Experimental Investigation of Shear- Critical Reactive Powder Concrete Beams without Web Reinforcement

جرت عملیة استقصاء عملی على سلوک عتبات خرسانیة عالیة المقاومة مصنوعة من المساحیق الفعالة. خمسة عشرة عتبة تحوی حدید تسلیح طولی تم صبھا وخالیة من تسلیح القص. المتغیرات الرئیسیة التی تم دراستھا ھی محتوى الالیاف الفولاذیة, نسبة حدید التسلیح الطولی, نسبة فضاء القص الى العمق الفعال ومحتوى السلیکا الفعالة. اعلى قیمھ لمقاومة الانضغاط کانت 110 میکاباسکال باستعمال نوع واحد من الالیاف الفولاذیة. تم اقتراح علاقات للتنبؤ بمقاومة اجھاد القص لعتبات خرسانة المساحیق الفعالة الخالیة من تسلیح القص. العلاقات االمقترحة اظھرت تطابقا جیدا لمقاومة اجھاد القص بالمقارنة مع النتائج العملیة

Nonlinear Finite Element Analysis of RPC Beams Failing in Shear

Reactive powder concrete (RPC) is a new type of ultra-high strength and high ductility concrete first developed in the 1990's in France. It is recognized as a revolutionary material that provides a combination of ductility, durability, and high strength. In this research work the nonlinear f ini t e element investigation on the behavior of RPC beams is presented. This investigation is carried out in order to get a better understanding of their behavior throughout the entire loading history. Also, a numerical parametric study was carried out on the RPC beams to investigate the influence of fibrous concrete compressive strength ( ) cf f ¢ , tensile reinforcement ratio ( ) w r , fiber content ( Vf ) and shear span to effective depth ratio (a/d) on the shear behavior and ultimate load capacity of these beams. The three- dimensional 20-node brick elements are used to model the concrete, while the reinforcing bars are modeled as axial members embedded within the concrete brick elements. The compressive behavior of concrete is simulated by an elastic-plastic work-hardening model followed by a perfectly plastic response, which terminated at the onset of crushing. In tension, a fixed smeared crack model has been used

Non-Linear Finite Element Analysis of Prestressed Concrete Members Under Torsion

       This paper is devoted to investigate the behavior of prestressed concrete beams under pure torsion using a non-linear three-dimensional finite element model. The 20-noded isoparametric brick elements have been used to model the concrete. The reinforcing bars are idealized as axial members embedded within the concrete element and perfect bond between the concrete and the reinforcement has been assumed to occur.            The behavior of concrete in compression is simulated by an elasto-plastic work hardening model followed by a perfect plastic response, which is terminated at the onset of crushing. On the other hand the behavior in tension is simulated by implementing a smeared crack model in connection with using a tension-stiffening model that account for the retained post-cracking stresses, and a shear retention model that modifies the shear modulus of rigidity as the crack widens. Also a model to simulate the reduction in the concrete compressive strength in presence of tensile transverse straining has been implemented in this study. Two types of prestressed concrete beams under torsion have been analyzed and the finite element solutions were compared with the experimental data. Several parametric studies have been carried out  to investigate the effect some important material parameters. In general, good agreement between the finite element solutions and the experimental results was obtained

Strength of Reinforced Concrete Columns with Transverse Openings

The present work is concerned with the investigation of the behavior and ultimate capacity of axially loaded reinforced concrete columns in presence of transverse openings under axial load plus uniaxial bending. The experimental program includes testing of twenty reinforced concrete columns (150 × 150 × 700 mm) under concentric and eccentric load. Parameters considered include opening size, load eccentricity and influence of the direction of load eccentricity with respect to the longitudinal axis of the opening. Experimental results are discussed based on load – lateral mid height deflection curves, load – longitudinal shortening behavior, ultimate load and failure modes. It is found that when the direction of load eccentricity is parallel to the longitudinal axis of openings, column behavior is more pronounced when than the direction is normal to the longitudinal axis of openings

Experimental Study and Shear Strength Prediction for Reactive Powder Concrete Beams

Eighteen reactive powder concrete (RPC) beams subjected to monotonic loading were tested to quantify the effect of a novel cementitious matrix materials on the shear behavior of longitudinally reinforced RPC beams without web reinforcement. The main test variables were the ratio of the shear span-to- effective depth (a/d), the ratio of the longitudinal reinforcement (ρw), the percentage of steel fibers volume fractions (Vf) and the percentage of silica fume powder (SF). A massive experimental program was implemented with monitoring the concrete strain, the deflection and the cracking width and pattern for each RPC beam during the test at all the stages of the loading until failure. The findings of this paper showed that the addition of micro steel fibers (Lf/Df = 13/0.2) into the RPC mixture did not dramatically influence the initial diagonal cracking load whereas it improved the ultimate load capacity, ductility and absorbed energy. The shear design equations proposed by Ashour et al. and Bunni for high strength fiber reinforced concrete (HSFRC) beams have been modified in this paper to predict the shear strength of slender RPC beams without web reinforcement and with a/d ≥ 2.5. The predictions of the modified equations are compared with Equations of Shine et al., Kwak et al. and Khuntia et al. Both of the modified equations in this paper gave satisfied predictions for the shear strength of the tested RPC beams with COV of 7.9% and 10%. Keywords: Beams, Ductility, Crack width, Absorbed energy, Reactive powder concrete, Steel fiber