International Journal of Structural Engineering (9 papers in press)
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; NLSA; 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.
Numerical Study on the Behaviour of End-Plate Beam-to-Column Connections Under Lateral Impact Loading
by Ali Al-Rifaie, Alaa Al-Husainy, Hayder Shanbara
Abstract: An extended study on the lateral impact response of end-plate beam-column connections is presented in this paper. A parametric study is presented based on validated finite element models that were built in the companion paper that investigates the behaviour of two types of connections named flush plate connection (FPC) and partial depth end-plate connection (PDEPC) under quasi-static and lateral impact loadings. It was demonstrated that the specimens subjected to quasi-static and lateral impact loading exhibited similar modes of failure. Maximum Dynamic Increase Factor (DIF)s of 1.38 and 1.45 were also proposed based on the results of experimental tests and numerical analysis, respectively. In the current study, the FE models were validated against additional two specimens tested with thick plates under lateral impact loading to raise the accuracy of the models. Using the validated models, different parameters were investigated such as the effect of mass and velocity, number of bolts, projectile shape and boundary conditions. Moreover, the study was extended to predict the lateral impact response of another type of connections named extended end-plate connection. The numerical results manifested that using thick end-plate is unfavourable to resist the lateral impact loading. Also, it was found that the impact capacity of connection is enhanced with a higher velocity and a lighter mass. Moreover, the deformation mode is not influenced by changing the projectile configuration or the boundary conditions.
Keywords: Lateral impact loading; End-plate; Beam column connections and Finite Element.
Shear Strengthening of RC Beams using GFRP Sheets
by Archana Kumari, Nibedita Dalai, Rama Ballav Swain, Amar Nath Nayak
Abstract: This paper presents an experimental investigation on the shear behaviour of RC beams strengthened with externally bonded glass fibre reinforced polymer (GFRP) sheets. The externally applied GFRP technique is significantly effective to enhance the ultimate load carrying capacity of RC beams. Two beams without GFRP and nine beams wrapped in different lay-up patterns with one/two layers of GFRP sheets have been tested for shear under two-point loading. Loads at first crack of beam/delaminating of GFRP, tearing point of GFRP and ultimate failure of the beam has been noted and types of failure have also been observed. Thereafter, a critical discussion is made with respect to increase in the strength of retrofitted beams with respect to the beam without GFRP in order to explore the optimal use of GFRP for strengthening the RC beams. The comparison is also made between the shear strength obtained from experimental results and that predicted from different design proposals available in the literature.
Keywords: Failure mode; GFRP fabrics; RC beam; shear; strengthening.
Effectiveness of Stainless Steel Wire Mesh in Shear Strengthening of Reinforced Concrete Flanged Beam
by Sunil Raiyani, Paresh Patel, Sagar Vora
Abstract: The Stainless Steel Wire Mesh (SSWM) is an emerging and viable alternative to Fiber Reinforced Polymer (FRP) in repair and rehabilitation of Reinforced Concrete (RC) structures. The present investigation aims to study the effectiveness of externally bonded SSWM in enhancing the shear strength of RC flanged beams with T-shape cross-section. To identify appropriate SSWM as a strengthening material, five locally available SSWM are selected based on the diameter of the wire and the opening size of mesh. Tension test is performed on SSWM coupons to determine the tensile strength of SSWM and bond test is performed to understand the bond behaviour between SSWM and concrete surface. Based on tensile strength, bond behaviour and ease of application on concrete surface, 40 x 32 type SSWM is selected as strengthening material for RC T-beams. An experimental investigation is conducted to study the behaviour of RC T-beams strengthened by externally bonded 40 x 32 type SSWM under transverse loading. Two beams are considered as control specimen, and four beams are externally strengthened by two different wrapping configurations. All six simply supported T-beams are tested under the two-point loading until failure. The load at formation of first crack and ultimate failure of controlled and SSWM strengthened RC T-beams are compared. Load-deflection behaviour, failure modes and crack propagation patterns of all specimens are also presented in this paper. Results of experimental investigation prove the effectiveness of SSWM strengthening in terms of increased shear capacity and reduced mid-span deflection. The numerical model of controlled and SSWM strengthened T-beam specimen is developed using finite element based software ABAQUS to validate experimental results. Ultimate load and corresponding deflection obtained from finite element analysis have good agreement with that obtained from experimental study.
Keywords: Stainless Steel Wire Mesh; Reinforced Concrete; Bond strength; Tensile strength; Shear strengthening.
Effect of Calcium Lactate and Bacillus Subtilis Bacteria on Properties of Concrete and Self-Healing of Cracks
by KUNAMINENI VIJAY, Meena Murmu
Abstract: The bio-mineralization method gives potential outcomes in the micro-structure of concrete by precipitating CaCO3 in concrete. Be that as it may, the micro-organisms need a supplement source for their better development in concrete. In this manner, calcium lactate is moreover included in the concrete as a supplement source for micro-organisms. It is imperative to know the impact of this calcium lactate and bacteria on the properties of concrete. In this study, an endeavor is made to know the impact of calcium lactate and bacillus subtilis bacteria on properties of concrete. Results demonstrate that there is a decrement in the carbonation rate and improvement in the compressive strength. Scanning electron microscope analysis shows that the dense matrix is obtained in bacterial concrete as compared to the control mix. The significant findings of this examination affirm that the performance of concrete improved by adding calcium lactate and bacillus subtilis bacteria into the concrete.
Keywords: Bacillus subtilis; Calcium lactate; Compressive strength; Carbonation; Calcium Carbonate.
Meta heuristic active and semi active control systems of high-rise building
by Seyed Hossein Hosseini Lavasani, Rouzbeh Doroudi
Abstract: This study focuses on the application of dampers installed in a structure to control the seismic responses of the building. Fuzzy logic controller is applied to estimate control force and voltage of ATMD and MR damper. To find out a suitable fuzzy logic controller which reduces the responses of structure, it is essential to tune membership functions, extract appropriate rule base. The dynamic parameters of TMD is very effective to decrease the responses of structure. The Observer-Teacher-Learner-Based Optimization algorithm (OTLBO) is used to optimize TMD parameters and fuzzy logic controller. The results show that the optimized models by this algorithm can effectively decrease the peak seismic response of the building.
Keywords: Structural control; Fuzzy logic control; Observer-Teacher-Learner-Based Optimization; Optimization; TMD; ATMD; Meta heuristic.
Proposing a simplified and parametric numerical shear stress-strain model for RC Deep beams
by Seyed Shaker Hashemi, Saeid Javidi, Mahmoud Malakooti
Abstract: In this paper, the behavior of reinforced concrete (RC) elements has been studied and a new shear stress-strain (SS-S) model is proposed for RC deep beams. Due to the high sensitivity of deep beams to the effect of shear deformations, two RC deep beams have been modeled numerically, and the results have been compared with their experimental behaviors. In order to consider the effect of bar-concrete interaction, simply supported deep beam is divided into several sub-elements, and individual degrees of freedom are assigned to bars, which allow them to act independently. To consider the effect of shear deformations, deep beams have been analyzed according to Timoshenko beam theory, and several SS-S models have been applied in analytical models to monitor their effects. Since SS-S model is highly sensitive to several factors, a numerical definition of RC deep beams shear behavior is presented after assessing the contribution of main effective parameters on RC elements shear behavior. After evaluating the analytical results with experimental behavior, a simplified numerical SS-S model is proposed. The mentioned model is a push curve which has three breaking points. Proposed SS-S model is composed of several mathematical equations which allows users to easily predict the shear behavior of RC deep beams without dealing with complex and time-consuming calculations.
Keywords: nonlinear analysis; fiber model; shear stress-strain; bar-concrete interaction; shear deformation; deep beam; MCFT.