Eren Uckan

Stability of locking and conventional 2.0-mm miniplate/screw systems after sagittal split ramus osteotomy: finite element analysis.

OBJECTIVE The aim of this study was to evaluate the mechanical stresses over the bone and hardware after sagittal split ramus osteotomy (SSRO) fixed with standard titanium or locking plate/screws using finite element analysis. STUDY DESIGN A 3-dimensional finite element model of the mandible was created, and SSRO and 5 mm advancement was simulated on a computer model. The model was fixed with either 2.0-mm titanium conventional miniplate/screw or 2.0-mm titanium locking miniplate/screw system, and oblique 200 N bite force was applied. RESULTS The values of von Mises stresses in the cortical layer of the distal segment using the locking plate system was higher. However, in the cortical layer of the proximal segment the stresses were higher at conventional plate system. In the spongiosa layers of both segments, stresses were higher with the conventional plate system. CONCLUSION The locking miniplate/screw system spreads the load over the plate and screws and diminishes the amount of force transfered to each unit.

Seismic vulnerability mitigation of liquefied gas tanks using concave sliding bearings

The aim of this paper is to evaluate the effectiveness of a concave sliding bearing system for the seismic protection of liquefied gas storage tanks through a seismic fragility analysis. An emblematic case study of elevated steel storage tanks, which collapsed during the 1999 İzmit earthquake at Habas Pharmaceutics plant in Turkey, is studied. Firstly, a fragility analysis is conducted for the examined tank based on a lumped-mass stick model, where the nonlinear shear behaviour of support columns is taken into account by using a phenomenological model. Fragility curves in terms of an efficient intensity measure for different failure modes of structural components demonstrate the inevitable collapse of the tank mainly due to insufficient shear strength of the support columns. A seismic isolation system based on concave sliding bearings, which has been demonstrated a superior solution to seismically protect elevated tanks, is then designed and introduced into the numerical model, accounting for its non-linear behaviour. Finally, a vulnerability analysis for the isolated tank is performed, which proves a high effectiveness of the isolation system in reducing the probability of failure within an expected range of earthquake intensity levels.

Towards Robust Fragility Relations for Buried Segmented Pipe in Ground Strain Areas

Seismic fragility relations of buried segmented pipelines are currently defined in terms of pipe repairs per unit length as a function of some measure of ground shaking or ground movement. In some current relations, both wave propagation (WP) and permanent ground deformation (PGD) damage are addressed by combining the hazard into a measure of ground strain. One troubling aspect of these fragility relations is that each new event seems to provide new data that in some cases, are significantly different from existing relations. Herein, we investigate the robustness of these expressions by using new data from the 1999 M = 7.4 Turkey earthquake. A methodology is presented to calculate ground strains, by considering relative PGD along the axis of the pipeline. Results indicate that, for the strain/damage range of interest, a linear function (on a log-log scale) provides a relatively robust fragility relation for buried segmented pipes.

A Study of the Response of the Mustafa Inan Viaduct to the Kocaeli Earthquake

During the 17 August 1999 Kocaeli earthquake in Turkey, some of the viaducts and overpasses located on the Trans European Motorway (TEM) incurred various types of damage. The Mustafa Inan (M. Inan) viaduct, which consists of 10 equally spaced, 40-m-long, simply supported cell box girders, was damaged at seismic buffer stops located at the second longest pier in the central span. The objective of this work is to assess the performance of the M. Inan viaduct in the Kocaeli earthquake by conducting both experimental and numerical studies. The epicenter of the earthquake was 5 km south of the site, and the nearest available ground-motion record was at a distance of 2 km. The records inherit typically near-fault characteristics with a displacement offset in the fault-parallel direction and an enhanced low-frequency velocity in the fault-normal direction. Ambient vibration tests were conducted before the earthquake to measure the dynamic characteristics of the structure and calibrate the finite-element (FE) model. The measurements indicated that the viaduct exhibits three different dynamic behaviors in three different frequency bands. In the low-frequency band of 0-1 Hz, the structural response of the piers was of major concern, and its influence was seen at the base moment and shear forces of the piers. In the intermediate frequency band of 1-2 Hz, the girders demonstrated pull-off and drop-collapse problems due to the out-of-phase movement of the central and side piers. In the high-frequency band of 3-5 Hz, the vibratory response of the elastomeric bearings appears to be more critical. The earthquake response of the bridge was modeled using a verified FE software, LUSAS version 13.2. The linear FE analysis revealed that shorter side piers sustain larger moment and shear forces than the longer middle piers. The snap-through behavior of the longer piers increases the second-order effects, whose influence was investigated using geometric nonlinear analysis. The results show a significant increase in forces of the longer middle piers in comparison with those of linear analysis. Manuscript received 15 September 2000.

Lifeline Damage Caused In the 23 October (Mw=7.2) 2011 and 9 November (M=5.6) 2011, Van Earthquakes in Eastern Turkey

On October 23 th and November 9 th , 2011, the province of Van in Eastern Turkey was hit by two earthquakes (Mw=7.2 and M=5.6) causing damage in buildings, industrial structures and utilities damages in Van and Ercis, with nearly 700 fatalities. This paper provides a brief overview of these damages through field observations. Observed pipe breaks due to permanent ground deformations (PGD) and wave propagation (WP) effects are quantified. Comparisons are given for the estimated vs. observed repair rates for segmented and continuous pipes as per relevant codes. Results reveal that the code based repair rate formulation for buried segmented and continuous pipes is compatible with the observations.

Performance-Based Design of Buried Steel Pipes at Fault Crossings

Buried steel pipes are commonly used in oil and gas industry for transmitting hydrocarbon products. Fault crossing is considered as one of the most important extreme events. Buried steel pipes are more vulnerable to compressive strains as compared to tensile strains. Therefore, the orientation angle of the pipe with respect to the fault should be arranged in such a way so as to promote net tension in the pipe.In this study, a numerical study is carried out on a simplified numerical model to determine the seismic demand on steel pipes at fault crossings. The proposed model permits plastic hinge formation in the pipe due to incrementally applied fault movements, allow determining the critical length of the pipeline and measure strains developed on the tension and compression sides in the pipe. Based on the analyses carried out on the simple model and previous studies, two performance levels are defined for pipelines; namely, fully functional and partially functional.Copyright

Earthquake Damage and Fragilities of Industrial Facilities

An industrial facility consists of many integrated components and processes. As such, operation of a facility depends upon the performance of its critical components. The greatest risk from an earthquake is that to life safety. However, in large earthquakes, industrial buildings and related machinery and equipment damaged may be costly to repair and there may be additional damage from fire and chemical spills. As such, the design (or seismic retrofit) of industrial facilities should preferably be based on performance-based methodologies with the objective of controlling structural and non-structural damage and the triggered technological disasters. In this paper industrial damages and losses that took place in past important earthquakes, especially in the 1999 Kocaeli earthquake, will be summarized. A general description of industrial-sector and component based earthquake performance and vulnerabilities will be provided.

Performance-Based Evaluation of Hydrocarbon Steel Pipes Under Internal Pressure

Hydrocarbon steel pipes have undertaken a very important and fundamental role in the oil and gas industries in the world. Although these pipes are simple structural forms, their structural behaviors are very complex and challenging for the structural engineering community. One of the fundamental problems for pipelines is plastic deformations under internal pressure. This study focuses on to develop a methodology for the performance evaluation of hydrocarbon steel pipes under internal pressure. In this perspective, a hydrocarbon pipe, which is used in natural gas pipelines, is modeled by nonlinear finite element model (FEM) and investigated in terms of structural behavior under different internal pressure conditions; operating pressure (100 bar), design pressure (150 bar) and high pressure (250 bar). In order to obtain an accurate solution, the finite element model is calibrated with a hydrostatic test, which is conducted on a pipe under 133 bar.

Optimal Passive Control of Adjacent Structures Using Viscous Devices

This paper investigates the optimal vibration control of two adjacent shear beam structures coupled with horizontally oriented viscous dampers. A design methodology that is valid for two-degrees of freedom models is extended to account for multi degree of freedom structures. The response of the coupled model due to linearly filtered white noise base motions is calculated and the effectiveness of the proposed methodology is validated by performing a parametric study. The optimal response of the structures with different coupling locations along the height and damping coefficients, are considered.Copyright

Earthquake protection of liquid storage tanks by sliding isolation bearings

Liquid storage tanks are critical components of industrial facilities since damage to such structures may cause spreading of hazardous material and environmental pollution. Tanks exhibit mainly two different seismic behaviors one of which is the long period movements due to sloshing of the liquid and the other is the impulsive vibrations generated as a result of the fluid structure interaction phenomena at higher frequencies. The overall base shear is the combination of these two loads. The seismic base isolation aims to control the impulsive load as it has appreciable amount of contribution to the base shear values. Among various types, the curved surface sliding bearings (FPS) are commonly used in liquid tanks since provide isolation periods which is independent of the tank weight (liquid height).In this paper a parametric analysis has been performed to investigate the efficiency of FPS bearings. The numerical model is based on the Haroun and Housner’s simplified lumped parameter model in which the sloshing and fluid-tank interactions are modeled by convective and impulsive masses, respectively. The effectiveness of the isolation system was investigated under a series of ground motions, isolation periods and tank aspect (slenderness) ratios. Results indicated that depending on the characteristics of the ground motion, the response of the isolated tank can be reduced in appreciable amounts as compared to the conventionally constructed one. On the other hand, some detrimental effects were also observed in lower isolation periods (Tb=2s) particularly in medium slender tanks under near fault ground motions. This undesirable situation was avoided by using higher isolation periods (Tb =3s) without much affecting the bearing displacements.Copyright