Diagonal Cracks Research Articles

Strengthening reinforced concrete bridge piers against heavy vehicle collisions with ultra-high performance concrete collars: A finite element analysis study

This paper investigates the effectiveness of ultra-high performance concrete (UHPC) collars in strengthening reinforced concrete (RC) bridge piers against heavy tractor-trailer collisions through finite element (FE) analysis. First, validated FE models of UHPC and a heavy tractor-trailer were provided. Then, FE analyses were conducted to evaluate the strengthening performance of the UHPC collar. The effectiveness of UHPC collar was compared with conventional RC collar, and the effects of varying UHPC collar thickness, height, and collar reinforcement were investigated. The results showed that the most severe damage observed on bridge piers due to heavy vehicle collisions primarily occurred below a height of approximately 2000 mm, manifested as diagonal shear cracks and plastic hinges. Therefore, the recommended minimum collar height is 2000 mm. The comparison between UHPC collar and RC collar strengthening demonstrated the superior effectiveness of UHPC collars. A 130-mm UHPC collar exhibited a similar strengthening effect as an 180-mm RC collar. Among the three investigated parameters of UHPC collar thickness, height, and collar reinforcement, the study found that collar thickness had the most significant influence on the effectiveness of the UHPC collar in terms of damage pattern, energy absorption, and maximum deflection. While collar height primarily influenced deflection, a larger collar height was beneficial in reducing pier deflection at the end of the strengthened segment. Adding a small amount of collar reinforcement improved the performance of piers; however, this improvement was limited. The findings of this study address the lack of research on using UHPC for strengthening full-scale bridge piers against heavy tractor-trailer collisions and provide valuable references for future designs with similar applications.

An adaptable rotated bounding box method for automatic detection of arbitrary-oriented cracks

Concrete crack detection is a crucial task for the safety and durability of engineering structures. Extensive research has been conducted on deep-learning methods employing horizontal bounding boxes (HBBs) for crack detection. However, due to the inherently random distribution of concrete cracks, HBB-based methods often produce excessive overlaps and encompass extensive background regions, obstructing the effective interpretation and adaptation of the detection results. To address this issue and achieve efficient utilization of bounding box space for detecting cracks at any orientation, a rotated bounding box (RBB)-based method, that is, Rotated Faster R-CNN with a post processing strategy (RFR-P), was proposed. To realize this method, an RBB-based crack annotation strategy was introduced to standardize the annotation baseline for the evolutionarily established RBB-based crack detection dataset. Then, an RBB-based post-processing strategy was inventively developed to quantify the patterns of cracks with their corresponding rotation angles encompassing longitudinal cracks, transverse cracks, and diagonal cracks. Subsequently, experimental results showed that the RFR-P method provides more reasonable and elaborate detection results in terms of crack distribution patterns when compared to HBB-based methods. Based on the comprehensive consideration of evaluation metrics and detected results, it can be concluded that the RFR-P is aptly designed for detecting cracks at any rotation angle with relatively high accuracy. Finally, an RBB-based concrete crack detection platform was established to automatically detect in situ concrete bridge cracks for real-world applications. The proposed RFR-P model introduces a new perspective on crack detection methods and offers practical references for structural condition evaluation.

Plastic Hinge Length for Flanged Reinforced Concrete Shear Walls with Asymmetric Sections

ABSTRACT This research investigates the determination method, spreading mechanism and influencing factors of the plastic hinge length for asymmetrical flanged walls using the finite element method. The plastic hinge length of flanged walls under flange-in-compression loading is generally greater than that under flange-in-tension loading. Based on the results, simple equations for predicting the plastic hinge length of flanged walls and which consider the contributions of the moment gradient, diagonal shear cracks, and strain penetration are proposed. Through comparison with the existing equations and design codes, the predicted plastic hinge lengths obtained from the proposed equations accord better with the test results.

A novel design model for predicting the shear resistance of reinforced concrete beams strengthened with EBR-CFRP systems

Shear resistance prediction of reinforced concrete (RC) beams strengthened with externally bonded reinforcements (EBR) is a challenging task due to the complex nature of shear resisting mechanisms and their intricate interaction. Existing design models often overlook these dependencies, leading to significant variations in prediction accuracy. In this paper, a design model is proposed by integrating the most relevant shear resisting mechanisms based on the evidence demonstrated by a large database of experimental results from RC beams shear strengthened with wet layup carbon fibre reinforced (CFRP) sheets applied according to the EBR technique. The developed approach integrates the simplified modified compression field theory (SMCFT) with a regression-based model. A global sensitivity analysis was conducted according to which closed form equations were derived to obtain the tensile stress factor in cracked concrete and the inclination angle of the critical diagonal crack. A reliability analysis is carried out, and resistance reduction factors are achieved for different levels of reliability index. The database, composed of 284 RC beams shear strengthened with EBR-CFRP technique, is utilized to validate the proposed model, and compare its performance against some well-established existing design models. The results show that the proposed model, with an adequate framework for its use on design practice, outperforms the other considered models.

Shear bearing capacity calculation of low-rise SFRC shear wall with CFST columns based on simplified softened strut and tie model

In the paper, an innovative shear wall, which is referred to as steel fiber reinforced concrete (SFRC) shear wall with concrete filled steel tube (CFST) columns, is introduced, based on the high bearing capacity and large stiffness of concrete filled steel tube column (CFSTC) and good cracking resistance and strong toughness of steel fiber reinforced concrete. The loading mechanism of steel fiber reinforced concrete shear wall (SFRCSW) with concrete filled steel tube columns is analyzed, and shear bearing capacity calculation method. A simplified model of the steel fiber reinforced concrete shear wall web softening tension bar is proposed, concrete and distributed web reinforcement to the shear bearing capacity of steel fiber reinforced concrete shear wall web is identified. Furthermore, a new algorithm to obtain the shear bearing capacity of steel fiber reinforced concrete shear wall with concrete filled steel tube columns is established, and then it is validated by using the test results of steel fiber reinforced concrete shear wall with concrete filled steel tube columns under low-cycle repeated loading. The results showed that all tested shear wall specimens exhibited obvious shear failure characteristics and a typical diagonal cracking pattern after test. The steel fibers obviously improved the crack forms of the steel fiber reinforced concrete shear wall web and the seismic behavior of steel fiber reinforced concrete shear wall with concrete filled steel tube columns. In addition, the proposed calculation method is scientific and accurate to analyze and predict the shear bearing capacity of low-rise steel fiber reinforced concrete shear wall with concrete filled steel tube columns.

Investigation of the bed joint reinforcement effect on the drift capacity of modern unreinforced masonry walls

Bed joint reinforcement significantly affects the shear capacity of masonry walls due to its effective ability to transfer shear forces through a diagonal crack, but how does this phenomenon impact its drift capacity? This paper presents an experimental study containing a series of four quasi-static cyclic tests conducted on masonry walls of same size. Two of them incorporated truss-type bed joint reinforcement, while the other two were completely unreinforced. All specimens were subjected to double bending boundary conditions to observe shear-controlled behaviour and were tested under two levels of compression load. The primary objective of this research is to determine the role of horizontal reinforcement in the seismic properties of unreinforced masonry walls focusing on the displacement capacity. The findings from this experimental study are expected to provide empirical evidence for subsequent numerical simulations and contribute to the development of analytical formulations. The results aim to enhance our understanding of the seismic response of masonry walls, ultimately informing design practices and seismic retrofitting strategies.

Structural retrofitting of RC slabs using bamboo fibre laminate: Flexural performance and crack patterns

Enhancing the durability of structural elements is a viable approach to promote sustainability in civil engineering. Research has shown that well-maintained slabs outperform degraded ones, which deteriorate rapidly due to insufficient upkeep. The occurrence of cracking and deformation in slabs subjected to sustained loads significantly impacts their functionality. However, the implementation of appropriate retrofitting techniques utilizing locally available materials can effectively minimize deflection and crack propagation while also improving flexural capacity. This particular study aimed to evaluate the flexural performance of slabs that were retrofitted using bamboo fibre laminate (BFL). Also, the study investigated two alternative replacement methods alongside the conventional mix; one involved replacing all fine aggregates with ceramic fine aggregate and the other involved a complete replacement of coarse aggregates with ceramic coarse aggregate. These mixes were represented in both the retrofitted and non-retrofitted samples. The retrofitting process included using the combined external bonding and near surface-mounted method. Twelve slab samples were made, with six being non-retrofitted and the other six retrofitted with BFL. Each of the samples had dimensions of 300 mm × 300 mm × 50 mm for reinforced concrete (RC) slabs. The slabs were tested employing the three point-bending system, and the retrofitted slabs with the conventional mix exhibited the highest ultimate failure load and flexural strength (62.1 kN), which compared to the non-retrofitted slabs of the same mix was a 60.76% increase. Additionally, the study did a thorough analysis of the presence of flexural and diagonal shear cracks, as well as the occurrence of debonding between BFL and the slabs. Non-destructive tests were also conducted on the slab samples to further confirm accurate results. These findings offer helpful insights into the development and application of a sustainable retrofitting material that can remarkably improve RC slabs.

Experimental investigation of bearing capacity of 3D printed concrete segmental girder

3D concrete printing (3DCP) technology represents a new approach to producing contemporary concrete structures. The application of sophisticated equipment such as a 3D printer has brought numerous advantages, which were noted through significant practical application. Currently, 3DCP technology is being developed in two main directions: on-site production of entire structures and prefabricated construction. However, 3DCP technology has not yet reached its full potential in prefabrication as the connections between individual segments and their capacities under horizontal and vertical loads, have not yet been extensively investigated. This paper focuses on the experimental testing of the bearing capacity of a beam constructed by connecting individual segments of 3D printed concrete. The segments are connected using post-tensioning steel bars. The experimental program included testing a single segment as well as a segmental girder in a 3-point test. In the case of the individual segment, failure occurred due to the loss of tensile capacity of the concrete. For the segmental beam, failure occurred when the shear capacity was reached. Shear fracture was accompanied by diagonal cracks extending from the point of force application towards the beam supports.

Self-sensing concrete masonry structures with intrinsic abilities of strain monitoring and damage detection

Self-sensing cementitious materials are emerging technologies for Structural Health Monitoring (SHM) of civil structures. Their application for SHM of concrete masonry elements was not investigated in previous studies. The effects of triaxial strain/stress states of masonry joints and units on their self-sensing response are still unknown. Therefore, this work aimed to investigate mechanical and self-sensing properties of masonry elements produced with self-sensing mortar joints, solid concrete bricks and/or hollow concrete blocks fabricated with carbon black nanoparticles. The intrinsic abilities of strain monitoring and damage detection were evaluated in piezoresistive tests of masonry prisms, based on variations in the type of unit, mortar bedding approach, bonding arrangement, relative strength of mortar and units, joint thickness and location of self-sensing regions. These variations did not affect significantly the gauge factor of cementitious sensors embedded into the prism units. In contrast, the gauge factor of self-sensing horizontal or vertical joints was statistically affected by most of these variations. Stages of balance and abrupt increases in fractional changes in electrical resistivity (FCRs) during the plastic regime of the prisms provided an anticipated warming associated with the propagation of vertical and diagonal cracks associated with tensile splitting and crushing failure of units. The strong non-linearity on the electrical output of self-sensing joints provided an evidence of the mortar pore collapse. In conclusion, the self-sensing units and mortar joints were found to be promising alternatives for strain monitoring and damage detection in smart concrete masonry structures.

Seismic performance of truss-wall joints in high-rise connected structures

This paper presents an experimental study of the seismic behavior of joint between steel-truss viaduct and reinforced concrete (RC) seismic walls in connected structures. To investigate the seismic performance of the connection joints, two types of joints with different details (i.e., a common connection joint and a friction energy-dissipation connection joint) were prepared and quasi-statically tested using a cyclic loading protocol. Diagonal concrete cracks in the RC seismic wall, concrete crushing, and the fracture of the weld at the upper chord joint were observed during the test. Unexpected plastic deformation occurred in the embedded chord within the RC seismic wall. The seismic performance of the joints was evaluated in terms of strength degradation, rigidity degradation, ductility, and energy dissipation capacity. The deformation capacity and energy dissipation capacity of specimen CWTJ2 was better than that of CWTJ1. The yield displacements Δy of both specimens were similar. However, the ultimate displacement Δu of CWTJ2 was 34.9% larger than that of CWTJ1, and the accumulated energy Ea of CWTJ2 was 2.23 times of CWTJ1. The load transfer mechanism analysis based on the stress distribution indicates that the embedded column and chords transmitted the load to the seismic wall, which caused the seismic wall to be damaged during the loading process. The experimental results suggest that the truss-wall joints in connected structures can transfer seismic loads effectively. However, the welding between embedded column and chord shall be carefully treated.

Post-Cracking Shear Stiffness Model of Reinforced Concrete Beams

Macro diagonal cracks can significantly reduce the stiffness of slender reinforced concrete (RC) beams, which results in excessive deflection compared with limitations from design specifications. To evaluate the post-cracking stiffness of slender RC beams with diagonal cracks, a shear degradation model that considers shear deformation is proposed. Based on the variable angle truss model, this study deduced the strut angle formula based on the minimum energy principle. Then, the relationship between the stirrup yielding shear stiffness and elastic shear stiffness was modeled. Finally, the calculation procedure was developed by quantifying the stiffness degradation tendency. The comparison between the experimental results of deflection and the proposed analytical method showed good agreement. Additionally, the proposed method can capture the full-range features of shear strain curves.

Fatigue behavior of deep concrete beams with critical shear cracks

AbstractReinforced concrete deep beams in bridges and other critical infrastructure are subjected to millions of load cycles during their service life. At the same time, they typically work with high shear and develop critical diagonal cracks. The cyclic loading across the cracks results in fatigue damage of the shear‐resisting mechanisms, which needs to be taken into account in the assessment of existing structures, and in particular in members with small amount of shear reinforcement built according to early design codes. To aid the development of advanced assessment approaches for such structures, this paper presents five large‐scale fatigue tests of deep beams with a stirrup ratio of 0.134%. The beams are preloaded to develop complete diagonal cracks, and then are subjected to cycles with different minimum and maximum load. The focus is placed on detailed crack measurements, needed for the development of crack‐based assessment approaches. The crack data is analyzed with the help of the two‐parameter kinematic theory to quantify important deformations. It is shown that the fatigue across the shear cracks is associated mainly with degradation of aggregate interlock and progressive damage in the critical loading zones. It is also shown that as the maximum load is decreased, the fatigue life increases, and the failure mode can switch from shear to flexure.

Reinforcement of Silty Soil via Regenerated Fiber Polymer: A Study on Microscopic Mechanisms.

Utilizing regenerated polyester fibers (RPFs) for the reinforcement of silty road bases not only enhances the soil's engineering performance but also offers a sustainable method for repurposing waste polyester bottles. To investigate the engineering properties and microscopic behaviors of this reinforced silty soil, a series of extensive physico-mechanical tests were conducted, supplemented by Scanning Electron Microscopy (SEM) analyses. These evaluations focused on the influence of variables such as fiber content, fiber length, moisture content, and curing duration on the modified soil's performance. The fiber content of the test was 0-1%, and the fiber length was 6-17 mm. The results indicate that curing age had a less significant impact on liquid and plastic limits than the addition of fiber, along with a marginal decline in the plasticity index over time. The rate of shrinkage in the unmodified soil was between 1.04 and 1.45 times higher than that in the fiber-reinforced soil, indicating effective shrinkage control by the fibers. However, variations in maximum dry density (ρdmax) were insignificant across different fiber contents, while a slight increase was observed in the optimum moisture content (OMC) as fiber dosage increased. After a 28-day curing period, the resilient modulus and California Bearing Ratio (CBR) met highway road base design standards. A decline in unconfined compressive strength was noted when the fiber dosage exceeded 0.2%. The addition of fibers mitigated diagonal cracking and shifted the failure pattern towards a more ductile mode. This research contributes scientific insights for the broader application and promotion of silty road base improvement techniques using RPFs.

Unbonded Pre-Tensioned CF-Laminates Mechanically Anchored to HSC Beams as a Sustainable Repair Solution for Detachment of Bonded CF-Laminates

The present article outlines a Finite Element Model (FEM) that was created and validated by comparing it to prior experimental investigations to estimate the flexural performance of HSC beams strengthened with exterior bonded, unbonded, and unbonded pre-tensioned Carbon Fibre Reinforced Polymer (CFRP) sheets in several patterns. Nonlinear analysis was performed on three-point-loaded beams using ANSYS software, incorporating the constitutive characteristics of various components (concrete, CFRP, and steel). The comparison of FE-models and experimental data, namely for load-deflection curves, crack patterns, and failure modes, revealed that the developed numerical FE-models and experimental outcomes are in good accord. There has been numerous prior research on the behavior of beams strengthened with externally bonded CFRP sheets, but few on those reinforced with externally unbonded CFRP laminates, and even fewer on HSC beams reinforced with externally unbonded pre-tensioned CFRP laminates. Therefore, the major contribution of this article is to investigate the flexural behavior of HSC beams strengthened utilizing externally unbonded pre-tensioned CFRP laminates. The analysis revealed that the bending performance of RC-beams strengthened using external unbonded pre-tensioned CFRP-laminates is quite similar to that of bonded CFRP-strengthened beams, indicating a high potential for tackling the durability issues caused by detachment of bonded CFRP-strips in such structural elements. The existence of a fully wrapped CF sheet forced the beam to develop diagonal shear cracks in the region between the wrapped CF sheet and beam supports while also enhancing the flexural cracked zone at mid-span to change from smeared to discrete fractures. The flexural fractures spread over a deeper and wider area of the beam as a result of the incorporation of a half-wrap CF laminate. Externally unbonded CFRP-sheets pre-tensioned with 45% of the CFRP ultimate strength utilizing various patterns (straight and U-wrap) performed similarly to bonded CFRP-sheets, with a slight boost in load capacity of around 4.5% and notable reduces in deflection ranging from 9.7% to 16.24%. Using exterior unbonded CFRP laminates to strengthen RC-beams resulted in a flexural capacity increase ranging from 22.3% for NC beams to 71.6% for HSC beams.

Method of computational models of resistance for reinforced concrete

Based on a comprehensive analysis of the experimental studies from the standpoint of their convergence with the theoretical solutions, the computational models of resistance (CMR) of reinforced concrete are proposed. These models include CMR1 - modeling of normal cracks, CMR2 - modeling of inclined cracks, CMR3 - modeling of diagonal cracks, CMR4 - modeling of intersecting cracks in the wall, CMR4* - modeling of cracks in a flat slab, and CMR5 - modeling of spatial cracks in torsion with bending, CMR5* - modeling of spatial cracks in bending with transverse force. Also, a hierarchy of computational models of the second and third levels is proposed. The distribution of intensity of working reinforcement along the cross-section of the calculated element was obtained in an analytical form by creating closed equations of blocks, corresponding to the blocks of the reinforced concrete element under the condition of equality to zero of partial derivatives of the Lagrange function to determine the maximum crack opening width. It is considered the effect proposed by the author on the additional deformation impact of the reaction “concrete - reinforcement” from the discontinuity of concrete during the formation of the crack by means of a special model of the two-cantilever element of fracture mechanics. Hypotheses about the distribution of linear and angular deformations during cross-section with account of gradients of deformations caused by formation of cracks were formulated for a complex-stressed element subjected to torsion with bending. Crack opening is defined as mutual displacements of reinforcement and concrete, taking into account deformation. The consolidation of substructures in the building system is performed by the method of initial parameters.

Behavior of non-prismatic RC beams with conventional steel and green GFRP rebars for sustainable infrastructure

This study presents an experimental and finite element analysis of reinforced concrete beams with solid, hollow, prismatic, or non-prismatic sections. In the first part, a total of six beams were tested under four-point monotonic bending. The test matrix was designed to provide a comparison of structural behavior between prismatic solid and hollow section beams, prismatic solid and non-prismatic solid section beams, and prismatic hollow and non-prismatic hollow section beams. The intensity of shear was maximum in the case of prismatic section beams. The inclusion of a tapered section lowered the demand for shear. In the second part, Nonlinear Finite Element Modeling was performed by using ATENA. The adopted modeling strategy resulted in close agreement with experimental crack patterns at ultimate failure. However, the ultimate failure loads predicted by nonlinear modeling were generally higher than their corresponding experimental results. Whereas in the last part, the developed models were further extended to investigate the effect of the strength of concrete and ratio of longitudinal steel bars on the ultimate load-carrying capacity and cracking behavior of the reinforced concrete beams with solid, hollow, prismatic, or non-prismatic sections. The ultimate loads for each beam predicted by the model were found to be in close agreement with experimental results. Nonlinear modeling was further extended to assess the effects of concrete strength and longitudinal reinforcement ratio on failure patterns and ultimate loads. The parametric study involved beams reinforced with glass fiber-reinforced polymer (GFRP) bars against shear and flexural failure. In terms of ultimate load capacities, diagonal cracking, and flexural cracking, beams strengthened with GFRP bars demonstrated comparable performance to the beams strengthened with steel bars.

Failure mechanisms of equipment hatch area in prestressed concrete containment vessel

The failure mechanisms of the equipment hatch area under two load cases (LCs), i.e. in-plane shear/tension and tension/tension to consider the combined action of ground motion and internal pressure and the action of internal pressure only, respectively, were experimentally studied with three specimens for each LC.The results show that the failure of the LC1 specimens is due to the eccentric tension in the vertical direction. The shear force in the lateral direction changes the stress distribution in the specimensand thus influence the crack nucleation and propagation. The failure modes of the LC2 specimens depend on the magnitude of the lateral tension. With the increase of the maximum lateral tension, the failure modes vary in the sequence of the horizontal cracking of concrete at the bottom of the specimen, the critical diagonal cracks on the top of the specimen and the failure of the narrowest part of the specimen.

Meso-scale numerical simulation of the mechanical behaviour of brick masonry in earth mortar

The paper discusses the mechanical behaviour of masonry composed of fired solid bricks and earth mortar. Such masonry is a typical construction technique in South and Southeast Asia. As its mechanical behaviour is complex due to high anisotropy attributed to noticeable difference in stiffness and strength between bricks and earth mortar, it is still considered challenging to comprehend the mechanical behaviour of such masonry. Taking into account this background, the present research addresses the formulation of the mechanical behaviour of brick masonry in earth mortar. Numerical analysis was performed to reproduce uniaxial compression and diagonal compression tests, referring to empirical evidences on interface behaviour between bricks and earth mortar. Meso-scale analysis was performed, applying a multi-surface failure criterion composed of cracking, shearing and crushing to unit-joint interfaces. The analysis showed very similar stress-strain relations and failure patterns to the tests. The simulation of the uniaxial compression test presented that the distributions of compressive stress shifted along with the progress of cracks. In the reproduction of the diagonal compression test, vertical stress was irregularly distributed after diagonal stepwise cracks appeared. Two comparative studies were conducted to examine the shear performance of brick masonry in earth mortar. First, sensitivity analysis indicated the noticeable influences of compressive strength, friction angle and facture energy of unit-joint interfaces. Second, macro-scale analysis was conducted, using a homogeneous material model. The observed diagonal crack patterns were similar to the test. The paper contributes to the understanding of the mechanical behaviour of brick masonry in earth mortar.

In situ damage characterization of CFRP under compression using high-speed optical, infrared and synchrotron X-ray phase-contrast imaging

The strain rate dependency and failure modes of carbon fiber reinforced plastic (CFRP) laminate were investigated under out-of-plane compressive loading. Simultaneous high-speed optical and infrared imaging were used to measure full-field deformation and temperature in the dynamically loaded specimens. The damage initiation and propagation inside the CFRP laminates at high strain rates were characterized using in-situ ultra-fast synchrotron X-ray phase contrast imaging (XPCI). The visually observed damage onset occurs at the strain value of 4.2 ± 0.6% as a transverse shear fracture at the free edge of specimens. The local temperature increases significantly to 185 °C due to damage initiation at high strain rates, while at low strain rates the temperature rise occurs after the final shear band forms. The XPCI and post-failure analysis provide an integrated perspective on the formation of a diagonal shear crack and disintegration of the specimen into two pieces with the fracture of plies in the in-plane transverse direction. Scanning electron microscopic (SEM) study was integrated with XPCI results to append the time scale for the post-mortem failure pattern as well as the length scale for microcracks and filament-level failure.

Shear Capacity of Hollow Reinforced Concrete Members without Stirrups

This paper presents experimental results on the shear capacity of hollow reinforced concrete members without stirrups. The area of the hollow was 2.32% of the concrete cross-sectional area. The hollow size used in this study is smaller than the maximum percentage required in the code, where the maximum hollow area was 4% of the total cross-sectional area. The longitudinal reinforcement used in the specimen varies with the three types of reinforcement ratios. The test was carried out using the four-point shear test to achieve the expected shear failure mode. The loading was given monotonically until the specimen failed. Analytical flexural capacity was also calculated using the fiber element method. The specimens failed in shear failure mode, indicated by large diagonal cracks in the observed shear span. The influence of the hollow on the shear strength was also compared with the theoretical shear capacity proposed by the code. This comparison shows that the calculated theoretical shear capacity is conservative for hollow reinforced concrete structural elements with a hollow area smaller than 4%. The results of the flexural analysis show that all the specimens did not reach the flexural capacity due to premature shear failure.