Measurement of the Level of Knowledge of the Sands Used in Constructions in Togo

Faced with the proliferation of quarries extracting silty sand and river sand used in the building and public works sector in Togo, recognition of the granular properties of these materials remains a major challenge for builders. This study aims to take stock of the use of sand in construction in Togo. One hundred and eighteen (118) sand quarries in operation, including thirty-eight (38) silty sand quarries and eighty (80) river sand quarries, were identified following surveys carried out among stakeholders involved in the chain of construction on 40% of the national territory. It appears from these surveys that river sands (59.43% to 84.68%) are prioritized over silty sands (15.32% to 40.57%). Three (3) main reasons are behind the choice of sand type;namely, proximity (28%), cleanliness (25%), good appearance (25%). These three (03) reasons partly explain the strong dependence of users on the sands located in their vicinity as well as the related expenses. Thus, making data available on the characteristics of sand, the materials most used in construction in Togo, would contribute to improving the housing conditions of the Togolese population. .

The Technique of the Tri-Layer Coating: An Effective Solution for the Protection of Earthen Constructions

The problem with earth constructions is their low resistance to water. Step by step, the water degrades the exterior facings of the structures and ends up creating zones of weakness through the structures, making them collapse and creating enormous socio-economic problems, especially in rural areas. The solutions proposed to date, like the use of straw, cow dung, boiled skins, banana leaves, tar, cement soil, have shown their limits. Generally, the poor adhesion between the protected material and the protective layer means that the latter always ends up peeling off. This work, which is inspired by the traditional practice where plant tannins are used to brush the earthen walls to waterproof them, proposes a tri-layer coating composed of soil, powder and hydrolysable tannins extracted from the stem bark of Bridelia. This work focuses on the geotechnical characterization of the soil, the extraction of hydrolysable tannin, the manufacture of the micro-coating, the resistance tests carried out on the micro-coating, the technique of implementation and the test of evaluation of the performance of the tri-layer coating. The results obtained show that not only does the tri-layer coating adhere perfectly to the layer to protect, but it also waterproofs it and protects it against shocks.

Nonlinear Analysis of the Seismic Response of a Reinforced Concrete Structure Built in High Seismic Region in Algeria

The objective of this paper is to analyze the seismic response of a reinforced concrete structure dimensioned according to the Algerian seismic rules. First, we expose the approach of nonlinear time history method. Next, we describe a ten-storey reinforced concrete building braced by shear walls, implanted in the high seismicity region in Algeria. This structure is submitted to different seismic records. Finally, we analyze and interpret the seismic response in function of the deformability, shear strength, flexural strength and the bearing capacity under the compressive stress together with the local ductility. The results obtained showed that the identified structure represents a satisfied nonlinear behavior under the seismic recording of medium intensity contrary that obtained under higher earthquake of El Centro which remains unacceptable and requests a constructive improvement in the Algerian seismic rules.

A Silicon Monoxide Lithium-Ion Battery Anode with Ultrahigh Areal Capacity

Silicon monoxide(SiO)is an attractive anode material for next-generation lithium-ion batteries for its ultra-high theoretical capacity of 2680 mAh g−1.The studies to date have been limited to electrodes with a rela-tively low mass loading(<3.5 mg cm^(−2)),which has seriously restricted the areal capacity and its potential in practical devices.Maximizing areal capacity with such high-capacity materials is critical for capitalizing their potential in practi-cal technologies.Herein,we report a monolithic three-dimensional(3D)large-sheet holey gra-phene framework/SiO(LHGF/SiO)composite for high-mass-loading electrode.By specifically using large-sheet holey graphene building blocks,we construct LHGF with super-elasticity and exceptional mechanical robustness,which is essential for accommodating the large volume change of SiO and ensuring the structure integrity even at ultrahigh mass loading.Additionally,the 3D porous graphene network structure in LHGF ensures excellent electron and ion transport.By systematically tailoring microstructure design,we show the LHGF/SiO anode with a mass loading of 44 mg cm^(−2)delivers a high areal capacity of 35.4 mAh cm^(−2)at a current of 8.8 mA cm^(−2)and retains a capacity of 10.6 mAh cm^(−2)at 17.6 mA cm^(−2),greatly exceeding those of the state-of-the-art commercial or research devices.Furthermore,we show an LHGF/SiO anode with an ultra-high mass loading of 94 mg cm^(−2)delivers an unprecedented areal capacity up to 140.8 mAh cm^(−2).The achievement of such high areal capacities marks a critical step toward realizing the full potential of high-capacity alloy-type electrode materials in practical lithium-ion batteries.

Predicting roof-surface wind pressure induced by conical vortex using a BP neural network combined with POD

This study aims to examine the feasibility of predicting surface wind pressure induced by conical vortex using a backpropagation neural network(BPNN)combined with proper orthogonal decomposition(POD),in which a 1:150 scaled model with a large-span retractable roof was tested in wind tunnel under both laminar and turbulent flow conditions.The distributions of mean and fluctuating wind pressure coefficients were first described,and the effects of inflow turbulence,wind direction,roof opening were examined separately.For the prediction of wind pressure,the POD-BPNN model was trained using measurement data from adjacent points.The prediction results are overall satisfactory.The root-mean-square-error(RMSE)between test and predicted data lies mostly within 10%.In particular,the prediction of mean wind pressure is found to be better than that of fluctuating wind pressure.The outcomes in this study highlight that the proposed POD-BPNN model can be well used as a useful tool to predict surface wind pressure.

Revisited dynamic modeling and eigenvalue analysis of the cable-stayed beam

In this study,the Hamilton’s principle is applied to revisit the dynamic modeling of the cable-stayed beam,and the motion equations governing the nonlinear response of the cable-stayed beam are derived.The corresponding boundary terms are transformed to the dynamic equilibrium conditions through the continuity of the displacement at the anchoring point.Following the standard condensation procedure,the condensed model of the cable-stayed beam is determined.The eigenvalue analysis is performed to determine the closed-form eigenvalue solution of the linear problems,and two types of eigenvalue solution are obtained.It is shown that the frequency spectrum of the cable-stayed beam exhibits the curve veering and crossover phenomena.Corresponding to these phenomena,the mode shapes of the cable-stayed beam may exhibit the coupling characteristic.Finally,the discrete model of the cable-stayed beam is determined,and the possible nonlinear interactions are discussed.

Improvement of sludge dewaterability with modified cinder via affecting EPS

The relationship between the improvement of sludge dewaterability and variation of organic matters has been studied in the process of sludge pre-conditioning with modified cinder, especially for extracellular polymeric substances （EPS） in the sludge. During the conditioning process, the decreases of total organic carbon （TOC） and soluble chemical oxygen demand （SCOD） were obviously in the supernatant especially for the acid modified cinder （ACMC）, which could be attributed to the processes of adsorption and sweeping. The reduction of polysaccharide and protein in supernatant indicated that ACMC might adsorb EPS so that the tightly bound EPS （TB-EPS） decreased in sludge. In the case of ACMC addition with 24 g·L^-1, SRF of the sludge decreased from 7.85 × 10^12 m·kg^-1 to 2.06× 10^12 m·kg^-1, and the filter cake moisture decreased from 85% to 60%. The reconstruction of ＂floc mass＂ was confirmed as the main sludge conditioning mechanism. ACMC promoted the dewatering performance through the charge neutralization and adsorption bridging with the negative EPS, and provided firm and dense structure for sludge floc as skeleton builder. The passages for water quick transmitting were built to avoid collapsing during the high-pressure process.

Predicting the capacity of perfobond rib shear connector using an ANN model and GSA method

Due to recent advances in the field of artificial neural networks(ANN)and the global sensitivity analysis(GSA)method,the application of these techniques in structural analysis has become feasible.A connector is an important part of a composite beam,and its shear strength can have a significant impact on structural design.In this paper,the shear performance of perfobond rib shear connectors(PRSCs)is predicted based on the back propagation(BP)ANN model,the Genetic Algorithm(GA)method and GSA method.A database was created using push-out test test and related references,where the input variables were based on different empirical formulas and the output variables were the corresponding shear strengths.The results predicted by the ANN models and empirical equations were compared,and the factors affecting shear strength were examined by the GSA method.The results show that the use of ANN model optimization by GA method has fewer errors compared to the empirical equations.Furthermore,penetrating reinforcement has the greatest sensitivity to shear performance,while the bonding force between steel plate and concrete has the least sensitivity to shear strength.

Environmental impact assessment of aircraft elevator made with new lightning protection material

The non-metallic lightning strike protection film covering carbon fiber reinforced polymers(NM-LSP covering CFRP)can reduce the weight and thus the fuel consumption of aircraft by replacing the traditional lightning strike protection(LSP)materials.In the present study,in order to study the environmental influence of utilizing NM-LSP covering CFRP in an aircraft elevator,a new elevator was designed and manufactured,replacing the aluminium net and glass fiber reinforced polymers(GFRP)with NM-LSP covering CFRP,with the same mechanical and LSP abilities.A comparative life cycle assessment was conducted between the two kinds of aircraft elevators,including material extraction,transportation,elevator manufacturing phase,service phase,and end-of-life procedures.Additionally,the environmental impacts of producing two LSP materials were compared by considering the environmental effects of different buy-to-fly ratios and recycling strategies on the production of aluminium net.The analysis indicates that the new elevator achieved reduction for all the environmental impact categories used,such as human toxicity potential and marine aquatic ecotoxicity potential(3.83%and 3.20%reduction).Furthermore,it is found that the service phase makes the greatest contribution to the environmental impact of the elevators under investigation.When recycling is excluded,NM-LSP covering CFRP is more environmentally friendly than the traditional material.At the same time,CFRP prepreg and electricity from the production of NM-LSP covering CFRP contribute to a higher environmental impact compared to the NM-LSP film.From the sensitivity analysis,it is believed that NM-LSP covering CFRP can reduce environmental impact compared with traditional LSP materials.

封闭式鞍形张拉膜模型风致气弹响应研究（英文）

目的:明确张拉膜结构风致气弹响应特征及气弹失稳机理。,创新点:1.采用无接触测量技术设计鞍形张拉膜结构气弹模型风洞试验;2.研究鞍形张拉膜结构的气弹响应特征;3.给出鞍形张拉膜结构的失稳机理。方法:1.在风洞中测量两个形状相同但预张力不同的封闭式鞍形张拉膜结构气弹模型在不同风速下的均匀流中的位移响应及膜面上方不同高度的风速时程;2.通过对位移响应及风速时程进行,分析,明确结构的响应随风速变化特征及气弹失稳原因。.结论:1.膜结构在风荷载作用下变形到平衡位置,并.围绕该平衡位置以特定振幅进行振动;2.大部分风向角下,多个模态被激发,结构振幅及各阶模态阻尼比随风速增大而逐渐增大;3.特定风向角下,只有单阶模态被激发;低风速下,结构振幅和模态阻尼比随风速增大而缓慢增大;超过一定风速后,结构发生涡激共振引起的气弹失稳,振幅随风速增大开始迅速增大,达到不发生涡激共振时的2–4倍,结构阻尼比随风速增大发生迅速衰减;随着风速的继续增大,结构振动中可能出现其他模态的气弹失稳;4.结构前两阶模态的无量纲气弹失稳临界风速约为0.8–1.0。