Impact Behavior of Composite Reinforced Concrete Beams with Pultruded I-GFRP Beam

The present study experimentally and numerically investigated the impact behavior of composite reinforced concrete (RC) beams with the pultruded I-GFRP and I-steel beams. Eight specimens of two groups were cast in different configurations. The first group consisted of four specimens and was tested under static load to provide reference results for the second group. The four specimens in the second group were tested first under impact loading and then static loading to determine the residual static strengths of the impacted specimens. The test variables considered the type of encased I-section (steel and GFRP), presence of shear connectors, and drop height during impact tests. A mass of 42.5 kg was dropped on the top surface at the mid-span of the tested beams from five different heights: 250, 500, 1000, 1500, and 1900 mm. Moreover, nonlinear Finite Element (FE) models were developed and validated using the experimental data. Static loading was defined as a displacement-controlled loading and the impact loading was modeled as dynamic explicit analysis with different drop velocities. The validated models were used to conduct a parametric study to investigate the effect of the concrete compressive strength on the performance of the composite beams under static and impact loadings. For the composite specimen with steel I-sction, the maximum impact force was 190% greater than the reference specimen NR-I at a drop height of 1900 mm, whereas the maximum impact forces for the specimens composite specimens with GFRP I-sction without and with shear connectors were 19% and 77%, respectively, more significant than the reference beam at the same drop height. The high stiffness for the steel I-beams relative to the GFRP I-beam was the reason for this difference in behavior. The concrete compressive strength was more effective in improving the impact behavior of the composite specimens relative to those without GFRP I-beams.

Cyclic performance of exterior R.C beam-column strengthened with different thicknesses of CFRP sheets

The recent ground motion results indicated that the RC buildings are required to be retrofitted by different strengthening techniques. Nowadays, the external strengthening gain interest since its easy, cost effective and not required redesign of buildings. The CFRP sheets are suitable solution and utilized by a number of researchers. However, the numerical cyclic performance of connection strengthened with different thicknesses of CFRP need to be well investigated. This study assessed the performance of RC exterior beam column connection strengthened with CFRP sheets First, two grades of concrete are utilized to be control specimens, normal concrete compressive strength (C20) and high concrete compressive strength (C50) then, the specimens are retrofitted with different thicknesses (1.2, 2.4, 3.6mm) of CFRP sheets. The stresses and damage states showed the importance of connection retrofitting. The CFRP shift the plastic hinge zone away from the panel zone. Furthermore, the results demonstrated that by increase of CFRP thickness the connection resistance will be improved. The comparison between the hysteresis curves demonstrated that the yield and ultimate loading were enhanced for strengthened connection for both concrete grades and the incremental in thicknesses also increase them. The outputs also exhibited that the stiffness and ductility has increased for retrofitted specimens indicating that the CFRP comprehensively overcome the applied cyclic loading and the beam column connection is able to resist such type of loading.

Lightweight concrete as covers on floating house platforms made from expanded polystyrene system (EPS) material

Floating houses can be utilized in coastal areas as they are equipped with platforms made from expanded polystyrene system (styrofoam) and lightweight concrete covers. A lightweight concrete cover on a floating house platform made from styrofoam can improve the feasibility of housing in terms of strength, comfort and cleanliness. This research aims to obtain mixture that meet the weight and compressive strength requirements of lightweight concrete and produce them as covers on floating houses platform. The compositions of lightweight concrete materials in this research use volume ratios of 1 Pc: 2 Sand: 3 Styrofoam, 1 Pc: 1.5 Sand: 2.5 Styrofoam and 1 Pc: 1.25 Sand: 2.75 Styrofoam. The research results show that the concrete made with styrofoam qualifies as lightweight concrete with average volume weight of concrete produced between 1000-1300 kg/m3. The lightest concrete weight (1097.88 kg/m3) could be obtained from variations of mixture of 1 Pc: 1.25 Sand: 2.75 Styrofoam, The highest concrete compressive strength results were obtained from the mixture of 1 Pc: 2 Sand: 3 Styrofoam (119.26 kg/cm2). The variations of concrete mixture of 1 Pc: 2 Sand: 3 Styrofoam can be considered as lightweight concrete (≤ 1900 kg/m3).

Continuous Deep Beams Behavior Under Static Loads: A Review Study

Few studies discussed the continuous deep beams CDB behaviour in spite of its great importance in building constructions due to the usual use in bridges and tall buildings as a load distributer. The behaviour of CDB shows a different behaviour when comparing with the simply supported one, so the expected behaviour of SDB does not match with the CDB. So, this paper deals with reviewing the behaviour of CDB in the past researches. It has been concluded that, the CDB resist the applied loads by flexural and shear together, the flexural behaviour appears at the first loading stage then the beam start to resist by shear capacity. The amount of resistance of beam by flexural depends on a/h ratio, main and web steel reinforcement and concrete compressive strength. Flexural behaviour may not appear for very small a/h ratio or over main reinforcement. Also, main steel reinforcement at both top and bottom of beam does not reach to yielding point expected one case, which is, the main steel ratio is less than 0.6%, thereby, tie failure will governs.

Use of Industrial Waste – (Red Mud) in the Production of Self Compacting Concrete

Red mud is industrial waste and causing threat to environment so to reduce the cost of the construction also to make structure more durable. Aluminium is now consumed during manufacture red mud, which is used and while remaining red mud has been undertaken sothat it can be used for construction fashion of the concrete by blending or by replacing the cement by red mud. Keywords: Red mud, self-compacting concrete, Compressive Strength, Tensile Strength, Flexural Strength

The Analysis of Beam-Column Joint Reinforced with Cross Bars according to SK SNI T-15-1991-03 on Cyclic Loads

The primary structural component supporting the other structural loads in a building is the beam-column joint. It is considered a critical area of a building which needs to be accurately designed to ensure energy is dissipated properly during the occurrence of an earthquake. Beam-column joint has the ability to offer a proper structure required to transform cyclic loads in the inelastic region but also has a direct impact on the components connected to it during the occurrence of any failure. This is one of the reasons the beam-column connection needs to be designed carefully. Therefore, this study focused on designing a beam-column joint with reinforcement according to SK SNI T-15-1991 in order to withstand cyclic loads. The test specimen used was observed to have a concrete compressive strength of 19.17 MPa while the dimension of the beam was 120 x 30 x 40 cm and the column was 30 x 30 x 200 cm, having 8Ø13.4 mm bars with 310.03 MPa yield strength (fy) as well as Ø9.8-100 mm stirrup reinforcement with (fy) 374.59 MPa. The test was initiated through the provision of 0.75 mm, 1.5 mm, 3 mm, 6 mm, 12 mm, 24 mm monotonic cyclic loads at the end of the beam up to the moment the specimen cracked. A maximum load of 68.35 kN for the compression and 49.92 kN for the tension was required to attain the cyclic load capacity. The maximum load was attained at 50.98 mm displacement. Furthermore, beam-column with 23.93 mm displacement caused a reduction in capacity. Meanwhile, the load at 24 mm produced the cycle's highest dissipation energy of 13.25 but this can be increased through the addition of stirrups to provide stiffness in the joint. The stiffness value was also observed to have increased after the structural repairs.

FIBER-REINFORCED CONCRETE FOR RIGID ROAD PAVEMENTS MODIFIED WITH POLYCARBOXYLATE ADMIXTURE AND METAKAOLIN

Increasing the strength and durability of road surfaces is crucial. Therefore, the concrete compressive strength, flexural strength, frost, and abrasion resistance of fiber-reinforced concrete for rigid pavements are investigated in this study an experiment is performed based on an optimal plan, in which four factors of concrete composition are varied: the amounts of Portland cement, polypropylene fiber, metakaolin, and polycarboxylate type admixture. Experimental statistical models for investigating the effects of composition factors on concrete properties are established. It is discovered that owing to the use of metakaolin and a superplasticizer, the concrete compressive strength increases. Furthermore, the use of modifiers and fiber reinforcement increases the flexural strength, frost resistance, and wear resistance of concrete. X-ray phase analysis of the fiber-reinforced concrete structure confirm the effectiveness of the modifier effect, in particular the positive role of metakaolin as an active pozzolana. The developed fiber-reinforced concrete for rigid pavements with rational modifiers, depending on the Portland cement content, exhibits compressive strengths from 55 to 70 MPa, flexural strengths from 8 to 9.5 MPa, frost resistances from F350 to F450, and abrasion resistances from 0.3 to 0.4 g/cm2. Such properties ensure the high durability of fiber-reinforced concrete and allow it to be used on road pavements that support heavy loads and traffic.

ANN-based Fatigue Strength of Concrete Under Compression

<p>When concrete is subjected to cycles of compression, its strength is lower than the statically determined concrete compressive strength. This reduction is typically expressed as a function of the number of cycles. In this work, we predict the reduced capacity as function of a given number of cycles by means of artificial neural networks (ANN). A 203-point experimental dataset gathered from the literature was used. The proposed ANN model results in a maximum relative error of 5.1% and a mean counterpart of 1.2% for the whole dataset. It’s shown that the proposed analytical model outperforms the existing design code expressions.</p>