APPLICABILITY OF TRADITIONAL DESIGN PROCEDURES TO MODULAR STEEL BUILDINGS

Modular Steel Buildings (MSBs) have unconventional detailing requirements, compared to traditional onsite steel buildings. This may affect their design and performance. Currently, traditional design procedures are followed in their design. This thesis evaluates the performance of MSBs under gravity and seismic loads. It documents for the first time a detailed description of this unique steel building system and its detailing requirements and provides the first analytical experimental investigation that aims at improving its design methodology. The effect of directly welded stringer-to-beam connections used in MSBs on behaviour and design of MSBs floors is investigated using the finite element method. The results obtained revealed that this unique connection type affects the design of the floor stringers and welded connections but has little effect on the floor beams. Empirical relations and a simplified model were developed to predict the forces and moments likely to develop in MSB floor stringers. Nonlinear seismic performance and characteristics of braced frames of a typical MSB were studied using cyclic tests, nonlinear static pushover analysis, and incremental dynamic analyses. These studies consist of (i) an experimental investigation of the hysteretic behaviour of a scaled one-bay one-storey MSB braced frame; (ii) the strength and ductility design of braced frames of a typical MSB dormitory; (iii) the development of analytical models of selected braced frames of MSBs accounting for their unique detailing requirements and the hysteresis of steel bracing members; (iv) a study of the effect of design philosophy on the nonlinear behaviour of MSB braced frames using pushover analyses; (v) the evaluation of structural overstrength and displacement ductility of the braced frames using pushover analyses; and (vi) the assessment of seismic inelastic drift and ductility demands and capacities of the braced frames using an incremental dynamic analysis. It is concluded that while the MSB frame configuration may not significantly affect certain design and behavioural characteristics, in some others its unique detailing requirements need to be considered during design to eliminate undesirable seismic response

Cyclic Behavior of Lightly Reinforced Concrete Beams

The cyclic behavior or seven lightly reinforced concrete cantilever beams is studied as a function of reinforcement ratio, nomina 1 stirrup capacity, stirrup spacing, and ratio of positive to negative reinforcement. An energy dissipation index, Di, is developed to serve as a measure of the performance of reinforced concrete beams subjected to cyclic loading. Di studies. is used to compare the test results of this study with those of four other Recommendations for design are made. Based on the experimental work, the use of a low reinforcement ratio reduces the maximum shear and compressive stresses in beams subjected to cyclic loading, and thus, reduces the rate of degradation. A reduced stirrup spacing and an increased positive to negative steel ratio, AS/As, increases the number of inelastic cycles endured and the total energy dissipated. However, an increased A~/As ratio also increases the induced shear and the energy demand, thus reducing the effectiveness of the increased positive reinforcement. Di appears to provide a consistent measure of beam performance. The analyses based on Di indicate that a decrease in maximum shear stress, and an increase in concrete strength and nominal stirrup capacity will improve the performance of reinforced concrete beams subjected to cyclic loading

STR-883: CYCLIC RESPONSE OF STRUCTURAL STAINLESS STEEL PLATE UNDER LARGE INELASTIC STRAINS

Contemporary seismic design of steel braced systems is based on dissipating earthquake energy through significant inelastic deformation in the bracing members under cyclic excursions. The structure is designed such that the first significant yield occurs at ground intensity levels that are at or above the design earthquake forces. Thus, delaying the yielding of brace elements is deemed a good design but it could also lead to subsequent loss of stiffness and strength, large residual deformation or even dynamic instability and collapse. To enhance the post-yield performance of the brace system, a steel component with high strain hardening character may be required. The stress-strain behaviour of structural stainless steel, the austenitic 304L type, shows an early deviation from linearity at a much lower stress level than carbon steels, but with a much stronger strain hardening character. In this study, the austenitic 304L stainless steel material is characterised under large inelastic cyclic strains. Coupons were carefully designed and machined from 304L stainless steel and 350WT carbon steel plates, and were tested under constant cyclic strain amplitudes. Results of these tests have shown that 304L stainless steel exhibits greater cyclic hardening with maximum cyclic stress values up to nearly three times the yield stress. However, the carbon steel showed greater low-cycle fatigue life