Strength Of Steel Reinforcement Research Articles

Experimental, Numerical, and Analytical Investigation of the Reinforced Concrete Hidden and Wide Beams

AbstractThis research presents an experimental, analytical, and numerical study to predict the flexural behavior of reinforced concrete hidden and wide beams embedded in slabs. The experimentally studied parameters of testing eight specimens include beam depth, beam width, and beam eccentricity from the column. The obtained test results were compared to the predictions of finite element analysis using the ANSYS program. A numerical parametric study was conducted by the ANSYS program to explore other parameters affecting the ultimate flexural strength of beams. The studied parameters encompass concrete compressive strength, steel reinforcement strength, bottom reinforcement ratio, top-to-bottom reinforcement ratio, and web reinforcement ratio. The results revealed that an increase in beam depth led to higher ultimate load and secant stiffness, along with a decrease in deflection. The increase in beam width significantly affected beam depth, resulting in increased ultimate load and secant stiffness and a slight decrease in deflection. The increase in beam eccentricity from the column resulted in a decrease in ultimate load and secant stiffness while increasing the deflection. Comparisons between experimental and numerical results were made against calculations based on the ECP 203-2017 and ACI 318-19 codes, and the comparison yielded satisfactory results.

Study on the Bond Performance of Epoxy Resin Concrete with Steel Reinforcement

Epoxy resin concrete, characterized by its superior mechanical properties, is frequently utilized for structural reinforcement and strengthening. However, its application in structural members remains limited. In this paper, the bond–slip behavior between steel reinforcement and epoxy resin concrete was investigated using a combination of experimental research and finite element analysis, with the objective of providing data support for substantiating the expanded use of epoxy resin concrete in structural members. The research methodology included 18 center-pullout tests and 14 finite element model calculations, focusing on the effects of variables such as epoxy resin concrete strength, steel reinforcement strength, steel reinforcement diameter and protective layer thickness on bond performance. The results reveal that the bond strength between epoxy resin concrete and steel reinforcement significantly surpasses that of ordinary concrete, being approximately 3.23 times higher given the equivalent strength level of the material; the improvement in the strength of both the epoxy resin concrete and steel reinforcement are observed to marginally increase the bond stress. Conversely, an increase in the diameter of the steel reinforcement and a reduction in the thickness of the protective layer of the concrete can lead to diminished bond stress and peak slip. Particularly, when the steel reinforcement strength is below 500 MPa, it tends to reach its yield strength and may even detach during the drawing process, indicating that the yielding of the steel reinforcement occurs before the loss of bond stress. In contrast, for a steel reinforcement strength exceeding 500 MPa, yielding does not precede bond stress loss, resulting in a distinct form of failure described as scraping plough type destruction. Compared to ordinary concrete, the peak of the epoxy resin concrete and steel reinforcement bond stress–slip curve is more pointed, indicating a rapid degradation to maximum bond stress and exhibiting a brittle nature. Overall, these peaks are sharper than those of ordinary concrete, indicating a rapid decline in bond stress post-peak, reflective of its brittle characteristics.

Investigation on the Ductility Capacity of Concrete Columns with High Strength Steel Reinforcement under Eccentric Loading.

Ductility-based structural design is currently the mainstream method. In order to analyze the ductility performance of concrete columns with high-strength steel reinforcements under eccentric compression, corresponding experimental studies have been performed. Numerical models were established, and their reliability was verified. Based on the numerical models, the parameter analysis was carried out, where eccentricity, concrete strength, and reinforcement ratio were considered to systematically discuss the ductility of the concrete column section with high-strength steel reinforcement. The results show that the ductility of the section under eccentric compression increases with the strength of the concrete and eccentricity, and decreases with the reinforcement ratio. Finally, a simplified calculation formula capable of quantitatively evaluating the section ductility was proposed.

Non Linear Analysis of Reinforced Concrete Column Strengthened by Reinforced Concrete Jacketing with High Strength Steel

The strengthening column structure elements with reinforced concrete jacketing were chosen in this study because it is the most common and easy to apply practically to existing column structures. Modeling data using test specimens from Ersoy et. al by adhering to constitutive models of concrete materials from Attard and Stunge and Bilinear steel. The purpose is to perform non-linear analysis modeling through the behavior of the section of the RC column reinforced with RC jacket by taking into account the influence of interface slip and initial strain by using a two-dimensional sectional analysis approach with a fiber-based method made using MATLAB. Non-linear analysis was performed to obtain the moment-curvature relationship and validate the modeling results with the experimental model then make modeling variations based on the variations high strength steel reinforcement and evaluate the results in curvature ductility and index ductility. The prediction results showed a fairly good fit with the experimental results and modeling variations showed that the greater value of interface slip coefficient, the higher the curvature ductility and index ductility, the variation modeling using high-strength steel in longitudinal reinforcement can increase flexural, axial and lateral capacity, but it is lower in ductility, while using normal strength steel for longitudinal reinforcement and high strength steel for lateral reinforcement with tighter spacing provides higher ductility.

Behaviour of composite beam-column joint with fin plate connection subjected to impact loads

Falling-debris impact on a remaining building is detrimental and may lead to propagation of initial damage by abnormal loadings (gas, explosion, etc.), if the structure is not able to resist the impact. This in turn will lead to progressive collapse of the whole structure. For a frame structure, fin plate (or shear tab) connections ideal for gravity-dominant design is normally weaker than seismic connection. Therefore, its integrity under dynamic loading is of great importance for anti-progressive collapse performance. A series of tests on composite joints with fin plate connections subjected to impact loads was conducted to investigate the dynamic behaviour, which served as an unfavourable loading scenario for falling-debris impact which occurred close to the beam-to-column connection. Three middle joints and one side joint were designed and tested in the experimental programme. The test parameters included impact load, joint type and composite slab thickness. Structural response, failure mode and development of strains were investigated. A comparison of test results and design predictions of ultimate strength was conducted. The comparison was also extended to composite joints subjected to quasi-static loads. It was found that an intermediate level of strain rate in the order of 1 s−1 was recorded for the impact tests and it would lead to maximum increases of 28 % in concrete strength and 16 % in steel reinforcement strength, respectively. Compared to quasi-static tests, strain rate effect in the impact tests could increase compressive arch, catenary and flexural resistance of composite FP joints. Moreover, composite slab effect was beneficial to flexural resistance and detrimental to tying resistance, since deformation capacity of fin plate connection was consumed for flexural resistance at small deformation stage.

Experimental and numerical evaluation of compression confinement techniques for HSC beams reinforced with different ratios of high strength steel reinforcement

This work presents experimental and numerical research to evaluate the compression confinement techniques of HSC beams reinforced with different ratios of high-strength steel reinforcement. Twelve specimens of high-strength reinforced concrete beams with two different compression confinement techniques were tested experimentally. The first method is used carbon fiber reinforced polymers sheets (CFRPs) around the compression zone, CF, and the steel fibers reinforced concrete is used in the compression zone by 1% of volume fraction, SF, in the second case. A 3-D finite element analysis was done; using the ANSYS program to simulate and idealize all experimental specimens. The numerical and experimental results of the RC beams were validated and compared in this work. The results showed that there is a good idealization using 3-D finite element models with the experimental specimens. Also, it was found that using the suggested techniques can increase the strength ratio and increase the ductility index depending on the tensile reinforcement ratios. Moreover, the energy absorption and the mode of failure were enhanced.

Database trends and critical review of seismic performance tests on high strength steel reinforced concrete components

The use of High Strength Steel (HSS) reinforcement in concrete construction is emerging rapidly, especially in high performance concrete applications. The ACI 318–19 code has permitted the use of HSS reinforcement Grades 80 (550 MPa) and 100 (690 MPa) in earthquake-resistant concrete components. This change was motivated by recent experimental and analytical research to assess the benefits and drawbacks of using HSS reinforcement in seismic design of concrete. The use of HSS reduces bar congestion and provides more effective confinement to concrete, however, great attention must be paid to its drawbacks. Examples of such drawbacks are lower hysteretic energy, higher bond stresses, lower plasticity spread due to local strain concentrations, and potential for premature confined concrete crushing before full utilization of HSS full capacity. This study reviews past experimental research on cyclic performance of various concrete structural components reinforced with HSS, including columns, beams, beam-column joints, walls, and coupling beams. In addition, a comprehensive database of cyclic tests on HSS reinforced components is established, presented and evaluated. An HSS reinforced flexural section parametric study is performed to aid in interpreting database trends and literature results. The effect of HSS design parameters and cyclic response measures of these components such as load-deformation relationships, strength, curvature and strains, ductility and energy dissipation capacity are discussed and compared to their conventional steel reinforced concrete counterparts based on literature and the database trends observed. The database and the cyclic behavior observations presented may serve as basis for future experimental and analytical studies concerned with characterizing seismic response, modeling and design of HSS reinforced concrete components.

Experimental seismic behavior of ultra-high performance concrete columns with high strength steel reinforcement

Ultra-High Performance Concrete (UHPC) is an advanced cementitious composite material that exhibits high ductility and durability with superior mechanical properties, e.g. compressive strength in excess of 22 ksi (150 MPa) and sustained post-cracking tensile strength greater than 0.7 ksi (5 MPa). These characteristics have promoted UHPC to be considered for new construction applications specially for next-generation bridge structures. Currently, UHPC is commonly used in limited structural applications, such as joints and connections between precast structural elements. However, there is a growing interest in larger UHPC applications and new designs of full structural members as the UHPC market keeps growing and material becomes more available. One potential application for structural elements is full UHPC columns, which is the focus of this study. This paper presents an experimental investigation of the structural and seismic behavior of large-scale full UHPC columns reinforced with conventional and high strength steel reinforcement. The UHPC columns were tested under combined axial and quasi-static cyclic lateral loading at the University of Nevada, Reno. The testing program included four columns where the seismic performance of three different columns with grade 100 reinforcement is compared with a reference UHPC column with regular grade 60 reinforcement. Thus, the varied experimental parameters included the longitudinal reinforcement ratio and grade as well as the transverse reinforcement ratio. Results demonstrate that UHPC columns have reasonable ductility and drift capacity. Moreover, higher reinforcement ratio or grade is needed to better utilize the superior mechanical properties of UHPC and recommended to inform future design.

Minimum Depth-Span Ratio of Beams in order to Control Maximum Permissible Deflection

Background: ACI code and other building codes and standards include the provisions for deflection control and depth-span limitations, also including the maximum permissible deflection for specified concrete and steel reinforcement strength. In this study, the effects of applied load intensity, steel reinforcement index amount as a ratio to the balancing reinforcement index (ρ/ρb), concrete strength (fc' ) and beam width on the depth-span ratio of the beam with different types (simply supported, fixed ended, propped and cantilever) were investigated. Objective: This study aimed to study the effect of applied load intensity, steel reinforcement index amount as a ratio to the balancing reinforcement index (ρ/ρb), concrete strength (fc' ) and beam width on the depth-span ratio of the beam of different types (simply supported, fixed ended, propped and cantilever). Methods: This study theoretically investigates the effect of applied load intensity, steel reinforcement index amount as a ratio to the balancing reinforcement index (ρ/ρb), concrete strength (fc' ) and beam width on the depth-span ratio of the beam of different types (simply supported, fixed ended, propped and cantilever). Results: The results show that the effect of the ratio (ρ/ρb) is small on the depth-span ratio, and the required depth of the beam increased with increasing the applied distributed load value and decreased with increasing the concrete strength for all beam types. Discussion: Deflection of slabs and beams can be controlled by the addition of steel reinforcement bars or using pre-stressing concrete, loading type and value, material properties (E), section properties (I), and the type of the member. The results showed that the effect of the ratio (ρ/ρb) was small on the depth-span ratio, and the required depth of the beam increased with increasing the applied distributed load value and decreased with increasing the concrete strength for all beam types. Conclusion: - A modification of ACI Code span-depth ratio is suggested to include the effect of tension reinforcement area which is represented by the reinforcement indices ratio (ρ/ρb), applied distributed load (w), concrete compressive strength (fc' ) and cross section width (b) in order to control the maximum deflection of the beam within the ACI limit of the maximum permitted deflection. - The value of span-depth ratio (N = L / h) is determined for four types of beam (simply supported, fixed ended, propped and cantilever) for concrete strengths (fc' = 21, 28, 35, 42, 63 & 84 MPa), applied distributed load (w = 14.6, 29.2, 43.8 & 58.4 kN/m), cross width (b = 150, 200, 250 & 300 mm) and (ρ/ρb = 0, 0.5 & 1) in addition to (ρt /ρb & ρmax /ρb). - The effect of the reinforced indicia ratio (ρ/ρb) is small on the span-depth ratio (N = L / h) for all values of applied load and concrete compressive strength. - The span-depth ratio (N = L / h) decreased with increasing the applied load, or in other words, the required depth increased with increasing the applied load for all values of concrete strength and beam width. - The span-depth ratio (N = L / h) increased with increasing the concrete strength (fc' ), i.e. the required depth decreased with increasing concrete strength for all values of applied loads and beam width. - The same behavior and conclusions are obtained for all beam types (simply supported, fixed ended, propped and cantilever).

Development of performance limit states for concrete bridge piers with high strength concrete and high strength steel reinforcement

Current design codes and guidelines do not permit reinforcing the plastic hinge region of bridge piers using high strength steel (HSS) rebars. This is due to the lack of adequate research on the seismic response of HSS reinforced bridge piers. The objective of this study is to develop analytical expressions for predicting the drift at the onset of different performance limit states for high strength concrete (HSC) bridge pier reinforced with HSS reinforcement. Utilizing damage data obtained from incremental dynamic analysis of HSC circular bridge piers reinforced with HSS, this study developed drift ratio relationship accounting for the aspect ratio, concrete and steel material properties, axial load ratio, and reinforcement ratio, using validated finite element models. Analytical equations are developed for estimating the drift at the inception of rebar yielding, concrete spalling, and bar buckling using multivariate regression analysis. The proposed equations showed reasonable precision when corroborated against experimental results.

Numerical simulation and damage analysis of RC bridge piers reinforced with varying yield strength steel reinforcement

A force-based fiber beam-column element was developed to simulate the seismic performance of reinforced concrete (RC) bridge piers reinforced with high-strength steel bars (HSSB) with/without a distinct yield plateau. The finite element model (FEM) adopted in this paper considers cracking and spalling of cover concrete, buckling and low-cycle fatigue of longitudinal steel bars, as well as bond-slip (strain penetration) between longitudinal bars and concrete. A fiber-based damage model based on material strains of concrete and reinforcing steel was used to predict the evolution and progress of damage in RC bridge piers. Two sets of test data of RC specimens were used to verify the applicability of the FEM and the damage model. A parametric analysis was conducted to derive suitable modeling parameters for reinforcing steel to accurately simulate the mechanical properties of HSSB with/without distinct yield plateau, and the resulting seismic performance of RC piers. The FEM used herein could reflect the effects of buckling and low-cycle fatigue of longitudinal steel bars as well as bond slip (strain penetration) on cyclic response of RC piers. The fiber-based damage model was shown to not only predict the damage development progress in RC piers reinforced with HSSB, but also able to convincingly reveal the causes of damage of RC piers with different axial load ratios.

Effect Bonding Strength Steel Reinforcement with Epoxy Coating on the Character Destruction of Autoclaved Aerated Concrete Beams in Bending

Many of the complex reinforced Autoclaved Aerated Concrete characteristics under shear and flexure are yet to be identified to employ this material advantageously and economically, as it has many advantages of low weight, fire resistance, acoustic and thermal insulation. It is observed in the article that under two-points loading system, diagonal cracks are usually the first cracks to be observed in the deep beam clear span. The diagonal cracks first are developed in relatively deep beams and the flexural cracks are first developed in shallower beam. The principal mode of failure in the deep beams having adequate reinforcement is diagonal tension cracking. The shear failure is a common type for all beams. This indicates a weak the bond strength between lightweight concrete and reinforcing steel. There are many factors affecting the bond strength between the lightweight concrete and reinforcing steel, where the compressive strength plays an important role in bond strength, and the bond strength is increased by increasing the compressive strength. The AAC beams have the potential to be an excellently energy-saving construction material and is believed to emerge as an alternative to traditional reinforced concrete beam in the near future. This is proved by the experimental analysis.

Numerical Analysis of RC beam with High Strength Steel Reinforcement using CDP model

The article is based on preliminary research on use of high strength steel for RC elements. A reinforced concrete beam with a span length of 5700 mm has been subjected to four-point bending test. The bottom reinforcement of the beam was made of SAS670/800 high strength steel. This type of steel has no specific yield point. The yield limit declared by the manufacturer is specified as 670 MPa and the ultimate strength is equal to 800 MPa. The aim of the research was to establish a numerical model that would render properly the real beam behaviour. The model was created in the ABAQUS software using the CDP (Concrete Damage Plasticity) material model for concrete. The paper analyses the influence of several parameters on the results of numerical computations. The author’s aim is to define values of the dilation angle that should be implemented in the model. Generally, the value of this parameter is established a priori, without any justification. The analysis reveals that in a situation when the dilation angle is greater than or equal to 25 deg, the numerical model predicts properly the damage obtained in the experiment. For lower values of the dilation angle, the failure mode is not consistent with the actual beam behaviour in the experiment. Another issue is whether and how the results from the model are influenced by the choice of specified concrete tensile behaviour. In the CDP model, this property may be set in three ways: by giving the stress - displacement relation, stress - cracking strain relation or determining the fracture energy. All three alternatives are analysed and compared. Another aspect described in the paper, is the difference in load application through force control and displacement control as well as the influence of the amount of shear reinforcement. In order to analyse mesh size sensitivity, the results obtained for models with various mesh densities were compared.

N-M AND M-K RELATIONSHIPS OF REINFORCED CONCRETE COLUMNS IN TEC2018

Reinforced concrete elements subject to moment, shear and axial force due to different level of static and dynamic loads based on their location and material characteristics. These elements disseminate the loads based on their connections with other elements. In particular, each column in the structure exhibits "combined bending" behavior together with the resulting moment of the eccentric axial force exerted. In the case of the axial load acting on one of the symmetry axes (x or y axis) the uniaxial bending, and the axial load acting out of the symmetry axis, biaxial bending occurs. Also, since the structures are composed of two directional frames and slabs, the reinforced concrete columns are subject to combined bending effects in both directions. Therefore, the determination of the ultimate strength and behavior of the reinforced concrete columns depends on the interaction of axial force (N) and moment (M). In this study, the N-M diagram of reinforced concrete columns is given considering the section geometry, concrete and steel reinforcement strength and placement of the longitudinal reinforcements. The given N-M diagrams are prepared based on the axial force limits in codes. In addition, the N-e diagram showing the axial force and eccentricity relation of reinforced concrete column sections is given. Ductility ratios are given by plotting the moment curvature diagrams of the column sections at various axial force levels of the N-M diagram.

Kajian Kapasitas Lentur Balok Beton Bertulangan Bambu Petung

Reinforced concrete generally use steel reinforce material. Steel is quarry material that someday be exhausted and relatively high price. Hence,need to find the substitution material which a more affordable with the structure power that equivalent. Bamboo can be assessed solution as a substitution material of steel reinforce. This research looked at a bending capacity of the bamboo petung reinforce concrete beams with notch is 2 cm and 3 cm. The sectional form of the reinforce bamboo of arch ( 1 / 4 ) circle and ( 1 / 2 ) circle. Tensile testing sample of bamboo obtained average value of bamboo tensile strength is 288.81 mpa .A mixture of concrete f‘c = 17.5 MPa with the mixtures by virtue of SNI 7394-2008 .The testing results of compressive strength at the age of 3 days concrete 9.837 MPa . Sample beams made about 9 type reinforcement .From the flexural testing at the age of 28 days type reinforcement TB4 have flexural strength of 10.167 MPa value flexural approach strength steel reinforcement beams of 12.00024 Mpa.Keywords : bamboo petung, flexural beams, reinforcement bamboo

Flexural behavior of ECC-concrete composite beams reinforced with steel bars

This paper presents analytical technique and simplified formulas for the calculations of cracking, yield and ultimate moments of different cases as well as deflections of ECC-concrete composite beams reinforced with steel bars. The technique is based on the simplified constitutive models of materials, strain compatibility, perforce bond of materials and equilibrium of internal forces and moment. Experimental testing of eleven ECC-concrete composite beams reinforced with steel bars is also presented. All beams tested had the same geometrical dimensions but different steel reinforcement strength and ECC thickness. The proposed formulas showed good agreement with the experimental results of various moment values and deflections. A parametric analysis shows that yield and ultimate moments increase with the increase of concrete strength in case of compression failure but, essentially, remain unchanged in case of tensile failure. With increasing the tensile resistance, for example by increasing ECC height replacement ratio, reinforcement ratio, strength of steel reinforcement and ECC, ultimate curvature and energy dissipation increase in case of tensile failure and decrease in case of compressive failure. On the other hand, ductility and energy dissipation ratio decrease with the increase of reinforcement ratio and strength, but, essentially, remain unchanged with increasing the height replacement ratio and strength of ECC.

Evaluation of the influence of design factors on the CO2 emissions and costs of reinforced concrete columns

Reinforced concrete (RC) is one of the structural materials that produce environmental pollution. The objective of this study is to present design guidelines for reducing CO2 emissions or costs associated with structural materials in the structural design phase of RC columns. After identifying the cross-sections of RC columns with the minimum CO2 emissions or costs while satisfying the structural design conditions via a parametric study, the influence of the design factors (i.e., concrete strength, steel reinforcement strength, cross-section size, and amount of steel reinforcement) on the CO2 emissions and costs of RC columns are investigated. The results confirm that increasing the strength and amount of steel reinforcements is efficient for sustainable design, whereas increasing the strength of the structural materials and the amount of concrete is efficient for economical structural design.

Fracture toughness of thermostressed reinforcement and the effect of temperature variations

The effect of thermomechanical loading on the strength of steel reinforcement was examined in terms of fracture toughness. The fracture behavior of 35GS and 25G2S reinforcing steel specimens determined by temperature variations along the reinforcing bars was analyzed in fracture toughness estimation.

Enhancing the performance under close-in detonations with polymer reinforced CRC

Compact Reinforced Composite, CRC, is a high-strength cement-based composite possessing an enormous flexural and energy-absorbing capacity due to close-spaced high strength steel reinforcement and a high-strength cement-based fiber DSP matrix. The material has been used in various construction projects including as protection for explosion hazards. In connection with explosive impact, the fraction of shear reinforcement needed to obtain full flexural capacity is controlled by the stand-off distance. For close-in detonations, a high fraction of shock reinforcement is needed to obtain full flexural capacity without breaching. This paper introducesan efficient method for implementing high fractions of polymer shock reinforcement into a CRC element. Experimental tests and a preliminary finite element analysis were performed to assess the potency of this material.

Some controversial aspects of the seismic design of reinforced concrete building structures

Significant differences exist between the recommendations for seismic design of the codes and guidelines for reinforced concrete of different countries. Performance criteria for building structure to avoid unacceptable damage during various levels of earthquake hazard need to be refined. More accurate recommendation for the effective flexural rigidity of reinforced concrete members are required for linear elastic structural analysis to enable better estimates of the periods of vibration and the lateral deflections of statically indeterminate structures including the effects of cracking of concrete. Current code recommended values for flexural rigidity will generally lead to estimates of the periods of vibration and lateral deflections, which are on the low side. The capacity design approach to ensure the most appropriate mechanism of yielding will occur in the event of a severe earthquake is generally recognized by codes but to varying degrees of clarity, and the degrees to which capacity design is incorporated in each code varies significantly. High strength concrete and high strength non-prestressed steel reinforcement can be used in the design of buildings but the brittle behaviour of high strength concrete and the unusable yield strength of high strength steel reinforcement need to be considered. Important differences between codes exist in the rules for the quantity of confining reinforcement placed in reinforced concrete columns to ensure ductile behaviour. Significant differences also exist between the quantities of shear and confining reinforcement required in beam-column joints and in the anchorage of length of longitudinal reinforcement passing through beam-column joints. Precast concrete structures can be designed successfully for earthquake resistance but design codes in seismic regions contain provisions for precast concrete to varying degrees.