Aykut Erkal

Evaluation of environmental impact on historical stone masonry through on-site monitoring appraisal

This paper presents the design and application of an environmental monitoring system on the historical site of Odda’s Chapel in Deerhurst, Gloucestershire, UK, and the determination of hygroscopic behaviour of the original building materials to obtain long-term moisture content variation. The monitoring system provides a comprehensive profile of hygrothermal conditions in the walls at the locations where moisture conditions are potentially causing decay and damage. The system makes use of temperature and relative humidity sensing technology placed on the wall construction, providing continuous data including rainfall, wind-driven rain and runoff rain measurements. The relative merits and results of the designed system are evaluated and discussed, as well as the implications of its application in the conservation of historical structures. The environmental monitoring results show general deterioration in the shell of the building. Internal wall surface measurements are essential for the documentation of wall interior response and should be conducted across the wall section at several locations. The fact that 91% of in-wall recorded relative humidity (RH) values are greater than 75% RH throughout the monitoring period demonstrates the need for measures to conserve this historical stone masonry.

Investigation of the Rail-Induced Vibrations on a Masonry Historical Building

Increasingly historic masonry buildings are subjected to higher levels of traffic and rail vibrations due to urbanization and population growth. Deterioration and destabilisation of these buildings may result, especially if they were previously damaged (e.g. earthquakes or settlement problems). To better understand building response, vibration measurements were conducted on the Little Hagia Sophia Mosque, located adjacent to Istanbul’s Sirkeci-Halkali railway line. Transport-induced vibrations were recorded at several points on the ground and building. Attenuation characteristics in the ground and amplification features on the building were examined. Peak particle velocities often exceeded previously established thresholds for human perception and in some cases for structural damage. These are evaluated with respect to the building’s condition.

Assessment and Code Considerations for the Combined Effect of Seismic Base Isolation and Viscoelastic Dampers

To propose an initial formulation for the passive control section of the Turkish Earthquake Code, the impact of base isolation and viscoelastic dampers on a four-storey reinforced concrete (RC) frame building was considered under various one-dimensional quake excitations. Both statically equivalent seismic load methods (comparing Turkish Earthquake code with Uniform Building Code) and linear time history analyses were applied to the RC building based on a portion of the 1999 Kocaeli Earthquake ground motion record (modified to possess predominant spectral periods of 𝑇1=0.13 sec and 𝑇2=1.43 sec representing hard and soft soil conditions, resp.). Effective peak ground acceleration was set to 0.40 g. Time history variations of upper column dis-placements and bending moments were compared, as well as storey drift ratios. Reductions of the fixed-base case column bending moments were obtained of up to 73% under base isolation, up to 25% with viscoelastic dampers, and up to 83% (with a unified response reduction factor) when both devices were both present.

Laboratory testing of non-standard original historic building materials and related implications for conservation

For an assessment or an analysis of a historic building, determination of the material properties is always crucial. However, this is usually a challenging issue because material extraction from a historic building for standard laboratory testing is usually not allowed or the amount of material available for testing is very limited. Lack of comprehensive standards for testing irregularly shaped and non-standard-size specimens, taken from historic buildings, unfortunately compounds the uncertainty. This paper offers a discussion of such issues by using the case study of Odda’s Chapel in Gloucestershire, UK, and describing the systematic examination of a total of six lime mortar and Blue Lias stone samples extracted from this Grade I listed building. The programme of testing and the results obtained are compared with the latest European standards relating to sampling and testing of material of cultural properties. Internal microstructure, hygroscopic sorption and water absorption characteristics, and the density and mechanical properties of the materials are documented and alternative testing techniques are compared. Identification of some of the above-mentioned material properties shows that the agreement between results obtained from the various test methods is considered satisfactory, depending on the testing approach and material heterogeneity.

Value and vulnerability assessment of a historic tomb for conservation.

Monumental tombs reflect various social, cultural, architectural, religious, economic, and engineering features of a community. However, environmental weathering, natural disasters, poor maintenance, vandalism, and misuse unfortunately pose serious threats to these cultural assets. Historic monuments are often exposed to the highest risk due to their vulnerability. The Ottoman-style Nişancı Hamza Paşa tomb located in Karacaahmet Cemetery, Istanbul, the largest and oldest public cemetery in Turkey, is a case in point. The tomb consisting of six granite columns and a brick dome supported by six arches was constructed in 1605. Cracks, material loss, and decay as a result of adverse environmental effects and past earthquakes are evident. Therefore, this paper analyses the overall value of the tomb with respect to its historical, communal, evidential, and aesthetic aspects. Using the finite element approach and data on the tombs material properties, a structural analysis under the self-weight and a time history analysis based on the earthquake ground motion data recorded in Duzce, Turkey, in November 1999 were conducted to encourage the conservation of this tomb and similar cultural heritage assets all over the world. The damage observed in the structure is congruent with the analysis results.

Theoretical Solutions for Strength-Scaled Unreinforced Masonry for Scaled Soil-Structure Experimentation

Reduced-scale masonry testing offers advantages of lower costs and shorter schedules compared to full-scale testing, but achieving results reflective of full-scale behavior requires development and fulfillment of appropriate scaling relationships. In many model-scale experiments, geometric scaling occurs, but kinematic and/or dynamic similitude is not fully satisfied. This paper describes the theoretical basis and evolution of the equations necessary to achieve kinematic similitude for soil-structure testing at one-gravity for unreinforced masonry. Critical considerations relate to preventing the soil from being overloaded. By adopting a standard linear relationship of increased soil stiffness with depth, the controlling principle becomes the application of restricted scaled-loads throughout the entirety of the structure-soil system. As such, material strength and stiffness must be scaled accordingly to respond appropriately under the reduced stress. An example is provided for an adjacent excavation experiment with related empirical verification and computational quantification.

CASE STUDIES A RAPID TECHNIQUE TO DETERMINE ALLOWABLE BEARING PRESSURE

Based on a variety of case histories of site investigations, including extensive bore hole data, laboratory testing and geophysical prospecting, an empirical formulation is proposed for the rapid determination of allowable bearing capacity of shallow foundations. The proposed expression corroborates consistently with the results of the classical theory and is proven to be rapid, reliable and safe. It consists of only two soil parameters, namely, the insitu measured shear wave velocity, and the unit weight. The unit weight may be also determined with sufficient accuracy, by means of another empirical expression, using the Pwave velocity. It is indicated that once the shear and P-wave velocities are measured insitu by an appropriate geophysical survey, the allowable bearing capacity may be determined rapidly and reliably through a single step operation. Such an innovative approach, using the seismic wave velocities only, is considerably cost and time-saving, in practice.