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please share this document; Development of Fragility Curve Considering Aging of Oil Storage Tanks and Its Application to Risk Assessment of Industrial Complexes
by: Yoshihisa Murakami
ASME 2010 Pressure Vessels and Piping Division/K-PVP Conference (PVP2010)
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Small-Scale Modeling of Reinforced Concrete Structural Elements for Use in a Geotechnical Centrifuge
Author: Knappett, J., Reid, C., Kinmond, S., and O’Reilly, K. | Size: ?? MB | Format:PDF | Quality:Unspecified | Publisher: Journal of Structural Engineering | Year: 2011 | pages: 9
This paper discusses the modeling of reinforced concrete structural elements for use in geotechnical centrifuge modeling of soil-structure interaction problems. Centrifuges are employed in geotechnical modeling so that the nonlinear constitutive behavior of soil in small-scale models can be correctly modeled at prototype scale. Such models typically necessitate large scale factors of between 1∶20 and 1∶100, which is significantly larger than most conventional small-scale structural modeling. A new model concrete has been developed consisting of plaster, water, and fine sand as a geometrically scaled coarse aggregate that can produce a range of model concretes with cube compressive strengths between 25–80 MPa. Reinforcement is modeled using roughened steel wire (beams) or wire mesh (slabs). To illustrate the validity of the modeling technique, a series of three- and four-point bending tests were conducted on model beams designed to represent a 0.5×0.5 m square section prototype beam at 1∶40 scale, and model slabs designed to represent a prototype slab with plan dimensions of 4.8×4.8 m and 0.4 m deep (also at 1∶40 scale). The amount of longitudinal reinforcement was varied and tests both with and without shear reinforcement were conducted. The models were able to accurately reproduce both shear and flexural (bending) failures when loaded transversely. The load capacity (strength), bending stiffness, and ductility were shown to be simultaneously and appropriately scaled over a range of scaling factors appropriate for geotechnical centrifuge testing, and the technique therefore provides a significant improvement in the ability to accurately model soil-structure interaction behavior in centrifuge models.
An adequate longitudinal joint tie bar system is essential in the overall performance of concrete pavement. Excessive longitudinal joint openings are believed to be caused by either inadequate tie bar size or spacing or improper tie bar installation. If designed and installed properly, tie bars prevent the joints from opening and consequently improve load transfer efficiency between slabs and between slabs and shoulders, resulting in increased load carrying capacity. This study evaluated the longitudinal joint tie bar system currently used by CDOT, examining the criteria for proper use of tie bars and determining the maximum number of lanes that can be tied together without negatively impacting the concrete pavement structure. An improved mechanistic-empirical tie bar design method was developed. Tie bar design tables with recommended bar size and spacing were provided for each combination of pavement base types, CDOT concrete mixes, and weather stations. Field studies were conducted to investigate longitudinal joint performance and further evaluate the impact of factors related to design and construction practices. The experimental plan for this round of testing included the evaluation of tie bar alignment, measurement of joint load transfer, and measurement of relative slab movement at the joints. In addition, CDOT’s current specifications and practices related to longitudinal joint construction and tie bar design and placement were compared with those of other state agencies. Field testing results revealed that the measured joint openings at some tied longitudinal joints were in the typical range of non-tied slabs, implying that some tied joints performed as poorly as non-tied slabs. The results indicate the possibility of tie bar failure due to loss of concrete-steel bonding or yielding of tie bar steel. Another key finding was the possible impact of tie bar misalignment or misplacement on poor longitudinal joint performance. Testing indicated that the measured joint openings were wider when the tie bars did not connect to the other side of the joint, or when the embedment lengths were inadequate. On the other hand, tie bars with adequate embedment length on both sides of the joint, even when misaligned, appear to hold the joint tight. CDOT should adopt the mechanistic-empirical tie bar design procedure developed in this study. The research team recommends that CDOT conduct more rigorous experimental and field testing covering various base material types and concrete mixtures to obtain Colorado-specific model parameters for implementation.
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Synthesis of Performance Testing of Asphalt Concrete
Author: Dave, Eshan V Koktan, Philip | Size: 678 KB | Format:PDF | Quality:Original preprint | Publisher: University of Minnesota, Duluth | Year: 2011 | pages: 90
At present, like many other agencies, the Minnesota Department of Transportation asphalt material specifications rely primarily on volumetric properties to ensure good field performance. There have been considerable amounts of research efforts to develop so called “asphalt performance tests” that can link laboratory-measured parameters to pavement performance. Research efforts are also undertaken to refine the asphalt mix-design method so that laboratory tests and procedures can be incorporated into material specification. This research project explored availability of such tests, their suitability, and their use by other agencies.
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Finite Element Analysis of Deep Wide-Flanged Pre-stressed Girders to Understand and Control End Cracking
Author: Oliva, Michael G University of Wisconsin, Madison Okumus, Pinar | Size: 9.48 MB | Format:PDF | Quality:Original preprint | Publisher: University of Wisconsin, Madison | Year: 2011 | pages: 132
Hundreds of prestressed concrete girders are used each year for building bridges in Wisconsin. The prestress transfer from the prestressing strands to concrete takes place at the girder ends. Characteristic cracks form in this end region during or immediately after detensioning. Potential solutions to control end cracking were examined via finite element models and the impact of each solution on cracking was evaluated. Modifications to reinforcement bar size, debonding ratios, strand cutting sequence and use of draped strand patterns were simulated by the models. The results from different analyses were compared to quantify the success of each method in reducing strains causing girder end cracks. The tension strains leading to cracks of all types were responsive to debonding some of the bottom flange prestressing strands. Bottom flange cracking can be prevented by methodically debonding exterior strands, keeping the draped strands bonded, and evenly distributing the remaining bonded strands over the bottom flange.
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Numerical Modeling and Experimental Investigation of the Local Hydrology of a Porous Concrete Site
Author: Syrrakou, Christina Pinder, George | Size: 9.56 MB | Format:PDF | Quality:Original preprint | Publisher: University of Vermont, Burlington | Year: 2011 | pages: 86
Although porous pavement use has been accepted as a successful stormwater management practice in warm climates, application in regions with colder climates, like New England, is still under investigation. The Randolph Park and Ride Site, which is the area of interest of this specific study, is the first porous concrete site constructed in Vermont. The site, which was built in 2008 and is under use up to today, is quite unique in terms of the geology of the underlying materials and also the extensive instrumentation that has been applied in the field. The purpose of building this site was in part commercial, to provide the town of Randolph with a public parking lot, and part experimental, aimed at giving insight to the optimal design of porous pavements in New England. This study focuses on the experimental use of the site. The study initially aims at investigating the interaction between porous concrete utilization and local hydrology at porous concrete sites in New England. With this part achieved, a mathematical model can be developed and used prior to construction as a design tool for other porous concrete sites. It is also a secondary goal of this study to combine the mathematical model created with an optimization algorithm that will allow for optimal design of porous concrete sites in terms of minimal expense.
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The Texas Department of Transportation (TxDOT) has approximately 50,000 bridges in its inventory and the deterioration of concrete under these bridges, most of which are reinforced, has been a critical issue affecting the service condition. Recent research on deteriorated concrete columns on bridges in Texas indicated that microbial colonization might be a factor promoting the surface deterioration of bridge columns continuously exposed to water. Although microbial activities may be involved in the surface deterioration, it is however not clear how severe the deterioration is and whether it is a significant contributor to the deterioration. Field and laboratory investigations are needed to identify the impact of microbial induced deterioration (MID) on TxDOT bridges. To evaluate the severity of the deterioration and determine whether MID is a significant contributor to the deterioration, visual inspection and a number of in situ tests were performed on columns of twelve selected TxDOT bridges. Laboratory tests including microbial, chemical composition, mineralogy and petrographic analyses were performed to investigate the potential cause and extent of the deterioration. Results from this comprehensive study were used to provide evidence of concrete degradation and ascertain the degree of deterioration caused by microbial attack. The study also evaluated the effectiveness and consistency of various measurements used in this study and provided a suggested test procedure to identify microbial attack on concrete and evaluate the integrity of deteriorated concrete due to the attack. In addition, a preliminary evaluation of the microbial attack resistance of commonly used TxDOT mixes was performed through evaluation of resistance of a series of mixes subjected to field and/or sulfuric acid solution exposure.
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Development of Criteria for Using the Superpave Gyratory Compactor to Design Airport Asphalt Pavement Mixtures
Author: Rushing, John F | Size: 1.57 MB | Format:PDF | Quality:Original preprint | Publisher: U.S. Army Engineer Research and Development Center | Year: 2011 | pages: 247
Asphalt mix design for commercial airports in the United States is performed in accordance with guidelines set forth in the Federal Aviation Administration (FAA) Advisory Circular AC 150/5370-10D, “Standard for Specifying Construction of Airports, Item P-401—Plant Mix Bituminous Pavements.” Currently, two methods are used to compact asphalt pavement mixtures used in transportation surfaces. The Marshall method, the standard method for commercial airports, uses an impact device that imparts a repetitive stress to the mixture. The Superpave design method provides a kneading action to compact the mixture under constant strain conditions. Design of asphalt mixtures for airfields has been successfully accomplished using the Marshall method since the 1940s. The Superpave design method was developed and adopted by state departments of transportation beginning in the mid-1990s. Currently, most transportation departments have adopted this concept. Since most of the paving work by the asphalt industry is funded by state departments of transportation and private work (which typically use department of transportation criteria), it is becoming more difficult to find laboratories and contractors that continue to use the Marshall method. Hence, it is important that the Superpave method be adopted for airfield pavements. Prior to adopting Superpave as the primary method, it was necessary to determine the number of gyrations required to provide an adequate compactive effort for airfield pavements. This study evaluated the number of gyrations for a number of mixtures required to provide a density equal to 75 blows with the Marshall hammer. Since the 75-blow Marshall mixtures had performed well in the past, it was believed that providing a density with the gyratory compactor equal to that obtained with Marshall compaction would be a good way to adopt Superpave and still have confidence of good performance. This report describes the details of the study and provides a recommended number of gyrations with the Superpave gyratory compactor to provide a mixture that will perform similar to the 75-blow Marshall mixture. The study recommended that 70 gyrations are required to produce a mix similar to the 75-blow Marshall mixture. Additional research is also needed to correlate field performance of asphalt mixtures designed using Superpave methodologies.
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Finite Element Evaluation of Pervious Concrete Pavement for Roadway Shoulders
Author: Alam, Ashraful Haselbach, Liv Washington State University, Pullman Cofer, William Washington State University, Pullman | Size: 2.16 MB | Format:PDF | Quality:Original preprint | Publisher: Transportation Northwest Regional Center X (TransNow) | Year: 2011 | pages: 79
Stormwater quantity control is an important issue that needs to be addressed in roadway and ancillary transportation facility design. Pervious concrete has provided an effective solution for storm runoff for parking lots, sidewalks, bike trails, and other applications. It should be readily adaptable for use on roadway shoulders. Being a relatively new material for use in pavement for roadways, there is a lack of knowledge of the strength and behavior of pervious concrete slabs. While standard procedures for rigid pavement design with Portland cement concrete have been recommended, there are fundamental differences with pervious concrete pavement. These include a variation in concrete strength and stiffness through the depth of a slab and differences in the subgrade. Also, the main concern for a shoulder is the need to withstand wheel loadings from encroaching truck traffic. Both the strength of the pervious concrete pavement and the interface with the mainline pavement must be evaluated. Typically, tiebars are used at the interface to connect the shoulder and mainline slabs. The capacity and durability of pervious concrete at the tiebars is unknown, and steel reinforcing may not be an option with pervious systems. While full-scale testing of pervious concrete pavement is desirable, a preliminary evaluation can be performed quickly and economically through computer simulation. The Finite Element Method is a proven technique for the evaluation of solids and structures. With this approach, a number of loading scenarios can be applied to various pavement configurations to determine pavement capacity and evaluate the importance of connections with tiebars. The results of these analyses can be used to guide a full-scale testing program and help develop design procedures.
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