International Journal of Structural Engineering (6 papers in press)
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.
TEMPERATURE ANALYSIS OF SEGMENTAL BOX GIRDER BRIDGES
by MATHEW C S, R.K. Ingle
Abstract: Uniform temperature causes axial stresses and temperature gradient causes bending stresses on the structure. Therefore, to study the effect of temperature, two different parametric studies are conducted. Number of spans in the bridge are varied in the former and the span is varied in the latter. The segmental bridge is modeled in a finite element software and temperature loads are applied according to IRC 6-2016. The results obtained from finite element analysis are compared and validated with the conventional method for simple case. Effect of uniform temperature changes in segmental bridges are found to be negligible. But, temperature gradient causes significant moments and stresses; thus is found to be the governing temperature for the analysis and design of segmental bridges. It is also observed that, as span increases, the maximum values of bending moments and shear forces due to positive temperature gradient and negative temperature gradient decreases.
Keywords: bending moment; box girder; cross section; deformation; modelling; negative gradient; positive gradient; segmental bridges; shear force; stress; temperature.
Structural parameters approximation of existing symmetric-plan concrete buildings using finite element design and analysis program
by Sofiane Allaoua, Lakhdar Guenfaf
Abstract: In the field of earthquake engineering and structural dynamics, the knowledge of the structure properties is very important for structural health monitoring and structural control. In this paper, the widely used SAP2000 program by engineers in the design and analysis of civil engineering structures, is proposed to approximate the structural parameters of existing symmetric-plan concrete buildings. First, the existing building structure is designed in the program with respect to the real geometry and material properties. Also, an analytical model of the existing building is developed. In this model, an idealization in the formulation of the motion equations for the symmetric-plan concrete building is adopted. For this idealization, we assume firstly that the mass is concentrated at the floor levels, and secondly that a linear viscous damping mechanism represents the energy dissipation in the structure. Afterward, a modal analysis using SAP2000 program is performed. Then, the structural parameters can be approximated from the obtained results. To verify the precision of the approximated structural parameters, numerical calculation is performed. In this calculation, the response of the analytical model developed in MATLAB is compared to the response of the real structure designed in SAP2000. Different types of excitation are used, and the obtained results reveal that the proposed method can be used to approximate the structural parameters of existing symmetric-plan concrete building with 97% of precision.
Keywords: dynamic parameters of structure; symmetric-plan building; finite element method; SAP2000; analytical model.
Testing of Frequencies Identification Techniques on a Reinforced Concrete Building FE Model
by Nicola Ivan Giannoccaro, Francesco Micelli, Mattia Luperto
Abstract: The possibility of performing a dynamic analysis of frame buildings is an important task since it can increase the knowledge of its response to dynamic forces. This is also important in order to plan maintenance and retrofitting, rather than to evaluate the seismic vulnerability and the response to intense wind. In the last years, nondestructive techniques based on ambient vibration data have been developed in order to estimate the modal parameters (natural frequencies and mode shapes) of buildings. They have been performed mainly by using the accelerometers data of slender buildings. The present paper illustrates an assessment of identification techniques, applied to the numerical results of a Finite Element (FE) model obtained for a reinforced concrete rnframe building. The frame, with a four storey configuration, has been designed in accordance with the actual Italian seismic guidelines which respect the provisions of the Eurocodes. Several tests have been conducted in order to determine a suitable procedure that can permit to identify, from the data of virtual accelerometers placed on the building model, the relevant correct modal parameters. This procedure may permit to identify the correct number of accelerometers and their position within the structure, in order to guarantee a good frequency identification in real conditions in terms of external excitement. rn
Keywords: Dynamic analysis; reinforced concrete building; ambient vibration data; finite element model; operational modal analysis techniques.
NLFE investigation on the FRP bar reinforced concrete deep beams with and without openings
by RAMADASS SUBRAMANIAN, Job Thomas
Abstract: This study reports the details of the finite element (FE) analysis to predict the load-deflection response of twelve concrete deep beams reinforced with fibre reinforced polymer (FRP) bars that failed in shear. The analysis is carried out using the ANSYS software and the validation of the analysis is made by predicting the behaviour of the beams tested in the laboratory. The variables of the experimental study are shear span to depth ratio and FRP longitudinal reinforcement ratio. The nonlinear stress-strain relationships of both concrete and FRP bars are accounted for in the FE model. The non-linear finite element (NLFE) model fairly predicted the shear failure of the concrete deep beams. The influence of the material constants of concrete in NLFE analysis is also examined. Sometimes, it is necessary to provide holes in beams to provide the service lines in the buildings or other infrastructure. Hence, the influence of the location of openings in the deep beams reinforced with FRP bars is studied. In this study, a hole is provided at different locations along the span of the deep beam at mid-depth and analysed. The study revealed that the maximum reduction in the ultimate load carrying capacity of the deep beam is found to be 69.8% when the hole is provided on the inclined strut line located at the mid-depth of the beam. The study reveals that appropriate modification is to be introduced in the design factors when holes are provided in the beams and is illustrated. FE analysis can be used as a tool for finding the safety margin for the beams having holes.
Keywords: Concrete deep beams; FRP; ANSYS; shear; load; deflection response;.
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.