Ronaldas Jakubovskis

Serviceability Analysis of Concrete Beams with Different Arrangements of GFRP Bars in the Tensile Zone

AbstractExtensive experimental investigations were carried out to investigate the serviceability (deformations and crack opening width) of fiber–reinforced polymers (FRP) reinforced concrete members. However, most of the tests were limited to conventional arrangement of bars in a section. Considering glass fiber–reinforced polymer (GFRP) bars (one of the most frequently used types of composite reinforcement), this study experimentally and analytically investigated the serviceability behavior of beams with different arrangements of reinforcement bars in the tensile zone. With particular emphasis on tension-stiffening and bond behavior, the experimental program consisted of full-scale beams and bending bond specimens. The tests revealed specific features in the behavior of the beams due to distribution of tensile bars in three layers or enlarging the cover. A numerical procedure, based on local interaction of reinforcement and surrounding concrete, was applied for serviceability analysis. Several bond stres...

Serviceability Analysis of Flexural Reinforced Concrete Members

Abstract The paper presents a simple discrete crack model for analyzing the deformation and crack width of reinforced concrete beams. The model is based on a non-iterative algorithm and uses a rigid-plastic bond-slip law and elastic properties of materials. Curvatures and crack widths predicted by the proposed technique were checked against the test results of six experimental beams, reported by the authors and other investigators. The article also proposes and discusses a numerical procedure for deriving the average bond stress with reference to the test data. Serviceability analysis resulted in a reasonable agreement on the test measurements.

Mechanical Properties of the Bond Between GFRP Reinforcing Bars and Concrete

Results obtained in the pullout of GFRP and steel bars from concrete and in testing the contact zone between the rods and concrete in bending are presented.

Prediction of Concrete Shrinkage Occurring Prior to External Loading and Effect on Short-Term Constitutive Modeling and Design:

Although shrinkage effect is traditionally taken into account in the assessment of long-term deformation of concrete structures, it may significantly affect cracking resistance and deformations of reinforced concrete members subjected to short-term load. Though generally neglected, the shrinkage effect may be of high significance in constitutive modeling of tension-stiffening, particularly, when it is based on tests of reinforced concrete members. Disregarding the shrinkage effect may result in considerable errors of deflection predictions. This paper statistically investigates the accuracy of several well-known free shrinkage strain prediction techniques: Eurocode 2, ACI 209, CNIIS (Russia), Bažant & Bawejas (B3), and Gardner & Lockmans (GL 2000). Accuracy of shrinkage prediction models and the influence of shrinkage assessment errors on constitutive modeling and deformation prediction results are illustrated and discussed. Unlike the previous investigations, the present study considers a shrinking period characteristic to the age of a member at first loading. The manuscript reports recommendations useful for short-term constitutive and deformation analysis of reinforced concrete.

Experimental Investigation of Tension Stiffening in RC Ties

The increasing application of high-performance materials in civil engineering led to the development of reinforced concrete (RC) structures with reduced cross sections and increased spans. In such structures serviceability limit state often becomes the governing condition of the design. Present study investigates the deformation behaviour of high-strength RC ties reinforced with high-grade bars. Experimental investigation was carried out measuring the postcracking stiffness of the specimens at high strain levels. It was found that, despite the reduction in stiffness, a considerable part of the average tensile stresses were carried by the concrete at the advanced loading stages, thus effectively stiffening the RC member.

Experimental and numerical analysis of strain gradient in tensile concrete prisms reinforced with multiple bars

Abstract This work is a continuation of the ongoing research on deformation behavior of reinforced concrete elements under tension. The previous studies have revealed that deformation behaviors of elements reinforced with multiple bars and the traditional prismatic members reinforced with a center bar are essentially different. The latter layout, though typical of laboratory specimens, could not represent the norm of structures in real-life. Thus, a new test methodology to investigate the strain distribution in concrete prismatic members reinforced with multiple bars subjected to axial tension is devised. Prismatic concrete specimens with different reinforcement configurations were fabricated and tested using the proposed setup. Deformation behavior of the specimens is modeled with a tailor-designed bond modeling approach for rigorous finite element analysis. It is revealed that the average deformations of the concrete could be different from the prevailing approach of average deformations of the steel, and are dependent on the reinforcement configurations. Therefore, the efficiency of concrete in tension should be carefully taken into account for rational design of structural elements. The study endorses promising abilities of finite element technique as a versatile analysis tool whose full potential is to be revealed with the advent of computer hardware.

Determination of the Stress–Crack Opening Relationship of SFRC by an Inverse Analysis

Quantifying the residual stresses σfr in tension is one of the most critical issues in the theory of steel-fiber-reinforced concrete (SFRC). The objective of this investigation is to determine the stress–crack opening relation of SFRC. An inverse technique is proposed for the determination of σfr by employing experimental data from three-point bending tests on notched members. The nonlinear finite-element analysis program ATENA is utilized to verify the stress–crack opening relation obtained. A comparison of simulated load–crack tip opening displacement curves with experimental data attests to the adequacy of the inverse technique.