Alp Caner

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.

Structural Fire Safety of Circular Concrete Railroad Tunnel Linings

In many tunnel designs, lining cross section is selected based on construction requirements rather than design loads. A constant cross section is typically used along a tunnel especially for tunnels constructed by tunnel boring machines (TBMs). Factor of safety against failure is typically high at shallow depth regions of alignment. Minor repairable damage is targeted at rare events such as earthquakes, train derailments, explosions, and long-duration fires, and a reduction to service load factor of safety is applied in these types of events. The focus of this paper is to analytically investigate structural fire safety of circular tunnel linings in terms of reduction in service load safety due to time- and temperature-dependent material degradation and increase in load demand in a tunnel fire, and to develop recommendations for preliminary assessment of structural fire endurance of circular tunnel linings. Analytical methods accounting for thermal nonlinearity, material degradation, tunnel lining-ground interaction, and fire time stages are available to assess the structural fire safety of the concrete tunnel linings. Results of hydrocarbon fire tests of tunnel segments can be estimated by available analytical methods. TBM tunnels at soft soil can have a better fire performance compared to the ones located at stiff conditions with similar initial loading.

The 23 October 2011 MW7.0 Van (Eastern Turkey) Earthquake: Interpretations of Recorded Strong Ground Motions and Post-Earthquake Conditions of Nearby Structures

A major thrust-fault earthquake of MW = 7.0 occurred on 23 October 2011 at 10:41:21 UTC in the eastern Anatolian region of Turkey, severely affecting the nearby towns of Van and Erciş. In this study, a few strong-motion records from the epicentral area are analyzed in order to investigate the characteristics of the ground motions. Also reported are the post-earthquake field observations for various types of structures, such as buildings, bridges, historical structures, tunnels, and dams within the vicinity of the fault plane. The spatial distribution of damage indicates a noticeable hanging-wall effect. The special-type structures are observed to experience far less damage, as opposed to the building structures in the region pointing to the need for strict compliance to seismic building code and the corresponding construction requirements.

Evaluation of Successful Seismic Bridge Design Practice in Turkey

AbstractOn October 23, 2011, a destructive earthquake of Mw=7.1 occurred in Eastern Turkey. The event occurred on a previously unknown fault with a thrust mechanism and resulted in 604 deaths and major structural damage to the buildings. The highways at the Van earthquake zone were open to service of rescue operations, aid trucks, and regular traffic immediately after the devastating event. As a success story, the bridges closer to the fault line than the towns of Van and Ercis were observed to have minimal damage, such as minor support movements and cracks at the shear keys. Among the 14 highway bridges in the region evaluated by the authors, only two adjacent bridges, Bendimahi-II, had minor structural cracking along the column height. As expected, the bridges of concern were observed to perform in the essentially elastic state. The main focus of this study was to evaluate the seismic bridge design practice in Turkey, which resulted in a successful seismic performance of the earthquake-zone bridges. As ...

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.

Lateral Response Comparison of Unbonded Elastomeric Bearings Reinforced with Carbon Fiber Mesh and Steel

The vertical and horizontal stiffness used in design of bearings have been established in the last few decades. At the meantime, applicability of the theoretical approach developed to estimate vertical stiffness of the fiber-reinforced bearings has been verified in different academic studies. The suitability of conventional horizontal stiffness equation developed for elastomeric material, mainly for steel-reinforced elastomeric bearings, has not been tested in detail for use of fiber-reinforced elastomeric bearings. In this research, lateral response of fiber mesh-reinforced elastomeric bearings has been determined through experimental tests and the results have been compared by corresponding values pertaining to the steel-reinforced bearings. Within the test program, eight pairs of fiber mesh-reinforced bearings and eight pairs of steel-reinforced bearings are subjected to different levels of compressive stress and cyclic shear strains. Fiber-reinforced elastomeric bearings may be more favorable to be used in seismic regions due to lower horizontal stiffness that can result in mitigation of seismic forces for levels of 100% shear strain. Damping properties of these types of fiber mesh-reinforced bearings depend mostly on the selection of elastomeric material compounds. Suggestions have been made for the lateral response of fiber-reinforced elastomeric bearings. It has also been determined that the classical equation for lateral stiffness based on linear elastic behavior assumptions developed for elastomeric bearings does not always apply to the fiber-reinforced ones.

Performance of Ball Rubber Bearings in Low-Temperature Regions

This research is a complementary study to a recent experimental study on a newly developed seismic isolator called ball rubber bearing (BRB). BRB-type isolators can be easily manufactured similar to the standard elastomeric bridge bearings and can provide significant energy dissipation during an earthquake through friction provided by steel balls inside the cylindrical core. Structural response of BRBs at low temperatures has not been examined in previous research. In this research, behavior of BRBs exposed to different simulated weather conditions is tested under combined axial and cyclic lateral load. Comparison of room temperature and low-temperature test results indicates that the BRB can have slightly increased damping characteristics and horizontal stiffness in cold-weather conditions. This shift in performance has been included in the proposed design recommendations.

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...

Target damage level assessment for seismic performance evaluation of two-column reinforced concrete bridge bents

Displacement capacity verification analysis is usually used to evaluate the level of displacement at which structural elements reach their inelastic deformation capacities. In engineering practice, a modified version of displacement capacity analysis is used in the seismic performance assessment of bridge structures as an alternative to ductility and drift based approaches. In this seismic performance evaluation for a given target damage level, top bent displacement demand should not exceed a certain fraction of displacement capacity under safety evaluation earthquake level. A limited amount of study is available in the literature addressing the limiting values used in setting target damage levels. Furthermore, prediction of seismic response of structures over flexible foundations is not an easy task due to the complexities involved in the soil-structure interaction. The focus of this study is to investigate target damage levels by defining a relationship between displacement capacity to demand ratio and strain based damage levels for seismic performance assessment of two column reinforced concrete bridge bents over flexible foundations.

Stability of Bridge Piers Subjected to a Probable Flood Event Followed by a Probable Seismic Event

AbstractScour-induced reduction in bridge stability can develop vulnerabilities during a probable seismic event. This problem has been typically addressed by researchers as if these two extreme eve...