Reza Hassanli

Strength and Seismic Performance Factors of Posttensioned Masonry Walls

AbstractIn this study, the behavior of posttensioned masonry walls is investigated using a database of 31 tested walls. The accuracy of the current Masonry Standards Joint Committee (MSJC) in evaluating the strength of posttensioned masonry walls is studied using the available test results. Moreover, using the experimental results, the seismic performance factors including ductility, response modification factor, and displacement amplification factor are determined for different types of walls including fully grouted, partially grouted, ungrouted walls, walls with confinement plates, walls with supplemental mild steel, and walls with an opening. As a result of this study, it was determined that the MSJC underestimates the strength of fully grouted unbonded posttensioned walls by about 20%. Using the strain compatibility method to determine the flexural capacity of bonded masonry walls resulted in reasonable predictions of strength. Moreover, an average response modification factor of 4.27 to 7.76 and disp...

Seismic Performance of Precast Posttensioned Segmental FRP-Confined and Unconfined Crumb Rubber Concrete Columns

AbstractThis paper presents an experimental study carried out on unbonded posttensioned (PT) segmental precast concrete columns. In total, eight cylindrical columns were posttensioned and tested un...

An Evaluation of Design Code Expressions for Estimating in-plane Shear Strength of partiallY Grouted Masonry Walls

Abstract This paper aims to evaluate the in-plane shear strength expressions of partially grouted masonry (PGM) walls in four international design codes, including masonry design codes of practice in the United States, New Zealand, Canada and Australia. Experimental results of 89 partially grouted masonry walls that displayed shear failure were collected from published research. The shear strengths of the walls in the database were calculated using the different code equations and compared with those from the experimental results. In addition, the parameters that influence the shear strength of the walls, including masonry tensile strength, level of axial compressive stress, wall aspect ratio, and the amount and spacing of vertical and horizontal reinforcement are studied. Both univariate and multivariate regression analysis have been employed to investigate the effect of each parameter on the accuracy of the code shear strength predictions. This study illustrates poor correlation between code predictions and test results, indicating that current codes are unable to predict the shear strength of PGM walls. In some cases the code shear strength predictions are three to four times the experimentally measured shear strength, indicating that modifications are needed as the current provisions are unconservative. An equation is therefore proposed which better estimates the strength of PGM walls.

Simplified Approach to Predict the Flexural Strength of Unbonded Post-tensioned Masonry Walls

A simplified design approach is developed in this chapter to predict the flexural strength of unbonded PT-MWs. The accuracy of different flexural expressions is also investigated in this chapter according to experimental and finite element modelling results. An analytical procedure is developed to predict the force displacement response of PT-MWs. The accuracy of the analytical model is then validated against available experimental test results for unconfined and confined PT-MWs. Using a similar analytical procedure, a parametric study is performed to obtain the force-displacement response of walls with different features. Multivariate regression analysis is performed to develop an empirical equation to estimate the compression zone length in unbonded PT-MWs. The proposed equation for compression zone length is then incorporated into the flexural analysis of post-tensioned masonry walls and validated against experimental results and finite element results.

Effect of Dimensions on the Compressive Strength of Concrete Masonry Prisms

This chapter investigates the accuracy of the height-to-thickness ratio (h/t) correction factors presented in the ASTM standard (ASTM C1314-03) and in other international standards using numerical finite element analysis. The FEM is calibrated with experimental results, and then a parametric study is performed to examine the effect of size on the strength of masonry prisms. Calibration of masonry material provided in this chapter is then used in developing finite element models of PT-MWs presented in Chap. 5.

Pre-stressed Segmental Retaining Walls (PSRWs)

This paper introduces an innovative system of retaining walls named “pre-stressed segmental retaining walls (PSRWs)”. In this system, interlocking blocks are assembled together with dry joints (mortarless) and the integrity of the wall is maintained by pre-stressing forces. The pro-posed system has a collection of advantages over the conventional systems for construction of cantilever retaining walls or mechanically stabilized earth walls. In particular precast concrete/masonry segments can be incorporated which reduces the construction time and cost for cantilever type structures and if combined with mechanically stabilized earth wall system, it can reduce the number of layers of reinforcement and add flexibility to the design. These walls will be suitable for both water front and soil retention purposes.

Experimental Investigation of Unbonded Post-tensioned Masonry Walls

This chapter reports on an experimental program conducted as a part of this thesis that investigated the behavior of PT-MWs. The accuracy of the MSJC (2013) in ignoring the elongation of PT bars is investigated using the two design equations proposed in Chaps. 5 and 6 to predict the flexural strength of the tested walls. The accuracy of the analytical approach developed in Chap. 6 is verified against the presented experimental results.

Flexural Strength Prediction of Unbonded Post-tensioned Masonry Walls

A design equation is developed in this chapter to predict the in-plane flexural strength of unbonded PT-MWs. Using well-validated finite element models, a parametric study is performed to investigate the effect of different parameters on the wall rotation and compression zone length, including axial stress ratio, length and height of the wall, initial to yield stress ratio of PT bars and spacing between PT bars.

Use of Fine Rubber Particles as Fine Concrete Aggregates in Actively Confined Concrete

This study presents the results of the experimental study on the axial compressive behavior of the rubberized concrete under active confinement. Two different mixes of concretes with rubber replacement ratios of 0%, as a control mix, and 18% were prepared. The effects of the incorporation of rubber and the confining pressure on the compressive behavior of concrete were examined through tests of unconfined and actively confined concrete cylinders. The active confinement was applied by a Hoek cell at different pressures, including 5, 7.5, 10, 15, 20, and 25 MPa. The results indicate that the rubberized concrete exhibits lower compressive strength but higher axial and lateral deformation capacities than those of the conventional concrete.

Experimental and Numerical Study on the Behavior of Rubberized Concrete

In this study, the properties of rubberized concrete were examined and finite-element (FE) models were developed to investigate the accuracy of a current concrete material model in predicting the compressive behavior of rubberized concrete. The rubber particles, with a size of 1.18 mm were used at 0 %, 6 %, 12 %, and 18 % volume replacement of fine aggregate, keeping the proportions of gravel, water, and cement the same in all mixtures. Cylindrical and beam specimens were prepared and tested to evaluate the effect of rubber content on the density, compressive strength, elastic modulus, and damping ratio of the concrete. The results indicated that the damping ratio of rubberized concrete increased by 5.5 %, 27.8 %, and 64.8 % with rubber replacement of 6 %, 12 %, and 18 %, respectively. In addition to the experimental study, non-linear finite-element analysis was carried out using LS-DYNA software (Livermore Software Technology Corporation). The FE model developed in this paper was able to closely simulate the compressive behavior of the rubberized concrete specimens. The stiffness, compressive strength, volumetric response, and the dilation behavior obtained using the FE analysis agreed well with the values measured in the experimental work. The results show that the current concrete material model can be considered for rubberized concrete, provided that the compressive strength is modified to account for the reduction in strength caused by the added rubber.