Mehmet Ömer Timurağaoğlu

Zemin davranış analizleri yapının maruz kalacağı etkileri anlamak için önemli bir araç olmasının yanı sıra yapı-zemin etkileşimi analizlerinin önemli bir aşamasını temsil etmektedir. Öte yandan zeminin doğrusal olmayan davranışını temsil etmek için önerilen eşdeğer doğrusal yöntem literatürde sıklıkla kullanılmaktadır. Bu yöntem doğrusal olmayan zemin davranışını ardışık doğrusal analizler yardımıyla temsil etmeye çalışan pratik bir yaklaşımdır. Bu çalışmada maksimum yer ivmesinin eşdeğer doğrusal ve doğrusal olmayan analiz üzerindeki etkinliği 1-boyutlu zemin davranış analizleri üzerinden araştırılmaktadır. Bu vesileyle oluşturulan 30m derinliğinde homojen killi zemin tabakası farklı genliklere ölçeklenerek elde edilen kayıtlara maruz bırakılarak eşdeğer doğrusal ve doğrusal olmayan analizler gerçekleştirilmiştir. Analizlerde model tabanı rijit kabul edilmiştir. Zeminin kayma modülü ve sönüm davranışının kayma birim şekildeğiştirmeyle değişimi için literatürde yaygın bir şekilde kullanılan deneysel çalışma dikkate alınmıştır. Bu ilişkiler programda mevcut olan bir eğri uydurma aracı sayesinde kalibre edilmiştir. Gerçekleştirilen analizler sonucunda eşdeğer doğrusal analizlerin doğrusal olmayan davranışı belirli yer ivmesi değerine kadar temsil edebildiği, 0.25-0.50g aralığında eşdeğer doğrusal davranışın doğrusal olmayan davranıştan sapmaya başladığı ortaya çıkmıştır. Ayrıca büyük yer ivmesi genliklerinde eşdeğer doğrusal analizlerde elde edilen kayma gerilmesi değerinde doğrusal olmayan analizlere göre daha büyük tepkiler gözlenmiştir.

With the advancement of numerical modeling techniques, the problem of soil–structure interaction (SSI) has become the subject of extensive research in recent years. One of the most critical stages of this problem is the site response analysis (SRA). SRA provides designers with valuable insights into the soil's expected seismic response in the superstructure's absence. The present work investigates the influence of mesh type on dynamic SSI through three-dimensional (3D) finite element-based SRA. Models were developed using three different mesh types—hexahedral, tetrahedral, and hybrid—with absorbing boundary conditions applied along the lateral edges. The 3D model results were verified by comparison with one-dimensional (1D) analyses subjected to the same ground motion. In the study, the soil was assumed to exhibit linear elastic behavior, and all 1D and 3D analyses were performed based on this assumption. The 3D models could accurately represent the 1D site response through ground surface response spectrum. The findings reveal that the dynamic response of the soil system is mainly independent of the element type provided that a properly structured and sufficiently refined mesh is employed. Conversely, auto-generated irregular meshes tend to produce inaccurate results. Among the mesh types evaluated, hybrid meshes offer the most favorable balance regarding computational efficiency.

Kahramanmaraş Earthquake Sequence of 6th of February is the deadliest earthquake that happened in Turkey in the era of instrumental seismology, claiming more than 55 thousand lives and leaving torn down cities and towns behind. More than 450 km long lateral strike-slip fault ruptured during these catastrophic earthquakes. As a result, more than 38 thousand buildings collapsed causing life losses. Considering that the large share of the Turkish building stock consists of RC buildings, the vulnerable RC building stock is the main responsible for this picture. Deficiencies of the Turkish RC building stock are well known since they manifested themselves several times in the past earthquakes. However, considering the improvements in the seismic codes and the seismic hazard maps achieved in the last two decades, the widespread collapse of buildings constructed after year 2000 was rather unexpected. Some of the observed structural damage patterns are similar to those observed also in the pre-2000 buildings in recent earthquakes, however, some other types of damages, such as out-of-plane bending and shear failures or shear-friction capacity failure of RC walls, brittle fracture and bond-slip failure of reinforcement, tension failure of beams and slabs are usually not witnessed. This paper presents a carefully selected set of examples comparing the pre-2000 and post-2000 building damages and collapses, also referring to a detailed summary and comparison of the code developments in Turkey.

The present study aims at scrutinizing the static and dynamic behavior of pile-soil interaction in the context of p-y method using finite element analysis. For this purpose, a series of static and dynamic analyses are carried out for single pile, 2x2 and 3x3 group piles in homogeneous clayey soil. In the analysis, the nonlinear behavior of soil is taken into account using a kinematic hardening model, while piles are modeled as elastic. The soil model parameters are calibrated using experimental modulus degradation and damping curves. The pile-soil interface is modeled considering normal and shear behavior to account for separation and sliding between soil and pile elements. In the static analyses, variation of pile moments and displacements with depth and the back-calculated p-y curves are evaluated. The soil resistance is directly obtained by extracting the shear and normal forces of the nodes in a pile at any depth. The p-multipliers for 2x2 and 3x3 group piles are calculated and compared with that of the experiments. The variation of p-multipliers with depth and lateral displacement is also evaluated. In dynamic analyses, first, site response analyses are carried out and validated against one-dimensional results under different loading frequencies. Infinite elements are applied at the boundaries to provide non-reflective boundaries. Later, single, 2x2 and 3x3 group pile analyses are executed. The influence of loading amplitude and frequency on the response are investigated using moment-depth and displacement-depth relationships. Dynamic p-y curves are back-calculated and the results are deeply assessed by comparing with static curves.

Pile foundations are widely used in marine and coastal engineering structures. The correct analysis method must be used to ensure the safety of piled systems used in marine and coastal structures. Despite several methods available in the literature, the numerical method is increasingly applied for understanding the loading mechanism of pile-soil interaction under vertical, lateral, or seismic loadings. The present study focuses on the numerical validation of centrifugal test results of the single pile in dense sand under lateral loading. An extensive parametric study is carried out to validate numerical models due to the lack of experimental tests such as shear or triaxial tests. In the numerical model, the soil is represented by a kinematic hardening model, which is simple to calibrate in finite element analysis, whereas pile is modeled as an elastic material. The p-y family of the curve is back-calculated for a single pile and an algorithm is generated. Two interface models between soil and pile, namely full contact and frictional slip contact, are investigated to represent the behavior under horizontal loading. Then, the analyses are extended to vertical loading to assess the influence of interface models.