Seismic loss assessment of typical RC frame-core tube tall buildings in China and US using the FEMA P-58 procedure

Reinforced concrete (RC) frame-core tube buildings are widely constructed both in China and the United States (US). Their seismic performances greatly influence the economic loss of earthquakes. This study aims to compare the seismic losses of two typical RC frame-core tube tall buildings designed following the Chinese and the US seismic design codes. The prototype building is originally designed using the US seismic design codes, provided by the Tall Building Initiative (TBI) Project. Then the prototype building is redesigned according to the Chinese seismic design codes with the same design conditions and seismic hazard level. Detailed nonlinear finite element (FE) models are established for both designs. These models are used to evaluate their seismic responses at different earthquake intensities, including the service level earthquake (SLE), the design based earthquake (DBE) and the maximum considered earthquake (MCE). In addition, the collapse fragility functions of these two buildings are established using the incremental dynamic analysis (IDA). Subsequently, the seismic loss consequences (repair costs, repair workload, and casualties) of these two designs are calculated using the procedure proposed by FEMA P-58. The comparison shows that the Chinese design exhibits better seismic performances in most cases with smaller total repair cost, shorter repair time and a smaller number of casualties, except slightly longer repair time at the MCE level. For both designs, the repair cost of nonstructural components accounts for the majority of the total cost. The ceilings and elevators are the major causes of casualties at the MCE level

Hysteretic Behavior Simulation Based on Pyramid Neural Network:Principle, Network Architecture, Case Study and Explanation

An accurate and efficient simulation of the hysteretic behavior of materials and components is essential for structural analysis. The surrogate model based on neural networks shows significant potential in balancing efficiency and accuracy. However, its serial information flow and prediction based on single-level features adversely affect the network performance. Therefore, a weighted stacked pyramid neural network architecture is proposed herein. This network establishes a pyramid architecture by introducing multi-level shortcuts to integrate features directly in the output module. In addition, a weighted stacked strategy is proposed to enhance the conventional feature fusion method. Subsequently, the redesigned architectures are compared with other commonly used network architectures. Results show that the redesigned architectures outperform the alternatives in 87.5% of cases. Meanwhile, the long and short-term memory abilities of different basic network architectures are analyzed through a specially designed experiment, which could provide valuable suggestions for network selection.Comment: 41 pages, 14 figure

Probabilistic evaluation of the seismic performance of a concrete highway bridge in Queensland

Being intraplate, the Australian continent has shown low seismicity in its recorded history. However, Australia has been acknowledged as not completely free from seismic hazard. Performance-based earthquake engineering (PBEE) methodology has been widely developed during the past two decades, and has become a key approach for seismic analysis and design. Yet such an approach has not been implemented in Australian structural codes. Therefore, further research is required to develop a domestic approach for Australian applications. In this study, the seismic capacity of a concrete highway bridge is evaluated through a probabilistic method. For this purpose, an analytical model of a typical highway bridge in Queensland was built in OpenSees. The important seismic responses to be considered include the curvature ductility of columns, and the deformations in bearings and abutments. The main uncertainties are related to the source and ground motion models for potential Australian earthquakes. A set of synthetic intraplate ground motions, which was provided by the GeoscienceAustralian, is anticipated to be used in the generation of future probabilistic ground motion maps for Australia, and is presently used for nonlinear incremental dynamic analyses (IDA). The results of this study in the form of seismic capacity limit-states can be further employed for developing performance-based seismic design and/or seismic risk and fragility analyses of Queensland highway bridges

Current trends and developments in progressive collapse research on reinforced concrete flat plate structures

Progressive collapse of structures caused by extreme or accidental loads may lead to significant loss of life and property. Considerable research efforts have been made to date to mitigate the probability of progressive collapse and its consequences. This study summarises the fundamentals of progressive collapse in relation to the existing theoretical concepts and understanding. Specifically the existing theories pertinent to progressive collapse of building structures, in particular reinforced concrete (RC) flat plates, are examined from the following four key aspects: (1) definition of progressive collapse from deformation and/or strength perspectives with respect to the failure criteria of structural members and the entire structural system; (2) failure mechanisms of load-bearing systems undergoing progressive collapse with respect to the structural ultimate capacity, which has not been considered in the design process; (3) research methodologies for investigating collapse mechanisms, with emphases on experimental and numerical approaches; and (4) collapse-resistant design principles as covered in several international design standards in which a number of robustness requirements have been recognised. Based on the schematic review of the current trends and developments, gaps and limitations in progressive collapse research are identified and a new research direction is established to advance the progressive collapse study of RC flat plate structures

Editorial: Innovative methodologies for resilient buildings and cities

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Development and Application of a Simplified Model for the Design of a Super-Tall Mega-Braced Frame-Core Tube Building

This article discusses the development and application of a simplified nonlinear model to compare two design schemes of a super-tall mega-braced frame-core tube building

Seismic loss assessment for buildings with multiple LOD BIM data

Earthquake-induced economic loss of buildings is a fundamental concern for earthquake-resilient cities. The FEMA P-58 method is a state-of-the-art seismic loss assessment method for buildings. Nevertheless, because the FEMA P-58 method is a refined component-level loss assessment method, it requires highly detailed data as the input. Consequently, the knowledge of building details will affect the seismic loss assessment. In this study, a seismic loss assessment approach for buildings combining building information modeling (BIM) with the FEMA P-58 method is proposed. The detailed building data are automatically obtained from the building information model in which the building components may have different levels of development (LODs). The determination of component type and the development of the component vulnerability function when the information is incomplete are proposed. Finally, to demonstrate the rationality of the proposed method, an office building that is available online is selected, and the seismic loss assessments with multi-LOD BIM data are performed as case studies. The results show that, on the one hand, even if the available building information is limited, the proposed method can still produce an acceptable loss assessmenton the other hand, given more information, the accuracy of the assessment can be improved and the uncertainty can be reduced using the proposed method.The study is financial supported by the National Natural Science Foundation of China (No. 51578320)

Study on A Novel Sacrificial-Energy Dissipation Outrigger

The frame-core tube-outrigger structural system is widely used in tall buildings, in which outriggers coordinate the deformation between the core tube and the moment frame, leading to a larger structural lateral stiffness. Existing studies indicate that outriggers can be designed as a fuse of tall buildings through dissipating seismic energy after yielding, to protect the main structure. Under the action of the maximum considered earthquake (MCE), it is found that the hardening effect of BRB outriggers will increase the percentage of the inelastic energy dissipation of the other structural components. Meanwhile, due to the local buckling-induced severe deterioration and damage of conventional outriggers, conventional outriggers are difficult to repair after an earthquake. To overcome these problems, this study proposes a novel sacrificial-energy dissipation outrigger (SEDO) to improve the seismic resilience of tall buildings. The inclined braces of this novel SEDO are composed of a sacrificial part and an energy dissipation part. Therefore, it remains elastic under the design-based earthquake (DBE) and dissipates inelastic energy under the MCE. Moreover, the detailing of this novel SEDO are proposed based on experimental studies. The optimum strength ratio between the sacrificial part and the energy dissipation part is determined as 6:4 based on nonlinear time-history analyses (THAs). Afterwards, SEDOs are used in a tall building to verify its seismic performance through nonlinear THAs. Consequently, this study indicates that the novel SEDO is able to protect the other structural components and effectively improve the seismic resilience of tall buildings.The authors are grateful for the financial support from the National Natural Science Foundation of China (No. 51778341)

Analytical Model for Multi-Hazard Resilient Prefabricated Concrete Frame Considering Earthquake and Column Removal Scenarios

Research on multi-hazard prevention and mitigation in building structures is the most recent developing trend in civil engineering. In this study, an analytical model is proposed to calculate the structural resistance of a type of multi-hazard resilient prefabricated concrete (MHRPC) frame under earthquake and column removal scenarios. The MHRPC frame is assembled using prefabricated RC beams and columns, unbonded post-tensioning (PT) tendons, energy-dissipating steel angles, and large rotational shear plates. According to the experimental results, the MHRPC frame exhibits the features of low damage and self-centering under seismic loading. Meanwhile, when subjected to column removal scenarios, the MHRPC frame is proven to demonstrate a high progressive collapse resistance. In order to calculate the seismic and progressive collapse resistance of the MHRPC frame, analytical models for the critical components in the MHRPC frame (PT tendons and steel angles) are compared and selected based on the experimental results and numerical simulations. Furthermore, calculation methods for the seismic and progressive collapse resistance of the MHRPC frame specimens are proposed. The calculation results are validated using the experimental results. This study could provide a reference for the design of MHRPC frame structures, considering both earthquake and progressive collapse