ML20030B590

Assessment of Reinforcement on Capacity & Behavior of Masonry Walls

ML20030B590
Person / Time
Site:	Point Beach
Issue date:	08/31/1981
From:	COMPUTECH ENGINEERING SERVICES, INC.
To:
Shared Package
ML20030B586	List: ML20030B585 ML20030B590 ML20030B594
References
R553.04, TAC-42896, TAC-42897, NUDOCS 8108180329
Download: ML20030B590 (5)

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ASSESSMENT OF REINFORCEMENT ON THE CAPACITY AND BEHAVIOR OF MASONRY WALLS Prepared for Point Beach Nuclear Power Plant, Units 1 and 2 WISCONSIN ELECTRIC POWER COMPANY Milwaukee, Wisconsin Prepared by COMPUTECH ENGINEERING SERVICES, INC.

Berkeley, California l

l August,1981 REPORT NO. R553. 04 ffj8180329810814' O

ADOCK 05000266 PDR

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8 TABLE OF CONTENTS 1

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INT RO D U CTIO N....................................

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2 AS-BUILT CONDITION OF THE WALLS........................

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3 CAPACITY AND BnHAVIOR OF REINFORCED AND UNREINFORCED WALLS 1

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C O N C LU S I O N.....................................

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INTRODUCTION The Nuclear Regulatory Commission (NRC) sinff on June 9-11. 1981 reviewed the criteria and calculations performed on IE Bulletin 30-11 Masonry Wall Evalueun " for the Point Beach Nuclear Power Plant. Action item 15 resulting frorr' 114 review meeting required the licensee to provide an assessment of th? possible impact on wall capacity / behavior for neglecting the presence of an undefined amount of reinforcement in the masonry and assuming the walls as unreinforced in the analysis.

This short report is in response to Action item 15 and conta'ns a description of the as-built condition of the walls, the behavior / capacity of the wall for the reinforced and unreinforced case, and the conclusions.

2 AS-BUILT CONDITION OF THE WALLS The field survey conducted by Bechtel on IE Bulletin 80-11 for the Point Beach Nuclear Power Plant Indicated that there were inconsistencies in the occurrence and location of both horizontal and vertical reinforcement whenever it was specified in a given masonry wall. Location of the reinforcement was performed both with a rebar detector device and by visual inspection. Visual Inspection was performed by removing part of the face shell to determine the presence of reinforcement. The conclusion of the Inspection performed by Bechtel was that the amount and distribution of reinforcement could not be relled upon and therefore all walls should be evaluated as unreinforced walls.

3 CAPACITY AND BEHAVIOR OF REINFORCED AND UNREINFORCED WALLS All ways were assumed to be unreinforced and the criteria.'or re-evaluation was ba?3d on the assumption that the allowable stresses for tensicn both pe/allel and normal to the bed joint,ere such inal the wall would remain uncracked at these levels of allowable stresses. Therefore, all walls were analyzed using uncracked section properties. If the stresses due to the

?pplied loads did not exceed the allowables the walls would remalin uncracked.

The uncracked moment of inertia for an 8 inch ungrouted and grouted unit is 334.0 in'"4/f t ar.d 443.3 in'"4/ft.respectively. The moment capacity of an 8 inch ungrouted and grouted unit is 165.9 lb-in/m and 353.0 lb-in/in for a vertical strip and 333.9 lb-in/in and 663.5 lb-In/in for a horizontal strip as shown in Table 1.

In the analysis of a reinforced masonry wall the reinforcement does not contribute to the resistance of applied loads until the wall section cracks. The criteria used to re-evaluat0 the masonrv walls ensures that all walls remain uncracked and therefore the reinforement will not be activated. However, if it is hypothesized that the reinforemerit is activated as proposed In Action item 15 the effect of reinforcement can be assessed. The amount of reinforcement typically specified for the masonry walls was No. 4's at 32 in on center or No. 6's at 32 in on center vertically and No. 9 gage joint reinforcement at 16 in. on center horizontally. The cracked moment of inertia of 8 inch 1

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e masonry units with these three reinforcement patterns are 25.0 in**4/ft. 45.6 in"*4/ft, and 20.0 In*"4/ft. respectively as shown in Table 1. If these moments of inertia were used in the analysis of a cracked portion of the wall the frequency of the wall would decrease. This decrease in frequency may result in higher applied moments to the wall.

The moment capacities of a reinforced 8 inch masonry wall are showmn in Table 1 for the three reinforcement patterns typically specified. For the case of vertically reinforced walls the capacity of a reinforced wall is from 1.3 to 2.7 times greater ththe capacity of an unreinf orced grouted and ungrouted walls, respectively. For the amount of horizontal reinforcement specified the capacity of a reinforced section is significally less than an unreinforced section.

4 CONCLUSION The masonry walls at the Point Beach Nuclear Power Plant were re-evaluated on the basis that all walls were unreinforced. This was done because of inconsistencies in the occurrence and distribution of reinforcement when specified. The criteria for re-evaluation of the uncracked walls was based on the premise that the walls would remain uncracked when subjected to all applied loads. If a wall did not meet this criteria it was repaired.

If it is hypothesized that the walls are reinforced and that they crack so the reinforcement is activated then the frequency of a given wall will decrease since the moment of inertia of a cracked reinforced wall is lower than that of an uncracked wall. This may result in higher moments in the wall.

The allowable moment capacity of 8 inch vertically reinforced masonry walls is from 1.3 to 2.7 times greater than that of an equivalent unreinforced grouted and ungrouted wall respectively. The allowable moment capacity of an 8 inch horizontally reinforced wall is significantly less than that of an equivalent unreinforced wall.

The presence of the typical amounts of vertical reinforcement. If it is present, in the allowable provide an additional factor of safety above that inherent will stress for tension normal to the bed joint. The presence of the typical amounts of horizontal reinforcement, if it is present, wfil not provide any additional factor of safety above that inherent tr' the allowable stress parallel to the bed joint.

Based on the assumptions and criteria used to re-evaluate the masonry walls at the Point Beach Nuclear Power Plant the presence of reinforcement will will have any adverse effect. In fact the presence of vertical reinforcement not provide an additional factor of safety if the wall cracks when subjected to appiled loads. bjected to applied loads.

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r TABLE 1 Com'parison of Moment of inertia and Moment Capacity for an 8 inch Masonry Unit Reinforced Unreinforced & Grouted Unreinforced & Ungrouted Reinforcement Moment of Moment Moment of Mcment Moment of Moment inertia Capacity inertia Capacity inertia Capacity (in" *4/f D (Ib-in/in)

(in = "4/fD (lb-in/in)

(in * *4/ft)

(Ib-in/in)

1. 4932 in.

25.0 458 443.3 353 334.0 165.9

1. 6932 in.

45.6 1008 443.3 353 334.0 165.9

1. 9 Gage 916 in.

20.0 165 443.3 663.5 334.0 333.9 Note:

The moment capacity is based on the allowable stresses for factored loads i

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