linear

When a critical load such as (floods, explosions, earthquakes, or fire) enters the structure, the severity of the critical load depends on the strength of the load-bearing elements of the structure, whether the structure is completely destroyed or remains intact. Or some members are out of basic mode. Progressive failure is a nonlinear phenomenon that starts from the damage of a part of the structure and ends with the entire structure and its total destruction. Progressive failure is usually in the structure due to the loss of one of the main members, a column. A column in the structure at the node where the column is removed causes a location change with a seismic nature. This change of location has occurred, and the dynamic analysis's explanation of the force caused by removing the column on other elements is desired. It is checked that the side columns of the removed column can bear the explained load, or after explaining the load on the columns, they are destroyed due to buckling and breakage. This study uses the Alternative Path (AP) method, independent of the failure factor proposed by GSA and DoD. Nonlinear dynamic analysis is also used. Two types of column removal scenarios have been used. Since the AP method is independent of the failure factor, two concentrated loads with a very large size and opposite direction (more than the capacity of the column) are instantly entered into the ground floor column (shearing the column) and cause column failure. The research was conducted in three models on the 5, 10, and 15 floors, and the results are discussed.

In this paper, an explicit family with higher-order of accuracy is proposed for dynamic analysis of structural and mechanical systems. By expanding the analytical amplification matrix into Taylor series, the Runge-Kutta family with  stages can be presented. The required coefficients ( ) for different stages are calculated through a solution of nonlinear algebraic equations. The contribution of the new family is the equality between its accuracy order, and the number of stages used in a single time step ( ). As a weak point, the stability of the proposed family is conditional, so that the stability domain for each of the first three orders ( 5, 6, and 7) is smaller than that for the classic fourth-order Runge-Kutta method. However, as a positive point, the accuracy of the family boosts as the order of the family increases. As another positive point, any arbitrary order of the family can be easily achieved by solving the nonlinear algebraic equations. The robustness and ability of the authors’ schemes are illustrated over several useful time integration methods, such as Newmark linear acceleration, generalized-𝛼, and explicit and implicit Runge-Kutta methods. Moreover, various numerical experiments are utilized to show higher performances of the explicit family over the other methods in accuracy and computation time. The results demonstrate the capability of the new family in analyzing nonlinear systems with many degrees of freedom. Further to this, the proposed family achieves accurate results in analyzing tall building structures, even if the structures are under realistic loads, such as ground motion loads.

The present paper deals with the behavior of reinforced concrete beams in presence of plasticity and cyclic loadings. The model takes into account the nonlinear material behaviors of the constituents steel and concrete. A numerical model based on the finite element method is investigated for the study of the reinforced concrete beams under cyclic loads undergoing large deformation in the plastic range. In the study, nonlinear material behavior laws are introduced in presence of plasticity and cyclic behavior in the concrete in compression and in the reinforcement steel bars under tension stresses. The concrete steel interactions as well as the crack damage are also considered in the model. An incremental iterative method in adopted in the solution of the equilibrium equations. The model is validated and compared to some benchmark solutions available in literature. The agreement is good in the case of beams under monotonic loads or cyclic loads with high cycles.

The reinforced concrete (RC) moment-resisting frames with masonry infill walls is widely used in buildings. In this study, two-bay and three-storey RC Bare Frame (BF), RC Infill frame (IF) with Cement mortar (CM) interface combinations scaled to a factor (1:6) are analyzed. The objective is achieved by analytical studies. To investigate this, we modelled the behavior of frame structures with masonry IF in two ways such as a linear method and Pushover (PO) method. It is found that with the addition of masonry infill wall rigidly connected to the frame, the lateral strength, the stiffness of the BF RC frame increase significantly while the displacement ductility ratio decreases significantly. Numerical simulation of the BF and the IF frames is done with SAP2000 (Structural Analysis Package) a Finite Element Method (FEM) based software.

Comprehensive computational analysis was made for modelling the integrated hydrologic–hydraulics characteristics of varied unsteady flow in hydraulic structures as part of water engineering practices and river basin management. Several numerical skills, linear, non-linear, implicit, explicit methods were developed and tested with existing river analysis software of Danish Hydraulic Institute (DHI) and Hydrologic Engineering Centre (HEC) series models. Coupled hydrological and hydraulics analysis of storming run-off flows in broad waterway boundaries including flood plains of compound sections was performed. Application of models was encouraging, the complex water conveyance systems that transported lateral flows in natural rivers were modelled satisfactorily. Storming flow events in real rivers were coded and compared through different numeral techniques such as method of characteristics, Mac-Cormack, diffusive numeral model and Preissmann fully implicit model. Predicted results were close to observed values verified and confirmed the hand-written codes and programs in MATLAB environment. Enhanced modelling skills were justified by (HEC) series and Mike series computer software. Merits of this research were seen based on: numerical accuracy, consistency, stability and convergence results to observed targets.

The AASHTO code of practice for design of bridges shows that the ductility level for foundation is given equal to one. Bridges are classified in three classes. For class of essential and normal bridges a question for not to use ductility level due to the importance of bridges’ costs is become an important item in different countries particularly in Middle east.
This paper aimed to study on performance of bridges based on the effect of soil non-linear behavior. A comparison between Finite Difference (F.D), Finite Element (F.E) methods and close form solutions has been carried out on single and group piles under lateral loads in multilayered soils. Winkler model with non-linear springs, FLAC-3D, ANSYS5.4 and ABAQUS software were used for verifications. The Lagrangian method was considered in FLAC-3D and the Drucker-Prager was used in ANSYS. Pile behavior in sandy soils, uniform clayey soils, clayey deposits including sandy lenses, and Sand deposits with thin clay layers were analyzed. Verification between traditional close form solution methods with those analysis methods were carried out.
Results show the effectiveness of foundation ductility in compare with the expected ductility levels and structural performance for superstructure. The ductility level of substructure due to the pile soil interaction has found equal to 3.5 to 4.5 for different soil types. It show in “Pile and Deck (pier shaft)” model in bridges for the normal and essential bridges classes the use of ductility should be taken into account in accordance with soil-structure performance.
In conclusion the paper shows that for the pier shaft system it would be possible to use ductility level for foundations for normal and essential class of bridges and for those countries that they use the structural ductility for design of all components of structure including piles, the level of performance should be precisely investigated and using of structural ductility level is under question for design of pier shaft models.