Challenge Journal of Structural Mechanics

96-105

Authors: Robert Korol, Frank Greening, Paul Heerema

This article points out the benefits of employing a performance based analysis approach for ascertaining the likelihood that travelling fires in an office building could induce a localized failure that might trigger its collapse. The case study chosen is Building 7 of the World Trade Center complex. Based on the parametric study undertaken, our findings were that the fire-protected steel floor beam, identified as the initiator of the cascade of events that followed, could not have done so, virtually under any circumstance.

117-123

Authors: Naim Eser Reyhanoğulları, Uğurhan Akyüz

In this study, influences of vertical ground motion on seismically isolated bridges were investigated for seven different earthquake data. One assessment of bearing effect involves the calculation of vertical earthquake load on the seismically isolated bridges. This paper investigates the influence of vertical earthquake excitation on the response of briefly steel girder composite bridges (SCB) with and without seismic isolation through specifically selected earthquakes. In detail, the bridge is composed of 30m long three spans, concrete double piers at each axis supported by mat foundations with pile systems. At both end of the spans there exists concrete abutments to support superstructure of the bridge. SCBs which were seismically isolated with ten commonly preferred different lead-rubber bearings (LRB) under each steel girder were analyzed. Then, the comparisons were made with a SCB without seismic isolation. Initially, a preliminary design was made and reasonable sections for the bridge have been obtained. As a result of this, the steel girder bridge sections were checked with AASHTO provisions and analytical model was updated accordingly. Earthquake records were thought as the main loading sources. Hence both cases were exposed to tri-axial earthquake loads in order to understand the effects under such circumstances. Seven near fault earthquake data were selected by considering possession of directivity. Several runs using the chosen earthquakes were performed in order to be able to derive satisfactory comparisons between different types of isolators. Analytical calculations were conducted using well known structural analysis software (SAS) SAP2000. Nonlinear time history analysis was performed using the analytical model of the bridge with and without seismic isolation. Response data collected from SAS was used to determine the vertical load on the piers and middle span midspan moment on the steel girders due to the vertical and horizontal component of excitation. Comparisons dealing with the effects of horizontal only and horizontal plus vertical earthquake loads were introduced.

134-139

Authors: Hüseyin Serdar Küyük

Sakarya, one of the biggest cities in the Marmara prefecture, with 835 thousand population has suffered severe damages due to the North Anatolian Fault System (NAFS) which is a major active right lateral-moving fault in northern Anatolia running along the tectonic boundary between the Eurasian Plate and the Anatolian Plate. One of the biggest disasters was on 17 August 1999 Izmit earthquake with Mw 7.4. The occurrence and the source information of huge events in the region indicate that an earthquake is expecting in near future from the underneath of the Marmara Sea. Therefore, this seismically vulnerable city needs urgent strong motion prediction and reliable Earthquake Early Warning System. The city is preparing now for further NAFS earthquakes and it is essential to inform society about the warning time of a possible imminent earthquake so that precautionary actions can be taken by the government officials, companies and individuals. This study highlights available warning time for the city. Warning time is calculated by considering the theoretic P- and S- wave velocities for Marmara region. Results indicate that Sakarya will have approximately 37.9 second in average with 7.4 second standard deviation before the arrival of strong shaking to the city.

145-148

Authors: Sami Oğuzhan Akbaş, Süleyman Bahadır Yüksel

The design vertical loads on box culverts under embankments are commonly calculated using the soil-structure interaction factors (Fe) recommended by the American Society of Highway and Transportation Officials (AASHTO). Non-linear finite element analyses were used to update Fe given by AASHTO by considering the effects of backfill height, culvert stiffness, backfill material stiffness, backfill compaction, and the rigidity of the layer on which the culvert rests. A simplified reliability analysis was performed to determine the adequacy of safety level in AASHTO load resistance factor design (LRFD) code specifications.