Challenge Journal of Structural Mechanics

156-160

Authors: Semih Özmen, Tunç Bahçecioğlu, Özgür Kurç

This study focuses on developing a parallel solution framework for the linear dynamic analysis of large structural models on homogeneous PC clusters. The framework consists of two separate stages where the former is preparing data for the parallel solution that involves partitioning. The latter is a fully parallel finite element analysis that utilizes substructure based solution approach with direct solvers to perform implicit integration. The linear dynamic analysis of a large scale model was performed on a homogeneous PC cluster and the number of computers was varied in order to demonstrate the performance and the efficiency of the overall solution framework. The performance of the implemented framework was also compared with the widely acknowledged parallel direct solver, MUMPS.

168-172

Authors: Emre Ercan, Ninel Alver, Ayhan Nuhoğlu

Masonry is the oldest building technique that still finds wide use in today’s building industries. The variety and natural availability of the materials that is needed for masonry combined with the easiness of the construction, has resulted in usage of masonry for thousands of years. The lack of research and underdeveloped codes in masonry results in poor applications of masonry technique which causes invaluable loss of lives of people in earthquakes. Today modeling of stone masonry structures is still very difficult because of unknown material properties. This study focuses on estimation of the material properties by destructive testing methods (DT) and non-destructive testing methods (NDT) and analysis of a historic stone masonry arch bridge. After visual investigation, the geometry of the structure is determined and 3D model of the structure was generated and meshed for Finite Element Method (FEM). For evaluation of material properties, NDT methods such as; impact-echo and ultrasonic pulse velocity testing methods were used. Schmidt hammer test was applied for estimation of the hardness of the stones. Fallen stone and mortar samples from the bridge were taken to the laboratory and destructive tests applied on them to determine the properties of masonry components. The test results for the materials obtained from the DT and NDT methods were compared with each other. Using these results mechanical properties of the masonry were estimated using standards and codes. The gathered material properties were assigned to FE model and the model was analyzed.

185-191

Authors: Niyazi Özgür Bezgin

Need for elevated railways may arise when capacity of bus transit and light rail transit that share the right of way with roadways becomes insufficient and the cost of railways with dedicated right of ways such as underground railways becomes costly. A similar need arose in the city of Makah and in 2010 an 18-km long; elevated railway transit service began servicing between the districts of Mina, Arafat and Muzdalifah. Today the two-track elevated system serves along the route constructed by posttensioned 25-m long U-sections spanning between piers. This paper presents the analytical studies and the finite element model of an alternative 30-m long pretensioned boxed-section evaluated during the tender stage. Following a comparison with the applied choice, benefits of the U-section with respect to the analyzed alternative will be discussed.

198-201

Authors: Kemal Hacıefendioğlu, Fahri Birinci

This paper presents the seismic response analysis of offshore wind turbines subjected to multi-support seismic excitation by using a three dimensional numerical finite element model considering viscous boundaries. The sea water-offshore wind turbine-soil interaction system is modeled by the Lagrangian (displacement-based) fluid and solid-quadrilateral-isoparametric finite elements. The research conducts a parametric study to estimate the effects of different foundation soil types on the seismic behavior of the offshore wind turbine coupled interaction system. The results obtained for different cases are compared with each other.

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.

42-47

Authors: Mehmet Semih Yücemen, Çetin Yılmaz

A probabilistic model is developed for the assessment of the earthquake insurance premium rates for the structures taking place in the Bolu Mountain Crossing in the Gumusova-Gerede Motorway Section. The model requires two types of studies, namely: seismic hazard analysis and estimation of potential damage to structures. The computations are carried out according to the proposed model by using the seismic hazard results obtained from the time-dependent renewal model and the best estimate damage probability matrices developed in the study.

59-64

Authors: Kemal Hacıefendioğlu, Mehmet Akköse, Alemdar Bayraktar, Ali Aydın Dumanoğlu

The effect of the non-linear material behavior of a rock-fill dam subjected to random loads is investigated by the equivalent linear method that considers the non-linear variation of soil shear moduli and damping ratios as a function of shear strain. The Keban dam constructed in Elazığ, Turkey is chosen as a numerical example. The interaction of the rock-fill dam with the reservoir is neglected, but not the foundation rock. The properties of the dam materials were taken from the dam project and assumed to be isotropic in the analysis. A stationary and ergodicity assumption are made for stochastic dynamic analysis. The E-W component of the Erzincan earthquake recorded on March 13, 1992, Erzincan, Turkey is chosen as a ground motion since it occurred nearby the dam site. The component considered is applied to the dam in the horizontal direction. The non-linear stochastic responses of the Keban dam are compared to its linear stochastic and deterministic response.

71-77

Authors: Daniel Bobos, Zeno Iosif Praisach, Doina Frunzăverde, Gilbert Rainer Gillich, Ionica Negru

Corrosion, as the spontaneous process of material degradation produced by the environment, affects the reliability and safety of structures, both by reducing the section of the components, due to material loss and by diminution of the materials mechanical strength. The authors have found a mathematical relation between discontinuities in beams and changes of its natural frequencies and developed a method to identify these discontinuities. The present paper considers the more complex case of damage determined by corrosion, where beam thinning is accompanied by mass decrease. These impose considering natural frequency changes in both directions: decrease due damage and increase because of mass loss. FEM simulations and analytical investigations were carried out, in order to find the relation between mass change in different positions along the beam and the frequency increase. The results were correlated with the “classical” relation describing frequency decrease because of discontinuities. Finally, the authors developed a new relation, proper to be used for damage produced by severe corrosion, which was validated by laboratory experiments.

84-89

Authors: Sıddık Şener, Yasin Çağlar, Mehmet Akif Benzer, Kadir Can Şener

Vertical displacement of the Korror-Babeldaop (KB) Bridge in Palau is presented. This bridge was built in 1977 by the cantilever method and collapsed 3 months after remedial prestressing in 1996. KB Bridge was a segmental prestressed concrete girder having the world record of 241 m and maximum girder depth of 14.17 m. The final mid-span deflection was in design expected to be 0.53 to 0.65 m but after 18 years it reached 1.39 m and was still increasing. With a very limited amount of official information of the bridge was available and bridge was analyzed by ANSYS finite element program. Presented is an accurate analysis using 5392 hexahedral three-dimensional (3D) finite elements with 9614 nodes by ANSYS. Hognestad concrete model and Solid 65 element type were considered. The actual vertical displacements of free end of the cantilever bridge under truck loading were compared with the 3D finite element analyses results in order to come up with a benchmark model. The collapse reasons of KB Bridge were discussed.

1-8

Authors: A. Ghani Razaqpur, Francesco Bencardino, Lidia Rizzuti, Giuseppe Spadea

The capacity provisions of conventional Reinforced Concrete (RC) and Prestressed Concrete (PC) beams subjected to combined action of torsion, shear and flexure are well known and stated by international/national codes. Similar provisions lack for concrete members containing Fibre Reinforced Polymer (FRP) reinforcements. In general, there is paucity of research on the treatment of torsion combined with other stress resultants for FRP-RC/PC members. In this paper the theoretical method proposed by the Canadian standard CSA S806 for FRP-RC/PC structures is presented. The critical issues, related to this topic, such as the appropriate strength and inclination of the diagonal struts and failure criteria are critically analyzed and addressed. In order to assess the reliability of this study a comparison between available experimental data regarding FRP-RC/PC beams subjected to combined actions and their corresponding theoretical provisions derived by the CSA S806 standard is shown. Furthermore, another approach, available in literature, which is based on the space truss model, is examined and used for comparison in order to evaluate the theoretical provisions offered by this model against the tests value of the set of the beams analyzed in this study. Based on the critical analysis of the results, it can be highlighted that the CSA method is able to conservatively predict the capacity of these beams.

13-17

Authors: Hisato Hotta, Takeshi Nakajima

Partial walls separated from columns are generally treated as nonstructural elements because their behavior aren’t analyzed much. Partial walls jointed rigidly to RC frames raise horizontal load-carrying capacity, however they may give an influence on RC frames when they fall in brittle failure. Objective of this paper is to clarify the influence of partial walls falling in shear failure on RC frames through a static loading test and a shaking table test. The experiment shows that, after one of the partial walls fails, story drift rapidly increases. It shows progress of flexural deformation at one end of columns, and it may cause story collapse. The result is obtained from both loading tests.

22-26

Authors: Farzad Hejazi, Jamalodin Noorzaei, Abang Abdullah Abang Ali, Mohd Saleh Jaafar

Various types of interlocking mortarless (dry-stacked) block masonry systems have been developed worldwide. However, the characteristics of dry joints under compressive load, and their effect on the overall behavior of the interlocking mortarless system, are still not well understood. This paper presents an investigation into the dry-joint contact behavior of masonry and the behavior of interlocking mortarless hollow blocks wall construction subjected to seismic excitation. In the system developed, the blocks are stacked on one another and three-dimensional interlocking protrusions are provided in the blocks to integrate the blocks into walls. The response of the mortarless hollow block wall with respect to acceleration displacement and stress have been discussed.

32-37

Authors: Turgut Öztürk, Zübeyde Öztürk, Onur Öztürk

Earthquakes are one of the most important and hazardous natural disasters in the world and in our country. They also have lots of characteristics from the point of effects caused by them. For this reason it requires special engineering approach to analyze those effects and to design earthquake resistant structures. Almost all of the life losses caused by the earthquakes are related with improperly designed buildings safety of which are not ensured against severe earthquakes. Structural damages and collapses cause very important economical losses. So, understanding of the characteristics of an earthquake and correct determination of the behavior of buildings under earthquake excitation turn out to be the most important requirement to build earthquake resistant buildings. When we take into consideration the destructive effects of severe earthquakes that happened especially in recent years (Kocaeli 1999, Düzce 1999) one can easily see the importance of knowing the behavior of buildings under earthquake loads. In this study torsional effects that occur during earthquake excitations are analyzed in multi-story reinforced concrete buildings. In that manner the behavior of reinforced concrete structures under earthquake loads are examined and by the way the behaviors of structures having torsional irregularities are enlightened and clarified. Moreover the effects of rigidity, ultimate capacity and ductility on the behavior of structures under ground motion are summarized. Torsional irregularity is a key irregularity in determination of the method to be used in earthquake analysis. Definition of the torsional irregularity of a multi-story reinforced concrete building is explained in accordance with Turkish Earthquake Code and the related principles of computations that have to be followed according to the code are given. Multi-story reinforced concrete buildings are classified according to their plan geometry and the effects of plan geometry on the torsional irregularity are explained. While in certain structures torsional irregularity may happen in very high levels in some structures it may happen so small that can be safely omitted. For that reason buildings forming torsional irregularity are classified and their characteristics and torsional irregularity parameters are given. Shear walls without causing any torsional irregularity on buildings having different plan geometries are shown.