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The possibility of using demolished concrete waste as aggregate in fresh concrete in the production of prestressed concrete beams is checked in this research. As opposed to the use for road foundations or as fill-in material the use of the Recycled Aggregate (RA) for concrete structures requires more tests and processing of results. In fact to be able to use a material for construction it is essential to assess more than just its compressive strength. After the physical and chemical characteristics of the RA and the properties of both the wet and hardened Recycled Aggregate Concrete (RAC) have been determined, it is important to check if the mathematical models and numerical correlation normally used for design of ordinary concrete (such as mix-design procedure, design codes, non-linear analysis) are suitable for RAC. For this reason the main task of this investigations has been to ensure that RAC has satisfactory mechanical performance for structural use and later to guarantee a consistency of the results using methods checked for RAC. A mix-design procedure suitable for RAC to attain the desired workability and the target strength was the first step. Tests on durability of RA and RAC have been performed and the results reported. Finally three 15.0 metres span prestressd beams cast with different percentages of RA (one with 100% of RA, one with 100% of Natural Aggregate NA, and one with 50% of RA and 50% of NA) have been tested. The results show that it is practicable to make prestressed concrete elements using concrete made with Recycled Aggregate and that these elements can have satisfactory and predictable mechanical performance.

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Following the evolution of a damage avoidance design (DAD) frame system, with rocking beam-column joints, at the University of Canterbury, analytical studies are carried out to evaluate the performance of proposed structures, and verify the proposed design methodology. A probabilistic seismic risk assessment methodology is proposed, from which the expected annualised financial loss (EAL) of a structure can be calculated. EAL provides a consistent basis for comparison of DAD frame systems with state-of-practice ductile monolithic construction. Such comparison illustrates the superior performance of DAD frame systems. The proposed probabilistic seismic assessment methodology requires the response of the structure to be evaluated over a range of seismic intensities. This can be achieved by carrying out an incremental dynamic analysis, explicitly considering seismic randomness and uncertainty; or from a pushover analysis, and assuming an appropriate value of the dispersion. By combining this information with the seismic hazard, probabilistic response curves can be derived, which when combined with information about damage states for the particular structure, can be transformed into 'resilience curves'. Integration of information regarding the financial loss occurring due to each of the damage states, results in an estimate of EAL.

The seismic design of buildings is usually performed using one-way analysis for each of main axes independently. However, seismic events have fairly random behaviour and impose bidirectional solicitations on structures. In this work, the study of the response in structures subjects to earthquake loads with irregularity of l-shaped plan and soft story is carried out. For this, the linear time-story analysis (LTHA) of these has been carried out imposing seismic solicitations in two orthogonal directions. Thus, the structural response with incidence angle variations of 10 is obtained and compared with the response derived from the unidirectional analysis. Variations of up to 50% and 72% are obtained for model structures with l-shaped plan and soft story respectively.

Corrosion presents one of the greatest threats to the durability of reinforced concrete structures, yet it is also one of the least understood components of the design process for most engineers. The nation's infrastructure is rapidly deteriorating due to years of abuse and fatigue. Therefore, several economic and reliable solutions have been developed to repair the existing damage and extend the design life of structures at risk of corrosion. One popular method for protecting concrete structures from corrosion is the use of fiber-reinforced plastic (FRP) composite wraps. The premise is a simple one: placing an impermeable barrier around the surface of the concrete should prevent harmful substances such as chlorides from entering and corroding the imbedded reinforcing steel. However, little is known about the long-term effectiveness in preventing corrosion in reinforced concrete structures. The FRP wrap may in fact prevent the chlorides from passing through the concrete, however, the same principle might cause chlorides to be trapped beneath the surface and accelerate corrosion. In this study, the long-term behavior of laboratory specimens exposed to an aggressive chloride-rich environment were examined. This project was designed to develop a greater understanding of the long-term effects of FRP wrapping in preventing corrosion in reinforced concrete structures. Although TxDOT project 0_1774 involves both rectangular and cylindrical specimens, the focus of this thesis is on the specific impact of FRP wraps on partially wrapped versus unwrapped columns. The specimens included in this study are comprised of a wide range of construction parameters. However, despite the multitude of varying mix designs a noticeable trend has emerged as a result of this research. / text

Yes / Twelve reinforced-concrete continuous deep beams having web openings within interior shear spans were tested to failure. The main variables investigated were the opening size and the amount of inclined reinforcement around openings. An effective inclined reinforcement factor combining the influence of the amount of inclined web reinforcement and opening size is proposed and used to analyse the structural behaviour of continuous deep beams tested. It was observed that the end support reaction, diagonal crack width and load capacity of beams tested were significantly dependent on the proposed effective inclined reinforcement factor. As this factor increased, the end support reaction and increasing rate of diagonal crack width were closer to those of companion solid deep beams. In addition, a higher load capacity was exhibited by beams having an effective inclined reinforcement factor above 0.077 than the companion solid deep beam. A numerical procedure based on the upper-bound analysis of the plasticity theory was proposed to estimate the load capacity of beams tested. Comparisons between the measured and predicted load capacities showed good agreement.

yes / This paper presents a relatively simple column strengthening procedure using unbonded wire rope and T-shaped steel plate units. Twelve strengthened columns and an unstrengthened control column were tested to failure under concentric axial load to explore the significance and shortcomings of the proposed strengthening technique. The main variables investigated were the volume ratio of wire ropes as well as geometrical size and configuration of T-shaped steel plates. Axial load capacity and ductility ratio of columns tested were compared with predictions obtained from the equation specified in ACI 318-05 and models developed for conventionally tied columns, respectively. The measured axial load capacities of all strengthened columns were higher than predictions obtained from ACI 318-05, indicating that the ratio of the measured and predicted values increased with the increase of volume ratio of wire ropes and flange width of T-shaped steel plates. In addition, at the same lateral reinforcement index, a much higher ductility ratio was exhibited by strengthened columns having a volume ratio of wire ropes above 0·0039 than tied columns. The ductility ratio of strengthened columns tested increased with the increase of flange width, thickness, and web height of T-shaped steel plates. A mathematical model for the prediction of stress–strain characteristics of confined concrete using the proposed strengthening technique is developed, that was in good agreement with test results.

Este trabalho tem por objetivo a proposição de um conjunto de medidas visando trazer um incremento na produtividade do serviço de concretagem em Estruturas Reticuladas de Concreto Armado (ERCA). Inicialmente o trabalho baseou-se em um amplo levantamento sobre o tema produtividade da mão-de-obra no serviço de concretagem e sobre métodos de obtenção e avaliação de opiniões de pessoas. Procedeu-se, através da realização de entrevistas e por meio de estudo de campo ao levantamento de fatores intervenientes na produtividade do serviço concretagem. A análise dos fatores apontados nas duas abordagens subsidiou a elaboração de uma proposição de ações que potencialmente levariam a melhorias nos indicadores de produtividade da concretagem; um questionário Delphi serve ao propósito de escolher, dentro do conjunto de propostas, aquelas com maior expectativa quanto à relação custo-benefício com priorização de ações mais viáveis de serem implementadas. / This research had as an objective the proposition of a group of measures that can be used to improve labor productivity in buildings structures concrete placement. At first this work raised data on the subject of labor productivity in concrete placement and on the method of obtaining and evaluating persons\' opinions. By means of interview and field camp study, information could be raised about factors involved in concrete placement. Those factors\' analysis provided the elaboration of a proposition of actions that would help on the improvement of the labor productivity indexes in concrete placement; with the Delphi questionnaire the best propositions amongst all could be chosen in the aspect of cost-benefit and viability.

This thesis addresses the topic of local bond behaviour in RC structures. The mechanism of bond refers to the composite action between deformed steel reinforcing bars and the surrounding concrete. Bond behaviour is an open research topic with a wide scope, particularly because bond it is such a fundamental concept to structural engineers. However, despite many bond-related research findings having wide applications, the primary contribution of this research is an experimental evaluation of the prominent features of local bond behaviour and the associated implications for the seismic performance of RC structures. The findings presented in this thesis attempt to address some structural engineering recommendations made by the Canterbury Earthquakes Royal Commission following the 2010-2011 Canterbury (New Zealand) earthquake sequence. A chapter of this thesis discusses the structural behaviour of flexure-dominated RC wall structures with an insufficient quantity of longitudinal reinforcement, among other in situ conditions, that causes material damage to predominantly occur at a single crack plane. In this particular case, the extent of concrete damage and bond deterioration adjacent to the crack plane will influence the ductility capacity that is effectively provided by the reinforcing steel. As a consequence of these in situ conditions, some lightly reinforced wall buildings in Christchurch lost their structural integrity due to brittle fracture of the longitudinal reinforcement. With these concerning post-earthquake observations in mind, there is the underlying intention that this thesis presents experimental evidence of bond behaviour that allows structural engineers to re-assess their confidence levels for the ability of lightly reinforced concrete structures to achieve the life-safety seismic performance objective the ultimate limit state. Three chapters of this thesis are devoted to the experimental work that was conducted as the main contribution of this research. Critical details of the experimental design, bond testing method and test programme are reported. The bond stress-slip relationship was studied through 75 bond pull-out tests. In order to measure the maximum local bond strength, all bond tests were carried out on deformed reinforcing bars that did not yield as the embedded bond length was relatively short. Bond test results have been presented in two separate chapters in which 48 monotonic bond tests and 27 cyclic bond tests are presented. Permutations of the experiments include the loading rate, cyclic loading history, concrete strength (25 to 70 MPa), concrete age, cover thickness, bar diameter (16 and 20 mm), embedded length, and position of the embedded bond region within the specimen (close or far away to the free surface). The parametric study showed that the concrete strength significantly influences the maximum bond strength and that it is reasonable to normalise the bond stress by the square-root of the concrete compressive strength, √(f'c). The generalised monotonic bond behaviour is described within. An important outcome of the research is that the measured bond strength and stiffness was higher than stated by the bond stress-slip relationship in the fib Model Code 2010. To account for these observed differences, an alternative model is proposed for the local monotonic bond stress-slip relationship. Cyclic bond tests showed a significant proportion of the total bond degradation occurs after the loading cycle in the peak bond strength range, which is when bond slip has exceeded 0.5 mm. Subsequent loading to constant slip values showed a linear relationship between the amount of bond strength degradation and the log of the number of cycles that were applied. To a greater extent, the cyclic bond deterioration depends on the bond slip range, regardless of whether the applied load cycling is half- or fully-reversed. The observed bond deterioration and hysteretic energy dissipated during cyclic loading was found to agree reasonably well between these cyclic tests with different loading protocols. The cyclic bond deterioration was also found to be reasonably consistent exponential damage models found in the literature. This research concluded that the deformed reinforcing bars used in NZ construction, embedded in moderate to high strength concrete, are able to develop high local bond stresses that are mobilised by a small amount of local bond slip. Although the relative rib geometry was not varied within this experimental programme, a general conclusion of this thesis is that deformed bars currently available in NZ have a relative rib bearing area that is comparatively higher than the test bars used in previous international research. From the parametric study it was found that the maximum monotonic bond strength is significant enhanced by dynamic loading rates. Experimental evidence of high bond strength and initial bond stiffness generally suggests that only a small amount of local bond slip that can occur when the deformed test bar was subjected to large tension forces. Minimal bond slip and bond damage limits the effective yielding length that is available for the reinforcing steel to distribute inelastic material strains. Consequently, the potential for brittle fracture of the reinforcement may be a more problematic and widespread issue than is apparent to structural engineers. This research has provided information that improve the reliability of engineering predictions (with respect to ductility capacity) of maximum crack widths and the extent of bond deterioration that might occur in RC structures during seismic actions.