Wind effects on a long span steel roof structure: numerical simulation and equivalent static wind loads

A wind tunnel test is conducted in this study on the scaled model of the Guangzhou International Sports Arena (GISA). Simultaneous pressure measurements are conducted in a simulated suburban boundary layer flow field. A numerical simulation approach using Fuzzy Neural Networks (FNNs) is developed for the predictions of wind-induced pressure time series at roof locations which are not covered in the wind tunnel measurements. On the other hand, the wind-induced response of the roof are presented and discussed, which are directly calculated by the Complete Quadratic Combination (CQC) approach. Furthermore, the correlations between the background and resonant response components are discussed in detail, and the results show that neglecting the correlations between the two components would result in considerable error in the response estimation. Finally, the Equivalent Static Wind Load (ESWL) approach is used to estimate the wind-induced responses of the roof, which are compared with those obtained from the CQC approach to examine the effectiveness of the proposed ESWL approach in the design and analysis of large-span roof structures. It is shown through the example that the FNN and ESWL approaches can successfully predict the wind-induced pressures and responses respectively

Mechanical properties and structural health monitoring performance of carbon nanotube-modified FRP composites:A review

This article provides an extensive review of key publications covering topics of fabrication methods, enhancement of mechanical properties, and applications of CNT-modified FRP materials in structural health monitorin

Impact damage behavior of lightweight CFRP protection suspender on railway vehicles

The aim of the paper is to evaluate the impact damage behavior of a carbon fiber reinforced polymers (CFRP) protection suspender, a component on the railway vehicles that can prevent the falling joist and bolster from touching the rails and to avoid the derailment of trains. A three-dimensional impact model of CFRP protection suspender which considers the bolt preloads was established in ABAQUS/Explicit

Transactivated Epidermal Growth Factor Receptor Recruitment of α-actinin-4 From F-actin Contributes to Invasion of Brain Microvascular Endothelial Cells by Meningitic Escherichia coli

Bacterial penetration of the blood-brain barrier requires its successful invasion of brain microvascular endothelial cells (BMECs), and host actin cytoskeleton rearrangement in these cells is a key prerequisite for this process. We have reported previously that meningitic Escherichia coli can induce the activation of host's epidermal growth factor receptor (EGFR) to facilitate its invasion of BMECs. However, it is unknown how EGFR specifically functions during this invasion process. Here, we identified an important EGFR-interacting protein, α-actinin-4 (ACTN4), which is involved in maintaining and regulating the actin cytoskeleton. We observed that transactivated-EGFR competitively recruited ACTN4 from intracellular F-actin fibers to disrupt the cytoskeleton, thus facilitating bacterial invasion of BMECs. Strikingly, this mechanism operated not only for meningitic E. coli, but also for infections with Streptococcus suis, a Gram-positive meningitis-causing bacterial pathogen, thus revealing a common mechanism hijacked by these meningitic pathogens where EGFR competitively recruits ACTN4. Ever rising levels of antibiotic-resistant bacteria and the emergence of their extended-spectrum antimicrobial-resistant counterparts remind us that EGFR could act as an alternative non-antibiotic target to better prevent and control bacterial meningitis

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Studying the Characteristics of Chaos and Fractals of Construction Rocks under Different Loading Velocities

Rock is a widely used construction material; its mechanical properties change due to the influence of different load speed. In this study, the split Hopkinson pressure bar (SHPB) was used to test the dynamic properties of rock samples by loading four different pressures (0.05, 0.08, 0.14, and 0.23 MPa). The peak stress of the sample increases from 82.19 to 284.16 MPa, and the particle size of the sample debris decreases from 46.57 to 18.34 mm as the impact pressure increases from 0.05 to 0.23 MPa. As a chaos method in nonlinear dynamics, it is introduced into the quantitative evaluation of the sample at four loading pressures, which is then calculated. The damage evolution process of the sample under four loading pressures is calculated, and the chaotic characteristics contained in the process are analyzed. Based on the logistic mapping, the increase in the load velocity can delay the entry of the damage variable into the period-doubling bifurcation and chaotic states. Finally, the fractal dimension of the rock crack at the corresponding time under different load speeds is calculated, and the results showed that the increase in the load velocity can increase the uniformity of the crack distribution

Monitoring of Wind Effects on a Super-Tall Building under a Typhoon

Field measurements are critical to further understand the structural behavior of super-tall buildings under strong wind actions. This paper presents field measurements that reflect the wind characteristics and wind effects on Leatop Plaza under Typhoon Vicente. Wind field characteristics, including the turbulence intensity, gust factor, and power spectral density of wind speed in an urban area, were obtained on the basis of a statistical analysis of measured wind data. Subsequently, measured wind-induced accelerations were used to evaluate the dynamic characteristics of the building and the effects of wind on it. On the basis of the first several modes, the modal properties, i.e., the natural frequency and damping ratio, were identified via the fast Bayesian fast Fourier transform method and compared with those identified using the stochastic subspace method. The discrepancy between the identified results and finite element model predictions is presented and discussed. Finally, the variation in the modal parameters with respect to time and the vibration amplitude was analyzed while considering the associated posterior uncertainty

Analysis and Application of a New S-Type Bistable Generator Beam in Energy Harvester Featured in Reducing Stress Concentration

This paper presents a newly designed bistable S-type generator beam. For two typical energy harvesting scenarios in a low-frequency excitation environment (up-and-down vibration excitation and wind-induced vibration excitation), two kinds of energy harvesting devices are designed using this S-type generator beam and tested and analyzed, respectively. The results indicate that the S-type generator beam can make full use of materials to avoid premature fatigue failure caused by stress concentration. The peak stress of the S-type generator beam is 34.3% lower than that of the cantilever beam under the same excitation conditions. Furthermore, when the environmental excitation frequency is equal to the third natural frequency (3rd mode, 7.45 Hz) of the generator beam, the motion process of the beam surpasses the potential energy barrier and generates inter-well movement (snap-through). The peak output voltage in the two different environments is 14,350 mV and 17,630 mV, respectively. Additionally, the optimal external resistance of the circuit was determined to be 22 kΩ, with a power output of the energy collector of 0.534 mW and 0.545 mW, respectively

Study of the Properties of a Hybrid Piezoelectric and Electromagnetic Energy Harvester for a Civil Engineering Low-Frequency Sloshing Environment

In this paper a novel hybrid piezoelectric and electromagnetic energy harvester for civil engineering low-frequency sloshing environment is reported. The architecture, fabrication and characterization of the harvester are discussed. The hybrid energy harvester is composed of a permanent magnet, copper coil, and PVDF(polyvinylidene difluoride) piezoelectric film, and the upper U-tube device containing a cylindrical fluid barrier is connected to the foundation support plate by a hinge and spring. The two primary means of energy collection were through the vortex street, which alternately impacted the PVDF piezoelectric film through fluid shedding, and the electromotive force (EMF) induced by changes in the magnetic field position in the conducting coil. Experimentally, the maximum output power of the piezoelectric transformer of the hybrid energy harvester was 2.47 μW (circuit load 270 kΩ; liquid level height 80 mm); and the maximum output power of the electromagnetic generator was 2.72 μW (circuit load 470 kΩ; liquid level height 60 mm). The low-frequency sloshing energy collected by this energy harvester can drive microsensors for civil engineering monitoring

Study of the Properties of a Hybrid Piezoelectric and Electromagnetic Energy Harvester for a Civil Engineering Low-Frequency Sloshing Environment

In this paper a novel hybrid piezoelectric and electromagnetic energy harvester for civil engineering low-frequency sloshing environment is reported. The architecture, fabrication and characterization of the harvester are discussed. The hybrid energy harvester is composed of a permanent magnet, copper coil, and PVDF(polyvinylidene difluoride) piezoelectric film, and the upper U-tube device containing a cylindrical fluid barrier is connected to the foundation support plate by a hinge and spring. The two primary means of energy collection were through the vortex street, which alternately impacted the PVDF piezoelectric film through fluid shedding, and the electromotive force (EMF) induced by changes in the magnetic field position in the conducting coil. Experimentally, the maximum output power of the piezoelectric transformer of the hybrid energy harvester was 2.47 μW (circuit load 270 kΩ; liquid level height 80 mm); and the maximum output power of the electromagnetic generator was 2.72 μW (circuit load 470 kΩ; liquid level height 60 mm). The low-frequency sloshing energy collected by this energy harvester can drive microsensors for civil engineering monitoring