Seismic Design Method Research Articles

Seismic design method based on limit state for prefabricated RCS frames

The prefabricated reinforced concrete column-steel beam (RCS) frame is an innovative and efficient structural system. To promote the application of the prefabricated RCS frame, a practical seismic design method based on the limit state design was proposed. The elastic method based on the bearing capacity of components was adopted to design frames with different ground motion intensities. When the designed frames are under the strong-column-weak-beam criterion, the capacity and demand values of over-strength factors were calculated, and the over-strength factors were adopted to calculate the yield base shear. Based on the yield base shear and yield mechanism, the semi-rigid connections were designed according to the plastic method, while the beams and columns were designed based on the capacity method. The proposed design method was successfully applied to a six-story prefabricated RCS frame and validated by inelastic analyses. Furthermore, the proposed method can also provide references for other prefabricated frames.

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.

Seismic displacement response of SDOF systems with SMA slip friction dampers

Owing to superelastic behavior, shape memory alloy (SMA) has been widely utilized to develop self-centering damping devices. Recently, the authors developed a novel SMA damper, i.e. the SMA slip friction (SMASF) damper. The cyclic behavior of the SMASF damper not only depends on the hysteresis shape factors of SMA bars, but also on the coefficient of kinetic friction and the slope of the friction plates. Hence, the basic working mechanism of the SMASF damper is different from that of conventional SMA dampers. In the early work, the features of the SMASF damper have been revealed by static cyclic loading tests. However, the seismic displacement responses of this novel damper remain unknown. To this end, this paper initiates with a brief introduction of the damper, including the configuration, working mechanism, and testing results. And then, extensive seismic analyses based on single-degree-of-freedom systems were conducted. Based on the constant-strength ductility demand spectra, the displacement responses of the SMASF damper were understood through the comparisons with conventional SMA damper and friction damper. A wide range of fundamental periods, strength capacities and seismic intensity levels were considered. Further, parametric analysis was conducted to assess the effect of the hysteresis shape factors of SMA bars and the coefficient of kinetic friction and the slope of the friction plates. This study also sheds light on the force-based seismic design method for this damper.

Equivalent static methods for seismic design of straight integral abutment bridges

AbstractIntegral abutment bridges (IABs) are becoming the solution of choice in the low to mid‐length ranges because of their low cost compared with traditional solutions and their good performance under seismic actions. The main drawback of these bridges is the need to consider soil‐structure interaction to assess their performance, a problem that is more pronounced for actions implying horizontal deck movements, such as temperature or the specific focus of this paper, that is, seismic action. In IAB design, simplified models are often used, where soil‐structure interaction is modeled by means of beams on non‐linear Winkler springs for the evaluation of seismic behavior. This paper, starting from an existing non‐linear dynamic model (NLDM) that describes IABs longitudinal seismic response, derives two equivalent static models: one non‐linear and the other linear, for displacement‐ or force‐based design respectively. A parametric study is carried out to assess the static models performance in terms of the main design internal actions versus the NLDM. Finally, the assessed model errors are discussed in the context of partial factors safety format.

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.

Equal-displacement principle-based direct seismic-design method for single-yielding precast-concrete frame

This study aims to improve the seismic performance and reduce damage of a structure using energy-dissipation connectors, while avoiding the design difficulties of existing methods. In this study, a single-yielding–precast-concrete (SYPC) frame was proposed to realize the design of a controllable bending moment at the beam end. An equal-displacement principle-based direct seismic-design method was proposed for the SYPC frame. First, using a dynamic time–history analysis, the key parameters affecting the stiffness of the frame and the adjustment strategy were explored. Subsequently, based on the equal-displacement principle, the seismic intensity control and target interstory drift were directly determined. Finally, a direct seismic-design method for the SYPC frame based on the equal-displacement principle was proposed. A six-story SYPC frame was designed according to the proposed design method. An elastic–plastic dynamic time–history analysis was performed for the designed frame to verify the effectiveness and accuracy of the proposed design method. The results show that the equal-displacement principle can rapidly and accurately determine the target elastic–plastic displacement of the underground motions of the structure and effectively avoid the iterative solution of structural plastic characteristic parameters, such as equivalent damping and ductility coefficient, encountered in traditional design methods. The proposed design method not only effectively controls the deformation pattern of the structure but also realizes an ideal beam-hinge mechanism. Additionally, by controlling the length and section area of the replaceable energy-dissipating connectors (REDCS) to satisfy the ductility requirement, the stiffness was verified to satisfy the requirements of the frame deformation mechanism.

Seismic design and performance evaluation of hybrid braced frames having buckling-restrained braces and self-centering viscous energy-dissipative braces

Hybrid braced frames (HBFs) emerge as an innovative seismic-resilient system, synergizing the strengths of buckling-restrained braces (BRBs) and self-centering viscous energy-dissipative braces (SCVDBs). This novel system has the potential to simultaneously manage three key seismic demand parameters: peak inter-story drift (PID), residual inter-story drift (RID), and peak absolute floor acceleration (PFA). Nevertheless, a dedicated seismic design method for HBFs is yet to be developed. This research proposes a performance-based seismic design (PBSD) method specifically tailored for HBFs. The method's core relies on energy decoupling in the HBFs using a proposed energy distribution factor (η). To validate the proposed design method, sets of 4-, 8-, and 12-story braced frames are designed using varied η. A comprehensive seismic performance evaluation is conducted, utilizing nonlinear static and nonlinear time-history analyses. The findings indicate that the HBFs, designed utilizing different values of η, consistently meet predefined performance objectives. Within the scope of this study, the η value of 0.5 is shown to be optimal, enhancing the structural resilience of HBFs against PIDs and PFAs while exhibiting excellent self-centering performance comparable to the self-centering viscous energy-dissipative braced frame (SCVDF). Additionally, the HBFs demonstrate superior control over PFA compared to pure buckling-restrained braced frame (BRBF) and SCVDF.

Substructure Mass Participation Effect on the Performance-Based Seismic Design Method for Isolated Bridges

Substructure Mass Participation Effect on the Performance-Based Seismic Design Method for Isolated Bridges

Displacement-based seismic design of SMA cable-restrained sliding lead rubber bearing for isolated continuous girder bridges

The sliding of isolation bearings in a bridge structure can reduce bridge pier damage, but bearing sliding under the strong earthquake may cause excessive displacement of the girders or even falling girders. This study proposes an innovative shape memory alloy (SMA) cable-restrained sliding lead rubber bearing (SMA-SLRB), which can maximise the sliding advantages of the bearing whilst combining the displacement-limiting capacity and self-centering capacity of the SMA cable. The working mechanism of the SMA-SLRB is firstly revealed, and the mechanical model of the SMA-SLRB is verified by tests. Then, the multilevel fortification performance target of isolated continuous girder bridges with SMA-SLRB is proposed. A displacement-based seismic design (DBSD) method for the SMA-SLRB isolated continuous girder bridge is established. Next, with the single pier model of a five-span isolated continuous girder bridge taken as an example, the displacement-based design is implemented, and the seismic performance of the bridge is evaluated. Finally, the seismic responses of bridges with SMA-SLRB and SLRB under extremely rare earthquakes are compared. Results show that the energy dissipation capacity and stiffness of SMA-SLRB are improved to varying degrees compared with SLRB. The bridge basically achieves the design target displacement and meets the requirements of multilevel fortification performance, which confirms the effectiveness of the DBSD method. Under extremely rare earthquakes, the SMA-SLRB can effectively reduce the maximum displacement and residual displacement of the girder compared with the SLRB.

Shaking table test and numerical simulation of a precast frame-shear wall structure with innovative untopped precast concrete floors

An innovative discretely connected precast concrete floor (DCPCF) was presented, in which the adjacent precast concrete hollow or sandwich flat slabs were connected by mechanical connectors embedded in the precast concrete slabs and beams. This paper summarized the seismic performance observed during the shaking table test of a precast frame-shear wall structure adopting DCPCF. A 1/4-scale model of a 4-storey 2-bay single-span frame-shear wall structure was designed and tested on the shaking table to evaluate the dynamic characteristics and seismic responses of building structures adopting DCPCF. In addition, a finite element model, including detailed modeling of beam-column joint and slab joint connections, was established using nonlinear dynamic modeling program. The predictions on the seismic performance using the finite element model agreed well with the test results for the designed frame-shear wall structure. The precast concrete frame-shear wall structure adopting DCPCF had satisfactory seismic performance during the test process. The in-plane deformation of DCPCF was observed under the horizontal earthquakes, and DCPCF could not satisfy the requirements of rigid diaphragm assumption in most cases under design basis seismic intensity. The seismic design method based on semi-rigid floor diaphragm had large error and safety risk in calculating the seismic shear force of building structure adopting DCPCF. Additionally, design suggestions for multi-storey and high-rise building structures using DCPCF were proposed based on the observed seismic responses.

Seismic design methods for concrete buildings

Earthquake is a devastating natural disaster that can easily cause buildings to collapse, posing a serious threat to human life. Concrete, as a widely used building material, is of significant concern for its seismic performance. This paper mainly presents how seismic resistance can be considered in concrete building design and proposes two main solutions, the use of high-performance materials and rational structural placement. Through comparison and analysis, it finds that rationalization of the structural placement is the preferred and feasible solution for the future between the two. The successful development of computer software has dramatically reduced the workload of structural modeling and analysis. At the same time, the combination of considering the use of high-performance materials and rationalizing the structural placement is a highly effective approach, which requires more time from the researcher to solve the difficulties and challenges. This paper provides a clear direction for research into seismic problems in concrete buildings.

Evaluation of equivalent linearization methods of MDOF isolated structures in response spectrum analysis

In the seismic design of isolated structures, equivalent linearization of the hysteretic isolators is normally considered. There exist many equivalent linearization methods and evaluation of these methods has been widely studied. However, most of the previous studies concern a single degree of freedom system only, and the used analysis method is time history analysis. In such a case, the evaluation heavily depends on the ground motions selected. Note that the response spectrum analysis is a commonly used method for seismic design of structures. Therefore, it is more valuable to evaluate these equivalent linearization methods based on the response spectrum analysis. In this study, a multiple degree of freedom model is adopted due to the contribution of higher modes of the superstructure to the seismic responses, and the procedure of the response spectrum analysis in conjunction with the equivalent linearization method is presented in detail. Then, considering a series of parameters of isolators, a statistical study is performed to evaluate the accuracy of these equivalent linearization methods by comparing with the nonlinear time history analysis. Moreover, the effect of the damping reduction factor for the response spectrum on the accuracy of the equivalent linearization methods is discussed in terms of probability in a desirable error range. The analytical results show that the accuracy of the equivalent linearization methods is associated with the earthquake intensity. Meanwhile, for different response quantities the accuracy of each equivalent linearization method varies significantly. In addition, to estimate the seismic responses with a better accuracy in the response spectrum analysis, a suitable damping reduction factor should be considered.

Seismic behavior of embedded rubberized concrete-filled corrugated steel tube column-to-foundation connections: Experimental, numerical modelling, and design

A rubberized-concrete-filled corrugated steel tube composite column-foundation connection is proposed as a solution to mitigate local buckling, bulging, or tearing damage of concrete-filled steel tube columns during seismic load. This proposal aims to improve the ductility and energy dissipation capacity of the column. Experimental studies have been conducted to investigate the axial compressive strength of this novel column and the side shear performance of its connection to the foundation. A quasi-static experiment was carried out on three specimens to facilitate the application of the proposed connection. The influence of embedded depth on the seismic strength of such composite column-foundation connection was studied, and the cast-in-place specimen was used as a reference. The failure modes of the specimens were observed, and the evaluation indicators such as strength, stiffness, and ductility were analyzed. The results show that the connection of the composite column foundation can provide sufficient connection strength under seismic load. Furthermore, seismic design methods are explored and proposed, combined with the side shear database. These investigations aim to inform the design and application of such column-foundation connections.

Seismic performance of self-centering braced rocking frame with novel self-centering friction dampers characterized by low-secondary stiffness

Research has demonstrated that self-centering energy dissipation dampers (SCEDs) are effective devices for reducing the residual deformation of structures after a strong earthquake. However, the equivalent damping ratio of SCEDs is relatively lower than that of conventional dampers such as viscous dampers, BRBs, or friction dampers. According to displacement spectrums, the lower damping ratio could result in a lower natural period and higher equivalent stiffness of structures for a given displacement target, and thus the structures could attract more earthquake action to the structures. To alleviate the problem, a novel self-centering damper composed of elastic post-buckling plates and adjustable friction devices (PBSCFD) was proposed and used as the self-centering braces for a self-centering braced rocking frame (SBRF) structure for example. First, the theoretical force-displacement relationship of the PBSCFD was derived based on its configuration and work principle, and then a scaled PBSCFD was manufactured and tested to investigate its mechanical properties and verify the theoretical constitutive model. Subsequently, the SBRF structure with PBSCFDs was designed by the direct displacement-based seismic design method (DDBD), and its seismic performance was examined by elastic–plastic time-history analysis. Finally, the effects of the secondary stiffness ratio of the self-centering braces on seismic mitigation of the SBRF structure were investigated. The results show that PBSCFDs is characterized by classic self-centering behavior with low secondary stiffness, which can be designed to obtain significant control effects on the base/interstorey shear and interstorey drift ratio of the SBRF structure under rare and extremely rare earthquake compared to the conventional SCEDs with significant secondary stiffness.

Study on the seismic performance of prestressed steel-concrete vierendeel truss transfer story frame

Prestressed steel-reinforced-concrete (PSRC) Vierendeel truss transfer structures significantly increase the span of the transfer story and enhance the seismic performance with prestressing and steel-concrete techniques. A “three lines of defense” seismic design method was adopted in this study to further investigate the seismic performance of this structural system using the finite element software OpenSees to analyze the dynamic response of the PSRC Vierendeel truss transfer story spatial frame structure under an earthquake in the Intensity Region 8 (PGA = 400 Gal). To design four distinct PSRC Vierendeel truss transfer story frame structures, the number of bottom frame spans and the placement of the transfer truss were altered. An elastoplastic time-history analysis under a three-way rare earthquake was conducted by combining the quantitative control indices of the “three lines of defense” design method. The study shows that the PSRC Vierendeel truss transfer story structures designed by the “three lines of defense” seismic design method meet the requirements of the quantitative control indexes, and the structural seismic performance was satisfied.

A seismic resilient design method for structures equipped with two-level yielding dampers, accounting for extremely rare earthquakes

Current design methods for achieving seismic resilience of structures are limited to hazard levels of service level earthquake, design-based earthquake and maximum considered earthquake, but they do not account for the risk of extremely rare earthquake (ERE) that poses a significant challenge to structural and human safety. To address this issue, this paper proposes a new seismic resilient design method that considers ERE by incorporating two-level yielding dampers as the primary structural fuse while satisfying the performance objectives of all four seismic hazard levels. The paper presents a detailed derivation of the proposed design method and outlines a step-by-step design procedure. The proposed design method is applied to a seismic resilient system called the two-level yielding beam linked steel frame system (TYBLSFS), and two TYBLSFSs with three and six stories are designed and numerically modeled. Nonlinear dynamic analyses are then conducted to validate the effectiveness of the proposed design method. The results show that the two TYBLSFSs achieve the designed targets of roof drift ratio (RDR) and inter-story drift ratio (ISDR) and that the RDR-base shear curves obtained from the dynamic analyses match the design curves. The predetermined yielding mechanism and anticipated performance goals for all four seismic levels have been achieved. And the presented TYBLSFS can be effectively utilized as a seismic resilient system against very strong earthquakes.

Seismic design and performance analysis of perforated rubber buffer layer in tunnel

Tunnels may be damaged under earthquakes, which has been observed by many earthquake events, and the buffer layer is proposed and widely investigated as a damping measure. The rubber is considered as a qualified buffer layer material because of its small elastic modulus and super elasticity, but its high price makes it difficult to apply in practical engineering. Therefore, four types of rubber buffer layers are proposed in this study, including the common rubber buffer layer and three types of perforated rubber buffer layers (PRBL), which can reduce the seismic damage and cost of tunnels. A pseudo-static method for calculating the seismic response of tunnels under horizontal and vertical earthquake motions is proposed and verified. Based on proposed pseudo-static method, a seismic design method for the buffer layer is present, and the proposed seismic design process is used to study the seismic mitigation performance of buffer layers. The initial design of the buffer layer under earthquake action E1 is carried out by pseudo-static method, and then the seismic mitigation performance is verified through dynamic time history analysis method under earthquake action E2. The earthquake action E1 and earthquake action E2 are the earthquake actions with short and long return periods of the engineering site, respectively. The results show that the common rubber buffer layer has almost no seismic mitigation performance, and the three types of PRBLs have good seismic mitigation performance. The type IV buffer layer is strip-shaped PRBL and the holes are along the longitudinal direction of the tunnel, and it has optimal seismic mitigation performance. The effects of vertical earthquake motion and peak ground acceleration (PGA) on the seismic mitigation performance of the buffer layer are studied. The results show that vertical earthquake motion has little effect on the seismic mitigation performance of different types of buffer layers. For different PGAs, the type IV buffer layer is able to efficiently decrease the peak internal force of secondary lining. The results also prove the validity of design method.

Experimental analysis on the structural seismic behavior of steel frame-precast steel reinforced concrete (SRC) infill wall with lateral force resisting

The structural seismic performance of steel frame-precast steel reinforced concrete (SRC) infill wall with lateral force resisting is analyzed, and the structural strength of steel frame-precast SRC infill wall with lateral force resisting is improved. The structural seismic performance optimization model of SRC lateral force resisting wall based on buckling restrained brace is proposed. Through the finite element simulation software, the seismic performance and response results of ordinary steel frames, buckling restrained braced steel frames and a relatively new type of sacrificial-energy dissipation braced steel frames under earthquake are compared and analyzed to demonstrate the applicability and performance advantages of sacrificial-energy dissipation braced steel frames in the steel frame braced structure system. Under the action of horizontal earthquake, the supporting members experience reciprocating axial tension and compression cycles, which dissipate a large amount of seismic energy input into the structure. Therefore, the buckling restraint support method can be used in the structure to improve the support strength. Under horizontal reciprocating load action of earthquake, the ability to consume seismic energy through self-hysteresis of the brace is poor. Experimental research shows that, the unbalanced force formed in the beam of the frame beam under seismic action will form a plastic hinge at the beam end at both ends of the frame beam. Especially when the brace is buckling unstable and the stiffness of the frame beam is small, the plastic hinge effect at the beam end is significant. This phenomenon may cause damage to the frame beam or even local floor subsidence. The buckling restraint support has a full hysteresis area under axial tension and compression, and its mechanical performance is excellent. It is obviously superior to ordinary steel bracing in energy dissipation capacity and seismic performance. It can accurately predict the bearing capacity of reinforced concrete under strong earthquake, and the energy dissipation distribution is more in line with the requirements of “energy seismic design method”.

Floor response spectra and seismic design method of electrical equipment installed on floor in indoor substation

Electrical equipment installed on floors is a typical type of nonstructural component in indoor substations, which could be subjected to earthquake loading during seismic events. To investigate the seismic design method of floor electrical equipment in indoor substations, simulation models of four whole-indoor substations comprising main control buildings and their floor electrical equipment were established. Seismic response spectrum analyses of main-attachment structures were performed with a high number of ground motions as inputs. Using mathematical statistics and data fitting methods, this research suggested the calculation formula of amplification factor of floor acceleration response spectrum. Specifically, when the periodic ratio of electrical equipment to main control building is in the range of 0.9–1.1, the system would produce a strong resonance-like effect with a peak spectral amplification factor. The floor response spectrum for seismic design was influenced by four factors: equipment importance category, floor position, damping ratio of electrical equipment, and torsion effect of main control building. Following that, a seismic design method especially applicable for electrical equipment installed on floor in indoor substation, which combines amplification factor and calculation method of seismic action indicated in the relevant specification, was presented. Lastly, a typical 220 kV whole-indoor substation was taken as an example to validate the accuracy of the design method highlighted in this article.

A novel self-centering friction damper with elastic post-buckling plates to retrofit bridge bents

The self-centering energy dissipation dampers (SCEDs) have been demonstrated in mitigating the residual deformation of structures under strong ground motions. However, existing researches show that the damping force demand of SCEDs is higher than conventional dampers such as viscous dampers, BRBs or friction dampers for same design displacement of self-centering retrofitted structures, which could lead to higher base shear and acceleration responses of structures. In order to alleviate the problem, a novel self-centering damper composed of elastic post-buckling plates and adjustable friction devices (PBSCFD) was proposed. Compared with conventional SCEDs, the proposed PBSCFD has low secondary stiffness and adjustable energy dissipation capacity, which is beneficial to control the additional internal force of members adjacent to the damper in self-centering retrofitted structures. Based on the configuration and working principle of the PBSCFD, the theoretical force-displacement relationship of the damper was derived. Subsequently, a scaled PBSCFD was manufactured and tested under quasi-static loading to investigate its mechanical properties and to verify the theoretical constitutive model. In order to demonstrate the seismic performance of PBSCFDs, the double-column bridge bent retrofitted with PBSCFDs was designed by direct displacement-based seismic design method (DDBD), and its seismic performance was examined by elastic-plastic time-history analysis. Finally, effects of secondary stiffness ratio of self-centering dampers on seismic mitigation of self-centering retrofitted bridge bent were investigated. The results show that PBSCFDs have certain advantages in controlling the base shear and acceleration of the retrofitted bridge bent compared to conventional SCEDs with significant secondary stiffness.