Journal of Seismology and Earthquake Engineering
Volume:16 Issue: 4, Winter 2014

Pipelines are often referred to as lifelines, demonstrating that they play an important role in human's life. Based on the damage mechanism, the permanent ground movements of active faults can have the most severe earthquake effects on buried pipelines. In this study, the effects due to strike-slip faulting have been investigated using 3D FEM, Winkler model and analytical method. The non-linear response of buried pipeline under fault offset is analyzed using pseudo-static approach wherein the interacting soil-pipeline systemis modeled rigorously. The paper focuses on the effects of soil and pipeline parameters on the structural response of the pipe, with particular emphasis on identifying pipeline failure. Some influential factors, such as fault-pipeline crossing angle, backfill type, burial depth, pipe diameter to thickness ratio and pipe surface characteristics are considered in the analyses in order to draw some regular conclusions. The present investigation is aimed at determining the fault displacement at which the pipelines fail for design purposes.

In this paper, the ASTER Digital elevation model (DEM) corresponding to 30× 30 m data spacing (medium resolution) is used to produce slope steepness, slope variations in the Syrian territory. The topographic slope corresponding to time-averaged shear wave velocity model (Vs30) developed by Allen and Wald [1] has been used to derive empirical formula, and then to generate base data of Vs30 map for the Syrian territory. We have found that the values of Vs30 vary between Vs30 180 to 760 m/s and fit the geological and topographic setting of Syria. Site-specific amplification factors (Fa and Fv) maps have been estimated with respect to the empirical equations proposed by Borcherdt [2] . The value of short-period amplification factor Fa varies from 0.91 to 1.85, while the value of mid-period Fv lies in the range 1.16 - 3.15. Comparing the estimated values of amplification factors for the Syrian territory shows a good similarity to those assigned in IBC-2006 for the same site-class. The acceleration-independent amplification factor F found to be changing from 1.38 to 5.83. The reclassified amplification factor F map shows clearly the areas with high potential for amplifying ground motion. The obtained maps are highly required by the Syrian anti-seismic design code. These maps have stored numerically with a resolution of 30× 30 m. The results show that the slope angle-velocity model is an applicable technique for estimating seismic surface shear wave velocity (Vs30 ). Image processing and remote sensing data, as well as digital elevation model can be used successfully to derive amplification maps.

The present paper is an attempt to quantify probabilistic seismic demand of three-dimensional structures under two-component (vector-valued) ground motions, focusing on the collapse region of nonlinear response. While utilizing results of de-aggregated vector-valued probabilistic seismic hazard analysis (V-PSHA) as the seismic demand input, the assessment procedure is essentially based on results of nonlinear incremental dynamic analysis (IDA) of the three-dimensional (3D) model of the structure. Response of the structure is formulated based on the SRSS combination of the structure maximum inter-story drifts in plan orthogonal directions assuming log-normal distribution of the demands. The efficiency of the proposed procedure is demonstrated via a detailed step-by-step example with different period of vibrations and structural properties in orthogonal directions, which proves the adequacy of the method for practical vector-valued probabilistic seismic evaluation of regular and irregular structures.

With the aim of providing a tool for comprehensive seismic analyses of damaged steel moment resisting frames, this paper presents the development of a structural model that is able to describe the general behavior of damaged steel structures under repeated earthquakes. A regular 3D special steel moment frame designed using AISC 360-10 have been modeled to evaluate the effects of mainshockaftershock sequences on seismic behavior of structures. At first, rotations of each plastic hinge of the structure were determined under a set of records by the nonlinear dynamic analysis. Next, based on the deformation of hinges under main-shocks, suitable damaged hinges were assigned to each hinge. At last, again, the nonlinear time history analyses were carried out to evaluate the performance of damaged steel moment frame structures under repeated earthquakes. It seems that the effects of cumulative damage in Damaged Modified Method did not trigger special floors. The results have shown the importance of considering the effects of mainshock-aftershock sequences in design codes. Finally, the response of the structure computed by Damaged Modified Hinges method was compared with repeated method that is common in evaluation and vulnerability of structures under seismic sequences. Besides, it is shown that considering the initial damage in element behaviors could change the structural mechanism.

This paper presents experimental and analytical results of in-plane behaviour of confined URM walls retrofitted using steel-fiber and polypropylene shotcrete. In this paper, the experimental programconsists of testing three CURMwalls. The first specimen wall was tested as a reference wall without any retrofitting. The second and third specimens were retrofitted by using a 50 mmthick layer of steel-fiber and polypropylene-fiber shotcrete on one side in order to compare the behavior of them. The stiffness, shear strength, ductility, and failure mode of the wall specimens were determined and compared. The comparison of the tests results indicated that the shear capacity of the retrofitted walls with mesh-reinforced shotcrete and polypropylene shotcrete increased about 92% and 87%, respectively, compared to unretrofitted wall. Therefore, using steel-fiber was found to have considerable effect on the strength as well as the ductility of the wall compared to polypropylene. An analytical study was adapted based on micro finite element modelling to calibrate the behavior of the numerical models with the experimental walls in terms of shear capacity and cracking pattern. The analytical results showa reasonably agreement with the experimental data.

In this study, a new technique for monitoring the structural health of bridge piers, from the point of view of earthquake induced damages, was introduced and was then simulated and evaluated by the use of a scaled model of a typical bridge. This system use the detection of phase difference between two synchronous receiver nodes connected through a wireless sensor network, and is based on using an array of inexpensive high-frequency oscillator circuits (4 GHz) as wireless transmitters through placing them in some important structural positions of the bridge piers, receiving and analyzing the signals sent by these transmitters by two synchronous receiver nodes. The proposed monitoring system measures the changes in phase difference between two synchronous receiver nodes before and after induced damages (displacement or deformation). It showed an accuracy of a tenth of a millimeter in the simulations, as well as a high reliability in monitoring the structural health of bridge because it provides a real-time report of status of each transmitter (activated, deactivated, damaged). The proposed systemhas a low price compared to other SHM methods and also has a much lower volume and complexity of data processing compared with similar techniques. This study did not have any field trial, but a complete simulation by the use of an array of six transmitters (TX) and two receivers (RX) was conducted for a scaled model with six piers. Mathematical derivation, geometrical principles, signal processing and simulation details was thoroughly examined.