■ The analysis results identified the best-performing models for different scenarios, critical knowledge gaps and future research needs, and recommendations for ways current models could be further improved to achieve higher performance. In structural concrete, shear force must sometimes be transferred across an interface between two materials. The interface may be between two faces of a crack in monolithic concrete, two concretes cast at different times, or steel and concrete. Such shear transfer is usually modeled as a shear friction phenomenon. This approach, initially proposed in the 1960s by Birkeland and Birkeland, states that the shear strength of a concrete-to-concrete interface comes from the contribution of several resisting mechanisms, namely the cohesion between particles, the friction between concrete parts, and the shear force resisted by the reinforcement crossing the interface. The empirical parameters involved have been calibrated against experimental evidence by numerous investigators. Today, the shear friction theory is widely accepted and has been adopted by most design codes, including the PCI Design Handbook: Precast and Prestressed Concrete, the American Association of State Highway and Transportation Officials’ AASHTO LRFD Bridge Design Specifications, and Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary (ACI 318R-14).
{"title":"Shear Stress Transfer Across Concrete-to-Concrete Interfaces: Experimental Evidence and Available Strength Models","authors":"Otgonchimeg Davaadorj, P. Calvi, J. Stanton","doi":"10.15554/pcij65.4-04","DOIUrl":"https://doi.org/10.15554/pcij65.4-04","url":null,"abstract":"■ The analysis results identified the best-performing models for different scenarios, critical knowledge gaps and future research needs, and recommendations for ways current models could be further improved to achieve higher performance. In structural concrete, shear force must sometimes be transferred across an interface between two materials. The interface may be between two faces of a crack in monolithic concrete, two concretes cast at different times, or steel and concrete. Such shear transfer is usually modeled as a shear friction phenomenon. This approach, initially proposed in the 1960s by Birkeland and Birkeland, states that the shear strength of a concrete-to-concrete interface comes from the contribution of several resisting mechanisms, namely the cohesion between particles, the friction between concrete parts, and the shear force resisted by the reinforcement crossing the interface. The empirical parameters involved have been calibrated against experimental evidence by numerous investigators. Today, the shear friction theory is widely accepted and has been adopted by most design codes, including the PCI Design Handbook: Precast and Prestressed Concrete, the American Association of State Highway and Transportation Officials’ AASHTO LRFD Bridge Design Specifications, and Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary (ACI 318R-14).","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":"67573631","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 flexural performance testing indicated that including flexural reinforcement in the wythes, increasing insulation thickness, or providing diagonal load paths with the shear connectors can significantly increase the ultimate capacity of the panels. A typical precast concrete insulated wall consists of the exterior concrete layer, referred to as the architectural or facade wythe; the interior concrete wythe, which could be load bearing; and a rigid insulation sandwiched between the wythes. Precast concrete panels are usually used as exterior walls, spanning from the foundation to the floor or from column to column in a structure. The overall thickness of the panel is determined based on the applied loads, the thermal performance requirements, and the expected level of composite action between concrete layers. The type of insulation and its thickness have a direct impact on the thermal performance of the panel. Rigid cellular foam is generally used as insulation, and the most common forms of this foam are extruded polystyrene (XPS) and expanded polystyrene. Concrete wythes are connected to each other using tie connectors. These connectors are generally installed perpendicular to the face of the wall and carry mostly axial forces during handling but provide very little composite action. To reach a higher level of composite action for enhanced structural performance, shear connectors are used to transfer the shear forces between concrete wythes. Traditional shear connectors, such as discrete concrete blocks or steel connectors, cause thermal bridging, significantly affecting the thermal performance of the wall. For example, using steel connectors with as low as an 0.08% reinforcement ratio can reduce the thermal performance of the panel by 38%.
{"title":"Flexural Response of Double-Wythe Insulated Ultra-High-Performance Concrete Panels with Low to Moderate Composite Action","authors":"Valon Sylaj, A. Fam, Malcolm Hachborn, R. Burak","doi":"10.15554/pcij65.1-01","DOIUrl":"https://doi.org/10.15554/pcij65.1-01","url":null,"abstract":"■ The results of the flexural performance testing indicated that including flexural reinforcement in the wythes, increasing insulation thickness, or providing diagonal load paths with the shear connectors can significantly increase the ultimate capacity of the panels. A typical precast concrete insulated wall consists of the exterior concrete layer, referred to as the architectural or facade wythe; the interior concrete wythe, which could be load bearing; and a rigid insulation sandwiched between the wythes. Precast concrete panels are usually used as exterior walls, spanning from the foundation to the floor or from column to column in a structure. The overall thickness of the panel is determined based on the applied loads, the thermal performance requirements, and the expected level of composite action between concrete layers. The type of insulation and its thickness have a direct impact on the thermal performance of the panel. Rigid cellular foam is generally used as insulation, and the most common forms of this foam are extruded polystyrene (XPS) and expanded polystyrene. Concrete wythes are connected to each other using tie connectors. These connectors are generally installed perpendicular to the face of the wall and carry mostly axial forces during handling but provide very little composite action. To reach a higher level of composite action for enhanced structural performance, shear connectors are used to transfer the shear forces between concrete wythes. Traditional shear connectors, such as discrete concrete blocks or steel connectors, cause thermal bridging, significantly affecting the thermal performance of the wall. For example, using steel connectors with as low as an 0.08% reinforcement ratio can reduce the thermal performance of the panel by 38%.","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":"67572549","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 1, Experimental Study","authors":"Debrupa Dutta, A. Jawdhari, A. Fam","doi":"10.15554/pcij65.3-04","DOIUrl":"https://doi.org/10.15554/pcij65.3-04","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":"67573344","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}
■ Using bridge software for modeling and analysis, a prototype girder series and a proposed new girder series were studied to optimize the girder section and properties. Transportation agencies are interested in bridge structures that can be built rapidly at affordably. Prestressed concrete bulb-tee girders have been used for decades in the United States and offer significant structural and economic advantages (such as long spans, controlled cracking behavior, durability, and improved serviceability) compared with reinforced concrete girders. Precast concrete members enable a superior bridge system because they are produced in a controlled plant environment with high quality control and quality assurance. Cost savings are manifested in the employment of precast concrete bridge girders through reusable forms, reduced on-site construction time, and minimal traffic disruption.
{"title":"New LRFD-Based Prestressed Concrete Bulb-Tee Girders in Colorado","authors":"Y. J. Kim, Thushara Siriwardanage","doi":"10.15554/pcij65.3-03","DOIUrl":"https://doi.org/10.15554/pcij65.3-03","url":null,"abstract":"■ Using bridge software for modeling and analysis, a prototype girder series and a proposed new girder series were studied to optimize the girder section and properties. Transportation agencies are interested in bridge structures that can be built rapidly at affordably. Prestressed concrete bulb-tee girders have been used for decades in the United States and offer significant structural and economic advantages (such as long spans, controlled cracking behavior, durability, and improved serviceability) compared with reinforced concrete girders. Precast concrete members enable a superior bridge system because they are produced in a controlled plant environment with high quality control and quality assurance. Cost savings are manifested in the employment of precast concrete bridge girders through reusable forms, reduced on-site construction time, and minimal traffic disruption.","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":"67573099","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}
PCI Journal | July–August 2017 The use of precast concrete sandwich panels has increased significantly in the past few years due to their superior thermal and acoustic insulation properties. They are composed of two reinforced concrete layers (wythes) separated by a layer of rigid foam insulation. Unlike traditional noncomposite panels that rely only on the interior wythe to resist the load, composite sandwich panels rely on the composite action between the wythes, which can be achieved by using shear connectors that are mainly made from nonmetallic, diagonal fiber-reinforced-polymer (FRP) materials. FRP connectors are preferred by many manufacturers over traditional steel connectors because of their excellent thermal insulation properties and their corrosion resistance. The result of such a combination of materials is an energy-efficient sandwich panel that has a thinner inner wythe than a noncomposite wall, which can be used in many more applications than its counterpart noncomposite wall.
{"title":"Load-Carrying Capacity of Composite Precast Concrete Sandwich Panels with Diagonal Fiber-Reinforced-Polymer Bar Connectors","authors":"E. Hamed","doi":"10.15554/pcij62.4-03","DOIUrl":"https://doi.org/10.15554/pcij62.4-03","url":null,"abstract":"PCI Journal | July–August 2017 The use of precast concrete sandwich panels has increased significantly in the past few years due to their superior thermal and acoustic insulation properties. They are composed of two reinforced concrete layers (wythes) separated by a layer of rigid foam insulation. Unlike traditional noncomposite panels that rely only on the interior wythe to resist the load, composite sandwich panels rely on the composite action between the wythes, which can be achieved by using shear connectors that are mainly made from nonmetallic, diagonal fiber-reinforced-polymer (FRP) materials. FRP connectors are preferred by many manufacturers over traditional steel connectors because of their excellent thermal insulation properties and their corrosion resistance. The result of such a combination of materials is an energy-efficient sandwich panel that has a thinner inner wythe than a noncomposite wall, which can be used in many more applications than its counterpart noncomposite wall.","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":"67570263","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}
■ Load-deflection relationships predicted using the proposed analysis method were compared to the authors’ results from out-of-plane flexural testing of panel specimens and to experimental results reported by other investigators. Precast concrete insulated sandwich panels (ISPs) are a cladding system used to protect buildings from moisture ingress and heat loss. These panels are typically made of rigid insulation between two concrete layers. Mechanical connectors connect the concrete layers to each other. Like all cladding systems, these panels are subjected to out-of-plane wind and seismic loads. The out-of-plane loads induce out-of-plane shear forces and bending moments in the precast concrete ISP, thereby producing interlayer shear forces that are primarily transferred between the concrete layers by the mechanical connectors.
{"title":"Multistep Elastic Analysis of the Nonlinear Out-of-Plane Load-Deflection Behavior of Precast Concrete Insulated Sandwich Panels","authors":"N. Goudarzi, Y. Korany, S. Adeeb, R. Cheng","doi":"10.15554/pcij65.1-03","DOIUrl":"https://doi.org/10.15554/pcij65.1-03","url":null,"abstract":"■ Load-deflection relationships predicted using the proposed analysis method were compared to the authors’ results from out-of-plane flexural testing of panel specimens and to experimental results reported by other investigators. Precast concrete insulated sandwich panels (ISPs) are a cladding system used to protect buildings from moisture ingress and heat loss. These panels are typically made of rigid insulation between two concrete layers. Mechanical connectors connect the concrete layers to each other. Like all cladding systems, these panels are subjected to out-of-plane wind and seismic loads. The out-of-plane loads induce out-of-plane shear forces and bending moments in the precast concrete ISP, thereby producing interlayer shear forces that are primarily transferred between the concrete layers by the mechanical connectors.","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":"67572887","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}
■ Experimental results show 25% higher interface shear resistance results for the new mechanical connection than for the conventional connection. Full-depth precast concrete bridge deck systems have been increasingly used in new construction and as a replacement for deteriorating cast-in-place concrete decks because of their high quality, durability, and ease/ speed of construction. Full-depth precast concrete deck systems were originally used in the 1960s as noncomposite with the supporting girders, and their first use in composite construction was in 1973. Composite full-depth precast concrete deck systems provide economical design because they satisfy strength and serviceability requirements using smaller and shallower girder sections than are used in noncomposite systems. Precast concrete deck panels are usually made composite with the supporting girders via shear connectors, such as shear studs, bent bars, or threaded rods, projecting from the girder top flange and embedded in either discrete shear pockets or continuous longitudinal troughs (channels) in the deck panels. A summary of different deckto-girder connection details can be found in Tawadrous.
{"title":"Precast Concrete Deck-to-Girder Mechanical Connection for Accelerated Bridge Construction","authors":"G. Morcous, R. Tawadrous","doi":"10.15554/pcij65.3-01","DOIUrl":"https://doi.org/10.15554/pcij65.3-01","url":null,"abstract":"■ Experimental results show 25% higher interface shear resistance results for the new mechanical connection than for the conventional connection. Full-depth precast concrete bridge deck systems have been increasingly used in new construction and as a replacement for deteriorating cast-in-place concrete decks because of their high quality, durability, and ease/ speed of construction. Full-depth precast concrete deck systems were originally used in the 1960s as noncomposite with the supporting girders, and their first use in composite construction was in 1973. Composite full-depth precast concrete deck systems provide economical design because they satisfy strength and serviceability requirements using smaller and shallower girder sections than are used in noncomposite systems. Precast concrete deck panels are usually made composite with the supporting girders via shear connectors, such as shear studs, bent bars, or threaded rods, projecting from the girder top flange and embedded in either discrete shear pockets or continuous longitudinal troughs (channels) in the deck panels. A summary of different deckto-girder connection details can be found in Tawadrous.","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":"67573008","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}
■ PCI has devoted resources to study ways to meet UHPC implementation challenges, which include cost and the development of UHPC structural systems to capitalize on its unique capabilities. Ultra-high-performance concrete (UHPC) was first introduced as reactive powder concrete in the early 1990s by employees of the French contractor Bouygues. Since then, France, Japan, Malaysia, South Korea, and several other countries have made significant progress in using this material for bridge construction and other applications. The first roadway bridge with UHPC beams was built in France in 2001 and comprised five double tees with a beam section referred to as a pi shape.
{"title":"Ultra-High-Performance Concrete: A Game Changer in the Precast Concrete Industry","authors":"M. Tadros, D. Gee, Micheal Asaad, J. Lawler","doi":"10.15554/pcij65.3-06","DOIUrl":"https://doi.org/10.15554/pcij65.3-06","url":null,"abstract":"■ PCI has devoted resources to study ways to meet UHPC implementation challenges, which include cost and the development of UHPC structural systems to capitalize on its unique capabilities. Ultra-high-performance concrete (UHPC) was first introduced as reactive powder concrete in the early 1990s by employees of the French contractor Bouygues. Since then, France, Japan, Malaysia, South Korea, and several other countries have made significant progress in using this material for bridge construction and other applications. The first roadway bridge with UHPC beams was built in France in 2001 and comprised five double tees with a beam section referred to as a pi shape.","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"79 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67573567","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":"Behavior of Ductile Short-Grouted Seismic Reinforcing Bar–to–Foundation Connections Under Adverse Construction Conditions","authors":"T. C. Aragon, Y. Kurama, D. Meinheit","doi":"10.15554/pcij65.4-01","DOIUrl":"https://doi.org/10.15554/pcij65.4-01","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":"67573722","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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