Structures under construction have been damaged by winds. The damaging winds, typically, are much... more Structures under construction have been damaged by winds. The damaging winds, typically, are much lower than the design wind loads for completed structures. Little guidance is available to help engineers and contractors assess wind created risk during construction. There are various means however, of controlling the wind created risks during the planning-design-construction process.
Building code requirements for shrinkage and temperature reinforcement in reinforced concrete str... more Building code requirements for shrinkage and temperature reinforcement in reinforced concrete structures have remained virtually unchanged for almost 75 years. This article provides a checklist for ensuring that the code requirements are met. Two challenging design concerns are addressed in detail. The first concern is whether fiber reinforcement can be used instead of deformed bars to resist shrinkage and temperature stresses and, if so, what fiber dosage is needed. The second question considers how the designer can determine the amount of reinforcement needed when shrinkage and temperature movements are significantly restrained.
This investigation addresses the effects of material properties on the durability of bridge piles... more This investigation addresses the effects of material properties on the durability of bridge piles in the Tampa Bay area. Four bridges were selected for this study, namely, New and Old Gandy and New and Old Skyway Bridges, due to the similarity in the water salinity. These bridges cover a time span of approximately 20 years. The tools used in this study included wet chemical analysis, microscopy, x-ray diffraction and fluorescence, mechanical and physical testing. It was found that concrete ingredients in both bridges are not different in quantity or quality. Significant differences in physical properties with the older bridges of better quality were attributed to construction practices, specifically, consolidation. It is recommended that future work should address porosity and permeability, in addition to the effects of crystallization of salts, on concrete durability.
This paper provides an overview of some of the factors that affect curling in concrete slabs. Fac... more This paper provides an overview of some of the factors that affect curling in concrete slabs. Factors that may affect curling deflection include: amount of drying shrinkage, modulus of subgrade reaction, concrete compressive strength and modulus of elasticity, reinforcement ratio, slab thickness, joint spacing and curing. Some of these factors, such as reducing drying shrinkage, adding reinforcing bars and increasing slab thickness have been shown to have a major effect in reducing the amount of curling deflection, while other factors have little or no effect.
Finite element heat transfer computer programs are discussed in regard to their use in modelling ... more Finite element heat transfer computer programs are discussed in regard to their use in modelling cold weather concreting. The concrete material properties required for input to the finite element programs are reviewed. Information is also provided on the lack of experimental work regarding concrete properties. Results of a finite element heat transfer analysis of cold regions concreting are presented.
Mass concrete, as defined by the American Concrete Institute, is: "Any large volume of cast-... more Mass concrete, as defined by the American Concrete Institute, is: "Any large volume of cast-in-place concrete with dimensions large enough to require that measures be taken to cope with the generation of heat and attendant volume change to minimize cracking." Since specifications sometimes require contractors to control mass concrete member-generated heat, estimators needs to know which structural components are considered mass concrete and applicable temperature limits to bid accurately. The authors further define mass concrete and discuss how to reduce the cost of coping with heat generation. A box details how expectations regarding mass concrete member concrete must be written into specifications.
The objective of this study is to evaluate methods of determining the fly ash content of portland... more The objective of this study is to evaluate methods of determining the fly ash content of portland-pozzolan interground cement. Samples of industrial interground portland-pozzolan were obtained for this study. These samples were then used to evaluate the fly ash content by (1) x-ray diffraction; (2) selective dissolution; and chemical analysis by (3) energy dispersive scanning electron microscopy and (4) x-ray fluorescence. Selective dissolution is a promising method for quick check tests, and chemical analysis by x-ray fluorescence is the best quantitative test. The main conclusion is, when using x-ray fluorescence, the amount of the fly ash in the blended cement can be determined when the oxides of silica, aluminum, and iron are known for the fly ash and clinker, as well as for the blended cement.
To evaluate the public perception of pavements in Colorado, 24 individuals were driven over 69 pa... more To evaluate the public perception of pavements in Colorado, 24 individuals were driven over 69 pavement sections in the Denver Metro area. These individuals were asked to rate the pavement based on rideability and to determine whether that ride was acceptable or unacceptable. The 69 pavement sections that were rated include: 51 bituminous and 18 concrete sections, urban and rural roads, and 35 and 55 mph speed limits. These ratings were then scaled from 0 to 5, with 5 being the best ride. Using regression analysis, the scaled ratings were compared to the roughness of the pavement. The pavement roughness was measured by the Colorado Department of Highways using a Mays Index. The conclusions are: for bituminous pavements 10% of the public is unhappy at a present serviceability index of 2.50; for concrete pavements 10% of the public is unhappy at a present serviceability index of 2.21; and the public will tolerate rougher roads at slower speeds.
The article describes how if properly selected and carefully analyzed, railroad cars may be used ... more The article describes how if properly selected and carefully analyzed, railroad cars may be used for inexpensive low-volume bridges. The railroad cars are set on a foundation and used as bridges. Railroad car bridge superstructures are being constructed to meet a variety of demands: low-volume roads; work-bridges and platforms; temporary detour bridges; agricultural bridges; and for access to personal property. The properties of railroad cars are discussed. Railroad cars can support heavy vehicle loads. The selection of a railroad car requires the consideration of potential problem areas: material strength; fatigue strength; brittle fracture; effect of broken or damaged members; and previous overloading or cyclic loading. The need is also pointed out for performing condition surveys on cars. Comments are made on the design details of such bridges.
Reinforcing steel in concrete is protected by a passive layer that is destroyed when exposed to c... more Reinforcing steel in concrete is protected by a passive layer that is destroyed when exposed to chlorides. To maintain a bare deck, deicing salts that contain chlorides are used to remove the snow and ice. The chlorides penetrate the concrete, destroy the passive layer surrounding the reinforcing, and help initiate corrosion of the rebar. A computer program has been developed to calculate the chloride diffusion in concrete and to assist the engineer in analyzing existing bridge decks and future concrete repairs. The computer program calculates the diffusion coefficient, the applied surface chloride loads, and future chloride profiles based on chloride profiles from core tests. The program can evaluate different deck designs including changes in concrete cover, chloride loads, concrete type, sealer application and life, and other variables. The program is user-friendly and operates on a 386PC with a VGA screen.
[1992] Proceedings. 11th IAPR International Conference on Pattern Recognition
... Introduction Parameter estimation in structures is a useful founda-tion for methods of assess... more ... Introduction Parameter estimation in structures is a useful founda-tion for methods of assessing damage in structures, esti-mating remaining ... inspection, as well as ultrasonic, acoustic emission, mag-netic, electromagnetic, and electrical potential tests (Agbabian and Masri 1988 ...
Structures under construction have been damaged by winds. The damaging winds, typically, are much... more Structures under construction have been damaged by winds. The damaging winds, typically, are much lower than the design wind loads for completed structures. Little guidance is available to help engineers and contractors assess wind created risk during construction. There are various means however, of controlling the wind created risks during the planning-design-construction process.
Building code requirements for shrinkage and temperature reinforcement in reinforced concrete str... more Building code requirements for shrinkage and temperature reinforcement in reinforced concrete structures have remained virtually unchanged for almost 75 years. This article provides a checklist for ensuring that the code requirements are met. Two challenging design concerns are addressed in detail. The first concern is whether fiber reinforcement can be used instead of deformed bars to resist shrinkage and temperature stresses and, if so, what fiber dosage is needed. The second question considers how the designer can determine the amount of reinforcement needed when shrinkage and temperature movements are significantly restrained.
This investigation addresses the effects of material properties on the durability of bridge piles... more This investigation addresses the effects of material properties on the durability of bridge piles in the Tampa Bay area. Four bridges were selected for this study, namely, New and Old Gandy and New and Old Skyway Bridges, due to the similarity in the water salinity. These bridges cover a time span of approximately 20 years. The tools used in this study included wet chemical analysis, microscopy, x-ray diffraction and fluorescence, mechanical and physical testing. It was found that concrete ingredients in both bridges are not different in quantity or quality. Significant differences in physical properties with the older bridges of better quality were attributed to construction practices, specifically, consolidation. It is recommended that future work should address porosity and permeability, in addition to the effects of crystallization of salts, on concrete durability.
This paper provides an overview of some of the factors that affect curling in concrete slabs. Fac... more This paper provides an overview of some of the factors that affect curling in concrete slabs. Factors that may affect curling deflection include: amount of drying shrinkage, modulus of subgrade reaction, concrete compressive strength and modulus of elasticity, reinforcement ratio, slab thickness, joint spacing and curing. Some of these factors, such as reducing drying shrinkage, adding reinforcing bars and increasing slab thickness have been shown to have a major effect in reducing the amount of curling deflection, while other factors have little or no effect.
Finite element heat transfer computer programs are discussed in regard to their use in modelling ... more Finite element heat transfer computer programs are discussed in regard to their use in modelling cold weather concreting. The concrete material properties required for input to the finite element programs are reviewed. Information is also provided on the lack of experimental work regarding concrete properties. Results of a finite element heat transfer analysis of cold regions concreting are presented.
Mass concrete, as defined by the American Concrete Institute, is: "Any large volume of cast-... more Mass concrete, as defined by the American Concrete Institute, is: "Any large volume of cast-in-place concrete with dimensions large enough to require that measures be taken to cope with the generation of heat and attendant volume change to minimize cracking." Since specifications sometimes require contractors to control mass concrete member-generated heat, estimators needs to know which structural components are considered mass concrete and applicable temperature limits to bid accurately. The authors further define mass concrete and discuss how to reduce the cost of coping with heat generation. A box details how expectations regarding mass concrete member concrete must be written into specifications.
The objective of this study is to evaluate methods of determining the fly ash content of portland... more The objective of this study is to evaluate methods of determining the fly ash content of portland-pozzolan interground cement. Samples of industrial interground portland-pozzolan were obtained for this study. These samples were then used to evaluate the fly ash content by (1) x-ray diffraction; (2) selective dissolution; and chemical analysis by (3) energy dispersive scanning electron microscopy and (4) x-ray fluorescence. Selective dissolution is a promising method for quick check tests, and chemical analysis by x-ray fluorescence is the best quantitative test. The main conclusion is, when using x-ray fluorescence, the amount of the fly ash in the blended cement can be determined when the oxides of silica, aluminum, and iron are known for the fly ash and clinker, as well as for the blended cement.
To evaluate the public perception of pavements in Colorado, 24 individuals were driven over 69 pa... more To evaluate the public perception of pavements in Colorado, 24 individuals were driven over 69 pavement sections in the Denver Metro area. These individuals were asked to rate the pavement based on rideability and to determine whether that ride was acceptable or unacceptable. The 69 pavement sections that were rated include: 51 bituminous and 18 concrete sections, urban and rural roads, and 35 and 55 mph speed limits. These ratings were then scaled from 0 to 5, with 5 being the best ride. Using regression analysis, the scaled ratings were compared to the roughness of the pavement. The pavement roughness was measured by the Colorado Department of Highways using a Mays Index. The conclusions are: for bituminous pavements 10% of the public is unhappy at a present serviceability index of 2.50; for concrete pavements 10% of the public is unhappy at a present serviceability index of 2.21; and the public will tolerate rougher roads at slower speeds.
The article describes how if properly selected and carefully analyzed, railroad cars may be used ... more The article describes how if properly selected and carefully analyzed, railroad cars may be used for inexpensive low-volume bridges. The railroad cars are set on a foundation and used as bridges. Railroad car bridge superstructures are being constructed to meet a variety of demands: low-volume roads; work-bridges and platforms; temporary detour bridges; agricultural bridges; and for access to personal property. The properties of railroad cars are discussed. Railroad cars can support heavy vehicle loads. The selection of a railroad car requires the consideration of potential problem areas: material strength; fatigue strength; brittle fracture; effect of broken or damaged members; and previous overloading or cyclic loading. The need is also pointed out for performing condition surveys on cars. Comments are made on the design details of such bridges.
Reinforcing steel in concrete is protected by a passive layer that is destroyed when exposed to c... more Reinforcing steel in concrete is protected by a passive layer that is destroyed when exposed to chlorides. To maintain a bare deck, deicing salts that contain chlorides are used to remove the snow and ice. The chlorides penetrate the concrete, destroy the passive layer surrounding the reinforcing, and help initiate corrosion of the rebar. A computer program has been developed to calculate the chloride diffusion in concrete and to assist the engineer in analyzing existing bridge decks and future concrete repairs. The computer program calculates the diffusion coefficient, the applied surface chloride loads, and future chloride profiles based on chloride profiles from core tests. The program can evaluate different deck designs including changes in concrete cover, chloride loads, concrete type, sealer application and life, and other variables. The program is user-friendly and operates on a 386PC with a VGA screen.
[1992] Proceedings. 11th IAPR International Conference on Pattern Recognition
... Introduction Parameter estimation in structures is a useful founda-tion for methods of assess... more ... Introduction Parameter estimation in structures is a useful founda-tion for methods of assessing damage in structures, esti-mating remaining ... inspection, as well as ultrasonic, acoustic emission, mag-netic, electromagnetic, and electrical potential tests (Agbabian and Masri 1988 ...
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