Concrete Floor Systems Research Articles

Simulation Analysis of a Beam-Slab Floor Structure and Comparison on Project Economy

Combined with the specific project in this paper, the working principle of prestressed high-strength concrete beam and floor system arrangement are presented. The prestressed high-strength concrete beam is simulated using ANSYS finite element software, the bearing capacity, stiffness and deflection are checked and the results can meet the requirement. Finally the prestressed construction technology and engineering economy of a classroom floor structure are given. These can provide reference for rational design of similar floor system.

Shallow Flat Soffit Precast Concrete Floor System

A precast concrete floor system that eliminates the need for column corbels and beam ledges while being very shallow. The main advantages of the present system include a span-to-depth ratio of 30, a flat soffit, economy, consistency with prevailing erection techniques, and fire and corrosion protection. The present system consists of continuous precast columns, prestressed rectangular beams, hollow-core planks, and cast-in-place composite topping. Testing results have indicated that a 12 inch deep flat soffit precast floor system has adequate capacity to carry gravity loads (including 100 psf live load) in a 30 ft×30 ft bay size. Testing has also shown that shear capacity of the ledge-less hollow-core-beam connections can be accurately predicted using the shear friction theory.

Analysis of Slab and Beam’s Moment Influenced by Stiffness Ratio

In this paper ,taking industrial factory building , the size of 33 * 19.8 m2 for example, analyzes Integral reinforced concrete floor system under the loads by Finite element analysis software ANSYS. In the calculation process, beam element is beam4, slab element is shell63, Changing the line stiffness ratio of beam and slab, main beam and secondary beam, researches of moment on the main beam and the secondary beam by means of line stiffness ratio. It is showed that , when the value of line stiffness ratio is more than 10, mid-span moment is fewer obviously with the Increasing K ; when the value of line stiffness ratio is between 2 and 5, mid-span moment is fewer, too; when the value of line stiffness ratio is shorter than 2, mid-span moment does almost not changed.

Modelling the Fire Resistance of Prestressed Concrete Floors using Multi-Spring Connection Elements

The fire resistance of precast prestressed concrete floor systems is heavily influenced by the end connections and the stiffness of the surrounding structure, both of which must be considered in any analysis. Analysing floor slabs with beam or shell elements whose end nodes share the nodes of supporting beams leads to a major problem for precast prestressed flooring systems where the steel tendons terminate at the end of the flooring units, because the approach of sharing nodes of the supporting beam and floor assumes that these tendons are anchored into the supporting beams. In order to solve this problem, a "multi-spring" connection element has been developed. Experimental data available from previous research work has been used to validate the finite element model. It is concluded that the inclusion of the multi-spring connection results in more accurate predictions of prestressed hollowcore slab behaviour in fire conditions.

Experimental and Numerical Investigations of Steel and Concrete Composite Floors Subjected to ISO Fire Condition

The very positive membrane action of steel and concrete composite floor systems (concrete slabs connected to steel beams by means of headed studs) has been clearly demonstrated through various Cardington real fire tests. However, little evidence is established for fire performance of such structural system exposed to ISO fire condition, the lack of which still constitutes an obstacle for certain national authorities to accept totally the application of the design concept derived from above real fire tests, in particular for long duration ISO fire.On the basis of the above situation and in order to enlarge the application of the design concept based on membrane action to all types of fire, CTICM, within the scope of two different research projects FRACOF and COSSFIRE, performed successively two full scale ISO fire tests, both of which lasted for more than 120 minutes, with two different steel and concrete composite floor systems designed according to Eurocode. The observed fire performance of these floor systems during the tests was extremely satisfactory and revealed a solid robustness of such type of structure systems in fire situation. Considering the fact that the fire test of FRACOF project has been already presented in detail during SiF'08 and Eurosteel2008 conferences, this paper is focused especially on the comparison of above two tests with regard to structural configuration, loading condition, structural behaviour and failure modes.In addition, these tests have been subjected to a specific numerical investigation with help of a 3D hybrid structural FE model. It is illustrated through this numerical investigation that the actual advanced modelling technique is accurate enough to reproduce precisely the fire behaviour of complex structural systems and may be applied to fire safety engineering with high level of confidence.

Shear-Lag Phenomenon in Cast-in-Site Reinforced Concrete Hollow Floor System

Shear-lag phenomenon exits in many long-web structure especially when the stiffness of web is much larger than that of the flange’s. In this paper, Energy-Variation Method is applied to interpret shear-lag phenomenon in cast-in-site reinforced concrete hollow floor system. Finite Element Method (FEM) and is then used to validate the analysis results. The solution for the variation equation for effective flange width is proposed by solving the differential equations using proper boundary conditions.

Cost Optimization of Reinforced Concrete One-Way Ribbed Slabs Using Harmony Search Algorithm

Cost optimization of a reinforced concrete one-way joist floor system consisting of a hollow slab is presented in this paper. The cost of the system is considered to be the objective function, and the design is based on the American Concrete Institute’s ACI 318-05 standard. This function is minimized, subject to design constraints, using the harmony search algorithm. A numerical example is presented to illustrate the performance of the algorithm and a sensitivity analysis is performed. A parametric study is also conducted to investigate the effects of the beam span and the loading on the cost optimization of the ribbed slab.

Development of prefabricated timber–concrete composite floor systems

The timber–concrete composite structure consists of timber joists or beams effectively interconnected to a concrete slab cast on top of the timber members. This type of structure is finding new applications in multi-storey buildings and short-span bridges. Most of the research performed to date has focused on systems where ‘wet' concrete is cast on top of timber beams with mounted connectors. This paper presents a novel composite system where the concrete slab is prefabricated off-site with connectors already embedded and then connected to the timber joists on site. The advantages of this method include reduced cost and better quality control of the materials, absence of ‘wet' components on site during building erection and reduced concrete shrinkage effects on the composite beam. The paper reports an overview of a pilot research project conducted at Luleå University of Technology, Sweden, which includes direct shear tests to failure of different connection systems, bending tests to failure, dynamic (vibration) tests and long-term tests under sustained load of full-scale composite beams. The paper also reports the mechanical properties of the connection, which can be used within a simple design method given in Eurocode 5. The economic advantages of prefabrication and the possibility of demounting the structure make the proposed floor system very promising.

The Application of Reinforced Concrete Composite Floor System of Superimposing Box and Net Beam to Zibo Athletes Apartment

According to the construction site of Zibo athlete apartment and the relevant standards, the structure constitution of the composite floor system, construction method and the problems that should be paid attention during construction were introduced in detail. Reinforced concrete composite floor system of superimposing box and net beam consisted of small prefabricated components- two reinforced concrete plates locating at top and bottom of the box and the cast-in-site concrete beam. This composite floor system was a whole structure of beam and plate combination, with a continuous box section. The superimposing box undertook the loads action together with the rib beam. The floor system has many advantages such as the industrial prefabricated components, stable construction quality, reduction of labor intensity in construction site and the environmental pollution, and the integral structure.

Experimental Tests of Notched and Plate Connectors for LVL-Concrete Composite Beams

This paper reports the experimental results of symmetrical push-out tests performed on notched and toothed metal plate connectors for laminated veneer lumber (LVL)-concrete composite floor systems. The characteristic shear strength and slip moduli were evaluated for three types of connectors: (1) a 300-mm-long rectangular notch cut in the LVL joist and reinforced with a 16-mm-diameter lag screw; (2) a triangular notch reinforced with the same lag screw; and (3) two 333-mm-long toothed metal plates pressed in the lateral surface of two adjacent LVL joists. The shear force versus relative slip relationships are presented together with analytical prepeak and postpeak approximations which can be used to carry out nonlinear finite-element analyses of LVL-concrete composite beams. The failure mechanisms of the notched connections are also discussed. Analytical design formulas for shear-strength evaluation of notched connections derived in accordance with New Zealand Standards and Eurocodes are proposed based on four possible failure mechanisms. Good approximation was found if a slight modification of the Eurocodes formulas is introduced.

Mechanical equipment and ambulances. Strange bedfellows of cardiovascular services.

A case study will be presented regarding vibration and noise control design for an existing heart hospital. Facility expansion within a crowded site necessitates sandwiching a suite of new cardiac catheterization laboratories between mechanical equipment rooms above and the hospital’s main ambulance driveway below. The facility expansion also includes cardiac computed tomography, magnetic resonance imaging, and nuclear imaging, plus cardiovascular care, treatment, and administrative support spaces. Procedure and support spaces can be disturbed by mechanical equipment noise and vibration and noise from ambulance siren. Cardiac procedure instruments and imaging can be disturbed by low frequency noise and vibration from building mechanical systems, ambulance traffic, and building occupants. Design criteria for permissible building vibration and continuous background noise will be presented along with relevant sources and bases. Measurement evaluation results for design will be contrasted with criteria. Measures incorporated in design to mitigate vibration and noise on catheterization laboratories will be discussed. Measures considered in design include structural floor “detuning” concepts, stiffened supports for catheterization laboratory C‐arms, mechanical equipment vibration isolation mounts, and floating concrete floor systems for mechanical rooms. If available, postconstruction spectral analysis measurements of building noise and vibration will be presented.

Preliminary Research Towards A Semi-Prefabricated LVL– Concrete Composite Floor System for the Australasian Market

The choice of the best floor solution has always been a key issue in the design and construction of multi-storey timber buildings. Strict performance requirements such as effective acoustic separation of inter-tenancy floors, thermal mass, fi re resistance, limitation of deflection, resistance to vibrations and effective diaphragm action are very hard to comply with if only timber is used. The main purpose of this paper is to present the preliminary and some ongoing research in the short- and long-term carried out ainly at the University of Canterbury, New Zealand, for the realisation of a semi-prefabricated laminated veneer lumber (LVL)-concrete composite floor system in both the local and Australasian market. The paper discusses a novel semi-prefabricated LVL-concrete composite system where panels made from LVL joists and plywood flooring are prefabricated off-site. Once the panels are lifted onto the supports and connected side-by-side, a concrete topping is cast-insitu so as to form a continuous slab connecting all the panels. Composite action between the concrete topping and the panels is achieved using different types of connectors, such as various forms of notches cut from the LVL joists and reinforced with coach screws or toothed metal plates pressed in the LVL joists. After pointing out the advantages of the proposed system over traditional only-timber and only-concrete floor solutions, the paper describes push-out tests in the short-term on connections used in the LVL-concrete composite. Tests to failure of small LVL-concrete composite blocks (push-out tests) with different types and shapes of connection systems were performed at the University of Canterbury, New Zealand, and at the University of Technology Sydney, Australia. The results are parametrically evaluated and discussed in detail. The failure mechanism of the notched connection is highlighted together with the strength and stiffness values for each tested connection system. Subsequently, the four best connection systems were identified and used in beam specimens of 8–10 m in span. The experimental program on the beams is presented briefly in order to provide information of the different phases of the project.

A concrete slatted floor system for separation of faeces and urine in pig houses

A concrete slatted floor system that consists of a narrow-gap slatted floor and beneath it a slope bottom for separation of faeces and urine in pig houses was investigated. In the experiments, four concrete slatted floors with one of two slat profiles and one of two gap widths, and a steel wire slatted floor were studied to estimate their manure separation performance under practical conditions. To evaluate urine collection efficiency, seven slope gradients and two surface roughnesses of the slope bottom were investigated under laboratory conditions. The lowest percentage of faeces drainage (0.36%) and good urine drainage performance were obtained by a concrete slatted floor with 5 mm-wide gaps and a trapezoidal profile without sharp edges, indicating that separation of faeces and urine can be achieved on the surface of this slatted floor. Using the wet surface area of the slope bottom as an indicator of urine collection efficiency and emission source, a statistical model was developed based on slope gradient, surface roughness, amount of water and water drop height. It was found that the wet surface area of the slope bottom decreased as the slope gradient increased, but increased with increasing surface roughness. The wet surface area was much more sensitive to the variations of slope gradient at lower compared with higher gradient ranges. However, contrary sensitivity responses were obtained for surface roughness. A slope gradient of 20° with a surface coated with fine cement performed best and is recommended for the slope bottom design in the concrete slatted floor system.

In-Situ Load Testing: A Theoretical Procedure to Design a Diagnostic Cyclic Load Test on a Reinforced Concrete Two-Way Slab Floor System

The objective of this paper is to showcase to an engineer who is considering performing a diagnostic cyclic load test a theoretical procedure for determining the patch load, which when applied to a two-way reinforced concrete (RC) slab floor system would generate internal forces at critical locations equal to those resulting from the uniformly distributed load. This procedure should also help the practitioner to define a representative model of the structure and to update the magnitude of the target load at the end of each loading and unloading cycle by means of a real-time evaluation of boundary conditions and slab stiffness. The routine to design a cyclic load test is described theoretically first and then validated with the results of a load test on a concrete two-way RC slab floor system. Introduction The current role of testing within structural engineering has gained increasing importance, as it can now be applied to every phase of the structure’s life because of innovative materials and new design approaches. By focusing on either the preliminary testing of a new structure or the necessary control checks prior to assessing the strength of an existing one, in-situ load testing can determine the real behavior of the structure under the existing loading conditions. Accordingly, researchers can have an overall, accurate understanding of the mechanical properties of the structural members. In the United States of America, the current American Concrete Institute (ACI) 318 Building Code [1] provides requirements for load testing of concrete structures. ACI Committee 437 [2] proposes a diagnostic cyclic load (DCL) testing procedure consisting of the application of patch loads in a quasi-static way to the structural member according to loading and unloading cycles. Patch load magnitude and distribution shall simulate the uniformly distributed load defined in the ACI 318 Building Code. The DCL protocol [3,4] defines three acceptance criteria that can be easily computed, in real time, for any structural member by simply checking its behavior under the test load (see Fig. 1 for necessary notation). Repeatability and Permanency represent the behavior of the structure during two identical load cycles; Deviation from linearity represents the measure of the nonlinear behavior of a member being tested. Repeatability = 100 95 B B max r A B max r % % Δ − Δ × ≥ Δ − Δ ; (1) Permanency = 100 10 B r B max % % Δ × ≤ Δ ; (2)

Laboratory tests of composite wood–concrete beams

Exploratory research related to the effectiveness of layered composite solid wood–concrete floor systems is described. Rectangular beams comprised of a concrete layer atop a solid dimension lumber layer were load tested. Interlayer force transfer is accomplished by bearing in a notched shear key. A vertical anchor is utilized to restore tightness of the notch after the concrete cures. Test results indicated the structural merit of the concept based on the degree of partial composite action achieved.

Numerical Modeling of Greenhouse Floor Heating

A numerical simulation model of a greenhouse floor heating system was developed and validated using data collected in a research greenhouse located at Cook College, Rutgers University, New Brunswick, New Jersey. The model was then modified and used to evaluate two different heat pipe diameters and spacings that are typical in the greenhouse industry today: 13 mm (0.5 in.) diameter pipe placed on 22.9 cm (9 in.) centers, and 19 mm (0.75 in.) diameter pipe placed on 30.5 cm (12 in.) centers. Two heat pipe elevations within the solid concrete floor system were also simulated, and the effects of the pipe's vertical position, diameter, and spacing on surface heat flux, surface temperature, and surface temperature uniformity were evaluated. The simulation results showed that the smaller diameter pipe placed closer together and at a lower elevation provided the best temperature uniformity without compromising other performance criteria. The model was then further modified to simulate flats with growing media placed on the floor surface. Model simulations were conducted for six different supply water temperatures ranging from 32.2°C (90°F) to 60°C (140°F), while maintaining a target ambient greenhouse air temperature of 15.6°C (60°F). The simulation outputs showed that using the smaller diameter pipe placed closer together resulted in a higher surface heat flux, a higher growing media temperature, and greater temperature uniformity within the growing media, for each supply water temperature simulated.

Stability of the World Trade Center Twin Towers Structural Frame in Multiple Floor Fires

This technical note presents the results from a nonlinear finite element analysis of a very simple two dimensional model of the World Trade Center Twin-Towers structural frame subjected to fire. The analysis was carried out for a large range of fire scenarios and was reported in detail in a recently published paper. The paper further investigates the results of this analysis to obtain the details of the collapse mechanism found. An interesting series of events leading progressively to overall collapse are discovered and described in detail. The main reason for the failure is found to be the low membrane capacity in compression of the composite steel truss and concrete deck slab floor system.

Restraint of fire‐exposed concrete floor systems

AbstractThis paper describes the numerical analyses of restrained concrete floor slabs exposed to fire. The analyses of the slabs were carried out with the SAFIR finite element program considering a 200 mm thick slab, spanning 5 m between two end supports. The slabs were exposed to the ISO standard fire for up to 4 h and were analysed with pinned and rotationally restrained supports. Different heights of the line of thrust at the supports and different levels of axial restraint were also investigated. The analyses show that fully restrained pin‐supported slabs can survive the 4 h ISO fire without collapse if the position of the line of thrust is located near the soffit of the slab. If the position of the line of thrust is located much above the soffit of the slab, the slabs will rapidly undergo large deformations and sag into a catenary, imposing axial tensile forces at the supports. The analyses have shown that even if the line of thrust is located close to the soffit, the slab can still deform into a catenary if there is insufficient horizontal axial restraint. In this study, rotationally restrained slabs experience much smaller vertical deflections than pin‐supported slabs when exposed to fires. Rotationally restrained slabs with low levels of horizontal restraint do not collapse, due to the beneficial effects of moment redistribution. However, high levels of horizontal restraint can be detrimental, causing slabs to collapse at advanced stages of the fire. Copyright © 2004 John Wiley & Sons, Ltd.

Vibration characteristics of steel–concrete composite floor systems

AbstractTrends towards long‐span, lightweight floors in steel–concrete composite construction are resulting in structures possessing low natural frequencies, and potentially susceptible to vibration problems. The most common source of vibrations is caused by human activities on the floor, however, in some instances, mechanically induced vibrations from air conditioning plant, etc. may also be problematic. In this paper the serviceability assessment of floor vibration occasioned by walking activities is considered.Over 30 years ago concerns were raised regarding vibrations induced by walking on steel–concrete composite floors that satisfied traditional deflection criteria. In response to these concerns, design criteria based on a simple impulsive loading function from a person rising onto the balls of the feet, and suddenly dropping onto the heels has been used as a measure of floor acceptability. More recently, design procedures have been developed that more realistically consider the excitation of the floor from walking activities.In the first part of this paper a historical review of acceptability criteria for floor vibrations will be made. Following this, the current design methodologies for steel–concrete composite floors will be reviewed prior to the presentation of results from a series of in situ vibration tests on a wide variety of floor types. After comparing the test results with current guidance, design recommendations and suggestions for future research will be given.

８．メインテナンスの力学問題 コンクリートの劣化に及ぼす界面活性剤の影響

The purpose of this study is to examine the surfactant effect on the degradation of the concrete. In the experiment, the effect by surfactant and repeated-load were examined.Surfactants used by the experiment are the 5types such as windshield washer fluid used for the automobile and household detergent. First, the concrete test-piece was put in the surfactant aqueous solution, and the visual observation was carried out. As the result, analysis and mass decrease rate were obtained on the material that deposited in the concrete test-piece surface. And, the repeated-loadwas carried out using the test-piece that changed the condition of the concrete bridge beam floor system management, and the effect of the concrete on the degradation was examined.