 24 October 2020 in Soil Dynamics and Earthquake Engineering
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We introduced shape memory alloy (SMA) assisted nonlinear energy sink (NES) with negative stiffness for seismic vibration mitigation. The ability of dissipating energy through a hysteretic phase transformation of its microstructure triggered by cyclic loading is a notable feature. To utilize this feature, the nonlinear spring within NES is replaced by a SMA based spring. The nonlinear material behavior of SMA spring is modeled by the Greaser - Cozzarelli model utilizing the super-elastic effect of SMA. In order to ensure robust performance of the proposed controller, the tuning parameters of SMA assisted NES with negative stiffness are determined by solving a robust design optimization problem. To solve the RDO problem in an efficient manner, blind Kriging has been used as a surrogate model. A number of parametric studies are carried out to illustrate the robustness of the proposed controller. The results obtained clearly demonstrate the enhanced and robust performance of the proposed SMA enhanced NES with negative stiffness.

ACS Style

Sourav Das; Souvik Chakraborty; Yangyang Chen; Solomon Tesfamariam. Robust design optimization for SMA based nonlinear energy sink with negative stiffness and friction. Soil Dynamics and Earthquake Engineering 2020, 140, 106466 .

AMA Style

Sourav Das, Souvik Chakraborty, Yangyang Chen, Solomon Tesfamariam. Robust design optimization for SMA based nonlinear energy sink with negative stiffness and friction. Soil Dynamics and Earthquake Engineering. 2020; 140 ():106466.

Chicago/Turabian Style

Sourav Das; Souvik Chakraborty; Yangyang Chen; Solomon Tesfamariam. 2020. "Robust design optimization for SMA based nonlinear energy sink with negative stiffness and friction." Soil Dynamics and Earthquake Engineering 140, no. : 106466.

Journal article
Published: 21 October 2020 in Sustainability
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Proactive management of wastewater pipes requires the development of deterioration models that support maintenance and inspection prioritization. The complexity and the lack of understanding of the deterioration process make this task difficult. A semiparametric Bayesian geoadditive quantile regression approach is applied to estimate the deterioration of wastewater pipe from a set of covariates that are allowed to affect linearly and nonlinearly the response variable. Categorical covariates only affect linearly the response variable. In addition, geospatial information embedding the unknown and unobserved influential covariates is introduced as a surrogate covariate that capture global autocorrelations and local heterogeneities. Boosting optimization algorithm is formulated for variable selection and parameter estimation in the model. Three geoadditive quantile regression models (5%, 50% and 95%) are developed to evaluate the band of uncertainty in the prediction of the pipes scores. The proposed model is applied to the wastewater system of the city of Calgary. The results show that an optimal selection of covariates coupled with appropriate representation of the dependence between the covariates and the response increases the accuracy in the estimation of the uncertainty band of the response variable. The proposed modeling approach is useful for the prioritization of inspections and provides knowledge for future installations. In addition, decision makers will be informed of the probability of occurrence of extreme deterioration events when the identified causal factors, in the 5% and 95% quantiles, are observed on the field.

ACS Style

Ngandu Balekelayi; Solomon Tesfamariam. Geoadditive Quantile Regression Model for Sewer Pipes Deterioration Using Boosting Optimization Algorithm. Sustainability 2020, 12, 8733 .

AMA Style

Ngandu Balekelayi, Solomon Tesfamariam. Geoadditive Quantile Regression Model for Sewer Pipes Deterioration Using Boosting Optimization Algorithm. Sustainability. 2020; 12 (20):8733.

Chicago/Turabian Style

Ngandu Balekelayi; Solomon Tesfamariam. 2020. "Geoadditive Quantile Regression Model for Sewer Pipes Deterioration Using Boosting Optimization Algorithm." Sustainability 12, no. 20: 8733.

Journal article
Published: 06 October 2020 in International Journal of Pressure Vessels and Piping
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Corrosion of buried pipes is complex and difficult to model without considering corrosiveness of the soil. To estimate the external corrosion of buried and aged oil and gas pipelines, a Bayesian spectral analysis regression is proposed. The depth of the corrosion pit progression on a bare metallic pipe is linked to the soil factors that are assumed to influence its rate. The time the pipe is exposed to these factors and the annual precipitations are added to the selected soil influencing factors. The relationship between the identified factors (covariates) and the depth of the corrosion pit (response variable) is expressed as a semiparametric. Thus, the complex electrochemical process of corrosion is represented mathematically. The proposed approach is applied to the data published online by the National Institute of Standard and Technology in the US. The results allow a better quantification of the uncertainty in the predictions for each factor and an improvement in the performance of statistical prediction models of external depth of the corrosion pit.

ACS Style

Ngandu Balekelayi; Solomon Tesfamariam. External corrosion pitting depth prediction using Bayesian spectral analysis on bare oil and gas pipelines. International Journal of Pressure Vessels and Piping 2020, 188, 104224 .

AMA Style

Ngandu Balekelayi, Solomon Tesfamariam. External corrosion pitting depth prediction using Bayesian spectral analysis on bare oil and gas pipelines. International Journal of Pressure Vessels and Piping. 2020; 188 ():104224.

Chicago/Turabian Style

Ngandu Balekelayi; Solomon Tesfamariam. 2020. "External corrosion pitting depth prediction using Bayesian spectral analysis on bare oil and gas pipelines." International Journal of Pressure Vessels and Piping 188, no. : 104224.

Journal article
Published: 17 September 2020 in Sustainable Cities and Society
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Most cities in Canada do not charge a stormwater fee; consequently, stormwater programs may need to compete with other funding priorities in public works. This often leads to a lack of dedicated and predictable cash flow, which can limit municipalities' capacity to sustain stormwater services. In such situations, it is useful to identify available revenue sources and expected expenditures, so that sustainable funding strategies can be determined. In this paper, we explore a novel system dynamics model to investigate sustainable funding strategies. The model consists of a qualitative assessment that uses causal loop diagrams to provide a conceptual system representation and a mathematical formulation for a quantitative assessment. The model is used to explore the potential of introducing stormwater fees in the city of Vernon, Canada. It is shown that the model is helpful in strategic asset management decision making, and can be used to build arguments for implementing proactive asset management programs.

ACS Style

Yekenalem Abebe; Bryan T. Adey; Solomon Tesfamariam. Sustainable funding strategies for stormwater infrastructure management: A system dynamics model. Sustainable Cities and Society 2020, 64, 102485 .

AMA Style

Yekenalem Abebe, Bryan T. Adey, Solomon Tesfamariam. Sustainable funding strategies for stormwater infrastructure management: A system dynamics model. Sustainable Cities and Society. 2020; 64 ():102485.

Chicago/Turabian Style

Yekenalem Abebe; Bryan T. Adey; Solomon Tesfamariam. 2020. "Sustainable funding strategies for stormwater infrastructure management: A system dynamics model." Sustainable Cities and Society 64, no. : 102485.

Journal article
Published: 01 August 2020 in Journal of Water Resources Planning and Management
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ACS Style

Ngandu Balekelayi; Solomon Tesfamariam. Closure to “Graph-Theoretic Surrogate Measure to Analyze Reliability of Water Distribution System Using Bayesian Belief Network–Based Data Fusion Technique” by Ngandu Balekelayi and Solomon Tesfamariam. Journal of Water Resources Planning and Management 2020, 146, 07020002 .

AMA Style

Ngandu Balekelayi, Solomon Tesfamariam. Closure to “Graph-Theoretic Surrogate Measure to Analyze Reliability of Water Distribution System Using Bayesian Belief Network–Based Data Fusion Technique” by Ngandu Balekelayi and Solomon Tesfamariam. Journal of Water Resources Planning and Management. 2020; 146 (8):07020002.

Chicago/Turabian Style

Ngandu Balekelayi; Solomon Tesfamariam. 2020. "Closure to “Graph-Theoretic Surrogate Measure to Analyze Reliability of Water Distribution System Using Bayesian Belief Network–Based Data Fusion Technique” by Ngandu Balekelayi and Solomon Tesfamariam." Journal of Water Resources Planning and Management 146, no. 8: 07020002.

Journal article
Published: 24 July 2020 in Engineering Structures
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Outriggers have been proven to be an efficient system to reduce the dynamic responses of core-tube type high-rise buildings by utilizing the axial stiffness of the peripheral columns. However, outer columns and outriggers are subjected to excessive lateral force demands. To reduce the demand, the damped outrigger is used where dampers are installed between the perimeter columns and outriggers. To improve the performance and enhance the residual deformation, in this paper, the use of shape memory alloy (SMA) springs is introduced to dissipate energy. The SMA dissipates energy through a hysteretic phase transformation of its microstructure triggered by cyclic loading. In the mathematical model implementation, the nonlinear behavior of superelastic SMA is linearized by the stochastic equivalent linearization method. Stochastic uncertainty in the ground motion is considered, and the performance is assessed by minimizing the failure probability of the structure. To solve the optimization problem, Kriging is used as a surrogate model. For better accuracy of the surrogate model, an efficient global optimization scheme is used. The purpose of the optimization adopted in this study is to find optimal design parameters associated with the initial stiffness of the SMA and the location of the outrigger. The results clearly demonstrated the efficacy of the proposed SMA based outrigger.

ACS Style

Sourav Das; Solomon Tesfamariam. Optimization of SMA based damped outrigger structure under uncertainty. Engineering Structures 2020, 222, 111074 .

AMA Style

Sourav Das, Solomon Tesfamariam. Optimization of SMA based damped outrigger structure under uncertainty. Engineering Structures. 2020; 222 ():111074.

Chicago/Turabian Style

Sourav Das; Solomon Tesfamariam. 2020. "Optimization of SMA based damped outrigger structure under uncertainty." Engineering Structures 222, no. : 111074.

Journal article
Published: 10 July 2020 in Journal of Sound and Vibration
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This paper presents implementation of a reliability-based design optimization (RBDO) for Nonlinear Energy Sink (NES) system. The RBDO is implemented with consideration of uncertainties in structural system's parameters and ground acceleration. Negative stiffness based NES and sliding friction are utilized to enhance passive targeted energy transfer from the primary structure to the proposed control device. For a one-story steel moment resistant frame, shake table tests were carried out to show effectiveness of the NES, and the results are used to validate numerical models. Sensitivity analysis is carried out to demonstrate the performance envelops of the proposed control strategy for different stiffness ratios and peak ground acceleration values. Reliable performance of the proposed controller, through tuning parameters of the proposed NES, are determined through the RBDO framework. To reduce computational time, polynomial-chaos-based Kriging surrogate model is used in the RBDO analysis. The numerical results demonstrate efficiency of finding optimal design parameters of the proposed NES system under uncertainties with reasonable computational effort.

ACS Style

Sourav Das; Solomon Tesfamariam; Yangyang Chen; Zhichao Qian; Ping Tan; Fulin Zhou. Reliability-based optimization of nonlinear energy sink with negative stiffness and sliding friction. Journal of Sound and Vibration 2020, 485, 115560 .

AMA Style

Sourav Das, Solomon Tesfamariam, Yangyang Chen, Zhichao Qian, Ping Tan, Fulin Zhou. Reliability-based optimization of nonlinear energy sink with negative stiffness and sliding friction. Journal of Sound and Vibration. 2020; 485 ():115560.

Chicago/Turabian Style

Sourav Das; Solomon Tesfamariam; Yangyang Chen; Zhichao Qian; Ping Tan; Fulin Zhou. 2020. "Reliability-based optimization of nonlinear energy sink with negative stiffness and sliding friction." Journal of Sound and Vibration 485, no. : 115560.

Journal article
Published: 04 May 2020 in Soil Dynamics and Earthquake Engineering
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Nonlinear structural response of buried continuous pipeline undergoing strike-slip fault rupture, i.e., where soil masses get displaced in the horizontal plane along a fault line, is studied in a detailed manner. A detailed analysis technique employing ABAQUS/Standard with implicit formulation to study the behavior of buried continuous pipelines crossing fault movements is proposed and established with suitable validations. A three-dimensional nonlinear finite element (FE) model including both material and geometric nonlinearities is used for this study. Firstly, a non-linear sand constitutive model is adopted and implemented in commercial FE package ABAQUS. The adopted material model is validated with available experimental tri-axial test results. This material model is thereafter suitably calibrated to develop a FE model of buried pipeline undergoing fault rupture for a specific large-scale experimental test. The study identified important soil strength parameters from direct shear soil tests conducted for the large-scale test program and converted them suitably with respect to the adopted sand constitutive model. The FE model is then validated against full-scale experimental results. It is observed that the developed FE model yields highly accurate results in comparison to available numerical results for this experiment. Analysis results indicated that, consideration of sand non-linear mobilized shear strength appropriately in numerical modelling may result in significantly improved prediction of generated pipeline strains with increasing fault displacements.

ACS Style

Sandip Dey; Souvik Chakraborty; Solomon Tesfamariam. Structural performance of buried pipeline undergoing strike-slip fault rupture in 3D using a non-linear sand model. Soil Dynamics and Earthquake Engineering 2020, 135, 106180 .

AMA Style

Sandip Dey, Souvik Chakraborty, Solomon Tesfamariam. Structural performance of buried pipeline undergoing strike-slip fault rupture in 3D using a non-linear sand model. Soil Dynamics and Earthquake Engineering. 2020; 135 ():106180.

Chicago/Turabian Style

Sandip Dey; Souvik Chakraborty; Solomon Tesfamariam. 2020. "Structural performance of buried pipeline undergoing strike-slip fault rupture in 3D using a non-linear sand model." Soil Dynamics and Earthquake Engineering 135, no. : 106180.

Articles
Published: 26 March 2020 in Sustainable and Resilient Infrastructure
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Risk-based renewal planning is essential for the reliable and continuous functioning of infrastructure systems. In this paper, we propose a risk assessment framework for storm sewer networks considering both hydraulic capacity and asset deterioration. The method is designed for a city-scale analysis and can provide an insightful result even when there is incomplete information. The objective is to assign a relative risk score to each pipe to inform replacement priorities. Moreover, we adopt a dynamic framework to proactively assess risk in different time horizons to investigate the impact of climate change and urbanization. A Dynamic Bayesian Network (DBN) model is used to capture dependencies among indicators, quantify uncertainty, and update belief when new information becomes available. Geographic information system (GIS) applications are used to collect and process model input data as well as visualize analysis results. Finally, the method is demonstrated on a storm sewer network in the city of Vernon, Canada.

ACS Style

Yekenalem Abebe; Solomon Tesfamariam. Storm sewer pipe renewal planning considering deterioration, climate change, and urbanization: a dynamic Bayesian network and GIS framework. Sustainable and Resilient Infrastructure 2020, 1 -16.

AMA Style

Yekenalem Abebe, Solomon Tesfamariam. Storm sewer pipe renewal planning considering deterioration, climate change, and urbanization: a dynamic Bayesian network and GIS framework. Sustainable and Resilient Infrastructure. 2020; ():1-16.

Chicago/Turabian Style

Yekenalem Abebe; Solomon Tesfamariam. 2020. "Storm sewer pipe renewal planning considering deterioration, climate change, and urbanization: a dynamic Bayesian network and GIS framework." Sustainable and Resilient Infrastructure , no. : 1-16.

Journal article
Published: 01 February 2020 in Soil Dynamics and Earthquake Engineering
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Inter-story isolation (ISI) is a passive control technique that involves the placement of seismic isolation devices between stories. Multiple isolation layers installed at different story levels can reduce the response of the isolation devices, while maintaining control of the primary building. A multi-objective optimization (MOO) study is conducted in this paper to select the optimum stories of installation and the effective stiffness and damping properties of specified number of isolation layers. The maximum standard deviations of inter-story drift ratio (ISDR) and isolation drift, derived from random vibration analysis (RVA) of a shear-building model are used as the objective functions of the optimization problem, thus accounting for the seismic responses of both the primary building and the isolation devices. To solve the resulting mixed-integer problem, the combinations of integer variables are fully enumerated and a continuous-variable sub-problem is solved for each combination. Four metaheuristic and one derivative-free algorithms are comparatively assessed for solving the continuous-variable multi-objective sub-problems corresponding to the combinations of the integer variables. Along with the optimal trade-offs between the response objectives, multi-objective optimization reveals trends in response with varying isolation configuration as well as the enhancement of the ISI building performance with increasing number of isolation layers.

ACS Style

Konstantinos Skandalos; Hamid Afshari; Warren Hare; Solomon Tesfamariam. Multi-objective optimization of inter-story isolated buildings using metaheuristic and derivative-free algorithms. Soil Dynamics and Earthquake Engineering 2020, 132, 106058 .

AMA Style

Konstantinos Skandalos, Hamid Afshari, Warren Hare, Solomon Tesfamariam. Multi-objective optimization of inter-story isolated buildings using metaheuristic and derivative-free algorithms. Soil Dynamics and Earthquake Engineering. 2020; 132 ():106058.

Chicago/Turabian Style

Konstantinos Skandalos; Hamid Afshari; Warren Hare; Solomon Tesfamariam. 2020. "Multi-objective optimization of inter-story isolated buildings using metaheuristic and derivative-free algorithms." Soil Dynamics and Earthquake Engineering 132, no. : 106058.

Journal article
Published: 01 June 2019 in Journal of Architectural Engineering
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Timber shear wall systems dissipate energy through nail bending, nail withdrawal, and crushing of the sheathing around the nail hole. This dissipation mechanism is a pinching hysteretic response. Use of high-damping devices is an effective method for improving the earthquake resistance of a building. In this study, three wood friction connections were developed and tested to increase the damping of the wood shear walls. In this paper, cyclic experimental tests of the connectors and shear walls are presented. In addition, results of long-term performance assessments are also presented. The cyclic test response of the connections exhibited a rectangular hysteretic response, and the shear wall systems had an equivalent viscous damping ratio of around 0.3.

ACS Style

Yoshiaki Wakashima; Hidemaru Shimizu; Koichiro Ishikawa; Yasushi Fujisawa; Solomon Tesfamariam. Friction-Based Connectors for Timber Shear Walls: Static Experimental Tests. Journal of Architectural Engineering 2019, 25, 04019006 .

AMA Style

Yoshiaki Wakashima, Hidemaru Shimizu, Koichiro Ishikawa, Yasushi Fujisawa, Solomon Tesfamariam. Friction-Based Connectors for Timber Shear Walls: Static Experimental Tests. Journal of Architectural Engineering. 2019; 25 (2):04019006.

Chicago/Turabian Style

Yoshiaki Wakashima; Hidemaru Shimizu; Koichiro Ishikawa; Yasushi Fujisawa; Solomon Tesfamariam. 2019. "Friction-Based Connectors for Timber Shear Walls: Static Experimental Tests." Journal of Architectural Engineering 25, no. 2: 04019006.

Journal article
Published: 28 December 2018 in Journal of Safety Research
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Introduction: The safety of oil and gas pipelines is an increasing concern for the public, government regulators, and the industry. A safety management system cannot be efficient without having an effective integrity management program (IMP) and a strong safety culture. IMP is a formal document (policies, planning, scheduling, and technical processes) while safety culture is a measure of views, beliefs, and traditions about safety. For regulatory authorities and O&G companies, assessing the effectiveness of both the IMP and safety culture through regulatory audits is a daunting task with indistinct findings. Method: An integrated framework based on regulatory audits is developed to assess the maturity of safety culture based on IMP efficacy through risk-based approach by using failure mode and effect analysis (FMEA). The framework focuses on three distinct aspects, the probability of failure occurrence in case of the non-compliance of regulatory and program requirements, severity of non-compliance, and effectiveness of the corrective actions. Results: Program requirements and performance indicators are translated into assessment questions which are grouped into 18 IMP components. Subsequently, these components are linked with four safety culture attributes. Sensitivity analysis revealed that four IMP components, i.e., organizational roles and responsibilities, policy and commitment, risk assessment, and training and competency, significantly affect the safety culture maturity level. Conclusions: Individual assessment of IMP and safety culture in O&G sector consumes extensive time and efforts in the auditing process. The framework facilitates the process by pursuing common criteria between IMP and safety culture. The O&G companies and regulator can prioritize the improvement plans and guidelines using the framework's findings. Practicalapplications: The integrated framework developed in this research will improve the existing assessment mechanism in O&G companies. The framework has been effectively implemented on a case of 17 upstream O&G pipeline-operating companies in the province of British Columbia, Canada.

ACS Style

Hassan Iqbal; Bushra Waheed; Husnain Haider; Solomon Tesfamariam; Rehan Sadiq. Mapping safety culture attributes with integrity management program to achieve assessment goals: A framework for oil and gas pipelines industry. Journal of Safety Research 2018, 68, 59 -69.

AMA Style

Hassan Iqbal, Bushra Waheed, Husnain Haider, Solomon Tesfamariam, Rehan Sadiq. Mapping safety culture attributes with integrity management program to achieve assessment goals: A framework for oil and gas pipelines industry. Journal of Safety Research. 2018; 68 ():59-69.

Chicago/Turabian Style

Hassan Iqbal; Bushra Waheed; Husnain Haider; Solomon Tesfamariam; Rehan Sadiq. 2018. "Mapping safety culture attributes with integrity management program to achieve assessment goals: A framework for oil and gas pipelines industry." Journal of Safety Research 68, no. : 59-69.

Journal article
Published: 20 December 2018 in Structural Safety
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A new multi-variate approach for assessing the seismic performance of structures is proposed. The classical safety factor formulation in structural reliability is adopted considering multi-dimensional limit state functions that are defined in terms of demand-over-capacity ratios. Variable definitions of multi-dimensional limit state functions represent additional epistemic uncertainty in reliability problems. The use of different multi-dimensional limit state functions is investigated either in terms of variability on the resulting fragility curves and as effect on the risk by calculating the probability of exceeding prescribed limit states. The proposed method is demonstrated by analyzing four non-ductile reinforced concrete structures and by considering bi-dimensional damage measures in terms of maximum inter-story drift and residual drift. Results show that for limit states where the structure behaves elastically, there is no significant effect on the fragility and risk when alternative multi-dimensional measures are adopted. Conversely, average variations up to 10% on the assessment of the probability of failure are observed for limit states where the structure behaves nonlinearly; such variations can be as large as 50% for some particular cases.

ACS Style

Raffaele De Risi; Katsuichiro Goda; Solomon Tesfamariam. Multi-dimensional damage measure for seismic reliability analysis. Structural Safety 2018, 78, 1 -11.

AMA Style

Raffaele De Risi, Katsuichiro Goda, Solomon Tesfamariam. Multi-dimensional damage measure for seismic reliability analysis. Structural Safety. 2018; 78 ():1-11.

Chicago/Turabian Style

Raffaele De Risi; Katsuichiro Goda; Solomon Tesfamariam. 2018. "Multi-dimensional damage measure for seismic reliability analysis." Structural Safety 78, no. : 1-11.

Original research article
Published: 28 November 2018 in Frontiers in Built Environment
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Seismically deficient bridges, coupled with their aging and deterioration, pose significant threat to safety, integrity, and functionality of highway networks. Given limited funds available for bridge retrofitting, there is a need for an effective management strategy that will enable decision-makers to identify and prioritize the high-risk bridges for detailed seismic evaluation and retrofit. In this paper, a risk-based preliminary seismic screening technique is proposed to rank or prioritize seismically-deficient bridges. The proposed risk assessment entails hierarchically integrating seismic hazard, bridge vulnerability, and consequences of failure. The bridge vulnerability accounts for chloride-induced corrosion deterioration mechanisms. A Bayesian belief network based modeling technique is used to aggregate through the hierarchy and generate risk indices. The efficacy of the proposed method is illustrated on two existing bridges that are assumed to be located in high seismic zones and designed under different standards concerning their structural safety under seismic loads and durability performance.

ACS Style

Solomon Tesfamariam; Emilio Bastidas-Arteaga; Zoubir Lounis. Seismic Retrofit Screening of Existing Highway Bridges With Consideration of Chloride-Induced Deterioration: A Bayesian Belief Network Model. Frontiers in Built Environment 2018, 4, 1 .

AMA Style

Solomon Tesfamariam, Emilio Bastidas-Arteaga, Zoubir Lounis. Seismic Retrofit Screening of Existing Highway Bridges With Consideration of Chloride-Induced Deterioration: A Bayesian Belief Network Model. Frontiers in Built Environment. 2018; 4 ():1.

Chicago/Turabian Style

Solomon Tesfamariam; Emilio Bastidas-Arteaga; Zoubir Lounis. 2018. "Seismic Retrofit Screening of Existing Highway Bridges With Consideration of Chloride-Induced Deterioration: A Bayesian Belief Network Model." Frontiers in Built Environment 4, no. : 1.