Seismic Fortification Research Articles

Mechanical behaviors and seismic performance of a novel rotary amplification friction damper (RAFD): Experimental and analytical studies

Friction dampers are widely used energy dissipators for the seismic fortification of engineering structures, due to their efficiency, reliability, and cost-effectiveness. Since the friction force is proportional to the normal load applied on the sliding interfaces for given friction materials, increasing the applied normal load is always the only approach to enhance the energy dissipation capacity of friction dampers. However, a large applied normal load may result in serious wear problems at the interfaces, which in turn affects the functionality of the damper. To address the above issue, a novel rotary amplification friction damper (RAFD) is proposed in the present study, which can realize several times amplified friction force for a given normal load due to the adopted amplification system. The conceptual design and working mechanism of the proposed RAFD are first introduced. Subsequently, a damper prototype was manufactured and experimental studies were carried out to examine the behaviors of RAFD. Then, a nonlinear mechanical model considering the gap between the gear and rack is developed based on the experimental results. Finally, an analytical model of a single-degree-of-freedom (SDOF) system equipped with RAFD is established to investigate the control performance of RAFD in reducing the structural seismic responses and evaluate the influences of various parameters including gap and earthquake types (far-field and near-field ground motions). The analytical and experimental results demonstrate that the proposed RAFD showcases superior seismic control effectiveness compared to the traditional friction damper; the presence of a gap would reduce the control effectiveness of RAFD to some extent, while earthquake types have minimal impact.

Seismic behavior of prefabricated lightweight steel composite frame-sandwich wall with enhanced border structure

An innovative prefabricated lightweight steel composite frame-sandwich wall with an enhanced border structure (LSCF-SW), suitable for low-energy consumption low-rise residences, is proposed. Low cyclic loading experiment were conducted to study its seismic behavior. The main parameters include wallboard border type (composite border, mixed border) and steel reinforcement strength (HRB450, HRB500). One full-scale LSCF specimen and four full-scale LSCF-SW specimens are prepared, and their seismic behavior is investigated in terms of failure mode, hysteretic characteristics, ultimate bearing capacity, stiffness degradation, deformation capacity, energy dissipation, and strain characteristics. The results revealed that the sandwich wall (SW) with an enhanced border and lightweight steel composite frame (LSCF) is the primary and secondary seismic fortification lines of the structure, respectively. The LSCF-SW structure exhibited a damage evolution process with four stages. The failure mode involving concrete crushing at the bolted connection area is observed in the specimens with composite bordered sandwich walls (LSCF-SWC), and dense diagonal cracks are discovered in the specimens with mixed bordered sandwich walls (LSCF-SWM). Compared to LSCF-SWC specimens, the ultimate load of LSCF-SWM specimens increases by 23.0 %–50.3 %, and the initial stiffness improves by 16.3 %–42.3 %. The deformation capacity of LSCF-SWC specimens is superior to that of LSCF-SWM specimens. As the steel reinforcement strength increases, the ultimate bearing capacity and initial stiffness of the LSCF-SW also rise. A shear model for the bolt group and a local bending model for the wallboard border are proposed, establishing an ultimate bearing capacity calculation method for LSCF-SW. The calculation results closely align with the experimental results.

Design of a Six-Story Teaching Building: A Comprehensive Approach to Safety and Structural Efficiency

This paper describes teaching building design. The project, designed for the teaching building, prioritizes safety in its main structure, a reinforced concrete frame with six floors above ground. The story heights are 4.2m, 3.9m, 3.9m, 3.9m, 3.9m and 3.9m, respectively, and the building's total height is 27.6m. The construction site category is classified as type II, and the first group's seismic fortification intensity is 7 degrees. The process includes architectural design, structural design, and PKPM checking calculation. Architectural design mainly consists of a general description. The plan, elevation, section, and draft of the corresponding building are drawn according to the relevant information and requirements provided by the design task book. Structural design mainly includes load statistics, calculation of internal force and displacement of the frame, a combination of internal force, and calculation of staircase, slab roof, floor slab and frame structure. The calculation of displacement, internal force, and reinforcement of the whole frame structure is carried. Out using PKPM. In the course of architectural design, safety is a paramount consideration, in line with the principles of safety, applicability, beauty, economy, and energy-saving requirements, referring to national standards and relevant materials, and strictly following the requirements of relevant architectural design standards, the design of each link is not only a comprehensive scientific consideration of its own but also a related discussion with teachers, as detailed in the construction plan. The frame structure is adopted,in this structural type. It mainly includes structure layout and calculation sketch determination, load calculation, internal force calculation, internal force combination, main beam section design, and reinforcement calculation, frame column section design and reinforcement calculation, secondary beam section design and reinforcement calculation, floor and roof design, staircase design etc. Among them, the D-value method is used to calculate the internal force of the structure under horizontal load, and the distribution method is used to calculate the internal force of the structure under vertical load (dead load and live load).

Seismic behavior of lightweight steel frame with thin-walled steel skeleton-lightweight concrete wall

In this study, an innovative prefabricated lightweight steel frame with thin-walled steel skeleton-lightweight concrete composite wall structure (LSF-TSLC) is proposed. The proposed LSF-TSLC has the lightweight steel frame (LSF) as the vertical load-bearing system, whereas the thin-walled steel skeleton-lightweight concrete composite wall (TSLC) acts as the main component for horizontal earthquake resistance. A full-scale LSF specimen and three full-scale LSF-TSLC specimens were prepared considering the variables of wall installation method (embedded, external) and thin-walled steel skeleton distribution (frame type, truss type). The corresponding seismic behavior was experimentally investigated by evaluating the hysteretic characteristics, failure mode, ultimate bearing capacity, deformation performance, stiffness degradation, energy dissipation, and strain characteristics. The results showed that the plastic hinges appeared at the beam ends and column bases of LSF. Due to the shear failure, the embedded and external TSLC exhibited grid cracks and diagonal cracks, respectively. The LSF and TSLC had a good coordinating deformation capacity, while the LSF-TSLC structure had two seismic fortification lines. Compared with LSF, the ultimate bearing capacity and stiffness of LSF-TSLC were increased by 2.1 times and 5.1 times, respectively. The deformation capacity and energy dissipation of LSF-TSLC were significantly improved compared to LSF. The self-tapping nail joint of the embedded wall and the high-strength bolt joint of the external wall had reliable connectivity performance. The numerical simulation of LSF were conducted to verify the plastic analysis model for LSF. And the ultimate bearing capacity calculation method for the LSF-TSLC structure was proposed based on the Strut-and-Tie model.

Seismic Performance of a Single-Story Timber-Framed Masonry Structure Strengthened with Fiber-Reinforced Cement Mortar.

Timber-framed masonry structures are widely used around the world, and their seismic performance is generally poor. Most of them have not been seismically strengthened. In areas with high seismic fortification intensity, there are great potential safety hazards. And it is urgent to carry out effective seismic reinforcement. However, due to the complicated construction process of the existing reinforcement technology, the poor durability of the reinforcement materials, and the significant disturbance to the life of the original residents, an efficient single-story timber-framed masonry structure reinforcement technology suitable for comprehensive promotion and application has not been explored. In this paper, a fiber-reinforced cement mortar (FRCM) material was proposed. A 1/2 scale model of a single-story timber-framed masonry structure was taken as the research object. The method of strengthening a single-story timber-framed masonry structure with FRCM layer was adopted. And the shaking table test of the model before and after reinforcement was carried out in turn. The dynamic characteristics, failure modes, acceleration response and displacement response of the FRCM layer-strengthened structure were analyzed through comparisons of the two cases. The experimental results showed that the FRCM layer significantly improved the seismic performance of the seismic-damaged single-story timber-framed masonry structures. The X- and Y-direction natural frequencies of the model structure were increased by 31.30% and 30.22%, respectively, after the structure was strengthened with FRCM. During a rare eight-degree earthquake, the inter-story displacement angles in the X- and Y-direction of the unreinforced model reached 1/98 and 1/577, respectively, and the structure was destroyed, while the inter-story displacement angle of the FRCM-reinforced model was only 1/2 of that the unreinforced model. During a rare nine-degree earthquake, the X-direction inter-story displacement angle of the model strengthened with FRCM reached 1/78 and the Y-direction inter-story displacement angle reached 1/178. At this time, the reinforced model structure was destroyed, but there was no collapse of the structural components, which met the seismic design objectives of "operational under the design minor seismic intensity, repairable damage under the design seismic precautionary intensity, and collapse prevention under the design rare seismic intensity", which proved that the FRCM layer was an effective and feasible way to strengthen the existing single-story wood-masonry rural building.

Multi-level fortification strategies for double-tower cable-stayed bridges with safe-belt devices

While the current seismic fortification standards for cable-stayed bridges have been established, determining the return periods and fortification objectives remains insufficient. This study introduces a multi-level seismic fortification objective for cable-stayed bridges with safe-belt devices. The safe-belt device protects the primary components and enables transfers to the restraint system based on varying seismic requirements. For this investigation, a double-tower cable-stayed bridge was chosen as the case study. Three finite element models with varying structural configurations were developed. Subsequently, an elastoplastic time-history analysis was performed under four levels of seismic excitation across different site categories. The results indicate that the primary structures of traditional cable-stayed bridges, specifically the towers and lower crossbeams, are vulnerable to severe damage during extremely rare earthquakes. Incorporating safe-belt devices in a double-tower cable-stayed bridge effectively reduces the internal forces exerted on the primary structures by utilizing the combined action of the dual towers, thereby preventing severe damage. Additionally, these devices allow for controlled girder-end displacement until their capacity is reached. This double-tower cable-stayed bridge successfully meets the multi-level seismic fortification objectives and satisfies the performance requirements at each level.

Development and experimental study of disc spring-based negative-positive-uncoupled stiffness devices for structural multi-level seismic fortification

To achieve the structural multi-level seismic fortification objectives, this paper proposes a novel negative-positive-uncoupled stiffness device (NPUSD) based on combined disc springs with multi-linear elasticity characteristics. This device allows for independent variations in the negative stiffness range under small deformations and the positive stiffness range under large deformations. It primarily utilizes the negative stiffness mechanism for seismic mitigation during medium and small seismic events referring to existing research on traditional negative stiffness devices (NSDs) while providing positive stiffness to prevent collapse during major seismic events. The configuration and working principle of the NPUSD are discussed. By replacing the preloaded linear elastic spring of traditional NSDs with multi-linear elastic spring, the NPUSD can effectively and conveniently achieve stiffnesses decoupling. A design algorithm based on the successive area equivalence principle for the multi-linear elastic spring is proposed. Finally, based on a 56-story steel core-outrigger structure, a comparison between NSDs and NPUSDs is made under the four seismic intensity levels. Results show that the novel NPUSDs contribute to achieving structural multi-level seismic fortification objectives.

Study on the relevant parameters of direct economic loss assessment of reinforced concrete structure buildings considering seismic fortification and use function

The main cost and decoration cost of the building are the key parameters in the evaluation of the direct economic loss of the building. In the Earthquake Site Work Part 4 : Direct Loss Assessment of Disasters ( GB / T 18208.4-2011 ), considering factors such as economic development level, structural type, and building use, based on expert experience and engineering cost data, a grading index was developed and a corresponding correction coefficient was given to more accurately and reasonably assess the loss of the main building and the loss of decoration. In view of the rapid development of China 's economy and the acceleration of urbanization in the past ten years, the original grading indicators and coefficients need to be adjusted to adapt to the reality. This paper focuses on the reinforced concrete structure with various functions and wide distribution. By collecting a large number of corresponding building main body and decoration cost data, and combining with expert experience data, this paper analyzes the influence of seismic fortification level on the main body cost, as well as the influence of economic development level, decoration grade, use function and other factors on the decoration cost. The research results of this paper aim to provide reference for the update and refinement of several key parameters in the specification.

Theoretical Research and Shaking Table Test on Nominal Aspect Ratio of the Isolated Step-Terrace Structure

With the installation of rubber isolation bearings in the upper and lower ground layers, an isolated step-terrace structure was created. Considering the ultimate bearing capacity of the rubber bearing under tension as the critical condition, a comprehensive framework was established to evaluate the overturning failure mechanisms present in isolated step-terrace structures. The bound of nominal aspect ratio was identified as the principal control index within this framework, which incorporates critical parameters such as height ratio (α), width ratio (β), vertical tensile stiffness to compressive stiffness ratio (γ), seismic coefficient (k), and nominal vertical compressive stress (σ0) to provide a thorough analysis of the structural responses and potential failure scenarios. In order to further investigate this matter, a scaled model of an isolated step-terrace concrete frame structure featuring two dropped layers and a single span within an 8° seismic fortification zone was meticulously crafted at a 1:10 similarity ratio. Subsequently, a series of shaking table tests were conducted to analyze the structural response under seismic excitation. The findings indicate that: utilizing the bound of nominal aspect ratio as a metric to gauge the anti-overturning capacity of isolated step-terrace structures is a justified approach. In instances where the height ratio remains constant, the bound of nominal aspect ratio for both positive and negative overturning trended upward with an increase in the width ratio. Notably, the bound of nominal aspect ratio for positive overturning consistently registered lower values compared to that of the negative overturning, underscoring the heightened susceptibility of step-terrace structures to positive overturning. Moreover, in scenarios characterized by higher height and width ratios, the structural integrity remained unscathed by any overturning effects arising from insufficient tensile strength in rubber bearings. Furthermore, the bound of nominal aspect ratio exhibited an ascending trend as the seismic coefficient, nominal vertical compressive stress, and vertical tensile stiffness to compressive stiffness ratio decreased. The outcomes derived from the shaking table test not only confirm the impressive seismic performance of the structure, but also, by closely examining the instantaneous stress variations within the upper and lower isolation layers of the model, substantiate the existence of a positive overturning hazard in scenarios marked by higher seismic coefficients (k). This observation aligns seamlessly with the theoretical projections, thereby substantiating the efficacy of the structural overturning failure theory through direct empirical verification.

Predictive models of embodied carbon emissions in building design phases: Machine learning approaches based on residential buildings in China

As one of the major architectural forms, residential building construction consumes considerable resources, and it has been regarded as a crucial factor for the implementation of carbon peaking and neutrality targets. Estimation of carbon emissions is essential for making informed decisions regarding building design and carbon reduction measures. Some studies have established predictive models for building operational carbon emissions. However, there are relatively few studies concerning the prediction of embodied carbon emissions. This study established a dataset containing 850 residential building samples. Based on the trade-offs and combinations of different explanatory variables, including building features and material use, this study developed two-phase models. These models, incorporating six scenarios, predicted embodied carbon intensities using twelve machine learning algorithms. For the planning design phase, an extremely randomized tree model using the building height, structural form, seismic fortification intensity, delivery form, geographical region, and material cost as inputs was favored considering R2 as 0.821 on the testing dataset. For the preliminary design phase, an extreme gradient boosting model using both building features and material intensities provided superior performance with R2 and MAPE values of 0.917 and 0.038, respectively. The optimal models and relevant feature importance analysis can be helpful for efficiently predicting embodied carbon emissions, and therefore, facilitate low-carbon designs.

Study on the hysteretic characteristics of FRP-reinforced concrete shear wall with innovative friction dampers

FRP-reinforced concrete shear walls (FRCWs) are able to achieve satisfactory residual deformation and corrosion resistance compared with steel reinforced concrete walls (SRCWs). However, in the FRCWs, the failure of the plastic hinge region brings great challenges to the post-earthquake repair of the structure. Therefore, this paper designed one SRCW and two FRCWs with innovative friction dampers (FDs) at the feet, and steel truss and steel plate were embedded at the plastic hinge region of the two FRCWs respectively to supplement the weakened shear strength. Then pseudo-static tests were carried out twice before and after repairing the two FRCWs with FDs. Experimental results showed that compared with the SRCW at the same lateral drift, the damage of the FRCW was reduced by installing FDs at the feet, and the energy dissipation capacity was enhanced; the repaired FRCWs with FDs could still have acceptable seismic performance. Subsequently, the Park-Ang damage indices of wall webs of the FRCWs with FDs were calculated, which proved that the FRCWs with FDs could meet the four-level seismic fortification objective. In the end, two orthogonal tests were designed based on the established OpenSees models to evaluate the impact of the damper friction and FRP reinforcement ratio on the seismic behaviours of the FRCWs with FDs. It was recommended to adopt larger longitudinally distributed FRP reinforcement ratio to obtain satisfactory self-centering ability and hysteresis performance of the FRCW with FDs.

Land Use Sustainability: Assessment of the Dynamic Response of Typical Bedrock-Buried-Hill Earth Fissure Sites in the Su-Xi-Chang Area

Disaster prevention and the mitigation of earth fissures is a key issue in the sustainable development of urban land. Structures directly avoiding earth fissures are not conducive to the rational planning and efficient utilization of urban construction. The Su-Xi-Chang area, which consists of the cities of Suzhou, Wuxi, and Changzhou, surrounded by Taihu Lake, has developed bedrock buried-hill earth fissures that are rare in the rest of the country. Existing research results have identified the genesis mechanisms, distribution patterns, and developmental characteristics of this type of fissure. Not only does the slow-variable activity of earth fissures cause direct damage to surface and underground structures, but in addition, when an earthquake occurs, the presence of earth fissures may cause the seismic response of the site to be altered or even strengthened, leading to unknown damage or the possible destruction of structures near the fissures. However, no studies have been conducted to assess the dynamic effects of bedrock-buried-hill earth fissure sites. Therefore, in this research, based on six typical bedrock-buried-hill-type earth fissures in the Su-Xi-Chang area, and in order to accurately reveal the dynamic amplification effect law of the earth fissure sites, systematic spectral analyses and comparisons of the microtremor signals were carried out by using the linear analysis method (Direct Fourier Transform Analysis) and the nonlinear analysis method (Hilbert–Huang Transform). The results show that bedrock-buried-hill-type earth fissures have a significant amplification effect on the dynamic response of the site; the amplification effect of bedrock-buried-hill fissure sites follows the same attenuation pattern, and the furthest range of the dynamic response on the site is about 25 m, beyond which the original seismic fortification level can be maintained; the extreme value of the amplification factor of the two sides of this type of site, as derived from the Fourier and HHT methods, is about double, and the nearest earth fissure region should be considered to have a raised seismic fortification intensity of more than double the original. The Hilbert–Huang transform method has good applicability for processing microtremor data, and nonlinear signal analysis methods can be considered comprehensive for future microtremor signal processing.

Numerical Simulation Analysis of Seismic Performance for Framework Structure Based on Rayleigh Damping Algorithm

Seismic analysis of engineering structures can effectively ensure social and public safety, and in engineering practice. The elastic-plastic time history analysis of reinforced concrete frame structures is a more accurate analysis method for evaluating the seismic performance of the structure. According to relevant regulations, the seismic fortification intensity of a certain frame structure is 6 degrees. To analyze its seismic performance under earthquake action, this paper uses ABAQUS numerical simulation software combined with Ruili damping algorithm to establish a seismic model of the frame structure. The research results indicate that: (1) By calculating the interlayer displacement angle, the interlayer displacement angle of each layer meets the requirements of the specification, and the structure has good seismic performance. (2) The peak acceleration difference between the top layers of the structure decreases first and then increases from the bottom to the top. (3) There is a coupling relationship between structural deformation and the acceleration of the structure itself, and a coupling relationship between interlayer deformation and the peak stress at the top of the interlayer.

Site classification methodology using support vector machine: A study

The site effect is a crucial factor when analyzing seismic risk and establishing ground motion attenuation relationships. A number of countries have introduced building site classification into earthquake-resistant design codes to account for local site effects on ground motion. However, most site classification indicators rely on drilling data, which is often expensive and requires considerable manpower. As a result, the less detailed drilling data may lead to an undetermined site category of numerous stations. In this study, a Support Vector Machine (SVM) algorithm-based site classification model was trained to address this issue using strong ground motion data and site data from KiK-net and K-net. The classification model used the average HVSR curve of the labeled site and the combined inputs, including frequency, peak, “prominence, and “sharpness” extracted from the curve. The SVM classification model has an accuracy of 76.12% on the test set, with recall rates of 82.69%, 75%, and 63.64% for sites I, II, and III, respectively. The precision rates are 75.44%, 73.77%, and 87.50%, respectively, with F1 scores of 78.90%, 74.38%, and 73.68%. For sites without significant peaks in the HVSR curve, the HVSR curve value was used as the characteristic parameter (input), and the SVM-based site classification model was also trained. The accuracy of class I and II is 75.86%. The results of this study show higher recall and accuracy rates than those obtained using the spectral ratio curve matching method and GRNN method, indicating a better classification performance. Finally, the generalization ability of the model was verified using some basic stations in Xinjiang deployed by the “National Seismic Intensity Rapid Reporting and Early Warning Project”. The SVM-based site classification model that employs strong motion data can provide more reliable classification results for sites without detailed borehole information, and the site classification results can serve as a reference for probing ground motion attenuation relationships, ground motion simulation, and seismic fortification considering the site effect.

Cyclic shear test and finite element analysis of TRC-reinforced damaged confined masonry walls

Due to the low level of seismic fortification during construction, masonry walls are highly vulnerable to earthquakes, but some walls remain in service after repair. To investigate the strengthening effect of textile-reinforced concrete (TRC) on the seismic performance of seismically damaged confined masonry (CM) walls, tests were conducted on four masonry walls, and a finite element model was established for parametric analysis. A TRC facing improves the overall performance of the wall and increases the ductility of the wall. TRC reinforcement technology increases the peak load of CM walls by 19.9%-21.7%, the ductility factor by 42.1%-52.8%, and the cumulative energy dissipation by 95%-118%. The more severe the damage to the wall is, the less effective the strengthening effect of the TRC reinforcement. As the number of layers of textile increases, the load-bearing capacity, deformation capacity and energy dissipation capacity of the walls increase. When the vertical compressive stress increases, the increase in the shear bearing capacity and energy dissipation of walls due to the TRC facings first decreases and then increases. Moreover, TRC facings have limited effectiveness in reinforcing walls with high aspect ratios and high mortar strengths.

Shaking Table Tests of Chuandou-Type Timber Structure Building for Seismic Fortification High-Intensity Area

ABSTRACT This study investigated the seismic performance of Chuandou-type timber structure buildings intended for seismic fortification in a high-intensity zone. An earthquake simulation shaking-table test was conducted on a two-layer Chuandou-type structure constructed in Yunnan, China. The El Centro, Kobe, and artificial waves were used as input excitations. The natural frequency, stiffness, acceleration response, and displacement response to the earthquake events were determined. The experimental results indicate that as the acceleration intensity of the earthquake increases, the natural frequency and stiffness of the model structure decrease. The acceleration amplification coefficient of each layer varied from 0.47 to 1.95. The energy dissipation of column foot slip, mortise-tenon joint friction and extrusion were visible, and the dynamic amplification coefficient of the first layer was less than one except for Kobe wave excitation. When the input peak acceleration is 0.63 or 0.95 g, the model shocks violently and exhibits a spectacular whiplash effect, with the model’s maximum inter-story drifts being 1/23 and 1/26, respectively. However, the model did not tilt or collapse, which displays that the Chuandou-type structure had an overall good deformation and self-centering ability. Additionally, it satisfies the standards of the Chinese Code for Seismic Design of Buildings (GB2011–2010).

Incremental dynamic analysis method application in the seismic vulnerability of infilled wall frame structures

To reasonably evaluate the overall seismic performance of infilled wall frames, a corresponding nonlinear analysis model is constructed with infilled wall frames as the research object. It quantifies the failure levels of structural and non-structural components and proposes a method for extracting structural overall performance indicators. The vulnerability of the case frame structure is analyzed using the Incremental Dynamic Analysis (IDA) method. The results showed that the seismic performance of the infilled wall frame and the ordinary frame met the seismic fortification requirements, and the seismic capacity of the infilled wall frame was better. After implementing a 7-degree seismic fortification, the cumulative probability of basic integrity, minor damage, and moderate damage for infill wall frames reached 99.15 %, surpassing the fortification target of 1.5 g. However, the seismic capacity of ordinary frames was overestimated, as their cumulative probability of basic intact, minor damage, and moderate damage under a 7-degree seismic fortification was 99.7 %. Neglecting its impact, ordinary frames exhibited lower seismic performance compared to other structures, with a basic intact probability of only 48.49 % under frequent earthquake actions at 7 degrees. The research utilizes effective methods for evaluating the seismic vulnerability of infilled wall frames.

Seismic performance and vulnerability analysis for bifurcated tunnels in soft soil

This paper investigates the seismic performance of complex comprehensive interchange underground structures. As an example, the seismic performance of Nanjing underground bifurcated tunnels constructed in soft soil is analyzed. A three-dimensional (3D) numerical finite element analysis model is established considering soil-tunnel interaction to analyze the seismic response characteristics and failure mechanism of the bifurcated tunnels. The results show that the tunnel damage degree is closely associated with the deformation response, and that the inter-story drift ratio of the lower layer is significantly greater than that of the upper layer. The pushover analysis method is used to obtain the seismic performance curve of the tunnel, and inter-story drift ratio limits are defined. The IDA procedure is then used to conduct multiple non-linear dynamic time history analyses based on the 3D finite element model, and IDA curve clusters are drawn with peak ground acceleration (PGA) as the earthquake intensity measures and the peak inter-story drift ratio as the damage measures of tunnels. The corresponding IDA percentiles lines are calculated, and the seismic fragility curves of the bifurcated tunnels are established. The post-earthquake functional failure probability of the bifurcated tunnels is obtained under different seismic fortification performance level.

Analysis of the Influence of Structural System Selection on Foundation Isolation Houses

According to the modeling and analysis of the structural design software (ETABS and SATWE), the data are obtained, and the mechanical properties and preliminary economic indicators of the three structural systems of frame structure, frame shear structure and shear structure of shear wall structure in the basic isolation design.The time course analysis data are summarized and compared, and the actual foundation isolation in the selection stage.Under the premise of the site type, seismic fortification intensity and building height determination, the best structure selection and layout are obtained by analyzing the stress performance and economic indicators of the structure.The influence of the structure selection on the stress performance and economic cost is discussed.

Research on the Evaluation Method for Key Buildings Based on Seismic Damage Index Modification—Taking the Yangzonghai Area Seismic Fortification Planning of Kunming City as an Example

This article focuses on the evaluation of key buildings in seismic mitigation planning, based on the modified seismic damage index. In the evaluation process, a computational model for key building evaluation is proposed, including the coefficients for model modification. The weights of the model modification coefficients are quantitatively calculated, followed by the application of the model for evaluation and conclusion derivation. Taking the "Yangzonghai Regional Seismic Design Planning" as an example, in the key building evaluation section of the specific mitigation planning, the average seismic damage index of group buildings in Yunnan Province's zone of VIII degree is used as the basis for calculation. The average seismic damage index of group buildings is adjusted with weighted factors such as building structure, construction year, site type, compliance with regulations, and adoption of seismic isolation technology. The factors are further adjusted using expert scoring. Finally, the seismic damage index for each important building is calculated. By referring to the corresponding building damage level associated with the seismic damage index, the potential damage levels that each important building may experience during a seismic event of the designated design level are determined. This study provides preliminary guidance for the renovation and improvement of important buildings and serves as an initial reference for decision-making by relevant government departments.