Rupture Mode Research Articles

Unsteady slip pulses under spatially-varying prestress

It has been recently established that self-healing slip pulses under uniform background/ambient stress (prestress) τb are intrinsically unstable frictional rupture modes, i.e., they either slowly expand or decay with time t. Furthermore, their spatiotemporal dynamics have been shown to follow a reduced-dimensionality description corresponding to a special one-dimensional curve L(c), parameterized by τb, in a plane defined by the pulse propagation velocity c(t) and size L(t). Yet, uniform prestress is rather the exception than the rule in natural faults. Here, we study the effects of a spatially-varying prestress τb(x) (in the fault direction x) on 2D slip pulses, initially generated under a uniform τb along a rate-and-state friction fault. We consider both periodic and constant-gradient prestress distributions τb(x) around the reference uniform τb. For a periodic τb(x), pulses either sustain and form quasi-limit cycles in the L−c plane or decay predominantly monotonically along the L(c) curve depending on the instability index of the initial pulse and the properties of the periodic τb(x). For a constant-gradient τb(x), expanding and decaying pulses closely follow the L(c) curve, with small systematic shifts determined by the sign and magnitude of the gradient. We also find that a spatially-varying τb(x) can revert the expanding/decaying nature of the initial reference pulse. Finally, we show that a constant-gradient τb(x), of sufficient magnitude and specific sign, can lead to the nucleation of a back-propagating rupture at the healing tail of the initial pulse, generating a bilateral crack-like rupture. This pulse-to-crack transition, along with the above-described effects, demonstrate that rather rich rupture dynamics can emerge from a simple, spatially-varying prestress. Furthermore, our results show that as long as pulses exist, their spatiotemporal dynamics are related to the special L(c) curve, providing an effective, reduced-dimensionality description of unsteady slip pulses under spatially-varying prestress.

The 2021 and 2022 North Coast California Earthquake Sequences and Fault Complexity in the Vicinity of the Mendocino Triple Junction

ABSTRACT The Mendocino Triple Junction (MTJ), one of the most tectonically active and complex regions of California, has damaging earthquakes on the San Andreas and Mendocino faults, within the oceanic and subducting regions of the Gorda section of the Juan de Fuca plate, and within the overriding North American plate (NAP). Two recent earthquake sequences in the MTJ region, starting on 20 December 2021 and 20 December 2022, highlight the complex interactions of regional faults. We explore these sequences to better define the deep faults in the MTJ region, and their rupture modes. Our finite-source analysis shows the 2021 sequence began with two M ∼6.0 earthquakes separated by ∼11 s in time and 30 km in distance. The first earthquake occurred offshore on the Mendocino fault at a depth of 16.5 km. Its S waves triggered an “onshore” intraplate Gorda event at a depth of 27 km, which ruptured a vertical fault toward the northeast. Finite-source analysis of the mainshock of the 2022 sequence, M 6.4, indicates the rupture started offshore north of Cape Mendocino within the Gorda plate and propagated east-northeast, toward populated areas. Damage to towns and infrastructure was exacerbated by directivity and the sediment-filled valleys, as well as by a large aftershock (M 5.4) centered 20 km south-southeast of the mainshock rupture plane. The depths and mechanisms of the onshore 2021 and the 2022 earthquakes and their aftershock sequences indicate that they occurred on different strike-slip faults within the subducted portion of the Gorda plate. The faults active in these earthquakes are unrelated to mapped surface faults in the overriding NAP and are oblique to the tectonic trends seen at the surface. The 2021 and 2022 earthquakes are close to the boundary between two distinct regions of the Gorda plate, where offshore north–south horizontal compression transitions to east–west downslab tension.

Deep Tectonic Environment Analysis of the Lingshan Conjugate Earthquake within the Qinzhou Fold Belt, South China: Insights Derived from 3D Resistivity Structure Model

The Qinzhou fold belt, situated at the contact zone between the Yangtze and Cathaysia blocks in South China, was affected by the 1936 Lingshan M6¾ earthquake and the 1958 Lingshan M5¾ earthquake, both of which occurred within the conjugate structure. Understanding the deep seismogenic setting and causal mechanism of the Lingshan conjugate earthquake is of great significance for assessing the seismic disaster risk in the region. In this study, we utilized 237 magnetotelluric datasets and employed three-dimensional electromagnetic inversion to characterize the deep-seated three-dimensional resistivity structure of the Qinzhou fold belt and the Lingshan seismic zone. The results reveal that: (1) The NE-trending faults within the Qinzhou fold belt and adjacent areas are classified as trans-crustal faults. The faults exhibit crust-mantle ductile shear zones in their deeper sections, which are essential in governing regional tectonic deformation and seismic activity; (2) The electrical structure of the Qinzhou fold belt is in line with the tectonic characteristics of a composite orogenic belt, having experienced several phases of tectonic modification. The southeastern region is being influenced by mantle-derived magmatic activities originating from the Leiqiong area over a significant distance; (3) In the Lingshan seismic zone, the NE-trending Fangcheng-Lingshan fault is a trans-crustal fault and the NW-trending Zhaixu fault is an intra-crustal fault. The electrical structure pattern “two low, one high” in the zone has a significant impact on the deep tectonic framework of the area and influences the deformation behavior of shallow faults; and (4) The seismogenic structure of the 1936 Lingshan M6¾ earthquake was the Fangcheng-Lingshan fault. The earthquake’s genesis was influenced by the coupling effect of tectonic stress and deep thermal dynamics. The seismogenic structure of the 1958 Lingshan M5¾ earthquake was the Zhaixu fault. The earthquake’s genesis was influenced by tectonic stress and static stress triggering from the 1936 Lingshan M6¾ earthquake. The conjugate rupture mode in the Lingshan seismic zone is influenced by various factors, including differences in physical properties, rheology of deep materials, and the scale and depth of fault development.

Study on the influence of indentation depths on the fracture characterization and acoustic emission characteristics of minerals in granite using nanoindentation

To investigate the intrinsic mechanisms of rock rupture at the mesoscale, this study employed nanoindentation tests on three primary minerals in granite at various indentation depths. Concurrently, rupture signals generated throughout the indentation process were recorded using the PCI-2 acoustic emission (AE) system. The results revealed that crack lengths in quartz and feldspar increased with indentation depth, whereas mica exhibited negligible radial cracking, showing only short, irregular cracks around the edges of the indentation marks. As indentation depth increased, the intensity of plastic deformation at the indentation point also increased, leading to a gradual reduction in fracture toughness and a corresponding rise in AE amplitude and energy. All three minerals generally showed a higher proportion of high-frequency signals compared to low-frequency signals, with the distribution characteristics of these signals being significantly influenced by the mineral properties. Quartz and feldspar exhibited relatively balanced frequency distributions, while mica had a higher proportion of high-frequency signals. At different indentation depths, most signals displayed characteristics of higher RA values and lower AF values, indicating that, at the mesoscale, the rupture modes of the three major minerals in granite are predominantly shear failures.

Numerical experimental study on the fracture process of shale containing internal prefabricated cracks based on CT scanning with different quartz contents

The quartz content and internal fractures of shale are important factors affecting its mechanical properties and damage modes. To study the mechanical properties of shale under the effect of quartz content and internal cracks, this study used CT scanning technology and digital image processing technology, combined with finite element software to establish a three-dimensional numerical model of shale with different quartz contents and different angles of internal prefabricated cracks, and carried out numerical simulations of Brazilian splitting. Both the quartz content and internal prefabricated cracks in shale can significantly affect the tensile strength of shale. The tensile strength is positively correlated with the quartz content in shale, and tends to increase and then decrease with increasing angle of the internal prefabricated cracks. The quartz content and the internal prefabricated cracks together control the damage of shale, the quartz content increases the damage degree of shale, and the internal prefabricated cracks control the rupture mode of shale, The cracks will have a significant guiding role in crack expansion with increasing angle, and finally show a significant influence on crack expansion from type I to type II. The research results of this paper will play a certain role in promoting the exploitation of shale gas.

Experimental analysis of the tensile behavior of concrete reinforced with Brazilian glass textile

In this study, the mechanical behavior of concrete structures reinforced with one and two layers of the Brazilian glass textile “AR-360” was verified through direct tensile tests. The analysis of the mechanical behavior of the structures was performed with stress-strain curves, evaluating the transition points of the formed stages, rupture mode, rupture stress and strain, as well as an analysis comparing experimental results with analytics. Regarding the results, there was a structural inability of the pieces reinforced with a layer of glass textile. In the samples in which reinforcement with two layers of the aforementioned material was evaluated, the three stages present in the stress-strain curves were correctly identified, as predicted in the literature for the structures evaluated.

Behavior prediction of reinforced concrete beams shear strengthened with CFRP

This work presents the computational modeling of reinforced concrete beams, strengthened to shear with carbon fiber-reinforced polymers (CFRP), using the finite element method (FEM) and the customized ANSYS software, version 19.2. It is important to emphasize that contact elements and bilinear cohesive zone models provided by ANSYS were used to model the concrete-reinforcement interface. These models were used to identify the modes of premature failure caused by the debonding of the reinforcement, which causes poor use of the CFRP's resistance properties. The structural elements used in this analysis were twelve simply supported reinforced concrete beams, without and with shear reinforcement using CFRP, which were experimentally tested by Khalifa (1999). From the analysis of the results, it was observed that the developed numerical models were able to accurately predict the behavior of the simulated beams, both in terms of load-displacement, as well as the load and rupture mode of the beams.

Fracture characterization of fractured rock bodies based on acoustic and optical characteristics

Crack propagation is an important cause of damage to rock bodies. In this study, uniaxial compression tests were conducted on specimens with rock-like mass containing fissures with different inclination angles to study the effect of crack angle on the crack evolution and fracture characteristics of rock bodies. The specimen surface deformation and internal response characteristics during fracture were analyzed via digital image correlation (DIC) and acoustic emission (AE) techniques. The results indicated that the AE characteristics of the fractured specimens exhibited a high degree of activity during the pore compaction and crack propagation stages. The prefabricated fissure configuration affected the stress state at the fissure tip, leading to differences in the crack evolution paths and rupture modes of fissure specimens with different angles. Under the uniaxial peak intensity, the relative position of the normalized global strain curve peak point gradually shifted from the specimen tip to the middle of the specimen as the crack angle increased, which corresponded to the shear damage-tension-shear mixed damage-tension damage modes of the specimen. The findings of this study indicate that normalized global strain curves can reflect the characteristics of crack evolution and provide a basis for the discrimination of fissured rock mass damage modes.

Thermal runaway of Li-ion batteries caused by hemispherical indentation under different temperatures: Battery deformation and fracture

Thermal runaway (TR) of Li-ion batteries (LIBs) presents a disastrous safety hazard and a significant barrier to the wider adoption of electric vehicles (EVs). Internal short circuit (ISC) induced by mechanical abuse is one of the causes of battery TR. This paper uses hemispherical indentation tests to trigger ISC in the battery at different temperatures and studies the battery deformation and fracture mode. Results show as the initial temperature increases, the battery hardness and strength decrease, and the fracture mode of the laminar structure changes from shear fracture to localized rupture. In the shear fracture mode, the ISC homogeneously heats the battery, and it does not directly trigger TR. In the localized rupture mode, the ISC is only induced at the layers close to the indenter and generates a hot spot exceeding 200 °C, leading to the initiation of TR. Therefore, the mechanical properties of batteries under different conditions need to be studied in more detail to develop batteries that are safer under mechanical abuse.

Behavior of self-sensing masonry structures exposed to high temperatures and rehydration

High temperatures can compromise the structural integrity of structural masonry. Therefore, assessing the post-fire mechanical behavior is crucial for selecting suitable rehabilitation methods. Recent research has proposed the application of self-sensing cementitious composites for monitoring strains, stresses, and damage of structural masonry in room temperature. No previous research has been found on the self-sensing performance of fire-damaged masonry prisms exposed to elevated temperatures, with or without subsequent rehydration. Masonry prisms with integrated self-sensing joints and blocks were produced and exposed to different maximum temperature levels, followed or not by rehydration. Then, experimental tests for determination of compressive strength, modulus of elasticity, gauge factor (GF) and damage-detection performance were carried out. The exposure to 300 ºC caused a 7.4 % decrease in compressive strength and a 44.5 % reduction in elastic modulus. Rehydration methods had negligible effects in this case. After 600 ºC, substantial reductions of 42.2 % in compressive strength and 81.5 % in elastic modulus occurred. In this case, rehydration led to a 15.9 % increase in compressive strength and a 117.4 % increase in elastic modulus. Regardless of the exposure temperature, the predominant rupture mode initiated by vertical cracks originating at the block-mortar interfaces. After 300 ºC, slight GF increases occurred due to the thermal decomposition of hydrates of the cementitious matrix, while exposure to 600 ºC resulted in high GF increases due to partial oxidation of nanomaterials and substantial microcracking propagation. Post-fire curing improved the GF by sealing microcracks with nonconductive rehydration products and enhancing tunneling conduction mechanisms. The self-sensing prisms also demonstrated the ability for real-time damage detection and quantification, providing valuable predictive insights into the propagation of damage.

Onset and propagation of slip at adhesive elastic interfaces.

The transition from static to dynamic friction when an elastic body is slid over another is now known to result from the motion of interface rupture fronts. These fronts may be either cracklike or pulselike, with the latter involving reattachment in the wake of the front. How and why these fronts occur remains a subject of active theoretical and experimental investigation, especially given its wide ranging implications. In this work, we investigate the role of boundary loading in answering this question using an elastic lattice-network model under displacement/velocity controlled loading. Bulk elastic and interface bonds are simulated using a network of springs, with a stretch-based detachment and reattachment rule applied to interface bonds. We find that, contrary to commonly used rigid body models with Coulomb-type friction laws, the type of rupture front observed is very closely linked to the location of the applied boundary displacements. Depending on whether the sliding elastic solid is pulled, pushed or sheared-all equivalent in the rigid case-distinct interface rupture modes can occur. We quantify these rupture modes, evaluate the corresponding interface stresses that lead to their formation, and and study their subsequent propagation dynamics. Our results reveal quantitative analogies between the sliding friction problem and mode II fracture, with attendant wave speeds ranging from slow to Rayleigh. We discuss how these fronts mediate interface motion and implications for the general transition mechanism from static to dynamic friction.

Influence of The Type of Laying Joint on The Mechanical Behavior of Prisms Made With Ecological Bricks

Objective: This paper proposes the study of the influence of laying joints on the mechanical behavior of masonry prisms made with ecological bricks. Method: To this end, an experimental program was developed including prisms constructed with different types of joints: laying mortar, adhesive mortar and PVA glue (polyvinyl acetate). Results and Discussion: The adhesive mortar and the conventional mortar were characterized in terms of their compressive strength, obtaining a resistance approximately 1.36 times the compressive strength of the brick (6.92±0.51 MPa), while the settlement was close (0.99%). The average compressive strengths of the prisms were very different, demonstrating that the laying joint has a significant influence on cement-based masonry. It was found that the use of adhesive mortar made it possible to increase the resistance capacity of the prisms to compression by 75%, when compared to prisms made with joints that used PVA glue. However, the laying mortar showed a similar result, at 53%. The rupture mode observed in the prisms made with sticky and conventional mortar was due to traction cracking in the brick units. Research Implications: In this study, it can be concluded that when using ecological bricks with different types of joints, the thickness and type of mortar can have a significant influence on the final strength of the materials, however thin joints tend to maximize the effects defects and reduce the resistant capacity of these masonries.

Conduction mechanisms analysis of ZrO2-based electrochemical metallization RRAM in different RESET modes

Resistive random access memory (RRAM) based on electrochemical metallization (ECM) is a promising candidate for future nonvolatile memory applications. This paper discusses the resistive switching (RS) behavior and conduction mechanism in the ZrO2-based ECM nonvolatile memory devices. Whether Cu or Ni is used as the top electrode, two different types of I-V curves are found in the same device, representing different RESET modes. The I–V fitting analysis suggests that one RRAM cell can follow two significantly different conduction mechanisms under two types of RESET modes. Under sudden rupture mode, conduction at the high resistance state (HRS) is dominated by a space-charge-limited conduction (SCLC). In contrast, under slow dissolution mode, the devices at HRS tend to show an Ohmic conduction mechanism. These phenomena can be explained by a physical model based mainly on Joule heat or electric field, which is related to the degree of dissolution and rupture of multiple conductive filaments (CFs). Furthermore, the electrical field simulation results based on the solid electrolyte theory by MATLAB further demonstrate the coexistence of two conduction mechanisms in Cu (or Ni)/ZrO2/Pt devices HRS. This paper provides a direction for better understanding the conversion mechanism of ECM RRAM, which is of great significance for the further development of RRAM.

Effects of Oxygen Content on Microstructure and Creep Property of Powder Metallurgy Superalloy

The effects of oxygen content on the microstructure and creep properties of the FGH96 superalloy were investigated. When oxygen content increased from 135 ppm to 341 ppm, the prior particle boundary (PPB) rose from degree 2 to degree 3, the size of the γ′ phase on PPB enlarged from 1.07 μm to 1.27 μm, and the MC carbide size grew from 77.4 nm to 104.0 nm. Meanwhile, the steady creep rate accelerated from 4.34 × 10−3 h−1 to 1.87 × 10−2 h−1, and the creep rupture life shortened from 176 h to 94 h, the creep rupture mode transferred from intergranular and transgranular mixed fracture to along PPB fracture. During creep, the micro-twin formation and gliding will be restrained by ∑3 boundaries. FGH96 superalloy with higher oxygen content contains less ∑3 boundaries, and its micro-twins cross-slipped instead of single-direction slip in lower oxygen content superalloy. Consequently, samples with a higher oxygen content crept faster and ruptured earlier.

A comparative study on resistance spot and laser beam spot welding of ultra-high strength steel for automotive applications

In this study, the effect of resistance spot welding (RSW) and laser beam spot welding (LBSW) processes on evolution of microstructure, load endurance capabilities, heat affected zone (HAZ) softening, and corrosion resistance of ultra-high-strength (UHSS) steel joints welded in lap joint design is investigated. The UHSS sheets of dual phase 1000 grade (UHSDP1000) having 1.20 mm thickness were joined using the RSW and LBSW parameters optimized by response surface methodology (RSM). The microstructural features of welding regions of RSW and LBSW joints were studied using optical microscopy (OM). The load endurance capabilities of RSW and LBSW joints were assessed using the tensile shear failure load (TSFL) and cross-tensile failure load (CTFL) tests. The ruptured surfaces of TSFL and CTFL tested samples were examined utilizing scanning electron microscopy (SEM). The microhardness distribution of divergent regions of RSW and LBSW joints was evaluated and imputed to the TSFL and CTFL failure of joints. The corrosion resistance of RSW and LBSW joints was analyzed using potentiodynamic corrosion and immersion corrosion tests. The RSW joints showed 183% and 62.79% greater TSFL and CTFL endurance capabilities than LBSW joints. The TSFL and CTFL endurance capabilities of LBSW joints are inferior to RSW joints due to the smaller load bearing area. It causes the stress concentration in FZ and HAZ of LBSW joints. The RSW joints and LBSW joints disclosed TSFL and CTFL failure in button pull out rupture mode with tearing of HAZ. The failure of RSW and LBSW joints in HAZ is due to the softening caused by martensitic tempering and coarsening of grains. The LBSW joints disclosed inferior resistance to corrosion than RSW joints due to the higher martensite content which contributes to greater fraction of favorable pitting sites and decreased corrosion resistance.

Toughness behavior and deformation mechanisms in FCC-based Fe45Co30Cr10V10Ni5-xMnx high-entropy alloys: Insights from instrumented Charpy impact tests

This study investigated toughness properties of FCC-based Fe45Co30Cr10V10Ni5-xMnx high entropy alloys (HEAs). Ductile-dimpled rupture mode in all alloys and test temperatures complicated precise explanations on Charpy impact energy, but the instrumented Charpy test provided a breakdown of total energy (ET) into initiation energy (EI) and propagation energy (EP), offering critical insights into Mn-content- and temperature-related energy variations. Pmax and TP, reflecting maximum flow stress and time, respectively, until initiation of crack propagation from the notch tip, involved a transition of deformation mechanisms from slip to TWIP, then to BCC-TRIP, thereby inducing increased strain hardening and delaying plastic instability at the notch tip. At 25 °C, an increase in Mn content prompted a transition in deformation behavior from slip to TWIP and subsequently to BCC-TRIP, correlating well with increased Pmax and TP and consequently ET due to enhanced strain hardenability. At −196 °C, predominant BCC-TRIP activity in all alloys led to increased formation of BCC martensite, intensifying strain hardening and requiring higher Pmax for crack initiation than at 25 °C. Due to minimal slip line field formation associated with reduced plastic deformation, however, cracks initiated directly from the notch-tip center, representing fast initiation of crack propagation and consequently reduction in EI and ET. Thus, utilizing parameters from instrumented Charpy tests, including Pmax, TP, EI, EP, and ET, provided insights into fracture phenomena and their interrelations in the present HEAs.

Formulation of high-temperature strength equation of 9Cr-ODS tempered martensitic steels using the Larson–Miller parameter and life-fraction rule for rupture life assessment in steady-state, transient, and accident conditions of fast reactor fuel

This paper discusses the applicability of Straalsund et al.’s technique for combining the Larson–Miller parameter (LMP) and life-fraction rule to form a single high-temperature strength equation for 9Cr-oxide-dispersion-strengthened (ODS) tempered martensitic steels (TMS). It uses the extensive dataset on creep rupture, tensile, and temperature-transient-to-burst tests of 9Cr-ODS TMS cladding tubes in the α-phase, α/γ-duplex, γ-phase matrices, which are accumulated by the Japan Atomic Energy Agency so far. The technique is adequately applicable to 9Cr-ODS TMS cladding tubes. A single high-temperature strength equation expressing the mechanical strength in different deformation and rupture modes (creep, tensile, temperature-transient-to-burst) is derived for 9Cr-ODS TMS cladding tubes. This equation can predict the rupture life of the cladding tubes under various stresses and temperatures over time. The applicable range of the high-temperature strength equation is specified in this study and the upper limit temperature for the equation is found to be 1200 °C. At temperatures higher than 1200 °C, the coarsening and aggregation of nanosized oxide particles and the γ to δ phase transformation are reported in previous studies. The high-temperature strength equation can be well applied to the creep and tensile strength in the α-phase matrix, the creep strength in the γ-phase matrix and the temperature-transient-to-burst strength in both phases except for the low equivalent stress (43 MPa) at temperatures exceeding 1050 °C. The mechanism of the notable consistency between creep and tensile strength in the α-phase matrix is discussed by analyzing the high-temperature deformation data in the light of existing deformation models. The study suggested the thermal activation process is dominant even for the high-temperature deformation modes exceeding yield stress in the 9Cr-ODS TMS with the fine-grained matrix.

Coupling of surface and volume behaviors to understand the generation of TTS in pure magnesium proceeded by HPT

This study analyzes the formation of tribologically transformed structures (TTS) in pure magnesium (Mg) using high-pressure torsion (HPT) processing. Generally, studies conducted in such conditions do not focus on surface behaviors. The correlation between the friction and wear phenomena at the surface and the microstructural changes was investigated to supplement the knowledge on TTS formation during the first stage of rotation. An RHEOS apparatus was used to test the samples with an average grain size of 70 μm under a mean pressure of 1 GPa and a rotation speed of 0.5 rpm. The samples were conducted in an unconstrained setup at room temperature. Surface and microstructure changes were examined using optical microscopy, scanning electron microscopy (SEM), and the focused ion beam (FIB). Observation of surfaces shows that friction between the anvils and the surfaces of the sample was set to satisfy the sticking condition. Three different zones in surface contact are identified: the centre zone, the adhesion/sliding zones, and the edge zone, which generate consequently different behaviors. It was found that 0.5 turns of HPT produced a significant refinement in the grain size of the processed Mg. The TTS were considered a zone with a fine microstructure, where the initial grain size was reduced to the range of 300 nm to 1000 nm. The results show that TTS produced in these conditions are not homogenous. The deformation occurs differently, so the TTS were less or more refined. According to the different observations, a scenario of surface degradation was established. The accommodation mechanisms considered are the rupture and shear modes, which occurred, respectively, in the first material and the third body.

Numerical analysis on flat slabs with openings and SHEAR reinforcement

AbstractThe present study aims to parameterize the numerical models of flat slabs based on five experimental prototypes developed previously. The analyzed slabs had dimensions of 1800 mm × 1800 mm and a thickness of 130 mm. Two slabs did not have openings, and three slabs had stud‐type shear reinforcement. Subsequently, five new slab models were selected with position variations and several openings, with a fixed diameter of 75 mm and without shear reinforcement. After calibration of the models, the following results were obtained: the numerical rupture load approached at least 90% of the experimental rupture load, and the rupture modes and cracking patterns were similar to those observed in the experimental models. When it is impossible to move the column openings vertically, it is more beneficial to position them at the corners of the column rather than close to the same face of the column. Thus, it was possible to numerically analyze the effects of the position and number of openings in flat slabs.

Resistência ao cisalhamento longitudinal de lajes mistas modeladas em escala real considerando a geometria das mossas por meio do método dos elementos finitos

Abstract Slabs with cast-in-place steel formwork are composite structural elements composed of concrete and steel. The horizontal shear failure mode is the most common in composite slabs based on numerous experimental studies. This failure mode consists of loss of adherence and mechanical contact at the interface of the composite system and often occurs before the system reaches its full bending capacity. Thus, the design of this constructive system is determined by the value of the longitudinal shear strength, which can be computed by the semi-empirical so-called traditional m-k method based on the four-point bending test proposed by several standards. One of the most known factors to influence the longitudinal shear strength is the geometry of embossments present in the steel work. Calibrated computational simulation using the finite element method can be an alternative way to simulate this type of test. The present work modified and adapted a methodology explicitly including the geometry of embossments in the analysis in order to use materials and products with characteristics available to structural engineers in Brazil and used this methodology to derive m-k coefficients. This is being made with the objective of numerically simulating the effect of relevant parameters for determining the longitudinal shear strength at the concrete-steel interface of composite slabs. Force versus slip, force versus displacement graphs were obtained and the m-k coefficient values found were compared with those of other authors in the literature. The simulations presented values consistent with the literature and in relation to the rupture mode by longitudinal shear, the numerical simulations performed presented ultimate strengths with goodness-of-fit measured by the conventional coefficient of determination, reaching a good value for the semi-empirical relation using the results of the finite element data.