Ahmet Turer

Seismic Resistance Evaluation of Traditional Ottoman Timber-Frame Hımış Houses: Frame Loadings and Material Tests

Traditional Ottoman timber-frame houses (“hımış”) form the major part of the cultural heritage structures in Turkey. There are many studies in the literature regarding the seismic performance of hımış houses, which claim that these structures have an inherent seismically resistant property. However, these studies lack a quantitative engineering approach and are based on observations made after contemporary earthquakes. This study presents the results of the seismic resistance evaluation of traditional Ottoman houses, made by means of reverse cyclic frame tests conducted on six yellow pine and two fir frames with and without infill (brick and adobe) or cladding (bağdadi and şamdolma). The experimental study, which was intended to differentiate the effects of infill materials, frame geometry, and timber type, has revealed that frames with bağdadi cladding and adobe infill resulted in the best and worst structural performances, respectively, while high ductility and good energy dissipation capacity characteristics were determined.

ISSUES IN SUPERLOAD CROSSING OF THREE STEEL STRINGER BRIDGES IN TOLEDO, OHIO

A 371-ton (816.7-kip) cooling unit crossed over three steel stringer bridges in Toledo, Ohio. Any bridge damage was compensated if scientifically documented. Researchers predicted the superload responses by using finite element analysis and experimental test results, and then measured the superload responses to establish whether the event caused any damage. Although the conservative results of the finite element model predicted an overbound of critical stresses, experimental results gave closer predictions of the measured response under superload. During the superload crossing, the maximum stress levels at the girders remained at about 34.5 MPa (5 ksi). The cross braces were stressed up to 68.9 MPa (10 ksi), exceeding the girder stresses. The study included questions about the real behavior versus design assumptions regarding cross braces in steel stringer bridges. (Cross braces are the weak links that fail first, causing lateral instability and failure.) Research revealed the possibility of predicting superload responses and behavior quite reliably by using a combination of diagnostic tests and finite element analysis. These tools permit the best design for superload axle configuration, crossing paths and positions on bridges, and possible options for effective bridge strengthening when needed.

Reverse-Engineering Evaluation and Monitoring of Nemrut Monuments

The focus of this study is on the Nemrut Dağ monuments, which were constructed approximately 2000 years ago at the peak of Mount Nemrut, 2206 meters elevation, are among the most valuable historical heritage sites in Turkey. Since the discovery of Nemrut monuments in 1881, many questions are unresolved, such as how the monuments were destroyed and why the damage level is very different between the symmetric east and west terraces. Natural causes, such as earthquakes, snow, or wind or manmade damages in the case of grave theft attempts with explosives or digging might have caused the damage. This study presents reversed engineering (forensic) approaches for the evaluation of different damage scenarios. The region being approximately 5 km away from East Anatolian Fault zone, the possibility of damaging earthquake occurrence in the past two millennia is quite high. Snow-load evaluations were carried out using the Swiss Guidelines for the Design of Snow Supporting Structures. The nonlinear blast-loading calculations were carried out using LS-DYNA software for the documented crater sizes located on the tumulus. Wind loading was investigated using on-site 4-year monitoring and statistical analysis. Conclusions include the results regarding the failure modes of the monuments and anastylosis/strengthening methods were discussed.

A simplified approach for slope stability analysis of uncontrolled waste dumps.

Slope stability analysis of municipal solid waste has always been problematic because of the heterogeneous nature of the waste materials. The requirement for large testing equipment in order to obtain representative samples has identified the need for simplified approaches to obtain the unit weight and shear strength parameters of the waste. In the present study, two of the most recently published approaches for determining the unit weight and shear strength parameters of the waste have been incorporated into a slope stability analysis using the Bishop method to prepare slope stability charts. The slope stability charts were prepared for uncontrolled waste dumps having no liner and leachate collection systems with pore pressure ratios of 0, 0.1, 0.2, 0.3, 0.4 and 0.5, considering the most critical slip surface passing through the toe of the slope. As the proposed slope stability charts were prepared by considering the change in unit weight as a function of height, they reflect field conditions better than accepting a constant unit weight approach in the stability analysis. They also streamline the selection of slope or height as a function of the desired factor of safety.

A Proposal for a Comprehensive Approach to Safer Non-engineered Houses

Abstract Reducing earthquake disasters in non-engineered houses is an acute issue because they are a main cause of human casualties worldwide. Since non-engineered houses differ from engineered houses in many respects, the authors conducted a comparative study and clarified the characteristics of the former. Based on this study, they found that reducing disasters in non-engineered houses would require appropriate seismic technologies to be adopted by communities and effective channels to disseminate technical knowledge. Further, a comprehensive approach covering a wider field of activity and effort was found to be necessary as users/dwellers of non-engineered houses are low/middle-income people and a professional housing supply sector usually does not exist for such houses. This paper reports on the characteristics of non-engineered houses, indicates the items to be tackled in reducing earthquake disasters in such dwellings, and proposes an approach to safer non-engineered houses consisting of key issues and a comprehensive approach.

Testing and Seismic Capacity Evaluation of a Typical Traditional Ottoman Timber Frame

In Turkey, as well as in Balkan countries, examples of an extant housing tradition namely hımış, which was formed during Ottoman period, can still be observed. In spite of minor local differences according to geographical locations, these Ottoman hımış houses are distinguished with a number of common architectural and technical peculiarities that is worth to preserve. They have similar timber frame construction system with different infill materials. There are numerous reports claiming that the hımış houses are seismically more resistant than other construction types such as reinforced concrete and/or masonry structures. However, nearly all such reports are based on observations made after historical or contemporary earthquakes and lack quantitative engineering approach. For these reasons, within the framework of an ongoing research project, supported by The Scientific and Technological Research Council of Turkey (TUBITAK), coded 106M499, the seismic resistance of traditional timber frame houses in Turkey was investigated. A number of timber frames were tested in the laboratory under cyclic and reverse lateral loading, with and without infill. The results were reproduced with pertinent analytical work. As a result, it was shown that connections that were traditionally made with the sole use of standard nails were always the location of failure. In this paper, the results obtained for one of these frames is presented together with its capacity curve analysis to see whether strengthening is needed or not from seismic design point of view.

BOND CHARACTERISTICS OF OVERLAYS PLACED OVER BRIDGE DECKS SEALED WITH HIGH-MOLECULAR-WEIGHT METHACRYLATE

The bond strength between portland cement overlays and bridge decks treated with high-molecular-weight methacrylate sealers is examined. The data universally suggest that sealers reduce the available bond strength. However, extra surface preparation techniques, such as light sandblasting of the sealed surface or broadcasting sand over the surface immediately after sealing [at approximately 1 kg/m2 (20 lb/100 ft2)], restore the strengths to 80 or 85 percent, respectively, of the unsealed surface. Service-level fatigue testing and loading well beyond the serviceability limit state do not adversely affect the bond strength so long as the sealed surface is treated before the application of the overlay. Therefore, to seal the existing cracks, bridge decks may be sealed if either of the recommended secondary surface preparation techniques is followed.

Recycling of Scrap Tires

As Rachel Louise Carson (1907-1964) successfully noted in her phrase “The human race is challenged more than ever before to demonstrate our mastery not over nature but of ourselves”, we are challenged to find ways to produce more energy, reduce our waste production while minimizing use of limited natural resources. Although recycling of materials has a history going back to the times of Plato BC400 and collecting scrap bronze & metals in Europe in pre-industrial times (Wikipedia, 2011), the demand roar for raw materials in the 19th and 20th centuries with industrial development caused cheaper alternative of reusing scrap material rather than mining them out. Interestingly, 21st century’s major driving force has additional items on top of the existing reasons of using recycled material, such as reducing consumption of limited natural resources and lowering carbon dioxide emissions against the greenhouse effect. The increasing demand for energy production and dealing with larger amounts of waste contaminating the nature, forces mankind to find innovative ways to deal with the produced pollutant waste, emit lesser amounts of CO2, and generate more energy. Recycling of scrap tires turns out to be a perfect match for the recent requirements of the 21st century. This chapter discusses various ways of recycling scrap tires and how they relate to the recent energy, material, and nature needs of our times.

HEALTH MONITORING OF IRONTON-RUSSELL BRIDGE FOR RATING PURPOSES

The Ironton-Russell truss bridge spanning the Ohio River between the cities of Ironton, Ohio, and Russell, Kentucky, consists of a three-span cantilever through truss with a suspended truss in the center span and a fourth span that is essentially a simple-span through truss. Visual inspections of this bridge revealed that recent welded repairs and modifications to various truss members reduced their fatigue classification as well as modified original design and construction details. When the visual inspection team identified these details along with section loss at certain truss verticals and diagonals, it was their recommendation to reduce the allowable load on the bridge from 208 260 to 26 700 N (23.4 to 3 tons). However, a 26 700-N (3-ton) load limit would hinder the transportation of heavy materials across the bridge and therefore have a severe impact on the local economy. Consequently, a series of nondestructive field tests were organized and performed on the bridge to provide better assessments of load capacity and in situ structural health. Controlled truck load tests involving resistance-based strain gauges were conducted, and an instrumented monitor utilizing low-speed (vibrating-wire) strain gauges was installed at the site. The respective data recorded during these field efforts were used not only to evaluate environmental effects on the bridge but also to compute the load rating for each of the instrumented members. The resulting objective-based load ratings and their corresponding allowable live loads greatly exceeded the recommended 26 700-N (3-ton) load limit. Essentially, objective data identified or characterized in situ structural mechanisms and therefore provided the basis for more sound and realistic load ratings.

Structural identification-based condition assessment: a demonstration of methods applied to a laboratory scale model testbed

This paper reports on results from an ongoing project to study structural identification-based approaches to the condition assessment of constructed facilities. Under such an approach baseline and sequentially identified system models would be used comparatively to track changes in system parameters and to infer the onset, location, and extent of structural damage, deterioration, and/or defects. As part of the initial phases of this research a scale model grid representing a steel girder highway bridge was designed constructed, instrumented and tested at the University of Cincinnati. This paper presents the development, testing, and analysis of this scale model structure and offers the data generated as a benchmark problem on structural identification for the members of the research community.