Steady-state heat losses from a building floor slab with vertical edge insulation—I

The steady-state heat loss from an infinitely long slab-on-ground floor, insulated at its edges by vertical insulation into the ground, is calculated in two dimensions from a Fourier series solution of the temperature field in the ground. The temperature at the surface of the ground is assumed to change linearly from the inside of the building to the outside over a distance representing the wall thickness. The heat loss is calculated as a function of d/L, where d is the insulation depth and L is the building half-width. As d/L increases, there is a fairly rapid decrease in the heat loss at small values of d/L, and a much slower decrease beyond d/L = 1. The results indicate that it would be necessary to install an impracticably large depth of insulation to achieve a reduction in the floor heat loss comparable to that obtainable by insulating a wall.     

Rock mass—mine workings interaction model for Polish copper mine conditions

Geological and mining conditions characteristic for the Polish Legnicko–Glogowski Okreg Miedziowy (LGOM) copper mines as well as various exploitation systems utilized in that area are presented. The historical background of mining systems development as well as their classification are also reviewed.Presently, due to difficult mining conditions, a new more universal analytical tool for mine workings geometry selection is required. Therefore, a very useful in design process multi-plate analogy based physical model of rock mass—mine workings interaction has been developed and presented in the paper. The model utilizes the analytical approximation of pillar compression including the effect of pillar critical and residual strength on roof strata deflection resulting in the definite bump hazard level.The research performed in the past which dealt with the effect of size and slenderness on pillar strength is reviewed. A new approach for pillar strength calculation and its utilizing in a general problem of overburden–mine workings interaction is proposed. The problem has been illustrated by numerical examples concerning a rock mass static and dynamic behavior in the area of one of the underground Polish copper mines. By solving the numerical model based on the finite element method formulated in three dimensions, the effect of extraction path on mine workings safety in a static load domain has been proved. The dynamic load transfer from mine workings to a shaft lining has also been determined.     

Aluminum tubular sections subjected to web crippling—Part II: Proposed design equations

The web crippling design rules in the current American Aluminum Design Manual, Australian/New Zealand Standard, and European code for aluminum structures are assessed. Test strengths of aluminum square and rectangular hollow sections under end-two-flange (ETF) and interior-two-flange (ITF) loading conditions are compared with the design strengths (capacities) obtained using the aforementioned specifications. Furthermore, the test strengths are also compared with the design strengths obtained using the unified web crippling equation as specified in the North American Specification for cold-formed steel structural members. It is shown that the design strengths predicted by the aforementioned specifications are either quite conservative or unconservative, but in general the predictions are unreliable resulting from reliability analysis. Hence, two different unified web crippling equations for aluminum square and rectangular hollow sections under ETF and ITF loading conditions are proposed. The proposed unified design equation (A) uses the same technique as the North American Specification for the unified web crippling equation with new coefficients of C, C_N and C_h determined based on the test results obtained in this study. The proposed unified design equation (B) is similar to the unified web crippling equation in the NAS Specification, and the effect of the ratio N/h is also considered, where N is bearing length and h is the depth of the flat portion of web. Generally, it is shown that the proposed unified web crippling equation (B) compares well with the test results.     

Elastic/plastic buckling of a composite flat plate subjected to uniform edge compression

A theoretical approach, based on the plastic theory, has been developed for studying the elastic/plastic buckling behavior of a simply supported rectangular anisotropic plate subjected to edge compression. The said approach was employed to determine the critical buckling stresses of three different types of fiber reinforced composite plates, namely, carbon epoxy, glass epoxy and boron aluminum plates. Since the proposed approach is for a preliminary prediction of critical buckling loads of composite plates, the results obtained are deemed acceptable compared with those obtained by other authors experimentally.     

Control of activated sludge filamentous bulking—VII. Effect of anoxic conditions

The effect of anoxic conditions on the occurrence of filamentous organisms in mixed cultures was studied in laboratory activated sludge systems. It was repeatedly demonstrated that anoxic conditions are able to suppress the growth of some undesirable filamentous organisms, for instance, type 021N and Sphaerotilus natans. It was also found that severely filamentous mixed cultures had maximum rates of denitrification or nitrate respiration one order of magnitude lower than non-filamentous mixed cultures. On the basis of these findings it is concluded that some filamentous organisms cannot use nitrate nitrogen as an electron acceptor.     

Elements—columns, bars and beams

The first part of this general report is dedicated to the state-of-the-art in the field of coupled instabilities for bars, columns and beams. The second part gives a short review of the contributions to this session of the conference.     

Nonlinear vibrations of a clamped rectangular plate with initial deflection and initial edge displacement— Part I: Theory

Theoretical analyses are presented for nonlinear vibrations of a clamped rectangular plate under a uniformly distributed periodic load, with the effect of both initial deflection and initial edge displacement taken into consideration. The dynamic analog of the Marguerre equations is used and the steady-state solutions are obtained by first applying the Galerkin method and then the harmonic balance method. Actual calculations are carried out for the square plate under the assumption of the three degrees-of-freedom system and the frequency response characteristics and typical waveforms are determined under various initial edge displacements including initially buckled cases. Effects of both initial deflection and initial edge displacement on the static deflection as well as the lower natural frequencies are also clarified.     

Nonlinear vibrations of a clamped rectangular plate with initial deflection and initial edge displacement— Part II: Experiment

To compare with the theoretical results of Part I,¹ detailed experimental results have been obtained on the nonlinear response of a clamped square plate under a uniformly distributed periodic load, which is subjected to various initial edge displacements. An aluminum test specimen with side length 200 mm and thickness 0·51 mm was used and tests were conducted by shaking the supporting frame with a constant peak acceleration and measuring the relative displacement of the plate to the frame. For the steady-state symmetric periodic responses, the theoretical results are found to be in good agreement with the experimental ones, with the exception of some quantitative differences in the large amplitude vibrations. Besides the responses theoretically predicted, a variety of non-symmetric and non-periodic responses were observed in connection with the internal resonance, combination resonance and dynamic snap-through phenomena, for which the present experimental results seem to provide effective data facilitating further theoretical analyses.     

Planning — space analysis, academic buildings

Continuous change in research and education activities highlights the role flexibility and adaptation play in research buildings. Roberto Pietroforte of the Department of Civil Engineering at Massachusetts Institute of Technology, MIT, demonstrates that a systematic evaluation of space behaviour can give useful information to planners and designers for future needs.     

Elastic buckling of an axially compressed cylindrical panel with three edges simply supported and one edge free

The paper is devoted to a circular cylindrical panel with three edges simply supported and one edge free. This panel is axially compressed by a load uniformly distributed at both ends. The Donnell equations for linear buckling of shells are assumed and the adequate boundary conditions are defined. The deflection function and the force function–the Airy function are formulated with respect to the boundary conditions. The Donnell equations are reduced to a generalized eigenvalue problem with the use of Galerkin method. The results of numerical investigation are presented in figures.     

Elastic buckling of an axially compressed sandwich cylindrical panel with three edges simply supported and one edge free

The problem of elastic buckling of an open sandwich cylindrical thin-walled panel with three edges simply supported and one edge free under axial compression is considered in the paper. The classical broken line hypothesis is replaced by its modified generalized version. On the basis of force and moment equilibrium conditions for the shell element, a set of the fundamental equations is derived. The set is solved with the help of the orthogonalizational Bubnov–Galerkin method. The nonlinear algebraic equation is obtained. Physical and geometrical parameters of the shell, deflection factor and loading are connected in the equation. It is possible, among others, to obtain from here the critical load value.     

BEng,CEng, MSc,MICE, ... — eine Analyse angelsächsischer Visitenkarten

Visitenkarten ausländischer Gesprächspartner enthalten oftmals — insbesondere wenn der Eigentümer der Karte aus einem britisch geprägten Land kommt — eine Reihe von Abkürzungen, die dem Namen nachgestellt sind. Der Beitrag beschreibt, was sich hinter “Robert Smith BEng(Hons) PhD CEng MICE MIStructE“ verbirgt. Dazu wird zunächst verdeutlicht, dass erstens akademische Bauberufe in Deutschland und britisch geprägten Ländern nicht deckungsgleich sind, zweitens die Aus‐ und Weiterbildung maßgeblich von Berufsverbänden beeinflusst wird und drittens die Abkürzungen entweder akademische Abschlüsse oder von Berufsverbänden verliehene Qualifikationsstufen repräsentieren. Beispielhaft werden sodann die Aus‐ und Weiterbildung eines civil engineer und die sich daraus entwickelnde Visitenkarte beschrieben. Angefügt werden “Faustformeln”, die eine weitgehende Deutung der Visitenkarten baunaher Gesprächspartner ermöglichen. BEng, CEng, MSc, MICE, . . . — an analysis of Anglo‐Saxon business‐cards. Business‐cards from business partners often contain a number of abbreviations following the name ‐ especially if the person comes from a country which is either British or characterized as British. This article describes the meaning behind of “Robert Smith BEng(Hons) PhD CEng MICE MIStructE”. Firstly it is pointed out that academic professions in the construction industry are not directly comparable between Germany and Anglo‐Saxon countries, secondly the education and professional development are influenced significantly by professional institutions and, thirdly the abbreviations are either academic degrees or grades of memberships in professional institutions. As an example the education and professional development of a civil engineer and the resulting business‐card are described. Attached are empirical formulas which will enable the far reaching decoding of business‐cards from business partners from or related to the construction industry.     

Model tests on peat — Geotextile — Lightweight aggregate system

Considerable research has been done in recent years dealing with the interaction of normal weight aggregate and geotextiles overlying soft compressible soils. In some instances, lightweight aggregate is used instead of normal weight aggregate to reduce settlements, and in the bridge abutment areas, to minimize lateral forces and to reduce drag loads on piles. However when used with geotextiles, it is not known whether the overall roadbed stiffness is affected when lightweight aggregate is used in place of normal weight fill. This paper reports the results of experimental research dealing with interaction of lightweight aggregate and geotextiles overlying peat subgrades. Variables investigated in the present study are: differing aggregate types and densities, thickness of the aggregate layer and geotextile types. The results indicate that the overall roadbed stiffness is unaffected when lightweight aggregate is used instead of normal weight aggregate, for small deflections and initial load application.     

Energy — insulation

Correct application of insulation within a cavity is vital if heat transfer is not to be increased by natural convection, argues dr.ir. Jan Lecompte, formerly of the Laboratory of Building Physics at the University of Leuven.