National Center For Research On Earthquake Engineering Research Articles

Development of PISA4SB for Applications in the Taiwan School Building Seismic Retrofit Program

The National Center for Research on Earthquake Engineering (NCREE) in Taiwan has implemented the static pushover procedures for the detailed seismic evaluation of school buildings. In the pushover analysis, the hinge properties of columns, beams, brick walls and RC walls are carefully calibrated based on the full scale experiments conducted in NCREE in the past ten years. Additionally, auxiliary modules for calculating the hinge properties have been developed by NCREE researchers to enhance user friendliness. This could allow engineers to more accurately apply available commercial software. However, when the auxiliary modules are applied to commercial software, the user must first define then assign the sections to the corresponding columns, beams, brick and RC walls in the text-based files. Without the graphic user interface, errors have commonly been found in cross-platform operations. The Platform of Inelastic Structural Analysis for 3D systems (PISA3D) has been developed since 2002 in NCREE. PISA3D provides a friendly user interface and high computational efficiency for engineers and researchers to simulate the nonlinear systems under various kinds of load effects. In order to resolve these issues noted above in the application to commercial software, NCREE has customized the nonlinear structural analysis program, PISA4SB (Platform for Inelastic Structural Analysis of School Buildings) specifically for the school building structures. PISA4SB allows the user to conveniently construct the analytical models for typical low-rise school buildings. After the gravity load analysis is conducted, PISA4SB automatically incorporates the column axial loads in calculating the parameters for the multilinear fracture material properties of any plastic hinge. PISA4SB evaluates the capacity curve and computes the seismic performance point based on the given design response spectrum provided by the user for the school building site. Engineers can conveniently apply PISA4SB to complete the seismic evaluation of a school building without cross-platform operations. The detailed development and example applications of PISA4SB are illustrated in this paper.

Cyclic Test of a Coupled Steel Plate Shear Wall Substructure

This research aimed to investigate the seismic behavior and design of the Coupled Steel Plate Shear Wall (C-SPSW). A prototype six-story C-SPSW building was designed based on the model building code. A 40% scale specimen was constructed as the bottom two-and-half-story substructure of the six-story C-SPSW prototype. The reduced scale substructural specimen was cyclically tested using the Multi-Axial Testing System (MATS) at the National Center for Research on Earthquake Engineering (NCREE). In addition to the cyclic lateral forces, the constant vertical loading and cyclic overturning moments were applied on the specimen simultaneously. The test results show that the CSPSW specimen behaved in a ductile manner and dissipated significant amounts of hysteresis energy during the cyclic loadings. Finally, based on the experimental results, the implications in the capacity design for the bottom boundary column are discussed. A numerical simulation using finite element model was conducted. The analytical results quite match the overall and local experimental responses.

Optimum design and experimental study of multiple tuned mass dampers with limited stroke

AbstractThis paper develops a two‐stage optimum design procedure for multiple tuned mass dampers (MTMD) to reduce structural dynamic responses with the limitation of MTMD's stroke. A new performance index, which is a linear combination of structural response ratio and MTMD stroke ratio by a weighting factor α, is proposed; α is in the range from 0 to 1.0. The larger the α, the more important the stroke. The case of α=1.0 indicates that MTMD is locked. The analytical results show that the MTMD's stroke can be significantly suppressed with little sacrifice of structural control effectiveness when an appropriate α is selected. To verify the design algorithm, a 360 kg‐MTMD composed of five TMD units arranged in parallel was fabricated. Shaking table tests of a large‐scale three‐story building with and without the MTMD under earthquake excitations were conducted at the National Center for Research on Earthquake Engineering (NCREE) in Taiwan. The experimental results show that MTMD is not only effective in mitigating the building responses but also is successful in suppressing its stroke. Copyright © 2010 John Wiley & Sons, Ltd.

A bio-inspired structural health monitoring system based on ambient vibration

A structural health monitoring (SHM) system based on naïve Bayesian (NB) damageclassification and DNA-like expression data was developed in this research. Adapted fromthe deoxyribonucleic acid (DNA) array concept in molecular biology, the proposedstructural health monitoring system is constructed utilizing a double-tier regressionprocess to extract the expression array from the structural time history recordedduring external excitations. The extracted array is symbolized as the variousgenes of the structure from the viewpoint of molecular biology and reflects thepossible damage conditions prevalent in the structure. A scaled down, six-story steelbuilding mounted on the shaking table of the National Center for Research onEarthquake Engineering (NCREE) was used as the benchmark. The structuralresponse at different damage levels and locations under ambient vibration wascollected to support the database for the proposed SHM system. To improve theprecision of detection in practical applications, the system was enhanced by anoptimization process using the likelihood selection method. The obtained arrayrepresenting the DNA array of the health condition of the structure was first evaluatedand ranked. A total of 12 groups of expression arrays were regenerated from acombination of four damage conditions. To keep the length of the array unchanged,the best 16 coefficients from every expression array were selected to form theoptimized SHM system. Test results from the ambient vibrations showed thatthe detection accuracy of the structural damage could be greatly enhanced bythe optimized expression array, when compared to the original system. Practicalverification also demonstrated that a rapid and reliable result could be givenby the final system within 1 min. The proposed system implements the idea oftransplanting the DNA array concept from molecular biology into the field of SHM.

Cyclic responses of three 2-story seismic concentrically braced frames

Abstract Three full scale two-story steel concentrically braced frames (CBFs) were tested at the National Center for Research on Earthquake Engineering (NCREE) in Taipei. The specimen is a single bay with the braces arranged in a two-story X-brace configuration. The main differences among the three tests are the brace types (hollow structural or wide-flange section) and the design criteria adopted for the gusset plate connections. Results of these three tests confirm that the two-story X-shape steel CBFs all have rather good energy dissipation characteristics up to a story drift of about 0.03 radians under the cyclically increasing lateral displacements. Severe brace local buckling and out-of-plane displacements were observed during each test. Tests confirm that both the 2t-linear and 8t-elliptical designs of the gusset plate connection provide satisfactory ductility for the steel CBF. Hollow structural section (HSS) braces fractured at a story drift smaller than that found using wide flange sections. The nonlinear fine element method (FEM) program ABAQUS was used to simulate the responses of the specimen. The base shear versus the story drift relationships obtained from the tests and the FEM analytical results are quite agreeable in various levels of lateral frame displacement. The analytical results confirm that the severe out-of-plane buckling of the braces can be accurately simulated. FEM analyses also illustrate that the steel moment resisting frame takes about 40% story shear when the inter-story drift is greater than 0.02 radians.

Sub-structural pseudo-dynamic performance of two full-scale two-story steel plate shear walls

This paper describes two eight-meter tall and four-meter wide, two-story steel plate shear walls (SPSWs) that were fabricated and tested using sub-structural pseudo-dynamic testing procedures in the National Center for Research on Earthquake Engineering (NCREE). In the Phase I tests, all wall panels were restrained using horizontal tube restrainers on both sides in order to minimize both the out-of-plane displacement and the buckling sound. In the Phase II tests, damaged steel plates were removed and replaced with new plates without restrainers. Both specimens were tested under pseudo-dynamic loads using several scaled ground accelerations. This paper presents primarily the design of the specimen, experimental results, and simplified analytical modeling techniques for Phase I specimen. Results of the Phase I tests show that (1) the SPSW specimen sustained three earthquakes without significant wall fracture or overall strength degradation, (2) the horizontal restrainers were effective in improving the serviceability of the SPSW, (3) the responses of the SPSW can be satisfactorily predicted using the strip model and the tension-only material property implemented in the PISA3D computer program, (4) the energy-dissipating capacity of the SPSW specimen was found to be substantially reduced when it was subjected to the same ground motions again, and (5) if the boundary elements are properly proportioned using the capacity design principle, the equivalent brace model is effective for the response analysis of SPSW buildings subjected to strong ground motions.

Soil–structure interaction effects observed in the in situ forced vibration and pushover tests of school buildings in Taiwan and their modeling considering the foundation flexibility

AbstractIn the conventional structural seismic analysis, the rigid base model is usually adopted without considering the flexibility of the ground, leading to inaccurate estimation of the vibration characteristics and the seismic response of the structure. In 2007, several in situ tests were conducted by the National Center for Research on Earthquake Engineering (NCREE) on the school buildings in the Guanmiao Elementary School in Tainan, Taiwan. For the study of soil–structure interaction (SSI) effects, the forced vibration test (FVT) was performed, and the deformation of the foundation system was measured during the pushover test. In this paper, the results of these in situ tests are presented and discussed, and the finite element models of the school buildings were generated for the simulation of the FVT and for the pushover analysis in order to investigate the difference between the rigid base model and the flexible base model. Results show that the mechanical properties of the structure and the foundation could be demonstrated in these in situ tests. Additionally, the introduction of the flexibility of the foundation has a considerable influence on the results of structural analysis. Copyright © 2009 John Wiley & Sons, Ltd.

Settlements of saturated clean sand deposits in shaking table tests

Shaking table tests were conducted on saturated clean Vietnam sand in the large biaxial laminar shear box (1880 mm×1880 mm×1520 mm) at the National Center for Research on Earthquake Engineering (NCREE), Taiwan. The settlement of sand specimens was measured and evaluated during and after each shaking test. Without liquefaction, the settlement of sand caused by shaking is very small. Significant volume changes occur only when there is liquefaction of sand. The volumetric strain of liquefied sand was calculated according to the measured settlement and the thickness of liquefied sand in the specimen. Relations between volumetric strain after liquefaction and the relative density of saturated clean sand were developed for various shaking durations and earthquake magnitudes. They are not affected by the shaking amplitude, frequency, and direction (one- or multidirectional shaking).

Application of time series based damage detection algorithms to the benchmark experiment at the National Center for Research on Earthquake Engineering (NCREE) in Taipei, Taiwan

In this paper, the time series based damage detection algorithms developed by Nair, et al. (2006) and Nair and Kiremidjian (2007) are applied to the benchmark experimental data from the National Center for Research on Earthquake Engineering (NCREE) in Taipei, Taiwan. Both acceleration and strain data are analyzed. The data are modeled as autoregressive (AR) processes, and damage sensitive features (DSF) and feature vectors are defined in terms of the first three AR coefficients. In the first algorithm developed by Nair, et al. (2006), hypothesis tests using the t-statistic are applied to evaluate the damaged state. A damage measure (DM) is defined to measure the damage extent. The results show that the DSF's from the acceleration data can detect damage while the DSF from the strain data can be used to localize the damage. The DM can be used for damage quantification. In the second algorithm developed by Nair and Kiremidjian (2007) a Gaussian Mixture Model (GMM) is used to model the feature vector, and the Mahalanobis distance is defined to measure damage extent. Additional distance measures are defined and applied in this paper to quantify damage. The results show that damage measures can be used to detect, quantify, and localize the damage for the high intensity and the bidirectional loading cases.

Object-oriented development and application of a nonlinear structural analysis framework

This paper describes the framework and application of numerical simulation software on earthquake engineering research and practice. The analysis kernel is developed at the National Center for Research on Earthquake Engineering (NCREE) and is entitled as “Platform of Inelastic Structural Analysis for 3D systems (PISA3D)”. The design of PISA3D framework adopts the Design Pattern and the Unified Process. PISA3D provides structural modeling and high computational efficiency for engineers and researchers to simulate the responses of nonlinear systems under various kinds of load effects. It includes static or cyclic loads, displacements, earthquake ground accelerations, and earthquake aftershocks. PISA3D is easy to extend and maintain due to its object-oriented nature. Advanced users can derive or compose its objects’ libraries to perform different types of structural analyses. Based on object-oriented techniques, VISA3D (Visualization of Inelastic Structural Analysis for 3D systems) has been implemented with usage of OpenGL for 3D graphics and MFC for graphical user interface (GUI). Its framework allows further extension on new input formats and new element types. VISA3D has been mainly developed as a post-processor to examine the analytical results of PISA3D through 2D/3D static or dynamic graphic approaches. It includes graphical checking of the structural model, mode shapes, deformations, extents and locations of plastic hinges, plotting of nodal velocity, acceleration, and energy distribution time histories. This paper then introduces NCREE’s recent development on the pre-processing framework GISA3D (Graphical Interface of Inelastic Structural Analysis for 3D systems). The GISA3D does not only supply features as a “post-processor”, but also fully supports operations of “model generation” via mouse motion. Users can create, remove, modify and set elements/nodes through mouse clicking, dragging and selecting. Finally, this paper illustrates the networked sub-structural pseudo dynamic tests using PISA3D as the analysis engine, and concludes with several successful applications of PISA3D/VISA3D/GISA3D on various researches and actual structural engineering projects.

Comparison of three different methods in investigating shallow shear-wave velocity structures in Ilan, Taiwan

The Central Weather Bureau (CWB) and National Center for Research on Earthquake Engineering (NCREE) launched a project to build an engineering geological database for strong-motion stations in Taiwan in 2000. The project measures shear-wave velocity using the suspension PS-logging method. In this study, we conduct array measurements of microtremors and apply the stress wave propagation method (SWPM) at seven free-field strong-motion stations in Ilan County to estimate shallow shear-wave velocity structures. We focus on the sediment layers of the top 100 m to compare the shear-wave velocity structures of the three different methods. There are some misfits among the results of the three different methods; so we calculate the values of Vs 30, Vs 100 and plot S-wave travel-time curves of these methods for each site to analyze the misfits effectively. This analysis helped us to prove the efficiency of the microtremor array method in investigating shear-wave velocity structures in the shallow subsurface. Moreover, the horizontal-to-vertical ratios of microtremors for each survey point show the existence of divergence at the same site. We considered this as evidence that misfits are caused by the heterogeneous nature of sediments and also due to the nature of the methods as being one-, two- and three-dimensional. Furthermore, the average shear-wave velocity structure of microtremor arrays may be more representative of the whole site.

Enabling the creation of domain-specific reference collections to support text-based information retrieval experiments in the architecture, engineering and construction industries

The increasing importance of text-based information retrieval (IR) developments in the architecture, engineering, and construction industries (AEC) and the lack of sharable testing resources to support these developments call for an approach that can be used to generate domain-specific reference collections. To address this need, the authors investigated the characteristics of the testing environment in AEC and ways to adapt dominant collection preparation methods for the domain. This paper presents the authors’ collection generation approach through the preparation process of the Taiwanese National Center for Research on Earthquake Engineering (NCREE) collection. The collection’s Chinese-to-English translation instruments are also discussed as matching semantic/linguistic resources are highly valued in AEC’s text-based IR developments. The paper also includes a use case for the NCREE collection to show how a collection generated by the proposed approach could be applied to support research experiment and validation. The direct outputs, the NCREE collection and its translation instruments, are sharable and reusable testing resources, while mechanisms for seeking collections from other researchers are part of the extended research endeavors.

Theoretical and experimental studies on repaired and rehabilitated reinforced concrete frames

In this paper, an effective repair and rehabilitation working method is proposed for moderately damaged reinforced concrete (RC) building structures after major earthquakes. Three RC frames with nil, half-height, and full-height brick walls are designed and tested at the National Center for Research on Earthquake Engineering (NCREE), Taiwan. After the columns of these nonductile RC frames are damaged, steel wire cables with nonshrinkage mortar are used to repair the damaged columns, and carbon fiber reinforced polymers (CFRP) are used to rehabilitate the damaged columns. A stress–strain relationship of the confined concrete is used in the theoretical sectional analysis. The columns are confined by steel wires and CFRP, and the "equivalent column model" is proposed in this paper and used to analyze the brick walls inside the RC frames. The analytical results can reasonably predict the lateral force–displacement relationships of these RC frames. Key words: nonductile frame, carbon fiber reinforced polymers, steel wire cable, repair, rehabilitation.

Full‐scale experimental verification of resetable semi‐active stiffness dampers

AbstractBecause of many advantages over other control systems, semi‐active control devices have received considerable attention for applications to civil infrastructures. A variety of different semi‐active control devices have been studied for applications to buildings and bridges subject to strong winds and earthquakes. Recently, a new semi‐active control device, referred to as the resetable semi‐active stiffness damper (RSASD), has been proposed and studied at the University of California, Irvine (UCI). It has been demonstrated by simulation results that such a RSASD is quite effective in protecting civil engineering structures against earthquakes, including detrimental near‐field earthquakes. In this paper, full‐scale hardware for RSASD is designed and manufactured using pressurized gas. Experimental tests on full‐scale RSASDs have been conducted to verify the hysteretic behaviours (energy dissipation characteristics) and the relation between the damper stiffness and the gas pressure. The correlation between the experimental results of the hysteresis loops of RASADs and that of the theoretical ones has been assessed qualitatively. Experimental results further show the linear relation between the gas pressure and the stiffness of the RSASD as theoretically predicted. Finally, shake table tests have also been conducted using an almost full‐scale 3‐storey steel frame model equipped with full‐scale RSASDs at the National Center for Research on Earthquake Engineering (NCREE), Taipei, Taiwan, and the results are presented. Experimental results demonstrate the performance of RSASDs in reducing the responses of the large‐scale building model subject to several near‐field earthquakes. Copyright © 2007 John Wiley & Sons, Ltd.

A Large Biaxial Shear Box for Shaking Table Test on Saturated Sand

Abstract A large flexible laminar shear box was developed for the study of the behavior of saturated sand, especially liquefaction, and soil-structure interactions under two-dimensional earthquake shaking on a shaking table at the National Center for Research on Earthquake Engineering (NCREE) in Taiwan. The shear box is composed of 15 layers of aluminum alloy inner and outer frames with a specimen size of 1880 by 1880 by 1520 mm. The soil at various depths inside the shear box can move, without torsion, according to the two-dimensional wave action induced by the shaking table. The sand specimen inside the shear box is prepared by the wet sedimentation method from a large pluviation device. Instruments are installed to measure the displacements, accelerations, and water pressures at various locations. Shaking table tests of the laminar shear box with and without a sand specimen were conducted. The test results showed that the performance of the biaxial laminar box and the instrumentation are satisfactory.

Experimental evaluation of piecewise exact solution for predicting seismic responses of spherical sliding type isolated structures

The use of base isolation for enhancing seismic resistibility has been proven as an efficient method in experimental and theoretical studies. It is usual to insert a flexible device in the horizontal direction to permit the most of relative deformation of a structure at this level. Because the rigidity of the superstructure is much higher than that of the base isolator underneath the structure, the behavior of the superstructure can be idealized as a rigid body during earthquakes. In general, hundreds of degrees of freedom and a step-by-step time history analysis are the basic requirements for calculating the seismic response of a base-isolated structure under earthquakes. In order to develop a simple tool which can be easily adopted for calculating the seismic responses of the spherical sliding type isolated structures, a piecewise exact solution for predicting the seismic responses of base-isolated structures has been derived in this study. The comparison between the experimental results conducted at the National Center for Research on Earthquake Engineering (NCREE) in Taiwan and the analytical results obtained from the piecewise exact solution show that the formulation derived in this study can predict the seismic responses of the base-isolated structure with a very high accuracy. Copyright © 2005 John Wiley & Sons, Ltd.

Seismic behavior of steel beam and reinforced concrete column connections

This paper aims to investigate the seismic behavior of steel beam to reinforced concrete column connections with or without the floor slab, acting as a proof test for a three-story–three-bay reinforced concrete column and steel beam (RCS) in-plane frame tested at the National Center for Research on Earthquake Engineering (NCREE), Taiwan, by the Taiwan–USA international research cooperation group. In total, six cruciform RCS joint sub-assemblages were constructed and tested. Parameters considered included composite effects of the slab and beam, the tie configuration in the panel zone, effects of the cross-beam, and the loading protocol. Force–deformation behavior was also simulated by a nonlinear analysis program, DRAIN-2DX, with consideration of composite effects of the beam and slab as well as shear distortion in the panel zone. Test results showed that all specimens performed in a ductile manner with plastic hinges formed in the beam ends near the column face. It was found that the ultimate strength of the composite beam was increased by 27% on average, compared with that of the steel beam without the slab.

A Study on the Shear-Failure of Circular Sectioned Bridge Column Retrofitted by Using CFRP Jacketing

In this paper, analytical and experimental studies on the shear-failure and confinement of circular section RC bridge columns retrofitted by carbon fiber reinforced plastic (CFRP) jacketing were performed. An effective confined concrete constitutive model named Modified L-L Model proposed by Li et al. (Li, Y.-F., Lin, C.-T. and Sung, Y.-Y. (2003). A Constitutive Model for Concrete Confined with Carbon Fiber Reinforced Plastics, Mechanics of Materials, 35:603–619.) is introduced and used to determine the thickness of CFRP for retrofitting bridge columns, and to analyze the lateral force–displacement relationship of circular sectioned bridge columns. In the Modified L-L Model, the lateral confinement of the concrete comes from both steel reinforcement and CFRP composite material. Three 40%-scale bridge columns with shear-failure mode were tested under cyclic loading at the National Center for Research on Earthquake Engineering (NCREE). The analytical lateral force–lateral displacement relationship of bridge columns using the Modified L-L Model can predict the lateral force–lateral displacement relationship of experimental result very well, and the prediction shows that the Modified L-L Model can be used in seismic retrofit analysis. In the meantime, the performance of retrofitted bridge columns can be greatly improved by using CFRP composite material.

Identification of modal parameters from measured input and output data using a vector backward auto-regressive with exogeneous model

This paper proposes a modal identification system based on vector backward auto-regressive with exogeneous (VBARX) model. The model is an extension of vector backward auto-regressive (VBAR). Both the backward models offer the same benefits in selecting physical modes, since both can provide a determinate boundary that separates system modes from spurious modes. The VBAR model can identify the structural parameters from only output data. In some circumstances, if the input data are available, the extended model, VBARX model, provides an additional advantage over the VBAR model. In this study, an equivalent state-space model derived from measured input and output data is transformed from the VBARX model. Consequently, the structural modal parameters can be estimated accurately using the equivalent state-space model. Two examples of modal identification are presented to demonstrate the availability and effectiveness of the proposed VBARX method. (1) Numerical data simulated in a 3-d.o.f. dynamic system with various types of input data and various noise levels. (2) Experimental data obtained from the National Center for Research on Earthquake Engineering (NCREE) in Taiwan, concerning five-story 1 2 -scale steel structure under a shaking table test.

A preliminary study of earthquake building damage and life loss due to the chi‐chi earthquake

By using the data provided in the Chi‐Chi Earthquake Database and Management System (CEDAMS) of the National Center for Research on Earthquake Engineering (NCREE) and the model of earthquake loss estimation developed by McCormack and Rad (1997), this paper intends to evaluate the losses caused by the Chi‐Chi Earthquake of 1999 in Taiwan. The data has been adjusted and modified to fit the model. All the results show a close match to real damage. The robustness of the model suggests that it can be adopted for the prediction of future earthquake damage and therefore can support the government agencies in making better decisions on earthquake recovery activities.