Earthquake Input Research Articles

Inspection and evaluation of bridge structures for earthquakes risk

The 2017 Earthquake Source and Hazard Map Update in 2017 showed a significant change to the previous earthquake map. An increase in the number of active faults and high magnitude earthquake events indicates an increased potential for earthquake risk. The availability of qualified seismic manual is a must to support the direction of government policy in the provision of infrastructure, especially roads and bridges in a sustainable manner. This study aims to determine the value of the vulnerability of existing bridges against earthquakes and alternative reinforcement that can be done. The reinforcement philosophy is based on performance, similar to the philosophy used in the design of new bridges. Performance criteria are examined using earthquakes with a probability of exceeding 7% in 75 years. Performance criteria are determined based on the level of importance and remaining life of the bridge service. An example of a case study was made by examining and evaluating a prestressed girder bridge located in the earthquake zone 4 of the Jakarta area. Analysis and evaluation of bridge capacity is made using the SAP 2000 program. The 3 (three) dimension model is used to calculate the effect of 3 (three) structural dimensions on the dynamic behavior of the bridge. Earthquake input is made in the form of spectra response according to SNI 2833-2016. For earthquake loading in the X and Y direction the g/R scale factor is used (9.81/5), which is 1.96. The basic shear capacity of the column is calculated according to SNI 2833-2016 which consists of the shear capacity of the contribution of the concrete section and reinforcement. Based on the analysis, it was obtained that the column sliding capacity was 1333.3 kN. The value of the capacity is greater than the ultimate shear load of 519.07 kN so it can be concluded that the sliding capacity of the column still meets the earthquake load so that no structural reinforcement is needed.

Seismic Response Analyses of Transmission Towers under Multidimensional Ground Motions with Rocking and Torsion Components

AbstractMost current studies on the seismic responses of transmission towers are performed using two or three translational components of ground motion as earthquake inputs. In this study, a novel ...

Influences of earthquake input models on nonlinear seismic performances of minaret-foundation-soil interaction systems

Minarets, which are tall and slender structures, are important elements of mosques. Seismic performances of minarets can be strongly affected by the nonlinear dynamic soil-structure interaction and earthquake input mechanism models. The present paper investigates the influences of different earthquake input mechanism models on the nonlinear seismic performances of tall and slender minarets considering nonlinearity of both soil and structure behaviors. Three different minaret types constructed with concrete, masonry brick and stone materials are selected for the applications. Direct soil-structure interaction (SSI) approach is taken into account in the 3D finite element models of the minaret-foundation-soil interaction systems. Tie contact between the soil and foundation interfaces and infinite elements on the far sides of the soil domain are utilized in the 3D models. Nonlinear behaviors of masonry and concrete units, and homogenous soil domain are modeled using Concrete Damage Plasticity (CDP) and Mohr-Coulomb failure criteria. The standard rigid-base free, massless-foundation free, massed-foundation free and massed-foundation deconvolved earthquake input models are considered in the nonlinear seismic analyses. Three different earthquake records are selected for the nonlinear analyses and they are matched to the target response spectrum with return period of 475 years. The deconvolved ground motions at the rigid half-space bedrock are calculated from the matched records using the equivalent linear frequency domain analyses. Frequency and mode shapes, displacements, drift ratios, tensile strain and stress propagation patterns and damage ratios of brick, stone and concrete minaret models subjected to combined horizontal and vertical ground motions are determined for four earthquake input mechanism models and compared with each other.

Shaking table test study on seismic performance of inclined pile foundations in liquefiable soil

Inclined pile foundations are widely used in civil engineering by virtue of sufficient horizontal stiffness, but few studies have touched upon the seismic performance of inclined piles in liquefiable soil. To better understand the performance of the inclined piles in liquefiable soil under earthquake conditions, a series of 1 g shaking table tests of inclined and vertical piles in liquefiable soil were performed. Superstructure-pile-soil dynamic interaction was considered while three types of earthquake waves with different characteristics were selected as the applied earthquake motions. The horizontal acceleration of the superstructure and the pile cap, the rotational acceleration of the pile cap, the total base shear force, and the bending moment of two types of physical models were monitored and analyzed. The results show that inclined piles in liquefiable soil can effectively reduce the horizontal vibration of the superstructure and the pile cap, and the acceleration reduction of the pile cap is about 2.5 times larger than that of the superstructure. Meanwhile, inclined piles can also reduce the total base shear force, and the extent of reduction depends on the input earthquake wave. Besides, the results suggest that the maximum bending moment of inclined piles is located at the pile head, and its value is positively correlated with the amplitude of the earthquake wave, and is affected by the type of the input earthquake wave. Overall, inclined pile foundations show satisfactory seismic performance for a superstructure-foundation-liquefiable soil system, and this study, with a rich amount of data, can serve as an important reference for the seismic design of inclined piles in liquefiable soil.

Application of adaptive wavelet transform based multiple analytical mode decomposition for damage progression identification of Cable-Stayed bridge via shake table test

Extracting useful information (damage existence, location, identification, and quantification) from measured signals for damage identification is critical in structural health monitoring, while time-varying nature of most signals often require huge efforts. In this paper, adaptive wavelet analysis AWT is first introduced as a preprocessing approach of clearer, smoother and more accurate time–frequency representation. Optimized analytical mode decomposition (AMD) is then utilized for signal component extraction, with the help of AWT for bisecting frequency determination. Examples of time-varying signals of sinusoidal function and Duffing systems are used to illustrate the advantages of the algorithm, which proves to be successful in signal decomposition. Multiple AMD (MAMD) with the optimized algorithm is then utilized together with AWT for signal decomposition and system identification of the shake table test of a 1/20-scale cable-stayed bridge model. The extracted stiffness and damping coefficients retain a preliminary indication of the damage progression during the earthquake input.

Plastic damage analysis of pile foundation of nuclear power plants under beyond-design basis earthquake excitation

With the rapid development of nuclear industry in China, an increasing number of nuclear power plants (NPPs) are unavoidable to be constructed upon non-lithological foundations. Therefore, it is essential to optimize the current evaluation methods for non-lithological foundation reinforcement plans. By using the Octree discretization method combining with the scaled boundary polyhedron finite element method (SBFEM), a refined calculation model of a Generation III+ NPP is constructed. Due to the highly nonlinear dynamic characteristics of the system involved, this paper adopts a generalized plasticity model for the soil, a plastic damage model for the piles, and a nonlinear overburden layer-based seismic input method. Subsequently, large scale plastic damage analysis in detail to the NPPs under beyond-design basis earthquake inputs is performed. The results show that the pile foundation damage characteristics and distribution acquired from simulations agree well with the data from actual earthquake disasters. The most severe damage to the pile foundation occurred at the interface between the end of the pile and the base mat. The inclusion of plastic damage showed that the floor response spectra of the nuclear island experiences significant changes in three dimensions. Therefore, the effect of pile damage to the dynamic response of the power plants should be considered for strong earthquake excitation. The computational and analysis methods proposed in this paper can effectively reflect the dynamic nonlinear response of the nuclear power plants pile foundation-soil interaction.

Response of low-rise building with geotechnical seismic isolation system

The Geotechnical Seismic Isolation (GSI) is recently recommended as an innovative base isolation system placed below the foundation of the superstructure for protection from earthquake damages. Low-shear modulus and high damping material such as Sand-Rubber Mixture (SRM) is used for the GSI layer. However, the compressible nature of SRM in the GSI layer leads to low bearing capacity and high settlement of foundations. In view of this, a GSI system consisting of SRM and geogrid reinforcement is proposed for low-rise buildings in the present study. Finite element based two-dimensional numerical investigation on the seismic performance of a two-storied building supported on raft footing resting on the proposed GSI system was carried out considering the soil–structure interaction. The nonlinearities of the subsurface materials were duly considered using hypoelastic formulations to account for the strain-dependent response. The effectiveness of geogrid reinforcement for the GSI system is demonstrated through seismic settlement analysis based on which optimum geogrid layers were chosen. Effect of various factors such as the thickness of GSI layer, frequency content of earthquake input motions on the seismic demand of the framed structure resting on the proposed GSI system was investigated. While the contribution of SRM was predominant in reducing the peak ground acceleration experienced by the building, the contribution of geogrids was evident in reducing the seismic settlement and lateral deformations on the structure. The results demonstrate the suitability of using the proposed GSI system with a thickness of 0.1B–0.2B (B is the footing width) with double layered geogrid reinforcement in significantly reducing the seismic demands of low-rise building.

Assessment of three-dimensional RC moment-resisting frames under repeated earthquakes

Earthquakes are one of the major unavoidable natural disasters. These are characterized by the recorded ground motion data at a particular location. In any real earthquake event, shaking repeatedly occur several times within a few hours or days. In view of lack of time between the occurrences of tremors, the rehabilitation of the structure often becomes impractical, and the structural damages get accumulated. Hence, it is imperative to assess the behavior of reinforced concrete (RC) buildings under repeated earthquakes to prevent a disaster. The current practices of earthquake-resistant design utilize only a single strongest earthquake input in the form of a response spectrum, corresponding to the seismic code of practice at the site location. Hence, this investigation is primarily focused on vulnerability assessment of three-dimensional RC building frames conformed to the Indian standard codes of practice under bi-directional single and repeated ground motions. Incremental dynamic analysis is carried out to assess the inelastic behavior of the structure in terms of maximum horizontal displacement, residual displacement, and maximum inter-story drift ratio for particular spectral accelerations. The results obtained in this investigation conclude that the collapse capacity of RC building under repeated earthquakes reduces significantly compared to that of the most severe single earthquake. This emphasizes the need to account for repeated earthquake forces during the design phase in order to build a seismic resilient structure.

In-Cabinet Response Spectrum Generation Using Frequency Domain Analysis Method

Seismic qualification of instruments and devices mounted on electrical cabinets in a nuclear power plant is performed in this study by means of the in-cabinet response spectrum (ICRS). A simple method and two rigorous methods are proposed in the EPRI NP-7146-SL guidelines for generating the ICRS. The simple method of EPRI can give unrealistic spectra that are excessively conservative in many cases. In the past, the time domain analysis (TDA) methods have been mostly used to analyze a structure. However, the TDA requires the generation of an artificial earthquake input motion compatible to the target response spectrum. The process of generating an artificial earthquake may involve a great deal of uncertainty. In addition, many time history analyses should be performed to increase the accuracy of the results. This study developed a numerical analysis program for generating the ICRS by frequency domain analysis (FDA) method. The developed program was validated by the numerical study. The ICRS calculated by FDA thoroughly matched with those obtained from TDA. This study then confirms that the method it proposes can simply and efficiently generate the ICRS compared to the time domain method.

A shake table test study of reinforced concrete shear wall model structures exhibiting strong non-linear behaviors

Shake table test is one of the most important manners for the performance evaluation of structures under strong earthquakes and for the verification of refined numerical simulation methods. To this end, in the present paper, shake table tests on two concrete shear wall model structures, together with the tests of complete uniaxial compressive constitutive curves of concrete, were carried out. The purpose of the tests is to provide quantitative benchmark results for the verification and improvement of refined multi-scale numerical simulation method for structures exhibiting strong non-linear behaviors. Three important properties were carefully taken into account in the tests, including: (1) The scale ratio should not be too small so that detailed local damage could be revealed and the experimental results could serve as benchmark data; (2) The model structures should exhibit strong nonlinear behaviors but the accumulated damage between load cases should be avoided; (3) Concrete specimens should be simultaneously tested to capture the complete stress-strain curves rather than only the two parameters (the compressive strength and Young’s modulus); and (4) The unavoidable randomness involved in concrete structures should be quantified. To satisfy the above requirements, some special measures were taken, including: e.g., vertical prestressed tendons were exerted to make up the inadequacy of gravitational compression due to the inadequate density scaling; strong earthquake inputs were input directly after linear stage tests so that strong non-linearity occurred directly in the model structures, similar to practical structures subjected to real earthquakes; and 54 concrete specimens were tested for constitutive law and two model structures were tested for comparison and characterizing the effects of randomness. The experimental results, including frequencies and vibrational modes, the observed damage distributions and the responses of model structures are elaborately delineated and discussed in the paper. In particular, besides flexural-shear damage, compressive damage was also observed in the test model structures. This is frequently observed in practical earthquake damage but is usually not exhibited in most shake table tests. Such detailed information together with observed data provided valuable benchmark data for the verification and improvement of refined numerical simulation method, which will be detailed in other papers.

Smart Seismic Control System for High-Rise Buildings Using Large-Stroke Viscous Dampers Through Connection to Strong-Back Core Frame

An innovative structural control system is proposed for high-rise buildings. A damping layer is provided between a stiff upper core frame suspended from the top of the main building and a stiff lower core frame connected to the building foundation. As the ratio of stiffness of both core frames to that of the main building becomes larger, the relative displacement in the damping layer (damper deformation) approaches to the top floor displacement of the main building. The large displacement of the top floor displacement of the main building is taken full advantage in the proposed control system as most of the total displacement of the main building results from the damper deformation instead of interstory drift. Transformation of the multi-degree-of-freedom (MDOF) model into the single-degree-of-freedom (SDOF) model enables a simplified but rather accurate response evaluation for pulse-type and long-duration earthquake ground motions. The results of the time history response analysis of buildings including this control system are presented for various recorded ground motions. Finally, the effectiveness of the proposed structural control system is discussed from the viewpoint of earthquake input energy.

Assessment of the effectiveness of Multiple-Stripe Analysis by using a stochastic earthquake input model

Current practical approaches for probabilistic seismic performance assessment of structures rely on the concept of intensity measure (IM), which is used to decompose the problem into hazard analysis and conditional seismic demand analysis. These approaches are potentially more efficient than traditional Monte-Carlo based ones, but the performance estimates can be negatively influenced by inadequate setup choices. These include, among the others, the number of seismic intensity levels to consider, the number of structural analyses to be performed at each intensity level, and the lognormality assumption for the conditional demand. This paper investigates the accuracy and effectiveness of a widespread IM-based method for seismic performance assessment, multi-stripe analysis (MSA), through an extensive parametric study carried out on a three-story steel moment-resisting frame, by considering different setup choices and various engineering demand parameters. A stochastic ground motion model is employed to describe the seismic hazard and the spectral acceleration is used as intensity measure. The results of the convolution between the seismic hazard and the conditional probability of exceedance obtained via MSA are compared with the estimates obtained via Subset Simulation, providing a reference solution. The comparison gives useful insights on the influence of the main parameters controlling the accuracy and precision of the IM-based method. It is shown that, with the proper settings, MSA can provide risk estimates as accurate as those obtained via Subset Simulation, at a fraction of the computational cost.

Determining the location of sensors for seismic damage detection in steel girder bridges with elastomeric bearings

In planning a bridge health monitoring with minimum sensors for long-term monitoring, it is necessary to accurately predict the bridge behavior including its nonlinearity and identify the damaged bridge components when a strong earthquake strikes. This article presents a methodology for the selection of sensors and their arrangement for detecting seismic damage in an in-service steel plate girder bridge system. In this study, a detailed span-based model was developed for the finite element simulation including the effect of the rubber bearing and piers, and the damage control by the side blocks. The finite element dynamic simulation was carried out with input earthquake acceleration to investigate the seismic behavior and grasp the damageable parts during an earthquake. Based on the results of finite element dynamic simulation, a fault tree analysis was carried out to reveal more about the bridge behavior, the failure modes, and the occurrence of damage. It was found that the side block, the bearing stiffener, and the horizontal bracing on the fixed side of the bridge are most important to be monitored for the evaluation of soundness of a plate girder bridge immediately after an earthquake. Finally, a sensor arrangement for the bridge was proposed based on the analysis results.

Behavior of pile embedded in different soil types under the effect of earthquake

In the seismic areas, piles are often passed through shallow loose or soft soil deposits and rest on end bearing soils. Damages due to earthquakes in piles built in layered soils occurred close to interfaces separating layers with very different shear moduli. In this study 3D finite element analyses are performed to simulate a soil-pile system under earthquake excitation in different soil types. As an example, the soil profiles of active seismic zones in Iraq will be used. For this a data base was prepared for static and dynamic parameters of different Iraq soils which were gathered and typical profiles for north, middle and south of Iraq were established. The properties of soils were then used as input dynamic data for finite element program PLAXIS 3D 2013 to study the response of single pile foundation. As earthquake input data the recording one obtained from the April 20, 2012 earthquake which hit Ali Al-Gharbi in Missan Province in Iraq was used, because this was one of the influential earthquakes. As a result the maximum bending moment occurs at the influence of different soil layers, also according to the soil-pile interaction, the deflected shape have the same behavior of pile embedded in sand and clayey soil as well as the pile that embedded in two clayey soil layers with thin sandy layers in between.

Shaking table test on flexible joints of mountain tunnels passing through normal fault

Tunnels often suffered severe seismic damage when passing through the active fault in high intensity earthquake area. The fault movement might be divided into fault movement and seismic motion under the strong earthquake action, and both of them could have the significant influence on the stability of tunnel structure. To improve the seismic performance of the mountain tunnel through fault, a design idea or method of the between sectional tunnel structures with the flexible joint were put forward to run through the active fault and verified or analyzed by using the shaking table test. Firstly, the typical seismic damage characteristics of the tunnel passing through the fault were analyzed after Wenchuan earthquake; secondly, the sectional tunnel linings with the flexible joint were designed in the active fault zone under the strong seismic motion, and the basic theory of this design method was presented in detail. Thirdly, the scaled model shaking table test was carried out to study the seismic performance of flexible joints of tunnels under the normal fault action, and some key parameters of the test was designed, including similarity relationship, boundary condition, sensor layout, input earthquake wave and flexible joint design. The test results showed that the joints between sectional linings could make structure localize damage rather than global damage, and compared to seismic motion, the fault movement suffered more serious damage for the tunnel structure. The tunnel lining at hanging wall was more susceptible to damage or destroy than that at the footwall under the normal fault action, and the flexible joint could adapt to the differential deformation of fault during the strong earthquake. Lastly, the dynamic response of the tunnel lining demonstrated that the upper-structure of the tunnel mainly suffered the severe seismic load, while the lower-structure might experiences the imposed deformation of fault movement under strong earthquake motion. So the design method of the sectional tunnel lining with the flexible joint would be applied to tunnel structure design to improve the adaptive deformation ability of tunnel structure through active fault.

Failure Mechanism of Horizontal Layered Rock Slope under the Coupling of Earthquake and Weathering

In order to further reveal the dynamic failure process of horizontal complex layered rock slope in the coupling action of earthquake and weathering, based on the three‐dimensional particle flow software PFC3D, the rock triaxial test was first carried out to obtain the macroscopic rock mechanics parameters. Secondly, PFC3D was used to establish a three‐dimensional discrete element model of slope under 4 modes. Finally, the Wenchuan earthquake wave dynamic input is used to simulate the coupling effect of each model slope on earthquake‐weathering. Under the progressive failure process, the results show that, during the triaxial test, the mudstone particles and sandstone particles exhibited shear failure and tensile failure, respectively. The seismic failure mode of the horizontal complex layered rock slope model is divided into tensile fracture‐horizontal sliding failure (cavity depth 1.5 m and fissure depth 25%), tensile cracking‐caving‐dumping failure (cavity depth 3 m and fissure depth 37.5%), caving‐dumping‐rotation failure (cavity depth 4.5 m and fissure depth 50%), and caving‐slip‐rotation failure (cavity depth 6 m and fissure depth 62.5%), and the maximum vertical displacement of Model 2 can reach 6.2 m, and the maximum positive horizontal displacement is 7.8 m. With the deepening of the weathering degree, the coordination number of the rock block shows the attenuation advance effect and the elevation attenuation effect during the seismic period of 2–15 s. The total energy dissipation of the slope can be divided into two stages: fracture collision and overall collapse. The energy dissipation is more concentrated in the rock fracture collision stage, accounting for 89% to 95% of the total energy.

Performance Evaluation of Curved-TADAS Damper on Seismic Response of Moment Resisting Steel Frame

In this study, the performance of triangular added damping and stiffness (TADAS) dampers combined with curved dampers (Curved-TADAS damper) is evaluated in moment resisting steel frame (MRSF). These dampers are passive and install in the beam-column connection region. Variable parameters of this study involve the width of curved damper (50, 75 and 100 mm), the thickness of TADAS damper (5 and 10 mm) and the number of TADAS damper (2, 4 and 6). Evaluation of MRSF was performed using the finite element method by ABAQUS. Two different experimental studies were used in order to evaluate the validity of the numerical simulation method and a suitable agreement was obtained. The response of the frames in different modes was compared with parameters such as energy dissipation, strength, stiffness, hysteresis damping ratio, and ductility. In the end, the performance of the proposed dampers was compared with the curved damper. The results show that Curved-TADAS dampers reduce the structural responses to seismic loading and prevent structural failure due to the dissipation of a large amount of seismic input energy. The function of these systems is such that, by performing special deformations, they absorb and deplete a large amount of earthquake input energy of the structure.

Probability density evolution analysis of stochastic seismic response of structures with dependent random parameters

Performance evaluation and reliability assessment of real-world structures under earthquakes is of paramount importance. Generally, different mechanical property parameters of a structure are usually not independent, nor completely dependent, but partly dependent or correlated. Therefore, how to reasonably characterize such partial dependency and whether such partial dependency real matters in the stochastic response and reliability of structures under earthquakes are crucial issues. For this purpose, in the present paper, a novel physically-guided data-driven methodology of capturing the correlation configuration of basic random variables and the probability density evolution method are synthesized. The physically-guided data-driven methodology is firstly outlined. In this methodology, the underlying physical mechanism between dependent random variables is firstly involved to establish a random function model, and then the available observed data are adopted to identify the parameters in this model. What is more, physical constraints are also revealed for the initial modulus of elasticity and compressive strength of concrete. The probability density evolution method is then adopted, and the point selection by minimizing the GF-discrepancy is adjusted according to the correlation configuration and physical constraints. A reinforced concrete frame structure subjected to earthquake input is studied. It is found that when the structure is in the strongly nonlinear stage, the correlation configuration has considerable effects on the standard deviation of the stochastic responses, by a factor of nearly 2. In addition, whether the mechanical parameters in different floors are independent or not has great effects on the stochastic responses as well. Problems to be further studied are also outlined.

APPLICABILITY OF THE JAPANESE RECIPE FOR PREDICTING STRONG GROUND MOTIONS BY HERP TO EUROPE AND MIDDLE EAST CRUSTAL EARTHQUAKES

The procedure of evaluating fault parameters, so called Recipe, for predicting strong ground motions by the HERP [Headquarters for Earthquake Research Promotion, 2005], Japan, is often applied to assessment of design input earthquake motions for nuclear power plants in Japan. Due to this situation, the International Atomic Energy Agency [2015] adopted this Recipe in Safety Report Series No. 85. However, this Recipe was validated only for Japanese earthquakes. Hence, we examined the validation of the Recipe by comparing the estimated strong ground motions based on the Recipe with those by the GMPE (Ground Motion Prediction Equation) obtained by Akkar et al. [2014] from the Europe and Middle East crustal earthquakes. We concluded that the short-period level in the Recipe should be reduced to 50% for the second-stage earthquakes and that the stress drop equation of a circular crack should be altered. We also concluded that the short-period level should be reduced to 55% for the first-stage earthquakes under the condition that the stress drop equation of a circular crack should be maintained.

Peak ground acceleration prediction by fuzzy logic modeling for Iranian plateau

In this study, fuzzy logic modeling is applied to a complex and nonlinear set of data to predict both horizontal and vertical peak ground accelerations in Iranian plateau. The data used for the model include an up-to-date seismic catalogue from earthquakes in Iran for prediction of both horizontal and vertical acceleration of a probable earthquake. Fuzzy logic toolbox on MATLAB program was used for modeling. Earthquake magnitude ranging from 4 to 7.4, source-to-site distance from 7 to 80 km and three different site conditions were considered: rock, stiff soil and soft soil. Results are compared with those from worldwide and regional attenuation relationships, which show the higher capability of the model in comparison with the other models. After training the model, testing of the fuzzy model with the remaining data set was performed to confirm the accuracy of the model. Changes in the peak ground accelerations in connection with changes in input parameters are studied which are in agreement with basic characteristics of earthquake input motions.