Baigiamajame darbe projektuojamas Biurų centras „Royal“ dviejų aukštų su požemine automobilių stovėjimo aikštele, kurio bendras plotas – 1257,8 m2. Objekte planuojama vykdyti įvairias administracines paslaugas, tai būtų kalbų biuras, vairavimo mokykla, renginių organizavimo agentūra. Biurų centras projektuojamas iš fibo blokelių mūro apšiltinant jį putu polistirolu, perdangos plokštės, rygeliai ir gelžbetonio sijos bus atremiamos i sumontuotas 400x400 kolonas. Pastate bus dveji liftai, taip pat įrengti tualetai pritaikyti neįgaliesiams. Pastatas šildomas su dujiniu katilu. Projektuojamo pastato statybos sklypas yra Pramonės gatvėje Šiauliuose. Jo plotas - 1544 m2. Sklypas yra patogioje miesto dalyje, kur dideli žmonių srautai, šalia yra viešojo transporto sustojimo vieta. / In this final work is designed two-stores with underground parking for cars office center „Royal“ with an area of 1257,8 m2. The facility is planned to carry out a variety of administrative services, be it linguistic office, driving school, event marketing agency. Office center is designed with fibo blocks masonry with insulation of polystyrene, floor slabs, beams and reinforced concrete beams will be brought to 400x400 assembled columns. The building will be two lifts, as well as toilets adapted to people with disable. The building is heated with a gas boiler. Projected building plot is in Pramonės Street in Siauliai. Its area of - 1544 m2. The plot is conveniently located where are the large flow of people, close to public transport stopping place.

In the seismic design of reinforced concrete frames, plastic hinges are allocated to beams such that a ductile beam-sway mechanism will form in preference to other less ductile mechanisms in the event of a major earthquake. This is achieved by ensuring that the flexural strength of columns is greater than that corresponding to the maximum likely flexural strength of beam plastic hinges. Recent experimental studies in New Zealand have shown that elongation of ductile beam plastic hinges, and its interaction with nearby floor slab containing precast-prestressed floor units, increases the strength of beams much more than that specified in New Zealand and American Concrete standards. This level of strength enhancement has raised concern on the adequacy of the current design provisions. To further investigate this problem, a research project was initiated to examine the strength of beam plastic hinges in reinforced concrete frames containing precast-prestressed floor units. In this research, the strength of beam plastic hinges was assessed through experimental and analytical studies. A three-dimensional, one-storey, two-bay reinforced concrete moment resisting frame with prestressed floor units and cast-in-situ concrete topping was tested under quasi-static displacement-controlled cyclic loading. The experimental results provided insight into the mechanics associated with frame-floor interaction. Subsequently, improved design specifications were proposed based on the observed behaviour. To analytically predict the beam-floor interaction, a ductile reinforced concrete plastic hinge multi-spring element was developed and validated with experimental results from cantilever beam and frame sub-assembly tests reported in the literature. The comparisons have demonstrated the ability of the proposed plastic hinge element to predict the flexural, shear, axial, and most importantly, elongation response of ductile plastic hinges. The proposed plastic hinge element was implemented into an analytical model to simulate the behaviour of the frame-floor sub-assembly tested in this research. Specially arranged truss-like elements were used to model the linking slab (the region connecting the main beam to the first prestressed floor unit), where significant inelastic behaviour was expected to occur. The analytical model was found to be capable of predicting the non-linear hysteretic response and the main deformation mechanisms in the frame-floor sub-assembly test. The analytical frame-floor model developed in this study was used to examine the effect of different structural arrangements on the cyclic behaviour of frames containing prestressed floor units. These analyses indicated that slab reinforcement content, the number of bays in a frame and the position of frame in a building (i.e., perimeter or internal frame) can have a significant influence on the strength and elongation response of plastic hinges.

Concrete is the most widely used construction material in the world, so the assessment of damage in concrete is critical from the point of view of both safety and cost. Of particular interest are macro cracks that extend through the concrete cover of the reinforcement, which can potentially expose the reinforcement to corrosive elements. The high density of scatterers such as aggregate and voids in concrete makes quantitative imaging with coherent ultrasound difficult. As an alternative, this research focuses on diffuse energy based ultrasonic methods rather than coherent ultrasonic methods for crack depth assessment. Two types of ultrasonic measurements were made on real cracks formed under four point bending: one that focuses on time of flight measurements from an impactor; while the other uses the arrival time of maximum energy in a diffuse field excited by an impulsive load from a transducer. Each of these ultrasonic techniques is used to interrogate a macro crack in a concrete beam, and the results are compared to determine their accuracy and robustness. The actual crack depth is determined using direct surface measurements and a destructive dye-injected approach with drilled cores. The results suggest that the diffusion method, using a maximum energy approach, more accurately estimates the crack than visual inspection and impact echo methods, which overestimate the depth.

Although the knowledge and technology of seismic analysis and seismic risk assessment tools have rapidly advanced in the past several decades, current seismic design codes and damage estimation methods ignore the effect of successive earthquakes on structures. In light of recent strong seismic events, mainshock-damaged structures are shown to be more vulnerable to severe damage and collapse during subsequent events. The increase in vulnerability during aftershocks results in the likelihood of increased damage and loss-of-life and property. After a major earthquake, structural engineers must assess whether mainshock-damaged buildings can be re-occupied or not, with due consideration to the threat of aftershocks. The outcome of this post-earthquake inspection is utilized to quantifiably judge the current status of structures (so-called building tagging). This tagging criterion is closely related to the evaluation of the residual capacity of damaged buildings as well as the computation of the probability of being in a damage state after an aftershock (aftershock fragility). The increased vulnerability estimation associated with the additional damage plays a significant role in assessing potential losses to facilitate crucial decision making such as emergency response mobilization, inspection priority, recovery strategy, and re-occupancy decision. The main objective of this research is to develop a probabilistic framework for accounting for these increased vulnerabilities in terms of the extent of damage associated with mainshock ground motions. Aftershock fragility curves are developed accounting for both the uncertainty from the seismic hazard and the uncertainty from the structural capacity. This proposed approach also allows for the inherent variability, such as modeling characteristics associated with the design codes, present in non-ductile and ductile reinforced concrete frames found in California.

The premature deterioration of concrete bridge decks is a multi-billion dollar problem in the United States. In December 2003, the Federal Highway Administration estimated that approximately 27 percent of the 592,000 nation's bridges are considered structurally deficient or functionally obsolete. It would cost about 80 billion dollars to bring all of the nation's bridges to an acceptable and safe standard by either rehabilitation or replacement. Moreover, according to the data of the “national bridge inventory” obtained from the U.S. Department of Transportation, it is estimated that deficiencies occur mostly in the decks in more than half of the bridges in United States. Not only bridge deck deterioration is an economic problem; it is also a risk to those who traverse the structure. Forms of deterioration can range from slightly damaged deck surfaces, causing unpleasant sights and decreasing bridge deck serviceability, up to spalling of large pieces of concrete that reduces the structural integrity and it can be a danger for the public. Therefore, there is a compelling need to understand the behavior of bridge decks under service load and develop a reliable procedure to assess the serviceability of the deck, which will then serve as a decision-making tool for the rehabilitation or the replacement of the decks. In the United States, most of the bridge decks are constructed as reinforced concrete slabs supported by steel or precast prestressed girders. Such decks have traditionally been designed using the “strip method”, based on a conventional beam theory, which assumes that the slab is continuous over fixed supports. As a result, the top part of the slab is reinforced with steel bars to resist the negative moments, and the bottom part of the slab is reinforced with steel bars to resist the positive moments. Temperature and shrinkage reinforcement is added orthogonally at the top and at the bottom. When cracks occur in concrete, the top reinforcement can be subjected to environmental agents and aggressive chemicals; such as deicing salt, and it can start to corrode. The corrosion can result in a lateral expansion of the steel bars, leading to spalling of concrete cover and subsequent formation of potholes. Previous research in the United States and mainly in Canada showed that the flexural capacity of bridge decks can be increased by the presence of in-plane compressive forces, created when the deck is restrained by supports that cannot move laterally. This phenomenon is referred as “arching action” and is the basis of the empirical design provisions of the Ontario (Canada) Bridge Design Code (1993). This empirical method has been adopted in the current AASHTO LRFD code (2005), and it is referred to as isotropic reinforcement. According to the empirical method, arching action requires less steel reinforcement than that required by the strip method of AASHTO LRFD code (2005). Therefore, it is believed that the decks designed by empirical method are more resistant to deterioration due to fewer sources of corrosion (fewer steel rebars). At the present, there is no assessment method available to evaluate the serviceability and durability of bridge decks. Therefore, in this dissertation, a procedure for bridge decks evaluation is developed, which is focused on evaluation and comparison of bridge decks performance for the two aforementioned design procedures. A reliability based method associated with a state of the art nonlinear finite element analysis, calibrated using field tests, is developed in order to understand the structural behavior of the deck and to assess its performance.

In the past few years, some experimental investigations have been conducted to verify seismic behaviour of fiber reinforced polymer reinforced concrete (FRP-RC) beam-column joints. Those researches were mainly focused on exterior beam-column joints without lateral beams. However, lateral beams, commonly exist in buildings, can significantly improve seismic performance of the joints. Moreover, the way the longitudinal beam bars are anchored in the joint, either using headed-end or bent bars, was not adequately addressed. This study aims to fill these gaps and investigate the shear capacity of FRP-RC exterior beam-column joints confined with lateral beams, and the effect of beam reinforcement anchorage on their seismic behaviour. Six full-scale exterior beam-column joints were constructed and tested to failure under reversal cyclic loading. Test results showed that the presence of lateral beams significantly increased the shear capacity of the joints. Moreover, replacing bent bars with headed-end bars resulted in more ductile behaviour of the joints.

The overall objectives of this thesis are to determine if Indirect and Direct Design methods currently used for reinforced concrete pipe are able to accurately predict the capacity of the pipe, to identify discrepancies between the two methods, and to provide potential modifications to the methods to reduce inconsistencies. As part of this investigation, two 0.6 m pipes (nominal strength classes 100-D and a 140-D) and two 1.2 m pipes (a 65-D with Wall B and a 65-D with Wall C) were tested under single wheel pair loading at burial depths of 1.2, 0.6 and 0.3 m. The test pipes did not crack at the applied service load of 110 kN and did not pass the crack width limit until between 2.5 and 4 times the service load. A 0.6 m 100-D pipe was also tested under simulated deep burial and it was found that the calculated test D-Load is 1.9 times greater than the designated D-Load of the test pipe. It was found that both methods were conservative and that the Direct Design method should be modified to more closely align with the Indirect Design. An investigation of the Direct Design parameters found that by considering thick ring theory and the Modified Compression Field Theory with two layers of reinforcement, the required amount of steel from Direct Design could be made to align very closely with the Indirect Design. An additional test was completed to further assess the Direct Design method on a 0.6 m 140-D pipe to measure the pressure around the circumference of the pipe and compare this measured pressure to the commonly used pressure distribution for Direct Design. The results show that at the minimum cover (0.3 m) the test pressure is higher than predicted at the crown, lower than predicted at the invert, and nearly zero at the shoulder, springline, and haunch, which is inconsistent with most of the predicted results at these locations. / Thesis (Master, Civil Engineering) -- Queen's University, 2014-06-20 16:29:39.037

Gelžbetoninių elementų pleišėjimas priklauso nuo medžiagų fizikinių savybių, ilgalaikių procesų betone, armatūros ir betono sąveikos ir kt. Dėl betono ir armatūros sąveikos pasireiškia tempiamojo sustandėjimo efektas, turintis didelės įtakos elementų deformacijoms. Skirtingi mokslininkų tyrimai atskleidė, kad tempiamasis sustandėjimas yra sudėtingas netiesinis reiškinys, kuriam įvertinti būtina taikyti netiesinę skaitinę analizę. Medžiagų fizikinių modelių adekvatus pasirinkimas dažniausiai nulemia gaunamo galutinio rezultato patikimumą. Darbe atlikta skaitinė netiesinė tempiamųjų gelžbetoninių elementų analizė. Modeliavime panaudoti VGTU ilgalaike ir trumpalaike apkrova išbandytų tempiamųjų gelžbetoninių elementų eksperimentiniai duomenys. Bandymų tikslas – įvertinti tempiamojo sustandėjimo kitimą laikui bėgant, išnagrinėti atstumų tarp plyšių įtaką tempiamajam sustandėjimui, įvertinti susitraukimo ir valkšnumo efektų įtaką elementų deformacijoms. Netiesinio modeliavimo metu buvo išanalizuota įvairių parametrų įtaka gautiems skaitiniams rezultatams. Palyginus modeliavimo rezultatus su eksperimentiniais nustatyta, kad programinis paketas ATENA tiksliai apskaičiavo gelžbetoninių elementų poslinkius veikiant trumpalaikei apkrovai. Ilgalaikės apkrovos atveju gauti rezultatai su didesnėmis paklaidomis, jų analizei reikia išsamesnių tyrimų. Darbo struktūra ir apimtis – 76 p. teksto be priedų, 77 iliustracijos, 6 lentelės, 38 bibliografijos šaltinių sąrašas. / Behaviour of reinforced concrete structures mostly depends on physical characteristics of materials, long-term processes in concrete, interaction between steel and concrete, etc. The result of such an interaction is the effect of tension-stiffening, which has a great influence on deformations of reinforced concrete structures. Various researchers have shown that tension-stiffening is a complex, nonlinear phenomenon that might be assessed only by means of a non-linear numerical analysis. The choice of adequate material governs confidence of the results obtained by simulation. In this paper a non-linear numerical analysis of reinforced concrete ties was carried out. In the numerical simulation data from the short-term and long-term experiment conducted in VGTU was used. The subject of the experiment was to assess the degradation of long-term tension-stiffening effect in reinforced concrete as well as to evaluate influence of crack spacing, shrinkage and creep on long-term deformations of concrete members. Study on effect of various parameters on obtained results was carried out. Data from nonlinear analyses conducted by ATENA were compared to the experimental results and gave good agreement in terms of short-term loading. The results of long-term loading showed only moderate agreement and need further investigation. Thesis consists of: 76 p. text without appendixes, 77 pictures, 6 tables, 38 bibliographical entries.

Concrete is a very weak and brittle material in tension. It has been shown in previous researches that the addition of steel fibers to a concrete matrix can improve this behavior. The ability of fibers to control and redistribute stresses after cracking results in a number of improvements in the structural behaviour of concrete. A review of existing literature shows that the addition of steel fibers enhances concrete’s tensile resistance, crack control properties, ductility and damage tolerance. In beams, fibers can transform brittle shear response into a flexural response and promote ductility, thereby allowing for a full or partial replacement of traditional shear reinforcement. The enhanced shear capacity, ductility and damage tolerance of Steel Fiber Reinforced Concrete (SFRC) can also potentially be used to relax seismic detailing requirements in frames by partially replacing the required transverse reinforcement in the plastic hinge regions of RC beams. One of the drawbacks associated with SFRC is that the addition of steel fibers to a traditional concrete mix at high fiber contents can result in workability problems. The combined use of Self-Consolidating Concrete (SCC) and fibers can solve this problem and facilitate placement for a wider range of structural applications. Although several studies have been conducted on the behaviour of SFRC beams subjected to monotonic loading, there is limited research on the behaviour of SFRC beams under cyclic or reverse-cyclic loading. This thesis presents the results of an experimental and analytical study conducted on nine SFRC beam specimens tested under load reversals. The main objective of this research program was to investigate the effect of fibers on structural behaviour and to examine the ability of steel fibers to replace transverse reinforcement. The experimental and analytical results show that use of fibers results in several improvements in behaviour, including enhanced damage tolerance and post-peak ductility. The results also show that steel fibers can potentially be used to allow for a reduction of transverse reinforcement in beams, however further research is required.

This paper presents an analytical method for estimating the flexural strength of reinforced concrete (RC) beams strengthened with externally bonded fibre-reinforced polymer (FRP) laminates. The method is developed from the strain compatibility and equilibrium of forces. Based on the size of external FRP laminates, several flexural failure modes may be identified, namely tensile rupture of FRP laminates and concrete crushing before or after yielding of internal steel reinforcement. Upper and lower limits to the size of FRP laminates used are suggested to maintain ductile behaviour of strengthened RC sections. Comparisons between the flexural strength obtained from the current method and from experiments show good agreement. Design equations for calculating the size of FRP laminates externally bonded to RC sections to enhance their flexural strength are proposed.