Bending moment

About: Bending moment is a research topic. Over the lifetime, 14577 publications have been published within this topic receiving 158834 citations. The topic is also known as: bending moment.

Kinematic seismic response and bending of free-head piles in layered soil

Abstract: The paper studies the kinematic response of freehead piles. Such pile deformation has triggered structural damage in many strong earthquakes. In this Paper dimensionless parametric graphs for pile bending moments are presented which pertain to characteristic two-layer soil profiles. The results are derived by using an existing rigorous dynamic finite-element code, and by implementing a realistic beam-on-dynamic-Winkler-foundation formulation specifically developed for the kinematic response of piles in layered soil. The Winkler model is shown to reproduce quantitatively even detailed trends observed in the finite-element results; a simple analytical expression is thereby developed for estimating the Winkler stiffhess in terms of the local soil Young’s modulus and key dimensionless pile/ soil parameters. The study concludes that even relatively flexible piles may not exactly experience the wavy and abruptly changing ground deformation of the free field. The critical region of pile distress due to such kinematic loading is shown to he at or near the interface between alternating soft and stiff soil layers. The magnitude of the bending moment at such critical interface locations depends mainly on the stiffness contrast of the two layers through which the pile penetrates, the excitation frequency and the relative rigidity of the pile. A constraining cap may exert an important effect on such kinematic deformations.

Friction Damped Posttensioned Self-Centering Steel Moment-Resisting Frames

Abstract: A new connection for steel moment-resisting frames that incorporates posttensioning elements to provide a self-centering capacity along with friction mechanisms to dissipate energy is proposed and experimentally validated. The restoring force from the posttensioning elements in the connection makes the structure return to its undeformed state, even after experiencing large inelastic drifts. A bolt-prestressed friction mechanism with a frictional interface consisting of stainless steel and new nonasbestos organic break lining pads dissipates seismic input energy as the system undergoes lateral deformations. Cyclic tests were conducted to investigate the efficiency of the proposed friction interface and its performance under loading conditions that are expected during seismic loading. The test results showed that the frictional behavior is stable, repeatable, and predictable, although its friction coefficient is relatively low. Exterior and interior self-centering moment connections equipped with the proposed friction dampers were tested to study their structural behavior under cyclic loading. The results confirmed that friction damped posttensioned self-centering connections are capable of developing similar stiffness and strength characteristics to welded connections. They are also capable of undergoing large deformations with good energy dissipation characteristics, but without introducing inelastic deformations in the beams or the columns and without residual story drifts. Even at the ultimate stage, i.e., beyond the self-centering limit, the proposed connections can be detailed to exhibit a ductile response with the formation of flexural hinges in the beam sections, thus avoiding the sudden loss of strength and stiffness that occurs when the posttensioning elements are overloaded or when the beams buckle under excessive combined axial loads and bending moments.

Beam Bending Solutions Based on Nonlocal Timoshenko Beam Theory

Abstract: 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.