Compression Reinforcement Research Articles

Compressive Properties of BFRP and HFRP Bars

Durability of steel reinforced structures is one of the leading problems in construction field nowadays. Currently many studies are focused on the possibility of steel reinforcement replacement in concrete structures with a non-corrosive reinforcement, such as FRP (Fiber Reinforced Polymer) reinforcement. This paper presents and compare the results of compression testing of Basalt (BFRP) and a newly developed type of Hybrid FRP (HFRP) bars. The program examined 30 HFRP bars and 30 BFRP bars with a nominal diameter of 8mm and unbraced free-length varying from 50 to 220 mm. Compressive buckling load strength decreased as free length increased, and the modulus of elasticity under compression for diverse unbraced lengths bars slightly differed, but its value was similar to the modulus of elasticity at tensile. In addition, the test results showed that the ultimate compressive strength of non-buckled HFRP bars as a result of axial compression is about 46% of the ultimate strength. The relationships between the compressive buckling load strength and the unbraced length as well as the optimal unbraced length of the bars were determined. Current research is aiming to contribute the optimization of the transverse reinforcement design and the development of standard regulations in the area of elements with such compressed reinforcement.

Shear strength evaluation in the existance of axial compressive loads for reinforced concrete beams

ABSTRACT Response-2000 is a program developed to calculate the shear capacities of beams and columns under any combinations of shear, moment, and axial loads. It is based on the modified compression field theory. The capabilities of the program Response-2000 to obtain shear strength capacities in the existence of axial compressive loads are demonstrated. The comparison with the experimental tests proved that the program gives good estimate for the failure shear in this case. The shear provisions of the Egyptian reinforced concrete code (ECP203-2017) are also evaluated against the experimental results. It is found that the accuracy of the obtained results using Rseponse-2000 is better than those obtained using the shear equations of the Egyptian reinforced concrete code (ECP203-2017). The program Response-2000 is then used to generate 336 results for 7 different cross-sections considering different concrete compressive strengths, transverse reinforcement, and values of axial loads. These generated results along with 33 experimental results for other 7 cross-sections are used to develop a new formula for the shear strength capacity in the existence of axial compressive loads. This formula is found to give better results when verified against experimental data.

Derivation of statistical parameters for flexure and shear resistance of reinforced concrete beams

The objective of this paper is a study on factors influencing the derivation of statistical parameters of flexural resistance and shear resistance for reinforced concrete beams. A variety of RC beams under bending and shear forces are designed and analyzed, taking into consideration different cross-sectional sizes, compressive concrete strengths, reinforcement ratios, and statistical distributions. The latest version of the American Building Code ACI-318-19 and ASCE/SEI 7-16 are used. The coefficient of variation (V) and bias factor (λ) for the selected models of reinforced concrete beams in flexure and shear are determined using the Monte Carlo simulation technique.

Design and verification of reinforced concrete shell elements

abstract: Reinforced concrete shell elements are relevant in several civil and industrial structures. It is important to know the methods for designing and verifying such elements. In this context, the present paper aims at describing the iterative three-layer method proposed by Colombo et al. This method is based on the Model Code/1990, and it can be applied in the design of shell elements. An additional method for verifying reinforced concrete shell elements is also proposed and discussed. This one is based on the multilayer method proposed by Kollegger et al. Formulations as well as numerical examples are presented for both methods. The design proposed by Colombo et al. is verified by using the methodology based on the multilayer method. Although both methods lead to the equilibrium between applied and resistance loads using approximately the same amount of reinforcement, especially for small neutral axes in relation to the element thickness, one may conclude that the three-layer design method has limitations due to not considering strain compatibility along the thickness of the element and due to the impossibility to calculate the compression reinforcement. Although the multilayer method overcomes such limitations, it is a verification method, and more studies about its use in the design of reinforced concrete shell elements are necessary.

PERILAKU GESER BALOK BETON BERTULANG MUTU TINGGI DENGAN VARIASI FLY ASH BATU BARA, PASIR POZZOLAN DAN BONGKAHAN CANGKANG SAWIT

The utilization of high strength concrete particularly on construction is an option in structural elements. High Strength Concrete (BMT) is a compressive strength exceeding 6000 psi or 41 MPa. High quality concrete can be obtained by mixing superplasticizers (high range water reducers) and cementitious mineral additives in the form of fly ash, pozzofume (super fly ash), and microscopy (silicafume). In this study, it will used the substitution of cement material using coal fly ash, fly ash pozzolan sand and palm shell ash fly ash, fine aggregates using pozzolan sand, coarse aggregates palm shell. The aim of this study is to compare the shear behavior of normal high quality reinforced concrete beams and beams with the addition of material substitution. The high quality reinforced concrete beam specimens were designed to experience shear failure by strengthening the bending area. Reinforced concrete beam specimens of beam size 150 mm x 300 mm x 2200 mm with shear reinforcement diameter 6 mm (fy) 423.46 MPa, compressive reinforcement 16 mm (fy) 412.39 MPa and tensile reinforcement 19 mm (fy) 462, 24 MPa. The beam specimen is pure flexural tensile strength with a size of 150 mm x 150 mm x 600 mm and a cylindrical specimen with a diameter of 150 mm x 300 mm in height. The magnitude of the flexural tensile strength for BMT-N with f cc = 44.4 MPa is 4.5, and for BMT-FBPP with f cc = 51.04 MPa which is 5.35 with FAS 0.3. The results of the two beams experienced shear failure, with a comparison of laboratory and theoretical shear capacity of 2,292 BMT-N with a maximum load of 27,200 MPa, BMT-FBPP 1,720 with a maximum load of 21,410 MPa. The values of deflection and ductility tend to decrease in BMT-FBPP beams which are equal to 19.780% and 6%.

Enhancing the Structural Behavior of Wide Beams Through Reinforcement Schemes

In this paper , numerical analysis of wide beams was presented. The proposed models were loaded with a static seismic load. Diverse models of reinforced concrete wide beams were studied numerically by ANSYS platform , and a parametric study was conducted. The studied parameters were web reinforcement percentage, tensile reinforcement percentage, and compressive reinforcement percentage. The values of tensile reinforcement percentage were ( 1.5% , 1% , 0.7 % , 0.3% ) of cross-section area, compressive reinforcement percentage were ( 0.8 , 0.6 , 0.5 , 0.4 ) of the tensile reinforcement ratio and web reinforcement percentage were ( 0.13 % , 0.067 % ). The influence of these parameters was studied on ductility, dissipation, toughness, stiffness and over strength. The results demonstrated that the studied parameters affected all these properties, and the smallest ductility was noticed in the wide beam ( B7 ) which has a value of 1.1

DESAIN JEMBATAN T-GIRDER PADA SUNGAI JALAN ANTARA MENGGUNAKAN SNI 1725 2016

Bridges are part of the national transportation system that has an important facility. In Putri Sembilan Village, Rupat Utara District, there is a very important bridge where this bridge is the only alternative for residents of Putri Sembilan Village to the fishing port and plantation. The current condition of the bridge has been damaged with wood material that has been decayed and hollow. For this reason, a new bridge was planned using reinforced concrete structures. This plan refers to SNI 1725-2016 concerning the loading of bridges and SNI T-12-2004 concerning the planning of concrete structures for bridges in the hope of obtaining a bridge structure that is safe and in accordance with applicable standards. The design consists of bridge slabs, sidewalks, stamped plates, girder beams and diaphragm beams. As the result, the main reinforcement slab D16-200 mm and D13-300 mm are obtained. Reinforcement direction extending the stamp plate obtained reinforcement D16-200 mm while for the transverse obtained D16-250 mm. For the main reinforcement girder beam obtained 28D32 mm, compressive reinforcement used 8D32 mm reinforcement and shear reinforcement used Ø13-100 mm reinforcement. While the main reinforcement of the diaphragm beam using 3D16 mm and shear reinforcement obtained Ø13-200 mm reinforcement.

Comparison of Static and Dynamic Elastic Moduli in Concrete: Effects of Compressive Strength, Curing Conditions and Reinforcement

The elastic moduli are important parameters in engineering applications. In particular, the elasticity modulus and Poisson ratio are the main parameters for evaluating the bending and shear rigidity of concrete. Elastic modulus’s calculations are made by taking a fixed value of concrete’s Poisson ratio in the worldwide standards. The aim of this study is to show whether the Poisson ratio of concrete with different compressive strengths and different pores, saturation is a fixed value, and harmony with each other of the relationship between static and dynamic elastic moduli. Therefore, totally 540 samples were prepared. These samples consist of reinforced cubic, unreinforced cubic and unreinforced cylindrical concrete samples of the 9 concrete designs with different compressive strengths. In certain days, the ultrasonic P- and S-wave measurements and the uniaxial compressive strength test were performed on these samples exposed to water and air curing. In addition, the static and dynamic elastic moduli, the velocity ratio and the Poisson ratio of these samples were calculated using the obtained data. At the same time, the static and dynamic elastic parameters of the concrete were compared with each other depending on curing conditions because the elastic parameters could be effected from the water or air saturation of the concrete depending on location of existing structures. Consequently, new multi-parameters relationships with low RMSE were generated to determine the relationships among static and dynamic elastic parameters, and to demonstrate the effect of different curing and compressive strength conditions on static and dynamic elastic parameters. In addition, the Poisson ratio values were obtained between 0.22 and 0.34 for different curing conditions and compressive strength (2–70 MPa). This indicates that the Poisson ratio value is not a constant value.

Yüksek Çekme Donatısı Oranına Sahip T En-Kesitli Betonarme Kirişlerin Moment-Eğrilik İlişkisi

In this study, moment curvature the relation of T cross-section reinforced concrete beams with high tensile reinforcement ratio was investigated. The parametric study was performed for T cross-section reinforced concrete beams by taking the tensile reinforcement ratios as high and constant and changing the concrete grade and compression reinforcement ratios. Six types total 66 different T cross-section reinforced concrete beams having different parameters were designed. Moment-curvature relations of T cross section reinforced concrete beams were obtained by considering the nonlinear behaviors of beam materials. Moment-curvature values, curvature ductility values, ductility ratios and effective stiffness values were calculated for the case of yield and failure stages. The results obtained from different parameters from the analysis results are presented in tables and the results were evaluated. The behavior of T cross-section reinforced concrete beams has been interpreted using the values of curvature ductility, effective ductility ratio, effective rigidity, yield and maximum moment capacities of beams. As the compression reinforcement ratio of T cross-section reinforced concrete beams increase, yield moment and maximum moment bearing capacity values increase, but the yield curvature values decrease. Maximum curvature values of the T cross-section beam without compression reinforcement (ρ '= 0) were obtained lower than the beams with compression reinforcements. For the T cross-section beams with compression reinforcement between ρ '= 0.1ρ and ρ'=ρ, the maximum curvature values are stayed constant. It has been observed that the compression reinforcement has a positive effect on the curvature ductility, effective rigidity, maximum curvature, yield moment and maximum moment bearing capacity of the reinforced concrete beams with T section.

Experimental evaluation of strength assessment procedures for R.C. elements with sub-standard details

Today the vast number of older reinforced concrete buildings that do not meet modern seismic provisions are faced with uncertain predicament in terms of expected performance in earthquake events. This has motivated the need for development and proofing of methods of seismic assessment and strengthening and has fueled significant activity in that front over the past 20 years. A Rapid Seismic Assessment system (RSA), which uses capacity prioritizing concepts in order to estimate the failure load of columns as the lowest strength from among several competing mechanisms of resistance (such as flexure, shear, anchorage or lap–splice) is demonstrated experimentally in the present paper. A series of fifteen reinforced concrete prismatic members with substandard details, representative of former construction practices, have been tested under reversed cyclic lateral displacement reversals. Detailing of the specimens was provided so as to develop all the known modes of column failure, thereby illustrating the underlying mechanistic models for strength estimation where reinforcement arrangement is the driving consideration. It was also shown that load history can play a determining role both in the prevalence of strain-controlled modes of failure (compression reinforcement buckling) and in terms of attainment of the available deformation capacity of the structural component. The experimental evidence served as proof-test of the RSA procedure, indicating that it is possible to capture the onset of column failure with relatively simple practical tools.

Evaluation of Structural Performance of Concrete Beams Strengthened with Carbon Fiber Sheets and No-Slump Concrete

In this study, the compression and tensile sections of existing concrete were reinforced using carbon fiber sheet (CFS) and no-slump high-strength, ductility concrete (NSHSDC) to evaluate the structural response of the reinforced concrete. From the experimental test results, the CFS showed a low energy dissipation ability when reinforced at both the compression and tensile sections. However, the NSHSDC reinforcement exhibited high energy dissipation and the lowest deflection under maximum load at both the compression and tension sections. The NSHSDC without reinforcement in the compression section, and concrete reinforced with CFS, exhibited lower load resistance and concrete compression failure. Furthermore, a linear relationship between the compression reinforcement and structural performance was observed, which demonstrated the high load resistance and excellent structural performance of the member reinforced with NSHSDC at both the compressive and tensile sections.

Nonlinear finite element analysis of full-scale concrete bridge deck slabs reinforced with FRP bars

Bridges with reinforced concrete deck slabs are more vulnerable to environmental-induced deterioration mainly due to corrosion. Carbon and glass fiber reinforced polymer (FRP) bars are getting attention as an alternative to steel bars to enhance the overall performance of the concrete bridge deck slabs and minimize corrosion-induced deteriorations. This study presents a 3D nonlinear finite element analysis (NLFEA) simulating the response of full-scale concrete bridge deck slabs reinforced with FRP bars. A control slab model was developed initially and properly calibrated and validated against published independent experimental results. A parametric study was then conducted through creating 27 NLFEA models with different parameters: concrete compressive strength, reinforcement type (glass FRP, carbon FRP, and steel), and bottom transverse reinforcement ratio. Monotonic single concentrated load was applied at the center of the concrete deck slab over a contact area of 600 mm × 250 mm, simulating the footprint of sustained truck wheel load. The CFRP and GFRP bars reinforcement of bridge deck slabs had superior effects on the ultimate load, elastic stiffness, post cracking stiffness, elastic energy absorption and post cracking energy and a little impact on ultimate deflection compared with steel reinforcement. Punching shear failure with a very similar cracking pattern was observed almost in all slabs and the bottom transverse reinforcement ratio is the main parameter affecting the tensile strains. For all slabs reinforced with GFRP and CFRP bars, the maximum measured strains in the bars at failure were less than 50% of their ultimate strain. Increasing concrete compressive strength will increase the ultimate load capacity and corresponding deflection of the slab.

Fiber reinforcement as an alternative to the compressed zone linear reinforcement and the flexible concrete elements stretched zone prestressing

The results of a numerical experiment in the framework of a theoretical study of the strength and crack resistance of the reinforced concrete beams available or non-available in fiber reinforcement are presented. The fiber reinforcement presence influence on the strength and crack resistance of the reinforced concrete beams’ normal sections is determined by varying the following parameters: working reinforcement class; percentage of reinforcement with steel reinforcement; the presence and degree of the reinforced zone reinforcement prestressing; the presence or absence of the beam compressed zone reinforcement; the steel fiber reinforcement presence. Reinforcement of concrete with steel fiber had a significant impact on the theoretical strength and crack resistance of the reinforced concrete elements’ normal sections, both in the presence and in the absence of the working reinforcement prestressing. The calculation showed that in some cases the presence of fiber reinforcement will eliminate the prestressing of the working reinforcement or significantly reduce its level, abandon the reinforcement in the compressed zone and, under the certain conditions, replace the high-strength prestressed reinforcement A600 with the reinforcement A400 without increasing the total consumption of steel by the sample.

Long-term performance of lightweight aggregate reinforced concrete beams

The results of long-term sustained flexural loading tests of 17 large scale reinforced concrete beams fabricated with lightweight aggregate (LWAC) having a density of 1800 kg/m3 are presented. Deflections, strains and crack widths were recorded over a period of 30 years. Subsequently, each beam was tested to failure. The observations are compared to US, European and Chinese standard provisions for long-term concrete behaviour and LWAC concrete design. The dominant conclusion drawn from this study is that, accounting for reduced material properties, the long-term behaviour of LWAC exhibits no differences from that of normal weight concrete (NWC). Existing provisions for addressing long-term behaviour of NWC may be applied to LWAC and remain suitably conservative. Experimental results confirmed the beneficial effects of the presence of compression reinforcement or a wider compression flange (tee beam). Creep effects on deflection and compression strains were more pronounced that those on maximum measured crack width. The paper presents extensive data accumulated over the 30 year long-term load study reported.

Performance of reinforced concrete slabs under punching loads

The experimental program of this study consisted of 12 slab specimens. The parameters investigated include ratio of reinforcement in compression and tension, amount of shear reinforcement and arrangement of shear reinforcement. Flexural reinforcement ratio especially in tension had a noticeable effect on the mode of failure and ultimate punching capacity of slabs. The enhancement in the ultimate loads due to increasing tensile reinforcement ratio was ranging between 26.0 and 42.0%. Slightly enhancement (up to 12%) in ultimate loads was observed as a result of increasing compressive steel ratio. Provision of shear reinforcement was shown to be increased the perimeter of the failure. The ultimate loads were increased with the addition of single leg stirrups as shear reinforcement particularly in case of radial arrangement of shear reinforcement. The ECCS shows the most conservative prediction for punching shear capacity specially in case of using shear reinforcement and the mean predicted-to-experimental ultimate load is shown to be 0.7. The predictions following the ACI and CSA are closet to the experimental results. The mean predicted-to-experimental ultimate load is shown to be 0.8 for ACI and 0.96 for CSA. The BS provisions for punching shear analysis were shown to be overestimated in some cases, where the mean predicted-to-experimental ultimate load is shown to be 1.19.

Flexural performance of highly reinforced composite beams with ultra-high performance fiber reinforced concrete layer

The study aimed to obtain the composite beams with high flexural capacity by using the high compressive strength and deformation capacity of Ultra-High Performance Fiber Reinforced Concrete (UHPFRC). For this purpose, the composite RC beams consisting of UHPFRC layer in the compressive side and Normal Strength Concrete (NSC) in the tensile side were produced and the four-point bending tests were carried out on the beams. By making parametric study for the ratio of tensile reinforcements (ranging from 1.8% to 5.0%), highest ratio where sufficient ductility can be acquired in the beams were determined. Two different thicknesses (one-fifth of the beam height/one-third of the beam height) of UHPFRC layer were applied in the compressive side of the composite beams in order to determine the appropriate thickness. The flexural behavior characteristics (ductility, capacity, stiffness) of the composite beams were evaluated by comparing the pure NSC beams (reference beams) with the same properties. With the use of UHPFRC in the compressive side of the beams, significant advantages have been acquired in ductility, flexural capacity and stiffness compared to the NSC beams. However, the main advantage of the composite application was that it allows the use of very high amount of tensile reinforcement in the beam. The study indicated that it was possible to increase tensile reinforcement ratio of the composite beams up to 5% without using compressive reinforcement. Thus, the ductile composite beams with high flexural capacity were produced with the use of economical amount of UHPFRC. The UHPFRC layer thickness of one-third of the beam height was appropriate for the overall flexural performance at this type of composite beam.

Control of long-term deflections of RC beams using reinforcements and low-shrinkage concrete

An experimentally based programme was conducted to assess the influence of heterogeneity on the long-term deflection of reinforced concrete (RC) elements with compression reinforcement and low-shrinkage concrete. These two structural measures are usually employed by designers to mitigate deflection of concrete beams, slabs and bridge decks due to creep and shrinkage effects. Control of creep and shrinkage deflections is important for successful design of concrete elements as the deflections influence their sizing and thus the associated costs. A 5 year experimental study was undertaken to address the most common alternative design approaches to alleviate long-term deflections of concrete. These included variable reinforcement ratios within the compressive zone, variable tensile reinforcement ratios, low-shrinkage concrete within the compressive zone and a combination of these measures. In total, 12 cantilever beam specimens were tested in the laboratory under controlled environmental conditions, supported by a time-dependent finite-element model. Both numerical and experimental results showed RC beam deflection reductions of up to 85% could be achieved when both compressive reinforcement and low-shrinkage concrete were employed.

Effect of Using Different Types of Polymer on Shear Strength of Simply Supported High Strength Reinforced Concrete Beams

This work is an attempt to study shear behavior of high strength reinforced concrete (modified with different types of polymer) beams. Fourteen simply supported reinforced concrete beams under central load in two groups are tested (with and without stirrups). All beams have the same cross section of (300x200) mm, length of 1200mm with the same reinforcement. The main variables were the compressive strength, shear reinforcement, types, and percentages of the added polymer to study the shear behavior of beams.
 It has been found that by adding different types of polymer (powder and liquid) up to 1%, causes a reduction in water to cement ratio (w/c) from 0.35 to 0.23. The powder polymer improves the compressive strength for 39%, increasing of the splitting tensile strength (fsp) was 40%, improving the flexural strength (fr) was 64%.Whereas, the range of growth by using liquid polymer in compressive strength was 16%, increasing of the splitting tensile strength (fsp) was 16%, improving of the flexural strength (fr) was 59%. From these results and based on statistical analysis, a mathematical model has been drawn for high strength concrete modified with different types of polymer.

Crack Patterns Analysis on Structural Beam with Slag Cement

The more widespread use of concrete and the increasing development shows that there is a greater demand for concrete so a new innovation for concrete is needed in an alternative use of basic materials. Slag cement is the result of fine grinding of steel slag which has the properties of cement which can function as an aggregate adhesive in concrete mixtures and has a fineness level that is either equal or more than type I portland cement. This research aims to compare high quality concrete made from slag cement and conventional concrete mixtures. Concrete beam samples with the size of 20 cm × 30 cm × 240 cm, with 2D10 compressive reinforcement and 3D10 tensile reinforcement. The number of samples are 6 with a variation of 3 high quality reinforced concrete with type I portland cement and 3 using slag cement. Flexture test is by analyzing the behavior of beams due to loading, crack patterns, and visual results of the beam with slag cement. From the results of the research, at the same load of 8 tons obtained a maximum deflection value of 9.52 mm on structural beams with slag cement and 13.30 mm on normal structural beams, thus structural beams with slag cement have better rigidity. The crack patterns that occur is the flextural crack patterns that occur in 1/3 of the middle span with a number of 5 cracks and a maximum crack width of 0.218 mm that occurs in structural beams with slag cement.

Special Limit Condition Of Reinforced Concrete Structures And Its Normalization

One of the ways to improve the resilience of buildings in the event of failure of the bearing structure or emergency, seismic effects is a more complete account of the behavior of elements and their mates at short-term action of loads and dynamics of change of the scheme of the bearing system of the building. To do this, it is advisable to allow more cracks to open, the development of deflections and partial destruction of some sections, which contradicts the current criteria for the first and second limit states that ensure the operational suitability of structures and buildings. Therefore, it is necessary to introduce specific standards of a special limit state for structures. A special limit state is the stage of operation of the structure after reaching the load-bearing capacity for the first and the deformation limits for the second limit states. Exceeding this state, in which the structures do not fully meet the functional requirements, leads to their collapse. The implementation of this limit state is most appropriate in load-bearing systems with a high degree of static indeterminability and constructive interaction of all bearing elements. The introduction and consideration of a special limit stress-strain state of reinforced concrete structures make it possible to detect significant strength and deformation reserves, even after significant fragmentation of the compressed concrete zone and, as a result, reducing the working section of the structure. As the main criteria of a particular limit state for reinforced concrete structures, it is recommended to adopt: the ultimate deformations of compressed concrete and tensile reinforcement with higher values than permissible under normal conditions; as well as the deflections of elements, provided that the minimum allowable length of the zone of bearing and anchorage of reinforcement.