International Journal of Structural Engineering (8 papers in press)
Experimental and analytical study on reinforced concrete deep beams
by Asghar Amani Dashlejeh, Abolfazl Arabzadeh
Abstract: A new simple Strut-and-Tie Model was presented in this paper to study the behavior of reinforced concrete deep beams. This model was obtained based on bottle-shaped struts that can predict flexural, bearing, and shear modes of the failure. Also, the effect of web reinforcements was considered. The proposed model was verified by laboratory test results that obtained from five deep beams with the shear span-to-depth ratio of two and some other experimental results existing in the literature. Comparison of the results of the proposed model with relations from ACI 318 and AASHTO-LRFD codes and some other relations showed that the proposed model is efficiently capable of accurately predicting the ultimate load of simply supported deep beams. Also, comparison of experimental results demonstrated that the flexural capacity of deep beams obtained from the Strut-and-Tie Model is conservative.
Keywords: Deep beam; Strut and Tie Model; Reinforced concrete; Shear load.
Presentation of a new membrane strain based finite element for static and dynamic analysis
by Lemmouchi BOUZIDI, Lamine BELOUNAR, Khelifa GUERRAICHE
Abstract: A numerical solution using a strain-based quadrilateral finite element is presented to analyse static and dynamic behaviours for membrane structures. The proposed quadrilateral element which possesses two degrees of freedom (u and v) at the four corner nodes as well as at the central node is based on assumed strains. All the three components of strains have linear variation satisfying the compatibility equation. The validity of the developed element is first applied to several selected static examples. This element is further applied to analyse both free and forced vibrations.
Keywords: membrane; rectangular element; strain approach; finite element; vibration analysis.
FLUID - STRUCTURE- SOIL INTERACTION EFFECT ON DYNAMIC BEHAVIOUR OF CIRCULAR WATER TANKS
by ASHA JOSEPH, GLORY JOSEPH
Abstract: To investigate the seismic behaviour of concrete tanks on different soil conditions, fluid structure- soil interaction system is simulated using finite element analysis software ANSYS. The influence of soil properties on tanks dynamic behaviour is studied by performing modal and transient analyses of cylindrical tanks resting on different soil conditions. Considering four different soil properties, comparisons are made on response parameters such as displacement in radial direction at top of tank wall, maximum hoop force, bending moment and base shear. The effect of frequency content of earthquake on seismic behaviour circular concrete tank is investigated by conducting time history analyses of the tanks under three different earthquakes. All the analyses were performed for half fill and full fill condition. Transient analyses show that the soil property, frequency content of earthquake and water fill condition have significant effect on seismic response of the water tanks.
Keywords: cylindrical water tank; fluid – structure interaction; soil- structure interaction; water fill condition; frequency content of earthquake; time history analysis; finite element analysis.
Evaluation of a Multimode Pushover Procedure for Asymmetric and Non-regular in Plan Reinforced Concrete Buildings under Biaxial Seismic Excitation
by Grigorios Manoukas
Abstract: In the present paper a recently developed multimode pushover procedure is evaluated for non-regular in plan systems. The procedure is applicable to asymmetric in plan buildings under concurrent action of two horizontal seismic components and its main advantage is that it does not require independent analysis in two orthogonal directions. Thus, the use of simplified directional combination formulae, which is not valid in the nonlinear range, is avoided. The preliminary evaluation of the proposed methodology led to quite satisfactory results. However, the studies conducted up to date are limited to regular buildings. Hence, in the present study the procedure is applied to four asymmetric and non-regular in plan reinforced concrete buildings. The values of selected response quantities are compared to those resulting from a conventional pushover analysis variant as well as from nonlinear dynamic analysis. The whole evaluation study leads to the derivation of useful conclusions.
Keywords: nonlinear static procedure; multimode pushover analysis; equivalent single degree of freedom systems; reinforced concrete buildings; asymmetric buildings; non-regular buildings; biaxial seismic excitation; multidirectional seismic effects; directional combination; nonlinear dynamic analysis.
Multi-objective optimization of steel moment frames subjected to blast
by Nima Khaledy, Alireza Habibi, Parham Memarzadeh
Abstract: In recent decades, terrorist attacks have been increased all over the world. For this reason, the design of blast resistant structures is very crucial. On the other hand, for decades the optimum design of structures has been an interesting subject for structural engineers and researchers as it can provide cost and behavioural efficiencies. In the current research, the optimum design of steel moment frames under blast loading has been studied. Towards that end, first, a damage index is developed based on the maximum plastic strain in the members. Then, according to the damage index, a multi-objective optimization methodology is proposed to minimize the structural weight and the damage index. The method utilizes explicit nonlinear dynamic finite element analysis as the structural analysis method and NSGA-II optimization algorithm as the optimization technique. At the final point, based on the proposed method a framework is developed, and two numerical examples are studied. Results of this research show that the developed method is effective in achieving optimal designs with desired cost and damage.
Keywords: Blast loading; Plastic strain; Damage Index; Multi-objective; NSGA-II.
In-Plane Vibration Characteristics of Isotropic Plate with Elastic Edge Restraints
by Kavikant Mahapatra, S.K. Panigrahi
Abstract: It has been well established that in-plane vibration modes in structures occur at high frequencies. Hence, it is important from the perspective of design consideration to analyze the dynamic behaviour of built up structures subjected to high frequency excitation. Also, in-plane vibration becomes important along with transverse vibration, when there is a dynamic interaction of transmission of both low and high frequency frequencies at connected junctions in a structure.
In light of the above, the present analysis has been undertaken for analysis of in-plane free vibration characteristics of isotropic rectangular plates with boundary conditions elastically restrained against expansion, compression and in-plane shear. The analysis has been carried out using single Fourier series solution for the in-plane plate displacements along with four auxiliary function (presented in form of the product of a single Fourier series expansion and one trigonometric function). The auxiliary function has been so chosen as to remove any potential discontinuities existing in the Fourier series displacement function defined over the entire x-y plane. Rayleigh-Ritz procedure has been applied to determine the in-plane natural frequencies of the plate and the unknown expansion coefficients. The use of expansion coefficients has been made to establish the in-plane mode shapes. The demonstrated numerical examples provide an excellent accuracy and convergence of resulting solutions and bring out the effects of variation of boundary conditions on the in-plane vibration characteristics.
Keywords: In-plane Vibration; Elastic Edge Restraints; Fourier Series expansion; Rayleigh-Ritz Procedure; Trigonometric Function; Natural Frequency.
Evaluation of ultimate capacity of corrosion damaged reinforced concrete beam-columns using nonlinear sectional analysis
by Amina Mohammed, Husham Almansour, Beatriz Martín-Pérez
Abstract: A simplified nonlinear sectional analysis approach (NLSA) of aged reinforced concrete beam-columns based on numerical integration, enhanced inspection, material testing and/or empirical estimation of materials deterioration due to reinforcement corrosion is proposed. The proposed procedure is an iterative nonlinear technique that uses numerical integration of the sectional stresses and satisfies force equilibrium in every load increment step. The NLSA model incorporates corrosion-induced damage by reducing the steel cross section and ductility, removing the loss of concrete cover, and accounting for the loss of local bond in corrosion-damaged zones. Two case studies are presented to estimate the effects of corrosion on the structural behaviour of reinforced concrete beam-columns by taking into account critical damage states. The model results show good agreement with test results, high numerical stability and consistent convergence for all examined loading cases.
Keywords: nonlinear sectional analysis; rc beam-column; reinforcement corrosion; assessment framework; aged bridge structure.
Numerical Study of the Behavior of Geosynthetic-Reinforced Soil Retaining Walls Under a Uniform Surcharge
by Wafa Djebablah, Mohamed Salah Nouaouria, Souhila Adjabi
Abstract: The geosynthetic technique of reinforcing retaining walls is one of the technics that is currently being developed in the field of geotechnics. This article focuses on a numerical study, using two-dimensional finite difference Fast Lagrangian Analysis of Continua FLAC2D software, to investigate the influence of a uniform surcharge application on the behavior of a geosynthetic-reinforced soil retaining wall, especially on the maximum tensile force and wall displacement at the end of construction. A parametric study was undertaken taking into account the surcharge load, the width and its distance from the continuous facing panel. The results show that the tensile forces in the reinforcement and the horizontal displacements of the facing panel increase with increasing the uniform surcharge. Furthermore, a small effect was noted on the maximum tensile force in the geosynthetic layers with varying the surcharge distance from the back of the facing panel.
Keywords: Geosynthetic, retaining wall, surcharge, facing panel, Itasca, FLAC2D.