Theoretical Analysis and Application Research on Grid String Branch Structure

In the paper, not only the internal force and displacement of structure during subway tunnel construction with cover and cut reverse method, but also the displacement field and stress field of surrounding rock are analysed. From the numerical calculation it is shown that the bending moment of diaphragm wall is affected seriously by the distribution and value of the stiffness of horizontal support; the excavation phase of the soil of the second floor underground is the key phase of the construction process because the internal force of structure has large increase; the value of surface settlement, horizontal displacement of diaphragm wall, differential settlement between middle pillar and diaphragm walls all meet the requirements, so the construction is safe and the surrounding buildings are affected slightly.

Study on the structural behavior and reinforcement design of openings in subway station floor slabs

The purpose of this study is to investigate the impact behavior of composite pressure vessel (CPV) in‐service case. Additionally, graphene nanoplatelets (GnPs) were introduced to epoxy resin. [±55°]4 basalt/epoxy specimens were manufactured using the filament‐winding method, and the low‐velocity impact (LVI) response was investigated. The LVI tests of CPVs were performed at energy levels of 2.5, 5, 7.5, 10, 15, 20, and 25 J under 50 bar internal pressure. The prestress value considering the internal pressure used under service conditions was taken as 1:5 of the burst pressure of the basalt/epoxy CPVs. After the LVI tests, the contact force–time and force–displacement curves were acquired. Also, absorbed energy values by CPVs were calculated over the obtained curves. The effects of GnPs on damage formations on basalt/epoxy CPVs under LVI loads were evaluated based on microscopic analysis. According to evaluations, damage formations such as matrix cracks on outer and inner surfaces of CPV, transverse cracks, and delamination were detected. Test liquid was detected on the impact surface at 25 J LVI test. The leakage observed due to the 25 J impact energy proves that damages can result in a leakage path. Consequently, the areas of damage formed in the cross sections perpendicular to the axis of basalt/epoxy CPVs decrease with the addition of GnPs, and the CPVs are more resistant to LVI effects.

In this paper, the kinetic characteristics of high voltage power transformer under short-circuit operation are simulated and the influence of prestress is analyzed for the winding stability. Firstly, the finite element method (FEM) is applied to calculate the leakage magnetic field of transformer and electromagnetic force of windings. Secondly, the axial electromagnetic force under short-circuit condition acts on the transformer windings, which are regarded as complex viscoelastic system. The characteristics of the vibration responses, such as dynamic displacement and dynamic force, are illustrated and their frequency responses are analyzed. Finally, the relationship between prestress and peak value of dynamic force, and as well as displacements of each pancake coil, are discussed.

Seismic pounding is defined as the collision of structures during earthquakes when these structures have different dynamic characteristics. It is an instance of rapid strong pulsation like hammering and repeated heavy blows. This pounding of closely spacedbuildings can be seen largely in some densely populated urban areas. Some modern codes have included seismic separation gap requirement clauses for adjacent structures but since large parts of metropolitan cities in seismically active regions of India were built before such requirements were introduced, the seismic separation gap requirements have not been fulfilled. Pounding can be catastrophic and even more dangerous than the effect of earthquakes on a single building. Thus, the action of pounding of buildings needs to be mitigated to avoid loss of life and property during earthquakes. The problem of pounding is particularly common in many cities in India, located in seismically active zones, where due to various socio-economic factors and land usage requirements, buildings are often constructed crowded together. This paper is focused on the study of the seismic pounding between two RC buildings with different dynamic characteristics. A systematic study of response of seismic pounding between adjacent buildings and seismic hazard mitigation practices like effect of different separation distances and effect of providing dampers are investigated, using the ETABS software. A 12-storey and a 16-storey building have been considered for the study of pounding. Time history analysis is carried out for seven real earthquake ground motions on the models with varying separation gaps. The results were obtained in the form of pounding force and point displacements. It is revealed that the pounding effect varies inverselywith the separation distance. With increasing separation distance pounding effect is reduced greatly and so the damage to the neighbouring buildings is also minimized. Also, the pounding forces are seen to be decreasing considerably between the adjacent buildings due to the provision of dampers at suitable locations, as compared to the case of adjacent buildings without dampers. The study even confirms that the pounding effect can be mitigated considerably by installing dampers between adjacent structures.Dampers modelled in this study prove to be effective in reducing the displacement and driftin the range of15%-20%

The internal forces in a prestressed concrete structure are of special nature due to the existence of tendons. And flaws can be found in the traditional concept of secondary moment such that common computation method of secondary moment may produce unreasonable results. This article aims at getting a better understanding of internal forces in prestressed structures and solving the relevant problems. Starting from the basic principles of internal force analysis, a new system of internal forces is put forward by which the relationship between the compression resultant on concrete cross-section and the sectional internal forces is made clear. On this basis, a definition on the concept of current secondary moment (Mcs) is proposed and its superiority pointed out. Finally, theoretical analyses are carried out on the method for calculating Mcs in the posttentioned continuous beams with unbonded and bonded prestressing tendons.

Torsional deformation may occur in plan-asymmetric wall structures during seismic events. In most current seismic design codes, the torsional deformation is handled using the concept of design eccentricity, in which design loads may be excessively amplified. This approach has limitations in accurately estimating the torsional deformation of the plan-asymmetric structures, mainly because it is based on linear elastic material behavior. In this paper, we propose a simple method that can accurately evaluate the inelastic lateral displacement and rotation of plan-asymmetric wall structures and is suitable for use in the displacement-based design method. The effectiveness of the proposed method is verified by comparing its predictions with the results of rigorous time history analyses for a model problem. The comparison shows that the proposed method is able to provide accurate estimates of the inelastic torsional deformation for the plan-asymmetric wall system, while requiring less computational cost than the time history analysis.

A simplified seismic design procedure for steel structures with buckling-restrained braces (BRB) was proposed based on the energy balance concept and the equal energy assumption. The input seismic energy was estimated from a design spectrum, and the elastic and hysteretic energy were computed using energy balance concept. The size of braces was determined so that the hysteretic energy demand was equal to the hysteretic energy dissipated by the BRB. The validity of using equivalent single-degree-of- freedom systems to estimate seismic input and hysteretic energy demand in multi story structures with BRB was investigated through time-history analysis. The story-wise distribution pattern of hysteretic energy demands was also obtained and was applied in the design process. According to analysis results, the maximum displacements of the 3-story structure designed in accordance with the proposed procedure generally coincided with the target displacements on the conservative side. The maximum displacements of the 6- and 8-story structures, however, turned out to be somewhat smaller than the target values due to the participation of higher vibration modes.

Timely and accurate acquisition of the dynamic morphological characteristics of flexible cable structures is crucial for mitigating entanglement risks in tethered satellite systems and ensuring operational safety in deep-sea exploration. In this study, a shape-reconstruction method that integrates the Rotation-Minimizing Frame (RMF) theory with Optical Frequency Domain Reflectometry (OFDR)-based distributed fiber-optic sensing is proposed. This method overcomes the limitations of the classical Frenet frame, particularly its inability to define torsion at zero-curvature segments and its inherent instability during spatial curve evolution. By leveraging the optical fibers embedded within the cable as distributed sensors, the proposed approach enables high-resolution measurement of strain distribution along the entire length of flexible cable structures. An experimental platform for shape monitoring based on distributed fiber-optic sensing is constructed, and functional validation is carried out under representative loading conditions. The results demonstrate that the developed method provides essential technical support for health monitoring and digital-twin construction of space tethered-satellite systems and deep-sea flexible umbilical cables.

The anti-seismic and isolation simulation analysis of a 220 kV GIS equipment is carried out using finite element software. The response spectroscopy method is used to simulate the displacement and acceleration dynamic response of the whole structure under the two working conditions before and after the isolation device is installed, and to analyze the change of the natural frequency of the structure. The results show that the relative deformation of 220 kV GIS equipment is smaller than before isolation, and the vibration characteristics of the overall structure are close to the single-particle model, and the structure’s seismic performance is significantly enhanced for the maximum acceleration of the overall structure is reduced by 90%.

As an important functional component of the laser optical system, the laser support structure plays a key role in the Laser beam quality, stability and system efficiency of the laser. The static and dynamic characteristics of Laser support structure were analyzed based on ANSYS Workbench. The relationship between the modal frequency and the structural mode were determined, and the weak part of the shell was obtained. The laser shell was optimized by adding the stiffened plate. The optimization of structure has obtained the good effect. The result provides a reference for later design optimization of Laser design.

Unseating damages of bridge decks have been observed in many previous major earthquakes due to large relative displacement exceeding the available seat length. Steel cable restrainers are often used to limit such relative displacements. Present restrainer design methods are based on the relative displacements caused by the different dynamic characteristics of adjacent bridge structures. However, the relative displacements in bridge structures are not only caused by different dynamic characteristics of adjacent bridge segments. Recent studies indicated that differential ground motions at supports of bridge piers and Soil Structure Interaction (SSI) could have a significant influence on the relative displacement of adjacent bridge components. Thus the present design methods could significantly underestimate the relative displacement responses of the adjacent bridge components and the stiffness of the restrainers required to limit these displacements. None of the previous investigations considered the effects of spatially varying ground motions in evaluating the adequacy of the restrainers design methods. Moreover, the code recommendation of adjusting the fundamental frequencies of adjacent bridge structures close to each other to mitigate relative displacement induced damages is developed based on the uniform ground motion assumption. Investigations on its effectiveness to mitigate the relative displacement induced damages on the bridge structures subjected to spatially varying ground motion and SSI are made. This paper discusses the effects of spatially varying ground motions and SSI on the responses of the multiple-frame bridges with unseating restrainers through inelastic bridge response analysis.

Dynamic asymmetry of piezoelectric shell structures

A core system for buildings has been recognized as an effective tool for managing the response of the building when an earthquake happens by decoupling the building structure from potentially damaging earthquake-induced forces. A challenging issue in this context is the application of the configuration of the core system. A review of recent studies shows that the configuration of cores has not been substantial investigated. This study presents seismic design concepts in which different configurations of cores are applied to a building. Nine steel buildings were modeled with rectangular core, octagon core, circle core, lozenge core, cross core, multi core, irregular core 1, and irregular core 2. All structural models are subjected to components of the 1940 El Centro earthquake and are evaluated and compared with the response of a structure without core. All models were also compared with and without opening in cores. The performance of the structural models under seismic excitation was evaluated by conducting linear dynamic time history analysis. Seismic results are investigated in terms of joint displacement and structure internal member forces. Results show that the presence of irregular core 1 significantly reduces the seismic response of the structure in this plane.

Photovoltaic materials, which can directly turn light energy into electric energy, can offer the advantage of generating large voltages without external power supplies. When a near ultraviolet light illuminates on polarized PbLaZrTi (PLZT) materials, an electrical field can be generated along the spontaneous polarization direction due to the phovoltaic effect. This voltage generation mechanism exhibits many advantages, such as (1) high electrical output voltage, (2) wireless energy generation, (3) immune from electric/magnetic disturbances, (4) remote or non-contact control. In this study, Distributed vibration control of cylindrical shells using a hybrid photovoltaic/piezoelectric actuation mechanism is investigated. The light-driven photovoltaic generator induced voltage is used to drive a skew-quad piezoelectric actuator which can induce non-uniform control froces and control moments. Based on theoretical analysis and experimental validation, the constitutive equations defining the piezoelectric actuator induced actuation strain under the actuation mechanism are presented. Each region of the actuator system can induce both positive and negative control forces and moments using logical switches to shift the sign of control voltage of actuator system. Control effectiveness with constant light intensity control algorithm is evaluated and the time history analysis is presented.