Submitted by Wallison Medeiros (wamedeiros@hotmail.com) on 2019-01-22T10:58:45Z No. of bitstreams: 1 Medeiros_WA.pdf: 11036463 bytes, checksum: 842aff888e052eb4d2fc0aa7a42f3484 (MD5) / Approved for entry into archive by Lucas Paganine (lucaspaganine@ibict.br) on 2019-02-05T16:59:15Z (GMT) No. of bitstreams: 1 Medeiros_WA.pdf: 11036463 bytes, checksum: 842aff888e052eb4d2fc0aa7a42f3484 (MD5) / Made available in DSpace on 2019-02-05T16:59:18Z (GMT). No. of bitstreams: 1 Medeiros_WA.pdf: 11036463 bytes, checksum: 842aff888e052eb4d2fc0aa7a42f3484 (MD5) Previous issue date: 2018 / This research presents a study on the behavior of precast concrete frames with participating masonry infill to be considered in the design of a building lateral load bracing system. The study brings a literature review on the topic. An experimental testing of a reinforced concrete frame infilled or not with masonry is used to calibrate a finite element model using the Simulia Abaqus 2017 package. The model uses concrete damage plasticity to consider both the concrete and the masonry behaviour. Embedded elements are used to consider rebars inside the concrete. Masonry elements are considered homogeneous with contact surfaces along the concrete-masonry interface. After the properties were calibrated the numerical models showed excellent accuracy when compared to the experimental tests. Precast concrete frames, whose dimensions and properties were from a real case, was then modelled with and without the participating masonry frame. The column-corbel and beam connection was modelled with solid elements with contact surface on the interface allowing to close represent its behaviour. Models considered a frame with one, five and ten storeys, two masonry strength and the use or nor of a mortar layer to fix masonry under the concrete beam. Conclusion from the finite element model analyses indicate the influence of each parameter on the system behaviour. The FEM results were then used to calibrate the width of a diagonal truss to be used in simple bar element models. Finally, a 3D-frame model was used to evaluate a actual 10-story precast concrete building considering or not the participating infill masonry. Only two masonry walls, close to the building central core and without openings, were considered yet results indicate great influence on considering the participating infill leading to an efficient building design. Future work is proposed to experimentally evaluate the conclusions from the numerical analyses here reported. / O presente trabalho realizou um estudo sobre o comportamento de estruturas aporticadas em concreto pré-moldado preenchidas com painéis de alvenaria, para fim de contraventamento de edificações, considerando a contribuição dessa alvenaria de preenchimento no pórtico pré-moldado para análise de ações horizontais. O estudo traz uma revisão da literatura sobre o tema. Um ensaio experimental de um pórtico de concreto armado preenchido ou não com alvenaria é usado para calibrar um modelo de elementos finitos usando o pacote Simulia Abaqus 2017. O modelo utiliza o dano plástico do concreto (CDP) para considerar o comportamento do concreto e alvenaria. Elementos embutidos são usados para considerar armaduras dentro do concreto. Os elementos de alvenaria são considerados homogêneos com as superfícies de contato ao longo da interface concreto-alvenaria. Depois que as propriedades foram calibradas, os modelos numéricos apresentaram excelente precisão quando comparados aos testes experimentais. Os quadros de concreto pré-fabricados, cujas dimensões e propriedades eram de um caso real, foram então modelados com e sem o preenchimento de alvenaria participante. A conexão pilar-viga foi modelada com elementos sólidos com superfície de contato na interface permitindo representar seu comportamento. Os modelos considerados foram um quadro com um, cinco e dez andares, duas resistências de alvenaria e o uso ou não de uma camada de argamassa para fixar alvenaria sob a viga de concreto. A conclusão das análises do modelo de elementos finitos indica a influência de cada parâmetro no comportamento do sistema. Os resultados de MEF foram utilizados para calibrar a largura de uma diagonal equivalente para ser usado em modelos simples de elementos de barras. Finalmente, um modelo de pórticos em 3D foi usado para avaliar um prédio de concreto pré-moldado de 10 andares, considerando ou não a alvenaria participante. Apenas duas paredes de alvenaria, perto do núcleo central do edifício e sem aberturas foram consideradas, os resultados indicam grande influência ao considerar o preenchimento participante, levando a um projeto de construção eficiente. O trabalho futuro é proposto para avaliar experimentalmente as conclusões das análises numéricas aqui relatadas.

Postes tubulares pré-moldados de concreto armado foram instalados no Brasil pelas empresas de telefonia móvel ao implantar ou ampliar áreas de cobertura do sistema a partir de 1996. A grande maioria desses postes, da ordem de duas mil unidades, foi fabricada por uma mesma empresa, pelo processo de centrifugação. As alturas desses postes variam de 20 a 60 m. Alguns desses postes colapsaram depois de três ou quatro anos de utilização, tendose conhecimento de quatro deles, nos estados de São Paulo, Espírito Santo, Rio de Janeiro e Rio Grande do Sul. Todos os colapsos conhecidos desses postes, ocorreram com ruptura na emenda entre o módulo tubular 1, engastado ao solo, e o seguinte módulo. Após extenso trabalho de investigação e diagnóstico do problema, levado a cabo em 40 postes demolidos e estocados na cidade de Santana do Parnaíba/SP, ficou demonstrado que o problema patológico mais relevante encontrado era a emenda entre módulos. O diagnóstico apontou fadiga da emenda por traspasse devido ao excesso de armadura, com taxas variando de 8,5% a 18,2%. Essas taxas efetivas de armadura superaram em muito o limite máximo permitido por norma e recomendável do ponto de vista de transmissão de esforços nessa região. O objetivo principal desta tese é demonstrar que é possível aproveitar esses postes, sem necessidade de sua substituição, através de um procedimento de reforço, original e seguro, que corrija as deficiências iniciais do projeto. Várias alternativas foram propostas pelo meio técnico aos proprietários desses postes para solução do problema, mas nenhuma conseguiu satisfazer às necessidades operacionais, econômicas e técnicas requeridas. A solução estudada minuciosamente nesta tese, consiste, sucintamente, em preencher o fuste do poste na região do traspasse com graute de elevada resistência mecânica e realizar confinamento passivo com uma camada de fibra de carbono, reduzindo as taxas de armadura a níveis adequados e assegurando confinamento da emenda. Essa solução foi ensaiada em laboratório, utilizando-se postes já removidos, ou seja, em escala real, de forma a comprovar a eficiência do reforço proposto. Todos os ensaios com módulos de postes não reforçados mostraram ruptura por falha na transferência de esforços na região do traspasse de armaduras, apresentando mecanismo de ruptura muito próximo ao encontrado na prática, em postes que colapsaram. Todas as rupturas ocorridas em postes reforçados na região do traspasse com a solução proposta ocorreu por flexão no domínio III, sem nenhuma deterioração por fadiga da região do traspasse de armaduras, comprovando a eficiência do reforço proposto. O custo da reabilitação desenvolvida nesta tese é, em média, de um terço à metade do valor da substituição do poste por uma torre metálica , o que a torna uma alternativa altamente atrativa para as empresas do setor, contribuindo para a solução de um grave problema nacional de engenharia (ciência aplicada). / Precast reinforced concrete posts were installed in Brazil by mobile telephone companies when implanting and enlarging service areas of the system starting in 1996. The great majority of these posts were manufactured by a single company, using a centrifugal process. Approximately two thousand units of posts were produced of heights ranging between 20m [60 ft] and 60 m [197 ft]. Some of those posts collapsed after three or four years of use, reportedly being known of four cases, located in the states of São Paulo, Espírito Santo, Rio de Janeiro and Rio Grande do Sul. All of the known collapses happened with rupture in the reinforcement development length between the first module (the one fixed to the ground) and the second module. After an extensive investigation work and diagnosis of the problem, carried out in 40 dismounted posts that had been previously stocked in the city of Santana do Parnaíba/SP, it was demonstrated that the most relevant problem found was in the development length of the reinforcement between the modules. The diagnosis pointed the fatigue due to the elevated reinforcement area at the joint area, which ranged between 8,5% to 18,2%. Those rates exceed considerably the maximum limit allowed by standards in order to guarantee adequate conditions for stress transfer in that area. The main objective of this dissertation is to demonstrate that it is possible to use the posts without need of their substitution, through a reinforcement procedure, original and safe, that corrects the initial deficiencies of the project. Several alternatives were proposed by the technical community for the solution of the problem, but none of them could satisfy the operational, economical and technical needs requested by the owners of the posts. The proposed solution consists in filling the section of the posts in the joint area with a high mechanical strength grout and a layer of carbon fiber reinforcement in order to accomplish passive confinement, therefore reducing the reinforcement rates to appropriate levels. This solution was tested in laboratory, using real scale posts already removed in order to confirm the efficiency of the proposed reinforcement procedure. All of the tests with non reinforced posts showed rupture due to failure of stress transfer in the joint area, presenting a very close rupture mechanism to the one found in practice in the posts that collapsed. All of the ruptures occurred in the reinforced posts were due to flexure in the Section III domain without any deterioration of the joint area, proving so the efficiency of the proposed reinforcement. The rehabilitation cost of the solution developed on this dissertation varies, on average, between a third and a half of the cost of replacing the structure for a metallic tower, thus providing an attractive alternative for the companies in this business, contributing to the solution of a serious national problem of engineering (applied science).

Use of composite steel construction with precast hollow core slabs is now popular in the UK,but the present knowledge in shear capacity of the headed shear studs for this type of composite construction is very limited. Currently, all the information is based on the results obtained from experimental push-off tests. A finite element model to simulate the behaviour of headed stud shear connection in composite beam with precast hollow core slabs is described. The model is based on finite element method and takes into account the linear and non-linear behaviour of all the materials. The model has been validated against the test results, for which the accuracy of the model used is demonstrated. Parametric studies showing the effect of the change in transverse gap size, transverse reinforcement diameter and in-situ concrete strength on the shear connection capacity are presented.

Throughout the United States accelerated bridge construction is becoming increasingly popular to meet growing transportation demands while keeping construction time and costs to a minimum. This research focuses on eliminating the need to form full-depth concrete bridge deck overhangs, accelerating the construction of concrete bridge decks, by using full-depth precast prestressed concrete deck panels. Full-depth precast overhang panels in combination with cast-in-place (CIP) reinforced concrete are experimentally and analytically investigated to assess the structural performance. Experimental loaddeformation behavior for factored AASHTO LRFD design load limits is examined followed by the collapse capacity of the panel-to-panel seam that exists in the system. Adequate strength and stiffness of the proposed full-depth panels deem the design safe for implementation for the Rock Creek Bridge in Fort Worth, Texas. New failure theories are derived for interior and exterior bridge deck spans as present code-based predictions provide poor estimates of the ultimate capacity. A compound shear-flexure failure occurs at interior bays between the CIP topping and stay-in-place (SIP) panel. Overhang failure loads are characterized as a mixed failure of flexure on the loaded panel and shear at the panel-to-panel seam. Based on these results design recommendations are presented to optimize the reinforcing steel layout used in concrete bridge decks.

Self-consolidating concrete (SCC) is a new, innovative construction material that can be placed into forms without the need for mechanical vibration. The mixture proportions are critical for producing quality SCC and require an optimized combination of coarse and fine aggregates, cement, water, and chemical and mineral admixtures. The required mixture constituents and proportions may affect the mechanical properties, bond characteristics, and long-term behavior, and SCC may not provide the same inservice performance as conventional concrete (CC). Different SCC mixture constituents and proportions were evaluated for mechanical properties, shear characteristics, bond characteristics, creep, and durability. Variables evaluated included mixture type (CC or SCC), coarse aggregate type (river gravel or limestone), and coarse aggregate volume. To correlate these results with full-scale samples and investigate structural behavior related to strand bond properties, four girder-deck systems, 40 ft (12 m) long, with CC and SCC pretensioned girders were fabricated and tested. Results from the research indicate that the American Association of State Highway Transportation Officials Load and Resistance Factor Design (AASHTO LRFD) Specifications can be used to estimate the mechanical properties of SCC for a concrete compressive strength range of 5 to 10 ksi (34 to 70 MPa). In addition, the research team developed prediction equations for concrete compressive strength ranges from 5 to 16 ksi (34 to 110 MPa). With respect to shear characteristics, a more appropriate expression is proposed to estimate the concrete shear strength for CC and SCC girders with a compressive strength greater than 10 ksi (70 MPa). The author found that girder-deck systems with Type A SCC girders exhibit similar flexural performance as deck-systems with CC girders. The AASHTO LRFD (2006) equations for computing the cracking moment, nominal moment, transfer length, development length, and prestress losses may be used for SCC girder-deck systems similar to those tested in this study. For environments exhibiting freeze-thaw cycles, a minimum 16-hour release strength of 7 ksi (48 MPa) is recommended for SCC mixtures.

USF completed a research study in 2005, which prioritized the replacement of 85 deteriorating composite precast deck panel bridges. This thesis re-evaluates the original recommendations in the wake of failures of two of these bridges in 2007. Since funding will not allow all identified bridges to be replaced, it was necessary to determine the most effective repair methods. To assess USF’s recommendations, a forensic study was undertaken in which the most current inspection and work program documents on the two failed bridges were reviewed and FDOT personnel interviewed. The best repair procedures were determined by reviewing repair plans, specifications, reports and site visits. The study found the two bridges that failed had been correctly prioritized by USF (No. 1 of 18 and No. 8 of 15). A new, accelerated repair method encompassing complete bay replacement was developed in a pilot project funded by the Florida Department of Transportation.

Due to their structural efficiency and architectural elegance, concrete arches have long been used in bridge applications. However, the construction of concrete arches requires significant temporary supporting structures, which prevent their widespread use in modern bridges. A relatively new form of arch bridges is the network arch, in which a dense arrangement of inclined hangers is used. Network arches are subjected to considerably smaller bending moments and deflections than traditional arches and are therefore suitable for modern, accelerated construction methods in which the arches are fabricated off-site and then transported to the bridge location. However, service-level stresses, which play a critical role in the performance of the structure, are relatively unknown for concrete network arches and have not been sufficiently investigated in the previous research on concrete arches. The primary objective of this dissertation is to improve the understanding of short-term and time-dependent stresses in concrete arches, and more specifically, concrete network arches. The research presented herein includes extensive field monitoring of the West 7th Street Bridge in Fort Worth, Texas, which is the first precast network arch bridge and probably the first concrete network arch bridge in the world. The bridge consists of twelve identically designed concrete network arches that were precast and post-tensioned before they were transported to the bridge site and erected. A series of vibrating wire gages were embedded in the arches and were monitored throughout the construction and for a few months after the bridge was opened to traffic. The obtained data were processed, and structural response parameters were evaluated to support the safe construction of the innovative arches, identify their short-term and time-dependent structural behavior, and verify the modeling assumptions. The variability of stresses among the arches was also used to assess the reliability of stress calculations. The results of this study provide valuable insight into the elastic, thermal, and time-dependent behavior of concrete arches in general and concrete network arches in particular. The knowledge gained in this investigation also has broader applications towards understanding the behavior of indeterminate prestressed concrete structures that are subjected to variable boundary conditions and thermal and time-dependent effects.

Following development of rectangular prestressed, precast concrete panels (PCP) that could be used as stay-in-place formwork adjacent to expansion joints in bridge decks, the Texas Department of Transportation (TxDOT) initiated a research effort to investigate the use of PCP units at skewed expansion joints. The fabrication of trapezoidal PCP units was studied and the response of skewed panels with 45° and 30° skew angles was obtained. The panels were topped with a 4 in. thick cast-in-place (CIP) slab to complete the bridge deck. Specimens with 45° skew performed well under service and overload levels. The deck failed in diagonal shear at loads well over the design level loads. However, two 30° specimens failed prematurely by delamination between the topping slab and the PCP. The cause of the delamination was insufficient shear transfer capacity between the PCP and CIP topping slab. For the specimens tested at a square end, the failure mode was punching shear at high loads for all specimens. The surface condition of the PCP was specified to have a “broom finish” and the panel was to have a saturated surface dry (SSD) condition so that PCP units would not leach moisture from the CIP topping slab. Neither of these conditions was satisfied in the two panels that failed prematurely. Although the panels were specified to have a broom finish, the panel surface had regions that were quite smooth. The objective of this research project was to reinvestigate the response of 30° PCP at an expansion joint following specified procedures for finish and moisture conditions. One specimen was constructed with a rectangular panel placed between two 30° skewed panels. These panels had a much rougher surface texture than the previously tested panels that failed in delamination. The skewed ends of the specimen were subjected to monotonically increasing static loads at midspan of the panel ends. The panels failed in diagonal shear and the response of the tested specimen confirmed that the panel surface roughness, and not the skew angle, caused delamination with the previously tested specimens. While TxDOT does not currently specify a minimum panel surface roughness, a surface roughness of approximately 1/4 in. is required in some codes for developing composite action. In addition, wetting the panels to a SSD condition prior to placement of the topping slab further enhances shear transfer between the topping slab and the PCP. / text

Multiple experimental and computational tests are performed on precast concrete structures designed for damage avoidance. These structures accommodate non-linear behaviour by rocking at specially detailed connections. Unbonded prestress is employed to provide a restoring force and supplemental devices are used to dissipate energy. Tests are performed on a 30 percent scale bridge pier and an 80 percent scale 3D beam-column joint subassembly. Several detailing strategies are developed and tested. Straight and draped tendon profiles are considered. Supplemental energy dissipation is provided by yielding mild steel devices or lead-extrusion dampers. The lead-extrusion dampers are tested both externally and internally. Detailing at the joint region is refined in an effort to provide a cost-effective and simple solution. A closure pour is considered to simply the construction process. Results indicate it is possible to eliminate virtually all damage at the beam-column joint with minor increased cost from steel armouring. The lead-extrusion damper is shown to be 'resetable', and therefore would not have to be replaced following a seismic event. Two seismic financial risk methodologies are developed to investigate the enhanced performance inherent to ductile jointed structures. A rapid method is introduced which simplifies the intensive computational effort necessary to perform loss studies. A distribution-free computational method is also examined. The methods are demonstrated with a case study of bridge piers designed to different seismic design codes and a bridge designed for damage avoidance. The bridge pier designed for damage avoidance is shown to have an expected annual loss of approximately 25 percent that of the conventional ductile piers.

Conventional concrete is a poor insulating material but has good thermal mass, while lightweight concrete provides good insulation at the price of thermal mass. Precast concrete wall systems have not been widely used in residential homes due to poor thermal and acoustic performance, despite being high quality products that are easy to construct. The variable density concrete panel was designed to combine good thermal storage, insulation and high quality precast concrete. It is produced from a single concrete mix which is vibrated to get a lightweight top layer and a normal/heavyweight bottom layer. The lightweight layer is the wall exterior, having low thermal conductivity providing good thermal insulation while the normal/heavyweight layer is the dense wall interior, having high specific heat to provide good thermal mass and sufficient strength for construction handling and to withstand service loads. The intention of this research was to estimate the hardened performance; that is the structural, serviceability and durability performance of the variable density concrete panel. Further developments to the mix design were made where the fresh properties were measured and thermal performance estimated on hardened specimens. Most of the major technical concerns were proved not being as severe as first thought, making the production of variable density concrete panels promising. To ensure that the variable density concrete would stratify, the concrete mix had to have defined fresh properties. Defined rheological ranges gave a good indication of the stratification potential, but the degree of stratification was also found to be dependent on the intensity and time of vibration. Slump flow had to be within a certain range to achieve good stratification but this alone did not guarantee stratification. Variable density concrete was found to have adequate strength capacity both in axial compression and in tension for likely service loads but the strength required to withstand handling loads at early ages was not assessed. The strength of the variable density concrete was found to be affected by several factors such as; degree of stratification, relative strength and thickness of the layers, curing environment and amount of defects. As the stratification of the concrete increased the thermal insulation improved whereas the strength decreased. Warping was found not to significantly affect the serviceability of panels despite differential shrinkage within the element. The amount of warping was mainly related to the degree of stratification. Warping decreased with better stratification as more stress and strain was relieved in the lightweight layer. The lightweight concrete was significantly weaker as well as being less stiff than the structural concrete and therefore creeps to follow the structural concrete. The thermal properties aimed for were generally not reached, but these mixes were not designed to optimise the thermal performance and were tested before the concrete was fully dried. This increased thermal conductivity and therefore reduced the measured R-values. Stratified concrete had good absorption resistance, poor permeability properties and was highly porous. If the concrete was over-vibrated it tended to have a rough surface finish that would require a coating. Delamination of the panels was not assessed in this research but is a likely mode of failure.