R. Lequesne, William N. Collins, E. Lucon, D. Darwin, Ashwin Poudel
■ Proposed changes to ASTM A1061-16 are presented with the aim of providing clarity to the standard, reducing the frequency of improper test procedures, and improving the test precision. Multiwire steel prestressing strand is widely used in precast and post-tensioned concrete construction. Although the mechanical properties of strand products are relatively invariant across production runs, it is necessary for producers and some end users, such as state departments of transportation, to document whether a given sample of strand complies with applicable specifications. Samples of strand are therefore frequently tested in tension in accordance with ASTM A1061, Standard Test Methods for Testing Multi-Wire Steel Prestressing Strand. Problems occasionally arise when producers and end users obtain different results from tests of samples from the same strand. These problems can be difficult to resolve because the precision of the ASTM A1061 methods has not been previously quantified.
{"title":"Interlaboratory Study of Standard Methods for Testing Multiwire Steel Prestressing Strand","authors":"R. Lequesne, William N. Collins, E. Lucon, D. Darwin, Ashwin Poudel","doi":"10.15554/pcij65.4-03","DOIUrl":"https://doi.org/10.15554/pcij65.4-03","url":null,"abstract":"■ Proposed changes to ASTM A1061-16 are presented with the aim of providing clarity to the standard, reducing the frequency of improper test procedures, and improving the test precision. Multiwire steel prestressing strand is widely used in precast and post-tensioned concrete construction. Although the mechanical properties of strand products are relatively invariant across production runs, it is necessary for producers and some end users, such as state departments of transportation, to document whether a given sample of strand complies with applicable specifications. Samples of strand are therefore frequently tested in tension in accordance with ASTM A1061, Standard Test Methods for Testing Multi-Wire Steel Prestressing Strand. Problems occasionally arise when producers and end users obtain different results from tests of samples from the same strand. These problems can be difficult to resolve because the precision of the ASTM A1061 methods has not been previously quantified.","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":"67573535","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}
Pradeep Kankeri, S. K. S. Pachalla, N. Thammishetti, S. Prakash
■ ■ The paper reviews available literature related to fiber-reinforced concrete as well as provides results of full-scale testing conducted on hollow-core slabs specimens and reviews the applicability of analytical modeling. The main advantages of using precast concrete elements, such as hollow-core slabs, are high quality control and reduced construction time. Hollow-core slabs have longitudinal voids running along the spans, which reduces the slab’s weight and creates a more efficient cross section for prestressing. Hollow-core slabs are usually designed as uncracked elements under service loads. However, if a structure is overloaded due to change in use, architectural modifications, or material degradation, these elements can crack and may not meet the required serviceability design criteria. Because hollow-core slabs are produced via an extrusion process, the provision of additional reinforcement is not feasible. In such scenarios, the addition of structural synthetic fibers to the concrete during casting can enhance the performance of the slabs after cracking. Current American Concrete Institute (ACI) codes require at least 60 kg (130 lb) of deformed steel fibers per cubic meter of concrete for shear reinforcement. However, in prestressed hollow-core slabs, the beneficial effect of prestressing forces could relax the minimum fiber volume requirement.
{"title":"Behavior Of Structural Macrosynthetic Fiber-Reinforced Precast, Prestressed Hollow-Core Slabs at Different Flexure-to-Shear Ratios","authors":"Pradeep Kankeri, S. K. S. Pachalla, N. Thammishetti, S. Prakash","doi":"10.15554/pcij64.3-01","DOIUrl":"https://doi.org/10.15554/pcij64.3-01","url":null,"abstract":"■ ■ The paper reviews available literature related to fiber-reinforced concrete as well as provides results of full-scale testing conducted on hollow-core slabs specimens and reviews the applicability of analytical modeling. The main advantages of using precast concrete elements, such as hollow-core slabs, are high quality control and reduced construction time. Hollow-core slabs have longitudinal voids running along the spans, which reduces the slab’s weight and creates a more efficient cross section for prestressing. Hollow-core slabs are usually designed as uncracked elements under service loads. However, if a structure is overloaded due to change in use, architectural modifications, or material degradation, these elements can crack and may not meet the required serviceability design criteria. Because hollow-core slabs are produced via an extrusion process, the provision of additional reinforcement is not feasible. In such scenarios, the addition of structural synthetic fibers to the concrete during casting can enhance the performance of the slabs after cracking. Current American Concrete Institute (ACI) codes require at least 60 kg (130 lb) of deformed steel fibers per cubic meter of concrete for shear reinforcement. However, in prestressed hollow-core slabs, the beneficial effect of prestressing forces could relax the minimum fiber volume requirement.","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67571704","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}
■ Analysis of the results shows that deck cracking will occur, but approximately 50% of the prestress gain due to differential shrinkage will be retained after the deck cracks. As soon as a prestressing force is applied to a concrete member, loss of that prestressing force begins to occur. The method used for calculating prestress losses in the first edition of the American Association of State Highway and Transportation Officials’ AASHTO LRFD Bridge Design Specifications, was modeled on the 17th edition of the AASHTO Standard Specifications for Highway Bridges and considered losses due to elastic shortening, relaxation of prestressing strands, and creep and shrinkage in the concrete. While the effect of elastic shortening was calculated from mechanics, a simple formula was used to estimate the relaxation, creep, and shrinkage losses. For composite structures, the effects of adding a deck were not considered. These effects include the creep and shrinkage of the girder between the time the girder is fabricated and the time the deck is placed, the dead load of the deck when it is placed, and creep and shrinkage effects in the deck itself.
{"title":"Effect Of Deck Cracking On Prestress","authors":"Soumya Vadlamani, Richard A. Miller, G. Rassati","doi":"10.15554/pcij64.3-04","DOIUrl":"https://doi.org/10.15554/pcij64.3-04","url":null,"abstract":"■ Analysis of the results shows that deck cracking will occur, but approximately 50% of the prestress gain due to differential shrinkage will be retained after the deck cracks. As soon as a prestressing force is applied to a concrete member, loss of that prestressing force begins to occur. The method used for calculating prestress losses in the first edition of the American Association of State Highway and Transportation Officials’ AASHTO LRFD Bridge Design Specifications, was modeled on the 17th edition of the AASHTO Standard Specifications for Highway Bridges and considered losses due to elastic shortening, relaxation of prestressing strands, and creep and shrinkage in the concrete. While the effect of elastic shortening was calculated from mechanics, a simple formula was used to estimate the relaxation, creep, and shrinkage losses. For composite structures, the effects of adding a deck were not considered. These effects include the creep and shrinkage of the girder between the time the girder is fabricated and the time the deck is placed, the dead load of the deck when it is placed, and creep and shrinkage effects in the deck itself.","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67572076","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}
Following the design practice for cast-in-place concrete walls in which energy dissipation is a byproduct of the walls’ seismic response, force-based seismic design of precast concrete rocking walls uses a response modi cation coef cient, or R factor, of 5 and a minimum equivalent viscous damping ratio of about 8%. However, single rocking walls (SRWs) with total damping of 6% and precast concrete walls with end columns (PreWECs) designed with as much as 16% damping showed satisfactory responses when subjected to shake-table testing. These ndings suggest that the current design approach used for precast concrete rocking walls is unnecessarily restrictive and does not account for the superior behavior of the wall systems in design. To overcome this challenge, a damping-dependent R is proposed for the seismic design of precast concrete rocking walls and its effectiveness is demonstrated using a parametric study. A cost index is also developed to determine the relative bene ts of SRWs and PreWECs.
{"title":"Seismic Design Of Precast Concrete Rocking Wall Systems With Varying Hysteretic Damping","authors":"M. Nazari, S. Sritharan","doi":"10.15554/PCIJ64.5-04","DOIUrl":"https://doi.org/10.15554/PCIJ64.5-04","url":null,"abstract":"Following the design practice for cast-in-place concrete walls in which energy dissipation is a byproduct of the walls’ seismic response, force-based seismic design of precast concrete rocking walls uses a response modi cation coef cient, or R factor, of 5 and a minimum equivalent viscous damping ratio of about 8%. However, single rocking walls (SRWs) with total damping of 6% and precast concrete walls with end columns (PreWECs) designed with as much as 16% damping showed satisfactory responses when subjected to shake-table testing. These ndings suggest that the current design approach used for precast concrete rocking walls is unnecessarily restrictive and does not account for the superior behavior of the wall systems in design. To overcome this challenge, a damping-dependent R is proposed for the seismic design of precast concrete rocking walls and its effectiveness is demonstrated using a parametric study. A cost index is also developed to determine the relative bene ts of SRWs and PreWECs.","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67572637","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 paper investigates the structural behavior of the bonded link slab and identifies a step-by-step procedure for the design of bonded link slabs for bridge structures in the medium-span-length range. Precast, prestressed concrete girders offer a cost-effective solution for the construction of bridge structures in the medium-span-length range (between 12 and 42 m [40 and 140 ft]). Generally, the precast concrete girders are erected as simply supported (Fig. 1) and the reinforced concrete deck slab is placed afterward (either cast in place or by using precast concrete slab units). In multiple-span construction (Fig. 1), the deck slab is made continuous over the intermediate supports to minimize the use of expansion joints. The portion of the deck slab connecting two adjacent simple-span girders is referred to as the link slab (Fig. 1). The link slab can be cast with the deck slab or separately after all dead loads are placed.
{"title":"Analysis Of Bonded Link Slabs In Precast, Prestressed Concrete Girder Bridges","authors":"A. Gergess","doi":"10.15554/pcij64.3-03","DOIUrl":"https://doi.org/10.15554/pcij64.3-03","url":null,"abstract":"■ The paper investigates the structural behavior of the bonded link slab and identifies a step-by-step procedure for the design of bonded link slabs for bridge structures in the medium-span-length range. Precast, prestressed concrete girders offer a cost-effective solution for the construction of bridge structures in the medium-span-length range (between 12 and 42 m [40 and 140 ft]). Generally, the precast concrete girders are erected as simply supported (Fig. 1) and the reinforced concrete deck slab is placed afterward (either cast in place or by using precast concrete slab units). In multiple-span construction (Fig. 1), the deck slab is made continuous over the intermediate supports to minimize the use of expansion joints. The portion of the deck slab connecting two adjacent simple-span girders is referred to as the link slab (Fig. 1). The link slab can be cast with the deck slab or separately after all dead loads are placed.","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67571418","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":"Panelization And Connections For Rapid Erection Of High-Rise Elevator And Stair Cores","authors":"Charles E. Van Kampen, Alex Mihaylov","doi":"10.15554/pcij64.5-01","DOIUrl":"https://doi.org/10.15554/pcij64.5-01","url":null,"abstract":"","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67571960","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}
Edward S. Farmington, T. Anderson, L. Grant, Rita L. Seraderian
■ Specimens constructed with the industry standard of dual sealant and backer rod were also tested to serve as the control specimens and benchmark for data comparison. This paper discusses precompressed expandable foam as an option for sealing the joints of an architectural precast concrete panel building enclosure (referred to as precast concrete). The building enclosure is defined as the physical component or system of components of a building that separates the interior from the exterior environment. Architectural precast concrete building enclosures provide the facade of the building with more than just the environmental separation. Architectural precast concrete has had a successful long-term track record of use for building enclosures to control water and air penetration. Precast concrete wall designs are typically specified with a two-stage sealant joint between the concrete elements. This industry has accepted and recommended this approach. All exposed joint sealants require inspection, maintenance, and repair over time. Typical sealants degrade over time, and exposure to weather and ultraviolet rays can result in delamination and, subsequently, water leakage through the joint.
{"title":"Precast Concrete–To–Precast Concrete Facade Joints Using Precompressed Expandable Foam","authors":"Edward S. Farmington, T. Anderson, L. Grant, Rita L. Seraderian","doi":"10.15554/pcij64.6-05","DOIUrl":"https://doi.org/10.15554/pcij64.6-05","url":null,"abstract":"■ Specimens constructed with the industry standard of dual sealant and backer rod were also tested to serve as the control specimens and benchmark for data comparison. This paper discusses precompressed expandable foam as an option for sealing the joints of an architectural precast concrete panel building enclosure (referred to as precast concrete). The building enclosure is defined as the physical component or system of components of a building that separates the interior from the exterior environment. Architectural precast concrete building enclosures provide the facade of the building with more than just the environmental separation. Architectural precast concrete has had a successful long-term track record of use for building enclosures to control water and air penetration. Precast concrete wall designs are typically specified with a two-stage sealant joint between the concrete elements. This industry has accepted and recommended this approach. All exposed joint sealants require inspection, maintenance, and repair over time. Typical sealants degrade over time, and exposure to weather and ultraviolet rays can result in delamination and, subsequently, water leakage through the joint.","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67572482","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}
This paper highlights the results of the experimental phase of a comprehensive research project on the seismic performance of hollow-core diaphragms. The four specimens tested resembled a subdiaphragm region framed by beams. Variations in the boundary conditions of the hollow-core slabs and the inclusion of a cast-inplace concrete topping slab were considered. A bidirectional test fixture was used for simultaneous control of in-plane lateral load and bending deformations. Global and local behaviors were examined under a sequence of increasing cyclic demands. Untopped hollow-core diaphragm specimens exhibited stable behavior that was influenced by shear strength along longitudinal joints and a bearing mechanism that developed between the hollow-core slabs and the supporting beams. The performance of the topped specimen was affected by localized damage to the cast-in-place concrete topping and large demands on the welded-wire mesh reinforcement.
{"title":"Cyclic Behavior Of Hollow-Core Diaphragm Subassemblies","authors":"N. Angel, J. Correal, J. Restrepo","doi":"10.15554/pcij64.2-02","DOIUrl":"https://doi.org/10.15554/pcij64.2-02","url":null,"abstract":"This paper highlights the results of the experimental phase of a comprehensive research project on the seismic performance of hollow-core diaphragms. The four specimens tested resembled a subdiaphragm region framed by beams. Variations in the boundary conditions of the hollow-core slabs and the inclusion of a cast-inplace concrete topping slab were considered. A bidirectional test fixture was used for simultaneous control of in-plane lateral load and bending deformations. Global and local behaviors were examined under a sequence of increasing cyclic demands. Untopped hollow-core diaphragm specimens exhibited stable behavior that was influenced by shear strength along longitudinal joints and a bearing mechanism that developed between the hollow-core slabs and the supporting beams. The performance of the topped specimen was affected by localized damage to the cast-in-place concrete topping and large demands on the welded-wire mesh reinforcement.","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67571444","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}
V. Hariharan, G. Lucier, S. Rizkalla, P. Zia, G. Klein, H. Gleich
Open web reinforcement has been shown to be an effective alternative to closed stirrups in the webs of slender precast concrete L-shaped spandrel beams subjected to combined shear and torsion. For slender beams, an open reinforcement scheme is a better alternative to the traditional closed stirrups mandated by the American Concrete Institute’s (ACI’s) Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary (ACI 318R-14) because the beams are easier to produce with open reinforcement. Although the behavior of slender L-shaped beams (having aspect ratios of 4.5 or greater) with open web reinforcement has been well documented, the use of alternatives to closed stirrup reinforcement for compact L-shaped cross sections having aspect ratios much less than 4.5 has not been investigated previously. This paper presents an experimental study in which four full-scale, 46 ft (14 m) long, precast concrete, compact L-shaped beams were tested to failure. One of the test specimens served as a control and was designed with traditional closed stirrups. The remaining three beams were designed with alternative open and segmented reinforcement configurations. The results of the study demonstrate the viability of replacing closed stirrups with alternative open and segmented web reinforcement in compact L-shaped span-
{"title":"Behavior Of Compact L-Shaped Spandrel Beams With Alternative Web Reinforcement","authors":"V. Hariharan, G. Lucier, S. Rizkalla, P. Zia, G. Klein, H. Gleich","doi":"10.15554/pcij64.2-04","DOIUrl":"https://doi.org/10.15554/pcij64.2-04","url":null,"abstract":"Open web reinforcement has been shown to be an effective alternative to closed stirrups in the webs of slender precast concrete L-shaped spandrel beams subjected to combined shear and torsion. For slender beams, an open reinforcement scheme is a better alternative to the traditional closed stirrups mandated by the American Concrete Institute’s (ACI’s) Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary (ACI 318R-14) because the beams are easier to produce with open reinforcement. Although the behavior of slender L-shaped beams (having aspect ratios of 4.5 or greater) with open web reinforcement has been well documented, the use of alternatives to closed stirrup reinforcement for compact L-shaped cross sections having aspect ratios much less than 4.5 has not been investigated previously. This paper presents an experimental study in which four full-scale, 46 ft (14 m) long, precast concrete, compact L-shaped beams were tested to failure. One of the test specimens served as a control and was designed with traditional closed stirrups. The remaining three beams were designed with alternative open and segmented reinforcement configurations. The results of the study demonstrate the viability of replacing closed stirrups with alternative open and segmented web reinforcement in compact L-shaped span-","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67571692","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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