Routine Design Research Articles

Particle Swarm Optimization Algorithm Coupled with Finite Element Limit Equilibrium Method for Geotechnical Practices

This paper proposes a modified particle swarm optimization algorithm coupled with the finite element limit equilibrium method (FELEM) for the minimum factor of safety and the location of associated noncircular critical failure surfaces for various geotechnical practices. During the search process, the stress compatibility constraints coupled with the geometrical and kinematical compatibility constraints are firstly established based on the features of slope geometry and stress distribution to guarantee realistic slip surfaces from being unreasonable. Furthermore, in the FELEM, based on rigorous theoretical analyses and derivation, it is noted that the physical meaning of the factor of safety can be formulated on the basis of strength reserving theory rather than the overloading theory. Consequently, compared with the limit equilibrium method (LEM) and the shear strength reduction method (SSRM) through several numerical examples, the FELEM in conjunction with the improved search strategy is proved to be an effective and efficient approach to routine analysis and design in geotechnical practices with a high level of confidence.

Hot-Mix Asphalt Permanent Deformation Evaluated by Hamburg Wheel Tracking, Dynamic Modulus, and Repeated Load Tests

Permanent deformation (or rutting) is a common distress in hot-mix asphalt (HMA) pavements. As part of the HMA mix and structural design processes to optimize field performance, the Hamburg wheel-tracking, dynamic modulus, and uniaxial repeated load permanent deformation tests have been developed to characterize the HMA rutting resistance potential. The primary objective of this study was to compare the three laboratory rutting tests of HMA mixes and to relate their rutting predictive potential to actual field performance. The research methodology incorporated a two-phase approach: laboratory testing and field performance monitoring of selected mixes under both conventional traffic loading and accelerated pavement testing. For the HMA mixes evaluated, a good correlation was observed in the three laboratory tests and in comparison with actual in situ field performance. Overall, the findings indicated that the Hamburg wheel-tracking test was the most feasible test for daily routine HMA mix design and screening, while both the dynamic modulus and repeated load permanent deformation tests exhibited greater potential for comprehensive characterization of HMA material property (e.g., modulus) and applications for pavement structural design as research-level test tools.

Time-dependent behaviour of concrete-filled steel tubular columns: analytical and comparative study

Concrete-filled steel tubes (CFSTs) have become popular in both building and bridge applications over recent decades, and an accurate prediction of their time-dependent response is necessary. Different models are currently available to describe the time-dependent behaviour of concrete and these have been shown to lead to very different predictions. In the particular case of CFST members, there is no recommended method for service calculations for routine design. The particularity of the long-term behaviour of CFSTs relies on the fact that no moisture exchange occurs between the core concrete and the surrounding environment due to the presence of the steel section. In this context, this paper recommends a suitable concrete model using 81 tests for benchmarking purposes. An extensive parametric study is carried out to evaluate the influence of time effects for geometric cross-sections commonly used in real bridge applications. Finally, different algebraic methods suitable for design calculations are applied to the long-term modelling of CFST members and their accuracy is investigated based on the results obtained using the step-by-step procedure. The results indicate that, by considering a nil exposed perimeter, Eurocode 2 performs well in predicting the long-term behaviour of CFST members. The creep effect has a considerable influence on the static response of CFST members even when actions are applied at a very great concrete age, while shrinkage in the core concrete has a quite limited contribution to the overall deformation if the core concrete is of normal strength. The mean stress method is recommended for simple design calculations.

Functional design method for improving safety and ergonomics of mechanical products

In order to help companies to improve their competetiveness, it is important to develop new design methodologies. In this framework, a Functional And Robust Design (FARD) methodology dedicated to routine design of “highly productive” modular product ranges is proposed including principles of functional analysis, Design For Assembly (DFA), and techniques of modelling and simulation for ergonomics consideration. This paper focuses on the application of this original method applied to mechanical vibration and ergonomics problems of a scraper. Including biomechanical aspect in the design methodology, it is possible to identify the impact of a vibration tool on its users using numerical models of the tool coupled to a finite element model of the human hand. This method can proactively warn very early, in the design process, the risks of causing musculoskeletal disorders and facilitate an optimization of the mechanical tool. This study is a first step in a context of human-centered design.

Near-source strong ground motions observed in the 22 February 2011 Christchurch earthquake

This manuscript provides a critical examination of the ground motions recorded in the near-source region resulting from the 22 February 2011 Christchurch earthquake. Particular attention is given to reconciling the observed spatial distribution of ground motions in terms of physical phenomena related to source, path and site effects. The large number of near-source observed strong ground motions show clear evidence of: forward-directivity, basin generated surface waves, liquefaction and other significant nonlinear site response. The pseudo-acceleration response spectra (SA) amplitudes and significant duration of strong motions agree well with empirical prediction models, except at long vibration periods where the influence of basin-generated surface waves and nonlinear site response are significant and not adequately accounted for in empirical SA models. Pseudo-acceleration response spectra are also compared with those observed in the 4 September 2010 Darfield earthquake and routine design response spectra used in order to emphasise the amplitude of ground shaking and elucidate the importance of local geotechnical characteristics on surface ground motions. The characteristics of the observed vertical component accelerations are shown to be strongly dependent on source-to-site distance and are comparable with those from the 4 September 2010 Darfield earthquake, implying the large amplitudes observed are simply a result of many observations at close distances rather than a peculiar source effect.

Evaluation on Sectional Warping Constants of Equal Leg Angle with Lips

An equal leg angle with lips subjected to torsional moment will result in pure torsional shear, warping shear, and warping normal stresses. Evaluation of these torsion induced stresses is not a routine job for practicing engineers as one of major difficulties arises from the determination of sectional warping constant (Cw). Calculation of the warping constant (Cw) for the equal leg angle with lip steel section is a tedious and difficult task and thus presenting an obstacle to routine design. Although Cw formulas and values for selective cold-formed steel sections are available in the AISI manual, most practicing engineers have no idea how to evaluate Cw constants for sections that are not listed in the AISI manual. This paper provides a detailed step-by-step numerical procedure for evaluating the Cw value of the equal leg angle with lips steel open section. Comparison between the calculated values and those listed in the AISI manual shows virtually no differences, thus proving the reliability of our proposed procedure. Ultimately, we present an useful tool in computing the Cw for a equal leg angle with lips, without the use of sophisticated computer software.

Exact-to-precision generalized perturbation theory for source-driven systems

Presented in this manuscript are new developments to perturbation theory which are intended to extend its applicability to estimate, with quantifiable accuracy, the exact variations in all responses calculated by the model with respect to all possible perturbations in the model's input parameters. The new developments place high premium on reducing the associated computational overhead in order to enable the use of perturbation theory in routine reactor design calculations. By way of examples, these developments could be employed in core simulation to accurately estimate the few-group cross-sections variations resulting from perturbations in neutronics and thermal-hydraulics core conditions. These variations are currently being described using a look-up table approach, where thousands of assembly calculations are performed to capture few-group cross-sections variations for the downstream core calculations. Other applications include the efficient evaluation of surrogates for applications that require repeated model runs such as design optimization, inverse studies, uncertainty quantification, and online core monitoring. The theoretical background of these developments applied to source-driven systems and supporting numerical experiments are presented in this manuscript. Extension to eigenvalue problems will be presented in a future article.

Collapse Mechanisms of Composite Slab Panels in Fire

A simple folding mechanism, which considers the contributions of internal unprotected beams and protected edge beams, has been proposed for isolated slab panels in fire conditions. The current study extends the mechanism to include the reinforcement in the slab as well as continuity across the protected edge beams. Structural failure of the panel depends on the applied loads, the relative beam sizes, their locations within the building, their arrangement in the slab panel, the panel's location and the severity of fire exposure. These factors are considered in the development of a number of collapse mechanisms for verification so they may eventually serve as an additional check within the Bailey-BRE design method, to make it more robust for routine design of composite floors in fire. Comparisons are made with the finite element software Vulcan and other design acceptance criteria.

Seven-Year Field Monitoring of Four Integral Abutment Bridges

Integral abutment bridges (IABs) are now a routine construction and design of choice for many DOTs as bridges are replaced or for new roadways. However, current design and analysis methodologies have not matured substantially because of a lack of available long-term field data. Often current analysis methods predict bridge behavior that is much different from observed. Because of thermal loading, time-dependent effects, and soil-structure interaction, significant irreversible abutment displacements and rotations occur. The primary objective of this paper is to report the actual in situ measurements obtained at four short to medium-long IABs and one weather station, all located in central Pennsylvania. A total of 240 instruments was installed on four IABs during bridge construction and monitored continuously. Monitoring duration at each bridge ranges from 2.5 years to nearly 7 years, having initiated the program in 2002 and continuing to the present. Because of a unique environmental issue, the bridges wer...

Analytical solutions for skewed thick plates subjected to transverse loading

This paper presents analytical solutions for skewed thick plates under transverse loading that have previously been unreported in the literature. The thick plate solution is obtained in a framework of an oblique coordinate system. The governing equation is first derived in the oblique coordinate system, and the solution is obtained using deflection and rotation as partial derivatives of a potential function developed in this research. The solution technique is applied to three illustrative application examples, and the results are compared with numerical solutions in the literature and those derived from the commercial finite element analysis package ANSYS 11. These results are in excellent agreement. The present solution may also be used to model skewed structures such as skewed bridges, to facilitate efficient routine design or evaluation analyses, and to form special elements for finite element analysis. At the same time, the analytical solution developed in this research could be used to develop methods to address post-buckling and dynamic problems.

Analytical Solution for Skewed Bridges

In this paper, we report on an analytical solution for beam-type skewed highway bridges subjected to truck loading. To confirm the analysis derivation and the solution obtained, the moment and shear responses to the design truck load are acquired using the analytical method for a number of typical US highway bridges and compared with those from numerical finite element method (FEM) analysis. In addition, the lateral distribution factors for moment and shear used in routine design are investigated based on comparison of the analytical approach and FEM. The analytical solution is shown in good agreement with the FEM result. Furthermore, the relevant provisions in the American Association of State Highway Transportation Officials' (AASHTO's) LRFD Bridge Design Specifications are also discussed here for comparison. It is observed that the design code specified load distribution factor may not predict well, especially for shear and/or severe skew.

Load and Resistance Factors for Progressive Collapse Resistance Design of Reinforced Concrete Building Structures

Due to the absence of provision for the load and resistance factors in design codes in China, designers often quote the provisions which are given in criterion or guidance of other countries such as USA. However, the partial safety factors of the load are various in different criterions. Based on the reliability theory, the load and resistance factors for progressive collapse resistance design of building structures were determined in this study. Firstly the simplified format of design expression in the ultimate state was obtained according to the expression in routine structural design. Then the failure probability of a structure during design reference period was taken as the sum of the probability of all incompatible failure events in this period, and the objective reliability index of the structure could be obtained. Finally using trial-and-error procedure and JC method, reliability analysis was performed for structural members to obtain the partial safety factors of load effects and resistance and the coefficient for combination value of load effects in design expression in the ultimate state. In this paper the load and resistance factors for progressive collapse resistance design of reinforced concrete structures subjected to blast was calculated as an example, and the recommendation values were given for the application at last.

Distribution patterns of the crab Ucides cordatus (Brachyura, Ucididae) at different spatial scales in subtropical mangroves of Paranaguá Bay (southern Brazil)

Heterogeneity in the distribution of organisms occurs at a range of spatial scales, which may vary from few centimeters to hundreds of kilometers. The exclusion of small-scale variability from routine sampling designs may confound comparisons at larger scales and lead to inconsistent interpretation of data. Despite its ecological and social-economic importance, little is known about the spatial structure of the mangrove crab Ucides cordatus in the southwest Atlantic. Previous studies have commonly compared densities at relatively broad scales, relying on alleged distribution patterns (e.g., mangroves of distinct composition and structure). We have assessed variability patterns of U. cordatus in mangroves of Paranagua Bay at four levels of spatial hierarchy (10 s km, km, 10 s m and m) using a nested ANOVA and variance components measures. The potential role of sediment parameters, pneumatophore density, and organic matter content in regulating observed patterns was assessed by multiple regression models. Densities of total and non-commercial size crabs varied mostly at 10 s m to km scales. Densities of commercial size crabs differed at the scales of 10 s m and 10 s km. Variance components indicated that small-scale variation was the most important, contributing up to 70% of the crab density variability. Multiple regression models could not explain the observed variations. Processes driving differences in crab abundance were not related to the measured variables. Small-scale patchy distribution has direct implications to current management practices of U. cordatus. Future studies should consider processes operating at smaller scales, which are responsible for a complex mosaic of patches within previously described patterns.

Incorporating MATLAB® modules in reinforced concrete design instruction

ABSTRACTThe Civil Engineering Department at George Mason University offered a structural design course that combines reinforced concrete and structural steel prior to Fall 2009. With recent re‐designing of course offerings, the course is split into two separate design courses: reinforced concrete design and structural steel design. The new teaching format allows instructors to incorporate additional instruction methods in design classes that supplement traditional teaching. This article discusses the development and implementation of computational MATLAB design modules that are incorporated in the first and second offering of the new reinforced concrete design course. The main objective of the modules is to improve students' computational skills for solving routine design calculations without compromising the theoretical understanding of the subject matter. The graphical user interface driven modules are designed to include program descriptions, user‐friendly field inputs, and a detailed results summary with step‐by‐step design verifications. A classroom survey was conducted on the use of the design modules and results of the survey are presented. © 2011 Wiley Periodicals, Inc. Comput Appl Eng Educ 22:209–215, 2014; View this article online at wileyonlinelibrary.com/journal/cae; DOI 10.1002/cae.20547

A robust data mining approach for formulation of geotechnical engineering systems

PurposeThe complexity of analysis of geotechnical behavior is due to multivariable dependencies of soil and rock responses. In order to cope with this complex behavior, traditional forms of engineering design solutions are reasonably simplified. Incorporating simplifying assumptions into the development of the traditional models may lead to very large errors. The purpose of this paper is to illustrate capabilities of promising variants of genetic programming (GP), namely linear genetic programming (LGP), gene expression programming (GEP), and multi‐expression programming (MEP) by applying them to the formulation of several complex geotechnical engineering problems.Design/methodology/approachLGP, GEP, and MEP are new variants of GP that make a clear distinction between the genotype and the phenotype of an individual. Compared with the traditional GP, the LGP, GEP, and MEP techniques are more compatible with computer architectures. This results in a significant speedup in their execution. These methods have a great ability to directly capture the knowledge contained in the experimental data without making assumptions about the underlying rules governing the system. This is one of their major advantages over most of the traditional constitutive modeling methods.FindingsIn order to demonstrate the simulation capabilities of LGP, GEP, and MEP, they were applied to the prediction of: relative crest settlement of concrete‐faced rockfill dams; slope stability; settlement around tunnels; and soil liquefaction. The results are compared with those obtained by other models presented in the literature and found to be more accurate. LGP has the best overall behavior for the analysis of the considered problems in comparison with GEP and MEP. The simple and straightforward constitutive models developed using LGP, GEP and MEP provide valuable analysis tools accessible to practicing engineers.Originality/valueThe LGP, GEP, and MEP approaches overcome the shortcomings of different methods previously presented in the literature for the analysis of geotechnical engineering systems. Contrary to artificial neural networks and many other soft computing tools, LGP, GEP, and MEP provide prediction equations that can readily be used for routine design practice. The constitutive models derived using these methods can efficiently be incorporated into the finite element or finite difference analyses as material models. They may also be used as a quick check on solutions developed by more time consuming and in‐depth deterministic analyses.

Analytical and Numerical Modeling of Prestressed Continuous Steel-Concrete Composite Beams

A loading capacity analysis is conducted for prestressed continuous steel-concrete composite beams. On the basis of the basic theoretical framework of the solution of externally unbonded prestressed structures, formulas for calculating the three characteristic loads (crack, yield, and ultimate loads) of two-span prestressed continuous composite beams under symmetric concentrated loads are proposed and extended to general cases. The variation of tendon force is considered and the adopted limit equilibrium approach only requires the development of equilibrium equations, which avoids the solution of cumbersome simultaneous deformation compatibility equations. Furthermore, an elaborate finite element model is presented for simulating the nonlinear behavior of prestressed continuous composite beams by using the commercial finite element package. The numerical model considering both the material and geometric nonlinearities can fully reflect the complex behaviors of prestressed continuous composite beams during the whole loading process. The comparisons among the analytical, numerical, and experimental results demonstrate that the analytical method provides a convenient and reliable tool for a routine design practice and the finite element model provides an excellent numerical simulation for the nonlinear behavior of prestressed continuous composite beams.

Miniscrews: protocol and mechanics for treatment of Class II malocclusions

Miniscrews are the most important recent innovation in orthodontics and have won a place, we believe, in the routine appliance design of everyday orthodontic practice. They are, we think primarily applicable in the treatment of the most prominent feature of the malocclusions orthodontists regularly confront, an antero-posterior discrepancy. Accordingly we discuss the protocol for full banded and bonded Class II mechanotherapy with miniscrew anchorage for:

Building the AHP-Based Teaching Ability System for Martial Arts Teachers in Institutions of Higher Learning

This study builds with AHP (Analytic Hierarchy Process) the teaching ability system for martial arts teachers in institutions of higher learning, which falls into four layers: destination layer, criteria layer, feature layer and index layer. The destination layer refers to the teaching abilities of martial arts teachers; the criteria layer consists of two criterions, which are professional practice ability and teaching ability; the feature layer is made up of seven features, including martial arts skills, martial arts organization and judgment, martial arts culture, martial arts graph recognition and routine design, basic quality, basic skill and teaching organization; and the index layer consists of 19 indexes, which are self-defense skills, routine exercise skills, offensive and defensive skills, martial arts organization, martial arts judgment, schools of martial arts, martial arts culture, martial arts graph recognition, martial arts routine design, professional ethics, teamwork, humanistic quality, language expression, student management, teaching research, course design, teaching practice, teaching evaluation and teaching guide. The results show that the top five impact factors for the teaching ability of martial arts teachers in institutions of higher learning are course design, routine exercise skills, teaching practice, teaching research and martial arts routine design.

Design Seismic Demands from Seismic Response Analyses: A Probability-Based Approach

Earthquake-resistant design guidelines commonly prescribe that when conducting seismic response analyses: (i) a minimum of three ground motions can be used; (ii) if less than seven ground motions are considered, the maximum of the responses should be used in design; and (iii) if seven or more ground motions are considered the average of the responses should be used in design. Such guidelines attempt to predict the mean seismic response from a limited number of analyses, but are based on judgment without a sound, yet pragmatic, theoretical basis. This paper presents a rational approach for determining design seismic demands based on the results of seismic response analyses. The proposed method uses the 84thpercentile of the distribution of the sample mean seismic demand as the design seismic demand. This approach takes into account: (i) the number of ground motions considered; (ii) how the ground motions are selected and scaled; and (iii) the differing variability in estimating different types of seismic response parameters. A simple analytic function gives a ratio which, when multiplied by the mean response obtained from the seismic response analyses, gives the value to be used in design, thus making the proposed approach suitable for routine design implementation.

Search for a Laboratory Test to Evaluate Crack Resistance of Hot-Mix Asphalt

Fatigue cracking is one of the predominant distresses that occur in hot-mix asphalt (HMA) pavements and often costs highway agencies millions of dollars in road maintenance and rehabilitation activities. Ways to minimize this distress include material screening and selecting appropriate mix designs that produce crack-resistant HMA mixes. However, no standardized laboratory tests for fatigue cracking have been universally adopted for routine mix design or screening purposes in the evaluation of HMA crack resistance. Four cracking test methods—overlay tester (OT), direct tension (DT), indirect tension (IDT), and semicircular bending (SCB)—were compared for their potential application as simple tests for the routine crack evaluation and screening of HMA mixes in the laboratory. The evaluation criteria, based on commonly used Texas mixes, included (a) rationality of the test concept and tie to field performance, (b) repeatability and variability, (c) simplicity and practicality, (d) specimen fabrication process, and (e) simplicity of data analysis. Compared with the repeated-loading OT test, preliminary findings indicated that although the monotonically increasing loading DT, IDT, and SCB tests were more repeatable, those tests could not adequately discriminate crack resistance among the mixes evaluated on the basis of the tensile strength and strain parameters. Thus none of these monotonic tests would be recommended as a simple fatigue cracking test. Additional development of the test protocols is strongly recommended, including exploration of the repeated-loading IDT and SCB tests, use of strain–fracture energy concepts, establishment of pass-or-fail criteria for screening mixes, and validation with field performance data.