Seismic Design Parameters Research Articles

Seismic design parameters (R, Cd, and Ω0) for uncoupled composite plate shear walls−concrete filled (C‐PSW/CF)

AbstractComposite Plate Shear Walls−Concrete Filled (C‐PSW/CF) are an innovative seismic force resisting system recently adapted for building applications. The walls consist of parallel steel faceplates connected with tie bars and filled with concrete. This paper summarizes the results of a recent FEMA P695 study completed to verify seismic design parameters for uncoupled C‐PSW/CFs with rectangular flange plate boundary elements. Seven archetype structures were: (i) designed, (ii) modeled using a benchmarked fiber‐based finite element analysis approach, (iii) subjected to nonlinear pushover analysis, (iv) and to incremental nonlinear dynamic analysis to failure for 22‐sets of scaled ground motions, and (v) the results were statistically analyzed to assess performance. These structures ranged from three (3) to twenty‐two (22) stories and included both planar and C‐shaped configurations. As part of this design process, recommendations for stiffness approximations for linear analysis of C‐PSW/CFs were developed. Additionally, these nonlinear incremental dynamic analysis results were post‐processed to determine the rotation and strain demands at the base of these structures at the design basis, maximum considered, and failure level earthquakes. These results showed that the rotation and strain demand at failure level earthquakes were comparable regardless of the ground motion. Ultimately, this FEMA P695 approach verified the R factor of 6.5, Cd factor of 5.5, and Ω0 of 2.5 for C‐PSW/CFs with boundary elements.

A greedy algorithm for wavelet-based time domain response spectrum matching

U.S. Nuclear Regulatory Commission NUREG-0800, “Standard Review Plan,” Section 3.7.1, “Seismic Design Parameters,” Revision 4, describes acceptance criteria for seismic design time histories, including response spectrum matching and checking power spectral density functions. This paper is a focused introduction of a new algorithm developed for response spectrum matching, named as the Greedy Wavelet Method (GWM), which shows substantial advances in convergence characteristics over the RspMatch09 program. RspMatch09 is widely used by the nuclear industry and represents the results of multiple iterations of enhancement by international researchers since the basic method was first introduced in 1978. GWM modifies a seed acceleration time history by adding just one wavelet in each iteration, in contrast to RspMathc09 that adds a set of weighted wavelets, with the weights determined by solving an optimization problem in each iteration. GWM includes procedures to address two specific issues leading to convergence difficulties in response spectrum matching: The shape of the wavelets can be numerically distorted at high frequencies and the wavelet lead time previously recommended is not sufficiently long. These newly developed procedures made GWM unconditionally stable. For the benchmark problem, GWM was demonstrated to save 99.5% of the wavelets required by RspMatch09. We also implemented in GWM several advanced, interactive tools to perform baseline corrections and other related tasks. Examples provided in this paper are for demonstration purposes only.

Frequency-domain preliminary assessment of coupled site and SSI effects according to the Algerian seismic provisions

PurposeSeveral studies were made on paired site and soil–structure interaction (SSI) effects, but most of them were site specific. This paper aims to investigate the impact of SSI effects in conjunction with local soil condition effects on the seismic response of typical multistory low- to mid-rise–reinforced concrete (RC) buildings resting on Algerian regulatory design sites through a global explicit transfer function (TF).Design/methodology/approachA preliminary quantification of SSI effects associated with site effects is carried out through a frequency-domain solution based on the concept of rock-to-soil surface displacement TF performed for each design site category. It results from the combination of the TFs of structure, foundation and soil and reflects how seismic waves are amplified due to changes in the geological contrast between the rock and overlying soil deposits. As well, response modification factors, denoting displacement ratios of the building responses within the flexible and site-structure conditions with respect to the fixed-base one, are carried out.FindingsIn the context of Algerian seismic regulation, the study provides a clear vision of how and when site or SSI effects are expected to be influential, as opposed to the fixed-base hypothesis still retained by the current regulation. This helps engineers to be aware of the extent of the expected seismic damage.Research limitations/implicationsThe research applies to low- to mid-rise RC buildings within the Algerian seismic regulation, but it may also be expanded to other examples that fall under other seismic regulations.Practical implicationsThe response modification ratio is a quantitative approach to assessing response fluctuations. It draws attention to how the roof level drift varies depending on the condition. These results can be used as numerical parameters in structural seismic design when the structure is comparable because they provide useful information about how the two phenomena interact with the structure.Originality/valueThe study goes beyond particular situations dealing with site specific and offers effective indicators and quantitative evaluation of combined site and SSI effects according to the current national seismic provisions, where no indication about site or SSI effects exists.

Plastic hinge length and inelastic rotational capacity of reinforced concrete shear walls detailed with Self-Centering reinforcement

The application of damage-resisting reinforced concrete (RC) shear walls is a novel topic in structural engineering. In recent years, more studies have been performed on the response of damage-resisting RC shear walls. These studies were mainly conducted on one-story specimens with limited ranges of dimension, reinforcement ratio, and axial load ratio. Furthermore, the studies were mostly aimed at the performance parameters of damage-resisting walls and overlooked the seismic design parameters, such as the plastic hinge length and inelastic rotational capacity, of the walls.This paper presents a parametric finite element analysis study on the plastic hinge length and inelastic rotational capacity of three types of damage-resisting RC shear walls with improved self-centering properties under cylic lateral loads. The studied walls were reinforced with conventional steel bars and a type of self-centering reinforcement consisting of shape memory alloy (SMA) bars, glass fiber reinforced polymer (GFRP) bars, and post-tensioned high-strength steel strands. The study showed that the plastic hinge length was comparable in partially post-tensioned walls and conventional steel-reinforced RC walls, while the plastic hinge was longer in steel-GFRP reinforced walls and shorter in steel-SMA reinforced walls with respect to conventional steel-reinforced RC walls. It was also shown that the inelastic rotational capacity was comparable in partially post-tensioned and conventional RC walls, while the inelastic rotational capacity was larger in steel-GFRP reinforced walls and slightly smaller in steel-SMA reinforced walls with respect to conventional steel-reinforced RC shear walls.This paper also offeres a method to adapt the plastic hinge length and inelastic rotational capacity formulas of CSA and ACI standards for the seismic design of the studied steel-GFRP reinforced, steel-SMA reinforced, and partially post-tensioned RC shear walls.

Design and analysis of dissipative seismic resistant heavy timber frame structures equipped with steel links

The recent development of timber structures, thanks to new materials more and more efficient from the mechanical point of view, allows the application, as seismic resistant systems, of both framed and braced multistory multispan timber structures, which are already well consolidated in the field of steel constructions, they offering excellent seismic performances. Although materials are different, the structural systems have the similarity to be assemblage of structural members connected each other. Therefore it is possible to apply the same seismic design approach, by transferring the knowhow from steel to timber structures and adapting the design rules to the peculiarities of timber. In particular the seismic design parameters are to be calibrated and the dissipative zones to be characterized, they being the connections themselves or specific dissipative devices.In this context, the paper deals with the application of steel links for the development of seismic resistant dissipative heavy timber frames: steel links have the aim of dissipating seismic energy, while timber elements and steel connections remain in the elastic field, according to capacity design. Specifically, 2D single-storey timber structures equipped with dissipative links, in different structural configurations, are studied. They have been designed through linear dynamic analyses. Therefore, non-linear static analyses are performed, using the structural calculation program SAP2000, with the aim of evaluating the global behaviour and determining the behaviour factors for each structural type. The study proves the suitability and the efficiency of the proposed system and design procedure.

Proposed seismic design parameters for the moment-resisting knee-braced frame system

This paper proposes and verifies the seismic design parameters, including overstrength-related force modification factor, ductility-related force modification factor, deflection amplification factor, and design period, for the steel Moment-resisting Knee-braced Frame (MKF) system. The building selected in this study is an office located in Vancouver, British Columbia, Canada, in which MKFs act as the lateral load-resisting system. 14 prototype frames spanning a wide range of geometrical configurations are designed following the requirements of the 2015 National Building Code (2015 NBC) of Canada. Nonlinear static analyses are carried out on the prototype frames to determine the preliminary ductility and overstrength factors. Six new MKFs (assessment frames) are designed using the proposed overstrength and ductility factors, and their seismic and collapse performances are examined by comprehensive numerical analyses, considering the effects of the potential sources of ground motion expected on the Canadian west coast, namely subduction intraslab, subduction interface and shallow crustal events. The results of this study suggest that the MKF system shall be designed as a moderately ductile system using overstrength and ductility factors of 1.60 and 3.0, respectively, with a height not exceeding 40 m in regions of high seismicity.

Influence of earthquake characteristics on natural frequency and period of soil column for different subsoils in the Chennai region

An earthquake is one of the critical natural disasters that causes a massive impact on life and property in the areas it occurs. From the past earthquake patterns, the increase in the number of earthquakes in southern peninsular India can be observed. The increasing number of earthquakes is one of the critical reasons for shifting Chennai from zone II (least active) to zone III (moderately active) by the Bureau of Indian Standards. The soil column's natural frequency and time period are the key parameters for seismic design and construction. Furthermore, compared to shear wave velocity, the fundamental period is a key parameter for site amplification in the recent trend because it accounts for both stiffness and depth of soil sediments. In order to determine the fundamental frequency and typical site period, an equivalent linear 1-D ground response analysis was performed in the Chennai region using ProSHAKE 2.0 software. A contour map was created using ArcGISPro software for the study area's fundamental and characteristic site periods. The longer the soil column's site period, the greater the amplification and the greater the seismic threat. Finally, buildings with a natural period of 0.6 - 1 s should be avoided in the southeastern region of the study area because of the resonance.

Resilient seismic design of reinforced concrete framed buildings with metallic fuses including soil-structure interaction effects

In this paper, the authors propose and validate a code-oriented, resilient design methodology for reinforced concrete buildings with intermediate moment frames (RC-IMFs) and hysteretic energy dissipation devices (HEDDs) mounted in chevron steel bracing design as structural fuses, considering soil-structure effects. The design methodology is based on global lateral stiffness balances among different structural components (frames, bracings and HEDDs). Global seismic design parameters were specifically assessed for such stiffness ratios through extensive parametric studies for the subject structural system under study. In order to achieve an immediate occupancy seismic performance, the design sequence using capacity-design principles is clearly established and emphasized for the design of main structural elements. Soil-structure interaction (SSI) effects are included in the formal design process following the recommendations available in the seismic code for Mexico City. In order to fully test the efficacy of the proposed design methodology under a demanding seismic scenario, three buildings of 8, 15 and 24 stories were designed in soft soil sites of Mexico City close to resonant responses. Different types or HEDDs were considered and evaluated. Pushover analyses were performed in order to verify that subject buildings may achieve the objective resilient deformation mechanism (immediate occupancy) at the maximum useful ductility capacity assumed for the HEDDs. Nonlinear dynamic analyses were performed for the complete 3D designs according to the code under the action of eight pairs of acceleration records, representative of the site where the buildings were located. This was done in order to assess maximum inelastic demands, residual drifts, and fully verify and validate the proposed resilient, structural fuse code-oriented design. From the obtained results, it is confirmed that a resilient structural performance is feasible for RC-IMFs with HEDDs under the proposed code-oriented design methodology.

Near-Surface Views & News: Building bridges between geophysical and engineering communities

Over the last few years, the use of geophysics for engineering purposes has been increasing considerably. Geophysical applications within the engineering industry are quite diverse and can range from geotechnical to transportation purposes and to environmental and geohazards studies. Typical applications include detection of bedrock, landfill delineation, water table detection, karst exploration, dam/levee and seepage evaluation, foundation design, pipeline installation, landslide mitigation, earthquake and seismic design parameters, and pavement analysis, among others.

The application of seismic parameters conversion among different structure design codes

The main goal for structure engineer is to do safety design and make sure structures can resist seismic forces by adopting proper construction materials and structure systems. The seismic design parameters are the key factors to control the structure seismic design procedures and results. These parameters covered several items, such as seismic spectral response acceleration in 1 second (S1) and short period (SS), site classification(A~E), sites importance (Ie,), strong motion files with their pseudo-acceleration and displacement, etc. Around these parameters, different countries and regions also issued the domestic design principles correspondence. For international projects, no matter which area or country projects located in, every structure engineer should take more care about the proper seismic parameters to deploy seismic design, and the issues of seismic parameter conversion among various codes appeared a few decades ago. In this article, author focused on multiple stories hotel (RC) structure design with GB and ASCE seismic parameters controlling, demonstrate the difference of structure design principles between GB and ASCE, and applied specified seismic parameters conversion method, then deploy structure analysis based on these parameters, got series structure analysis results. In the end, author provided a few practical advice about developing strategies and decisions from consultant view. These conclusions not only can benefit developers, also strengthen the support from consultant agency, besides, the parameter screen procedures enhanced the structure designer’s driving ability on various structures which locate in different regions and countries.

Evaluation of 3D seismic survey design parameters through ray-trace modeling and seismic illumination studies: a case study

This paper describes a case study of wavefront construction-based ray-trace modeling to access the 3D seismic exploration parameters that significantly impact achieving the exploration target in seismic data acquisition. The traditional methods assessment is based on the horizontal reflector concept, which does not consider the subsurface's inhomogeneities. This case study provides a methodology by considering the effect of subsurface variations on the estimation of seismic survey parameters. As the first step in this methodology, an elastic earth model is created to propagate theoretical seismic rays from a 3D seismic survey to generate seismic ray properties. Then illumination maps and synthetic seismic sections are generated from these seismic ray attributes to evaluate seismic survey performance in seismic imaging targets. The results proved that the method helps estimate seismic survey efficiencies in seismic target imaging. Therefore, the ray-trace modeling methodology can help obtain the target fold coverage in complex geological settings by designing and verifying the seismic survey parameters.

Effect of the asymmetry level on collapse margin of torsionally stiff single-story buildings based on FEMA P695 methodology

The stiffness of many lateral force resisting elements depends on their strength. The early studies indicated a relatively better performance of the strength symmetric design model (zero-strength eccentric model) compared to other design models. However, further investigations claimed that the balance design model could endow the best seismic performance in asymmetric structures. In this study, single-story structural models with varied asymmetry levels and two cases with square and rectangular plans were considered. The models were evaluated by FEMA P695 methodology in various centers of mass, stiffness, and strength positions, including a balance model, strength symmetric, and code design model. The adjusted collapse margin ratios in these models were calculated as the performance index. The results showed a better seismic performance of the balance design model for the normalized yield eccentricity (ed/A) values below 15%. For ed/A values more than 15%, strength symmetric design model showed a superior seismic performance, while the code design model presented the weakest seismic performance. Evaluation of the seismic design parameters indicated that the code design model may not provide a satisfactory acceptance criterion with the existing standards, which necessitates re-evaluation of its design parameters.

Seismic reliability evaluation of steel gabled frames consisting of web-tapered members using joint analysis of hazard and fragility

Despite the wide application of steel gabled frame (SGF) systems in large industrial projects, the current literature lacks accurate information on their seismic performance to ensure satisfactory performance at different levels of earthquake intensity. Also, given the scant information on the structural performance and their seismic design parameters in most of the available guidelines, the use of joint analysis of hazard and fragility can be very important, since both the reference hazard on site and the structural performance are considered. To address this issue, in the present paper, incremental dynamic analysis (IDA) was performed using 20 ground motions on four SGFs and their results were collected in the form of fragility curves. Then to obtain the annual rate of exceedance, hazard curves of the study region were generated and combined with the fragility curves, and finally, the seismic reliability of SGFs was evaluated at design basis earthquake (DBE) and maximum considered earthquake (MCE) hazard levels. Seismic reliability results indicated that the available seismic design guidelines lead to a too conservative design for SGFs, especially when they have long periods, where at the MCE hazard level, long-period SGFs with about 58% safety margin do not even experience LS performance level. The results of this study can prove useful for a more efficient design of SGFs in seismic regions.

Variation Evaluation of Path Characteristic and Site Amplification Factor of Earthquake Ground Motion at Four Sites in Central Japan

The considered parameters in seismic design vary, with the Earthquake Ground Motion (EGM) having the largest variation. Since source characteristic, path characteristic, and Site Amplification Factor (SAF) influence the EGM, it is crucial to appropriately consider their variations. Source characteristic variations are mainly considered in a seismic hazard analysis, which is commonly used to evaluate variations in EGM. However, it is also important to evaluate variations in path characteristic and SAF with only a few studies having individually and quantitatively examined the variations of these two characteristics. In this study, based on strong-motion observation records obtained from four sites in central Japan, the three characteristics were extracted from seismograms using the concept of spectral inversion. After removing the source characteristic, the path characteristic and SAF were separated, and the variations in these two characteristics were quantified. To separate and obtain each characteristic from the observed record, one constraint condition must be imposed, whereas the variations in the constraint condition must be ignored. In that case, the variations in the constraint condition are included in the variations of the separated characteristics. In this study, this problem was solved by evaluating the variation in the constraint condition, which is the SAF at a hard rock site, by the use of the vertical array observation record at the site.

Effect of Volume Tie Ratio in the Engineered Cementitious Composites Plastic Hinges on the Seismic Performance of RC Composite Bridge Columns.

The feasibility that the transverse reinforcements in steel-reinforced Engineered Cementitious Composites (ECC) columns could be reduced or even totally eliminated has been experimentally demonstrated. However, due to the effect of the tie volume ratio in ECC plastic hinges on the seismic performance of RC composite bridge columns not being fully clarified as of yet, a numerical study was carried out. In this study, the analytical models based on the fiber element method, by considering the superposition of different lateral confinements resulting from ties and the ECC cover, were used to correlate with a target hybrid-loading experiment. Load-displacement hysteresis, strains in extreme fibers and longitudinal bars in analytical results correlated well with the experiments, verifying the accuracy of the analytical models proposed in this study. Based on the analytical results, it was found that the volume tie ratio had little effect on the stress-strain hysteresis of the ECC cover, but a lower volume tie ratio resulted in more significant nonlinear behavior longitudinally. Finally, the pushover analysis was conducted to investigate the effect of volume tie ratios on the seismic design parameters, and the results showed that a higher volume tie ratio resulted in a limited increase in the maximum allowable displacement for design.

Seismic design rules for lightweight steel shear walls with steel sheet sheathing in the 2nd-generation Eurocodes

The current structural European codes for seismic design EN1998-1 do not provide design criteria for cold formed steel (CFS) shear walls with steel sheet sheathing, limiting their use as a lateral force resisting system (LFRS) in lightweight steel (LWS) buildings. To overcome this lack of guidelines, a specific study has been carried out at the University of Naples “Federico II”. The main goals of the study are the validation/calibration of the Effective strip method (ESM) by Yanagi & Yu [26] and the definition of seismic design parameters according to the European format. The main results show that ESM gives a reliable prediction if the shear resistance of screw connections is evaluated based on equations from AISI S100 [1]. A safety factor for resistance equal to 1.25 can be used for the evaluation of the design wall resistance according to Limit state design (LSD) and an overstrength (expected resistance) factor equal to 1.4 can be adopted for the design of non-ductile components according to capacity design.

Analytical Fragility Curves for Seismic Design of Glass Systems Based on Cloud Analysis

Given the growing spread of glass as a construction material, the knowledge of structural response must be ensured, especially under dynamic accidental loads. In this regard, an increasingly popular method to probabilistically characterize the seismic response of a given structure is based on the use of “fragility” or “seismic vulnerability” curves. Most existing applications, however, typically refer to construction and structural members composed of traditional building materials. The present study extends and adapts such a calculation method to innovative structural glass systems, which are characterized by specific material properties and expected damage mechanisms, restraint details, and dynamic features. Suitable Engineering Demand Parameters (EDPs) for seismic design are thus required. In this paper, a major advantage is represented by the use of Cloud Analysis in the Cornell’s reliability method, for the seismic assessment of two different case-study glass systems. Cloud Analysis is known to represent a simple and immediate tool to analytically investigate a given (glass) structure by taking into account variations in seismic motions and uncertainties of structural parameters. Such a method is exploited by means of detailed three-dimensional (3D) Finite Element (FE) numerical models and non-linear dynamic analyses (ABAQUS/Standard). Critical issues and typical failure mechanisms for in-plane seismically loaded glass systems are discussed. The validity of reference EDPs are addressed for the examined solutions. Based on a broad seismic investigation (60 records in total), fragility curves are developed from parametric results, so as to support a multi-hazard performance-based design (PBD) procedure.

Effective stiffness and period-dependent seismic response modification factors for flexure-dominated fully-grouted reinforced masonry rectangular shear walls

The wall effective elastic stiffness, displacement ductility, and seismic force modification factors are important force-based seismic design (FBD) parameters for reinforced masonry (RM) shear walls. The effective stiffness, ke of reinforced masonry shear walls (RMSW) is crucial in computing the natural period and thus the elastic forces, and essential also in computing the displacements corresponding to the design seismic forces. This study analyzes previously reported test results of forty-three flexure-dominated fully-grouted rectangular RMSWs subjected to quasi-static cyclic load to evaluate the FBD parameters adopted by Canadian and American standards. In this study, based on the experimental results of 43 tested walls, a new stiffness reduction factor is proposed considering the effect of axial stress, vertical reinforcement ratio, and horizontal reinforcement ratio. Moreover, the seismic force modification factors are compared to the Canadian and US codes. The results showed that ductility related reduction factors should be dependent on the wall natural frequency and there is a room to relax the current proposed code values. In addition, incremental dynamic analysis was performed using a simplified numerical model to study the effect of dynamic loading on response modification factors and stiffness characteristics of the walls.

Dimensionless analysis of pulse-like effects on the seismic behavior of a dam based on wavelet-decomposed near-fault ground motions

In this paper, the inherent self-similarity between seismic characteristics and the dynamic behavior of a concrete gravity dam under decomposed near-fault ground motions is investigated. The representative low- and high-frequency components were decomposed using the continuous wavelet transform method to explore their effects on the dam response. The Koyna concrete gravity dam system was used as the basis for a numerical model. A series of dam dynamic responses under near-fault motion with and without pulse properties were obtained by numerical analyses. The relationship between the proposed dimensionless indices (intensity measure ratio (ΦIM), pulse period ratio (T1/Tp)), and response ratio (ΨEDP, m) was established to study the inherent self-similarity in the dynamic behavior of dams, which has an explicit physical significance with smaller dispersion. The response proportions of two main frequency components in the original near-fault record were revealed. Furthermore, a series of new threshold values were calculated based on the intersection of the pulse and high-frequency ratios, and the range of influence of the low- and high-frequency components was quantitatively divided. Finally, a predictive model was proposed for the dam responses to near-fault ground motions containing the proposed dimensionless indices that exhibited reasonable patterns. The pulse-like seismic characteristics and seismic responses to near-fault ground motions were analyzed and selected in the context of sensitivity, inherent self-similarity, threshold point, and regression error. Results show that the self-similarity between ΦSa(T1), ΦASI and ΨDVR,pulse,ΨDVRn,pulse is superior to that of other parameter ratios, indicating that more attention should be given to the role of intensity and pulse parameters in practical concrete dam seismic design.

Shaking table study on seismic response of marine reclaimed land

Coastal cities in Beibu Gulf of China are creating new lands by reclaiming from coasts, and are located in a seismic zone. The reclaimed land consists of a thick layer of marine soft soil overlain by sand. Earthquake in a soft-soil field usually leads to catastrophe, depending on the consolidation of soil and the amplitude of earthquake. In this paper, a scale model with a typical soft-soil stratigraphic section is presented to study the seismic responses of a soft-soil field under different consolidation conditions. The scale model was sequentially applied with several seismic waves at different epicentral distances to test the horizontal acceleration at different depths. The test results show that consolidation state, the earthquake amplitude and the spectral characteristics can greatly affect the predominant period, the horizontal acceleration amplification factor, and the seismic design parameters. Therefore, the earthquake characteristic and the consolidation state of soil should be taken into consideration comprehensively to ensure the safety of surface buildings on the reclaimed land during the earthquake.