Reliability analysis of slender columns using the general method with linear creep theory

To analyze the reliability of slender columns subjected to axial force and uniaxial bending moment, with a slenderness index between 100 and 140, 216 columns were modeled. The square cross-section was adopted, with three different configurations for longitudinal reinforcement. In the calculation, the general method with the linear creep theory was applied. Several factors were varied: slenderness index, reinforcement ratio, steel bars arrangement, compressive strength of concrete, and first-order relative eccentricity. For analysis purposes, the Monte Carlo method was adopted, followed by the First Order Reliability Method (FORM). Considering the results obtained, it was observed that the reliability index is usually higher for lower reinforcement ratios and varies according to the configuration of the cross-section.

Creep Behaviour of Reinforced Concrete Beam under Long-Term Bending

Concrete structure after casting will be subjected to external load, peripheral components and other constraints, the overall performance of the structure under a long-term loading state will change continuously. In practical engineering, reinforcement is usually calculated and configured based on external load, but the role of reinforcement in the continuous loading process of concrete structure is not fully considered. Based on the elastic creep theory, this paper deduces the concrete creep calculation formula considering the influence of reinforcement, and analyses the law of the influence of reinforcement ratio and loading age on the strain and stress of concrete. The results show that the reinforcement can effectively restrain the deformation of concrete and reduce the load level of concrete.

Method and software for finite element solution of two-dimensional creep problems at large deformations

The paper presents the formulation of a two-dimensional problem of the creep theory for the case of finite strains. A description of the foundations of the calculation method presents. The method is based on the use of the generalized Lagrange-Euler (ALE) approach, in which the boundary value problem in the current solid configuration is solved by using FEM. A triangular element is involved in the numerical modeling. At each stage of creep calculations in the current configuration, the initial problem is solved numerically using the finite difference method. The preprocessing data preparation is carried out in the homemade RD program, in which two-dimensional model is surrounded by a mesh of special elements. This feature implements the ALE algorithm for the motion of material elements along the model. The examples of preprocessing as well as of the mesh rebuilding in the case of finite elements transition are given. Creep calculations are performed in the developed program, which is based on the use of the FEM Creep software package in the case of finite strains. The regular mesh is used for calculations, which allow us to use the efficient algorithm for transition between current configurations. The numerical results of the creep of specimens made from aluminum alloys are compared with the experimental and calculated ones obtained by integrating the constitutive equations. It was concluded that for material with ductile type of fracture the presented method and software allow to obtain results very close to experimental only by use of creep rate equation. Creep simulations of material with mixed brittle-ductile fracture type demand use the additional equation for damage variable.

Landslide Analysis over Creep Theory - Crack Propagation of Shale Slopes in Şırnak Asphaltite Coal Mine Site 1 and 2

The soft rock and wet slopes increase landslides over 50 m long creep slide and risk assessment for long steep slide in Şırnak open-pit coal mining should be searched in asphaltite quarries. The Avgamasya quarries No1 and 2 at critical depths and road bench sites in Şırnak, reaching over 120 m height with 60–65° shale slopes, developing major creep factors and other factors for landslide in the deep quarry locations is resulting debris rock falling or free sliding. The pore pressure measurements by measurements of water levels in four wells and water flow counting as the mining safety in recent years. This research provided rock slope stability patterns and crack propagation control of the hazardous location and formation cracks. The stages of creep experimentation explored the geophysical characteristics and thaw and freeze testing of rock samples. For this aim, two different long sliding areas with similar geoseismical conditions, two main analyzing methods, and patterns of researches were developed. Firstly, data on crack propagation in situ rock shale faces over certain time periods were determined. Displacement measurements over highly saturated shale—limestone contacts over the base of crack counting in a meter scale such as Rock Quality Designation (RQD) scoring of drilling logs. Secondly, hydrological water level logs were taken into consideration. On the other hand, due to that creep effect over freeze crack propagation unseen cause instability over wet sliding surfaces over 50 m, long sliding surface matter over slopes, poly linear or circle type creep sliding or rock tumbling falling failure types, and GEO5 slope stability, slice analysis will be advantageous instead of Finite Element Method (FEM) method.

Safety evaluation of a vehicle–bridge interaction system using the pseudo-excitation method

A method for analysing the vehicle–bridge interaction system with enhanced objectivity is proposed in the paper, which considers the time-variant and random characteristics and allows finding the power spectral densities (PSDs) of the system responses directly from the PSD of track irregularity. The pseudo-excitation method is adopted in the proposed framework, where the vehicle is modelled as a rigid body and the bridge is modelled using the finite element method. The vertical and lateral wheel–rail pseudo-excitations are established assuming the wheel and rail have the same displacement and using the simplified Kalker creep theory, respectively. The power spectrum function of vehicle and bridge responses is calculated by history integral. Based on the dynamic responses from the deterministic and random analyses of the interaction system, and the probability density functions for three safety factors (derailment coefficient, wheel unloading rate, and lateral wheel axle force) are obtained, and the probabilities of the safety factors exceeding the given limits are calculated. The proposed method is validated by Monte Carlo simulations using a case study of a high-speed train running over a bridge with five simply supported spans and four piers.

Creep Behaviours of Argillaceous Sandstone: An Experimental and Modelling Study

Understanding the creep behaviours of rocks is essential for the long-term stability of underground excavations in mining engineering. Creep behaviours are more important when the mining depth is greater, which leads to the emergence of weak rock masses and high in situ stresses. In this study, the creep behaviours of argillaceous sandstone (AS) were systematically investigated. For the experimental investigation, creep tests were conducted on AS with different confining pressures (3, 6, 9, 12, 15, and 18 MPa) using an MTS815.02 rock mechanics test system. The mechanical characteristics of AS were analysed. For the numerical study, a nonlinear creep model of AS under equal and different confining pressures was established based on rock creep theory and plastic theory. The results showed that confining pressure could effectively improve the creep failure strength of AS, accelerating its creep deformation rate and process and reducing the final expansion volume. The nonlinear creep model was embedded in the FLAC3D software, and the experimental and numerical results agreed well. The experimental investigation and proposed creep model can provide important guidance in underground mines for safe long-term stability of underground excavations.

Steady Motion of a Slack Belt Drive: Dynamics of a Beam in Frictional Contact With Rotating Pulleys

We seek the steady-state motion of a slack two-pulley belt drive with the belt modeled as an elastic, shear-deformable rod. Dynamic effects and gravity induce significant transverse deflections due to the low pre-tension. In analogy to the belt-creep theory, it is assumed that each contact region between the belt and one of the pulleys consists of a single sticking and a single sliding zone. Based on the governing equations of the rod theory, we for the first time derive the corresponding boundary value problem and integrate it numerically. Furthermore, a novel mixed Eulerian–Lagrangian finite element scheme is developed that iteratively seeks the steady-state solution. Finite element solutions are validated against semi-analytic results obtained by numerical integration of the boundary value problem. Parameter studies are conducted to examine solution dependence on the stiffness coefficients and the belt pre-tension.