Inter-story Drift Ratio Research Articles

Classification of buildings' potential for seismic damage using a machine learning model with auto hyperparameter tuning

The research on the application of machine learning (ML) methods in the field of earthquake engineering shows a continuous and rapid progress in the last two decades. ML methods and models belonging to the category of supervised, unsupervised and semi-supervised learning are applied for the assessment of seismic vulnerability of structures and estimation of the expected level of seismic damage. These models lead to the classification of seismic damage into predefined classes through the extraction of patterns from data collected from various sources. However, the lack of detailed knowledge can affect their performance and ultimately reduce their reliability, as well as the generalizability that should characterize them. Towards this direction, the present paper attempts to compare and evaluate for the first time the ability of an extensive number of ML methods in the correct classification of R/C buildings at the first stage pre- and post-seismic inspection considering three seismic damage categories. A database consisting of 5850 training samples is used for this evaluation. This database is generated by solving 90 R/C buildings for 65 actual seismic excitations applying nonlinear time history analyses. For each one of the training samples the maximum interstory drift ratio is calculated as a damage index. In addition, a major contribution of this paper is the presentation and extensive documentation of the procedures required for the preprocessing of the data. Finally, an auto hyperparameter tuning method for the winning algorithm is proposed, so that the hyperparameters are automatically optimized utilizing Bayesian Optimization. The most significant conclusion extracted is that the studied ML algorithms extract very different classification results. In addition, the Support Vector Machine - Gaussian Kernel algorithm extracted the most accurate results of all the studied ML algorithms.

Inter-Story Drift Ratio Detection of High-Rise Buildings Based on Ambient Noise Recordings

The inter-story drift ratio (IDR) is a crucial parameter in structural health monitoring to judge the safety, stability, and serviceability of buildings. Real-time, continuous, and widely applicable detection on IDRs is essential. However, the current methods present some challenges in conducting such detection, including adverse effects from weather, the requirement for large amounts of space, and fragile instruments. This study proposes an alternative method to overcome these defects to measure IDRs and evaluate the structural conditions using ambient noise recordings. Ambient noise is a random and continuous wave signal with various sources and is modified by its propagating medium. Taking the Zhonghe Building on the campus of Tongji University, Shanghai, China, as an example, 24 three-component seismometers were deployed to capture and record the ambient noise continuously from 20 November 2021 to 9 December 2021. Using analysis of the polarization parameters of ambient noise during the building’s most dangerous time and ordinary time, a deflection curve, IDRs, and harmful IDRs of the Zhonghe Building during the most dangerous time were calculated. The computed maximum drift was 0.06 m, the maximum IDR was 1.140×10−3, and the maximum harmful IDR was −2.573×10−4. These results were compared with the relevant specifications in China, and it was found that the structure was in good condition. The study proposes an alternative method to measure IDRs with high applicability and continuity in real time and underscores the need for further research to achieve a localized and real-time structural health monitoring system.

Seismic performance evaluation of novel RC frame structure with kinked rebar beams and post-yield hardening columns through shaking table tests

The kinked rebar configuration proposed by the authors has previously demonstrated improved seismic performance and progressive collapse resistance through quasi-static tests on reinforced concrete (RC) beams and plane RC frame substructures. In this paper, shaking table tests were conducted to evaluate the seismic performance of the novel RC frame structure with kinked rebar beams and post-yield hardening columns. The beams of the proposed frame included longitudinal bars with a kinked rebar configuration, while carbon fiber reinforced polymer (CFRP) bars were adopted in the columns to achieve post-yield hardening behavior. A 1/4-scale 4-story novel RC frame was designed, constructed, and tested, with three ground motion records of varying intensity levels used in the shaking table tests. The results showed that the inter-story and residual drift ratios of the proposed novel frame were effectively reduced compared to the conventional frame, indicating better seismic performance and self-centering capability. Additionally, the damage of the novel frame was first observed at beam ends and gradually became more severe with increasing seismic intensity. However, no obvious damage was observed at column ends, even under an extremely large earthquake. Thus, a “strong column-weak beam” failure mode of the novel RC frame structure was successfully achieved, and its repairability was effectively improved.

Multiple-level earthquake-resistant design strategy for precast concrete frames with semi-rigid connections: A case study

The design of precast concrete (PC) structures with semi-rigid connections is primarily based on the design of cast-in-suit structures by adjusting the relevant parameters of PC connections. However, it is necessary to further verify whether the seismic collapse resistance capacity of these PC structures meets the requirements, and to examine how to achieve the optimal seismic resistance design of PC structures. To explore a more concise and effective design scheme for PC structures, the influence of different PC connection parameters and the number of structural stories on the collapse resistance capacity of PC structures is discussed based on a case study. In this work, we set three series of 8-story PC structures and one series of 18-story PC structures, based on different PC connection parameters. Firstly, a simplified algorithm of the inter-story drift (ISD) ratio, based on a modified Muto’s method, is performed to preliminarily screen PC structures subjected to frequent-level earthquakes, and the lower limit value of the semi-rigid connection coefficient of each series of structures can be determined. Next, based on the modal pushover analysis and the capacity spectrum, the ISD ratio of the structures subjected to rare-level earthquakes is analyzed to further screen out the structures that do not meet the specification limits. The distribution ratio of the hysteretic energy in each story of the PC structures is discussed using time history analysis. Then, in the collapse stage, based on a global damage model and incremental dynamic analysis, the collapse state points of the structure can be obtained so that the collapse probability curve of each PC structure is determined, and the collapse safety margin of PC structures can be analyzed. PC structures can be further screened based on the collapse margin ratio (CMR), and the influences of PC connection parameters on the CMR and failure path of PC structures are assessed. Finally, the optimization of structures with semi-rigid PC connections based on multilevel seismic action is realized.

Machine Learning-Based Rapid Post-Earthquake Damage Detection of RC Resisting-Moment Frame Buildings

This study proposes a methodology to predict the damage condition of Reinforced Concrete (RC) resisting-moment frame buildings using Machine Learning (ML) methods. Structural members of six hundred RC buildings with varying stories and spans in X and Y directions were designed using the virtual work method. Sixty thousand time-history analyses using ten spectrum-matched earthquake records and ten scaling factors were carried out to cover the structures’ elastic and inelastic behavior. The buildings and earthquake records were split randomly into training data and testing data to predict the damage condition of new ones. In order to reduce bias, the random selection of buildings and earthquake records was carried out several times, and the mean and standard deviation of the accuracy were obtained. Moreover, 27 Intensity Measures (IM) based on acceleration, velocity, or displacement from the ground and roof sensor responses were used to capture the building’s behavior features. The ML methods used IMs, the number of stories, and the number of spans in X and Y directions as input data and the maximum inter-story drift ratio as output data. Finally, seven Machine Learning (ML) methods were trained to predict the damage condition of buildings, finding the best set of training buildings, IMs, and ML methods for the highest prediction accuracy.

Shaking‐table test results of a full‐scale free‐standing building with base sliding and rocking

AbstractThis paper present results of shaking‐table tests conducted in 2015 and 2018 on a free‐standing base sliding and rocking system, which allows sliding and uplifting. A full‐scale 10‐story reinforced concrete (RC) building equipped with cast iron plates on the bottom surface of the grade beams was used as a specimen for 2015 and 2018 experiments. In 2018, the static friction coefficients of the specimen were 0.48 and 0.49, which was higher than that of the rustproofed specimens in 2015. In the experiments of 2015 and 2018, the normalized base shear (NBS) values when the sliding length of the building reached ≥1 mm were 0.0035–0.1795 and 0.1744–0.2748, respectively. In the shaking‐table test corresponding to moderate earthquake motions, the 2018 specimen showed almost no lateral movement, whereas the 2015 specimen moved laterally. Therefore, more seismic energy was input into the specimen, and the maximum interstory drift ratio of the 2018 specimen was larger than that of the 2015 specimen. However, when the 50% amplitude excitation results of the 2015 seismic structural system are compared with those of the 2018 free‐standing structural system, the 2018 results are approximately 0.57 times smaller. Thus, a free‐standing structural system with cast iron plates to reduce earthquake energy could reduce damage to buildings. The 2018 specimen satisfies the concept of a free‐standing base sliding and rocking system that does not move laterally during small to moderate earthquake motions but moves laterally during strong earthquake motions to suppress structural damage.

Energy-based procedures for seismic fragility analysis of mainshock-damaged buildings

In recent decades, significant research efforts have been devoted to developing fragility and vulnerability models for mainshock-damaged buildings, i.e., depending on the attained damage state after a mainshock ground motion (state-dependent fragility/vulnerability relationships). Displacement-based peak quantities, such as the maximum interstory drift ratio, are widely adopted in fragility analysis to define both engineering demands and structural capacities at the global and/or local levels. However, when considering ground-motion sequences, the use of peak quantities may lead to statistical inconsistencies (e.g., fragility curves’ crossings) due to inadequate consideration of damage accumulation. In this context, energy-based engineering demand parameters (EDPs), explicitly accounting for cumulative damage, can help address this issue. This paper provides an overview of recent findings on the development of aftershock-fragility models of mainshock-damaged buildings. Particular focus is given to state-of-the-art frameworks for fragility analyses based on cumulative damage parameters. Moreover, a literature review on damage indices and energy-based concepts and approaches in earthquake engineering is reported to better understand the main advantages of the mostly adopted energy-based parameters, as well as their limitations. Different refinement levels of seismic response analyses to derive fragility relationships of mainshock-damaged buildings are also discussed. Finally, the benefits of adopting energy-based EDPs rather than, or in addition to, peak quantities in state-dependent fragility analyses are demonstrated on a reinforced concrete frame building. Specifically, a refined lumped plasticity modeling approach is adopted, and sequential cloud-based time-history analyses of a Multi-Degree-of-Freedom (MDoF) model are carried out. The results highlight that energy-based approaches for fragility analysis effectively capture damage accumulation during earthquake sequences without inconsistencies in the obtained statistical models. On the other hand, estimating global or local structural capacity in terms of cumulative EDPs is still challenging. Further experimental data are needed to better calibrate the quantification of energy-based damaged states.

Seismic response modification factors evaluation of a 4-storey buckling-restrained braced frame (BRBF)

The availability of adequate strength and ductility to frames facilitate use of seismic response modification coefficient (R) for their design. The subcomponents of this R coefficients, namely the force reduction component due to ductility (Rμ) and over strength factor (Ω) have relevance in this context. The seismic code, such as ASCE 7-22 given values to R and Ω (considering the type of seismic lateral load resisting system) are mostly empirical in nature. That is, for a given type of lateral load resisting frame the code provided values may not ensure same level of safety as it do not account the variations in geometry and other parameters. Hence further investigations are needed in that direction. The case of buckling-restrained braced frames (BRBFs) are also not different from this. This study tries to assess the seismic response modification factors of a 4-storey BRBF designed as per the current United States code norms. For that, past study suggested design magnitude earthquake records are adopted. The case study frame is modelled in OpenSees and nonlinear incremental dynamic analyses (IDAs) are carried out in iterative manner to get the fully yielded base shear (Vy). Here 2% inter-story drift ratio (IDR) is set as the criteria for complete yielding. From the IDAs obtained 2% IDR corresponding peak ground acceleration, linear dynamic analyses are performed to get the relevant elastic base shear (Ve). Relating Ve, Vy and design base shear (Vs), the seismic response modification factors (Rμ, Ω and R) are evaluated. The results showed that the R coefficient assessed is 1.49 times larger than the code given value whereas Ω evaluated is 0.86 times less than the code stipulated value for the considered study frame.

Evaluation of Vibration Detection Using Smartphones in a Two-Story Masonry-Infilled RC Frame Building

For measuring the structural health of buildings, high-performance vibration detection devices are used in a structural health monitoring (SHM) system, which consists of a sensor and a data logger. Those devices are seismographs or devices with high-performance sensors which are expensive. Recently, smartphones are being used as seismographs to accumulate big data of earthquake wave detection because they have accelerometers of microelectromechanical systems. Since a smartphone has the functions of a detection sensor and a data logger, a low-cost SHM system can be developed by using a low-cost smartphone. In this paper, smartphones were used to confirm the possibility of the development of a low-cost SHM system. To evaluate the vibration detection performance from small displacement and large displacement, smartphones were installed in a specimen of a large shaking table test. The specimen is a scale model of a two-story non-reinforced masonry-filled reinforce concrete (RC) frame building. The natural period and interstory drift ratio were used as the evaluation criteria. The natural period estimated by the smartphone data agreed with that found by the piezoelectric accelerometer data. For estimating the building deformation, which is related to building stability, the measurement performance for large deformation using smartphones was evaluated. The smartphones have 90% or higher accuracies for the estimation of the maximum acceleration and displacement.

Seismic performance of RC frames with self-centering precast post-tensioned connections considering the effect of infill walls

This paper presents the seismic performance evaluation of self-centering precast post-tensioned concrete (SCPPTC) frames with infill walls. The SCPPTC connection system consists of all-steel bamboo-shaped energy dissipaters (SBED) and prestressed tendons, which provide energy dissipation capacity and self-centering capability, respectively. Using modeling parameters calibrated with experimental tests, nonlinear numerical models of SBED, SCPPTC connection, infill walls, and 2D SCPPTC frames were developed in OpenSees, to compare the performance of the structures with different types of infill wall layouts. Nonlinear static pushover and incremental dynamic analysis (IDA) were performed to study the effect of infill walls on the overall response of SCPPTC frames, in terms of stiffness, strength, maximum interstory drift ratio,θmax, the maximum residual interstory drift ratio, θr,max, and the normalized post-tensioned force. Using the IDA results, the study also developed fragility curves and estimated the collapse margin ratios. The results demonstrated that the shear strength of the SCPPTC frame was improved from 4.19% to 12.2%, and the initial secant stiffness of the SCPPTC frame was augmented from 22.9% to 88.3% with increasing filling rate. The totally infilled SCPPTC frame (SCPPTC-ToI) exhibits a 19.86% lower θmax than that of pilotis-infilled SCPPTC frame (SCPPTC-PiI) under rare earthquakes, and the maximum prestress of SCPPTC-ToI was also 7.14% lower than that of SCPPTC-PiI. With the increase in filling rate, θr,max increased by a maximum of 120.45%. The pronounced soft layer led to the highest failure and collapse probabilities of SCPPTC-PiI among all SCPPTC frames at the same performance level.

Blast reliability assessment and sensitivity analysis of steel MRFs equipped with NiTi SMA bolts

The probabilistic-based assessment of Moment Resisting Frame structure (MRFs) is significantly vital due to the high volatility of blast wave propagation parameters, material strength, and strain rate effect. In this study, the reliability and sensitivity of steel MRFs equipped with Nickel Titanium Shape Memory Alloy (NiTi SMA), and smart MRFs, subjected to Vehicle Borne Improvised Explosive Device (VBIED) are assessed. Since Eurocode does not address the design of a smart structure subjected to blast loading, the smart MRFs are designed based on the Eurocode-complying key design procedures proposed by the author’s previous works. It is always a question if the structure designed based on the proposed Eurocode-complying design methodology satisfies the safety level criteria. The newly developed reliability framework approach by the authors is employed to assess the safety level of the smart MRFs based on the criteria given in the international probabilistic design provisions. Performance functions are parameterized based on three failure modes: axial force and bending moments (global buckling) in the columns, maximum rotation demand at the connections, and system-level structural integrity through Inter-Story Drift Ratio (ISDR). The uncertainties of the charge weight, material strength, gravity loads, model uncertainties, connection behavior parameters, strain rate effects, and column cross-sectional dimensions are considered. The proposed reliability framework is applied to the 4-story, 7-story, 10-story, and 15-story smart MRFs. The results show that the developed smart MRFs satisfy the safety level criteria recommended in the international provisions’ probabilistic design requirement. Furthermore, the reliability-based outcome confirms the efficiency and applicability of the proposed Eurocode complying key design procedures and verifies the deterministic results of the smart MRFs. Finally, the sensitivity of the smart structures to various uncertain parameters is investigated. Among all the parameters, it is found that the Reliability Index (β) of the smart MRFs is more sensitive to the uncertainties of charge weight, column web length(s), connection behavior parameters, and material strength. The sensitivity analysis shows that the smart MRFs are safe under unknown extreme conditions, a very high Coefficient of Variation (COV).

Fragility framework for corroded steel moment-resisting frame buildings subjected to mainshock-aftershock sequences

This study proposes a framework for the seismic fragility assessment of steel moment-resisting frames exposed to different rates of corrosion and subjected to real mainshock-aftershock (MS-AS) sequences. The inherent uncertainties in the structural characteristics may significantly affect the structural performance. Thus, in addition to the demand parameters, the framework considers randomness in the capacity parameters using the Latin hypercube sampling. Three frames are modeled in OpenSees and then subjected to nine real as-recorded MS-AS sequences to illustrate the application of the framework. Four limit states are defined based on the maximum interstory drift ratio and the multiple stripe analysis is chosen for the fragility assessment. The presented framework allows for the plot of the fragility surfaces for each corrosion level conditioned on both the mainshock and the aftershock intensity. The results indicate that corrosion and aftershock may significantly affect the seismic fragility especially for the extreme limit states.

Tube-in-tube rigid beam to CFT column connection in moment-resisting frames: An experimental study

Using concrete-filled steel tube (CFT) columns in high-rise buildings has attracted considerable attention in recent years. Aside from its advantages, rigid beam to CFT column connections are followed by some challenges. Difficult construction and implementation, sophisticated details of connection, and most importantly, placing and welding internal stiffeners (continuity plates) are among the common challenges. In the present study, a novel connection called “Tube-in-Tube (TIT) connection” has been proposed. In TIT connection, an inner tube and a pair of vertical straps are utilized in the panel zone area. To investigate the proposed connection, two full-scale specimens were tested using cyclic reversal loading. The two specimens were identical in dimensions and detailing, except for their strap width and the diameter of inner tube. Specimen 1 and Specimen 2 were detailed with inner tube diameter equal to half and one-third of the column dimension, respectively. The inter-story drift ratio, joint's shear deformation, plastic hinge formation, and energy dissipation capacity were analyzed. Moreover, mechanical parameters such as yield and ultimate strengths, and ductility of the specimens were calculated. Specimen 2 showed 3% and 8% increase in the peak flexural strength and cumulative energy dissipation in comparison with Specimen 1. The results showed that the panel zone remain elastic during the test. In order to further investigate the proposed connection, finite element (FE) analysis was conducted on the specimen. The results of FE analysis confirmed the elastic behavior of the tube and straps.

Life-cycle cost analysis of steel frames with shape-memory alloy based dampers

The shape-memory alloy (SMA) based dampers are passive dampers, with their most important feature being their memory and super elastic effect. They significantly reduce the residual response displacements of the structure subjected to earthquakes. Although the initial cost of these dampers is high, they can lower the structural expected life-cycle costs subjected to earthquakes. This study dealt with the life cycle cost analysis to calculate the expected costs of the structures equipped with shape-memory alloy-based dampers. Subsequently, two 4- and 12-story steel frame structures were investigated in controlled and uncontrolled cases in terms of life cycle costs. The results revealed that these dampers can reduce the inter-story drift ratios and the residual displacements of the 4-story structure subjected to the design level seismic acceleration by 31% and 63%, respectively. This reduction for the 12-story structure was 39% and 83%, respectively. Also, these dampers would decrease the total life-cycle cost of the 4-story and 12-story by 53%, and 90%, respectively. Finally, the result indicated that the total life-cycle cost was reduced upon increasing the capacity of the SMA-based dampers up to a specific capacity, beyond which the dampers would not play a role in reducing total life-cycle costs.

Seismic Damage “Semaphore” Based on the Fundamental Period Variation: A Probabilistic Seismic Demand Assessment of Steel Moment-Resisting Frames

During strong earthquakes, structural damage usually occurs, resulting in a degradation of the overall stiffness of the affected structures. This degradation produces a modification in the dynamic properties of the structures, for instance, in the fundamental period of vibration (T1). Hence, the variation of T1 could be used as an indicator of seismic structural damage. In this article, a seismic damage assessment in four generic typologies of steel buildings was carried focused on verifying the variation of T1. To do so, several seismic damage states were calculated using the maximum inter-story drift ratio, MIDR, and following the Risk-UE guidelines. Then, a series of probabilistic nonlinear static analyses was implemented using Monte Carlo simulations. The probabilistic approach allows one to vary the main mechanical properties of the buildings, thus analyzing in this research 4000 buildings (1000 building samples for each of the four generic typologies). The variation of T1 was estimated using the capacity spectrum, and it was related to the MIDR for each damage state. As a main result of this study, the expected variation of T1 for several damage states is provided. Finally, a proposal for a seismic damage preventive “semaphore” and fragility curves are presented. These results may be useful as parameters or criteria in the evaluation of on-site structural monitoring for steel buildings.

Seismic performance of cruciform bolted joints with various reinforcing details in modular steel construction

Extensive research has been done on exterior T-shaped joints of modular structures. The modular structure consists of stacked modules that are not only connected vertically but also need to be connected horizontally. The horizontal connection between modules is another key for the modules to form an integral structure and resist lateral forces. This paper proposes a novel bolted joint that can be applied to multi-column module internal and external connections. By designing special loading supports, three internal cruciform joints and three external cruciform joints of the modular structure were tested under column end loading. The effects of different strengthening measures and the ratio of beam to column flexural bearing capacity on the seismic performance of the joints were compared. The results showed that all the joints had good seismic performance and satisfied the requirements of SMF systems in terms of inter-story drift ratio. The stiffness and bearing capacity of the internal joints after the beam-beam combination increased by 33.2% and 17%, respectively. However, the stiffness and bearing capacity of the cruciform joints strengthened by the cover plate are not significantly improved. For joints that meet the conditions of strong columns and weak beams, modular beams can reach full-section plasticity and can meet the requirements of full-strength joints.

A design method for seismic retrofit of reinforced concrete frame buildings using aluminum shear panels

Despite significant progress in research and development of aluminum shear panels in recent decades, their implementation for seismic retrofit of existing reinforced concrete (RC) buildings can still be significantly extended. Their application is limited by the general lack of relatively simple and effective design criteria and proper guidelines. This paper develops a design method for the seismic retrofit of reinforced concrete buildings using aluminum multi-stiffened shear panels as dampers. Both the nonlinearity in the structure and the dampers-structure interaction are considered to give an optimal distribution of the shear panels over the height of the building. The analytical laws refer to dissipative aluminum shear panels recently tested and analyzed by the authors. The proposed procedure has been described in detail. Its applicability has been demonstrated by analyzing two typical RC buildings having drift capacity-to-demand ratios ranging from 0.505 to 0.624. The design value of the panel-to-frame stiffness ratio has been found to range from 0.594 to 1.432 as a function of the lateral stiffness of the existing building. The verification of the proposed procedure has been carried out by checking the validity of the design assumptions. The first one (i.e., the mode shapes remain the same before and after retrofit) has been checked using the modal assurance criterion that gives values ranging from 0.992 to 0.998. The second one (i.e., uniform yield drift distribution over the building height) has been checked by comparing the yield drifts with their average value giving a standard deviation ranging from about 11 to 15%. The effectiveness of the design method has been finally validated through nonlinear time-history analysis for different seismic accelerograms and hysteresis models. The results show that the seismic retrofit design procedure is effective in significantly reducing inter-story drift (maximum inter-story drift ratio demands ranging from 1.04 to 2.07%) thus satisfying the acceptance criteria of the building, and avoiding drift concentration and consequential weak story collapse.

Non-linear study of the method of transition in mixed concrete/steel structures

A critical zone is formed at the junction of the lower concrete and upper steel sections in mixed concrete/steel structures in terms of gravity and lateral loads caused by the support reactions of the steel frame. There are two common approaches to transition from concrete section to steel one in this critical zone: the first is the direct pin connection of the steel frame to the concrete frame, and the second is the application of a concrete-steel composite story called the transition story. Until now, various studies have been conducted on mixed concrete/steel structures, but no study has investigated and compared the two mentioned approaches. Considering the importance of this issue, 18 models of mixed concrete/steel structures were formed in the present study according to the two approaches and the different places of connection of the concrete and steel sections along the height of the structure. Fragility curves were generated for all models using Incremental Dynamic Analysis (IDA) under 44 far-field ground motion records and probability function at the complete damage state based on HAZUS technical report. A comparison was made from the strength point of view considering the two approaches to transition. Next, to investigate the non-linear response of the structure at the complete damage state, the Peak Inter-Story Drift ratio (PISD) was obtained in the different levels of collapse intensity from IDA for different stories. The results showed that the application of transition story improves the seismic behavior of mixed concrete/steel structures and increases Median Collapse Capacity (MCC) in 7, 13, and 19-story structures up to 24.63%, 19.54%, and 17.99%, respectively. In addition, it makes the displacement of the structure more uniform and reduces the significant difference of drift in the critical zone.

Structural performance and damage prediction using a novel digital cloning technique

This paper presents a novel, mechanics-based framework to create digital twins for earthquake-affected pinched structures, like reinforced concrete framed buildings. It uses robust and accurate structural health monitoring (SHM) results delivered by the hysteresis loop analysis method as an input to create digital twin models to predict nonlinear dynamic responses of previously damaged structures under potential future seismic events. Method validation is implemented using unique real-world data from the Bank of New Zealand (BNZ) building in Wellington, New Zealand, which experienced severe structural damage due to three earthquakes (Events 1, 2, and 3) between 2013 and 2016.Results show the digital twin derived from the SHM results of Event 1 can predict the inter-story displacement of the BNZ building for Events 2 and 3 with average correlation coefficients of ∼0.95 and ∼0.97 between predicted and measured responses, respectively. Moreover, the maximum difference between the measured and predicted peak values of inter-story displacements was 13 mm, a negligible difference in inter-story drift ratio (IDR). These results were accurate and consistent for all stories. Finally, the accuracy of this framework in capturing IDR values makes it a promising tool for assessing potential future structural collapse risk and its consequent financial risks using well-known incremental dynamic analysis methods.

Reliability Assessment Methodology of Blast Protective Steel Moment Resisting Frame Using NiTi SMA-based Connection

This paper proposes a methodology framework for the reliability assessment of smart steel Moment Resisting Frame structures (MRFs) equipped with Nickle Titanium Shape Memory Alloy (NiTi SMA) connections subjected to blast loading. The reliability assessment framework is formulated based on a two-step approach algorithm. In the 1st Step, the Monte Carlo Latin Hypercube Sampling Strategy simulation (MC-LHS) is adapted to generate the uncertain parameters sample points. Considering the numerical simulations, the 2nd Step employs simplified performance functions and the generated random outcomes from the 1st Step. The proposed reliability approach is verified against direct Monte Carlo Simulation (MCS) and First-Order Reliability Method (FORM). The performance functions are columns’ axial force and bending moments, rotation capacity at the connections, and Inter-Story Drift Ratio (ISDR). Throughout the development of the reliability assessment, the probabilistic models are parametrized on geometrical properties, material properties, vertical loads, model errors, and charge weights. The developed reliability framework is applied to a prototype 4-story smart MRF. The structural safety level is obtained in terms of the Reliability Index (β). The results show that the reliability framework provides an accurate and efficient structural collapse prediction of the MRFs equipped with NiTi SMA-based connections. Finally, sensitivity analysis is performed to indicate the sensitivity of building collapse to blast wave characteristics, material strength, vertical gravity loads, and column profile dimensions. The sensitivity analysis results also confirm the efficiency of the proposed reliability framework in observing the highly sensitive parameters, which is explosive charge weight.