The present work aims to estimate the thermal mechanical behavior of composite slabs made with both normal weight concrete (NWC) and lightweight concrete (LWC) using a hybrid calculation method. This method combines the simple analytical approach outlined in Eurocode 4 (Eurocode 4 2005) with the thermal results of the finite element method (ANSYS). In this study, the key factors considered include the concrete type, the geometry of the steel profile and the airgap between the steel profile and the concrete. The results found show that the presence of the LWC decreases the temperature evolution by 22% and 41% for the trapezoidal and reentrant slab sections, respectively. It was also found that slabs with trapezoidal sections heat up more and lose more of their load-bearing capacity compared to slabs with reentrant sections. Concretes with higher mechanical performances result in a significant residual moment after heating, while the stability is still monitored. The development of the deflection is more important in LWC than in NWC. The suggested method, a novel contribution of this work, combines the simple analytical approach from Eurocode 4 with the finite element method, yields similar and promising results, aiding in more accurate the fire resistance time estimation.

Le recyclage de certains déchets est une question importante et très nécessaire pour préserver l'environnement et garantir de nouvelles sources d'approvisionnement en matières premières. Dans cette recherche expérimentale, une solution est proposée pour récupérer les déchets encombrants, comme les déchets de pneus, sous forme de granulats dans l'industrie du béton. Le travail réalisé consiste à intégrer les pneus usagés comme granulats par remplacement partiel du sable dans la confection d’un mélange de mortier suivant des pourcentages de substitutions en volume variant de 0 % à 50 %. Des essais de caractérisation physico-mécaniques ont été effectués sur des éprouvettes de mortier de dimension 4×4×16 cm3. Les résultats obtenus montrent que l'utilisation de déchet de pneus comme granulats dans la confection du mortier peut résoudre beaucoup de problèmes liés à leur élimination et économiser les ressources naturelles liées à l'extraction des granulats. Aussi, les résultats trouvés montrent qu’il est possible d’utiliser les déchets de pneus dans la fabrication de mortiers destinés pour des applications structurelles et non structurelles.

Purpose Investigate the fire performance of eccentrically loaded concrete partially encased column (PEC), using the advanced calculation method (ANSYS 18.2, 2017) and the simple calculation method in Annex G of Eurocode 4 (EN 1994-1-2, 2005). This work examines the influence of a range of parameters on fire behaviour of the composite column including: eccentricity loading, slenderness, reinforcement, fire rating and fire scenario. In this study, ISO-834 (ISO834-1, 1999) was used as fire source. Design/methodology/approach Currently, different methods of analysis used to assess the thermal behaviour of composite column exposed to fire. Analytical method named simplified calculation methods defined in European standard and numerical simulations named advanced calculation models are treated in this paper. Findings The load-bearing capacity of the composite column becomes very weak in the presence of the fire accident and eccentric loading, this recommends to avoid as much as possible eccentric loading during the design of construction building. The reinforcement has a slight influence on the temperature evolution; moreover, the reinforcement has a great contribution on the load capacity, especially in combined compression and bending. When only the two concrete sides are exposed to fire, the partially encased composite column presents a high load-bearing capacity value. Originality/value The use of a three-dimensional numerical model (ANSYS) allowed to describe easily the thermal behaviour of PEC columns under eccentric loading with the regard to the analytical method, which is based on three complex steps. In this study, the presence of the load eccentricity has found to have more effect on the load-bearing capacity than the slenderness of the composite column. Introducing a load eccentricity on the top of the column may have the same a reducing effect on the load-bearing capacity as the fire.

Over the past decades, the poultry meat processing industry’s growth has generated a huge amount of feather “waste”. This waste has given rise to a number of environmental concerns and had a low value-being when used in many industrial applications. Promoting the use of sustainable materials is now a pole of interest in engineering construction. Aiming to recover this waste in enhancing the properties of problematic soils, an experimental study is conducted using these materials. An earth material named Zebabdja clay is treated by the cement to improve its properties. The inclusion of waste byproducts such as chicken feather fibers would improve the characteristics of the soil with low load bearing capacity. The present work attempts to valorize this kind of natural fiber in the field of building and solve an environmental problem using local materials. The control parameters evaluated herein include cement content (6%, 8%, 10% et 12%) and chicken feather fibers contents (1%, 2% et 3%). The unconfined compressive and direct shear tests were measured at different curing times. The results found show that 10% is the needed amount of cement to be used in order to stabilize the clayey soil treated. An increase in chicken feather fibers up to 2% indicates an improvement of the mechanical performances of the clayey soil, which may constitute a very interesting engineering solution for the weak soil.

Composite structures made from the combination of steel profile and concrete have significant loadbearing capacity which depends on the behaviour of the two material components and their interaction, particularly in fire conditions. It is not possible to assess the fire resistance of composite members only by considering the temperature of the steel, because the presence of the concrete may contribute greatly to increase the resistance, strength and thermal inertia of the member, which improves consequently the fire behaviour of the element. The aim of this work is to develop an efficient non-linear 3D finite element model to investigate the behaviour of pin-ended axially loaded composite column made from high strength concrete (HSC) and normal strength concrete (NSC) at different fire rating classes. Two types of column section were selected, notably HEB 160 profile totally encased with concrete and HEB220 partially encased with concrete. The fire behaviour of the columns was tested according to ISO834 standard fire. The results show that the use of HSC in composite columns reduces the level of fire protection with the regard to NSC. NSC in composite structures accommodates higher deflections than HSC, which is safer in case of fire accident. The mechanical resistance in composite columns at room temperature is reduced more than twice after 30 min of fire exposure.

This 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.

Many rehabilitation operations of historic buildings have not succeeded to utilize appropriate material for purpose of the project. Currently, the use of construction waste, especially the waste brick, is largely expanded in the world due to construction and rehabilitation of buildings. For efficient and sustainable use of such material in the rehabilitation of the architectural ornaments, an experimental study was conducted to examine the influence of the waste brick content on the physical and mechanical properties of the gypsum mortar. The materials used to prepare the gypsum mortar were gypsum, natural sand, waste brick, water and superplasticizer. The main variable in this study were the waste brick content (0% to 100%) and the type of the substrate (limestone and brick). The W/B ratio of all the mixtures was kept constant to maintain a similar level of the workability. Several tests were performed to assess the physical and the mechanical behaviour of the gypsum mortars including the adhesion test, XRD and the SEM analysis. The results found show that the adhesion strengths in the mortars are more important when the substrate is made from limestone with the regard to the substrate made with brick. However, excessive percentage of waste brick in the mortar can lead to adverse effects and reduce the adhesive strength. Gypsum mortars made with 75% of waste brick should be recommended for the rehabilitation of the architectural ornaments. (C) 2020 Elsevier Ltd. All rights reserved.

The aim of this paper is to develop design-oriented models for the prediction of the ultimate strength and ultimate axial strain for concrete confined with glass fiber-reinforced polymer (GFRP) wraps. Twenty of most used and recent design-oriented models developed to predict the strength and strain of GFRP-confined concrete in circular sections are selected and evaluated basing on a database of 163 test results of concrete cylinders confined with GFRP wraps subjected to uniaxial compression. The evaluation of these models is performed using three statistical indices namely the coefficient of the determination (R-2), the root mean square error (RMSE), and the average absolute error (AAE). Based on this study, new strength and strain models for GFRP-wrapped concrete are developed using regression analysis. The obtained results show that the proposed models exhibit better performance and provide accurate predictions over the existing models.

In this study, the interfacial stresses in RC beams strengthened by externally bonded prestressed GFRP laminate are evaluated using an analytical approach, based on the equilibrium equations and boundary conditions. A comparison of the interfacial stresses obtained from the present analytical model and other existing models is undertaken. Otherwise, a parametric study is conducted to investigate the effects of geometrical and material properties on the variation of interfacial stresses in damaged RC beams strengthened by externally bonded prestressed GFRP laminate. The results obtained indicate that the damage degree has little effect on the maximum shear stress, with a variation less than 5% between the damaged and undamaged RC beams. However, the results also reveal that the prestressing level has a significant effect on the interfacial stresses; hence the damaged RC beam strengthened with an initial prestressing force of 100 kN gives 110% higher maximum shear stress than the damaged RC beam strengthened with an initial prestressing force of 50 kN. The values of shear stress obtained by the analytical approach are approximately equal to 44% of those obtained from the numerical solution, while the interfacial normal stresses predicted by the numerical study are approximately 26% higher than those calculated by the analytical solution.

Slag and other cement replacement materials provide an important route to low carbon footprint concrete construction. These materials are often by-products from other industries, and as such, their quality varies depending on source and processing. This paper examines the influence of a range of parameters on the reactivity of slag and its contribution to strength development to aid in its efficient and sustainable processing and use in construction. The investigation covers a wide range of factors including: chemical and physical properties of slag, mix composition and curing temperature. Two types of slag differing in their physical and chemical properties are investigated. The test parameters include the level of cement replacement (30, 50 and 70% by mass), the fineness of slag (250, 310, 410 and 500 m(2)/kg), the water/binder ratio (0.35, 0.4 and 0.45) and the curing temperature (20 degrees C, 40 degrees and 60 degrees C). Thermogravimetry was used to determine the degree of hydration at various ages, by measuring the chemically bound water. Slag hydration is thermally activated and for the temperatures studied, 40 degrees C curing seems to provide the greatest benefit in terms of strength and hydration. The extent to which these benefits are achieved depends on slag reactivity, and for similar slag fineness and glass count, this reactivity is due to the chemical composition of the slag. It was found that there is no significant increase in strength or bound water gained from grinding the slag finer than 310 m(2)/kg for slag cured at 40 degrees C, a temperature in the range for site cast and precast concretes. A statistical model was established demonstrating that compressive strength of paste is influenced by water/binder ratio, bound water, slag replacement level and curing temperature. (C) 2018 Elsevier Ltd. All rights reserved.

This investigation aims to determine the influence of pre-saturation and dried recycled concrete aggregates (RCA) on mechanical and rheological properties of concrete. Coarse ordinary aggregates (COA) were partially substituted with RCA and an amount of superplasticizer was added to keep the same workability. The results found show that concrete with dried RCA aggregates requires a great dosage of superplasticizer and achieves high compressive strength and rheological parameters. However, for concrete with pre-saturated RCA aggregates, the needed dosage of superplasticizer is reduced and the compressive strengths and the rheological parameters are decreased. The use of pre-saturated RCA aggregates is better to keep adequate superplasticizer dosage and relevant rheological parameters. Mathematical relationships are proposed to express the variation of the compressive strengths and the rheological parameters according to the concrete composition with fair correlation coefficients.

The lateral confinement in reinforced concrete structural components is an essential parameter to allow designer to use a sufficient percentage of transverse reinforcement in order to ensure the required strength and ductility for the structure. This paper deals mainly with the influence of lateral confinement on strength and ductility in reinforced concrete structures designed according to Algerian standards. An overview of the non-linear static analysis method is described below to better understand this analysis. Two different representative structures designed according to Algerian code for the design of earthquake resistant buildings (RPA99/v2003) are identified for the purpose of this study. This analysis provides the capacity curves for each structure with regard to the compressive strength and the volume percentage of the transverse reinforcement. The results obtained show that the lateral confinement improves widely the strength and the local ductility of the structure elements, although their effect on the overall behavior of the structure remains limited.

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.

The objective of this paper is to analyze the seismic behaviour of a few columns of bridges realized on the eastwest highway in Algeria, knowing that these bridges were designed before the application of the Algerian seismic code of bridges. First the method for nonlinear dynamic analysis of bridges was outlined. Next, we describe the evaluation method of resistant forces in reinforced concrete columns, based on numerical approaches. In the same context, the criteria of the strength and ductility of bridge piers in modern seismic codes were presented. In this study, the behaviour of columns of bridges, in terms of bending moment, shear and the ductility was analyzed under several seismic recordings in critical areas of columns of three bridges. The results obtained herein showed that the seismic behaviour of the considered columns was widely satisfactory under local seismic recordings even under strong earthquakes.

This work deals with the maximum ratio of longitudinal tensile reinforcement compatible with a given level of local ductility in reinforced concrete beams, when considering the effect of high strength concrete. First, the evaluation method of the ductility factor is revealed, where an assessment procedure is presented. Then, the influence of the tension reinforcement ratio on the local ductility is discussed for high strength concrete. Furthermore, the Eurocode 8 provision concerning the criterion of the local ductility in dissipative beams is illustrated. In this respect, this criterion is examined in sections having the maximum tension reinforcement ratio adopted by Eurocode 8, by varying the strength of concrete by up to 90 MPa. The obtained tensile reinforcement ratios for a given value of curvature ductility factor by means of the setting procedure of the equations of equilibrium and compatibility show that the amount of reinforcement should be less than that proposed by the Eurocode 8 equation. Finally, a modified formula for the maximum tension reinforcement ratio rho(max) is suggested instead of that recommended by Eurocode 8, which takes into consideration the effect of high strength concrete, where the validity of this formula is checked by a comparative study with other formulas for rho(max). (C) 2010 Elsevier Ltd. All rights reserved.

This experimental study was done to quantify the evolution of the mechanical strength modifications resulting from the presence of several supplementary cementitious materials (SCMs) in the mixture design of a mortar hardening under various curing temperatures. Mortars were made with various replacement levels of the cement by mass: 30 and 50% for slag; 10, 20, 30, and 40% for natural pozzolan; and 5, 15, and 25% for limestone powder. Samples were stored in a saturated-humidity moist room under various temperatures, namely 68, 104, and 140 degrees F (20, 40, and 60 degrees C). The results enable the verification of some hardening properties, such as half-strength age and long-term strength. The experimental results of half-strength age perfectly match with the previous studies that show a slower hydration of the cement with an increase in SCM. This effect decreases with the curing temperature. The long-term strength-depending on the curing temperature-is expressed by a parabolic expression contrary to the classical linear form in the case of ordinary portland cement (OPC). This new expression is more accurate in predicting the concrete long-term strength versus curing temperature with a part of cement replaced by SCM. Many experimental results obtained by other researchers have supported the proposed expression with a satisfactory accuracy, encouraging its generalization.