■ Survey results show general conformance to the recommendations of the PCI Design Handbook for 1⁄2 in. (13 mm) diameter strand loops but variability in many lifting-loop design parameters. Cut-off or waste prestressing strand (ASTM A416/ A416M) is often used to lift precast concrete elements at the casting yard and project site. These pieces of strands are mechanically bent into loops and cast into the concrete at the necessary embedment and projection above the surface to ensure safe lifting of the element. Prestressing strands are more commonly used than other lifting anchors because they are readily available and exhibit high strength and ductility properties, as well as being flexible and economical. Lifting-loop capacity depends on, but is not limited to, the following parameters:
{"title":"Industry Survey Results on the Use of Prestressing Strand Lifting Loops","authors":"Sandip Chhetri, R. Chicchi, Stephen J. Seguirant","doi":"10.15554/pcij65.4-05","DOIUrl":"https://doi.org/10.15554/pcij65.4-05","url":null,"abstract":"■ Survey results show general conformance to the recommendations of the PCI Design Handbook for 1⁄2 in. (13 mm) diameter strand loops but variability in many lifting-loop design parameters. Cut-off or waste prestressing strand (ASTM A416/ A416M) is often used to lift precast concrete elements at the casting yard and project site. These pieces of strands are mechanically bent into loops and cast into the concrete at the necessary embedment and projection above the surface to ensure safe lifting of the element. Prestressing strands are more commonly used than other lifting anchors because they are readily available and exhibit high strength and ductility properties, as well as being flexible and economical. Lifting-loop capacity depends on, but is not limited to, the following parameters:","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"65 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67573696","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Vasily S. Dudnik, L. Milliman, G. Parra-Montesinos
PCI Journal | July–August 2017 Precast, prestressed concrete hollow-core slabs are used in residential and office construction due to their light weight, economy, and rapid deployment. These structural members are typically manufactured through either an extrusion or a slip-form process. A nearly zero-slump concrete is used in extruded hollowcore slabs, while a slightly more workable concrete is used during a slip-form manufacturing process. In either case, however, the use of traditional shear reinforcement is not feasible, which limits the design shear strength of the member to that assumed to be provided by the concrete.
{"title":"Shear Behavior of Prestressed Steel-Fiber-Reinforced Concrete Hollow-Core Slabs","authors":"Vasily S. Dudnik, L. Milliman, G. Parra-Montesinos","doi":"10.15554/pcij62.4-02","DOIUrl":"https://doi.org/10.15554/pcij62.4-02","url":null,"abstract":"PCI Journal | July–August 2017 Precast, prestressed concrete hollow-core slabs are used in residential and office construction due to their light weight, economy, and rapid deployment. These structural members are typically manufactured through either an extrusion or a slip-form process. A nearly zero-slump concrete is used in extruded hollowcore slabs, while a slightly more workable concrete is used during a slip-form manufacturing process. In either case, however, the use of traditional shear reinforcement is not feasible, which limits the design shear strength of the member to that assumed to be provided by the concrete.","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"62 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67570172","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
■ Test results were used to create a design model for adhesive anchors postinstalled in thin concrete members. The model's accuracy and variability are similar to code-based models for other applications. Precast concrete sandwich wall panel systems have been used in the construction industry for the past 50 years because of their structural and thermal insulation efficiency. Precast concrete sandwich panels consist of two thin concrete layers separated by a thermal insulation layer. The concrete layers are commonly made structurally composite using shear connectors. The thickness of the layers typically ranges from 2 to 5 in. (50.8 to 127 mm). Postinstalled anchors are used in these panels for purposes including beam supports, repairing alignments, and installation of canopies and signs. However, anchorage in precast concrete sandwich panels can be challenging because of the thinness of the concrete layers and the lack of research and code provisions regarding anchorage in such members. In addition, codes and specifications impose limits on the minimum concrete member thickness and minimum anchor embedment depth. These limitations further hamper the use of postinstalled anchors in sandwich panels.
{"title":"Tensile behavior and design of adhesive anchors embedded in thin concrete members","authors":"Ahmad N. Tarawneh, B. Ross, T. Cousins","doi":"10.15554/pcij65.5-03","DOIUrl":"https://doi.org/10.15554/pcij65.5-03","url":null,"abstract":"■ Test results were used to create a design model for adhesive anchors postinstalled in thin concrete members. The model's accuracy and variability are similar to code-based models for other applications. Precast concrete sandwich wall panel systems have been used in the construction industry for the past 50 years because of their structural and thermal insulation efficiency. Precast concrete sandwich panels consist of two thin concrete layers separated by a thermal insulation layer. The concrete layers are commonly made structurally composite using shear connectors. The thickness of the layers typically ranges from 2 to 5 in. (50.8 to 127 mm). Postinstalled anchors are used in these panels for purposes including beam supports, repairing alignments, and installation of canopies and signs. However, anchorage in precast concrete sandwich panels can be challenging because of the thinness of the concrete layers and the lack of research and code provisions regarding anchorage in such members. In addition, codes and specifications impose limits on the minimum concrete member thickness and minimum anchor embedment depth. These limitations further hamper the use of postinstalled anchors in sandwich panels.","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"65 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67573384","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Brice, Stephen J. Seguirant, A. Mizumori, B. Khaleghi
■ This paper discusses fabrication, girder design, and shipping and handling considerations for precambered bridge girders. Building an intentional vertical curve into a precast concrete girder formwork system and the prestressing strand layout creates a girder with a prefabricated vertical curvature known as precamber. Precamber is the sum of the natural camber due to girder self-weight and eccentricity of the prestressing force plus the curvature built into the formwork (hereafter called formed camber). Precamber is an effective technique for matching the roadway profile grade for girders fabricated with a monolithic deck slab. For superstructures with a cast-in-place (CIP) concrete deck, this technique helps meet challenging vertical clearance requirements and reduces the slab haunch buildup associated with significant vertical curve profiles. Figure 1 shows a girder fabricated with substantial crest precamber to provide vertical clearance under the span. Girders have also been cast with sag curvatures to match required roadway profile grade.
{"title":"Fabrication and Design of Precambered Precast, Prestressed Concrete Bridge Girders","authors":"R. Brice, Stephen J. Seguirant, A. Mizumori, B. Khaleghi","doi":"10.15554/pcij65.3-02","DOIUrl":"https://doi.org/10.15554/pcij65.3-02","url":null,"abstract":"■ This paper discusses fabrication, girder design, and shipping and handling considerations for precambered bridge girders. Building an intentional vertical curve into a precast concrete girder formwork system and the prestressing strand layout creates a girder with a prefabricated vertical curvature known as precamber. Precamber is the sum of the natural camber due to girder self-weight and eccentricity of the prestressing force plus the curvature built into the formwork (hereafter called formed camber). Precamber is an effective technique for matching the roadway profile grade for girders fabricated with a monolithic deck slab. For superstructures with a cast-in-place (CIP) concrete deck, this technique helps meet challenging vertical clearance requirements and reduces the slab haunch buildup associated with significant vertical curve profiles. Figure 1 shows a girder fabricated with substantial crest precamber to provide vertical clearance under the span. Girders have also been cast with sag curvatures to match required roadway profile grade.","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"65 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67573087","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
■ Design recommendations were made for predicting stress relaxation behavior based on the model and test program. Precast, prestressed concrete and prestressed steel structures have been used in many applications, such as bridges, buildings, and nuclear cooling towers. More recently, precast, prestressed concrete offshore platforms have offered solutions for the exploration of oil and gas in the Arctic region, which holds about 13% of the undiscovered oil and 30% of the undiscovered gas in the world. Precast, prestressed concrete structures in the Arctic region are challenged by the harsh environment, especially the low temperatures, which reach about -70°C (-94°F).
{"title":"Stress Relaxation Behavior of Prestressing Strands Under Low temperatures","authors":"Jiabao Yan, Jian Xie, K. Ding","doi":"10.15554/pcij65.1-02","DOIUrl":"https://doi.org/10.15554/pcij65.1-02","url":null,"abstract":"■ Design recommendations were made for predicting stress relaxation behavior based on the model and test program. Precast, prestressed concrete and prestressed steel structures have been used in many applications, such as bridges, buildings, and nuclear cooling towers. More recently, precast, prestressed concrete offshore platforms have offered solutions for the exploration of oil and gas in the Arctic region, which holds about 13% of the undiscovered oil and 30% of the undiscovered gas in the world. Precast, prestressed concrete structures in the Arctic region are challenged by the harsh environment, especially the low temperatures, which reach about -70°C (-94°F).","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"65 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67573227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Experimental response of headed stud connections subjected to combined shear and bending actions","authors":"Otgonchimeg Davaadorj, P. Calvi, J. Stanton","doi":"10.15554/pcij65.5-02","DOIUrl":"https://doi.org/10.15554/pcij65.5-02","url":null,"abstract":"","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"65 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67573306","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Using Industry Competition to Augment Student Education","authors":"Austin D. Maue, Jill K. Walsh","doi":"10.15554/pcij65.3-05","DOIUrl":"https://doi.org/10.15554/pcij65.3-05","url":null,"abstract":"","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"65 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67573404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A New Studded Precast Concrete Sandwich Wall with Embedded Glass-Fiber-Reinforced Polymer Channel Sections: Part 2, Finite Element Analysis and Parametric Studies","authors":"A. Jawdhari, A. Fam","doi":"10.15554/pcij65.4-02","DOIUrl":"https://doi.org/10.15554/pcij65.4-02","url":null,"abstract":"","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"65 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67573435","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The effect of openings on the behavior of prestressed concrete hollow-core slabs and the efficiency of near-surface-mounted reinforcement as a strengthening technique are investigated. Five full-scale prestressed concrete hollow-core slabs were tested: one with no opening, two with openings in different locations, and two with identical openings strengthened with near-surface-mounted carbon-fiber-reinforced polymer (CFRP) strips. The slabs were tested in four-point bending. The openings were cut either in the pure flexural span or in the shear span. Test results showed that the presence of an opening along the flexure span or the shear span significantly decreased the postcracking flexural stiffness and capacity of the slab. In addition, strengthening openings with near-surface-mounted CFRP strips effectively enhanced the postcracking stiffness, increased the ductility of the member, restored the flexural strength deficit incurred as a result of cutting the openings, and provided a net increase in flexural capacity.
{"title":"Strengthening of Prestressed Concrete Hollow-Core Slab Openings Using Near-Surface-Mounted Carbonfiber- Reinforced Polymer Reinforcement","authors":"Karam Mahmoud, Steven Foubert, E. El-Salakawy","doi":"10.15554/pcij62.4-01","DOIUrl":"https://doi.org/10.15554/pcij62.4-01","url":null,"abstract":"The effect of openings on the behavior of prestressed concrete hollow-core slabs and the efficiency of near-surface-mounted reinforcement as a strengthening technique are investigated. Five full-scale prestressed concrete hollow-core slabs were tested: one with no opening, two with openings in different locations, and two with identical openings strengthened with near-surface-mounted carbon-fiber-reinforced polymer (CFRP) strips. The slabs were tested in four-point bending. The openings were cut either in the pure flexural span or in the shear span. Test results showed that the presence of an opening along the flexure span or the shear span significantly decreased the postcracking flexural stiffness and capacity of the slab. In addition, strengthening openings with near-surface-mounted CFRP strips effectively enhanced the postcracking stiffness, increased the ductility of the member, restored the flexural strength deficit incurred as a result of cutting the openings, and provided a net increase in flexural capacity.","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"62 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67569810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
■ The results of the study show that using a bilinear shrinkage profile for each concrete layer in the analysis accurately predicts the shrinkage strains and that early-age cracking can occur in precast concrete sandwich panels that are not properly cured or that have a high reinforcement ratio. Precast concrete sandwich panels (PCSPs) are becoming popular because of their advantages in terms of rapid speed of construction, superior energy conservation, and flexible and diverse aesthetic options. PCSPs are widely used as structural members in residential buildings, hospitals, industrial warehouses, and schools. Traditional noncomposite PCSPs are commonly used and usually comprise one thick reinforced concrete layer and one thin layer of concrete cladding connected using mechanical anchors. Composite PCSPs that use shear connectors in the form of diagonal steel or fiber reinforced polymer (FRP) reinforcing bars to connect the two reinforced concrete layers are becoming popular due to their improved shear transfer mechanism and material savings. In composite PCSP applications, the two reinforced concrete layers are the same thickness, and the overall thickness of the panel is about 1⁄2 to ∕3 of a comparable noncomposite panel while still offering relatively similar structural and thermal insulation properties. No official standards have been established to date for designing PCSPs, and relatively little research has been reported on their early-age structural behavior. Because PCSPs are normally designed to ensure crack-free performance, a careful look at all potential causes of cracking is needed, especially at the panels’ early age, while concrete is still immature with relatively low tensile strength.
{"title":"Early-Age Shrinkage Effects in Precast Concrete Sandwich Panels","authors":"Qian Huang, Ehab Hamed, R. Gilbert","doi":"10.15554/pcij65.1-04","DOIUrl":"https://doi.org/10.15554/pcij65.1-04","url":null,"abstract":"■ The results of the study show that using a bilinear shrinkage profile for each concrete layer in the analysis accurately predicts the shrinkage strains and that early-age cracking can occur in precast concrete sandwich panels that are not properly cured or that have a high reinforcement ratio. Precast concrete sandwich panels (PCSPs) are becoming popular because of their advantages in terms of rapid speed of construction, superior energy conservation, and flexible and diverse aesthetic options. PCSPs are widely used as structural members in residential buildings, hospitals, industrial warehouses, and schools. Traditional noncomposite PCSPs are commonly used and usually comprise one thick reinforced concrete layer and one thin layer of concrete cladding connected using mechanical anchors. Composite PCSPs that use shear connectors in the form of diagonal steel or fiber reinforced polymer (FRP) reinforcing bars to connect the two reinforced concrete layers are becoming popular due to their improved shear transfer mechanism and material savings. In composite PCSP applications, the two reinforced concrete layers are the same thickness, and the overall thickness of the panel is about 1⁄2 to ∕3 of a comparable noncomposite panel while still offering relatively similar structural and thermal insulation properties. No official standards have been established to date for designing PCSPs, and relatively little research has been reported on their early-age structural behavior. Because PCSPs are normally designed to ensure crack-free performance, a careful look at all potential causes of cracking is needed, especially at the panels’ early age, while concrete is still immature with relatively low tensile strength.","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"65 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67573124","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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