In this paper, three-dimensional elasto-plastic finite element analysis was performed on flexible pavements under vertical repeated traffic loads to evaluate their shakedown behavior. Six different pavements with different structural number (SN) were modeled and subjected to a wide range of cyclic vehicle loads. Shakedown limits were obtained considering both failure and serviceability restraints. Results indicate that shakedown coefficient and shakedown bearing capacity increase with a rise in SN for all load types. Lower limit of shakedown bearing capacity versus SN can be regarded as a criterion for pavement design. Besides, shakedown failure-displacement factor (SFDF) was introduced as an index which is able to include both failure and serviceability criteria to compare pavements in terms of their shakedown behavior. Results suggest increase in SFDF with increasing SN, particularly for light loads. Furthermore, results indicate that increase in asphalt layer thickness always improves shakedown bearing capacity, while increase in base and subbase layer thickness is not only ineffective beyond an effective thickness but may also be damaging. In addition, the results of the present study were compared to lower bound and upper bound shakedown analysis for verification and showed reasonable agreement.

This paper includes description of reliability based design optimization of elasto-plastic skeletal structures under multi-parameter static loading. Presented approach is based on the assumption that the complementary strain energy of the residual forces is considered as an overall measure of the plastic performance for plastic shakedown analysis and optimal design of the structure, and this measure is an uncertain quantity responsible for resistance of the structure by assuming Gaussian distribution. The problems yield to nonlinear mathematical programming which are solved by the use of bi-level sequential quadratic algorithm. Simple portal frames are optimized to illustrate the proposed approaches.

Influence of creep on ratcheting behavior of rotating hollow disks under load and deformation controlled cyclic loading is investigated in this article. The disk material is assumed to obey nonlinear strain hardening curve and the Prager and Armstrong-Frederick kinematic hardening models are used to evaluate the back stress tensor in the stress space. A secondary creep equation is assumed to evaluate effect of creep time on cyclic loading behavior of the rotating hollow disks. The angular velocity is cycled within the two different stress limits of yield stress and twice the yield stress respectively. An interesting conclusion is that when creep is considered, both models predict the same ratcheting or shakedown behavior while; if creep is excluded, the models predict different ratcheting or shakedown behavior under mentioned loading conditions.

Progressive deformation (ratcheting) can occur as a response to variable loads as soon as the elastic limit is exceeded. If this is the case, strains and displacements accumulate in the event of cyclic loading in each load cycle.Widely known as triggers for ratcheting and already being considered in some design codes are configurations, in which a structure is subjected to at least two different types of load, namely a constant load (the primary load) and a superimposed cyclic load. In this paper, another mechanism that generates ratcheting is introduced. It can be attributed solely to the effect of a single load. In the simplest case, this can be explained by the successive activation of (an infinite number of) plastic hinges if a load of constant magnitude is moved in space. The increments of strains and displacements can decrease or increase from cycle to cycle, when the material is hardening, or if elastic foundation is present, or if the equilibrium condition is formulated for the deformed system (second-order theory) or if ‘‘large’’ rotations are taken into account (third-order theory).

The tension forces of cables in cable-stayed bridges during their construction and operation may differ from initial conditions, which could affect the amount and distribution of internal forces on other parts of the bridge. If some bridge elements are loaded to their yield limits, alternating plasticity and incremental collapse could occur under moving and repeated loading. This study investigated the effect of the initial tension force on the stiffness, strength, shakedown limit load, and alternating plasticity of cable-stayed bridges, which has not been studied so far. Two case study bridge models with cables having different initial forces were tested using nonlinear static analysis under gravitational force and nonlinear dynamic analysis under transient moving loads. The results showed that changes in the initial cable forces did not change the initial stiffness, ultimate strength, shakedown limit, alternating plasticity, or bridge reliability. These results were theoretically validated using plastic analysis theorems. This paper presents a new construction method for cable-stayed bridges based on the finding that adjusting the cable tension to the design value is not necessary during construction and operation. This method eliminates the need for tension adjustment and ensures that the final geometric shape of the bridge matches the expected profile. The proposed method offers a simpler and more efficient approach to constructing cable-stayed bridges without compromising the safety and durability of the structure.

The isotropic hardening theory of plasticity is used to evaluate the cyclic loading behavior of thick walled vessels under the load and deformation controlled stresses. The loads are of mechanical and thermal types. The method of successive approximation is used to calculate the stresses and strains in the vessel due to cyclic loadings. The results of the analysis are checked with the known experimental test. It is concluded that the isotropic hardening theory under all assumed conditions, excluding creep phenomenon, will always result in shakedown of vessel structures. This conclusion contradicts the results of the experimental tests for load controlled stresses.

Although bearing capacity of footings on top of slopes under monotonic loadings have been investigated widely so far, safety and bearing capacity of these structures against repeated dynamic loads have not been considered well enough. In this paper, lower bound dynamic shakedown theorem in its numerical form has been employed to firstly obtain bearing capacity of strip footings on top of slopes, and secondly to determine safety factor of slopes by strength reduction method subjected to repeated dynamic loads. Following a try and error procedure, factor of safety against cyclic loads were determined based on the strength reduction concept.Results indicate that bearing capacity of footings is affected by dynamic properties of both slope and the loads so that minimum bearing capacity obtained when resonant occurs. Furthermore, results show that the safety factor of slopes is extremely affected by dynamic properties of both slope and dynamic load as well.The minimum factor of safety was found to arise at resonance. Besides, findings suggest that unlike Pseudo-Static method that does not differentiate between embankments (with wide crest) and slopes, here factor of safety of slope and embankment are not the same due to their difference in dominant natural period.