Darius Bacinskas

SHRINKAGE IN REINFORCED CONCRETE STRUCTURES: A COMPUTATIONAL ASPECT

Abstract This paper introduces the recent state of research on shrinkage of concrete. It reviews prediction models of shrinkage strain and curvature analysis methods of reinforced concrete members. New test data on concrete shrinkage has been presented. Various factors that influence shrinkage have been discussed. A calculation technique on short‐term deformations of cracked reinforced concrete members including shrinkage has been introduced. The technique is based on layer model and smeared crack approach. Shrinkage influence on behaviour of reinforced concrete beams was investigated numerically and compared with test data reported in the literature. It has been shown that shrinkage has significantly reduced the cracking resistance and leads to larger deflections.

Deformational analysis of prestressed high‐strength concrete members using flexural constitutive model

Abstract In this paper, an attempt has been made to extend application of the recently proposed Flexural constitutive model to short‐ and long‐term deformational analysis of flexural partially prestressed concrete members. The effect of tension stiffening and non‐linear time effects of creep and shrinkage are taken into account. Effective modulus method is used for modelling long‐term deformations. The proposed calculation technique is based on the layered approach and use of material stress‐strain relationships. Curvatures prediction results were tested against experimental data of partially prestressed concrete beams reported in literature.

Mechanical simulation of reinforced concrete slabs subjected to fire

Abstract There are many buildings and civil engineering works under construction which are at risk of fire. The fire resistance analysis of reinforced concrete structures constitutes an important part in their design. However, the analysis of the behaviour of load‐bearing members under high temperature conditions is very complicated. Various factors that influence the behaviour of the members need to be taken into account. Analytical and computation methods have been developed in the field of reinforced concrete building exposed to high temperature or accidental fire. Unfortunately, such models are computationally too demanding and their application are limited even for a simply supported reinforced concrete members (beams, plates etc). In this paper, an attempt has been made to extend application of the Flexural model to stress and strain analysis of flexural reinforced concrete members subjected to high temperature. Constitutive models and key material parameters describing thermo‐mechanical behaviour o...

LAYERED APPROACH FOR LONG-TERM DEFLECTIONS ANALYSIS OF REINFORCED CONCRETE BEAMS

Santrauka Straipsnyje integralinis fizikinis deformatyvumo modelis [1,2] pritaikytas lenkiamųjų gelžbetoninių elementų ilgalaikėms deformacijoms nustatyti. Pasiūlytas inžinerinis skaiciavimo metodas pagrįstas senėjancios medžiagos efektyviojo modulio (age-adjusted modulus) [3] ir sluoksnių metodais bei relaksacijos procedūra, kurią pasiūlė Bresleris ir Selna [4]. Svarbi pasiūlytojo modelio dalis yra modifikuotos gniuždomojo bei tempiamojo betono įtempių-deformacijų diagramos. Gniuždomajam betonui modeliuoti taikoma modifikuota Hognestado [5] diagrama, nustatyta trumpalaikio apkrovimo atvejui. Si diagrama pateikta 1 pav., o jos kylancioji dalis aprasoma (1) priklausomybe. Ilgalaikio stiprumo ribos sumažejimas įvertinamas israiska (2), pasiūlyta Jasino [6]. Maksimalius įtempimus atitinkancios deformacijos bei ribinės gniuždomojo betono deformacijos nustatomos atitinkamai pagal (3) ir (4) priklausomybes. Tempiamojo betono modeliavimui taikoma modifikuota integralinė įtempių-deformacijų diagrama (2 pav.). Kri...

DEFLECTION ESTIMATES OF REINFORCED CONCRETE BEAMS BY DIFFERENT METHODS

Santrauka Neseniai buvo pasiūlyta supleisėjusio tempiamo betono įtempių-deformacijų priklausomybė [4] lenkiamųjų gelžbetoninių elementų deformacijoms apskaiciuoti. Si priklausomybė buvo isvesta, taikant novatoriską metodą. [4–6], kuriuo is eksperimentinių lenkiamų gelžbetoninių sijų momentų-kreivių ir (arba) momentų-deformacijų diagramų nustatoma visa tempiamo betono vidutinių įtempių-deformacijų diagrama, įskaitant ir jos krintanciąją dalį. Apdorojus įvairių autorių eksperimentais gautas tempiamo betono įtempių-deformacijų diagramas, buvo pasiūlyta minėtoji medžiagos priklausomybė, aprasyta (13) priklausomybe. Sio darbo tikslas yra patikrinti pasiūlytosios priklausomybės tikslumą. Ją taikant dideliam eksperimentinių gelžbetoninių sijų (isbandytų kelių tyrinėtojų) skaiciui buvo apskaiciuoti įlinkiai ir palyginti su kitų žinomų analitinių metodų apskaiciavimo rezultatais. Trumpai apibūdinami penki lenkiamųjų gelžbetoninių elementų įlinkių skaiciavimo metodai. Pirmieji trys—tai amerikiecių [1], Euronormų [2...

Developing three-dimensional digital image correlation techniques to detect the surface smoothness of construction materials

A low-cost three-dimensional digital image correlation coefficient method, 3-D DIC equipped with one advanced digital camera and high-speed computer to detect the flatness of plaster of Paris casts is proposed in this research. The test and analysis results show that this proposed method can easily reveal the rugged surface of plaster cast. No matter what the absolute displacement, rotate on z-axis, strain on z-axis and von Mises strain of analysis results are extremely close to the real situation of this test sample. Then, the joint roughness coefficient (JRC) is used to compare the test results of 3-D DIC with the test results of laser scanner. These results indicate that the JRC values measured by laser scanner are very similar to that measured by 3-D DIC. Therefore, the accuracy degree of this 3-D DIC method is high enough for applying it to achieve the three-dimensional surface smoothness of construction material.

Experimental Investigation on Short- and Long-Term Deformations of Cracked Reinforced Concrete Ties

The current study reports the test results on deformations of cracked reinforced concrete (RC) ties. Four ties were tested under shortand long-term loading for 315 days. To perform the long-term tests, four testing rigs were constructed. The experimental results were compared with the Model Code 2010 predictions. It was revealed that the code overestimates the cracking load by 65-90%, and it is most likely due to the neglect of the shrinkage effect. It has been shown that 30-45% of the strain increment due to the long-term loading occurred during the first two-three days. The deformations of RC ties have practically stabilized after almost 300 days. The code quite accurately predicted the ultimate long-term strains. However, the prediction model was found to be too simplified to assess the increment of the long-term deformations. INTRODUCTION Structures are designed to satisfy both strength and serviceability requirements. In consequence of the extensive studies, the ultimate load behavior of reinforced concrete (RC) flexural members is well understood. Nevertheless, due to the use of refined ultimate state theories as well as higher strength materials, resulting in structures with longer spans and smaller depths, control of deformations is often the governing design criterion. Adequate modelling of cracking and, particularly, post-cracking behavior, as one of the major sources of physical nonlinearity, is the most important and difficult task of structural mechanics. Complex physical phenomena, such as concrete creep, shrinkage, and cracking greatly contribute to deformation increments: the long-term deformations might increase up to 3-4 times above the initial values (Gribniak et al. 2013). Most of the studies of the long-term deformations of RC members were dedicated to the investigation of bending members and only a few experimental programs were devoted to RC ties (Jaccoud 1987, Beeby and Scott 2005, Wu and Gilbert 2008, Vilanova et al. 2014). To fill this gap, the current study reports experimental results of four RC ties tested under short-term and under sustained load for a period of 315 days. The results gathered from the short-term experiments were compared to the deformations predicted by the Model Code 2010. CONCREEP 10 958

Development of Digital Imagine Correlation (DIC) Method for Three-Dimensional Rugged Surface of Construction Material

Digital Image Correlation, DIC method is developed a low-cost digital image correlation coefficient method based on advanced digital cameras and high-speed computers. Traditionally, two or more cameras are widely applied for conducting 3-D monitoring. There are numerous parameters need to be accurately calibrated. Therefore, the results of 3-D accuracy are worse than that of 2-D accuracy. The feasibility of a single camera to collect image to analyze the three-dimensional rugged surface of material is proposed in this study. A three-dimensional facial mask-like human makeup test and plaster cast are used to test. The test results reveal that the coordinate error between these two photos of the three-dimensional facial mask-like human makeup test is only 0.002mm and the absolute displacement, rotate on z-axis, strain on z-axis and von Mises strain of analysis results are extremely close to the real surface plaster cast.

Dynamic Testing of Railway Truss-Bridge

The study results of the historic narrow-gage railway steel truss bridge built in the last century and still used are provided in this paper. Only one of the spans results is provided herein. Field tests with the original locomotive were carried out in order to develop an analytical model that will be used to evaluate the capacity of the bridge. Responses (dynamic displacements, accelerations, mode shapes, corresponding to the resonance frequencies and modal damping values) for the construction of the bridge were found. Studies have shown that the bridge meets the requirements and has enough reserve to work safely.

Experimental Investigation of the Deformation Behavior of SFRC Beams with an Ordinary Reinforcement

The paper reports test results for steel-fiber-reinforced concrete beams. Four-point bending tests on 12 full-scale beams (with longitudinal reinforcement ratios of 0.3 and 0.6%) were carried out to investigate the postcracking behavior of the members. The content of fibers, spaced at equal intervals, ranged from 0 to 120 kg/m3, resulting in the amount of 0, 0.5, 1.0, and 1.5% by volume. A simple deflection analysis technique based on a linear interpolation between the cracking and yielding points is discussed. It is shown that this technique adequately assesses the bending moment at yielding, but significantly overestimates the corresponding deflections. It is concluded that the model discussed should be improved by taking into account the tension stiffening effect.