Optimization of cylindrical wall domes via metaheuristic algorithms

Optimization is a widely used phenomenon in various problems and fields. Because time and resources are very limited in today's world, it can be said that the usage area of the optimization process will be expanded and spread in all areas of life. Although different methods are used in the realization of the optimization process, the performance of metaheuristic algorithms in solving problems has led to an increase in research on these methods. As in other fields, the application examples of these algorithms are diversifying and increasing in the field of structural engineering. In this study, the performance comparison of five different algorithms for the optimum design of an axisymmetric cylindrical wall with a dome is investigated. These algorithms are Jaya (JA), Flower pollination (FPA), teaching-learning-based optimization (TLBO) algorithms and two hybrid versions of these algorithms. ACI 318 regulation was used in reinforced concrete design with a flexibility method-based approach in the analyses. In the analyzes with five different situations of the wall height, some statistical values , and data of analysis numbers were obtained by running the algorithms a large number of times. According to the analysis results, Jaya algorithm is slightly better in terms of the speed of reaching the optimum result, but also all algorithms are quite effective and reliable in solving the problem.

Experimental and numerical investigation of T section connections

The paper summarizes recent experimental research on determining the full-range behaviour of steel beam-to-column connections. Unlike the connection types in the literature, numerical modeling was done with various experiments to determine the behavior of two types of connection types. In these joints, T joints have been studied, but unlike the literature, T joint's element is made of plates; It was obtained from 1/2 IPE profile, not by welding. Thus, it is thought that the problems such as workmanship errors, break point formation and in situ welding failures, which occur in the welding of T joints, are eliminated. Necessary studies have been carried out to have sufficient information about the behavior of the T joint to be manufactured from the IPE profile and thus to provide the opportunity for its use. In the light of the data obtained, numerical modeling is done and the torque rotation relation and behavior of semi-rigid joints are numerically modeled. Thus, thanks to the calibrated model with the experiments, the closest results to the real behavior were obtained for the unexamined combinations.

Decision-making model based multilayer perceptrons for estimation of optimum design properties for truss structure

Many branches of the structural engineering discipline have many problems, which require the generating an optimum model for beam-column junction area reinforcement, weight lightening for members such a beam, column, slab, footing formed as reinforced concrete, steel, composite, and so on, cost arrangement for any construction, etc. With this direction, in the current study, a structural model as a 5-bar truss is handled to provide an optimum design by determining the fittest areas of bar sections. It is aimed that the total bar length is minimized through population-based metaheuristic algorithm as teaching-learning-based optimization (TLBO). Following, the decision-making model is developed via multilayer perceptrons (MLPs) by performing an estimation application to enable directly foreseen of the optimal section areas and total length of bars, besides, the approximation and correlation success are evaluated via some metrics. Thus, determination of the real optimal results of unknown and not-tested designs can be realized with this model in a short and effective time.

Design of cylindrical steel liquid tanks with stepped walls using One-foot method

Cylindrical steel tanks are used in most countries to store bulk volumes of both solid and liquid products such as water, oil, gasoline and grain. Such steel tanks are prone to buckling when subjected to external pressure either due to vacuum or due to wind. These types of shell structures are generally controlled by elastic buckling failure because of the thin wall thickness. Cylindrical shells are commonly constructed with stepwise variable wall thickness due to economic reasons. The thickness of the tank shell wall is designed to increase from top to bottom because the stress resultants on the tank wall gradually increase towards the base of the tank. For open-top tanks, a primary stiffening ring is required at or near the top to maintain roundness under all loads. Stress resultants in a primary stiffening ring were previously identified by the Author for uniform wall thick tanks. In this new study, the applicability of this hand calculation method in stepped wall tanks has been investigated. Pursuant to this goal, a specified tank shell was designed considering One-foot method. Then, the stepped wall tank was transformed into an equivalent 1-course tank for hand calculation. Using the previously developed hand calculation method by Author, a test for the in-plane bending moment in the ring was conducted to achieve an acceptable value for stepped wall tanks. The analysis results show that the previously proposed method for uniform wall thick tanks may also be used for stepped wall tanks considering an equivalent thickness. On the other hand, using Linear Buckling Analysis (LBA), the buckling mode was obtained for two different stepped wall tanks in the study.

Evaluation of the period and soft story conditions of reinforced concrete buildings with and without infill walls

Since the ground floor of most of the buildings in our country is designed as a shop or ground floor (in the buildings created as a workplace), there is very little infill wall ratio on the ground floors due to architectural and functional reasons, and some of them do not even exist at all. However, infill walls significantly increase the horizontal rigidity and strength of the structure, thus causing a decrease in the period value that determines the earthquake loads that will affect the structure. However, the infill wall meets the first destructive forces of the earthquake, and during this time, it cracks and absorbs some of the earthquake energy. The structural system elements of the building (columns and shear walls) start to meet the earthquake forces only when the infill walls are damaged and fail. In this direction, the aim of this study is to investigate to what extent the amount of infill wall on the ground floor affects the period of the building, and whether there are soft storey irregularities in the building according to the change in the amount of infill wall on the ground floor. In this study, while there are infill walls on all floors and all axes of buildings of various heights (3, 6, 9 and 11 floors), the amount of infill walls in the x and y directions on the ground floors is reduced to a certain extent, and many models are created until the ground floor is completely without infill walls. All these models created were analyzed with the support of the SAP2000 program, and the period values were determined and examined according to the soft storey problems and compared with the case of the entire building with and without infill walls. In addition, it was examined whether the period formulas determined as a result of the studies and taking into account the infill wall give realistic results for the situation examined in this study.

A comparative study on the structural performance of an RC building based on updated seismic design codes: case of Turkey

The destructive earthquakes and structural damages reveal the importance of the rules of earthquake-resistant structural design. The need of update and renewal of these rules periodically become inevitable as a result of scientific developments, innovations in construction technologies and building materials. Turkey which is an extremely region in terms of seismicity was adapted to these changes through time. The last five seismic design codes (1968, 1975, 1998, 2007 and 2018) were taken into account within the scope of this study. The differences in dimension and material grades of structural elements such as columns as beams have been compared in detail for each code. Three different analysis types have been performed for a 4-story reinforced-concrete model such as eigenvalue, pushover and dynamic time-history via the minimum conditions for these elements in each code. The natural vibration period of the building was obtained with empirical formulas stipulated in different codes for the sample RC building, additionally. The size and the type of the materials used in beams and columns within the last five codes have been changed. We see that the changes in these two important parameters which affect the behavior of buildings during an earthquake, enhance the performance of the building. It has been revealed that changes and renewals in seismic design codes are a necessity and gain. It has been clearly revealed that each amended code increases the stiffness and enhance the seismic capacity of a structure. Each updated seismic design code is aimed to complete the deficiency of the previous one. The results revealed that there are changes to be made to increase the seismic capacity of the structure at the point of reducing earthquake damage.

A numerical study on influence of strain gradients on lattice rotation in micro-machining of a single crystal

In latest years small scale machining has been widely used in advanced engineering applications such as medical and optical devices, micro- and nano-electro-mechanical systems. In micromachining of metals, a depth of cut becomes usually smaller than an average crystal size of a polycrystalline structure; thus, the cutting process zone can be localized fully indoors of a single grain. Due to the crystallographic anisotropy, development of small scale machining models accounting for crystal plasticity are essential for a precise calculation of material removal under such circumstances. For this purpose, a 3D finite-element model of micro-cutting of a single grain was developed. A crystal-plasticity theory accounting for gradients of strain, implemented in ABAQUS/Explicit via a user-defined material subroutine VUMAT, was used in the computations. The deformation-induced lattice rotations in micro-cutting of a single crystal were analyzed extensively.

Investigation of moment-curvature and effective section stiffness of reinforced concrete columns

In determining the seismic performance of reinforced concrete (RC) structures in national and international seismic code, it is desired to use effective section stiffness of the cracked section in RC structural elements during the design phase. Although the effective stiffness of the cracked section is not constant, it depends on parameters such as the dimension of the cross-section, concrete strength and axial force acting on the section. In this study, RC column models with different axial load levels, concrete strength, longitudinal and transverse reinforcement ratios were designed to investigate effective stiffness. Analytically investigated parameters were calculated from TBEC (2018), ACI318 (2014), ASCE/SEI41 (2017), Eurocode 2 (2004) and Eurocode8 (2004, 2005) regulations and moment-curvature relationships. From the numerical analysis results, it is obtained that the axial load level, concrete strength, longitudinal and transverse reinforcement ratios have an influence on the effective stiffness factor of RC column sections. The calculated effective stiffness for RC columns increases with increasing transverse reinforcement ratio, longitudinal reinforcement ratio and concrete strength. Due to the increase of axial force, effective stiffness values of concrete have increased.

Buckling analysis of natural fiber reinforced composites

In the recent years natural fiber reinforced composites are increasingly receiving attention from the researchers and engineers due to their mechanical properties comparable to the conventional synthetic fibers and due to their ease of preparation, low cost and density, eco-friendliness and bio-degradability. Natural fibers such as kenaf or flux are being considered as a viable replacement for glass, aramid or carbon. Extensive experimental studies have been carried out to determine the mechanical behavior of different natural fiber types such as the elastic modulus, tensile strength, flexural strength and the Poisson’s ratio. This paper presents a review of the various experimental studies in the field of fiber reinforced composites while summarizing the research outcome about the elastic properties of the major types of natural fiber reinforced composites. Furthermore, the performance of a kenaf reinforced composite plate is demonstrated using finite element analysis and results are compared to a glass fiber reinforced laminated composite plate.

A comparative study on yield line mechanisms for four bolted extended end-plated connection

Extended end-plated connections are preferred in moment resisting frames due to their advantages such as no required in-situ welding, accurate fabrication and economic feasibility compared to flange welded moment connections. The capacity of the extended end-plated connections depends on bolt configurations, end-plate thickness, bolt diameter and their material properties excluding column part. The thickness of end-plate can be computed using yield line mechanisms. Different yield line patterns are available in the literature and some of these are adopted in seismic codes to estimate the thickness of end-plate. In this study, the accuracy of different yield line patterns is compared using collected experimental data and numerical analysis. A parametric numerical analysis was conducted utilizing the finite element tool, ABAQUS. The results of experimental data and parametric study were evaluated for both unstiffened and stiffened four bolted extended end-plated connections. The results revealed that the capacity of the end-plate connections significantly depends on the yield line mechanism. Therefore, selecting an accurate yield line mechanism is essential in order not to overestimate the thickness of the end-plate. More importantly is that these yield line mechanisms can be directly implemented to AISC 358 and Turkish Building Earthquake Code 2018 (TBEC-2018).