Search

When composite honeycomb sandwich structures are subjected to low energy impacts, the upper panel or the honeycomb core often suffers large damages, which are invisible, but affects the structural safety. To achieve non‐destructive detection of these damages, an epoxy resin film (ERF) was designed as a functional coating to display the internal failure features on structure surface. The effect of low energy impacts on the damage modes of the ERF was first investigated, and then the correspondence between the ERF damage characteristics and the structural internal failure was established. Simulation and experimental results showed that with the increase of impact energy, cracks on the ERF expanded from the radial radiation with a small extension range to the circumferential pattern with an increased damage area. Meanwhile, localized delamination appeared inside the upper panel, while the degree of flexure and crushing damage to the core continued to increase. Based on the analysis of the crack extension pattern of the ERF and the damage state of the upper panel and honeycomb core, a specific link between the ERF crack characteristics and the internal damages to the sandwich structure was obtained, which might offer a novel non‐destructive testing method for composite impact damages. Highlights: Low energy impact damage in honeycomb sandwich structures was a concern.Impact damage response of epoxy resin film on sandwich composites was studied.Crack extension of the film showed a particular change from radial to annular.Specific link between film crack and sandwich structure damage was established.The results would be helpful for damage detection in sandwich composites. [ABSTRACT FROM AUTHOR]

Through 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. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shanghai Jiaotong University (Science) is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This research aimed at studying the effect of fiber content on the flexural strength and behavior of steel fiber reinforced concrete (SFRC) beams with steel rebars. The study employed finite element (FE) analysis to simulate the behavior of SFRC beams. The simulation results of the FE model were validated against experimental data. Subsequently, the validated model was utilized to analyze the strength and crack patterns of SFRC beams with steel rebars in comparison to conventional RC concrete beams without fibers. The parametric study indicates an average 9% increase in RC beam capacity for every 1% increment in fiber volume fraction. Moreover, this study reveals more substantial effects of steel fibers on beams with low reinforcement ratios. Crack analysis shows that cracks in the SFRC beams are distributed more evenly compared to plain RC beams at regions with the same bending moment, indicating enhanced strength to sustain loads, reduced deflection, and improved beam ductility. [ABSTRACT FROM AUTHOR]

Flat slabs have an important role in concrete buildings due to their architectural flexibility and speed of construction. Punching shear is one of the most important phenomena to be considered during the design of reinforced concrete flat slabs, as this type of failure is brittle and does not predict previously raised alarms before failure. The main factors that affect punching strength in concrete are compressive strength, flexural reinforcement, and punching reinforcement in the form of stirrups, shear studs, or other shapes. This paper is part of a research program operated at the reinforced concrete laboratory of the Faculty of Engineering, Cairo University, to evaluate the contribution of horizontal flexural reinforcement, horizontal compression reinforcement, and vertical punching reinforcement on the punching strength of reinforced concrete flat slabs. In this research, fifteen half-scale specimens are cast and tested. The specimens had dimensions of 1100×1100 mm and a total thickness of 120 mm. All specimens were connected to a square column of dimensions 150×150 mm and loaded at the four corners with a supported span of 1000 mm. The main parameters considered in this research included spacing between stirrups, width of the stirrups, number of stirrup branches, ratio of the compression reinforcement, and ratio of the tension reinforcement. During testing, ultimate capacity, steel strain, cracking pattern, and deformation were recorded. The experimental results were analyzed and compared against values estimated from different international design codes. [ABSTRACT FROM AUTHOR]

This work aims to reveal the effect of cyclic disturbance frequency, i.e., 0.01, 0.1, 0.5, and 1.0 Hz, on damage cracking and energy dissipation characteristics of rock‐backfill composite structure specimens. Testing results show that fatigue volumetric strain and secant modulus increase with increasing disturbance frequency; low‐frequency disturbance leads to an earlier volume expansion. In addition, the strain energy density increases with increasing disturbance frequency. Most of the energy are dissipated for the specimen under high‐frequency disturbance. Finally, computed tomography scanning reveals the influence of disturbance frequency on failure modes; tensile‐splitting failure and shear failure are likely to occur at the surrounding rock subjected to high‐ and low‐ frequency disturbances. Low‐frequency‐disturbed stress seems easily to stimulate cracks at the rock‐backfill interfaces and the backfill; the backfill can absorb much more energy than high‐frequency circumstances. It is suggested that the role of backfill in energy absorption, contact support, and stress isolation is disturbance frequency dependent. Highlights: The effects of cyclic disturbance frequency on damage‐cracking are revealed.The energy dissipation magnitude is negatively correlated to the disturbance frequency.Cracking at interfaces and backfill is relatively severe under low frequency disturbance.The backfill can absorb much more energy under low‐frequency disturbance conditions. [ABSTRACT FROM AUTHOR]

This paper focuses on the design as well as on the experimental and numerical validations of the mechanical behavior of a precast ultra-high performance fibre reinforced concrete (UHPFRC) retaining walls. The design, made in accordance with the Canadian Highway Bridge Design Code (CSA S6, 2019), led to the fabrication of a full-scale UHPFRC retaining wall with 3% fibre content which had dimensions of 3 m in height, 2 m in length, 2 m in width, with two vertical and horizontal stiffeners, and very thin vertical and horizontal panels of 40 and 65 mm, respectively. The experimental tests showed that the UHPFRC retaining wall exceeded by 42% the ultimate limit state (ULS) design factored bending moment and showed a very ductile behavior under flexural loading. At service limit state (SLS), the retaining wall had maximum crack opening between 0.15 and 0.28 mm, and a maximum lateral displacement of 4 mm. The finite-element model developed for the application captured accurately the flexural behavior of the UHPFRC retaining wall and was used later in parametric studies to optimize the design. The retaining wall optimal design includes UHPFRC with 3% fibre content and stiffeners with variable cross-section which allows volume reductions of 73% for concrete and 86% for rebars in comparison to the conventional reinforced concrete design. [ABSTRACT FROM AUTHOR]

Composite construction has proven to be cost-effective, as this method merges precast and cast-in-place elements while preserving the effectiveness and seamless nature of monolithic construction. There are no experimental research results on the behavior of glass fiber-reinforced polymer (GFRP)-reinforced composite beams in the case of horizontal shear transfer in composite T-beams. This research aims to investigate a novel and sustainable approach using noncorroding GFRP as shear-transfer reinforcement in composite reinforced concrete (RC) T-beams. A total of six fullscale RC T-beams (one monolithic RC beam and five composite RC beams) measuring 4200 mm (165.4 in.) in length, 420 mm (16.5 in.) in depth, and 250 mm (9.8 in.) in width were constructed and tested until failure. The main experimental variables evaluated were shear reinforcement type (GFRP or steel stirrups); ratio (0.32, 0.35, or 0.48%), and shape (stirrups or bent bars). The test results were analyzed in terms of ultimate horizontal shear stress, deflection, slippage, and reinforcement strain. The experimental results indicate that the GFRP shear reinforcement provided adequate sheartransfer capacities compared to steel when provided across rough concrete interfaces. Moreover, the test results show that increasing the shear reinforcement ratio enhanced the performance of the composite RC T-beams in terms of horizontal shear capacity and slip. Furthermore, the available equations specified in design provisions, such as CAN/CSA S6-19 (2019) and AASHTO LRFD (2018), exhibited unduly conservative predictions of the interface shear strength of the GFRP bars. The results of this study unequivocally establish the viability and promise of employing GFRP bars as shear connectors in composite T-beam applications. [ABSTRACT FROM AUTHOR]

To investigate the deformation and failure taw of deep sandstone, the relationship between plastic zone development, crack propagation and acoustic emission (ABE) characteristics is established. Tang deep sandstone samples as the research object, the axal static compression ABE test is charred out, the evolution law of plastic zone and maternal crack of rock samples is analyzed by numerical simulation. The results show that the dissipation of maternal energy density is relatively stable in the compaction and e!mastic stage,gradually increases in the hp!mastic stage, and all the energy is released immediately before allure. There is a strong core!nation between the hp!mastic zone and crack ABE characteristic.. The ranging count and energy Increase first and then decrease in the compaction stage. Before the elastic stage, the plastic zone and micro-cracks appear from both sides of the rock scamp! In the e!mastic stage, the ranging count and energy continue to increase,the Increase of the latter is greater than that of the former,the hp!mastic zone develops diagonally inward, and the number of cracks increases. In the hp!mastic stage, the ringing count continues to increase, the energy surges, and the plastic zone develops outwards. In the allure stage, both the ringing count and energy surge,and the simulation test shows a shape shear crack, which is consistent iii the actual allure crack. [ABSTRACT FROM AUTHOR]

Processes of random tessellations of the Euclidean space $\mathbb{R}^d$ , $d\geq 1$ , are considered that are generated by subsequent division of their cells. Such processes are characterized by the laws of the life times of the cells until their division and by the laws for the random hyperplanes that divide the cells at the end of their life times. The STIT (STable with respect to ITerations) tessellation processes are a reference model. In the present paper a generalization concerning the life time distributions is introduced, a sufficient condition for the existence of such cell division tessellation processes is provided, and a construction is described. In particular, for the case that the random dividing hyperplanes have a Mondrian distribution—which means that all cells of the tessellations are cuboids—it is shown that the intrinsic volumes, except the Euler characteristic, can be used as the parameter for the exponential life time distribution of the cells. [ABSTRACT FROM AUTHOR]

The glass fiber reinforced polymers (GFRP) bars are considered as an alternative to steel reinforcement in certain structures cases due to their non corrosive aspect. Perhaps, they exist with different surface treatment helically wrapped (GFRP-HW) and sand coated (GFRP-S). Thus, each rebar type is performed by a particular bond behavior with the concrete and it affects the concrete crack formations. In the first part of this paper, an experimental and analytical study of the bond behaviour between the (GFRP), rebars and concrete were carried-out. Pull out test tests have been applied on concrete cylindrical slabs in order to identify experimentally the bond behaviour between the self-compacting concrete and GFRP. Various parameters were taken in account in this experimental study: the rebar diameters, the concrete age, and the rebar roughness. Based on the experimental results, the failure mode of the bond specimens, the variation of the bond load, and the bond-slip variation are analyzed. Two failure modes of the GFRP rebars were experimentally identified: the pull-out failure mode and the splitting one. According to the experimental data, it was proven that the GFRP-S rebars and the steel ones exhibit a more bond performant than that of the GFRP-HW rebars. In the second part, an analytical identification of the BPE and the CMR models was established. Subsequently, a tension tie model was extended analytically in order to predict the crack patterns of concrete elements reinforced with the GFRP rebars and steel rebars. The expressions of the cracking parameters issued from the tension tie model have been developed. It can be deduced that the GFRP-HW and GFRP-S reinforced concrete element exhibits a longitudinal strain less than that of the steel reinforcement case. Hence, the GFRP reinforced element undergoes cracks that are characterized by more important width measurements than those of the cracks deduced from the case of the reinforced steel element. Finally, the stress-strain analytical diagram of a GFRP tension member has been plotted and compared to the steel tension element. [ABSTRACT FROM AUTHOR]

The lifespan of a reinforced concrete (RC) structure can be greatly influenced by the spatial variability of its material characteristics which, in particular, explains the observed or measured reduction of the tensile strength at first crack when the volume under tension increases. This paper discusses the ability of accounting for the spatial variability of the tensile strength of concrete in RC structures using a stochastic finite element (SFE) method based on random field simulations. In this work, the generation of random fields on the concrete tensile strength aims at computing the force corresponding to the first crack occurrence, and the reduced tensile strength of the structure. The method can be applied in particular to large‐sized structures, which show a pronounced size effect, for different types of loading. The method consists of, first, estimating the mean of the random field, using the analytical approach of the weakest link and localization method (WL 2A${2}_A$). Then, the discretized random field is defined on a particular 2D or 3D grid, and it is finally projected on the finite element mesh of the studied structure. The study of the parameters that influence the prediction of the cumulative density functions (CDFs) of the rupture force or the tensile strength is highlighted using experimental series of concrete beams having different volumes and subjected to 4‐point bending loading. Moreover, the SFE method is applied to a RC tie‐beam under tensile loading, characterized by a weak stress gradient, which complicates the prediction of crack positions. [ABSTRACT FROM AUTHOR]

This study aims to investigate the crack-filling effect of gel generated by the alkali–silica reaction (ASR) on the mechanical behavior of concrete and propose an analytical model to predict the compression behavior of ASR-damaged concrete. To identify the mechanical contribution of the gel-filling cracks, the distribution of the chemical compositions and elastic moduli of the crack-filling gels were observed using SEM–EDS analysis and nano-indentation tests. The experimental results showed that the elastic modulus of the gel with a high-calcium composition ranged from 30 to 40 GPa, which is comparable to the elastic modulus of concrete. In addition, through literature reviews of the time-dependent compression behaviors of ASR-affected concrete, it was hypothesized that crack-filling gels can contribute to the recovery of ASR damage, and that the mechanical contribution of gels depends on the ASR crack patterns and changes with time. Based on these assumptions, the resistance of the gels filling the cracks in the compression, shear, and recontact behaviors of ASR-damaged concrete was reflected in the proposed model, in which the gel resistance increased with time and became larger as the ratio of microcracks to total cracks increased. The proposed model was verified through a comprehensive comparison of analysis and test results of compression behavior of ASR-damaged specimens, and it appeared that the change in mechanical properties of concrete according to the degree of damage (ASR expansion) and time was well simulated by the proposed model. [ABSTRACT FROM AUTHOR]

This research aimed at studying the effect of fiber content on the flexural strength and behavior of steel fiber reinforced concrete (SFRC) beams with steel rebars. The study employed finite element (FE) analysis to simulate the behavior of SFRC beams. The simulation results of the FE model were validated against experimental data. Subsequently, the validated model was utilized to analyze the strength and crack patterns of SFRC beams with steel rebars in comparison to conventional RC concrete beams without fibers. The parametric study indicates an average 9% increase in RC beam capacity for every 1% increment in fiber volume fraction. Moreover, this study reveals more substantial effects of steel fibers on beams with low reinforcement ratios. Crack analysis shows that cracks in the SFRC beams are distributed more evenly compared to plain RC beams at regions with the same bending moment, indicating enhanced strength to sustain loads, reduced deflection, and improved beam ductility.

This paper aims to assess the ultimate bearing capacity of a strip footing on the ground surface of a silty sand soil layer. It considers structural failures and geotechnical changes, including the impact of moisture content, using numerical simulation in PLAXIS 3D V21. The structural damage assessments on a student center building located in the northern part of Peninsular Malaysia were performed by visual inspection, and thirty-six sub-points of rebound hammer tests were conducted on three selected different points (Point 1, 2, 3) of the building to evaluate concrete strength and record crack characteristics for severity classification. Subsequently, an extensive geotechnical laboratory tests were performed to investigate the effects of moisture content on physical and mechanical properties of silty sand including, soil compositions, Atterberg limits, compaction characteristics and unconfined compressive strength (UCS) from the building area which resulted to structural damage caused by differential settlement beneath the building. The visual inspection assessment has shown the student center building experienced severe damage category at Point 1 with crack width and length are 25 mm and 3 m respectively. At Point 2, there was minimal damage to the surface structure, with a crack measuring 1 mm in diameter and 0.1 m in length. Furthermore, crack width and length are 1 mm and 0.2 m respectively are recorded for Point 3. The study fills in a gap in the research by combining geotechnical and structural tests on the bearing capacity of silty sand with moisture content. The effect of soil saturation, matric suction, and the unsaturated strength of soil are affected by these factors in the analysis of the bearing capacity of the foundation. The exact solution gives us 568.213 kPa for a zero degree of saturation and 385.34 kPa for a 100 percent degree of saturation. The incorporation of geotechnical and structural assessments aims to find reliable strategies for failure remediations for instance patched and sealed with a concrete patching compound.

Reinforced concrete beams reinforced with Fiber Reinforced Polymer (FRP) have several failure patterns, one of which is Concrete Cover Delamination. To prevent this failure, in this study, FRP U-Wrap was installed which was calculated using Strut and Tie Modelling (STM). The specimens of reinforced concrete beams with a length of 3300 mm, a width of 300 mm, and variations in height of 500, 600, and 700 mm were loaded with the two-point load method. Data collection and analysis was carried out using Digital Image Correlation, LVDT, strain gauge, and data logger. The bending behaviour reviewed in this study is ductility, crack pattern, type of failure, flexural capacity, and stiffness. In this study, the addition of U-Wrap did not have a significant effect on flexural behaviour when compared to beams without U-Wrap FRP. All beams experienced a failure pattern of FRP Debonding, so that the Concrete Cover Delamination did not occur.

Semi-rigid base is widely used in asphalt pavement construction, because they provide the potential to reduce rutting and lower pavement construction budgets. However, questions remain about the long-term performance of asphalt pavements with a semi-rigid base in terms of their propensity for transverse cracking. This study presents the results of a long-term field investigation of transverse cracking. The study collected 202 field cores extracted from 14 field test roads, and covers different pavement ages, traffic volumes, and recycled asphalt pavement (RAP) content across eastern China. Data regarding crack spacings, lengths, and propagation over time were obtained, while crack widths, depths, and patterns were analyzed using the field cores. The results show that crack spacings tend to be dense over the years until reaching an extreme value and the crack propagation can be clearly divided into three stages (0–4 years for initiation, 4–8 years for steady development, and a boost after 8 years) for the projects evaluated. The transverse crack can be categorized into four categories: surface-initiated cracking, reflective cracking with small area unpenetrated, reflective cracking, and thermal cracking. Surface-initiated cracking is the primary crack pattern found in asphalt pavements constructed with a semi-rigid base. A finite-element model was constructed, and the simulation results indicate that the surface-initiated crack tends to appear if the modulus of the base layer is higher, the asphalt top layer is more aged, the thickness above the base layer was thicker, or the cooling rate was faster. [ABSTRACT FROM AUTHOR]

Perfobond rib shear connectors (known as PBL shear connectors) are structures widely used to transfer loads between concrete and steel structural elements. The performance of PBL shear connectors under monotonic loads has been extensively reported; however, their shear resistance under cyclic loads is not well investigated. A total of 13 PBL shear connector specimens were designed to explore their performance under cyclic displacement. The crack patterns and hysteretic load-slip responses of the specimens were observed. The cyclic displacement changed the crack development and accelerated the deterioration of the cohesive strength and shear-friction force. Cyclic loading weakened the transverse expansion of the damaged concrete dowel and reduced the contribution from the transverse reinforcement. On the basis of the test results, a theoretical method for estimating the peak shear resistance of a PBL shear connector under cyclic loading is proposed. The proposed model exhibits good accuracy in comparison with the test results. [ABSTRACT FROM AUTHOR]

A series of stress‐controlled fatigue–creep interaction loading tests were performed on rock–backfill composite structure (RBCS) samples. The testing results reveal the influence of cement/tailing (c/t) on deformation, energy dissipation, damage evolution, and macro–meso failure patterns. The equivalent lifetime of RBCS is the largest for a sample with smaller stiffness filling, a smaller stiffness filling leads to weaker volumetric expansion. Additionally, strain energy is relatively large for larger stiffness filling, indicating a larger proportion of energy release at failure. A dissipated energy‐based damage evolution model is proposed to describe damage propagation at the entire fatigue–creep process which fits well with the experimental data. Moreover, the macro–meso failure pattern reveals the interactions between surrounding rock and filling material, failure seems to change from tension splitting to shear with increasing c/t. Good agreement was found among the volumetric deformation, energy dissipation, and failure pattern. It is suggested that flexible backfilling is benefit to prevent rock spalling and collapse. Highlights: Fatigue–creep interaction loading tests were conducted on RBCS samples.The equivalent lifetime of RBCS first decreases and then increases with increasing c/t.RBCS sample with smaller stiffness filling can absorb much more energy during failure.It is suggested that flexible backfilling material is beneficial to prevent rock spalling. [ABSTRACT FROM AUTHOR]

Low-density Zeolite Aggregate (LDZA) is obtained by thermally treated zeolite in a furnace under 500°C. Thus, the water evaporates, and zeolite aggregates (ZA) are obtained with porous structures in which water molecules that make LDZA have endogenous processing properties. In this research, experimental behavior using ZA is used as a replacement portion of fine and Coarse-grained aggregate to obtain Low-density concrete (LDC) beams. The performance of normal reinforced concrete beams was contrasted with that of LDC beams based on their load-deflection behavior, ultimate load capacity, deformation profile, and crack pattern Under the effect of static load. In addition, apertures of different diameters (25, 38,50,60) mm were made in the tensile region along the aperture length of beams to minimize the self-weight of the beams. As a result of the use of zeolite aggregates, there was a decrease in the weight and density of the concrete used in casting the beams, and the results for the Normal Concrete (NC) beam were close to the results from the beam LDC. However, using Apertures in LDC beams in the tensile zone gradually reduced ultimate loads and mid-span deflection. Therefore, it is recommended to use zeolite aggregates to make LDC for use in reinforced concrete elements. [ABSTRACT FROM AUTHOR]

One of the most common statistical systems used in structures especially for wide span slabs are ribbed slabs with shallow wide beams (SWB). This experimental study aimed to investigate and enhance the flexural behavior of high-strength concrete SWB using hybrid longitudinal reinforcement from steel and advanced composite materials as a tensile main reinforcement in SWB. Longitudinal advanced composite bars locally manufactured from ribbed glass fiber reinforced polymer (GFRP) and the second type was ribbed basalt fiber reinforced polymer (BFRP). A group of six half scale SWB were examined in structures laboratory of American University in Cairo with dimensions 2.1 x 0.6 x 0.25 m for length (L), width (B) and depth (d) respectively with constant size effect (d/B). The first three specimens were completely reinforced at tension side with Steel, GFRP or BFRP ribbed bars to be considered a control specimen. Use of GFRP and BFRP bars enhanced the flexural capacity of SWB with 41% and 43% respectively compared to specimen completely reinforced with steel. But on the other hand, the crack propagation of specimens completely reinforced with GFRP and BFRP developed more quickly and had larger crack width compared to specimen completely reinforced with steel. Hybrid reinforcement from Steel with GFRP, Steel with BFRP and Steel with GFRP and BFRP specimens are used to enhance the crack pattern and mode of failure without a significant loss in flexural capacity of SWB. The flexural capacity of these three specimens was enhanced with 26%, 30% and 41% with a significant enhancement in crack pattern and ductility. [ABSTRACT FROM AUTHOR]

Reinforced concrete beams reinforced with Fiber Reinforced Polymer (FRP) have several failure patterns, one of which is Concrete Cover Delamination. To prevent this failure, in this study, FRP U-Wrap was installed which was calculated using Strut and Tie Modelling (STM). The specimens of reinforced concrete beams with a length of 3300 mm, a width of 300 mm, and variations in height of 500, 600, and 700 mm were loaded with the two-point load method. Data collection and analysis was carried out using Digital Image Correlation, LVDT, strain gauge, and data logger. The bending behaviour reviewed in this study is ductility, crack pattern, type of failure, flexural capacity, and stiffness. In this study, the addition of U-Wrap did not have a significant effect on flexural behaviour when compared to beams without U-Wrap FRP. All beams experienced a failure pattern of FRP Debonding, so that the Concrete Cover Delamination did not occur. [ABSTRACT FROM AUTHOR]

This paper aims to create a unified model that effectively combines continuous 2-dimensional elements and discrete components to capture the nonlinear characteristics and failure mechanisms of solid and perforated masonry infill panels. Given that masonry infill behavior is primarily influenced by shear deformations, an equivalent model is developed by using multiple small square panels arranged diagonally and interconnected by two-component springs, encompassing axial and shear behavior at their intersections. For the sake of simplicity, the divided panels are assumed to behave elastically, with plasticity concentrated only in the axial component of the connector springs. Plastic behavior in the boundary elements was considered to involve both flexural and shear plastic hinges to provide an accurate estimation of the entire infill panel's behavior. To validate this approach, the simplified model is benchmarked against eight experimental masonry infill panels surrounded by steel or reinforced concrete frames and with or without openings. The results including global behavior and crack pattern were compared with available numerical predictions based on finite element method from the literature in addition to experimental outcomes. Ultimately, this comparison demonstrated that the homogeneous model could effectively predict the non-linear lateral behavior of the panels and accurately forecast crack patterns. Additionally, the use of unidirectional non-linear springs and the appropriate arrangement of elastic panels significantly reduced both pre-processing and analysis time.

Existing databases containing measurements of crack width and spacing are usually limited in size and based on isolated experimental studies. These databases are used to develop new formulas to describe crack patterns in concrete structures. A database obtained from multiple sources of experimental programmes is required to quantify the accuracy of those formulas. To this end, a database containing crack width and crack spacing measurements was created, based on 30 different experimental programs described in literature. The results of each program were described in .xlsx format and queried to a database (.csv) using Structured Query Language (SQL). The structural elements considered in the database are reinforced and prestressed ties, beams, and reinforced slabs with varying geometry, concrete and reinforcement properties. From the considered experimental programs, over twenty thousand data points were extracted using a systematic approach. The data points consist of the metadata, materials, structural element preparations, test setups and measured crack widths and spacings. The database's applied structure is robust and valuable: it can be implemented in subsequent research focussing on cracking in concrete, such as assessing existing formulas to describe the crack widths and spacings in concrete structures, or deriving new formulas, potentially improving the prediction of the remaining service life of concrete structures.

The paper proposes a new equation for the prediction of punching shear strength of reinforced concrete flat slabs. The basis of the new predictive equation is a detailed numerical parametric study conducted using the nonlinear 3D finite element analysis using FE software MASA. For this, results of the previously tested flat slabs from literature are used as reference for validation of the numerical model. The numerical modelling procedure is validated with two previously tested slabs, one failing in pure punching prior to yielding of flexural rebar, and the second failing in flexure-punching which resulted in yielding followed by punching. The result shows that the load-displacement behavior, failure modes and the crack pattern are captured well by the analysis. Following the validation, a detailed parametric study is performed to investigate the influence of slab depth, concrete strength, longitudinal reinforcement ratio, column size and effect of reinforcement spacing. From the evaluation of results, it is observed that the punching resistance increases with slab depth but at a decreasing rate (size effect). The punching shear strength also increases with increasing longitudinal reinforcement ratio, concrete strength as well as the column area. All the reinforcing bars placed within a distance of 3.5 times the effective depth of the slab from the column center contributes significantly towards dowel action. With increasing column size, the deformation at the peak load also increases. Based on the evaluation of the results of the analyses, an empirical equation for the prediction of punching shear is derived. The results of the equation are compared with the results of a large experimental database of 235 tests, and it is shown that the proposed equation leads to better agreement with the test results compared to the equations given in the current codes (ACI, Canadian, Eurocode, Japanese code). The comparison shows that generally the predictions by existing equations in the codes tend to be unconservative for large slab with low reinforcement ratio.

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.

Crack patterns provide critical information about the structural integrity and safety of concrete structures. However, until now, there has been a lack of sufficient studies on using the Finite Element (FE) method to investigate the characteristics of the crack patterns of reinforced concrete (RC) beams. Therefore, this study aims to develop an FE model to analyze the load–displacement and crack characteristics of a beam under a four-point bending test using the concrete damaged plasticity (CDP) model that accounts for the influence of mesh size. The simulation results were validated against experimental results, including mesh convergence analysis, energy balance, load characteristics, and crack patterns. A parametric study was then conducted using this model to investigate the influence of the rebar's diameter, number, and spacing on the RC beam's load–displacement characteristics and crack behavior. The findings demonstrate that the FE model accurately simulates the working behavior of the RC beam, with a maximum deviation at a cracking load of 8.7% and crack patterns with a maximum deviation in the mean crack height of 12.1%. In addition, the results of the parametric study suggest that the rebar configuration significantly affects the RC beam's loading carrying capacity. This study provides deeper insights into the use of FE modeling for analyzing the behavior of RC beams, which can be useful for designing and optimizing structures in civil engineering. [ABSTRACT FROM AUTHOR]

This research studies and assesses the possibility of employing ultra-high performance fiber reinforced concrete (UHPFRC) in exterior beam-column joints (BCJs). Eight specimens with various concrete material characteristics and steel reinforcing details are cast and examined under repeated loads. Normal concrete with seismic reinforcing details is used as a control specimen. For certain specimens, UHPC, UHPFRC with 1% steel fiber, and UHPFRC with 2% steel fiber are poured into all BCJs, and others are poured into the critical zone only. The consequences of removing stirrups from the joint were studied. All specimens' crack patterns, hysteresis and envelope curves, ductility factor, stiffness degradation?, and energy dissipation are assessed and corresponded to the control sample. The results demonstrate that UHPFRC strengthened the joint, prevented crack development and extension and the shear failure in the joint, and formed the plastic hinge in the beams. UHPFRC outperforms normal concrete with seismic reinforcing details and UHPC without steel fiber in bearing capacity, ductility, stiffness, and energy dissipation. UHPFRC with 1% steel fiber enhanced joint behavior, while UHPFRC with 2% steel fiber was better. Casting the whole sample with UHPFRC achieved very little improvement. The presence of stirrups in the UHPFRC beam-column joint has little effect on its properties. It is more economical to cast UHPFRC in the joint zone only and reduce or eliminate these stirrups in the case of UHPFRC.

This paper develops a deep learning tool based on neural processes (NPs) called the Peri-Net-Pro, to predict the crack patterns in a moving disk and classifies them according to the classification modes with quantified uncertainties. In particular, image classification and regression studies are conducted by means of convolutional neural networks (CNNs) and NPs. First, the amount and quality of the data are enhanced by using peridynamics to theoretically compensate for the problems of the finite element method (FEM) in generating crack pattern images. Second, case studies are conducted with the prototype microelastic brittle (PMB), linear peridynamic solid (LPS), and viscoelastic solid (VES) models obtained by using the peridynamic theory. The case studies are performed to classify the images by using CNNs and determine the suitability of the PMB, LBS, and VES models. Finally, a regression analysis is performed on the crack pattern images with NPs to predict the crack patterns. The regression analysis results confirm that the variance decreases when the number of epochs increases by using the NPs. The training results gradually improve, and the variance ranges decrease to less than 0.035. The main finding of this study is that the NPs enable accurate predictions, even with missing or insufficient training data. The results demonstrate that if the context points are set to the 10th, 100th, 300th, and 784th, the training information is deliberately omitted for the context points of the 10th, 100th, and 300th, and the predictions are different when the context points are significantly lower. However, the comparison of the results of the 100th and 784th context points shows that the predicted results are similar because of the Gaussian processes in the NPs. Therefore, if the NPs are employed for training, the missing information of the training data can be supplemented to predict the results. [ABSTRACT FROM AUTHOR]

The capabilities of a parametric model for crack patterns simulation are presented. Planar tessellations are partitions of the plane into convex polygons (called cells) without overlapping. The Voronoi tessellations and Poisson line tessellations are the most prominent models; however, to model crack patterns, it is more appropriate to deal with tessellations that are generated by a cell division process. We describe the STIT tessellation as a reference model for crack patterns and introduce several modifications. Having described a variety of 40 parametric models and appropriate simulation algorithms, we delineate and specify tuning methods to optimize the adaption of the model to real crack pattern data. An example of a metalized polydimethylsiloxane demonstrates the capability of our approach. The results indicate that this approach yields a considerable improvement in modeling compared to previous studies.

This paper focused on the behavior of the dam when exposed to seismic loading and ability of the dam to withstand the applied loads from various seismic events. The chosen concrete dam to be referred to in the twodimensional analysis is Beris Dam located in Kedah, Malaysia. A nonlinear dynamic analysis is chosen to analyse the behavior of Beris Dam under selected ground motion. Analysis of the dam is performed using the finite element method by utilizing ABAQUS software. From the cracking analysis pattern, a crack appeared at the upstream face of the dam caused mainly by the excessive tensile stress. Based on the results, the displacement of the dam is increased with the increasing of ground motion data where the displacement occurred in the horizontal direction. The maximum stresses exerted by the dam structure do not exceed the allowable capacity of concrete dams. The stress behaviour of the dam was satisfactorily acceptable as the maximum normal stress and shear stress of the dam when numerous seismic loadings are applied do not exceed the allowable stress capacity which is 800 kN/m2. [ABSTRACT FROM AUTHOR]

This research studies and assesses the possibility of employing ultra-high performance fiber reinforced concrete (UHPFRC) in exterior beam-column joints (BCJs). Eight specimens with various concrete material characteristics and steel reinforcing details are cast and examined under repeated loads. Normal concrete with seismic reinforcing details is used as a control specimen. For certain specimens, UHPC, UHPFRC with 1% steel fiber, and UHPFRC with 2% steel fiber are poured into all BCJs, and others are poured into the critical zone only. The consequences of removing stirrups from the joint were studied. All specimens' crack patterns, hysteresis and envelope curves, ductility factor, stiffness degradation, and energy dissipation are assessed and corresponded to the control sample. The results demonstrate that UHPFRC strengthened the joint, prevented crack development and extension and the shear failure in the joint, and formed the plastic hinge in the beams. UHPFRC outperforms normal concrete with seismic reinforcing details and UHPC without steel fiber in bearing capacity, ductility, stiffness, and energy dissipation. UHPFRC with 1% steel fiber enhanced joint behavior, while UHPFRC with 2% steel fiber was better. Casting the whole sample with UHPFRC achieved very little improvement. The presence of stirrups in the UHPFRC beam-column joint has little effect on its properties. It is more economical to cast UHPFRC in the joint zone only and reduce or eliminate these stirrups in the case of UHPFRC. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on the flexural behavior of composite Reinforced Concrete (RC) beams having a monolithic Engineered Cementitious Composites (ECC) layer at the tension face. Due to the brittle nature of normal concrete, clear cover on the tension side of beam cracks results in spalling and corrosion of reinforcement. The proposed technique overcomes the inherent brittle behavior of normal concrete with the incorporation of ECC on the tension face. This also helps in reducing bond-splitting, cover-spalling, and buckling of reinforcement in RC flexural members. For testing purposes, six full-scale beam specimens (225 mm x 300 mm x 2400 mm) with the same reinforcement were cast and tested. Out of six, two specimens were made of conventional concrete, whereas the remaining four (two each) had an ECC layer of 75 mm and 100 mm thick at the tension face respectively. Each specimen was installed with three strain gauges (one each at the midspan top & bottom surface of concrete and one midspan rebar on the tension face) and one LVDT at midspan. The samples were then subjected to simple monotonic loading under a third-point bending test as per ASTM C78. The load-displacement, stress-strain and momentcurvature curves were obtained for all the tested specimens. It was found that ECC-strengthened beam samples displayed an increased flexural performance at first crack, yield, and ultimate load-carrying capacity as compared to conventional RC specimens. Whereas a better crack arrest with even distribution of cracks and improvement in ductility was observed for the ECC-strengthened composite beams. [ABSTRACT FROM AUTHOR]

This work aims to reveal the influence of disturbed frequency on the failure of deeply buried granodiorite under triaxial cyclic and multistage unloading confining pressure (CMSUCP) conditions. Testing results show that volumetric deformation is obviously influenced by the disturbed frequency. The volumetric strain was characterized as an early dilatancy‐dominant behavior for a sample under low disturbed frequency. The deformation development at the unloading confining pressure stage is larger than at the cyclic loading stage. The hysteresis damping decreases with increasing disturbed frequency indicating that much energy loss occurs due to damage accumulation. A first slow followed by accelerated damage propagation is expressed using a radial irreversible strain‐based damage evolution model. Macro‐meso failure pattern analysis reveals that rock dominant failure changes from mixed tensile‐shear failure to pure shear failure and a transmission from softening to hardening characteristics. It is suggested that failure develops fully for rock subjected to low disturbed frequency. Highlights: Rock triaxial cyclic and multistage unloading tests were performed.Deformation development at the unloading stage is larger than at the cyclic loading stage.A radial irreversible strain‐based damage evolution model was proposed.Macro‐meso failure reveals a dominant mixed tensile‐shear failure to pure shear failure. [ABSTRACT FROM AUTHOR]

This paper is devoted to investigate the effect of burning by fire flame on the behavior and load carrying capacity of rectangular reinforced concrete rigid beams. Reduced scale beam models (which are believed to resemble as much as possible field conditions) were suggested. Five end restrained beam specimens were cast and tested. The specimens were subjected to fire flame temperatures ranging from (25-750) ºC at age of 60 days, two temperature levels of 400ºC and 750ºC were chosen with exposure duration of 1.5 hour. The cast rectangular reinforced concretebeam (2250×375×375 mm) (length× width× height respectively) were subjected to fire. Results indicate remarkable reduction in the ultrasonic pulse velocity and rebound number of the rigid beams after cooled in water were (2-5 %) more than rigid beam specimens cooled in air. Load-deflection curves indicate deleterious response to the fire exposure. Also, it was noticed that the maximum crack width increases with increasing fire temperature.

This work aimed to investigate experimentally the effect of incorporating waste glass powder on the shear behaviour of reinforced concrete beams under bending load in terms of load- vertical displacement relation, load-strain relation, cracks pattern/propagation, load –cracks relation, and mode of failure. The replaced cement partially with waste glass powder achieves two main goals; the first is an economic benefit represented by reducing the cost of supplementary materials and the second one is an environmental benefit represented by solving some of the solid waste problems that waste causes and saving energy. The experimental program consists of testing nine simply supported beams of 150 × 150 × 900 mm designed to fail in shear. Three parameters have been studied; glass powder content (0, 10, and 15% as partial replacement of cement), steel reinforcement ratio equal to 0.02267 (2Φ16mm), and 0.013785 (2Φ12mm), and spacing between stirrups (65 and 170 mm). The test results showed that using glass powder improved the strength capacity of the beam and that can be seen through the increase in ultimate load for beams incorporating glass powder compared to the control beam. Recorded load at failure increased by 39% and 23% for 10% and 15% replacement compared with the control beam. For the same waste glass powder content, an increase in the amount of longitudinal steel reinforcement from 2Φ12 mm to 2Φ16 mm led to an increase in ultimate load but decreases in the corresponding vertical displacement, which refers to more brittle behaviour. In addition, reducing the spacing among the stirrups from 170 mm to 65 mm led to a decrease in ultimate load and increasing in the corresponding vertical displacement. The incorporation of waste glass powder made the behaviour of beams more brittle i.e. for the same load the vertical displacement for beams incorporating waste glass powder (especially for 15%) is lower than for reference beams without waste glass powder, which is not desired. To take advantage of the property of waste glass powder by improving the ultimate strength of the beam, which appeared by increasing the maximum load at failure compared to the reference beam and at the same time preventing the property of brittle failure caused by the addition of this material, it is suggested to use waste glass powder with fibers. [ABSTRACT FROM AUTHOR]

Earthen sites have important historical, cultural, artistic, social, and scientific values. However, they have been seriously destroyed by weathering. The methods of in situ replacement and sacrificial layer were previously presented to protect the surface of the earthen sites. This work presents the feasibility of the polyvinyl alcohol (PVA)-treated soil in a mud state as the anti-weathering material for these two methods. The desiccation cracking behaviour of soil was the main concern, and the surface peeling, hardness, and colour difference were used as the auxiliary evaluation criteria. The results showed that the PVA solution with a high degree of alcoholysis effectively inhibited soil cracking, but cannot eliminate all cracks even if the content reached 1%. The cracks of samples with the PVA mainly developed when the water content exceeded water content corresponding to air-entry value. Filamentous (or meshy) connections and cementation between particles were the main reason to inhibit the development of the cracks. The obvious advantages of the PVA in the decohesion index, hardness, colour difference, and so on cannot be also ignored. Based on these evaluation indicators, a PVA content of 0.8% may be the best choice for anti-weathering of earthen sites. [ABSTRACT FROM AUTHOR]

A type of cellular foam concrete called lightweight concrete is made of cement paste or mortar with air spaces or structural pores created by the use of a foaming agent. Examining the crack pattern of lightweight concrete under compressive and tensile loads is the goal of this study. A lightweight concrete specimen was made using foam, fine aggregate, and Portland Composite Cement. Foam agent and water are combined in a 3:10 ratio to produce foam. There were three different foam volume variants used: 15.7 liters, 25.12 liters, and 37.68 liters. As a sample, a cylinder with dimensions of 10 cm by 20 cm was employed. Using compressive and indirect tensile strength tests at curing ages of 3, 7, and 28 days, the crack pattern of lightweight concrete was assessed. The findings revealed that the fracture pattern for the compressive and indirect tensile strength tests was almost same; because the crack pattern was parallel to the direction of the load, it was categorized as a columnar crack pattern at 3, 7, and 28 days. Throughout time, the frequency of crack patterns in lightweight concrete decreased. It might be said that concrete becomes more resistant as it ages. [ABSTRACT FROM AUTHOR]

The Moon Bay City Wall of Sanxingdui is built of pale yellow sand and yellowish brown clay. The yellowish brown layers are suffering severe cracking and spalling. Hence, this paper conducts a specific investigation and performs evaporation and drying–wetting cycle tests on five rectangular specimens with different aspect ratios. The results show that the damage ratio first increases to 50.7% and then declines as the height of the layers rises. The average water content of the layers decreases from 21.8% to 12.8% by increasing the height of the layers. The pattern of the primary crack networks is related to the aspect ratio of the soil blocks. In fact, when the aspect ratio of the blocks is always greater than six, the main crack network has a parallel pattern. When the aspect ratio of the blocks is either greater than six or less than one-sixth, a laddering pattern is possibly created. When the aspect ratio of the blocks equals one, the cracks probably form a polygonal pattern. Moreover, under drying–wetting cycle conditions, the number of the main cracks is basically stable, but the average crack opening increases. A large number of tiny cracks are also formed and propagated rapidly, which further leads to spalling of the soil layers. [ABSTRACT FROM AUTHOR]

Any waste material that is found to be appropriate for use for structural concrete will not only serve as efficient means of waste disposal but also an innovative way of converting waste to wealth. This paper presents the results of the investigation conducted to assess the structural behaviour of reinforced concrete beams made with palm kernel shell as replacement for coarse aggregates. The properties investigated are: workability, density and mechanical properties of concrete specimens containing palm kernel shell as partial replacement of coarse aggregates using a mix ratio of 1:2:4 and water cement ratio of 0.65. The percentage replacement of coarse aggregates was varied from 0% to 100% by weight at intervals of 25%. For the density and compressive strength tests, 150 x 150 ×150 mm cube specimens were used, while 2370 x 225 x 225 mm reinforced beam specimens were cast for the flexural strength test according to BS EN 12350:2000. The test specimens were moist and air cured for 28 days....

Reinforced concrete half-joints are susceptible to deterioration mechanisms primarily due to the leakage of surface water, often contaminated with chlorides from de-icing salts, through the expansion joint. Due to the joint geometric form, favourable conditions can be created inside the joint for the corrosion of steel reinforcement. To this end, seven reinforced concrete half-joints were tested to failure under three-point bending to investigate the effect of reinforcement reductions that simulate common deterioration scenarios arising from the corrosion of reinforcement. The results were then compared to the predictions of nonlinear finite element analyses and the strut-and-tie method. The results demonstrated that a reduction in the amount of reinforcement close to the re-entrant corner has major influence on the load-deflection response of reinforced concrete half-joints. The largest reductions in load-carrying capacity were obtained from the half-joints with a full removal of diagonal bars and a combined removal of diagonal and U-bars, both showing reductions in load capacity of more than 50 %. The failure mode in each case of simulated deterioration scenarios involved a shear failure at the nib, except one case which displayed a shear failure in the full depth section due to the reduced anchorage of the bottom reinforcement. Furthermore, it was shown that nonlinear finite element analyses provide accurate predictions of the load-deflection response and failure crack patterns. The strut-and-tie method was found to result in overly conservative predictions, with an average observed-to-predicted load ratio of 1.48 and a coefficient of variation (COV) of 10.2 %. This is considerably higher than an average load ratio of 1.05 and a COV of only 3.1 % obtained from the nonlinear finite element analyses. • Detailed response of seven half-joints, six with reinforcement reductions, presented. • Significance of diagonal reinforcement for limiting the extent of damage at the re-entrant corner highlighted. • Reduced anchorage of the bottom reinforcement led to a full-depth shear failure. • Nonlinear FE analyses provided accurate assessment of load capacity, mode of failure, and internal mechanisms of resistance. • Detailed strain maps provided new insights into damage progression under loading. [ABSTRACT FROM AUTHOR]