Author(s): Mashayekh, Adel | Advisor(s): Uang, Chia-Ming | Abstract: Steel Special Moment Frames ... more Author(s): Mashayekh, Adel | Advisor(s): Uang, Chia-Ming | Abstract: Steel Special Moment Frames (SMF) are one of the most popular lateral force-resisting systems for multistory building construction in high seismic regions due to their architectural versatility. With a significant amount of research that was conducted after the 1994 Northridge, California earthquake, AISC has published design guidelines (AISC 341 and AISC 358) to avoid brittle fracture of beam-to-column welded moment connections that occurred in more than 100 steel buildings. This dissertation addresses two issues related to the moment connection design of SMF.Unless the column flanges are sufficiently thick, AISC 341 requires that continuity plates be installed, and that expensive complete-joint-penetration (CJP) groove welds be used to connect the continuity plates to the column flanges; the conservative nature of this requirement stems from a lack of procedure that the designer can use to quantify the required s...
AbstractFor seismic applications in special and intermediate steel moment frames, the design stan... more AbstractFor seismic applications in special and intermediate steel moment frames, the design standard provides a number of prequalified connections. This assumes that the beam frames orthogonally i...
AbstractFor seismic applications in special and intermediate steel moment frames, the design stan... more AbstractFor seismic applications in special and intermediate steel moment frames, the design standard provides a number of prequalified connections. This assumes that the beam frames orthogonally i...
, we conduct a numerical investigation to study the dynamics of RBCs in low-shear-rate flows by a... more , we conduct a numerical investigation to study the dynamics of RBCs in low-shear-rate flows by applying a multiscale fluid-structure interaction model. By employing a spheroidal stress-free state in the cytoskeleton, we are able to numerically predict an important feature, namely that the cell maintains its biconcave shape during tank-treading motions. Furthermore, we numerically confirm the hypothesis that, as the stress-free state approaches a sphere, the threshold shear rates corresponding to the establishment of tank treading decrease. By comparing with the experimental measurements, our study suggests that the stress-free state of RBCs is a spheroid that is close to a sphere, rather than the biconcave shape applied in existing models (the implication is that the RBC skeleton is pre-stressed in its natural biconcave state). It also suggests that the response of RBCs in low-shear-rate flows may provide a measure to quantitatively determine the distribution of shear stress in the RBC cytoskeleton in the natural state.
Author(s): Mashayekh, Adel | Advisor(s): Uang, Chia-Ming | Abstract: Steel Special Moment Frames ... more Author(s): Mashayekh, Adel | Advisor(s): Uang, Chia-Ming | Abstract: Steel Special Moment Frames (SMF) are one of the most popular lateral force-resisting systems for multistory building construction in high seismic regions due to their architectural versatility. With a significant amount of research that was conducted after the 1994 Northridge, California earthquake, AISC has published design guidelines (AISC 341 and AISC 358) to avoid brittle fracture of beam-to-column welded moment connections that occurred in more than 100 steel buildings. This dissertation addresses two issues related to the moment connection design of SMF.Unless the column flanges are sufficiently thick, AISC 341 requires that continuity plates be installed, and that expensive complete-joint-penetration (CJP) groove welds be used to connect the continuity plates to the column flanges; the conservative nature of this requirement stems from a lack of procedure that the designer can use to quantify the required s...
IABSE Congress, Ghent 2021: Structural Engineering for Future Societal Needs
In existing building renovation projects, the strength of the structure is often limited by the c... more In existing building renovation projects, the strength of the structure is often limited by the capacity of existing foundations. Foundation strengthening typically consists of expanding existing footings and/or adding piles to supplement load-carrying capacity. These traditional methods are generally not feasible for the retrofit of mat foundations where increasing the mat footprint is unlikely to reduce bearing pressure considerably and adding piles outside the mat will change the distribution of internal stresses and may affect the long-term differential settlement behaviour of the structure.This paper presents finite element analyses that were performed as part of the development of a new approach to retrofitting mat foundations which consists of enlarging the footprint of the existing mat and adding piles that include an innovative axial capacity-limiting mechanism. The maximum resistance provided by these piles to the existing foundation can be tuned to not exceed the maximum ...
AISC 341-16 requires welding continuity plates to column flanges with expensive complete-joint-pe... more AISC 341-16 requires welding continuity plates to column flanges with expensive complete-joint-penetration groove welds in a structural steel Special Moment Frame (SMF). Mashayekh and Uang (2017) conducted two large-scale experiments on reduced beam section (RBS) beam-to-column connections with continuity plates welded to column flanges with fillet welds. The two connections performed well and met the acceptance criteria described by Seismic Provisions for Structural Steel Buildings (ANSI/AISC 341), Section E3.6b. The continuity plates and welds were designed using a flexibility-based formulation introduced by Tran et al. (2013), slightly modified by Mashayekh (2017) based on experimental test program results. Inspired by the successful experimental program, this paper presents a practical design procedure for the design of continuity plates welded to column flanges with fillet welds.
When required in the moment connection design for Special Moment Frames, AISC 341 provides a pres... more When required in the moment connection design for Special Moment Frames, AISC 341 provides a prescriptive requirement for the continuity plate thickness and specifies complete-joint-penetration (CJP) groove welds to connect the continuity plates to the column flanges. Recently, Tran et al. (2013) proposed a procedure that gives the designer freedom in sizing the continuity plate thickness and using alternate (i.e., economical) weld joints. In this research, full-scale testing of two one-sided moment connection specimens with a Reduced Beam Section (RBS) was conducted to verify the adequacy of this design procedure. In designing the test specimens, the original procedure was slightly modified so that the strength check of the continuity plate included not only normal and shear forces but also moment in the plane of the continuity plate. The specimen design followed AISC 341 and 358, except that the continuity plate thickness and welds were sized based on the modified procedure. The design resulted in fillet welds to connect the continuity plates to the columns. One specimen used a deep (W24) column, and the other one had a shallow (W14) column. To evaluate the effect of yielding in the continuity plates, these plates for the shallow column specimen were undersized. The specimens were also designed such that significant shear yielding in the panel zones would result in kinking of the column flanges to further "challenge" the fillet welds.
The AISC Seismic Provisions require that continuity plates in a special moment frame (SMF) welded... more The AISC Seismic Provisions require that continuity plates in a special moment frame (SMF) welded moment connection be connected to the column flanges by complete-joint-penetration groove welds. have proposed a design procedure that allows the designer to evaluate the required forces in the continuity plates such that more economical welds (e.g., fillet welds) can be used; the required thickness of the continuity plates also need not be the same as that prescribed in the AISC Seismic Provisions. With some minor modifications to the original design procedure, two one-sided reduced beam section moment connection specimens were designed and constructed for experimental verification of the proposed design procedure. To evaluate the effect of potential column kinking on the fillet-welded joints between the continuity plates and the column flanges, weaker panel zones that still satisfied the code requirement were used. Although the AISC Seismic Provisions implicitly assume that continuity plates should remain essentially elastic, the continuity plate thickness of one specimen was intentionally undersized to evaluate the effect of continuity plate yielding on the connection performance. Test results showed that using fillet welds is feasible; no damage was observed in these fillet welds, and the connection performance was not affected by the type of weld joints used. The design procedure also indicates the significant effect of in-plane moment in the continuity plate's strength check, especially when shallow columns are used.
Inspired by the recent experiment on erythrocytes (red blood cells, RBCs) in weak shear flows by ... more Inspired by the recent experiment on erythrocytes (red blood cells, RBCs) in weak shear flows by Dupire et al. conduct a numerical investigation to study the dynamics of RBCs in low-shear-rate flows by applying a multiscale fluid-structure interaction model. By employing a spheroidal stress-free state in the cytoskeleton, we are able to numerically predict an important feature, namely that the cell maintains its biconcave shape during tank-treading motions. Furthermore, we numerically confirm the hypothesis that, as the stress-free state approaches a sphere, the threshold shear rates corresponding to the establishment of tank treading decrease. By comparing with the experimental measurements, our study suggests that the stress-free state of RBCs is a spheroid that is close to a sphere, rather than the biconcave shape applied in existing models (the implication is that the RBC skeleton is pre-stressed in its natural biconcave state). It also suggests that the response of RBCs in low-shear-rate flows may provide a measure to quantitatively determine the distribution of shear stress in the RBC cytoskeleton in the natural state.
Author(s): Mashayekh, Adel | Advisor(s): Uang, Chia-Ming | Abstract: Steel Special Moment Frames ... more Author(s): Mashayekh, Adel | Advisor(s): Uang, Chia-Ming | Abstract: Steel Special Moment Frames (SMF) are one of the most popular lateral force-resisting systems for multistory building construction in high seismic regions due to their architectural versatility. With a significant amount of research that was conducted after the 1994 Northridge, California earthquake, AISC has published design guidelines (AISC 341 and AISC 358) to avoid brittle fracture of beam-to-column welded moment connections that occurred in more than 100 steel buildings. This dissertation addresses two issues related to the moment connection design of SMF.Unless the column flanges are sufficiently thick, AISC 341 requires that continuity plates be installed, and that expensive complete-joint-penetration (CJP) groove welds be used to connect the continuity plates to the column flanges; the conservative nature of this requirement stems from a lack of procedure that the designer can use to quantify the required s...
AbstractFor seismic applications in special and intermediate steel moment frames, the design stan... more AbstractFor seismic applications in special and intermediate steel moment frames, the design standard provides a number of prequalified connections. This assumes that the beam frames orthogonally i...
AbstractFor seismic applications in special and intermediate steel moment frames, the design stan... more AbstractFor seismic applications in special and intermediate steel moment frames, the design standard provides a number of prequalified connections. This assumes that the beam frames orthogonally i...
, we conduct a numerical investigation to study the dynamics of RBCs in low-shear-rate flows by a... more , we conduct a numerical investigation to study the dynamics of RBCs in low-shear-rate flows by applying a multiscale fluid-structure interaction model. By employing a spheroidal stress-free state in the cytoskeleton, we are able to numerically predict an important feature, namely that the cell maintains its biconcave shape during tank-treading motions. Furthermore, we numerically confirm the hypothesis that, as the stress-free state approaches a sphere, the threshold shear rates corresponding to the establishment of tank treading decrease. By comparing with the experimental measurements, our study suggests that the stress-free state of RBCs is a spheroid that is close to a sphere, rather than the biconcave shape applied in existing models (the implication is that the RBC skeleton is pre-stressed in its natural biconcave state). It also suggests that the response of RBCs in low-shear-rate flows may provide a measure to quantitatively determine the distribution of shear stress in the RBC cytoskeleton in the natural state.
Author(s): Mashayekh, Adel | Advisor(s): Uang, Chia-Ming | Abstract: Steel Special Moment Frames ... more Author(s): Mashayekh, Adel | Advisor(s): Uang, Chia-Ming | Abstract: Steel Special Moment Frames (SMF) are one of the most popular lateral force-resisting systems for multistory building construction in high seismic regions due to their architectural versatility. With a significant amount of research that was conducted after the 1994 Northridge, California earthquake, AISC has published design guidelines (AISC 341 and AISC 358) to avoid brittle fracture of beam-to-column welded moment connections that occurred in more than 100 steel buildings. This dissertation addresses two issues related to the moment connection design of SMF.Unless the column flanges are sufficiently thick, AISC 341 requires that continuity plates be installed, and that expensive complete-joint-penetration (CJP) groove welds be used to connect the continuity plates to the column flanges; the conservative nature of this requirement stems from a lack of procedure that the designer can use to quantify the required s...
IABSE Congress, Ghent 2021: Structural Engineering for Future Societal Needs
In existing building renovation projects, the strength of the structure is often limited by the c... more In existing building renovation projects, the strength of the structure is often limited by the capacity of existing foundations. Foundation strengthening typically consists of expanding existing footings and/or adding piles to supplement load-carrying capacity. These traditional methods are generally not feasible for the retrofit of mat foundations where increasing the mat footprint is unlikely to reduce bearing pressure considerably and adding piles outside the mat will change the distribution of internal stresses and may affect the long-term differential settlement behaviour of the structure.This paper presents finite element analyses that were performed as part of the development of a new approach to retrofitting mat foundations which consists of enlarging the footprint of the existing mat and adding piles that include an innovative axial capacity-limiting mechanism. The maximum resistance provided by these piles to the existing foundation can be tuned to not exceed the maximum ...
AISC 341-16 requires welding continuity plates to column flanges with expensive complete-joint-pe... more AISC 341-16 requires welding continuity plates to column flanges with expensive complete-joint-penetration groove welds in a structural steel Special Moment Frame (SMF). Mashayekh and Uang (2017) conducted two large-scale experiments on reduced beam section (RBS) beam-to-column connections with continuity plates welded to column flanges with fillet welds. The two connections performed well and met the acceptance criteria described by Seismic Provisions for Structural Steel Buildings (ANSI/AISC 341), Section E3.6b. The continuity plates and welds were designed using a flexibility-based formulation introduced by Tran et al. (2013), slightly modified by Mashayekh (2017) based on experimental test program results. Inspired by the successful experimental program, this paper presents a practical design procedure for the design of continuity plates welded to column flanges with fillet welds.
When required in the moment connection design for Special Moment Frames, AISC 341 provides a pres... more When required in the moment connection design for Special Moment Frames, AISC 341 provides a prescriptive requirement for the continuity plate thickness and specifies complete-joint-penetration (CJP) groove welds to connect the continuity plates to the column flanges. Recently, Tran et al. (2013) proposed a procedure that gives the designer freedom in sizing the continuity plate thickness and using alternate (i.e., economical) weld joints. In this research, full-scale testing of two one-sided moment connection specimens with a Reduced Beam Section (RBS) was conducted to verify the adequacy of this design procedure. In designing the test specimens, the original procedure was slightly modified so that the strength check of the continuity plate included not only normal and shear forces but also moment in the plane of the continuity plate. The specimen design followed AISC 341 and 358, except that the continuity plate thickness and welds were sized based on the modified procedure. The design resulted in fillet welds to connect the continuity plates to the columns. One specimen used a deep (W24) column, and the other one had a shallow (W14) column. To evaluate the effect of yielding in the continuity plates, these plates for the shallow column specimen were undersized. The specimens were also designed such that significant shear yielding in the panel zones would result in kinking of the column flanges to further "challenge" the fillet welds.
The AISC Seismic Provisions require that continuity plates in a special moment frame (SMF) welded... more The AISC Seismic Provisions require that continuity plates in a special moment frame (SMF) welded moment connection be connected to the column flanges by complete-joint-penetration groove welds. have proposed a design procedure that allows the designer to evaluate the required forces in the continuity plates such that more economical welds (e.g., fillet welds) can be used; the required thickness of the continuity plates also need not be the same as that prescribed in the AISC Seismic Provisions. With some minor modifications to the original design procedure, two one-sided reduced beam section moment connection specimens were designed and constructed for experimental verification of the proposed design procedure. To evaluate the effect of potential column kinking on the fillet-welded joints between the continuity plates and the column flanges, weaker panel zones that still satisfied the code requirement were used. Although the AISC Seismic Provisions implicitly assume that continuity plates should remain essentially elastic, the continuity plate thickness of one specimen was intentionally undersized to evaluate the effect of continuity plate yielding on the connection performance. Test results showed that using fillet welds is feasible; no damage was observed in these fillet welds, and the connection performance was not affected by the type of weld joints used. The design procedure also indicates the significant effect of in-plane moment in the continuity plate's strength check, especially when shallow columns are used.
Inspired by the recent experiment on erythrocytes (red blood cells, RBCs) in weak shear flows by ... more Inspired by the recent experiment on erythrocytes (red blood cells, RBCs) in weak shear flows by Dupire et al. conduct a numerical investigation to study the dynamics of RBCs in low-shear-rate flows by applying a multiscale fluid-structure interaction model. By employing a spheroidal stress-free state in the cytoskeleton, we are able to numerically predict an important feature, namely that the cell maintains its biconcave shape during tank-treading motions. Furthermore, we numerically confirm the hypothesis that, as the stress-free state approaches a sphere, the threshold shear rates corresponding to the establishment of tank treading decrease. By comparing with the experimental measurements, our study suggests that the stress-free state of RBCs is a spheroid that is close to a sphere, rather than the biconcave shape applied in existing models (the implication is that the RBC skeleton is pre-stressed in its natural biconcave state). It also suggests that the response of RBCs in low-shear-rate flows may provide a measure to quantitatively determine the distribution of shear stress in the RBC cytoskeleton in the natural state.
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