Generalized solution to Coulomb’s seismic active earth pressure acting on rigid retaining wall with cohesive backfill and trial application for evaluation of seismic performance of retaining wall

In this paper, a general solution for evaluating the Coulomb-type seismic active earth pressure that acts on a rigid retaining wall from the cohesive backfill soil is shown together with its derivation process. In the proposed solution, the mobilization of the cohesion on the failure plane in the backfill soil of the retaining wall and the associated increase in shear strength are considered in the pseudo-static limit equilibrium approach under the assumption that the cohesion is uniformly distributed in the backfill soil. The angle of the failure plane and the seismic active earth pressure calculated by the proposed equation completely agree with the calculation results by the trial wedge method, which shows the validity of the proposed solution. In addition, by combining the concept of the Modified Mononobe-Okabe method and the proposed equation, a calculation method for the seismic active earth pressure is proposed. It can consider the effect of backfill cohesion and can be applied even under a large seismic load. Furthermore, a series of trial analyses on the effect of backfill cohesion on the seismic performance of the retaining wall is also conducted using the proposed equation. A series of analyses using the case of a retaining wall damaged during the 1995 Hyogo-ken Nanbu earthquake shows that the effect of backfill cohesion is significant in the seismic performance evaluation and the design of aseismic reinforcements.     

Seismic stability analysis of gravity retaining wall supporting c–φ soil with cracks

This article presents an analytical approach for the seismic stability analysis of gravity retaining wall with c–φ backfill soil. Cracks which are pre-existing (open before the collapse) and are form as part of slope collapse are considered. For a translational failure mechanism assumed, formulas are provided to calculate directly the yield acceleration and the inclination of failure surface. Factors such as cracks and cracks opening, wall back inclination, soil-wall friction, backfill slope are easily to be coupled into the formulations. Both the depth and most adverse location of the crack can be determined from the optimization procedure. Comparisons are made with existing methods and the influences of cracks opening are discussed. The influence of a crack presence on seismic stability of soil-wall system is distinct and pre-existing (opened) cracks have more adverse effect.     

Stability and interaction in the housing market: Log‐linear and vacancy chain models

Although one may find some examples of vacancy chain analysis in which the chain is actually traced, most researchers use Markov vacancy chain models now, because these are less demanding in their data requirements. In constructing this kind of model a number of assumptions have to be made, viz. regarding homogeneity, stationarity and markovicity. Before applying these models the validity of these assumptions will have to be clarified. In this contribution we will present an empirical test for some of these assumptions, using a log‐linear approach. We will also use the log‐linear model to measure the interaction among various housing submarkets. It will be shown that three types of interaction can be distinguished and measured—segmentation, dominance and substitution. Although these aspects are crucial to the study of vacancy chains, they cannot be derived directly from the results of the vacancy chain models.     

Influence of the strip–backfill interaction model in the analysis of the behavior of a mechanically stabilized earth wall

To improve the modeling of friction between the ground and reinforcing inclusions, such as steel strips in reinforced earth walls, a specific type of finite element was introduced in the CESAR-LCPC finite element code. Simulations were carried out, in which these elements were used in combination with a linear elastic-perfectly plastic model to describe the interaction between the ground and the inclusions. With this simple interaction model, however, it was not possible to reproduce the observed behavior of a full-scale, experimental wall or the results of pull-out tests carried out on the same wall under the same set of parameters. Therefore, two more complex models were introduced for the soil–inclusion interaction, which led to a much better agreement between the numerical results and the experimental observations.     

Estimating Undrained Shear Strength of Soft Clay Ground Improved by Pre-Loading with PVD — Case History in Bangkok—

The installment of pre-fabricated vertical drain (PVD) combined with pre-loading is an efficient way to gain the prescribed strength and compressibility of very soft clay over a short period of time. This note describes case histories of such improvement performed in Bangkok. The change in undrained shear strength, s_u, before and after the ground improvement was investigated at two sites in Bangkok area by means of field vane test (FVT) and flat dilatometer test (DMT). The results of FVT showed that the s_u value of soft Bangkok clay increased over nearly the full depth down to the tip of the PVDs. It is also demonstrated that DMT may be a useful tool for promptly assessing the change of s_u in soft clay due to pre-loading. Applicability of the SHANSEP method in estimating the profile of s_u with depth in recently overconsolidated clay ground after pre-loading is also discussed.     

Strength enhancements in cold-formed structural sections — Part II: Predictive models

Cold-formed structural sections are manufactured at ambient temperature and hence undergo plastic deformations, which result in an increase in yield stress and a reduction in ductility. This paper begins with a comparative study of existing models to predict this strength increase. Modifications to the existing models are then made, and an improved model is presented and statistically verified. Tensile coupon data from existing testing programmes have been gathered to supplement those generated in the companion paper [1] and used to assess the predictive models. A series of structural section types, both cold-rolled and press-braked, and a range of structural materials, including various grades of stainless steel and carbon steel, have been considered. The proposed model is shown to offer improved mean predictions of measured strength enhancements over existing approaches, is simple to use in structural calculations and is applicable to any metallic structural sections. It is envisaged that the proposed model will be incorporated in future revisions of Eurocode 3 [2,3].     

Corridor wall linings— Effect on fire performance

During December 1964 and January 1965, research was conducted to determine the effects of three types of wall linings on fire performance within a partially ventilated corridor. Temperature and light transmission data were recorded, and gas samples were collected for immediate and later analysis. This information was supplemented by the recorded comments of observers, stationed in rooms adjacent to the corridor during the tests. Note: Based on the report “Effect of Wall Linings on the Fire Performance Within a Partially Ventilated Corridor” by Messrs. Schaffer and Eickner, publisherd by the Forest Products Laboratory, Madison, Wisconsin, 53705, in cooperation with the American Hardboard Association.     

Business models in project-based firms – Towards a typology of solution-specific business models

Project suppliers are taking increasing responsibility for their customers’ businesses by servicing and operating their installed base of equipment. Simultaneously, the locus in value creation in the project suppliers’ deliveries and business models has changed from short-term project deliveries to also include the operation of systems. We analyze five solutions delivered by a power plant supplier firm. The term ‘solution’ here refers to an offering which includes a project component and an after-delivery service component. We assess the distinctive features in the business models of the solution deliveries. This paper contributes to the existing knowledge by suggesting use of solution-specific business models with six key business model elements and by developing a typology of five solution-specific business models. The typology can also be used for assessing the performance of individual solutions. Our suggestion of a solution-specific business model is especially novel in the research of integrated solutions and business models: although existing literature argues that on a general level a firm can have several business models, prior research has not suggested the use of project-specific or solution-specific business models. Therefore, our finding of solution specificity of business models contributes significantly to the existing knowledge.     

Pesticide‐microbial interaction in the soil

Soils collected from the Gezira irrigation scheme in Sudan were incubated with five pesticides (pyrolan, α‐and β‐endosulphan, γ‐HCH and dieldrin), using three independent methods (incubation of microbial culture with soil and leachates, with carbon‐based growth media and with carbon‐free mineral salt agar). Endosulphan isomers were degraded by soil micro‐organisms to a much greater extent than pyrolan, dieldrin or γ‐HCH. When applied at low concentration (280 ppm), α‐endosulphan was broken down by both bacteria and fungi; whereas, β‐endosulphan was degraded mostly by bacteria and dieldrin was utilized by fungi. However, at high concentration (4000 ppm), γ‐HCH increased the growth of micro‐organisms (gram positive bacilli); but at this high concentration, the other pesticides inhibited all micro‐organisms in the Gezira soil.     

Wind–structure interaction in conductor bundles in transmission lines

The use of transmission line conductors arranged in bundles is presently being considered as an attractive technology in order to reduce losses in long distance energy transportation. Although the technology leads to significant increases in power capacity per line, the dynamic behaviour of arbitrary bundle configurations under wind action has not yet been fully clarified. In this paper, a procedure to determine the dynamic response of the bundle under operating conditions is presented. The model considers the fluctuations of the incident turbulent wind flow and the motion of the conductors, as some cables may be immersed in the variable wake of others. A solution is obtained by numerical integration in the time domain of the equations of motion of a discrete non-linear model of the bundle, which includes criteria to assess the forces on spacers and cables by means of aerodynamic coefficients obtained experimentally in wind tunnel studies. The predicted response of a three-conductor bundle is compared with experimental results available in the technical literature. Results of simulation studies of various bundle configurations subjected to turbulent wind action are also given.     

Back Analysis of Reclamation by Pump-Dredged Marine Clay—Influence of Ground Water Lowering—

When pump-dredged clays are discharged into a pond, suspended soil particles settle loosely to create sediments, which subsequently consolidate due to their own weight over a long period of time. In planning the capacity of such a disposal pond, it is important to estimate the time dependent volume change of dredged clays during the reclamation process. As the land thus created is extremely soft, ground improvement work is necessary if there exists a further plan of utilising the land. Predicting the soil profile of reclaimed land is absolutely necessary for designing the ground improvement. In this paper the authors i) outline the 18-year reclamation history of the Kanda Disposal Pond, ii) introduce a program to analyse self-weight consolidation under fully submerged condition, iii) modify the program to represent the suction effect due to ground water lowering, and iv) verify the applicability of the modified program by comparing the calculated results with the measured data.A simple analysis under fully submerged condition cannot explain the record of an 18-year reclamation, even if various combinations of consolidation parameters are used. The code modified to include the suction effect successfully simulates the actual behaviour when the appropriate parameters concerning the suction are chosen.     

Local–global mode interaction in stringer-stiffened plates

A recently developed nonlinear analytical model for axially loaded thin-walled stringer-stiffened plates based on variational principles is extended to include local buckling of the main plate. Interaction between the weakly stable global buckling mode and the strongly stable local buckling mode is highlighted. Highly unstable post-buckling behaviour and a progressively changing wavelength in the local buckling mode profile are observed under increasing compressive deformation. The analytical model is compared against both physical experiments from the literature and finite element analysis conducted in the commercial code Abaqus; excellent agreement is found both in terms of the mechanical response and the predicted deflections.     

Shared mental models—linking team cognition and performance

In order to meet the increasingly complex demands of design in multidisciplinary teams, designers have to interact and thereby to interweave their mental models (MM). Yet, neither is it clear which content of MM should be shared to perform design tasks effectively, nor is the process of the development of shared mental models (SMM) quite understood. The two studies presented in this article were conducted to gain insights into the cognitive processes of designers working together in a team, and to clarify the impact of SMM on team performance. Process-oriented research strategies were applied to groups of mechanical engineering students and to multidisciplinary project teams in the automobile industry. The results indicated that not the SMM of the whole group but the SMM of subgroups were related to group performance. Moreover, this link to performance is only supported by the SMM about team members' skills (SMM_team) and about the process of interaction (SMM_process). As a conclusion of the latter result, more attention should be paid to the development of common knowledge about group interaction and team members' abilities in the everyday work life of project teams. In addition, observational data showed that motivational aspects like the feeling of competence should be considered when analysing the influence of SMM. Finally, a conceptualisation of the development and interplay of mental submodels is proposed.     

“Third places” and social interaction in deprived neighbourhoods in Great Britain

This paper explores social interaction in local ‘public’ social spaces such as local shops, pubs, cafés, and community centres in deprived neighbourhoods. More specifically, it examines the importance, role and function of these places, which have been described by Oldenberg and Brissett (Qual Sociol 5(4):265–284, 1982), Oldenburg (Urban design reader. Architectural Place, Oxford, 2007) as being “third places” of social interaction after the home (first) and workplace (second). It does so by drawing on data gleaned from in-depth interviews with 180 residents in six deprived areas neighbourhoods across Great Britain, conducted as part of a study of the links between poverty and place funded by the Joseph Rowntree Foundation. The paper notes that local third places are an important medium for social interaction in these areas, although their importance appears to vary by population group. It notes that shops appear to be a particularly important social space. It also identifies some of the barriers to social interaction within third places and concludes by highlighting some of the key implications for policy to emerge from the research.     

Reinforcement schemes for cold-formed steel joists with a large web opening in shear zone—An experimental investigation

The floor joists of cold-formed steel (CFS) structures often require large web openings. Reinforcement of such openings may mitigate the detrimental effects arising from such web openings. This paper is based on an experimental investigation conducted to establish reinforcement schemes for CFS joists with a large web opening located in high shear zones. The investigation considered a large web opening cut out in the middle of the web of a lipped channel section. Circular and square large web openings of about 65% web depth were considered. The shear tests involved short span specimens, simply supported at the ends, and subjected to a mid-span point load. This paper presents the experimental set-up, and the test results associated with 27 individual tests consisting of nine sets of three identical tests. These test sets consist of cold-formed steel joists sections with (a) no web opening, (b) webs having circular or square openings, (c) webs having reinforced openings. Three different reinforcement schemes were investigated, however, the test results indicated that the proposed “Vierendeel truss type reinforcement scheme” can restore the original shear strength of such sections having circular or square openings. Overall, this study establishes a cost-effective reinforcement scheme for cold-formed steel joists having a large web opening in high shear zone.     

Axial–flexural interaction in circular FRP-confined reinforced concrete columns

External confinement by fibre reinforced polymers (FRPs) is now a widely implemented technique to strengthen reinforced concrete (RC) columns. To date, the vast majority of experiments on FRP-confined concrete have considered short, unreinforced, small scale concrete cylinders, with aspect ratios of less than three and tested under concentric axial load. In practice, RC columns invariably have aspect ratios larger than three and are subjected to inadvertent load eccentricities or combined axial–flexural (P–M) loading. Limited available research suggests that the effectiveness of FRP confinement is reduced under P–M loading. This paper presents the results of a systematic test program on circular FRP-confined RC columns of realistic slenderness under eccentric axial loads to study the mechanics and performance of these types of members. Test data are compared against theoretical P–M interaction diagrams, as well as against recently published design guidelines for P–M interaction in FRP-confined RC columns.     

Influence of soil——structure interaction on seismic collapse resistance of super-tall buildings

Numerous field tests indicate that the soilestructure interaction(SSI) has a significant impact on the dynamic characteristics of super-tall buildings,which may lead to unexpected structural seismic responses and/or failure.Taking the Shanghai Tower with a total height of 632 m as the research object,the substructure approach is used to simulate the SSI effect on the seismic responses of Shanghai Tower.The refined finite element(FE) model of the superstructure of Shanghai Tower and the simplified analytical model of the foundation and adjacent soil are established.Subsequently,the collapse process of Shanghai Tower taking into account the SSI is predicted,as well as its final collapse mechanism.The influences of the SSI on the collapse resistance capacity and failure sequences are discussed.The results indicate that,when considering the SSI,the fundamental period of Shanghai Tower has been extended significantly,and the collapse margin ratio has been improved,with a corresponding decrease of the seismic demand.In addition,the SSI has some impact on the failure sequences of Shanghai Tower subjected to extreme earthquakes,but a negligible impact on the final failure modes.     

Simulation of particle deposition in ventilation duct with a particle–wall impact model

Particle deposition velocities and locations in horizontal ventilation ducts are investigated by incorporating the effect of particle–wall collision. Particle deposition onto two types of surfaces, stainless steel surface and tedlar surface, are simulated and compared. The RNG k–? model is employed to predict the air turbulence, and the Lagrangian particle tracking method integrated with particle–wall impact model is used to reveal particle physical behaviors. Turbulent dispersion of the particles is taken into account by adopting the discrete random walk (DRW) model. Particle deposition velocities and distributions onto the wall, ceiling and floor are simulated and analyzed. For both stainless steel and tedlar ducts, reasonable agreements are achieved between the simulation data and experimental data for particles with larger relaxation time. Particle deposition velocity is related to particle relaxation time and surface materials. The particle–wall impact model affects the prediction of deposition velocity and distribution. As the effects of Brownian diffusion and turbulent fluctuation on particle deposition are not considered, the presented model applies better to the particles with relatively large relaxation time.     

Challenges of forest landscape modeling—Simulating large landscapes and validating results

Over the last 20 years, we have seen a rapid development in the field of forest landscape modeling, fueled by both technological and theoretical advances. Two fundamental challenges have persisted since the inception of FLMs: (1) balancing realistic simulation of ecological processes at broad spatial and temporal scales with computing capacity, and (2) validating modeled results using independent, spatially explicit time series data. The paper discusses the current status and future directions regarding these two challenges.