Discrete Sizing of Steel Frames Using Adaptive Dimensional Search Algorithm

Adaptive dimensional search (ADS) algorithm is a recently proposed metaheuristic optimization technique for discrete structural optimization problems. In this study, discrete sizing optimization problem of steel frames is tackled using the ADS algorithm. An important feature of the algorithm is that it does not use any metaphor as an underlying principle for its implementation. Instead, the algorithm employs an efficient performance-oriented methodology at each iteration for convergence to the optimum or a near optimum solution. The performance of the ADS is investigated through optimum design of five real-size steel frame structures and the results are compared versus several contemporary metaheuristic techniques. The comparison of the obtained numerical results with those of available designs in the literature reveals the reliability and efficiency of the ADS in optimum design of steel frames

Bladder Lymphangioma Treated by Holmium Laser: Extremely Rare Case Report

Introduction: Lymphangioma is a sporadic benign tumor of the bladder. It is a congenital disorder and based on the size of lymphatic spaces, it is divided into 3 types of capillary, cavernous, and cystic.Case Report: In this paper, we presented a 40-year-old woman with microscopic hematuria and a normal urinary ultrasound. Urethrocystoscopy showed a flat 4 mm highlighted strawberry-like lesion on the right lateral wall of the bladder. After a cold cup biopsy, the lesion was coagulated by the holmium: YAG (Ho: YAG) laser.Conclusion: In Bladder Lymphangioma Based on the size of the lesion, partial cystectomy or minimally invasive surgeries such as laser modality would be the principal treatment. 

Retrograde-assisted Percutaneous Cystolitholapaxy versus Transurethral Cystolithotripsy with Holmium-YAG Laser, A Retrospective Study

Introduction: The retrograde approach is a modification that makes the percutaneous cystolitholapaxy (PCCL) a more trendy method, especially in operating rooms with limited facilities. The transurethral approach for bladder calculi lithotripsy by a laser has become popular among urologists. In this study, we investigate the feasibility and safety of retrograde assisted access for PCCL in comparison with transurethral cystolithotripsy by the holmium-YAG laser (Ho:YAG).Methods: According to the type of intervention, the patients were stratified to two matched groups. In the retrograde-assisted percutaneous cystolitholapaxy (RPCCL) group, a Benique was conducted through the urethra into the bladder; palpating the suprapubic region, an about 1.5 cm incision was done over the tip, then an Amplatz sheath was placed over it, treading into the bladder; further cystolitholapaxy was done by a routine order. In transurethral Ho: YAG laser lithotripsy (TULL) via 200 μm fiber vaporize the stone.Results: A total of 124 male patients with the mean age of 50.33 ± 9.64 years and the average stone burden of 3.35 ± 1.07 cm were included in the study. The most common cause of vesical calculi was spinal cord injury. Statistically significant differences were found in terms of the mean operation time in favor of the RPCCL group (P ≤ 0.05) and the mean hospital stay in favor of the TULL group (P ≤ 0.05). The stone-free rate (SFR) was 100% in both methods after a one month follow-up. None of the interventions changed to open surgery. There were not any major complications in both methods.Conclusion: RPCCL is a safe and effective method in bladder stone treatment and is applicable inmedical centers without Ho: YAG equipment

Upper bound strategy for metaheuristic based design optimization of steel frames

Optimum design of structural systems based on metaheuristic algorithms suffers from enormously time-consuming structural analyses to locate a reasonable design. In this paper an upper bound strategy (UBS) is proposed for reducing the total number of structural analyses in metaheuristic based design optimization of steel frame structures. The well-known big bang-big crunch algorithm as well as its two enhanced variants are adopted as typical metaheuristic algorithms to evaluate the effect of the UBS on computational efficiency of these techniques. The numerical results reveal that the UBS can significantly lessen the total computational cost in metaheuristic based design optimization of steel frames

Structural Optimization Using Big Bang-Big Crunch Algorithm: A Review

The big bang-big crunch (BB-BC) algorithm is a popular metaheuristic optimization technique proposed based on one of the theories for the evolution of the universe. The algorithm utilizes a two-phase search mechanism: big-bang phase and big-crunch phase. In the big-bang phase the concept of energy dissipation is considered to produce disorder and randomness in the candidate population while in the big-crunch phase the randomly created solutions are shrunk into a single point in the design space. In recent years, numerous studies have been conducted on application of the BB-BC algorithm in solving structural design optimization instances. The objective of this review study is to identify and summarize the latest promising applications of the BB-BC algorithm in optimal structural design. Different variants of the algorithm as well as attempts to reduce the total computational effort of the technique in structural optimization problems are covered and discussed. Furthermore, an empirical comparison is performed between the runtimes of three different variants of the algorithm. It is worth mentioning that the scope of this review is limited to the main applications of the BB-BC algorithm and does not cover the entire literature

Structural Optimization Problems of the ISCSO 2011-2015: A Test Set

Beginning in 2011 an international academic contest named as International Student Competition in Structural Optimization (ISCSO) has been organized by the authors to encourage undergraduate and graduate students to solve structural engineering optimization problems. During the past events on the one hand a unique platform is provided for a fair comparison of structural optimization algorithms; and on the other hand it is attempted to draw the attention of students to the interesting and joyful aspects of dealing with optimization problems. This year, after five online events successfully held with support and help of our advisory and scientific committee members from different universities all around the world, the authors decided to gather the test problems of the ISCSO in this technical report as an optimization test set. Beside the well-known traditional benchmark instances, the provided test set might also be used for further performance evaluation of future structural optimization algorithms

Behaviour and Design of Fabricated Concrete-Filled Stainless Steel Tubular Columns

The present thesis starts by investigating the local and post-local buckling behaviour of fabricated box and circular concrete-filled stainless steel tubes (CFSSTs) as well as stainless steel partially-encased I-sections. A comprehensive set of experiments considering austenitic, duplex, and lean duplex stainless steel grades is carried out followed by an extensive numerical parametric study. The results are then summarised to propose, for the first time, axial slenderness limits and effective width/diameter formulae for the studied section types. The investigation on the local stability is extended in the next part of the thesis where a comprehensive numerical study is conducted to clarify the role of concrete infill in the local buckling behaviour of circular tubes. The results strongly suggest that the concrete infill has limited effect on enhancing the local buckling strength of circular tubes. The enhancement is found to be much lower than that implied in international design standards. The roots for this discrepancy are identified and it is suggested that the axial slenderness limit for hollow circular tubes can be significantly relaxed to bring it closer to that of filled circular tubes. The final part of the thesis focuses on the response of compact and slender box CFSSTs under axial and flexural actions. An experimental programme is first carried out comprising compact and slender CFSSTs fabricated from austenitic and lean duplex plates. Stub columns under axial compression as well as combined compression and bending, CFSST beams under pure bending, and long CFSST columns under axial compression are all included in the experiments. The tests are followed by an extensive numerical study. Outcomes of the investigations are then synthesised to develop comprehensive procedures for the design of compact and slender box CFSSTs under compression, bending, and combined loading. Such procedures have not yet been established for CFSSTs in international design standards

Çelik çerçeveli sistemlerde kullanılan çapraz ve değiştirilebilir bağ kırışlerının nümerik incelenmesi

Concentrically braced frames (CBFs) and eccentrically braced frames (EBFs) are among popular lateral load resisting systems for steel structures. The present study investigates different aspects of these systems. The part devoted to EBFs begins with a comprehensive review of research where 22 future research needs are identified and presented. This is followed by an experimental study on the low-cycle fatigue behavior of links, which are the most important members of an EBF. Results of the experimental study are then combined with a comprehensive database of previous experiments available in the literature and synthesized to calibrate a cumulative damage law for estimating the exhausted as well as the remaining life of a link during an earthquake. A simple 8-step algorithm was outlined which utilizes the developed damage law for estimating the accumulation of damage as well as the instant of link fracture in nonlinear time history analysis under earthquake-induced loading histories. The algorithm can also contribute significantly to the decision-making process of the post-earthquake replacement of EBF links. In addition, in the EBF part of the thesis, a replaceable link detail with a mid-splice connection (referred to herein as the detachable replaceable link concept), recently developed at METU, is numerically investigated. After reviewing the previous experiments conducted on the concept, a comprehensive parametric study is carried out and a design equation is developed for estimating the axial force that the midsplice connection can experience due to large link deformations and end restraint effects. In order to further investigate the application of the proposed detail for larger (deeper) shear links than those previously tested, another set of sophisticated simulations is conducted. The analysis results further suggest the potential of the detachable concept for practical applications. For the CBF part of the thesis, first, the seismic design rules recommended by American and European provisions are thoroughly reviewed and compared. A series of CBF archetypes are then designed based on American and European provisions and subjected to a large set of earthquakes in order to investigate and compare their seismic performances. Results of more than 800 nonlinear time-history analyses reveal that the differences which exist between these provisions can lead to significant differences in the observed seismic performances. The most notable difference is the occurrence of soft-story behavior at the top stories of the CBF archetypes designed according to European provisions. Possible reasons for this phenomenon are investigated and recommendations are provided. In the last part of the thesis, the effect of rapid shortening of braces during earthquakes on the seismic behavior of CBFs is investigated. Axially loaded members might experience compressive forces above their static buckling capacity as a result of dynamic buckling under such rapid shortenings. A theoretical background on the topic is provided followed by a comprehensive parametric study considering several CBF configurations under a large set of earthquakes. Results of a total of 1600 nonlinear time-history analyses are utilized to demonstrate the frequency of occurrence and importance of this phenomenon particularly for the capacity design of columns, beams, and gusset plates of CBFs. The implications of these extra forces were discussed, and a simple formula was developed which can be used for the estimation of the ultimate brace force (considering the dynamic buckling effect) during the capacity design of CBF systemsMerkezi Çaprazlı Çerçeveler (MÇÇ’ler) ve Dışmerkez Çaprazlı Çerçeveler (DÇÇ’ler) çelik yapılar için kullanılan yatay yük taşıyıcı sistemler arasındadır. Bu çalışma, bahsi geçen sistemlerin farklı yönlerini araştırmaya yöneliktir. DÇÇ'lere ayrılan bölüm, gelecekteki 22 araştırma ihtiyacının belirlendiği ve sunulduğu kapsamlı bir araştırma incelemesi ile başlamaktadır. Bunu, DÇÇ’lerin en önemli elemanı olan bağ kirişlerinin düşük çevrimsel yorulma davranışı üzerine deneysel bir çalışma izlemektedir. Deneysel çalışmanın sonuçları literatürde mevcut olan deneysel sonuçlarla birleştirilerek bir veritabanı oluşturulmuştur. Veritabanı doneleri kullanılarak deprem sırasında bağ kirişlerinin tükenen ve kalan ömrünü tahmin etmek için kümülatif bir hasar yasası kalibre edilmiştir. Deprem kaynaklı yükleme geçmişleri altında doğrusal olmayan zaman tanım alanı analizinde hasar birikimini tahmin etmek için geliştirilmiş hasar yasasını ve bağ kirişinin göçme anını kullanan basit bir 8 aşamalı algoritma özetlenmiştir. Algoritma ayrıca deprem sonrası DÇÇ bağ kirişlerinin değiştirilmesinin karar verme sürecine önemli ölçüde katkıda bulunabilecek niteliktedir. Ayrıca tezin DÇÇ bölümünde son zamanlarda ODTÜ'de geliştirilen orta ek bağlantılı değiştirilebilir bir bağ kiriş detayı numerik olarak incelenmiştir. Ayrılabilir değiştirilebilir bağ kirişleri üzerinde yapılan önceki deneyler gözden geçirildikten sonra, yüksek bağ kiriş deformasyonları ve uç kısıtlama etkileri nedeniyle orta ek bağlantısının maruz kalacağı eksenel kuvveti tahmin etmek için kapsamlı bir parametrik çalışma gerçekleştirilmiş ve bir tasarım denklemi geliştirilmiştir. Deneysel olarak incelenen bağ kirişlerinden daha derin kesme bağ kirişleri için önerilen detayın uygulanmasını araştırmak için numeric simülasyonlar yapılmıştır. Analiz sonuçları ayrılabilir değiştirilebilir bağ kirişi konseptinin pratik uygulamalar için potansiyelini ortaya koymaktadır. Tezin MÇÇ kısmı için öncelikle Amerika ve Avrupa şartnameleri tarafından önerilen sismik tasarım kuralları iyice gözden geçirilmiş ve karşılaştırılmıştır. Daha sonra bir dizi MÇÇ modeli, Amerikan ve Avrupa şartnamelerine göre tasarlanmış ve sismik performanslarını araştırmak ve karşılaştırmak için geniş bir deprem setine tabi tutulmuştur. Sekizyüzden fazla doğrusal olmayan zaman tanım alanı analizinin sonuçları, bu şartnameler arasında var olan farklılıkların gözlemlenen sismik performanslarda önemli farklılıklara yol açabileceğini ortaya çıkartmıştır. En dikkate değer fark, Avrupa şartnamelerine göre tasarlanan MÇÇ modellerinin en üst katlarında yumuşak kat davranışının ortaya çıkmasıdır. Bu olayın olası nedenleri araştırılmıştır ve öneriler sunulmuştur. Çalışmanın son bölümünde depremler sırasında çaprazların yükleme hızının MÇÇ'lerin sismik davranışına etkisi araştırılmıştır. Eksenel olarak yüklenmiş elemanlar, ani yüklemeler altında dinamik burkulmanın bir sonucu olarak statik burkulma kapasitesinin üzerinde basınç kuvvetlerine maruz kalabilirler. Konuyla ilgili teorik bir arka plan ve ardından geniş bir deprem dizisi altında çeşitli MÇÇ konfigürasyonlarını dikkate alan kapsamlı bir parametrik çalışma yapılmıştır. Toplam 1600 doğrusal olmayan zaman tanım alanı analizinin sonuçları, özellikle MÇÇ'lerin kolonlarının, kirişlerinin ve guse levhalarının kapasite tasarımı için bu durumun ortaya çıkma sıklığını ve önemini göstermek için kullanılmıştır. Bu ekstra kuvvetlerin etkileri tartışılmış ve MÇÇ sistemlerinin kapasite tasarımı sırasında, dinamik burkulma etkisi dikkate alınarak, nihai çapraz kuvvetinin tahmin edilmesi için kullanılabilecek basit bir formül geliştirilmiştirPh.D. - Doctoral Progra