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<p class="MsoNormal"><span style="font-size:13.5pt;font-family:"Arial",sans-serif;color:black;mso-ligatures:none"><img width="598" height="170" style="width:6.2291in;height:1.7708in" id="_x0000_i1043" src="cid:image001.png@01DBAE1E.5DBBEB10" alt="Dissertation Defense Announcement at the Cullen College of Engineering"></span><span style="font-size:11.0pt;mso-ligatures:none"><o:p></o:p></span></p>
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<b><span style="font-size:18.0pt;font-family:"Times New Roman",serif;color:#C8102E;mso-ligatures:none">Characterizing the Shear Behavior of </span></b><span style="font-size:11.0pt;mso-ligatures:none"><o:p></o:p></span></p>
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<b><span style="font-size:18.0pt;font-family:"Times New Roman",serif;color:#C8102E;mso-ligatures:none">Ultra-High-Performance Concrete through the Universal Panel Tester</span></b><span style="font-size:11.0pt;mso-ligatures:none"><o:p></o:p></span></p>
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<b><span style="font-size:13.5pt;font-family:"Times New Roman",serif;color:black;mso-ligatures:none">Abdulrahman Salah</span></b><span style="font-size:11.0pt;mso-ligatures:none"><o:p></o:p></span></p>
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<span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:black;mso-ligatures:none">April 28, 2025, 9 a.m. to 11 a.m. (CST)<br>
Location: N137 Conference Room - Civil & Environmental Engineering Department</span><span style="font-size:11.0pt;mso-ligatures:none"><o:p></o:p></span></p>
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<b><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:black;mso-ligatures:none">Committee Chair:</span></b><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:black;mso-ligatures:none"><br>
Dr. Dimitrios Kalliontzis, Ph.D.</span><span style="font-size:11.0pt;mso-ligatures:none"><o:p></o:p></span></p>
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<b><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:black;mso-ligatures:none">Committee Members:</span></b><span style="font-size:11.0pt;mso-ligatures:none"><o:p></o:p></span></p>
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<span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:black;mso-ligatures:none">Dr. Abdeldjelil Belarbi, Ph.D. | Dr.Yi-Lung Mo, Ph.D. | Dr. Theocharis Baxevanis, Ph.D. | Dr. Tian Chen, Ph.D.</span><span style="font-size:11.0pt;mso-ligatures:none"><o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:11.25pt;line-height:16.5pt"><b><span style="font-family:"Arial",sans-serif;color:#C8102E;mso-ligatures:none">Abstract</span></b><span style="font-size:11.0pt;mso-ligatures:none"><o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify"><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:black;mso-ligatures:none">The limited understanding of the shear behavior of Ultra-High-Performance Concrete (UHPC), especially under axial load
and varying structural scale, poses challenges to the formulation of reliable design models. Although UHPC is being increasingly utilized in structural applications, owing to its superior compressive strength and post-cracking tensile strength, its complex
behavior under combined stress states and the influence of fiber alignment are yet to be well characterized. This dissertation presents a comprehensive experimental and analytical investigation of the shear behavior of UHPC, considering axial load, size, and
fiber alignment effects.</span><span style="font-family:"Aptos",sans-serif;mso-ligatures:none"><o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify"><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:black;mso-ligatures:none"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-align:justify"><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:black;mso-ligatures:none">The experimental program consists of three phases. During the first one, pure shear and combined shear-axial load tests
were conducted on rebar-free UHPC panels using the Universal Panel Tester (UPT). The post-peak behavior and the effect of fiber alignment were evaluated. A series of material companion tests were performed along with large-scale Tension Strip Tests (TSTs).
The second phase examined the contribution of bar reinforcement in UHPC shear resistance by testing bar-reinforced UHPC panels. Results indicated that axial loads have a significant effect on shear strength of UHPC, more than conventional concrete. A correlation
was observed between fiber alignment and tensile strength, which influenced UHPC’s shear strength.</span><span style="font-family:"Aptos",sans-serif;mso-ligatures:none"><o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify"><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:black;mso-ligatures:none"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-align:justify"><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:black;mso-ligatures:none">In the third phase, a set of shear panel tests was used to investigate size effects in the shear behavior of UHPC. Two
sources of size effect were observed: (1) the classical depth size effect observed in conventional concrete and (2) a fiber alignment-related size effect which is dependent on formwork geometry and boundary layer effects during casting. Comparisons with uniaxial
tension tests and beam shear datasets provided additional evidence for UHPC's scale-dependent behavior related to fiber alignment.</span><span style="font-family:"Aptos",sans-serif;mso-ligatures:none"><o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify"><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:black;mso-ligatures:none"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-align:justify"><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:black;mso-ligatures:none">The experimental findings informed improvements to the Softened Membrane Model for UHPC (SMM-UHPC) to capture the effects
of fiber alignment and axial loads. Combining experimental and analytical findings led to the proposal of a one-way shear design model for UHPC beams that contain no transverse reinforcing bars. The model integrates material, geometric, and fiber alignment
parameters within a framework that is compatible with the current ACI 318 provisions. Overall, this work contributes to a better understanding of UHPC shear behavior.</span><span style="font-family:"Aptos",sans-serif;mso-ligatures:none"><o:p></o:p></span></p>
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