International Journal of Structural Engineering (15 papers in press)
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.
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.
Scheme for Beam Progressive Collapse Mitigation
by Bilal El-Ariss, Said Elkholy
Abstract: Latest recommendations have made provisions to improve structure resistance to progressive collapse in the event of interior support collapse. This paper defines a mitigating scheme to repel progressive collapse in reinforced concrete beams due to damaged interior column by providing a new path to transfer the loads to other columns. The mitigating scheme suggests the use of unbounded unstressed externally installed fiber reinforced plastic cables with straight profile and three deviators. An open source finite element package for structural analysis (ZEUS-NL) using fiber element approach is adopted to model the mitigated beam. The proposed numerical model evaluates progressive collapse of such beams using a push-down analysis simulating column removal. It assumes that anchorage and deviator locations of external cables act as rigid arms that connect external cables to the beam. Numerical results demonstrate that the defined mitigating scheme increases the beam resistance to progressive collapse due to interior column failure.
Keywords: progressive collapse; FRP external unbounded cables; fiber element approach; cable deviators; catenary action.
Evaluation of Steel Special Moment Resisting Frame Structures with Different Spans and Story Numbers
by Mehdi Babaei, Mohsen Jabbar
Abstract: Optimal topology design of structures has always been a challenging issue for engineers and designers. Some studies have been carried out in this regard and optimal layouts for buildings have been proposed. Many of them, however, suggested unpractical or impossible design from construction technology point of view. On the other hand, a good design has to satisfy not only structural but also architectural requirements, which provides cost-effective building with useful areas and spaces. In this article, performance of special steel moment resisting frames were evaluated in terms of the required materials and the architectural requirements. For this purpose, different building models including different arrangements of columns, different story numbers, and different sites were defined to cover all possibilities. Since static analysis method were employed to analyze the structures, building models up to 14 stories have been evaluated. To obtain comparable results, a same plan was defined for models so that all architectural requirements for parking areas of two, three and four cars to be satisfied. Required materials and structural costs for building models with five, ten, and fourteen stories with different layouts were obtained and compared. Results showed that moderate (not large/not short) beams were almost the optimal design for mid structures, and when the story numbers increases, larger spans were required to provide optimal design.
Keywords: special moment resisting frame; optimization; span; regular building; story.
Nonlinear System Identification from Noisy Measurements
by Abdullah Al-Hussein, Achintya Haldar
Abstract: A novel nonlinear system identification procedure using noisy measurements for health assessment of real civil infrastructure systems is presented. The important features of the procedure are that it can identify a structural system using only a limited number of highly noise-contaminated responses measured for a very short duration. To compensate for the use of very short duration response time-histories, multiple weighted global iteration (WGI) procedure is introduced in the unscented Kalman filter (UKF) algorithm to help the convergence process. It is denoted as UKF-WGI procedure. The algorithm is a finite element-based nonlinear system identification technique. It identifies not only the integrity of the whole structure, but also the locations and severity of the defects. Since no similar studies are reported in the literature, the superiority of UKF-WGI over the extended Kalman filter-based procedure in the presence of noise is established with the help of several illustrative examples.
Keywords: nonlinear system identification; structural health assessment; damage detection; unscented Kalman filter; extended Kalman filter; finite element; noisy measurement.
A Consistent triangular thin flat shell finite element with drilling rotation based on the strain approach
by HAMZA GUENFOUD, Mohamed Himeur, Hassina Ziou, Mohamed Guenfoud
Abstract: In the present paper, we offer a new flat shell finite element. It is the result of the combination of a membrane element and a bending element, both based on the strain based formulation. It is known that C
Keywords: Finite Element Method; membrane; plate; shell; condensation; deformation approach; True rotation.
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 American Association of State Highway and Transportation Officials (AASHTO) 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 behaviour 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.
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, the performance of welded splices in RCC member is judged with respect to lapped 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, 12 mm, 16 mm and 20 mm (fy = 500 MPa and weldable) rebars were used, having an electrode of E60Ksi. Selected bars were welded together with different welding lengths ranging between 25 to 150 mm and conducted tension and bending tests on them. It was found that 100 mm welding was adequate for all bars. So, this length 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. The effects of load on beam, column and slab for both types of bars were observed and found almost same when 100mm welded splices are used.
Keywords: welding; rebar; splice; tension; compression; bending; lapping.
Topology optimisation of the discrete structures with the minimum growing ground structure method
by Ali Ghoddosian, Mojtaba Riyahi Vezvari, Mojtaba Sheikhi Azqandi, Mohammad Amin Karimi
Abstract: In previous works in the field of topology optimisation 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 the structure. In order to overcome this disadvantage of the structural topology optimisation, 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 optimisation method is used to obtain the optimal topology of the 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 optimisation; size and topology optimisation; discrete structures; truss structure.
Damage evaluation in plates using modal data and firefly optimisation 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 newly 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%. 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; MDC; modal damage criterion; FA; 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 B. Raguvaran Balasubramanian, Rajaram Baskar
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 (FEA). The load carrying capacity of the 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; FEA; finite element analysis; ANSYS.
Comparative study 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 the capacity level and seismic demand on structures by taking into account their inelastic behaviour 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 the structural behaviour and its responses are dominated by the fundamental vibration modes. Displacement-based adaptive pushover analysis (DAP) is one of the performance assessment tools for improving the accuracy of the obtained results of the nonlinear static analysis in estimating the seismic demands of structures. The paper attempts to use DAP method to evaluate the performance of 6, 9, 12 and 15 storey RC moment resisting frame, analysed for seismic Zone V and designed as per provisions of IS codes. It is observed from the study that DAP analysis shows better results compared to static pushover analysis.
Keywords: moment resisting frame; nonlinear static pushover analysis; DAP; displacement based adaptive pushover analysis; IDA; incremental dynamic analysis.