Beam Bending Solutions Based on Nonlocal Timoshenko Beam Theory

This paper is concerned with the bending problem of micro- and nanobeams based on the Eringen nonlocal elasticity theory and Timoshenko beam theory. In the former theory, the small-scale effect is taken into consideration while the effect of transverse shear deformation is accounted for in the latter theory. The governing equations and the boundary conditions are derived using the principle of virtual work. General solutions for the deflection, rotation, and stress resultants are presented for transversely loaded beams. In addition, specialized bending solutions are given for beams with various end conditions. These solutions account for a better representation of the bending behavior of short, stubby, micro- and nanobeams where the small-scale effect and transverse shear deformation are significant. Considering particular loading and boundary conditions, the effects of small-scale and shear deformation on the bending results may be observed because of the analytical forms of the solutions.     

Recent developments in optimal reinforcement of RC beam and column sections

Recent advances in approaches to the design of reinforced concrete sections have culminated in a theorem of optimal (minimum) sectional reinforcement. This theorem is articulated on the basis of patterns observed in the optimal reinforcement of rectangular sections, obtained with a new approach for the analysis and design of reinforcement. Using the hypotheses for ultimate strength design sanctioned by ACI 318-05 (2008), the minimum total reinforcement area required to provide adequate resistance to axial load and moment is shown to occur for particular constraints on longitudinal reinforcement area or distributions of strain. These constraints are identified along with the solutions for minimum total reinforcement area. Optimal reinforcement may be selected from among the potential solutions identified by the theorem. An example illustrates the application of the theorem to the design of a reinforced concrete cross-section. Implications for teaching and practice of reinforced concrete design are discussed.     

Theoretical Study on Short-Term and Long-Term Deflections of Fiber Reinforced Polymer Prestressed Concrete Beams

This paper presents the methods for predicting the short-term and time-dependent deflections of fully or partially prestressed concrete beams with fiber reinforced polymer (FRP) tendons under sustained bending moment and axial force. The age-adjusted effective modulus method is used to model the creep behavior in the concrete and the relaxation in the FRP prestressing tendons. A tension-stiffening model is proposed to evaluate the stiffness of the section after cracking. The analytical values are compared to the test results and it is found that the analytical values are in good agreement with the experimental results.