Ahwahnee_-_URS_seismic_report_2002_Part_2_of_3.pdf
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Preliminary Description of Foundation Seismic Retrofit to mitigate Liquefaction Effects
Introduction This attachment presents preliminary conceptual retrofit schemes to mitigate liquefaction-induced damage during the design earthquake at the Ahwahnee Hotel. In developing these schemes, we considered liquefaction mitigation techniques that would be least invasive and be most compatible with the archeological and historic nature of the building and its environ. This section describes the basic concepts of two selected retrofit schemes that were finally selected and presents a preliminary cost estimate of each of these techniques. In developing these preliminary concepts, we based our evaluation on our firm's experience in similar projects and on our conversations with specialty contractors in ground modification.
Scope The scope of this section includes:
Identification of technically feasible and cost effective techniques to mitigate liquefaction;
Evaluation of the constructibility of such techniques for the existing conditions of the building;
Evaluation of the potential impacts of these techniques to the existing foundation and structure;
Evaluation of the successful application of such techniques in the foundation remediation of historic buildings;
Preliminary evaluation of effects of these techniques to the environment; and Preliminary cost estimate of each of the selected retrofit systems evaluated.
Objectives of the liquefaction retrofit The main objective of the remediation schemes is to minimize the total and relative settlement induced by liquefaction the structure is subjected to. Because the extent and depth of the liquefied volume is large, any scheme involving the modification of the whole liquefiable volume under the structure would be excessively expensive and require a more intrusive technique. Our concept involves the underpinning of individual footings with a continuous vertical support extending down to deeper layers. At the ground surface, it estimated that the design ground motions would produce settlements on the order of 14 inches. Differential settlements will probably be several inches. At a depth of about 40 to 45 feet, however, the cumulative liquefaction-induced total and differential settlement are estimated to be only 1.5 to 2 inches, and one inch, respectively. Because the bearing mechanism is transferred down to these deeper layers, the damaging effects at the surface are decoupled from the structure. As the ground adjacent to the building may liquefy and settle with respect to the structure, incoming pipelines and conduits, as well
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CAMurdock Highlight footing and in-between the four primary columns. Because of the reduced space, special equipment is necessary.
The main advantages of this solution are that the injection under high pressure not only produces a more or less continuous grout cylinder but also densify the soil in-between and outside columns. As a result, the liquefaction potential and the associated settlement can be significantly reduced. It anticipated that the relatively large diameters obtained with compaction grout, although smaller than those with jet grouting, would be adequate to provide bearing capacity at depth in the event the deposit liquefies. Because the compact grout columns would occupy a relatively small portion of the volume of soil underneath the hotel, it is estimated that the impact to the soil in-situ hydraulic conductivity and potential modification to the current groundwater flow will not be significant. It is estimated that the replacement volume of the treated area is about 10 to 15%. Spoils with this technique are minimal or nonexistent. Because the grout is a low-slump mixture with relatively low water content, it is expected that this material will not settle as much as jet grouting and will be more stable against groundwater flow.
Special requirements concerning the peak injection pressure and grout take will be necessary at shallow depths to prevent soil fracture and damage to the existing structure.
Continuous structural monitoring will be necessary during grout injection. Pre construction tests are recommended to ensure that the continuity and good control over the achieved diameter of the column over the entire depth can be achieved.
The scheme presented above is preliminary. The diameter, depth, and number of columns may decrease as further engineering analyses and evaluations are conducted.
Therefore, the estimate cost will vary accordingly. The scheme presented above, however, is estimated to be a conservative scenario.
Archeological and Environmental Impacts The environmental impacts of each retrofit scheme should be evaluated according to existing pertinent documents, e.g., National Environmental Policy Act (NEPA) guidelines drafted by the National Park Service (NPS, 1997).
It is known that there is an intact deposit of a prehistorichistoric Indian village site located near the parking lot and employee dormitory areas. The assessment of the impact of the proposed retrofit schemes to historic resources must be performed following procedures in accordance with the National Historic Preservation Act, and other federal and state agencies including the Advisory Council on Historic Preservation (ACHP) and the California State Historic Preservation Officer (SHPO). In addition, these procedures include consultation with Indian Tribes. Procedures to minimize impacts on cultural resources should be carefully developed.
Environmental and cultural resources impact assessments are beyond the scope of this seismic evaluation. Although the retrofit schemes presented earlier may be feasible from the technical and economic viewpoints, it is not known at this time the impact environmental and archeological considerations will have on the proposed solutions.
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Page Job NO.: 43-00066652-15 Client: National Park Service Job Name: Seismic Rehabilitation Alternatives for the Ahwahnee Hotel, Yosemite National Park, CA
Summary of Schemes A, B & C Conceptual Cost Estimate
11 Scheme A - Life Safety Conceptual Cost Estimate
Structural Cost $ 14,642,837.00 Non-Structural Cost $ 3,329,887.00
Total Estimated Cost - Scheme B - Life Safety Conceptual Cost Estimate bi
I
Structural Cost
I" Non-Structural Cost $ $- Total Estimate Cost -
Cii Scheme C.-.Limited Damage Conceptual Cost Estimate
Structural Cost Non-Structural Cost
$m $m Total Estimated Cost -
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NATIONAL PARK SERVICE
SEISMIC SAFETY PROGRAM
SEISMIC REHABILITATION OF THE AHWAHNEE HOTEL
YOSEMITE PARK, CALIFORNIA.
SCHEME A LIFE SAFETY CONCEPTUAL ESTIMATE
SUMMARY 10131 100
NO. DESCRIPTION TOTAL COSTISF
1 DEMOLITION
2 SITEWORK
3 CONCRETE
4 MASONRY
5 METALS
6 WOOD & PLASTICS
7 THERMAL 81 MOISTURE
8 DOORS 81 GLAZING 0
9 FINISHES 727,199
10 SPECIALTIES 0
11 EQUIPMENT 0
12 FURNISHINGS 0
13 SPECIAL CONSTRUCTION 150,000
14 CONVEYANCES 0
15 MECHANICAL 200,000
16 ELECTRICAL 100,000
DIRECT COST SUBTOTAL
8,070,347
GENERAL CONDITIONS
G.C. MARK UP & BOND
m m
ESTIMATEIDESIGN CONTINGENCY 0
TOTAL CONSTRUCTION COST
ESCALATION TO 2003=2YRS@4% P.A. 0
TOTAL PROJECT COST $-
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SEISMIC REHABILITATION OF THE AHWAHNEE HOTEL
YOSEMITE PARK, CALIFORNIA.
SCHEME A LIFE SAFETY CONCEPTUAL ESTIMATE
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SEISMIC REHABILITATION OF THE AHWAHNEE HOTEL
YOSEMITE PARK, CALIFORNIA.
SCHEMES A & B
NON STRUCTURAL ITEMS CONCEPTUAL ESTIMATE
SUMMARY 10/31/00
TOTAL
1,835,255
1,835,255
367,051 264,277
616,646
3,083,228
246,658
$ 3,329,887
20% 12%
25%
8%
NO.
COSTISF DESCRIPTION
SCHEMES A & B
NON STRUCTURAL ITEMS
DIRECT COST SUBTOTAL
GENERAL CONDITIONS
G.C. MARK UP & BOND
ESTIMATEtDESIGN CONTINGENCY
TOTAL CONSTRUCTION COST
ESCALATION TO 2003=2YRS@4% P.A.
TOTAL PROJECT COST
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SEISMIC REHABILITATION OF THE AHWAHNEE HOTEL
YOSEMITE PARK, CALIFORNIA.
SCHEMES A & B
NON STRUCTURAL ITEMS CONCEPTUAL ESTIMATE
DATE : 1 013 1 100
NO. DESCRIPTION IQUANTIT~ UNIT RATE AMOUNT
AHWAHNEE HOTEL
NON STRUCTURAL ITEMS
SCHEMES A &-B
UNISTRUT, REBAR & GROUT AT CLAY PARTITIONS - 7/S11 - 0
CEILING BRACE, PER 8lS11
STONE ANCHORS, STAINLESS
STONE ANCHORS TO EA STONE <4 SF EA ALLOWANCE
TOTAL NON STRUCTURAL
SUMMARY
SEISMIC SAFETY PROGRAM
SEISMIC REHABILITATION OF THE AHWAHNEE HOTEL
YOSEMITE PARK, CALIFORNIA.
SCHEME B LIFE SAFETY CONCEPTUAL ESTIMATE
SUMMARY 10131100
NO.
DESCRIPTION
DEMOLITION
SITEWORK
CONCRETE
MASONRY
METALS
WOOD & PLASTICS
THERMAL & MOISTURE
DOORS & GLAZING
FINISHES
SPECIALTIES
EQUIPMENT
FURNISHINGS
SPECIAL CONSTRUCTION
CONVEYANCES
MECHANICAL
ELECTRICAL
DIRECT COST SUBTOTAL
GENERAL CONDITIONS
G.C. MARK UP & BOND
ESTlMATElDESlGN CONTINGENCY
TOTAL CONSTRUCTION COST
ESCALATION TO 2003=2YRS@4% P.A.
TOTAL PROJECT COST
20% 12%
25%
8%
TOTAL
193,861 3,473,700 1,405,577
29,000 1,580,380
1 19,390 33,040
726,865
150,000
200,000 100,000
8,011,812
1,602,362 1,153,701
2,691,969
13,459,844
1,076,788
$ 14,536,632
COSTISF
SEISMIC REHABILITATION OF THE AHWAHNEE HOTEL
YOSEMITE PARK, CALIFORNIA.
SCHEME B LIFE SAFETY CONCEPTUAL ESTIMATE
SEISMIC REHABILITATION OF THE AHWAHNEE HOTEL
YOSEMITE PARK, CALIFORNIA.
NON STRUCTURAL ITEMS CONCEPTUAL ESTIMATE
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