Neural network-based metamodel for scaffolding behavior: Application for structural load analysis and safety enhancement

SummaryThere has been a significant increase in the size of building structures in recent years. Huge structures such as high‐rise buildings and large‐domed stadiums require high‐performance structural control, including the use of high‐capacity dampers, especially in an earthquake‐prone country like Japan. The objective of the present study was the enhancement of both human and structural safety in such structures through the development of a rate‐dependent type of damper with a high damping capacity. Among the various available types of rate‐dependent dampers, the authors focused on the oil damper owing to its stable performance against long‐duration vibrations. The target maximum damping force was 6000 kN, which is higher than that of any existing oil damper utilized in building structures. The authors developed a novel concept for achieving this high capacity while maintaining the size of the damper within acceptable dimensions from an architectural point of view. The concept involves the use of multiple damper units that produce mechanically parallel damping forces spatially arranged in series. As a prototype, a 1500‐kN oil damper was fabricated by combining three 500‐kN dampers. The 1500‐kN prototype damper was conceived as a full‐scale prototype of a damper that is more slender than comparable commercially available dampers in Japan, and as a scaled model of the proposed 6000‐kN damper.Sinusoidal loading tests were conducted on the prototype damper using a frequency range of 0.1–1.5 Hz and a velocity range of 0.4–300 mm/s. The results confirmed that the damper produced the design damping forces. The results of earthquake loading tests also revealed that the damper exerted a stable damping force against a large earthquake and maintained its performance after the earthquake. The damper is particularly effective against earthquakes with long‐period components that could increase the temperature of a damper. This is afforded by its high heat capacity compared to conventional dampers.Considering that the proposed 6000‐kN damper will generate a damping force that is about 2–3 times that of the strongest conventional oil damper, existing manufacturer test machines would be inadequate for evaluating its full performance characteristics. To address this issue, the authors also propose a test method for evaluating the overall damping force. The method is premised on the fact that the characteristic feature of the proposed damper is its combination of multiple damper units. The overall performance is thus evaluated using the test results for the individual damper units while the other dampers are bypassed. This method was verified by the results of the abovementioned sinusoidal loading tests, with the error for the 1500‐kN prototype damper found to be less than 5%. Copyright © 2016 John Wiley & Sons, Ltd.

This article is devoted to a mathematical model of a new piezoelectric sensor used for measuring bending strains. The first simple model of a piezoelectric sensor of bending deformations (we will call it a classical sensor) was presented in our previous paper. The classical sensor is a one-dimensional three-layer structure, in which the two outer layers are made of piezoelectric ceramic with preliminary polarization across the thickness of the sensor, and one elastic middle layer is located between these piezoelectric layers. In the present modified model of the new sensor, piezoelectric stacks are used instead of simple piezoelectric elements. As shown in the paper, this kind of piezoelectric composite sensor with stacks allows us to significantly increase the value and stability of the measured electrical signal and increase the accuracy of strains measurement. Piezoelectric ceramic is a brittle material. The use of stacks significantly reduces brittleness by enclosing thin layers of piezoelectric ceramic in a metal matrix. Piezoelectric laminated stacks have a periodic structure, and we will use the mathematical homogenization method to correctly determine their effective moduli (physical constants). Increasing the reliability of the proposed sensors, as well as the accuracy and stability of their deformation measurements, is aimed at enhancement of the mechanical safety of building structures, increasing the efficiency of their monitoring. The most important characteristic of any sensor is its efficiency. Our first classical bending strain sensor has a simple structure and an efficiency approaching the value of the coupling coefficient k31 (k31 is a constant describing a known physical property of a piezoelectric material). Our classic piezoelectric flexural strain sensor has an efficiency of the order of the coupling coefficient k31. For piezoelectric materials with a strong piezoelectric effect, the k31 value is approximately 0.30–0.35. The efficiency of our classical sensor is hundreds of times greater than the efficiency of the most popular tangential (longitudinal) strain sensor, developed by Lord Kelvin. The efficiency of the flexural strain sensor using stacks is of the order of the coupling coefficient k33. For the sensor with piezoelectric stacks, the value of efficiency is approximately 0.60–0.70. Note that the efficiency of the improved sensor is twice as high as the efficiency of our classic flexural strain sensor.

Dedicated to Prof. Dr. Akimitsu Kurita on his 70th birthdayIn current bridge design codes or specifications, the dynamic effects of vehicles are considered by using a dynamic amplification factor (DAF) or dynamic load allowance (IM). However, a DAF is defined based on the ratio of the maximum dynamic load responses to the static load responses, and it is more appropriate for maximum value‐based strength design. For fatigue design, stress cycles other than the maximum stress ranges could contribute to fatigue damage accumulations. Meanwhile, on the capacity side, a reduction in fatigue strength due to structural deterioration, which is related to local environmental conditions, including temperature, humidity, etc., could introduce more uncertainties into structural safety and reliability evaluation. However, such multiple stress range effects and structural deterioration are not included in current bridge fatigue design. To evaluate the vehicular dynamic effects for the life cycle fatigue design of short‐span bridges, the present study proposes a new dynamic amplification factor for life cycle bridge fatigue design (DALC), which is defined as the ratio of the life cycle nominal live load stress range to the maximum static stress range. In contrast to other traditionally defined dynamic factors, the newly defined DALC includes information about both the structural loading and the structural capacity. Therefore, the multiple stress cycles from vehicle‐induced vibrations and the structural deteriorations from road surface conditions and corrosion of structural members are included. Parametric studies of DALC were carried out for multiple parameters and variables in the bridge's design life cycle, for instance, possible faulting days in each year, fatigue strength exponent, corrosion parameters and corrosion level. The stochastic properties and uncertainties from these variables are also considered in the DALC calculation.

<strong class="journal-contentHeaderColor">Abstract.</strong> Wind turbines are a key technology for producing clean energy, but the noise they generate can create environmental concerns. This study explores how serrated edges on turbine blades influence noise, structural safety, and energy output. A prototype wind turbine was equipped with serrated blades and tested at a field site in China. Measurements showed that the serrated design reduced aerodynamic noise by nearly four decibels. At the same time, computer simulations revealed that this design caused a small increase in structural loads and a slight decrease in annual electricity generation. The findings suggest that serrated blades can help reduce the noise impact of wind turbines, but they also highlight the need to carefully weigh the trade-offs between quieter operation, safety margins, and efficiency.

Robust fuzzy structural safety assessment using mathematical programming approach

The Cargo-X UAV aircraft is a UAV aircraft designed to carry medicines, packages and blood bags in areas that require fast and efficient handling. One of the important components of the Cargo-X UAV aircraft is the wing, so the strength of the wing structure must be seriously considered to ensure safety during flight under unexpected conditions. The purpose of this study was to analyze the wing structure of the UAV Cargo-X aircraft made of sandwich composite material to determine the level of safety of the wing structure. The loading of the wing structure uses the load due to the lift. The wing structure modeling uses CATIA software, while the analysis uses PATRAN/NASTRAN software. From the analysis results, the skin and spar wing structures are safe against loading, while the core section is not safe against loading.

The utmost important characteristics in aircraft design were the structure load and safety. One of the main part of an aircraft is Fuselage. Depending on mass scattering of fuselage, the inertia forces will change along the length of the fuselage. Fuselage tends to bend down about axis wing due to Inertia force scattering. This bend will generate tension in upper part of fuselage simultaneously fuselage bottom part will experience compression. This work reveals the issue of the compression buckling of stiffened panels in the bottom portion of the fuselage. A linear static analysis will be carried out on a part of fuselage structure with scattered inertia load. The panels with extreme compression load is recognized for buckling analysis. From static analysis, compression load acting on each panel can be extracted and buckling factor is discovered. MSC PATRAN and MSC NASTRAN are used for this study. From the value of Buckling Factor for both Global and Local analysis of fuselage with different cross-sections, it is clear that the design of the fuselage stiffened panel with ‘L’ and ‘Z’ cross-section is safe one.

As a major international event， the Beijing Winter Olympics used a large number of scaffolding for the construction of temporary stands or stages. The temporary stand support frame with plug-in joints was taken as the research object. A 2×2 full-scale model was designed and manufactured， and unidirectional horizontal loading tests were conducted to investigate its slip modes， displacement response， and strain distribution under no load， 0.5 kN/m²， 2.0 kN/m²， and 3.5 kN/m² conditions. The load-displacement curve was plotted to determine the structural slip load. For experimental comparison， wind loads corresponding to Level 10-12 wind forces in the competition zone were selected to verify the safety and stability of the frame structure in practical engineering applications. An 8×2 analytical model was established using SAP2000 to evaluate the mechanical properties indicators such as modal characteristics， anti-overturning stability， and stress ratios of the overall structure.The results showed that the frame structure exhibited excellent anti-slip stability， and most of the members remained in an elastic stress state during the test. Since the external load applied in the test was much higher than the actual wind load， the structural system possessed a large safety reserve. This study can provide technical support and reference for the practical application of plug-in scaffold support frames.

Load recovery plays a key role in the safety and performance optimization of mechanical structures, and its accuracy is affected by a variety of factors such as sensor position and direction. Most current sensor optimization methods are based on discrete simulation data, resulting in the optimization quality dependent on the degree of data discretization. This article aims at recovering mechanical structure load using strain response, construct surrogate model to achieve a continuous mapping relationship between the data, and obtain the globally optimal strain gage placement through an optimization method. Firstly, based on the limited simulation data, the comprehensive strain information of the structural surface is obtained by using the spatial strain conversion principle and the local coordinate systems construction method. Secondly, based on the linear superposition relationship between strain response and load, the strain-load coefficient matrix is obtained, and the surrogate model between the strain gage placement and the strain-load coefficient is constructed. Then, the minimization of the variance of the load recovery is taken as the objective function for optimization, and the optimal result is obtained. Finally, both simulation and engineering case studies are carried out. The results verify that the proposed method is capable of accurately recovering the load with an error within 10 –3 %. Moreover, the load recovered at the optimal placement based on the strain response is less susceptible to perturbations. Its corresponding load recovery error is at least 70% lower than that of other placement methods, which indicates a high level of robustness. The proposed method also provides reference and technical support for optimizing strain gage placement on complex surfaces and major equipment.

Concrete was considered to be very durable material for a long time. However many constructions have shown degradations during their service life. To ensure safety, stability and serviceability of civil engineering structures, understanding of deterioration processes and their effect on the residual structural load capacity is necessary. This paper is based on the experimental study of short prismatic concrete columns under the hygrothermo-mechanical accelerated aging. To investigate the effects of the exposure conditions on the strength of specimens, combined ultrasonic pulse velocity testing and compression loading testing was used. It can be observed from the results obtained in this work that the ultrasonic pulse velocity measurements agree well with the experimental results obtained from the compression loading testing. Results indicate that in first time, degradation of specimens occurs slightly. After that the degradation becomes notable. It also indicates that the degradation due to the combined effect of the hygrothermo-mechanical aging is higher than when we consider hygrothermal and mechanical process separately

The use of aluminium as material of choice in the manufacture of window and door openings in Mauritius has escalated significantly in recent years. This has given rise to a considerable number of small-and medium-sized companies operating in the aluminium fabrication sector. The main aim of this study was to identify and investigate the common problems reported with aluminium openings and to assess the structural resistance, water-tightness and safety of the openings. A survey was carried out among local aluminium importers and fabrication companies to gather information about the different profiles and grades of aluminium commonly used for exterior window and door applications in the residential sector. A questionnaire was designed and circulated to clients of aluminium fenestration products. This helped to identify the most common problems encountered with aluminium openings. Site visits were also conducted which enabled the investigation of some common problems identified such as water ingress and rigidity of moving parts. The structural loading of openings was assessed using finite element analysis using SolidWorks. Models of openings of different sizes and corresponding to typical opening designs used locally were created and a uniform pressure was applied on the frames. This uniform pressure was derived from a wind speed of 280 km/h – the maximum wind speed used for design calculations for buildings in Mauritius. The resulting deflections were analysed and compared to the maximum permissible deflections – which were calculated using the guidelines of North American Fenestration Standard (NAFS-11). Results showed that the maximum deflections for frames sizes exceeding a span of 1.5 m, exceeded the maximum allowable values, and necessitated the use of more rigid profiles. Deflections observed in the triple frame design were also higher than those in the double frame. These observations point out to the need of selecting the right profiles for different sized applications to ensure that openings do not incur significant deflections when subjected to wind loads, which would be encountered during severe cyclonic conditions in the island.

For a flexible tension structure, the first thing to do is to perform a form-finding analysis to obtain a reasonable initial state of the structure. The initial state includes the structure's own weight and the cable force distribution under the additional dead load and the corresponding geometric configuration. The geometric configuration and expectations must be ensured to be consistent with the geometry of the building. This paper used the MIDAS software to first establish the zero-state model of the structure, and then added reasonable prestress to ensure that the initial configuration of the structure under prestress, structure dead weight and additional dead load is basically the same as that under zero state, thus ensuring the feasibility and accuracy of later structural load analysis and construction process analysis, and providing ideas and methods for related projects.

Introduction R ECENT rapid development in aerospace explorationhas stimulated extensive use and studies of highly  exible structures (HFSs). i 4 Figure 1 shows a representative load-de ection curve of HFS systems. It can have local buckling, snap-through,bifurcation, self-locking, snap-back, etc. Low-frequency vibration modes of HFSs are usually localized vibration modes, and hence local buckling is more likely to happen to HFSs. Local buckling results in signiŽ cant load increase at some local areas, and hence plastic deformation may occur well before the entire structure collapses. For HFSs the design load can be chosen to be greater than the local buckling load, and hence the residual strength (the strength beyond the local buckling load) can be taken into account in the design. Snap-through happens when the load passes a limit point, and it causes serious dynamic effects. Hence, the load corresponding to the snap-through is often assumed to be the collapse load of an on-earth structure. However, if a structure can sustain the dynamic loadscausedby the snap-through,the structurecan be designedwith a design load greater than the snap-through load. In this situation the dynamic effects caused by snap-through need to be carefully analyzed to ensure safety. Unfortunately dynamics of HFSs are essentially nonlinear because of high  exibility, and modal interactions caused by geometric nonlinearitieswould be the main cause of their complicated nonlinear dynamic responses,which is always a challenging problem. Moreover, multiple possible solution paths coexist around a bifurcationpoint of a load-de ection curve. To ensure structural safety, all of these possible solution paths need to be traced, which is a difŽ cult numerical problem. Some nonlinear behaviors of HFSs can be used to design large space structures. For example, the self-lockingphenomenoncan be used to design jointless deployable structures.3 However, to push the design load beyond the local buckling load or even the snapthrough point, it requires advances in modeling large deformations and complex stress states of HFSs, more efŽ cient computational methods, and large static and dynamic tests to validate numerical simulations.Moreover, it is a new challenge to structural engineers to design large deployable/in atableHFSs that can be packaged in a small volume for a space shuttle to carry and can be easily deployed or constructed in space. Here we present some considerations and solutions to the modeling and design of HFSs based on the development and use of an in-house nonlinear Ž nite element code.

Design and analysis of blast resistant structures is an important area of safety research in nuclear, aerospace, chemical process and vehicle industries. Institute for Nuclear and Energy Technologies (IKET) of Research Centre Karlsruhe (Forschungszentrum Karlsruhe or FZK) in Germany is pursuing active research on the entire spectrum of safety evaluation for efficient hydrogen management in case of the postulated design basis and beyond the design basis severe accidents for nuclear and non-nuclear applications. This report concentrates on the consequence analysis of hydrogen combustion accidents with emphasis on the structural safety assessment. The transient finite element simulation results obtained for 2gm, 4gm, 8gm and 16gm hydrogen combustion experiments concluded recently on the test-cell structure are described. The frequencies and damping of the test-cell observed during the hammer tests and the combustion experiments are used for the present three dimensional finite element model qualification. For the numerical transient dynamic evaluation of the test-cell structure, the pressure time history data computed with CFD code COM-3D is used for the four combustion experiments. Detail comparisons of the present numerical results for the four combustion experiments with the observed time signals are carried out to evaluate the structural connection behavior. For all the combustion experiments excellent agreement is noted for the computed accelerations and displacements at the standard transducer locations, where the measurements were made during the different combustion tests. In addition inelastic analysis is also presented for the test-cell structure to evaluate the limiting impulsive and quasi-static pressure loads. These results are used to evaluate the response of the test cell structure for the postulated over pressurization of the test-cell due to the blast load generated in case of 64 gm hydrogen ignition for which additional sets of computations were performed. The computational results are also confirmed with the simplified analytical computations for the structural dynamic behavior and collapse load prediction for the quasi-static and impulsive loading of the test-cell structure.

Extremum hybrid intelligent-inspired models for accurate predicting mechanical performances of turbine blisk