Crack Patterns Research Articles

Discontinuum Micromodelling of Unstrengthened and FRCM-Strengthened Masonry Cross-Vaults Subjected to Seismic Excitation

ABSTRACT Many historical buildings employ masonry cross-vaults as flooring systems. The structural response of such cross-vaults to seismic excitation still needs to be fully understood and requires investigation through experimental studies or accurate numerical simulations. This article presents a finite element discontinuum micromodelling technique to simulate a full-scale mortared masonry cross-vault (unstrengthened and subsequently strengthened with textile-reinforced mortar) recently tested on a shake table as part of a blind prediction competition. The numerical technique uses shell elements to model the brick and mortar geometry explicitly within the STKO+OpenSees finite element framework. Both brick and mortar materials are modeled using an advanced damage-plasticity constitutive model, addressing potential convergence issues associated with strain-softening materials through a novel implicit-explicit integration algorithm. The numerical models predicted the failure mechanisms and crack patterns in close agreement with the experimental results. The strengthened model displayed severe cracks spreading across a larger part of the cross-vault, whereas the unstrengthened model exhibited in-plane shear failure along the groin lines. The strengthened vault showed an almost twofold increase in peak ground acceleration capacity, demonstrating the effectiveness of textile-reinforced mortar. The proposed numerical technique will be helpful in the design of effective retrofit measures for heritage structures.

Behavior and shear strength of prestressed steel reinforced concrete composite deep beam

In order to optimise the utilisation of material properties, simplify the construction process and enhance the industrialisation of steel reinforced concrete beams, an innovative prestressed steel reinforced concrete composite beams(PSRCC) was proposed, which was achieved by integrating prestressing technology and prefabricated technology to steel reinforced concrete structure. To investigate the shear PSRCC deep beams, a static load test was conducted on 7 PSRCC deep beams. The study investigated the effects of parameters such as shear span-depth ratio, prestressed tendons degree, form, height and application sequence on the failure mode, crack pattern, load-displacement behavior, strain response and damage evolution. A model was established to predict the shear strength of PSRCC deep beams, considering the steel-concrete interaction, using the von Mises yield criterion and the SST model, which assessed the contributions of composite strut, prestressed tendons and shear steel web for shear strength. The test results showed that the prefabricated and cast-in-situ concrete components maintained good integrity, and PSRCC deep beams eventually experienced typical diagonal compression failure. Applying prestressing and reducing the shear span-depth ratio under identical conditions would reduce the deformation capacity of PSRCC deep beams. When the shear span-depth ratio was reduced from 1.0 to 0.5, the cracking load and peak load of the specimens increased by 17.31 % and 16.53 % respectively. Increasing the prestress level from 0 to 0.3 and 0.6 increased the cracking load of the specimens by 1.41 and 2.36 times, respectively, but the peak load of the specimens increased by only 3.37 % and 8.17 %. The cracking load of the parabolic tendon specimen increased by 2.18 for the comparison specimen but was 8.33 % lower than that of the linear tendon specimen with the same degree of prestressing. Comparison of the two prestressing sequences showed that the cracking load of the specimen with tensioning prestressed tendons after pouring the entire beam section increased by 29.84 %, but the peak load increased by only 3.11 %. As the height of the prestres tendons increased, the cracking and peak loads of the specimen reduced by 5.84 % and 5.71 % respectively. Consequently, the shear strength of PSRCC deep beams was significantly influenced by the shear span-depth ratio and minimally affected by prestress-related parameters. The proposed model accurately predicted the shear strength of PSRCC deep beams compared to existing codes, offering valuable guidance for design.

Effect of water-absorbent polymer balls in internal curing on punching shear behavior of bubble slabs

Abstract The punching shear capacity of bubbled slabs is one of the main problems due to its decreased thickness; when there is inadequate curing, the problem becomes more critical, causing the building’s structural performance to deteriorate and exposing it to the risk of collapse. This study aimed to investigate the effect of using water-absorbent polymer balls in internal curing on the punching shear behavior of bubble slabs. Six concrete slabs were cast (1,000 mm × 1,000 mm × 70 mm). The main variables in this study are the type of slab (solid and bubble), type of curing (water and air), and ratio of water-absorbent polymer balls (5 and 10%). Studying the performance use of polymer balls and recycled plastic balls together and in normal strength concretes is limited. Also, investigating their behavior can provide insight into the efficiency of using these materials to improve concrete structures. Results showed that the most effective ratio for using polymer balls in internal curing is 5%, which had a good effect on the ultimate load, the first crack load, deflection, and crack pattern compared to the water-curing sample (reference sample). The water-absorbent polymer balls used in this study can absorb water when added to a concrete mixture. They release the water absorbed and subsequently contract, forming voids that are equivalent in size to the balls. This process facilitates internal curing while reducing the weight of concrete through the air voids left by the balls after they are dry.

Damage Evolution and Fractal Characteristics of Granite under the Influence of Temperature and Loading

To study the damage characteristics and evolution law of granite under the influence of temperature and loading rate, uniaxial compression tests at different loading rates were performed for granite samples at 30 °C, 40 °C, 60 °C, and 80 °C. The damage characteristics and evolution law of granite were studied in conjunction with acoustic emission ringing, acoustic emission b values, acoustic emission signaling constellations, and fractal dimensions. The results showed the following: (1) At a low loading rate (0.005 mm/s), the peak stress of the granite increases gradually as the temperature increases. At high loading rates (0.01 mm/s and 0.02 mm/s), the peak stress of the granite first decreases, then increases as the temperature increases. The elastic modulus at different loading rates decreases first, then increases as the temperature increases. The elastic modulus of the granite is the lowest at 40 °C; (2) At the same temperature, specimens subjected to higher loading rates exhibit accelerated internal damage progression, with a precipitous decrease in the b-value occurring earlier. At a loading rate of 0.005 mm/s, the total number of acoustic emission ring-down events is at least 1.7 times greater than that at other loading rates, indicating a more complex development of internal cracks in the granite specimens. Moreover, as the temperature increases under a constant loading rate, the concentration of acoustic emission ring-downs intensifies during the unstable crack development and failure phases, accompanied by progressively larger fluctuations in the b-value; (3) Under the same temperature conditions, the acoustic emission signals in the specimens loaded at 0.005 mm/s and 0.01 mm/s propagate from one end to the other. At 0.02 mm/s, emissions appear simultaneously at both ends of the specimen and converge toward the center. The proportion of damage and energy associated with compression differs with temperature; at 30 °C and 40 °C, damage and energy are concentrated in the early phase of compression, whereas at 60 °C and 80 °C, they are more significant during the later stages; and (4) The fractal dimension of the granite specimens generally decreases, then undergoes a phase of fluctuating growth, followed by a decline. With increasing loading rates at a constant temperature, the compaction of the granite specimens decreases; the orderliness of the crack patterns gradually increases. As the temperature increases, the distribution of cracks during the compaction and failure phases becomes more orderly. During the crack initiation and development phases, the dispersion of cracks and the formation of crack networks are more pronounced. These findings provide a theoretical reference for understanding the microscale damage and failure mechanisms of granite under varying loading rates and temperatures.

Crack Behavior of Eccentrically Braced Frame Type-V with Ground Granulated Blast Furnace Slag

To make the structure stronger and stiffer, which is more susceptible to earthquake forces, a special mechanism is required to improve the structure's lateral stability. EBF-V with a horizontal link beam is a brace that can enhance structural performance by providing good stiffness and ductility. On the other hand, GGBFS, as a partial OPC replacement material, was applied to contribute to using more environmentally friendly materials. Besides offering a smaller carbon footprint, GGBFS also positively improves the mechanical properties of concrete. Thus, this study focuses on investigating the crack propagation pattern of reinforced concrete braced frames combined with 20% GGBFS in EBF-V with three variations of link beam element lengths of 0 cm (CBF), 15 cm (EBF-V-) and 25 cm (EBF-V-25). As a result, the CBF specimen showed the best seismic performance. In EBF specimens, there is an increase in the collapse mechanism to be more ductile. The link beam plays a role in making the crack pattern more focused. EBF-V-15 performs well under seismic loading with large lateral capacity and ductility. The cracks in the frame are evenly distributed, dominated by fine cracks, and symmetrical on both sides. This validates that GGBFS plays a good role in improving the frame performance with its pore-filling effect and pozzolanic reaction.

Load-bearing behavior of short-fiber-reinforced textile-reinforced concrete for a wrapping process

In the research project titled Wrapping process for highly fiber-reinforced concrete using the example of a pump sump (WiFaPu), a new production process for components made of short-fiber-reinforced textile-reinforced concrete was developed. The idea of wrapping concrete continuously around a formwork evokes high-level requirements on the workability of concrete while matching reinforcement properties. In this study, the load-bearing behavior of wrappable short-fiber-reinforced textile-reinforced concrete with an uncoated textile reinforcement made of AR-glass is investigated via tensile and bending tests. The concrete inserted into the wrapped layers by casting, laminating or spraying and the short fiber content and warp/weft direction of the uncoated fabric have a major influence on the load-bearing behavior of the tested specimens with regard to the utilized tensile strength and crack spacing. Members produced by inserting the concrete in a spraying or laminating process showed low tensile strength and unsatisfactory cracking patterns in the warp direction of the fabric due to the lacing of rovings, which led to lower matrix penetration. For rovings in the weft direction without lacings, higher utilized tensile strengths and fine crack patterns are observed. The casting of specimens leads to significantly higher utilized textile tensile strengths if the reinforcement is slightly tightened in the formwork. Compacting fine-grained concrete leads to better roving penetration than does the spraying process. The addition of short fibers generally benefits the cracking pattern and partially compensates for the negative effects of the textile weave on the utilized tensile strength as well as on the warp direction of the crack pattern. The load increase in tensile and bending tests is proportional to the increase in short fiber content and fiber length. Finally, the influence of different coatings is examined for another uncoated textile reinforcement made of AR-glass with a more favorable textile weave. The utilized tensile strength of the reinforcement is almost doubled when impregnated with a fine cement suspension and directly installed in the formwork and cast. An impregnation process such as this can also be integrated into the wrapping process.

Effect of Drying and Wetting Cycles on the Surface Cracking and Hydro-Mechanical Behavior of Expansive Clays

Expansive clays present serious issues in a variety of engineering applications, including roadways, light buildings, and infrastructure, because of their notable volume changes with varying moisture content. Tough weather conditions can lead to drying and shrinking, which alters expansive clays’ hydro-mechanical properties and results in cracking. The hydro-mechanical behavior of Al-Ghatt expansive clay and the impact of wetting and drying cycles on the formation of surface cracks are addressed in this investigation. For four cycles of wetting and drying and three vertical stress levels, i.e., 50 kPa, 100 kPa, and 200 kPa, were investigated. The sizes and patterns of cracks were observed and classified. A simplified classification based on main track and secondary branch tracks is introduced. The vertical strain measure at each cycle, which showed swell and shrinkage, was plotted. The hydromechanical behavior of the clay, which corresponds to three levels of overburden stress as indicated by its swell potential and hydraulic conductivity was observed. It was found that at low overburden stresses of 50 kPa, the shrinkage is high and drops with increasing the number of cycles. Al-Ghatt clay’s tendency to crack is significantly reduced or eliminated by the 200 kPa overburden pressure. The results of this work can be used to calculate the depth of a foundation and the amount of partial soil replacement that is needed.

Performance of carbon nanomaterials incorporated with concrete exposed to high temperature

Abstract In recent decades, there have been initiatives to incorporate carbon nanomaterials (CNMs) into cement composites, particularly graphene oxide (GO), carbon nanotubes, graphite (GP), and mild carbon (MC). Nevertheless, little is known about how these CNMs interact with the cement matrix itself. In this research, the impact of CNM incorporation at high temperatures (250, 500, 750, and 1,000°C) on cement’s mechanical characteristics and microstructure was investigated. Nine mixes were created with the CNM content (0.1 and 0.3%) being taken into consideration. The microstructure of the CNM composites was further investigated using X-ray diffractometry, thermogravimetry, derivative thermogravimetry, digital microscopy, and micro-computed tomography (micro-CT). Based on research observations, the study demonstrated that the mechanical properties of most specimens could be enhanced through the introduction of CNMs. The recommended proportions of GP-0.1, GO-0.1, and MC-0.1, in accordance with the weight of the binder, and the impact of the CNMs on the elastic modulus were also assessed. As a consequence, the CNM’s porous structure and apparent crack pattern were identified using microstructure analysis.

Experimental and analytical investigations into flexural behavior of composite beams with UHPC T-section and HRS H-section

This study investigated the flexural behavior of composite beams with ultra-high performance concrete (UHPC) T-section and hot rolled steel (HRS) H-section. First, a four-point bending test on six specimens was conducted. The effects of stud spacing and tensile reinforcement ratio on flexural performance were investigated in terms of crack patterns, failure modes, ultimate load, load-strain response, relative interfacial slip, and ductility. The experimental results indicated that the stud spacing and the presence of tensile reinforcement had a visible effect on the crack patterns of UHPC web. The distribution of group cracks was observed at UHPC web of specimens with unreinforced UHPC bulb. During the failure stage, the whole HRS H-section in the constant moment region yielded. In particular, the partial cross section of HRS entered the strain hardening stage. In addition, an analytical approach verified by six tested specimens was developed to study the moment-curvature response of HRS-UHPC composite beams (HUCBs). The comparison results indicated the good accuracy of the analytical approach. Then, the proposed sectional analysis model was utilized to investigate the effects of the strength of HRS and UHPC, the total depth of cross section, and the depth of HRS H-section on yielding moment, including ultimate moment and ductility. The analytical results revealed that the strength of HRS and the total depth of cross section had a significant impact on the moment-curvature response of HUCBs. The sectional analysis also illustrated that the yielding point was mainly determined by the yielding of HRS H-beam. Compared with UC120, the ultimate moment and ductility coefficient of the composite beam using UC200 increased by 20.6 % and 87.7 %, respectively. However, the tensile strength of UHPC had a slight influence on the yielding and ultimate moment as well as ductility.

Hydration heat generation and dissipation in diaphragm walls

This study focuses on the complex dynamics of heat dissipation within diaphragm walls during concrete hydration, crucial in construction engineering. Experimental measurements from three sites in Poland, featuring diaphragm walls of varying thicknesses, ranging from 1 to 1.5 meters, were compared to a numerical model. The model, using a Finite Difference Method, incorporated stages of execution of adjacent panels and their thermal influence. The results closely mirrored the measured temperatures, validating the accuracy of its predictions. Despite minor discrepancies, mostly within ±3°C, the method effectively approximated real-life scenarios. Suggestions for model enhancements include incorporating the effect of concrete admixtures and refining the modeling of sequential panel execution. The thermal soil parameters, their possible range, and their impact on hydration heat dissipation in deep foundations emerged as crucial insights. This research serves as a foundation for deeper investigations into early-age behavior in deep foundations, aiming to extend the analysis to stress and strain domains to unravel characteristic cracking patterns observed in diaphragm walls.

Assessing Activation Quality through Evaporative Drying Patterns of Zr-MOF (UiO-66) Colloidal Droplets.

We demonstrate a simple droplet diagnostic approach to monitor the UiO-66 MOF (metal-organic framework) synthesis and its quality using the sessile droplet drying phenomenon. Drying a sessile droplet involves evaporation-driven hydrodynamic flow and particle-nature-dependent self-assembled deposition. In general, the MOF synthesis process involves different sizes and physicochemical nature of particles in every synthesis stage. Equivalent quantities of each of purified pore-activated UiO-66 MOF, yet-to-be-purified pore-inactivated UiO-66 MOF, and reaction precursors of UiO-66 MOF give different deposition patterns when a well-dispersed aqueous droplet of these materials undergoes drying over substrates of varying stiffness and wettability. Yet-to-be-purified, pore-inactivated UiO-66 MOF nanoparticles undergo transport toward the droplet periphery, leading to a thick ring-like deposition at the dried droplet edge. Under appropriate drying conditions, such a deposit leads to desiccation-type mud-like reticular cracking. We study the origin of such ring-like deposits and cracks to understand how the surface charge density of UiO-66 particles controls their stability. We demonstrate that ZrOCl2 salt trapped in a nonpurified pore-inactivated UiO-66 MOF moiety is the principal reason for ring-like deposit formation and subsequent cracking in its dried aqueous droplet edge. Qualitatively, we identified Lewis acid salts that are capable of acting as Bro̷nsted acid upon hydrolysis (like FeCl3, SnCl2, and ZrOCl2), influence surface charge density and colloidal stability of dispersed UiO-66 MOF particles. As a result, immediate particle coagulation is avoided, so those travel to the droplet edge, forming ring-like deposition and subsequent cracking upon drying. Further, we show that crack patterns on such deposits are highly dependent on the stiffness and temperature of depositing substrates via a competition between axial and lateral strains at the deposit-substrate interface.

Phase Field Fracture Model for Assessing the Load Bearing Capacity of Fractured Glass

The use of glass as structural material has highlighted the need for more reliable numerical approaches to analyze its mechanical behavior, especially in the accidental eventuality of fracture. Modelling the behavior of fractured laminated glass, in fact, is fundamental to assess the Post-Fracture load-bearing capacity. However, this is a highly challenging task because of the many interplaying factors, such as the viscoelastic and thermal-dependent behavior of the interlayer, the presence of a highly complex and variable crack pattern and the interaction among fragments. The objective of the present work is the development and testing of a robust numerical model that can naturally introduce the generated crack pattern into virtual specimens and manage the interaction among many fragments. The phase field fracture model is herein explored, by assigning the damage variable to fit the pre-existing crack pattern. Then, the specimen is loaded letting the phase field managing the fragments interaction. The dependence of the stress tensor with the damage variable is herein defined through the Cleavage-Deviatoric model, since it prevents fully damaged regions from transmitting tensile and shear stresses yet keeping their ability to bear compressive forces. Indeed, this model can asymptotically reproduce unilateral and frictionless contact conditions between the existing crack lips. Preliminary case studies are discussed to check the potentiality of the proposed approach.

Flexural strengthening of LWRC beams using RSHCC reinforced with glass fiber textile mesh

This study aims to explore the flexural behavior of crushed clay brick (CCB) lightweight concrete (LWC) beams strengthened with rubberized strain-hardening cementitious composite reinforced with glass fiber textile mesh layers (GFTM-RSHCC) at the tension side. For this purpose, an experimental investigation consisting of seven simply supported beams, including one un-strengthened specimen, was produced and tested using a monotonic 4-point loading scheme. All specimens had a 120 × 250 mm cross-section, a total length of 2400 mm, and a loaded span of 2200 mm. The studied parameters were the number of GFTM inside the RSHCC (1, 2, or 3) and the thickness of GFTM-RSHCC layer (30 or 40 mm). All the following aspects were tracked: crack pattern, ultimate load, mid-span defection, and ductility. The results show that increasing the number of layers of GFTM and the thickness of RSHCC generally leads to an increase in the ultimate loads and ductility, up to 68% and 83%, respectively, compared to the control beam. Finally, a proposed equation considering the contribution of the GFTM-RSHCC layer was developed to predict the flexural capacity of the strengthened beams. The proposed equation showed good agreement with the experimental results.

Exploring engineering properties of sustainable multi‐grade concrete: Materials, structural, and environmental aspects

AbstractThrough experimental and theoretical studies, this research explores the materials, structural, and environmental aspects of multi‐grade concrete (MGC), a potentially sustainable structural concrete. The experimental part investigates the compressive, split cylinder, flexural, and shear strengths of MGC, essential parameters for the design of structural members composed of MGC. It also provides the relationships between various strengths. The compressive behavior is correlated with the cracking pattern and the confinement effect caused by the end platens. The theoretical study involves determining the carbon emissions (CEs) and modifying ASTM/ACI expressions for the flexural tensile strength (FTS) and shear capacity applicable to MGC. Three uni‐grade concretes (UGCs) with distinct materials, properties, and grades: grade 17 (G17), grade 25 (G25), and grade 30 (G30), were poured in layers of varied thicknesses to make two variants of MGC. Experimental investigations showed that the higher‐strength concrete (HSC) confined the lower‐strength concrete (LSC) part thus increasing the compressive strength. Replacing 50% of LSC with HSC led to an increase in compressive and shear strengths by 21% and 40%, respectively. The shear strength values of reinforced MGC beams observed experimentally are aligned with those obtained through the modified expressions developed by the authors. A trade‐off analysis among the strengths, CEs, and costs of UGC and MGC can aid in selecting MGC customized to specific requirements, thereby contributing to the development of sustainable structural concrete.

Stochastic fracture of concrete composites: A mesoscale methodology

The accurate prediction of concrete composites’ fracture behaviour requires precise meso-structural characterization, appropriate fracture modelling, and pivotal uncertainty assessment. Towards this goal, we adopt a dynamics approach with CT images to generate numerical concrete models using real aggregates with 30%-60% contents. An image slicing method is then developed to obtain a large number of realistic models in 2D, whose heterogeneity is characterised by aggregates, mortar and interfaces. Monte Carlo simulations of uniaxial tension are performed, incorporating cross-scale fracture evolution through a phase-field cohesive zone model. Statistical analyses reveal that the stochasticity of crack patterns and stress-displacement curves, especially post-peak softening responses, is inherently dependent on the random meso-structures. It is observed that increasing aggregate content accelerates the deterioration rate of peak stress, decreases the softening curve, and leads to more tortuous crack paths, considering the ITZ crack channels. On the other hand, the tensile strength of mortar has significant impacts on the load-carrying capacity, while the fracture energy primarily influences the ductility and has negligible effects on the peak stress and the pre-peak nonlinear part. Besides, the ratios of mortar-ITZ tensile strength and fracture energy are found to affect the crack paths. The proposed numerical framework holds promise to reveal complex fracture mechanisms of concrete with more insights into other loading or environmental conditions.

Domain decomposition methods and acceleration techniques for the phase field fracture staggered solver

AbstractThe phase field modeling of fracture is able to simulate the nucleation and the propagation of complex crack patterns. However, the relatively small internal lengths that are required usually lead to very fine meshes and high computational costs, especially for three‐dimensional applications. In the present work, additional cost also comes from the implicit dynamics regularization of unstable crack propagations which potentially leads to a large variation of time steps when switching from quasi‐static to dynamic regimes. To reduce the time to solution in this context, this study proposes a domain decomposition framework and acceleration techniques for the phase field fracture staggered solver. The displacement subproblem and the phase field one are solved with parallel domain decomposition solvers. Dual domain decomposition methods provide low cost preconditioner well adapted to the phase field subproblem. For displacement subproblems undergoing unstable crack propagations, primal domain decomposition methods are preferred to be less sensitive to the treatment of floating substructures. Preconditioners performances are assessed and scalability studies over academic test cases, up to 324 subdomains, are presented. Finally, the robustness of the approach is illustrated on two semi‐industrial simulations.

Inverse interaction of shear between steel-stirrups and externally bonded carbon fiber-reinforced polymers in shear-strengthened reinforced concrete beams: Analytical and numerical models

Shear failure in reinforced concrete (RC) beams have always been a serious concern due to its brittle fracture mode. In addition, many questions are raised about the accuracy of current design guidelines for predicting the shear resistance contribution of externally bonded carbon fiber-reinforced polymers (EB-CFRPs) to the ultimate shear strength of strengthened RC beams, particularly with regard to the inverse interaction of the shear contribution between steel-stirrups and EB-CFRPs. The main objective of the present study is to implement experimental and numerical tests to develop analytical and numerical models for RC beams strengthened in shear using EB-CFRPs. Emphasis is placed on the negative inverse interaction between the steel-stirrups and the EB-CFRPs as the ratio of EB-CFRP-to-steel-stirrups increases with increasing the CFRP rigidity (CFRP thickness and CFRP width). The inverse interaction is not included in the design models proposed by most current guidelines, although it has a considerable effect on shear resistance as predicted by the guidelines. In fact, the shear contribution associated with EB-CFRP decreases as the ratio of EB-CFRP-to-steel-stirrups increases. Therefore, proposing reliable effective strains by including these parameters improve the calculated shear contribution of EB-CFRPs. First, an analytical model is proposed for CFRP effective strain considering the inverse interaction between EB-CFRPs and steel-stirrups. Afterward, a validation of the proposed model with experimental data is done by conducting a parametric study of the increasing trends with respect to the ratio of EB-CFRP-to-steel-stirrups. A numerical finite-element model for the reduction factor and the corresponding effective strain based on the inverse interactions between EB-CFRPs and steel-stirrups is also proposed, and the results are compared with various current guidelines. The results are presented in terms of shear crack patterns, load-midspan deflections, shear stresses, strain responses along the fibers, maximum strain profiles for all the CFRPs and specimens, applied shear forces and strains for all the steel-stirrups and EB-CFRPs, and interactions between steel-stirrups and EB-CFRPs based on their maximum strain contributions at the maximum shear forces and the maximum strain they experience after shear failure.

Behavior of Fatigue Damaged Reinforced Concrete One-Way Slabs Repaired With CFRP Sheets

Abstract The results of experimental research involving nine one-way slabs are detailed in this report. The objective was to investigate the impact of different parameters on the structural performance of these slabs in their absence and with strengthening. Externally bonded CFRP sheets strengthened six of the nine slabs; the three remaining slabs served as control specimens. Before subjecting the specimens to monotonic loading, pre-fatigue damage of 50% and 70% repeated loading was induced. An exhaustive assessment was conducted on each slab, in which it was compared to its control slab. Several crucial elements were incorporated into the evaluation, including the ultimate load capacity, the reason for failure, crack patterns, and load-deflection curves. Examining these metrics was intended to provide insight into the efficacy and structural performance of the employed fortification technology. Compared to unenhanced reinforced concrete slabs (control slab), the highest stresses on slabs supported with bonded CFRP sheets are between 20 and 44% better. Compared to the control slab, an almost 70% reduction in deflection was observed. The flexural performance of compromised reinforced concrete slabs repaired with this technology can be brought up to date and enhanced.

Behavior of hybrid R.C. columns under the effect of fire furnace (experimental and numerical study)

ABSTRACT When fire exposes the hybrid reinforced concrete R.C. columns, it seriously damages the mechanical qualities of steel bars, concrete, and glass fiber reinforced polymer G.F.R.P. bars. This study focused on hybrid reinforced concrete R.C. columns’ behaviour and failure modes that were eccentrically and concentrically loaded during the fire until a failure. The behaviour of these R.C. columns will be quantified by demonstrating and going over the load-displacement relationships, failure mechanisms, crack patterns, strain distribution at failure, ductility, and stiffness. The number and width of cracks in the columns heated to 300 ºC, 500 ºC, and 700 ºC were significantly more than in the unheated columns. When the specimen is exposed to high temperatures, less force is needed to cause a first crack, and the ultimate strength decreases as the applied load and eccentricity ratio values increase. Hence, all specimens’ axial and lateral displacement values increase. This can be explained by two factors: the depth of the practical section because of the thermal expansion effect and the cracking expansion of concrete when subjected to high temperatures, and heating causes a loss in stiffness of column because the elasticity of concrete’s modulus of elasticity drops.

Behavior of Lightweight Aggregate Wide Reinforced Concrete Beams with Shear Steel Plates Under Repeated Loading

Abstract This study describes an experimental research focusing on the behaviour of Lightweight Aggregate Wide Reinforced Concrete Beams (LAWRCB) using shear steel plates. This technique represents an inexpensive way which reduces structural and building complexities. Wide beams can provide adequate cross-sectional areas to meet the specified capacity in a shallower depth than a system of narrower beams placed similarly in the design. Also, WB treats the crowd of stirrups because the shear component provided by concrete is very small compared with high depth concrete Beams. This research is also trying to minimize the weight of a wide concrete beam using light weight concrete instead of using conventional concrete which has effects on the deflection, crack patterns, and load carrying capacity. This investigation consists of reviewing the previous work and an experimental program consisting of testing mixes to produce lightweight concrete. In addition, several simply supported wide beams with various parametric studies will be designed, cast, and tested. After the specimen tests are carried out, comparisons and discussions of the results will be made with code requirements.