Shear behavior of reactive powder concrete beams

مقدم أطروحة جامعية

Rida, Maha Muhammad Saeed

مشرف أطروحة جامعية

Sarsam, Qays Fuad
al-Shaarbaf, Ihsan Ali Saib

الجامعة

الجامعة التكنولوجية

الكلية

-

القسم الأكاديمي

قسم هندسة البناء و الإنشاءات

دولة الجامعة

العراق

الدرجة العلمية

دكتوراه

تاريخ الدرجة العلمية

2010

الملخص الإنجليزي

Reactive Powder Concrete (RPC) is an ultra-high strength, low porosity material with high cement and silica fume contents and steel fibers.

RPC uses low water-binder ratios and new generation super plasticizers with eliminating the coarse aggregates, and in brief all optimized particle size less than 600 micrometers.

In laboratories across the world, RPC was developed in the 1990's of the last century.

RPC can be readily used in a wide variety of structural applications, including situations where the concrete is required to carry substantial tensile stresses due to shear and bursting forces.

The present research can be divided into three categories following the respective three main objectives.

The first objective is to study the behavior and shear strength characteristics of RPC beams subjected to combined bending and shear.

Fifteen reinforced beams made with RPC were tested.

The studied variables were the volume fraction of steel fibers (VF), shear span to effective depth ratio (a/d), longitudinal reinforcement ratio (ρw) and percentage of silica fume powder (SF).

The effect of the above mentioned parameters on deformation characteristics of test beams including the deflection characteristics, concrete strains, crack propagation, crack patterns, crack width, failure mode, diagonal cracking loads and ultimate loads were elaborately covered in this study.

Comparison of the crack patterns for the specimens showed that the amount of fibers in RPC mixture did not significantly affect the cracking load but did have an influence on the rate of crack growth and on crack width.

For a given loading among otherwise similar specimens, the diagonal cracking and ultimate shear strength increased by about (20 to 40) % and (87.3 to 132.4 %) respectively, due to the addition of straight steel fibers to the RPC beams.

Fibrous RPC beams exhibited significantly greater ductility of behavior than that of nonferrous RPC beams.

Fibers also changed the mode of failure to a more ductile one, instead of the catastrophic type of failure for nonferrous RPC beam.

The second objective is to derive two expressions for evaluating the ultimate shear stress resistance of RPC beams based on present work test results.

The expression covers different characteristics of fibers and other principal parameters.

A comparison between computed values and the experimentally observed values is shown to validate the proposed theoretical treatment.

The proposed expressions gave good prediction for the shear strength of the tested beams-the proposed expressions predicted the shear stress resistance of Tested / calculated values with low COV : (6.1) % and (8.3 )% for the two proposed expressions of design.

The third objective is to analyze the tested beams using nonlinear finite element solutions.

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 is terminated at the onset of crushing.

In tension, a fixed smeared crack model has been used with a tension-stiffening model to represent the retained post-cracking tensile stresses and a shear retention model that modifies the shear modulus after cracking.

The results obtained by finite element solutions showed good agreement with experimental results.

Also, a numerical parametric study was carried out on the RPC beams to investigate the influence of fibrous concrete compressive strength (fα) tensile reinforcement ratio, (Pw) fiber content (Vf) and shear span to effective depth ratio (a / d) on the shear behavior and ultimate load capacity of these beams-e.g.

for RPC beams, increasing (fα) from (125 to 200) MPa, led to an increased ultimate load by about 33.9 %.

التخصصات الرئيسية

الهندسة المدنية

• APA
• MLA
• AMA

لغة النص

الإنجليزية

نوع البيانات

رسائل جامعية

رقم السجل

BIM-305235