This paper describes a numerical evaluation of the seismic design of precast concrete buckling-restrained braced frames based on the Federal Emergency Management Agency’s Quantification of Building Seismic Performance Factors (FEMA P695) methodology. A set of 32 archetype braced frames covering a range of parameters were designed using a procedure consistent with current U.S. building code requirements. Nonlinear numerical models were developed and verified against existing experimental data. The results show that large axial compression and tension forces develop in both beams and columns, thus requiring these members to be designed with large reinforcement ratios or higher-grade reinforcing bars and beams to be designed like column members. Recommended beam and column effective (cracked) linear-elastic axial and flexural stiffness reduction factors provide reasonable estimates of story drifts and brace deformations under design lateral forces. Nonlinear monotonic static pushover and incremental dynamic analyses of the archetypes support an overstrength factor of 2.5, response modification coefficient of 8, and deflection amplification factor of 8 for the seismic design of this system.
{"title":"Seismic design and analysis of precast concrete buckling-restrained braced frames","authors":"S. Oh, Y. Kurama, Jon Mohle, B. Saxey","doi":"10.15554/pcij66.5-03","DOIUrl":"https://doi.org/10.15554/pcij66.5-03","url":null,"abstract":"This paper describes a numerical evaluation of the seismic design of precast concrete buckling-restrained braced frames based on the Federal Emergency Management Agency’s Quantification of Building Seismic Performance Factors (FEMA P695) methodology. A set of 32 archetype braced frames covering a range of parameters were designed using a procedure consistent with current U.S. building code requirements. Nonlinear numerical models were developed and verified against existing experimental data. The results show that large axial compression and tension forces develop in both beams and columns, thus requiring these members to be designed with large reinforcement ratios or higher-grade reinforcing bars and beams to be designed like column members. Recommended beam and column effective (cracked) linear-elastic axial and flexural stiffness reduction factors provide reasonable estimates of story drifts and brace deformations under design lateral forces. Nonlinear monotonic static pushover and incremental dynamic analyses of the archetypes support an overstrength factor of 2.5, response modification coefficient of 8, and deflection amplification factor of 8 for the seismic design of this system.","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67574630","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}
Quantifying the seismic resistance of reinforced concrete buildings after fire is difficult because of the lack of information regarding their strength and ductility under earthquake loads. In this study, four full-scale flexure-controlled reinforced precast concrete columns were subjected to quasi-static reversed cyclic lateral loading under constant axial load to examine the seismic response of reinforced precast concrete columns damaged by 30, 60, and 90 minutes of fire. For the first time, the impact of fire damage on force-displacement behavior, moment-curvature relationship, stiffness, energy dissipation capacity, and residual displacements was investigated through postfire seismic tests. Test results clearly indicated that the fire exposure did not significantly affect the lateral-load-bearing capacity, failure modes, and ductility of the columns, with the exception of the specimen subjected to 90 minutes of fire exposure. The analytical study consisting of thermal and fiber-based structural analysis demonstrated that conventional principles of structural mechanics are valid for estimation of the postfire seismic behavior of reinforced precast concrete columns when the deteriorations in materials are realistically taken into account and the given algorithm is followed.
{"title":"Post-fire seismic performance of precast reinforced concrete columns","authors":"U. Demir, M. Green, A. Ilki","doi":"10.15554/pcij65.6-01","DOIUrl":"https://doi.org/10.15554/pcij65.6-01","url":null,"abstract":"Quantifying the seismic resistance of reinforced concrete buildings after fire is difficult because of the lack of information regarding their strength and ductility under earthquake loads. In this study, four full-scale flexure-controlled reinforced precast concrete columns were subjected to quasi-static reversed cyclic lateral loading under constant axial load to examine the seismic response of reinforced precast concrete columns damaged by 30, 60, and 90 minutes of fire. For the first time, the impact of fire damage on force-displacement behavior, moment-curvature relationship, stiffness, energy dissipation capacity, and residual displacements was investigated through postfire seismic tests. Test results clearly indicated that the fire exposure did not significantly affect the lateral-load-bearing capacity, failure modes, and ductility of the columns, with the exception of the specimen subjected to 90 minutes of fire exposure. The analytical study consisting of thermal and fiber-based structural analysis demonstrated that conventional principles of structural mechanics are valid for estimation of the postfire seismic behavior of reinforced precast concrete columns when the deteriorations in materials are realistically taken into account and the given algorithm is followed.","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"65 1","pages":"62-80"},"PeriodicalIF":1.1,"publicationDate":"2020-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43977126","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 new PCI “Recommended Practice to Assess and Control Strand/Concrete Bonding Properties of ASTM A416 Prestressing Strand” specifies two new threshold limits for pullout tests conforming to ASTM A416 and new equations for the transfer and development length of prestressing strand. This article provides a summary of more than 30 years of research and knowledge advancement on the bond between concrete and prestressing strand related to the development of the new recommended practice. Discussions regarding the adoption and incorporation of the new recommended practice into structural design, strand production, and precast concrete fabrication and quality control practices are ongoing.
{"title":"Background for the new PCI recommended practice on strand bond","authors":"J. Brewe","doi":"10.15554/pcij65.6-05","DOIUrl":"https://doi.org/10.15554/pcij65.6-05","url":null,"abstract":"The new PCI “Recommended Practice to Assess and Control Strand/Concrete Bonding Properties of ASTM A416 Prestressing Strand” specifies two new threshold limits for pullout tests conforming to ASTM A416 and new equations for the transfer and development length of prestressing strand. This article provides a summary of more than 30 years of research and knowledge advancement on the bond between concrete and prestressing strand related to the development of the new recommended practice. Discussions regarding the adoption and incorporation of the new recommended practice into structural design, strand production, and precast concrete fabrication and quality control practices are ongoing.","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"65 1","pages":"27-32"},"PeriodicalIF":1.1,"publicationDate":"2020-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48837713","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}
Construction is regarded as an essential industry, at least in a limited capacity, in many states, and it is currently challenged to keep workers safe on the jobsite Social distancing, the first line of defense, requires workers to be a minimum of 6 ft (2 m) apart But construction, especially concrete construction, often requires teams to be much closer together for some work functions, so other measures become important Work on construction sites is being made safer through health screening, respirators and other face coverings, and frequent cleaning, among other things
{"title":"Making offices and construction sites safer from SARS-CoV-2","authors":"J. Nasvik","doi":"10.15554/pcij65.6-04","DOIUrl":"https://doi.org/10.15554/pcij65.6-04","url":null,"abstract":"Construction is regarded as an essential industry, at least in a limited capacity, in many states, and it is currently challenged to keep workers safe on the jobsite Social distancing, the first line of defense, requires workers to be a minimum of 6 ft (2 m) apart But construction, especially concrete construction, often requires teams to be much closer together for some work functions, so other measures become important Work on construction sites is being made safer through health screening, respirators and other face coverings, and frequent cleaning, among other things","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"65 1","pages":"21-26"},"PeriodicalIF":1.1,"publicationDate":"2020-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47404650","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":"Recommended practice to assess and control strand/concrete bonding properties of ASTM A416 prestressing strand","authors":"","doi":"10.15554/pcij65.6-06","DOIUrl":"https://doi.org/10.15554/pcij65.6-06","url":null,"abstract":"","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43184417","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 proposes flexural design recommendations for precast, pretensioned ultra-high-performance concrete members, including experimental verification and numerical examples. The experimental program includes three examples: a precast, prestressed concrete decked I-beam; a precast, prestressed concrete floor slab; and a precast, prestressed concrete bridge box beam. A comprehensive design example of a 250 ft (76.2 m) long decked I-beam is presented. A design spreadsheet is available online to aid designers in implementing the proposed recommendations.
{"title":"Flexural design of precast, prestressed ultra-high-performance concrete members","authors":"Chungwook Sim, M. Tadros, D. Gee, Micheal Asaad","doi":"10.15554/pcij65.6-02","DOIUrl":"https://doi.org/10.15554/pcij65.6-02","url":null,"abstract":"■ This paper proposes flexural design recommendations for precast, pretensioned ultra-high-performance concrete members, including experimental verification and numerical examples. The experimental program includes three examples: a precast, prestressed concrete decked I-beam; a precast, prestressed concrete floor slab; and a precast, prestressed concrete bridge box beam. A comprehensive design example of a 250 ft (76.2 m) long decked I-beam is presented. A design spreadsheet is available online to aid designers in implementing the proposed recommendations.","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"65 1","pages":"35-61"},"PeriodicalIF":1.1,"publicationDate":"2020-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41693351","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. Anay, L. Assi, V. Soltangharaei, A. Abdulshaheed, H. Gleich, P. Ziehl
This study investigated the out-of-plane shear performance of a newly developed shape memory alloy (SMA) connector and a commonly used shear/alignment connector. The innovation lies in developing a durable and easily installed and maintained flange-to-flange connector between precast concrete double-tee members. The proposed connector consists of a superelastic SMA curved bolt inserted into a duct that is then cast into the precast concrete member. Two types of sealant materials were used: polyurethane elastomeric sealant and nonshrink cementitious grout. The shear/alignment and SMA connectors were tested under monotonic vertical shear. The tests were conducted on 4 ft × 4 ft × 4 in. (1.2 m × 1.2 m × 100 mm) slab specimens. The resulting capacities and associated damage were summarized. Higher stiffness and lower ductility were observed for the SMA connector with nonshrink grout compared with the shear/alignment connector with polyurethane elastomeric sealant. The average stiffnesses of the SMA and shear/alignment connector specimens were 116,681 lb/in. (20,434 kN/m) and 31,300 lb/in. (5481 kN/m), respectively. The ductility of the SMA connector was improved when using polyurethane elastomeric sealant; however, more tests should be done to confirm this behavior. The SMA rod was reused in several tests through reheating of the SMA element. The shear/alignment connector cannot be reused.
研究了一种新开发的形状记忆合金(SMA)连接器和一种常用的剪切/对准连接器的面外剪切性能。创新在于在预制混凝土双三通构件之间开发一种耐用且易于安装和维护的法兰对法兰连接器。所提出的连接器由插入管道的超弹性SMA弯曲螺栓组成，然后将其浇铸到预制混凝土构件中。采用了两种密封材料:聚氨酯弹性体密封胶和非收缩胶凝灌浆。剪切/对准和SMA连接器在单调垂直剪切下进行了测试。试验尺寸为4英尺× 4英尺× 4英寸。(1.2 m × 1.2 m × 100 mm)板试件。总结了由此产生的能力和相关的损害。与使用聚氨酯弹性体密封胶的剪切/对准连接器相比，使用非收缩灌浆的SMA连接器具有更高的刚度和更低的延性。SMA和剪切/校直接头试件的平均刚度为116,681 lb/in。(20,434 kN/m)和31,300 lb/in。(5481 kN/m)。使用聚氨酯弹性体密封胶可以提高SMA连接器的延展性;但是，需要做更多的测试来确认这种行为。通过对SMA元件的再加热，在多次试验中重复使用了SMA棒。剪切/对准连接器不能重复使用。
{"title":"Development of a double-tee flange connection using shape memory alloy rods","authors":"R. Anay, L. Assi, V. Soltangharaei, A. Abdulshaheed, H. Gleich, P. Ziehl","doi":"10.15554/pcij65.6-03","DOIUrl":"https://doi.org/10.15554/pcij65.6-03","url":null,"abstract":"This study investigated the out-of-plane shear performance of a newly developed shape memory alloy (SMA) connector and a commonly used shear/alignment connector. The innovation lies in developing a durable and easily installed and maintained flange-to-flange connector between precast concrete double-tee members. The proposed connector consists of a superelastic SMA curved bolt inserted into a duct that is then cast into the precast concrete member. Two types of sealant materials were used: polyurethane elastomeric sealant and nonshrink cementitious grout. The shear/alignment and SMA connectors were tested under monotonic vertical shear. The tests were conducted on 4 ft × 4 ft × 4 in. (1.2 m × 1.2 m × 100 mm) slab specimens. The resulting capacities and associated damage were summarized. Higher stiffness and lower ductility were observed for the SMA connector with nonshrink grout compared with the shear/alignment connector with polyurethane elastomeric sealant. The average stiffnesses of the SMA and shear/alignment connector specimens were 116,681 lb/in. (20,434 kN/m) and 31,300 lb/in. (5481 kN/m), respectively. The ductility of the SMA connector was improved when using polyurethane elastomeric sealant; however, more tests should be done to confirm this behavior. The SMA rod was reused in several tests through reheating of the SMA element. The shear/alignment connector cannot be reused.","PeriodicalId":54637,"journal":{"name":"PCI Journal","volume":"65 1","pages":"81-96"},"PeriodicalIF":1.1,"publicationDate":"2020-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44382117","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}
Stephen J. Seguirant, R. Brice, A. Mizumori, B. Khaleghi
The allowable level of temporary concrete compressive stress in precast, prestressed concrete components has been a source of debate in t e co cr te industry for many years. Traditionally, hese str sses have been considered to originate ly from the effects f prestress combined with he self-w ight of a plumb component, evaluated about the major axis. The maximum compressive stress divided by the coefficient of the compressive stress limit det rmines th r quired concrete strength. Although these emporary stresses can occur at any time f om fabrication through erect on into the structure, the critical case is usually at transfer of prestress and subsequent lifting from the form. At this stage, the prestress force is higher and the concrete strength is lower than at any other point in the life of the component. At this early age, concrete is also more susceptible to damage from high compressive stress. As materials and fabrication capabilities in the precast, prestressed concrete industry advance, components are becoming longer and slenderer, particularly within the transportation sector. Such components require serious consideration of lateral stability during handling, which introduces bending about the minor axis. This lateral bending will increase maximum tensile and compressive stresses at the extremities of the component. These localized stresses traditionally have not been used to determine the required concrete strength, and doing so at current stress limits can significantly increase the required concrete strength. This paper is intended to reconcile the interaction between the temporary concrete compressive stresses traditionally used to determine the required concrete strength and the requirements for lateral stability, primarily the additional stresses due to lateral bending. The assumption is made that compressive stresses govern the determination of the required concrete strength. It is normally not efficient to determine the required concrete strength based on tensile stresses, which can be satisfied in a different manner.
{"title":"Lateral Stability and Concrete Strength Requirements for Precast, Prestressed Concrete Components","authors":"Stephen J. Seguirant, R. Brice, A. Mizumori, B. Khaleghi","doi":"10.15554/pcij65.2-02","DOIUrl":"https://doi.org/10.15554/pcij65.2-02","url":null,"abstract":"The allowable level of temporary concrete compressive stress in precast, prestressed concrete components has been a source of debate in t e co cr te industry for many years. Traditionally, hese str sses have been considered to originate ly from the effects f prestress combined with he self-w ight of a plumb component, evaluated about the major axis. The maximum compressive stress divided by the coefficient of the compressive stress limit det rmines th r quired concrete strength. Although these emporary stresses can occur at any time f om fabrication through erect on into the structure, the critical case is usually at transfer of prestress and subsequent lifting from the form. At this stage, the prestress force is higher and the concrete strength is lower than at any other point in the life of the component. At this early age, concrete is also more susceptible to damage from high compressive stress. As materials and fabrication capabilities in the precast, prestressed concrete industry advance, components are becoming longer and slenderer, particularly within the transportation sector. Such components require serious consideration of lateral stability during handling, which introduces bending about the minor axis. This lateral bending will increase maximum tensile and compressive stresses at the extremities of the component. These localized stresses traditionally have not been used to determine the required concrete strength, and doing so at current stress limits can significantly increase the required concrete strength. This paper is intended to reconcile the interaction between the temporary concrete compressive stresses traditionally used to determine the required concrete strength and the requirements for lateral stability, primarily the additional stresses due to lateral bending. The assumption is made that compressive stresses govern the determination of the required concrete strength. It is normally not efficient to determine the required concrete strength based on tensile stresses, which can be satisfied in a different manner.","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":"67572842","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}
■ Case studies analyzed with the proposed rational approach indicate that fire-resistance predictions for double-tee slabs under current prescriptive approaches for evaluating fire resistance are overly conservative. Double-tee, prestressed concrete slabs offer numerous advantages over traditional slab systems in terms of higher load-carrying capacity, better use of space, cost-effectiveness, and optimized production. Consequently, the use of these slabs as a structural solution has gained popularity in recent decades. Double-tee slabs are often used in parking structures, where their longer spans reduce the total number of required columns, allowing better use of space.
{"title":"A Rational Approach for Fire-Resistance Evaluation of Double-Tee, Prestressed Concrete Slabs in Parking Structures","authors":"Puneet Kumar, V. Kodur","doi":"10.15554/pcij65.2-01","DOIUrl":"https://doi.org/10.15554/pcij65.2-01","url":null,"abstract":"■ Case studies analyzed with the proposed rational approach indicate that fire-resistance predictions for double-tee slabs under current prescriptive approaches for evaluating fire resistance are overly conservative. Double-tee, prestressed concrete slabs offer numerous advantages over traditional slab systems in terms of higher load-carrying capacity, better use of space, cost-effectiveness, and optimized production. Consequently, the use of these slabs as a structural solution has gained popularity in recent decades. Double-tee slabs are often used in parking structures, where their longer spans reduce the total number of required columns, allowing better use of space.","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":"67573202","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}
■ Variations in girder depth, total number of strands, and debonding ratio were reviewed with the finite element analysis models. To meet bridge load demands efficiently, pretensioned concrete bulb-tee girders are heavily prestressed in most cases. Although the pretension force is transferred gradually to concrete near girder ends, tensile stresses developing in the anchorage zones can be large enough to create cracks in relatively thin girder webs. Deeper girders with larger prestressing forces tend to have more, longer, or wider cracks. When end zones are not encased in concrete diaphragms, cracks may create concerns for corrosion. Tadros et al. recommended repairing cracks between 0.012 and 0.050 in. (0.30 and 1.27 mm) in width and rejecting girders with cracks larger than 0.050 in. in width.
{"title":"Debonding strands as an anchorage zone crack control method for pretensioned concrete bulb-tee girders","authors":"Emre Kizilarslan, Pinar Okumus, M. Oliva","doi":"10.15554/pcij65.5-04","DOIUrl":"https://doi.org/10.15554/pcij65.5-04","url":null,"abstract":"■ Variations in girder depth, total number of strands, and debonding ratio were reviewed with the finite element analysis models. To meet bridge load demands efficiently, pretensioned concrete bulb-tee girders are heavily prestressed in most cases. Although the pretension force is transferred gradually to concrete near girder ends, tensile stresses developing in the anchorage zones can be large enough to create cracks in relatively thin girder webs. Deeper girders with larger prestressing forces tend to have more, longer, or wider cracks. When end zones are not encased in concrete diaphragms, cracks may create concerns for corrosion. Tadros et al. recommended repairing cracks between 0.012 and 0.050 in. (0.30 and 1.27 mm) in width and rejecting girders with cracks larger than 0.050 in. in width.","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":"67574002","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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