Journal of Materials and Engineering Structures
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Comparative research on the mechanical behaviour of underground parking constructed by Top-down and Semi-Top-down method: A case study of Tran Hung Dao underground parking (Hanoi)
Full text linkHanoi (Vietnam) has approximately 8.5 million inhabitants and suffers from severe traffic infrastructure insufficiency. The parking spaces in the city are lacking and have become one of the leading causes of traffic congestion. Underground parking facilities could be a solution. The Top-down, Bottom-up, and Semi-Top-down methods have been applied worldwide to construct shallow underground structures in soft soil. Comparative studies are needed to clarify their impacts on underground structures during construction. This paper presented the research on a shallow underground structure constructed by the Top-down and Semi-Top-down methods using numerical modelling. A model of 4-floor underground parking at the Tran Hung Dao station (Hanoi) was built, and the FEM analysis was realised. The behaviour of the parking structure, the diaphragm walls and the surrounding ground was investigated. The impact of the soil’s bulk modulus and the wall’s stiffness on the model’s responses was also studied. The obtained results show the clear influence of soil and the construction procedure on the behaviour of the numerical model. The research was hoped to enrich the knowledge on the construction of shallow social infrastructures in soft soil
Aggregate Packing Density Approach for Sustainable SCC using Un-Processed Coarse Recycled Concrete Aggregates
Full text link The production of Self Compacting Concrete (SCC) needs a large amount of binder (cement) to fulfill its flow requirements. The production of cement is associated with high energy consumption and CO2 emissions, which result in serious environmental pollution. Making SCC with Coarse Recycled Concrete Aggregate (CRCA) throws further challenges. Mix proportions of a 40 MPa SCC-CRCA were estimated using the aggregate proportions obtained by aggregate packing density method (APD), Indian Standard (IS 10262), and those based on Compressible Packing Method (CPM). It was observed that the APD method yielded an SCC-CRCA with reduced binder content by 5.40% and 26%, as compared to the other two methods. Also, in the SCC-CRCA mixes proportioned by using APD method, resulted in a reduction in total energy consumption by 5.10%, total emission of CO2 by 9.23 % and material cost by 14.44 % at the prevailing rates in comparison to the IS 10262 design method. No significant variation in the flow and mechanical properties of SCC-CRCA was observed up to a replacement of 45 %, in the total coarse aggregate which is higher than that recommended in Indian (20 %) and International specifications (35 %) for traditionally vibrated (conventional) concrete
Assessing sustainability performance by applying the TOPSIS method in road construction projects
Full text linkThe sustainability of road development projects must be evaluated holistically. These guarantees roads are constructed to endure fluctuating climatic circumstances and decreasing overall costs and environmental implications. Establishing a comprehensive methodology and framework to evaluate the sustainability level of infrastructure investment projects is crucial. This study presents a methodology that combines the Life Cycle Approach with the TOPSIS technique to conduct a comprehensive assessment of the sustainability level. The social, conventional environmental, and economic implications were initially evaluated through a life cycle method. The TOPSIS technique was subsequently utilized to rank the alternatives according to the metrics obtained from these evaluations. For validation, three pavement options in a project are compared to select the most sustainable alternative by using the proposed integrated TOPSIS technique. The results signify that option Y3 has superior sustainability performance relative to Y1 and Y2. Consequently, option 3 (normal Asphaltic Concrete) emerges as the most sustainable selection among the evaluated choices
Analysis of the behavior of composite steel beam and lightweight concrete slab with glass fiber reinforced composite
Full text linkThis study proposes a novel design for lightweight concrete slabs reinforced with glass fiber-reinforced polymer (GFRP) for application in steel girder bridges. The lightweight concrete, with a compressive strength of 30 MPa, incorporates Keramzit as a lightweight aggregate and GFRP reinforcement to construct the bridge deck slabs. Numerical simulations are conducted to analyze the behavior of the slabs under both static and dynamic loading conditions, adhering to standard load combinations. The results demonstrate that the proposed lightweight concrete slabs offer significant weight reduction, improved load-bearing capacity, and enhanced durability compared to traditional concrete. The finite element analysis using Midas FEA software reveals minimal deformation and cracking under dynamic loading, with a maximum displacement of 0.641 mm, well within safety limits. Furthermore, GFRP reinforcement exhibits superior performance in reducing tensile stress and minimizing crack propagation. These findings validate the feasibility of integrating GFRP-reinforced lightweight concrete slabs in steel girder bridges, offering a cost-effective, sustainable, and efficient solution for modern bridge construction, particularly in Vietnam's demanding infrastructure environment. The study provides a strong foundation for future computational modeling and experimental investigations to further optimize this innovative structural design
Comparative analysis of corrosion mass loss of SKK490 and Q345 steel pipe piles in marine conditions
Full text linkVietnamese seawater, characterized by high chloride concentrations, presents unique challenges for corrosion in steel materials used in marine environments. This study conducts a comparative analysis of corrosion-induced mass loss in SKK490 and Q345 steels, commonly employed in steel pipe piles for coastal and offshore structures, under simulated Vietnamese seawater conditions. Accelerated corrosion tests were carefully designed with controlled factors, including temperature, humidity, and chloride concentration, using a simulated seawater solution containing 3.5% NaCl to replicate real-seawater conditions. Steel samples were partially immersed and connected to an external power source to accelerate the corrosion process over duration of 72 to 240 hours. The results show that Q345, containing protective elements like Nb, V, and Ti, exhibits better corrosion resistance, with a corrosion rate 1.32 times lower than SKK490. The findings underscore the need for material selection prioritizing corrosion-resistant steels or the application of protective measures such as coatings or cathodic protection. Additionally, the research provides valuable data for optimizing the design and durability of marine infrastructure in Vietnam. Future research should validate these results through long-term field studies and explore advanced anti-corrosion technologies
Synthèse « sol-gel » des nanocristaux de TiO2 et Ag-TiO2 par dopage direct : Caractérisation et application dans la dégradation du CH3OH.
Full text linkTiO2 and doped Ag-TiO2 nanoparticles have been synthesized via a « sol-gel » technique, starting with titan isopropoxide in the presence of ethanol (≥99,8% purity), of distilled water (at pH = 9) and of ammonium hydroxide (NH4OH 30%). The powders obtained were identified as pure TiO2 and doped Ag-TiO2 through XRD and FTIR methods. The nanoparticles of TiO2 prepared through our procedure compared well with those of the commercial TiO2 (TiO2 Degussa P25) and they were tested in the photocatalytic degradation of methanol.Dans la présente investigation, la photocatalyse hétérogène a été utilisée pour dégrader le CH3OH en phase aqueuse. Pour y parvenir, les nanoparticules de TiO2 pur et de Ag-TiO2 dopé ont été synthétisées par voie « sol-gel », à partir d’un précurseur l’isopropoxyde de titane (pureté ≥ 99,999%) en présence d’éthanol (pureté ≥99,8%), d’eau distillée (pH = 9) et d’ammoniaque (30%). Les poudres synthétisées, ont été identifiées comme du TiO2 pur et dopé Ag-TiO2 par DRX et FTIR. Les nanopoudres synthétisées exhibent une cristallisation à 87,2% anatase et 12,8% rutile à 700 °C, cette composition dépasse le taux d’anatase de TiO2 P25 « Degussa P25 » commercial dont la cristallisation est à 80 % anatase + 20 % rutile. En outre ces nanopoudres intrinsèque et extrinsèque se sont révélées très efficaces dans la photodégradation du CH3OH mais celle-ci était plus importante en utilisant la poudre dopée (Ag-TiO2) à cause d’une action synergique entre le TiO2 et des propriétés catalytiques propres du métal, qui augmente la conductivité du semi-conducteur (TiO2). Les nanocristaux de TiO2 préparés ont révélé une dégradation un peu plus quantitative que le TiO2 P25 « Degussa P25 » due à son taux élevé en anatase
Damage estimation of low to medium rise reinforced concrete buildings considering vertical irregularity
Full text linkIn current study, Damage estimation is carried out using new methodology using parameters such as absorbed energy and degrading stiffness by pushover analysis. A new stiffness-based damage index is developed for each increasing step of pushover analysis, which takes into account the cumulative effects of increasing each lateral load and displacement. Non-cumulative absorbed energy-based damage index is calculated using the pushover curve's first maximal hysteretic cycle. These suggested methods can be utilised to quickly calculate the global damage index for low to medium rise vertical irregular buildings. The proposed two methods are evaluated using three regular and vertical irregular buildings considering various parameters such as varying heights, setback orientations, plastic hinges and monotonic loads. Furthermore, existing deformation and strength-based damage indices are used to calibrate the proposed damage indices. Both proposed damage indices may calculate damage index at any point on the pushover curve, however the damage indices are computed at different performance levels. The research based on damage index showed that two approaches for evaluating damage to irregular buildings are easy to use and accurate, Also, using the results of pushover analysis, structural designers may estimate the global damage index as a performance criterion in short period of time
Effect of Molecular Weight and Carboxylic Density of Polycarboxylates Ether Superplasticizer on Its performance in Cement Pastes
Full text linkThe main difficulty encountered in the formulation of high performance concrete (HPC) consists in choosing the most efficient cement-superplasticizer pair allowing to obtain maximum water reduction, good workability of the concrete in the fresh state and very good mechanical resistance in the hardened state. The aim of this work is to test the efficient of three polycarboxylate ether based superplasticizers (PCE) marketed in Algeria with CEMI 52.5 R cement and to study the effect of chemical structure of PCE on zeta potential, rheological and mechanical properties of cement pastes. The property of the polymers in cement was tested by a Malvern Zetasizer 2000 apparatus and VT 550 viscometer. Results showed that the zeta potential and its rheological properties are related with the molecular weight and the carboxylic density of PCE. The PCE with a moderate molecular weight and highest carboxylic groups had the best dispersion (high value of zeta potential) and lowest viscosity. The effect of chemical structure of PCEs on mechanical properties are evaluated by formulation of cement mortar with this PCEs, the result shows that there are a correlation between zeta potential of polymer and compressive strength of cement paste
Comparison between experimental and analytical behaviour of the steel – concrete composite pushout specimen with stud and channel shear connector
Full text linkTo investigate the behaviour of composite action with various shear connectors, push-out tests were performed for eight specimens. Test parameters includes are type of shear connector (headed stud connector and channel connector), number of connectors (one and two) and specimen with or without decking sheet. Test results showed that performance of the push-out specimens depends greatly on type of connector and decking sheet. From the experimental study it was observed that the performance and shear capacity of channel connector was 60 % more than the stud connector. The shear resistance between the steel and concrete was enhanced up to 50 % for the push out specimen without decking. The specimen with two numbers of stud and channel connector increases the strength by 58% and 23% respectively as compared to specimen with single connector. The behaviour of the push out specimen was stimulated by three-dimensional finite element model using software ANSYS workbench. The analytical behaviour was well agreement with the real push out specimen studied experimentally
Dynamic response of dancing floor: An example of designing RC floor of a wedding hall
Full text linkBuilding new wedding halls has been flourishing as one of the catching investments in Sudan in recent years. These halls typically require large open spaces with no permeant partitions or furniture that reduces the superimposed dead load considerably. This paper presents an example of designing a reinforced concrete wedding hall floor, using two flooring systems, namely, flat slab and two way solid slab considering dancing induced dynamic load. Firstly an initial sizing based on only dead and live load was carried. The dynamic response was assessed following three methods: 1) the fundamental frequency limit; 2) equivalent static load; and 3) the acceleration limit. The results of the dynamic assessment has shown that a little to no-design alteration has to be made in the concrete flooring systems to satisfy safety. However, problems of vibration perception and comfort may require further structural adjustment to meet the acceptable level of vibration in the project specification based on the anticipating floor usage