Strypinės armatūros išdėstymo įtaka betoninių elementų deformacijoms ir pleišėjimui

The aim of this work is to investigate the arrangement effect of bar reinforcement to deformations and cracking behaviour of concrete elements subjected to short-term loading. The study experimentally verifies the effective concrete area concept and analyses peculiarities of cracking process of reinforced concrete (RC) members with the emphasis on arrangement of the bar reinforcement. The test results of 9 beams and 119 ties with different reinforcement and loading layouts are reported. Results of the beam tests do not reveal a clear correlation between the crack widths and the crack spacing when the reinforcement layout changes, while the number of the reinforcement layers correlates with the flexural stiffness. An iterative procedure has been proposed for localizing the end effect in the ties. This procedure allows identifying the representative geometry for assessing the cracking parameters of RC ties. It was observed that scatter of the experimental outputs increases with the concrete cover. Specific equipment has been developed for tests of the ties with multi-ple reinforcement bar. The test results (maximum and average crack spacings) are practically independent of the reinforcement parameters, while the Eurocode 2 and the Model Code 2010 predictions of the maximum crack spacing are dependent on the ratio of the bar diameter to the reinforcement ratio. These results enable formulating a hypothesis that the crack parameters (spacing and width) are mainly dependent on the geometry of the con-crete prism and, particularly, the cover depth. Deformation behaviour of the ties with multiple reinforcement bars was also modelled with nonlinear finite element software ATENA. The results of numerical simulations and physical tests indicate that the strain gra-dient in the concrete varies not only along the bar, but also within the cover. The outputs support a conclusion that the “effective area” concept has a limited application related with the loading conditions, stress-strain state, cover, and configuration of the unreinforced area. The thesis is composed of three chapters: literature survey, experimental programs, and discussion of the results. The literature survey is focused on the effects responsible for deformation and cracking performance of rein-forced concrete members. The experimental study deals with deformations and cracking of flexural and tensile elements with different arrangement of the reinforcement in the tension zone. The last chapter discusses predominant characteristics of serviceability performance of flexural and tensile reinforced concrete members. The author have published 14 articles on the topic of the dissertation (five of them in the journals with an Impact Factor and three in the conference proceedings reffered by the Clarivate Analytics Web of Science)

Experimental and Numerical Analysis of Strain Gradient in Tensile Concrete Prisms Reinforced with Multiple Bars

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

Comparative analysis of flexural stiffness of concrete elements with different types of composite reinforcement systems

Various materials and reinforcement technologies have been created for concrete structures. However, there is no uniform methodology to compare the mechanical characteristics of different reinforcement systems. In structural systems, residual stiffness can estimate the efficiency of the reinforcement. This study introduces a simplified approach for the flexural stiffness analysis. It employs a new testing layout designed with the purpose to form multiple cracks in a small laboratory specimen. The achieved solution requires neither iterative calculations nor a description of the loading history. Several composite reinforcement schemes, including internal glass fibre reinforced polymer (GFRP) bars, carbon fibre reinforced polymer (CFRP) sheets and near-surface mounted (NSM) strips are considered. The analysis of the test results reveals a substantial efficiency of the external CFRP reinforcement systems. Article in English. Skirtingomis kompozitinėmis sistemomis armuotų betoninių elementų lenkiamojo standumo lyginamoji analizė Santrauka Betono konstrukcijoms armuoti naudojamos įvairios medžiagos ir technologijos, tačiau unifikuotos metodikos, kuria būtų galima palyginti skirtingų armavimo sistemų mechanines savybes, nėra. Konstrukcinės sistemos armavimo efektyvumas gali būti vertinamas atsižvelgiant į elementų liekamąjį standumą. Šiame straipsnyje pateikiamas supaprastintas lenkiamojo standumo analizės metodas. Jis apima naują bandymų schemą, kuria siekiama gauti tolygų plyšių pasiskirstymą mažame laboratoriniame bandinyje. Siūlomas analitinis sprendimas nereikalauja nei iteracinio skaičiavimo, nei detalaus apkrovos istorijos aprašymo. Nagrinėjamos kelios kompozitinio armavimo sistemos: taikant stiklo pluoštu armuotus polimerinius (GFRP) strypus, išdėstytus elemento viduje, anglies pluoštu armuotus polimerinius (CFRP) lakštus, priklijuotus elemento išorėje, ir sijų paviršiuje tvirtinamas anglies pluoštu armuotas polimerines (NSM) juostas. Tyrimo rezultatai rodo anglies pluoštu armuotų polimerų (CFRP) sistemų, išdėstytų elementų išorėje, efektyvumą. Reikšminiai žodžiai: betono kompozitas, armavimas, liekamasis standumas, analitinis modelis, lenkimo bandymai

Simplified technique for constitutive analysis of SFRC

Steel fibre reinforced concrete (SFRC) has become widespread material in areas such as underground shotcrete structures and industrial floors. However, due to the absence of material models of SFRC reliable for numerical analysis, application fields of this material are still limited. Due to interaction of concrete with fibres, a cracked section is able to carry a significant portion of tensile stresses, called the residual stresses. In present practices, residual stresses used for strength, deflection and crack width analysis are quantified by means of standard tests. However, interpretation of these test results is based on approximation using empirically deduced relationships, adequacy of which might be insufficient for an advanced numerical analysis. Based on general principles of material mechanics, this paper proposes a methodology for determination of residual stress-crack opening relationships using experimental data of three-point bending tests. To verify the constitutive analysis results, a numerical modelling is utilised employing a nonlinear finite element analysis program ATENA. Simulated load-crack width relationships and moment-curvature diagrams were compared with the experimental data by validating adequacy of the derived constitutive models

Structural Analysis of GFRP Truss Bridge Model

Experimental investigation of structural behavior of glass fiber reinforced polymer (GFRP) space truss bridge model subjected to static loading is discussed in this paper. Bridge prototype was assembled using GFRP profiles produced by Fiberline Composites Ltd, steel bolts and GFRP brackets. In order to load the structure, wooden bridge deck was installed. Total load of 13.3 kN was applied in four stages while measuring the bridge node displacement. Flexural behavior of the truss structure was monitored at every loading stage. In order to perform the comparison analysis of truss structural behavior, numerical model was created employing finite element software Solidworks. Comparative analysis has shown good agreement between experimental and numerical results (the margin of error varied from 0,3 up to 10,5%). The obtained results show, that designed and tested bridge model has a sufficient reserve of structural stiffness. Performed investigation reveals that GFRP profiles are suitable for real pedestrian bridge superstructures.12th international conference “Modern Building Materials, Structures and Techniques” (MBMST 2016)The authors gratefully acknowledge the financial support provided by the Research Council of Lithuania (Research project No. MIP-093/2015). The authors wish to thank Fiberline Composites A/S for providing structural profiles and FibroLT Ltd. for technical support. Technical assistance provided by MSc student T. Dulskas during the preparation of the pedestrian truss bridge model is greatly acknowledged

Mechanical behavior of concrete prisms reinforced with steel and GFRP bar systems

Being immune to corrosion, and having a tensile strength up to three times higher than structural steel, glass fiber reinforced polymer (GFRP) bars are suitable for reinforcing concrete structures exposed to aggressive environmental conditions. However, a relatively low elasticity modulus of GFRP bars (in respect to the steel) favors the occurrence of relatively large deformability of cracked reinforced concrete. Lack of ductility and degradation of properties under high temperature can be also identified as debilities of GFRP bars over steel ones. Combining GFRP and steel bars can be a suitable solution to overcoming these concerns. Nevertheless, the application of such hybrid reinforcement systems requires reliable material models. The influence of the relative area of GFRP and steel bars on the tensile capacity of cracked concrete (generally known as tension-stiffening effect), was never investigated from the experimental point of view, mainly crossing results from different tools on the assessment of the cracking process. This paper experimentally investigates deformations and cracking behavior of concrete prisms reinforced with steel bars and GFRP bars in different combinations. The test results of 11 elements are reported. A tensile stress-strain diagram is conceptually proposed for modelling the tension-stiffening effect in elements with such hybrid combination of the reinforcement. The cracking process in terms of crack width and crack spacing is analyzed considering the hybrid reinforcement particularities and a preliminary approach is proposed for the prediction of the crack width for this type of reinforced concrete elementsResearch Council of Lithuania (Research Project S-MIP-17-62). The second author also 590 wish to acknowledge the support provided by FCT through the PTDC/ECM591 EST/1882/2014 projec

How effective is today`s regulations about payments made for execution process and how capable are those regulations in order to protect one`s right`s not to be involved in a perpetual legal proceedings to have those payments back?

Sėkmingas sprendimų vykdymo procesas neįmanomas be tinkamo finansavimo. Nuo 2003-01-01 pradėjus veikti privačiai antstolių sistemai pasikeitė ir vykdymo proceso finansavimo tvarka. Valstybė vykdymo proceso finansavimo naštą perkėlė išieškotojui. Pagal šiuo metu galiojančią tvarką, išieškotojas pateikdamas sprendimą priverstiniam vykdymui privalo apmokėti ir visas su tokio sprendimo vykdymo susijusias išlaidas. Vykdymo išlaidų atlyginimo tvarkos teisiniame reglamentavime įtvirtintas bendrasis principas, kad įvykdžius vykdomąjį dokumentą visos vykdymo išlaidos išieškomos iš skolininko. Tačiau kaip vėliau darbe atskleidžiama, praktinis minėto principo taikymas kelia daug problemų visiems vykdymo proceso dalyviams.The main target for this work is to find out how effective is today`s regulations about payments made for execution process and how capable are those regulations in order to protect one`s right`s not to be involved in a perpetual legal proceedings to have those payments back?. There were four tasks author had to do. First to have an analysis in law regulating payment for execution process. Second task was to find out if those regulation have any dearth`s. If results were positive, than how they affects parties rights in execution process in order to keep their assets and not to be forced to pay for those proceedings again and again and not to start court proceedings. Third there was a need to define how important is to have better regulations about payments made for execution process. Fourth task was to give suggestions about how to improve regulations about payments made for execution process in order to have parties assets protected and annul all chances to start court proceedings for the same question. In order to get better results for his researches author has tried to separate each party. In that way it was possible to learn from each parties perspective exactly how civil execution costs and the order of reimbursing them, affects their material and procedural rights. In doing that first party was the bailiff. For him our regulations in most of the cases establishes broadly acknowledged principle that all expenses he suffers must be compensated by recoverer Meanwhile for recoverer the process to recover execution costs can be started only when the receiving-order is executed. One may think that some exceptions not to pay for bailiffs services established in our by-law has a direct objection to some Constitutional principles like everyone has right to by paid for ones work and further objects to some law in our civil code. Author agrees that in some cases there is no legit way for bailiff to be paid for the work he did. It means that in some cases the bailiff will be forced to use his property in order to fulfill courts or other institutions orders without ever being paid. Looking form recoverer`s positions he never can be sure he will retrieve all expenses paid for execution process. It may never happen because our law order for reimbursing civil execution costs can be effective in only one way – when debtor pays them voluntarily. One may ask how it happens? As it was mentioned before one taking receiving-order to the bailiff ought to pay same execution costs. If debtor after receiving-order is fulfilled refuses to reimburse the cost mentioned before, the bailiff goes to the court and asks to adjudicate all the expenses concerned with fulfilling receiving-order in favor of the recoverer. Court reads the case and gives new receiving-order for recovering the execution cost concerned with older receiving-order. Recoverer then takes newly obtained receiving-order to the bailiff, pays him some execution cost and all process starts anew. Such an imperative requirement to have courts adjudication supposedly was implement to protect debtors rights and to prevent bailiff`s abuse for counting too much. The main reason for that ineffectiveness is that in order to obtain reimbursement for civil execution costs our jus leaves no other way but the court proceedings. After analyzing various aspects of present-day`s regulations regarding reimbursement for execution expenses comes some conclusions and suggestions. Order for reimbursing execution costs in Lithuania’s law is supported by broadly acknowledged principle that all expenses suffered in fulfilling receiving-order finally must be compensated by debtor. But Lithuania`s jus in order to implement last mentioned principle has created too much complicated process. It neither can provide effective solutions if debtor is in insolvency state or refuses to reimburse the execution costs, neither can it guarantee for execution parties that they will not be involved in a perpetual legal proceedings. One thinking to improve situation for reimbursing execution costs, establishing more guarantees for all parties in some situations should consider to allow retrieving execution cost without court`s adjudication. Bailiff should have right to retrieve execution costs on his own decision. It should be applicable in every situation when debtor do not argue size of execution expenses. It should save parties time, expenses, improve civil execution process and it could still adequate guarantee parties right`s cause they would preserve their opportunities to complain. Lithuania`s code of civil process establishes that all parties in civil proceedings should be treated equally but when it comes about reimbursing execution costs, state starts to discriminate other recoverer`s. There is an opportunity for the state not to pay civil proceedings expenses, meanwhile others recoverers do not have such opportunity. It is unclear then who and how should compensate execution expenses if receiving-order was not fulfilled. Author finds no reasons why state should be privileged against other recoverers.Vytauto Didžiojo universiteta

Determining the residual strength of sfrc flexural members

The application of steel fibre reinforced concrete (SFRC) isconstantly increasing. However, due to the absence of universallyaccepted guidelines for SFRC, the application fields of this materialare still limited. Post-cracking load carrying capacity is aproperty of concrete most benefited by steel fibre reinforcement,usually designed by the residual strength of SFRC in tension, ffr.However, the quantification of ffr is one of the most critical issues.The research reported in this paper is dedicated to determining theresidual strength of SFRC in tension. The experimental results often notched beams with the fibre content of 0.5% and 1.0% byvolume subjected to a three-point loading scheme are presented.Considering SFRC as a homogeneous material, a mechanicallysound method for the inverse analysis of SFRC was proposed.The adequacy of the calculated results was validated using experimentaldata on standard flexural specimens. Computationaleffectiveness was proved employing derived residual strengthmodels into the nonlinear finite element analysis program. Article in Lithuanian. Lenkiamųjų plieno plaušu armuotų betoninių elementų liekamojo stiprio nustatymas Santrauka. Dispersiškai armuotas betonas vis dažniau naudojamas statybos pramonėje, deja, platesnį šios medžiagos taikymą riboja visiems priimtinų ir patikimų projektavimo normų stoka. Pagrindinė to priežastis – sudėtingas supleišėjusio dispersiškai armuoto tempiamojo betono elgseną apibūdinančio parametro, t. y. liekamųjų įtempių, nustatymas. Liekamieji įtempiai nusako elemento įtempius plyšyje, kuriuos plyšį varžantis plieno plaušas perduoda betonui. Šiame straipsnyje nagrinėjami plieno plaušu armuoti lenkiamieji betoniniai elementai. Aptarti dažniausiai naudojami supleišėjusio tempiamojo dispersiškai armuoto betono elgseną aprašantys modeliai. Pasiūlytas alternatyvus liekamųjų įtempių nustatymo būdas, naudojant standartinių sijų bandymų rezultatus. Nagrinėtų skaičiavimo modelių adekvatumas tikrintas baigtinių elementų programa ATENA. Apskaičiuotos sijų apkrovos ir plyšio pločio priklausomybės palygintos su eksperimentinėmis, gautomis lenkiant plieno plaušu armuotas sijas viena koncentruota apkrova. Reikšminiai žodžiai: liekamieji įtempiai, plieno plaušu armuotas betonas, lenkiamieji elementai, plyšio plotis

Experimental investigation of cracking and deformations of concrete ties reinforced with multiple bars

Interpretation of test results may be inadequate even for simple test layouts. On the one hand, conventional tests, that investigate a concrete prism reinforced with a single bar in the centre, do not allow to account for the effect of variation of the diameter-to-reinforcement ratio (£/p). This important limitation should be related to the use of simple specimens in constitutive modelling. On the other hand, a tie-test typically provides measurements of average deformations of the internal reinforcing bar and the concrete surface. The experimental evidence, however, often contradicts the general assumption of the equivalence of the mean strains of reinforcement and concrete. The strain difference is closely related to the width of the concrete cover. This paper investigates the effect of distribution of bar reinforcement on deformation and cracking behaviour of tensile elements. Special testing equipment has been developed to investigate ties reinforced with multiple bars. The test program consists of 23 ties. The number and diameter of the bars vary from 4 to 16 and from 5 mm to 14 mm, respectively. Two different covers (30 mm and 50 mm) are considered as well. The deformation analysis is based on measurements of the average reinforcement and concrete surface strains. The development of cracks was investigated using digital image correlation (DIC). The Model Code 2010 and Eurocode 2 predictions are compared with the experimental data. While the Design Codes predict that the maximum crack spacing is dependent on the £/p ratio, the test results indicate that the crack distances are actually much less dependent on the reinforcement characteristics.The authors gratefully acknowledge the financial support provided by the Research Council of Lithuania (Research Project MIP–050/2014)

Experimental data of deformation and cracking behaviour of concrete ties reinforced with multiple bars

The data presented in this article are related to the research article entitled “Experimental Investigation of cracking and deformations of concrete ties reinforced with multiple bars” (Rimkus and Gribniak, 2017) [1]. The article provides data on deformation and cracking behaviour of 22 concrete ties reinforced with multiple bars. The number and diameter of the steel bars vary from 4 to 16 and from 5 mm to 14 mm, respectively. Two different covers (30 mm and 50 mm) are considered as well. The test recordings include average stains of the reinforcement and the concrete surface, the mean and maximum crack spacing, final crack patterns, and crack development schemes obtained using digital image correlation (DIC) system. The reported original data set is made publicity available for ensuring critical or extended analyses. Keywords: Reinforced concrete, Multiple bars, Tensile tests, Deformations, Crackin