Compression Reinforcement Research Articles

Effect of concrete strength and tensile steel reinforcement on RC beams externally bonded with fiber reinforced polymer composites: A finite element study

Due to the continual deterioration of concrete infrastructures, the construction industry faces challenges in terms of their serviceability, structural strength, and durability. Therefore, efficient rehabilitation strategies are required to enhance their performance. Externally bonding fiber reinforced polymers (FRP) have evolved as a simple and convenient retrofit technique when compared to conventional techniques of strengthening. FRPs can be powerful toolsfor strengthening concrete structural members in shear and flexure because of their exceptional mechanical characteristics. Flexural strengthening is generally achieved by externally bonding FRP strips or laminates in the soffit side of beams, resulting in improved ultimate strength and bending capacity. This study aims to conduct a numerical parametric investigation on reinforced concrete (RC) beam specimens flexurally strengthened by externally bonding FRP. Three-dimensional finite element models of four RC beams strengthened with FRP and with different concrete compressive strength and flexural steel reinforcement were developed to predict their load capacity. Models were developed and simulated using finite element software called ABAQUS. The beam behavior was evaluated with the help of different material models available in the ABAQUS library. Study considerations included concrete damage plasticity, Hashin's damage in CFRP, and perfect bonding between CFRP and concrete interfaces. The parametric study included two groups of beams: one with varying concrete compressive strength (i.e., 25 MPa and 50 MPa) and the other with varying tensile steel reinforcement (5#14 mm diameter bars and 2# 22 mm diameter bars). The ABAQUS results were verified using experimental data from the previousliteratures.The computed numerical resultsand experimental results demonstrated reasonable accuracy for load–displacement curves and ultimate load capacity. It was found that the ultimate load increased significantly in high-strength (M50) beams with a higher number and smaller diameter (5#14 mm) tensile bars. In conclusion, RC beams with more compressive strength and tensile steel reinforcement boost the effectiveness of the external bonding technique.

Calculation of the formation of normal cracks in a reinforced concrete element based on the deformation theory of plasticity of concrete by G.A. Geniev

The authors present a refined method of determining the moment of cracking in reinforced concrete bar constructions using the diagram of deformation of concrete built on the basis of the deformation theory of plasticity by G.A. Geniev in which the stress and strain invariants of concrete are linked by nonlinear dependences. In the resulting defining equations, the hypothesis of flat sections, as well as the premise of reaching the limit values of concrete deformations on the stretched fibers of the cross-section are used. Stresses in concrete are determined through deformation values in accordance with the nonlinear deformation diagram of concrete. On the basis of the assumptions accepted, analytical dependences for determining the moment of cracking in the sections of bending elements with single and double reinforcement have been acquired. The formulas obtained were used in the analysis of various factors influence on crack resistance of bendable reinforced concrete elements. It was found out that the moment of crack formation practically does not change when percentage of reinforcement of longitudinal tensile or compressed reinforcement changes. The most effective method of crack resistance improvement is the increase of concrete strength. The proposed methodology is verified by comparison with experimental results on reinforced concrete prototypes. It is concluded that the use of the diagram of nonlinear deformation of concrete on the basis of the theory of plasticity by G.A. Geniev allows to estimate more strictly the crack resistance of reinforced concrete rod elements.

Betonarme Kirişlerin Moment-Eğrilik ve Etkin Kesit Rijitlkleri

In determining the seismic performance of reinforced concrete (RC) structures in national and international earthquake regulations, it is desired to use effective section stiffness of the cracked section in RC structural elements during the design phase. Although the effective section stiffness of the cracked section is not constant, it depends on parameters such as the concrete strength and reinforcement ratio. In this study, RC beam models with different concrete strength, tensile and compression reinforcement ratios were designed to investigate nonlinear moment-curvature relationships and effective stiffness coefficients. Analytically investigated parameters were calculated from TBEC (2018), ACI318 (2014), ASCE/SEI41 (2017), Eurocode2 (2004) and Eurocode8 (2004, 2005) regulations and moment-curvature relationships. The effective section stiffness coefficient obtained from the analyses were compared with the effective section stiffness coefficient given for RC members in different regulations. The results obtained at the end were examined by comparing them according to different parameters and models. For constant concrete strength and tensile reinforcement ratio in RC beams, with increasing compression reinforcement ratio, effective stiffness coefficient values increase. In RC beams with constant compression and tensile strength ratio, effective stiffness coefficient values increase with increasing concrete strength. The compression reinforcement ratio has been proved to be effective on the maximum moment bearing capacity of the RC beams, effective flexural stiffness and effective stiffness coefficient and ductility of the sections.

Development of strength interaction diagrams for designing precast concrete tunnel lining segments reinforced with GFRP bars

Replacing conventional steel reinforcement with noncorroding glass fiber-reinforced polymer (GFRP) reinforcement can be an effective solution to mitigate the corrosion problem in precast concrete tunnel lining (PCTL) segments. PCTL segments should be effectively designed to withstand the applied load during production, transportation, construction, and service stages. The literature, however, offers limited design recommendations or guidelines for designing GFRP-reinforced PCTL segments. In this study, an experimental program was conducted to investigate the effect of reinforcement ratio and tie configuration on the behavior of GFRP-reinforced PCTL segments at the service and ultimate stages. Novel procedures and equations were developed to obtain axial load–bending moment interaction diagrams at the ultimate and service stages. In addition, interaction diagrams were developed to consider the creep-rupture stress limits in GFRP bars. Furthermore, axial load–shear-strength interaction diagrams were developed for GFRP-reinforced PCTL segments, as well as a simplified procedure to control cracking. Afterward, a parametric study was performed to evaluate the effect of concrete compressive strength, reinforcement ratio, and cross-sectional thickness on the axial load–bending moment interaction diagrams of GFRP-reinforced PCTL segments. The analytical results were compared to the experimental results from the current study and the literature. The comparison revealed that the proposed analytical procedure was suitable for designing GFRP-reinforced PCTL segments.

Investigation of the effect of using geogrid, short glass, and steel fiber on the flexural failure of concrete beams

This research studies the flexural behavior of concrete beams reinforced with biaxial geogrids, distributed short glass and steel fibers. No longitudinal steel reinforcement bars were used. Therefore, an amount of short glass and steel fibers was used to improve the concrete beam behavior against flexural failure. Eleven specimens of single reinforced (flexural reinforcement) concrete beams and double reinforced (compression and flexural reinforced) concrete beams using two biaxial geogrids sheet layers, with randomly distributed short glass and steel fibers were cast. The samples were tested using two points of load along the beam specimen span with an increment of loading by 5 KN to evaluate several parameters. The studied parameters are using geogrids as a main flexural reinforcement, using geogrid sheet layers as a flexural and compression reinforcement, using short glass and steel fibers as an additional reinforcement of concrete with various ratios 0.25 %, and 0.75 %. The test results indicated that the use of geogrid layers as the main flexural reinforcement improved the behavior of the concrete beam specimens at failure. As well as; more enhancement of beam specimens at failure was observed when using short glass and steel fibers with geogrid reinforcement in concrete beams. The tested beam specimens which were reinforced by geogrids in the flexural and compression zone using 0.75 % of steel fibers gave better results due to modes of failure, toughness, failure load capacity, crack width, and post cracking stiffness.

Calculation on flexural capacity of recycled aggregate concrete beams

Based on the constitutive relation of recycled aggregate concrete (RAC, referred to as recycled concrete), from the calculation formulas of the equivalent rectangular block parameters in the compression zone of recycled concrete beams under different recycled coarse aggregate replacement ratios, the calculation formulas of the key parameters 𝛼1 and 𝛽1 of recycled concrete are deduced. Based on 𝛼1 and 𝛽1, the flexural bearing capacity of recycled concrete beams is given. In addition, the nonlinear finite element method is applied, and the simulation results are compared with the calculation results to verify the accuracy of the calculation results. Then, the limit compression zone height and maximum reinforcement ratio of recycled concrete beams, as well as the variation characters of compression zone height and reinforcement ratio under certain size and load are analyzed and obtained.

Emergency stop lane design on national road in West Sumatra (case study: Panorama 1 Sitinjau Lauik)

West Sumatra Province has geographical conditions consisting of lowlands and highlands. These geographical conditions certainly affect the geometric conditions of the road, especially on the Panorama 1 Sitinjau Lauik National Road Section. One of the factors that cause accidents is a vehicle that has failed brakes. This study aims to calculate the length of the emergency stop lane; plan the structure of the building; and plan a modeling design. The results of the Emergency Stop Route Design research showed that the overall dimensions were 240 m. Preliminary design results are as follows: Beam (600 mm width and 1100 mm height), Amount of flexural reinforcement: Compression reinforcement 8 D – 25 mm; Tensile reinforcement 4 D – 25 mm; Amount of shear reinforcement: Area of support 2Ø13-100 mm, Area of field 2Ø13-150 mm. Cross beam width 300 mm and height 600 mm. Amount of flexural reinforcement: compression reinforcement 3 D 16 mm; Tensile reinforcement 3 D 16 mm. Number of shear reinforcement: Support area 2Ø13-100 mm and field area 2Ø13-150 mm. For longitudinal reinforcement, the diameter is ø10 – 200 mm, the tie reinforcement has a diameter of ø10 – 200 mm and the vertical reinforcement has a diameter of ø16 – 150 mm.

ОСОБЕННОСТИ ДЕФОРМИРОВАНИЯ СЕЧЕНИЙ ИЗГИБАЕМЫХ ЖЕЛЕЗОБЕТОННЫХ ЭЛЕМЕНТОВ ПРИ ДЕЙСТВИИ НАГРУЗОК БОЛЬШОЙ ИНТЕНСИВНОСТИ

Many buildings are exposed to special effects of high intensity. When calculating reinforced concrete constructions both for special emergency loads and for seismic loads, the development of plastic strains in reinforcement is supposed just at the design stage. The experimental investigation of plastic deformations influence of the stress-strain state of normal sections of bending reinforced concrete elements has been made. According to the results of experiments, it has been found, that the hypothesis of plane sections is not observed in all cases. The approximation of deformations graph along the cross-section height by the bilinear function, variable during the load process, i.e hypothesis of bilinear sections, is more accurate. The dependence of coefficient A of the hypothesis of bilinear sections on the coefficient of plasticity for reinforcement deformations has been determined based on the results of numerical calculations of beams with symmetric reinforcement and beams without compressed reinforcement in a finite element software package Abaqus. The comparison of obtained numerical results with experimental data has been made, which has shown their satisfactory convergence. The maximum deviation does not exceed 13 %. The assessment of influence of coefficient of hypothesis of bilinear sections on the limit value of coefficient of plasticity for curvature, corresponding to the beginning of the destruction of compressed area of concrete is given.

Role of shear reinforcements on the punching shear resistance of two-way RC slab subjected to impact loading

• Numerical analysis of punching shear resistance of RC slab subjected to impact loading. • Impact test setup is modeled in ABAQUS/Explicit computer code. • Computational results compared with the experimental ones from literature. • Parametric study to analyze the effect of stirrups’ width, spacing, and the number of compression reinforcement bars. • Shear reinforcement was able to improve the impact resistance of slab against punching. The possibility of acting impulsive loads such as blast and impact on gravity load-carrying structural members such as slabs during their construction and service life cannot be ruled out. Studies on the response of RC slabs under impact loading are available in the literature. However, the role of the shear reinforcements in the slab under impact is not fully understood and therefore needs further investigation. The slab subjected to concentrated impact loading in the form of falling construction equipment, landslip hazards, and other similar events may cause damage through punching or perforation. Under quasi-static concentrated loading, the design parameters that contribute to the shear resistance against punching are (1) concrete strength, (2) flexural steel, and (3) shear stirrups. In this work, a three-dimensional finite element model of a square concrete slab of normal strength concrete (30.10 MPa), 1000 mm × 1000 mm × 75 mm, with tension reinforcement only (0.88 %) subjected to low-velocity drop-weight impulsive impact is developed in ABAQUS/Explicit computer code considering Concrete Damage Plasticity and Johnson-Cook models with strain rate effects and validated with the experimental results in the open literature. The nonlinear interaction between the concrete and steel reinforcements is taken into account. The drop weight is a hard steel cone frustum-headed striker/impactor with a flat impact face of a total mass of 105 kg allowed to fall from 2500 mm height, impacting the slab at its centroid. To study the effect of the shear reinforcement on the impact resistance of the slab, the shear reinforcement has been varied by varying the stirrups’ width, spacing, and the number of compression reinforcement bars while keeping the impact load and other design parameters such as concrete/steel strength, support conditions, slab thickness, span, and flexural tension steel constant. Numerical simulations are executed and the outcomes are presented in terms of displacement–time plots, damage/stress profiles, damage modes, and damage dissipation energy. The results so extracted are discussed and compared. It has been found that the increase in shear reinforcement by decreasing the spacing of the stirrups improves the impact resistance of the slab against punching.

Additional Shear Strength of RC Beams due to Compression Reinforcement

Additional Shear Strength of RC Beams due to Compression Reinforcement

Experimental Study on Steel Fiber Reinforced Concrete

Abstract: As of today, there are no official set of rules for designing fiber reinforced structures, but there are several suggestions for rules which are described in the report. Mechanical properties of concrete and mortar reinforced with randomly distributed smooth steel fibers were investigated to understand the mechanism of fiber reinforcing. Different volumes, lengths, orientations and types of fibers were used. Fibers were compared with conventional reinforcement in flexure, tension and compression. It was observed that the significant reinforcing effect of fibers is derived after the cracks are initiated in the matrix, just as with conventional tensile and stirrup reinforcement. The post-cracking resistance of fibers is considerably influenced by their lengths, orientation, and stress-strain relationship. The spacing of reinforcement appears to have little influence on crack propagation below a certain length. This Project consist of M20 Grade concrete where the compression test and split tensile test are done. The cubes and cylinders are casted for 7,14 and 28 days of curing. Steel fibers are used in this project with three different volume percentage of fibres (0.50%,0.75% and 1.0%). The inclusion of fiber showed improvement of compression strength and tensile strength.

Numerical investigation on DE-strengthened-RC beams without steel shear reinforcement

This study presents a two-dimensional nonlinear finite element (FE) model for Deep Embedment (DE) strengthened reinforced concrete (RC) beams without existing steel shear links. The FE model was developed and validated against experimental results reported in published literature. The parametric study was thereafter conducted to examine important parameters influencing the strengthened behavior. The parameters were concrete compressive strength, beam width, beam size, and tension reinforcement ratio. The FE model accurately predicted experimental results with a mean predicted-to-experimental value of 1.04. The FE results showed that the percentage of shear strength provided by embedded steel bars was almost constant once both concrete strength and tension reinforcement ratio were increased. However, an increase in the beam width resulted in a decrease in the percentage of shear strength gain due to embedded steel bars. Shear stress at failure decreased once beam size was increased for both unstrengthened (control) and DE-strengthened beams. The percentage of shear strength provided by embedded steel bars decreased from 47.9% to 27.6% as effective depth was increased from 261.5 mm to 523 mm.

Analytical model of deformation of reinforced concrete columns based on fracture mechanics

When conducting seismic calculations of reinforced concrete buildings and structures, it is quite important to use nonlinear models of structural performance, including those taking into account the overcritical operation in the fracture stage. The application of such models is especially important if the structures have an initial damage from fire or corrosion, as well as mechanical damage caused by force factors. The purpose of this study is to develop an analytical model of the deformation of eccentrically compressed reinforced concrete columns considering the stage of failure, which includes such processes as spelling of the protective layer, loss of stability of compressed reinforcement, and softening of confined concrete after reaching the design resistance. The existing models describing hysteresis behavior of reinforced concrete structures under low-cycle loading have been reviewed. The models have been analyzed in terms of considering the defining monotone curves, which are the boundaries of cyclic deformation. The model proposed in the research is constructed by analyzing the stages of the stress-strain state of a reinforced concrete column. At each stage, formulas are found for determining moment and curvature by solving equations of equilibrium of internal forces. Calculations based on the obtained model for a particular reinforced concrete column are carried out, monotonous diagrams are obtained, and a conclusion about the significant influence of the level of axial load on the character of deformation is made. On the basis of the obtained model, the construction of hysteresis diagrams under low-cycle loading is expected in the future.

Numerical analysis of high-strength reinforcing steel with conventional strength in reinforced concrete beams under monotonic loading

Abstract This work presents finite element (FE) modeling using the ABAQUS program to investigate the effect of steel reinforcement with three different types of high-strength steels, grades 420, A1035, and SD685 on the flexural behavior of RC beams under monotonic loading. Experimental findings from the literature have been used to validate the proposed model. The numerical load, deflection, mode of failure, failure concrete strain, and bottom steel strain at failure of 24 numerical specimens with collapsed conditions of tension-controlled, balanced, and compression-controlled are recorded. Also, the effect of compression reinforcement is being investigated. The results reveal that the flexural behavior of the experimental test for the three steel grades is well validated by FE analysis. The ductile and brittle behavior features of yield strength (YS) larger than 420 can be predicted for specimens designed according to current standards ACI-318M-19. Also, the compression reinforcement improves load capacity while reducing displacement. It may be argued that when YS decreases, tensile stress and strain of flexural rebar rise, causing the beam to become more ductile. When the YS increased, the brittle behavior was induced.

Behavior of dispersion-reinforced concrete under dynamic action

The work of structures under alternating dynamic load has also been studied and modeled. Based on the results of experimental studies, a comparison was made of the work of dispersed-laminated structures under alternating dynamic action of high intensity with the work of reinforced concrete beam elements under similar influences. Dispersed concrete reinforcement changes the properties of the latter. The results of comparative experimental studies of cubes and prisms with different degrees of compression reinforcement are presented. The research results showed a significant effect of dispersed reinforcement on the operation of structures under the investigated influences and the feasibility of combined reinforcement of structures. The use of dispersed reinforcement in structures will improve their performance.

Experimental Study on Axial Compressive Load-Bearing Performance of RC Short Columns Strengthened by All-Light Ceramsite Concrete

Previously conducted studies have established that all-light ceramsite concrete has the characteristics of light weight and high strength. It is a good material for strengthening and has a good application prospect when strengthening existing RC columns by the enlarged cross-section method. Additionally, a good combination of new-to-old concrete is crucial to the best performance of RC columns strengthened by the enlarged section method. Therefore, to investigate more comprehensively the axial compression reinforcement effect of RC short columns strengthened with all-light ceramsite concrete, one unreinforced short column, one RC short column strengthened by ordinary concrete, and four RC short columns strengthened by all-light ceramsite concrete with different interface treatments were produced. Moreover, axial pressure tests were conducted on them. The findings showed the following: (i) Short-column specimens strengthened by all-light ceramsite concrete had obvious ductile damage characteristics. (ii) The type of bonding surface greatly affected the strengthening effect. The order of ultimate load-bearing capacity improvement was post-installed rebar + epoxy resin interface agent, epoxy resin interface agent, post-installed rebar, and chiseling. (iii) When post-installed rebar + interface agent was used, the epoxy resin interface agent played the primary role during the pre- and mid-loading period. The post-installed rebar started to function only in the mid- and late-loading period. (iv) Strain growth of the existing longitudinal bar and strengthening longitudinal bar was not synchronized in the late-loading period. The strain in the existing longitudinal bar grew rapidly and nonlinearly, while the strengthening longitudinal bar still grew linearly. (v) The calculation formula in specification GB50367-2013 is also applicable to ceramsite concrete, and the correction factor can still be 0.8. When the interface treatment method is post-installed rebar + epoxy resin interface agent, the correction factor can be 0.9.

ANALISIS MUTU STRUKTUR BETON BERTULANG PROYEK PEMBANGUNAN X-CHANGE MALL 2

Every construction is expected to run well and will be completed in accordance with the planning. Therefore, project quality control is needed. Project quality control is extremely useful for one-time development so that the building can achieve its predetermined quality and standards. The purpose of this study is to find out the quality control system of reinforced concrete of upper structures on Columns, Beams, and Plates and whether the quality results of the reinforced concrete structure can meet the specified requirements. The data used in this study were the results of concrete compressive strength tests and steel reinforcement tests that had been carried out in the laboratory. This research was needed to minimize delays and costs so as not to miss the predetermined quality and standards. This research used the AS/NZS 4360 calculation method in which the analysis was carried out by taking into account the level of risk of the probability that occurs and the impact on costs, where the quality applied must be in accordance with the RKS that has been set on the project, the calculation was carried out using Excel in accordance with the formula to determine the level of risk in each structural work. The data were collected by distributing the questionnaire to each individual where the questionnaire contained work items to be analyzed from the division. The calculation analysis has obtained the result of the risk level for each structural work, column work worth 5.20, beam work 5.97 and floor plate work worth 6.00 which means that the work of the structure has a moderate level of risk. Keywords: Quality Control, Construction Implementation, Risk Factors, AS/NZS 4360.

Stress–strain relationship of ductile materials and flexural behavior of ductile over-reinforced concrete beams

This paper aimed to investigate the effect of using ductile materials in the compression zone on the flexural performance of over-reinforced concrete beams. In order to avoid brittle compression failure, partial replacement of concrete with ductile materials layer in the compression zone was used. Four over-reinforced concrete beams of size 120 × 180 × 1,300 mm were cast and tested under three-point loading conditions. The steel fibers reinforced concrete (SFRC), slurry infiltrated fiber concrete (SIFCON), and ultra-high performance fiber reinforced concrete (UHPFRC) were used as ductile materials. The flexural capacity of the beams, failure modes, crack patterns, load-deflection relationships, ductility index, and toughness were investigated. The results showed that using ductile materials in the compression zone is an effective technique to increase the ultimate load, ductility, and toughness by up to 52.46, 84.78 and 279.93%, respectively, compared to the reference beam. In addition, the failure mode changed from brittle to ductile failure. Noting that the use of SFRC layer enhanced the ductility of over-reinforced concrete beams more than using UHPFRC and SIFCON layers. Also, one of the main advantages of this technique is led to increase the tensile reinforcement ratio up to 8.548% without needing the compressive reinforcement. Thus, ductile composite beams with a high flexural capacity were generated using an economical amount of ductile materials.

Behavior of CFRP-reinforced concrete columns at elevated temperatures

Current design codes preclude FRP bars being used as main reinforcement in compression members because of the general recognition that the compressive strength of FRP bars is lower than their tensile strength and the lack of reliable data related to their performance at elevated temperatures. The present study evaluates the properties of CFRP bars as compression reinforcement in RC columns and investigates experimentally the structural performance after cooling of the columns reinforced with CFRP bars that were subjected to elevated temperatures. Twenty-four short columns specimens were fabricated considering the use of CFRP bars or steel bars as main reinforcement, the spacing of tie bar confinement and the exposure temperature (0, 150, 300 and 450 °C). The test members were subjected to concentric axial loading and the test results measured after cooling down to room temperature were compared with analytic results based on current standard for concrete columns. The investigation showed that, compared to the CFRP-reinforced columns let at room temperature, those exposed to elevated temperatures experienced compressive resistance that first improved by 3 % to 15.9 % at 150 °C, but degraded at higher temperatures by 7 % to 13.6 % at 300 °C, and by more than 50 % at 450 °C.

Experimental and numerical evaluation of the structural performance of corroded reinforced concrete beams under different corrosion schemes

The effect of steel corrosion on the structural performance of reinforced concrete (RC) beams is a complex phenomenon concerning all types of reinforcing steel (tension, compression, and shear reinforcement) which has not been fully investigated experimentally or through modelling. The parameters used in models have not been fully employed in the non-uniform corrosion of steel bar, the buckling effect of corroded compression reinforcement or bond slip at the steel to concrete interface due to the combined effects of longitudinal and shear reinforcement corrosion. The objectives of this paper are i) to experimentally investigate the effect of three corrosion schemes (tension reinforcement corrosion; tension and compression reinforcement corrosion; tension, compression and shear reinforcement corrosion) on the structural performance of RC beams through the investigation nine beams, each with dimension of 150 mm width, 200 mm height and 2100 mm length ii) to employ a finite element method (FEM) to model both the control and corroded RC beams in which non-uniform corrosion of steel bars has been modelled by varying the bar diameters and the locations of corrosion pits including the buckling effect of compressive reinforcing steel bar, iii) to propose a modified bond slip model at the longitudinal steel–concrete interface due to the combined effect of longitudinal and shear reinforcement corrosion. The experimental results show that the yield and ultimate strength of the RC beams reduced under the three corrosion schemes. The yield strength of corroded RC beams is affected by the tension reinforcement corrosion while the ultimate strength is influenced by both the tension and compression reinforcement corrosion. Shear reinforcement corrosion contributes to the reduction in flexural strength of the RC beams due to the reduction in confinement of concrete. The failure modes and the ductility of the corroded RC beams are influenced by the non-uniformed corrosion and its distribution along the steel bars. The proposed FEM demonstrates good correlation with the experimental results, with the difference in ultimate flexural strength from the FEM and the experimental test in the range of 0.1 % to about 4 % for small pitting corrosion beams and up to 10 % for critical pitting corrosion beams.