Abstract in English:Abstract This work presents a new computational approach to estimate the fatigue life in welded joints, taking into account three-dimensional, non-proportional, and out-of-phase stresses; the thermomechanical properties of steel; parameters of the welding process; and the effects of residual stresses. We use the mechanical equations of continuous and cumulative fatigue damage found from Multiaxial RainFlow, the Wang and Brown and critical plane methods, and the Findley criteria approach. The numerical finite element method, available with software, is used to simulate the formation of residual stress and quantify its influence by solving equations. Based on the analysis of numerical results, we were able to prevision the crack location and angles of propagation of a high cycle fatigue crack with totally random loads in a metallic structure. We conclude that the result of the computational method is valid and can be used to estimate and life in fatigue in welded joints.
Abstract in English:Abstract The static and dynamic compression mechanical properties of the prefabricated artificial filled rock joints specimens with different fillings and different joint thicknesses are tested, respectively. Then, the strength, deformation, wave propagation and energy dissipation laws of the filled joints are analyzed. The experimental results show that the static and dynamic compression strength of filled joints increases with the strength of filling materials while decreases with the filling thickness. The deformation characteristics of filled joints under static and dynamic compression are positively correlated with the properties of filling materials and the thickness of filled joints. With the increasing of the filling thickness, the reflection coefficient increases while the transmission coefficient decreases. With the increase of the strength of the fillings, the reflection coefficient decreases while the transmission coefficient increases. The energy dissipation ratio decreases with the increase of the filliing thickness and increases with the increase of the strength of the filling material.
Abstract in English:Abstract Steel open-web sandwich floors (SOSFs) have been applied in several pioneering industrial and public buildings. The traditional square tube shear key (STSK) is changed into a flanged cruciform section shear key (FCSK) to further improve the bearing capacity of SOSFs. A half-scale test model is designed. A graded static loading test is performed to measure deflection and strain. The calculation formula of the intersection beam analogy method (IBAM) considering the influence of shear stiffness is proposed. A finite element (FE) analysis was also performed. The results of the test, IBAM and FE method are compared. The maximum deviation of the deflection obtained by them is less than 5%, and the maximum strain error is less than 7%. These figures prove that all three methods have high precision in the elastic range. Compared SOSFs use a different shear keys with the same grid size and chords, the maximum Mises stress is reduced by 55.9% and the maximum displacement is reduced by 36.1%. The new shear key imparts the structure with improved bearing capacity and safety margin.
Abstract in English:Abstract In this study, a dynamic centrifuge experiment is designed to investigate the seismic behavior of an existing bridge subjected to the earthquake-induced lateral movement of soft clay soil. The pile-supported bridge abutment at the movable bearing side is modeled at the 1/75 scale. The material and thickness of the soft clay layer are set as the experimental parameters. Under the effect of the lateral movement of the soft clay layer during base shaking, a collision between the bridge abutment wall and the girder occurs, and the bridge abutment wall is restrained at the top; however, the footing largely moves forward, resulting in the large backward inclination of the bridge abutment wall. In addition, it is confirmed that during base shaking, the pile bending moment largely increases due to the ground lateral movement and then remains nearly constant, even at the end of the base shaking phase. Furthermore, it is found that when the soft clay has a high shear strength, the ground lateral movement may cause a high pile earth pressure, resulting in the large corresponding internal bending moment on the pile sections; however, when the soft clay layer is very thick, the high pile earth pressure generally occurs locally, instead of along the whole pile length.
Abstract in English:Abstract This work presents a second-order inelastic analysis of steel arches. The analysis of shallow and non-shallow arches with several cross sections and boundary and loads conditions are discussed. The computational platform used is the homemade CS-ASA, which performs advanced nonlinear static and dynamic analysis of structures. The nonlinear geometric effects are considered using a co-rotational finite element formulation; the material inelasticity is simulated by coupling the Refined Plastic Hinge Method (RPHM) with the Strain Compatibility Method (SCM), and the static nonlinear solution is based on an incremental-iterative strategy including continuation techniques. In the simulated nonlinear steel arch models, special attention is given to the equilibrium paths, the influence of rise-to-span ratio, support and loading conditions and full yield curves among other factors. The numerical results obtained show good agreement with those from literature and highlight that the arch rise-to-span ratio has great influence on the structure resistance and that the shallow arches can lose stability through the snap-through phenomenon.
Abstract in English:Abstract In the recent era, built-up columns have been continuously used by the engineers in the design and analysis of tall buildings and bridges. Vibration analysis of these types of columns is essential to understand the failure modes of such columns. In that aspect, this study aims to analyze a concrete-encased built-up column made by configuring cold-formed steel angle sections connected by means of battens encased by normal weight and lightweight concrete with and without the inclusion of basalt fibre. Eight columns with battens were simulated, and it is encased with four different types of concrete and subjected to axial cyclic loading. The experimental results were correlated with the numerical investigation performed using FEA. The results indicated that the type of concrete dramatically influences the behaviour of columns. Higher ultimate strength and ductility was observed for all specimens, which is due to lower shear capacity of the battens. It was observed that the intensity of the axial cyclic load has a significant effect on the ultimate strength and deflection of columns, but it is less influential on the yield strength. It was concluded the results of experimental and FEA shows good compatibility between each other and depicts an error of 7.48%.
Abstract in English:Abstract An alternative geometrically nonlinear total Lagrangian finite element is presented and applied to solve cable, cable nets and a very long suspended bridge in both three and two-dimensional spaces from its setting-up through its response to earthquake. It includes dynamics, pseudo-dynamics regularization, elastic actuators and automatic stress calibration. Dynamics and pseudo-dynamics are used to perform transient structural analysis and the setting-up of very unstable structures. Elastic actuators allow pre-stressing structural members for the iterative structural design and cables natural length definition. Automatic stress calibration comprises continuous cables in complicated structures without sliding contact devices. The formulation is applied to model main cables of suspended bridges passing through saddle points. Inertial terms are introduced by an alternative mathematical way. Two simple examples are used to validate all aspects of the proposed formulation. Finally, a representative application is performed, i.e., the numerical design and analysis of a very long span suspension bridge by the proposed strategy.
Abstract in English:Abstract The paper is regarding to the structural dynamics of a saddle shaped cable-net structure with two high points and two low points at the corners. The net cables are pre-stressed by stretching the four edge cables that are supported at the corner points. A series of parametric nonlinear dynamic analysis is utilized to evaluate the dynamic response of the system under the different structural masses and geometries, pretensions and alignments of cables and the amplitudes of dynamic excitation. An equivalent single-degree-of-freedom model is presented as a simplified method to estimate the dynamic response of the full finite element model. The simulation results show that the equivalent model can accurately estimate the displacement response of multi-degree-of-freedom model under dynamic excitation. Furthermore, a nonlinear active control algorithm is applied to decrease the structural response under the transient wind excitation and the results indicate the effectiveness of the proposed control algorithm.
Abstract in English:Abstract This paper provides guidelines for cyclic loading bending test simulation and modal analysis of a reinforced concrete I-beam. For this purpose, experimental and numerical cyclic bending test were performed. In the experimental study, the natural frequencies of the structure in the intact and damaged states were measured. The simulation of the cyclic bending test was done with Concrete Damaged Plasticity model (CDP), implemented in Abaqus finite element software. Based on the experimental results, different constitutive models for concrete were evaluated. In order to evaluate the dynamic behavior of the structure in the numerical model, the automatic calibration of the finite element model by Genetic Algorithm (GA) was used. With the calibrated numerical model, methodologies for estimating the overall damage of the structure based on its dynamic properties were proposed. The results confirm that the well-designed numerical model is able to efficiently represent the cyclic loading bending test. In addition, the proposed global damage estimates demonstrate the coherence between numerical and experimental models.
Abstract in English:Abstract The methodologies for designing pile foundations can be complex since the simultaneous interactions among the block, piles and surrounding soil should be taken into account. Therefore, in addition to the discussions on construction, instrumentation, testing and simulation of a defective pile, this paper discusses the practical issues arising from the observed numerical using three-dimensional finite elements and experimental studies. The main issues discussed in this paper refer to as the decrease in load capacity of bored instrumented piles when subjected to a structural defect. It was observed in the results that given the presence of the defect, the failure load of the system has decreased from 190 kN to 110 kN, i.e. around 40% reduction of the intact reference value. Using the data obtained by numerical analysis, laboratory test, and field application, it was possible that the results were satisfactory and reasonable, enhancing our understanding of this complex foundation system’s behavior, especially in the presence of a defective pile.