Thesis (M.S.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references (leaf 184). Also available via World Wide Web.

Thesis (Ph. D.)--Lehigh University, 2003. / In two parts. Includes vita. Includes bibliographical references (leaves 394-397).

Existing reinforced concrete (RC) beams often need to be strengthened due to material deterioration or a change in usage. The bolted side-plating (BSP) technique, i.e., attaching steel plates to the side faces of RC beams using anchor bolts, effectively enhances the bearing capacity without significant loss in deformability thus receives wide acceptance. However, as a newly developed technique, only limited information is available in literature, which mainly focused on the overall load–deflection performance of lightly reinforced BSP beams. Little studies have been conducted on the partial interaction between steel plates and RC beams which is closely related to the performance of BSP beams. The longitudinal and transverse slips, which control the degree of partial interaction, have yet to be determined precisely. Accordingly, in this thesis, extensive experimental, numerical and theoretical studies on BSP beams are presented. The experimental behaviour of BSP beams was investigated. For the first time, special effort was put in precisely measuring the profiles of longitudinal and transverse slips. In order to investigate the behaviour of BSP beams under other load cases and beam geometries, a nonlinear finite element analysis was conducted. The numerical method is more economical and capable of overcoming the difficulty in measuring the transverse slips precisely. A new approach to evaluating the transverse bolt shear force was also developed through a parametric study. New partial interaction models were developed by isolating and considering the longitudinal and the transverse partial interaction separately. A longitudinal slip model was developed based on the BSP beam section analysis, in which different strains of steel plates and RC beams were considered but the difference in deflection hence the difference in curvature was not taken into account. Meanwhile, a piecewise linear model was also proposed for the transverse slip and bolt shear transfer by introducing Winkler’s model and defining the transverse slip as the difference in deflection. Formulas for the slips, the plate forces, the strain and the curvature factors that indicate the degree of partial interaction, were also deduced. Furthermore, these formulas allow us to evaluate the effect of partial interaction in the BSP strengthening design. A numerical program was originally developed to evaluate the performance of BSP beams with partial interaction. The balance between strengthening effect and strengthening efficiency was also achieved by a parametric optimization study, which would simplify the design procedure of BSP strengthening significantly. According to the numerical and theoretical results, a new design approach for BSP beams, which needs only minor modification to existing design formula for RC beams, was proposed to aid engineers in designing this type of BSP beams and to ensure proper details for desirable performance. Compared to the conventional design methods that assume a full interaction between steel plates and RC beams, this new method not only retains the features such as ease of use and fast calculation, but also yields results that are more reliable. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

The stress-strain relationship of concrete in flexure is one of the essential parameters in assessing the flexural strength and ductility of reinforced concrete (RC) structures. An overview of previous research studies revealed that the presence of strain gradient would affect the maximum concrete stress and respective strain developed in flexure. Previously, researchers have conducted experimental studies to investigate and quantify the strain gradient effect on maximum concrete stress and respective strain by developing two strain-gradient-dependent factors k3 and ko for modifying the flexural concrete stress-strain curve. In this study, the author established a new analytical concrete constitutive model to describe the stress-strain behavior of both normal-and high-strength concrete in flexure with the effect of strain gradient considered. Based on this, comprehensive parametric studies have been conducted to investigate the combined effects of strain gradient and concrete strength on flexural strength and ductility design of RC beams and columns with concrete strength up to 100 MP a by employing the strain-gradient-dependent concrete stress-strain curve using non-linear moment-curvature analysis. From the results of the parametric studies, it is evident that both the flexural strength and ductility of RC beams and columns are improved under strain gradient effect. A design value of ultimate concrete strain of 0.0032and anew equivalent rectangular concrete stress block incorporating the combined effects of strain gradient and concrete strength have been proposed and validated by comparing the proposed theoretical strength with the strength of 198 RC beams and 275 RC columns measured experimentally by other researchers. It is apparent from the comparison that the proposed equations can predict more accurately the flexural strength of RC beams and columns than the current RC design codes. Lastly, for practical engineering design purpose, design formulas and charts have been produced for flexural strength and ductility design of RC beams and columns incorporating the combined effects of strain gradient and concrete strength. / published_or_final_version / Civil Engineering / Master / Master of Philosophy

Not available / text

This thesis is based upon a need to re-examine the assumptions and expand upon the results arrived at in recent studies on the flexural stiffness of reinforced concrete columns. A survey is presented of concrete column design over the last 200 years. Elastic and plastic behavior of concrete columns is discussed with respect to stiffness and Euler's buckling load. Some limitations and applications of buckling load are considered. Various current code approximations of stiffness are presented. Four possible methods for computing a more exact stiffness (EI) and their advantages and disadvantages are discussed. The formula EI = M/φ provides the best solution. The two dimensional program RECTCOL which is based on the P-M-φ relationships is developed and explained. Then RECTCOL is used to show how the column flexural stiffness varies with axial load, reinforcement ratio, yield strength of the reinforcing steel, concrete strength, cover, and column dimensions. A flow chart and source code are included by RECTCOL.

No description available.

No description available.

No description available.

No description available.