Building Floor Slab Research Articles

Seismic strengthening and seismic improvement of timber structures

In European seismic areas timber structures are found as building frames, in combination with masonry infills, in bridges, but most frequently in roof structures and floor slabs of traditional buildings. Seismic strengthening of existing structures should provide a well-defined and simple path to seismic forces, maintain timber members elastic, and develop as much as possible the post-elastic behaviour of joints. Provisions must be adopted to avoid sudden loss of capacity and brittle failure, and to foster ductility. Different criteria for seismic strengthening of floor slabs and of carpentry joints are presented.

Super-light concrete decks for building floor slabs

This paper presents investigations carried out at the Technical University of Denmark (DTU) on a prototype series for a super-lightweight prestressed concrete deck element called the SL-Deck. The intention behind making a new prefabricated deck element is to improve performance with respect to flexibility, sound insulation and fire resistance compared with present-day prefabricated structures. Full-scale tests and theoretical investigations show that the deck structure performs as intended. Also, that it is possible to assess by calculation the loadbearing capacity in bending and shear, and assess the pull-out strength of prestressing wires, the fire resistance and the acoustic insulation. Based on the results of the investigations, recommendations are given for further development of the structure before fully automated mass production is established.

Energy absorption potential of concrete floors containing secondary (shrinkage and temperature) reinforcements

This paper experimentally investigates the energy absorption potential of two types of concrete floors, namely, normal density concrete and structural low-density concrete, containing secondary (shrinkage and temperature) reinforcements. The test program considered the following secondary reinforcements: 1) traditional welded-wire steel mesh, 2) steel fiber and 3) poly composite fiber. To estimate the extent to which crushing of floor slab materials would help absorb energy, a series of concrete penetration tests employing patch loading was undertaken on scaled down model slabs. Each concrete-secondary reinforcement combination considered slabs of 50 mm in depth with square plan dimensions ranging from 50 to 500 mm, resulting in a total of 30 test specimens. The first part of the paper discusses the test specimens, the test setup, and the test procedure. The second part of the paper presents the experimental results and establishes the energy absorption of different concrete-secondary reinforcement combinations. Sieve analysis results of the crushed specimens were used to derive a “work index” value that relates the pulverized particle size distributions to energy inputs. The work index values of concrete-secondary reinforcement systems can be used to assess the energy dissipation potential associated with such floor slabs in buildings undergoing progressive collapse. The results indicate that floors with secondary reinforcements could play an important role in helping arrest global progressive collapse.

Effectiveness of Distributed Mass Damper Systems for Lightweight Superstructures

AbstractDistributed mass damper (DMD) systems are discussed as a method of suppressing lateral motions of superstructures during wind storms and earthquakes. Potentially, DMD systems are a technology that is economical enough for widespread application to buildings or other structures. Focus is placed on lightweight superstructures as a reflection of the trend toward the use of ultra-lightweight floor slabs in high-rise buildings. Results of model-scale experiments are presented that show that tuned mass damper (TMD) systems that add between 1.3 and 2% to the total superstructure gravitational mass are effective methods of increasing damping in superstructures and reducing peak lateral accelerations during forced vibration events. In those experiments, tuned sloshing dampers (TSDs) were employed in conjunction with floor and roof plates that simulated ultra-lightweight slabs constructed from cross-laminated timber (CLT), which is a new material option in North America. The use of TSDs was a surrogate for ...

An estimated prediction of the deformability of mineral wool (MW) slabs under long-term compressive stress

This paper presents the results of testing the strength and deformability of mineral wool slabs used for insulating flat roofs, facades, cast-in-place floors and external basement walls as well as for sound insulation in the floor slabs of buildings. The empirical equations for calculating the stress σ10%, tangential modulus of elasticity E and ultimate relative strain ɛcr (which, when exceeded, causes a considerable strain increase) of mineral wool slabs under short-term compression are provided. A regression model of the interrelationship between the predicted pointwise values of creep strains for a lead time of 10years and parameters such as the density, long-term compressive stress σc=0.35·σ10% and ultimate relative strain ɛcr of slabs under short-term compression is suggested.

Damage states and cyclic behaviour of drywalls infilled within RC frames

Drywalls are the typical infill or partitions used in new structures. They are usually located within structural frames and/or between upper and lower floor slabs in buildings. Due to the materials used in their construction, unlike masonry blocks, they can be considered as light non-structural infill/partition walls. These types of walls are especially popular in New Zealand and the USA. In spite of their popularity, little is known about their in-plane cyclic behaviour when infilled within a structural frame. The cause of this lack of knowledge can be attributed to the typical assumption that they are weak non-structural elements and are not expected to interact with the surrounding structural system significantly. However, recent earthquakes have repeatedly shown that drywalls interact with the structure and suffer severe damage at very low drift levels. In this paper, experimental test results of two typical drywall types (steel and timber framed) are reported in order to gather further information on; i) their reverse cyclic behaviour, ii) inter-storey drift levels at which they suffer different levels of damage, iii) the level of interaction with the surrounding structural frame system. The drywall specimens were tested using quasi-static reverse cyclic testing protocols within a full scale precast RC frame at the Structures Laboratory of the University of Canterbury.

Predation on bats by Great Kiskadees

Great Kiskadees (Pitangus sulphuratus) are found in a variety of habitats from Argentina north to the United States and are the most generalist tyrant flycatcher in both foraging behavior and food habits. These kiskadees are known to occasionally prey on small vertebrates, but, to our knowledge, bats have never been reported as a prey item. We observed a breeding pair of Great Kiskadees preying on bats (Myotis spp.) at the field station Base de Estudos do Pantanal (BEP) in the southern Pantanal, Brazil. At BEP, there are fissures under the building's floor slabs that allow two species of bats, black myotis (Myotis nigricans) and silver-tipped myotis (M. albescens), to access internal galleries and use them as day roosts. We found that bats, insects, and fruits were the most common food items fed to nestlings by adult kiskadees. Bats (N = 10) were captured when kiskadees landed on ground below a building, looked up through a fissure, and then reached through the fissure and captured a bat in their bill. On one occasion, a kiskadee flew from a perch and captured a bat in flight. Our observations provide further evidence of the opportunistic feeding behavior of Great Kiskadees.

The analysis of dynamic model of the building floor slab fragment

The analysis of dynamic model of the building floor slab fragment

Buildability Factors Influencing Micro-Level Formwork Labour Productivity of Slab Panels in Building Floors

Buildability is one of the most important factors influencing labour productivity. Nevertheless, a thorough investigation of the literature revealed a dearth of research into the effects of buildability on the labour productivity of an integral trade of in situ reinforced concrete construction, namely formwork. In comparison with beamless slabs, the formwork operation of beam—slab floor configurations is a labour-intensive process, which is associated with substantial additional labour inputs. Therefore, the objective of this research is to explore the buildability factors influencing the formwork labour productivity of building floor slab panels. To achieve this objective, a sufficiently large volume of labour productivity data is collected, at the activity level, and analysed using the categorical interaction-regression method. As a result, the main and interaction effects of repetition, panel areas and geometry of panels on labour productivity are determined. The findings show a significant influence of these factors and corroborate the importance of applying the concepts of design rationalization, standardization and repetition to the design stage of construction projects. The results may be used to provide designers with feedback on how well their designs consider the requirements of buildability principles, and the consequences of their decisions on the efficiency of the operation.

A special BEM for elastostatic analysis of building floor slabs on columns

This work presents a boundary element formulation for the analysis of building floor slabs, without beams, in which columns are coupled with the plate. An alternative formulation of boundary element method is presented, which considers three nodal displacements values ( w, ∂ w/∂ n and ∂ w/∂ s) for the nodes at the boundary of the plate. In this formulation three boundary equations are written for all nodes at the boundary and in the domain of the plate. As the nodes of the column-plate connections are also represented by three nodal values, all these structural elements can be easily coupled. It is supposed that the cross-sections of the columns remain flat after the deflection and consequently the assumption of linear variation of the stress in the plate–column contact surface is also valid.

Evaluation of vadose zone biodegradation of BTX vapours

Soil vapour transport to indoor air is an important potential exposure pathway at many sites impacted by subsurface volatile organic compounds (VOCs). The inclusion of biodegradation in vadose zone transport models for benzene, toluene and xylene (BTX) and fuel hydrocarbons has been proposed; however, there is still significant uncertainty regarding biodegradation rates and the local effects of buildings or ground surface cover on fate and transport processes. The objective of this study was to evaluate biodegradation processes through comprehensive monitoring at a site contaminated with BTX and model simulation. Study methods included extensive vertical profiling of BTX vapour and light gas (oxygen and carbon dioxide) concentrations and moisture content, and semi-continuous monitoring of oxygen and pressure below a building floor slab. Significant vadose zone biodegradation over a relatively small depth interval was observed. Based on the observed soil vapour profile, first-order biodegradation rates were estimated by fitting an analytical solution for diffusion and biodecay to the data. Degradation rates were found to compare well to other reported laboratory and field data. A two-dimensional (2-D) numerical model incorporating vapour-phase diffusion, advection, sorption and biodegradation was used to simulate the effect of a building floor slab on transport processes. Model results demonstrate the sensitivity of vapour-phase BTX and oxygen transport to partial barriers to diffusion (e.g. building foundation) and highlight the importance of using a model that ties biodecay to oxygen availability. In addition, depressurization within a building and advective transport is shown to have a potentially significant effect on BTX fate, in soil below.

Transient boundary element algorithm for elastoplastic building floor slab analysis

A direct boundary element algorithm is developed for the dynamic analysis of thin elastoplastic building floor slabs directly supported by columns. The formulation employs the classical boundary element methodology dedicated to the analysis of elastoplastic plates. The method uses the static fundamental solution of the thin elastic plate problem. In this case, boundary as well as interior elements are used in the space descritization of the problem. This is due to the presence of plasticity and inertial effects in the integral formulation. An explicit time integration algorithm, employed on the incremental form of the matrix equation of motion, leads to the solution of the problem. Simple practical examples illustrate the accuracy and the efficiency of the proposed algorithm.

The development of a numerical analysis method for structure borne sound of building floor slabs, and its application to the evaluation of heavy weight floor impact sounds.

In order to construct an evaluation method for structure-borne sound in building floor slabs, the dynamical analysis method for floor slab vibration in audio-frequency ranges and the numerical calculation method for sound radiation produced from slabs have already been developed. In the present paper, the heavy weight floor impact sound is numerically calculated by generalizing these developed methods, and the effectivity of this simulation method is shown. The vibrational characteristics of the diverse floor slabs and the stiffening effects of beams in particular are also clarified using this method

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

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 γ=k i/k s, d/L and δ/L, where k i and k s are the conductivities of the insulation material and soil respectively, d is the insulation depth, δ is the insulation thickness, and L is the building half-width. The heat loss for small but nonzero values of γ and δ/L can be considerably greater than for the idealized situation of infinitesimally thin, perfectly insulating vertical edge insulation.

Steady-state heat losses from a building floor slab with horizontal edge insulation

The steady-state heat loss from a slab-on-ground floor insulated at its edges by horizontal insulation under the slab is calculated in two dimensions from a Fourier series solution of the temperature field in the ground. The temperature above 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 h 1, h 2/h 1 and δ/( L+2 ϵ), where h 1 and h 2 are measures of the surface film conductance, where h 2 includes the effect of the insulation, δ is the insulation length, L the building half-width and 2ϵ is the wall thickness. For small values of h 2/h 1, there is a fairly rapid decrease in the heat loss at small values of δ/( L+2 ϵ), and a slow decrease beyond δ/( L+2 ϵ)=0.3. As h 2/ h 1 increases, the rate of decrease in the heat loss becomes correspondingly slower.

Evaluation of Stiffness on Building Floor Slabs

Evaluation of Stiffness on Building Floor Slabs

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.

The bearing capacity of joints between walls and floor slabs in multistorey buildings

The paper deals with determination, by traditional and probabilistic methods, of the bearing capacity of joints between walls and floor slabs. All principals factors affecting the probability of limit states being attained are taken into account. The probability analysis is based on specific statistical data.

Composite Action Without Shear Connectors

In composite construction of building floor slabs, the common method for transferring shear stresses from the concrete slab to the steel beam is to use stud shear connectors. An alternate method, which is seldom used, is to completely encase the steel beam in concrete. When the steel beam is completely encased, the 1970 AISC Specification assumes the beam to be interconnected to the concrete by natural bond without additional anchorage. This assumption may be used when at least 2 in. of concrete cover is provided over the sides and bottom of the beam and at least 1½ in. of cover is provided at the top. An additional requirement is that adequate mesh or reinforcing steel be used in the encasement to prevent spalling of the concrete. In most composite construction the neutral axis of the composite section is located either in the floor slab or at a very small distance below the bottom of the slab. Since the specifications do not permit the concrete on the tension side of the neutral axis to be used as a structural element, the concrete below the neutral axis on a fully encased beam does not theoretically increase the stiffness of the beam. The tension concrete does provide more bond area between the steel and concrete; however, the advantage of this additional bond may be offset by the additional dead weight of the concrete used to encase the beam.