[pt] Este trabalho apresenta uma análise experimental de cinco vigas de concreto, simplesmente apoiadas, protendidas com cabos sintéticos externos, com o objetivo de estudar a influência da resistência do concreto na variação da força nos cabos de protensão e na resistência à flexão das vigas. A protensão das vigas foi feita com cabos sintéticos conhecidos como Parafil, com resistência a tração de 1950MPa e módulo de elasticidade de 126000MPa. A única variável considerada foi a resistência do concreto, cujo valores foram 36, 57, 73, 74 e 104MPa. O concreto das vigas com resistência de 57, 73, 74 e 104MPa foram feitos com o uso da microssílica e aditivo superplastificante, com exceção da viga com resistência de 36MPa que foi feita com concreto comum. Os resultados mostraram que a influência da resistência do concreto sobre a resistência à flexão das vigas não é tão grande. Para o aumento de 189% na resistência do concreto, houve um aumento na variação da força no cabo de apenas 13.6% e um aumento de 33% no momento de ruptura. Na comparação dos resultados experimentais com os resultados das principais normas e modelos propostos verificou-se que todos fornecem bons resultados e subestimam os valores experimentais. Na comparação dos resultados experimentais com o modelo de Campos (1993) observou-se que os valores da variação na força no cabo superestimam os valores experimentais. / [en] An experimental investigation on five concrete beams prestressed with external aramid tendons was carried out for the purpose of studying the influence of concrete on the flexural behaviour at service and ultimate loads. The beams were prestressed with Type G Parafil tendons, which are made of Kevlar 49 fibres. The strength and elastic modulus of the cables are 1950 MPa and 12600 MPa respectively. The main variable considered in the testes was the strength of the concrete with values of 36, 57, 73, 74 and 104 MPa. The results show that for an increase of 189% in the strength of the concrete, an increase of only 33% in the ultimate moment is observed. Experimental results were compared with results predicted by some Codes of Practice. This comparison shows that the theoretical models give good results. / [es] Este trabajo presenta un análisis experimental de cinco vigas de concreto, simplemente apoyadas, protendidas con cables sintéticos externos, con el objetivo de estudiar la influencia de la resistencia del concreto en la variación de la fuerza de los cables de protensión y en la resistencia a la flexión de las vigas. La protensión de las vigas fue hecha con cables sintéticos conocidos como Parafil, con resistenciaa la tracción de 1950MPa y módulo de elasticidad de 126000MPa. La única variable considerada fue la resistencia del concreto, cuyos valores fueron 36, 57, 73, 74 y 104MPa. El concreto de las vigas con resistencia de 57, 73, 74 y 104MPa fueron construidos con el uso de la microsílica y aditivo superplastificante, con excepción de la viga con resistencia de 36MPa que fue construida con concreto común. Los resultados mostraron que la influencia de la resistencia del concreto sobre la resistencia a la flexión de las vigas no es grande. Para el aumento de 189% en la resistencia del concreto, se produjo un aumento en la variación de la fuerza en el cable de apenas 13.6% y un aumento de 33% en el momento de ruptura. Comparando los resultados experimentales con los resultados de las principales normas y modelos propuestos se verificó que todos ofrecen buenos resultados y subestiman los valores experimentales. Comparando los resultados experimentales con el modelo de Campos (1993) se observó que los valores de la variación en la fuerza en el cable superestiman los valores experimentales.

The influence of the recommended LRFD Guidelines for the seismic design of highway bridges in Virginia was investigated by analyzing two existing bridges. The first bridge has prestressed concrete girders and is located in the Richmond area. The second bridge has steel girders and is located in the Bristol area. The analysis procedure for both bridges is similar. First the material and section properties were calculated. Then the bridge was modeled in RISA 3D. Live and dead load were imposed on the bridge to calculate the cracked section properties of the bridge. The period of vibration of the bridge was also calculated. After the soil class of the bridge was determined, the design response spectrum curve of the bridge was drawn. The spectral acceleration obtained from the design spectrum curve was used to calculate the equivalent earthquake loads, which were applied to the superstructure of the bridge to obtain the earthquake load effects. Live and dead loads were also applied to get the live and dead load effects. The combined effects of the dead, live and earthquake loads were compared to the interaction diagram of the columns and moment strength of the columns. The details of the bridge design were also checked with the corresponding seismic design requirement.A parametric study was performed to explore the effects of different column heights and superstructure heights in different parts of Virginia. The column longitudinal reinforcing was increased to satisfy the bridge axial loads and moments that are not within the column interaction diagram. / Master of Science

Corrosion damage reduces the load-carrying capacity of bridges which poses a threat to passenger safety. The objective of this research was to reduce the resources involved in conventional bridge inspections which are an important tool in the condition assessment of bridges and to help in determining if live load testing is necessary. This research proposes a framework to link semi-automated damage detection on prestressed concrete bridge girders with the estimation of their residual flexural capacity. The framework was implemented on four full-scale corrosion damaged girders from decommissioned bridges in Virginia. 3D point clouds of the girders reconstructed from images using Structure from Motion (SfM) approach were textured with images containing cracks detected at pixel level using a U-Net (Fully Convolutional Network). Spalls were detected by identifying the locations where normals associated with the points in the 3D point cloud deviated from being perpendicular to the reference directions chosen, by an amount greater than a threshold angle. 3D textured mesh models, overlaid with the detected cracks and spalls were used as 3D damage maps to determine reduced cross-sectional areas of prestressing strands to account for the corrosion damage as per the recommendations of Naito, Jones, and Hodgson (2011). Scaling them to real-world dimensions enabled the measurement of any required dimension, eliminating the need for physical contact. The flexural capacities of a box beam and an I-beam estimated using strain compatibility analysis were validated with the actual capacities at failure sections determined from four destructive tests conducted by Al Rufaydah (2020). Along with the reduction in the cross-sectional areas of strands, limiting the ultimate strain that heavily corroded strands can develop was explored as a possible way to improve the results of the analysis. Strain compatibility analysis was used to estimate the ultimate rupture strain, in the heavily corroded bottommost layer prestressing strands exposed before the box beam was tested. More research is required to associate each level of strand corrosion with an average ultimate strain at which the corroded strands rupture. This framework was found to give satisfactory estimates of the residual strength. Reduction in resources involved in current visual inspection practices and eliminating the need for physical access, make this approach worthwhile to be explored further to improve the output of each step in the proposed framework. / Master of Science / Corrosion damage is a major concern for bridges as it reduces their load carrying capacity. Bridge failures in the past have been attributed to corrosion damage. The risk associated with corrosion damage caused failures increases as the infrastructure ages. Many bridges across the world built forty to fifty years ago are now in a deteriorated condition and need to be repaired and retrofitted. Visual inspections to identify damage or deterioration on a bridge are very important to assess the condition of the bridge and determine the need for repairing or for posting weight restrictions for the vehicles that use the bridge. These inspections require close physical access to the hard-to-reach areas of the bridge for physically measuring the damage which involves many resources in the form of experienced engineers, skilled labor, equipment, time, and money. The safety of the personnel involved in the inspections is also a major concern. Nowadays, a lot of research is being done in using Unmanned Aerial Vehicles (UAVs) like drones for bridge inspections and in using artificial intelligence for the detection of cracks on the images of concrete and steel members. Girders or beams in a bridge are the primary longitudinal load carrying members. Concrete inherently is weak in tension. To address this problem, High Strength steel reinforcement (called prestressing steel or prestressing strands) in prestressed concrete beams is pre-loaded with a tensile force before the application of any loads so that the regions which will experience tension under the service loads would be subjected to a pre-compression to improve the performance of the beam and delay cracking. Spalls are a type of corrosion damage on concrete members where portions of concrete fall off (section loss) due to corrosion in the steel reinforcement, exposing the reinforcement to the environment which leads to accelerated corrosion causing a loss of cross-sectional area and ultimately, a rupture in the steel. If the process of detecting the damage (cracks, spalls, exposed or severed reinforcement, etc.) is automated, the next logical step that would add great value would be, to quantify the effect of the damage detected on the load carrying capacity of the bridges. Using a quantified estimate of the remaining capacity of a bridge, determined after accounting for the corrosion damage, informed decisions can be made about the measures to be taken. This research proposes a stepwise framework to forge a link between a semi-automated visual inspection and residual capacity evaluation of actual prestressed concrete bridge girders obtained from two bridges that have been removed from service in Virginia due to extensive deterioration. 3D point clouds represent an object as a set of points on its surface in three dimensional space. These point clouds can be constructed either using laser scanning or using Photogrammetry from images of the girders captured with a digital camera. In this research, 3D point clouds are reconstructed from sequences of overlapping images of the girders using an approach called Structure from Motion (SfM) which locates matched pixels present between consecutive images in the 3D space. Crack-like features were automatically detected and highlighted on the images of the girders that were used to build the 3D point clouds using artificial intelligence (Neural Network). The images with cracks highlighted were applied as texture to the surface mesh on the point cloud to transfer the detail, color, and realism present in the images to the 3D model. Spalls were detected on 3D point clouds based on the orientation of the normals associated with the points with respect to the reference directions. Point clouds and textured meshes of the girders were scaled to real-world dimensions facilitating the measurement of any required dimension on the point clouds, eliminating the need for physical contact in condition assessment. Any cracks or spalls that went unidentified in the damage detection were visible on the textured meshes of the girders improving the performance of the approach. 3D textured mesh models of the girders overlaid with the detected cracks and spalls were used as 3D damage maps in residual strength estimation. Cross-sectional slices were extracted from the dense point clouds at various sections along the length of each girder. The slices were overlaid on the cross-section drawings of the girders, and the prestressing strands affected due to the corrosion damage were identified. They were reduced in cross-sectional area to account for the corrosion damage as per the recommendations of Naito, Jones, and Hodgson (2011) and were used in the calculation of the ultimate moment capacity of the girders using an approach called strain compatibility analysis. Estimated residual capacities were compared to the actual capacities of the girders found from destructive tests conducted by Al Rufaydah (2020). Comparisons are presented for the failure sections in these tests and the results were analyzed to evaluate the effectiveness of this framework. More research is to be done to determine the factors causing rupture in prestressing strands with different degrees of corrosion. This framework was found to give satisfactory estimates of the residual strength. Reduction in resources involved in current visual inspection practices and eliminating the need for physical access, make this approach worthwhile to be explored further to improve the output of each step in the proposed framework.

The Diploma’s thesis is focused on the design of selected parts of reinforced concrete exhibition hall (prestressed concrete purlin, prestressed concrete girder, reinforced concrete column, reinforced concrete footing, post-tensioned concrete girders). The load calculation (the self weight, the permanent load, the wind load, the snow load and imposed load), the design and the review of selected reinforced concrete items and the drawing documentation are included in this thesis.

In recent years the use of carbon fiber reinforcing polymers (CFRP) to repair damaged structural components has become more accepted and practiced. However, the current reference for designing FRP systems to repair and strengthen reinforced concrete (RC) and prestressed concrete (PSC) girders has limitations. Similarly, very few resources address solutions for the debonding problem associated with CFRP laminates or the use of CFRP laminates to repair structural members with pre-existing damage. The included experimental program consists of testing both RC and PSC girders with simulated lateral damage and CFRP repairs. A total of 34 RC beams were statically tested under a 4-point loading until failure and had cross-section dimensions of 5” x 10” (14cm x 25.4cm), were 8’ long (2.44m), and were reinforced with either #3 or #4 mild steel rebar. 13 PSC girders having cross-section dimensions representing a half-scaled AASHTO type II shape, were 20’ long (6.1m), and were prestressed with five 7/16” (11.1mm) diameter low-lax 7-wire strands. Ten of the PSC girders were statically loaded until failure under a 4-point testing setup, but 3 PSC girders were dynamically tested under fatigue loading using a 3-point arrangement. Different configurations of CFRP laminates, number and spacing of CFRP transverse U-wraps, and amount of longitudinal CFRP layers are studied. The results present the flexural behavior of all specimen including load-deflection characteristics, strain characteristics, and modes of failure. Ultimately, results are used to recommend important considerations, needed criteria, and proper design procedures for a safe and optimized CFRP repair configuration.

The diploma‘s thesis deals with the design and assessment of prestressed cocrete tank of biogas station at ultimate limit state and also at serviceability limit state, according to ČSN EN 1992-1-1: Design of concrete structures. Specifically, the design of wall of the tank and foundation slab. The text part contains general information on the desing of the structure, static idealization of the structure, type of load and method for calculation of inner forces. Attachments contain drawing documentation and structural analysis, which completes the text part and solves in detail said structure.

The aim of the final thesis is to design and structural design report of selected elements of prefabricated storage hall. Processing of foundation drawing, element composition and for each designed element formwork drawing and reinforcement. It is a single-storey hall, where the main structural system consists of a transversal frame columns and prestressed girder. In this final thesis I designed and structural assessed prestressed girder, reinforced concrete purlin, roof bracing, column, grade beam and foundation pad. The calculation software Scia Engineer is used to calculate the effects of internal forces. The results are compared using a simplified method. The design and structural assessment are made according to valide standards. The designed construction complies with the limit state of ultimate and serviceability.

The Diploma thesis deals with the reconstruction design of a footbridge in the city of Kroměříž, Czech Republic. The footbridge would serve as safe transport for pedestrians over the Morava river. The main objective of the thesis is to conceive two or three reconstruction designs. The most suitable one will be opted for and elaborated in more detail. Eventually, strengthening of the bridge by means of additional prestressing using mono-strand post-tensioning systems is picked as the best solution of the planned reconstruction. The monostrand post-tensioning system is led under the deck, the cross section being outside. External cables are anchored in concrete blocks built around existing supports. Load-generated internal forces are calculated on a spatial bar model with non-linear first-order analysis. The calculation is executed using the finite element method in the midas Civil programme. The chosen reconstruction design is then assessed against load capacity limit states, and functionality. Also, the designed reconstruction is assed for dynamic effects. Results are compared with existing structure, and verified against the real-time tensometric measurement-obtained data. Dimensions, assessment of load-bearing structure, and structural details are all made according to valid Eurocodes.

This thesis deals with a construction-technology plan of two-story nursery school in Brno, district Bystrc. Thesis contains engineering report, financial and time schedule for structures, project of construction site, noise study, technological notes and inspection and test plans for cast-in-place reinforced concrete slabs and for prestressed concrete Spiroll floor slabs, formwork study, list of main machines used during construction, time schedule, needed quantity of workers and itemized budged for carcass, budged for whole building and comparison of cranes. Moreover, in appendices are drawings of approaches and processes during construction in its different phases.

This diploma thesis presents a project documentation for construction of a community centre with a restaurant. Its construction site is located on the outskirts of town Jaroměřice nad Rokytnou, Poděbradova street. The building is composed from three parts, which are connected to each other. The first part houses the restaurant with its facilities. This part is a single floor structure covered by a flat green roof. Its façade is formed by white boards composed into an asymmetrical pattern. The second part serves as a backstage area where all the necessary facilities are located. This second part of the building is as the first part a single floor structure covered by a flat green roof. Its façade is formed by façade timber boards. The main entrance is located in the middle part, which is the third part the building. It has two floors and it houses an auditorium, a bar and amenities. Its façade is formed by trapezial boards. The construction system is formed by load bearing walls and by prestressed concreted floor panels or in some parts by cast-in-place reinforced concrete slabs. The building has strip foundations. Its interior walls are built from sand-limestone bricks with acoustic properties. The perimeter walls are covered with ventilated façade with mineral wool thermal insulation. The heating of the community centre is powered by gas boiler connected to single-vent chimney with ventilation shaft.