Çelik bağlantı sistemleri için yeni hibrit bir sönümleyici geliştirilmesi.

A new hybrid energy dissipation device named as “Backbone Damper” is introduced. The device assembly is composed of two main components: a viscoelastic (VE) unit and an internal displacement amplification mechanism. Energy dissipation is generated through deformations of the VE unit and friction within the mechanism. The mechanism is designed to remain elastic. The effectiveness of the device is verified through numerical simulations of tests of full-size prototypes. A comprehensive three-dimensional solid model of the device is developed to produce the parts of the assembly. The manufactured prototypes are tested under reversed sinusoidal cycles of displacement inputs over a range of frequencies and displacements. The test results evidence a promising device with significant energy dissipation capacity and stable behavior. Prototype tests are used to monitor the device response under different dynamic motions to quantify the design parameters of expected prevalent effect on the Backbone damper performance. vi The device demonstrates a stable hysteretic performance, satisfactory energy dissipation capacity and no damage after 100 cycles of reversed loading. Neither strength nor stiffness degradation are observed in the device performance. Numerical simulations are performed to monitor some of the parameters that are not measured during tests. To this aim, detailed three-dimensional numerical models of a prototype are developed in ABAQUS finite element analysis software. The numerical model is verified against the test results of the device. The test results are also studied to analyze the device behavior and provide estimates for the upper and lower bound values of device modelling parameters. Finally, the response of five buildings equipped with Backbone dampers under an ensemble of strong ground motions is analyzed. A significant improvement of structural response is recorded. The final aim and contribution of the research can be divided in three modules: (1) introduction of a new patented passive energy dissipation device; (2) assessment of its performance and (3) setting design parameters to control its response.Ph.D. - Doctoral Progra

Merkezleme Özelliği Olan Yenilikçi Bir Sönüm Cihazının Deneysel İncelenmesi

Patent başvurusu yapılmış olan merkezleme özelliğine sahip yenilikçi bir sönüm cihazı deneysel olarak incelenecektir. Geliştirilen sönümleyici cihaz birden fazla yararlı ve yenilikçi özelliğe sahiptir: içerdiği büyütücü mekanizma ile artan verim, merkezleme özelliği, sönüm ve rijitlik arasındaki hassas dengenin pratik bir yöntemle ayarlanabilmesi (dolayısıyla artan verimlilik), maliyet verimliliği, uygulama kolaylığı. Bu özellikleriyle, geliştirilen cihaz mevcut sönümleyici teknolojilerinin bir adım önüne geçerek yenilikçi bir çözüm ve pratik bir uygulama sunmaktadır. Proje kapsamında, geliştirilen bu cihazın özelliklerinin ve sağladığı yararın deneysel çalışmalar sonucunda belirlenmesi öngörülmktedir. Deneyler için Orta Doğu Teknik Üniversitesi İnşaat Mühendisliği Bölümü Yapı Mekaniği Laboratuvarındaki mevcut düzenek ve teçhizatlar kullanılacaktır

Prototype Testing of a New Passive Energy Dissipation Device for Seismic Retrofit of Bridges

The increasingly demanding performance requirements trigger the development of new devices to eliminate the limitations concerning the post-earthquake performance of available seismic protection systems. The prerequisite for economical earthquake-resistant bridges is the structures’ capacity to absorb and dissipate a large amount of seismic energy. A widely considered strategy for enhancing this capacity is through the use of passive energy dissipation systems for seismic protection of structures. It has been known that majority of the available energy dissipation systems are non-usable after a major earthquake, which increases the risk of collapse during an aftershock. The focus of the current study is given to introduce a new type of passive energy dissipation device with a pending patent that is testified to have an improved energy dissipation capacity without suffering any damage while absorbing energy. Thus, the proposed damper does not require an immediate expensive replacement and keeps its operational capabilities and effectiveness during aftershocks. The paper presents the dynamic performance tests of the first full-scale prototype of the damper that eventually prove it to be a promising design with an improved energy dissipation capacity and stable behavior during and after the dynamic event

SEISMIC RETROFIT OF OLD BRIDGES WITH SEISMIC ISOLATION

A standard highway bridge has usually multi simple spans supported over piers by elastomeric bearings in Turkey. The bearings usually do not provide a positive connection but in contact with girder and pier by only gravitational forces. In this study, a model test bridge of about ½ scale have been shaken under low to moderate earth quakes to determine the change in response of the bridge with different seismic isolation configurations. Three configurations of bearings are elastomeric bearings, lead core bearings and ball rubber bearings. The bridges supported with lead rubber or ball rubber bearings’ deck displacements are dampened out in a short period of time compared to the tests of bridges with elastomeric bearings as expected. The seismic retrofit goals can be defined for the old bridges based on the target structural response in terms of displacements and force

Seismic retrofit of buildings with backbone dampers

Dampers have been effectively used in new designs and seismic retrofit of old structures in many parts of the world. The common seismic retrofit practice in Turkey is almost purely based on stiffening the structure with additional shear walls or adding braces to limit the excessive seismic drifts. Such an approach usually results in expensive interior works and enlargements of foundations. The stiffening of the structure typically results in attracting more seismic force. Utilization of dampers as seismic protection devices have not been so much popular in Turkey and have been considered to be used only in some few retrofits. However, use of seismic protection devices can significantly improve the structural response and reuse of the structure after the earthquake. A new type of damper system called backbone damper has been recently developed and tested at the laboratories of METU. The results of more than 1000 tests indicated that the response of backbone damper is stable under the same conditions and more than 20% damping can be achieved at story drifts of 10-20 mm of movements. The harmonic motion test speeds reached up to 400 mm/sec in some cases and a maximum frequency of 7 Hz is achieved during some tests. It shall be noted that the backbone damper has an internal displacement amplifier that helps the system to damp even at small movements. The dampers do not get damage at the end of tests and has the ability to re-center themselves. The solid model of the damper has been prepared using the ABAQUS software. The focus of the paper will be given to application of this new damper system to improve the seismic response of the existing structures. In this scope, one typical hospital building with different selection of damper performance has been investigated in the case study. Three ground motions have been applied to the structures with and without dampers. The ground motion records are scaled to have a equivalent design response spectrum curve. The results of non-linear time history analysis performed in LARSA 4D have indicated that the seismic response of the structures can be improved significantly in terms of displacments

Vehicle effects on seismic response of a simple-span bridge during shake tests

Presence of vehicles on a bridge has been observed many times during past earthquakes. Although in practice, the engineers may or may not include the live load contribution to seismic weight in design, current bridge design codes do not specify a certain guideline. A very limited research has been conducted to address this issue from design point of view. The focus of this research is to experimentally assess the effect of a vehicle on the seismic response of a bridge through a large-scale model. In this scope, a 12-meter long bridge, having a one lane deck with concrete slab on steel girders, has been shaken under five different ground motions obtained from recent earthquakes that occurred in Turkey, in its transverse direction, both with and without a vehicle on top of the deck. The measured results have indicated that top slab transverse acceleration and bearing displacements can reduce up to 18.7% in presence of a vehicle during seismic tests, which is an indication of reduction in substructure forces. The main reason for the reduction in seismic response of the bridge in the presence of live load can be ascribed to the increase in damping of the system due to mass damper-like action induced by the vehicle. This beneficial effect cannot be observed in vertical seismic response. Copyright (c) 2014 John Wiley & Sons, Ltd

Seismic resilience of interdependent built environment for integrating structural health monitoring and emerging technologies in decision-making

The functionality of interdependent infrastructure and resilience to seismic hazards have become a topic of importance across the world. The ability to optimize an engineered solution and support informed decisionmaking is highly dependent on the availability of comprehensive datasets and requires substantial effort to ingest into community-scale models. In this paper, a comprehensive seismic resilience modeling methodology is developed, with detailed multi-disciplinary datasets, and is explored using the state-of-the-science algorithms within the Interdependent Networked Community Resilience Modeling Environment (IN-CORE). The methodology includes a six-step chained/linked process consists of 1) community data and information, 2) spatial seismic hazard analysis using next-generation attenuation, 3) interdependent community model development, 4) physical damage and functionality analysis, 5) socio-economic impact analysis and 6) structural health monitoring (SHM) and emerging technologies (ET). An illustrative case study is presented to demonstrate the seismic functionality and resilience assessment of Shelby County in Memphis, Tennessee, in the United States. From the results discussion, it is then concluded that data from structural health monitoring and emerging technologies is a viable approach to enhance characterising the seismic hazard resilience of infrastructure, enabling rapid and in-depth understanding of structural behaviour in emergency situations. Moreover, considering the momentum of the digitalization era, setting a holistic framework on resilience, which includes SHM and ET, will allow reducing uncertainties that still a challenge to quantify and propagate, supported by sequential updating techniques from Bayesian statistics