Hasil untuk "Structural engineering (General)"

Peter Trusov, Pavel Gladkikh

The most important element of mathematical models of thermomechanical processing of metals and alloys is the constitutive model. In recent decades, multilevel physically-oriented constitutive models (CMs) have found widespread application. The first two-level model was the rigid-plastic theory of J. Taylor,a rigorous mathematical justification of which was developed by J. Bishop and R. Hill (TBH type models). The main disadvantage of this model is the uncertainty of the choice of active slip systems when more than 5 systems are activated. Despite this, the TBH models have become widespread, and its basic provisions have been preserved in many later developments. It seems that limiting the number of active slip systems to 5 has no physical justification and is determined only by the numerical procedure for implementing the model. Since the 1970s, elastic-viscoplastic models have emerged; it has been shown that as the velocity sensitivity parameter tends to zero, the macroparameters determined in the modeling converge to a solution using an elastic-plastic model. However, the system of equations becomes rigid, requiring the use of implicit schemes and extremely small time steps, which significantly reduces the computational efficiency. The paper proposes a modification of elastic-plastic model of the TBH type, in which a procedure for overcoming the above-mentioned drawback is proposed. To compare the computational efficiency of the elastic-plastic and elastic-viscoplastic models, a series of numerical experiments was carried out.

Bongseok Ryu, Soyoung Bang, Dongyoup Kwak

To enable the engineering application of earthquake ground motion records, this study establishes a standardized preprocessing procedure and systematically analyzes how each preprocessing step affects the characteristics of the ground motion data. Due to recent expansion of seismic networks in South Korea, low- to mid-amplitude seismic ground motions become abundant. However, raw ground motion recordings contain instrument responses and ambient noise and are often affected by baseline drift, which leads to divergence in the integrated displacement time histories. Therefore, reliable use of these records in engineering analysis requires a comprehensive preprocessing procedure that includes instrument response correction, signal windowing, filtering, and baseline correction. In this study, we performed a sensitivity analysis on ground motion data recorded in South Korea to quantitatively assess how key preprocessing parameters influence ground motion characteristics. Based on the findings, a standardized preprocessing workflow is proposed to support the effective use of ground motion records in site response analysis, dynamic structural analysis, and seismic hazard assessments.

Z.M. Najem , Thaer Alrudaini

This study investigates the effect of spans length, reinforcement ratio and continuity of flexural reinforcement on the progressive collapse performance of double span beams over failed columns. The investigations focus on initial flexural resisting mechanism to prevent the progressive collapse. Detailed nonlinear finite element simulation of double span beam-column sub-assemblages subjected to residual gravity loads that initially carried by the failed column is adopted for the investigations. Nonlinear static pushover analysis is conducted in which capacity curves are derived and compared with demanded capacities. The effect of spans length, reinforcement ratio and number of continuous bottom flexural reinforcement on progressive collapse are considered in the investigations. Analysis results show that the strength to resist progressive collapse has decreased by 25.4 % and the ductility increased by 103 % following the increasing in span length from 5 m to 7 m. On the other hand, increasing reinforcement ratio of top flexural reinforcement from 0.447 to 1.089 leads to 26.27 % increasing in strength accompanied with a decrease in ductility equal to 16.42 %. In addition, extending all bottom bars rather than the minimum specified two bars resulted in 12 % increasing in strength and 40.28 % decreasing in ductility.

Alba Soler Estrela

La arquitectura valenciana vivió un momento de esplendor durante los siglos XIV, XV y XVI en un tiempo de desarrollo económico, en correspondencia con la expansión por el Mediterráneo de la Corona de Aragón. Personajes nobles construyen casas señoriales y palacios que destacan por su riqueza arquitectónica, y acabados decorativos. Entre ellos cabe señalar los dibujos geométricos de la carpintería de sus puertas y ventanas, que resultan característicos de este tipo de edificio en la época y entorno geográfico mencionado. En algunos casos pueden suponerse originales, pero dadas sus características, es un elemento que ha podido sufrir renovaciones y sustituciones, en algunos casos datadas en el siglo XX. Se presenta una aportación a su conocimiento, aplicando una metodología de análisis de los trazados decorativos, que puede ser complementaria a estudios de tipo histórico, dentro de un enfoque multidisciplinar. A partir de un número representativo de casos se analiza la generación de formas en base a las teselaciones regulares y semirregulares, descubriéndose un variado repertorio. Ello permite establecer una clasificación y descripción de los distintos tipos, que se definen gráficamente y se ilustran con ejemplos de aplicación concreta y de adaptación a las formas de las portadas y ventanales.

Fawzi Latosh, Abobakr Al-Sakkaf, Ashutosh Bagchi

Unlike steel reinforcements in concrete, Fiber Reinforced Polymer (FRP) materials are light and free from corrosion. Therefore, FRP materials are increasingly being used in structural engineering as a replacement for steel reinforcements. While the use of FRP bars as longitudinal reinforcements in concrete deep beams has been studied somewhat widely, their use and effectiveness as web reinforcements are not well studied. In this study, the effect of the FRP web reinforcements on the behaviour and strength of FRP-reinforced concrete deep beams were investigated in an experimental study. Four glass fiber-reinforced concrete (RC) simply supported deep beam specimens were tested under a concentrated load with different shear span-to-depth ratios and web reinforcement ratios. The behaviour of the deep beams was described in terms of load–deflection behaviour, crack developments, strain in FRP reinforcements, and failure modes. The experimental investigation emphasized the significance of web reinforcements in determining the reinforced concrete deep beam behaviour, such as mid-span deflection, crack breadth, failure modes, and ultimate strengths. Furthermore, to predict the behavior of deep beams, numerical Finite Element models using Abaqus software were created. The present test results were compared to those predicted using the Finite Element models. This investigation shows that web reinforcement is quite important for FRP-RC deep beams to achieve a robust behaviour by enhancing its capacity and deformability.

Nikita A. Penkov, Sergey Yu. Zhachkin, Anatoliy I. Zavrazhnov

Introduction. The article deals with the problem of calculating the strength of the shaft of the wheel drive of agricultural machinery. The strength conditions of both the maximum torque and the values of relative deformations of the shaft are taken into account. Aim of the Article. Of the research is to determine the limits of external influences on a structural element, caused by the distributed weight of the motor-tractor machinery, at which it is necessary to construct not only the torque and strain diagrams, but also to determine the extreme values at each section, where the strength index of the structure is nonlinear. Materials and Methods. In calculations, the main provisions of continuum mechanics, theory of machines and mechanisms, as well as the basics of design in mechanical engineering are used. Central attention is paid to the influence of external influencing factors on the character of internal force distribution in the shaft. Results. The obtained area of variation of parameters P-q allows us to determine the necessity of more detailed calculation of strength parameters of the considered part. This is due to the emergence of extreme areas outside the boundaries of individual areas of consideration of the shaft work. The results are presented as a two-dimensional graph of the ratio of external influences, at which the specified effect takes place. Discussion and Conclusion. In comparison with typical calculations, regulated by normative documents, the proposed algorithm at the preliminary stage allows to determine the cases when nonlinear regions of bending moment changes require additional investigations. The use of the proposed algorithm allows, without resorting to time-consuming numerical methods of calculating the strength indicators of a wheel drive shaft, such as the finite element method, to obtain a more detailed picture of the nature of distribution of internal forces and deformations in the part under study.

Jianhe Li, Weizhe Sun, Guoshao Su et al.

The geomechanical parameters in underground engineering are usually difficult to determine, which can pose great obstacles in underground engineering. A novel displacement back-analysis method is proposed to determine the geomechanical parameters in underground engineering. In this method, the problem of geomechanical parameter determination is converted into an optimization problem, regarding the geomechanical parameters as the optimization parameters, and the error between the calculated results and the field measurement information as the optimization objective function. The grasshopper optimization algorithm (GOA), which offers excellent global optimization performance, and the Gaussian process regression (GPR) machine learning, offering powerful fitting ability, are combined to address the time-consuming numerical calculations. Furthermore, the proposed method is combined with the 3D numerical calculation software FLAC^3D to form the GOA-GPR-FLAC^3D method, which can be used in the displacement back-analysis of geomechanical parameters in underground engineering. The results of a case study show that the proposed method can greatly improve computational efficiency while ensuring high precision compared with the GOA. When applied to the Tai’an Pumped Storage Power Station, this method can obtain more accurate results compared with the GOA under the same evaluation times and is more suitable for the back-analysis of rock parameters in underground engineering.

Xiaomiao Chen, Junwu Xia, Bo Xu et al.

This study presents an experimental investigation into the mechanical performance of built-up columns composed of four cold-formed square steel tubes under axial load. The four tubes were assembled together with several C-shaped connectors through two self-tapping screws in each junction. The influence of parameters including spacing between tubes, type of connectors and transverse diaphragm were analyzed based on the failure modes, ultimate loads, load-displacement relationships and load-strain relationships measured in the tests. Moreover, a further numerical analysis was carried out to study the effect of the number of connectors, web height of connectors and installing connectors at column ends by means of the verified finite element models. Finally, the numerical results were compared with the strengths predicted by the AISI-S100-2012 code. Results show that the performance of built-up columns can be influenced by the change in the number of connectors and ratio of web height of connectors to spacing between tubes as well as the installation of connectors at column ends. In addition, the current AISI-S100-12 specifications do not provide a good prediction of the built-up columns composed of four cold-formed square steel tubes.

Costanzo Bellini, Vittorio Di Cocco, Francesco Iacoviello et al.

Industry needs new materials that present very high structural characteristic, such as high strength, low weight and high damage tolerance. To obtain these characteristics a new class of materials has been introduced: Fibre Metal Laminate (FML); they consist in metal sheets alternated to composite material layers: in such manner, the good characteristics of each constituent material confer the utmost properties to the FMLs. However, the mechanical properties depend, among other factors, on the thickness and the numerousness of the layers constituting the FML, as well as the interface between metal and composite. Therefore, in this paper, the influence of the abovementioned factors on the material answer to flexural load was investigated. In particular, different kinds of laminates were produced varying the layers adhesion and the layers thickness, but maintaining unaltered the metal/composite volume ratio and the total laminate thickness. Then their structural behaviour was investigated through three-point bending test, and it was found that the flexural behaviour was affected by both the investigated factors; in fact, the maximum flexural load diminished incrementing the number of layers and inserting an adhesive layer at the metal/composite interface.

X. L.Zhu, H. Zhang

The acceleration of construction of cities and towns motivates the development of the construction industry. Prefabricated residential building is extensively concerned by the public for its small damages to the surrounding environment and high quality. In this study, different construction stages of the prefabricated residential building were analyzed, and factors influencing the construction cost in different stages were discussed. The construction technique, speed, civil work cost and environmental benefits were compared between the traditional concrete building and the prefabricated residential building. Moreover the differences of costs in different stages were compared in a real case. Several effective measures for controlling construction cost were put forward. The results demonstrated that the cost of the prefabricated residential building was much lower than that of the traditional concrete building. The suggestions for reducing construction cost can provide a reference for similar projects.

Daniele Dordenoni, Taís Zago Mariani, Bruno Ceotto Sobrinho et al.

In the present paper, a study on the design of reinforcements to resist shear efforts in reinforced concrete beams was developed. In the literature review, the main topics related to stirrups dimensioning were addressed according to calculation models I and II of NBR 6118:2014. From the bibliographic review, and using Microsoft Excel, an electronic spreadsheet was developed to calculate shear reinforcement areas for rectangular section concrete beams. Then, a case study was conducted in which were designed transversal reinforcements for 15 beams, according to calculation models I and II. The beams were organized in three sets, covering the most recurrent design widths (15, 20 and 25 cm), and in each set, the heights were chosen among the five most recurring design measures (20, 30, 40, 50 and 60 cm). In the case study, it was obtained for each beam the maximum and minimum shear reinforcement area according to the calculation models I and II, and other NBR 6118: 2014 requirements. In this research it was concluded that, for the set of beams analyzed, the calculation model II, for concrete strut with a 30º, has a greater saving area in relation to model I, however, with percentages varying according to each studied case.

Faisal Nurdin, Hendri Silva, Imbardi Imbardi

Berdirinya Universitas Lancang Kuning (UNILAK) diprakarsai oleh Pemerintah Provinsi Riau dan tokoh-tokoh masayarakat Riau, UNILAK memeliki 2 prodi pasca sarjana, yaitu pascasarjana prodi manajemen yang terletak di samping perpustakaan dan pasca sarjana prodi hukum yang letaknya masih terpisah-pisah, disamping itu adanya wacana menambah prodi pasca sarjana lain seperi prodi ilmu budaya yang sedang dalam proses perizinan, prodi ilmu lingkungan dan prodi administrasi publik, berkaitan dengan hal tersebut maka di butuhkan pembangunan fasilitas baru untuk mewadahi aktifitas tersebut. Karena masih terpencar-pencarnya Gedung Pascasarjana di Universitas Langcang Kuning, maka di buatlah suatu gagasan atau rencana dari kampus untuk membangun Gedung Pasca Sarjana menjadi satu lokasi, dan untuk mendukung visi dan misi unilak yaitu menjadi perguruan ringgi yang unggul pada tahun 2030, maka untuk mencapai target tersebut di butuhkan fasilitas seperti Gedung Pasca Sarjana Unilak. Gedung Pascasarjana Unilak ini diharapkan dapat menciptakan sebuah tempat atau wadah yang dapat menunjang peningkatan kualitas pendidikan Pascasarjana di Unilak dengan konsep arsitektur tropis.

Ali Mehmanparast, Oyewole Adedipe, Feargal Brennan et al.

Residual stresses are often inevitably introduced into the material during the fabrication processes, such as welding, and are known to have significant effects on the subsequent fatigue crack growth behavior of welded structures. In this paper, the importance of welding sequence on residual stress distribution in engineering components has been reviewed. In addition, the findings available in the literature have been used to provide an accurate interpretation of the fatigue crack growth data on specimens extracted from the welded plates employed in offshore wind monopile structures. The results have been discussed in terms of the role of welding sequence in damage inspection and structural integrity assessment of offshore renewable energy structures.

R.C.O. Góes, J.T.P. Castro, M.A. Meggiolaro

Notches and cracks are usually approximately modeled as two-dimensional problems using solutions from plane elasticity to quantify localized stress/strain concentration effects around their tips. However, they may be associated with high gradients that can severely restrict local Poisson-induced transversal strains and cause important 3D stress fields around those tips. Fatigue crack initiation and growth, plastic zone sizes and shapes, and localized constraint effects that affect toughness are typical problems associated with such 3D effects, which may lead to non-conservative damage and life predictions if neglected. To quantify how important they can be, first finite element techniques are used to simulate thickness and notch-tip radius effects in the fields around such tips, and to evaluate their importance from the structural design point of view. Then, versatile sub-modeling techniques are used to study similar effects along the fronts of short and long cracks, and a stepwise re-meshing routine is used to show how an initially straight crack must slightly curve its front during its propagation by fatigue, due to the unavoidable 3D effects that always surround real crack tips.

A. De Iorio, M. Grasso, F. Penta et al.

When the compliance with the European Code of some rail steel has to be verified, the need of carrying out the experimental activities in accordance with several testing Standards forces the operator both to solve the problems related to the choice of a suitable testing practice and often to interpret subjectively Standards guidelines. This does not facilitate the comparability and/or the quality of the results produced by several laboratories. With reference to a series of fatigue, fracture toughness and fatigue crack growth tests carried out by the authors on specimens extracted from rails, the main lacks in the current standards, related to both the choice of the control parameters and the testing procedures, are pointed out. Regarding the crack growth testing, several procedures to compute the crack growth rates to be compared with the limits prescribed by the Code are proposed. These procedures have been applied to a data set produced during the aforementioned testing activity, in order to highlight, by comparison of the results obtained by them, the significant differences in the crack growth rate estimates and the magnitude of the errors that can be done due to the lacks in the standard practices currently adopted.