@article{morrison_schweizer_quayyum_hassan_2019, title={An Unstiffened Eight-Bolt Extended End-Plate Moment Connection for Special and Intermediate Moment Frames}, volume={145}, ISBN={1943-541X}, DOI={10.1061/(ASCE)ST.1943-541X.0002332}, abstractNote={AbstractBolted extended end-plate (BEEP) moment-resisting connections are prequalified for use in special and intermediate moment frames. The current limits of this prequalification dictate that ro...}, number={7}, journal={JOURNAL OF STRUCTURAL ENGINEERING}, author={Morrison, Machel L. and Schweizer, Doug Q. and Quayyum, Shahriar and Hassan, Tasnim}, year={2019} }
 @article{morrison_gould_charit_hassan_2019, title={Performance Evaluation of Surface-Activated Solid-State Welding for ASTM A992 Structural Steel}, volume={31}, ISBN={1943-5533}, DOI={10.1061/(ASCE)MT.1943-5533.0002805}, abstractNote={AbstractThis paper presents the results of a pilot study to evaluate a solid-state welding technology, called surface activated solid-state (SASS) welding, for joining structural steel members. SAS...}, number={8}, journal={JOURNAL OF MATERIALS IN CIVIL ENGINEERING}, author={Morrison, Machel L. and Gould, Jerry and Charit, Indrajit and Hassan, Tasnim}, year={2019} }
 @inproceedings{robert_morrison_hassan_2017, title={Influence of notch geometry on the notch vicinity stress and strain responses}, DOI={10.1115/pvp2016-63287}, abstractNote={The most common method used to determine the crack initiation life of a component containing a stress raiser in the low cycle fatigue regime is to calculate the maximum strain and then to use a strain-life curve. General practice is to base fatigue life estimates on the stabilized strain amplitude and to neglect the effects of transient behavior due to cyclic hardening or softening and ratcheting. For certain structures in which the accumulation of plastic strains may be significant, a separate check may be performed to ensure that these strains remain below a specified level. An objective of this research is to understand the notch tip local strain ratcheting and shakedown through finite element analyses and physical experiments. Towards planning a set of notched flat coupon experiments, this study performed analyses of various notched coupons under force-controlled cyclic loading. A question that will be addressed, what is the notch tip failure mechanism under a force-controlled load cycle with a non-zero mean force? Smooth specimens under such a force-controlled load cycle normally results in strain ratcheting. It is investigated whether notch tip strain responds in a similar manner under a force controlled loading cycle. The analysis results show that the strain ratcheting rate at the notch tip depends on the sharpness of the notch. In case of semi-circular and blunt elliptical notches shakedown of strain ratcheting within 25 cycles is observed, whereas for the sharp elliptical notch strain ratcheting doesn’t shakedown after 300 cycles. A novel observation made from the analysis results is that the mean stress at the notch tip gradually decreases with inelastic cycle while the stress amplitude remains unchanged. These result and future experimental plan on notch specimens are presented in this article.}, booktitle={Proceedings of the ASME Pressure Vessels and Piping Conference, 2016, Vol 1A}, author={Robert, A. and Morrison, M. L. and Hassan, T.}, year={2017} }
 @article{morrison_quayyum_hassan_2017, title={Performance enhancement of eight bolt extended end-plate moment connections under simulated seismic loading}, volume={151}, ISSN={["1873-7323"]}, DOI={10.1016/j.engstruct.2017.08.040}, abstractNote={Extended end-plate (EEP) moment resisting connections provide the advantage of eliminating field welding and by virtue of this, facilitate fast field erection of building frames. The eight bolt stiffened (8ES) EEP connection is one of the prequalified moment connections in the AISC 358 standard for special moment frames (SMFs) in seismic regions. In this connection, a stiffener plate is welded between the end plate and the beam flanges to strengthen the extended portion of the end plate. This stiffener reduces prying action and more uniformly distributes flange forces among the bolt group. In experimental studies, the 8ES connection has shown ductile response to simulated seismic loading with test specimens typically failing due to beam buckling and gradual strength degradation. However, cracks initiating at the toe of the stiffener leading to brittle fracture of the beam flange has also been observed due to the high stress concentration in this region. The study reported herein proposes an eight-bolt EEP connection in which the end plate stiffener is removed and the bolt arrangement is modified to promote uniform distribution of flange forces among the bolt group. The proposed connection was developed through detailed finite element analysis in which various bolt arrangements for stiffened and unstiffened eight-bolt EEP connections were considered. The proposed connection displayed reduced beam flange stress and strain concentrations, delayed or reduced rate of strength degradation from local buckling and more uniform distribution of bolt forces when compared to the alternatives. Furthermore, when compared to the currently prequalified 8ES connection, despite requiring thicker end plates, the proposed connection is anticipated to result in cost savings from the removal of the end plate stiffener. Future analytical and experimental needs for further development of the proposed connection are discussed.}, journal={ENGINEERING STRUCTURES}, author={Morrison, Machel and Quayyum, Shahriar and Hassan, Tasnim}, year={2017}, month={Nov}, pages={444–458} }
 @inproceedings{morrison_ahmed_hassan_2017, title={Thermomechanical fatigue response and constitutive modeling for Haynes 230}, DOI={10.1115/pvp2016-63283}, abstractNote={Design by analysis is usually performed by commercially available finite element analysis (FEA) software. Constitutive models available in the FEA software are developed and validated using limited experimental data. Hence, a broad set of thermomechanical fatigue experiments with strain dwell at compressive peaks are performed to understand local fatigue failure responses of high temperature components. This study developed a unified viscoplastic model based on nonlinear kinematic hardening of Chaboche type with added features of strain range dependence, rate dependence, temperature dependence, static recovery, and mean stress evolution. The robustness of the constitutive model is demonstrated by comparing its simulations against the experimental responses.}, booktitle={Proceedings of the ASME Pressure Vessels and piping conference, 2016, vol 5}, author={Morrison, M. and Ahmed, R. and Hassan, T.}, year={2017} }
 @article{morrison_hassan_2016, title={Resilient welded steel moment connections by enhanced beam buckling resistance}, volume={127}, ISSN={["1873-5983"]}, DOI={10.1016/j.jcsr.2016.07.012}, abstractNote={This study develops two (2) simple but effective techniques for enhancing buckling resistance of welded steel moment connections (WSMCs). The ANSI/AISC 358-10 prequalified connections satisfy the 4% interstory drift requirement, however experimental studies have shown that their strength degradation may initiate as early as 3% drift. This strength degradation has been observed to be initiated by buckling of the beam web which is followed by buckling of the beam flange and twisting of the beam. Consequently, buildings with the prequalified connections may sustain significant buckling damages under severe earthquakes and it is questionable as to whether these connections are capable of resisting gravity loads or lateral loads from strong aftershocks following a severe earthquake. To improve upon these shortcomings, two (2) performance enhancing techniques are proposed and investigated through finite element analysis (FEA). The more promising of the two involves reinforcing the beam web in the expected plastic hinge with a web reinforcement plate. Finite element analysis demonstrated that this reinforcement enhances the beam buckling resistance of WSMCs and thereby significantly reduces the beam buckling damages even at 5% interstory drift. The potential of this technique is analytically and experimentally demonstrated for the recently developed heat-treated beam section (HBS) WSMC. Test results confirm that the web reinforcement plate was effective in reducing local buckling damage and associated strength degradation, thereby improving the performance of HBS WSMCs. Areas for application and future development of the proposed techniques are identified.}, journal={JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH}, author={Morrison, Machel L. and Hassan, Tasnim}, year={2016}, month={Dec}, pages={77–91} }
 @article{morrison_schweizer_hassan_2016, title={Seismic Enhancement of Welded Unreinforced Flange-Bolted Web Steel Moment Connections}, volume={142}, ISSN={["1943-541X"]}, DOI={10.1061/(asce)st.1943-541x.0001575}, abstractNote={AbstractWidespread damage to welded unreinforced flange-bolted web (WUF-B) steel moment connections during the 1994 Northridge earthquake led to intensive research study of this connection. Despite the improvements to weld metal and connection details, the post-Northridge WUF-B connection was unable to attain sufficient ductility for use in special moment frames (SMFs). This study presents detailed finite element (FE) analysis of post-Northridge WUF-B connections to better understand the mechanisms which limited connection ductility in laboratory tests. Observations made from the FE analysis led to the development and numerical study of a modified WUF-B connection that combines a new bolted web design with a recently validated technique to promote plastic hinging of the beam away from the connection joint. The proposed connection provides the benefit of reduced field welding and UT inspection without sacrificing connection ductility and seismic performance. Finally, the proposed connection is experimental...}, number={11}, journal={JOURNAL OF STRUCTURAL ENGINEERING}, author={Morrison, Machel Leigh and Schweizer, Douglas Quinn and Hassan, Tasnim}, year={2016}, month={Nov} }