Seismic Capacity Research Articles

Seismic capacity of purely compressed shells based on Airy stress function

Purely compressed shells are often elegant and highly efficient structural forms, but this leanness may create risk if they are subjected to unexpected patterns and magnitudes of loading, such as may arise due to seismic events. In the same way that historic masonry structures were designed to sustain loads by activating purely compressive force paths, a modern metamaterial can be designed for specific purposes following the same logic. Conventional analysis methods for compression-only shells and vaults, often developed for masonry structures, have tended not to model combined vertical and horizontal loads directly. This has created a significant challenge for engineers assessing historic vaults or designing new shells. To address this gap, this paper presents an enhanced method based on membrane equilibrium analysis (MEA) and the static theorem of limit analysis. This approach is the first application of MEA to directly consider vertical and horizontal body forces acting on a compression-only shell through a parametric formulation of an Airy stress function. The method is applied to a case study of a sail vault subjected to vertical and horizontal loads. Moreover, it is demonstrated how this approach can be used to define iso-resistant shapes that offer more sustainable design options while preserving structural capacity.

Seismic Capacity of Unstrengthened and FRP Strengthened Masonry Arches: Tilting Test and Nonlinear Numerical Analysis

ABSTRACTCultural heritage preservation requires a deeper understanding of their seismic response and imposes the use of effective strengthening methods. Fibre‐reinforced polymers (FRP) have emerged as an effective solution for strengthening masonry structural elements. The decision over the optimal configuration for a FRP‐based strengthening is a trade‐off between different objective functions such as strength, inelastic stiffness and cost. Although some studies have explored design alternatives and topology optimisation, experimental investigation remains limited, especially regarding the evaluation of seismic response. This study investigates the seismic capacity of unstrengthened and strengthened mortared–masonry arches through tilting table experiments and numerical simulations. The optimal strengthening arrangement is obtained through topology optimisation, and experimental results demonstrate its performance. A three‐dimensional numerical model, following a macro‐modelling approach through the so‐called concrete damage plasticity material model, is adopted. Numerical results are validated with existing literature and experimental data. A parametric study is conducted for full‐scale arches to evaluate the effect of dimensions and the embrace angle of masonry arches. The study reveals that the numerical model successfully replicates masonry arches' nonlinear behaviour and hinge mechanism. In addition, both experimental and numerical results highlight the effectiveness of optimised strengthening placement achieved through topology optimisation.

Parameter Analysis of Resilient Precast Concrete Beam–Column Joints

Conventional precast structures often face the challenge of post-earthquake repair, especially at beam–column joints. A new type of precast concrete beam–column joint with a replaceable energy dissipation device consisting of cross-shaped and H-shaped steel was proposed in this paper, which was characterized by the use of replaceable energy-dissipating devices to improve the seismic capacity. Based on the previous test results of the group, this paper used ABAQUS to investigate how factors like the thickness of the H-shaped steel webs and the size and number of openings affected the seismic performance of precast concrete beam–column joints with replaceable energy dissipation devices. The results showed that (1) an increase in the H-shaped steel’s thickness in the REDDC could improve the load-carrying capacity of the node, but the energy dissipation capacity was weakened, and (2) the length and width of the H-shaped steel openings had almost no effect on the ultimate load-carrying capacity within a certain range, but increasing the size of the openings could improve the energy dissipation capacity and reduce the ultimate load-carrying capacity at the same time. Compared with the length of the openings, the width of the openings had a more significant impact on the energy dissipation capacity. (3) The peak load-carrying capacity decreased with an increase in the number of openings in the H-shaped steel.

Evaluation of the seismic capacity of cultural heritage in case of aggregate buildings: the Castle of Rosignano Marittimo

The partitioning of masonry buildings in Structural Units (SUs), or aggregate of Structural Units, is a useful tool to simplify the analysis of the buildings and the study of static and seismic vulnerability. However, this allocation is affected by uncertainties, simplification, and sometimes unavoidable miscalculation due to the directionality of this subdivision. This procedure exposes the results to discrepancies due to the way the building is divided. The Castle of Rosignano is emblematic. In this paper, the dependence of the results on how the Structural Units are considered is analyzed, as well as the role of structural in plan and elevation irregularities on various SUs and their combination. Non-linear static analysis corresponding to different distributions of the building in Structural Units, the uncertainties about material properties, and different directions of the seismic action are analyzed, and the respective results are discussed here. A simplified approach, for the study of aggregate buildings on an urban scale, is based on the so-called “tabular method”. Several Authors proposed and improved similar methods applied to different urban contexts. A comparison of simplified methodologies with the results of the detailed FEM analysis is also discussed and presented here. Finally, a simplified approach is proposed based on the regularity parameter of the building in aggregate. Taking the evidence from FEM analysis as a physical-mechanical base, the authors propose the quantitative definition of irregularity parameters and the use of them to determine the building vulnerabilities. The proposed procedure aimed to be a practical tool to determine, in an expeditious manner, the seismic capacity of a masonry building in aggregate. The model proposed in this paper, applied to the case of the study of Rosignano Marittimo (a typical situation of aggregate building in a historical context in Tuscany, Italy) shows emblematic results that can be extended to analogous configuration.

Analysis of characteristics of ground motion and typical bridge performance in the Baoshan earthquake

A Ms5.2 earthquake occurred in Longyang District, Baoshan City, Yunnan Province on 2 May 2023. The earthquake caused some degree of damage to power facilities and roads. Since then, small and medium sized earthquakes have occurred frequently in this region. In order to better analyze the characteristics of ground motion in this area and the coping strategies of related bridges, the response spectra, omnidirectional response spectra and omnidirectional representations of other indexes of intensity measure from records of strong ground motion were analyzed using the seismic records recorded by stations near the epicenter. Four typical bridges near the epicenter were selected for modeling and seismic response analysis to derive their damages under the action of ground motion, and structural displacements of the bridges with the strong ground motion were compared to analyze directional linkages. The Incremental Dynamic Analysis (IDA) method was used to analyze the fragility of the four bridges, and the seismic capacity of different bridges under the ground motion was compared. The omnidirectional displacement response spectra of the two stations and the omnidirectional representations of other indexes of intensity measure have obvious directionality, and the predominant direction is perpendicular to the direction of the fault, reflecting the rupture directionality of the earthquake. Comparing the corresponding period of the structural displacement response with seismic action with the omnidirectional displacement response spectra, it was found that the bridge structural displacement is correlated with the predominant cycle and predominant direction of the omnidirectional displacement response spectra. Under the same seismic action, the maximum moment of the deck arch bridge in the transverse direction is larger than that in the bridge direction; the larger the span of the deck arch bridge, the larger the maximum moment at the arch footing. According to the analysis of fragility, it can be seen that the seismic capacity of the continuous rigid frame bridge is much lower than that of the deck steel truss arch bridge under this ground motion. Compared to the deck-type concrete arch bridge, the deck steel truss arch bridge has greater seismic capacity. In this paper, based on the structural analysis and fragility analysis of these four bridges close to the fault, the structural damage and damage levels in the future earthquake are speculated, which provide suggestions for the follow-up maintenance and reinforcement work, and are also conducive to the resilience evaluation and rapid repair work after the real earthquake damage.

Influence of damage degree of recycled coarse aggregate concrete-filled steel tube columns strengthened with envelope steel jacket under seismic load

ABSTRACT In order to discuss the influence of damage degree of recycled coarse aggregate concrete-filled steel tube columns strengthened with envelope steel jacket (ESJ) under seismic load, eight columns were designed and manufactured to simulate seismic loading, with the design of ESJ strengthening after pre-damage and destruct tests under seismic load. This experiment was conducive to accurately evaluating the influence mechanism and synergistic effect of seismic damage degree and recycled coarse aggregate on the hysteresis curve, skeleton curve, ductility performance, energy dissipation performance, and bearing capacity performance of each specimens, and a suitable seismic damage model was proposed. The ductility coefficient is from 3.36 and 4.64, satisfying the requirements of seismic design. The research results indicate that the degree of seismic damage and recycled coarse aggregate are unfavorable to improve the seismic performance of recycled coarse aggregate concrete-filled steel tube columns strengthened with ESJ under seismic load; Taking the ductility coefficient of specimen SEJS-0 as the basic data, specimens SEJS-1 to SEJS-3 and FC-0 to FC-3 increased by 22.02%, 20.24%, 8.33%, 18.15%, 38.10%, 35.71%, and 23.51%, respectively. Under moderate and severe damage, the ductility performance of enveloped steel jacket-strengthened seismic-damaged specimens decreased by 15.47% and 15.18%, respectively, and the reduction amplitude of both was similar. As the degree of seismic damage increases, the value of the ultimate bearing capacity first decreases and then increases. The method of using recycled coarse aggregate to replace half of natural coarse aggregate has certain feasibility in the field of concrete-filled steel tube columns. Recycled coarse aggregate has a significant impact on the bearing capacity of each stage, while the degree of seismic damage only has a greater impact on the ultimate stage. The established seismic damage model for recycled coarse aggregate concrete-filled steel tube columns strengthened with ESJ under seismic load is feasible and can be used for quantitative evaluation of the seismic capacity of such components.

An Investigation of Parameter Sensitivity and a Dynamic Analysis of Subsurface Storage Chambers Utilizing the Finite Difference Method

Underground compressed air energy storage chambers are a promising emerging energy storage technology with strict limitations relating to the stability of the surrounding rock. This study conducted displacement and plastic zone analyses during the excavation and stabilization phases of the chamber utilizing the finite difference method based on engineering data, demonstrating that the stability of salt rock can effectively withstand internal pressures ranging from 0 to 9 MPa, with an average of 15 mm in the Z-axis and 19.23 mm in the X-axis. To further investigate the feasibility of subterranean energy storage reservoirs, the FOS for various surrounding rocks was calculated at different burial depths. These results facilitated a parameter sensitivity analysis on the stability of the surrounding rock of the underground energy storage reservoir. The dynamic reaction of the underground chamber was studied using synthetic seismic wave technology, demonstrating that the seismic capacity of the structure adhered to the code, and the post-seismic displacement remained within the safe range (Z-axis 34 mm, horizontal 19 mm). The results demonstrate the stability analysis method of the chamber and establish a foundation for the extensive implementation of CAES which will contribute to the development of energy storage technology.

Study on failure mechanism and seismic performance of RC Frame-Infilled walls structures reinforced by CFRP

The reinforced concrete (RC) frame structure with continuous half-height infilled walls is a common structural form. However, the existence of infilled walls alters the structure’s force mechanism and failure mode, making the frame columns susceptible to brittle failure and adversely affecting the overall seismic performance. To enhance the seismic capacity of such systems, quasi-static tests were conducted on RC frame-infilled wall models reinforced with different CFRP methods. Based on the test results, numerical analysis models of RC frame-infilled walls were established to perform parametric studies and quantitatively assess the impact of various CFRP reinforcement methods on seismic performance. The results indicate that both full wrapping and strip reinforcement methods can improve the failure mode and enhance the seismic capacity of the frame-infilled wall structure, but the degree of improvement varies significantly. Compared to the unreinforced frame, the ductility, ultimate bearing capacity, initial stiffness, and energy dissipation of the fully wrapped and strip-reinforced frames increased by 42.86% and 58.76%, 30.43% and 10.65%, 68.76% and 9.55%, 298.01% and 340.92%, respectively. Considering the overall seismic demand and CFRP utilization rate, the strip reinforcement method is more suitable for the seismic strengthening of half-height infilled wall frame structures. When using the same amount of CFRP without other improvement measures, it is recommended that the ratio of strip spacing to strip width be between 1.1 and 1.25.

A Comprehensive Evaluation Method for Assessing the Seismic Resilience of Building Sites Based on the TOPSIS Model and the Entropy Method

The seismic design philosophy based on resilience represents the latest development in structural seismic design theory and is currently the most advanced concept in the field of seismic design research. A building site serves as the foundation and environment for structures, and evaluating its seismic resilience is a crucial aspect of designing and assessing buildings’ seismic resilience. To meet the needs of evaluating building seismic resilience, the concept of seismic resilience for building sites is introduced in this paper. This evaluation is approached from three dimensions: seismic action, site seismic capacity, and site recovery capability. An indicator system for evaluating the seismic resilience of building sites is constructed using 23 key indicators that reflect the site’s seismic resilience. A seismic resilience evaluation model for building sites is established based on the TOPSIS model and the entropy method. The feasibility and rationality of the proposed evaluation method are demonstrated through application examples. The research findings in this paper provide a valuable reference for advancing the evaluation of both building seismic resilience and site seismic resilience.

Seismic performance of perforated-steel plate shear wall with different perforation layouts

The Perforated-Steel Plate Shear Wall in ANSI/AISC 341-16 requires the plate to have a regular hole pattern with parallel holes and a uniform diameter. There are also rules regarding the minimum number of holes. It becomes a challenge if the opening requirements do not comply with these provisions. This study proposes the percentage value of perforation as a parameter to obtain the seismic capacity of shear wall plates. Experimental studies were conducted on six shear wall plates to achieve this goal. Three specimens were made with a straight perforation layout, and the rest were staggered. All plates had a thickness of 2 mm and were given circular perforations with a diameter of 65 mm. Each group of specimens was assigned a perforation percentage ranging from 10.25%-49.59%. The ultimate load, a measure of material strength, decreases as the percentage of perforations increases. Based on the results of experimental testing with cyclic load, the impact of the perforation layout on seismic behavior shows that the staggered configuration can accept greater average loads than the straight layout by 12.5%-40.3%. Specimens with the same percentage of perforations show no significant difference in dissipation energy when observed from the start of loading to a drift ratio of 6%. The difference in total energy dissipation between specimens with the same perforation percentage is less than 30%. However, both show similar patterns of stiffness reduction and pinching effects.

Influence of retrofitting in the seismic behaviour of precast reinforced concrete industrial buildings

Previous destructive earthquakes caused large economic losses as well as human losses. Seismic risk studies are of paramount importance to predict the impact of future earthquakes and support seismic risk mitigation policies. The present study presents a seismic risk assessment based on the cost and direct loss assessment of precast industrial buildings with different retrofitting levels in terms of horizontal strength. In this evaluation, a comparative analysis between the configurations of retrofitted buildings and the original building is performed. The effects of retrofitting solution strategies are first investigated in a single building. Then a study is carried out to assess which retrofit solutions level are most appropriate depending on the exposure and seismic risk. The results showed the use of bracing in the PRC building can improve seismic behaviour, with significant increases in horizontal strength. The cost of intervention is reduced, with a slight increase of less than 1% to almost 2% of the cost of the structure. From the derivation of seismic fragility functions for different retrofitting solutions level, the seismic risk analysis with dozens of existing PRC industrial buildings in Portugal points to a large reduction in economic losses as from retrofitted buildings, like an improvement of the seismic capacity of the buildings attributed to the retrofit systems considered. In general, among the different types of retrofit studied, there is an increase in the reduction of total economic losses, namely 49% when retrofitted with a 50% increase in horizontal strength, 58% when retrofitted with a 75% increase in horizontal strength and 64% for retrofitted with 100%.

Seismic capacity evaluation of corroded reinforced concrete frame structures

Seismic capacity evaluation of corroded reinforced concrete frame structures

Collapse-based seismic design method

Continuing the structural analysis until the model reaches its ultimate capacity using an incremental nonlinear time history analysis can incorporate all the behavioral complexities of the structure. This approach ensures that all factors influencing the seismic behavior of structures, which can be simulated in numerical modeling, are fully considered in the analysis. This technique addresses many shortcomings in seismic analysis and structural design, using simple criteria for the accurate design of members. With this perspective, this paper explores the collapse-based seismic design method and provides an approach to determine the ultimate tolerable seismic intensity for a structure, or an appropriate collapse seismic intensity. It also establishes design criteria based on the maximum capacity of structural members under maximum loading and utilizes the endurance time method to perform incremental nonlinear time history analysis quickly and easily. Evaluations show that models designed using this method achieve the desired performance level at different seismic hazard levels, provide sufficient seismic capacity, meet all minimum requirements of the seismic code and standards, and are optimized. Therefore, the procedure presented in this paper is introduced for the analysis, design, evaluation, and retrofitting of structures with simple, accurate, and uniform principles.

Seismic capacity assessment of Shikhara style temple with and without traditional seismic enhancement

Brick masonry heritage structures have long been understood as highly vulnerable under earthquake excitation. Due to preservation constraints and considerations, modern materials are not allowed in seismic strengthening or post-earthquake reconstruction of heritage structures. Thus, traditional strengthening techniques are mandatory in heritage structures. The present paper reports the outcome of reconstruction initiative in a Shikhara style temple located in a world heritage site using timber element based seismic enhancement. Using numerical modeling, capacity assessment with and without timber elements is performed. For capacity assessment pushover analysis is performed for both as built and reconstructed models. The results show considerable increase in seismic capacity even with traditional improvement techniques, i.e. vertical timber elements. 18.05% increase in seismic capacity is found when vertical timber elements are used. Also, about 8% increase in the fundamental vibration frequency is observed after strengthening. The paper reports the details of geometrical features, reconstruction aspects, and numerical analysis results comprising modal analysis and capacity assessment.

Seismic performance enhancement of underground structure influenced by CFRP wrapping schemes

The seismic failure mechanism of underground structures showing structural collapse is attributed to the deformation incompatibility between the central columns and the sidewalls, especially the insufficient deformation capacity of the central columns. Therefore, the approaches to improve the seismic performance of underground structures mainly aim at avoiding the damage of central columns. This paper presents a comparative study on the seismic performance of underground structures with the central columns retrofitted with different numbers of Carbon Fiber Reinforced Plastics (CFRP) layers. Seismic capacity of the CFRP retrofitting reinforced concrete (RC) columns was explored in detail through experimental and numerical approaches. Then numerical models were built and verified to simulate the behaviors of the CFRP retrofitting RC columns, and the seismic performance of the CFRP retrofitting underground structures was numerically simulated. Based on the numerical results, the damage of the CFRP retrofitting underground structures was calculated, and damage classification illustrated that the seismic performance of underground structures was enhanced remarkably. Finally, parametric studies were conducted to discuss about how the number of CFRP layers and the earthquake intensity affect the earthquake-induced damage of underground structures. Conclusions from this study could be referenced for seismic retrofitting of existing underground structures.

Optimised rotational-spring component-based modelling strategy for seismic resistant steel-concrete composite joints and frames with continuous or isolated slab

Joints and frames in steel-concrete composite systems represent complex mechanical assemblies that require specific calculation procedures to optimise their detailing and structural capacity, particularly under seismic loads. To this aim, component-based modelling approaches should be able to account for the most relevant mechanisms and resistance/stiffness behaviours of individual members, and their mutual interaction. In this paper, two different simplified non-linear approaches are considered for steel-concrete composite beam-to-column joints, and are specifically applied to a seismic resistant case-study frame with X-concentric bracings. Both beam-to-column joints with or continuous (“JA” joint) or fully isolated (“JB” joint) slab are examined. First, non-linear axial springs are assembled and calibrated on the base of a previous study (“Type 1″ model (“T1″)), according to force-displacement relationships proposed in the DPC-ReLUIS Italian guidelines. Successively, a novel modelling approach based on non-linear rotational springs is presented (“Type 2″ model (“T2″)), to further simplify the computational cost of T1 strategy, and allow to efficiently account for the moment-rotation behaviour of the examined joints. The preliminary numerical validation is carried out based on past literature experiments. Moreover, the optimized T2 approach is used to explore the in-plane lateral, seismic performance of a 2D steel-concrete composite frame, which is specifically designed with X-concentric bracings. The seismic capacity of the frame (and the associated interaction of components, especially the joint zone with the bracing system) is addressed on the base of pushover analyses.

Seismic fragility analysis of nuclear containment structure with Bayesian cloud analysis framework

Nuclear containment structure plays a critical role in safe operation of nuclear power plant. Seismic safety of nuclear power plant structures has become a hot issue in nuclear engineering community following Fukushima nuclear accident. Seismic fragility analysis, as a key element in probabilistic safety assessment of nuclear power plants, is widely used in nuclear power plant structures. This study presents an innovative method for seismic fragility analysis of engineering structures. The proposed methodology combines conventional Cloud analysis method and Bayesian framework. The accuracy and efficiency of the proposed methodology were demonstrated by a single-degree-of-freedom system, heavy computational efforts but high accuracy seismic fragility analysis method was adopted for comparison. Seismic fragility analysis of a typical prestressed concrete nuclear containment structure was analyzed using the proposed method. Results indicated that method proposed in this study can improve the accuracy of seismic fragility analysis. Furthermore, with the enhance of performance level, the increasing ratios for median seismic capacity of the nuclear containment structure was decreasing.

Cyclic axial loading tests on mortar-filled rectangular tube with various connection details

Although a mortar-filled rectangular hollow structural section (RHS) under monotonic loading has achieved large tensile capacity using various connection details and buckling capacity of RHS members, the structural capacity of the mortar-filled RHS tubes has not been investigated under cyclic loading. In this study, the seismic performances of newly developed mortar-filled RHS tubes with various connection details were evaluated under cyclic axial loading. The major test parameters included the end connection type, the thicknesses of the RHS tube, cap plate, and cleat plate, as well as the length of the RHS tube. The test results showed that the RHS tube in all specimens failed by tensile fracture before axial compression failure. The seismic performance of the embedded shear plate end connection with penetrating rebar was superior to that of a conventional welded T-end connection. The test results were compared with the current design code to evaluate the seismic capacity of the RHS tube according to the connection details. Design considerations for the connections of the mortar-filled rectangular tubes were also provided.

Seismic capacity evaluation of a reinforced concrete frame infilled with precast modular block wall for enhancing the horizontal load

In this study, we propose a new concept for seismic retrofitting using precast modular block walls (PMBWs) to improve and complement the shortcomings of conventional retrofitting methods for reinforced concrete (RC) frames infilled with shear walls, masonry walls, and precast panels. The PMBW retrofitting method maximizes the advantages of factory-produced modular blocks, innovatively enhancing the constructability and integrity of connections between the existing frame and the infilled PMBW. Additionally, the PMBW reinforcement method improves seismic resistance without significantly increasing structural weight, and the required amount of reinforcement can easily be calculated because the strengthening technique involves typical frame infilling. For RC buildings with non-seismic details dominated by shear failure, the application of this seismic reinforcement method readily ensures sufficient strength. A pseudo-dynamic test was conducted on a full-scale two-story frame, based on an existing RC building with non-seismic details, to evaluate the restoring force characteristics, strength enhancement effects, reinforcement strain, and seismic response control capabilities of the PMBW reinforcement system. Based on the pseudo-dynamic test results, the restoring force characteristics for nonlinear dynamic analysis of the PMBW-reinforced specimen were identified. Finally, nonlinear dynamic analysis was conducted using the proposed restoring force characteristics, and the results were compared with the pseudo-dynamic test results. The unreinforced RC frame experienced shear failure at a design basis earthquake magnitude of 200 cm/s2. However, the frame reinforced with the PMBW sustained only minor damage. Even at higher magnitudes under maximum considered earthquake conditions of 300 cm/s2 and large-scale earthquake conditions of 400 cm/s2, only a slight amount of damage was projected from the analysis. Thus, the newly developed PMBW frame infilling system shows great promise for seismic reinforcement.

Rapid simulation method for assessing seismic damage to building curtain walls on a regional scale using designed wind load capacity

This study introduces a rapid simulation method for assessing seismic damage to building curtain walls at a regional scale. Although the results are approximate, this approach enables quick evaluations, making it an important instrument for emergency responses during disaster situations. This method’s independence from numerical models is a noteworthy advantage. Unlike conventional approaches, it eliminates the need for structural analysis models when evaluating the seismic capacities of curtain walls regionally. Creating reliable structural analysis models is both time-consuming and labor-intensive, primarily due to the detailed design information they require. In contrast, the presented method leverages the wind load capacities for which curtain walls are designed. It is based on the core premise that most curtain walls, primarily designed for wind resistance, possess wind load capacities that could serve as substitutes for their seismic capacities, even if they are not explicitly designed for such seismic loads. To assess the method’s effectiveness, it was applied to seismic damage assessments across regions experiencing varying wind intensities: weak, moderate, and strong. The results suggest the likelihood of curtain walls sustaining seismic damage in regions with weak wind could be five times higher than in regions with strong wind. This underscores the importance of seismic design considerations for curtain walls. Moreover, the findings closely match the actual seismic damage assessment data from a region with a moderate to strong wind intensity.