During the fall of 2012, two separate Interstate 15 highway bridges over the 400 South roadway in Orem, Utah were demolished after 50 years of service. Four post-tensioned girders were salvaged from both the north-bound and south-bound bridge. A series of tests was performed with these girders in the System Material And Structural Health Laboratory (SMASH Lab). The girders were tested with different loading criteria to determine the strength and material properties of the girder. The experimental results were compared with the American Association of State Highway and Transportation Officials Load Resistance Factored Design (AASHTO LRFD) Bridge Design Specifications and a finite-element model using ANSYS. The AASHTO LRFD Specification was fairly conservative on predicting capacity and capable of predicting the type of failure that occurred. The ANSYS model was developed and calibrated to model the girder behavior. The concrete properties in the model were significantly adjusted in order to be comparable to the experimental results. Further exploration in ANSYS needs to be done to precisely model the actual behavior of the girder.

The present dissertation contributes to advancing methods of determining the elastic and inelastic buckling resistance of compressive members with single angle and back-to-back double angle cross-sections with end conditions representative of those commonly used in steel construction. The first contribution develops an elastic buckling solution for members with asymmetric sections, such as unequal-leg angle members, connected to gusset plates at both ends and subjected to pure compression. In this case, the gusset plate connections at the member ends provide a fixity restraint to the member within the plane of the gusset and nearly a pin restraint in a plane normal to the gusset. Since both directions do not coincide with the principal directions of the member, the classical flexural-torsional buckling solutions provided in standards become inapplicable. In this context, a variational principle is formulated based on non-principal directions and then used to derive the governing differential equations and associated boundary conditions for the problem. The coupled equations are then solved analytically subject to the boundary conditions, and the characteristic equations are recovered and solved for the flexural-torsional buckling load of the member. The validity of the solutions derived is assessed against 3D shell elastic eigen-value buckling models based on ABAQUS for benchmark cases and the solution is shown to accurately predict the elastic buckling load and mode shapes. The effect of non-principal end restraints on the buckling load of compression members is then investigated for members with angle and zed cross-sections in a parametric study. It is observed that when a member end is fixed about a non-principal direction and pinned about the orthogonal direction, the flexural-torsional buckling load of the member is significantly influenced by the angle of inclination between the fixity axis and the minor principal axis. The second contribution aims to obtain the inelastic buckling resistance for single angle compression members with end gusset plate connections by taking into consideration the effects of material and geometric nonlinearity, initial out-of-straightness, residual stresses, and load eccentricity induced by the offset of the member centroidal axis from the end gusset plate connection. Towards this goal, a series of 3D shell models based on ABAQUS are developed and validated through comparisons against experimental results by others and then used to generate a database of compressive capacities for over 900 eccentrically loaded angle members with various geometrical dimensions and load eccentricities. The database is then used to investigate the effect of slenderness ratio, leg width ratio, connected leg width-to-thickness ratio and gusset plate-to-angle thickness ratio on the compressive resistance of the members, assess the accuracy of solutions available in present design standards, and develop improved design expressions for the compressive resistance for the members. The third contribution develops solutions for predicting the elastic buckling resistance of back-to-back double angle assemblies with end gusset plates and intermediate interconnectors subjected to compressive loads. Towards this goal, two novel models are developed. (1) A thin-walled finite element buckling solution is formulated and implemented into a MATLAB code. The formulation treats each angle member as a line of 1D thin-walled beam elements where then both angle members are connected at intermediate points along the span at the locations of interconnectors. The formulation is equipped with a multi-point constraint feature to enforce the kinematic constraints at the interconnector locations and at both extremities of the member. The model captures the tendency of both angles to open relative to one another in between interconnectors while undergoing flexural-torsional buckling. (2) An analytical buckling solution is developed for the limiting case where enough interconnectors are provided between members to force the two angles to essentially behave as a monolithic entity. The resistance predicted by the former model was then shown to asymptotically approach that predicted by the later model as the number of interconnectors is increased. The validity of the finite element model is assessed against 3D shell models based on ABAQUS and published experimental results, and then used to assess the validity of present design rules based on the effective slenderness concept. The present models are then used to carry out a parametric study of 1250 runs while varying the member slenderness ratio, leg width ratio, connected leg width-to-thickness ratio, and angle spacing-to-thickness ratio. The database of results generated is used to develop a simple expression to characterize the elastic buckling load/stress of the assembly. The possible integration of the new expression with present design provisions in standards to predict the inelastic buckling resistance of the member is illustrated through a design example.

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OBJECTIVE: Flexural strength values of multilayer zirconia may vary depending upon the specimen dimension, layers distribution, especially the layer in maximum tension side, i.e., loading configuration. Although the previous studies have examined flexural strength of the separate layers in one zirconia disc, capturing flexural strength across all layers of multilayer zirconia is still challenging yet important for their clinical indications. The objective of this study aimed to evaluate the flexural strength of multilayer graded translucent zirconia by three loading configurations with the full thickness of layers. MATERIALS AND METHODS: Four types of zirconia materials were selected namely KATANA Yttria Multi Layered (KATANA YML, Kuraray Noritake), IPS e.max ZirCAD Prime (ZirCAD Prime, Ivoclar Vivadent), and Origin Beyond + Hybrid (Origin Beyond, B&D Dental Technologies) multilayer zirconia, as well as monolithic InCoris translucent zirconia (inCoris TZI, Dentsply Sirona). The bar specimens were prepared by sectioning the zirconia discs with diamond blade to get the dimensions of 31.0 mm x 4.6 mm x 11.0 mm for KATANA YML and Origin Beyond, 42.0 mm x 6.4 mm x 13.1 mm for ZirCAD Prime, and 31.0 mm x 4.2 mm x 10.0 mm for inCoris TZI. The specimens were sintered with a Zircar high temperature furnace by following the protocols of manufacturers accordingly. The four longitudinal surfaces of all bar specimens for all materials were polished with diamond discs in a sequence of 125, 70, 45, 15, and 6 mm, and down to 0.5 mm finish. All polished specimens were subjected to the annealing treatment at 1000 oC for 15 min before mechanical testing. The three-point bend testing with three loading configuration was performed for flexural strength on the Universal Testing Machine (Instron 5566A) with a loading rate of 0.5 mm/min. The fracture surfaces of these bar specimens were examined by a field emission scanning electron microscope. The yttria (Y2O3) and hafnia (HfO2) concentrations were analyzed by energy disperse spectroscopy on polished surfaces. RESULTS: The highest mean 3 point bending flexural strength for all layers direction was for inCoris TZI with 786.55 MPa, whereas the lowest for Origin Beyond with 505.36 MPa. The inCoris TZI had overall highest flexural strength with vertical (enamel or dentin layer in tension) of 845.18 MPa. ZirCAD Prime had overall highest flexural strength with the loading configuration of dentin layer in tension of 906.22 MPa while Origin Beyond had the lowest flexural strength of 686.79 MPa. Under the loading configuration of enamel layer in tension, the flexural strength of all three multilayer materials ZirCAD Prime, Origin Beyond and KATANA YML had no significant difference, having a strength value range of 498-504 MPa. The dentin layer had the lowest yttria concentration while the enamel had the largest one, and the transition layer was between them. The distribution of hafnia concentration of different layers for all multilayer materials was consistent. CONCLUSION: Within the limitations of this in vitro study, we can conclude that material, and loading configurations as well as the interaction between material and loading configurations had a significant effect on flexural strength of multilayer zirconia. ZirCAD Prime showed a significantly higher flexural strength than KATANA YML whereas Origin Beyond had the lowest flexural strength. The flexural strength of dentin layer in tension was significantly higher than all layers in tension, while the flexural strength of all layers was significantly higher than enamel layer in tension. The yttria concentration of multilayer zirconia gradually increased from dentin layer to enamel layer whereas the hafnia concentration was consistent across different layers. These findings in this study could enrich the knowledge of clinicians when selecting the multilayer zirconia materials in the clinical settings.

Aim: The aim of this study is to investigate if biaxial flexural strength for pressed glass ceramic with glazed, polished and grinded surface is affected by the acidic beverages Coca Cola and red wine. Material and method: 63 specimens were manufactured in IPS e.max Press®, divided into 6 test groups and one control group (KG) with 9 specimens in each group, in the dimensions 12 mm in diameter and in thickness, 1,8 mm without notch and 2,2 mm with notch. The specimens subdivided by different surface treatments; glazed surface (CCG, RVG), polished surface (CCP, RVP) and ground surface (CCS, RVS). Three groups underwent thermocycling for 970 cycles in 8°C Coca Cola® and three groups red wine at room temperature. Results: The results show significant difference between the groups with α=0,001. Biaxial flexural strength test showed that the CCS group had the highest mean value (340 MPa) and CCP the lowest mean value (214 MPa). CCS showed significant differences to all groups except RVP and RVS. Furthermore the RVP group showed no significant difference to any other group and RVS only towards CCP. Conclusion: Within the limitations of this in vitro study the following conclusions can be made; Acidic beverages do not affect the flexural strength for pressed lithium disilicate based glass ceramics. The flexural strength is affected by surface treatment, where grinding with sandpaper results in higher flexural strength. / Syfte: Syftet med föreliggande studie är att undersöka om den biaxiala böjhållfastheten på litiumdisilikatbaserad glaskeram som framställts genom pressteknik med tre olika ytbehandlingar (glansbränd yta eller för att efterlikna ocklusal inslipning eller abraderat slitage) påverkas av de sura dryckerna Coca Cola® och rödvin.Material och metod: 63 provkroppar tillverkades av IPS e.max Press®. Provkropparna delades in i 6 testgrupper, och en kontrollgrupp (KG), á 9 i varje, med måtten 12 mm i diameter och tjocklek 1,8 mm utan notch och 2,2 mm med notch. Provkropparna delades in utifrån olika ytbehandlingar, glansbränd (CCG, RVG), polerad (CCP, RVP) och slipad med sandpapper (CCS, RVS). 3 grupper genomgick termocykling i 970 cykler i 8°C Coca Cola®, och 3 grupper i rödvin i rumstemperatur, varvat med destillerat vatten i 37°C. Därefter utfördes biaxialt böjhållfasthetstest och resultaten analyserades med One-way ANOVA, Tukey’s test, signifikansnivå α= 0,05.Resultat: Resultaten visar att det finns signifikant skillnad mellan grupperna α=0,001. Det biaxiala böjhållfasthetstestet påvisade att gruppen CCS hade högst medelvärde (340 MPa) och CCP hade lägst medelvärde (214 MPa). CCS visade signifikant skillnad jämfört med samtliga grupper, förutom RVP och RVS. Vidare uppvisade RVP ingen signifikant skillnad jämfört med någon av de övriga grupperna och RVS endast mot CCP.Slutsats: Inom denna in vitro-studies begränsningar kan följande slutsatser dras; Sura drycker påverkar inte böjhållfastheten på litiumdisilikatbaserad glaskeram som framställts genom pressteknik. Hållfastheten påverkas beroende på ytbehandling. Genom att slipa ytan med slippapper resulterade det i högre biaxial böjhållfasthet.

BACKGROUND: Polymer-infiltrated zirconia ceramic, benefiting from the synergistic effect of the ceramic matrix providing strength and the polymer enhancing toughness, has the potential to mimic the structure of natural teeth in its optical and mechanical properties. OBJECTIVE: To determine the effect of additives and various sintering temperatures on the optical and mechanical properties of zirconia ceramic matrix composites. MATERIALS AND METHODS: Groups consisted of unmodified zirconia powder, and zirconia modified with porcelain and porogens to form the porous ceramic matrix. Three types of Tosoh zirconia powder, TZ-3YSB-E, Zpex, and Zpex Smile, were used to fabricate porous blocks. Zirconia powder and porcelain powder were ball-milled separately. Zirconia powder was dry pressed and then cold isostatic pressed. The blocks were sintered at 1000 and 1150 ºC and sectioned into discs (n=10). For zirconia with additives groups, 10% of Titankeramik and 5% of PEG8000 were mixed to zirconia powder using a high-speed mixer. The zirconia blocks were pressed and sintered at 1000, 1150, 1200 and 1300 ℃, and sectioned into discs (n=10). Porous discs were treated with a 10% wt solution of 10-MDP for 4 hours and then dried in a vacuum oven for 24 hours. TEGDMA-UDMA resin monomers were infiltrated into discs and cured at 90°C under pressure. Polymer-infiltrated ceramics specimens were polished to 1.5 mm in thickness. Optical properties were determined with an X-rite spectrophotometer. Biaxial flexural strength and Vickers indentation tests were performed using an Instron universal mechanical tester. Vickers hardness and indentation fracture toughness values were calculated by measuring the indent dimensions under FESEM, in addition to microstructure assessment. Statistical analyses were performed using computer software, Microsoft Excel 2016 and JMP Pro 15. RESULTS: This study revealed that the type of zirconia powder utilized for the fabrication of porous ceramics for polymer-infiltration structures did not significantly influence their optical properties. Mean values of fully sintered zirconia showed significantly higher biaxial flexural strength (628.5-1277.4 MPa) than polymer-infiltrated groups (105.4-433.6 MPa), with P-3Y1150 achieving the highest value. Higher pre-sintering temperature from 1000 ℃ to 1150 ℃ led to enhanced biaxial flexural strength for polymer-infiltrated pure zirconia specimens, with values rising from 126.5-158.2 MPa to 243.4-433.6 MPa. Adding porcelain and porogens did not significantly affect the optical or specific mechanical properties, such as biaxial flexural strength and Vickers hardness, despite increasing the sintering temperature to 1300 ℃. Nevertheless, a significant increase in indentation fracture toughness was noted with ZPTKPEG1200 (7.65±0.55 MPa·m1/2) and ZPTKPEG1300 (7.09±0.61 MPa·m1/2), values that were markedly higher than those in all control groups of fully sintered zirconia (p<0.001). Sintering temperature was found to be a key determinant in influencing the ceramic matrix's microstructure, porosity, and density, as well as the biaxial flexural strength, Vickers hardness, and indentation fracture toughness of polymer-infiltrated zirconia. While changes in temperature did not affect optical properties, and polymer infiltration did not enhance all attributes, it did substantially elevate the indentation fracture toughness in mixed zirconia samples with additives, offering a potential area for further research. CONCLUSION: The mechanical properties of polymer-infiltrated ceramics responded significantly to the sintering temperature and the type of zirconia powder utilized, most notably in the 3Y-TZSB-E group. A notable increased indentation fracture toughness was discernible when Zpex powder, mixed with additives, was subject to polymer infiltration and sintered at temperatures between 1200-1300 °C. Even though polymer infiltration and additive incorporation did not uniformly enhance all properties, a noticeable improvement in fracture toughness was observed. These findings open the door to future research, especially in potential applications of dental restorative materials that demand superior fracture toughness.

Yes / Flexural performance of concrete beams reinforced with steel–FRP composite bar (SFCB) was investigated in this paper. Eight concrete beams reinforced with different bar types, namely one specimen reinforced with steel bars, one with fiber-reinforced polymer (FRP) bars and four with SFCBs, while the last two with hybrid FRP/steel bars, were tested to failure. Test results showed that SFCB/hybrid reinforced specimens exhibited improved stiffness, reduced crack width and larger bending capacity compared with FRP-reinforced specimen. According to compatibility of strains, materials’ constitutive relationships and equilibrium of forces, two balanced situations, three different failure modes and balanced reinforcement ratios as well as analytical technique for predicting the whole loading process are developed. Simplified formulas for effective moment of inertia and crack width are also proposed. The predicted results are closely correlated with the test results, confirming the validity of the proposed formulas for practical use. / National Natural Science Foundation of China (51678514), China Postdoctoral Science Foundation (2018M642335), the Science and Technology Project of Jiangsu Construction System (2018ZD047), the Cooperative Education Project of Ministry of Education, China (201901273053), the Blue Project Youth Academic Leader of Colleges and Universities in Jiangsu Province (2020), the Six Talent Peaks Project of Jiangsu Province (JZ038, 2016) and the Yangzhou University Top Talents Support Project