Earthquake Action Research Articles

Seismic Performance Comparison of Three-Type 800 m Spherical Mega-Latticed Structure City Domes

With changes in the city environment and advances in engineering technologies, there is an increasing demand for the construction of super-large span city domes that can cover a large area to create a small internal environment within a specific region. However, the structural design must overcome various challenges in order to break the current structural span limitations. Moreover, there is little research on structures achieving such large spans. The seismic performance of the selected Kiewitt-type, Geodesic-type, and Three-dimensional grid-type mega-latticed structures is further investigated upon previous studies of the model selection, static and stability analysis results of the 800 m span mega-latticed structures. Finite element models were established with ANSYS to analyze the modal properties and earthquake response of the structures. The study evaluated the impact of earthquake directionality on the structural response as well as the response pattern of the structure under frequent and rare earthquake actions. It was found that the overall integrity of the structures is good, with strong coupling effects in three directions. The multi-dimensional seismic input method should be applied to solve the structural response. Combining the plastic development of the structure under rare earthquakes, the top and the circumferential trusses of the third and fourth rings are relatively weak parts of the structures. According to this study, given the known static analysis results, the maximum displacement and maximum stress of the structures under frequent and rare earthquake actions can be estimated. Furthermore, the study highlights that Three-dimensional grid-type mega-latticed structures should be prioritized designing structures with spans of 800 m, providing helpful guidance for the practical application of this type of structure.

Mechanical Analysis of Junction Pier of Fuzhou-Xiamen High-Speed Railway Rigid-Frame Bridge

The continuous rigid structure bridge on both sides of the Quanzhou Bay Crossing Bridge uses double-limbed thin-walled flexible piers for the junction piers between the links, and the whole bridge has no bearings. In China, the monolithic bearing-free prestressed concrete continuous rigid-frame bridge is used in railway bridges. The junction pier between the two adjacent couplets is a double-leg thin-walled flexible pier. The single leg thin-walled pier is connected with half of the pier-top segment. During the construction process, the block with numbered zero on the top of the pier is temporarily anchored and connected. Symmetrical cantilevered baskets are used on both sides for construction, and after the mid-pier cantilevered construction is completed, the temporary anchoring device for the block with numbered zero is removed. Because the structural system conversion is required in the construction, the mechanical properties of the junction pier will change greatly before and after the conversion, so it is very necessary to calculate and analyze it to master. In this paper, the finite element model of the connecting pier is established accurately, the stress and deformation of each part of the connecting pier under unfavorable working conditions is analyzed in detail, the seismic spectrum analysis under the action of common earthquake and rare earthquake is carried out, and the stress and deformation law of the structure is expounded, which can provide some reference for the construction of similar projects in the future.

Seismic Performance Analysis of Conjoined Structures with Inhomogeneous Stiffness Distribution

<p>Two or more independent towers are joined together through a connectome to form a conjoined structure. The deformation and internal force of the tower are complex, and the coupling effect between the two towers is remarkable when the earthquake is subjected. In this paper, elastic -plastic time -history analysis is adopted to research the dynamic dynamic response under the action of rare earthquakes. Moreover, in order to analyze the influence of symmetry and span parameters on the dynamic response of structures, elastic-plastic time-history analysis is carried out on structures with different symmetries, different stiffness distributions in planes and different spans.</p>

Analysis of the Dynamic Stability of Tailing Dams: An Experimental Study on the Dynamic Characteristics of Tailing Silt

With the improvement in tailing mining-grade requirements and in mineral processing technology, tailing materials tend to be fine-grained. Under the action of earthquakes, a tailing dam is prone to liquefaction, which endangers the safety and stability of the dam. To further explore the dynamic properties of tailing silt under cyclic stress, through a series of dynamic triaxial experiments, we investigated the growth of the hysteresis curve, the development of pore pressure, and the energy dissipation law of tailing silt. The experimental findings indicated that increasing the density of the sample significantly improves its liquefaction resistance and the pore pressure development curve can be fitted using the BiDoseResp function. At the same cyclic stress ratio, the sample’s anti-liquefaction strength did not rise monotonically with increasing confining pressure but changed variably at values near a specified low confining pressure; when the sample density rose under the same settings, the specific confining pressure reduced. We also further discussed the evolution law of the stress–strain curves of tailing silt. The results further explored the dynamic characteristics of tailing silt, which can provide some reference for the seismic design and reinforcement measures of many fine-grained tailing dams.

Seismic performance of supplemental inerter and spring with on-off effects for base-isolated structures

The present study investigates the performance of supplemental inerter and spring with on-off effects (ISWOE) in the mitigation of the seismic response of base-isolated structures. Firstly, the response of the rigid base-isolated structure with ISWOE is investigated to see the response control effects of ISWOE under stationary earthquake excitation. The performance of ISWOE in the response reduction of the isolated structure is compared with the corresponding passive inerter and spring. The equivalent damping that was added to the base-isolated structures by the ISWOE was used to measure its performance in mitigating the seismic response. The equivalent damping of the ISWOE is obtained for different values of the isolation period and damping ratio. Subsequently, equations for the equivalent damping of the ISWOE and displacement responses are proposed, and it is observed that they match well with the obtained numerical results. Secondly, using the non-linear model of the ISWOE, the seismic response of flexible base-isolated structures is determined for actual earthquakes, considering different values of the isolation period and ISWOE parameters. The trends of the results of isolated structures with ISWOE under the actual earthquake motions were in good agreement with those under stochastic excitation. Finally, the seismic response of isolated structures with ISWOE by non-linear analysis is compared with the corresponding linear analysis with equivalent parameters of the ISWOE. The isolator displacement of the structures with the ISWOE by the non-linear analysis was observed to match those achieved using the equivalent parameters and by the linear analysis.

Procedure for the seismic analysis of reinforced concrete tunnels using the finite elements method

Considering the sensitivity of reinforced concrete tunnels moving on soft soil foundations to earthquake action, some degree of damage to earthquake action, and the uncertainty of tunnel dynamic performance under earthquake action, an analysis procedure based on the finite element method is proposed, which considers ground deformation caused by earthquake action. The analysis can obtain the stress-strain states produced in the tunnel structure as a consequence of the seismic action, which are compared with the kinematic procedure for the seismic analysis of tunnels.

Structural Design and Analysis of a Super-High Building in Nanjing, China

This study analyzes a high-rise building with B-level height (i.e., a total height of 146.5 m) and a shear wall structure. Since the project contains many plane irregularities (including 1a torsional irregularity, 1b eccentric arrangement, and 2a plane convex irregularity), it should be treated as a super high-rise building. This study introduces the main characteristics and overrun conditions of the project and describes the structural design of the foundation and the basement, upper structural layout, force conditions under frequent, fortified, and rare earthquake actions, and structural performance-based objectives in detail. The following measures can be adopted to address the overrun problem. First, the floor at the thin waist of the structure was thickened to 150 mm and reinforced in the bilayer and bidirectional patterns, with a reinforcement ratio of no less than 0.25%. The damage condition on the floors under a great earthquake was analyzed. The vertical components at the waist were reinforced to constrain the extension of the edge components toward the top. Second, the structure’s peripheral stiffness was strengthened to enhance the anti-torsional performance and minimize the adverse effects on torsional irregularities. Third, using two software programs, the performance-based envelope design under medium earthquake action and dynamic elastoplastic analysis under great earthquake action were analyzed to ensure structural safety. Fourth, the edge components were constrained for the shear wall columns with axial-to-compressive stress strength ratios exceeding 0.3. For the overall structure and critical parts, force conditions under frequent, fortified, and rare earthquake conditions were calculated and examined with the SATWE, MIDAS GEN, and SAUSAGE software packages. The calculation results revealed that the structure shows favorable anti-seismic performance, with an overall anti-seismic C-level and a safe and reliable structure. The structural design method introduced in this article can promote the sustainable development of structural design.

Dynamic response characteristics of moraine-soil slopes under the combined action of earthquakes and cryogenic freezing

Freeze-thaw and earthquake are significant factors for the stability and failure of moraine soil slopes in high-altitude cold and strong earthquake area. The cryogenic freezing (CF) and heat thawing (HT) of moraine soil slopes were completed by using a self-designed constant-temperature test chamber, and several shaking table tests under different seismic intensity were carried out. In these tests, the displacement and acceleration responses were recorded by the non-contact measurement system and accelerometers, and the slope dynamic responses were clarified by the displacement, acceleration and energy. The results showed that: (1) the seismic responses of the CF slope are larger than that of the HT slope. (2) The failure process of the CF slope under earthquakes could be summarized into three phases: elastic deformation phase with seismic magnitude <0.4 g, brittle failure phase with seismic magnitude from 0.4 g to 0.8 g, and failure slip phase with seismic magnitude >0.8 g. (3) The failure mode of the HT slope is characterized by the overall collapse of loose moraine soil, and the particle size of the collapsed moraine soil redistributes during the sliding process. The failure mode of CF slope is a frozen block landslide with the soil-ice interface as the sliding surface. (4) The peak acceleration of the input wave, slope surface and elevation have amplification effect on the slope dynamic response, and the top of slope surface is the main deformation and failure area. (5) Reinforcement measures such as soil improvement of slope surface, weight reduction at slope top and backpressure at slope toe, heat pipes are recommended for moraine soil slopes in cold and strong earthquake area. Such findings may provide scientific basis for the damage state identification and seismic reinforcement of moraine soil slopes in alpine and strong earthquake areas.

Seismic Damage Scenarios for Existing Masonry Buildings for Educational Use in the Mostaganem City

Mostaganem, in Algeria, has experienced several seismic activities in recent years. It was classified in a zone of high to medium seismic activity according to the actual Algerian earthquake regulation. This ensures the safety of new constructions, however, the code done not include a technical reference for the seismic analysis and protection of existing constructions, in Algeria. The aim of this research is to constitute seismic scenarios of the masonry buildings used for educational purpose; therefore, the realization of seismic scenarios consists in crossing the data resulting from the seismic hazard (intensities) with those resulting from the analysis of the vulnerability. The analyses of the urban system will make it possible to interpret the scenarios in terms of functional damage. Seismic vulnerability of existing buildings was assessed under the RISK-UE method, which was selected to be suitable and applied to Algerian buildings for its convenience and simplicity. As a sample, 29 educational establishments (among of 199 masonry buildings for different use: primary school, middle school, secondary school, universities.) located in the historic city center of Mostaganem were assessed to identify the seismic vulnerability index, to allow to simulate seismic scenarios. The seismic vulnerability index is varied between 0.6 and 1.10 according to the diagnoses of each building carried out in the study area, The data from the vulnerability analysis are combined according to the RISK-UE approach (beta law) with the latter estimate by seismic hazard (seismic intensity), This correlation led to the birth of eight seismic scenarios expressing the results in terms of functional damage. As a result, moderate to heavy damage is expected for vulnerable constructions, significant economic losses are also expected for IEMS-98 >8 intensities. These seismic scenarios were considered and incorporated through a geographic information system (GIS) Guide decision makers estimated the severity and magnitude of the seismic risk for the remaining educational buildings in Mostaganem; or in other cities of the country to implement preventive measures and naturally reduce the risk of disaster by reducing vulnerability. Recommendations can be proposed to the Algerian authorities to simulate and facilitate efforts to take concrete preventive measures to strengthen existing educational buildings in order to reduce the negative effects of future earthquakes.

A comparative study on the lateral displacement of a multi-story RC building under wind and earthquake load actions using base shear method and ETABS software

The aim of this study is to propose a comparison between wind and seismic loads on a multi-story reinforced concrete (RC) building. The investigation focuses on lateral displacements and story drifts of a 6-story RC structure, which are determined manually using the base shear method and with the aid of the ETABS software tool. The study considers a linearity of the structure and uses the Chinese building design code for lateral displacement analysis. The base shear method is a simplified method that only considers one degree of freedom for each story, neglecting the non-linearity of the structures. However, the Chinese building code permits its use when considering the consistent vertical distribution of the building's mass and stiffness, which leads to shear deformation prevailing during seismic and wind reactions. The lateral displacements under wind and seismic loads are estimated, and the story drift limitation criteria of the Chinese building design code are assessed. Both the base shear method and ETABS's story drift computation (story drift 1/550) meet the design code criteria. This indicates that the base shear technique approach of RC frame structures can reasonably predict the tale drift on each story, despite relying heavily on simplifications. To compare the outcomes from the ETABS program to the internal forces under seismic and wind load activities, the story displacements and drifts are computed. The results show little discrepancy between the base shear method and ETABS software. Hence, the base shear approach can be utilized when there is no irregularity, and the building height is less than 40 m. Overall, the findings of this study indicate that the base shear method can provide a good approximation for the lateral displacements and story drifts of multi-story RC constructions under wind and seismic loads, provided that the Chinese building code criteria are met. The study highlights the importance of using appropriate design codes and tools in ensuring the safety and reliability of structures. Further research can explore the applicability of similar simplified methods in more complex and irregular structures, and the development of more accurate and efficient design tools.

A numerical study of influential parameters on rocking response of shallow foundations of single degree of freedom (SDOF) structures

In recent years, designing structures with rocking foundations has been introduced as an effective method to decrease seismic energy transmission to the superstructure and reduce the structure’s ductility demand. In this approach nonlinear behavior of the soil-foundation system dissipates the earthquake energy. Despite the promising results of this technique, it is not considered as a practical method yet. The main reason could be the uncertainties about the rocking foundation deformations during an actual earthquake. The present study uses the finite element method to evaluate the response of a single degree of freedom (SDOF) type structure under lateral monotonic and seismic loading. The influence of the static safety factors against soil bearing capacity failure, ground motion characteristics, and the foundation embedment depth on system behavior is investigated. Results demonstrate that due to these parameters, the response of a system with rocking foundation may change drastically during seismic events.

Seismic isolation effect of a new type of friction pendulum bearing in high-speed railway girder bridge

Residual displacement exists in the traditional friction pendulum bearings (FPB) under the action of earthquakes, which makes them fail to self-reset. In view of this, a new type of FPB called double concave friction pendulum with spring (DCFPS) is proposed. Firstly, the restoring force model and hysteresis characteristics of the theoretical DCFPS are derived. Then, the seismic isolation effect of the high-speed railway simply supported girder bridges (HRSB) equipped with the DCFPS is evaluated. Finally, the optimal spring parameters of the DCFPS are determined in terms of the efficiency coefficient and the optimal order method. The results show that the DCFPS has superior self-reset performance, and the hysteresis curve is “S” shaped. The stiffness of the DCFPS gradually increases with the swing displacement, which heightens the overall stiffness of the structure equipped with DCFPS. After HRSB is installed DCFPS, the displacement of the girder and the residual displacement of the DCFPS itself are reduced. The optimal stiffness and the initial tension of spring for the bridges exemplified in the paper are suggested as 3000 kN/m and 9 kN, respectively, through the efficiency coefficient method and the optimal order method. This research proposes a feasible solution for reducing the maximum displacement and residual displacement of bearings under an earthquake.

Reliability evaluation of reservoir bank slopes with weak interlayers considering spatial variability

Reservoir bank slopes with weak interlayers are common in the Three Gorges Reservoir area. Their stabilities are affected by multi-coupled factors (e.g., reservoir water fluctuations, rainfall, and earthquakes in the reservoir area). Meanwhile, the differences in mechanical parameters of reservoir banks make it more difficult to determine the dynamic stability of bank slopes under complex mechanical environments. In this paper, the multiple disaster-causing factors and spatial variability of the landslide were comprehensively considered to study the long-term evolution trend of the bank slopes with weak interlayers. Specifically, the limit equilibrium method combined with the random field was performed to calculate the reliability. Furthermore, the long-term effects of dry-wet cycles on reservoir bank landslides and the sensitivity analysis of the statistical parameters of the random field were discussed. The results show that the earthquake action had the most significant impact on the failure probability of the landslide. The failure probability was more significantly affected by the vertical fluctuation range of the parameters and the coefficient of variation of the internal friction angle. The increase in failure probability under the action of dry-wet cycles was mainly caused by the reduction of the parameters of the weak interlayer. The reliability evaluation method of reservoir bank slopes can be applied to predict the long-term stability of the coastal banks.

Slope Stability and Effectiveness of Treatment Measures during Earthquake

Slopes are prone to instability during earthquakes, which will cause geological disasters such as landslides and pose a great threat to people’s lives and property. Therefore, it is necessary to analyze the stability of slopes and the effectiveness of treatment measures during earthquakes. In this study, an actual slope in the creeping slide stage was selected and located in an area where earthquakes occur frequently. Once the slope experiences instability, it will produce great damage. Therefore, a finite difference program, Fast Lagrangian Analysis of Continua in Two Dimensions (FLAC2D), was employed in the numerical simulation to explore the stability of the slope before and after treatment under earthquake action. Different from previous studies, this study explores the effectiveness of various treatment measures on slope stability during earthquake. The computed results show that the stability of the slope is greatly influenced by earthquakes, and the slope displacement under seismic conditions is far larger than that under natural conditions. Three treatment measures, including excavation, anti-slide piles, and anchor cables, can significantly reduce slope displacement and the internal force on anti-slide piles, and improve the stability of a slope during an earthquake. This will provide a valuable reference for the strengthening strategies of unstable slopes. The analysis technique as well as the derived insights are of significance for slope stability and the effectiveness of treatment measures.

Resilience of HP/HT pipelines to combined seismic and thermal loadings

Resilience of unburied high pressure/high temperature (HP/HT) pipelines with different outside diameter-to-wall thickness (OD/t) ratios and subjected to the combined action of both earthquake and thermal loads is studied numerically. Unlike most of the existing research on buried or trenched pipelines, the current work analyses the resilience to combined seismic-thermal actions of an unburied pipeline laid on the seabed and resting on a sleeper. By using finite element analyses (FEA), the thermal and seismic responses of pipelines with different OD/t ratios are captured. The pipeline-soil and pipeline-sleeper interactions are modelled using Mohr-Coulomb constitutive contact behaviour. Empirical equations of critical temperatures causing lateral buckling in pipelines with OD/t between 10 and 50 are developed. Rayleigh damping coefficients are calculated following modal analyses, whereby the pipeline-soil system frequencies are found. Resilience to failure under combined seismic and thermal actions is load-path dependent; the earthquake imposed on a laterally buckled pipeline represents the most detrimental scenario. It is understood that the introduction of seismic load can amplify the buckle amplitudes beyond the pre-defined controlled buckle amplitude and thus cause overstressing and/or local buckling in the buckle crown segment. Local buckling due to the interaction between thermal and seismic loading is found to be more pronounced in pipelines with OD/t > 40.

Slope Response Characteristics Under the Coupled Action of Rainfall and Earthquake: A Case Study with Numerical Modelling

Slope Response Characteristics Under the Coupled Action of Rainfall and Earthquake: A Case Study with Numerical Modelling

Dynamic stability of single-layer spherical reticulated shell structures under earthquake action

In past decade, earthquake disasters have seriously damaged nonstructural components, so it is very important to study their dynamic stability. However, the existing researches mainly focus on the dynamic stability of multistory and high-rise buildings, and there are still deficiencies in the analysis of dynamic stability of reticulated shell structures under earthquake action. This paper takes the 40 m span K8 single-layer spherical reticulated shell structure with practical engineering significance as the research object, we study its dynamic instability characteristics under earthquake action, and propose a dynamic stability judgment method. The influence of various parameters on the critical loads of emotional stability of reticulated shell structures is systematically analyzed, including the impact of horizontal seismic action, the vertical seismic activity, and the three-dimensional seismic movement, considering the influence of material elastoplasticity; the result of different seismic inputs, the effects of initial geometric imperfections; the effects of varying rise span-ratio. In this paper, to investigate the nonlinear time-history response analysis, we uses the finite-element package ABAQUS. We first analyze the rise-span ratio as the dynamic stability of 1/3 single-layer reticulated shell structure under the action of the El Centro (1940) earthquake to reveal the dynamic loss of reticulated shell structure under earthquake action stable feature. The practical method for determining the proposed dynamic stability has a clear physical meaning and a range of applications. Our findings highlight that the critical load for dynamic stability under horizontal earthquake action is significantly lower than vertical earthquake action, and the critical load is the lowest under three-dimensional earthquake action. Material elastoplasticity influences the critical loads for dynamic stability of reticulated shell structures under different ground motions. The critical load of dynamic stability of single-layer structures with a larger rise-span ratio is lower, while those with a smaller one is higher. The initial geometric defects of the structure should be considered in practical engineering applications. The reticulated shell structure with a larger rise-span ratio needs to consider the dynamic stability problem in the strong earthquake area.

Japanese attitudes toward risk control in seismic design in light of observation, prediction, and actual performance of building structures

AbstractDespite recent international efforts toward a risk‐conscious approach to advancing seismic design, Japan, a country very prone to earthquakes, remains conservative regarding the consideration of risk‐based seismic hazards in developing seismic designs. This article attempts to interpret the reasons. First, the evolution of Japanese seismic design codes and specifications is introduced, noting that the design seismic loads have remained essentially the same since the revisions implemented in 1981. Second, Japanese efforts in providing and renewing seismic hazard maps are briefly introduced and discussed. The maps have been developed using the data recorded by Japanese strong motion networks. Some unique challenges in preparing seismic hazard maps for the territory of Japan are presented, in light of the observations of actual earthquakes in the past three decades. On many occasions, the damage disclosed in modern buildings remained limited even when the recorded ground motions significantly exceeded the design earthquake level. An inherent conservatism is embedded in the performance criteria imposed on structural systems and elements. Third, political‐legal and sociocultural aspects are discussed. Centralized operation is commonly exercised in Japan for post‐disaster relief efforts, and the general public also values “equality” for such support. The factors naturally encourage cautiousness for the revision of relevant seismic codes and specifications.

Numerical Investigation on the Pulling Resistant Capacity of Steel Beam-Concrete Wall Joints with T-stub Connectors

The steel frame-reinforced concrete core tube structural system is widely used in mid-rise and high-rise buildings due to its good seismic behaviour and high construction efficiency. Since the steel frame and the reinforced concrete core tube are supposed to deform synergistically under earthquake action, the steel beam-concrete wall joint (SBCW joint for short) will be subjected to a significant pull-out force. Therefore, the pulling resistant capacity of the SBCW joint is quite important for the seismic performance of the overall structure. In response to the shortages of the existing SBCW joint types, a new SBCW joint with a T-stub connector was proposed and studied. The experimental and analytical research has indicated that there are different failure modes and force mechanisms of the SBCW joint under pull-out load, and further studies are required for the pulling resistant capacity. On the basis of recent research findings, a numerical investigation on the pulling resistant capacity of the joint is conducted in this study. An elaborate 3D finite element model of the SBCW joint is proposed, and the load performance, strain and stress development, deformation characteristics and failure modes are analysed in detail. Then, a series of parametric analyses are carried out based on the finite element model, indicating that the length and the web height of the T-stub connector, the number of shear studs on the connector and the reinforcement ratio of stirrups have an obvious effect on the pulling resistant capacity. Finally, the critical value of the embedded depth of the connector, which is found to be one of the most important parameters for the failure mode and pulling resistant capacity of the joint, is determined, and design recommendations are proposed for the SBCW joints with T-stub connectors.

Diagrid Core-tube Structure Seismic Performance Based on Equivalent Stiffness Ratio of Inner and Outer Tubes

To study the relationship between the stiffness ratio of the inner and outer tube of the diagrid core-tube structure of high-rise buildings and the redistribution of the storey shear force, the structural ductility, overstrength factor and the seismic performance, a total of 12 kinds of diagrid core-tube structures of equivalent stiffness ratios were established at 71°, 77° and 80° diagonal angles. Based on the static pushover analysis method, combined with the principle of capacity spectrum and demand spectrum, the characteristics and laws of the position change of the weak layer, the redistribution of the storey shear force, the shear lag effect of the bottom compression flange and the overall ductility of the structure are analyzed under the action of the frequent earthquake (70 gal), fortification earthquake (200 gal), rare earthquake (400 gal), extremely rare earthquake (510 gal) and huge earthquake (620 gal). The results show that under different earthquake actions, there is an obvious redistribution of floor shear force in the diagrid core-tube structure, and the storey shear coefficient decreases with the increase of earthquake level and equivalent stiffness ratio. The diagonal angle is the main factor affecting the location of the weak floor and the shear lag effect. The shear lag effect of the structure increases with the increase of the seismic fortification level. The structural ductility with a diagonal angle of 77° is generally optimal. When the equivalent stiffness ratio is 0.64, the structural ductility reaches the optimal value of 1.46, which is 1.1 times that of 71° and 80° diagonal angles. In the structure with the same diagonal angle, the overstrength factor increases with the increase of the equivalent stiffness ratio.