Concentrated Load Research Articles

Study Performance of Floating Columns Subjected to Vertical Loads

In many cases, we need large areas in the building that are free of columns, especially on the lower floors, such as the ground floor and the basement, in order to use them as car parking or otherwise. The load path will change and new terms will appear, including the term ”floating column”, which is the column above the removed column, and the term Transfer beam, is the beam that the floating column is based on it as a concentrated load and then transfers the loads to the adjacent columns. In this paper, the effect of vertical load on a concrete building containing a floating column has been studied and compared to another one without a floating column. Also, the results of the Transfer beam were compared in a number of parameters such as moment, shear force, and deflection. A building consisting of G+4 was studied and analyzed using ETABS, SAFE, and Midas programs, A number of results were reached, the most important is the concept of load path redistribution, also this paper concluded that in normal buildings case all beams have an approximately equal result of bending, shear, and deflection but in floating column building the beams above the Transfer beam have different values which decrease when going upward.

Predicting the web crippling capacity of cold-formed steel lipped channels using hybrid machine learning techniques

Cold-Formed Steel Lipped (CFSL) channels are susceptible to a localized failure mechanism known as web crippling, triggered by concentrated loads or reactions applied to the web of the section. These loads induce buckling and distortion in the web, ultimately leading to the member's collapse. It is a challenging task to accurately determine the web crippling capacity of a CFSL channel due to its complexity and various influencing factors. This paper presents hybrid soft computing techniques for accurately predicting the web crippling capacity of CFSL channels subjected to two flange load cases. The developed soft computing techniques combine Artificial Neural Networks (ANN) with either Genetic Algorithms (GA) or Particle Swarm Optimization (PSO) to improve computational efficiency and accuracy. The finite element models of CFSL channels are developed and validated by experimental results and then employed to generate a database, which is used to train machine learning models, including ANN, GA-ANN, and PSO-ANN. Analysis is undertaken on the reliability of existing design formulas for determining the web crippling capacity of CFSL channels. It is shown that the PSO-ANN model outperforms the other models in terms of prediction accuracy. The existing design codes and formulas are not reliable in estimating the web crippling capacity of CFSL channels. However, the proposed model yields good correlation with finite element analysis results. A user- friendly graphical interface tool is developed for the practical design of cold-formed steel lipped channels.

Experimental and Analytical Study on Recycled Aggregate RC Columns: Short and Slender Loaded Axially and Eccentrically

To protect the environment and preserve natural resources, it is crucial to use recycled aggregate (RA) in construction. The recycled coarse aggregate reinforced concrete columns with the addition of steel fiber evaluated under concentric and eccentric loadings for short and slender columns were examined experimentally and analytically in this research. Twenty-four column specimens were built for this study to examine the impact of steel fiber, recycled aggregate, slenderness, and eccentricity on the behavior of reinforced concrete columns. This research examined the failure mode, maximum load-carrying capacity, strain in the concrete, strain in the reinforcement, and ductility. Based on the results, it can be concluded that employing recycled concrete aggregate is a potential approach to meet design codes. The addition of 1% steel fiber effectively prevents concrete from crushing and spalling. Steel fiber, however, improved the columns’ ductility and strength. The results showed the maximum load-carrying capacity of the specimens and the results of using ACI-318 code equations agreed very well. Furthermore, a model is proposed for columns with both natural and recycled aggregate and which accounts for the eccentricity and slenderness to forecast the load-carrying capacity. The outcomes demonstrated that the design principles were met well. Plots of load–moment interaction diagrams for short and slender columns made with the ACI-318 method are compared to the findings of the experiments.

Experimental investigation of the effectiveness of strengthening methods in reinforced concrete flat slabs with multiple openings under punching load

In this study, an experimental investigation was carried out to strengthen reinforced concrete flat slabs with multiple openings against punching load via three different strengthening methods. The methods applied in this investigation are (a) shear stud method, (b) textile reinforced mortar (TRM) method, and (c) carbon fiber-reinforced polymer (CFRP) method. Thirthy-eight specimens with dimensions of 2000 mm × 2000 mm x 120 mm were produced, and the study was conducted in four series. The first series, consisting of ten specimens, was selected as the reference series in which strengthening operation was not applied; one specimen was produced as solid (no opening) and the rest with openings. The second series was identical to the first series and strengthened with the shear stud method.The third and fourth series were formed from nine specimens with openings, and each sequence was strengthened by textile-reinforced mortar and carbon fiber-reinforced polymer methods, respectively.The variables planned to be examined in this study were chosen as the presence, the location, the dimension of the openings, and the strengthening type. Load-displacement graphs were obtained for each specimen subjected to concentric monotonic static loading, and by employing these graphs; the essential performance indexes such as ultimate load-carrying capacity, initial stiffness, and energy dissipation capacity of the specimens were calculated. It has been revealed that the size and the position of the openings are effective on the performance indexes of the specimens. Significants increases in the ultimate load-carrying capacity, initial stiffness and energy dissipation capacities of the strengthened specimens are among the main findings of this study. Furthermore, the effectiveness of the strengthening methods was discussed by comparing the performance indexes at the end of the study.

Vibration diagnostics of transportation structures on railroads

The article presents the results of the natural frequencies of vibrations of the span structure during the express-diagnostics, to excite the process of vibrations of the structure the pulse impact of the concentrated load of small mass is applied in the middle of the span structure (the method of small pulse impacts – “human jump”). The analysis of the obtained data, allowed to establish the parameters of free vibrations of unloaded span structures, the predominant frequencies on the graph of spectral density of dispersion are identical, regardless of the number of jumps, that is, the frequency of impact, if the time between jumps corresponds to the complete damping of vibrations. Of practical interest in the assessment of the technical condition is a quantitative assessment of the change in the natural frequency of vibration of girder metal and reinforced concrete spans depending on the presence of defects accumulated during the operation of the bridge. The obtained characteristics can serve as initial data, increasing the accuracy of calculations for calculations of artificial structures for seismic resistance, as well as in dynamic stability calculations for prospective loads and in the development of a model of the structure, the formation of algorithms of tasks to identify defects.

Structural Behavior of Circular Concrete Columns Reinforced with Longitudinal GFRP Rebars under Axial Load

This paper presents experimental and theoretical assessments of the structural behavior of circular steel fiber-reinforced concrete (SFRC) columns reinforced with glass fiber-reinforced polymer (GFRP) bars subjected to a concentric axial compressive load. Laboratory experiments were planned to evaluate and compare the effect of different design parameters on the structural behavior of column specimens based on experiments and finite element (FE) analysis. The experimental variables were (i) concrete types, i.e., conventional concrete (CC) and fiber-reinforced concrete (FC), (ii) longitudinal reinforcement types, i.e., steel and GFRP bars, and (iii) transverse rebar configurations, i.e., tied and spiral with different pitches. Sixteen column specimens were fabricated and categorized into four groups with respect to rebar configurations and concrete types. The results showed that the failure modes and cracking patterns of those four column groups were comparable, particularly in the pre-peak branches of load-deflection curves. Even though the average ultimate load of the columns with longitudinal GFRP bars was 17.9% less than that with longitudinal steel bars, the ductility index (DI) was 10.2% greater than their counterpart on average. The addition of steel fibers (SF) to concrete increased the axial peak load by up to 3.1% and the DI by up to 6.6% compared to their counterpart CC columns without SFs. The DI of specimens was increased by higher volumetric ratios (up to 12%) and spiral types (up to 5.5%). The concrete damage plastic (CDP) model for FC columns was updated in the finite element software ABAQUS 6.14. Finally, a new simple equation was theoretically proposed to predict the axial capacity of specimens by considering the inclusion of longitudinal GFRP rebars, volumetric ratio, and steel spiral/hoop ties. Good agreement between the proposed model predictions and the experimental/numerical results was observed.

Indentation of an elastic arch on a frictional substrate: Pinning, unfolding, and snapping.

In this study, we investigate the morphology and mechanics of a naturally curved elastic arch loaded at its center and frictionally supported at both ends on a flat, rigid substrate. Through systematic numerical simulations, we classify the observed behaviors of the arch into three configurations in terms of the arch geometry and the coefficient of static friction with the substrate. A linear theory is developed based on a planar elastica model combined with Amontons-Coulomb's frictional law, which quantitatively explains the numerically constructed phase diagram. The snapping transition of a loaded arch in a sufficiently large indentation regime, which involves a discontinuous force jump, is numerically observed. The proposed model problem enables a fully analytical investigation and demonstrates a rich variety of mechanical behaviors owing to the interplay among elasticity, geometry, and friction. This study provides a basis for understanding more common but complex systems, such as a cylindrical shell subjected to a concentrated load and simultaneously supported by frictional contact with surrounding objects.

Initial factors impacting vertical displacement, stresses, and propagation of cracks in three-layered steel fiber concrete beams

The main aim of the study is to examine the input parameters of three-layered steel fiber concrete beams. Bending RC beams is studied by many different scientists. Multilayer RC beams using SF concrete are one way. In high compressive and tensile stress zones, this method improves beam load strength and reduces cracks. The main goal is to decrease beam stress. Repairing broken three-layered SF-reinforced concrete beams by adding more concrete on top or below the current layer is a benefit. Modifying input parameters during three-layered beam design greatly affects beam efficacy. In this paper, the authors conducted a study using ANSYS simulation and nonlinear material analysis. The objective was to investigate the behavior of three-layered bending RC beams subjected to two concentrated loads. Specifically, the study examined the impact of varying the content of SF in the RC, as well as the effects of stirrup at the ends of the beams. Furthermore, the study explored the influence of changes in the quantity and size of steel bars in the region of tensile strength, along with the effect of varying the SF concrete layer's thickness. The survey results on three-layered beams were used to create diagrams that depict the relationship between load and vertical displacement and load and stress area. These diagrams also help determine the initiation and progression of cracks in three-layered beams, starting from the application of load until the beams become damaged. Ultimately, this information allowed us to identify the specific load level that caused the beams to crack and become damaged.

Application of the Green's function method for static analysis of nonlocal stress-driven and strain gradient elastic nanobeams

This paper focuses on the static analysis of a generally restrained Euler-Bernoulli nanobeam (GRNB), which is subjected to arbitrary distributed or concentrated loads. The small length scale effect is introduced through a strongly nonlocal integral elastic law called the stress-driven nonlocal Euler-Bernoulli beam model, and a weakly nonlocal elastic law called the strain-gradient Euler-Bernoulli beam model. The stress-driven nonlocal theory and the strain gradient elasticity theory are both employed, to formulate the differential equation governing the Euler-Bernoulli nanobeams. Both theories are ruled by a similar 6th order differential equation, with distinct higher-order boundary conditions. The paper demonstrates that the strain gradient theory can be also reformulated as a stress-driven nonlocal theory with unsymmetrical kernel, in contrast to the initial stress-driven nonlocal theory which has symmetrical exponential kernel. Additionally, some theoretical backgrounds about both nonlocal elasticity theorems are provided. Exact solutions for both nanobeam models are presented, using Green's function method. The parameters of the Green's functions are derived for each beam theory, and then utilized to establish the static displacement function of both nanobeam theories. Exact solutions are provided for the bending of both nanobeams with various end boundary conditions, that account for the small length scale effects. The paper also compares the responses of the stress-driven Euler-Bernoulli beam and the strain gradient Euler-Bernoulli beam, showing close deflections and similar effects of increasing the nonlocal parameter on beam stiffness. A major difference highlighted between the two theories is that the strain gradient theory predicts a homogeneous strain state for homogeneous stress state, as opposed to the stress-driven theory.

Predicting the indentation load of FRP facesheet / foam core sandwiches

Due to concentrated bending loads, indentation is a common failure mode for sandwich structures. Indentation restricts the efficient use of sandwiches and is seriously affected by the sandwich design. Currently-used Traditional Analytical Models (TAM) are insufficient to predict the indentation load of the sandwiches with fiber-reinforced polymer (FRP) composite facesheets and foam core. Because of anisotropic features of FRP composites, experimental stiffness data is required to implement TAM. Their prediction accuracy is also disputable for different fiber orientations of facesheets. In this study, a modified analytical model (MAM) was developed to predict core yield and indentation failure loads without needing the experimental data of FRP composite facesheets. The modification is applied to currently-used two different traditional indentation models, and it is based on the analytically-obtained stiffness terms. The results obtained by MAM were then compared with the results determined by TAM and with the flexural test results of various sandwich structures. The modified analytical model, presented herein, yielded more accurate results than the TAM even for angle-ply configurations. An analytical solution to predict indentation is ultimately more attractive to structural sandwich designers because it provides rapid predictions that eliminate trial-and-error experimental efforts.

АНАЛИТИЧЕСКИЙ ПОДХОД К ОПРЕДЕЛЕНИЮ ПРОДОЛЬНОГО СМЕЩЕНИЯ СУЩЕСТВУЮЩЕГО СБОРНОГО ТОННЕЛЯ ПРИ ВЫЕМКЕ КОТЛОВАНА ПО ВСЕЙ ДЛИНЕ

In the realm of urban construction employing excavation techniques, safeguarding existing underground structures from detrimental consequences arising from surface construction operations poses a formidable challenge. The reduction of loads due to excavation activities can induce unintended responses, potentially jeopardizing subterranean infrastructure, particularly high-safety-demanding structures like Tunnel Boring Machine (TBM) tunnels. This article introduces an uncomplicated method for ascertaining the axial displacement of TBM tunnels amidst concurrent surface excavation activities. Primarily, the approach entails the identification of stress variations encountered during soil excavation at the tunnel face. Subsequently, employing the solutions derived for the determination of tunnel deformation subjected to concentrated loads, the deformation incurred by the tunnel due to alterations in excavation-induced stress is quantified. The analytical outcomes are meticulously juxtaposed against results generated from a three-dimensional computational model. The comparative analysis demonstrates that the displacement values and axial deviations calculated using the proposed analytical method exhibit only marginal disparities of 4,3% and 1%, respectively, when compared to those obtained through finite element analysis. This study underscores the efficient predictive capabilities of the analytical method in assessing tunnel deformations, enabling a preliminary estimation of critical parameters associated with the excavation pit. These findings have significant implications for mitigating adverse impacts on existing subterranean infrastructure in densely populated urban areas.

Experimental design of 4-point supported belt robot for sanding large convex surfaces

In general, sanding robots that move as if drawing a line along a surface are mainly used when sanding objects with a large area; however, they require a long working time, and it is difficult to secure a uniform sanded area. This study focuses on large-area sanding robots, such as those for ships, storage tanks, and tank lorries, and proposes an adaptive belt tension robot equipped with a 4-point supported belt mechanism capable of sanding variable curved surfaces. In addition, a sanding normal force prediction formula is proposed to describe the sanding performance of the contact surface. This equation consists of the concentrated load function due to the belt movement and the normal force due to the vertical and horizontal elongation of the belt. A video image analysis was performed to calculate the sanding area. Therefore, we determined whether the area was uniformly sanded. The dimensions of the test bench (W ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes $$\\end{document} D ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes $$\\end{document} H) were 1700 mm ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes $$\\end{document} 1450 mm ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes $$\\end{document} 900 mm. Experiments were performed using the proposed techniques on convex specimens with radii of 725, 1000, and 2100 mm. The sanding performance was improved by 43 %\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\%$$\\end{document} compared with that of a general belt-sanding robot.

Stress Analysis of Semi-covered Excavation Foundation Pit in Metro Stations based on Incremental Method

The station foundation pit of Ningbo Metro Line 2 is taken as engineering background, the support structure form of the semi covered excavation foundation pit is introduced. The standard section of the foundation pit is considered as a plane strain problem, a force calculation and analysis model for the half cover system structure is established based on the incremental method, concentrated load of a waste truck is applied within 5.0 m cover plate range outside the middle column and an impact coefficient of 0.4 is considered, overload with value of 20kPa is applied to the rest parts of the cover plate and 5.0 m outside the diaphragm wall. The excavation of the foundation pit is divided into 5 stages, the surface overload, structural self weight, soil pressure and elastic resistance increment, and support axial force are applied respectively, and the bending moment increment of the connecting wall and cover plate system at each excavation stage are calculated. The bearing capacities of the diaphragm wall and cover plate reinforcement are respectively calculated based on the rectangular bending normal section components, and they both meet the strength requirements.

Strengthening of two-way slabs with fiber-reinforced polymer composites: A new system using grooving technique and fans

The flexural capacity of a reinforced concrete (RC) two-way slab can be efficiently enhanced using fiber-reinforced polymer (FRP) composites if FRP debonding is postponed. On the other hand, with the increase in flexural capacity, the vulnerability of the slab to punching shear failure increases. In this context, the current study examines FRP strengthening of lightly reinforced slabs using the externally bonded reinforcement on grooves (EBROG) technique, which has already been proven successful in postponing FRP debonding. Four slab specimens are tested in two groups under concentric loading. The first group consists of two specimens reinforced with headed shear studs: one reference specimen and one specimen strengthened in flexure with FRP. The second group includes two specimens without internal punching shear reinforcement: one reference specimen and one specimen strengthened with a new simultaneous flexural and punching shear strengthening system, taking advantage of FRP fans. According to the results, flexural strengthening of the slab in Group 1 increased its ultimate load capacity by 77%, and the proposed strengthening system in Group 2 led to a 94% enhancement of the ultimate load capacity. A calculation method based on the yield-line theory is presented to predict the load capacity of the test specimens. According to this method, graphs simplifying the estimation of the flexural capacity of FRP-strengthened slabs are proposed.

Multimodal Resonance Response of Incompressible Hyperelastic Moderately Thick Cylindrical Shells

Based on the modified third-order shear deformation theory, the harmonic balance method, and the pseudo-arclength continuation method with two-point prediction, the nonlinear forced vibration response of incompressible hyperelastic moderately thick cylindrical shells subjected to a concentrated harmonic load at mid-span and simply supported boundary conditions at both ends is investigated. The algorithmic procedure for solving steady-state periodic solutions of strongly nonlinear systems of differential equations is presented. The structural response characteristics of shells under different excitation amplitudes and structural parameters are analyzed. The numerical results indicate that the aspect ratio of moderately thick hyperelastic cylindrical shells has a significant effect on the natural frequency ratio. Different frequency ratios lead to varying nonlinear mode coupling effects. The coupling effects among modes result in complex nonlinear behavior in the vibration response of each mode, leading to abundant multi-valued phenomena in the response curve.

Internal stress transfer characteristics of coal–rock medium under concentrated force based on particle flow method

To solve the problem that the macroscopic deformation and failure of coal–rock medium under external loads are easy to be observed while the internal stress transfer mode and path are unclear. Based on the discrete element idea, the numerical models for pure coal or rock samples and coal–rock combination samples with different lithologies and combination methods under concentrated force are established by PFC2D software. Then the influence of coal or rock strength and combination methods on the internal stress transfer law and distribution evolution characteristics of coal–rock medium are discussed from the perspectives of macroscopic stress and mesoscopic force chain, respectively. The results showed that under concentrated load, the macroscopic stress transfer paths within pure coal or rock samples and coal–rock combination samples are primarily in the form of ‘point source radiation’. However, when transferring between coal–rock interfaces, there is a certain interface effect. For pure coal or rock samples, differences in lithology does not change the transfer rules and macro distribution patterns of internal stress, but it can cause changes in internal unit transfer stress value and local area transfer direction. For coal–rock combination samples, the greater the difference in lithology between the two sides of the interface, the more likely the interface effect will occur. In addition, the internal stress transfer is also influenced by the relative stratigraphic relationships of coal and rock. When the stress is transferred from a higher-strength rock to a lower-strength coal mass, the interface effect will be more significant. However, regardless of the combination pattern, the locations where significant stress surges occur are always within the higher strength rock mass near the interface. The findings are helpful to understand the mechanical properties and failure mechanism of mining coal and rock mass, and provide a theoretical basis for the study of the mining-induced mechanical behavior of the floor under the action of the coal pillar.

An application of stability charts to prediction of buckling instability in tapered columns via Galerkin’s method

This work tackles the mathematical modeling of buckling problem to obtain their critical loads in tapered columns subjected to concentrated and axial distributed loads. The governing model is a general eigenvalue problem that has no exact solution due to some new terms included. A semi-analytical technique satisfying the boundary conditions is proposed for the solution procedure. The minimum residual Galerkin’s method is suggested due to its effectiveness as a semi-analytical tool for the buckling problem to obtain the buckling shape modes by using admissible periodic functions. The study investigates the buckling instability and the responses of tapered columns with different periodic trial shape functions as approximations to the exact solutions. Based on the eigenvalue problem, Galerkin’s method is employed to obtain the transition curves to represent the critical loads. The stability charts (Ince–Strutt diagrams) among the parameters of the problem are proposed to explain the elastic stability of different tapered columns subjected to different shapes of cross sections and distributed weights. Consequently, the influences of the included parameters on the critical buckling loads are discussed. Among the different tapered columns presented, some parameters in the proposed distributions have a big influence on the critical buckling load and the creation of the instability regions in the chart for the clamped-clamped boundary conditions. The results are verified using the analytical solutions for some specific known problems.

The role of CFRP strengthening in improving the punching shear behavior of heat-damaged flat slabs with openings of different sizes and locations

The punching shear behavior of twenty simply supported RC flat slabs of mm3) dimensions was examined in this study where concentrated loading was applied using a 150 mm central square column. However, the effect of the following parameters was evaluated: (1) CFRP strengthening, (2) ambient and elevated temperatures (23 C, 200 C, 400 C, and 600 C), (3) opening existence (with or without), (4) opening location (directly at the column face or 60 mm a way), and (5) square opening side length (70 mm or 200 mm). Strengthening was done by four 75 mm wide CFRP strips applied at the bottom face of the slab to surround the column and opening region. It was found that the cracking intensity is directly affected by the exposure temperature with the cracking visibility at the opening internal sides. In addition, strengthening increases the slab’s stiffness by larger percentages for slabs with small openings compared to those with larger ones at ambient and normal temperatures with the differences being reduced at higher temperatures. Moreover, strengthening plays a major role in improving the slab’s deflection capacities by 10–90 % compared to the control specimen. Finally, the punching shear failure brittleness was significantly reduced by the CFRP-strengthening as the ductility of the strengthened specimens was increased as a result of the cracking intensity reduction.

Research on the deformation and settlement characteristics of tunnel lining structures based on distributed fibre optic sensing technology

To study the deformation and settlement characteristics of tunnel lining structures, a tunnel lining structure model was designed based on distributed fibre optic sensing technology. Compared to the cylindrical model used in traditional tunnel lining structural model experiments, in this study, a reinforced concrete structural model was adopted, which can embed fibre optics in the structure, which is closer to actual tunnel engineering conditions. Central and symmetrical concentrated loading experiments were carried out with a simply supported reaction frame. The results of the distributed fibre optic monitoring were compared and analysed with those of traditional monitoring methods to verify the reliability of the distributed fibre optic monitoring results. The numerical simulations of the experiments were conducted by using finite element analysis. By comparing and analysing the simulation and experimental results, the correctness of the simulation calculation results were verified. On this basis, the impact of concrete strength, circumferential reinforcement spacing, and longitudinal reinforcement strength on the deformation and settlement of the tunnel lining structure were analysed. The results show that the hierarchical effect of the strain monitoring results obtained by the embedded fibre optic is more obvious, indicating that the radial monitoring effect of the embedded fibre optic on the tunnel structure is less affected by other external factors than the strain gauge, and the monitoring data are more accurate and effective, with good engineering characteristics. Improving the concrete strength, appropriate circumferential reinforcement spacing, and increasing the longitudinal reinforcement strength can effectively enhance the ability of the structure to resist deformation at the stress location. These factors play a significant role in improving the overall resistance to deformation and safety of the structure. The research results provide a theoretical basis and experimental data for the application of distributed fibre optics in monitoring the deformation and settlement of tunnel lining structures.

ONE-WAY SLABS IN TRANSITION BETWEEN ONE-WAY SHEAR AND PUNCHING: EXPERIMENTS AND RECENT INSIGHTS FOR EVALUATION

Bridge deck slabs are members on which one-way reinforced concrete slabs are found frequently loaded by concentrated loads. Although the one-way shear failure mechanism has gathered more attention in the past years, both one-way shear and two-way shear mechanisms may be critical for such loading conditions. This paper addressed the ultimate capacity of thin one-way reinforced concrete slabs subjected to concentrated loads and yielding of the flexural reinforcement. In practice, the test setup studied was devised to represent short-span rural bridges frequently found in Brazil. The experimental program included 12 tests performed on 6 slabs applying the concentrated loads at varied positions. All tests started to fail by punching shear. Nevertheless, both one-way shear and punching shear cracks were observed at ultimate states after shear redistribution. The reinforcement yielding followed by excessive flexural cracking hampered the arching action activation for loads closer to the support. The comparison of experimental and calculated resistances using standard code-based expressions suggests that improvements in unitary shear capacity could be supported as a result of slabs' transverse load distribution capacity. Alternatively, increasing the effective shear width can help estimate one-way shear capacity for loads near to the support.