Journal of Materials and Engineering Structures
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Evaluation of loading capacity of corroded reinforced concrete beams using experiment and finite element method
Full text linkThe purpose of this paper is to evaluate the performance of corroded reinforced concrete (RC) beams using experiments and a proposed finite element (FE) model, which is able to consider the reduction of the reinforcement diameter and adhesion force. The developed FE model comprised of three main components including concrete elements, reinforcing bar elements, and adhesion elements, in which the plane cross-section hypothesis was adopted. Thus, the necessary number of elements in the model of corroded RC beam was greatly reduced, while the accuracy of the model was still ensured. An experimental test was employed to verify the developed FE model. The results show that the proposed FE model in this study is capable of modeling RC beams under corrosion effects. Additionally, the rebar diameter and adhesion force have a significant influence on the load-carrying capacity of corroded RC beams. Moreover, a series of experimental tests of corrosive RC beams including 1-month, 2-month, and 3-month corrosion levels was conducted for various exposed times to investigate the influences of the corrosion time on the strength of RC beams. It reveals that the effect of the corrosion time on the strength of RC beams show to be pronounced
Experiment and FEM Modelling of Bond Behaviors between Pre-stressing Strands and Ultra–High–Performance Concrete
Full text linkThe objective of this paper is to investigate the bond properties of prestressing strands embedded in Ultra–High–Performance Concrete (UHPC).The UHPC was made in laboratory using local materials in Vietnam.Its mixture contains: silica aggregates, portland cement PC40, fly ash, silica fume, polycarboxylate superplasticizer and the micro steel fibers.The experimental process is realized on a pull-out test. The volume fraction of micro steel fibers in UHPC was 2%. The prestressing strand with diameters of 15.2mm was considered. The interface shear strength between strand and UHPC is identified based on the results of force and displacement obtained during the pull-out test. The Cohesive Zone Model (CZM) is implemented in finite element model to study this interface behavior. This model described by a piecewise linear elastic law. The CZM’s parameters are identified based on experimental results of pull-out test.The numerical studies are used the CZM in ANSYS software. Two numerical tests are realized and compared with experimental results: pull-out test and other test to verify the deflection of I girder due to prestressing force
Sensitivity study of load-dependent Ritz vectors on modal and seismic responses of cable stayed bridges
Full text linkIn the present article, 3D Finite Element Model (FEM) of a bridge structure under load dynamics is performed in order to assess the sensitivity study of Load-Dependant Ritz vectors (LDR) on modal and seismic responses of cable stayed bridges. In this context, two techniques are examined in the present study for solving structural dynamics problems; the Traditional Modal Superposition (TMS) technique and that of Load-Dependent Ritz orthogonal vectors (LDR). The latter is based on a very efficient algorithm allowing the systematic generation of Load-Dependent Ritz orthogonal vectors (LDR), the accuracy of this method is significantly influenced by the selection of LDR vectors used for the modeling of the structural behavior. The cable-stayed bridge connecting two districts in eastern Algeria, characterized by an expected Peak Ground Acceleration (PGA) equal to 0.275g in accordance with Algerian seismic design code is selected in order to perform critical modal properties such as, frequencies, shapes of the required vibration modes and effective mass participation as well as the dynamic response of the cable stayed bridge under earthquake loadings in three orthogonal directions (longitudinal, transversal and vertical). The results of this study reveal that the LDR vectors method which has the important advantages of short Central Processing Unit (CPU) time as compared to traditional modal method is very efficient for modal and seismic analyses of cable stayed bridges
Assessment of the ternary coarse aggregates for economic production of sustainable and low-cost concrete
Full text linkThis paper study the effects of construction and agricultural wastes (CAW) as coarse aggregates in ternary blends on the properties of concrete. A concrete mix ratio of 1:2:4 by weight of cement, sand and granite was adopted with water-cement ratio of 0.50. Five different concrete mixes were prepared in this study; one natural aggregate concrete (NAC) and four concretes with 10%, 20%, 30% and 40% recycled aggregate and 40%, 30%, 20% and 10% palm kernel shell (PKS) contents in reverse order at constant 50% natural coarse aggregate (NCA). The results of slump tests showed an increase in workability as the percentage replacement level of RCA reduces and PKS respectively. The compressive strength of concrete mixes was observed to be less than the strength of lightweight concrete recommended by standards by 23.2%, 28.87%, 31.2%, 43.2% and 45.6% respectively. Based on the result of calculated thermal conductivity, it was observed that as the %RCA content reduces with increasing %PKS content significant amount of energy was saved. Also, an analysis of variance (ANOVA) was carried out to determine the effect of the % replacement and curing period on the compressive strength of concrete. It showed that % replacement had a statistically significant effect on the concrete performance. This type of concrete can be classified as lightweight concrete based on the strength and bulk density
Effect of limestone fines on the mechanical properties and durability of mortar made with crushed sand
Full text linkThis study investigate the influence of limestone fines (LF) on the mechanical properties, hydration heat and durability (acid and sulfate environments) of mortars made with crushed sand (CS) and different rate replacement of limestone fines of the CS (0%, 5%, 10%, 15%) using three types of cement, that is, ordinary Portland cement, limestone cement and pozzolanic cement. The obtained results show that the limestone fines increase the compressive strength and generate more hydration heat for all the used cements. Mortars made with blended cements, limestone or pozzolan, with 5% and 10% limestone fines, have low expansion when imerged in 5% Na2SO4 solution. In addition, when immerged in acids environment, the mortars with limestone fines exhibit negative effect at long-term durability. However, the mortar manufactured with ordinary Portland cement containing 15% of limestone fines will be strongly affected. It was found that no benefit can be gained from eliminating limestone fines fraction from the CS
Evaluating permeability and groutability of Souk Tleta dam site based on Lugeon tests, RQD, SPI and trial grouting
Full text linkThis study is conducted mainly to evaluate the permeability and the groutability at Souk Tleta dam site. It is an embankment dam with a height of 95 m and a crest length of 200m located in the Tizi-Ouzou province in Northern Algeria. The foundation of the dam consists of thick deposits of pervious alluvium of about 21 m and Burdigalian sandstone formations. The main problem of this dam is that the bedding plains of Burdigalian sandstone in the dam site are parallel to the flow direction. To conduct this study, permeability of formations is evaluated by Lugeon test and secondary permeability index. Rock quality is evaluated by geological assessment and RQD values. Results indicate that the overall permeability of the foundation rock mass before trial grouting in more than 54% of the Lugeon tests is high and requires treatment. To investigate effect of grouting in reducing permeability of rock mass and to evaluate the grout take in rock masses, two trial grouting programs are carried out on dam foundation and left abutment of dam site up to maximum depths of 70 m and 67 m, respectively
Valorisation of Dune Sand Treated with Lime and Scrap Tyre Rubber Powder as a Road Foundation Material.
Full text linkThe purpose of the work presented in this paper is the treatment of dune sand; which is abundant in the region of Djelfa (Algeria), with different lime and tyre rubber powder in order to valorise them in road construction. Several steps were considered in this research. A method of blend formulation has been proposed which is based on stabilization of the studied sand using a hydraulic binder (lime) and scrap tyre rubber powder with different percentages. For each mixture, the optimum Proctor, shear strength, immediate and immersion CBR index, compressive strength and tensile strength were determined. After that, an analysis of the results was made to examine the influence of treatment agents on the characteristics of the mixtures. The results show that the replacement of lime and tyre rubber powder at optimum content has a positive impact on the physical and mechanical behaviours of the treated dune sand mixtures; increases its compressive and tensile strengths, improves its cohesion and increases its immediate and immersion CBR indexes. The selected optimum formulation has sufficient performances to be used as road material
Selection of the best alternative for a road project to replace a section in a flood-prone area using GIS and AMC tools
Full text linkDecision-making involves the selection from various possible alternatives and generally implicates huge financial resources. In addition, one characteristic of a territory making it difficult to make a decision is its multi-criteria aspect. These multi-criteria generally have antagonistic effects and analytical methods are most congruent for solving this kind of difficult decision-making situation. The work presented in this article focuses on the problem of decision-making in order to identify the most favorable road alignment with regard to a series of topographical, geometric, geological and economic criteria. The main goal of this study is to select the best road alignment project to replace part of the road section of the CW 42 connecting the city of Sidi Belattar to National Road 90 (RN 90) using GIS and AMC tools. This road section has been blocked several times in recent years during rare winter flooding. The proposed approach deals with the following points: First, determination of the relevant criteria using GIS, then evaluation and classification of the various alternatives by applying the AHP method using AMC Expert-choice software and PROMETHEE-GAIA algorithms (laboratory-developed web.d-sight software, coded SMG, ULB). Four variants were recommended to replace the vulnerable section. From these four variants a classification was made, according to the two methods AHP and PROMETHEE. The calculated consistency of the results confirms the effectiveness of the proposed approach. Finally, Alternative 2 and Alternative 1 were ranked first by both AHP and PROMETHEE methods and are therefore a recommended choice. This work aims at helping decision makers to rank four road projects of the study area in order to replace the most vulnerable section
Parametric study of the seismic vulnerability of steel structures and their vulnerability curves
Full text linkThe use of metal structures is increasingly used. This is due to the fact that these structures are quick to erect (saving time and money) and make it possible to obtain interesting technical characteristics (spans and heights). These structures can be built in seismic zones and therefore despite their ductility can be damaged. This aspect has been very little addressed. Therefore, it is proposed within the framework of this study to investigate the seismic vulnerability of steel structures using the "vulnerability index" method. Parameters having an influence on the seismic behavior of steel frames were identified and then weighting coefficients for these parameters were calculated using the "Push-over" method. To do this, finite element models were developed and vulnerability classes were defined. Damage probability matrices and seismic vulnerability curves as well as a classification of metallic structures according to their vulnerability were developed. Validation and application cases have been processed and the obtained results are in adequacy what observations made in situ
Mechanical Properties of Concrete and Mortar Containing Low Density Polyethylene Waste Particles as Fine Aggregate
Full text linkIraq industrial activities related to huge amounts of solid, non-biodegradable waste, waste low density Polyethylene (LDPE) plastic being among the well-known. So in this study, the scarped LDPE food boxes were transformed into fine particles and used as a sand for cement mortar and concrete. LDPE wastes were utilized to alter 0 to 25% of fine aggregates in mortar mixtures and 0% to 30% in concrete mixes at an increment of 5%. Compressive strength and dry density were tested for all mortar and concrete specimens. In addition, splitting tensile strength and ultrasonic pulse speed were tested for specimens of concrete. Results show that mass, pulse speed of ultrasonic, splitting and compressive tensile strengths were lowered as the size of LDPE raised. The lowest value of dry density, compressive strength and splitting strength was 2240 kg/m3, 18.7 MPa and 1.68 MPa, respectively, for 15% replacement of sand by the LDPE waste in concrete specimens. Whilst, the value of ultrasonic pulse velocity of LDPE concrete mixtures tends to decline lower than the reference values, but it remains nearly to the stander concrete mixtures and can be classified as excellent quality concrete. The density and compressive strength were decreased by using LDPE waste in mortar mixes for all replacement ratios reaching 12% and 42% respectively for 25% substitute