International Journal of Structural Engineering (16 papers in press)
Bending Characteristics of SWCNT Reinforced Composites Plate
by Shivaji Chavan
Abstract: The present work proposes a finite element formulation bending analysis of single walled carbon nanotube reinforced composite (SWCNTRC) plate via well-established higher order shear deformation theory (HSDT). The effective elastic property evaluated using Mori-Tanaka method for functionally graded SWCNT reinforced plate. A seven degree of freedom and C0 continuity finite element model using eight noded isoperimetric elements is developed for precise computation of stresses and deflection of SWCNTRC plate subjected to uniform transvers loading. The finite element implementation is carried out through a finite element code developed in MATLAB; the results obtained by present approach are compared with available in various literatures. Investigated deformation and stress behavior of SWCNTRC plate is presented with different parameters such as volume fraction, aspect ratio (a/h) and z/h ratio are considered.
Keywords: (SWCNTRC) plate; Micromechanics Model; HSDT; FEM Formulation.
Effect of Structural Control on Wind Fatigue Mitigation in Suspension Bridges
by Luca Martinelli, Marco Domaneschi
Abstract: Vibrations induced by wind actions are regarded as one of the sources of fatigue failures for the structural steel members of long-span bridges. This work deals with structural control solutions, namely passive and decentralized semi-active ones, which can give a significant contribution in mitigating such effects. The selected control strategies, which were optimized in a previous research work on a validated finite element model of an existent suspension bridge, are herein evaluated for controlling wind induced fatigue problems in the steel deck.rnStandard deviation of the bending moment along the bridge deck, in association with local stresses in structural details, is recognized as a parameter related to fatigue damage accumulation. The proposed control strategies demonstrate able to significantly reduce such damage. Furthermore, passive and semi-active solutions have comparable effectiveness in terms of mitigating damage due to fatigue.
Keywords: Structural Control; Wind; Fatigue; Bridge Deck.
Mathematical modelling of energy absorption in thin-walled grooved conical tubes with considering of strain hardening phenomena
by Mohammad Javad Rezvani, Mohammad Damghani Nouri
Abstract: In this article, a mathematical model is developed to evaluate the influence of strain hardening on energy absorption and mean crushing load of thin-walled grooved conical tubes. For this purpose, the tubes are shaped with the inner and the outer grooves at different positions along the axis. These grooves facilitate the creating of uniform plastic hinges, and controlling the mode of collapse. The effects of various geometric parameters such as groove distances, groove depth and half apex angle of conical on the collapse response, energy absorption and mean crushing load are investigated. In this analytical model, the variation of circumferential strain and the strain hardening during formation of a fold has been taken into account. In order to verify these analytical results, quasi-static compression tests are performed. The results of this research indicate good agreement between the analytical model and the experimental findings for grooved conical tubes as an energy absorber.
Keywords: strain hardening; energy absorption; mean crushing load; grooved conical tube.
Evaluation of Mechanical characteristics of Concrete Beams under Constant Loading with Alkali-silica reaction (ASR)
by Alireza Joshaghani, Mohammad Amin Moeini, Erfan Hajibandeh
Abstract: This experiment studies the damaging Alkali-Silica Reaction (ASR) expansion effects on the structural performance and mechanical properties of reinforced concrete beams. The beams were cured under standard conditions. In order to provide in-service situations, flexural loading was applied on beams to induce cracks. The newly formed strains on concrete beams were measured along with the compression and tension sections. The results showed that beams with high reactivity in aggregates suffered from more compression strain. It is noteworthy that increasing compression steel with constant tension steel eventuated to substantial effects on tension expansion. Furthermore, increasing the tension steel, while keeping compression steel constant, resulted in minor influences on compression-expansion. Effects of ASR phenomena on the mechanical characteristics and the expansion of concrete are more important and noticeable on reinforced concrete beams. In concrete beams with ASR, ultimate loading was decreased because of largely irreversible steel strains.
Keywords: Alkali-silica reaction (ASR); Concrete; Crack; Tension; Compression; Reinforced beams.
Identification of viscous and structural damping in the dynamic system
by Vikas Arora
Abstract: Damping still remains one of the least well-understood aspects of general vibration analysis. In this paper, a new experimental damping identification method, which can able to identify both viscous and structural damping in the dynamic system, is proposed. The proposed method is a direct method and gives explicit structural and viscous damping matrices. The proposed method requires prior knowledge of accurate mass and stiffness matrices. So experimental viscous-structural damping is identified in two steps. In the first step, mass and stiffness matrices are updated and subsequently viscous and structural damping matrices are identified using updated mass and stiffness matrices obtained in the step 1. The identified viscous-structural damping matrices are both symmetric and positive definite. The effectiveness of the proposed structural damping identification method is demonstrated by numerical and experimental examples. First, two numerical study of lumped mass system and fixed-fixed beam are presented which is followed by an experimental example of cantilever beam. The effects of coordinate incompleteness and different level of damping are investigated. The results have shown that the proposed method is able to identify accurately both viscous and structural damping in the dynamic system.
Keywords: Finite element model updating; Damping identification; Viscous-Structural damping; Dynamic system; Direct method.
FINITE ELEMENT MODELLING OF A COLD CURVED STEEL PLATE GIRDER
by Jihad Rishmany, Issam Tawk, Antoine Gergess
Abstract: Cold bending is a cost-effective solution that is sometimes used for curving structural steel girders. Current usage for bridge structures is limited to projects that fall outside the jurisdiction of AASHTO (American Association of State Highway and Transportation Officials) because of the lack of technical knowledge surrounding this technique. This paper presents results from a three-dimensional finite element model to assess the structural behavior exhibited by steel girders during bending for a proprietary cold curving system. A non-linear FE model is validated against measured data obtained from a previously tested girder. The FE model is extended to explore the performance of all structural components of the girder during bending such as deformations in flanges and web, residual stresses and plastic strains. Findings from this paper provide a framework for accurately predicting the cold bent geometry and how to incorporate residual stresses and plastic strains in the design of curved girders.
Keywords: Cold bending; steel girder; curving; finite element; non-linear; lateral offsets; residual stresses; web; flange; plastic strains.
A STUDY ON PROPERTIES AND EFFECTS OF COPPER SLAG AND MARBLE DUST IN CONCRETE
by Mahesh Patil
Abstract: Marble dust is by-product from marble cutting method. The aim of this paper is to seek out the possibility of using marble dust along with the copper slag as partial replacement to fine aggregate in concrete. Marble dust was employed in mixes containing copper slag as partial substitute to sand in quantities starting from 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, and 50%. The hardened properties of concrete were checked for 7, 28, 56 and 112 days. Results show that up to 60% replacement of marble dust and copper slag to fine aggregate there is increase in compressive strength. Also split tensile strength, flexure, density and modulus of elasticity shows increase in strength at 60% replacement. Permeability on the other hand goes on decreasing up to 60% replacement and increases beyond 60% replacement of marble dust and copper slag. These findings of the analysis state that marble dust will be used as the possible replacement material to sand to provide high strength copper slag concrete.
Keywords: copper slag; concrete; hardened properties; marble dust; partial replacement.
Assessment of welded splices in Beam, Column and Slab
by H.M.A. Mahzuz, Md. Aminul Islam, Saikat Ahmed, Md. Abu Jobair
Abstract: In this study, performance of welded splices in RCC member is judged with respect to lapping splices having straight bars. The objective of this experiment is to find out a safe weld length for welded splices which can be used in beam, column and slab. For that, 12mm, 16mm & 20mm (fy=500Mpa and weldable) rebars were used, having an electrod of E60Ksi. Selected bars were welded together with a welding length of 25 to 150mm respectively and conducted tension and bending tests and found that 100mm welding to be adequate for all bars. So, 100mm welding was considered the safe weld length for welded splices. Specimens of beam, column and slab were prepared and tested with welded splices and straight bars. Effects of load on beam, column and slab for both types of bars were observed and found almost same when 100mm welded splices is used.
Keywords: Welded; Splices; Tensile; Compressive; Bending; Lapping.
Finite Element Analysis of Confined High Strength Concrete Bridge Columns with Opposing-Spiral Reinforcement
by Mohammed Al-Osta, Sabreena Nasrin, Ahmed Ibrahim, Riyadh Hindi
Abstract: The spiral reinforcement is a very common technique used for reinforcing columns in active seismic regions due to its high ductility and high ability of energy absorption. This paper presents a nonlinear finite element analysis of high-strength concrete confined with opposing circular spiral reinforcements. The results are compared with tested scaled concrete columns made with opposing spirals under monotonic axial loads. The proposed technique is developed to improve strength and ductility of concrete columns confined with conventional spiral systems. The finite element (FE) analysis results have showed that the proposed model could predict the failure load and crack pattern of columns with reasonable accuracy. In addition, the concrete plasticity damage model showed very good agreement in simulating columns with opposing spirals. The developed FE model is used to investigate the effect of spiral spacing, γ (ratio of the core diameter to the whole cross section diameter) and compressive strength on behavior of circular spiral reinforced concrete column confined with opposing circular spiral reinforcements. The results of the parametric study demonstrated that for the same spacing between spirals and same strength of concrete, increasing γ will result into increasing the failure load of the column. It is also observed from the study that the ductility of the studied columns is not affected by changing the value of γ. In addition, a correlation between the γ factor, three different compressive concrete strength, and the spacing of opposing spirals was developed in this paper.
Keywords: Finite element model; Column; Spiral reinforcement; Spiral spacing; Confined concrete strength.
EVALUATION OF RESPONSE REDUCTION FACTOR BY PUSHOVER ANALYSIS
by RONAK MOTIANI, J.R. Kunal, Shefali Gahrana, Anurag Nambiar, Mayank Desai
Abstract: Estimation of seismic forces plays a vital role in design of structure and generally these forces are computed using linear static method with aid of response reduction factor. Response reduction/ modification factor (R) incorporates the nonlinear response of any structure during a seismic event, allowing the designer for a linear force based design while reckoning the nonlinear behaviour and deformation limits of the structure. This research focuses on estimation of the response modification factor for realistic RC moment frame buildings laid out as per norms mentioned in the Indian standard. The importance is given into computation of R at a rather component-wise level with the effects and consideration included by various analyses. The result shows that the value suggested by IS1893 focuses upon a general consideration for the value of R which actually shall vary with storey height of the structure, Thus the value of R being either underestimated or overestimated.
Keywords: Response Reduction factor; Pushover Analysis; Linear Static Analysis.
Characteristic of double bottom responses under powered-hard grounding scenario with idealised rock indenter
by Aditya Rio Prabowo
Abstract: Concern regarding accidental-load type to marine structures has become a main priority for various parties in the field of ocean engineering. Remarkable amounts of damage have occurred to ship structures, and unacceptable levels of environmental pollution have been caused by several incidents, which have caused immense losses. The grounding phenomenon included in a load-type accident has been classified as a top-two marine incident, particularly accounting for the oil spills that occur after it takes place. This study aims to present a numerical analysis for estimating ship responses under a hard grounding scenario. This analysis was validated through a pioneering penetration experiment that was re-calculated using the finite element method. In the grounding simulation, the sea floor rock was idealised as a conical indenter penetrating the ship structure. Crashworthiness criteria were considered as the structural response in this work. It was determined that the crushing of the centre girder opened tears in two of the double-bottom compartments. An estimation based on the indenter geometry showed that a steep angle of the conical indenter is capable of producing deeper damage and more visibly predicted initial failures to the centre girder than a blunt indenter under a powered hard grounding scenario.
Keywords: Ship grounding; Rock model; Penetration experiment; Finite element method; Double bottom responses.
RC skew slabs behavior: a finite element model
by Eman Ismail
Abstract: Skew slabs enable to achieve a variety of solutions in, for instance, roadway alignments which contribute to a minor environmental impact for new road construction projects. But the force flow in skew slabs is much more complicated than in straight slab. Thus, the problem is more critical when constructing skew slabs. The complex behavior of skew bridge slabs makes the utilization of Finite Element method (FEM) the most critical and essential analytical tool to model reinforced concrete (RC) skew slab and calculate the non-linear behavior of its structural members with considerable accuracy. This paper uses the general purpose of 3D-finite element and ABAQUS software to design straight and skew slabs. Six separate bridge slab models/sketches of different angles were produced. Same material and material properties, loading, boundary conditions and meshing were used to determine the response and behavior of each bridge slab. The slab is made of concrete class C35/45.
Keywords: Skew slabs; RC concrete; Loading; Slab; Finite Element.
Topology optimization of the discrete structures with the minimum growing ground structure method
by Mojtaba Riyahi Vezvari, Ali Ghoddosian, Mojtaba Sheikhi Azqandi, Mohammad Amin Karimi
Abstract: In previous works in the field of topology optimization of discrete structures, the starting point of the algorithm in the most cases is a structure that consists of all members (ground structure). In this case, too much computing is needed to obtain optimum topology of structure. In order to overcome this disadvantage of the structural topology optimization, the minimum growing ground structure method (MGGSM) was proposed. The method consists of three phases. In the first phase, the minimum stable structure is constructed. In the second phase, this structure, by applying the growth idea becomes a feasible and acceptable structure, and in the third phase, a meta-heuristic optimization method is used to obtain the optimal topology structure. The comparison between the results obtained by the MGGSM and other methods for standard examples shows the efficiency of the MGGSM algorithm to obtain the optimum state.
Keywords: structural optimization; size and topology optimization; discrete structures; truss structure.
Damage evaluation in plates using modal data and firefly optimization algorithm
by Niusha Navabian, Reza Taghipour, Mohsen Bozorgnasab, Jamal Ghasemi
Abstract: This paper presents a method to identify the location and severity of the damages in plates. The location of damage is detected using a new damage index (MDC), based on the mode shapes and their derivatives. The mode shapes are calculated via modal analysis and their derivatives are obtained through central finite difference approximation. The results are fed into the proposed damage index to find the location of damaged areas. Thereafter, the quantity of damage in the damaged area is assessed using Firefly Algorithm (FA). The capability of the proposed damage evaluation procedure is shown through some examples. According to the results, the new proposed index is capable of finding the damage locations with acceptable accuracy. In addition, FA can assess the damage severities in the damaged zones with an error less than 2 percent. The proposed approach has the ability to identify the damages even for noisy polluted data.
Keywords: Structural damage evaluation; Modal analysis; Mode shape; Modal curvature; Modal Damage Criterion; Firefly Algorithm; Plate-like structure; Damage scenario; Damage location; Damage severity; Damage index.
Performance study of steel-concrete composite beam involving flexible shear connector
by Raguvaran Balasubramanian, Baskar Rajaram
Abstract: The paper presents the results of an investigation on steel-concrete composite beam subjected to static loading. An experimental investigation and analytical study using finite element analysis. The load carrying capacity of steel-concrete composite beam is presented. The steel-concrete composite beam is embedded with 19 mm stud shear connector. The interaction of steel-concrete layers of composite beam with headed stud shear connector due to the application of flexural load is analysed. The experimental results are compared with those of analytical modelling using ANSYS 10.
Keywords: Headed stud shear connector; Steel-concrete composite beam; Flexural loading; Finite element analysis (FEA); ANSYS.
Comparative study of nonlinear static pushover analysis and displacement based adaptive pushover analysis method
by Rutvik Sheth, Jayesh Prajapati, Devesh Soni
Abstract: A major challenge in performance-based earthquake engineering is to develop simple and practical methods for estimating capacity level and seismic demand on structures by taking into account their inelastic behavior instead of complicated nonlinear time history analysis. However, in nonlinear static procedure both predetermined target displacement and force distribution pattern are based on a false assumption that structural behavior and its responses are dominated by the fundamental vibration modes. Displacement-based Adaptive Pushover Analysis (DAP) is one of the performance assessments tool for improving accuracy of the obtained results of nonlinear static analysis in estimating the seismic demands of structures. The paper attempts to use DAP method to evaluate performance of 6, 9, 12 and 15 storey RC moment resisting frame, analyzed for seismic Zone V and designed as per provisions of IS codes. It is observed from study that DAP analysis shows better results compared to static pushover analysis.
Keywords: Moment resisting frame; Nonlinear Static Pushover Analysis; Displacement based adaptive pushover analysis (DAP); Incremental dynamic analysis (IDA).