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The principle purpose of the current study is to hybridize firefly algorithm (FA) as a nature-inspired meta-heuristic developed based on the flashing patterns and biogeography-based optimization (BBO) to present a qualified algorithm in the case of optimization of steel frame (SF) structures. In the proposed meta-heuristic algorithm, FA works as a global search engine while BBO achieves the local search task. The proposed algorithm is termed as a firefly algorithm–biogeography-based optimization (FA–BBO). FA–BBO algorithm was employed for the optimization of benchmark SF problems for the validity in the case of a new algorithm. The numerical outputs demonstrate that the new FA–BBO algorithm presents a better computational performance in the comparison of the current algorithms. No sponsor

Beam-column joints require a high ductility during the unexpected loadings that necessitate theneed for ductile concrete in such unprotected locations. Alternatively, self-compacting concrete (SCC) isa sort of concrete which has generated tremendous interest throughout the last decades in order to reach aductile structural elements during the seismic actions. Specific properties of this type of concrete includehigh performance, high resistance against segregation and needless to internal or external vibration inorder to compact. In the seismic regions, ductility is one of the most important factors in the design ofreinforced concrete (RC) members, especially structural joints flexural performance; it is due to theenhance in the capability of plastic deformability. This paper describes load-displacement behavior ofexperimental and theoretical analysis of four SCC beam-column joints with different percentage of theratio of the reinforcing bars (ρ). In the theoretical phase of this investigation three-dimensional nonlinearfinite element method (FEM) model i.e., Seismostruct was used and the load-deflection diagrams wereplotted to compare the test results with the numerical output. The experimental results and nonlinear FEMmodeling indicate that using SCC as a workable concrete in beam-column joints of reinforced concretestructures has satisfactory performance in terms of ductility and energy dissipations., Yüksek süneklik gerektiren kolon-kiriş düğüm noktaları gibi korunmasız bölgelerde, beklenmedikyüklemeler altında, sünek betona ihtiyaç duyulmaktadır. Alternatif olarak, kendiliğinden yerleşen beton(KYB), deprem etkisi altinda elemanların daha sünek davranış gösteren bir yapıya ulaşmak için sonyıllarda büyük ilgi yaratan bir beton türüdür. Bu tipteki betonların belirgin özellikleri yüksek performans,segregasyona karşı yüksek direnç ve yerleşme için iç veya dış vibrasyona ihtiyaç duyulmamasıdır.Deprem bölgelerinde, süneklik, özellikle eğilmeye maruz kalan yapısal bağlantı noktalarınınperformansında önemli bir faktördür ve bu davranış plastik yerdeğiştirme kapasitesindeki artıştankaynaklanmaktadır. Bu makalede, KYB kullanılan ve farklı donatı oranlarındaki dört adet kolon-kirişdüğüm noktasının yük-yerdeğiştirme davranışının deneysel ve teorik analizleri açıklanmaktadır. Buaraştırmanın teorik aşamasında, üç boyutlu sonlu elemanlar metodu (SEM), Seismostruct doğrusalolmayan yazılımı kullanılarak, deneysel-nümerik sonuçlar karşılaştırılmış ve yük-yerdeğiştirmediyagramları çizdirilmiştir. Deneysel sonuçlar ve doğrusal olmayan SEM modeli, kolon-kiriş düğümnoktalarında işlenebilir beton olarak KYB’un kullanımının, betonarme yapılarda süneklik ve enerji yutmakapasitesi bakımından tatmin edici bir performansa sahip olduğunu göstermiştir.

In recent decades, self-compacting concrete (SCC) has gradually gained popularity based on its unique workability without any internal and external vibration. SCC development must ensure an acceptable level of balance between deformability and stability by following the characteristics of materials and the mix proportions. In the case of the structural performance of reinforced concrete (RC) structures throughout the earthquake, beam-column connections behavior is one of the most common causes of failures. On the other hand, T-shaped beam-column connections on the top floor have a critical condition based on the different types of live loads. As an alternative, SCC with specific properties includes workability and resilience against segregation, which is a great solution to improving the behavior of RC connections in a seismic area. In this paper, experimentally and numerically, investigation of six T-shaped SCC beam-column connections through different reinforcing bars ratio (ρ) are presented to better understand their behavior during the gravitational load like heavy snow, particularly in terms of failure mechanisms and cracking performance. In the experimental stage, firstly, the mechanical specifications of SCC have been examined in terms of slump flow, V funnel, J ring, and L box tests. Secondly, the load-displacement performance of T-shaped beam-column connections at the top floor has been reported in terms of bonding behavior, ductility, and energy dissipation capacity. The displacement ductility of the experimental results are decreased from 12.4 to 3.5 while the ratio of the reinforcing bars was increased from %15 to %66 of the balanced section, and the energy dissipations capacity was increased by increasing the reinforcing ratios until %56 of the balanced section then started to decrease. In the theoretical part of the study, a three-dimensional nonlinear finite element method (FEM) model (ABAQUS) was employed along with the load-deflection curves were reported to compare the experimental results with the numerical output. The test results demonstrate, employing SCC as a type of concrete that has enough workability in RC connections had successful fulfillment in terms of ductility, load-carrying capacity, and energy dissipation.

The main purpose of this study is to respond to an important question in the field of structural engineering: is the seismic collapse capacity of optimally designed concentrically steel braced frames acceptable or not? The present work includes two phases: performance-based design optimization and seismic collapse safety assessment. In the first phase, three nature-inspired metaheuristic algorithms, namely improved fireworks algorithm, center of mass optimization, and enhanced colliding-bodies optimization are employed to carry out the optimization task. In the second phase, seismic collapse capacity of the optimally designed concentrically steel braced frames is evaluated by performing incremental dynamic analysis and generating fragility curves. Two design examples of 5- and 10-story concentrically steel braced frames with two different topologies of braces are presented. The numerical results indicate that the center of mass optimization algorithm outperforms the other algorithms. However, all of the optimal designs found by all algorithms are of acceptable seismic collapse safety. No sponsor

The growing concern about global climate change and its adverse impacts on societies is putting severe pressure on the construction industry as one of the largest producers of greenhouse gases. Given the environmental issues associated with cement production, Geopolymer Concrete (GPC) has emerged as a sustainable construction material. This research experimentally studied the effect of partially substituting ground granulated blast-furnace slag (GGBS) with silica fume (SF) and natural zeolite (NZ) (by 0–30% with 5% increments) in the GPC activated by sodium hydroxide (NaOH) solution with different concentrations (4, 6 and 8 M) and sodium silicate (water glass) solution on the compressive strength. Obtained results revealed that increasing the NaOH concentration reduced the concrete strength, while adding SF and NZ to the concrete yielded an improvement in the compressive strength. Moreover, this study proposed an Artificial Neural Network (ANN) to predict the compressive strength of pozzolanic GPC based on GGBS (i.e., at the ages of 7, 28, and 90 days). The compressive strength of GGBS-based GPC (i.e., 117 concrete specimens manufactured out of 39 various mixtures) obtained by experimental tests was used to develop the model. The specimen age, NaOH concentration, contents of NZ, SF, and GGBS were considered as inputs variables for developing the ANN model. The predicted results establish the accuracy and high prediction ability of the proposed model. The findings of this study can bring significant benefits for the range of organizations involved. No sponsor

One of the feasible retrofitting techniques for existing reinforced concrete (RC) structures is to use Fiber Reinforced Polymers (FRPs). On the other hand, the efficiency of the FRP jacketing strategy in rectangular RC columns is less than square and circular cross-section. For this purpose, the seismic retrofit of five full-scale substandard rectangular RC columns is evaluated both numerically and experimentally in terms of load–displacement performance, failure mechanism and autopsy after the test. Besides, the study introduces an enhanced strategy employing carbon fiber reinforced polymers (CFRPs) as well as external steel ties to retrofit the full-scale RC columns with rectangular cross-section loaded through the weak direction. The findings demonstrate that the CFRP jackets and external steel ties considerably usefulness in comparison to the used retrofitting strategy specifically concerning ductility and energy dissipation capacity. Regarding the analytical work, the non-elastic performance of the retrofitted and reference specimens was established by using realistic material models employing Seismostruct as a finite element platform. Lastly, the analytical forecasting carried out employing the FRP retrofitting design methods presented by the Turkish Seismic Design Code (TSDC), ACI 440.2R and Eurocode 8 Part 3 are compared with experimental results. No sponsor

Brittle behavior of substandard columns during earthquakes is among the most common reasons of structural failures. Because capacity design principles and ductile detailing concepts have not been properly adopted during the construction of a large portion of existing buildings, many of them require seismic retrofitting. Among other deficiencies, lack of sufficient ductility is generally the major problem. External fiber-reinforced polymer (FRP) jacketing of columns is a feasible and promising method to overcome the problem of insufficient column ductility in existing substandard buildings. However, experimental data on the behavior of full-scale substandard columns is scarce, particularly in the case of columns with extended rectangular cross sections. Consequently, current standards do not allow FRP jacketing for the enhancement of ductility against seismic actions when the cross-sectional aspect ratio is higher than 1.5. Therefore, in this study, the seismic performance of full-scale substandard columns with extended rectangular cross sections is investigated both experimentally and theoretically. The columns are tested before or after retrofitting with carbon fiber-reinforced polymer (CFRP) jacketing. The findings of the study clearly demonstrate the efficiency of FRP jacketing for substandard columns, even for the case of extended rectangular cross sections. Furthermore, nonlinear analyses of reference and FRP-retrofitted columns, and comparison of the results of analytical study with experimental data, revealed that FRP retrofit design methods recommended by the American Concrete Institute (ACI) and Turkish codes are quite conservative, leading to unfeasible retrofit options, whereas the Eurocode approach leads to more realistic and economical retrofit solutions. No sponsor https://doi.org/10.1061/(ASCE)CC.1943-5614.0000907