The magnitudes of seismic forces which develop in floor diaphragms were investigated in this report to enable the development of a desktop floor diaphragm force design method for use in a structural design office. The general distributions of the forces which develop within the floor diaphragm were also investigated. Two and three dimensional, non-linear numerical integration time history analyses were performed to determine the trends and estimates of inertial and self-strain compatibility transfer forces within floor diaphragms. Sensitivity studies were carried out to determine which simplifying analytical modelling assumptions could be made in the analytical models. It was found that foundation flexibility, shear deformations in walls and the type of plastic hinge model, all affected the magnitudes of forces within floor diaphragms. A range of buildings with different stiffness, strength, height, types of lateral force resisting systems and different locations of the building including different seismic zones and soil types were modelled with the time history analyses method. The results indicated that the magnitudes of inertial forces were primarily related to higher dynamic modes of the structure and the transfer forces were related to the lower modes of vibration of the structure. It was identified that the maximum magnitudes of inertial and transfer forces do not occur simultaneously. The results also indicated that larger inertial and transfer forces, than those predicted by the Equivalent Static Analysis method, developed in the lower levels of the buildings. From these results a static force floor diaphragm design method was developed. Comparisons were made between both the inertial and transfer floor diaphragm forces obtained from the proposed static method, to values from time history analyses. These comparisons indicated that the floor forces obtained by the proposed method were generally larger than the floor forces obtained by the time history results. Elastic and inelastic finite element analyses were used to estimate the in-plane distributions of floor diaphragm forces for floor diaphragms with different geometries and lateral force resisting elements. Comparisons were made between the total tension forces obtained from the finite element analyses and Strut and Tie Analysis methods; these comparisons indicated the relative levels of redistribution of internal forces which could induce cracking within the floor. The comparisons indicated that redistribution cracking in the floors could develop around corner columns, re-entrant corners and openings.

A lightweight carbon fiber reinforced polymer (CFRP) sandwich panel has been developed for floor use in commercial office building construction. CFRP laminate skins were combined with low-density rigid polyurethane foam to create a composite sandwich panel suitable for floor use. The CFRP sandwich panel was optimized to withstand code prescribed office-building live loads using a 3D finite element computer program called SolidWorks. The thickness of the polyurethane foam was optimized to meet both strength and serviceability requirements for gravity loading. Deflection ultimately was the controlling factor in the design, as the stresses in the composite materials remained relatively low. The CFRP sandwich panel was then subjected to combined gravity and lateral loading, which included seismic loads from a fictitious 5-story office building located in a region of high seismic risk. The results showed that CFRP sandwich panels are a viable option for use with floors, possessing sufficient strength and stiffness for meeting code prescribed design loads, while providing significant benefits over traditional construction materials.