Reinforced Concrete Masonry Research Articles

Experimental In-Plane Strength Investigation of Reinforced Concrete Masonry Walls with Openings

This paper presents test results of eight partially grout-filled perforated concrete masonry walls that were subjected to cyclic lateral loading. Test results obtained from this research indicated that the size of openings and the length of trimming reinforcement significantly affected the lateral strength of perforated masonry walls. It was shown that the current New Zealand nonspecific masonry design standard NZS 4229 unsafely overpredicts the strength capacity of concrete masonry walls with small openings, and an amendment is proposed to rectify this matter. It was also shown that NZS 4229 is increasingly conservative as the height of openings increased. Diagonal cracking patterns that formed during testing were observed to align well with the load paths by which lateral shear force was assumed to be transferred to the foundation when using strut-and-tie analysis. This observation supports the use of the strut-and-tie technique as a viable tool to evaluate the flexural strength of walls of this type.

Design Expression for the In-Plane Shear Strength of Reinforced Concrete Masonry

Aspects relating to codification of the in-plane shear strength of concrete masonry walls when subjected to seismic loading are presented in this paper. Particular emphasis is placed on a model that is capable of representing the interaction between flexural ductility and masonry shear strength to account for the reduction in shear strength as ductility level increases. The simple method proposed here allows the strength enhancement provided by axial compression load to be separated from the masonry component of shear strength and is considered to result from strut action. In addition, minor modifications are made to facilitate adoption of the method in the updated version of the New Zealand masonry design standard, NZS 4230:2004. Prediction of shear strength from NZS 4230:2004 and alternative methods are compared with results from a wide range of masonry walls tests failing in shear. It was established that the shear equation in the former version of the New Zealand masonry standard (NZS 4230:1990) was overly conservative in its prediction of masonry shear strength. The current National Earthquake Hazards Reduction Program (NEHRP) shear expression was found to be commendable, but it does not address masonry shear strength within plastic hinge regions, therefore limiting its use when designing masonry structures in seismic regions. Finally, the new shear equation implemented in NZS 4230:2004 was found to provide significantly improved shear strength prediction with respect to its predecessor, with accuracy close to that resulted from NEHRP.

Experimental In-Plane Shear Strength Investigation of Reinforced Concrete Masonry Walls

This paper presents test results of ten single-story reinforced concrete masonry shear walls. Test results are summarized and compared with design formulae specified by the New Zealand masonry design standard NZS 4230:1990 and by the National Earthquake Hazards Reduction Program. It was determined that the test walls exhibited shear strength significantly exceeding the NZS 4230:1990 maximum permissible shear stress, confirming that NZS 4230:1990 was overly conservative in accounting for masonry shear strength. It was also confirmed from the test results that masonry shear strength increases with the magnitude of applied axial compressive stress and the amount of shear reinforcement, but that the shear strength decreases inversely in relation to an increase in wall aspect ratio. In addition, it was shown that the postcracking performance of shear dominated walls was substantially improved when uniformly distributing the shear reinforcement up the height of the walls.

Flexural Behavior of Reinforced Concrete Masonry Walls under Out-of-Plane Monotonic Loads

This paper presents the test results of an investigation carried out to study the behavior and flexural strength of vertically spanned reinforced concrete block masonry walls under out-of-plane monotonic loading. The study presented in this paper, which is part of the U.S.-Japan Coordinated Program on Masonry Building Research, addresses the elastic and inelastic behavior of reinforced block masonry walls. Six walls were tested to determine the effects of percentage and location of vertical reinforcement, block size, and extent of grouting. The behavior included cracking patterns and cracking moments, load-deflection curves up to and beyond the peak load, and displacement ductility. Test results showed that the percentage and location of vertical steel (centrally located versus staggered) had a significant effect on wall load-deflection curves, strength, and ductility. The extent of grouting (partially versus fully grouted) affected cracking load and consequently, flexural rigidity and deflection under service loads. The extent of grouting, however, did not show an adverse effect on wall stability in the inelastic range. The specified value of the modulus of rupture in the UBC-94 code is much lower than the experimental values of maximum tensile stress at first crack obtained for fully grouted walls. The theoretical analysis for the ultimate strength based on the Whitney stress block method that is included in the UBC-94 code showed a good correlation with the experimental results. Displacement ductility ratios ranged from 1.79 for the wall with 0.44 percent vertical steel to 16 for the wall with 0.19 percent steel. As expected, the displacement ductility of the wall panels decreased as the percentage of vertical reinforcement increased.

Analysis of Concrete Masonry Beams

This paper presents an in-depth structural engineering and structural reliability analysis of concrete masonry beams. The ductile response of masonry beams was studied in detail. A limit-state design methodology for reinforced-concrete masonry beams is presented in this paper based on the principles of structural reliability. Recommended values of capacity-reduction factors were developed that explicitly account the design safety of the limit states. The reinforcing steel bars are uniformly distributed throughout the beam section. Three different ductility definitions (strain, curvature, and displacement) were derived and presented. This paper also formulated a structural reliability analysis method to establish limitations on the quantity of steel in masonry beams. Equations were derived for the expected capacity at yield and ultimate limit states. An important part of this paper was to quantify the uncertainty in the design capacity of concrete masonry beams of different limit states resulting from the ...

Shear Strength of Reinforced Concrete Masonry Beams With Web Reinforcement

First Name is required invalid characters Last Name is required invalid characters Email Address is required Invalid Email Address Invalid Email Address

1044 コンクリートブロック造の施工は果たして信頼できるか : コンクリートブロック積工資格認定試験を通してみた積工の実態と技能(材料・施工)

1044 コンクリートブロック造の施工は果たして信頼できるか : コンクリートブロック積工資格認定試験を通してみた積工の実態と技能(材料・施工)