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Development of an Innovative Resilient Steel Braced Frame with BellevilleDisk and Shape Memory Alloy Assemblies.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Development of an Innovative Resilient Steel Braced Frame with BellevilleDisk and Shape Memory Alloy Assemblies.
Author:	Asgari Hadad, Alireza.
Published:	Ann Arbor : ProQuest Dissertations & Theses, 2021
Description:	185 p.
Notes:	Source: Dissertations Abstracts International, Volume: 83-04, Section: B.
Contained By:	Dissertations Abstracts International83-04B.
Subject:	Engineering.
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28730696
ISBN:	9798535575964

Development of an Innovative Resilient Steel Braced Frame with BellevilleDisk and Shape Memory Alloy Assemblies.
Asgari Hadad, Alireza.

Development of an Innovative Resilient Steel Braced Frame with BellevilleDisk and Shape Memory Alloy Assemblies. - Ann Arbor : ProQuest Dissertations & Theses, 2021 - 185 p.

Source: Dissertations Abstracts International, Volume: 83-04, Section: B.

Thesis (Ph.D.)--University of Cincinnati, 2021.

This item must not be sold to any third party vendors.

An innovative structural bracing system for steel structures is introduced in this research. The system is based on the application of stacked Belleville disks and Nitinol rods. By combining the two structural elements in one assembly and then adding it to a steel bracing system, the bracing system transforms into a resilient bracing system for structures in seismic regions. Belleville disks are responsible for carrying the compression load in the brace. A comprehensive investigation on the behavior of large-size stacked Belleville disks was carried out in this research. Nitinol rods are used to carry the tensile load. A constitutive material model for shape memory alloys was selected and the parameters used in the model were calibrated by comparing the obtained numerical results with the ASTM standard values and the values recorded in the literature.Afterwards, a unique assembly out of Belleville disks and Nitinol rods was introduced. The proposed assembly was then added to a regular steel bracing system to eliminate buckling and residual deformations of the system under the maximum-considered-event (MCE) loads. After proportioning the assembly, an appropriate connection detailing was suggested in the research to add the resilient assembly to the steel bracing system. Multiple assemblies were designed for different strength and stiffness values and the cyclic behavior of the designed assemblies was studied through finite element simulations. After analyzing the results, a modeling technique for the cyclic behavior of the new brace was selected in order to simulate the obtained cyclic behavior in a structural analysis software. Since the new resilient system is to be used in chevron configuration, the recently introduced chevron effect analysis method was used in this research to analyze the buildings. The commonly used approach, known as the Net Vertical Force method, is not capable of finding the chevron beam demands accurately, according to the analytical investigations performed in this research on the behavior of chevron beams.Three pairs of prototype steel buildings with different number of stories were designed in order to evaluate the performance of the proposed resilient bracing system: two 5-story buildings, two 10-story buildings, and two 15-story buildings. Each pair of buildings consisted of two structural systems: one system had special concentrically braced frame (SCBF) and the other used the new resilient structural system. The buildings were designed and then modeled in a structural analysis software in order to obtain and later compare their seismic responses under different levels of seismic hazard. A suite of seven strong ground motions were selected and then scaled properly according to the target seismic hazard analysis to represent three levels of seismic hazard: (1) 10% probability of occurrence in 50 years (Design Base Event), (2) 2% probability of occurrence in 50 years (Maximum Considered Event), and (3) 1% probability of occurrence in 50 years (user defined event).Incremental dynamic analyses were performed in order to obtain the performance fragility curves of the systems. Additionally, consequence functions were developed for the systems in order to obtain the economic losses due to the applied seismic hazards. Finally, the resiliency of the systems was measured through analysis of the required repair time and costs of the systems.According to the results, the construction cost (considering the structural members only) of the 5- story building was increased by 5% when the new resilient structural system was compared to the SCBF system. In the cases of 10- and 15-story buildings, the construction costs were decreased by 23% and 25% respectively, when the new resilient structural system was compared to the SCBF system. On average, the application of Nibellen brace increased the bracing costs of the buildings by 145% due the usage of new materials and new design methodology. However, the Nibellen bracing tensile and compressive mechanism forces are closer to each other in magnitudes, in comparison to regular SCBF brace-section mechanism forces. Thus, less demand is applied on chevron beams and columns in the braced frames of the Nibellen buildings. This leads to lighter beam and column section, and lower overall constructions costs in the 10- and 15- story Nibellen buildings. On average, the costs of beams and columns were decreased by 35% and 14%, respectively, in the Nibellen buildings when compared to the SCBF buildings.The new resilient system proved its superiority when the buildings’ required repair time and costs were compared. Under the design base event (DBE) hazard level, the repair costs were decreased by 100% for 5-story building, 82% for 10-strory building, and 79% for 15-story building when the new resilient system was compared to the SCBF system. Under maximum credible event (MCE) hazard level, the repair costs were decreased by 95% for 5-story building, 53% for 10-strory building, and 56% for 15-story building when the new system was used. Collectively, the ultimate results showed application of the proposed system improved the resiliency of all the buildings by 5% (in average) under all levels of seismic hazards.

ISBN: 9798535575964Subjects--Topical Terms:

210888
Engineering.
Subjects--Index Terms:

Belleville disks

Development of an Innovative Resilient Steel Braced Frame with BellevilleDisk and Shape Memory Alloy Assemblies.
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245 1 0 $a Development of an Innovative Resilient Steel Braced Frame with BellevilleDisk and Shape Memory Alloy Assemblies.
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520 $a An innovative structural bracing system for steel structures is introduced in this research. The system is based on the application of stacked Belleville disks and Nitinol rods. By combining the two structural elements in one assembly and then adding it to a steel bracing system, the bracing system transforms into a resilient bracing system for structures in seismic regions. Belleville disks are responsible for carrying the compression load in the brace. A comprehensive investigation on the behavior of large-size stacked Belleville disks was carried out in this research. Nitinol rods are used to carry the tensile load. A constitutive material model for shape memory alloys was selected and the parameters used in the model were calibrated by comparing the obtained numerical results with the ASTM standard values and the values recorded in the literature.Afterwards, a unique assembly out of Belleville disks and Nitinol rods was introduced. The proposed assembly was then added to a regular steel bracing system to eliminate buckling and residual deformations of the system under the maximum-considered-event (MCE) loads. After proportioning the assembly, an appropriate connection detailing was suggested in the research to add the resilient assembly to the steel bracing system. Multiple assemblies were designed for different strength and stiffness values and the cyclic behavior of the designed assemblies was studied through finite element simulations. After analyzing the results, a modeling technique for the cyclic behavior of the new brace was selected in order to simulate the obtained cyclic behavior in a structural analysis software. Since the new resilient system is to be used in chevron configuration, the recently introduced chevron effect analysis method was used in this research to analyze the buildings. The commonly used approach, known as the Net Vertical Force method, is not capable of finding the chevron beam demands accurately, according to the analytical investigations performed in this research on the behavior of chevron beams.Three pairs of prototype steel buildings with different number of stories were designed in order to evaluate the performance of the proposed resilient bracing system: two 5-story buildings, two 10-story buildings, and two 15-story buildings. Each pair of buildings consisted of two structural systems: one system had special concentrically braced frame (SCBF) and the other used the new resilient structural system. The buildings were designed and then modeled in a structural analysis software in order to obtain and later compare their seismic responses under different levels of seismic hazard. A suite of seven strong ground motions were selected and then scaled properly according to the target seismic hazard analysis to represent three levels of seismic hazard: (1) 10% probability of occurrence in 50 years (Design Base Event), (2) 2% probability of occurrence in 50 years (Maximum Considered Event), and (3) 1% probability of occurrence in 50 years (user defined event).Incremental dynamic analyses were performed in order to obtain the performance fragility curves of the systems. Additionally, consequence functions were developed for the systems in order to obtain the economic losses due to the applied seismic hazards. Finally, the resiliency of the systems was measured through analysis of the required repair time and costs of the systems.According to the results, the construction cost (considering the structural members only) of the 5- story building was increased by 5% when the new resilient structural system was compared to the SCBF system. In the cases of 10- and 15-story buildings, the construction costs were decreased by 23% and 25% respectively, when the new resilient structural system was compared to the SCBF system. On average, the application of Nibellen brace increased the bracing costs of the buildings by 145% due the usage of new materials and new design methodology. However, the Nibellen bracing tensile and compressive mechanism forces are closer to each other in magnitudes, in comparison to regular SCBF brace-section mechanism forces. Thus, less demand is applied on chevron beams and columns in the braced frames of the Nibellen buildings. This leads to lighter beam and column section, and lower overall constructions costs in the 10- and 15- story Nibellen buildings. On average, the costs of beams and columns were decreased by 35% and 14%, respectively, in the Nibellen buildings when compared to the SCBF buildings.The new resilient system proved its superiority when the buildings’ required repair time and costs were compared. Under the design base event (DBE) hazard level, the repair costs were decreased by 100% for 5-story building, 82% for 10-strory building, and 79% for 15-story building when the new resilient system was compared to the SCBF system. Under maximum credible event (MCE) hazard level, the repair costs were decreased by 95% for 5-story building, 53% for 10-strory building, and 56% for 15-story building when the new system was used. Collectively, the ultimate results showed application of the proposed system improved the resiliency of all the buildings by 5% (in average) under all levels of seismic hazards.
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