One-way Slabs Research Articles

Sustainable construction system with Egyptian metakaolin based geopolymer concrete sandwich panels

As one of the largest environmental offenders, the construction industry is a prime candidate for the application of the principles of sustainability. Sustainability could be achieved by using environment friendly materials and structural systems in construction industry. This paper aimed to study using geopolymer concrete as a structural board in constructing insulation sandwich panels under different types of loading. Four compression tests were performed on wall specimens in order to study the behavior of the panels under vertical in plane forces. Axial capacity prediction of wall panels was discussed using four published design equations. Eight one-way slab sandwich panels specimens were tested under flexure loading with different shear span ratios in order to compare the flexural behavior of conventional concrete and geopolymer concrete sandwich panels. The capacities of the slab panels were estimated using the conventional concrete codes provisions and compared to the experimental values. Geopolymer sandwich panels approved its ability to sustain different type of loading in the same manner as that of conventional concrete. A prototype was constructed to assess the constructability and the construction cost of the proposed system. The lack of production lines of geopolymer ingredients increases the material cost. On the other hand, the calculated total cost for different construction systems revealed that the labor cost is lower for the cast in place structural insulated panels CIP-SIP system.

Flexural behavior of one-way ferrocement slabs with fibrous cementitious matrices

Concrete compressive strength enhancement is considered as one of the popular topics in the field of civil engineering. It has received a massive attention by material and structural engineers over the past decades. The aim of this study is to investigate thin mortar matrix for the impacts of the combination of reinforcing steel meshes with discontinuous fibers, and to do this, one-way Ferrocement slabs were tested under bending with steel fibers and meshes, focusing more on the number of mesh layers (1, 2, & 3) as the studied parameter. The percentages of fiber content as volumetric ratio 0.25, 0.5 and 0.75 and type of fibers golden steel fibers and waste aluminum fibers from waste metallic cans. Results showed that at general the adding of fibers regardless of its type increased the ductility of tested slabs. In addition, results showed that steel fibers are more effective than aluminum fibers.

Flexural strengthening of RC slabs with nonprestressed and prestressed CFRP strips using EBROG method

This paper proposes a fully nonmetallic system for strengthening RC one-way slabs with prestressed CFRP composites. The flexural behaviors of RC slabs strengthened with nonprestressed and prestressed CFRP strips were compared through four-point bending tests. The externally bonded reinforcement on grooves (EBROG) method was utilized to delay premature debonding of the CFRP composites and was compared with conventional externally bonded reinforcement (EBR). The experimental results indicated a significant enhancement in slabs flexural performance of slabs that were strengthened via the EBROG method and the novel anchorage system. The nonprestressed and prestressed CFRP plates attached using the EBROG method increased the bending capacity by 34% and 77%, respectively, compared with the nonprestressed EBR CFRP plate. Furthermore, the maximum CFRP strain reached 8.9‰ for the nonprestressed EBROG CFRP strip, whereas that for the nonprestressed EBR CFRP strip was only 5.9‰. Thus, the EBROG method delayed CFRP debonding and increased the strain in the reinforcement by 50% compared with the EBR method. In the prestressed CFRP strip, the strain reached 12.4‰ prior to the debonding, confirming the high efficiency of the proposed strengthening system.

An Innovative Method of Voided Reinforced Concrete One-Way Slabs Using Bundled Waste PET Bottled Tubes

Sustainability in concrete structure has been developed rapidly for ensuring the requested for a new thinking about construction by concrete elements. This paper deals with using buddle using polyethylene terephthalate PET bottles and steel meshes for fabricating and modeling one way RC voided slab. That is very useful to reduce the weight of slab, also reduced the wastes in same time. For both the voided and solid ones, the load-displacement curves were almost identical from beginning until the load reaches ultimate stages, where the increasing in depth of voided slab showed higher strengths and lower displacement at same load level.

Flexural performance of Reinforced Concrete One-way Slabs Strengthened by FRP Grid

Fiber reinforced polymer (FRP) grid is a kind of two-way fiber material. Its transverse reinforcement and longitudinal reinforcement have the same physical characteristics. Experiments on the reinforced concrete one-way slabs strengthened by FRP grid were conducted to study the influences of bonding area and FRP anchors on its flexural performance. The results showed that the flexural capacity of reinforced concrete one-way slabs strengthened by FRP grid is increased by 7% - 21%. FRP grid can effectively slow down the crack expanding, increases the stiffness and improve the flexural behavior of the slab.

Flexural strengthening of RC one way slabs with high-performance fiber-reinforced cementitious composite laminates using steel and GFRP bar

This experimental study aims to evaluate the contribution of the High-Performance Fiber-Reinforced Cementitious Composite (HPFRCC) laminate with steel and GFRP bars to the flexural behavior of RC slabs. In this study, the HPFRCC material was first investigated to determine the mix proportion. HPFRCC laminates with and without longitudinal steel reinforcements were then tested. Finally, strengthened slabs were investigated by four-point flexural testing. The experimental results were suggestive of the effect of the properties of the HPFRCC laminate, including its application procedure, steel fiber volume fraction, incorporation of longitudinal reinforcement, and the type of reinforcement (steel or GFRP bars), on the increase in the load-bearing capacity of the slab. Adding longitudinal bars to the HPFRCC laminate improved the weaknesses of the crack pattern, load-carrying capacity, ductility, and stiffness. HPFRCC-laminate strengthening enabled a 92–326% increase in the load-bearing capacity of the slabs. This experimental undertaking is the first time that the HPFRCC laminate is reinforced with GFRP, successfully, with satisfactory results. Analytical models were developed to predict the flexural capacity of the one-way slab strengthened using HPFRCC laminate and the experimental results compared to the predicted theoretical models. Analytical and experimental results showed excellent consistency with an average difference of 6% and a maximum of 18%.

Performance of high-strength concrete one-way slabs with embedded BFRP bar reinforcement

In this paper, a theoretical study has been concluded using ANSYS-15 software to investigate the performance of reinforced concrete one-way slabs with embedded basalt fibre reinforced polymer (BFRP) bars under monotonic loads. Six slabs have been considered, two were simply supported, and four were continuous each with two-span. Several parameters have been studied, such as continuity condition, reinforcement ratio, the position of the reinforcement and the effect of replacement basalt bars by steel bars. It is found that the finite element analysis (FEA) agree with experimental results in a range of 1% - 9% in deflection compared with the maximum difference of ACI440 committee of 49%. For simply supported slabs, it is found that increasing the reinforcement from 0.2% to 0.5% resulted in increased capacity by 86%. For continuous slabs, it is observed that increasing the reinforcement for top and bottom from 0.2% to 0.5% resulted in increased capacity by 60% while the maximum deflection is reduced by 56%. Moreover, it is found that with an efficient distribution of bars a slab with a reinforcement ratio of 0.7%, the load capacity is improved by 12.5% and a reduction in maximum deflection 46%. Furthermore, it is found that for simply supported slabs, it is better to use higher ratios of BFRP reinforcement,0.5% instead of 0.2% due to a good improvement in capacity. Regarding dissipation in energy, it is found that the difference in predicting toughness by FEA by ANSYS was 1% - 15% for simply supported slabs while for continuous slabs the dissipation in energy was in the range of 20% - 50% compared with experimental results.

Experimental Study on One-Way BFRP Bar-Reinforced UHPC Slabs under Concentrated Load.

The application of fiber-reinforced polymer (FRP) bars and ultra-high performance concrete (UHPC) in the field of civil engineering is promising. An innovative FRP bar-reinforced UHPC short-ribbed bridge deck slab, with low self-weight and high structural performance, was proposed in this study. The behavior of one-way basalt FRP (BFRP) bar-reinforced UHPC slabs under concentrated load was experimentally investigated, and compared with that of a steel bar-reinforced UHPC slab. The ultimate capacity of the one-way BFRP bar-reinforced UHPC slab was 0.59 times that of the steel bar-reinforced UHPC slab, while its ductility was better. Increasing the reinforcement ratio and loading area was beneficial to the ductility of one-way BFRP bar-reinforced UHPC slabs. Moreover, the model proposed by EI-Gamal et al. was found to be suitable for evaluating the punching shear capacities of one-way BFRP bar-reinforced UHPC slabs. However, the model failed to consider the unique strain-hardening characteristics of UHPC, which led to conservative prediction.

Equivalent uniform live loads under transit vehicles for floor slab of long-span urban transportation hubs

ABSTRACT Rapid development of long-span urban transportation hubs arouses higher requirements of structural design methods. However, the current design codes do not give effective provisions of the equivalent uniform live load for long-span transportation hubs. A revised equivalent uniform live load is developed by considering the aspect (length-to-width) ratio of the one-way slab system for the urban transportation hubs. The most unfavorable loading positions of the bus tires are determined, and the equivalent uniform live load is computed by using the Chinese Load Code. The structural response under equivalent uniform live load is further compared to that under actual load, then the original equation of the equivalent uniform live load with the Chinese Load Code is revised by considering the aspect ratio of one-way slab. An actual engineering computation of equivalent uniform live load is carried out. The results reveal that the calculation methods of the Chinese Load Code cannot reflect the force transmission characteristics of the small-area tire load on the one-way slab. The structural responses under the revised equivalent uniform load are in good agreement with that under the actual load. The revised calculation method is suitable for most areas in this urban transportation hub and similar structures.

Flexural behavior of reinforced concrete one-way slabs strengthened via external post-tensioned FRP tendons

External prestressing is an efficient technology to strengthen existing structures, and using fiber-reinforced polymers instead of steel in external tendons is advantageous to avoid corrosion-related problems, though anchoring external fiber-reinforced polymer tendons is still a major issue. An innovative anchoring technology is proposed in this paper for the external fiber-reinforced polymer tendons aimed to strengthen one-way reinforced concrete slabs. Six slab specimens were designed and manufactured to check the feasibility and reliability of the proposed technology. In one slab no external prestressing was applied (reference slab), while the remaining five slabs were strengthened by means of external post-tensioned glass fiber-reinforced polymer tendons, using the proposed anchoring system. The strengthened slabs differ for the prestressing level and external-tendon ratio. All slabs were tested up to failure and their flexural behaviors and failure modes were thoroughly investigated. The tests show that the proposed anchoring technology is reliable and efficient. A method for the calculation of the stress in the tendons at ultimate is also proposed. Finally, the numerical results are shown to agree fairly well with the test results.

Blast resistance evaluation of urban utility tunnel reinforced with BFRP bars

To improve corrosion-resistance of shallow-buried concrete urban utility tunnels (UUTs), basalt fiber reinforced polymer (BFRP) bars are applied to reinforce UUTs. As the UUT must have excellent survival capability under accidental explosions, a shallow-buried BFRP bars reinforced UUT (BBRU) was designed and constructed. Repetitive blast experiments were carried out on this BBRU. Dynamic responses, damage evolutions and failure styles of the BBRU under repetitive explosions were revealed. The tunnel roof is the most vulnerable component and longitudinal cracks develop along the tunnel. When the scaled distance is larger than 1.10 m/kg1/3, no cracks are observed in the experiments. When the BBRU is severely damaged, there are five cracks forming and developing along the roof. The roof is simplified as a clamped-supported one-way slab, proved by the observation that the maximum strain of the transverse bar is much larger than that of the longitudinal bar. Dynamic responses of the roof slab are predicted by dynamic Euler beam theory, which can consistently predict the roof displacement under large-scaled-distance explosion. Compared with the UUT reinforced with steel bars, the BBRU has advantages in blast resistance with smaller deflections and more evenly-distributed cracks when the scaled distance is smaller than 1.260 m/kg1/3 and the steel bars enter plastic state. Longer elastic defamation of the BFRP bars endows the UUT more excellent blast resistance under small-scaled-distance explosions.

Evaluation of span-to-depth ratio provisions for deflection control of one-way RC construction

This paper deals with the span-to-depth ratios (SDR) limitation, which is commonly offered as a simplified substitute for a detailed calculation of the deflection, as part of the service limit design verification. The study examines the European (EC2) and the Israeli (SII) codes simplified SDR-based methods. The derivation of the SII approach, which has never been published, is presented. The study is based on comparison of the cross-section depths required by the two simplified procedures, with two detailed procedures - the commonly used European and the American (ACI) ones. This is done through examination of one-way slabs and beams under two extreme typical loads for a wide range of spans. The main purpose of the paper is to show that although the simplified methods are expected to yield conservative results they do not always do. The conclusions further consider the EC2-simplified procedure required iterations, involving the reinforcement amounts, compared with the SII-simplified method that refers only and directly to the given service loads and therefore requires simpler iterations.

Behavior of one-way RC slabs flexurally strengthened with prestressed NSM CFRP laminates – Assessment of influencing parameters

The efficacy of the NSM technique using prestressed CFRP laminates for the flexural strengthening of RC slabs was assessed experimentally. The results obtained indicated that the application of NSM CFRP laminates with a certain level of prestress is a suitable strategy to increase the load-carrying capacity of slabs in terms of service limit state (SLS) conditions. The higher is the CFRP prestressed level the larger is the performance of the NSM technique in the improvement of the behavior of the slabs at SLS conditions, but the deflection at the maximum load of the slabs decreased with the increase of the prestress level. The prestressed NSM CFRP laminates were more effective in the slabs with the lower concrete strength class, mainly at SLS conditions. The increase of the percentage of the flexural reinforcement had a detrimental effect on the performance of prestressed NSM CFRP laminates. An analytical formulation was developed for predicting the cracking, yielding and maximum loads of RC slabs flexurally strengthened with prestressed NSM CFRP laminates and a very good predictive performance was obtained. An upper limit is proposed for the prestress level for ensuring a compromise of ductility and strengthening effectiveness of this type of structural elements.

Behavior of Self Compacting Reinforced Concrete One Way Bubble Deck Slab

Reinforced concrete slab with plastic voids (Bubbled Deck system) is a new type of slabs which has two-dimensional arrangement of voids within the slab that is developed to decrease the slab self-weight while maintaining approximately the same load carrying capacity as compared with the solid slabs. Plastic voided slabs have the ability to reduce concrete amount by about 30 percent and this reduction is so important in terms of cost saving and enhancement the structural performance. In this research paper investigation is carried out to study the shear strength behavior of one-way bubble deck slab using self-compacting reinforced concrete. The experimental program consists of testing thirteen one-way slabs with dimensions of (1700 length, 700 width and 150 thick) mm. One of the tested slabs is a solid slab (without balls) is used as a reference, the remaining twelve bubbled slabs with ball diameter (73, 60) mm are divided into five groups according to the parameters of the experimental work, the parameters of the experimental work include: type of slab (bubble and solid slabs), ball diameter (73, 60) mm, shear reinforcement and spacing between balls. The experimental results showed that the bubbled slabs without shear reinforcement have a decrease in the ultimate load as compared to solid slab by about 3.7% to 14.3% and an increase in the deflection at ultimate load by about 10% to 22%, at the same time the first crack load decreases by about 15.3% to 42.4% as compared to solid slab due to decreases of moment of inertia of bubble slab compared to solid slab. Also, the results showed that the bubbled slabs withe shear reinforcement (multi-leg) have an increase in the ultimate load as compared to solid slab by about 35.4% to 57.3% and an increase in the deflection at ultimate load by about 1% to 15%, at the same time the first crack load decreases by about 2.8% to 27.4% as compared to solid slab.

3D numerical simulation of the cracking behaviour of a RC one-way slab under the combined effect of thermal, shrinkage and external loads

Cracking control of reinforced concrete (RC) is of paramount importance to ensure a proper service behaviour on RC structures, during their lifespan, without excessive maintenance costs. Current design codes and recommendations for RC structures provide methodologies for reinforcement design on elements subjected to the independent effects of either external loads or restraints due to imposed deformations. However, the determination of restraint forces and crack width control in structures subjected to the combination of such two effects is still a challenge, due to the lack of knowledge about the complex interplay between the effect of bending, viscoelasticity and imposed deformations on crack width development. In this paper, the serviceability behaviour of a restrained one-way slab, subjected to a quasi-permanent load combination, is simulated with a 3D thermo-hygro-mechanical analysis. In this multi-physical approach, which has been cumulatively implemented and validated by this research team over the last years, the thermal and moisture fields of the slab are determined based on a thermo-hygrometric analysis, and the non-uniform distribution of stresses caused by self-imposed deformations due to heat of hydration and drying shrinkage are taken into account in a structural non-linear mechanical model. Results show that the axial restraint force acting on the slab is significantly smaller than the cracking force of the slab if analysed under pure tension. This is caused by bending stresses, as well as self-imposed non-uniform stresses, and is in line with the current state of the art. However, a comparison with simplified approaches, where the effect of heat of hydration is disregarded and/or a uniform moisture field is considered, shows significant differences in behaviour until crack stabilization, in relation to the multi-physical approach presented and adopted in this work.

Reduced-order modeling of composite slabs in fire. II: Thermal-structural analysis.

This paper describes a reduced-order modeling approach for thermal and structural analysis of fire effects on composite slabs with profiled steel decking. The reduced-order modeling approach, which uses alternating strips of layered shell elements to represent the thick and thin portions of the slab, allows both thermal and structural analyses to be performed using a single model. The modeling approach accounts for the trapezoidal profile of the concrete in the ribs; the structural resistance provided by the steel decking, including the webs of the decking; and the orthotropic behavior of the decking, which provides greater resistance along the ribs than transverse to the ribs. The modeling approach is validated against experimental data from one-way composite slabs tested under ambient-temperature, a one-way composite slab tested under fire conditions, and a two-way composite slab tested under fire conditions. Both implicit and explicit solution schemes are evaluated for the structural analysis, and the results show that it is feasible to scale down the hours-long fire duration to a simulation time of seconds in an explicit dynamic analysis, without adversely affecting the accuracy of the results. The steel decking contributes significantly to the structural resistance at ambient temperature, but as expected, its contribution is found to decrease rapidly under fire exposure. The modeling approach can account for the location of reinforcing bars (i.e., at a specified depth in either the thick or thin portion of the slab), and it is found that reinforcement location can have a significant effect on the structural response, because heat transfer in the composite slab results in higher temperatures in the thin portions of the slab between the ribs.

Neural network-based formula for shear capacity prediction of one-way slabs under concentrated loads

According to the current codes and guidelines, shear assessment of existing reinforced concrete slab bridges sometimes leads to the conclusion that the bridge under consideration has insufficient shear capacity. The calculated shear capacity, however, does not consider the transverse redistribution capacity of slabs, and thus leads to overly conservative values. While mechanics-based models have attempted to describe the problem of one-way shear in concrete slabs under concentrated loads, this problem is still not fully understood. Therefore, this paper proposes an artificial neural network (ANN)-based formula to come up with estimates of the shear capacity of one-way reinforced concrete slabs under a concentrated load that are as good as possible based on 287 test results obtained from the literature. The methods used for this purpose are: (i) the development of the database with experimental results from the literature, and (ii) the development of the ANN-based matrix formulation. For the latter purpose, many thousands of ANN models were generated, based on 475 distinct combinations of fifteen typical ANN features. The proposed “optimal” model yields maximum and mean relative errors of 0.0% for the 287 datapoints. Moreover, it was illustrated to clearly outperform (mean Vtest / VANN = 1.00) the Eurocode 2 provisions (mean VE,EC / VR,c = 1.59) for that dataset. A step-by-step assessment scheme for reinforced concrete slab bridges by means of the ANN-based model is also proposed in this work, which results in an improvement of the current assessment procedures.

Performance Evaluation of One-Way Concrete Slabs Reinforced with Hybrid FRP Reinforcements

Performance Evaluation of One-Way Concrete Slabs Reinforced with Hybrid FRP Reinforcements

Moment redistribution in continuous steel-fibre-reinforced concrete slabs

The phenomenon of moment redistribution in steel-fibre-reinforced concrete (SFRC) members has not been adequately studied. In this study, the phenomenon was investigated by conducting point-load tests on seven two-span, one-way continuous slabs without traditional reinforcement. Significant redistribution of moments from the elastic values was observed at the critical mid-span and interior support sections. An analytical approach to predict the moment–curvature response of SFRC is presented, with which the predicted variation of moments with increasing load compared to the observed trends with reasonable accuracy. Also, the analytical approach predicts the load-carrying capacity of the slabs within 8% of the average observed values, with a standard deviation of 8%. In addition, the load–deflection curves of the slabs were well predicted. The results are beneficial for the analysis and design of a SFRC slabs-on-pile system by considering moment redistribution due to slab continuity.

Flexural Behavior of Basalt Fiber–Reinforced Concrete Slab Strips with BFRP Bars: Experimental Testing and Numerical Simulation

AbstractThis study investigated the flexural behavior of a new one-way concrete slab system reinforced longitudinally with basalt fiber–reinforced polymer (BFRP) bars and cast with basalt fiber–rei...