Building Research Establishment Research Articles

Use of Computational Fluid Dynamics for Simulating Enclosure Fires

This paper reports on comparing results on the fire environment predicted by using the technique of computational fluid dynamics (CFD) (or field modelling) on simulating an enclosure fire at the preflashover stage with those results reported experimentally in the literature. The theory behind this is to solve a system of partial differential equations describing conservation of mass, momentum and heat with the k-ε turbulence model. The computer pro gram PHOENICS is used as the simulation tool. By specifying the geometrical configurations of the enclosure and the location, size and thermal power of the fire source, it is possible to predict the fire-induced flow and temperature fields. The package can be executed in an IBM personal computer at or above 486 level. Experiments reported by Steckler et al. at the National Bureau of Stan dards, U.S.A. on a single fire chamber; Nakaya et al. at the Building Research Institute, Japan on a double room fire chamber; the corner fire plume by Tran and Janssens; the two-room fire experiment reported by Hagglund at the Na tional Defence Research Establishment (abbreviation: FOA), Sweden; and in the full-scale burning hall by Ingason and Olsson at the Swedish National Test ing and Research Institute (abbreviation: SP), Sweden are considered. Some of the results on the temperature and interface height of the smoke layer are com pared with the popular fire zone model CFAST.

Determination of Slag and Pulverized Fuel Ash in Hardened Concrete—The Method of Last Resort Revisited

Abstract The paper briefly reviews the standard United Kingdom (UK) procedure for the determination of cement content of hardened concrete. It then points out the special problems that occur when attempting to determine the cement content and the amount of mineral admixture in concrete. The method described in this paper, originally devised by the Building Research Establishment, employs a total analysis of the concrete and control samples of the cement, aggregates, and mineral admixture. The method usually used is quantitative X-ray fluorescence (XRF) analysis. The analytical results are examined by the application of a simultaneous equation mathematical approach to resolve the content of the individual components. Application of the method in a case history is used for illustration.

Light shelves: Computer assessment of daylighting performance

A light shelf is a horizontal or near horizontal baffle fitted part way up a window to control and redistribute incoming sunlight and daylight. This paper describes a computer program to analyse light shelves and other daylighting systems. The program agreed well with measurements made in experimental rooms at the Building Research Establishment. Experimental measurements had revealed that an internal light shelf could improve the uniformity of daylight in a room and provide some solar shading, but without significantly increasing illuminances at the back of the room. The computer analysis confirmed these findings and provided information on optimum shelf depth and the benefits of an exterior light shelf. Light shelves should be as reflective as possible, and to work best need a high ceiling. In relative terms light shelves perform best in rooms with external obstructions, when they can increase core illuminances by around 15%.

Appropriate Sampling Strategies for the Measurement of Formaldehyde in Indoor Air

Active and passive sampling methods are available for the determination of maximum formaldehyde concentrations and average formaldehyde concentrations respectively. The present work compares the performance of an active cartridge type sampler with an impinger method and a diffusive monitor which have previously been used at the Building Research Establishment. Good agreement between the three methods was found in a comparison at two formaldehyde concentration levels. The sampling strategy required to obtain a representative reading of the formaldehyde concentration in an indoor atmosphere was investigated using a commercially available diffusive sampler. An investigation of spatial variation in five rooms suggests that sampling in one location should give a representative reading of the formaldehyde concentration in a room, providing the sampler is not placed near a major source of formaldehyde. An initial investigation of temporal variation in six rooms found that one three day sampling period was sufficient to obtain a representative reading of the mean monthly formaldehyde concentration. Between month variation was found to be higher than within month variation although no strong seasonal effects were observed. The results suggest that more than one three day sampling period should be used to estimate the annual mean formaldehyde concentration and two measurements (summer and winter) may be a reasonable approach. Further work in a larger number of homes is in hand to verify the effectiveness of this sampling strategy.

Part L and energy rating applied to UK housing

Examines the new energy regulation proposals set out in the revised Approved Document Part L of the 1995 Building Regulations. Assesses the ways in which the New Requirement L1 calls for better standards of building fabric insulation, improved space heating and hot water controls and the limitation of heat loss. Also considers the more stringent method of calculating U‐values and the attention given to limiting air infiltration and potential thermal bridging effects around windows, doors and other openings. Discusses the equations from the Building Research Establishment Domestic Energy Model (BREDEM) used to calculate the space and ventilation heating requirements of a dwelling, together with a rationale for using a two‐zone model. Assesses the concept of an “energy label” and how this can be expanded using software tools to give estimates of fuel use to an accuracy of ±10 per cent with cost benefits of increased insulation standards.

Luminance models for overcast skies: Assessment using measured data

Sky luminance models are important tools for daylighting planning. In this paper some selected overcast sky models have been evaluated and compared with measured data from the Building Research Establishment, Garston, UK. Against the fully overcast sky data used, the CIE standard overcast sky performed best.

The behaviour of steel frames subject to fire

The Building Research Establishment has developed a computer program for elevated temperature structural analysis. The applications of this program are discussed. A comprehensive parametric study to investigate various aspects of steel frame behaviour under fire conditions is carried out and the results documented. A comparison with limiting temperatures obtained from existing fire-resistant design codes is made and recommendations to simplify the design procedure are postulated.

GIS System for the Restoration Planning in the Area Struck by the Hyougo-ken Nanbu Earthquake

In early morning of January 17, 1995, a magnitude 7.2 earthquake struck Metropolis, Kobe, Japan. This violent shaking caused misery and destruction. More than 5, 500 fatalities had occurred and over 300, 000 left homeless. The Building Research Institute has been trying to set up the Geographical Information System for Restoration Planning in Hyougo-ken Nanbu Earthquake Area. This paper includes way to make new GIS for restoration after disasters on a massive scale, information required to set up in GIS, way to collect information and how to use this GIS in restoration planning. This experience will indicate quick response to case of a future large disaster.

Radon Remediation of Dwellings with Suspended Timber Floors - Case Studies from the Building Research Establishment (UK)

Abstract Dwellings with suspended floors and high radon levels are proving difficult to remediate. This paper reports on the experience of the Building Research Establishment in dealing with such dwellings. Brief details of the remediation of 14 houses are given, and comparisons are made between the effectiveness of the different techniques adopted. Natural ventilation, mechanical supply ventilation and mechanical extract ventilation are three techniques that have been used successfully as radon remedial measures. Preliminary results suggest that supply ventilation is more effective than extract ventilation.

Radon Reduction Techniques for Suspended Timber Floors and Pressure Field Extension Assessment of Hardcore Specifications

Abstract This paper comprises two case studies. The first describes a series of mitigation measures carried out in a small primary school fitted with a suspended timber floor. Radon levels had been successfully reduced but the floor subsequently collapsed due to an outbreak of dry-rot. The floor was replaced with a ground-bearing concrete slab fitted with a typical example of one of 200 or so sump-and-fan systems fitted by Cornwall County Council (CCC). Following consultation with the Building Research Establishment (BRE) a network of small bore pipes was fitted below the floor during construction to record variations in radon levels and pressures. The second case study describes the floor replacement at a second, similar school but with a permeable layer of material under the concrete slab and more pressure measurement points. The pressure measurements and their subsequent analysis are described and the performance of the two installations compared. Using BRE and CCC expertise, this technique is now being applied to a number of other replacement floors in order to assess pressure field extension in a variety of hardcore and blinding materials. It is hoped that by careful selection of hardcore and blinding specifications the increased pressure field extension obtained could result in new-build properties requiring fewer underfloor suction points and/or a reduction in fan power consumption with a greater degree of confidence of success than at present. The selection and design of suction systems to date has been on a very pragmatic basis.

Radon Remediation of Dwellings with Suspended Timber Floors - Case Studies from the Building Research Establishment (UK)

Radon Remediation of Dwellings with Suspended Timber Floors - Case Studies from the Building Research Establishment (UK)

The Efficacy and Durability of Radon Remedial Measures

Abstract In the UK, over 16,000 homes, from an estimated 100,000, with annual average radon concentrations exceeding the UK Action Level of 200 Bq.m-3 have been discovered. Some 600 householders who have taken action have sought confirmatory measurements from NRPB. Results for 345 such homes are discussed. A number of remedied homes are being remeasured annually to determine the durability of the remedies: results for the first year follow-up measurements are given. In a separate exercise, homes having the highest radon levels known in the UK have been enrolled in a research programme of the Building Research Establishment. The results for 53 homes in which BREW surveyed, designed and supervised remedial work are presented.

The Efficacy and Durability of Radon Remedial Measures

In the UK, over 16,000 homes, from an estimated 100,000, with annual average radon concentrations exceeding the UK Action Level of 200 Bq.m-3 have been discovered. Some 600 householders who have taken action have sought confirmatory measurements from NRPB. Results for 345 such homes are discussed. A number of remedied homes are being remeasured annually to determine the durability of the remedies: results for the first year follow-up measurements are given. In a separate exercise, homes having the highest radon levels known in the UK have been enrolled in a research programme of the Building Research Establishment. The results for 53 homes in which BREW surveyed, designed and supervised remedial work are presented.

A comparison of sky luminance models with measured data from Garston, United Kingdom

Sky luminance distribution is one of the most important quantities for calculating daylight in buildings and the associated energy savings. At the Building Research Establishment, Garston, sky luminance distributions have been measured on a long term basis for the first time in the UK. These data have been used to assess a number of models which aim to predict the hourly variation of sky luminance distribution. It is concluded that the three best models analysed would all perform well in a computer program to simulate internal daylight levels and lighting energy use.

The performance of innovative daylighting systems

Innovative daylighting systems have four key aims; to increase daylight levels deep within rooms, to improve daylight uniformity, to control direct sunlight and to reduce glare. Results from experimental studies at the Building Research Establishment (BRE) indicated that the systems tested (prismatic glazing, prismatic film, mirrored louvres and light shelves) usually reduced illuminances at the rear of rooms compared with unshaded windows. It is concluded that, in the UK at least, innovative daylighting systems should be designed primarily as shading devices, controlling glare while admitting more daylight than conventional blinds.

The effects of aircraft trailing vortices on house roofs

This paper describes work carried out by the Building Research Establishment to investigate the phenomenon of aircraft trailing vortices and their effect on the roofs of domestic dwellings. As part of this investigation the roof of a house close to runway 27R at Heathrow Airport was instrumented to detect vortices. Measurements of pressure and velocity were carried out for nearly 3000 h during a 12 month period in 1991/92. During this period 399 vortex strikes were detected on the test house giving an average strike rate of 1.5/day. The majority of these strikes produced pressures within the range ± 150 Pa . On 6 occasions suctions exceeded −500 Pa with a maximum suction of −1190 Pa (−25 lb/ft 2) . Over 70% of all vortex strikes occured when the ambient mean wind speed was below 5 m/s. Peak instantaneous tangential velocities of up to 40 m/s were recorded at the anemometer location.

Technical Factors Influencing Decisions to Select Underpinning on Shrinkable Clay

While the tendency for clay to shrink in dry weather and to damage buildings has been known for more than a century, the post‐war work of the Building Research Establishment and recent availability of insurance funds to pay for rectification of subsidence damage have led to a focus on this aspect of building failure, where millions of pounds are spent annually. At some point in each case a decision is made as to whether underpinning is required or not. Reports results of a survey of the technical factors which engineers consider when making a decision of whether to recommend underpinning. Analysis of the data indicated that only one factor, the quantity of damage, significantly influenced the under‐pinning decision.

BRECEM: A RAPID HARDENING CEMENT BASED ON HIGH ALUMINA CEMENT.

The Building Research Establishment (BRE) has developed a blended cement based on high alumina cement (HAC) with ground granulated blastfurnace slag. This cement has been given the trademark 'BRECEM' and the properties of concrete made from the new cement are being studied at BRE in collaboration with the industry. In this paper, the chemical and thermal stability of BRECEM and HAC mortars and concretes is compared as a necessary preliminary to determining engineering properties in due course. Concrete durability studies are at an early stage and, as such, the uses for this cement are still under development. The addition of slag alters the course of hydration reactions in HAC. A chemical compound, gehlenite hydrate (stratlingite), not seen in plain HAC in significant amounts, forms readily and becomes the major hydrate constituent in due course, and is thought to provide a more stable phase assemblage. Studies to determine the chemical and physical properties of BRECEM in mortars and concrete over a range of temperatures and storage conditions have been set up at BRE. BRECEM mortars show excellent sulphate resistance. HAC and BRECEM concrete durability specimens have performed very well following storage for a year in aggressive sulphate, marine and soft water environments. Longer term tests will be carried out at two, five and 10 years. BRECEM concretes have shown a greater tolerance to high water-to-cement ratio mix designs in forming stable assemblages with reduced temperature rises and enhanced durability, and there are cost savings compared with HAC concretes. A number of potential, practical applications have been advocated.

Urban architecture and identity‐a Danish approach

Interest in urban architecture is growing, not only in Denmark but in the rest of Europe as well. This interest now encompasses not only individual buildings, but also whole areas, such as a street or an entire district. Furthermore, it is not only buildings of special architectural or historical value that are of interest, but also what we might call the everyday architecture in the more anonymous parts of towns, which—although, perhaps containing not a single house of special value—have a totality and identity that are worth preserving. The research on urban architecture that has been going on at the Danish Building Research Institute (SBI) since 1988 has produced a working method that can lead to guidelines for new building and alteration which preserve the special character of such areas without obstructing the constant change and development that must be possible in living urban areas.

Compression tests on cold-formed steel columns with monosymmetrical section

This paper presents the results of an experimental study on cold-formed steel columns made at the Building Research Institute of Timisoara. The specimens were press-braked and their thickness ranged from 2 to 4 mm. Channel sections and lipped channel sections were tested, including columns and stub columns tests. Theoretical ultimate capacities were determined by bdAISI, ECCS and Eurocode 3—Annex A specifications. Differences between designed and experimental values for these three methods are insignificant, and theoretical results are confirmed by experimental tests for stub columns. For columns, good agreement with theoretical predictions is obtained by applying the reduction coefficients for ultimate loads given in specifications. Both for columns and stub columns, the results are more conservative for channel than for lipped channel sections.