Performance-based Seismic Design Research Articles

Performance-Based Seismic Design for Bridge Bents Retrofitted with BRBs Using the Ductility Demand Spectra of SDOF Oscillators with Bilinear Fuses

ABSTRACT Reinforced concrete bridge bents with double columns in bridge substructures are commonly used, but it has suffered severe damage during strong earthquakes. The seismic retrofit with structural fuses is used to effectively mitigate seismic damage of bridge bents. To obtain the displacement ductility demand for dual systems including the primary structure (PS) and structural fuses (SF), the corresponding ductility demand factor spectra were developed. The interaction between the PS and SF is described by defining two parameters of dual systems: the yield displacement ratio (α) and the initial stiffness ratio (β), and the influence of α, β, and strength reduction factor on the ductility demand factor spectra are also analyzed. For seismic retrofitting in bridge bents, buckling-restrained braces (BRBs) are used as energy dissipation fuses, and the steel core lengath of BRBs with three configurations forms, including diagonal, inverted-V, and toggle systems, are also explored. Then, based on the structural fuses concept and ductility demand factor spectra of dual systems, a performance-based seismic design procedure is proposed for bridge bents retrofitted with BRBs to ensure that the bridge bents maintain the target ductility under design-level earthquakes. Finally, the procedure was utilized to design the bridge bents with BRBs, and the procedure’s feasibility was verified by nonlinear time-history analysis.

Development of novel two-level SMA-based self-centring steel columns for seismic resilience

This paper presents an innovative two-level shape memory alloy (SMA)-based self-centring (SC) steel column, referred to as TSSSC. The TSSSC is interconnected by two series of SMA bolts, differing in diameters and lengths, to achieve multi-yielding. This is intended to fulfil multiple performance-based design objectives and augment the structural ductility of SMA elements. Utilizing the distinctive material property of phase transformation inherent in SMA, the two-level bolts can accomplish multi-level yielding in a straightforward yet effective manner. This is achieved by employing SMA elements of varying diameters in series and sequentially activating them via the material's inherent stiffness hardening. The behaviours of the TSSSC are meticulously analysed through refined finite element models (FEMs), which are corroborated by previous test results. The TSSSC demonstrates commendable multi-yielding behaviour and SC capacity during cyclic behaviour studies. In comparison to conventional SMA-based SC structures, the TSSSC exhibits markedly superior ductility, exceeding 10, whereas traditional structures typically range between 4 and 6. This enhanced ductility ensures that the TSSSC can comprehensively meet the multiple design objectives stipulated in the current performance-based seismic design. The SC and energy dissipation (ED) capacity of the TSSSC can be activated during frequent seismic events, thereby providing a safety buffer for severe earthquakes due to seismic uncertainty. Furthermore, parametric studies are conducted to identify critical design parameters, including the vertical design load, prestress in SMA bolts, and the linear stiffness ratio between the short and long bolts of the two-level SMA bolts. Design recommendations are subsequently proposed based on the findings of these parametric studies.

Performance-based Seismic Design of reinforced concrete Structure - A Review

In recent times, in multistory buildings, the seismic demands were met using the code-based method of seismic analysis and design of the structure ,although the design of building can be more optimized by a more modern and realistic design approach in the form performance based design .As per the code, the building performance under seismic response are categorized into different levels of performance checks for the actual ground motions or some sets of ground motions ,limiting the global damage and thereby creating a scope for optimization at material level and at cross section level of the reinforced concrete structure .The building can be designed or checked based on this code prescribed performance levels, reducing the potential risk of the future earthquake as well as the damage or the loss caused due the earthquake. This review paper highlights numerous studies done by researchers comparing the responses from the code-based design and performance-based design, paving the way for use of performance-based design in the structure.

A novel constitutive model for S30408 stainless steel considering strain memory effect: Formulation and implementation

To predict seismic behavior of steel structures and conduct performance-based seismic design, a precise constitutive model to accurately reflect the elastic-plastic response of structural steel under various loading protocols is always needed, so that the strength, deformation capacity, and energy dissipation capacity of a steel component or system in case of a severe earthquake can be reasonably evaluated. On the other hand, the constitutive model should be convenient for practical engineering implementation and application. Previous studies show that certain type steel like stainless steel S30408 shows complex features under various strain ranges such as pronounced strain memory effect, unsaturated cyclic softening/hardening under small/large strain amplitudes, which differ from mild steel and low yield point steel. Therefore, the stainless steel S30408 is taken as the research object in this study to develop a new constitutive model to describe structural steels with such complex mechanical properties. First, a new nonlinear isotropic and kinematic hardening rule is extended based on the classical Chaboche model and a functional relationship between the hardening rate (defined as the variation value of peak stress in every adjacent cycle during cyclic loading) and the applied strain amplitude is established through a logistics function to describe the coupling effects. Second, the numerical implementation technique for three-dimensional is elaborated in detail. Third, the numerical implementation technique is extended to plane stress cases by the improved P projection method. Using the numerical integration algorithm, the proposed constitutive model can be successfully incorporated into ABAQUS/Standard through the UMAT subroutine interface which is suitable for both solid and shell elements.

Performance-based versus conventional seismic design: comparative assessment on a 4-story RC moment frame

AbstractFive different design approaches are compared on a single mid-rise reinforced concrete building, pitting two performance-based designs against three conventional methods in delivering a solution that satisfies different sets of performance objectives. Two of the conventional designs stem from the literature, and they represent 2003 IBC compatible solutions. Another employs the yield point spectra to deliver a code-like solution, satisfying the design norms without needing iterations. The final two are based on the yield frequency spectra to offer a design that can satisfy more detailed performance objectives in a single step. Overall, all five methods are shown to deliver what is expected. Conventional methods can safely capture the code requirements, yet they are disadvantaged when treading in beyond-life-safety territory, where Immediate Occupancy or Collapse Prevention objectives cannot be easily satisfied, a problem that is not shared by performance-based approaches.

Data-based equations for damage evaluation of reinforced concrete columns with square cross sections

This study aims to develop simple equations for assessing the damage of reinforced concrete (RC) columns subjected to seismic loading. A fiber element model in OpenSees, validated against experimental data, was used to generate a large dataset of 56548 data values for various RC columns. The Monte Carlo Hierarchical Adaptive Random Partitioning (MC-HARP) strategy was then applied to evaluate the sufficiency of the dataset and propose reliable equations for estimating the residual displacement ratio (RDR), damage index (DI), and residual curvature of RC columns under given displacement demands. A relationship between these parameters and the structural performance levels was also established. Residual displacement is a practical measure that can be observed in the field after an earthquake. The proposed equations facilitate the determination of the performance level of the structure after an earthquake event. The findings of this paper can also be used in designing new structures within a performance-based seismic design (PBSD) context.

Seismic design of reinforced concrete buildings equipped with viscous dampers using simplified performance-based approach

Passive control systems, such as Fluid Viscous Dampers (FVDs), have gained significant consideration in the design of earthquake-resistant structures. However, simple analysis and design methods are scarce for more practical and feasible implementation. This study provides a simplified procedure for performance-based seismic design of Reinforced Concrete (RC) special moment resisting frame using nonlinear FVDs. It adopts an extended performance-based design approach, focusing on maximum displacement along with floor acceleration to control the overall behavior of the structure. The fundamental principle of the method is to achieve the fully stressed (effect of FVDs on response indices) design approach to place dampers, which is attained by placing dampers among the storeys where drifts exceed the pre-decided performance limits. Further, a uniform damage distribution concept is followed to maximize the dampers' capacity. This study examines a rectangular-shaped RC SMRF with dampers to get the required performance when subjected to design basis and maximum considered earthquake levels. To check the efficacy, the proposed method is contrasted with a practical design method and a standard placement method employed in previous studies for RC structures with dampers. The analysis shows that the structure meets the performance targets of the design basis and the maximum considered level of earthquake hazards using the proposed step-by-step procedure. The comparison with the other two methods confirmed that the structure with dampers improved seismic behavior with the suggested process. Structural engineers can refer to the proposed method for the design of RC buildings with FVDs.

Consequences of consequence models: The impact of economies of scale on seismic loss estimates

The detailed evaluation of expected losses and damage experienced by structural and nonstructural components is a fundamental part of performance-based seismic design and assessment. The FEMA P-58 methodology represents the state of the art in this area. Increasing interest in improving structural performance and community resilience has led to widespread adoption of this methodology and the library of component models published with it. This study focuses on the modeling of economies of scale for repair cost calculation and specifically highlights the lack of a definition for aggregate damage, a quantity with considerable influence on the component repair costs. The article illustrates the highly variable and often substantial impact of damage aggregation that can alter total repair costs by more than 25%. Four so-called edge cases representing different damage aggregation methods are introduced to investigate which components experience large differences in their repair costs and under what circumstances. A three-step evaluation strategy is proposed that allows engineers to quickly evaluate the potential impact of damage aggregation on a specific performance assessment. This helps users of currently available assessment tools to recognize and communicate this uncertainty even when the tools they use only support one particular damage aggregation method. A case study of a 9-story building illustrates the proposed strategy and the impact of this ambiguity on the performance of a realistic structure. The article concludes with concrete recommendations toward the development of a more sophisticated model for repair consequence calculation.

Probabilistic analysis of FRP efficacy in seismic risk reduction

Engineers are tasked with the challenging task of evaluating the performance and analyzing the risk of systems in the context of performance-based seismic design. All sources of random uncertainty must be taken into account during the design phase in order to complete this assignment. The performance limit states for a structure must be defined using appropriate procedures that take into consideration the system characteristics describing the structure, the soil, and the loads applied to the structural reactions. The main objective of this study is to conduct an in-depth analysis, both linear and non-linear (Pushover), of seismic vulnerability for a reinforced concrete (RC) structure. This aims to probabilistically evaluate the effectiveness of composite materials, particularly those reinforced with glass and carbon fibers, in reducing seismic risk when used to reinforce structural columns. The outcomes of this study will provide valuable insights into the efficacy of FRP reinforcements in enhancing seismic resistance, regardless of the analytical approach adopted (linear or non-linear). They reveal a seismic risk reduction of 48 % for structures equipped with glass fiber-reinforced columns and 67 % for those with carbon fiber-reinforced columns.

Performance Assessment of Reinforced Concrete Bridges Under Coupled Horizontal and Vertical Ground Motions Using Fragility Surfaces

ABSTRACT The objective of this study is to explore the seismic fragility of reinforced concrete bridges, specifically in response to the vertical components of ground motions, utilizing fragility surfaces. The examination of bridge responses involves the application of optimally selected intensity measures through three-dimensional nonlinear time-history analyses, encompassing uncertainties in both superstructure materials and soil–structure interaction effects. In this investigation, an extended Probabilistic Seismic Demand Model (e-PSDM) is employed, leveraging fragility surfaces to concurrently consider vertical and horizontal excitations. The results obtained from this approach are compared with traditional fragility curves. This study emphasizes Pile-cap displacement and drift ratio as pivotal engineering damage parameters, acknowledging their sensitivity to the influences of both soil–structure interaction effects and vertical ground motion. The fragility surfaces derived from the study reveal a correlation between increased vertical spectral accelerations and elevated probabilities of surpassing both slight damage and collapse limit states. These observations underscore the critical significance and practical utility of fragility surfaces in the context of performance-based seismic assessment and design for reinforced concrete bridges. The findings from this research contribute valuable insights into the nuanced behaviour of reinforced concrete bridges under seismic conditions, emphasizing the relevance of incorporating vertical components in fragility assessments for a more comprehensive understanding of structural vulnerability.

Analysis of Bridge Tests on Sandy Overburden Site with Fault Dislocating

Performance-based seismic design methods for bridges are advancing, yet limited research has explored the damage mechanisms of bridges subjected to extreme seismic effects, such as those near or across faults. To investigate the damage mechanisms under bedrock dislocation and bridge rupture resistance, providing essential insights for the standardized design and construction of bridges in close proximity to seismic rupture sites, we developed a large-scale device to model bridges in the immediate vicinity of tilted-slip strong seismic rupture sites. This included a synchronous bedrock dislocation loading system. Four sets of typical sandy soil modeling tests were concurrently conducted. The results indicate: (1) The overall shear deformation zone of the foundation and surface uneven deformation primarily concentrate the overburdened soil body along the fault dip. The damaged area under the low-dip reverse fault is lighter on the surface and inside the soil body compared to the high-dip-positive fault. (2) The presence of bridges reduces the width of the main rupture zone and avoidance distance to some extent. However, this reduction is not as significant as anticipated. The damage to the bridge pile foundation along the fault dislocation tendency notably leads to the bending damage of the bridge deck. (3) Input parameters for fracture-resistant bridge design (surface rupture zone location, extent, maximum deformation, etc.) can be deduced from the free site. Within the rupture zone, a “fuse” design can be implemented using simply supported girders. Additionally, combining the “fuse” design with simple supported girders on both sides and utilizing simple support beams for “fuse” design within the rupture zone, along with structural “disconnection”, allows for reinforcing measures on the bridge structure’s foundation platform and pile in the soil body.

A two-level performance-based plastic design method for multi-story steel frames with double-yielding systems

The performance-based seismic design (PBSD) is usually conducted under design basis earthquakes (DBE), and then, the performance of the designed structures is examined under maximum considered earthquakes (MCE). As a result, it is challenging to simultaneously satisfy the performance targets associated with the DBE and MCE levels. To this end, this study proposes a two-level performance-based plastic design (PBPD) method. The fused steel frames exhibiting trilinear capacity curves are selected as the example structures. The peak interstory drift ratios under the DBE and MCE levels are defined as the performance targets and they are explicitly utilized at the beginning of the design procedure. The expressions of two energy modification factors are first obtained by establishing energy balance equations for single-degree-of-freedom (SDOF) systems under the DBE and MCE levels, respectively. Nonlinear time history analyses (NLTHA) for SDOF systems with various trilinear capacity curves are conducted to derive necessary design parameters. The versatility and flexibility of this design method are achieved by enabling both the primary and secondary yielding systems to yield under the DBE level. To demonstrate and validate the proposed design method, a six-story benchmark steel frame equipped with idealized metallic yielding damping braces is selected and designed with two sets of performance targets. The nonlinear static and NLTHA results proved that the designed structures can simultaneously meet the prescribed performance targets under both DBE and MCE levels.

Shape memory alloy-reinforced UHPC tube confined bridge piers for enhancing the seismic resistance of highway bridges

Multi-span continuous highway bridges supported with reinforced concrete (RC) bridge piers may experience large permanent deformation after strong earthquakes. To overcome the limitations, an innovative UHPC tube-confined SMA reinforced bridge pier, i.e., shape memory alloy (SMA) replacing the steel rebars at the plastic hinge region and a prefabricated UHPC tube substituting the cover concrete, is proposed. To fully utilize the tensile strength of UHPC, the UHPC tube is embedded into the foundation. A performance-based seismic design procedure considering target residual drift as engineering demand parameter (EDP) is proposed to design this novel UHPC-SMA pier. The seismic responses of novel bridge systems supported by UHPC piers (Bridge II) and UHPC-SMA piers (Bridge III) are investigated and compared with reference bridge (Bridge I) having RC piers. The results indicate that both UHPC piers and UHPC-SMA piers are efficient in improving the seismic resistance of highway bridges. Compared with Bridge I, the prefabricated UHPC tube significantly decreases the residual deformation of Bridge II piers by 22.9 % as a result of the bridging effect of steel fibers. Due to the excellent self-centering property of SMA, the residual deformation of Bridge III piers decreases further by 57.8 % in comparison to reference bridge. The UHPC tube increases the low stiffness of bridge piers caused by SMA rebars at the plastic hinge region. The combination of UHPC tube and SMA can effectively prevent core concrete from severe damage with less dissipated energy of bridge piers.

Performance-based seismic design method for disc spring-based self-centering viscous dissipative braced steel frame

Disc spring-based self-centering viscous damper (SCVD) has emerged as a novel technology, offering velocity-dependent energy dissipation and exceptional self-centering capabilities. Integrating this damper in structural bracing systems can effectively enhance passive control over critical structural demands such as peak deformation, residual displacement, and floor acceleration. Nevertheless, a seismic design method specifically tailored for self-centering viscous dissipative braced steel frames (SCVDFs) needs further refinement. This study proposes a performance-based seismic design (PBSD) method for SCVDFs, which is grounded in the performance-based plastic design (PBPD) approach. The proposed procedure primarily considers the effects of two critical hysteresis parameters: the post-activation stiffness ratio and the viscous damping ratio. To verify the effectiveness of the design method, a set of SCVDFs was designed, each utilizing different combinations of design parameters. Nonlinear static and dynamic analyses were performed on these archetypes to evaluate their seismic performance. The evaluation findings demonstrated that the properly designed SCVDFs can achieve the expected design performance and effectively suppress the peak inter-story drift, residual inter-story drift, and peak absolute floor acceleration of the structure, thereby achieving a favorable trade-off in the design outcome and maximizing the advantages of the SCVDF in seismic resilience.

Prediction model and sensitivity analysis of ultimate drift ratio for rectangular reinforced concrete columns failed in flexural-shear based on BP-Garson algorithm

Considering that the deformation capacity of reinforced concrete (RC) columns is crucial in performance-based seismic design, the ultimate drift ratio of RC columns failed in flexural-shear are studied using BP neural network and Garson (BP-Garson) algorithm. Firstly, this study employed data onto tests conducted on 35 rectangular RC columns with flexural-shear failure. Nine influencing factors including axial load ratio, shear span ratio, longitudinal reinforcement configuration, transverse reinforcement configuration, and material strength were selected as variables, a BP neural network was used to establish the relationship between the ultimate drift ratio and these variables. Accordingly, a predictive model for the ultimate drift ratio of RC rectangular columns failed in flexural-shear was constructed. Then, the Garson algorithm for local sensitivity analysis was applied to determine the sensitivity of each influence of the ultimate drift ratio of RC rectangular columns failed in flexural-shear. The results showed that the BP neural network could accurately predict the ultimate drift ratio of RC rectangular columns with flexural-shear failure, of which the primary influencing factors are shear span ratio, axial load ratio, volume transverse reinforcement ratio and longitudinal reinforcement ratio. The BP-Garson algorithm integrates model development with influence analysis, which could improve computational efficiency and serves as a reference for evaluating the sensitivity of seismic performance and its influencing factors in other structural components.

Seismic Vulnerability Assessment in Tunnels: A Review

Vulnerability analysis is an important method for earthquake prevention and disaster reduction research in the field of tunnel engineering. Firstly, a detailed overview of the research history and current status of tunnel seismic vulnerability at home and abroad was provided; Secondly, the main methods for analyzing the seismic vulnerability of tunnels at home and abroad were summarized, and the practical applicability of various methods was summarized; Subsequently, the steps for evaluating the seismic vulnerability of tunnels were proposed, and three key contents in establishing theoretical vulnerability curves using numerical simulation as the main method were discussed: (1) Input parameter determination; (2) Classification of destructive states; (3) Calculation of relevant uncertainty parameters; Finally, point out some urgent problems and future research directions in this field. By summarizing the existing studies on the seismic vulnerability of tunnels at home and abroad, the results show that the seismic vulnerability analysis of tunnels can reflect the performance of tunnels under seismic loading by considering the relevant uncertainty factors, which is conducive to the future risk assessment and loss estimation, and is of great significance to the development of performance-based seismic design of tunnels.

Nonlinear time domain seismic response and performance evaluation of A-frame jumbo-size container cranes

Seismic responses of A-frame jumbo-size container cranes are comprehensively studied by exciting them as realistically as practical to evaluate the adequacy of the conventional static approach routinely used for their design. Multiple design earthquake time histories corresponding to the structure and site-specific earthquake design spectra corresponding to specific return periods are selected for the nonlinear time domain dynamic analyses. Cranes are considered to be in service (i.e., boom down), (2) at rest (i.e., boom up or stowed) with a friction contact support condition, and (3) at rest with tie-downs installed conditions. They are represented by finite elements, and appropriate dynamic properties are used following the practices commonly used in the profession. The seismic responses, in terms of base shear force, vertical wheel load, main member stress, portal drift ratio, and uplift, are estimated to define several performance objectives and their corresponding limits. Two container cranes with different dynamic properties and their responses are used to make the final recommendations. The in-service operating condition appears to be the most critical. The variation in the stress responses between the cranes in the at-rest and in-service conditions is about 17 %. However, the uplift in the stowed crane can be about 82 % higher than that in the in-service crane. The commonly used lateral load method using the static concept may not always be conservative, especially for the base shear force and vertical wheel load. For example, the method significantly underestimates the base shear force by about 52 % for the slender crane and 26 % for the relatively stiffer crane. Thus, the nonlinear time domain approach proposed here should always be used. It will satisfy the performance-based seismic design concept under development at present.

Research on seismic design methods for high-rise building structures

In recent years, with the increase of the number of high-rise buildings and the increase of the frequency of earthquakes, the requirement of seismic design of high-rise buildings is getting higher and higher. Therefore, this paper mainly studies the requirements of the existing seismic design code and the basis of designing the seismic performance of high-rise buildings. The results of this paper show that the performance-based seismic design method is the most popular and practical seismic design method at present. It also concluded that the seismic capacity of high-rise buildings can be improved by changing the calculation method of bearing capacity and adopting stable lightweight materials. In addition, this paper also introduces the new seismic methods such as preset yield mode, so as to improve the seismic ability of tall buildings as a whole. In the future, more new and innovative technologies will be applied to the seismic design of high-rise buildings to provide a stable and safe environment for peoples production and life.

An approach for optimum performance-based seismic design of 3D steel moment frames

An optimal performance-based design (PBD) of a three-dimensional (3D) structure requires repeated evaluation; thus, proposed approaches should attempt to significantly reduce the number of evaluations required during optimization. The current study proposes a multi-step approach for optimal PBD of a 3D steel moment frame in which the structure is examined at each step for one performance level in a specific direction. To advance to the next step, the acceptance criteria for linear static analysis of the steel moment frame from ASCE 41-17 should have been satisfied in the previous step. An objective function has been formulated using the proposed stepped penalty function to achieve a feasible space, the value of which can be determined based on the number of unexamined steps. Finally, the optimal PBDs for 3D three-story and nine-story steel moment frames were evaluated using EVPS and WSA metaheuristic algorithms to evaluate the proposed process. The final optimal designs were assessed using the acceptance criteria of nonlinear static analysis. The number of performance level evaluations in each direction during optimization showed approximately 60 % and 70 % reductions during analysis by the proposed method for the WSA and EVPS algorithms, respectively.

Seismic Design of Large-Span, Heavy-Load Transfer Truss for Zhanjiang Bay R&D Building

The Zhanjiang Bay Laboratory R&D Building project aims to create a favorable working, research, and living environment. Zone II of the Zhanjiang Bay Laboratory R&D Building is equipped with a large-span, heavy-load transfer truss to obtain a large space on the ground floor. The overall structure adopts a steel frame-core tube structure system. In order to reduce the deflection of the large-span, heavy-load transfer truss, eight diagonal pull rods are installed between the large-span, heavy-load transfer truss and the core tube. The Q235 cross-shaped replacement section can consume construction load energy. Adopting replacement methods can reduce the stress and damage of diagonal pull rods caused by construction loads. The structure adopts a performance-based seismic design method for seismic calculation and analysis. In addition, a special analysis was conducted on the single frame structure. The major results can be summarized as follows: during small earthquakes, all structural components are in the elastic stage; during large earthquakes, frame beams yield first, but frame columns and core tubes do not yield; even without considering out-of-plane constraints, the structure can still meet the requirements.