Seismic Design Method Research Articles

A Nonlinear Static Procedure for the Seismic Design of Symmetrical Irregular Bridges

Displacement-based seismic design methods support the performance-based seismic design philosophy known to be the most advanced seismic design theory. This paper explores one common type of irregular-continuous bridges and studies the prediction of their elastoplastic displacement demand, based on a new nonlinear static procedure. This benefits to achieve the operation of displacement-based seismic design. Three irregular-continuous bridges are analyzed to advance the equivalent SDOF system, build the capacity spectrum and the inelastic spectrum, and generate the new nonlinear static analysis. The proposed approach is used to simplify the prediction of elastoplastic displacement demand and is validated by parametric analysis. The new nonlinear static procedure is also used to achieve the displacement-based seismic design procedure. It is tested by an example to obtain results which show that after several combinations of the capacity spectrum (obtained by a pushover analysis) and the inelastic demand spectrum, the simplified displacement-based seismic design of the common irregular-continuous bridges can be achieved. By this design, the seismic damage on structures is effectively controlled.

Applicability analysis of high-speed railway system under the action of near-fault ground motion

Studying the applicability of existing bridge and track systems of high-speed railway in near-fault areas is crucial and urgent, because the current seismic design methods seldom consider the characteristics of the near-fault ground motion. By comprehensively considering the uncertainties in ground motion and structural parameters, a large-sample analysis method for near-faults area was proposed. In addition, an integrated finite element model for beam bridge-track system of high-speed railway was used to calculate the seismic response of the structure under the action of near-fault ground motion. The over-limit state and applicability of seismic response of key components and systems were predicted and evaluated. The analysis results indicate that the statistical characteristics of structural seismic response and over-limit state tend to be stable with increasing number of samples. Under the near-fault ground motion: (i) the piers of high-speed railway are hard to yield (ii) bearings are damaged severely, and (iii) the piers have insufficient shear capacity and the characteristics of structural seismic damage are not in accordance with the concept of ductility design. The sliding layer of the track structure is severely damaged by the transverse and longitudinal ground motions, while the CA mortar layer and fastener are mainly damaged by the transverse ground motion. The applicability of bearings, the anti-shearing behavior of piers, and the inter-layer structure of tracks make it difficult to achieve the goal of the near-fault fortification against ground motion.

Feasibility Study on Strain-Based Seismic Design Criteria for Nuclear Components

In this paper, the feasibility study to develop strain-based seismic design criteria applicable for the components of nuclear power plants are carried out as an alternative rule to the current stress-based criteria. To do this, two acceptance criteria are investigated through the detailed example of an application for the surge line nozzles in a nuclear steam supply system, which are known as one of the seismic fragile components in nuclear power plants. These strain-based seismic design criteria are primarily to prevent two types of failure modes, such as a ductile fracture and a cyclic fatigue-induced damage due to continuous large amplitude cyclic loads during seismic event. Through the example problem, the required procedures are described step-by-step with calculations of an accumulated plastic strain, triaxiality factor by the elasto-plastic seismic analysis using the finite element method. For a precise inelastic seismic analysis, the Chaboche kinematic and Voce isotropic hardening material parameters are identified by the test data and used for an inelastic material model. The results by the strain-based criteria are compared with those by the ASME (American Society of Mechanical Engineers) stress-based design criteria for a service level D limits. From the study, it is expected that the strain-based seismic design method investigated in this paper will be beneficial for the nuclear components, especially when the design basis earthquakes are large enough to cause severe plastic strains at a critical location.

Performance-Based Seismic Design of RC Moment Resisting Frames with Friction-Damped Self-Centering Tension Braces

ABSTRACT This paper presents a performance-based seismic design method of RC moment resisting frame with friction damped self-centering tension braces (FSTB-Frame). The structural configuration and theoretical model of FSTB is introduced, and the numerical model of FSTB is established and validated through cyclic loading tests of a FSTB specimen. Based on the equivalent linear method, the seismic design procedure is developed and verified through 3-, 6-, 9-, and 12-story structures with different design performance objectives. Numerical models of FSTB-frames are established and used to verify whether the design performance targets are achieved through nonlinear dynamic analyses using the design-basis earthquake (DBE) ground motions. The research results show FSTB-frames can achieve the intended performance levels in terms of story drift, residual story drift and base shear, and the maximum and residual story drift of RC frames can be significantly decreased after equipping FSTBs.

Seismic design of space steel frames using advanced static inelastic (pushover) analysis

A rational and efficient seismic design method for regular space steel frames using inelastic (pushover) analysis (PA) is presented. This method employs an advanced static finite element analysis that takes into account geometrical and material non-linearities and member and frame imperfections. Resistances (strengths) are computed according to Eurocodes 3. The PA is employed with multimodal lateral loads along the height of the building combining the first few modes. The design starts with assumed member sections, continues with deformation and damage check at three performance levels with the aid of PAs and ends with the adjustment of member sizes. Thus, it can sufficiently capture the limit states of displacements, strength, stability and damage of the structure and its individual members so that separate member capacity checks through the interaction equations of Eurocode 3 or the use of the behavior factor q suggested in Eurocode 8 are not required. One numerical example dealing with the seismic design of a one bay in both horizontal directions and three storey steel moment resisting frame is presented to illustrate the method and demonstrate its advantages.

Structural Design and Elastic–Plastic Analysis of Zhangzhou Theater

Zhangzhou Theater is a complex composed of an opera house, a cinema, businesses and underground supporting facilities. It adopts a frame shear wall structural system and is 48 m tall. Owing to the multiple ultralimits of torsional irregularity, large local holes, multiple inclined columns and large space of the structure, a performance-based seismic design method is needed. In this study, response spectrum analyses of the structure were carried out using two types of software and compared. Moreover, elastic time-history analysis, yield and elastic analysis under intermediate earthquakes, and elastic–plastic time-history analysis under rare earthquakes were implemented. Relevant reinforcement measures were applied to weak positions according to the analysis results. The failure mode and failure region of main stress components in the structure under the rare earthquakes were analyzed to ensure that weak positions and important positions of the structure would meet elastic–plastic deformation requirements under rare earthquakes.

RETRACTED: A new seismic design method of simply supported girder bridges for very rare ground motions in the transverse direction

In most seismic design codes, usually two seismic hazard levels are taken into account, for example, Design Earthquake and Maximum Considered Earthquake. Several disastrous earthquakes have proved that seismic safety evaluation may underestimate seismic risks, which would result in serious damage of bridge structures. Therefore, a new higher level of seismic hazard named Very Rare Ground Motion (VRGM for short) is proposed innovatively to be considered in this paper for very important bridges. A novel seismic design method of simply supported girder bridges in the transverse direction for VRGMs is proposed at first. In the proposed method, seismic isolation bearings, tension-only braces and ductile piers are combined to improve the seismic performance and meet seismic requirements of VRGMs. Taking a simply supported girder bridge as a numerical analysis example, the proposed method is compared with two bridge seismic design methods adopted in current seismic codes and its parametric analysis is conducted. It’s shown that the proposed seismic design method can combine the ductility capacities of piers and the functions of seismic isolation bearings and reduce all the concerned structural seismic responses in VRGMs effectively. This work provides an educational demonstration for engineers dealing with similar problems.

A Hybrid Force/Displacement Seismic Design Method for Reinforced Concrete Infilled-MRFs and Wall-Frame Dual Systems

ABSTRACT A hybrid force/displacement (HFD) performance-based seismic design method is proposed for two types of plane reinforced concrete structures, i.e., infilled moment-resisting frames (I-MRFs) and wall-frame dual systems (WFDS). The HFD seismic design method is a force-based method which controls with high accuracy both structural and non-structural deformation limits. The behavior factor is related here to the inter-storey drift ratio and the member plastic rotation by taking into account both geometrical and dynamic structural characteristics. The HFD is herein developed through an extensive parametrical study involving non-linear time-history analyses of 19 I-MRFs, and 19 WFDS under 100 far-fault ground motions.

Seismic Performance Evaluation of Steel Moment-Resisting Frames Designed According to 3rd and 4th Editions of 2800 Seismic Code

Current design codes have prepared linear analysis methods instead of nonlinear ones in order to reduce time, cost and other factors such as less need of these methods for expert knowledge. In linear analysis method, elastic strength demand of structure is decreased by applying a response modification factor called behavior factor (R) and by considering the design code regulations, structure members will be permitted to experience nonlinear response (in the time of middle-to-severe earthquakes). Because of different assumptions for linear (force-based method that has deficiencies) and nonlinear methods and whereas seismic stability or instability is not merely related to the strength of structure, rather it depends largely on the capability of structure to resist drifts, seismic performance evaluation of structures designed by linear procedure appears to be necessary using standards for evaluation. In this research, seismic performance of steel moment frames once designed based on 3rd edition of 2800-Iranian seismic code and allowable stress design (ASD) method and another time based on new ones, the 4th edition of 2800 seismic code and load and resistance factor design (LRFD) method, are compared with each other through nonlinear pushover and time-history analyses according to ASCE/SEI 41–13. Results showed positive change of design codes procedure with respect to alteration of design method in both types of ductile design, intermediate and special. Since mean of overstrength values and mean of ductility values have increased a little, mean of behavior factor values has become closer to the recommended values of the new seismic code. Also, a small number of structures met total collapse during nonlinear time-history analyses.

Structure and Stress Mechanism of Snti-buckling Support for High-rise Connected Structures

This article explores the characteristics, composition, and design requirements of high-rise intelligent buildings, analyzes their superiority and social benefits, and studies their construction principles and future development trends. It is people-oriented, device-oriented and function-oriented. The original three major structural systems have been increasingly unable to meet new requirements. This paper seeks a new seismic system that is both safe and able to protect the instruments and equipment inside the building, and can be connected to the main structure of the structure for normal operation and economically. After a thorough discussion of the latest proposed seismic design methods and performance-based seismic design, this paper proposes performance-based structural seismic design countermeasures with the characteristics of high-rise intelligent buildings. Determine the target performance according to the owner’s requirements and building functions and investment benefit criteria; then determine the safety indicators of the high-performance intelligent building based on the performance structural design; compare the three optimization decision models for the reliability of the performance-based structural targets; An evaluation model of initial cost, inspection and maintenance costs, and failure loss costs. A reliability optimization decision-making model based on performance and earthquake resistance for a high-rise intelligent building is established. The research results show that the maximum displacement of the model structure in the X direction is 14.8mm and 13.8mm, and the maximum displacement in the Y direction is 13.7mm and 12.9mm, respectively. The maximum displacement of the latter in the X and Y directions is compared with the former. From the perspective of the curve change, the displacement change curve of the anti-buckling support frame is always smaller than the displacement curve of the ordinary support frame.

Improvement of the Performance Based Seismic Design Method of Cable Supported Bridges with Resilient-Friction Base Isolation Systems (II-Proposal for the Seismic Design Procedure)

In a previous paper, ambient vibration tests were conducted on a cable stayed bridge with resilient-friction base isolation systems (R-FBI) to extract the dynamic characteristics of the bridge and compare the results with a seismic analysis model. In this paper, a nonlinear seismic analysis model was established for analysis of the bridge to compare the difference in seismic responses between nonlinear time history analysis and multi-mode spectral analysis methods in the seismic design phase of cable supported bridges. Through these studies, it was confirmed that the seismic design procedures of the “Korean Highway Bridge Design Code (Limit State Design) for Cable Supported Bridges” is not suitable for cable supported bridges installed with R-FBI. Therefore, to reflect the actual dynamic characteristics of the R-FBI installed on cable-supported bridges, an improved seismic design procedure is proposed that applies the seismic analysis method differently depending on the seismic isolation effect of the R-FBI for each seismic performance level.

Improvement of the Performance Based Seismic Design Method of Cable Supported Bridges with Resilient-Friction Base Isolation Systems (I- Analysis of Field Testing of Cable Supported Bridge)

In this study, a field bridge test was conducted to find the dynamic properties of cable supported bridges with resilient-friction base isolation systems (R-FBI). Various ambient vibration tests were performed to estimate dynamic properties of a test bridge using trucks in a non-transportation state before opening of the bridge and by ordinary traffic loadings about one year later after opening of the bridge. The dynamic properties found from the results of the tests were compared with an analysis model. From the result of the ambient vibration tests of the cable supported bridge with R-FBI, it was confirmed that the dynamic properties were sensitive to the stiffness of the R-FBI in the bridge, and the seismic analysis model of the test bridge using the effective stiffness of the R-FBI was insufficient for reflecting the dynamic behavior of the bridge. In the case of cable supported bridges, the seismic design must follow the “Korean Highway Bridge Design Code (Limit State Design) for Cable supported bridges.” Therefore, in order to reflect the actual behavior characteristics of the R-FBI installed on cable-supported bridges, an improved seismic design procedure should be proposed.

Correction to: A direct displacement‑based seismic design method using a MDOF equivalent system: application to R/C framed structures

This erratum is published as proofing errors were introduced in fig.1 during typesetting and needs to be correctly read as.

Improvement of the Performance-Based Seismic Design Method of Cable Supported Bridges with the Resilient-Friction Base Isolation Systems

In areas of civil engineering, the resilient friction base isolator (R-FBI) system has been used due to its enhanced isolation performance under seismic excitations. However, because nonlinear behavior of the R-FBI should be reflected in seismic design, effective stiffness (Keff) of the R-FBI is uniformly applied at both peak ground acceleration (PGA) of 0.08 g and 0.154 g which use a multimodal response spectrum (RS) method analysis. For rational seismic design of bridges, it should be required to evaluate the dynamics of the R-FBI from in-field tests and to improve the seismic design procedure based on the performance level of the bridges. The objective of this study is to evaluate the dynamics of the R-FBI and to suggest the performance-based seismic design method for cable-supported bridges with the R-FBI. From the comparison between the experiments’ results and modal shape analyses, the modal shape analyses using primary (Ku) or infinite stiffness (fixed end) showed a great agreement with the experimental results compared to the application of Keff in the shape analysis. Additionally, the RS or nonlinear time history method analyses by the PGA levels should be applied by reflecting the dynamic characteristics of the R-FBI for the reasonable and efficient seismic design.

An improved displacement based seismic design method of prestressed fabricated concrete frame

Due to the randomness of ground motion and the variation of the material itself, it is unreasonable to regard the inter-layer target displacement angle of the structure as a certain amount in the direct displacement-based seismic design. In this paper, an improved displacement seismic design method is proposed, which is characterized by: (1)Considering the reliability when determining the target displacement angle between layers, and combining the probability characteristics of the target displacement angle between layers, the seismic design of the structure has a certain probability meaning.(2)According to the quantitative relationship between damage index and displacement ductility, combining structural damage performance target, the displacement ductility of the structure is determined by the damage index in the displacement-based design method, and the determination of displacement ductility is directly related to the damage performance target. Finally, it is applied to the design of prestressed precast concrete frame structure, then OpenSees modeling is used to verify the improved displacement design method, and at the same time compared with the original design method. The results show that the improved displacement seismic design method proposed in this paper can well control the elastoplastic response of the structure and meet the performance of the structure. The original displacement design method is more conservative than the improved displacement seismic design method.

Structural selection and design analysis of a super high-rise office building

A super high-rise building, with a height of 238 meters, 4 floors underground and 50 floors above the ground, exceeds the Class B height limit of the specification, and belongs to an ultra-high over-limit structure. Through the selection of different structural systems, its structural system is determined as the frame core tube structure. This structure uses YJK, SATWE, PKPM-SAUSAGE for structural analysis, uses performance-based methods for seismic design, and the weak parts of the structure are strengthened accordingly. Structural analysis mainly includes elasticity analysis of small earthquakes, elastic time history analysis of small earthquakes, elastic and inflexion analysis of moderate earthquakes, inflexibility analysis of large earthquakes and elastoplastic time history analysis of large earthquakes.

Structural analysis of a Concrete supertall buildings

A high-rise building, with a height of 146 meters, 4 floors underground and 32 floors above the ground, is a Class B limit of the specification, and belongs to an ultra-high over-limit structure. Through the selection of different structural systems, its structural system is determined as the frame core tube structure. This structure uses YJK, SATWE, PKPM-SAUSAGE for structural analysis, uses performance-based methods for seismic design, and the weak parts of the structure are strengthened accordingly. Structural analysis mainly includes elasticity analysis of small earthquakes, elastic time history analysis of small earthquakes, elastic and inflexion analysis of moderate earthquakes, inflexibility analysis of large earthquakes and elastoplastic time history analysis of large earthquakes.

Effect of Axial Compression Ratio on Seismic Behavior of GFRP Reinforced Concrete Columns

Traditional reinforced concrete columns have demonstrated poor seismic performance especially in corrosive environment as the reinforcement bars experience severe corrosion under such conditions. To overcome the problem of steel corrosion, glass fiber-reinforced polymer (GFRP) reinforced concrete columns have gained significant attention in recent years. However, the seismic performance of GFRP reinforced concrete column is not well understood yet. One of the main challenges associated with the use of GFRP bars is its brittle behavior. Therefore, it is necessary to investigate the mechanical properties and failure modes of GFRP reinforced concrete structures under seismic action. In this research, the seismic behavior of GFRP reinforced concrete columns and conventional columns under different axial compression ratios are analyzed by low-cycle repeated pseudo-static loading tests. As a result, the deformation and the seismic energy dissipation capacity of GFRP reinforced concrete columns are investigated and discussed. Furthermore, the failure mechanism of GFRP bar structure is studied to provide the basis for improving the seismic design method of GFRP reinforced concrete structure and modifying the code for seismic design. In addition, the influence of axial compression ratio on the seismic behavior of full GFRP reinforced concrete columns is investigated. The results of this experiment demonstrate that with the increase of axial compression ratio, the ultimate bearing capacity of GFRP reinforced concrete columns increases, while the deformation and the cumulative energy dissipation capacity decrease.

Reliability analysis and multi-level response modification factors for buckling restrained braced frames

This study aims to assess the seismic performance of buckling restrained braced frames (BRBFs) using a probabilistic approach and develop multi-level response modification factors for performance-based design of these systems. Unlike traditional seismic design methods, the proposed response modification factors can take into account the seismic conditions of the site as well as the target design performance level. An engineering damage parameter method (EDP-Based) is adopted for reliability analysis of 4, 8 and 12 storey BRBFs using systems of parallel and serial components. In general, the results demonstrate the high seismic reliability of BRBFs for high levels of earthquake intensity. Considering the axial strain of the brace core as the local damage index, it is shown that the studied models remain in performance levels higher than life safety under the design hazard level (return period of 475 years). The upper bond response modification factor for the life safety and collapse prevention performance levels is estimated to be around 8.4 and 10.0 with the corresponding intensities of 0.68 and 0.85, respectively. Based on the outcomes of this study, in general, using a response modification factor between 4 and 8 for seismic design of BRBFs would guaranty their adequate performance under both the design basis and maximum considered earthquake levels.

A direct displacement-based seismic design method using a MDOF equivalent system: application to R/C framed structures

An improved version of the direct displacement-based design (DDBD) method for the seismic design of plane moment resisting frames in the framework of performance-based design approach is presented. The method employs a multi-degree-of-freedom equivalent system instead of the single-degree-of-freedom equivalent system used by the conventional DDBD method. Thus, the proposed method can take more rationally and with higher accuracy into account the higher mode and P-Δ effects than the conventional one. This is accomplished with the aid of the concept of deformation dependent equivalent modal damping ratios previously developed by the present authors for other purposes and the concept of the design modal displacements developed herein. These design modal displacements are determined on the basis of target inter-storey drift ratios for every performance level and the first few modes significantly contributing to the structural response. Thus, one can determine from the displacement spectrum with high amounts of viscous damping the required modal periods for known values of the design modal displacements. From those modal periods, the corresponding required modal stiffness and hence the modal base shear forces can be obtained. The final required design base shear can be obtained by a combination rule, like the SRSS rule. Numerical examples involving the seismic design of two moment resisting reinforced concrete plane frames are presented in detail for illustrating the proposed approach and demonstrating its merits over the conventional DDBD method and the force-based design method of Eurocode 8.