DYNAMIC PROBLEM FOR A THIN-WALLED BAR WITH A MONOSYMMETRIC PROFILE

The paper presents an analytical solution to the dynamic problem for a thin-walled elastic rod, thecross-section of which has one axis of symmetry. The solution is constructed for an arbitrary dynamic load and two types of boundary conditions: hinged support in constrained torsion and free warping of the end sections of the rod; rigid fastening with constrained torsion and absence of warping. The peculiarity of the mathematical model lies in the fact that the differential equations of motion contain a complete system ofinertial terms. Spectral expansions obtained as a result of using the method of integral transformations are represented as an effective method for solving linear non-stationary problems in mechanics. The structuralalgorithm of the method of finite multicomponent integral transformations proposed by Yu.E. Senitsky is used.

Finite Beam Element for Curved Steel–Concrete Composite Box Beams Considering Time-Dependent Effect

Curved steel–concrete composite box beams are widely used in urban overpasses and ramp bridges. In contrast to straight composite beams, curved composite box beams exhibit complex mechanical behavior with bending–torsion coupling, including constrained torsion, distortion, and interfacial biaxial slip. The shear-lag effect and curvature variation in the radial direction should be taken into account when the beam is sufficiently wide. Additionally, long-term deflection has been observed in curved composite box beams due to the shrinkage and creep effects of the concrete slab. In this paper, an equilibrium equation for a theoretical model of curved composite box beams is proposed according to the virtual work principle. The finite element method is adopted to obtain the element stiffness matrix and nodal load matrix. The age-adjusted effective modulus method is introduced to address the concrete creep effects. This 26-DOF finite beam element model is able to simulate the constrained torsion, distortion, interfacial biaxial slip, shear lag, and time-dependent effects of curved composite box beams and account for curvature variation in the radial direction. An elaborate finite element model of a typical curved composite box beam is established. The correctness and applicability of the proposed finite beam element model is verified by comparing the results from the proposed beam element model to those from the elaborate finite element model. The proposed beam element model is used to analyze the long-term behavior of curved composite box beams. The analysis shows that significant changes in the displacement, stress and shear-lag coefficient occur in the curved composite beams within the first year of loading, after which the variation tendency becomes gradual. Moreover, increases in the central angle and shear connection stiffness both reduce the change rates of displacement and stress with respect to time.

Experimental and Numerical Study of RC Thin-Walled Channel Beam under Torsion

The reinforced concrete thin-walled channel beams are widely designed as bridges in urban railway and city roads. The swing force in the driving which cause constrained torsion becomes a safety factor. The torsion resistance of concrete members is not adequate to thin-walled channel beams, which is based on the theory of spatial truss with variable angle. An experiment was conducted to test the mechanical properties of the thin-walled channel beam under torsion. The mechanical properties of RC thin-walled channel beam under restrained torsion were also researched with Finite Element software, and were compared to the result of the experiment. The result of FE model agreed well with the experiment.

Stress and Strain Definition of an Open Profile Thin-Walled Beam at Constrained Torsion by Boundary Element Method

Stress and Strain Definition of an Open Profile Thin-Walled Beam at Constrained Torsion by Boundary Element Method Thin-walled beams with open profile at constrained torsion are investigated in this paper. A thin-walled beam loaded by an external bi-moment at constrained torsion is investigated in this paper. An analytical variant of the boundary element method (BEM) is presented, which is based on a new scheme of the integral ratios transformation of the initial parameters method in a system of linear algebraic equations. Only one dimensional integrals are used defining the one dimensional continuum.