Flexural Shear Cracks Research Articles

Comparative Study of Numerical Methods for Predicting Crack Propagation in Reinforced Concrete Hollow Core Slabs

Hollow core slabs are commonly used in prefabricated building construction and are calculated and constructed using gravity loads. The dead loads of the structure are reduced by using this slab system. Different criteria, such as the initiation and propagation of cracks in the hollow core slab, are used to analyze these slabs. Fracture mechanics is the basis for studying crack propagation. The present study was conducted to analyze the propagation of cracks in hollow core slabs under common loading conditions using the finite element method and numerical modeling to analyze cracks in reinforced concrete members. This research is theoretically conducted using finite element software. This research takes into account the potential varieties of cracks in concrete slabs. Slabs should consider all three types of cracks, which are shear, flexural, and flexural-shear cracks obtained from the reference test. Two Contour integral and XFEM methods are used to analyze cracks in Abaqus software. To validate and control the modeling process, the laboratory results of the research of Ibrahim N. Najma, Raid A. Daudb, and Adel A. Al-Azzawi. December 2, 2019, has been used. The outcomes of this study showed that the probability of the formation of a flexural-shear crack in the slab is higher than in other crack forms.

Flexural behaviour of GFRP-reinforced concrete pontoon decks under static four-point and uniform loads

Concrete pontoon decks are subject to flexural loading actions under concentrated and uniform loads caused by self-weight, live loads, and wave actions. This study investigated the structural behaviour of concrete pontoon decks reinforced with glass fiber-reinforced polymer (GFRP) bars under static four-point and uniform loading conditions. Five large-scale GFRP-reinforced concrete decks with a length of 2400 mm, width of 1500 mm, and thickness of 125 mm were tested to evaluate their moment capacity, strain behaviour, cracking propagation, and failure mechanism. The effects of the loading configurations, reinforcement arrangement, and cutout simulating the piles' location were evaluated. The edge cut-out initiated flexural-shear cracks, causing the pontoon decks to fail at an effective bending stress 10% lower than the solid decks. Decreasing the span-to-depth ratio from 5.6 to 4.0 increased the induced shear stress of a section and caused the deck to fail by shear compression. Uniform loading resulted in an even load distribution and minimized the stress concentration around the cutout. An increase in the effective depth improved all deck flexural characteristics. The equations in ACI 4401. R-15 and CSA S806–12 provided an accurate prediction for solid decks but overestimated the ultimate flexural strength of the GFRP-reinforced concrete decks with a cutout.

Data-driven reliability framework for qualitative damage states of reinforced concrete beams under blast loading

The incessant demand for protective infrastructure research has been motivated by recent accidental and intentional explosion events. This has led to a significant increase in blast design approaches and modern methods of structural analysis. When considering the analysis and response of blast-loaded members, like the identification of crack patterns and failure modes (CP & FM) of reinforced concrete (RC) beams, the current literature heavily depends on complex numerical modeling. Recently, the adoption of machine learning (ML) modeling to readily predict damage state labels of blast-loaded RC beams has emerged as a competitor to numerical methods. In either modeling method, outputs of damage states are often oversimplified as deterministic labels without elaborating on the possibility of alternative damage state. To extend on the practical usage of deterministic modeling, the present study introduces a probabilistic framework which integrates ML models towards ascertaining the probability of different CP & FM classes via the Monte Carlo simulation. The framework accounts for the uncertainties of different beam and blast parameters and incorporates four damage states of flexural cracking, bending failure, flexural-shear cracking, and crushing failure. The developed framework was evaluated against forty-two blast-loaded RC beams available from several previous experimental studies and exhibited excellent predictive performance while providing significant insight to the occurrence of all four damage states. In addition, extensive Blast Reliability Curves (BRC) were developed for eighteen RC beam cases over a wide range of blast intensities and the effects of beam and blast parameters on qualitative damage states were evaluated. The most notable observation was that the sensitivity of both concrete and steel strengths on damage state probabilities increased with reinforcement ratio. The BRCs depicted an elaborate transition of damage states with varying blast magnitudes. Also, the limitations, sources of error, and further improvements associated with the proposed methodology were clearly defined. Overall, the resulting probabilistic structural blast analysis introduced by the proposed framework serves as an intricate approach to providing greater comprehension to the CP & FM response of RC beams under blast loading which aims to promote confidence in decision making within protective design processes.

Flexural performance of concrete composite metal decking with different base-metal-thickness new smart system

Industrial Revolution 4.0 has led to the age of automation and industrialized building systems. Composite slabs gain its popularity in the modern construction industry due to its speed of construction and cost saving features with lightweight structure. However, from time to time the manufacturer will introduce new corrugated roll forming cold formed steel metal decking systems, which cause the end user to ponder if the product is up to desired performances. The aim of this research is to study the structural performance of SMARTDEK composite slab composed of 0.75 mm and 1.0 mm thickness compared to the conventional reinforced concrete slab under flexural strength, deflection, and failure mode. Concrete slab with thickness of 130 mm was constructed to uncover the ultimate load capacity of the slabs. The novelty of this research is the discovery of longitudinal shear resistance constant through derived equations and the new SMARTDEK profiled composite slab performs better than the conventional slab. Four-point flexural tests were conducted according to ASTM C293 standards to determine the performance of the slabs, and three linear variable displacement transducers (LVDTs) were used to determine the deflection of the slabs. Load-Deflection graphs were plotted for the specimens to determine the yielding point and ultimate point of the slabs. The composite slab with 1.0 mm Base-Metal-Thickness (BMT) had the highest ultimate strength at 75 kN, followed by the composite slab with 0.75 mm BMT at 65 kN, and finally the conventional slab at 39 kN. The failure mode of the conventional slab was pure flexural; while the composite slab first failed in flexural, followed by longitudinal slip failure due to flexural and flexural-shear cracks, which disabled the composite action between the concrete slab and metal decking. The finding showed that the increasing thickness of the metal decking improves the slab strength which results in higher ultimate strength and reduces the overall deflection of the slab. Moreover, the breakthrough of this research is that increasing the overall thickness of the slabs increases the performance in loading’s capacity which could result in higher ultimate strength.

Analysis of cracking evolution mode of the monobloc sleeper

PurposeMonobloc sleepers have several problems related to bending cracking, especially longitudinal cracking and cracking at rail seat under preload release. Therefore, the purpose of this study is to describe the behavior and cracking mode of prestressed concrete railroad sleepers under static loads using the positive test. Experimental tests followed by 3-D numerical models were performed of the same test.Design/methodology/approachTwo steel supports were placed on the rail seat. During a progressive loading, the initiated cracks had approximately the same amplitude as those obtained from the numerical model. The type of cracking depends on the intensity of the applied static load and the loading rate. A validated three-dimensional digital model was established. The obtained results showed a perfect resemblance to the experimental tests. The final design was optimized and verified using a validated numerical simulation.FindingsAt low static loading levels, the first flexural shear cracks appeared at a vertical position located between the two steel supports. At higher static loading levels, bending shear cracks have occurred. The latter are inclined at the steel supports. It was proven that for higher loading levels, shear cracks were the primary mode of failure.Research limitations/implicationsOwing to the sensitivity of monobloc sleepers to technology production, the results are limited by the maximal loading and press used.Practical implicationsNumerical modeling greatly reduces uncertainties in laboratory testing and is an important tool for visualizing and quantifying rail seat cracks to understand behavior and predict collapse.Social implicationsEnsuring human life during rail operations is one of our the long-term priorities. This cannot be done unless the authors manage to master the manufacturing tool for sleepers while controlling the limitation of crack propagation.Originality/valueThe three-dimensional numerical established model has been checked and validated against the experimental results using the positive test to understand the behavior and the cracking mode of prestressed concrete railroad sleepers under static loads. The proposed numerical model has been more refined for a later more complex application by reducing the computation time.

Fresh and hardened state performance of self-compacting slag based alkali activated concrete using nanosilica and steel fiber

This study investigates the fresh and hardened state performance of slag-based self-compacting alkali-activated concretes (SCAAC) reinforced with steel fibers (SF) and nano-silica (NS), cured at an ambient temperature. Two different hooked-end SF with two fiber volumes and NS were used to examine the combined effect of the SF volume ratio, SF aspect ratio, and NS on the fresh and hardened state performance of SCAAC. In extension, the influence of specimen thickness to steel fiber length (d/FL) ratio on the failure modes of the bending specimens was evaluated. The fresh state properties were evaluated via T50 value, slump flow, V-funnel, and L-Box tests, while the hardened state properties were studied through compressive strength, splitting tensile strength, modulus of elasticity, and flexural tensile strength tests. The relationship analyses were carried out among fresh and hardened state properties, and scanning electron microscopy (SEM) was also conducted to examine the microstructure. The results indicated that fresh state performance was favorably affected by NS inclusion but adversely influenced by SF content and aspect ratio. The hardened state performances enhanced with a higher amount of SF volume and an aspect ratio. Also, the NS improved the splitting tensile and flexural strength but decreased the compressive strength and elasticity modulus of the specimens. The d/FL ratio was found a significant parameter on failure modes, and the specimens having a d/FL ratio of 3.33 showed flexural cracks. In contrast, the specimens having a d/FL ratio of 1.25 exhibited inclined flexural-shear cracks, especially for 1% SF.

Investigations on rheological and mechanical properties of self-compacting concrete (SCC) containing 0.6 μm eggshell as partial replacement of cement

Present research for the continually expanding construction sector has advanced to an investigation of Self-Compacting Concrete (SCC). As a result of the impact on economic and sustainable values, the demand for such innovation is growing rapidly. SCC is a self-consolidating concrete that does not require any kind of compaction. Numerous researchers have boosted the growth of the existing SCC via eco-materials. In particular, in the production of SCC, it is environmentally friendly to substitute cement with eco-materials. Eggshell is one of the possible substitutes for cement powder as it encompasses a compound of calcium. The key reason for this initiative is the restriction of the site area and the intention to lessen the warming effect. This research describes SCC beams’ flexural performance and crack behaviors through experimental evaluation. The SCC mixing proportion containing 0.6 µm eggshell was engineered and its compressive strength tested. Slump flow, L-box and sieve segregation tests were used to estimate the material characteristics of concrete mixture. Mechanical properties such as compressive and flexural strengths of all SCC specimens were evaluated at 28 days. Flexural characteristics, such as the load–deflection relationship and the crack propagation of the SCC beams, were evaluated in the light of the different shear span to the effective depth ratio (a/d). The ultimate flexural strength and crack width of the SCC beams were compared with the theoretical values. Experimental findings revealed that the flexural strength of the SCC beams containing eggshell are comparable with Eurocode2. The crack width was below Eurocode2 allowable crack control in most cases. On the SCC beam specimens, three types of crack patterns were found, categorized as flexural, shear and flexural-shear cracks.

Finite Element Analysis of One-Way Hollow Plate Capacity with Bamboo Apus and Bamboo Petung

Design capacity is one of the main parameters in the analysis of concrete slab behavior. In general, bent tests for concrete slab will be tested experimentally in the laboratory. However, it requires a lot of energy, cost, and a long time. For that we need a simulation approach with numerical methods that is the finite element method using ABAQUS program. The test object is a composite structure in the form of a one-way hollow plate with bamboo Apus and Petung as structural reinforcement, the test object is modeled in a 3D solid model with a concentrated load. Furthermore, material will be inputted their properties based on the result of experimental tests. Numerical analysis using ABAQUS shows similar collapse behavior with experimental analysis, yet the result of concrete slab capacity to the ultimate and the deflection indicates a difference in the value of the experimental tests. Tests with numerical and experimental methods, both concrete slab specimens with bamboo apus and petung produce a similar crack pattern, namely flexural shear crack. The maximum stress hollow concrete slab bamboo apus +17.71 Mpa and bamboo petung +23.2 Mpa

Debonding Failure in FRP Reinforced SHCC Beams Induced from Multiple Flexural-Shear Cracks under Three-Point Bending Test

Strain hardening cement-based composites (SHCC) beam externally bonded with glass fiber-reinforced polymer (FRP) plate was examined under three-point flexural test. The effects of the type of substrate used (plain cement mort... | Find, read and cite all the research you need on Tech Science Press

Pengaruh Sambungan Beton Pracetak Hollow Block terhadap Pola Retak yang Timbul

<p>Hollow block precast concrete which was combined into a beam casting by adding concrete and steel inside and called as “hollow block reinforcement concrete beam”. The aim of this research was to knowing the crack pattern due to the connection of hollow block reinforcement concrete beam. The specification of ACI (American Concrete Institute) 211.3R-02 and ASTM (American Society for Testing of Materials) were used in this research. The object were two normal reinforcement concrete beam and two hollow block reinforcement concrete beam with size 15 cm x 20 cm x 210 cm. The reinforcement concrete beam was tested by using load cell. The result showed the variety of crack pattern which are flexural crack and flexural-shear crack. For normal reinforcement concrete beam, flexural crack formed at 0.95 ton and flexural-shear crack at 2.83 ton with its duration was 5 minutes and 29 seconds. For hollow block reinforcement concrete beam, flexural crack formed at 1.16 ton and flexural-shear crack at 1.98 ton with its durat on was 6 minutes and 8 seconds. The result also showed that hollow block reinforcement concrete beam was more ductile due to crack pattern than normal reinforcement concrete beam.</p>

Assessment of performance criteria of reinforced concrete beams retrofitted with FRP fabrics subjected to extreme impulsive loading

The study performed in this paper is limited to the reinforced concrete structures, in which the behavior of reinforced concrete beams retrofitted with FRP fabrics subjected to extreme loading is investigated. In this regard, numerical modeling using finite element software LS-DYNA is carried out. Numerical results are validated against the results of laboratory experiments. Strengthening of beams with an external composite layer of carbon, glass and Kevlar fibers are considered. Common performance criteria of concrete members such as deflection ratio, support rotation, and ductility ratio as well as crack pattern and energy absorption are investigated. Results show full wrapping mode with carbon fibers leads to the most reductions in the growth of flexural cracks as well as flexural-shear cracks along the free span of the beam. The ductility of the beam is reduced in different states of retrofitting, which the greatest amount of ductility reduction is obtained when reinforced with carbon fibers. Elastic and plastic energies absorbed by the retrofitted beam are, respectively, increased and decreased in all of the investigated cases. Retrofitting with carbon fibers in different states shows the largest increase in the absorption of elastic energy and also the greatest reduction in the plastic energy absorption.

Simplified mechanics-based approach for modeling of flexurally dominated reinforced masonry structural wall systems subjected to lateral load

This paper presents a simplified analytical approach for modeling the behavior of both individual reinforced masonry structural walls (RMSWs) (component level) and systems of RMSWs as the main lateral load resistance system (LLRS) (system level) under lateral loading. Analytical modeling of individual RMSWs, with different end configurations (rectangular, flanged & end-confined), was achieved by generating the load-displacement relationships for these walls based on simple mechanics and accounting for plastic hinging. Knowing that plastic hinging is concentrated at the base of cantilever structural wall, its value was estimated based on experimental results and plasticity theory, taking into consideration the effect of strain penetration inside concrete foundation, inclined flexural-shear cracking and variation of curvature profile following yielding. Also, analytical modeling of a system of RMSWs may be conducted and the displacement of each wall can be calculated by simple geometrical relations, if the displacement of the center of mass (CM) and the rotation angle of the building are known. Results of some experimental tests were used to verify the results of the developed analytical models for individual RMSWs. The maximum error obtained in all models at maximum load, deformation at maximum load and deformation at 80% strength degradation, compared to experimental results, were 8.05%, 8.55% and 9.87% respectively. A third-scale building composed of several RMSWs as its main LLRS was used to verify the developed analytical algorithm for a system of RMSWs and the results showed that the value of building resistance was lower than the average value between push and pull cycles from experimental results by 7.38%. The analytical algorithms developed for both individual RMSWs and systems of RMSWs throughout this study were simply relying on analytical application program. As a result, better understanding of the behavior of systems of RMSWs when subjected to seismic loads can be achieved. The factors affecting the accuracy of the developed modeling technique are presented and discussed in this paper. Recommendations for problems faced through developing this modeling technique and the governing factors are presented throughout this study. Based on the analytical verification presented, a parametric study was carried out to investigate the effect of different parameters as lateral load eccentricity, torsional effects, and presence of walls orthogonal to the loading direction.

Shear Performance of Pretensioned Prestressed Concrete Beam with Steel Fibre

The use of steel fibre has proven to be effective in enhancing the performance of concrete structure. However, its application in the prestressed concrete is not fully understood. Therefore, this study presents the application of steel fibre in the prestressed concrete beam. An investigation on the crack pattern and load-deflection relationship of prestressed concrete beam filled with steel fibre was carried out and a comparison is made with the prestressed concrete beam without the steel fibre. A total of three configurations of beams with size of 150 × 200 × 1200 mm were employed. Steel fibres were added with two different volume fractions of 3% and 5%. Experimental results showed that the control beam experienced shear crack pattern, while the other two beams experienced the flexural-shear crack. In comparison between two different percentages of steel fibre in the beam configurations, more cracks were observed in the prestressed beam that filled with 3% steel fibre compared to the prestressed beam filled with 5% of steel fibre.

Impact force profile and failure classification of reinforced concrete bridge columns against vehicle impact

Numerical simulations are utilized in this study to define the impact force profile generated by vehicle collisions on reinforced concrete bridge columns (RCBCs) and classify the dynamic responses and failure of the columns under collision events. The results indicate that both the column properties (i.e. dimension of the cross-section and concrete strength) and initial conditions of vehicles (i.e. vehicle velocity, engine mass, and vehicle mass) play a crucial role in determining the impact force profile from the vehicle collision. A new vehicle impact force model is proposed for engineers to use in design of RCBCs under vehicle collisions in which the influence of shear failure of the column on impact force is considered. Based on the shear mechanism of RCBCs under impact events, the maximum dynamic shear capacity of a column is defined. Furthermore, the bending moment and shear force distributions, as well as the failure mode of RCBCs have been classified into two categories, i.e. flexural response and shear response governed failure with respect to the peak impact force (PIF) on the column. For the flexural response governed failure mode, flexural cracks at the intermediate sections are formed in the positive side of the column, while the diagonal shear or punching shear failure at the impact area together with negative flexural-shear cracks occur in the column if the shear failure mode dominant the column responses.

Influence of loading conditions on the shear capacity of post-tensioned beams with low shear reinforcement ratios

The majority of shear tests reported in the literature has been performed on simply supported reinforced concrete beams under point loads. In contrast, this paper focuses on the shear behaviour of post-tensioned T-beams with no or a minimum amount of transverse reinforcement under various loading conditions. Several test setups were used to investigate the influence of different distributions of the internal forces (due to uniformly distributed load and point loads, respectively) and of the shear slenderness on the shear resistance of the beams. Furthermore, the difference in the shear responses at the end support and the intermediate support of the beams was analysed using the experimental results. The experimental programme consisted of eight shear tests carried out on four specimens. With the aid of close-range photogrammetry, detailed measurements of the kinematics of the critical flexural shear cracks were taken. Linking well-known constitutive laws for concrete and steel with the relationship between the opening and sliding of critical cracks (determined using digital image correlation of experimental results) allowed the contributions of several shear transfer actions to the shear resistance to be estimated. In this paper, it is demonstrated that this approach leads to a better mechanical understanding of the actual shear behaviour of post-tensioned beams. The analysis illustrates that arching action plays a major role regarding the shear resistance of slender post-tensioned beams.

Cracking strut-and-tie model for shear strength evaluation of reinforced concrete deep beams

In the present study, a novel cracking strut-and-tie model (CSTM) is developed to better predict the shear strength of a deep beam. The principal concept of strut-and-tie model (STM), the experimental phenomena of diagonal crack patterns, and strain distribution of longitudinal bars in shear span are considered. The proposed CSTM divides the diagonal strut into two parts according to the location of the critical shear crack (CSC). In the part above the CSC that is not affected by the flexural-shear cracks, its effective compressive strength is defined as the ultimate compressive strength of normal concrete strut. On the other hand, the effective compressive strength of the part below the CSC is derived from the forces transferred by the aggregate interlock, web reinforcement, and dowel action of longitudinal bars on the CSC surface. The improvement of aggregate interlock action under compression on the CSC surface, and the interaction between transverse reinforcement and longitudinal bars are theoretically considered. For practical design, a simplified CSTM is also proposed. The proposed method is applied to 355 existing test specimens, to predict the shear strength of deep beams with and without web reinforcement. The predicted results are compared with existing test results and the predictions of existing STMs. The results show that the prediction of the proposed model is better than those of other models. Further, parametric analysis is performed to evaluate the contribution of each shear mechanism. The analysis results show that the proposed CSTM is able to describe well the influences of main design parameters (i.e., shear span-to-depth ratio, longitudinal bar ratio, web reinforcement ratio, concrete compressive strength, and effective depth) on the shear resistance of deep beams.

Critical shear displacement theory: on the way to extending the scope of shear design and assessment for members without shear reinforcement

AbstractThis paper presents a new theory for the shear capacity of reinforced concrete members without shear reinforcement. While recognizing that there are multiple failure mechanisms, the theory attributes the opening of a critical flexural shear crack as the lower bound of the shear capacity. It proposes that the shear displacement of an existing flexural crack can be used as the criterion for the unstable opening of the critical flexural shear crack. Based on the theory, the paper presents a simplified shear evaluation model. Compared with the current shear provisions in the design codes, the model is characterized by good accuracy and a solid physical background. It demonstrates a great flexibility for dealing with complex design conditions. As an example, the paper discusses the possibility of extending the theory to the shear resistance of higher‐strength concrete. The suggested method provides a more logical and fluent transition from normal‐ to high‐strength concrete and shows good agreement with experimental observations.

Shear behaviour of hybrid composite-concrete beams: Experimental failure and strain analysis

The combination of high performance composites and concrete results in hybrid composite-concrete elements which no longer resemble the traditional reinforced concrete structures. Consequently, these hybrid elements have a different structural behaviour that requires new evaluation procedures. This paper focusses on hybrid TRC-composite-concrete elements which are used as a substitute for reinforced concrete beams within a floor system. Their shear behaviour is experimentally investigated by the examination of ten short-span hybrid beams with different geometries.Visual inspection shows that shear failure occurs by an inclined flexural shear crack in the concrete. A rosette strain gauge analysis proves that the principal strain and stress orientations are in accordance with theoretical predictions. Finally, the small influence of shear deformation on the total deflection of these beams is illustrated.

Behaviour of Reinforced Concrete Beams Strengthened by CFRP Wraps with and without End Anchorages

Use of Carbon Fibre Reinforced Polymer (CFRP) strips as externally bonded reinforcement, is a technically sound and practically efficient method of strengthening and upgrading reinforced concrete (RC) members. Externally bonded CFRP strips help in improving the structure performance by reducing deflections and/or cracking and increasing ultimate strength. The ultimate capacity of the strengthened beam is controlled by either compression crushing of concrete, rupture of CFRP and flexural shear cracking induced de-bonding atconcrete-CFRP interface. Present study deals with the use of externally bonded CFRP wraps instead of strips to strengthen RC beams in flexure with and without end anchorages. Six beams strengthened with CFRP wraps at bottom with and without anchorages, were tested with different a/d ratios. It was observed that use of CFRP wraps resulted in significantly increasing the stiffness and ductility of the RC beams along with increasing load carrying capacities of the strengthened RC beams with end anchorages.

SEISIMIC-FORCE-RESISTING MECHANISMS OF FLEXURAL MULTI-STORY STRUCTURAL WALLS SUPPORTED ON PILES

Reinforced concrete multi-story structural walls supported on pile foundations are commonly designed assuming that they stand on solid foundation without considering their interaction. In this paper, two specimens were tested to simulate their seismic force resisting mechanisms. They consisted of the lowest three floors of structural wall, the first floor slab, a foundation beam and the part of piles. Flexural-shear cracks formed in the structural wall developed to the foundation beam, and the part of the structural wall, the foundation beam and the compressive pile made a solid assemblage rotated about the lower flexural compressive region of the foundation beam. Proposed macro model focusing on the dominant flexural-shear crack made it possible to distinguish fracture modes and to simulate lateral load-deformation angle relationship of the specimens with good accuracy.