Interaction of soil static and dynamic stiffness and buried pipeline under harmonic vibration

Problem statement: When earthquake is occur, many damages were occurred in pipelines that San Francisco (1906) and Manson (1908), Kobe (Japan) and ate are samples of this topic. So many researchers studied on the pipelines and dynamic forces. Approach: Determine static and dynamic performance parameters of the pipeline and the surrounding soil such as static stiffness, dynamic stiffness, damping and additional mass share of soil which take part with pipe mass in dynamic performance. In the static case relationship between friction forces and joint deflections in a buried element pipe had be calculated and with using of some experimental results and results are compared together. For dynamic cases, Dynamic equilibrium equation of pipeline element axial vibration in continuous system, with neglecting the effect of soil mass share which participates in producing vibration and with considering of it were abstained and values of displacement and forces were calculated. In continuous, these formulations were process for many cases and were drawn in graphs for comparison. Results: Stiffness for ω/ωn1, the ratio of dynamic to static stiffness rises rapidly and by increasing the additional mass, the value of dynamic stiffness in case of ω/ωn>1 would increase highly. Conclusion: The static performance between soil and pipe is nonlinear in axial direction and when the hysteric dominates grows, the value of force dominates between soil and pipe and dynamic stiffness would ascend. Also by increasing damping ratio, the dynamic stiffness would increase too however it depends on the static to dynamic stiffness ratio and the damping ratio

The Dynamic Behavior of a Network of Pipelines and Liquefaction of Soil Caused by the Earthquake Acceleration

Risk analysis pipelines in the quake as one of the most vital arteries in the current circumstances in the world is of special importance. in our everyday activities, used to underground structures such as pipes, tunnels, wells and so on for services such as transporting water, transportation, irrigation, drainage, sewage disposal, transporting oil and gas, carrying acid waste, industrial, household and so on. With regard to the huge investments structures, especially buried underground pipes, we need to study these constructs in response to the earthquake, is clearly felt. Pipelines used for transporting gas and other fluids, are widely distributed in all areas. These lines due to passing through the densely populated areas are always buried in the earth. Seismic behavior of these pipes as a result of the interaction between the soil and the pipe is different from the above-ground structures. The manner of modelling of the effects of soil liquefaction on the pipes in this thesis is that two shear springs and a normal spring is defined between soil and the pipe that in liquefaction mode minimize the friction shear strength

Probabilistic evaluation of seismic vulnerability of multi-span ‎bridges in north of Iran

Bridges are known as the most susceptible components of any and transportation system. That is why before the earthquake in vulnerability assessment, to take the necessary actions. The ‎generation of vulnerability functions in the form of fragility curves is a common approach for assessing bridges ‎seismic vulnerability. The purpose of this study, Using an analytical method for the production of ‎fragility curves for a road bridge in Mazandaran Province. Since this curves used for planning before and after the ‎earthquake, and in order to increase the reliability of them, in this study we tried to use the most accurate analytical ‎methods (non-linear time history analysis) and most prestigious modeling assumptions. Due to the specific ‎characteristics of far fault earthquakes, effects of such earthquakes on bridges have been investigated using fragility ‎curves. Due to the geometry of the bridge for exact analysis, bridges was under 100 pairs of earthquake ‎records in orthogonal directions and fragility curves was drawn and then were compared. Observed that changing the diameter of the bridge piers affect how much on the. One of ‎the common simplifications used in modeling are: elimination of abutment and foundation and pile by fixing the ‎abutment and foundations in modeling. It can be seen that by eliminating this effect, increase the median values of ‎fragility and in fact to reduce probability of vulnerability in Charts. After time history analysis it was found that by ‎reducing the diameter of the piers, relative displacement (drift) in the longitudinal direction and in the transverse ‎direction increases

Dynamic Behaviour of Different Types of Cable-Stayed Bridges Due to Earthquake Loads

Construction of large-scale structures has been considered as one of the human's main achievements.  With their suitable view and high economical aspects, High-strength steel cables have been developed for analysis and erection of cable-stayed bridges in light of high speed development in computer technology. This type of bridges, while providing different behavior due to cable flexibility, has been recognized as one of the most practical choices for mid to large span bridges. This paper studies the non-linear dynamic behavior of cable bridges and the effect of some parameters (such as cable arrangement and shape of pylon) on them. For this purpose, CSI Bridge software with the direct integration method of dynamic analysis has been used and the behavior of structure under different earthquake components has been analyzed for various conditions of cable arrangements and pylon shapes. Results indicate that the most suitable behavior would be for cable bridges with H-shape pylons arranged in series and also with A-shape pylons in radial arrangement

A New Collection of Compressed Damage Indices for Multi-Damage Detection of Cold Formed Steel Shear Walls Based on Neural Network Ensembles

This study presents a methodology that utilizes a new combination of two compressed damage indices as input data of an artificial neural network (ANN) ensemble to detect multi-damages in the braces of cold formed steel (CFS) shear walls. To identify an efficient input data for ANN, first, three main groups of damage indices are considered: modal parameter-based damage indices; frequency response functions (FRFs)-based damage indices and time series -based damage indices. Furthermore, principal component analysis (PCA) technique is applied to reduce the dimensions of FRFs and time series -based input pattern. By a sensitivity study, two suitable damage indices of PCA-compressed time series dataand PCA-compressed FRFs are identified and then combined together to produce a new efficient input data for a hierarchy of ANN ensembles. The numerical results show that the ANN ensemble-based damage detection approach with the proposed collection of two damage indices is effective and reliable.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author