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This paper presents a model for evaluation of the rear face damage in concrete barriers subjected to impact of non‐deforming projectiles. This is an improved and extended version of a previously published model, which now covers both plain and steel fiber reinforced concrete (SFRC) barriers. The rear face damaged area commonly measured in tests is characterized by an equivalent diameter, evaluated by the model. Calibration and then validation are based on published experimental data. Different sets of experiments, of plain concrete and SFRC, reported by different researchers, were used for the model's calibration and for its validation. The calibrated model's predictions show reasonable agreement with the reported experimental results, especially in view of their considerable scatter. The main findings from a parametric study of the model's predictions refer to the influence on the rear face damage (at barrier thickness lower than the scabbing limit thickness) of including steel fibers in the concrete mix, the barrier thickness, impact level, and the projectile diameter. The model's predictions demonstrate the lower extent of damage in SFRC barriers, compared to plain concrete. The use of the model enables quantitative assessment of this damage and of its reduction in SFRC barriers. [ABSTRACT FROM AUTHOR]

This paper describes a work that examines a new solution to the problem that arises from the relatively high amount of transverse reinforcement required in HSC columns. It presents an alternative to common transverse steel reinforcement, a dual system comprising steel ties and a carbon-fiber mesh (CFM) applied internally together with steel ties. The behavior of the proposed system was examined in this work in a series of twelve laboratory tests of circular stub column specimens. The experiments performed in this work focused on the columns' load and displacement capacities. The tests were planned with the aid of an analytical model that was originally developed for a hybrid system of external fiber-reinforced polymer (FRP) sheets and internal steel, and was adapted for the current system. An analysis of the results shows that for a given amount of conventional transverse steel, the application of the carbon-fiber meshes adds efficiency to the rebar confinement system, in terms of both the load bearing capacity and the ductility, and for specimens with the hybrid confinement system, the higher the carbon fiber amount the larger the ductility improvement. Furthermore, fair to good agreement was observed between the model and the measured stress–strain curves, especially those of the peak stresses. Based on the above findings and the added benefit of fire resistance, the hybrid method appears to be promising for confining HSC columns. [ABSTRACT FROM AUTHOR]

The paper presents a model to analyze the response of a buried structure to surface loading, which is based on a discrete-continuous concept, taking into consideration a possible variation of the soil arching coefficient with depth. The structure and the soil are represented by equivalent two degree of freedom and one-dimensional column system. The shear soil resistance is represented by a vertical friction traction that depends on the relative displacement between the column and the free field. At the bottom, the system is supported by a semi-infinite medium. An analytical solution for the mid-roof deflection and average contact pressure has been derived and verified against published experimental results. Examination of the effects of the soil parameters on the mid-roof deflection demonstrates their different weights in the analysis. The present model may be used for future solutions of corresponding dynamic problems, for which the variation of the arching coefficient with depth is especially important. Key words: arching coefficient, buried structures, soil-structure interaction. Dans le cadre de cet article, on presente un modele afin d'analyser la reponse d'une structure souterraine au chargement de surface, modele qui est fonde sur un concept discret-continu, prenant en consideration une variation possible du coefficient d'effet de voute en fonction de la profondeur. La structure et le sol sont representes par un systeme equivalent a deux degres de liberte et une colonne 1D. La resistance du sol au cisaillement est representee par une traction de friction verticale qui depend du deplacement relatif entre la colonne et le champ libre. Au fond, le systeme est supporte par un milieu semi- infini. On a derive une solution analytique pour le flechissement au milieu du toit et la pression de contact moyenne, et on les a compares aux resultats experimentaux publies. L'examen des effets des parametres du sol sur le flechissement au milieu du toit demontre leurs differents facteurs de ponderation dans l'analyse. Le present modele peut servir a trouver des solutions futures a des problemes dynamiques correspondants, pour lesquels la variation du coefficient de l'effet de voute selon la profondeur est particulierement importante. [Traduit par la Redaction] Mots-cles : coefficient d'effet de voute, structures souterraines, interaction sol-structure., Introduction An important parameter in the design of buried structures, such as conduits or protective structures is the load acting on its roof (Nowak et al. 2001). A common loading [...]

This article presents an experimental study aimed to identify and quantify the cracking localization (CL) phenomenon in under‐reinforced R/SFRC beams. Results of current experiments together with those of previous tests published by the authors were used for quantification of the cracking localization level (CLL) considering the effect of fiber content, Vf, and of longitudinal reinforcement ratio, ρs, over a wide range of ρs and the effect of rebar yield and ultimate strengths. The experimental program consisted of four‐point bending tests of normal strength R/SFRC beam specimens with 400 and 500‐MPa steel and fiber volumetric contents Vf of 0.5 and 0.76%. A new definition is introduced for "significantly wide cracks" that yields a unique definition of the CLL when this phenomenon diminishes. Moreover, it is now proposed to change the definition of CLL. The study identified the existence of a transition point (TP), beyond which addition of fibers to the concrete mix do not affect CLL anymore. Observations from the experimental results prove the consistency of the newly proposed CLL definitions as well as the dependency of CL on both the amount and stress hardening of the tension steel. Their use enables a clear delineation of the CL phenomenon in R/SFRC beams. The importance of this finding refers to the reported decrease of flexural ductility in R/SFRC beams due to high CLL. Hence, the importance of the ability, achieved in the current findings, to quantify the conditions for TPs in various cases. [ABSTRACT FROM AUTHOR]

The paper presents the methodologies and results of an experimental study aimed at measuring the soil contact pressures which develop on a buried structure as it interacts with the surrounding soil under load. The study has been based on measurements made on model structures tested in a pressure chamber filled with a fine uniform sand. The buried model structure was a very rigid right cylinder designed such that it could be fitted with roofs of different thicknesses. The structure bottom and roof were instrumented with newly designed and constructed soil pressure cells based on the null response concept. The device is unaffected by the issues that affect the use of traditional soil pressure cells. The development of pressure on the structure was measured as uniform pressure was applied to the soil surface. The results illustrate the effect of roof stiffness on the development of pressure at the roof center. The midroof pressure was seen to increase with roof stiffness, however the development of pressure was also seen to be dependent upon the actual deflection. In the case of a flexible roof it was seen that the development of contact pressure is a nonlinear function of the pressure applied at the soil surface and is highly dependent upon stress history. In contrast, it was seen that pressure on a stiff roof develops as a linear function of pressure applied at the soil surface and is less dependent of stress history. The results of the model tests together with soil stiffness data supplied in the paper will be useful in the calibration and validation of numerical and analytical frameworks. CE Database subject headings: Soil pressure; Measurement; Underground structures; Validation.