scholarly journals Gaussian Process Regression-Based Structural Response Model and Its Application to Regional Damage Assessment

2021 ◽  
Vol 10 (9) ◽  
pp. 574
Author(s):  
Sangki Park ◽  
Kichul Jung

Seismic activities are serious disasters that induce natural hazards resulting in an incalculable amount of damage to properties and millions of deaths. Typically, seismic risk assessment can be performed by means of structural damage information computed based on the maximum displacement of the structure. In this study, machine learning models based on GPR are developed in order to estimate the maximum displacement of the structures from seismic activities and then used to construct fragility curves as an application. During construction of the models, 13 features of seismic waves are considered, and six wave features are selected to establish the seismic models with the correlation analysis normalizing the variables with the peak ground acceleration. Two models for six-floor and 13-floor buildings are developed, and a sensitivity analysis is performed to identify the relationship between prediction accuracy and sampling size. A 10-fold cross-validation method is used to evaluate the model performance, using the R-squared, root mean squared error, Nash criterion, and mean bias. Results of the six-parameter-based model apparently indicate a similar performance to that of the 13-parameter-based model for the two types of buildings. The model for the six-floor building affords a steadily enhanced performance by increasing the sampling size, while the model for the 13-floor building shows a significantly improved performance with a sampling size of over 200. The results indicate that the heighted structure requires a larger sampling size because it has more degrees of freedom that can influence the model performance. Finally, the proposed models are successfully constructed to estimate the maximum displacement, and applied to obtain fragility curves with various performance levels. Then, the regional seismic damage is assessed in Gyeonjgu city of South Korea as an application of the developed models. The damage assessment with the fragility curve provides the structural response from the seismic activities, which can assist in minimizing damage.

2014 ◽  
Vol 17 (11) ◽  
pp. 1693-1704 ◽  
Author(s):  
E.L. Eskew ◽  
S. Jang

An increasing threat of global terrorism has led to concerns about bombings of buildings, which could cause minor to severe structural damage. After such an event, it is important to rapidly assess the damage to the building to ensure safe and efficient emergency response. Current methods of visual inspection and non-destructive testing are expensive, subjective, and time consuming for emergency responders' usage immediately after an attack. On the other hand, vibration-based damage detection methods with wireless smart sensors could provide rapid assessment of structural characteristics with low cost. For blast analysis, structural response is usually determined using a simplified SDOF version of the undamaged structure, such as used in a Pressure-Impulse (P-I) Diagram, or using more complex FEM (finite element method) models. However, the simplified models cannot take into account damage caused by blast focus at a specific location or on a specific element, which may induce local failure leading to potential progressive collapse, and the more complex FEM models take too long to derive applicable results to be effective for a rapid structural assessment. In this paper, a new method to incorporate vibration-based damage detection methods to calculate the multi degree of freedom structural stiffness for determining structural condition is provided to create a framework for the rapid structural condition assessment of buildings after a terrorist attack. The stiffness parameters are generated from the modal analysis of the measured vibration on the building, which are then used in a numerical simulation to determine its structural response from the blast. The calculated structural response is then compared to limit conditions that have been developed from ASCE blast design codes to determine the damage assessment. A laboratory-scale building frame has been employed to validate the developed use of experimentally determined stiffness by comparing the P-I diagram using the experimental stiffness with that from numerical models. The reasonable match between the P-I diagrams from the numerical models and the experiments shows the positive potential of the method. The framework and examples of how to develop a rapid condition assessment are presented.


Author(s):  
Ф.Ф. Аптикаев

Задание сейсмических воздействий в отечественных строительных нормах практически не меняется в течение последних 60 лет. Накопленные эмпирические данные по сильным движениям позволяют коренным образом усовершенствовать методику расчета зданий и сооружений на сейсмостойкость. Ожидается снижение погрешностей расчета примерно вдвое. Цель работы. В последнее время много внимания уделяется проблемам построения карт сейсмической опасности в ускорениях. Однако по традиции в нашей стране такие карты оценивают сейсмическую опасность в баллах шкалы сейсмической интенсивности. В большинстве стран сейсмическая опасность оценивается именно в ускорениях. Строились такие карты и в нашей стране. В частности, карты ОСР-97 и ОСР-2012 имели вариант и в ускорениях. Построение карт сейсмической опасности в ускорениях не имеет принципиальных трудностей. Проблема в том, что ускорения не являются адекватной мерой сейсмических воздействий. Более половины века тому назад американские ученые на эмпирическом материале показали, что связь ускорений с баллами, а, следовательно, и с повреждаемостью зданий неоднозначна: шкалы сейсмической интенсивности различны для разных расстояний и грунтов. Ошибка в оценке последствий землетрясения по ускорениям грунта может достигать 2 баллов. Следовательно, расчет ожидаемых воздействий следует производить с учетом других характеристик сейсмических волн. К тому же, попытки построения карт сейсмической опасности строились без учета данных инженерной сейсмологии и с нарушениями правил теории вероятностей и поэтому обладают не только определенными достоинствами, но и серьезными недостатками. Некоторые исследователи считают, что скорости колебаний лучше коррелируются с повреждениями сооружений, по крайней мере, многоэтажных зданий и подземных трубопроводов. Методы работы. Однако анализ эмпирических данных показал, что использование ускорений, скоростей и смещений характеризуется примерно одинаковой точностью. Рассмотрены способы построения карт общего сейсмического районирования. В действующей шкале сейсмической интенсивности ГОСТ Р 57546.2017 приведены оценки корреляции повреждаемости зданий с различными параметрами сейсмических колебаний: ускорениями, скоростями, смещениями, мощностью колебаний грунта. Оценено влияние продолжительности колебаний. Результаты работы. Показано, что дальнейшее повышение надежности расчетов объектов на сейсмостойкость связана с представлением сейсмических воздействий не с амплитудами колебаний, а с энергетическими характеристиками сейсмических волн The specification of seismic effects in domestic building codes has remained practically unchanged over the past 60 years. The accumulated empirical data on strong ground notions make it possible to radically improve the methodology for calculating buildings and other structures for seismic resistance. It is expected that the calculation errors will be reduced by about half. Aim. Recently, much attention has been paid to the problems of developing seismic hazard maps in accelerations. However, by tradition in our country, such maps assess the seismic hazard in terms of the seismic intensity scale. In most countries, seismic hazard is assessed in terms of accelerations. Such maps were also built in our country. In particular, OSR-97 maps also had a variant in acceleration. The construction of seismic hazard maps in accelerations has no fundamental difficulties. The problem is that accelerations are not an adequate measure of seismic effects. More than half a century ago, American scientists, using empirical material, showed that the relationship between accelerations and points, and, consequently, with the damage to buildings, is ambiguous: the seismic intensity scales are different for different distances and grounds. The error in assessing the consequences of an earthquake in terms of ground acceleration can reach 2 points. Therefore, the calculation of the expected impacts should be based on other characteristics of the seismic waves. In addition, attempts to construct seismic hazard maps were built without taking into account the data of engineering seismology and with violations of the rules of probability theory and therefore have not only certain advantages, but also serious drawbacks. Some researchers believe that vibration velocities correlate better with structural damage, at least in multi-storey buildings and underground pipelines. However, the analysis of empirical data showed that the use of accelerations, velocities and displacements is characterized by approximately the same accuracy. Methods. Methods for constructing maps of general seismic zoning, which have a higher accuracy in comparison with existing maps, are considered. In the current scale of seismic intensity GOST R 57546.2017 estimates of the correlation of damage to buildings with various parameters of seismic vibrations are given: accelerations, velocities, displacements, power of ground vibrations. The influence of the duration of the oscillations is estimated. Results. It is shown that a further increase in the reliability of calculations of objects for seismic resistance is associated with the representation of seismic effects not with vibration amplitudes, but with the energy characteristics of seismic waves


2014 ◽  
Vol 08 (05) ◽  
pp. 1450015 ◽  
Author(s):  
Rita Greco ◽  
Alessandra Fiore ◽  
Giuseppe Carlo Marano

In structural engineering earthquakes are often represented as random phenomena. Frequently, filtered white noise stochastic processes are adopted to properly model their frequency content. In order to model the time variation of earthquake intensity, these processes are assumed nonstationary, and time modulation functions (MFs) are used. For these, different shapes and formulas have been proposed in literature till now, but only few works have dealt with their comparison in terms of structural response. This paper focuses on this topic: at this aim, a simple linear single degree of freedom (SDoF) system, which represents a structure vibrating in its fundamental mode, is considered subject to a time modulated filtered stochastic process. Different shapes of the MF are considered and the influence on two structural response indices, i.e. the maximum displacement standard deviation and the failure probability, is investigated. A sensitivity analysis is finally performed by varying peak ground acceleration (PGA), Arias intensity and structural period.


Author(s):  
Muhammad Hamid ◽  
◽  
Fayyaz Ur Rahman ◽  
Qaisar Ali ◽  
◽  
...  

Pounding between adjacent buildings is a common phenomenon which can be observed during moderate to high ground shakings that can result in structural damage and even loss of life. As this phenomenon is related to the life safety, therefore, it is imperative to consider it in the modelling stage of structural analysis and design. The current study is intended to evaluate, numerically, the effect of pounding phenomenon in RC frame structures. Three dimensional models of two hypothetical buildings are analyzed by subjecting to three ground acceleration histories that are scaled and matched with BCP-SP07 design spectrum. The analysis results such as inter storey drift, maximum displacement, pounding forces and its effects on bending moment, axial forces, shear and torsional forces in structural members are compared. The results show that pounding forces decrease with increase in gap size and are dominant in top five stories with maximum force at the top floor level. Pounding increase displacement up to 2 times and acceleration up to 240 times as compared to without pounding case. Pounding increase the axial forces up to 250 times and bending moment up to 2 time in the beams parallel to colliding forces. Similarly, the shear forces and torsional moments are almost doubled as a result of pounding. Finally, a 20 storey building consists of four blocks separated by 3-inch expansion joints is modelled combinedly in Etabs and analyzed to see the effect of pounding. Based on the results it is concluded that pounding must be considered at modelling stage of the design to account for the forces induced in the structural members.


2020 ◽  
Vol 12 (3) ◽  
pp. 892
Author(s):  
Xiaorong Hu ◽  
Zhiguang Zhou ◽  
Hao Chen ◽  
Yongqiang Ren

Seismic fragility of an engineering structure is the conditional probability that damage of a structure equals or exceeds a limit state under a specified intensity motion. It represents the seismic performance of structures and the correlation between ground motion and structural damage, playing an indispensable role in structural security assessment. A practical evaluation procedure of acquiring the fragility curves of tunnels in a soft soil has been proposed in this paper. Taking a typical metro tunnel in Shanghai as an example, two-dimensional finite element models of soil-tunnel cross-section were established. The nonlinear characteristics of soil layers were considered by the one-dimensional equivalent linear analysis in the equivalent-linear earthquake site response analyses (EERA) program. The ground motions were selected based on seismic station records. Comparing the analytical fragility curves with the empirical curves derived from American Lifelines Alliance (ALA) and HAZUS shows that the proposed method is reliable and feasible. Further study about the influence of buried depths on the fragility of the tunnel was performed. The results indicate that the failure probability of the tunnel is not monotonically decreasing with the increase of the buried depth for a given peak ground acceleration (PGA.)


2020 ◽  
Vol 1 (1) ◽  
pp. 31-39
Author(s):  
Narayan Ghimire ◽  
Hemchandra Chaulagain

Fragility curves are derived from fragility function that indicates the probability of damage of structure due to earthquake as a function of ground motion parameter. It helps to predict the level of structural damage and consequently reduce the seismic risk in specific ground motion. In this scenario, this study is focused on the construction of fragility curve of institutional reinforced concrete (RC) building of Pokhara University. For this, the building of School of Health and Allied Science (SHAS) is considered as a guiding case study. For the numerical analysis, the study building blocks are modelled in finite element-based software. The non-linear static and linear dynamic analyses are employed for numerical analysis. In dynamic analysis, building models are subjected to the synthetic accelerograms of the 2015 Gorkha earthquake. Based on the analyses, the analytical fragility curves are plotted in terms of probability of failure at every 0.1 g interval of peak ground acceleration (PGA) with log normal distribution. Finally, the results are highlighted for different seismic performance level in buildings: slight damage, moderate damage, extensive damage and complete damage for the earthquake of 475 years return period.


2020 ◽  
Vol 12 (18) ◽  
pp. 7803
Author(s):  
Kichul Jung ◽  
Daeryong Park ◽  
Sangki Park

This study aims to provide an enhanced model for rapid responses from natural disasters by estimating the maximum structural displacement. The linear regression, support vector machine, and Gaussian process regression (GPR) models were applied to obtain displacement estimates. Further, normalization (NM) and standardization (SD) of variables, and principal component analysis (PCA) were applied to improve model performance. The k-fold cross-validation approach was used to assess the results from the models based on the root-mean-square error and the R-squared indices. According to the results, the GPR model with NM and SD tended to provide the best estimates among the three models. The model that was based on a PCA value of 97% yielded better displacement estimation than the models with PCA values of 95% and 100%. Based on the displacement estimation, the maximum inter-story drift ratio was used to produce the fragility curve that can be used for risk assessment. The fragility curve parameters obtained from the actual numerical and predicted models were investigated and yielded similar responses. The proposed model can thus provide accurate and quick responses in disaster case by rapidly predicting the structural damage information.


Sensors ◽  
2018 ◽  
Vol 18 (5) ◽  
pp. 1571 ◽  
Author(s):  
Jhonatan Camacho Navarro ◽  
Magda Ruiz ◽  
Rodolfo Villamizar ◽  
Luis Mujica ◽  
Jabid Quiroga

Author(s):  
A. Sandoli ◽  
G. P. Lignola ◽  
B. Calderoni ◽  
A. Prota

AbstractA hybrid seismic fragility model for territorial-scale seismic vulnerability assessment of masonry buildings is developed and presented in this paper. The method combines expert-judgment and mechanical approaches to derive typological fragility curves for Italian residential masonry building stock. The first classifies Italian masonry buildings in five different typological classes as function of age of construction, structural typology, and seismic behaviour and damaging of buildings observed following the most severe earthquakes occurred in Italy. The second, based on numerical analyses results conducted on building prototypes, provides all the parameters necessary for developing fragility functions. Peak-Ground Acceleration (PGA) at Ultimate Limit State attainable by each building’s class has been chosen as an Intensity Measure to represent fragility curves: three types of curve have been developed, each referred to mean, maximum and minimum value of PGAs defined for each building class. To represent the expected damage scenario for increasing earthquake intensities, a correlation between PGAs and Mercalli-Cancani-Sieber macroseismic intensity scale has been used and the corresponding fragility curves developed. Results show that the proposed building’s classes are representative of the Italian masonry building stock and that fragility curves are effective for predicting both seismic vulnerability and expected damage scenarios for seismic-prone areas. Finally, the fragility curves have been compared with empirical curves obtained through a macroseismic approach on Italian masonry buildings available in literature, underlining the differences between the methods.


Sign in / Sign up

Export Citation Format

Share Document