Shear Lag and Effective Breadth in Rectangular Plates with Material Orthotropy. Part 1: Analytical Formulation

Symbolically derived closed-form solutions for the integration constants in series solutions for rectangular orthotropic plates under in-plane boundary shear are derived, enabling the exact stress distribution for such problems to be readily obtained. The ensuing expressions complement an earlier derivation for in-plane normal loadings along longitudinal boundaries, so that totally arbitrary stresses on these boundaries can now be studied.

Simple formulae for the longitudinal stress distribution are listed, and these provide the basis for a subsequent parametric investigation of shear lag and effective breadths in wide orthotropic flanges.     

The structural behaviour of liquid-filled spherical vessels. Part 2: Parametric study and examples

In this, the second of two articles devoted to the study of spherical tanks filled to capacity with liquid, the analytical expressions derived earlier are used to conduct a comprehensive parametric investigation of their structural response, espicially as regards the bending disturbances in the region of the vertical supports. The relative importance of these bending effects (both in magnitude and in extent) is illustrated by comparing the total stresses with their membrane counterparts for several typical liquid containers which cover the practical range of radius-to-thickness ratios.     

Shear capacity of steel plate girders with large web openings, Part I: Modeling and simulations

Numerical simulations are carried out in order to provide data for the development of a design model for the shear capacity of steel girders with web openings, with and without transverse stiffeners and opening reinforcements. The numerical model is designed such that the girder is in a state of pure shear at the opening center. Results are presented in terms of ultimate shear capacity and distribution of transverse web deformations and von Mises stresses. Based on the numerical data, a design model is presented that accounts for the reduction in web shear area, shear buckling of the web and the effect of opening position, vertical stiffeners and opening reinforcements.     

Optimization of ventilation systems in office environment,Part II: Results and discussions

Whether one considers the issues related to office workers' well-being and productivity or the issues from an energy and environmental perspective, there are clear evidences in favor of improving the quality of office environment. Part I of this paper proposed a simulation-based optimization approach by using computational fluid dynamics (CFD) techniques in conjunction with genetic algorithm (GA), with the integration of an artificial neural network (ANN) for response surface approximation (RSA) and for speeding up fitness evaluations inside GA loop. In this part, the results from data preparation for ANN model construction, ANN training and testing, and sensitivity analysis (regarding the impact of weighting factors in the objective function on the optimization results) are presented. Final optimization results indicate that the present choices of objective function and optimization approach are able to result in great improvement in the design and operation of ventilation systems in an office environment, with the goal of enhancing the thermal comfort and indoor air quality (IAQ) without sacrificing the energy costs of ventilation.     

Static and dynamic numerical analysis studies of hemispheres and spherical caps. Part II: Results and strength predictions

Shell-like structures are prevalent in nature. However, because of their slenderness they are prone to buckling, and to such an extent that this is often the dominant consideration in their design.Early attempts to determine buckling pressures were unsatisfactory. Although initial geometric distortions are now recognised as the cause of this, little comprehensive work has been conducted on doubly-curved shells, particularly hemispheres, subjected to external pressure and having asymmetric initial shapes. This paper presents the results of such a study, in two parts.In Part I, which was presented in the previous issue of Thin-Walled Structures, the background research on doubly-curved shells was briefly reviewed. The kinematic, equilibrium and constitutive equations used in the work were stated. The adopted numerical procedure which can generate static or dynamic solutions was described along with the results of convergence studies.In this Part, the effect of various initial shapes and their location is described: the critical combination is identified. The parameters selected to nondimensionalise the results are indicated, followed by those of the study which primarily involve initial deformation magnitude and shell slenderness. Two strength formulations which conveniently represent the results of the study are presented.     

Experimental analysis of simulated reinforcement learning control for active and passive building thermal storage inventory: Part 2: Results and analysis

This paper is the second part of a two-part investigation of a novel approach to optimally control commercial building passive and active thermal storage inventory. The proposed building control approach is based on simulated reinforcement learning, which is a hybrid control scheme that combines features of model-based optimal control and model-free learning control. An experimental study was carried out to analyze the performance of a hybrid controller installed in a full-scale laboratory facility. The first paper introduced the theoretical foundation of this investigation including the fundamental theory of reinforcement learning control. This companion paper presents a discussion and analysis of the experiment results. The results confirm the feasibility of the proposed control approach. Operating cost savings were attained with the proposed control approach compared with conventional building control; however, the savings are lower than for the case of model-based predictive optimal control As for the case of model-based predictive control, the performance of the hybrid controller is largely affected by the quality of the training model, and extensive real-time learning is required for the learning controller to eliminate any false cues it receives during the initial training period. Nevertheless, compared with standard reinforcement learning, the proposed hybrid controller is much more readily implemented in a commercial building.     

Behaviour and design of restrained steel column in fire: Part 2. Parameter study

This paper investigates behaviours of the restrained steel column in fire. For the restrained steel column under axial load only, investigated parameters include the axial load, the axial restraint stiffness, and the column slenderness; for the restrained steel column under combined axial load and bending moment, studied parameters included the axial load, the bending moment load, the axial restraint stiffness, the column slenderness and the end moment ratio.The results of parametric studies show that (1) the axial restraint causes a reduction in the failure temperature of the restrained column. The reduction increases with the increase in the axial restraint stiffness. However, when the axial restraint stiffness ratio is greater than a certain value, no further reduction occurs; (2) the difference between failure and buckling temperatures of a restrained column is great for columns with great axial restraint stiffness or great slenderness or small load ratio. This means that in this situation, the fire resistance of the restrained column can be increased from the column buckling temperature by considering the post-buckling behaviour; (3) an increase in the column axial load ratio or bending moment ratio causes both the column buckling and failure temperatures to decrease; (4) with an increase in the column end moment ratio, the failure temperature of restrained column decreases. The results of parametric studies will form the basis of a simplified calculation method to be presented in the companion paper.     

CO_2和H_2S共存酸性环境OCTG材料选用研究

针对5个公司在CO2和H2S共存酸性环境下石油管材(OCTG)选材规范及NACE MR0175/ISO 15156标准进行对比分析。对影响管材安全性的因素进行分析,给出各环境条件下不同公司选材规范之间的异同和适用范围。研究综合选材方案及操作步骤,编制OCTG材料综合选材软件。以新疆油田三高气井(高温、高压、高硫化氢环境)为例进行具体分析,给出影响材料抗腐蚀性能的计算公式,并根据材料的不同性质选择不同的选材准则。结果表明:影响酸性环境下OCTG选材的主要因素为H2S分压和CO2分压、温度及Cl-含量;得到了最优的选材推荐区间。     

Seismic resistance of composite beam-columns in multi-storey structures. Part 2: Analytical model and discussion of results

The observations and results from an experimental investigation of the seismic resistance of partially encased beam-columns given in the companion paper are used to assemble and verify analytical models incorporating the salient behavioural features of the test specimens. The analytical models, which employ either the commonly used bilinear kinematic hardening constitutive relationship for structural steel or the more advanced multi-surface plasticity model, are shown to achieve good agreement with the experimental results, while remaining sufficiently economical for application to larger structures. The relative performances of both material models are compared, the seismic resistance of partially encased beam-columns as identified by the experimental investigations is evaluated and the implications of the use of such structural elements in the earthquake-resistant design of multi-storey structures is discussed.     

Flow-induced vibration of two circular cylinders in tandem arrangement. Part 2: Suppression of vibrations

This paper presents an experimental investigation on suppression of cross-flow vibrations of two circular cylinders in tandem arrangement, conducted at the fluid mechanics laboratory of Kitami Institute of Technology, Japan. To suppress the vibrations of the cylinders, tripping wires were deployed, attached symmetrically about the leading stagnation lines of the cylinders. Five spacing ratios were examined, i.e., L/D=0.1, 0.3, 0.8, 2.0 and 3.2 (L is the gap spacing between the two cylinders; D is the diameter of cylinder), which are representative for five Regimes I (0.1≤L/D<0.2), II (0.2≤L/D<0.6), III (0.6≤L/D<2), IV (2≤L/D<2.7) and V (L/D≥2.7), respectively, as classified in Part 1 [Kim et al., 2009. Flow-induced vibrations of two circular cylinders in tandem arrangement (part 1: characteristics of vibration). Journal of Wind Engineering and Industrial Aerodynamics, submitted together for publication]. Tripping wire position θ measured from the leading stagnation lines of the cylinders was changed from 20° to 60° to determine the optimum range of θ for suppressing structural vibrations. The shear layers separated from the two cylinders were investigated based on flow visualization. The main findings are: (i) the flow-induced vibration on the two cylinders depends strongly on θ, (ii) at θ=20–30° the vibrations on both cylinders are almost completely suppressed for all regimes except V, and (iii) for θ≥40° the vibration amplitudes of both cylinders are considerably larger than those of the plain cylinders, particularly at θ=40°, where the vibration of the upstream cylinder becomes divergent.     

Postbuckling and imperfection sensitivity analysis of structures in the plastic range: Part 2. Shallow shell analysis

This is the sequel to the author's paper on model analysis, in the current volume. The scheme developed there to tackle the problem of the postbuckling and imperfection sensitivity analysis of structures in the plastic range is extended to shallow shells. A parameter characterizing the extension of the unloading area is used as the perturbation parameter, and the systematic perturbation method designed in the previous paper is modified to solve moving boundary problems in two variables. Relevant formulations are presented and discussed.     

Leeches as in situ biomonitors of chlorinated phenolic compounds. Part 2: Pulp mill investigations

Leeches (Nephelopsis obscura Verrill) were evaluated as in situ biomonitors of chlorinated phenolic compounds in the Fraser River at Prince George, BC, downstream from three bleached kraft pulp mills practising chlorine dioxide (ClO₂) substitution. Five biomonitoring periods, of 7 days duration, were selected to cover a full range of seasonal river conditions.Leeches bioconcentrated tri- and tetrachlorinated phenolics (bioconcentration factors: 465–6000) in proportions similar to those present in both mill effluent and river water. Leeches showed 3,4,5-trichloroguaiacol (3,4,5-TCG) to be the most consistent tracer of bleached kraft mill discharge. Leeches provided direct evidence that increasing ClO₂ substitution reduces amounts of chlorinated phenolics accumulated by aquatic organisms, with sharp decreases observed at ClO₂ levels greater than 90%. This study suggests that leeches could be applied as routine biomonitors for environmental impact monitoring.     

Stresses in thin spherical shells with imperfections. Part I: Influence of axisymmetric imperfections

A finite element model of axisymmetric geometry is used to obtain stress and moment fields in the region of an imperfection in thin, spherical shells. In Part I the studies are restricted to axisymmetric imperfections with a cosine variation along the meridian. Parametric studies are carried out to identify the main parameters controlling the response for internal pressure and gravity load. The results show that the behaviour of the shell is similar to the imperfect cylindrical shell with the same radius as in the spherical shell.     

Stresses in thin spherical shells with imperfections. Part II: Influence of local imperfections

The changes in stress resultants in thin spherical shells, associated with a local imperfection introducing curvature errors in all directions, are investigated. An axisymmetric finite element model of the shell and imperfection is employed to carry out the linear elastic analysis. Parametric studies have been performed, to identify the main parameters controlling the response, for the case of internal pressure. The results are compared with those obtained in Part I for axisymmetric imperfections, and bounds for maximum elastic stress resultants are established to cover the possibility of both local and axisymmetric imperfections.     

Experimental testing of joints for seismic design of lightweight structures. Part 2: Bolted joints in straps

An experimental testing campaign on tensile bolted joints between straps is reported. Two dominant failure modes are identified: (1) tilting, bearing and tearing of the sheets (TS) and (2) tilting, bearing and net-section failure (NSF). The analysis in terms of ductility and strength shows that bolted connections are less adequate than screwed connections (reported in Part 1 of this paper) for the seismic design of X-braced shear walls in lightweight structures. NSF joints are more ductile than TS joints in the sense that they undergo larger displacements before failure. However, if washers are not used, both types of connections fail before energy dissipation through yielding of the diagonal straps can occur. Some design recommendations to improve the seismic performance of bolted joints, including the use of washers, are given. The accuracy of Eurocode 3 formulas to predict the ultimate load is also analyzed.     

Bending and stretching actions in shallow domes. Part 2. A comparative study of various boundary conditions

In this, the second of the two-part series of articles on the interaction o bending and stretching effects in shallow axisymmetric shells, this interaction is examined by means of the two-surface shell theory, with particular reference to the influence of boundary conditions.     

Pollutant dispersion in a large indoor space. Part 2: Computational fluid dynamics predictions and comparison with a scale model experiment for isothermal flow

This paper reports on an investigation of the adequacy of computational fluid dynamics (CFD), using a standard Reynolds Averaged Navier-Stokes (RANS) model, for predicting dispersion of neutrally buoyant gas in a large indoor space. We used CFD to predict pollutant (dye) concentration distribution in a water-filled scale model of an atrium with a continuous pollutant source in the absence of furniture and occupants. Predictions from the RANS formulation are comparable with an ensemble average of independent identical experiments. Model results were compared with pollutant concentration data in a horizontal plane from experiments in a scale model atrium. Predictions were made for steady-state (fully developed) and transient (developing) pollutant concentrations. Agreement between CFD predictions and ensemble averaged experimental measurements is quantified using the ratios of CFD-predicted and experimentally measured dye concentration at a large number of points in the measurement plane. Agreement is considered good if these ratios fall between 0.5 and 2.0 at all points in the plane. The standard k-epsilon two-equation turbulence model obtains this level of agreement and predicts pollutant arrival time to the measurement plane within a few seconds. These results suggest that this modeling approach is adequate for predicting isothermal pollutant transport in a large room with simple geometry. PRACTICAL IMPLICATIONS: CFD modeling of pollutant transport is becoming increasingly common but high quality comparisons between CFD and experiment remain rare. Our results provide such a comparison. We demonstrate that the standard k-epsilon model provides good predictions for both transient and fully developed pollutant concentrations for an isothermal large space where furnishings are unimportant. This model is less computationally intensive than a large eddy simulation or low Reynolds number k-epsilon model.     

Sources of elastic deformations in steel frame and framed-tube structures: Part 2: Detailed subassemblage models

This paper examines the accuracy of a set of equations for computing Displacement Participation Factors (DPFs) for beam-column subassemblages of steel moment resisting frame buildings. These factors allow the analyst to determine how the entire subassemblage or individual components of a subassemblage contribute to a given structural displacement. Additionally, the component’s contribution to displacement may be evaluated in terms of sources of axial, flexural, or shear deformation.When applied to a set of 12 isolated subassemblages, it was shown in Part 1 of the paper that deformations in the beam-column joint are very significant, and that flexural deformation in the joint, which is often ignored, should be considered in all analyses. The total displacement predicted through the use of the DPFs correlates extremely well with the results of detailed three dimensional finite element analyses of the same subassemblages. However, it was also shown that there is considerable uncertainty in the bending moments and moments of inertia that are used to compute joint flexural deformations.The objective of this paper, which is the second part of a two-part paper, is to further investigate the accuracy of the DPF expressions developed in Part 1. This is done by computing DPFs from the results of detailed three dimensional finite element analysis, and comparing these to those computed through the use of the simple expressions.The results of the analysis show that the joint flexural deformations are accurately predicted by the simple DPF expressions, but that this accuracy arises from compensating “errors” in the simplified analysis. It is also shown that the use of beam flange continuity plates has a marginal effect on computed displacements. The paper ends with recommendations for using the simplified expressions for computing subassemblage deformations, and for including such deformations in structural analysis of steel frame and tube structures.     

A mathematical deterministic river-quality model. Part 2: Use in evaluating the water-quality management of the blackwater catchment

A deterministic river-quality model has been used to predict river qualities in the Blackwater System (part of the River Thames catchment). It was tested under the relatively dry conditions of 1973 and more normal conditions of 1974, and it was concluded that satisfactory agreement between predicted and observed data was obtained.

On this basis, the use of the model was extended to simulate conditions for 1981 and 1991 in an attempt to evaluate what the effect on the river quality would be if certain capital works programmes were or were not proceeded with. It was demonstrated that with the potential expansion in this catchment area, the quality of the Blackwater would not improve unless capital works programmes are carried out.