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In order to improve the seismic resistance capacity of the multi-storey gymnasium frame, based on the finite element analysis method, the dynamic response characteristics were analyzed, and the natural frequencies and vibration modes were obtained. Based on the results of the modal analysis, different reinforcement methods were proposed for verification. Under the excitation conditions of Borego waves, the vibration responses of different nodes in initial model were obtained. Modal verification was carried out by using two methods of shear strengthening and support rod strengthening respectively. The analysis results show that the bearing capacity of the single-span frame is insufficient, the lateral stiffness is small, and it is prone to cause severe torsional vibration damage. It can also be known that the seismic resistance capacity of the support rods reinforcement is more balanced in different directions. It can not only effectively improve the lateral stiffness and bearing capacity of the structure, but also improve the seismic performance of the main structure through the energy dissipation of component yield, which is more suitable for multi-story buildings. [ABSTRACT FROM AUTHOR]

The gymnasium is mainly composed of truss structure, with a large span, and requires high seismic performance. To ensure greater stability of the truss structure, modal analysis was conducted on the mechanical model, yielding the natural frequencies and modal shapes. In order to improve the seismic performance, BRB rods were added to the support points, and the frame structure was reinforced with diagonal braces. Through modal verification, it can be seen that the stiffness of the truss structure was significantly improved. The internal forces of the truss were simulated under the El Centro and Taft seismic wave conditions. The results show that the optimized structure can significantly reduce the internal forces and improve the overall seismic performance. The fundamental natural period of the reinforced structure is less than that of the unreinforced structure, and the stiffness of the reinforced steel structure increases, making it more sensitive to vertical seismic motion. [ABSTRACT FROM AUTHOR]

Introduction. Research was carried out on the performance of monolithic reinforced concrete buildings of varying heights with and without a seismic isolating sliding belt when subjected to the most unfavourable earthquake accelerograms. The objective of the study is to assess the effectiveness of seismic isolation in the form of a sliding belt at the foundation level under the action of the most unfavourable earthquake accelerograms using a direct nonlinear dynamic method.Materials and methods. The study employed a direct dynamic method based on an explicit integration scheme of the equation of motion (the central difference method). To determine the most unfavourable earthquake accelerograms, a method was used that accounted for all the most significant natural frequencies of the building under consideration.Results. Based on the calculations conducted, relative displacements and stress intensities for the building as a whole and in detail for the most loaded floor were determined. The analysis of the obtained results showed a significant reduction in shear displacements and stress intensities with the use of seismic isolation in the form of a sliding belt at the foundation level.Conclusions. When selecting the type of seismic isolation, its cost, as well as the labour intensity of manufacturing and installation, must be considered. It is necessary for the seismic isolation systems used to be available for mass construction, less complex, and maximally effective. Proven materials and technologies for the installation of these systems, which do not require specific skills and qualifications, should be used. Seismic isolation should provide comprehensive protection against the most likely seismic impacts. Conducted research shows that the seismic isolating sliding belt meets the above requirements. Unlike widely used rubber-metallic and pendulum sliding bearings, seismic isolation in the form of a sliding belt at the foundation level does not require factory manufacturing and can be implemented directly at the construction site.

The consequences of destructive earthquakes show that the problem of analyzing the response of reinforced concrete frames under seismic loads after a fire is relevant. The calculation models used for individual elements and buildings as a whole must take into account the nonlinear properties of concrete and reinforcement. In the spectral calculation method, the nonlinear properties of materials are taken into account by introducing a reduction coefficient to the elastic spectrum. When determining the reduction coefficient, a common deformation criterion is based on the use of the plasticity coefficient. The seismic resistance of a three-span, five-story reinforced concrete frame under four different fire exposure options is considered. The residual strength and stiffness of frame elements after a fire is assessed by performing a thermal engineering calculation in the SOLIDWORKS software for a standard fire. For the central sections of the elements, the highest temperatures were obtained after heating—during the cooling stage. The reduction coefficient is estimated by performing a nonlinear static analysis of reinforced concrete frames in OpenSees and constructing load-bearing capacity curves. Fracture patterns and damage levels in plastic hinges are analyzed. Based on the numerical modeling of reinforced concrete frames after exposure to fire, it was revealed that the most dangerous scenario is the occurrence of a fire on the first floor of the building. Based on the obtained plasticity coefficients, reduction coefficients were determined in the range of 2.62 to 2.44. The influence of fire on the permissible damage coefficient of a reinforced concrete frame is assessed using the coefficient φK—the coefficient of additional damage after a fire, which is equal to the ratio of the reduction coefficients for the control and fire-damaged frames. Depending on the percentage of damaged structures on the first floor, the following values were obtained: 50% or less—φK = 1.09; 100%—φK = 1.17. The obtained coefficients are recommended to be used when assessing the seismic resistance of a reinforced concrete frame after a local fire. [ABSTRACT FROM AUTHOR]

This work is dedicated to theoretical and experimental research on constructing a digital twin for a 24‐story building located in a seismic zone with the possibility of seismic vibrations of up to eight on the Richter scale. A digital model of the building was developed considering the changes in its geometry (damage or absence of structural elements). This requires detailed field inspections of partially constructed buildings and consideration of the inspection results when constructing a digital model. The boundary conditions, in addition to the geometric characteristics of the building, include the physical and mechanical characteristics of all its structural elements obtained through nondestructive testing methods. Discrepancies between the structural elements' design and actual concrete classes were identified. The initial conditions included real accelerograms at the location of the building, which served as input data for the direct dynamic analysis. Thus, there is a need to develop a hybrid system for modeling the stress–strain state of a 24‐story building that uses information technologies (Internet of Things) with sensors during research. Such an IoT system, combined with one information network using cloud technologies, allows us to obtain the necessary information in real‐time, highlighting the features of the building (the second stage of constructing the digital twin). The bar and spatial models of buildings with distributed parameters of structural stiffness at bending and shear and the mass and mass moment of inertia were considered. The results of numerical studies of the first form of natural vibrations for the building rod (according to the expressions obtained by the authors) and spatial models (performed using the LIRA‐CAD software package developed in Ukraine based on the finite element method) are presented. A comparison with the first experimental form of natural vibrations confirmed that considering the moment of inertia of the building mass makes it possible to determine the ordinates of the self‐form of vibrations and seismic horizontal loads more accurately. The experimental first frequency and form of natural vibrations of a 24‐story residential building in Odesa were obtained from the results of vibration monitoring at the construction stage (16 floors were erected) and after all 24‐floor erection. The direct dynamic method of building calculations for seismic effects specified by earthquake accelerograms was used along with the method proposed by the authors to consider damping during forced building vibration calculations and the actual physical and mechanical characteristics of concrete and reinforcement obtained by non‐destructive testing methods. The calculated vibration amplitudes at the top of the building cantilever model were compared with the damping parameters obtained using the Voicht model and the authors' method under the influence of an accelerogram recorded during the powerful 1977 Bucharest earthquake with an epicenter in the Vrancea area (Romanian Carpathians). [ABSTRACT FROM AUTHOR]

This study is dedicated to advancing practical and experimental knowledge within sustainable construction and enhancing community productivity, focusing on cattail schoenoplectus californicus, Cyperaceae fibers in Imbabura, Ecuador. The research aims to meticulously analyze and understand cattail fibers' physical and mechanical properties, characteristics, and potential applications through extensive laboratory testing. The study strives to contribute significantly to the ongoing discussions surrounding sustainable building materials by offering a rich repository of scientific data and insights from our in-depth investigations. Furthermore, we delve into biotechnology and biomimicry, seeking inspiration from the natural world to innovate our construction methodologies. Our exploration also encompasses the technical dimensions of a building, artisanal craftsmanship, eco-conscious design principles, and the evaluation of seismic strength within architectural, structural, and acoustical design frameworks. Through this comprehensive approach, we aspire to illuminate new pathways for employing cattail in sustainable construction practices. [ABSTRACT FROM AUTHOR]

The object of research is seismic design, and the subject of the study is the determination of the reduction coefficient. One of the important problems of earthquake-resistant design is to determine the effect of low-cycle fatigue of reinforced concrete on the reduction coefficient and determine its optimal value. This problem is not disclosed and is not specifically taken into account in the standards for earthquake engineering when determining the maximum bearing capacity of types of structures due to the lack of study of the issue. To solve the problem, a series of experimental studies were carried out on low-cycle fatigue of reinforced concrete bending elements and frame units. The range of results of the reduction coefficient values and the degree of influence of monocyclic fatigue on the properties of the reduction coefficient are obtained. A feature and characteristic of the results obtained is that the reduction coefficient Rμ depends on the nature of the hysteresis deformation pattern and the plastic life of structural elements estimated by the plasticity coefficient μ, which is significantly influenced by low-cycle fatigue manifested at peak accelerations of strong seismic impacts. The above test algorithm, the feature and characteristics of the results obtained made it possible to solve the problem under study. The results obtained are accepted for practical use in the action of seismic loads: on the calculation of strength taking into account new low-cycle coefficients, reduction coefficients for determining the spectra of design reactions and seismic loads, taking into account energy absorption. New reduction coefficients are proposed for determining the spectra of calculated reactions and seismic loads. [ABSTRACT FROM AUTHOR]

Introduction. At the present time, when calculating structures for seismic effects, usually only the translational components of seismic effects are taken into account. However, the analysis of emerging defects in buildings and structures subjected to seismic action indicates the spatial nature of structural behavior, which indicates the necessity to take into account also the rotational components of seismic action in the design of all buildings and structures in seismic regions. The objective of this study is to assess the influence of rotational components on the stress-strain state of simple systems. In the scope of this study, the rotational components of accelerograms are obtained from both the action of only one translational component and from the action of two translational components of seismic action for an integral seismic motion model; and the equation of motion has been derived considering them.Materials and methods. The differential equations of motion for the investigated systems were solved in both planar and spatial settings. The problem in the plane formulation was solved using the central differences method in LS-DYNA software and the fourth-order Runge – Kutta method in the MATLAB software, considering one translational component and also considering one translational and one rotational component. The problem in the spatial setting was solved in the LS-DYNA software, considering only three spatial components and also considering three translational and three rotational components.Results. During the study, maximum and minimum displacement values and von Mises stress values were obtained, resulting from the action of only translational components and from the combined action of translational and rotational components.Conclusions. Based on the results of the study, a comparative analysis was conducted, leading to the conclusion that the influence of rotational components of seismic action on the stress-strain state of the investigated systems is insignificant. However, the increase in the contribution of rotational components to the stress-strain state of the system is proportional to its height.

Through low-cycle reciprocating tests on 11 masonry wall specimens strengthened using reinforced-concrete–masonry composite columns, the effects of the position of the composite column, height-to-width ratio, column reinforcement ratio, and axial load ratio on their load-carrying capacity, stiffness, ductility, and energy dissipation capacity were investigated. It was experimentally found that, by strengthening brick walls with RC–masonry composite columns, the concrete and masonry parts can work together effectively, the failure mode shifts from shear to flexural failure, and the strengthened walls exhibit improved bearing capacity, ductility, and energy dissipation performance compared to unstrengthened masonry walls. It is suggested the composite columns can be placed at the ends of the wall if a strengthening measure is required. For walls with height-to-width ratios greater than 1, placing composite columns in the middle of a wall has little effect on the bearing capacity and stiffness of the wall but can improve the ductility of the wall. The height-to-width ratio is a primary factor influencing the structural performance of masonry walls strengthened using composite columns. A smaller height-to-width ratio leads to higher load-carrying capacity and stiffness but may result in reduced ductility. In comparison, the impact of the column reinforcement ratio and axial load ratio is relatively weaker. The flexural capacity of the masonry wall after strengthening can be obtained using the calculation method for concrete members subjected to a combined action of flexure and compression, in which the compressive strength of the masonry is considered. [ABSTRACT FROM AUTHOR]

There was a development of сomposite cements (CC), that include aluminosilicates (AS), obtained by enrichment of ash-to-slag mixture (up to 65 wt. %), cement clinker, and gypsum. Based on the developed CC, wide range of injection mortars, including crushed granite, was created. Injection mortars are capable of effectively fixing of underground structures foundations soils, providing high strength (25.6 MPa) with deformation modulus 10.1 GPa. These materials have percentage of water separation from 22.5 % at W/B=1 to 36.5 % at W/B=2. Viscosity indicators of these materials indicate high penetrating ability, since time for mortars to flow through Marsh viscometer is 39 and 33 seconds at W/B=1.5 and W/B=2, respectively. Effect of increasing density of injection mortars at 28 days was maximum at AS dosage of 45 wt. %, then it decreased with aluminosilicate content increase. There are high ratios of strength values on second day to those in grade age: for compressive strength 0.24 (0.20–0.22 for additive-free clinker compositions), for flexural strength 0.16 (0.15 for additive-free compositions; with AS content increase above 45 %, this ratio decreases to 0.14). High early strength makes it possible to effectively use injection mortars for urgent fixing of soils during the repair of underground structures.

Introduction. The objectives of this work are to study the influence of degradation of the frequency parameters of reinforced concrete buildings under the action of seismic loading and to evaluate the nature of destruction depending on the number of storeys of the building itself, using numerical experiments in the LS-DYNA software package. To obtain natural frequencies and forms at certain times in a problem solved by an explicit integration scheme, solutions are sought using an implicit scheme.Materials and methods. Five structures of different storeys are considered. The design schemes of the buildings use direct reinforcement of load-bearing elements. The Continuous Surface Cap Model (CSCM) is used to model the concrete. This material allows the accumulation of damage to be taken into account. The ideal elastic-plastic Prandtl model is used to model reinforcement. The reinforcement was modelled with rods and was directly immersed in concrete. To implement this, the Euler-Lagrange equation was used. The calculation was carried out on a rigid base, taking into account physical, geometric and structural non-linearities. The seismic impact was specified in the form of 2-component accelerograms normalized to 8 points on the MSK-64 scale.Results. Various results of the study were obtained. Curves of change and degradation of natural frequencies for frames of different number of storeys are obtained. Damage accumulation curves for the entire framework were also obtained.Conclusions. The analysis of the obtained results shows that during an earthquake with an intensity of 8 points, there is a significant (up to 30 %) reduction of frequencies of natural oscillations of the considered frames. The greatest amount of damage occurs at the stage of active phase of seismic impact. With the increase in the number of storeys, the intensity of degradation of natural frequencies increases, the rate of accumulation and the amount of damage increase.

Objective. This article is a continuation of the topic raised in the article “Systems with optimal geometric shapes”, published in the previous issue of this journal. The purpose of the study is to develop design diagrams and explanations for them, outline the principles of their operation, design features that provide the necessary seismic resistance.Method. To ensure adaptability, various design techniques are used: switching connections, switching connections, switching connections, buildings and structures consisting of various structural blocks having different frequencies of natural oscillations. Thus, the blocks of the building dampen each other during vibrations, thereby providing the necessary seismic resistance during earthquakes.Result. Structural systems with adaptive properties that impart high seismic resistance to buildings and structures are presented.Conclusion. The design techniques outlined in the article ensure high seismic resistance of buildings and structures, which can be used in the practice of designing and constructing earthquake-resistant systems.

Analytical, computer and experimental modeling methods are applied in the study of seismic resistance and changing dynamic parameters of long-term loaded non-linearly deformed large-span spatial shell structures. Physically and geometrically nonlinear deformation models and computational algorithms for solving dynamic problems are proposed for estimating the stress-strain state of smooth and ribbed spatial systems with variable stiffness caused by damage accumulation and orthotropic structure reinforced by ribs. The possibility of using the proposed method of taking into account variable dynamic stiffness in calculations for solving problems of dynamic strength and stability of spatial large-span shells of unique buildings of complex geometry is shown.

The consequences of destructive earthquakes show that the problem of analyzing the response of reinforced concrete frames under seismic loads after a fire is relevant. The calculation models used for individual elements and buildings as a whole must take into account the nonlinear properties of concrete and reinforcement. In the spectral calculation method, the nonlinear properties of materials are taken into account by introducing a reduction coefficient to the elastic spectrum. When determining the reduction coefficient, a common deformation criterion is based on the use of the plasticity coefficient. The seismic resistance of a three-span, five-story reinforced concrete frame under four different fire exposure options is considered. The residual strength and stiffness of frame elements after a fire is assessed by performing a thermal engineering calculation in the SOLIDWORKS software for a standard fire. For the central sections of the elements, the highest temperatures were obtained after heating—during the cooling stage. The reduction coefficient is estimated by performing a nonlinear static analysis of reinforced concrete frames in OpenSees and constructing load-bearing capacity curves. Fracture patterns and damage levels in plastic hinges are analyzed. Based on the numerical modeling of reinforced concrete frames after exposure to fire, it was revealed that the most dangerous scenario is the occurrence of a fire on the first floor of the building. Based on the obtained plasticity coefficients, reduction coefficients were determined in the range of 2.62 to 2.44. The influence of fire on the permissible damage coefficient of a reinforced concrete frame is assessed using the coefficient φK—the coefficient of additional damage after a fire, which is equal to the ratio of the reduction coefficients for the control and fire-damaged frames. Depending on the percentage of damaged structures on the first floor, the following values were obtained: 50% or less—φK = 1.09; 100%—φK = 1.17. The obtained coefficients are recommended to be used when assessing the seismic resistance of a reinforced concrete frame after a local fire.

Introduction. The consequences of destructive earthquakes show that the problem of analyzing the response of reinforced concrete frames under seismic loads after a fire is urgent. The calculation models applied in this case for individual elements and buildings as a whole should take into account the nonlinear properties of concrete and reinforcement. The low-cycle nature of seismic action leads to the necessity of developing hysteresis models, which would reflect the specific behaviour of the structure not only during loading but also during unloading and subsequent application of force in the opposite direction. A brief review of hysteresis models for reinforced concrete elements under low-cycle loading with emphasis on the stiffness properties during unloading is presented. Hysteresis models for reinforced concrete elements after fire have not been developed at present.Materials and methods. The proposed model is based on a bilinear diagram for the calculation eccentrically compressed reinforced concrete columns damaged by fire. Only three parameters are required to describe the model: limiting moment, limiting curvature, and effective initial stiffness. In determining the unloading stiffness, a method based on direct consideration of the stress and strain distribution in the stress-strain stage corresponding to full unloading is used. The model takes into account different levels of axial loading, indirect reinforcement by transverse clamps, longitudinal bending and non-uniform stress distribution in the compressed zone of concrete.Results. Based on the proposed model, a comparison of bilinear diagrams of deformation and stiffness at unloading for reinforced concrete columns subjected to standard fire of different duration was carried out. Calculation results showed a significant decrease in the bearing capacity and stiffness of the damaged columns and an increase in their plasticity. The unloading stiffness for reinforced concrete columns was less than the initial one. The decrease in unloading stiffness is the more intensive the longer the fire exposure was.Conclusions. The obtained model is easy to use and suitable for most engineering calculations. The model can be used as a basis for constructing a hysteresis diagram for low-cycle impacts after a fire, which is necessary for seismic analysis of structures in the time domain.

El territorio de la República del Ecuador presenta una alta sismicidad. En Ecuador el 95.9% de estructuras de vivienda son construidas con el uso de mamposterías. Se observa que entre los profesionales de la construcción en Ecuador existe un desconocimiento generalizado sobre las propiedades de los materiales constitutivos de las mamposterías y las normas para su diseño estructural. Tal desconocimiento ha generado la proliferación de construcciones que no cumplen con estándares técnicos de sismorresistencia y seguridad estructural, lo que puede generar considerables pérdidas económicas y sobre todo poner en riesgo la integridad física de las personas. El objetivo de esta investigación es determinar de manera cuantitativa la realidad local sobre el conocimiento técnico y uso de mamposterías en Ecuador. Los resultados evidencian principalmente que, el 82% de profesionales de la construcción son profesionales jóvenes; el 33.8% no supera los 30 años de edad; el 51.2% posee una experiencia profesional menor a 5 años; el 71% nunca o casi nunca realiza el diseño estructural incluyendo las mamposterías como elementos del sistema estructural; el 81% nunca recibió contenidos académicos sobre diseño estructural de mamposterías durante sus estudios superiores en Ecuador; existe un desconocimiento generalizado sobre las propiedades mecánicas de los materiales para mamposterías y la norma ecuatoriana para el diseño de mampostería estructural presenta importantes falencias. Abstract The territory of the Republic of Ecuador has a high seismicity. In Ecuador, 95.9% of housing structures are built with the use of masonry. It is observed that among construction professionals in Ecuador there is a general lack of knowledge about the properties of the constituent materials of masonry and the standards for their structural design. This lack of knowledge has led to the proliferation of constructions that do not comply with technical standards of seismic resistance and structural safety, which can generate considerable economic losses and, above all, put the physical integrity of people at risk. The objective of this research is to quantitatively determine the local reality of the technical knowledge and use of masonry in Ecuador. The results show that 82% of construction professionals are young professionals; 33.8% are under 30 years of age; 51.2% have less than 5 years of professional experience; 71% never or almost never carry out structural design including masonry as elements of the structural system; 81% never received academic content on structural design of masonry during their higher education in Ecuador; there is a general lack of knowledge about the mechanical properties of masonry materials and the Ecuadorian standard for the design of structural masonry has significant shortcomings.

In this study, the test of reinforced concrete (RC) frames protected with bracing-friction dampers is simulated via a finite element analysis, based on the new connecting method in which a deformed steel bar is passed through a RC frame. Moreover, the influence of the diameter difference of the deformed steel bar on the behaviors of the RC frame and damper is examined. The bar yielded when the diameter of the deformed steel bar was reduced. Therefore, the degree of crack closure in the RC beam after unloading was low, and it was difficult to produce a stable damper axial deformation. [ABSTRACT FROM AUTHOR]

When performing structural calculations for dynamic loads including seismic impacts, the STARK ES software package allows to implement various damping models. In this paper, a comparative analysis of three types of the damping models used to increase the calculated seismic resistance of structures is carried out. These are the models of nonlinear viscous dampers, in which the reactive force depends non-linearly on the velocity of the rod movement, equivalent (for an energy dissipated) linear-viscous dampers and equivalent (for a maximum force and an energy dissipated) elastic – perfectly plastic elements. As an example, an analytical model of the structural system of a projected building on a site with a seismicity of more than 8th intensity level is used.

A quantitative study is performed to determine the performance degradation of Y-shaped reinforced concrete bridge piers owing to long-term freeze-thaw damage. The piers are discretized into spatial solid elements using the ANSYS Workbench finite element analysis software, and a spatial model is established. The analysis addresses the mechanical performance of the piers under monotonic loading, and their seismic performance under low-cycle repeated loading. The influence of the number of freeze-thaw cycles, axial compression ratio, and loading direction on the pier bearing capacity index and seismic performance index is investigated. The results show that freeze-thaw damage has an adverse effect on the ultimate bearing capacity and seismic performance of Y-shaped bridge piers in the transverse and longitudinal directions. The pier peak load and displacement ductility coefficient decrease with increasing number of freeze-thaw cycles. The axial compression ratio is an important factor that affects the pier ultimate bearing capacity and seismic performance. Upon increasing the axial compression ratio, the pier peak load increases and the displacement ductility coefficient decreases, the effects of which are more significant in the longitudinal direction.

In Europe, a monopile is the most commonly used foundation type for offshore wind turbines. Existing connections between the monopile (MP) and transition piece (TP) are generally bolts or grout, but another new method is the slip joint. In this method, the joints between the MP and TP are conically shaped and are simply joined together, which is expected to improve workability and reduce maintenance and management costs. In order to apply this structure in Japan, it is necessary to verify its seismic resistance. This paper reports the results of shaking table tests using a scaled specimen to verify the structural safety of the structure against earthquakes. [ABSTRACT FROM AUTHOR]

Low-cycle fatigue testing was carried out for the welded joints of constructional steels containing 0% V + 0.0021% N and 0.10% V + 0.0078% N, and the effects of V-N microalloying on the low-cycle fatigue property of the welded joints were investigated. The results showed that when the total strain amplitudes were 1.2%, 1.4% and 1.6%, the mean low-cycle fatigue lives of the welded joints of steel containing 0.10% V + 0.0078% N were 5050, 2372 and 1535 cycles, respectively, which were significantly higher than those of the welded joints of steel containing 0% V + 0.0021% N; however, when the total strain amplitudes increased to 1.8% and 2.0%, the mean low-cycle fatigue lives of the welded joints of steel containing 0.10% V + 0.0078% N were 575 and 367 cycles, respectively, which were gradually lower than those of the welded joints of steel containing 0% V + 0.0021% N. The reasons causing the difference of low-cycle fatigue life were explained by the dislocation structure and precipitates in the welding heat-affected zone, plastic strain energy density of the welded joints, and fatigue fracture morphology. When the low-cycle fatigue life is between 100 and 200 cycles, the cyclic toughness of the welded joint of steel containing 0.10% V + 0.0078% N is between 57.48 and 78.22 J/cm3, which is higher than that of the welded joint of steel containing 0% V + 0.0021% N, indicating that the welded joint of steel containing 0.10% V + 0.0078% N is able to absorb more energy in a seismic condition, therefore possessing better seismic resistance. [ABSTRACT FROM AUTHOR]

In a seismic design of a pile foundation, a subgrade reaction generated with a displacement of piles when the seismic load is applied must be appropriately evaluated. The ratio of the subgrade reaction to the amount of displacement of a pile is defined as the subgrade reaction modulus (SRM). There are two ideas about the SRM's depth distribution: one assumes a constant depth distribution, while another assumes a monotonously increasing depth distribution. There are various types of pile foundations based on different inclination angles of a pile. In design practice, SRM is not seen as being dependent on the pile type. In this study, we targeted anchor piles with the main goal of bearing a horizontal load and conducted a horizontal loading experiment. We prepared a model considering that anchor piles are usually not embedded into the bedrock and evaluated the depth distribution of SRM by changing the inclination angle of the pile from 0 to 30° with 10° intervals. The experimental result showed that though SRM increases monotonously in the depth direction, the distribution was different from what was assumed in design practice, where a local maximum was present at a specific depth in the ground, and the value decreased below that depth. We then proposed equations to calculate the degree of change in SRM corresponding to the inclination angle of a pile. Furthermore, it was shown that the position of a local maximum for SRM depends on the location of the rotational center for the pile. [ABSTRACT FROM AUTHOR]

Copyright of ABE: Advances in Building Education is the property of Departamento de Tecnologia de la Edificacion, Universidad Politecnica de Madrid and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Through low-cycle reciprocating tests on 11 masonry wall specimens strengthened using reinforced-concrete–masonry composite columns, the effects of the position of the composite column, height-to-width ratio, column reinforcement ratio, and axial load ratio on their load-carrying capacity, stiffness, ductility, and energy dissipation capacity were investigated. It was experimentally found that, by strengthening brick walls with RC–masonry composite columns, the concrete and masonry parts can work together effectively, the failure mode shifts from shear to flexural failure, and the strengthened walls exhibit improved bearing capacity, ductility, and energy dissipation performance compared to unstrengthened masonry walls. It is suggested the composite columns can be placed at the ends of the wall if a strengthening measure is required. For walls with height-to-width ratios greater than 1, placing composite columns in the middle of a wall has little effect on the bearing capacity and stiffness of the wall but can improve the ductility of the wall. The height-to-width ratio is a primary factor influencing the structural performance of masonry walls strengthened using composite columns. A smaller height-to-width ratio leads to higher load-carrying capacity and stiffness but may result in reduced ductility. In comparison, the impact of the column reinforcement ratio and axial load ratio is relatively weaker. The flexural capacity of the masonry wall after strengthening can be obtained using the calculation method for concrete members subjected to a combined action of flexure and compression, in which the compressive strength of the masonry is considered.

The seismic resistance of nuclear power plant equipment and piping is determined, inter alia, by the seismic resistance of their steel supporting structures. During the operation of the nuclear power plant power unit, mechanical loads from the elements installed on them are transferred to the steel supporting structures of the equipment and piping. During an earthquake, seismic loads are added to these loads. By state building codes, when considering steel structures in special operating conditions (in particular, exposed to seismic hazards), it is necessary to comply with additional requirements that reflect the features of these structures. Given this, the issue of developing approaches to the compilation of load combinations in assessing the seismic resistance of steel supporting structures of nuclear power plants equipment and piping is acute, taking into account the specific conditions of their operation. The paper is also relevant as it is one of the priority areas of science and technology under the legislation of Ukraine. The development of approaches to the compilation of the calculated load combinations will contribute to the improvement and development of methods for assessing the safety of nuclear power facilities. The paper presents the results of the review of the provisions of state building codes on the calculated combinations of loads when assessing the strength of steel structures. Approaches to the compilation of the calculated load combinations in assessing seismic resistance of steel supporting structures power units of nuclear power plants equipment and piping taking into account the specific conditions of their operation have been developed.

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Walls, as components of the lateral-force-resisting system of a building, are defined as shear walls. This study aims to determine the behavior of shear wall panel cross-laminated-timber-based mangium wood (Acacia mangium Willd) (CLT-mangium) in earthquake-resistant prefabricated houses. The earthquake performance of CLT mangium frame shear walls panels has been studied using monotonic tests. The shear walls were constructed using CLT-mangium measuring 2400 mm × 1200 mm × 68 mm with various design patterns (straight sheathing, diagonal sheathing/45°, windowed shear wall with diagonal pattern and a door shear wall with a diagonal pattern). Shear wall testing was carried out using a racking test, and seismic force calculations were obtained using static equivalent earthquake analysis. CLT-mangium sheathing installed horizontally (straight sheathing) is relatively weak compared to the diagonal sheathing, but it is easier and more flexible to manufacture. The diagonal sheathing type is stronger and stiffer because it has triangulation properties, such as truss properties, but is more complicated to manufacture (less flexible). The type A design is suitable for low-intensity zones (2), and types B, D, E1 and E2 are suitable for moderate-intensity zones (3, 4), and type C is suitable for severe-intensity zones (5). [ABSTRACT FROM AUTHOR]

In this study, the Park–Ang damage model was refined based on the displacement and energy dissipation response behaviors of multi-ribbed steel-plate shear walls during earthquake. A novel method was developed to determine the inter-story displacement performance metrics of the steel-plate shear walls using damage indices. Building upon relevant experimental studies, the numerical modeling methods for the multi-ribbed low-yield-point steel-plate shear walls were validated based on relevant experimental research. By using the improved models, the effects of the wall height-to-thickness ratio, frame column dimensions, and wall-plate yield strength on the final displacement, displacement at yield, shear force at yield, and total energy dissipation of the shear walls were assessed. Further, an appropriate damage model based on the dual parameters of deformation and energy dissipation was developed for multi-ribbed steel-plate shear walls. The validity of the damage model was substantiated, while the damage index boundary values for various damage states were proposed as seismic performance objectives for the shear wall structures. The damage assessment results of the model correspond with the experimentally observed patterns. This study effectively describe the sequence of damage development in ribbed steel-plate shear walls and enables the accurate calculation of damage limits for a range of structural damage magnitudes, thereby providing benchmarks for the seismic design, assessment, and reliability analysis of such structural systems. • A refined damage model for multi-ribbed steel plate shear walls has been proposed. • A new method suggested for determining inter-story displacement metrics of steel plate shear walls using damage indices. • The damage evolution patterns of multi-ribbed steel plate shear walls have been ascertained. • The distribution of damage indices for various performance points of the component was illustrated. • The damage index thresholds serve as a benchmark for seismic design, assessment and reliability analysis of structural systems. [ABSTRACT FROM AUTHOR]

The results of experimental studies of the strength of masonry walls made of cellular concrete blocks under various force influences are presented. It is noted that the use of walls made of cellular concrete blocks with a density of D400-D600 in seismic areas can significantly reduce the magnitude of the seismic load on the structure. According to the results of the research, the behavior of the masonry under the action of loads modeling seismic impacts, considering its reinforcement with composite materials based on carbon fiber reinforced polymer (CFRP) and bazalt fiber reinforced polymer (BFRP). Data on tests on the vibration platform of full-size wall samples, considering external reinforcement with CFRP tapes, are presented. An increase in the seismic resistance of reinforced structures due to the use of composite materials has been revealed. The nature of the destruction of wall panels reinforced and non-reinforced with composite canvases is shown. According to the results of tests of fragments of walls made of cellular concrete blocks using reinforcement composite mesh based on basalt fiber, the effect of its use in axial stretching of masonry was noted. The use of a composite mesh with a 25×25 mm cell based on basalt fiber made it possible to increase the tensile strength of the masonry across the cross section by 28%. [ABSTRACT FROM AUTHOR]

In the paper, there was researched sensitivity of the criteria for evaluation of seismic resistance of reinforced structures (modes and frequencies of oscillations, displacements, and strains) in relation to various position of fire impact as exemplified by three-span five-storey reinforced concrete space frame. The relevance of the study is justified, the degree of the problem's development is grounded. There were analyzed the main lines of the research connected with experimental and numerical testing of both discrete structures and full-sized buildings. Numerical analysis was conducted by means of the software complex Ansys, the linear-spectral method was used. Fire impact is simulated by means of damages to reinforced concrete members in one of the building's units. 16 variants of points of fire outbreak were considered. According to the calculation results, it was stated that for all the variants of fire outbreak frequencies of self-oscillations for reinforced concrete frames after the fire had been found lower than for the non-damaged frame. The modal analysis has shown that the type of longitudinal and bending oscillations had undergone changes. The maximum amplitude of frames' oscillations after the fire was found insignificantly lower than for the non-damaged frame. Within the floor of fire outbreak location, the displacement increased immensely so that led to failure to comply with the value of inter-floor shifts and the increase of the 2nd order effects. Redistribution of bending moments in reinforced concrete framings was observed. The loading in damaged members decreased due to the members' strain capacity whereas the extra loading is added to the adjacent members. If compared with the case of the frame non-damaged by fire, overloading of columns can reach up to 20%. Conceptual description of fracture behavior of the frame is outlined assuming its non-linear behavior. The possible lines of further development are set for the methods of seismic analysis of the buildings with reinforced concrete frame after the event of fire. [ABSTRACT FROM AUTHOR]

For a unique building in the form of a tower with a core of rigidity in the center, experimental studies of natural oscillations by the standing wave method with theoretical calculations based on a finite element model are performed and compared. From the experiment, ten translational horizontal modes of natural oscillations, five torsional modes of natural oscillations, and eight vertical modes of natural oscillations were identified and investigated. The finite element model is used to calculate the natural oscillations corresponding to all experimentally isolated oscillation modes. The experiment and theory are compared over the entire set of natural frequencies. Differences in natural frequencies reached 20%. After the studies, if possible, correction of the computational model ensured the difference between the experiment and the theory in terms of the values of natural frequencies of no more than 7.5%. Verification of design models of buildings using the standing wave method is an effective approach to assessing the physical condition of buildings and their seismic resistance. [ABSTRACT FROM AUTHOR]

• The numerical model of a horizontally laid out gas-cooled micro-reactor was simplistically established and evaluated. • A collision test was conducted to determine the appropriate stiffness and damping values for the rigid body model. • A simple method for parameter identification is used to obtain the stiffness and damping parameters through collision tests. • The stress assessment was conducted to evaluate the graphite core using a probabilistic failure model. To evaluate the structural safety of the graphite core in a gas-cooled micro-reactor and to assess its structural response under seismic loads, a study was conducted. By comparing the acceleration and velocity curves obtained from small-sized graphite block collision experiments and collision simulations, it was determined that the simulation results accurately represent the real collision behavior of graphite blocks. The collision stiffness and damping parameters were derived from these curves. Subsequently, simulations of graphite components in the core were performed to establish the stiffness and damping parameters of the graphite blocks, which were then incorporated into the core analysis calculations. To validate the accuracy of the core numerical model and simplify the vibration form, the core model was divided into in-plane and axial models. A full-core model calculation was then carried out to determine the forces between graphite components. The final results confirm that the graphite core adheres to the ASME design specifications under seismic loads. [ABSTRACT FROM AUTHOR]

An algorithm to confirm the seismic resistance of equipment by a calculation method is proposed, and the limits of its application are determined. A mathematical model of the equipment is developed, and an example of the determination of natural frequencies and stresses for a three-dimensional structure is given. Two main types of calculation were used – static and dynamic. In the static calculation, the stress-strain state of a structure was determined. The values of the obtained stresses were compared with the allowable ones for the materials used, on the basis of which conclusions were made about the strength of the structure under seismic effects. The dynamic calculation resulted in the determination of the rigidity of the structure. The comparison of the stress values obtained for this equipment allowed us to make a conclusion regarding its resistance to seismic effects. The seismic resistance of the equipment was estimated on the example of the K-1000-60 / 1500 steam turbine condenser, and calculated at a seismic intensity of 6 points on the MSK-64 seismic intensity scale. In the course of solving this problem, results of the stress distribution in the housing and other structural elements of the condenser due to the action of combined normal operation and design-basis seismic loads were obtained. The seismic resistance of the equipment was calculated using the finite element method. This allowed us to present a solid body in the form of a set of individual finite elements that interact with each other in a finite number of nodal points. To these points are applied some interaction forces that characterize the influence of the distributed internal stresses applied along the real boundaries of adjacent elements. To perform such a calculation in CAD modeling software, a three-dimensional model was created. The obtained geometric model was imported into the software package, which significantly reduced complexity. The use of the calculation method allows us to significantly reduce the amount of testing when confirming the seismic resistance of equipment. Results of the assessment of the spatial complex stress state of the steam turbine condenser design due to the action of combined normal operation and design-basis seismic loads are obtained.

Guadua cane is a noble material, little exploited, sustainable, and economical, which has great physical and mechanical capacities, so it is very common to be used as a construction material, however, the structures of this material have a disadvantage compared to horizontal loads and are excessive displacements. For this reason, in this investigation the behavior of this type of structures was reviewed when they are joined with artisanal brick. For this, four hexagonal structures were built with Guadua angustifolia cane, Kunth 1822, reinforced with handcrafted brick masonry; For the joints, the Simón Vélez connection was used with a small modification in the shape of the hook. The structures were subjected to cyclic lateral loading to obtain the hysteresis curves, which allowed to determine ductility, secant stiffness and variation of viscous damping of the structures. The four structures presented an increase in resistance and controlled displacements in comparison with tests in structures without infill masonry. Therefore, it was concluded that the inclusion of artisanal brick masonry between the G. angustifolia cane structure significantly increases the resistance and rigidity of the structure, achieving a significant decrease in drift. [ABSTRACT FROM AUTHOR]

The revitalization of existing masonry buildings, built decades ago, is a very topical and complex structural engineering issue, especially when the building was built in the area of significant seismic activity. A large number of masonry buildings in the city of Niš, as well as in other places in Serbia, were built in the period before the adoption of technical regulations on the design and construction of seismically resistant structures and they are at insufficient safety level in the event of an earthquake. Therefore, it is necessary that structural strengthening meets the seismic resistance requirements laid down in Eurocode 8 or other relevant codes. In order to choose the method of structural strengthening, detailed seismic analyses must be carried out in several variants along with the application of relevant technical regulations. The effects of five analyzed structural strengthening methods were checked against the provisions of Eurocode 8, Part 1 and Part 3, which relate to the recommendations for the geometric characteristics of shear walls, and they were applied on two types of existing masonry buildings in Niš. On the basis of the performed analyses, conclusions were drawn regarding the methodological approach of the assessment of the condition of the structure, its seismic resistance and decision-making on remediation and/or strengthening measures.