Hand Calculation Method Research Articles

Buckling strength verification of cantilevered cylindrical shells subjected to transverse load using Eurocode 3

At present, there are only a few studies concerning the application of different types of buckling strength verification according to Eurocode 3 at combined loading. Besides the stress design as classical hand calculation method of checking cylindrical steel shells against buckling failure, the new Eurocode 3 also offers two global numerical analyses at different modelling levels. The linear buckling analysis (LBA) combined with a materially nonlinear but geometrically linear analysis (MNA) is the simpler concept from the perspective of the modelling and calculation effort. The more sophisticated method is a geometrically and materially nonlinear analysis of the imperfect structure (GMNIA). This paper presents the application of both numerical concepts to the cantilevered shell subject to a transverse load at the free edge. The results are compared to those from stress design. There are specific features at both types of numerical analysis: As the determination of the plastic reference resistance and the buckling parameters is the main focus at MNA/LBA, the choice of proper equivalent geometric imperfections demands special diligence at GMNIA. The presented analyses show that the GMNIA concept in connection with consistent equivalent geometric imperfections may lead to a safe and economic design of cylinders subject to combined loading. At the particular load case the MNA/LBA concept currently suffers from the lack of proper regulations concerning the determination of the overall buckling reduction factor.

Predicting shipboard noise using 3-D acoustic modeling

Predicting and controlling shipboard noise is a daunting task, particularly when the commonly accepted, one-dimensional prediction approaches are used. Numerous powerful acoustic sources are often located in close proximity to sensitive receiver spaces and the ship's structures and systems themselves are not amenable to straightforward abatement techniques. In addition, treatments usually impose adverse space, weight and cost impacts yet the crew and passengers need to be protected. This paper presents an alternative to the common spreadsheet and hand calculation methods of shipboard noise analysis. The paper discusses an SEA based noise prediction method. The primary purpose of this engineering prediction method is to facilitate rapid predictions that preserve the accuracy required for the design of effective treatment of shipboard noise. Two case studies are presented indicating the features and application of the tool.

Measurement and prediction of evaporator shell-side pressure drop

The pressure drop across a heat exchanger is an important parameter, along with the heat transfer capacity. In fact, the operating cost throughout the life of the exchanger depends on the pressure losses. Therefore, it is important to be able to predict pressure drop accurately as it is to predict heat transfer. A new data set of shell-side pressure drop measurements taken during isothermal flow of brines in shell and tube evaporators was collected in the Alfa Laval laboratory. It covers several different configurations of industrial shell and tube evaporators and a wide range of operating conditions, with cross flow Reynolds number ranging from 170 to 33,000. The database is compared against two predictive procedures available in the literature for computing shell-side pressure drop, showing that no method is accurate enough for design purpose. As a further step, a new suggested procedure is presented, which extends the Wills and Johnston [Wills MJN, Johnston D. A new and accurate hand calculation method for shellside pressure drop and flow distribution. 22nd National Heat Transfer Conference, HTD N. 36. New York: ASME; 1984, p. 67–79] method to the low Reynolds number range and improve its capability to predict experimental data.

중력식 콘크리트 댐에 작용하는 양압력이 응력확대계수에 미치는 영향

The modeling of uplift pressure within dam, on the foundation on which it was constructed, and on the interface between the dam and foundation is a critical aspect in the analysis of concrete gravity dams, i.e. crack stability in concrete dam can correctly be predicted when uplift pressures are accurately modelled. Current models consider a uniform uplift distribution, but recent experimental results show that it varies along the crack faces and the procedures for modeling uplift pressures are well established for the traditional hand-calculation methods, but this is not the case for finite element (FE) analysis. In large structures, such as dams, because of smaller size of the fracture process zone with respect to the structure size, limited errors should occur under the assumptions of linear elastic fracture mechanics (LEFM). In this paper, the fracture behaviour of concrete gravity dams mainly subjected to uplift Pressure at the crack face was studied. Triangular type, trapezoidal type and parabolic type distribution of the uplift pressure including uniform type were considered in case of evaluating stress intensity factor by surface integral method. The effects of body forces, overtopping pressures are also considered and a parametric study of gravity dams under the assumption of LEFM is performed.

Analysis of catenary action in steel beams using a simplified hand calculation method, Part 2: validation for non-uniform temperature distribution

To enable the general analytical method, presented in the companion paper, to be applied to beams with non-uniform temperature distributions, additional assumptions are made about the beam’s deflection profiles. In this paper, it is assumed that for a beam with non-uniform temperature distribution and under concentrated loads, its mechanical deflection profile should be the average of the deflection profile under uniformly distributed load and the free bending moment profile of the beam under concentrated load. The results of various validation examples show that this assumption and the general analytical method are able to give close approximation to numerical simulation results. From detailed investigations, it has been found that catenary forces in a beam are not sensitive to different non-uniform temperature distributions. Furthermore, for safe prediction of catenary forces, complete end axial restraint and zero end rotational restraint may be assumed.

Analysis of catenary action in steel beams using a simplified hand calculation method, Part 1: theory and validation for uniform temperature distribution

This and the companion papers present, in detail, the development and validation of a simple analysis method of catenary action in steel beams at elevated temperatures, which may be adopted as the basis of a design calculation method. Although the analysis is suitable for beam behaviour over the entire temperature region, the present discussions will emphasize on catenary action. The main assumptions of the analytical model are the beam’s deflection profile and interaction between axial load and bending moment. The beam’s deflection profile depends on its loading condition and end rotational restraint. For simply supported beams under distributed load or beams with complete end rotational restraint, the beam deflection profile may be assumed to be a polynomial that satisfies the beam’s geometric boundary conditions. For simply supported beams under point loads, the beam’s deflection profile may be assumed to take the shape of its free bending moment diagram. For flexible end rotational restraints, linear interpolation may be adopted as a function of the degree of end rotational restraint. For combined axial load and bending moment, the proposed analysis allows the beam’s axial load to change in isolation and the beam’s bending moment is then calculated from the axial load–bending moment interaction equation. This is a simplifying assumption that does not comply with stress distribution in the beam. It will be found that this method will predict higher catenary forces, which is on the safe side. This paper will present validation studies, by comparing results of the proposed method and numerical simulations using ABAQUS, for beams with uniform temperature distribution. The companion paper will give additional equations to be used in the proposed method and validation examples for beams with non-uniform temperature distributions.

Performance Based Fire Safety Design of Structures — A Multi-Dimensional Integration

Design codes for fire safety in buildings can be either a prescriptive type or performance-based type. It is now widely recognized that performance-based codes provide greater advantages over the prescriptive codes in that it allows designers to use the fire engineering methods to assess the fire safety of the structure. However, as the assessment of the whole structure performance is not easy, most codes currently used are still prescriptive codes or a combination of prescriptive codes and performance-based codes. The key feature for implementing the performance-based fire design codes is the assessment of the fire resistance of the structure. This paper provides an overall view on performance-based code and the approaches for designing steel structure in fire considering a multi-dimensional integration of fire engineering simulation, emergency evacuation and structural resistance. Various fire models and heat transfer analysis methods are reviewed and discussed. The basis to modelling of large deflection and plasticity using appropriate stress-strain relationship at elevated temperature is explained. Finally, structural response calculations from simplified hand calculation method to advanced numerical procedures are presented. Future trends for research are identified.

Axial strength of cold-formed thin-walled steel channels under non-uniform temperatures in fire

This paper presents the results of a numerical investigation into the axial strength of cold-formed thin-walled channel sections (columns) under non-uniform high temperatures in fire. The non-uniform temperature distributions are based on the results of a thermal analysis of thin-walled stud panels carried out by the authors. The general finite-element package ABAQUS is used to obtain strengths of columns with different lengths at different fire exposure times. To aid development of a hand calculation method of column strength in fire, the accuracy of using two ways of simplifying the non-uniform temperature distribution is investigated. The ambient temperature design method for cold-formed thin-walled columns in Eurocode 3 Part 1.3 (EN1993-1-3, Eurocode 3: design of steel structures, Part 1.3: general rules, supplementary rules for cold formed thin gauge members and sheeting, European Commission for Standardisation, Brussels, 2001) is modified to take into account the change in the strength and stiffness of steel at elevated temperatures and thermal-bowing effects. The results of this design method are compared to the ABAQUS simulation results.

The readability of pediatric patient education materials on the World Wide Web.

Literacy is a national and international problem. Studies have shown the readability of adult and pediatric patient education materials to be too high for average adults. Materials should be written at the 8th-grade level or lower. To determine the general readability of pediatric patient education materials designed for adults on the World Wide Web (WWW). GeneralPediatrics.com (http://www.generalpediatrics.com) is a digital library serving the medical information needs of pediatric health care providers, patients, and families. Documents from 100 different authoritative Web sites designed for laypersons were evaluated using a built-in computer software readability formula (Flesch Reading Ease and Flesch-Kincaid reading levels) and hand calculation methods (Fry Formula and SMOG methods). Analysis of variance and paired t tests determined significance. Eighty-nine documents constituted the final sample; they covered a wide spectrum of pediatric topics. The overall Flesch Reading Ease score was 57.0. The overall mean Fry Formula was 12.0 (12th grade, 0 months of schooling) and SMOG was 12.2. The overall Flesch-Kincaid grade level was significantly lower (P<.0001), at a mean of 7.1, when compared with the other 2 methods. All author and institution groups had an average reading level above 10.6 by the Fry Formula and SMOG methods. Pediatric patient education materials on the WWW are not written at an appropriate reading level for the average adult. We propose that a practical reading level and how it was determined be included on all patient education materials on the WWW for general guidance in material selection. We discuss suggestions for improved readability of patient education materials.

Projectile motion with Mathematica

This note describes how to use the computer algebra system (CAS) Mathematica to analyse projectile motion with and without air resistance. For a projectile fired from ground level with an initial velocity ν ft/s at an angle θ degrees from the horizontal (0 < θ < 90°), it is well known that in the absence of air resistance, the projectile follows a parabolic path. However, this is not true if air resistance is taken into account. In the presence of air resistance, the equations of motion become complicated, thus making traditional handcalculation methods quite ineffective, and a powerful CAS such as Mathematica becomes an invaluable tool to better understand projectile motion. The note discusses how Mathematica can be used to create simulated experiments of projectiles with and without air resistance. These experiments result in several conjectures, leading to theorems.

Evacuation of a theatre: exercise vs calculations

An evacuation exercise without previous notice was arranged with over 600 participants in September 1995 at a leading theatre during a dress rehearsal of an upcoming play. The exercise was organized by the theatre in co-operation with fire authorities and an insurance company. The exercise was started shortly before the end of the first act of the play when the fire drop-curtain of the stage went down and a pre-recorded announcement was read over the public announcement system. No smoke or other effects were used. The audience left the auditorium in an orderly fashion and the auditorium was completely evacuated in 3 min 37 s. Everyone left the auditorium through the normal entrance. No signs of panic were observed during the evacuation. The personnel of the theatre carried out their duties planned for emergency situations without any complications. After the exercise, the response of the audience was very positive, but a number of the actors were quite upset and requested the theatre management never to organize such exercises while they were on stage. The quantitative data of the evacuation exercise have been used to assess various kinds of calculation methods, one of which is a traditional hand-calculation method and four generally available computer models. Of the computer programs one is an optimization model while three are different simulation models. The results show that the calculations concerning the movement phase of the evacuation are in reasonable agreement with the observations from the exercise. Copyright © 1999 John Wiley & Sons, Ltd.

Evacuation of a theatre: exercise vs calculations

An evacuation exercise without previous notice was arranged with over 600 participants in September 1995 at a leading theatre during a dress rehearsal of an upcoming play. The exercise was organized by the theatre in co-operation with fire authorities and an insurance company. The exercise was started shortly before the end of the first act of the play when the fire drop-curtain of the stage went down and a pre-recorded announcement was read over the public announcement system. No smoke or other effects were used. The audience left the auditorium in an orderly fashion and the auditorium was completely evacuated in 3 min 37 s. Everyone left the auditorium through the normal entrance. No signs of panic were observed during the evacuation. The personnel of the theatre carried out their duties planned for emergency situations without any complications. After the exercise, the response of the audience was very positive, but a number of the actors were quite upset and requested the theatre management never to organize such exercises while they were on stage. The quantitative data of the evacuation exercise have been used to assess various kinds of calculation methods, one of which is a traditional hand-calculation method and four generally available computer models. Of the computer programs one is an optimization model while three are different simulation models. The results show that the calculations concerning the movement phase of the evacuation are in reasonable agreement with the observations from the exercise. Copyright © 1999 John Wiley & Sons, Ltd.

Clinical application of the computer picture archiving and communicating system to stereotactic radiosurgery

Stereotactic radiosurgery, a rapidly evolving technology, provides precise high-dose irradiation to brain lesions and tumors. A new method using digital subtraction angiographic images of a personal computer-image display terminal interfaced to our picture archiving and communication system (PACS) performs measurements and calculations of the coordinates of the location of the center of the lesion to be treated. The time required to calculate the coordinates was performed by three methods: hand calculation, digitizer method, and PACS method. These three coordinates were compared in 10 cases. The hand calculation method required approximately 50 minutes, the digitizer method required approximately 10 minutes, and the PACS method approximately 3 minutes. The difference is statistically significant (P < .001). The three methods were equally accurate. This type of PACS application using inexpensive personal computers interfaced more directly to a PACS is an emerging trend that facilitates wider access to images and to manipulating them for specialized applications.

Methods of removing single variable static hazards in Boolean functions

Two methods are presented in this paper for removing single variable static hazards in Boolean Functions. The first method is a hand calculation method that uses a single variable static hazard cover algorithm. The hand calculation method can be used in the classroom and does not require computer assistance. The second method involves using a single variable static hazard cover software synthesis tool. The second method is more convenient to use outside the classroom on a PC that is available for engineering student use or perhaps on personal computers. To illustrate the process of obtaining single variable static hazard covers, the standard Karnaugh map approach is also used. A commercially available design synthesis tool and schematic capture/simulation timing tool are also used in this paper.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A TCF approach to the criticality aspects of fissile solution systems

It is shown that in dilute fissile solution systems the neutron leakage probability is primarily dependent on the hydrogen concentration. A simple hand calculation method is proposed based on the Trombay criticality formula (TCF) to quickly estimate the radius of a subcritical dilute solution sphere with the required K eff.

Buckling of stepped crane columns

Despite the proliferation of computer hardware and software, there is still a role for simple hand-calculation methods. This paper is a contribution to that philosophy with respect to the buckling loads of stepped crane columns within rigid frame buildings. Graphs of three factors are presented which enable the design engineer to calculate the buckling load and hence the effective length factors for the more heavily-loaded stepped column. The method is easy to use, is direct without trial and error procedures and is illustrated by numerical example.

Extending of the merchant-rankine formula for the assessment of the ultimate load of frames with semi-rigid joints

The influence of the actual characteristics of beam-to-column joints on the ultimate strength and the stability of steel frames is significant and no longer needs to be proved. At present, several experimental and theoretical research works are being carried out in this field. They aim on one side at a better knowledge of the non-linear behaviour of joints and on the other side at the development of numerical procedures that would take account of the non-linear characteristics of joints and would insure an accurate simulation of the response of individual members (beam or column) or of frames. The carrying capacity of non-linearly and restrained columns as well as the strength and the deformability of beams with semi-rigid joints at their ends can now be determined by means of hand calculation methods. This paper presents a hand calculation procedure for the evaluation of the collapse load of semi-rigid frames, making it possible to take account of both main aspects of a steel frame study: strength and stability. The suggested method is applied to an example, and lastly the results are compared with those obtained numerically by means of the FINELG program.

Practical applications: Procedure for quantitative analysis

Numerous hand calculation methods and computer models are available as tools for quantitative fire hazard analysis. However, these tools are useful in only one phase of a complete s tudy of a hazard. A comprehensive assessment of a hazard must consist o f 3 steps: problem formulation, analysis and evaluation. The analysis step is the step on which the greatest emphasis is placed in engineering education curricula. However, the formulation and evaluation steps are equally important, as discussed in this paper.

Computing Core-Yield Limits for Case-Hardened Rolling Bearings

Core yielding has been identified as a major source of premature failure in case-hardened ball and roller bearings. Design criteria have been established and accepted to prevent core-crushing failures in these bearings. Vendors have made substantial advances in understanding core yielding and in designing to prevent failures. However, the user is in need of a simplified, straightforward method of assuring himself that core failure will not occur. A simplified computational method is constructed from the established design criteria and presented. With minimal geometry information and a case-core specification, the core-yield limit, in terms of maximum allowable element load, can be computed for a given bearing. Numerous hand-calculation methods for arriving at maximum element loads from applied loads exist. In this manner, core-yield adequacy can be easily verified. A numerical example is presented. Presented at the 39th Annual Meeting in Chicago, Illinois, May 7–10, 1984

Energy and nutrient calculations using an Optical Character Reader system

A new application of the Optical Character Reader (OCR) system for dietary data tabulation has been presented. Comparison of the reproducibility of energy and nutrient values, when hand calculation, on-line computer, and OCR methods of calculation are used, revealed no significant differences. The OCR system increased turn-around time for obtaining results, but use of a clinician's time was greatly reduced in comparison to either the hand calculation or the on-line computer method. Once the initial investment for an OCR system had been made, a significant reduction was realized in the cost of a clinician's time used for energy and nutrient calculations. When the factors of reproducibility, time, and cost were considered, this study found the OCR method for dietary calculations as acceptable as either hand calculation or on-line computer methods. Clinicans using the OCR or hand calculation method did not need computer facilities, but computer keyboard terminals were required for the on-line method.