Inter-story Displacement Angle Research Articles

Transverse seismic analysis method of underground interchange prefabricated utility tunnel

The rapid development of underground utility tunnels has led to the formation of a large number of interchange utility tunnels. Due to significant differences in the lateral resisting stiffness in orthogonal directions, coupled with the close relationship between soil deformation and the depth of the utility tunnel, the seismic response mechanism of the interchange utility tunnel is complex. This paper proposes a method for transverse seismic analysis of the underground interchange utility tunnel based on the response displacement method. A load-structure analysis model of a certain underground cross-type interchange utility tunnel is first established. Then, the different conditions corresponding to maximum relative deformation between layers of the interchange node are discussed, and the proposed method is validated via the time-history analysis method. Based on the proposed analysis method in this paper, seismic response analysis is performed on the interchange utility tunnel considering the condition of vertical incidence of three different input seismic waves. Discussions are conducted in terms of internal forces, inter-story displacement angles, and damage responses under seismic excitations in different principal axis directions. The results show that under major earthquakes, the maximum inter-story displacement angle of the interchange node exceeds the standard limit by up to approximately 184 %, while the tensile damage can reach up to 0.985, significantly surpassing the tensile damage limit. Accordingly, the interchange node is the weakest part of the interchange utility tunnel. There exists deformation inconsistency between the interchange node and standard segments due to significant stiffness differences, with the influence range of the interchange node on internal forces, inter-story displacement angles, joint deformations and damage of the utility tunnel is approximately 7, 6, 8, and 6 prefabricated standard segments, respectively. Since the maximum relative deformation between layers of the interchange node does not occur simultaneously, for double-layered and multi-layered interchange utility tunnels, it is necessary to comprehensively consider the maximum inter-story displacement angle between each layer to determine their most unfavorable condition. The analytical method and related research conclusions presented in this paper can provide references for the transverse seismic design of interchange utility tunnels.

Assessment of the seismic failure of reinforced concrete structures considering the directional effects of ground motions

Seismic intensity measures at different levels significantly impact the seismic damage of building clusters. Reinforced concrete (RC) structures are a type of building widely used in different regions worldwide. A large amount of field seismic damage observation data indicates that within the same seismic intensity zone, the directional effects of varying ground motions lead to significant differences in damage to RC structures on different floors. However, relatively little research has been conducted on estimating the seismic fragility and vulnerability of RC structures considering the directional effects of seismic action. To further study the directional effect of seismic motion on the damage of different floors, this study conducted dynamic time history and spectral analyses on 1472,379 acceleration records in multiple directions obtained from monitoring at nine actual seismic stations during the 2008 Wenchuan earthquake in China. This paper innovatively reports on the actual damage features of RC structures during the Mw6.2 magnitude Jishishan earthquake in Gansu Province, China, on December 18, 2023 (the most severe destructive earthquake in China in 2023) and analyses the influence of earthquake directionality on the damage to different floors of RC structures. A three-dimensional numerical model of a four-story RC frame structure was established using numerical simulation and the finite element method. Different intensity measures were taken to input seismic excitations of different intensities into the RC structure in the 0°, 30°, 60°, and 90° directions, and damage simulation analysis was conducted. The nonlinear dynamic time history curves of structures under multiple directions of seismic excitation in different intensity zones have been developed. Using the interstory stiffness and interstory displacement angle as engineering demand parameters, damage assessment curves and stress clouds for RC structures with 1–4 floors considering different seismic directional effects were generated. The analysis results and major findings indicate that the seismic sequence in the 0° direction has a relatively heavy impact on the first floor of the RC structure in zone IX, which is consistent with the actual field observation results.

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.

The Seismic Performance of Self-Centering Ribbed Floor Flat-Beam Frame Joints

To achieve rapid post-earthquake repair of self-centering ribbed floor flat-beam frame structures, a ductile hybrid joint consisting of dog-bone-shaped, weakened, energy-dissipating steel bars connected to the upper and lower column sections through high-strength threads is proposed based on the damage control design concept. By moving the ductile energy-dissipating zone out to the locally weakened section of the energy-dissipating steel bars and the locally unbonded prestressed steel bars in the core area, the residual deformation was limited and the seismic performance improved. Based on the working principle of hybrid joints, low cycle loading tests were conducted on two joint specimens to analyze the influence of lateral prestress on the seismic performance of the hybrid joints. Numerical modeling methods were used to compare the position of the energy-dissipating steel bars in the composite layer and the friction performance of the joints. The research results indicated that the hybrid joint had stable load bearing, deformation, and energy dissipation capabilities, with damage being primarily concentrated in the energy-dissipating steel bars. Even at an inter-story displacement angle of 5.5%, the upper and lower column segments remained elastic. After unloading, the connection seam at the joint was closed, and the self-centering performance was good. When the inter-story displacement angle reached 5.5%, the lateral prestress increased from 150 kN to 250 kN, the ultimate bearing capacity of the joint increased by 16.3%, and the cumulative energy consumption increased by 30.0%. The influence of the friction coefficient of the joint surface on the structural performance was set at a threshold of 0.7. When it was less than the threshold, the ultimate bearing capacity and initial stiffness of the joint increased with the increase in the friction coefficient. After reaching the threshold, the increase in the ultimate bearing capacity of the joint slowed down, and the rate of stiffness degradation gradually accelerated. This joint showed excellent seismic performance and can thus achieve post-earthquake repair of structures.

Seismic performance investigation of irregular and complex connected structures based on the influence of ground fissure activity

To investigate the dynamic response of irregular and complex connected structure, the comprehensive soil and connected structure model was developed, which is considered the site condition of different foundation soils. This study explored on the deformation law of the connected structure, and analyzing the structural displacement, acceleration, and torsional response under various seismic conditions. The findings revealed that the presence of ground fissures significantly amplifies the dynamic response of connected structures, with a greater influence from the hanging wall. Additionally, the lag effect was observed in the generation of the peak ground acceleration (PGA) in the site model considering ground fissures, but the result surpassed those in ordinary sites. During the elastic-plastic loading stage, the study observed that the maximum inter-story displacement angle remained within the limits prescribed by specifications. Due to the varying distances between column bases of the main area and ground fissures, there is a significant magnification effect in inter-story torsional angle. The incorporation of sliding supports emerged as an effective measure in mitigating the relative displacement of connected structures, consequently reducing the translational-torsional coupling effect during rarely occurred earthquake. The research results provide reference for the seismic performance analysis of connected structures under complex site conditions.

Analysis of Seismic Performance and Applicable Height of a Cooperative Modular Steel Building

As an innovative building system, the modular steel structure demonstrates a high degree of industrialization and assembly efficiency. However, no linkage exists between the components of modular units, leading to issues such as diminished load capacity and excessive steel usage in modular construction. In order to tackle these challenges, finite element numerical simulations are employed to examine the inter-column connectors and the cooperative modular steel buildings. This simulation calculates the initial stiffness across various degrees of freedom in these connectors. In addition, it analyzes the displacement response, changes in internal forces, and height of cooperative modular steel structures under varying seismic precautionary intensities. The results revealed that cooperative modular steel buildings substantially improve overall stiffness and lateral performance compared to their non-cooperative counterparts. There is a maximum reduction in the inter-story displacement angle of up to 36.1%, and the maximum reduction of the top displacement can reach 16.2%. This enhancement also increases structural stiffness, a shortened natural vibration period, and an augmented bottom shear force. Based on these findings, it is advised that the height of cooperative modular steel buildings should not exceed 21 m at 7 degrees (0.10 g), 21 m at 7 degrees (0.15 g), and 12 m at 8 degrees (0.20 g).

Post-Fire Seismic Performance of Concrete-Filled Steel Tube Frame Structures Considering Soil-Structure Interaction (SSI)

Currently, reinforced thin-walled irregular steel tube concrete frame structures have been applied in engineering, but there are few researches on the seismic performance of this type of structures after fire. The seismic performance of structures after fire is generally carried out based on rigid foundation conditions. Therefore, it is of certain engineering and theoretical value to study the seismic performance considering the SSI (soil–structure interaction) in this paper. ABAQUS is employed to establish the finite element models of the reinforced thin-walled irregular steel tube concrete frame structure considering the SSI after a fire. The paper analyzes the impact of different site conditions and fire durations on the structural natural vibration period, maximum acceleration, inter-story shear force, and maximum inter-story displacement angle. The results show that the consideration of the SSI increases the basic natural vibration period of the structure by 10–30%. The softer the soil and the longer the fire duration, the more significant the increase. For harder soil, lower seismic intensity, and shorter fire duration, the acceleration assigned to the structure and foundation after considering the SSI is smaller than the results assuming a rigid foundation. The change in inter-story shear force is mainly determined by the acceleration of the structure and foundation. The inter-story displacement angle increases when considering the SSI, and the increase is more significant with softer soil, larger seismic wave acceleration amplitude, and longer fire duration.

Application and Performance Evaluation of Superelastic Shape Memory Alloys in Building Vibration Isolation Systems

Abstract In this study, the intrinsic model of Shape Memory Alloys (SMA) is employed to facilitate a comprehensive analysis of the phase transition process, encapsulating the evolution of stress and strain across varying temperatures. The martensite volume fraction is quantitatively described using a cosine function, culminating in the formulation of a cosine-type SMA phase transition equation. This model enables the simulation of superelasticity, shape memory effects, and the elastic-thermal behavior of SMA by varying the loading conditions. This approach allows for an assessment of how different material parameters influence SMA properties. Notably, the results highlight that the heating temperature significantly affects the hyperelastic energy dissipation properties of SMA. The energy dissipation coefficient increased by 15.3% when the temperature was increased from 350 to 550 and decreased by 36.3% when the temperature was increased from 550 to 650. The peak values of top acceleration and interstorey displacement of the SMA-isolated structure were 0.826 m/s² and 0.641 mm for EL-centro waves at 7+ seismic intensities. The values of non-isolated were 1.151 m/s², 0.856 mm. 10 ground shaking, the SMA braced structure relative to the steel frame structure on the maximum peak inter-story displacement angle and the structure of the top layer of the permanent displacement, have different degrees of reduction. Therefore, the SMA material possesses good damping performance in the seismic isolation system.

Study on seismic performance of nanometakaolin-reinforced fluororubber sector damper (NFSD)

In order to improve the mechanical performance of the core energy-dissipating material of the viscoelastic damper, a novel Nanometakaolin-reinforced Fluororubber Sector Damper (NFSD) is proposed for providing a strong guarantee for the seismic safety of the structure joints subjected to seismic earthquake. Firstly, in order to systematically study the shock absorption performance of NFSD, the core energy dissipation material(nano metakaolin reinforced fluororubber composite) of NFSD is prepared by melt blending method, and the vulcanization performance and microscopic mechanism of the nano composite are analyzed by vulcanization test and X-ray diffraction test. Secondly, the nanocomposite material is used as the core energy dissipation material, and NFSD based on nano reinforced fluororubber is proposed. Finally, the dynamic characteristics of NFSD and the structural seismic performance of NFSD controlled reinforced concrete (RC) frames are studied using refined finite element simulation methods. The research results indicate that 20 phr NMK increase the maximum torque MH of FKM by 20 %, while also shortening the scorching time t10 by 0.28 min. It means greatly improving the vulcanization performance of FKM. Compared to uncontrolled structures, NFSD reduces the peak displacement, interstory displacement angle, and maximum vertex acceleration of the 4-story RC structure by 16.2 %−67.4 %, 12.4 %−64.6 %, and 16.8 %−43 %, respectively. NFSD possesses excellent seismic absorption performance.

Analysis and Application of Double Steel Plate Concrete Composite Shear Wall in the R&D Building of Zhanjiang Bay Laboratory

The R&D Building of Zhanjiang Bay Laboratory is a high-rise structure with multiple irregular items exceeding the specification limit, employing a steel frame-shear wall structural system. The outer frame consists of square steel tube concrete columns and solid-web steel beams, while the core shear wall uses a double steel plate concrete composite shear wall. This paper employs the architectural structural calculation software YJK-EP to perform a dynamic elastic-plastic time-history analysis under rare earthquake action. The shear and bending resistance of the shear wall at the maximum shear force and bending moment are checked to meet the requirements of the “Technical Specifications for Concrete Structures of High-rise Buildings”. The maximum inter-story displacement angle meets the requirements of the “Code for Seismic Design of Buildings”. The double steel plate concrete composite shear wall Wall-1, connected to a large-span and heavy-load transfer truss, was verified under significant seismic action using the ABAQUS software. The results indicate that Wall-1 can meet the design target requirements under major earthquake conditions. Finally, a dynamic nonlinear analysis method was employed using MIDAS-GEN software to study the structure’s anti-progressive collapse performance. The results show that under seven different scenarios, the maximum rotational angle of the remaining structural horizontal members is 2.02°, far less than the limit set by GSA, indicating that a progressive collapse did not occur. In the scenario where the corner column is removed, both the maximum shear and bending moment values for Wall-1 are far below its shear and bending resistance capacities, satisfying the load-bearing requirements. The removal of the corner column has a significant impact on the displacement of the columns on the same level nearby, with the peak displacement change rate reaching 702.65%.

Effect of axial-load ratio and shear-span ratio on seismic behavior of the prefabricated structures for cast-in-place RC boundary elements confined uniform hollow panels

To meet the requirements of seismic safety, energy efficiency, and convenient transport, while achieving efficient construction of low or multi-story building structures. A prefabricated structure was developed with uniform hollow panels as the main force elements and cast-in-place RC provides restraint. The safety of the connection between the elements was verified by a low cyclic loading experiment and numerical analysis. In addition, the influence of the axial-load ratio and the shear-span ratio on the seismic performance of the structure was investigated, and the damage characteristics of progressive failure were revealed. The study found that as the axial-load ratio increased from 0.15 to 0.30, the cracking of the uniform hollow panels progressed, but the cracking of the columns was delayed, and the tendency of the edge member to separate from the uniform hollow panel increased. The ultimate lateral load capacity increased by 9.96 %, but the deformation capacity decreased, and the ductility coefficient decreased from 3.19 to 2.45. As the shear-span ratio decreased from 1.35 to 0.95, the uniform hollow panel and the structural columns cracked earlier and later, respectively, and the ultimate lateral load-bearing capacity increased by 25.03 %. However, the cracks at the base of the column increased, the deformation capacity decreased, and the ductility coefficient decreased from 3.19 to 2.15. Meanwhile, it is observed that the structure exhibits a three-stage progressive failure characteristic, i.e., the joint working stage, transformation transition stage, and weak frame stage. This greatly improved the deformation and energy dissipation capacity of the structure, which maintained good stability even when the inter-story displacement angle reached 1/50. This paper also established the calculation method for the lateral load resistance of this prefabricated structure, which showed accurate and reliable results. In general, the results of this research can provide an important reference for building design code and the application of this structure.

Global method for nonlinear seismic analysis of embedded base-isolated nuclear island buildings in layered sites

Owing to the increasing scarcity of high-quality sites, the seismic analysis of base-isolated nuclear power plants (NPPs) under complex non-lithology sites has gained important engineering significance. In this study, a global method for nonlinear numerical analysis was developed for the seismic evaluation of base-isolated NPPs in complex layered sites. The seismic analysis of layered sites is realised using the equivalent linear method and one-dimensional wave propagation theory, the radiation damping of the infinite domain is modelled with a visco-elastic artificial boundary, and the nonlinear behaviour of the isolators is fully considered using a bilinear hysteretic model. Using this method, the influence of soil–structure interaction (SSI) and soil nonlinearity on the behaviour of base-isolated NPPs under the design basis earthquake and beyond design basis earthquake was analysed and compared, in terms of the floor response spectra (FRS) and inter-story displacement angle. In addition, the influence of embedment is also studied. The results show that in layered sites, the SSI significantly amplifies the response values for base-isolated NPPs, and as the ground motion input increases, the soil nonlinearity more effectively inhibits the response of base-isolated NPPs. In addition, embedding can significantly reduce the response, but it increases the FRS at some frequency domains. The isolation effect of base-isolated NPPs decreases significantly when SSI effects are considered, and the soil nonlinearity and embedment have little impact on the base isolation capacity. The method proposed in this study can be easily applied to study base-isolated NPPs in layered sites.

Seismic Performance Analysis of the Upper Wood Structure of Guangyue Tower considering the Influence of Walls

Taking the wood structure of Guangyue Tower as the research object, whether to consider the influence of the wall, two finite element models were established. Modal analysis was conducted to obtain its self-oscillation frequencies, and the results were compared with the field test to verify the rationality of the finite element model. The results show that the walls have greater influence on the first three order frequencies of the structure and smaller influence on the higher order frequencies. The seismic response analysis of the two finite element models shows that the peak acceleration of the model with wall is larger than that of the model without wall, and the angle of the relative ground displacement and interstory displacement are vice versa. The angle of the maximum interstory displacement with and without wall is 1/78 and 1/61 respectively, which are less than the standard limit value, thus the structure is safe. The presence of walls make the lateral stiffness of the structure increase and the interstory displacement angle decrease. The presence of the walls make the structural lateral stiffness increase and the interstory displacement angle decrease. The study results provide a theoretical basis for the protection of the wood structure.

Influence of 3D spatial effect of underground structure on the nonlinear seismic response of subway station based on the comparison of 2D and 3D models

This paper takes an actual station of Nanjing Metro Line 2 as the research object and establishes the corresponding 2D and 3D overall time-domain nonlinear finite element models, respectively. By analyzing the results of the two models, the influence of the 3D spatial effects of the underground structure on the seismic response of the structure is studied. The results show that the 2D model cannot correctly reflect the deformation characteristics of the 3D station structure at the middle of the longitudinal length. The results obtained from the 2D model are roughly equivalent to the results at 1/4 of the longitudinal length of the 3D station structure. The overall longitudinal bending deflection of the station's top and middle slabs in their own plane can well reflect the 3D cooperative work degree of the station. Based on this, the conversion coefficient of the maximum inter-story displacement angle proposed in this paper can better convert the 2D model results. The minimum error between the converted 2D model results and the 3D model results is only 0.78%, and the maximum error is only about 10%. The maximum inter-story displacement angle conversion coefficient with 95% probability guarantee finally given is 1.447. Through the statistical analysis of the internal force ratio of the 3D model and the 2D model at the key cross-sections, this paper also gives the conversion coefficients with 95% probability guarantee for the bending moment, the axial force and the shear force of the key cross-sections, which are 0.696, 0.773, and 0.785, respectively.

Investigation on Seismic Performance of the Fully Assembled Steel Frame Applying Beam-Column Joints with Replaceable Energy-Dissipating Elements

Based on the application of a beam-column joint with replaceable energy-dissipating elements and hinged beam-column proposed by the author, the seismic performance of a fully assembled steel frame with this joint was investigated in this paper. Through two projects of a traditional steel frame (TSF) and an assembled steel frame applying beam-column joints with replaceable energy-dissipating elements (ASFWREE) and their numerical simulation calculation by SAP2000, the main structural design indicators such as natural vibration period, period ratio, mass participation coefficient, base shear force, inter-story displacement angle, rigid-weight ratio, and shear-weight ratio of two frames under frequent earthquake, and their influence factors were compared and analyzed. By carrying out the elastic–plastic dynamic time–history analysis of two projects under a rare earthquake, the maximum inter-story displacement angle, base shear force, stiffness between floors, maximum vertex displacement, and the occurrence sequence and distribution of plastic hinges of the two items were compared. The results show that the deformation of ASFWREE had the characteristics of the shear deformation of TSF and the deviation of the natural vibration period was less than 5% when the ratio of the linear stiffness of the energy-dissipating element to the steel beam was approximately 0.8, the ratio of horizontal length to span was about 0.25, which was close to the strength grade of the steel beam. The seismic performance under the rare earthquake was close to or higher to that of the TSF, can ensure that the beam and column are not damaged, and the structure does not collapse. The failure mode of the ASFWREE is consistent with the experimental research of the beam-column joints.

Sensitivity Analysis of Random Parameters for Earthquake Response of Hakka Tulou in Fujian

The seismic response analysis of the Fujian tulou structure considers the influence of six input random variables of the tulou structure. It obtains the seismic response of the apex displacement, the maximum inter-story displacement angle, and the base shear force of the tulou structure. An analysis method based on moment-independent importance measure is proposed and applied to the stochastic parameter sensitivity (importance measure) analysis of structural seismic response. The results show that the importance metric analysis method of the seismic response of the structure based on the moment-independent importance measure analysis method generates consistent outcomes with the importance measure method of the variance. However, the method in this study can better reflect the actual earthquake response of the tulou structure, and it is also an efficient method.

Selection of optimal seismic intensity measures using fuzzy-probabilistic seismic demand analysis and fuzzy multi-criteria decision approach

A fuzzy decision-theoretic computational approach for selecting optimal intensity measures (IMs) under the conditions of randomness, fuzziness and uncertainty is proposed in this paper. The main objectives of this study are twofold: (a) to quantify the contribution of multiple evaluation criteria, and (b) to improve the credibility of decision-making results by selecting the appropriate multi-criteria decision making (MCDM) method. To achieve these, three components of the methodology for this approach are utilized: (1) Fuzzy-probabilistic seismic demand analysis (FPSDA) is employed to consider the aleatory and epistemic uncertainties in the seismic demand analysis. (2) Fuzzy analytical hierarchical process (FAHP) is used to determine the importance weights of multiple evaluation criteria. (3) A combination of FAHP and fuzzy technique for order preference by similarity to ideal solution (FTOPSIS) is utilized to determine the optimal IM alternatives. First, the FPSDA method in which the interval PSDA is applied to evaluate the IM performance is developed. The interval results are transformed into triangular fuzzy numbers to establish a fuzzy decision-making matrix. Subsequently, the FAHP is employed to estimate the importance of each evaluation criterion. Then, FAHP–FTOPSIS is utilized to rank the orders of the IM alternatives and select the optimal IM. An illustrative application of the proposed methodology to a five-story reinforced concrete frame structure is presented. The decision results demonstrate that by considering the maximum inter-story displacement angle (θmax), top displacement (Dt), maximum floor velocity (Vmax) and maximum floor acceleration (Amax) as engineering demand parameters (EDPs), the average spectral displacement (Sdam), Sdam, average spectral velocity (Svam), and Vamvatsikos spectral acceleration (VSa2) are the most optimal IMs, respectively. The decision-making results for multiple EDPs indicate that Svam is the optimal IM. Furthermore, the Cordova spectral acceleration (CSa) considering period prolongation has the highest closeness coefficient among the acceleration-related IMs. To verify the effectiveness of the new framework and methodology, the performance of the proposed approach is compared with that of the traditional MCDM method while ignoring fuzziness. The proposed methodology can be applied to other engineering structures and provide a reference for solving similar problems.

Seismic Vulnerability Analysis of Masonry Structures Built with Disassembled Brick Wall Sections

Disassembling brick wall pieces into brick wall sections and constructing masonry buildings with disassembled brick wall sections (DBWSs) can reduce construction waste production at source and help achieve carbon peak and carbon neutrality. A finite element model (FEM) for typical MSBD is established based on the calibrated finite element analysis method to evaluate the seismic performance of masonry structures built with disassembled brick wall sections (MSBD). Subsequently, the peak ground acceleration is selected as the ground motion intensity index, and the maximum inter-story displacement angle is chosen as the structural damage index. The 20 ground motion records are selected and scaled by peak acceleration in 0.2 g steps to form 120 structure-ground vibration samples for incremental dynamic analysis (IDA) and seismic vulnerability analysis. The IDA results indicated that with the gradual increase in peak ground acceleration, the maximum inter-story displacement angle increases and the model transits from the elastic stage to the elastoplastic stage. Because the characteristics of ground motion records are different, the order of structural plasticity development will be different and the number of ground motion records needs to be considered in the seismic performance assessment. The calculation model will not collapse under the 7 and 8 degree design-based earthquake and the probability of moderate and severe damage of the structure under the rare earthquake is minimal, according to the seismic vulnerability curves. The seismic vulnerability analysis results indicate that MSBD has good seismic performance under earthquakes and meets the requirements of “perfect subjected to frequent earthquake, reparable subjected to design based earthquake, no collapse subjected to rare earthquake.” The seismic vulnerability analysis based on probability statistics can provide a reference for seismic design and evaluation of earthquake damage.

Experimental study on seismic behaviors of prefabricated embedded concrete-filled steel tube special-shaped column exterior frame

The new type of prefabricated embedded concrete-filled steel tube (CFST) special-shaped column structure delivers green and environmentally-friendly strengths and high space. In this study, a full-scale frame test piece with one frame façade, two stories and two spans are designed and fabricated for purposes of exploring the seismic performance and node connection safety of filled built-in steel tube concrete-filled special-shaped column, and low cyclic load testing is implemented. The bearing characteristics, deformation capacity, energy-dissipating capacity, ductility and stiffness degradation of the test piece are analyzed. The results showed that the failure mechanism is typical beam hinge mechanism. The fabricated beam-column and column-column connection nodes in this paper are safe and reliable. The hysteretic curve of fabricated embedded CFST special-shaped column is full, the ductility and energy dissipation capacity of fabricated embedded CFST special-shaped column are better than such indexes of ordinary reinforced concrete special-shaped column. The inter-story displacement angle is 1/32 when the test piece is damaged, being significantly higher than the limit value of elastic-plastic inter-story displacement angle of 1/50 under strong earthquake. The precast embedded steel-reinforced concrete special-shaped column structure is only required to be connected with steel ribs to significantly improve the construction speed and quality, delivering great economy.

Effect of confinement materials and damage degree on the seismic behavior of RRACFST columns

In order to investigate the influence of seismic pre-damage and reinforcement materials on seismic behavior of seismic-damaged rectangular recycled aggregate concrete-filled steel tubular (RRACFST) columns, seven columns were designed and manufactured, which composed of three undamaged RRACFST columns, two moderately pre-damaged RRACFST columns and two severely pre-damaged RRACFST columns. The inter-story displacement angle of 1/100 and 1/50 were used to simulate the moderate pre-damage and severe pre-damage of the specimens, which were then strengthened with carbon fiber reinforced polymer sheets (CFRPs) or enveloped-steel jacket (ESJ). The quasi-static destructive experiment results indicate that, with the increase of seismic pre-damage, the fullness and area of hysteresis curves decreases gradually, and the stiffness, energy dissipation capacity and deformation performance of specimens decrease significantly, due to different reinforcement materials. The average ductility coefficient and the average peak load of CFRPs and ESJ strengthened specimens were increased by 30.3%, 22.3%, 14.3%, 22.0%, 20.2%, 8.3% and 22.0%, 17.0%, 2.9%, 31.7%, 26.8%, 8.9% respectively. After being strengthened, the severely pre-damaged specimen, due to the moderate improvement of its ductility and bearing capacity, can resist earthquakes again. The research result will provide basis for the seismic evaluation and reinforcement technical specifications of the RRACFST structure.