Unreinforced Shear Wall Evaluation Seismic Displacement Demand

Nonlinear time history analyses are performed on the validated single degree of freedom models of two unreinforced masonry walls. Evaluation of seismic displacement demand for unreinforced masonry shear walls. Print chapters, sections, and subsections for frequently used code.
The purpose of this chapter is to promote public safety and welfare by reducing the risk of death or injury that may result from the effects of earthquakes on existing unreinforced masonry bearing wall buildings.

But it still needs to meet code required minimum reinforcement requirements. 


www.youtube.com/watch?v=w5gqkjrtolI Evaluation of seismic displacement demand for unreinforced masonry shear walls – Unreinforced Masonry Shear Wall



Experimental work indicated that the walls with medium to high aspect ratios failed in diagonal tensile shear failure mode while squat walls exhibited both sliding shear and diagonal shear cracks.

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The provisions of this chapter are intended as minimum standards for structural seismic resistance, and are established primarily to reduce the risk of life loss or injury.

Fvs is required, then the program will back calculate a spacing, s, that will satisfy the steel shear capacity required. When shear reinforcement is required the program will also meet the d/2 or 48″ spacing required by 8.3.5.2.1. Lateral load from wind, seismic, earth pressure etc.
Tensile stress from flexural moment due to lateral load, eccentric moment, etc.
Allowable flexural tension stress for hollow core concrete masonry unit, psi.
Level 1 & 2 rooms, roof treatment and perforated bricks masonry parapet walls using hydrated lime, brick surkhi and jute as mortar. Because there was no observed damages due to bed-joint sliding, rocking and/or toe crushing. Much of the material presented in this book examines building structures. Various properties such as displacement ductility factors, ultimate drift ratios, coefficient ofnequivalent viscous damping, stiffness degradation and modulus of rigidity were determined using thenexperimental data from quasi-static cyclic tests on the piers.

Similarly, the effectnof drift ratio on the coefficient of equivalent viscous damping was also studied. The role of the shear ratio in the shear failure mechanisms is put in evidence and shear strength formulae are proposed accordingly. Experimental results show how ultimate drift seems to be a parameter with high regularity for walls failing in shear. T we can then define the boundary zone steel required. Each iteration of the steel area is based on the amount of steel needed to create a 0.005 ksi difference in the calculated bending stress (fb) and is carried out until the calculated value of required reinforcement is less than the reinforcement provided.

From this analysis fm is calculated. Mu is plotted and the code check is then calculated.
In this lower portion of the interaction diagram, the bending capacity changes in a linear fashion with respect to axial force. Delta effects, moment and deflection calculations are iterative. Iequiv is taken from the maximum moment in a wall region and used to update the stiffness of the entire height of the wall.

If the program iterates through this procedure 100 times it means that the wall is either too slender or too highly loaded. Wall is failing in bending.” is reported. Fvs is required, then the program will back calculate a spacing, s, that will satisfy the steel shear capacity required. When shear reinforcement is required the program will also meet the d/2 or 48″ spacing required by 8.3.5.2.1. The detail report shows a stirrup with two legs. Diameter of core multiplied by its length or the area of the side of a square prism. Cross-sectional area of unreinforced masonry pier or wall, square inches (10-6 m2). Total area of the bed joints above and below the test specimen for each in-place shear test, square inches (10-6 m2). In-plane width dimension of pier, inches (10-3 m), or depth of diaphragm, feet (m). Least clear height of opening on either side of a pier, inches (10-3 m). Span of diaphragm between shear walls, or span between shear wall and open front, feet (m). The plans shall indicate all existing and new crosswalls and shear walls and their materials of construction. The type of interior wall and ceiling materials, and framing. The extent and type of parapet corrections that were previously performed, if any. All other plans, sections and details necessary to delineate required retrofit construction. Unreinforced masonry walls used to carry vertical loads or seismic forces parallel and perpendicular to the wall plane shall be tested as specified in this section.

Veneer wythes shall not be included in the effective thickness used in calculating the height-to-thickness ratio and the shear capacity of the wall. Grouted or ungrouted hollow concrete or clay block and structural hollow clay tile shall be laid in a running bond pattern.
Steel blocks, the size of the end of the brick, should be used on each end of the ram to distribute the load to the brick.

The load should be applied horizontally, in the plane of the wythe. A bed joint intersection with a head joint shall be in the center of the core. This alternative should be limited to recently constructed masonry. An accurate record of all such tests and their locations in the building shall be recorded, and these results shall be submitted to the building department for approval as part of the structural analysis.

Lecture 4 5 Urm Shear Walls

In any case, not less than one test per 1, 500 square feet (139.4 m2) of wall surface and not less than a total of eight tests.

The shear strength of any wall class shall be no greater than that of the weakest wythe of that class. Preparation and mortar pointing shall be performed with special inspection. At the discretion of the code enforcement official, incidental pointing may be performed without special inspection.
All new embedded bolts shall be subject to periodic special inspection in accordance with the building code, prior to placement of the bolt and grout or adhesive in the drilled hole.

Capacity reduction factors need not be used. Unreinforced masonry shall be assumed to have no tensile capacity.
The resistance values of the existing anchors shall be the average of the tension tests of existing anchors having the same wall thickness and joist orientation.

Higher values may be justified only in conjunction with a geotechnical investigation.

External Shear Strengthening Of Unreinforced Damaged Masonry Walls