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)

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The effect of initial out-of-straightness of steel beams with wide flange cross-sections on their elastic lateral torsional buckling strength is investigated analytically and numerically. A variational principle is first developed and then used to obtain the governing equilibrium conditions and associated boundary conditions for a beam with general patterns of initial out-of-straightness and initial angles of twist. The principle is then used to develop a finite element formulation to characterize the lateral torsional response of beams with initial out-of-straightness under general transverse loading. The validity of the finite element formulation is verified through comparison against results from models based thin-walled beam finite element and shell element models available in ABAQUS. Since the load lateral displacement responses do not exhibit a distinct point of loss of stability, two design criteria are proposed for the characterization of the failure. The first criterion is based on a threshold value for additional lateral displacement and the second criterial is based on a threshold value for the normal stresses. Both criteria are applied in conjunction with the analytical solution and finite element formulation in order to determine a moment resistance based on lateral torsional buckling that incorporates the effect of initial out-of-straightness. The moment capacity based on the displacement-based criterion is shown to solely depend on the ratio between the initial out-of-straightness component associated with the first buckling mode and the additional displacement threshold value specified. To the contrary, moment capacity based on the stress criterion, was found to depend upon the initial out-of-straightness magnitude, the normal stress threshold value and the geometry of the cross-section. The effects of the above parameters on the predicted moment capacity were investigated for beams with common sections in a systematic parametric study. Possible means of modifying the present provisions of CAN-CSA S16 relating to elastic lateral torsional buckling to incorporate the effect of initial out-of-straightness effects are discussed and illustrated through examples. The load-deformation plots for beams with initial out-of-straightens as predicted by the formulations developed in the present study are then used to extend the Southwell plot technique, originally developed for buckling of column with initial out-of-straightness, to the lateral torsional buckling of beams with initial out-of-straightness. The study shows that the plot, either experimentally or analytically obtained, of the applied load versus lateral displacement, at any point or angle of twist at any section, for a beam with initial out-of-straightness case can predict (a) the elastic critical moment of an analogous initially straight beam, and (b) the first buckling mode contribution to the initial out-of-straightness.

No / In composite steel beams with precast hollow core slabs, the amount of transverse reinforcement can have a significant effect on the shear and slip capacity of the mechanical shear connectors. The issue of connector ductility becomes especially important when partial shear connection is adopted, as premature failure of the shear connectors would lead to sudden failure of the composite beam. This chapter presents its findings on the effect of transverse reinforcement on connector ductility and proposes design equations. Transverse reinforcement is used to provide ties for the slabs and confined concrete from splitting. The ductility of the shear connector, that is, slip capacity is directly affected by the amount of transverse reinforcement. Design equations presented in this chapter for estimating the shear capacity of the headed shear stud show a good correlation with the push-off test results. For full shear connection design, pre-splitting shear capacity of the headed stud can be used for the composite design, while for partial shear connection design, post-splitting shear capacity of the headed stud should be used. In general, a minimum transverse reinforcement of T16 bars should be used if partial shear connection design is used to ensure a minimum ductility of 6mm slip.

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No / The chapter discusses the behavior of composite steel beams with precast hollow core slabs in hogging moment regions. Full-scale composite beams to column semi-rigid connections with precast hollow core slabs are tested in the chapter. The chapter presents a steelwork connection consists of a flush end plate bolted to column flanges. The main variables studied are shear stud's spacing and degree of shear connection. Comprehensive instrumentations are used for all the tests, based on the experimental data, and equations to predict the rotation and the moment capacity for this type of composite connection are proposed in the chapter. A precast composite hollow core floor is a newly developed composite system for building that use precast hollow core slabs as the structural flooring. However, research on composite construction incorporating steel beams with precast hollow core slabs is still relatively new in comparison to the more traditional composite metal deck flooring.

No / Composite construction incorporating steel beams and precast hollowcore slabs is a recently developed composite floor system for building construction. As the construction industry demands for rapid construction with reduction in cost and environmental impacts, this form of composite construction, which does not require major onsite concreting, has become very popular among the designers and engineers in the UK. This form of composite construction is so far limited to simple beam-column connections. A semi-rigid composite joint is developed which can provide sufficient moment and rotation capacity required for plastic analysis in composite beams design. An analytical model for the semi-rigid composite connection is proposed and is verified with the experimental data and good agreement is obtained.

no / Composite beams formed by connecting the concrete slabs to the supporting steel beams have been in use for many years. Much of the research into this form of construction has concentrated on the more traditional reinforced concrete and metal deck construction. In composite beam design, the strength of the shear connector is of great importance since longitudinal shear forces must be transferred across the steel-concrete interface by the mechanical action of shear connectors. The shear strength and stiffness of the connection is not only dependent on the strength of the connector itself, but also on the resistance of the concrete slab to longitudinal cracking caused by the high concentration of shear force at each connector. Present knowledge of this behaviour is limited to shear connectors in solid reinforced concrete slabs and concrete slabs with profiled sheeting, little information is given for the shear connector capacity on composite steel beam with precast hollow core slabs. A new horizontal push off test is proposed to determine the shear capacity of the connector on the composite beams with precast concrete hollow cored floor slabs. The results showed the new test is compatible with all type of floor and shear connectors, and can replace the existing vertical push off tests.

The increased depth of castellated beams presents stability problems, specifically during erection. During erection the castellated beam must support the weight of an erector and self-weight until the continuous bracing of the floor deck is in place. The stability of the unbraced member is based on its resistance to lateral-torsional buckling. The cross-sectional properties that are related to lateral-torsional buckling, such as out-of-plane bending, warping constant, and torsional constant were calculated using three different approaches to model the unique geometry of castellated beams. These properties were used in various lateral-torsional buckling solutions to determine which procedure should be used to check for this mode of failure. Two specimens were tested to evaluate the results of the analytical unbraced length determination process. The tests results were used to better model the contribution of the web-to-column flange double angle connection on the stability of the castellated beam. / Master of Science