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An effective, viable design solution for the elevated viaduct guideway for Universal Freight Shuttle (UFS) system championed by Texas Transportation Institute (TTI) is presented. The proposed precast elevated UFS bridge system is analyzed for the operational vehicular loading as provided by TTI and a number of design alternatives for the various bridge components are provided. This includes: the design of the fully precast deck panels for long continuous spans, design of the shear connectors resisting interface shear at bridge deck-girder interface, design of structurally efficient and cost-effective trough girders and its design alternative with I-girders, and economic and long-term serviceable design of bridge piers. A literature review and study of the existing precast bridges is presented for the state-of-the-art and practice, design specifications and publications by AASHTO, State Department of Transportation and other agencies. These existing systems are refined to determine the most appropriate specification for the proposed bridge components by integrating the planning, design, fabrication and construction techniques to ensure high precision freight shuttle movement, construction feasibility, safety, life-cycle cost, durability and serviceability requirements. The design concept presented is a deviation from the conventional railways and highways design. The best practices and specifications of AASHTO and AREMA are combined suitably in this research to suit the major requirements of the project. A combination of the design philosophy with appropriate construction techniques has been blended to devise a system which is efficient for offsite manufacture of components for construction of the bridge and adaptable to the different bridge configurations. Based on the design results, it is found that precast concrete deck panels in combination with precast, prestressed concrete trough girders provides the most efficient superstructure solution for this project. The Damage Avoidance Design for the precast bridge piers along with the precast superstructure provides a system with comparable structural performance along with other benefits such as long term serviceability, economical sections, practically transportable units, modular simplicity for relocation as desired and ability to offer space for commercial usage. The steps for construction of the bridge is schematically presented and sequentially explained.

This study presents the behavior of a precast skewed integral abutment bridge (IAB) using the recently developed NEXT-F Beam section in particular. In order to understand the bridge response, a 3-dimensional finite element model of a bridge (Brimfield Bridge) was developed to examine the thermal effect on the response of the bridge structural components. Eighteen months of field monitoring including abutments displacements, abutment rotations, deck strains, and beam strains was conducted utilizing 136 strain gauges, 6 crackmeters, and 2 tiltmeters. The behavior of the NEXT beams during construction was examined by conducting hand calculation considering all factors that could affect strain readings captured by strain gauges embedded in the 6 beams. Parametric analysis and model validation were conducted considering the effect of soil conditions, distribution of thermal loads, and the coefficient of thermal expansion used for the analyses. Using the validated model, the effect pile orientation was investigated. All the results and illustration plots are presented in detail in this study. As a result of this study, the behavior of the NEXT beams during construction was explained. Long term behavior of the bridge was also explained using field data and FE model. Furthermore, it was concluded that the coefficient of thermal expansion of concrete and temperature variation along the bridge depth and transverse direction can have a significant effect on the strain readings and calculated response, respectively. Lastly, it was found that orienting piles with their web perpendicular on the bridge centerline or with their web perpendicular to the abutment centerline will result in small ratio of moment demand to moment capacity.

Motivated by Robert Mast's original papers on lifting stability, this research study provides a method for predicting beam behavior during lifting, with application in the construction of bridges. A beam lifting cracking limit state is developed based on analytical equations for calculating the roll angle of the beam, the internal forces and moments, the weak-axis and strong-axis deflections, and the cross-sectional angle of twist. Finite element simulations are performed to investigate the behavior of concrete beams during lifting and to validate the proposed method. Additionally, a statistical characterization of beam imperfections is presented, based on recently conducted field measurements of beam lateral sweep and eccentricity of lift supports. Finally, numerical examples for two typical precast prestressed concrete beam cross-sections are included to demonstrate the proposed method. / Master of Science

In the precast construction market, the competitive situation is significantly affected by price, cost, productivity, and quality factors. Since self-consolidating concrete (SCC) was first introduced to the concrete industry in the late 1980s, it has been used worldwide in variety of applications. Despite the documented technical and economic advantages of SCC in precast, prestressed applications, the use of SCC has been limited in some countries due to some technical uncertainties of such innovative material. To explore some unsolved issues related to SCC and to contribute to a wider acceptance of SCC in precast, prestressed applications, this study was undertaken to assess the effect of mixture proportioning and material characteristics on the performance of SCC and recommend performance-based specifications for use of SCC in the precast, prestressed applications. The thesis presents an experimental program that contains four parts: (1) a parametric study to evaluate the influence of binder type, w/cm, coarse aggregate type, and coarse aggregate nominal size on the modulus of elasticity and compressive strength developments; (2) a parametric study to evaluate the effect of mixture proportioning and material characteristics on fresh and hardened properties of SCC; (3) a fractional factorial design to identify the relative significance of primary mixture parameters and their coupled effects on SCC properties; and (4) a field validation using full-scale AASHTO Type II girders cast to investigate constructability, material properties, and structural performance (the latter part was carried out by the research team of Professor Denis Mitchell at McGill University). Based on the experimental test results, SCC exhibits similar compressive strength and modulus of elasticity to that of conventional high-performance concrete (HPC) of normal slump consistency. SCC and HPC mixtures made of a given binder type exhibit similar autogenous shrinkage. However, SCC exhibits up to 30% and 20% higher drying shrinkage and creep, respectively, at 300 days compared to HPC made with similar w/cm but different paste volume. The results of the experiment program show that among the investigated material constituents and mix design parameters, the w/cm has the most significant effect on mechanical and visco-elastic properties. The binder content, binder type, and sand-to-total aggregate ratio (S/A) also have considerable effect on those properties. The thickening-type viscosity modifying admixture (VMA) content (0 to 150 ml/100 kg CM) does not significantly affect mechanical and visco-elastic properties. Based on the findings, some mixture parameters regarding the overall performance of SCC designated for precast and prestressed applications can be recommended: SCC made with relatively low w/cm (such as 0.34 vs. 0.40) should be selected to ensure desirable compressive strength, modulus of elasticity (MOE), flexural strength, as well as less drying shrinkage and creep; the use of crushed aggregate with 12.5 mm MSA is suggested since it provides better mechanical properties of SCC compared to gravel; the use of low S/A (such as 0.46 vs. 0.54) to secure adequate mechanical and visco-elastic properties is recommended; the use of thickening-type VMA can help to secure robustness and stability of the concrete in the case of SCC proportioned with moderate and relatively high w/cm; and the use of Type MS cement can lead to lower creep and shrinkage than Type HE cement and 20% Class F fly ash. However, SCC mixtures made with Type HE cement and 20% Class F fly ash can result in better workability and mechanical properties. Therefore, it is recommended to use Type HE cement and 20% Class F fly ash and reduce binder content (such as 440 kg/m[exposant 3] vs. 500 kg/m[exposant 3]) to assure better overall performance of SCC. Validation on full-scale AASHTO-Type II girders using two HPC and two SCC mixtures show that girders casting with SCC can be successfully carried out without segregation and blocking for the selected optimized mixtures. The surface quality of the girders cast with SCC is quite satisfactory and of greater uniformity than girders cast with HPC. Both HPC and SCC mixtures develop similar autogenous shrinkage for mixtures made with similar w/cm. Again, the two evaluated SCC mixtures develop about 20% greater drying shrinkage than comparable HPC mixtures. Modifications of existing models to assess mechanical and visco-elastic properties of SCC used in the precast, prestressed applications are proposed. Based on the comparisons of various code provisions, the ACI 209 and CEB-FIP codes with suggested material coefficients can be recommended to estimate compressive strength. The modified AASHTO 2007 model can be used for predicting the elastic modulus and flexural strength. The AASHTO 2004 and 2007 models with suggested material coefficients can be used to estimate drying shrinkage and creep, respectively. The CEB-FIP 90 code model can be used to predict both drying shrinkage and creep. Finally, the modified Tazawa and Miyazawa 1997 model with material modifications can be used to estimate autogenous shrinkage of SCC.

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.

The Precast/Prestressed Concrete Institute (PCI) is the technical institute for precast/prestressed concrete industry. The plant involves activities such as placing high tensile steel strings inside the concrete products before they harden. This process needs the strings to be "stressed" hydraulically with high tension, which provides possibility of breaking the strand. Hence, employees may face a severe injury around the stressing bed. As various activities take place on the plant at the same time, employees must follow certain safety protocols while being around the plant. Another safety concern on the precast plant is silica exposure. Occupational Safety and Health Administration (OSHA) has provided various guidelines and tools to minimize silica exposure. Employees need to be careful and follow these safety protocols, otherwise it may lead to severe lung disease. Thus, employees need the appropriate safety training which will motivate them to follow safety protocols rigorously. The Bayesian Network (BN) methodology helps analyze plant structure to understand potential risk factors and causes that can be fixed by the employer paying more attention. The current traditional training methods such as videos, PowerPoint slides, or on-paper training, are not as effective in conveying the severity of the risky situations. This research focuses on precast plant activities while trying to identify the factors affecting plant safety. The current results suggest that using the BN study for the factors, such as stressing, chipping, leg injuries, tripping, and suspended loads, that may cause accidents or affect plant safety have a major impact on overall plant safety. Further sections of the dissertation discuss Fault Tree Analysis for risk assessment. It is observed that the BN study outperforms the risk assessment. Improvisation in safety protocols associated with these factors will help mitigate overall plant risks. In addition, study includes the development of immersive training methods and comparison of the immersive method to current safety training methods. Virtual Reality (VR) training module provides significant evidence to improvement in motivation level compared to traditional training. Knowledge gain concerning the safety protocols proves to be increasing for employees after the VR training method compared to the traditional training methods.

Este trabalho enfoca a análise estrutural de um dos tipos de laje que vem ganhando espaço no mercado brasileiro, que é a laje formada por vigotas de concreto protendido. O objetivo principal do trabalho é contribuir na avaliação do comportamento desse tipo de laje com relação aos momentos fletores negativos no apoio, mediante análise teórica. Esta análise foi realizada a partir da relação momento x curvatura proposta pelo CEB-90 em conjunto com a técnica do carregamento incremental para a consideração da não-linearidade física do concreto. Esse método foi avaliado através da comparação com resultados experimentais de painéis alveolares encontrados na literatura, verificando que o modelo teórico representa satisfatoriamente o comportamento estrutural de lajes formadas por elementos pré-moldados protendidos. A partir disto, fez-se análises em situações representativas de projeto de lajes formadas por vigotas protendidas, chegando-se as seguintes conclusões: a) a utilização da continuidade favorece fortemente a redução dos deslocamentos; b) os deslocamentos praticamente independem da taxa de armadura de continuidade; c) a evolução do momento fletor negativo no apoio e momento fletor positivo máximo no vão apresentou um comportamento padrão para os casos analisados; d) esse comportamento foi independente da taxa de armadura de continuidade e e) a taxa de armadura de continuidade afetou praticamente o valor da carga última. / This work aims the structural analysis in a type of slabs that is increasing its utilization in Brazil. These slabs are made by precast prestressed joists. The main objective of this work is the evaluation of the behavior of this type of slabs by theoretical analysis of the bending moments on the supports of continuous slabs. In the theoretical analysis was carried out the consideration of the non-linear of the concrete behavior through the moment x curvature relationship of Model Code CEB-90 add incremental load technique. This methodology was appraised with experimental results of panels of hollow core slabs and this methodology was able to represent satisfactorily the behavior of slabs made by precast prestressed elements. Analysis of representative cases of slabs with precast prestressed joists was carried out and the main conclusions were: a) the use of continuity aids highly to decrease the displacements; b) displacements were practically independent of reinforcement ratio on the support; c) the development profiles of the bending moments had a standard behavior to the analysed cases; d) this behavior was independent of reinforcement ratio on the support and e) the reinforcement ratio on the support affected practically the ultimate load value.

The objective of this study is to reduce the interstory drifts, floor accelerations, and shear forces experienced by masonry houses subject to seismic excitation. Ambient vibration testing was performed on a case study structure in Maip�, Chile, to identify characteristics of the system. Upon creating a multiple degree-of-freedom (MDOF) model of the structure, the effect of implementing several base isolation techniques is assessed. The isolation techniques analyzed include the use of friction pendulum systems (FPS), high-damping rubber bearings (HDRB), two hybrid systems involving HDRB and shape memory alloys (SMA), and precast-prestressed pile (PPP) isolators. The dynamic behavior of each device is numerically modeled using analytical formulations and experimental data through the means of fuzzy inference systems (FIS) and S-functions. A multiobjective genetic algorithm is utilized to optimize the parameters of the FPS and the PPP isolation systems, while a trial-and-error method is employed to optimize characteristic parameters of the other devices. Two cases are studied: one case involves using eight devices in each isolation system and optimizing the parameters of each device, resulting in different isolated periods for each system, while the other case involves using the number of devices and device parameters that result in a 1.0 sec fundamental period of vibration for each baseisolated structure. For both cases, the optimized devices are simulated in the numerical model of the case study structure, which is subjected to a suite of earthquake records. Numerical results for the devices studied indicate significant reductions in responses of the base-isolated structures in comparison with their counterparts in the fixed-base structure. Metrics monitored include base shear, structural shear, interstory drift, and floor acceleration. In particular, the PPP isolation system in the first case reduces the peak base shear, RMS floor acceleration, peak structural shear, peak interstory drift, and peak floor acceleration by at least 88, 87, 95, 95, and 94%, respectively, for all of the Chilean earthquakes considered. The PPP isolation system in the second case (yielding a 1.0 sec period) and the FPS isolation systems in both cases also significantly reduce the response of the base-isolated structure from that of the fixed-base structure.

Precast, prestressed concrete panels (PCPs) have been widely used in Texas as stay-in-place formwork in bridge deck construction. Although PCPs are widely popular and extensively used, Texas is experiencing problems with collinear cracks (cracks along the strands) in panels. One reason for the formation of collinear cracks is thought to be the required level of initial prestress. Currently, PCPs are designed assuming a 45-ksi, lump-sum prestress loss. If the prestress losses are demonstrated to be lower than this value, this could justify the use of a lower initial prestress, probably resulting in fewer collinear cracks. For this purpose, 20 precast, prestressed panels were cast at two different plants. Half of those 20 panels were fabricated with the current TxDOT-required prestress of 16.1 kips per strand, and the other half were fabricated with a lower prestress of 14.4 kips per strand based on initially observed prestress losses of 25 ksi or less. Thirteen of those panels were instrumented with strain gages and monitored over their life time. Observed losses stabilized after five months, and are found to be about 24.4 ksi. Even with the reduced initial prestress, the remaining prestress in all panels exceeds the value now assumed by TxDOT for design. / text