Performance Of Floors Research Articles

Experimental and numerical investigation of seismic response of access floors based on shake-table tests using 2-story steel moment frame

In this study, a full-scale shake-table test was conducted utilizing a 2-story steel moment frame to evaluate the seismic performance of access floors (or raised floors). A total of four access floor specimens were fabricated that are typically used in offices and computer/server rooms. Based on test results, critical failure modes and nonlinear behavior of access floors were discussed in detail. Specimen utilizing a flexible 600 mm-high access floor (FH600-F) exhibited several cracks in its joint connection plates (or pedestal heads) before the specimen eventually collapsed under the 60% RRS intensity test (PFA = 0.65 g). Due to a partial pull-out of the pedestal heads from their supporting columns, a highly pinched hysteretic response was also observed. A simplified SDOF numerical model was presented that can effectively capture the complex pinching behavior of access floor specimens. Based on the calibrated numerical analysis, it was identified that the partial pull-out of pedestal heads caused about 60% strength loss during the reverse cyclic phase of the specimen, which was the main source of the high pinching. The specimen also exhibited severe stiffness-degradation, which may have resulted from the cracks that developed in a significant number of its joints. The initial stiffness of the specimen was reduced by about 30% before its eventual collapse. Extensive numerical analyses were also conducted to evaluate the effects of pinching and stiffness-degradation on the acceleration response of access floors based on the floor motions obtained from the time history analysis of four multi-story building models.

The Role of Abrasion Resistance in Determining Suitability of Low-Density Plantation Timber for Engineered Flooring

Abrasion resistance is an important property for the functional performance and serviceability of timber floors. Although hardness is the conventional criterion used in selecting species for flooring applications, it shows greater variations and restricts the use of low-density species, whereas abrasion resistance could generate a more reliable indication of a product’s surface performance. Eucalyptus nitens is a fast-grown global plantation species extensively available in Tasmania, Australia. Until recently, this material has been perceived as unsuitable for appearance applications such as flooring. This study assesses several engineered flooring prototypes comprised of E. nitens—sawlog managed and fibre-managed resources—compared to an existing market product (E. obliqua and a commercial engineered timber flooring product with UV-cured coating). Tests were performed in accordance with the EN 14354:2016, sandpaper method using Taber abraser and further modified to test flooring prototypes. The highest abrasion resistance was observed in the E. nitens veneer composite product. Fibre-managed E. nitens resulted in the greatest level of abrasion, while sawlog-managed E. nitens was comparable to native regrowth E. obliqua, a commonly used flooring species historically used in Australia. Therefore, the findings from this research suggest there are suitable flooring applications for plantation E. nitens as engineered wood products in some domestic and residential dwellings when compared to existing native products.

Effects of surface hardeners on the performance of concrete floors prepared with different mixture proportions

Constant growth in the concrete floor sector claims new techniques to improve concrete performance and avoid undesirable issues. In this way, materials used in concrete floors are essential, and it is critical to investigate them. Therefore, this study evaluated the influence of surface hardeners on the surface hardness determined by the rebound hammer test of concrete floors prepared with distinct water/cement ratios, curing ages, and cement types. The control parameters of the concrete’s production, including the compressive strength, flexural tensile strength, and bleeding tests were analyzed. In addition, data were assessed by multifactorial analysis of variance (ANOVA). Thus, hardeners increased the surface resistance of the composites, therefore reducing the chances of pathological manifestations occurring. Taken together, we demonstrated that hardeners improved the concrete surface prepared with all mixture proportions, but it was more significant when using the cementitious hardener and higher w/c content (0.6).

Effect of Spring-Mass-Damper Pedestrian Models on the Performance of Low-Frequency or Lightweight Glazed Floors

For structural design purposes, human-induced loads on pedestrian systems can be described by several simplified (i.e., deterministic equivalent-force models) or more complex computational approaches. Among others, the Spring-Mass-Damper (SMD), Single Degree of Freedom (SDOF) model has been elaborated by several researchers to describe single pedestrians (or groups) in the form of equivalent body mass m, spring stiffness k and damping coefficient c. For all these literature SMD formulations, it is proved that the biodynamic features of walking pedestrians can be realistically reproduced, with high computational efficiency for vibration serviceability assessment of those pedestrian systems mostly sensitive to human-induced loads (i.e., with vibration frequency f1 < 8 Hz). Besides, the same SMD proposals are characterized by mostly different theoretical and experimental assumptions for calibration. On the practical side, strongly different SMD input parameters can thus be obtained for a given pedestrian. This paper focuses on a selection of literature on SMD models, especially on their dynamic effects on different structural floor systems. Four different floors are explored (F#1 and F#2 made of concrete, F#3 and F#4 of glass), with high- or low-frequency, and/or high- (>1/130th) or low- (1/4th) mass ratio, compared to the occupant. Normal walking scenarios with frequency in the range fp = 1.5–2 Hz are taken into account for a total of 100 dynamic simulations. The quantitative comparison of typical structural performance indicators for vibration serviceability assessment (i.e., acceleration peak, RMS, CREST) shows significant sensitivity to input SMD assumptions. Most importantly, the sensitivity of structural behaviours is observed for low-frequency systems, as expected, but also for low-mass structures, which (as in the case of glazed floor solutions) can be characterized by the use of lightweight modular units with relatively high vibration frequency. As such, major attention can be required for their vibrational analysis and assessment.

Evaluation of the dynamic response for scaled models of shaped concrete floor slabs

The dynamic response of building structures is an essential design consideration in building acoustics. However, building design is increasingly driven by sustainability goals. Floors can be optimized to reduce material consumption and corresponding carbon emissions, yet geometric changes may cause sound insulation and vibration problems. Although the dynamic performance of traditional floors is well established, the performance of non-traditional shapes is less understood. Before trusting the results of building simulations encompassing optimized floors, the dynamic results should first be validated experimentally. This paper details a numerical finite element analysis method to ascertain the dynamic response of four shaped concrete slabs, with experimental modal analysis used to validate the numerical results. The material properties in the numerical model are updated to match the experimental results. The findings support a computational framework for determining the dynamic response of shaped structures that can then be implemented in future large-scale building models.

Lantai Panggung untuk Efisiensi Energi pada Rumah Deret di Tropis Lembap

The application of stilt floors in row houses can increase the flow of wind under the pit. This study uses the literature review method to map research on the performance of stilt floors, study energy efficiency in row houses, and study the research gap that connects stilt floors, row houses, and energy efficiency. Materials for research are papers from the last ten years. To analyze research gaps using VOSViewer software, while analyzing research variables that have been used by researchers using Atlas.ti software. The results of the study indicate that more measurable research on building performance is still needed regarding the application of stilt floors to help energy efficiency. Energy efficiency in row houses is difficult to obtain due to limited land and the arrangement of row houses.

Review of Vibration Assessment Methods for Steel-Timber Composite Floors

Human comfort is recognized as an essential serviceability requirement for timber floors. Although several standards and design criteria are available for designing steel and concrete floors, there is no consensus among researchers on the applicability of such design methods to timber composite floors. Adding steel to timber floors is intended to create long spans, however, vibration is still a major challenge in achieving longer spans. To highlight the extent of this issue, a comprehensive search in the literature was conducted. The most common vibration criteria that may be used to assess the performance of steel-timber composite floors under human-induced vibrations were reviewed. For lightweight composite floors, the 1 kN deflection limit was found to be the most suitable vibration limit based on a wide range of subjective evaluation studies. For composite floors comprising steel and heavier timber subfloors, the relevance of 1 kN deflection criterion and other criteria suggested in the literature are questionable due to the lack of subjective evaluation studies. In the advent of advanced computing and data analysis, conducting detailed numerical analysis validated by accurate on-site measurements is recommended. Special attentions should be given to accurate estimation of connection stiffness and damping ratio according to the findings of this study.

Experimental study of the behavior of box floor with orthogonal ribbed beams by poplar LVL

Considering the unidirectional layout of ribbed beams and simple structure in traditional wooden floors, it is not suitable for large-span wooden buildings. Six groups of floor ribbed beams with plane size of 4.8 m×3.6 m were designed and manufactured by using poplar laminated veneer lumber (LVL), among which five floor specimens were orthogonal ribbed beams and the other one was traditional. A bending performance test was carried out to analyze the influence of different ribbed beam spacing and high span ratio on the mechanical performance of poplar LVL orthogonal ribbed beams, and its results were compared with that of the traditional floor with ribbed beams. The results showed that the box floors with orthogonal ribbed beams had good integrity during the bending process. Moreover, the change of the high span ratio had an important influence on the bending performance of the box floors with orthogonal ribbed beams, and the change of the spacing of the ribbed beams had a relatively small influence on the flexural performance of the box floors with orthogonal ribbed beams. Under the same conditions, the bending performance of the box floors with orthogonal ribbed beams was better than that of traditional floor.

Impacts of storey number of buildings on solar chimney performance: A theoretical and numerical approach

Under the fact that solar chimney was less investigated in multi-storey buildings, a theoretical model was then developed for solar chimney-induced buoyancy-driven natural ventilation. This is the first study addressing the influences of the storey number on ventilation rates for multi-storey solar chimney (SC) buildings. A storey correction coefficient was proposed to predict the SC-induced ventilation at various floors with identical air inlet areas. The theoretical model was established to elucidate the relationship among ventilation flow rates, solar radiation intensity, vent sizes and storey number (f), where the numerical results have also been validated. Although the total SC ventilation performance is enhanced, its enhancement with a higher chimney cavity was less effective when compared to those solar chimneys in single-storey buildings. This is due to the higher chimney cavity hindering the ventilation performance of the lower floors. The volume flow rate decreased exponentially for the top floors of each building when the two-storey building increased to a seven-storey building. For buildings with more than three storeys, the overall volume flow rate was more sensitive to the cavity gap than the solar radiation intensity, with an improvement in ventilation by 45.6% compared to 26.0% under the same conditions, respectively. To maximize the total flow rate, the optimal cavity gap should increase gradually from 0.2 m to 1.5 m for single-to seven-storey buildings. The findings of this study contribute to a further application of solar chimneys in multi-storey buildings.

Structural performance of cross-laminated timber-concrete composite floors with inclined self-tapping screws bearing unidirectional tension-shear loads

This study investigated the structural performance of cross-laminated timber (CLT)-concrete composite floor with inclined self-tapping screws bearing unidirectional tension-shear loads. Five groups of push-out tests were conducted to evaluate the shear behavior of the inclined screw connector. The results showed the embedded depth of the inclined screw in the CLT had a significant influence on the shear performance of the connectors, and the vertical screws demonstrated enhanced ductility. Next, six groups of specimens were subjected to four-point bending tests to study their flexural behavior under various parameters. A screw spacing that was too small led to premature failure, whereas an increased section height greatly improved the bending performance of these specimens. One specimen in particular exhibited a plate-end shear enhancement accompanied by excellent performance in terms of flexural stiffness and bearing capacity. Furthermore, a computational optimization method for determining an effective bending stiffness of the composite floor was proposed based on ‘γ-method’. This approach expanded the application scope of traditional methods, and the calculated values were in good agreement with the experimental values. Finally, a simplified finite element model was established, and parametric finite element analysis verified that improving the shear efficiency of the connector could bring economic benefits.

Vibration and flexural performance of cross-laminated timber – glulam composite floors

This paper presents experimental research on composite cross-laminated timber (CLT) glulam floors. The composite action was achieved using three different types of connectors. The connector stiffness and strength were determined with small-scale shear tests. Quasi-static monotonic four-point bending and vibration tests were conducted on six full-scale (9.1 m long, 1.6 m wide) double T-beam floor segments consisting of 3-ply CLT panels and two glulam beams. The vibration test results indicated that the three connection types had negligible influence on the dynamic properties of the composite floor segments, while the allowable vibration controlled span of the composite panel was around 7.2 m with acceptable subjective evaluations. The load-deformation behaviour observed in the full-scale testing was linear up to failure which was brittle tension at mid-span in one of the glulam beams for all specimens. The ratio between experimental and expected bending stiffness was close to 1.0 for all three connector types demonstrating the adequacy of applying the gamma method to predict the performance of CLT-glulam composite floors. The findings from this research supported the design and construction of the floors for two new school buildings.

Evaluation of the bending performance of glued CLT-concrete composite floors based on the CFRP reinforcement ratio

A study was conducted on the reinforcement of cross-laminated timber (CLT) concrete composite floors with carbon fiber reinforced plastic (CFRP) to improve its mechanical performance and reliability in wood composite structures. A four-point bending test evaluation was completed on three types of cross-laminated timber concrete composite floors produced with different carbon fiber reinforced plastic reinforcement ratios (33%, 66%, and 100%) on the entire surface of the tensile portion. An increase in the carbon fiber reinforced plastic reinforcement ratio of the composite floors led to an increased bending capacity and a slightly improved yield performance. In the case of a composite floor with a reinforcement ratio of 33%, premature failure occurred in the elastic region due to defects of the CLT such as knots and slopes of the grain. Failure mode analysis revealed that tensile and shear failure coexist when the composite floor has a CFRP reinforcement ratio of 33%. In contrast, reinforcement ratios of 66% and 100% prevented premature failures in the elastic region caused by defects and induced a consistent failure mode. These reinforcement effects reduced the variability in the increased bending capacity of the composite floors and improved the accuracy of the theoretical prediction design via the γ-method. Meanwhile, the shear connections between the cross-laminated timber and concrete via epoxy adhesive exhibited full-composite behavior without being affected by the reinforcement ratio.

Influence of Wood Properties and Building Construction on Energy Demand, Thermal Comfort and Start-Up Lag Time of Radiant Floor Heating Systems

Radiant floor heating is becoming increasingly popular in cold climates because it delivers higher comfort levels more efficiently than conventional systems. Wood is one of the surface coverings most frequently used in radiant flooring, despite the widely held belief that in terms of thermal performance it is no match for higher conductivity materials if a high energy performance is intended. Given that the highest admissible thermal resistance for flooring finishes or coverings is generally accepted to be 0.15 m2K/W, wood would appear to be a scantly appropriate choice. Nonetheless, the evaluation of the thermal performance of wooden radiant floor heating systems in conjunction with the building in terms of energy demand, thermal comfort, and start-up period, has been insufficiently explored in research. This has led to the present knowledge gap around its potential to deliver lower energy consumption and higher thermal comfort than high-thermal-conductivity materials, depending on building characteristics. This article studies the thermal performance of wood radiant floors in terms of three parameters: energy demand, thermal comfort, and start-up lag time, analysing the effect of wood properties in conjunction with building construction on each. An experimentally validated radiant floor model was coupled to a simplified building thermal model to simulate the performance of 60 wood coverings and one reference granite covering in 216 urban dwellings differing in construction features. The average energy demand was observed to be lower in the wood than in the granite coverings in 25% of the dwellings simulated. Similarly, on average, wood lagged behind granite in thermal comfort by less than 1 h/day in 50% of the dwellings. The energy demand was minimised in a significant 18% and thermal comfort maximised in 14% of the simulations at the lowest thermal conductivity value. The vast majority of the wooden floors lengthened the start-up lag time relative to granite in only 30 min or less in all the dwellings. Wood flooring with the highest thermal resistance (even over the 0.15 m2K/W cited in standard EN 1264-2) did not significantly affect the energy demand or thermal comfort. On average, wood flooring lowered energy demand by 6.4% and daily hours of thermal comfort by a mere 1.6% relative to granite coverings. The findings showed that wood-finished flooring may deliver comparable or, in some cases, higher thermal performance than high-conductivity material coverings, even when their thermal resistance is over 0.15 m2K/W. The suggestion is that the aforementioned value, presently deemed the maximum admissible thermal resistance, may need to be revised.

Experimental Investigation on the Structural Performance of Mass Timber Panel-Concrete Composite Floors with Notched Connections

Mass timber panel (MTP)-concrete composite floors are gaining increasing interest from builders and designers due to their optimized structural performance, light self-weight, and aesthetically exposed wood ceilings. Among various connecting techniques between timber and concrete, notched connections made by cutting grooves on timber and filling them with concrete are considered as one of the most structurally efficient and cost-saving connecting solutions. Numerous ways of making and reinforcing the notched connections, however, hinder the standardization and development of the design guidelines for this type of connection, which reduces the competitiveness of MTP-concrete composite floors. In this study, experiments were carried out to investigate the performance of MTP-concrete composite floors with different connection designs. Nine composite floor specimens with varying span, connection number, notch depth, concrete thickness, and loading direction were designed and tested under bending. The bending stiffness, load-carrying capacity, ductility, and failure mode of tested specimens were studied and discussed. Test results show that the connection number, notch depth, and concrete thickness affect the bending stiffness and strength of the floor positively, an increase in floor span impacts the floor performance negatively, whereas the effect of a limited number of self-tapping screws in the notch is negligible. The study also shows that MTP-concrete composite floors with high strength, high stiffness, and good ductility can be achieved through the optimized design of notched connections.

Analysis of instant and long-term performance of timber-concrete floors with boundary conditions other than simply supported

This paper describes an analytical procedure for designing timber-concrete composites (TCC) subjected to boundary conditions other than simply supported. Currently available investigations of TCCs are mainly focused on simply supported slabs, as it is a typical configuration for timber buildings. However, in other structural applications, and remarkably for reinforced concrete buildings, the boundary conditions of the TCC slabs are not likely to be simply supported. Such distinct boundary conditions can significantly reduce the cross section height, mid-span deflection and self weight of the structure, the last one being crucial in seismic regions. The proposed procedure is derived from two simplified methods available in the literature, one general in its nature while the other being valid for simply supported beams. The short-term analytical model was compared against finite element models (FEM) and to the only experimental investigation on partially restrained TCCs available in the literature, while the long-term analytical model was compared only against FEM. At the end of the investigation, a full-scale continuous TCC beam was tested in the serviceability range, to compare with the prediction of the proposed analytical model. The model underestimated the mid-span deflection at 4.5 kN by 13%, concluding that the proposed simplified procedure is valid for boundary conditions other than simply supported. Further experimental campaigns are needed in the future to assess the versatility of the model in a wider range of boundary conditions, including short-term and long-term tests, which should enhance the applicability of TCC slabs in structures different from timber buildings and bridges.

Towards Seismic Performance of Tall Buildingswith Transfer Floors

Towards Seismic Performance of Tall Buildingswith Transfer Floors

Finite Element Modelling for Structural Performance of Slim Floors in Fire and Influence of Protection Materials

Slim floor systems are very common nowadays and various types are currently being used for the construction of high-rise buildings and car parks. Concrete in slim floor beams encases the steel beam section which helps to improve their fire resistance. Despite their higher fire resistance, several fire protection materials like intumescent coatings are often used to achieve a higher fire resistance where desired. The thermal properties and behaviour of various intumescent coating materials were previously studied through experimental investigations. This paper presents finite element analyses to simulate the response of unprotected and protected slim floor beams in fire using different simulation tools. For this purpose, fire tests conducted on unprotected slim floor beams and intumescent coating materials are modelled using research and commercial software. Results from the analyses are compared and verified with the available test data. These validated models are later combined to study the behaviour of protected slim floor beams in fire. Results from the study show that the research and the commercial software replicate the behaviour of slim floor beams and protection materials with good accuracy. Due to the presence of the intumescent coating, the protected slim floor beams displayed a better fire resistance as the temperature of the steel part remained below 400 °C even after 60-min of standard heating. The protected slim floor beams continued to support the external loads even after 120 min of heating.

Experimental Investigations and Numerical Simulations of the Vibrational Performance of Wood Truss Joist Floors with Strongbacks

This paper provides an experimental study and computer modeling analysis of vibration performance of full-scale wood truss joist floors, related to the static deflection and vibration mode/frequency and single-person-induced vibration. The vibration behavior of full-scale truss joist floors was investigated and the influences of the strongbacks on the vibration behavior were assessed. The results showed that the simulated predictions agreed well with the measured results. Strongbacks do not significantly affect the fundamental frequency of the truss joist floors but influence the second and third modal frequencies. The use of strongback rows at mid-span effectively decreased the maximum deformation of point loading at floor center. The effect of adding strongbacks at one-third of each span on decreasing maximum deformation at the floor center was minimal. The case of walking parallel to the joist produced higher acceleration response at the floor center than that of walking perpendicular to the joist. The closer the placements of strongbacks were to the mid-span, the more significant reduction of the vibration at floor center was. Two strongback rows at mid-span performed the best effect on reduction of vibration response at floor center. However, the use of strongbacks had limits of reduction peak acceleration of the sheathing between the joists. The study provides a valuable guide for future vibration serviceability study and design optimization of wood truss joist floors.

Experimental and theoretical investigation of long-term performance of steel-timber composite beams

The structural performance of the steel-timber composite floors under sustained long-term loads was investigated by laboratory tests over a period of 22 months. The long-term deflections, end-slips, and strain distributions over the cross-section were measured and reported for six beams with a loading span of 5.8 m. Effects of different shear connectors, arrangement of the timber panels and timber slab segmentations and the magnitude of applied loads were studied. The timber slab segmentation had a detrimental effect on the short- and long-term stiffness of the tested beams. The long-term effects (after 22 months) led to a maximum 19% increase in the midspan deflections. Furthermore, the moisture transport, variation of mechanical properties with respect to moisture content, long-term compressive deformation of the panels and long-term slip moduli of the shear connectors were investigated to provide a thorough understating of the long-term behaviour of the steel-timber composite system. A simplified analytical model for estimating the flexural stiffness of the steel-timber composite beams was proposed and employed to estimate an overall creep deformation factor for the composite beams. The creep deformation factor of the tested beams was in the range of 0.29–0.39 depending on the shear connector type and timber slab orientation.

Seismic Performance of Precast Hollow-Core Floors: Part 2—Assessment of Existing Buildings

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