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FRPs (fiber reinforced polymer) possess many favorable characteristics suitable and applicable for construction industry when compared with steel reinforcement. There are new ideas to use FRPs as longitudinal or transverse reinforcement for new concrete elements particularly for bridge decks or beams. Although high tensile strength of FRP is main characteristic for applications at both areas, its weakness to bending and linear stress-strain behavior with virtually no ductility, makes it vulnerable to probably premature failures under reversal tension-compression loading during earthquake. A pilot research project has been conducted to explore the characteristics of large-scale cantilever concrete beams reinforced with FRP re-bars and grids and were tested under either simulated cyclic loading or monotonically increasing lateral loading. This paper presents the test parameters and results obtained during research. The analytical relationships are compared with those recorded experimentally, and test results showed the diagonal cracks and either rupturing of FRP bars in tension or stability failure in compression bars at long or short shear span beams. The comparison of nominal moment capacities between analytical and experimental values confirms that plane section analysis is applicable to FRP reinforced concrete members.

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Confined masonry buildings are used in rural and urban areas of Iran. They performed almost satisfactory

during past moderate earthquakes of Iran. There is not a methodology in Iranian Seismic Code (Standard 2800-3rd

edition) to estimate their capacities quantitatively. In line with removing this constraint, an attempt is made to study

in-plane behavior of two squared confined masonry walls with and without opening by using a numerical approach.

These walls are considered based on Iranian Seismic Code requirements. Finite element 2D models of the walls are

developed and a pushover analysis is carried out. To model the non-linear behavior of the confined masonry walls, the

following criteria are used: (1) The Rankine-Hill yield criterion with low orthotropic factor to model the masonry

panel (2) The Rankine yield criterion to model reinforced concrete bond-beams and tie-columns (3) The Coulomb

friction criterion with tension cutoff mode to model the interface zone between the masonry panel and reinforced

concrete members. For this purpose, the unknown parameters are determined by testing of masonry and concrete

samples and by finite element analysis. Comparing the results show that the initial stiffness, the maximum lateral

strength and the ductility factor of walls with and without opening are different. Also, the severe compressed zones of

the masonry panels within the confining elements are found different from what are reported for the masonry panels

of infilled frames by other researchers. This study shows that a further investigation is needed for estimating capacity

of confined masonry walls with and without opening analytically and experimentally. Also where openings, with

medium size are existed, the confining elements should be added around them. These issues can be considered in the

next revisions of Iranian Seismic Code.

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In this paper a new method based on Strut-and-Tie Model (STM) is proposed to determine the shear capacity of simply supported RC deep beams and an efficiency factor for concrete with considering the effect of web reinforcements. It is assumed that, the total carried shear force by RC deep beam provided by two independent resistance, namely diagonal concrete strut due to strut-and-tie mechanism and the equivalent resisting force resulted by web reinforcements, web reinforcing reduces the concrete compression softening effect with preventing from the diagonal cracks opening or concrete splitting. The unknown function and parameters are determined from 324 experimental results obtained by other researchers. To validate the proposed method, the obtained results are compared with some of the existing methods and codes such as ACI 318-05 and CSA. The results indicate that the proposed method is capable to predict the shear strength of variety of deep beams with acceptable accuracy.

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An experimental-analytical investigation was conducted to study the behavior of high-strength RC deep beams a total of sixteen

reinforced concrete deep beams with compressive strength in range of 59 MPaOf'c O65 MPa were tested under two-point top

loading. The shear span-to-effective depth ratio a/d was 1.10 all the specimens were simply supported and reinforced by

vertical, horizontal and orthogonal steel bars in various arrangements. The test specimens were composed of five series based

on their arrangement of shear reinforcing. The general behavior of tested beams was investigated. Observations were made on

mid-span and loading point deflections, cracks form, failure modes and shear strengths. The test results indicated that both

vertical and horizontal web reinforcement are efficient in shear capacity of deep beams, also the orthogonal shear reinforcement

was the most efficient when placed perpendicular to major axis of diagonal crack. Concentrating of shear reinforcement within

middle region of shear span can improve the ultimate shear strength of deep beam. The test results were then compared with the

predicted ultimate strengths using the ACI 318-08 provisions ACI code tended to either unsafe or scattered results. The

performed investigations deduced that the ACI code provisions need to be revised.

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In order to investigate the flexural behaviors of RC beams after freeze-thaw cycles, compressive strength test of concrete cubes after 0, 50, 100, 125 freeze-thaw cycles were made, and static flexural experiment of 48 RC beams after 0, 50, 100, 125 freeze-thaw cycles were made. The relationships of relative compressive strength, mass loss rate, relative dynamic elastic modulus and numbers of freeze-thaw cycles were analyzed. The influences of different numbers of freeze-thaw cycles on the flexural behaviors of RC beams with different concrete grades were studied. The results show that concrete cubes’ mass, relative dynamic elastic modulus and compressive strength decrease with the increasing of freeze-thaw cycles, and high-strength grade concrete could slow down the damage caused by freeze-thaw cycles. Experimental values of test beams stiffness under short-term load were smaller than theory value. Some under-reinforced RC beams occurs over-reinforced failure mode after freeze-thaw cycles. Boundary reinforcement ratio of RC beams after certain numbers of freeze-thaw cycles was derived and its correctness was verified by experiment. Current code for design of concrete structures about crack load and ultimate load are still suitable for RC beams after freeze-thaw cycles.

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Complex nature of diagonal tension accompanied by formation of new cracks as well as closing and propagating preexisting cracks has deterred researchers to achieve an analytical and mathematical procedure for accurate predicting shear behavior of reinforced concrete, and there is the lack of a unique theory accepted universally. Shear behavior of reinforced concrete is studied in this paper based on recently developed constitutive laws for normal strength concrete and mild steel bars using nonlinear finite element method. The salient feature of these stress-strain relations is to account the interactive effects of concrete and embedded bars on each other in a smeared rotating crack approach. Implementing the considered constitutive laws into an efficient secant-stiffness based finite element algorithm, a procedure for nonlinear analysis of reinforced concrete is achieved. The resulted procedure is capable of predicting load-deformation behavior, cracking pattern, and failure mode of reinforced concrete. Corroboration with data from shear-critical beam test specimens with a wide range of properties showed the model to predict responses with a good accuracy. The results were also compared with those from the well-known theory of modified compression field and its extension called disturbed stress field model which revealed the present study to provide more accurate predictions.