Semih S. Tezcan

Seismic amplification at Avcılar, Istanbul

Based on the soil data established previously by a team of researchers at the Technical University of Istanbul, a wave amplification study is conducted for the town of Avcilar, Istanbul, located at about 120 km west of the epicentre of the Kocaeli earthquake of August 17, 1999. It is determined, through the use of well known computer program SHAKE, that the three major predominant periods of the ground are, 1.60, 1.00 and 0.70 s. Thus, the reasons of extensive damage occurred to 5–8 storey high residential buildings in the region, may be attributed to both the long distance effects of the high period waves of the earthquake and soil amplification.

Parametric analysis of irregular structures under seismic loading according to the new Turkish Earthquake Code

In order to investigate the effects of torsion on moment and shear values of vertical structural elements, a typical model building has been selected. Torsional irregularity has been created in the building by changing the location of the shear walls. Three cases of different centers of rigidity for 1, 5, and 10-story buildings have been considered. Each case has been analyzed by both the methods of equivalent earthquake loading and dynamic analysis, and the results compared. In order to investigate the effects of nonorthogonality on the distribution of moments and shears of the vertical structural elements, a 5-story building has been studied with one nonorthogonal and two orthogonal shear walls. Three cases of different orientations of the nonorthogonal wall have been considered. Each case has been analyzed for five different directions of earthquake.

A reconnaissance report: 1995 Dinar, Turkey, earthquake

During the 1st October 1995 Dinar, Turkey, earthquake, a total of 90 people died and about 240 people were injured. The number of collapsed or heavily damaged buildings exceeded 8000 within a radius of 20 km around the epicentre. The ground rupture was about 11 km long along an unexpected, new fault line. The reinforced concrete moment resisting framed structures as well as brick masonry houses experienced the most severe damage, especially those situated on soft soil layers of alluvium formations.

Drift control and damage in tall buildings

The interstorey drift limitations in earthquake codes of various countries around the world, have been reviewed. It is emphasized that, the aseismic safety of a tall building as well as its susceptibility to nonstructural damage are primarily indexed to its ability to restrict the relative storey displacements, in addition to its adequate strength, ductility and toughness. A moment resisting frame building satisfying all requirements of strength and ductility may still be subject to severe nonstructural damage, if the interstorey drifts are not restricted properly by means of shear walls. Several stringent deflection criteria as well as a damage control index are introduced to be conscientiously determined and checked during the design calculations for the purpose of controlling damage especially to nonstructural elements.

Efficiency of helical springs and viscodampers in base isolation

Abstract Results of an experimental testing are presented for a five-storey steel frame model, subjected to horizontal and vertical earthquake vibrations with varying intensities. The dynamic testing included the fixed base conditions, as well as full isolation by means of neoprene pads and helical springs, coupled with or without viscous dampers. The response of the structural model to both horizontal and vertical vabrations has been thoroughly recorded, and these records have been correlated with those of the analytical investigations. The main conclusion of the study is that the vertical vibrations may unexpectedly cause response amplifications at very high undesirable levels, especially when the structure is base isolated by means of rubber pads. No such deficiency occurs, however, when helical springs and viscodampers are used.

A Refined Formula for the Allowable Soil Pressure Using Shear Wave Velocities

Based on a variety of case histories of site investigations, including extensive bore hole data, laboratory testing and geophysical prospecting at more than 550 construction sites, an empirical formulation is proposed for the rapid determination of allowable bearing pressure of shallow foundations in soils and rocks. The proposed expression corroborates consistently with the results of the classical theory and is proven to be rapid, and reliable. Plate load tests have been also carried out at three different sites, in order to further confirm the validity of the proposed method. It consists of only two soil parameters, namely, the in situ measured shear wave velocity and the unit weight. The unit weight may be also determined with sufficient accuracy, by means of other empirical expressions proposed, using P or S — wave velocities. It is indicated that once the shear and P-wave velocities are measured in situ by an appropriate geophysical survey, the allowable bearing pressure as well as the coefficient of subgrade reaction and many other elasticity parameters may be determined rapidly and reliably.

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.

P25 scoring method for the collapse vulnerability assessment of R/C buildings

It is historically a fact that Turkey experiences frequent earthquakes, on the order of one damaging earthquake of magnitude 6–7 approximately every 2 years, causing extensive losses to economy, life and limb. Every strong earthquake leaves behind poverty and tens of thousands of homeless people. In order to mitigate especially the losses of life due to earthquakes, a rapid scoring technique called the P25 – Preliminary Assessment Method is proposed herein. The purpose of the method is to determine, for a reinforced concrete-framed building, whether there is any vulnerability to collapse during a strong earthquake. By identifying those buildings, which are most likely susceptible to collapse inside a particular building stock, and consequently strengthening or demolishing them, practically no loss of life will occur. In this presentation, details of P25 – Preliminary Assessment Method are discussed and the high degree of prediction reliability of the method is demonstrated on 323 case study buildings, which experienced wide ranges of damage during past earthquakes.

Use of Analytical Tools for Calibration of Parameters in P25 Preliminary Assessment Method

There exist several vulnerability assessment procedures including code-based detailed analysis methods as well as preliminary assessment techniques which are based on inspection and experience to identify the safety levels of buildings. Various parameters affect the seismic behaviour of buildings, such as dimensions and lay-out of structural members, existence of structural irregularities, presence of soft story or/and weak story, short columns and pounding effects, construction and the workmanship quality, soil conditions, etc. The objective of this study is to examine the effect of four essential structural parameters on the seismic behaviour of existing RC structures by using the most updated analytical tools. The effect of the concrete quality, corrosion effects, short columns and vertical irregularities have been examined. Parametric studies have been carried out on case study real buildings extracted from the Turkish building stock, one of which was totally collapsed in Kocaeli Earthquake of 1999. A control building has been considered for each sample structure with ideal parameters (i.e. without vertical irregularity or good quality of concrete, etc.). Nonlinear static push-over and cyclic analyses have been performed on 2D and 3D models. Base shear versus top displacement curves are obtained for each building in two orthogonal directions. Comparisons have been made in terms of shear strength, energy dissipation capability and ductility. The mean values of the drop in the performance are computed and factors are suggested to be utilized in preliminary assessment techniques, such as the recently proposed P25 method which is shortly summarized in this Chapter.

Risk Management and a Rapid Scoring Technique for Collapse Vulnerability of RC Buildings

It is emphasized that Turkey experiences frequent earthquakes, on the order of one damaging earthquake of magnitude 6.0–7.0 at almost every two years, causing extensive losses to economy, life and limb. Every strong earthquake leaves behind poverty and tens of thousands of homeless people. In order to mitigate the losses due to earthquakes, a number of issues are identified to be studied and managed properly on a national scale. Firstly, the importance of education and research about earthquakes and earthquake preparedness, from cradle to grave, is stressed. Secondly, for a successful solution of the risk mitigation problems, the legislative and financial structures as well as the social and technical organizations are presented. Recommendations are given, concerning the disaster management, dealing with emergency matters during and after the earthquake, and also the risk management, dealing with preparations before the earthquake. Finally, the problems related to inventory of buildings, repair and retrofitting issues, earthquake insurance, supervision of design and construction of buildings are discussed. A reference is made to the project of “zero” loss of life during future strong earthquakes which eliminates the necessity for large scale retrofitting of the existing building stock and saves lives. A rapid scoring technique called “P25- Assessment Method” is also introduced for determining the collapse vulnerability of RC buildings.