Özgür Avşar

Analytical Fragility Curves for Ordinary Highway Bridges in Turkey

This study focuses on the development of analytical fragility curves for the ordinary highway bridges constructed after the 1990s. Four major bridge classes were employed based on skew angle, number of columns per bent, and span number (only multispan bridges). Nonlinear response-history analyses (NRHA) were conducted for each bridge sample using a detailed 3-D analytical model subjected to earthquake ground motions of varying seismic intensities. A component-based approach that uses several engineering demand parameters was employed to determine the seismic response of critical bridge components. Corresponding damage limit states were defined either in terms of member capacities or excessive bearing displacements. Lognormal fragility curves were obtained by curve fitting the point estimates of the probability of exceeding each specified damage limit state for each major bridge class. Bridges with larger skew angles or single-column bents were found to be the most seismically vulnerable.

Identifying Bridge Rehabilitation Needs Using an Analytical Method Developed for Interpretation of Visual Inspection Data

Bridge management systems generally rely on the accurate interpretation of findings determined from planned bridge inspections. Bridge inspections typically focus on the overall condition of the bridge and the condition of its components. During a recent bridge in- spection with multinational team, it was observed that the overall grade of a bridge could be significantly high, even though it contains one or more failing subcomponents. Over the years, it has been observed that failure of a deteriorated component could result in catastrophic failure of bridges. The focus of this paper is to develop an analytical method to interpret the bridge inspection data in such a way that failing components can be identified with reasonable accuracy for a bridge with a good inspection grade in general. The proposed mathematical model can be used in bridge management systems and in maintenance programs for bridge owners to identify immediate rehabilitation needs. DOI: 10.1061/(ASCE)CF.1943-5509.0000233.

Structural damages of the May 19, 2011, Kütahya–Simav earthquake in Turkey

Reconnaissance observations are presented on the building damage caused by the May 19, 2011, Kütahya–Simav earthquake in Western Turkey as well as an overview of strong ground motion data recorded during the earthquake is given. According to Disaster and Emergency Management Presidency of Turkey, the magnitude of the earthquake is 5.7 in local magnitude scale. Although the earthquake can be regarded as a moderate event when considering its magnitude and strong motion recordings, it caused excessive structural damage to buildings in Simav district and several villages in the near vicinity. During the field investigation, different types of structural damage were observed mainly in the reinforced concrete frame buildings with infill walls and masonry buildings with various types of construction materials. Observed damage resulted from several deficiencies in structural and non-structural components of the buildings. Poor construction materials and workmanship, non-conforming earthquake-resistant design and construction techniques and non-ductile detailing are the main reasons for such an extensive damage, as observed in many past earthquakes in Turkey.

Retrofit of non-seismically designed beam-column joints by post-tensioned superelastic shape memory alloy bars

A series of tests on three full-scale substandard exterior beam-column joints were performed to investigate the efficiency of the proposed retrofit configuration, which is the use of externally applied post-tensioned shape memory alloy (SMA) bars. A major group of structural deficiencies resulting from lack of shear reinforcement in the joint, use of low strength concrete and plain round bars were taken into account in the construction of test specimens. While the reference specimen represents the as-built subassembly, the other two were retrofitted by the post-tensioned SMA and steel bars to compare the contribution of superelastic and conventional material on the response. The specimens were exposed to quasi-static cyclic loading up to 8% drift ratio to simulate an intensive level of seismic hazard. The reference specimen underwent a brittle shear failure as excessive cracks mostly concentrated in the joint panel while there was almost no damage in the rest of the RC components. A joint failure with enhanced response quantities was observed in the specimen retrofitted by post-tensioned steel bars. The specimen incorporating the retrofit solution via post-tensioned SMA bars was capable of performing an adequate performance and promoting minimization of the damage in the joint panel, which results in more ductile behavior. The hysteretic response of the SMA retrofitted specimen was validated with a refined numerical model in ATENA Science software. Experimentally observed response was also verified by an analytical model based on fracture mechanics considering the nonlinear behavior of plain concrete under tension. Due to inherent uncertainties in material constitutive laws, the analytical model was evolved to a stochastic level to propose a more advanced model for estimating the capacity of the reference and retrofitted joint. It is found that the experimental results were within the prominent range of Probability Density Functions (i.e. mean ± 1 SD) of the estimated joint tensile stress especially for the shear damaged specimens.

In-Depth Investigation of Seismic Vulnerability of an Aging River Bridge Exposed to Scour

AbstractThe stability and structural performance of aged structures under extreme events are rarely investigated. The severe deterioration in current condition of aged bridges can trigger premature...

Influence of Structural Walls on the Seismic Performance of RC Buildings during the May 19, 2011 Simav Earthquake in Turkey

AbstractReinforced concrete (RC) buildings having the adequate amount of structural wall area with a symmetrical arrangement have been proven to have a satisfactory seismic performance in past earthquakes. Properly constructed structural walls can even eliminate the poor seismic response of RC buildings due to the adverse effect of structural irregularities or deficiencies such as soft story, short column, insufficient confinement, poor detailing in beam-column joints, poor material quality, etc. The positive effect of structural walls was observed by comparing the performance of two RC buildings, which were affected by the May 19, 2011 Simav earthquake in Turkey. Although one of the buildings with no structural wall collapsed, the building with structural walls survived without any structural damage. Analytical models of the two buildings were developed to investigate the influence of structural walls on the seismic performance of RC buildings by conducting response history and pushover analyses. Results...

Application of Different Rehabilitation and Strengthening Methods for Insufficient RC Beam-Column Joints

Earthquake is one of the most destructive natural disasters that cause loss of life and property in the earthquake prone regions. Unsuitable soil conditions, inadequate material properties and deficiencies in the structural system can lead to costly seismic damages to structures. In this study, damages caused by the earthquake were examined for reinforced concrete beam-column joints. The most common damage type observed in earthquakes is the beam-column joint damage that decreases the lateral load bearing capacity and might be the reason for total collapse of structures. Weak bonding between concrete and reinforcing bars, absence of transverse reinforcement and incapable shear strength of RC beam-column joint are the most common causes for RC beam-column joint damage. After numerous experimental works, different strengthening methods were developed in literature. This paper discusses various strengthening methods including conventional and new techniques as well as their technological application details and the issues arise in practice

A Conceptual Design of a Cable Stayed Bridge with a Curved Back Span

The existing Komurhan Bridge was built over the dam reservoir prior to water storage. The aging segmental post-tensioned concrete bridge with two lanes had an active sagging problem at its mid-span. As the traffic demand increased over the years, the authorities decided to add two more lanes to have a twin two-lane road for this part of highway network. Therefore, a need was developed to build a new bridge. Unlike the existing one, the suggested crossing needed to pass 300 meters wide water body with a depth of 45 meters to avoid piers at water body. Couple of alternatives was considered to cross the deep water at conceptual design phase. The focus of this study is given to the conceptual design of a cable-stayed bridge with two towers crossing the water at the narrowest location. This option results in a curved back span at one side of the water. A three-dimensional computer model was developed to assess challenges in design. Special care is given to the design details of the cables and the superstructure. Even if one of the back spans is curved, the proposed conceptual cable-stay bridge design is satisfactory under service and earthquake loads.