Mete A. Sozen

Seismic Vulnerability Assessment of Low-Rise Buildings in Regions with Infrequent Earthquakes

This paper presents a simplified method of ranking reinforced concrete, low-rise, monolithic buildings according to their vulnerability to seismic damage. The ranking process requires only the dimensions of the structure. The process is tested using a group of buildings that suffered various level of damage during the Erzincan earthquake of 1992. The ranking procedure reflected the observed damage satisfactorily. - buildings; earthquake resistant structures; earthquakes; evaluation; failure; inspection; reinforced concrete; school buildings.

The Pentagon Building Performance Report

This report will be of interest to structural and forensic engineers, as well as historians and general readers seeking first-hand, technical knowledge of the Pentagons resistance to progressive collapse.

Displacement History Effects on Drift Capacity of Reinforced Concrete Columns

Results from 16 tests of reinforced concrete columns subjected to different displacement histories are presented. It is concluded that the drift capacity of a reinforced concrete column depends not only on the properties of the column and the applied axial load, but also on the displacement history. A numerical model to calculate drift capacity as a function of displacement history is presented.

Performance of School Buildings in Turkey During the 1999 Düzce and the 2003 Bingöl Earthquakes

Several school buildings were surveyed in the disaster areas of the Marmara (17 August 1999, Mw =7.4), Düzce (12 November 1999, Mw =7.2), and Bingöl (1 May 2003, Mw =6.4) earthquakes in Turkey. Among them, 21 reinforced concrete buildings were found to have an identical floor plan. Lateral load resisting structural system consisted of reinforced concrete frames (moment-resisting frame) in 16 of the buildings and structural concrete walls integrated with the moment-resisting frame (dual system) in the remaining five buildings. The number of stories above ground in these buildings ranged from two to four. These school buildings provide a nearly ideal test of the effect of a single important structural characteristic on the performance of buildings with structural designs that are uniform in all other respects. Our observation is that the presence of structural walls improves the behavior of reinforced concrete systems drastically.

Analysis of Circular Concrete-Filled Steel Tube Specimen under Lateral Impact

This paper mainly discusses the derivation and usage of simplified analysis model of circular concrete-filled steel tube specimen under lateral impact. At first, the robust software, LS-DYNA, is employed in this paper to simulate a test of circular concrete-filled steel tube (CFT) specimen under drop impact carried out by Li (2007). The numerical simulations results agree well with the experiment results and it shows good prediction of dynamic response of the CFT specimen under lateral impact could be achieved. Further analysis based on LS-DYNA model is then made to investigate the stain rate effect of the CFT column with fixed-simple supported ends. At last, a simplified analytic model is derived based on the combination of the tests results, the numerical simulation and theoretical analysis. The comparison between the maximum deflections at the mid-span obtained from the proposed simple analytical model and the numerical simulation shows that the proposed method gives good predictions of the maximum deflection of the CFT specimen under lateral impact.

Producing high-quality visualizations of large-scale simulation

This paper describes the work of a team of researchers in computer graphics, geometric computing, and civil engineering to produce a visualization of the September 2001 attack on the Pentagon. The immediate motivation for the project was to understand the behavior of the building under the impact. The longer term motivation was to establish a path for producing high-quality visualizations of large scale simulations. The first challenge was managing the enormous complexity of the scene to fit within the limits of state-of-the art simulation software systems and supercomputing resources. The second challenge was to integrate the simulation results into a high-quality visualization. To meet this challenge, we implemented a custom importer that simplifies and loads the massive simulation data in a commercial animation system. The surrounding scene is modeled using image-based techniques and is also imported in the animation system where the visualization is produced. A specific issue for us was to federate the simulation and the animation systems, both commercial systems not under our control and following internally different conceptualizations of geometry and animation. This had to be done such that scalability was achieved. The reusable link created between the two systems allows communicating the results to non-specialists and the public at large, as well as facilitating communication in teams with members having diverse technical backgrounds.

An emendation of elastic rebound theory: Main rupture and adjacent belt of right-lateral distortion detected by Viaduct at Kaynaşli, Turkey 12 November 1999 Düzce Earthquake

The fault trace of the 12 November 1999 earthquake in theDüzce-Bolu region in Anatolia crossed the alignment of a 2.4 kmviaduct in Kaynaşli that had been carefully surveyed. The builders of theviaduct, the ASTALDI-BAYINDIR Co., resurveyed the viaduct after theearthquake. We repeated the survey for approximately one kilometre of theeastern end of the viaduct and obtained essentially identical results. Thoughit was unfortunate that the earthquake damaged the new structure, the piersdid produce a very rare record of ground deformation of an earthquake.In effect, the viaduct was a giant strain gage that yielded reliable data aboutground movement and distortion near a fault. This paper describes thesurvey data and their evaluation leading to convincing evidence that (a) thefault trace must be considered, not as a fault line or plane, but as a faultzone with a finite width and that (b) the structural damage within the zonewas caused, not primarily by ground acceleration, but by ground distortion.Along the right-lateral fault at Kaynaşli, the fault zone consists ofright-lateral movement at the main trace, a zone of right-lateral distortionnear the trace, bounded by left-lateral distortion. The 12 November 1999event in Turkey, like the ground deformation and fracturing at Landers,California (Johnson et al., 1994, 1996), thus affirmed a forgottenconclusion from the studies by Lawson (1908), Gilbert and Reid (1910)of the 1906 San Francisco earthquake that earthquake ruptures typicallyoccur throughout zones or belts, rather than along linear traces or planes.

Dominant Factor in the Collapse of WTC-1

The behavior of the World Trade Center Tower 1 on September 11, 2001 is studied in light of experimental data on the effect of elevated temperature on mechanical properties of structural steel. It is concluded that the damage inflicted by aircraft impact on the insulation of the core framing was the dominant factor in the collapse of the structure.

The Velocity of Displacement

During the twentieth century, consideration in design of drift response has moved with speed from a minor serviceability criterion to a central proportioning issue. It is suggested that the time is ripe for uncoupling the drift computation from calculated and often unrealistic lateral design forces and relating it directly to a design displacement spectrum. It is also argued that the “cracked-section” concept for determining stiffness of reinforced concrete structures may be realistic for gravity loading but is not for earthquake effects.

Surrealism in Facing the Earthquake Risk

The possibility of a violent ground motion in a population center poses multiple threats to the safety and continuity of society. It has to be met on multiple planes including the political and the economical. It is not an exaggeration to claim that the construction trades in many parts of the world understood the threat only in twentieth century. In many towns and cities in seismic zones, a strong ground motion can destroy 10 % or more of the existing buildings. To locate the vulnerable, it is necessary to investigate all. If this study is to be done in detail using codified criteria, it may involve an investment that would be unacceptable to a political system that seldom appreciates the risk. That condition constrains the engineering effort to the minimal and requires a procedure that has to be simple and transparent. Above all, data acquisition needs to be within the reach of workers without technical degrees. The paper investigates such a procedure, the Hassan Index, using available information from five earthquake events and finds it imperfect but useful.