This book provides state-of-the-practice guidelines for the computation of wind-induced forces on industrial facilities with structural features outside the scope of current codes and standards. Without adequate standards, companies and their engineers developed techniques to calculate the wind loads for their facilities.
This report is intended for use by engineers who design industrial facilities and assumes familiarity with Standard ASCE 7, Minimum Design Loads for Buildings and Other Structures. It will also be useful to company managers who are responsible for establishing wind-load design and construction standards and to local building authorities.
The result is a wide variation in practice and inconsistent structural reliability. To encourage uniform wind load calculations, this report first reviews existing design practices for pipe racks and bridges, open and partially clad frame structures, vessels, tanks, steel stacks, cooling towers, and air coolers.
Then, recommended guidelines are presented for design methods and the analytical determination of wind loads. Worked calculations for six example situations are included to illustrate the application of the recommended guidelines.
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This publication encompasses the educational materials developed during the past five decades on the welding of steel structures and specifically directs it toward structural engineers and other design professionals. Effort has been made to condense the vast technological information into this volume. Numerous reading materials have been referenced at the end of each chapter for the reader to pursue further study.
This publication is useful both as a primer for design engineers who are searching for welding knowledge, and as an important source book for welding information. Major topics addressed in this publication are as follows:
Welding Processes
Health and Safety
Welding Terms and Definitions
Welding Codes and Standards
Weld Joints, Weld Types and Welding Symbols
Metal Arc Welding Processes (SMAW, GMAW, FCAW, SAW)
Welding Metallurgy
Residual Stress and Distortion
Fracture and Fatigue of Welded Structures
Welding Design Principles
Welds Faults and Inspection
Weld Cost Estimating
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Dear fellow CivilEAns,
I would like to count the number of "accepted" or "deferred" automatically using excel formulae.
You may write out , in excel, "accepted" and "deferred" a number of times so you may show me using excel formulae how they may automatically be counted say 5 accepted and 10 deferred. the 5 and 10 should be automatically generated using excel and not manually (because this gets hectic).
An image is appended.
Development of Precast Bridge Deck Overhang System
Author: Trejo, David Kim, Young Hoon | Size: 1.18 MB | Format:PDF | Quality:Original preprint | Publisher: Texas Transportation Institute | Year: 2010 | pages: 60
The implementation of full-depth, precast overhang panel systems has the potential to improve constructability, productivity, and make bridges more economical. Initial testing and analyses reported in the 0-6100-2 report resulted in a design that required a large number of shear pockets in the overhang panels. The general design methodology used in this report was to determine the number of connectors based on the shear capacity of a girder with conventional R-bars (not necessarily based on the required demand). The large number of shear pockets reduced the constructability and economy of the precast overhang system. Report 0-6100-1 (produced after 0-6100-2) used the American Association of State Highway Officials Load and Resistance Factor Design (AASHTO LRFD [2008]) demand requirements to design the number of shear pockets for a precast overhang panel system and reported that the number of pockets per panel could be reduced from the numbers reported in report 0-6100-2. However, this report only included an analysis for one beam type and one span length. In addition, the demand load used did not include all factors typically used by designers. Additional testing was required to assess different connector systems and further analyses were needed for the new Texas Department of Transportation (TxDOT) girders. The testing and analyses documented in this report (0-6100-3) provides a new equation for determining the number of shear pockets required for the various shear connector/coupler systems evaluated in this research. This equation was used to determine the number of shear pockets required for the newer TxDOT girders. Results from this research indicate that the roughened surface provides strong adhesion between the top girder surface and a precast panel. Steel reinforcing hoops placed in the shear pocket and shear reinforcing hoops placed in the overhang panel around the opening of the shear pocket provided limited or no improvement in capacity of the shear connector/coupler system. Hollow structural section (HSS) steel tubes placed around the perimeter of the shear pocket during fabrication did result in samples with higher shear capacities and could result in overhang panels with fewer shear pockets. This system could make constructing bridges with precast overhang systems more constructible, economical, and could reduce the construction time.
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The design of prestressed concrete bridge girders has changed significantly over the past several decades. Specifically, the design procedure to calculate the shear capacity of bridge girders that was used forty years ago is very different than those procedures that are recommended in the current AASHTO LRFD Specifications. As a result, many bridge girders that were built forty years ago do not meet current design standards, and in some cases warrant replacement due to insufficient calculated shear capacity. However, despite this insufficient calculated capacity, these bridge girders have been found to function adequately in service with minimal signs of distress. The objective of this research was to investigate the actual in service capacity of prestressed concrete girders that have been in service over an extended period of time. The actual capacity was compared with calculated values using the AASHTO LRFD Specifications.
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Author: Morcous, George | Size: 3.37 MB | Format:PDF | Quality:Original preprint | Publisher: University of Nebraska, Omaha | Year: 2010 | pages: 54
The National Bridge Inspection Standards require highway departments to inspect, evaluate, and determine load ratings for structures defined as bridges located on all public roads. Load rating of bridges is performed to determine the live load that structures can safely carry at a given structural condition. Bridges are rated for three types of loads, design loads, legal loads, and permit loads, which is a laborious and time-consuming task as it requires the analysis of the structure under different load patterns. Several tools are currently available to assist bridge engineers to perform bridge rating in a consistent and timely manner. However, these tools support the rating of conventional bridge systems, such as slab, I-girder, box girder and truss bridges. In the last decade, NDOR has developed innovative bridge systems through research projects with the University of Nebraska - Lincoln. An example of these systems is tied-arch bridge system adopted in Ravenna Viaduct and Columbus Viaduct projects. The research projects dealt mainly with the design and construction of the new system, while overlooking the load rating. Therefore, there is a great need for procedures and models that assist in the load rating of these new and complex bridge systems. The objective of this project is to develop the procedures and models necessary for the load rating of tied-arch bridges, namely Ravenna and Columbus Viaducts. This includes developing refined analytical models of these structures and performing rating factor (RF) calculations in accordance to the latest Load and Resistance Factored Rating (LRFR) specifications. Two-dimensional and three-dimensional computer models were developed for each structure and RF calculations were performed for the primary structural components (i.e. arch, tie, hanger, and floor beam). RFs were calculated assuming various percentages of section loss and using the most common legal and permit loads in the state of Nebraska in addition to AASHTO LRFD live loads. In addition, the two structures were analyzed and RFs were calculated for an extreme event where one of the hangers is fully damaged.
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The Load and Resistant Factor Design (LRFD) approach is based on the concept of structural reliability. The approach is more rational than the former design approaches such as Load Factor Design or Allowable Stress Design. The LRFD Specification for Bridge Design has been developed through the 1990s and 2000s. In the development process, many factors were carefully calibrated such that a structure designed with LRFD can achieve a reliability index of 3.5 for a single bridge girder (probability of failure of about 2 in 10,000). As the initial development of the factors in the LRFD Specification was intended to be applied to the entire nation, state-specific traffic conditions or bridge configuration were not considered in the development process. In addition, due to lack of reliable truck weigh data in the early 1990s in the U.S., the truck weights from Ontario, Canada measured in the 1970s were used for the calibration. Hence, the reliability of bridges designed with the current LRFD specification needs to be evaluated based on the Missouri-specific data and the load factor needs to be re-calibrated for optimal design of bridges. The objective of the study presented in this report is to calibrate the live load factor in the Strength I Limit State in the AASHTO LRFD Bridge Design Specification. The calibration is based on the Missouri-specific data such as typical bridge configurations, traffic volume, and truck weights. The typical bridge configurations and the average daily truck traffic of the bridges in Missouri are identified from statistical analyses of 2007 National Bridge Inventory. The Weigh-In-Motion (WIM) data from 24 WIM stations in Missouri are used to simulate realistic truck loads. Updated material and geometric parameters are also used to update the resistance distributions. From this study, it was found that most representative bridges in Missouri have reliability indices higher than 3.5. For many bridges in rural areas with Average Daily Truck Traffic (ADTT) of 1,000 or less, the average reliability indices are higher than 5.0. This study proposes a table of calibration factors which can be applied to the current live load factor of 1.75. The calibration factor is developed as a function of ADTT such that bridge design practitioners can select a calibration factor considering the expected ADTTs of a bridge throughout its life span. Impact of the calibration factor on the up-front bridge construction cost is also presented.
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Monitoring and Load Distribution Study for the Land Bridge
Author: Ghorbanpoor, Al | Size: 8.73 MB | Format:PDF | Quality:Original preprint | Publisher: University of Wisconsin, Milwaukee | Year: 2010 | pages: 179
A monitoring program and a live load distribution study were conducted for the Land Bridge, located on State Highway 131 between Ontario and LaFarge in southwest Wisconsin. The bridge is a 275-ft long curved double trapezoidal steel box girder construction. Hybrid HPS70W and A588 weathering steels were used for the construction of the bridge. The monitoring program included measurements of live load and thermal strains as well as displacements for the girders over a four-year period. The effects of the in-service live load, in terms of both the applied stresses and the number of load cycles, were found to be insignificant. The thermal stress levels were found to be more significant but with only a limited number of load cycles. It was also found that there was no significant change in the load pattern, for both the stress level and number of load cycles, over the four years of the monitoring program for the bridge. The observed stress levels in the bridge were found to be below the fatigue stress threshold prescribed by AASHTO. This indicated that an infinite life could be expected for the bridge when fatigue is a consideration for the steel box girders. The live load distribution study for the Land Bridge included a field testing, a 3-D numerical simulation, and a comparative study of the results with those determined by the provisions of the AASHTO standard and LRFD specifications. Good agreement was achieved between the load distribution factor values that were obtained from the field testing and the numerical simulation. The comparison of the results with the values obtained from the AASHTO specifications indicated that over-conservative results yielded from the standard specifications while the results from the LRFD specifications were under-conservative. It is recommended that an additional study be performed to overcome this shortcoming of the current design specifications.
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Calibration of Resistance Factors Needed in the LRFD Design of Drilled Shafts
Author: Abu-Farsakh, Murad Y | Size: 911 KB | Format:PDF | Quality:Original preprint | Publisher: Louisiana Transportation Research Center | Year: 2010 | pages: 110
The first report on Load and Resistance Factor Design (LRFD) calibration of driven piles in Louisiana (LTRC Final Report 449) was completed in May 2009. As a continuing effort to implement the LRFD design methodology for deep foundations in Louisiana, this report will present the reliability based analyses for the calibration of the resistance factor for LRFD design of axially loaded drilled shafts. A total of 16 cases of drilled shaft load tests were available to authors from Louisiana Department of Transportation and Development (LADOTD) archives. Out of those, only 11 met the Federal Highway Administration (FHWA) "5%B" settlement criterion. Due to the limited number of available drilled shaft cases in Louisiana, additional drilled shaft cases were collected from state of Mississippi that has subsurface soil conditions similar to Louisiana soils. A total of 15 drilled shafts from Mississippi were finally selected from 50 available cases, based on selection criteria of subsurface soil conditions and final settlement. As a result, a database of 26 drilled shaft tests representing the typical design practice in Louisiana was created for statistical reliability analyses. The predictions of total, side, and tip resistance versus settlement behavior of drilled shafts were established from soil borings using the FHWA O’Neill and Reese design method via the SHAFT computer program. The measured drilled shaft axial nominal resistance was determined from either the Osterberg cell (O-cell) test or the conventional top-down static load test. For the 22 drilled shafts that were tested using O-cells, the tip and side resistances were deduced separately from test results. Statistical analyses were performed to compare the predicted total, tip, and side drilled shaft nominal axial resistance with the corresponding measured nominal resistance. Results of this showed that the selected FHWA design method significantly underestimates measured drilled shaft resistance. The Monte Carlo simulation method was selected to perform the LRFD calibration of resistance factors of drilled shaft under strength I limit state. The total resistance factors obtained at different reliability index were determined and compared with those available in literature. Results of reliability analysis, corresponding to a target reliability index of 3.0, reveals resistance factors for side, tip, and total resistance factor are 0.20, 0.75, and 0.5, respectively.
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Development of Load and Resistance Factor Design for Ultimate and Serviceability Limit States of Transportation Structure Foundations
Author: Salgado, Rodrigo Purdue University Woo, San Inn Kim, Dongwook | Size: 3.57 MB | Format:PDF | Quality:Original preprint | Publisher: Joint Transportation Research Program | Year: 2011 | pages: 76
Most foundation solutions for transportation structures rely on deep foundations, often on pile foundations configured in a way most suitable to the problem at hand. Design of pile foundation solutions can best be pursued by clearly defining limit states and then configuring the piles in such a way as to prevent the attainment of these limit states. The present report develops methods for load and resistance factor design (LRFD) of piles, both nondisplacement and displacement piles, in sand and clay. With the exception of the method for design of displacement piles in sand, all the methods are based on rigorous theoretical mechanics solutions of the pile loading problem. In all cases, the uncertainty of the variables appearing in the problem and of the relationships linking these variables to the resistance calculated using these relationships are carefully assessed. Monte Carlo simulations using these relationships and the associated variabilities allow simulation of resistance minus load distributions and therefore probability of failure. The mean (or nominal) values of the variables can be adjusted so that the probability of failure can be made to match a target probability of failure. Since an infinite number of combinations of these means can be made to lead to the same target probability of failure, the authors have developed a way to determine the most likely ultimate limit state for a given probability of failure. Once the most likely ultimate limit state is determined, the values of loads and resistances for this limit state can be used, together with the values of the mean (or nominal) loads and resistances to calculate load and resistance factors. The last step in the process involves adjusting the resistance factors so that they are consistent with the load factors specified by American Association of State Highway and Transportation Officials (AASHTO). Recommended resistance factors are then given together with the design methods for which they were developed.
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