THE ROLE OF SOIL-STRUCTURE INTERACTION ON STRUCTURAL DESIGN

Yapı temel sistemlerinin projelendirilmesinde, yapı-temel-zemin üçlüsü arasındaki etkileşimin dikkatealınması, zemine aktarılan yükler nedeniyle zemin tabakalarında oluşan deformasyonların temel elemanı veüstyapı taşıyıcı sistemindeki iç kuvvetler ve yük dağılımı üzerindeki etkilerinin hesaba katılması gerekir.Bu gereklilik rutin mühendislik uygulamalarında, yapı ve zemin arasındaki ilişkiyi sabit yatak katsayısı ilekuran Winkler yöntemi kullanılarak sağlanmaya çalışılmaktadır. Ancak Winkler yönteminin temel tabanbasıncı dağılımını temsil etmekte yetersiz kaldığı literatürde belirgin bir biçimde ortaya konmuştur. Temelelemanının elastik eğrisini gerçeğe daha yakın modelleyen yöntemler geçmişte birçok araştırmacıtarafından önerilmiştir. Ne var ki, yatak katsayısı modelinin betonarme yapı tasarımı üzerindeki rolüşimdiye dek ortaya konmamıştır. Bu çalışmada zemin yapı etkileşiminin yapısal tasarıma etkisi örnek biranaliz çalışmasıyla incelenmiştir. Rijit yapı-zemin, sabit ve değişken yatak katsayısı yöntemleri ile yapısalçözümler gerçekleştirilmiştir. Yürürlükteki ulusal yönetmelikler çerçevesinde betonarme kolonkesitlerindeki donatı oranları hesaplanarak, yapı-zemin etkileşiminin yapısal tasarımdaki etkisi ortayakonmuştur While designing foundations of structures, structure-foundation-soil interaction must be considered andthe effect of deformations occurring due to the structural loads in soil layers on the load distributions andsectional forces of structural elements must be taken into account. Winkler method is used in order torelate the soil and the structure by means of constant subgrade modulus in routine engineeringapplications. In the literature, it is clearly stated that, Winkler method is insufficient to represent thecontact pressure distribution beneath the foundation. In the past, methods capable of modeling actualelastic curve of the foundation element were suggested by researchers. However, the role of subgradereaction on the structural design has not been stated yet. In this study, the effect of soil-structureinteraction on structural design of reinforced concrete structures is investigated via a case analysis study.Structural analyses were performed using fixed base-soil, constant subgrade modulus and variablesubgrade modulus methods. Reinforcement ratios in reinforced concrete column sections were calculatedaccording to national codes and specifications. The effect of soil-structure interaction on structural designis presented

Use of slurry infiltrated fiber concrete (SIFCON) in improving the seismic behaviour of reinforced concrete structures

Sunulan çalışmada, mevcut betonarme binaların kolon-kiriş birleşimlerinin genel yetersizlik unsurlarını barındıran dış kolon-kiriş birleşimi numunelerinin depremi benzeştiren tersinir tekrarlı yükler altındaki davranışı incelenmiş, bu birleşimlerin SIFCON (çimento şerbeti emdirilmiş lifli beton) bloklar ve kimyasal ankrajlar kullanılarak güçlendirilmesi amacıyla tez kapsamında önerilen yöntemin etkinliği incelenmiştir. Güçlendirme yönteminin hedeflerine uygun geometride, çelik lif dozajı-matris dayanımı ve kalınlık açısından çeşitli seçeneklerde hazırlanan kompozit köşe blokların tersinir tekrarlı yükleme altında histeretik performansları araştırılmıştır. Genel davranış, yanal rijitlik azalımı, enerji tüketimi vb. açısından göz önüne alınan birleşim numunelerinin güçlendirilmesine uygun seçenek belirlenmiştir. Mevcut binaların birleşimlerini temsil edecek şekilde düşük beton dayanımlı, birleşiminde kayma donatısı bulunmayan, düz donatı ile detaylandırılmış vb. özellikte hazırlanan dış kolon-kiriş birleşimi numuneleri sabit eksenel yük ve tersinir tekrarlı yatay yükler altında test edilmiş ve gevrek göçme davranışı göstermiştir. Aynı yetersizlikleri içeren birleşimler tez kapsamında önerilen yöntemle çeşitli ankraj seçeneklerinde güçlendirilmiş, kolon tepesinden uygulanan sabit eksenel yük ve tersinir tekrarlı yatay yükler altındaki davranışları incelenmiştir. Güçlendirilen numunelerin yanal dayanımı ve enerji tüketim performansı yalın halde test edilen birleşim numunelerine göre belirgin bir şekilde geliştirilmiş, numunelerin birleşim kesme hasarı geciktirilmiş, gevrek göçmesi engellenmiş ve davranışları daha sünek olan kiriş eğilme göçmesine dönüştürülmüştür. Ayrıca kolon-kiriş birleşimlerinin deney sonuçları ile kalibre edilmiş sayısal modelleri oluşturulmuştur. In this study, behavior of existing beam-column joints under cyclic loading conditions similar to those under earthquake action is investigated and a novel seismic retrofitting technique is proposed. This technique uses prefabricated slurry infiltrated fiber concrete blocks (SIFCON) anchored on the joints with anchorage rods. In compliance with the objective of the retrofitting technique, L-shaped various composite block specimens with different steel fiber density and different thicknesses were produced and tested under cyclic loadings. With these component tests, hysteretic performance of the blocks were investigated and the most ideal choice was decided based on the factors such as lateral stiffness and energy dissipation capacity etc. Sub-standard beam-column connections were prepared and tested under quasi-static cyclic loading with a specified constant axial load. In these specimens, brittle failure mechanism with very little energy dissipation capacity under earthquake-like cyclic loads was observed which is attributed to the pinching phenomenon. The designed specimens showed consistent behavior with similar specimens tested and documented in the literature. These sub-standard specimens were retrofitted with proposed novel technique with different anchorage conditions and tested under cyclic loading conditions. It is shown that in the retrofitted specimens, shear failure was postponed and plastic hinge formation moved away from column surfaces allowing specimens to fail in flexure without any indication of brittle failure, and lateral strength, stiffness, energy dissipation and ductility of the specimens are greatly improved

Potential Use of Locked Brick Infill Walls to Decrease Soft-Story Formation in Frame Buildings

The objective of this study is to investigate the effects of a new type of infillcalled locked brick infill adopting horizontal sliding jointsin reducing the soft-story formation in reinforced concrete (RC) frames with code-conforming seismic detailing. Nonlinear static time-history analyses were performed on multistory planar frames with only the upper stories infilled in order to force the soft-story irregularity. The parameters of frame and infill elements that were used in numerical simulations were obtained from half-scale RC infilled frame tests that had been performed by the author covering single story-single bay frames infilled with standard and locked bricks. The numerical simulations showed that the use of locked bricks to form infill walls has the potential to decrease the soft-story/weak-story formation in comparison to standard bricks due to its shear sliding mechanism and decreased upper-story/first-story stiffness, even in buildings that have noninfilled first stories. (C) 2014 American Society of Civil Engineers

Numerical Model Calibration and a Parametric Study Based on the Out-Of-Plane Drift Capacity of Stone Masonry Walls

Failure under seismic action generally occurs in the form of out-of-plane collapses of walls before reaching their in-plane strength in historical stone masonry buildings. Consistent finite element (FE) macro modeling has emerged as a need for use in seismic assessments of these walls. This paper presents the numerical model calibration of U-shaped multi-leaf stone masonry wall specimens tested under ambient vibrations and out-of-plane (OOP) load reversals. The uncertain elastic parameters were obtained by manual calibration of the numerical models based on ambient vibration test (AVT) data of the specimens. To obtain nonlinear calibration parameters, static pushover analyses were performed on FE models simulating quasi-static tests. The calibrated numerical models matched well with the experimental results in terms of load–drift response and damage distribution. As a result, the modulus of elasticity and tensile and compressive degrading strength parameters of masonry walls were proposed. A parametric study was conducted to examine the effects of different materials and geometric properties (tensile strength, aspect ratio, slenderness ratio, and geometric scale) on the OOP behavior of stone masonry walls. A quite different strain distribution was obtained in the case of a large aspect ratio, while it was determined that the geometric scale had no effect on the strain distribution. Tensile strength was the dominant parameter affecting the load–drift response of the models. Within the presented work, a practical tool for out-of-plane seismic assessment has been proposed for the structures covered in this paper

Strengthening of non-seismically detailed reinforced concrete beam-column joints using SIFCON blocks

This article aims to propose a novel seismic strengthening technique for non-seismically detailed beam column joints of existing reinforced concrete buildings, typical of the pre-1975 construction practice in Turkey. The technique is based on mounting pre-fabricated SIFCON composite corner and plate blocks on joints with anchorage rods. For the experimental part three 2/3 scale exterior beam column joint specimens were tested under quasi-static cyclic loading. One of them was a control specimen with non-seismic details, and the remaining two with the same design properties were strengthened with composite blocks with different thickness and anchorage details. Results showed that the control specimen showed brittle shear failure at low drift levels, whereas in the strengthened specimens, plastic hinge formation moved away from column face allowing specimens to fail in flexure. The proposed technique greatly improved lateral strength, stiffness, energy dissipation, and ductility