In this work, carbon fiber-reinforced high-performance concrete (CF-HPC) slabs with coarse aggregate content of 25 vol%/35 vol%/45 vol% and carbon fiber content of 0.6 vol%/0.8 vol%/1.0 vol% were ...cured by ohmic heating (OH) curing under realistic severely cold condition for practical on-site construction. Results indicated that the coarse aggregate content has a substantial influence on the electrical resistance and curing time of concrete slab. Higher and lower content of coarse aggregate will lead to insufficient ohmic heats and curing time. On the contrary, carbon fiber content only has a limited influence on OH curing feature, such as slight value difference of electrical resistance and curing temperature. Besides, the correlation between the curing temperature of concrete slab and the associated factors (OH curing power, ambient temperature) was quantitatively analyzed. It is found that the OH curing power had a strong correlation with the concrete temperature during the most time of curing period, while the snowfall weather enhanced the correlation between ambient temperature and concrete temperature. At last, a criterion of feasible resistance range based on the experimental results and theorical analysis was proposed to evaluate the feasibility of OH curing and assist the concrete mix design.
•Carbon fiber-reinforced concrete slab was cured in realistic severely cold weather by ohmic heating curing.•Effect of coarse aggregate and carbon fiber content on electrical properties was analyzed.•Correlation between concrete slab temperature, ohmic heating power and ambient temperature was quantitatively evaluated.•The feasible resistance range was proposed to assess the feasibility of ohmic heating curing.
High efficiency, environmental protection and sustainability have become the main theme of the development of the protection engineering, requiring that the components not only meet the basic ...functions, but also have chemical properties such as acid and alkali corrosion resistance and aging resistance. Polyisocyanate-oxazodone (POZD) polymer has the above characteristics, it also has the advantages of strong toughness, high strength and high elongation. The concrete slab sprayed with POZD material has excellent anti-blast performance. In order to explore the damage characteristics of POZD sprayed concrete slabs under the action of contact explosion thoroughly, the contact explosion test of POZD concrete slabs with different charges were carried out. On the basis of experimental verification, numerical simulation were used to study the influence of the thickness of the POZD on the blast resistance of the concrete slab. According to the test and numerical simulation results that as the thickness of the coating increases, the anti-blast performance of the concrete slab gradually increases, and the TNT equivalent required for critical failure is larger. Based on the above analysis, empirical expressions on normalized crater diameter, the normalized spall diameter and normalized spall diameter are obtained.
•Experimentally investigated performance of 14 concrete slabs under impact loads.oConcrete slabs were 1000 × 1000 × 75 mm.oTested under drop weight impact loads.•Examined:oinfluence of volume ...fraction of steel fibers,onumber of GFRP sheet layers, andoarrangement of GFRP sheets.•Increase in the bottom layer enhances the behavior of RC slabs under impact loads.•Slabs with bottom GFRP layers generally perform better than those with steel fibers.
Recently, to improve the dynamic behavior of Reinforced Concrete (RC) slabs under impact load, the methods of externally bonding Glass Fiber Reinforced Polymer (GFRP) sheets to slab and internally reinforcing concrete by steel fibers have been proposed. Nevertheless, it is required to investigate the comparison between these two methods on response of RC slabs under impact loads. In this study, the influence of volume fraction of steel fibers, the number of GFRP sheet layers (one or two) and the arrangement of GFRP sheets (covering the whole or parts of surface), are examined.
Performance of fourteen 1000 × 1000 × 75 mm concrete slabs including one plain slab, one steel RC slab, three steel RC slabs containing steel fibers with different volume fractions and nine steel RC slabs strengthened with externally bonded GFRP sheets or strips under impact loads induced by drop weight is experimentally examined. In this article, crack development, failure modes and dynamic responses including displacement-time, strain-time, as well as acceleration-time are investigated and compared between slabs with various configuration. In addition, finite element analyses are carried out using LS-DYNA explicit software. The results indicate that increasing the bottom layer GFRP enhances the performance of RC slabs under impact loads. In general, slabs with totally bottom GFRP layers provide better performance than those with steel fibers.
This paper presents an experimental and computational study on the behavior of two composite subassemblies under a column removal scenario. The two specimens, designed as beam-joint-beam (B-J-B) ...subassemblies with reinforced concrete slabs on top of steel beams, were extracted from a prototype steel frame building with composite floor systems. One subassembly with the joint above the removed column was loaded under sagging deflection, and the other with the joint adjacent to the removed column was loaded under hogging deflection, simulating a center column removal scenario at a two-span beam-column subsystem. Detailed finite element models were also developed and analyzed for the two composite subassemblies. The observed failure modes were captured by the numerical models, and the computed load-versus-displacement curves agreed reasonably well with the measured data. To investigate slab effect, test results of the test specimens and steel subassemblies similar to the test specimens but without slab were compared. It showed that the load carrying capacities of the composite subassemblies were >63% higher than the steel subassemblies. Under sagging deflection loading, the composite subassembly showed a greater initial stiffness than the steel subassembly. Unlike the steel subassemblies, notable compressive axial forces were developed in beams of the composite subassembly subjected to sagging deflection at the early loading stages, indicating arching action contributed to the load resistance at small deformation as well as the initial stiffness. Contributions to the load capacity by resistant mechanisms, e.g. flexural action, arching action and catenary action were characterized and discussed.
•Middle and side composite subassemblies with reinforced concrete slab were tested in a column removal scenario.•The load carrying capacities of the composite subassemblies were improved about 63% than the steel subassemblies.•For middle column specimens, the slab improved the initial stiffness and produced compressive arching action.•The side column specimens exhibited similar resistant mechanisms with the steel subassembly.
This paper presents the experimental and theoretical results of an investigation carried on reinforced concrete plates placed on yielding supports along their perimeter under short-term dynamic ...loading. The yielding supports are made of elements with annular cross-section. Their functionality allows operations in elastic and elasto-plastic stages with a further turning to hardening stage. This particular support scheme has been adopted in order to simulate the different boundary conditions that r.c. slabs subjected to impacts may encounter in practical applications of civil engineering (e.g. roofs, vertical panels, retaining walls, guardrails, etc.). The experimental results showed that influence of support deformability on the structural response under impact depends on their rigidity and on the deformation stage. The results of numerical simulations based on a simple mechanical model qualitatively agree with the experimental results. Therefore the model can be adopted for simulation and design of reinforced concrete panels under impact or high-strain loading situations.
The use of thin reinforced concrete slabs for buildings has more advantages than beam supported slabs, slabs with column capitals, and drop-down panels because of its easier construction and economic ...feasibility. However, it is susceptible to localized failure due to punching shear resulting in progressive collapse of the structure. Therefore, the attempt has been made to study the behaviour of thin reinforced concrete slabs 1200 × 1200 mm having thicknesses of 50 and 30 mm under repeated loading through the experiment and simulations. The mass of the impactor was 60 kg with 35 and 70° angular motion and the corresponding impact velocity were 2.62 and 4.97 m/s, respectively. Based on the member response under static conditions using analytical methods, the flexural failure was found to be more prominent and the ultimate flexural load for 50 mm thick slab was found to be 101.7% higher as compared to 30 mm thick slab. It was concluded that the resistance of the target was found to increase by 36% when the target thickness increased from 30 to 50 mm at 35° pendulum impact whereas the same was found to be 63% increment at 70° pendulum impact, during the first impact. Under repeated impacts, the impulse on both 30 and 50 mm thick slab was found to decrease gradually against 35° pendulum impact whereas the abrupt decrease in impulse was observed at 70° impact. The numerical analysis was performed using ABAQUS/EXPLICIT to predict the response of the slab under multi-impact loading. The numerical model was able to accurately predict the peak impact force on both 30- and 50-mm thick slab, up to the fourth impact.
•This paper presented the flexural behavior of RC slabs strengthened with TRM improved with short PVA fibers.•The improved TRM composite can improve the cracking load of strengthened slabs.•The ...bearing capacity and deflection of tested slabs were predicted based on the flexural model.•A predicted formula of tensile strength of the improved TRM was applied to correct the flexural model.
Textile reinforced mortar (TRM) composite is a viable and effective solution for fiber reinforced polymer (FRP) in some limited environments. Short and dispersible polyvinyl alcohol (PVA) fibers were applied in TRM matrix to remedy the lack of cracking strength of TRM composite, which was conducive to improve the cracking capacity and serviceability of flexural members. The effects of the matrix improved with and without short fibers and the reinforcing ratio of textiles on the flexural behavior of reinforced concrete (RC) slabs were studied in this work. Six RC slabs were fabricated and tested under four-point flexural loading, including one control slab, one with one layer of carbon TRM composite without short fibers, one with a matrix improved by short fibers and three with carbon TRM composite improved with short fibers. The results showed that short PVA fibers could increase the cracking capacity of RC slabs by 90 ~ 105%. The flexural capacity of strengthened slabs was increased with the increasing of reinforcing ratio of textiles. Based on the strain compatibility and force equilibrium, an analytical model was given. Moreover, the model was further improved according to the predicted formula of tensile strength for TRM. The theoretical and experimental results showed a very good agreement.
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.
This paper presents research on the response and behavior of both high strength concrete (107 MPa) and normal strength concrete (27.6 MPa) slabs doubly reinforced with high strength low alloy ...vanadium (HSLA-V) reinforcement (VR) and conventional steel reinforcing bars (NR) subjected to explosive loads. Four types of reinforced concrete (RC) slabs namely High Strength Concrete (HSC) with HSLA-V Steel Reinforcing bars (HSC-VR), High Strength Concrete with Conventional Steel Reinforcing bars (HSC-NR), Normal Strength Concrete (NSC) with HSLA-V Steel Reinforcing bars (NSC-VR), and Normal Strength Concrete with Conventional Steel Reinforcing bars (NSC-NR) have been studied and compared both experimentally and numerically. The slabs were subjected to blast loads using a shock tube capable of generating both positive and negative phase pressures. Data collected during the dynamic experiments consisted of reflected pressure obtained from several pressure gages arranged along the perimeter of the test article and mid-span deflections captured from an accelerometer, a laser device, and high speed video. The numerical analysis was performed with the commercial program LS-DYNA using two material models. The concrete material models considered were Winfrith Concrete Model (WCM) and Concrete Damage Model Release 3 (CDMR3). Results from the numerical simulation are compared with the experimental values to determine material parameters and other finite element model related constraints. Mesh sensitivity and crack propagation studies were also conducted. From this study it was observed that CDMR3 and WCM can be used over a wider range of concrete compressive strengths. The advantages and disadvantages of using high strength materials are discussed.
•Experimental data from uniform blast loading on doubly reinforced concrete slabs presented.•Comparison of performance of combination of slabs made of high strength concrete and steel.•Finite element analysis using two concrete models in LSDYNA gave good comparison with deflection data.•High strength concrete was very effective in reducing the level of response.•Default material models with default properties can be used to reasonably predict the response of such slabs.
•The fire behavior of reinforced concrete tunnel slabs during both the heating and cooling phases are simulated.•Three modeling strategies are investigated using beam, shell, and solid elements.•Five ...recent fire tests on loaded and restrained large-scale tunnel slabs, with varying concrete strengths, restraint levels, and fire scenarios, are selected to verify the models.•Temperature and displacement evolutions during heating and cooling obtained from the numerical models are compared with the experimental test data.•Shell elements perform the best by achieving a balance between model accuracy and efficiency.
This paper examines different modeling approaches to simulate the behavior of reinforced concrete (RC) tunnel slabs under fire during both the heating and cooling phases. Three modeling strategies are investigated by using beam, shell, and solid elements in addition to different methods to capture the effect of axial restraint on the slabs. The models consider temperature-induced plastic deformations and irrecoverable degradation of materials. The models also utilize distinct concrete properties for heating and cooling as well as account for the transient creep strain explicitly in the calculations. The results obtained from different modeling strategies are compared to five recent fire tests on loaded and restrained large-scale RC tunnel slabs, with varying concrete strengths, restraint levels, and fire scenarios. Temperature and displacement evolutions during heating and cooling obtained from the numerical models are compared with the experimental test data. When considering model accuracy and efficiency as the primary performance metrics, using shell elements to analyze the fire performance of reinforced concrete tunnel segments resulted in the best balance between the two. The numerical models and techniques developed in this paper will enable practicing engineers to reliably and rapidly assess fire damage to reinforced concrete tunnel linings, and to explore cost-effective designs of tunnels for fire.
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