Side Of Slab Research Articles

Experimental study on the flexural performance of concrete hollow composite slabs with tightly connected panel sides

The performance of joint connections in composite slabs is crucial for ensuring their bidirectional load-bearing capacity and overall structural integrity. To effectively address the challenge of protruding rebar in precast components, a new structural form of a tightly connected hollow concrete composite slab without protruding rebar on the slab side is proposed. To investigate the mechanical performance and failure modes of this slab-side tight-joint connected hollow concrete composite slab, bending performance tests under monotonic load were conducted on three tightly connected hollow composite slabs and one seamless hollow composite slab. The analysis focused on the failure modes, crack distribution, bending capacity, and bending stiffness of additional steel bars at the joints of the slabs. The results indicate that, under normal operating conditions, the flexural performance development of concrete hollow composite slabs with tightly connected slab sides is generally consistent with that of the non-spliced cast hollow composite slab. Under ultimate conditions, tearing or brittle fracture failure at the joint interface is likely to occur in the composite slabs, leading to a reduction in flexural bearing capacity. With an increase in joints, the bending capacity of the hollow composite slab decreases by 17.1%, Conversely, when joints are positioned away from the most stressed section, the flexural stiffness of the section increases by 13.5%. A comparison of experimental data and theoretical calculations indicates that the additional rebar at the joints effectively contributes to the lateral load transfer in the hollow composite slab, achieving bidirectional load-bearing capacity. This further validates that the design of the single-joint, tight-joint connected hollow concrete composite slab without protruding rebar meets the requirements for bidirectional load-bearing performance.

Numerical simulation of macrosegregation in continuously cast slab with application of S-EMS and MR

A 3D numerical model was built to investigate the transport phenomena in slab continuous casting process to investigate the influence of strand electromagnetic stirring (S-EMS) combined with mechanical reduction (MR) on macrosegregation in continuously cast slab. The model was validated by measured strand surface temperature and magnetic induction intensity. The results show that the S-EMS with two pairs of electromagnetic stirring rollers in the opposite direction significantly affects the crater end profile and centerline carbon segregation in slab. The maximum solidification end position difference along the crater end profile of slab ΔL reduced from 0.82 m to 0.52 m, and the centerline carbon segregation is improved by the weak S-EMS, when the current intensity increases from 0 to 250 A. But, the maximum solidification end position difference along the crater end profile of slab ΔL increases from 0.52 m to 1.05 m, the carbon segregation at the 1/4 centerline length position near the right narrow side of slab deteriorates when the current intensity increases from 250 to 350 A. With the combined application of MR near the crater end of continuously cast slab, the solidification delay phenomenon caused by the S-EMS can be significantly improved. But, the solidification delayed cannot be suppressed with current intensity higher than 250A. Therefore, the harmonious application of weak stirring of S-EMS with current intensity of 250A and MR with reduction amount of 4 mm just before the crater end of slab is most benefit for the centerline carbon segregation improvement in continuously cast slab.

Multi-layered slab 1D conduction heat transfer for buildings discrete event simulations

The 1D conduction heat transfer in multi-layered slabs is fundamental to building energy simulation. Its solution could be split into two big categories: finite difference and root-finding methods. These latter are also known as Laplace or Conduction heat Transfer Function methods (CTF).The paper briefly reviews why none of them, in its current formulation, fits the new trend based on event-driven simulation. It proposes a new CTF whose inputs are the conduction heat fluxes q̇ and the responses are the superficial temperature speeds Ṫ on both slab sides. Thus it could be classified as a root-finding procedure. However, it employs a solution rooted in the uncommon Successive State Transition (SST) method from the 80’s Japanese school. Moreover, it proves that both superficial temperatures T can also be solved using this SST method. The outcome is a solution procedure with many advantages; the main one is that it does suit the novel event-driven paradigm.Finally, the paper illustrates the procedure with an example.

Longitudinal shear behavior and design method of UHPC connection for prefabricated slabs in composite beams

Ultra-high-performance concrete (UHPC) has advantages in mechanical properties and bond properties, which was available to connect the precast members of prefabricated composite structures. In this paper, some kinds of wet connections with post-cast UHPC applied in the composite beam with prefabricated components (slab and steel beam) were designed, and the longitudinal force-slip behaviors for the above UHPC connections were investigated through a series of push-out tests. In the case of the specimens with the post-cast UHPC rectangular connection, which failed in the interface between the precast slab and UHPC connection instead of the concrete region around the stud connectors, the increase in interface reinforcement ratio was beneficial for enhancing the interface shear resistance. The arrangement of two layers of steel bars out of the precast slab side could make full use of the plastic properties of bottom interface reinforcements to strengthen the ultimate shear strength and ductility of the interface. Compared with the rectangular connection, the post-cast UHPC connection with T-section presented a better interface performance by increasing the bond area, while the increase of the transverse width only worked in a limited range due to the interface shear lag effect. Based on the experimental and theoretical analyses, the formulas corresponding to different types of post-cast UHPC connections in prefabricated composite beams were proposed to calculate the longitudinal shear capacity, then the composition of equations and the reduction factors corresponding to different conditions were recommended.

Process for sandblasting silicon slabs as part of semiconductor transistor manufacture

Aim. The paper aims to develop a process for treating the back side of silicon slabs and giving them a surface texture that enables good adhesion with printed metal with an even thickness and no mechanical stress, cracks or chipping. That is achieved by sandblasting slabs before contact material application. Silicon carbide (SiC) with particle size not exceeding 6 um is used as the abrasive material. Methods. The proposed method of sandblasting improves chip bonding by eliminating surface stress, formation of microcracks and crystal grain within the chip. The research was conducted using a sandblaster and electronic microscope. Results. It was shown that, after sandblasting, metal coating in the process of transistor collector area contact delineation improves the adhesion of the substrate semiconductor. Additionally, no mechanical stress was observes as compared to grinding, polishing and chemical treatment that are normally done before transistor contact encapsulation. Conclusions. The process of thin metal film evaporation as part of semiconductor-based device manufacture affects their dependability. The treatment and preparation of the back side of the silicon slab with finished transistor configurations is one of the key operations as part of transistor manufacturing process that affects the adhesive properties of the surface before evaporation, output characteristics of the semiconductor-based devices, yield and cost.

Application of a chamfer technology to overcome bulging deformation of slab narrow side during mechanical reduction process

Application of a chamfer technology to overcome bulging deformation of slab narrow side during mechanical reduction process

Push-out tests on adhesively bonded perfobond shear connectors for timber-concrete composite beams

In this paper, perforated shear connectors (perfobond), used extensively in steel-concrete composite (SCC) beams, are implemented in timber-concrete composite beams (TCC) and experimentally investigated. In contrast to its original use, the perfobond connector is connected with an adhesive to the timber beam while welded in the SCC solution. On the concrete slab side, connection is achieved using the original concept, a combination of dowel action with bearing between concrete and connector. In this paper the mechanical behaviour of the shear connection using the perfobond connector in TCC beams is investigated by means of push-out tests. Concrete type, concrete strength and surface roughness of the connecter were the testing variables. The results are compared with the common shear connections for TCC in terms of strength, stiffness and ultimate slip. From this work, it can be concluded that perfobond connections give promising strength and stiffness results, however, for the geometries covered in the experimental program, the ultimate slip is limited. Nevertheless, the high stiffness and load capacity presented by this connection demonstrates a significant potential for its implementation in TCC, as high composite action can be achieved.

Deformation, Strain and Stress Concentration of Slab Narrow Side Induced by Different Reduction Amount

A numerical simulation model has been established to obtain the deformation, strain and stress concentration of slab narrow side. The simulated temperature profiles of slab show a agreement with the results of measured temperatures by using infrared thermal camera. Moreover, the deformation, stress and strain of the slab have been investigated systematically, especially at the slab narrow side along the thickness direction. The relationship between the reduction amount and deformation, stress and strain concentration of slab narrow face has been investigated.

Stiffness of Post-Tensioned Girderless Floor With Different Column Grids

The paper considers models of monolithic flat floor slabs with five spans in both directions. The cell sizes are 6×6m, 6×9m, and 6×12m. The calculation method is based on the application of temperature load and rope modeling of rod elements. It is shown that post-stressing should be used for slab side lengths over 7 m, as the installation of pre-stressed reinforcement for shorter lengths is less feasible and causes high economic costs.

Optimisation of porous slab parameters for jet-impingement microchannel heat sink performance enhancement

PurposePorous media can provide excellent performance in thermal energy transport applications. This study aims to optimise the square porous slabs (placed in the middle of the channel) parameters to enhance the cooling performance of the jet-impingement microchannel heat sink.Design/methodology/approachThree levels of each design parameters, i.e. porous slab side, porous slab height, type of material, permeability and quadratic drag factor, are studied; and an L27 orthogonal array is adopted to generate the design points in the specified design space. Optimum designs of the porous media slabs are achieved to minimise the maximum-wall temperature, thermal resistance and pressure drop and maximise the average heat transfer coefficient and figure of merit (FOM).FindingsResults exhibited that the porous media material and permeability are the most, whereas drag factor is the least significant factors with respect to the overall performance of the heat sink. The optimum value of FOM for the proposed hybrid heat sink model belongs to the set of design variables, i.e. 0.4 mm slab side, 0.6 mm slab height, 5 × 10−11 m2 permeability, 0.21 drag factor and copper as substrate material.Originality/valueThis study proposes a novel design and a hybrid approach to investigate and optimise the hydrothermal performance of jet impingements on porous slabs inserted in the microchannels.

Efficient electronic passivation scheme for computing low-symmetry compound semiconductor surfaces in density-functional theory slab calculations

Removing artificial bands from the back side of surface slabs with pseudohydrogen atoms has become the method of choice to boost the convergence of density-functional theory (DFT) surface calculation with respect to slab thickness. In this paper we apply this approach to semipolar compound semiconductor surfaces, which have recently become attractive for device applications. We show that approaches employing saturation of dangling bonds by pseudohydrogen atoms alone are inadequate to properly passivate the surfaces, remove spurious surface states from the fundamental band gap, and achieve flat band conditions in the slab. We propose and successfully apply to technologically interesting semipolar wurtzite surfaces of III-N, III-V, and II-VI semiconductors a reconstruction-inspired passivation scheme that utilizes native anions to passivate cation dangling bonds and pseudohydrogen atoms to obey the electron counting rule and compensate for polarization-induced surface-bound charges. This scheme is generic and robust and can be straightforwardly implemented in DFT investigations of low-symmetry surfaces as well as in high-throughput and machine learning studies.

Punching Strength of Reactive Powder Reinforced Concrete Flat Slabs

This research is devoted to investigating experimentally the punching shear strength of reactive powder concrete slabs under monotonic loading. All slabs have the same flexural reinforcement and same dimensions (1000mm length,600mm width,50mm thickness). The experimental program includes casting and testing of sixteen slabs tested under monotonic loading. The major parameters adopted in the current research include the shape of column (circle, square), column size (twocolumn sizes), number of columns (one, two), and the distance between two columns (3d,5d,7d). Results showed that, the slabs with circular column sections have slightly higher ultimate load than those with square column sections. An increasing column area increases the load of punching shear failure. It was found that the ultimate failure load for slabs with two columns is greater than the slabs with one column. Related to the effect of distance between the two columns for monotonic, it was found that the slabs maximum load reaches the maximum value at distance between the two columns equal to(7d) for a circular section with a diameter of 85mm and 113mm and square section with dimensions of (100*100)mm. While the maximum failure load reaches the maximum value when the distance between two columns (d) for a square section with the dimension of (75*75)mm. Related to the crack patterns, it was noticed that for slabs with larger columns sections with the distance between columns equal to 7d, the failure zone extended (in a large direction) to the slab sides.

Effect of Strengthening Methods on Two-Way Slab under Low-Velocity Impact Loading

In this study, the performance of reinforced concrete slabs strengthened using four methods was investigated under impact loads transferred from the top side to bottom side. The top and bottom sides of test slabs were strengthened by no-slump high-strength, high-ductility concrete (NSHSDC), fiber-reinforced-polymer (FRP) sheet, and sprayed FRP, respectively. The test results indicated that the test specimens strengthened with FRP series showed a 4% increase in reaction force and a decrease in deflection by more than 20% compared to the non-strengthened specimens. However, the specimen enhanced by the NSHSDC jacket at both the top and bottom sides exhibited the highest reaction force and energy dissipation as well as the above measurements because it contains two types of fibers in the NSHSDC. In addition, the weight loss rate was improved by approximately 0.12% for the NSHSDC specimen, which was the lowest among the specimens when measuring the weight before and after the impact load. Therefore, a linear relationship between the top and bottom strengthening of the NSHSDC and the impact resistance was confirmed, concluding that the NSHSDC is effective for impact resistance when the top and bottom sides are strengthened. The results of the analysis of the existing research show that the NSHSDC is considered to have high impact resistance, even though it has lower resistance than the steel fiber reinforced concrete and ultra-high-performance-concrete, it can be expected to further studies on strengthening of NSHSDC.

Performance enhancement of damaged two way concrete slabs

This paper studying the flexural behavior of reinforced concrete with two-way slabs repairing by (CFRP). Normal concrete was used to cast the reinforced concrete two-way slabs. The experimental works includes testing four reinforced concrete with two-way slabs having dimensions (1050 mm x1050 mm x 60 mm) and with reinforcement (Ø8 @100 mm). All slabs had been subjected to concentrated load and tested as simply supported for all four sides of slabs. So this work including one slab which is not repairing as (control) and three slabs with repairing, the three slabs can be divided into two groups tested as different percentage (50 % and 75 %) of load, and as different configuring shapes of repairing (two shapes).

Subduction Dynamics and Mantle Pressure: 2. Towards a Global Understanding of Slab Dip and Upper Mantle Circulation

AbstractWe investigate the relationship between the global distribution of deep slab dips (at 250‐ to 300‐km depth) and pressure and circulation in the upper mantle. Using an analytic method to compute dynamic pressure in a 3‐D global upper mantle domain, and a force balance between slab dip, slab buoyancy, and pressure, we model dips for all major subduction zones. Overall, our models suggest that global‐scale mantle flow, as dictated by the shapes and velocities of Earth's plates and slabs, plays a fundamental role in creating the global pattern of slab dips. The dip trends of the South American and western Pacific subduction zones are controlled, in our models, by spatial variations in the dynamic pressure associated with flow. Our best fitting models produce global root mean square dip misfits of less than 10° for asthenospheric viscosities of 2.5–4.0 × 1020 Pas. This result is only obtained with a large flux of asthenosphere from upper to lower mantle at subduction boundaries, occurring on the overriding plate side of slabs, without which dips are significantly steeper than observed. This effect cannot be resolved by processes that affect only certain subduction systems and requires flux of asthenosphere into the lower mantle at subduction systems globally (or an alternative mechanism that produces more negative pressures on the overriding plate side of slabs). Upper mantle pressure fields that fit global slab dips yield negative dynamic pressure on the upper plate side of slabs, positive pressure on the subducting plate side, and an east‐to‐west pressure increase beneath the Pacific Plate.

Synthesis of Rectenna for Powering Micro-Watt Sensors by Harvesting Ambient RF Signals’ Power

In the article, a dual and wide band antenna array suitable for RF rectenna applications was synthesized and global rectenna systems are presented. The array consists of two bowtie-shaped patches, printed on the one side of a dielectric slab (FR4). On the other side of the slab, an aperture-textured metallic ground layer, is printed. Examples of full-wave rectifiers connected, through matching networks, to the antenna elements and forming integrated rectenna systems for radio-frequency (RF) power harvesting at 868 MHz, from 920 to 960 MHz and at 1.8 GHz, are presented. Statistical results over frequency and the directions of arrival (DoAs) of incoming waves were received showing, at the rectifier, mean direct current (DC) voltage of 580 mV, and mean power of 58 μW, for circularly polarized waves of field intensity of 1.8 V/m. The DC voltage can reach 800 mV, the power 120 μW and the efficiency 68% when the waves come from DoAs of maximum antenna’s gain. Due to the wideband performance of the antenna, it could be used at various frequency slots as long as the matching network’s operation frequency is changed. Thus the proposed rectennas could be suitable for energizing low-power sensors or at least to charge their batteries.

Experimental and numerical investigations on the impact resistance of SHCC-strengthened RC slabs subjected to drop weight loading

In this paper, a thin layer of Strain-Hardening Cementitious Composites (SHCC) is provided in either tension or compression side of RC slabs aiming to improve their impact resistance under the effect of drop weight loading. The main parameter of the current study is the condition of the contact surface between the substrate slab and the SHCC overlay that was prepared by grinding, grinding plus steel dowels or grinding plus epoxy adhesive. Accordingly, 63 RC slabs were prepared and tested under the effect of drop weight falling from three different heights; 1, 1.5 and 2 m. It was found that the SHCC strengthening layer enhanced the impact resistance of the strengthened slab when added at either tension or compression side. However, in order to attain the outermost impact resistance showing ductile performance, it is better to provide a thin layer of the SHCC at the tension side of the slab connected to the substrate slab by epoxy resin applied on pre-prepared grinded surface. Furthermore, numerical simulations based on ABAQUS software package were performed on the strengthened slabs. Their results showed good agreement with the experimental findings from the viewpoint of the kinetic energy. Besides, the impact failure loads were determined numerically for the studied slabs and compared with those obtained from incremental static loading tests.

Propagation Properties of Airy Beam through Periodic Slab System with Negative Index Materials

Based on light transfer matrix and electric field vector equation, the evolution of Airy beam propagating in periodic slab system with three negative index materials (NIMs) and its transmission mechanism are investigated. The intensity profiles on emergent surface of periodic slab system and side view of Airy beam propagating in each right handed material (RHM) and double negative material (DNM) unit including lossless and losses DNMs are discussed. It is revealed that the self-recovery Airy beam can be achieved in long distance by using lossless periodic slab system as long as the negative refractive index nl=-nr and each unit length L=Z. As to losses slab system contained DNMs, the smaller the collision frequencies are, the better the Airy beam quality is formed. It is expected that the proposed manner of beam transmission and corresponding conclusions can be useful for extension applications of optical control, especially for optical communication and optical encryption technique.

Experimental studies on the thickness of upward flame over poly(methyl methacrylate) slabs

SummaryExperiments were performed to investigate the flame thickness of the upward flame on the poly(methyl methacrylate) slabs with width of 100‐400 mm. The results indicated that the flame thickness exhibited an increase first and then decrease trend in the upright orientation, and the maximum thickness location was approximately equal to the pyrolysis front location. The thickness of the flame along the lateral side of slab was less than that of the interior flame. The flame maximum thickness as a function of pyrolysis height and width was obtained, which showed the maximum thickness provided a power law increase with the pyrolysis height and width. Furthermore, the maximum thickness exhibited a power law increase with the total heat release rate as well. Based on the obtained flame thickness, the radiation heat flux at the pyrolysis height was estimated by using a simplified model. Comparison with the calculated convective heat flux revealed approximated pyrolysis heights for upward flame transition from convective heat flux controlled to radiation heat flux controlled.

A Comparative Study of Strength of Two-Way Rectangular Slabs with and without Openings

The present work uses yield-line theory to find the strength of uniformly loaded rectangular reinforced concrete slabs with and without rectangular openings. Five positions of openings are considered, i.e. the slab centre, the slab corner, the centre of a short side, the centre of a long side and the opening eccentric to the slab centre. All possible admissible yield line patterns are considered for all given configurations of the slab subjected to uniformly distributed load keeping in view the basic principles of yield line theory. The ratios of the corresponding lengths of the sides of the opening and the slab are different and sizes of opening up to 0.4× the length of the slab sides are considered. Symmetric edge conditions like continuous slab, simply supported, two long sides continuous and two short sides continuous are considered for various sizes of openings in order to plot the design charts for isotropic reinforcement coefficients only. Affine transformation is also performed for slab with openings.