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When fastener holes are made in structural beams, the Canadian Steel Design Code CAN/CSA-S16.01 -Clause 14.1 (CSA, 2003) states that no deduction in flexural strength is needed for holes up to 15% of the gross flange area. This clause was established many years ago, however, over the years the mechanical characteristics of structural steel have changed. This research study focused on the effects of flange holes on the flexural behavior of steel I-beams made of ASTM A992 steel. This study was conducted primarily based on an experimental investigation involving 25 beam specimens. Holes of various diameters, ranging from 0% to 48% of the gross flange area were laid by drilling holes (a) in the midspan of the tension flange and (b) in the midspan of both the tension and compression flanges. Additionally, beams having holes with fasteners (snug tight) were performed. Based on the test results, this study recommended a design approach, which is analogous to an axial tension member provision as per the current CAN/CSA-S16.01 (CSA, 2003) standard. Accordingly, the effects of holes on the flexural strength can be ignored if the gross-section plastic moment is greater than a modified net-section fracture moment hence, beam members shall be designed to carry the gross-section plastic moment. Otherwise, the beam members shall be designed to carry the modified net-section fracture moment. The comparison of the recommended procedure with the 15% exemption rule as per current steel standard S16.01 (CSA, 2003) demonstrated that the current code provision is unnecessarily conservative for steel grades such as A992 steel. On the other hand, the current provision may be more conservative for high strength steels such as HSLA 80 steel, ASTM A913 Grade 60 and HPS-485W having a minimum yield-to-ultimate strength ration value of more than 0.85. The analytical portion of the research study involved the application of nonlinear finite element method to verify and comprehend the experimental results. The analytical study was conducted using ADINA FE program. The test beams were modeled using 4-node shell element that includes both geometric and material nonlinearities. The material model utilized in the FE analysis was developed based on the experimental-numerical simulation of standard tensile coupons. / Thesis / Doctor of Philosophy (PhD)

The purpose of the edge beam is to support the railing and the pavement, function as part of the drainage system and in the case it is integrated into the bridge deck it can serve to distribute concentrated loads. It is located in road environment and therefore exposed to water and salt with chlorides as well as subject to impacts during accidents. It deteriorates in a greater pace than the rest of the bridge and therefore has a shorter lifespan than the bridge in full. A deteriorated edge beam put the safety of the bridge users in jeopardize and increases the need of maintenance, repair and replacement work. These activities affect the surrounding traffic flow due to reduced speed limits as well as closure of traffic lanes. A literature study has been performed to get an understanding of how edge beams are designed and constructed. A great part of this was done by examining codes and regulations. By meeting engineers from different building companies it has been possible to obtain a picture of how it is done in real life and how the path to the final design looks like. Building site visits were carried out to see the process from design to construction i.e. how it is applied in real life. A design study was performed, including a check of crack width in an integrated edge beam over a support, height of bridge deck when a pre-fabricated (brokappa) is used and a comparison in the magnitude of the clamping moment in a steel-concrete bridge with and without an edge beam. All proposals are presented by the Edge Beam Group (EBG, in Swedish, Kantbalksgruppen), which is composed of experienced engineers that works within the frame of the project social optimal edge beam systems governed by the Swedish Transport Administration. The literature research showed that even if the edge bean is prone to deteriorate its lifespan does not have to be governed by its condition. Planned expansion of bridge width and maintenance strategies including the replacement of waterproofing layer could also be a reason for replacement in some cases. A significant increase of reinforcement in the edge beam and top part of the bridge deck over support is needed to obtain an acceptable crack width of 0.15mm. This would however aggravate the casting phase. The use of a pre-fabricated edge beam result in an increase of the bridge deck height. A solution could be to strengthen the anchoring capacity but this could in turn give an over reinforced structure. When it comes to the clamping moment in a steelconcrete composite bridge the integrated edge beam leads to a better distribution of the traffic load. On the other hand, due to the higher dead weight, a bridge deck without an edge beam would result in a lower total moment in the cantilever.

The paper presents details of a numerical analysis and simplified construction of strengthened glue laminated beams. Glue laminated beams are strengthened through the use of steel reinforcements embedded between the lamellas of the beams. The study compares the numerical results from reinforced and prestressed beams, simply reinforced beams and non-modified beams. Parametric studies were undertaken to evaluate the effects on reinforcement thickness, beam span, prestressing force and prestressing loss. Modified and prestressed beams with wide spans and large dimensions had a significantly higher design load compared to non-modified beams with similar geometry and span. In the most beneficial cases, a load increase of 438% was observed for point load at midspan and 346% for uniformly distributed load.

The nonlinear nonplanar steady-state responses of cantilever beams to direct and parametric harmonic excitations are investigated using perturbation techniques. Modal interactions between the bending-bending and bending-bending-twisting motions are studied. Using a variational formulation, we obtained the governing equations of motion and associated boundary conditions for monoclinic composite and isotropic metallic inextensional beams. The method of multiple scales is applied either to the governing system of equations and associated boundary conditions or to the Lagrangian and virtual-work term to determine the modulation equations that govern the slow dynamics of the responses. These equations are shown to exhibit symmetry properties, reflecting the conservative nature of the beams in the absence of damping. It is popular to first discretize the partial-differential equations of motion and then apply a perturbation technique to the resulting ordinary-differential equations to determine the modulation equations. Due to the presence of quadratic as well as cubic nonlinearities in the governing system for the bending-bending-twisting oscillations of beams, it is shown that this approach leads to erroneous results. Furthermore, the symmetries are lost in the resulting equations. Nontrivial fixed points of the modulation equations correspond, generally, to periodic responses of the beams, whereas limit-cycle solutions of the modulation equations correspond to aperiodic responses of the beams. A pseudo-arclength scheme is used to determine the fixed points and their stability. In some cases, they are found to undergo Hopf bifurcations, which result in limit cycles. A combination of a long-time integration, a two-point boundary-value continuation scheme, and Floquet theory is used to determine in detail branches of periodic and chaotic solutions and assess their stability. The limit cycles undergo symmetry-breaking, cyclic-fold, and period-doubling bifurcations. The chaotic attractors undergo attractor-merging and boundary crises as well as explosive bifurcations. For certain cases, it is determined that the response of a beam to a high-frequency excitation is not necessarily a high-frequency low-amplitude oscillation. In fact, low-frequency high-amplitude components that dominate the responses may be activated by resonant and nonresonant mechanisms. In such cases, the overall oscillations of the beam may be significantly large and cannot be neglected. / Ph. D.

Yes