Response History Research Articles

Estimating Vestibular Perceptual Thresholds Using a Six-Degree-Of-Freedom Motion Platform

Vestibular perceptual thresholds refer to the motion intensity required to enable a participant to detect or discriminate a motion based on vestibular input. Using passive motion profiles provided by six degree-of-motion platforms, vestibular perceptual thresholds can be estimated for any kind of motion and thereby target each of the sub-components of the vestibular end-organ. Assessments of vestibular thresholds are clinically relevant as they complement diagnostic tools such as caloric irrigation, the head impulse test (HIT), or vestibular evoked myogenic potentials (VEMPs), which only provide information on sub-components of the vestibular system, but none of them allow for assessing all components. There are several methods with different advantages and disadvantages for estimating vestibular perceptual thresholds. In this article, we present a protocol using an adaptive staircase algorithm and sinusoidal motion profiles for an efficient estimation procedure. Adaptive staircase algorithms consider the response history to determine the peak velocity of the next stimuli and are the most commonly used algorithms in the vestibular domain. We further discuss the impact of motion frequency on vestibular perceptual thresholds.

Estimating Vestibular Perceptual Thresholds using a Six-Degree-of-Freedom Motion Platform.

Vestibular perceptual thresholds refer to the motion intensity required to enable a participant to detect or discriminate a motion based on vestibular input. Using passive motion profiles provided by six degree-of-motion platforms, vestibular perceptual thresholds can be estimated for any kind of motion and thereby target each of the sub-components of the vestibular end-organ. Assessments of vestibular thresholds are clinically relevant as they complement diagnostic tools such as caloric irrigation, the head impulse test (HIT), or vestibular evoked myogenic potentials (VEMPs), which only provide information on sub-components of the vestibular system, but none of them allow for assessing all components. There are several methods with different advantages and disadvantages for estimating vestibular perceptual thresholds. In this article, we present a protocol using an adaptive staircase algorithm and sinusoidal motion profiles for an efficient estimation procedure. Adaptive staircase algorithms consider the response history to determine the peak velocity of the next stimuli and are the most commonly used algorithms in the vestibular domain. We further discuss the impact of motion frequency on vestibular perceptual thresholds.

Prediction of nonlinear structural response under wind loads using deep learning techniques

The wind actions on buildings are continuous in nature and could range from a few minutes to more than hours. Such long duration high intensity winds can push the structure to enter post elastic structural range and cause nonlinear behavior. Therefore, unlike performance-based earthquake engineering, where the structural simulations require seismic loads acting for a few seconds, the simulations for performance-based wind engineering (PBWE) requires wind load models acting for much longer durations. However, the nonlinear 3D model of a tall building will contain thousands of connections and structural members making it a complex finite element model. Dynamic time history analysis of such a model under loads lasting for hours can be tedious and often fail to achieve convergence. Using data-driven techniques that utilizes limited numerical and field data to obtain accurate structural responses under long duration loads is an exciting alternative. Deep learning techniques have been extensively used in the studies for structural health monitoring and earthquake engineering. However, the implementation of such data-driven techniques is very limited and has the potential for exploration in problems related to wind dynamics on tall buildings. This paper aims to predict the nonlinear structural response of tall buildings under sustained durations of wind loads using deep learning models. A Long Short-term Memory (LSTM) architecture is used to assess the efficiency of data-driven methods to replace computationally intensive 3D finite element analyses. The architecture will be tested on a 150 m tall building for response predictions under long duration wind loads. The robustness of the architecture will be further evaluated with predicting the acceleration response history of a scaled aeroelastic model based on experimental studies conducted at the Wind Simulation and Testing Laboratory (WiST) at Iowa State University.

Best Practices for Developing Geotechnical Models and Seismic Hazard Procedures for Critical Infrastructure: The Viadotto Italia Case Study in Southern Italy

The performance of a large number of critical infrastructure systems needs to be periodically re-evaluated. This is especially so when such systems are located in seismic areas and are subjected to ageing effects. Seismic re-evaluations are typically performed using numerical response history analyses based on a geotechnical model of the infrastructure and using hazard-consistent ground motions. We depart from the Viadotto Italia (the tallest multi-span bridge in Italy, located in a high-seismicity region) to draw best practices on how to construct a robust geotechnical model and derive appropriate target response spectra to be used in forward applications. Our proposed framework starts with the analysis of historical and new information and data. We then describe how to perform a multi-epoch consistency analysis that deals with the reliability and level of uncertainty of the data, culminating with the definition of a pragmatic geotechnical model that builds upon all available data, including investigation information produced at different spatial resolutions and quality levels. We also propose a consistent approach to perform site-specific probabilistic seismic hazard analysis to develop appropriate ground motions. This last step builds upon experiences with a data-rich high-seismicity zone in southern Italy, where both shallow crustal faults and deep subduction sources are present.

Generating spectrum-matched bidirectional time histories using Hilbert–Huang Transform

Response history analyses are usually conducted to evaluate seismic performance of buildings. Since azimuth-dependent buildings are quite common in practice, bidirectional ground motions are considered to be important input motions for the analyses. Based on RotDpp target response spectrum that is widely used to characterize seismic loads of bidirectional ground motions, this study proposes a method to generate spectrum-matched bidirectional time histories using Hilbert–Huang Transform (HHT). To demonstrate applicability of the proposed method, 15 pairs of spectrum-matched bidirectional time histories are generated by the proposed method for a nuclear power plant site. The study further discusses compatibility between these generated bidirectional time histories and the RotDpp target response spectrum. After that, these spectrum-matched time histories are applied to calculate floor response spectra of a service building for a nuclear power plant. After analyzing relative errors of the calculated floor response spectra, advantages of the proposed method are demonstrated. The study finds that, bidirectional time histories generated by the proposed method well match the RotDpp target response spectrum, and they could also provide accurate seismic response analysis of three-dimensional buildings.

Effects of Lead Core Heating on the Response of Isolated-Base and Fixed-Base Regular and Irregular Reinforced Concrete Structures

In this study, the seismic behavior of isolated- and fixed-base regular and irregular reinforced concrete structures was investigated. For this purpose, a three-dimensional, eight-story reference building model without any irregularity was designed in accordance with the Turkish Building Earthquake Code (TBEC-2018). Later, the building models with irregularities were created using the reference building model. In the building models with seismic isolators and fixed supports, fiber hinges were used for columns and beams to model nonlinear behavior. Moreover, nonlinear behavior at the isolation level was taken into account in building models with seismic isolators. Eleven different earthquake records were scaled using the geometric scaling method. Bi-directional nonlinear response history analysis (NRHA) was performed simultaneously for both horizontal components of the earthquake records in all building models. In addition to boundary analyses (Lower Bound and Upper Bound), which do not take into account the strength loss defined by the codes, analyses considering the strength loss as a result of heating in the lead core due to cyclical motion (Temperature Including) were carried out for building models with seismic isolators. In the analyses, displacement, acceleration, story drift ratio, base shear ratio, and damage mechanisms in the columns and beams obtained from the fixed-base and isolated-base structures were compared. In addition, the results of the analysis, in which the loss of strength due to temperature increase due to cyclical motion in the lead core is taken into account, were compared with the results obtained from the boundary analysis. As a result of the study, it was deduced that significant improvements were observed in the structural behavior of all regular and irregular models with seismic isolators under earthquake effects.

Analytical design models for geotechnical seismic isolation systems

Geotechnical Seismic Isolation (GSI) can be defined as a new category of seismic isolation techniques that involve the dynamic interaction between the structural system and geo-materials. Whilst the mechanism of various GSI systems and their performance have already been demonstrated through different research methods, there is a missing link between fundamental research and engineering practice. This paper aims to initiate the development in this direction. A new suite of equivalent-linear foundation stiffness and damping models under the same framework is proposed for four GSI configurations, one of which is a novel combination of two existing ones. The exact solutions for the equivalent dynamic properties of flexible-base systems have also been derived that explicitly include the foundation inertia and the strain-dependent equivalent damping of foundation materials, which are both significant for GSI systems. The application of the proposed analytical design models has been illustrated through response history analyses and a detailed hand-calculation design procedure has also been outlined and demonstrated.

Input motion extraction and closely-spaced modes recognition through partial system identification: An orthogonality-aided blind source separation approach

This research proposes an output-only procedure to extract seismic input motion and identify systems with severe closely-spaced modes incorporating a partial system identification approach. The proposed framework employs new methods to detect free vibration portion of the response histories and clustering the candidate points to find the first mode shape in a blind modal identification (BMI) procedure. The first mode frequency and damping along with mass matrix distribution of the system are calculated then using an orthogonality-based optimization process. The mentioned identified features are utilized next for the input motion extraction without any need to know the higher mode characteristics of the system. Next, higher mode characteristics are detected in succeeding steps considering the removal of each identified mode share from the total response at the end of each step. The perfect performance of the framework was proved against two simulated synthetic structures with mild and severe closely-spaced modes.

Evaluation of seismic force provisions for nonstructural systems supported on marine structures considering effects of nonlinearity

The investigation reported in this article focuses on evaluation of seismic force provisions for nonstructural systems proposed in Marine Oil Terminal Engineering and Maintenance Standards (MOTEMS) considering the effects nonlinearity in either primary (supporting), secondary (nonstructural), or both systems. The current provisions were developed based on prior research conducted using linear elastic behavior of both primary and secondary systems. This investigation evaluated effects of system nonlinearities on seismic forces in nonstructural systems by utilizing a 2 degrees-of-freedom model and a suite of 20 ground motions. It is found that the MOTEMS simplified and alternate formula may significantly underestimate the force in the secondary system for the ratios of secondary and primary system periods between 0.5 and 1.5. Therefore, it is recommended that engineers avoid systems within this period range. Outside this period ratio range, the MOTEMS simplified formula leads to significant overestimation, which can exceed 100% but the alternate formula generally provides forces that are very close to those from response history analysis. When the secondary systems are expected to respond beyond the linear elastic range, both the simplified and alternate MOTEMS formulae may lead to significant underestimation of forces in the secondary system for period ratios less than 0.5. Therefore, engineers are cautioned against designing secondary systems in this period range for forces much lower than those required to remain linear elastic. The MOTEMS alternate formula reduces overestimation or provides very good estimates of forces in the secondary systems compared to the simplified formula. Therefore, the MOTEMS alternate formula is preferable when information on period ratio is available.

Optimal Mixed Placement and Capacity Distribution of Buckling-Restrained Braces and Conventional Braces on a Large Metal Spatial Structure Without Rigid Diaphragm Assumption

This paper presents a design application of the proposed generalized response spectrum analysis (GRSA)-based seismic optimization method to a large metal spatial structure (constructed in Japan) where a rigid diaphragm assumption is not available and displacement responses are disproportionally distributed in a story. It also discusses the optimal mixed placement and capacity distribution of buckling-restrained braces (BRBs) and conventional braces (CBs) to minimize both the story drift response and the number of BRBs (i.e., the introduction cost of expensive energy-dissipation devices used as dampers). GRSA is a quick and efficient analysis method for estimating the reduced seismic responses of structural models with a large degree of freedom, and GRSA-based computational optimization enables a more efficient seismic design process than trial-and-error approaches with time-consuming nonlinear response history analysis. In this study, the efficiency is verified through a comparison with the Japanese standard BRB design method. According to the results, the optimal design solution by the proposed method has approximately 20% less steel tonnage of BRBs than that obtained from the standard method, whereas the seismic performance is equal to or better than the others. Moreover, although engineers should still consider the possibility of damage concentration, the brace configuration of the substructure where BRBs and CBs are arranged in adjacent stories is the most effective for reducing both the number of BRBs and the story drift response.

Comparative study and performance evaluation of steel moment resisting frames design with: Force-based design and performance-based plastic design

Incremental Dynamic Analysis (IDA), Nonlinear Response History Analysis (NLRHA) and Nonlinear Static Pushover Analysis (NSPA) has been carried out to evaluate seismic performance of Steel Moment Resisting Frames (SMRF). SMRF’s are used as the lateral resisting systems which consist of columns and beams joined by welding or using high strength bolts or combination of both. The resistance offered to the lateral forces is due to rigid frame action which develops bending moment and shear force in the frame members and joints. The 9-storey SMRF is been evaluated for two frames designed by Force Based Design (FBD) method and Performance Based Plastic Design (PBPD) method. The FBD frame is designed by using codal provision of ASCE 7 (American Based Seismic Code) and AISC (American Institute of Steel Construction) whereas PBPD frame is designed as per proposed work of Lee and Goel (2001) in which energy balance equation and pre-selected yield mechanism is considered. The evaluation study showed that the PBPD method for steel moment resisting frame is significantly more efficient in achieving a certain inelastic displacement/ductility for given seismic hazards compared to the existing design standards/specification for this system. By Nonlinear Static Pushover Analysis (NSPA) the PBPD method has achieved the target yield drift of 1.11% and FBD method has achieved 1.22% where the assumed yield drift was 1%. From NLRHA the percentage difference in achieved ductility factor for frame design by FBD method is 46.28% whereas for PBPD method it is 16.81%. From IDA inter storey drift is observed maximum in AISC design frame compared to PBPD design frame. Therefore, PBPD method frames responded as intended in design with much improved performances over those of the corresponding FBD method.

COVID-19 vaccination antibody responses in patients with aplastic anaemia and paroxysmal nocturnal haemoglobinuria

COVID-19 vaccination antibody responses in patients with aplastic anaemia and paroxysmal nocturnal haemoglobinuria

Influence of Gravity Framing on the Collapse Probability of Steel Buildings with Special Moment Frames

This paper presents the influence of gravity framing on the collapse risk of steel frame buildings with perimeter special moment frames (SMFs) designed in Turkey. For this, four- and eight-story buildings have been designed considering the related current specifications and codes. Header end-plate connections are used for the beam-to-column joints of the gravity frame system. A nonlinear analytical model that simulates the hysteretic behavior of header end-plate connections is calibrated with past experimental data. Nonlinear static pushover analysis (NSPA) and nonlinear response history analyses (NRHAs) were implemented for both four-story and eight-story SMFs with and without the gravity framing to quantify their collapse performance and monitor the system-level seismic response of the building through collapse. The advantage of presence of the gravity framing is investigated and differences in structural responses between the models are also examined. When the models were excited by different ground motions, median responses of the detailed models showed an increase in lateral force carrying capacity and a decrease in first-story drift demand, compared to the nonlinear static pushover analyses results. Furthermore, the results demonstrate that gravity frames in a structure profoundly decrease the possibility of collapse.

Pediatric allergy: a common occurrence with multifarious implications

Pediatric professionals treat nature’s most benevolent creation i.e., the child.It is important to focus not only on oral health but also on the overall health of the pediatric patient because oral health is an integral part of total development.There are various dental materials ranging from diagnosis to rehabilitation for the management of oral diseases that are not devoid of posing a potential risk of inducing allergic reactions to Pediatric patients in the dental setting.Most importantly, a dental practitioner must be trained in medical emergencies and be capable of resuscitating a patient. Not only the dentist but also the assistants present in the clinic should be trained on how to manage any allergic emergency conditions in children in dental settings.As some of these diseases have higher rates of morbidity and mortality, management of such conditions requires a multidisciplinary medical team approach consisting of physicians, dermatologists, Pediatric dentists, and ophthalmologists.So, this review involves in-detail information regarding what is an allergy, history of allergy, allergic and immunological responses of the oral mucosa, dental materials prone to allergies, its diagnosis, and treatment modalities in child hoping that it will be helpful to every practicing pediatric professional. Â

P-573 Women's age is the best success predictor in a cohort of poor responders: A retrospective analysis according to POSEIDON criteria

Abstract Study question Are there differences between patients classified according to the Poseidon criteria regarding IVF sucess rates? Summary answer POSEIDON groups differ from each other. Woman's age, more than the ovarian reserve, is the main factor of poor prognosis in IVF cycles. What is known already Poor ovarian response to stimulation in an IVF cycle has an estimated incidence of 9-24%. The criteria used to characterize this group of patients are heterogeneous, making it difficult to address risk factors, to determine prognosis and to propose novel treatment options. The most used diagnostic criteria are the Bologna criteria and more recently the Poseidon classification. Study design, size, duration An observational, retrospective cohort study, based on 558 ART cycles performed between 2015 and 2018 at a single center in Brazil. Participants/materials, setting, methods Group division was acording to POSEIDON criteria: groups 1A (n = 15), 1B (n = 19), 2A(n = 48), 2B (n = 59), 3 (n = 17) and 4 (n = 50). Two control groups were stablished for comparison purposes: C1 with no previous poor response, normal ovarian reserve and women's age < 35 years (n = 157) and C2 with women's age ≥ 35 years (n = 193). Data was obteined from clinical records and analyzed with SPSS program. Main results and the role of chance Groups 3, 4 and 2A of Poseidon had less oocytes recovered (p < 0,001). Group 4 formed fewer embryos (p = 0,001). A previous history of poor response in younger patients wasnt't found to translate in a poor response in a second cycle, since there was no difference between groups 1A and 1B compared to group C1 regarding number of oocytes retrieved. Groups 1B and C1 had a higher clinical pregnancy rate (p = 0,028) and groups 2 and 4 had lower pregnancy rates per started cycle (p < 0,001). Limitations, reasons for caution Retrospective and observational study. Wider implications of the findings The findings of this study play a role in improving patients counselling. The results are encouraging for young women with normal reserve and a previous bad response, since they weren't found to have poor outcomes in a new cycle. Woman's age should be the main criteria to determine patient prognosis. Trial registration number not applicable

Amplitude scaling of ground motions as a potential source of bias: Large‐scale investigations on structural drifts

AbstractThe question of whether amplitude scaling of ground motion (GM) records introduces bias is controversial in earthquake engineering. In this study, this research question is formally defined with a focus on evaluating bias in determining an engineering demand parameter (EDP) as a result of nonlinear response history analyses (NLRHA) when using scaled rather than unscaled GM that have the same level of intensity. The analysed structures are 10 planar steel frame buildings ranging from low‐ to high‐rise, where the EDP of interest is the maximum interstory drift ratio, while the structural responses range from linear to collapse. A unique contribution is the depth of the research, which employs an unprecedented number of more than 17,000 recorded GM, resulting in approximately 3.4 million NLRHA. For a thorough investigation, the most relevant intensity measures are discussed and considered, as well as novel spectral information describing the sustained vibration amplitude. The introduction of bias is examined from different points of view, using first simple and intuitive statistical methods, then machine learning techniques, and finally a novel GM selection approach. In the numerous investigations, no bias could be detected under the inherent uncertainty of the calculations. The results indicate that scaled records can be safely used in NLRHA to assess the seismic structural behaviour if spectral and scenario compatibility are ensured and it is verified that the sustained amplitude is also consistent.

The effect of pollination on the growth and reproduction of oilseed rape (Brassica napus)

Phenotypic plasticity is an organism's ability to alter its development and life history in response to environmental conditions. In plants, biotic and abiotic factors drive the distribution of resources between growth and reproductive traits. One such biotic factor is pollination. Studies show that wind and insect pollination enhance oilseed rape (Brassica napus) yield. However, the impact of pollination on resource allocation towards growth and reproduction is less understood. We conducted a controlled experiment to assess the effect of pollination on growth and functional reproductive traits. We compared two simulated supplementary pollen deposition methods (representing wind and insect pollination) alongside a non-supplementary control. Pollinated plants allocated resources towards growth and reproduction similarly, irrespective of deposition method. Plants receiving no supplementary pollination produced fewer seeds, allocating resources to growth, more prolific and persistent flowering, and heavier seeds. Pollinated plants had a reduced flowering period and were shorter, indicating resources were allocated to seed production rather than growth or the production of additional flowers. This allocation of resources from growth and flowering metrics can increase yield directly through increased seed production and indirectly through shorter plants and a reduced flowering period with seeds that mature earlier (agronomically beneficial traits).Wind and insect pollination can enhance and stabilise oilseed rape yield under various environmental conditions by acting in complementary ways. Since pollination limits yield in oilseed rape, it must be considered an input that can be actively managed. Successful management of pollination services requires growers to detect pollination deficits. Inadequately pollinated oilseed rape plants exhibit apparent morphological changes (e.g. taller plants that flower for longer), acting as an early warning to growers. Equipping growers with this knowledge provides them with a means of detecting deficits and thus enables them to take positive action to restore pollination services by introducing honeybees or enhancing wild pollinators.

Abstract 1155: cBioPortal for cancer genomics

Abstract cBioPortal for Cancer Genomics is an open-source platform for interactive, exploratory analysis of large-scale cancer genomics data sets. cBioPortal provides a user-friendly interface that integrates genomic and clinical data, and provides a suite of visualizations and analyses, including OncoPrints, mutation “lollipop” plots, variant interpretation, group comparison, survival analysis, expression correlation analysis, alteration enrichment analysis, cohort and patient-level visualization. cBioPortal also integrates external tools including CIViC, Cancer Digital Slide Archive, Next-Generation Clustered Heat Map, IGV and Bioconductor to facilitate interpretation. The public site (https://www.cbioportal.org) is accessed by ~35,000 unique visitors each month and hosts data from >325 studies spanning individual labs and large consortia. In addition, >67 instances of cBioPortal are installed at academic institutions and pharmaceutical/biotechnology companies worldwide. In 2021 we added data from 32 studies, totaling >24,000 samples, to the public site. All data is also available in the cBioPortal Datahub: https://github.com/cBioPortal/datahub/. We also host a dedicated instance for AACR Project GENIE, enabling access to the GENIE cohort of >135,000 clinically sequenced samples from 19 institutions (https://genie.cbioportal.org). In addition, the GENIE Biopharma Collaborative (BPC) enables the collection of comprehensive clinical annotations, including response, outcome, and treatment histories. The first BPC release contains data from >1,800 non-small cell lung cancer samples and will be released in early 2022. The growing GENIE cohort and the BPC clinical data have driven a number of recent developments, including performance improvements (the load time for the GENIE cohort was reduced from minutes to seconds). To leverage the BPC clinical data, we enabled sample selection based on treatment status, extended support for outcome analysis, and enhanced the patient timeline representation to incorporate response data. Additional development work has focused on improvements to variant interpretation, enhancements to the Mutations tab, and support for novel molecular assays via the ‘generic assay’ data type. Documentation on these new features and many others is available at https://www.cbioportal.org/news. cBioPortal is fully open source (https://github.com/cBioPortal/) under a GNU Affero GPL license. Development is a collaborative effort among groups at Memorial Sloan Kettering Cancer Center, Dana-Farber Cancer Institute, Children’s Hospital of Philadelphia, Princess Margaret Cancer Centre, Bilkent University and The Hyve. We welcome open source contributions from others in the cancer research community. Citation Format: Jianjiong Gao, Tali Mazor, Ino de Bruijn, Adam Abeshouse, Diana Baiceanu, Ziya Erkoc, Elena Garcia Lara, Benjamin Gross, David M. Higgins, Prasanna K. Jagannathan, Priti Kumari, Ritika Kundra, Xiang Li, James Lindsay, Aaron Lisman, Divya Madala, Ramyasree Madupuri, Angelica Ochoa, Oleguer Plantalech, Sander Rodenburg, Baby A. Satravada, Robert Sheridan, Lucas Sikina, Jessica Singh, S. Onur Sumer, Yichao Sun, Pim van Nierop, Avery Wang, Manda Wilson, Hongxin Zhang, Gaofei Zhao, Sjoerd van Hagen, Kees van Bochove, Ugur Dogrusoz, Allison Heath, Adam Resnick, Trevor J. Pugh, Chris Sander, Ethan Cerami, Nikolaus Schultz. cBioPortal for cancer genomics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1155.

Equivalent static loads for double-layered domes supported by multistorey buckling-restrained braced frames

Curved gridshells are excited not only in the horizontal direction but also experience large anti-symmetric vertical accelerations when subjected to horizontal earthquake ground motions. In addition to the coupled response, gridshells exhibit closely spaced modes and substructure-roof interaction. Nevertheless, previous studies have proposed elastic horizontal and vertical equivalent static seismic forces considering these complex dynamic response characteristics. These are determined from the input horizontal acceleration at the substructure’s roof level, an assumed acceleration distribution, nodal roof masses and amplification factors derived from the dynamic characteristics of the dome and substructure. To extend this methodology to nonlinear substructures with displacement-dependent damping devices, this paper investigates the applicability of ductility reduction factors (or Rμ factors) to estimate the inelastic response spectra and an alternative equivalent linearisation approach to compute the peak horizontal acceleration of multistorey substructures with buckling-restrained braces. This is achieved by modelling the curved roof as a rigid mass for the substructure model, and using its idealised base shear-roof displacement relationship obtained from modal pushover analyses. The peak horizontal acceleration of the substructure is then used to obtain the equivalent static loads of the curved roof using amplification factors, and the accuracies are verified against the results from nonlinear response history analyses. It was confirmed that the Rμ [Formula: see text]factors combined with the roof amplification factors provide a simple way to estimate the peak roof response with sufficient accuracy for preliminary design of domes with multistorey substructures having low post-yield stiffness.

Seismic design of low-rise steel building frames with self-centering hybrid damping connections

This paper develops a practice-oriented seismic design procedure for an emerging lateral force resisting system. The system combines the favorable re-centering feature with the attractive hybrid damping capacity. The system overcomes the detrimental frame expansion effect that occurs in conventional self-centering building frames without the cost of building space. Following the proposed design procedure, multiple designs with different parameters to achieve performance objectives were performed for a representative three-story building in which the considered lateral force resisting system is used to resist the seismic forces. Nonlinear response history analyses were performed for the designs to evaluate the applicability and adequacy of the proposed design approach. Based on the analyses conducted in this research, it was found that the considered system designed using the proposed approach can meet both transient and residual inter-story drift requirements specified for the selected performance objectives. While an initial design per the proposed design approach may be inadequate, the re-design strategy recommended can help transform the design to an acceptable one after only one round of modification. Moreover, the composition of hybrid damping may affect the maximum floor acceleration responses. In this study, the maximum floor acceleration can be reduced 12.75% at most by replacing hysteretic damping with viscous damping. This should be included in design consideration in the proposed approach through adjusting the hybrid damping composition.